阅读说明：本技术 形成的具有平滑边缘及可选地可剥离表面的热塑性制品 (Formed thermoplastic article with smooth edges and optionally peelable surfaces ) 是由 米勒德·F·*** 于 2018-02-28 设计创作，主要内容包括：本发明涉及形成具有平滑外周的成形热塑性制品。许多热塑性制品具有在模塑原料片材或从原料片材切割出制品时(例如在热成形之后)形成的尖锐边缘。这种尖锐边缘会损坏它们接触的塑料薄膜或肉体,并且希望使这种边缘平滑化。本文描述了通过使尖锐边缘翻转而为这种带尖锐边缘的制品形成平滑外周的方法。通过以下内容执行平滑化操作：形成可偏转凸缘,其中可偏转凸缘包括通过间隔件与潜在尖锐的外周边缘间隔开的弯折区域,使可偏转凸缘的一部分偏转以及将可偏转凸缘的至少一个弯折部分软化以在冷却时产生平滑的外周。内衬片材可以在形成之前、期间或之后附接到原料片材上并且可以从该原料片材上剥离。(The present invention relates to forming shaped thermoplastic articles having smooth outer perimeters. Many thermoplastic articles have sharp edges that are formed when the sheet of stock material is molded or the article is cut from the sheet of stock material (e.g., after thermoforming). Such sharp edges can damage the plastic film or flesh that they contact, and it is desirable to smooth such edges. Methods of forming a smooth periphery for such articles with sharp edges by inverting the sharp edges are described herein. The smoothing operation is performed by: forming a deflectable flange, wherein the deflectable flange includes a bend region spaced apart from the potentially sharp peripheral edge by spacers, deflecting a portion of the deflectable flange and softening at least one bend portion of the deflectable flange to create a smooth outer perimeter upon cooling. The liner sheet may be attached to the stock sheet before, during or after formation and may be peeled from the stock sheet.)

1. An article formed from a thermoformable sheet having a peripheral edge and being sufficiently rigid to define a configuration of the article, the article comprising a body having an extension extending peripherally away from the body, the extension comprising the peripheral edge of the thermoformable sheet and a bent portion between the peripheral edge and a connection between the body and the extension; the bent portion has a smooth outer periphery and is bent sufficiently such that the peripheral edge of the thermoformable sheet is displaced from the outer periphery of the article, whereby the article has a smooth outer periphery.

2. The article of claim 1, wherein the body has the shape of a rounded rectangular tray and a recessed compartment is formed in the rounded rectangular tray, the extension completely surrounding the outer perimeter of the compartment.

3. The article of claim 1, wherein the folded portion of the extension is folded sufficiently such that a plane extending through the thermoformable sheet at the outer peripheral edge is offset from a plane of the extension between the folded portion and the connection by an angle of no less than 120 degrees.

4. The article of claim 3, wherein the plane offset is not less than 135 degrees.

5. The article of claim 3, wherein the plane offset is not less than 180 degrees.

6. The article of claim 3, wherein the plane offset is not less than 270 degrees.

7. The article of claim 1, wherein the extension comprises: a fold region between the peripheral edge and a connection between the main body and the extension; and a spacer introduced between the peripheral edge and the bending region; the bending region includes a curved portion.

8. The article of claim 7, wherein the inflection region connects the spacer with a portion of the extension between the connection and the inflection region at an angle of about 90 degrees.

9. The article of claim 7, wherein the bend portion comprises at least one of the bend region and the spacer.

10. The article of claim 1, wherein the extension comprises: a fold region between the peripheral edge and a connection between the main body and the extension; and a peripheral flange interposed between the peripheral edge and the bend region; the bending region includes a curved portion, and the peripheral flange is connected to the bending region by a bend.

11. The article of claim 10, further comprising a spacer interposed between the bend region and the bend.

12. The article of claim 1, wherein the extension includes a fold region between the peripheral edge and a connection between the main body and the extension; wherein the fold region comprises a curved portion, wherein the extension has an inverted configuration whereby the curvature of the fold region and fold portion displaces the peripheral edge anti-peripherally from the periphery of the article.

13. The article of claim 12, wherein the curvature of the fold region and the fold portion displaces the peripheral edge sufficiently so that the peripheral edge is not directly visible from the exterior of the article.

14. The article of claim 12, wherein the curvature of the fold region and the fold portion displaces the peripheral edge sufficiently so that the peripheral edge is not perceptible to a person moving a finger along the periphery of the article.

15. The article of claim 1, wherein the body has the shape of a tray and a recessed compartment is formed in the tray, the recessed compartment having an opening, the extension completely surrounding a periphery of the opening, the extension having a rollover edge around the entire periphery.

16. The article of claim 15, wherein the shape of the body does not include any conventional stacking lugs, and wherein the extension carries a rounded stacked extension of turned edges at least one location on the outer periphery of the article.

17. The article of claim 15, further comprising a plastic film contacting the smooth periphery of the article around the entire periphery of the opening.

18. The article of claim 17, wherein the plastic film is substantially permanently sealed to the article around the entire periphery of the opening.

19. An article formed from a thermoformable sheet having a peripheral edge and sufficient rigidity to define a configuration of the article, the article comprising a body and having an extension extending peripherally away from the body, the extension comprising a deflectable flange comprising a spacer with a peripheral edge of the thermoformable sheet, the spacer being connected to the extension at a substantially right angle by a bend region, the bend region having a smooth profile.

20. The article of claim 19, wherein the spacer comprises: a peripheral flange at a peripheral edge of the deflectable flange; and a bend connecting the peripheral flange to the remainder of the spacer at an angle other than 180 degrees.

21. The article of claim 19, wherein the article does not comprise a metal foil.

22. A method of manufacturing a shaped article having a body with a smooth outer periphery, the method comprising:

Forming a thermoplastic into a shape including the body and a deflectable flange at an outer peripheral portion of the body,

The deflectable flange including a spacer with a peripheral edge of the thermoplastic, the spacer connected to the main body by an extension extending peripherally away from the main body and a bend region interconnecting the spacer and the extension,

The fold region has a smooth profile and interconnects the spacer and the extension at a substantially right angle;

Impacting an impact head against the spacer to deflect the spacer toward the extension, whereby a magnitude of an angle between the spacer and the extension decreases as a result of a pre-impact position of at least a portion of the deflectable flange relative to the at least a portion becoming bent, the bend selected from the group consisting of the extension, the bent region, and the spacer;

Heating the bent portion to at least the glass transition temperature of the thermoplastic; and

The impact head is disengaged from the spacer, whereby the bent portion is maintained at a position deviated from the before-impact position of the bent portion even when the impact is interrupted, to produce a body having a smooth outer periphery.

23. The method of claim 22, wherein the impact head is disengaged from the spacer after cooling the bent portion below the glass transition temperature.

24. The method of claim 22, wherein the inflection region interconnects the spacer and the extension at an angle of no less than 75 degrees but less than 105 degrees.

25. The method of claim 22, wherein the inflection region interconnects the spacer and the extension at an angle of about 90 to 93 degrees.

26. The method of claim 22, wherein the bent portion is cooled below the glass transition temperature after disengaging the spacer from the impact head.

27. The method of claim 22, wherein the thermoplastic is formed into a shape comprising a body having a recessed compartment with an opening and the deflectable flange around an entire periphery of the opening.

28. The method of claim 27, further comprising sealing the compartment with a membrane that contacts the smooth outer periphery of the body around the entire outer periphery of the opening.

29. The method of claim 28, wherein the compartment is sealed by overwrapping the body with the film and sealing the film to itself to enclose the body.

30. The method of claim 28, wherein the compartment is sealed by applying the film across the opening of the compartment and sealing the film around the periphery of the opening.

31. The method of claim 30, further comprising evacuating gas from the compartment prior to sealing the membrane around the periphery of the opening.

32. The method of claim 31, further comprising injecting an atmosphere into the compartment prior to sealing the film.

33. The method of claim 22, wherein the impact head is impacted against the spacer to deflect the peripheral edge away from the periphery of the shaped article sufficiently that a flexible film tightly overwrapping the shaped article does not contact the peripheral edge after cooling the bent portion.

34. The method of claim 22, wherein the spacer comprises a bend and a peripheral flange at a peripheral edge of the deflectable flange, the bend connecting the peripheral flange to a remainder of the spacer at an angle other than 180 degrees, wherein the impact head is caused to impact the peripheral flange to deflect the spacer, and wherein the peripheral flange is heated to at least the glass transition temperature of the thermoplastic.

35. The method of claim 22, wherein the shape is formed by: thermoforming the thermoplastic sheet into the shape and then cutting the shape from the sheet to produce the peripheral edge of the shape at the location of the shape cut from the sheet.

36. The method of claim 22, wherein after impacting the impact head against the spacer and heating the bent portion to at least the glass transition temperature, the impact head is further impacted against the spacer to further deflect the spacer toward the extension and then disengage the impact head from the spacer.

37. The method of claim 22, wherein the impact head impacts the spacer at an upper surface of the impact head, the upper surface having a profile that deflects inwardly toward the body, whereby greater impact of the spacer against the upper surface of the impact head deflects the peripheral edge more toward the body.

38. The method of claim 37, wherein the upper surface is sufficiently curved such that increased impact of the spacer against the impact head rotates the peripheral edge toward the body.

39. The method of claim 37, wherein said upper surface is sufficiently curved such that increased impact of said spacer against said impact head rotates said peripheral edge at least about 180 degrees relative to an orientation of said peripheral edge prior to impact.

40. A method of manufacturing a container having a recessed compartment and a smooth outer perimeter, the method comprising:

Forming a thermoplastic sheet into a shape comprising a main body and a deflectable flange, the main body comprising the recessed compartment and the deflectable flange surrounding the compartment at a periphery of the main body, the periphery being formed by cutting the shape from the sheet to form a peripheral edge of the shape,

The deflectable flange including a spacer with the peripheral edge, the spacer connected to the main body by an extension and a bend region, the extension extending peripherally away from the main body and the bend region interconnecting the spacer and the extension,

The spacer comprising a peripheral flange and a bend, the peripheral flange comprising the peripheral edge, and the bend connecting the peripheral flange to the remainder of the spacer at an angle other than 180 degrees,

The fold region has a smooth profile and interconnects the spacer and the extension at a substantially right angle;

Impacting an impact head against the spacer to deflect the spacer toward the extension, whereby a magnitude of an angle between the spacer and the extension decreases as a result of a pre-impact position of at least a portion of the deflectable flange relative to the at least a portion becoming bent, the bend selected from the group consisting of the extension, the bent region, and the spacer;

Heating the bent portion to at least the glass transition temperature of the thermoplastic;

Cooling the bent portion below the glass transition temperature, whereby the bent portion maintains a pre-impact position that is offset from the bent portion even when an impact is interrupted, an

Disengaging the impact head from the spacer to create the body with a smooth outer perimeter.

41. A method of forming a smooth outer perimeter on a thermoformed article made of thermoplastic and having a sharp peripheral edge, the method comprising:

Forming a deflectable flange around the peripheral edge of the article,

The deflectable flange comprising a spacer comprising a peripheral edge of the article, the spacer being connected to the article by an extension extending peripherally away from the article and a bend region interconnecting the spacer and the extension,

The fold region has a smooth profile and interconnects the spacer and the extension at a substantially right angle;

Impacting an impact head against the spacer to deflect the spacer toward the extension, whereby a magnitude of an angle between the spacer and the extension decreases as a result of a pre-impact position of at least a portion of the deflectable flange relative to the at least a portion becoming bent, the bend selected from the group consisting of the extension, the bent region, and the spacer;

Heating the bent portion to at least the glass transition temperature of the thermoplastic;

Cooling the bent portion below the glass transition temperature, whereby the bent portion maintains a pre-impact position that is offset from the bent portion even when an impact is interrupted, an

Disengaging the impact head from the spacer to produce the article having a smooth outer periphery.

42. A system for manufacturing a shaped article having a body with a smooth outer periphery, the system comprising:

A thermoforming machine comprising at least one mold for forming a thermoplastic sheet into a shape comprising the body and a deflectable flange located around an outer periphery of the body,

The deflectable flange comprising a spacer with a thermoplastic peripheral edge, the spacer being connected to the article by an extension extending peripherally away from the article and a fold region interconnecting the spacer and the extension,

The spacer comprising a peripheral flange and a bend, the peripheral flange comprising the peripheral edge, and the bend connecting the peripheral flange to the remainder of the spacer at an angle other than 180 degrees,

The fold region has a smooth profile and interconnects the spacer and the extension at a substantially right angle;

An impact head operatively connected to the thermoformer to cause the impact head to impact the spacer to deflect the spacer toward the extension, whereby a magnitude of an angle between the spacer and the extension decreases as a result of a pre-impact position of at least a portion of the deflectable flange relative to the at least a portion becoming bent, the bend selected from the group consisting of the extension, the bend region, and the spacer; and

A heater for heating the bent portion to at least the glass transition temperature of the thermoplastic.

43. The system of claim 42 further comprising a trimmer for trimming a peripheral edge of the body around the periphery to within a few millimeters of the elbow.

44. A tray adapted to be sealed with a sealing film using each of Overwrap (OW), Vacuum Seal Packaging (VSP) and Modified Atmosphere Packaging (MAP) sealing techniques, the tray being

An article formed from a thermoplastic sheet having a peripheral edge, the article comprising a tray-shaped body having a recessed portion surrounded by an extension portion, the extension portion extending peripherally away from the recessed portion;

The extension includes a peripheral edge, a flat sealing surface surrounding the recessed portion, and a folded portion between the peripheral edge and the sealing surface, the sealing surface adapted to seal the sealing membrane to the sealing surface using any of VSP and MAP sealing techniques; and is

The article has a smooth outer periphery and the bent portion is bent sufficiently so that the peripheral edge turns at least generally opposite the outer periphery.

45. The tray of claim 44, wherein a gap exists between the bent portion and the recessed portion of the main body.

46. The tray of claim 45, wherein the gap occurs around the entire periphery of the article.

47. The tray of claim 44, wherein the folded portion has a configuration that is rolled in a direction opposite to an outer periphery of the tray.

48. The tray of claim 47, wherein the folded portion is folded under an interior side of the extension and includes the peripheral edge, the folded portion and the peripheral edge defining a folded edge.

49. The tray of claim 44, wherein the sealing surface has a substantially constant width around the entire recessed portion, the width being measured in a direction extending peripherally away from the recessed portion of the body.

50. The tray of claim 44 having a sealing membrane sealed to the sealing surface around the entire perimeter of the recessed portion.

51. The tray of claim 50, wherein the sealing membrane extends peripherally from the sealing surface around the fold.

52. The tray of claim 50 wherein the sealing film is thermosettable, extends at least about 90 degrees around the smooth outer periphery of the article, and is below its glass transition temperature.

53. The tray of claim 50, wherein at least the recessed portion of the tray is visually transparent.

54. The pallet of claim 44, wherein the extension comprises

A fold region between the sealing surface and the peripheral edge, an

A spacer interposed between the fold region and the peripheral edge,

The bending region has a smooth contour and interconnects the spacer and the part of the extension with the sealing surface, and

The fold portion at least partially contains at least one of the spacer and the fold region.

55. The tray of claim 54 wherein the spacer includes a flat portion and is provided with the bent portion at an end of the spacer with the peripheral edge, and wherein the bent region interconnects the flat portion of the spacer and the portion of the extension with the sealing surface at a substantially right angle.

56. A shaped article, comprising:

a) A thermoformable sheet having a peripheral edge and being sufficiently rigid to define a configuration of the article, the article comprising a body having an extension extending peripherally away from the body, the extension comprising the peripheral edge of the thermoformable sheet and a bent portion between the peripheral edge and a junction between the body and the extension; the bent portion has a smooth outer periphery and is sufficiently bent such that the peripheral edge of the thermoformable sheet is displaced from the outer periphery of the article, whereby the article has a smooth outer periphery; and

b) At least one flexible inner liner sheet conformable to and peelably attached to the thermoformable sheet.

57. The shaped article of claim 56, wherein at least one inner liner sheet is peelably attached to each of the inner portion, the extension, and the bent portion of the thermoformable sheet.

58. The shaped article of claim 56, wherein each of the peripheral edge, the bent portion, and the extended portion completely surrounds the inner portion, and wherein each of the inner portion, the extended portion, and the bent portion of the thermoformable sheet has a liner sheet peelably attached thereto.

59. The shaped article of claim 58, wherein the same inner liner sheet is peelably attached to each of the inner portion, the extension, and the bent portion of the thermoformable sheet.

60. The shaped article of claim 56 wherein the liner sheet delaminates from the thermoformable sheet at least a portion of the peripheral edge.

61. The shaped article of claim 56, wherein a graspable tab is introduced between the liner sheet and the thermoformable sheet at least one location along the peripheral edge.

62. The shaped article of claim 56, further comprising a lid attached to the liner sheet completely around the interior portion.

63. The shaped article of claim 56, wherein the thermoformable sheet comprises a storage portion that is recessed away from the interior portion and entirely within the interior portion, and wherein at least the peelably attached liner sheet furthest from the surface of the thermoformable sheet is perforated with perforations through the liner sheet at the storage portion, does not conform to the thermoformable sheet at the storage portion, and is not peelably attached to the thermoformable sheet at the storage portion, whereby liquid in the lumen of the interior portion can pass through the liner sheet at the storage portion.

64. The shaped article of claim 63, comprising

i) A non-perforated inner liner sheet peelably attached to the thermoformable sheet at each of the storage portion, the interior portion, the extension, and the fold portion of the thermoformable sheet, an

ii) a perforated inner liner sheet attached to the non-perforated inner liner sheet.

65. A shaped article, comprising:

a) A thermoformable sheet having a shape including a recessed inner portion and a peripheral edge, the thermoformable sheet including a spacer with a peripheral edge, the spacer being connected to a main body by an extension extending peripherally away from the main body and a fold region interconnecting the spacer and the extension, the fold region having a smooth profile and interconnecting the spacer and the extension at a substantially right angle

b) At least one inner liner sheet conformed to and laminated over the thermoformable sheet.

66. The shaped article of claim 65, wherein the at least one inner liner sheet is peelably attached to each of the inner portion, the extension, and the bent portion of the thermoformable sheet.

67. An article of manufacture, comprising:

A thermoformable sheet having a peripheral edge and defining

A forming body having an extension extending peripherally away from the body, the extension including the peripheral edge, an

A fold portion between the peripheral edge and a connection between the main body and the extension portion, the fold portion having a smooth outer perimeter and being sufficiently folded such that the peripheral edge of the thermoformable sheet is displaced from the outer perimeter of the article, thereby producing an article having a smooth outer perimeter; and

A flexible liner peelably attached to the thermoformable sheet.

68. The article of claim 67 comprising a plurality of flexible inner liners peelably attached to the thermoformable sheet.

69. The article of claim 67 wherein the peelable layer is a non-thermoplastic material.

70. The article of claim 67 wherein the peelable layer is selected from the group consisting of metal foil and paperboard.

Technical Field

The present invention relates generally to the field of forming shaped thermoplastic articles.

Background

It is well known to form shaped articles from thermoplastic materials. A variety of different methods, such as thermoforming, casting, molding and spinning (spinning), can be used to impart shape to a molten thermoplastic or a preformed thermoplastic sheet that has been softened or melted.

Trimming waste material from one or more edges of a shaped article is a common trimming technique, but if sharp edges are left, it may cause flesh to damage or tear or cut material that comes into contact with the edges. One common use of shaped thermoplastics is to form containers that can be sealed with plastic films, such as trays, bowls, or boxes (bins) that are intended to contain food and are intended to be sealed with clear plastic films. Another common use is to contain items and insulate them from moisture or other materials that may come into contact with the container. Sealing of such containers typically involves extending or stretching the film across the compartment formed in the container and sealing the film around the periphery of the compartment, which is typically located near the trimmed edge of the article comprising the compartment. If the edge is sharp, the film may be cut or damaged, thereby interfering with the sealing process.

Three well-known sealing techniques are commonly used to seal food and foodstuffs to form containers for commercial transportation, storage, display and sale. These are referred to herein as OW, VSP and MAP techniques. All of these techniques involve combining the container and the plastic film. Due to the fragility of such films, and in many cases the need to minimize or eliminate the puncturing and tearing of the film portions defining (with the container) the sealed compartments, it is critical to minimize the chance of the container tearing, puncturing or abrading the film of the same or nearby containers. In addition to being used to seal such containers, plastic films are also used to transport containers, such as "mother bags" (i.e., generally thin plastic bags) used to hold products in a plurality of container packages during transport and grocery bags used by consumers to transport goods purchased from retailers. This may be achieved by reducing or eliminating sharp or rough container edges at least at locations on the container where such edges may moderately contact the film during packaging, storage, shipping, or display.

The Over Wrap (OW) technique involves, after placing food or other items on one or more sides of an article, enclosing or wrapping a shaped article (e.g., a thermoformed tray, sheet, bowl, or multi-compartment container) with a plastic film (typically transparent), and then sealing the film to itself (e.g., by heating the overlapping portions of the film). In such OW techniques, sharp or rough edges of the shaped article can cut, abrade, or puncture the film, potentially allowing material to pass through the film and defeat one or more of the purposes of the film. To date, the OW technique has been used primarily with foam trays or boxes that do not have sharp edges. Many municipal recycling programs do not include or take foam into account, and thus these materials are becoming less and less popular with consumers. It would be desirable if thermoformable plastic containers suitable for use with a variety of wrapping techniques, including the OW technique, could be manufactured, since thermoformable materials tend to be widely accepted in recycling programs.

Vacuum Seal Packaging (VSP) techniques involve adhering a plastic film (again, typically transparent) to the face of a shaped article bearing food (e.g., or as an alternative example, a moisture-sensitive object) against the face of the shaped article. When using VSP technology, the article to be packaged is placed on the surface or within the cavity of the shaped article, covered with the film such that the article is between the shaped article and the film, air (or any other gas that may be present) is drawn from the space between the film and the shaped article (optionally in conjunction with applying a positive pressure to the exterior of one or both of the film and the shaped article) such that the film is in close opposition to the surface of the shaped article and/or article, and the film is sealed (e.g., by an interposed adhesive, by heat bonding, or by electrostatic charge bonding) to the surface of the shaped article across the desired area (typically completely surrounding the article), and any excess film can be trimmed away from the desired area. The seal may be resistant to gas flow so as to maintain a gas-evacuated state inside the sealed container. The resulting VSP-sealed package typically has a topology that mimics the shape of the surface of the shaped article having the article thereon.

MAP is an abbreviation for modified atmosphere packaging and refers to a sealing technique in which a flexible (usually transparent) film is sealed (e.g., using heat or an adhesive) around the periphery of a substantially rigid shaped article. When the formed article is otherwise closed (i.e., no other openings than the one sealed by the film), the gas present within the container may be controlled when sealing the film to the article. Thus, if the article and film are sealed in the presence of a selected atmosphere (e.g., such as a gas selected to exclude oxygen or promote ripening of the fruit), the selected atmosphere may be maintained within the sealed MAP package during subsequent storage, transport and display of the package.

As is known in the art, shaped articles used in OW, VSP and MAP sealing processes tend to have a variety of industrially acceptable geometries and properties that are different in all three types, making shaped articles that can be used in one type of sealing process generally unsuitable for use in one or both of the other sealing processes.

For example, containers for OW sealing tend to have rectangular and tray or sheet shapes with smooth, blunt edges and rounded corners. The absence of sharp, rough or sharp edges or corners can reduce the likelihood of the film used for the overwrapped container being torn or punctured when wrapped. OW-containers typically have a flat portion (e.g., on the "bottom" of the container, relative to its intended display configuration) where the overwrapped film can be pushed against itself to seal the film to itself (e.g., applying an amount of heat to the overlapping film portions sufficient to create such a seal, thereby enclosing the container and any items on or in the container).

Containers for VSP sealing tend to have faces or surfaces (sometimes within recesses) that are adapted to carry the items to be sealed between the film and the container and are adapted to receive the sealing film due to the absence of sharp points, protrusions or edges. The absence of these features reduces the likelihood of the film being punctured or torn when pulled to a surface. Unlike an OW-receptacle, a VSP-receptacle can have sharp edges, corners or protrusions at least at portions outside the film-receiving surface, since these portions need not contact the film during sealing. However, such sharp portions may still damage the sealing film, particularly when VSP-sealed packages are stored, shipped, or displayed in close proximity to one another, as the sharp portions of one container may damage the film of another container (or the film or tissue in the vicinity of the container).

Containers for MAP-sealing tend to have a flat surface (e.g., a wide, flat rim), the opening to be sealed is enclosed by applying a piece of film over the opening to be sealed, the film is sealed to the surface (typically substantially irreversibly), and then the film is trimmed around the outer edge of the seal. Such containers must be configured so that the film can be applied to a surface before and during sealing without significant risk of tearing or puncturing, and configured to facilitate trimming of the film from the sealed container. However, because the membrane typically only contacts a limited portion of the MAP-container during sealing, the MAP-container may, and typically does, include sharp, pointed or abrasive features at locations not involved in the sealing process.

It would be beneficial if the sharp edges of the shaped thermoplastic article could be displaced in such a way that the risk of damaging and marring the sealing film could be reduced. It would be further beneficial if such a single shaped article could be used with a variety of known sealing techniques, such as two or more of the OW, VSP and MAP techniques. It would also be advantageous to reduce the sharpness and tendency to damage and disfigure the thermoformed article, even in the absence of a seal. The subject matter disclosed herein addresses this shortcoming of existing shaped thermoplastic articles.

Others have recognized the necessity of reducing the occurrence of sharp edges at the edges of the tray to be overwrapped. For example, Nelson et al (U.S. patent application publication No. 2015/0001127) discloses a packaging tray formed by thermoforming a sheet of film to produce a precursor tray having a generally U-shaped flange around its periphery, the open end of the U facing the sealing surface, and the peripheral edge of the tray projecting at the periphery. The Nelson tray is made by cutting the precursor tray from a sheet of thermoformable material to produce an end in which the peripheral edge extending peripherally is located at the end of the outer arm of the U (relative to the tray body). Nelson then compresses the outer arms inwardly toward the tray body so that there is a smoother curled portion of the U-shaped flange at the periphery of the tray with the potentially sharp peripheral edge extending toward the sealing surface. In this manner, Nelson et al create a tray that is said to be suitable for use in an outer wrapping film for urging the outer arm of the U-shaped flange toward or against the inner arm. However, because the tray retains a sharp peripheral edge where it is possible to cut the film (e.g., in fig. 13A of Nelson, the peripheral edge of the Nelson tray can be seen in contact with the outer wrapping film and the film of the outer wrapping adjacent tray), the Nelson tray is still not suitable for all OW applications and is generally not suitable for use with VSP and MAP techniques. A tray without a sharp peripheral edge or sharp curl of the accessible film (the tray of Nelson also has this property-see item 124 in fig. 12A of Nelson) would preferably be used with each of these sealing techniques. Trays for VSP and/or MAP packaging are preferably free of sharp peripheral edges (see, e.g., peripheral edge 120 in fig. 12A of Nelson) and any relatively sharp curl (see item 124 in fig. 12A of Nelson) in the material forming the tray because such edges and curls can snag, puncture, or tear the film during or after the sealing process.

The subject matter disclosed herein includes shaped thermoformed articles suitable for sealing with a variety of techniques.

Thermoformed drinking cups having a smooth, curled edge are also known. Such cups are made by thermoforming a cup with a flange around the outer edge of the cup opening, the flange comprising a potentially sharp peripheral edge at the end of the flange remote from the interior of the cup. The flanged cups are stacked in a nested manner, their flange portions are heated, and then the flanged cups are passed through a spiral seaming thread to form a seam. This technique is only used to roll the edge around a circular hole and is therefore of no practical value in the manufacture of shaped articles having a rolled edge surrounding a non-circular opening. The rolled edge drinking cup is also not designed to be wrapped or sealed with a plastic film.

Disclosure of Invention

The present invention relates to a method of displacing a sharp edge from the periphery of an article made of thermoplastic material, wherein the sharp edge might otherwise damage surface contact with the periphery of the article. The invention also relates to articles treated according to these methods and to an apparatus for carrying out such treatment.

The present invention relates to a method of forming a smooth edge, i.e. a smooth periphery, on an article made of thermoplastic material. The method includes the step of forming a deflectable flange at an edge of the article body. The deflectable flange includes a peripheral edge of thermoplastic material at a peripheral end of the deflectable flange, optionally on a peripheral flange extending peripherally from the deflectable flange. In one embodiment, the peripheral flange is connected to the spacer by an elbow and extends peripherally beyond the spacer by a peripheral flange distance. The peripheral flange distance may be selected to produce a desired degree of deflection when the peripheral flange is subjected to a surface impact. In one embodiment, the peripheral flange distance is selected to be zero (i.e., the peripheral edge is present where it would otherwise be a bend). The spacer is connected to the body by a fold region that defines an angle (which may be acute or obtuse, and is preferably substantially right angle) between the spacer and the body. The deflectable flange is urged within an interior of the cavity defined by the upper body, e.g., a distance between the bend and the interior is less than the peripheral flange distance, such that the deflectable flange deflects at the bend region when a portion of the interior of the cavity impacts the peripheral flange. Sufficient heat is applied to the bent portion of the deflectable flange (here the bend region) to soften the thermoplastic material at the bend region. The upper body and the article are separated whereby the bend region remains deflected upon cooling, thereby creating a smooth edge (i.e., periphery) on the article.

The method may be used to form a smooth edge around the entire periphery of the article. To this end, a deflectable flange is formed around all edges of the article, and the interior of the cavity is configured to simultaneously impinge on the deflectable flange around all edges of the article as the deflectable flange is urged within the interior. In the resulting article, the peripheral edge is effectively "hidden" (e.g., it is deflected behind or away from the deflected peripheral flange) so that material (e.g., plastic film or animal tissue) that is in contact with the periphery of the article will be less likely to be in contact with the peripheral edge of the thermoplastic material from which the article is made.

The invention also relates to a method of forming a sealed compartment. The method comprises the following steps: thermoforming a thermoplastic sheet to form an article having a recessed compartment surrounded by a substantially planar sealing surface; cutting the article from the periphery of the sheet to the sealing surface; forming a smooth edge around the entire periphery of the article as described herein; the top sheet is then sealed to the sealing surface to form a sealed compartment. In one embodiment of the method, the periphery of the top sheet is trimmed around the sealing surface after sealing the top sheet to the sealing surface. In another embodiment, the top sheet is heat sealed to the sealing surface.

The invention further relates to a method of forming a sealed compartment. The method comprises the following steps: thermoforming a thermoplastic sheet to form an article having a recessed compartment surrounded by a substantially planar sealing surface; cutting the article from the periphery of the sheet to the sealing surface; forming a smooth edge around the entire periphery of the article as described herein; a flexible plastic film is then wrapped and sealed around the article to form a sealed compartment.

In some embodiments of the methods described herein, after the deflectable flange is pushed within the cavity interior and before the upper body and article are separated, the impact head can be pushed into the interior and in close opposition to the interior, behind the deflectable flange to the extent that one face of the impact head impacts and further deflects the deflectable flange, e.g., at the bend region. For example, the face may be substantially planar. The face may also be substantially perpendicular to the portion of the inner portion that strikes the peripheral flange. The face may define an obtuse angle with the portion of the inner portion that strikes the peripheral flange. The face may have a concave profile relative to the interior. If the impact head is heated, pushing the impact head against the deflectable flange causes the portion of the deflectable flange in contact with the impact head to bend and further deflect the peripheral edge of the thermoplastic sheet away from the periphery of the shaped article.

In a non-heating based embodiment, the present invention relates to a method of forming a smooth edge on an article made of a plastic material (e.g., a thin plastic material supported by a deformable metal layer). The method includes forming a deflectable flange at an edge of the body, the deflectable flange including a peripheral edge of thermoplastic material at a peripheral end of the peripheral flange. In one embodiment, the peripheral flange is connected to the spacer by an elbow and extends peripherally beyond the spacer by a peripheral flange distance (which is effectively zero if there is no peripheral flange). The spacer is connected to the main body or an extension from the main body by a bending region. The fold region defines an angle (which may be acute or obtuse, and is preferably substantially right or slightly obtuse) between the spacer and the body. The deflectable flange may be urged within an interior of a cavity defined by the upper body, the spacer being spaced from the interior a distance less than the peripheral flange distance or impacting a shaped impact head surface that deflects the deflectable flange inwardly. Thereby, the deflectable flange is deflected upon impact, for example at the bend region. Sufficient pressure is applied to irreversibly bend the plastic material. The upper body and the article are separated whereby the deflection flange remains deflected when pressure is removed, resulting in a smooth edge on the article.

Drawings

FIG. 1 is comprised of FIGS. 1A, 1B and 1C and illustrates the basic operations of the structures and methods described herein. The parallel straight lines "//" indicate locations where structures, dimensions and proportions may optionally be present have been omitted for clarity.

Fig. 1A shows a cross-sectional view of a thermoplastic article 100 having a deflectable flange 160 formed at an edge thereof. Deflectable flange 160 in this embodiment includes extension 50, inflection region 150, spacer 140, and peripheral flange 120. The extension 50 connects the shaped body 10 of the article 100 to the bend region 150 of the deflectable flange 160. The spacer 140 may be (and preferably is) interposed between the inflection region 150 and the peripheral flange 120. The peripheral flange 120 is connected to the spacer 140 by a bend 130, which in the embodiment shown is a right angle bend. The bend region 150 connects the extension 50 with the spacer 140 at a substantially right angle (the angle marked a). The peripheral flange 120 terminates at the peripheral edge 110 (indicated by the thick solid line in this figure) of the thermoplastic material forming the article 100.

FIG. 1B shows the thermoplastic article 100 inserted into the interior of the upper body 200, which is shown in phantom (in bold lines). In this embodiment, the impact of the peripheral edge 110 of the peripheral flange 120 on the inner surface 202 of the upper body 200 causes the deflectable flange 160 to deflect due to the bending of the deflectable flange 160 at one or more points B within the bending region 150.

FIG. 1C shows the result of inserting impact head 300 (only a cutaway portion shown in bold lines) into the interior of upper body 200 behind thermoplastic article 100 (i.e., when impact head 300 is inserted into the configuration shown in FIG. 1B). Impact head 300 is in close opposition to inner surface 202 of upper body 200 and peripheral edge 110 of peripheral flange 120 impacts upper surface 302 of impact head 300, thereby deflecting deflectable flange 160 even more and creating a circular periphery of article 100 at point B within bend region 150.

Fig. 2 consists of fig. 2A, 2B, 2C and 2D and shows the mating upper body 200 and impact head 300 for deflecting one or more deflectable flanges 160 formed on the outer periphery of a shaped thermoplastic article having the configuration of a rectangular tray with rounded corners. Fig. 2A shows upper body 200 disposed above impact head 300, and fig. 2B shows upper body 200 engaged with impact head 300. FIG. 2C is a cross-sectional view of the joined upper body 200 and impact head 300 shown in FIG. 2B, and shows a portion of the impact head 300 fitting within and in close opposition to the inner surface of the recess in the upper body 200. Fig. 2D is a detail of the cross-section shown in fig. 2C and shows the close opposition between the impact head 300 and the interior of the upper body 200. In fig. 2D, the inclined configuration of the upper surface 302 of the impact head 300 is evident.

Fig. 3, consisting of fig. 3A, 3B and 3C, are images of the smoothed outer perimeter and corners of a transparent shaped thermoplastic article having the configuration of a rectangular tray with rounded corners. The article is smoothed using an upper body 200 and an impact head 300 similar to that shown in fig. 2. In fig. 3A, the finger is visible inside the tray and the smoothed corner is visible to the left of the finger. The stacking lug can also be seen at the portion where the finger is located, which is the portion of the corner of the tray that extends peripherally to a greater extent than the portion of the corner below the finger. The smooth straight side walls of the tray extend from the smooth corners (downward in the figure). The folds of the peripheral flange can be seen below the smoothed corner, and the deflection of the peripheral flange below the smoothed straight edge can be seen behind the left corner of the figure. Fig. 3B is another view of a smoothed corner of a similarly manufactured tray, also seen from below the tray edge. The protruding extension directly below the rim at the corner is a stacking lug. Fig. 3C is a view of a smoothed corner with a finger pointing at a smoothed area formed by bending, softening, bending and cooling the bent area of the deflectable flange. As shown in fig. 3A and 3B, the smooth area may, for example, be pushed against the plastic film without easily tearing the plastic film, since the relatively sharp edges of the thermoplastic material forming the tray are bent under the corners.

Fig. 4 shows a cross-section taken through an article of storage containers 100 formed using the methods described herein (parallel lines "//" indicate locations where structures, dimensions, and proportions that may optionally be present are omitted for clarity). In this figure, the article 100 has a deflectable flange 160 formed on each side of the container visible in the figure. The unitary upper body 200 extends across the entire container, including around the side where the deflectable flange 160 is located. An integral impact head 300 (only two portions shown) has been inserted inside a cavity in upper body 200 behind article 100. The peripheral edge 110 of the thermoplastic sheet forming the article 100 abuts the upper surface 302 of the impact head 300 at each deflectable flange 160 such that the deflectable flanges 160 are deflected inward toward the body of the article 100 by bending at one or more portions B of the bending region 150 of each deflectable flange 160. Applying heat at B in an amount sufficient to soften the thermoplastic sheet causes the deflectable flange 160 to generally retain the configuration shown in the figure, wherein the peripheral edge 110 of the thermoplastic sheet is positioned anti-circumferentially (i.e., within the outer perimeter of the article 100, occurring at the location indicated by B in the figure) to create a smooth outer perimeter for the formed container as the softened portion cools.

Fig. 5 consists of fig. 5A, 5B, and 5C, each showing a cross-section taken through a storage container article 100 formed using the methods described herein (parallel lines "//" indicate locations where structures, dimensions, and proportions that may optionally be present are omitted for clarity). In this figure, the article 100 has a deflectable flange 160 formed on each side of the container visible in the figure. Deflectable flanges 160 have been deflected inwardly by the impact of upper surface 302 of integral impact head 300 (only two portions shown) against the deflectable flanges 160 at each deflectable flange 160. Peripheral edge 110 of the thermoplastic sheet forming article 100 impacts upper face 302 of impact head 300 at each deflectable flange 160 such that deflectable flange 160 is deflected inwardly toward the body of article 100 by bending at one or more portions B of bending region 150 of each deflectable flange 160. Applying heat at B in an amount sufficient to soften the thermoplastic sheet causes the deflectable flange 160 to generally retain the configuration shown in the figure, wherein the peripheral edge 110 of the thermoplastic sheet is positioned anti-circumferentially (i.e., within the outer perimeter of the article 100, occurring at the location indicated by B in the figure) to create a smooth outer perimeter for the formed container as the softened portion cools. In this embodiment, the two portions of the impact head 300 are shown as having different profiles (one flat and one curved) to account for differences in deflection that may be caused by the different profiles. Fig. 5A, 5B and 5C differ in the distance between the joint and the peripheral edge, which is greater in fig. 5A than in fig. 5B and zero in fig. 5C.

Fig. 6A, 6B, 6C, 6D and 6E illustrate deflectable flanges formed in a tray-shaped article thermoformed from a sheet of thermoplastic material. In each of fig. 6A and 6B, a finger touches a sharp edge (i.e., the peripheral edge 110 at the periphery of the peripheral flange 120) of a position where the tray has been cut out of the sheet. In these figures, the deflectable flange has not yet been softened, deflected and cooled, so the sharp edge is still positioned around the periphery of the tray. In contrast, the sharp edges have been deflected inwardly and away from the outer periphery of the tray shown in fig. 3 and the tray shown in the lower portion of fig. 6C. The tray shown in the upper portion of fig. 6C is the same as the tray shown in the lower portion, except that the tray in the upper portion is not "flipped over" with its deflectable flanges as the tray in the lower portion. Figure 6D is a view of the underside of a rounded rectangular tray having "flip" edges around its entire periphery. It can be seen that there are no sharp edges at or near the periphery of the tray. Fig. 6E is an oblique view of three initially identical trays, each having "flipped" edges as described herein, in which the edges have been "flipped" to varying degrees. The tray labeled "1" has a peripheral edge that is only slightly "flipped" (i.e., the portion of the deflectable flange that includes the peripheral edge 110 has been deflected inward no more than about 45 degrees from the plane of the remainder of the spacer 140, the majority of which is still substantially flat in the tray). The tray labeled "2" has a peripheral edge that is more fully "flipped over" -so that the peripheral edge 110 is barely visible (it has been rolled over behind the still visible portion of the spacer 140). On the tray labeled "3", the deflectable flange has been turned even further and the peripheral edge 110 cannot be seen. The deflectable flange of tray "3" is flipped to a greater extent than the deflectable flange of tray "2", which can be detected by virtue of the still visible portion of spacer 140 being shorter on tray "3" than on tray "2" (and the visible portion of spacer 140 of each of tray "2" and tray "3" being shorter than the visible portion of spacer 140 of tray "1"). Thus, the three trays shown in fig. 6E can be considered to illustrate the discrete degree of "flipping" of the deflectable flanges.

Fig. 7 consists of fig. 7A, 7B, and 7C, and shows an article 100 formed of a thermoplastic sheet material resting on a horizontal surface (solid horizontal line) (straight parallel lines "//" indicate locations where structures, dimensions, and proportions that may optionally be present are omitted for clarity) with its peripheral edge embodiment smoothed as described herein. In this embodiment, the upper body 200 (two portions shown in this cross-section) is lowered in the direction indicated by the opening arrow to the upper article 100, causing each of the two deflectable flanges 160 of the article to deflect inwardly. In fig. 7A, when the upper body 200 is lowered onto the article towards a horizontal surface, the flared portion of the upper body 200 just contacts the peripheral flange 120 of the article 100; the deflectable flange begins to deflect at the region labeled "B". In fig. 7B, the upper body 200 has been lowered onto a horizontal surface and the peripheral edge 110 and peripheral flange 120 of the article 100 have been partially deflected inwardly towards the body 10 of the article 100. In fig. 7C, the impact head 300 is inserted into a cavity in the upper body 200 behind the article 100 in the direction indicated by the hollow arrow and further deflects the peripheral flange 120 (and the deflectable flange 160 with it) by bending the thermoplastic sheet forming the article at the region labeled "B".

Fig. 8 is comprised of fig. 8A, 8Ai, 8B, 8Bi, 8C, 8Ci, 8D, 8Di, 8Dii, 8E, 8F, 8G, 8H, 8J, and 8K, and illustrates the deflection and eversion of deflectable flange 160 (including its sharpened peripheral edge 110) using impact head 300 as described herein. Each of fig. 8A-8C, 8E-8G, and 8H-8K is a cross-sectional view including only one edge of the article; it may be necessary to perform the same edge deflection and inversion of multiple edges (e.g., all edges) of the article by using multiple impact heads of the impact head that contact all edges to be processed. Fig. 8Ai, 8Bi, and 8Ci are copies of fig. 8A, 8B, and 8C, respectively, each identifying an offset angle OA.

Fig. 8A, 8B, and 8C illustrate in sequence the effect of shaped article 100 in each figure being pushed further in the direction indicated by the hollow arrow against impact head 300, as can be seen by comparing the portion of the article presented in the left-hand portion of each figure. In the embodiment shown in fig. 8A-8C, deflectable flange 160 has no bends and no peripheral flanges. The initial (prior to impact by the impact head) configuration of the shaped article is as shown in fig. 9A.

In fig. 8A, the article has been pushed against the impact head such that the deflectable flange 160 of the article contacts the upper surface 302 of the impact head at its peripheral edge. When the deflectable flange contacts the sloped portion of the upper surface 302, the deflectable flange 160 deflects from its pre-contact position by virtue of the resistance to motion encountered by the deflectable flange. In this figure, the peripheral edge 110 of the deflectable flange rests on the upper surface at a location where the sloped portion of the upper surface transitions to a curved profile and a portion of the spacer abuts the impact head that is heated and transfers heat thereto.

FIG. 8B illustrates the effect of the article 100 depicted in FIG. 8A being pushed further against impact head 300. As impact head 300 shown in fig. 8B is heated, the impact head softens the material from which deflectable flange 160 is fabricated at the portion of the deflectable flange that abuts or contacts upper surface 302 of the heated impact head. Due to the shape of the upper surface 302, the deflectable flange 160 reaches a position where it can no longer be advanced by merely sliding along the upper surface. Because article 100 (including deflectable flange 160) is pushed in the direction indicated by the hollow arrow, and because the material from which the deflectable flange is constructed has been softened by impact head 300, the deflectable flange may deform (at location B) to follow the contour of upper surface 302 of the impact head as the deflectable flange is advanced against the impact head.

Fig. 8C illustrates the effect of the article 100 shown in fig. 8B being pushed on against the heated impact head 300. As the article (including deflectable flange 160) is pushed in the direction indicated by the hollow arrow, the deflectable flange continues to bend at the location softened by contact with the heated impact head (i.e., at location B). As the movement of the deflectable flange against the impact head continues, the peripheral edge 110 of the deflectable flange eventually reaches the edge of the upper surface 302 of the impact head. The portion of the deflectable flange including the peripheral edge continues to soften for a further period of time (which period of time depends in a predictable manner on operating conditions). The peripheral end portion may thereby deflect (e.g., upward, as implied in the embodiment shown in fig. 8C) if it contacts a portion of the article 100 while softening. The deflection of the portion of the peripheral flange that is in contact with the upper surface may also be affected by the contour of the upper surface 302, for example, such that a "curled" or "spiral" configuration is produced as shown in fig. 8C.

Fig. 8D illustrates the use of one or more objects to assist in the deflection and flipping of the deflectable flange as described herein. An object 401 (referred to elsewhere herein as a plug) is disposed within the interior compartment of the shaped article 100 and abuts the interior face of the shaped article 100 during impact of the deflectable flange 160 on the impact head 300 to reduce or prevent inward deflection of the interior face during operation. In this embodiment, the object 403 exerts a downward pressure (open arrows) on the extended portion 50 of the deflectable flange 160 to cause the deflectable flange 160 to impinge on the upper surface 302 of the impact head 300. In this embodiment, object 402 is rigidly connected with object 401 and object 403. The filled arrows depict the force exerted on the article 100 when downward pressure is applied. Fig. 8Di depicts a shaped article in the form of a rounded rectangular tray T having an interior and a plug P of a shape and size capable of fitting within the interior to serve as the object 401 in fig. 8D and to reduce or prevent inward deflection of the side walls of the tray T during inversion of the deflectable flanges of the tray T, fig. 8Dii showing the plug inserted into the interior of the tray.

Fig. 8E, 8F, and 8G (similar to fig. 8A, 8B, and 8C) illustrate in sequence the effect of pushing shaped article 100 closer to impact head 300 in the direction indicated by the hollow arrow in each figure. In the embodiment shown in fig. 8E-8G, deflectable flange 160 comprises a peripheral flange 120 at a peripheral end of spacer 140. In this figure, it can be seen that peripheral flange 120 deflects during bending of deflectable flange 160 to the extent that the peripheral flange becomes indistinguishable from spacer 140.

Fig. 8H, 8J, and 8K (similar to fig. 8A, 8B, and 8C; fig. 8I is intentionally omitted) illustrate in sequence the effect of urging shaped article 100 closer to impact head 300 in the direction indicated by the hollow arrow in each figure. In the embodiment shown in fig. 8H-8K, deflectable flange 160 includes a peripheral flange 120 at a peripheral end of spacer 140. In these figures, it can be seen that the peripheral flange 120 deflects during bending of the deflectable flange 160 to the extent that the peripheral flange becomes completely bent over the spacer 140, thereby forming a "hook" configuration. B in fig. 8J indicates that the bend occurs in the portion of deflectable flange 160 that spans the indicated portion of upper surface 302 of impact head 300.

Fig. 9 consists of fig. 9A, 9B, 9C, 9D, 9E, and 9F and illustrates the beneficial features of one embodiment of the shaped article disclosed herein.

Fig. 9A is a cross-sectional view of one edge of article 100, illustrating the configuration of deflectable flange 160 of the article prior to undergoing the flipping operation described herein, including the following properties: the potentially sharp or rough peripheral edge 110 may contact the film used to seal the article or another nearby film or object. Figure 9B is a cross-sectional view of one edge of article 100 having peripheral edge 110 turned over by the technique shown in figures 8A-8C. With respect to the article engaged with the impact head shown in fig. 8C, the deflectable flange 160 of the article has "bounced" in a circumferential direction after disengagement from the impact head. Because the plastic material from which the article is constructed is flexible, the upturned edge shown in fig. 9B exhibits "give" when pushed in a direction perpendicular to the plane of the figure (such as in the direction shown by the open arrow).

Fig. 9C is a cross-sectional view of the edges of three of the articles 100 shown in fig. 9B, wherein the articles are stacked in a nested configuration. Because each article has the same shape (e.g., a tray as shown in the lower portion of fig. 6C), each article can be nested with other articles and pushed together until its flipped edge contacts the tray above and/or below the article. Fig. 9C shows three such stacked nested trays, with open arrows indicating where a standard de-nesting apparatus can be employed to separate the nested trays. For example, fingers or threads may engage the inter-tray areas at these locations, which may be manipulated with the fingers or threads (following a common de-nesting procedure) to separate the trays from each other for individual use.

Fig. 9D is an image of a prior art thermoformed plastic tray with stacking tabs (finger-directed, edge-down corner extensions in the image). The stacking lugs are used to maintain a controlled separation distance between stacked trays, as shown in the left-hand portion of fig. 9E (fig. 9E is an image of two of these prior art trays stacked on top of each other, with the inter-tray distance being limited by the stacking lugs). The right-hand portion of fig. 9E shows two stacked nested trays with a flipped edge (as schematically shown in fig. 9C with three trays). The inter-tray partition can be seen between the edges of two stacked trays. Fig. 9E shows that two trays with a flipped edge as described herein can be stacked in a separable manner in a smaller volume than prior art trays with stacking tabs can be stacked into. Fig. 9F shows three nested and stacked trays on their left side, with the trays having turned edges and with stacking extensions 180 formed in the corners of the trays to increase the spacing between the straight edges of the stacked trays. It can be seen that the three stacked trays with stacking extensions 180 have a spacing (left brace of the figure) that is greater than the spacing (right brace of the figure) of the three otherwise-identical stacked trays without stacking extensions.

Fig. 10 is composed of fig. 10A, 10B, and 10C. Fig. 10A is an image of an impact head 300 having a shaped article 100 in the form of a rounded rectangular tray with edges carried by the impact head. At the lower right portion of the image, an upper surface 302 can be seen in which a second article can be disposed, but which is not currently carrying an article. In the article 100 carried by the impact head 300 in the upper part of the figure, it can be seen that the extensions 50 connect the deflectable flange spacer 140 and the peripheral flange 120 portions to the body 10 of the article 100. Spacer 140 and peripheral flange 120 are carried by the upper surface of impact head 300 in the upper portion of the figure, and therefore cannot be directly seen (similar to upper surface 302 in the lower right portion of the figure). "10B" represents a portion of impact head 300 shown in fig. 10B (with shaped article 100 removed). In FIG. 10B, a portion of upper surface 302 of impact head 300 can be seen. Dashed lines 10C-10C in fig. 10B represent approximate locations of the cross-section shown in fig. 10C and include letters a-E as landmarks so that the surface configuration of impact head 300 may be better understood by comparing fig. 10B with fig. 10C. FIG. 10C is a schematic cross-section of the impact head 300 shown in FIG. 10B and includes landmark letters A-E.

Fig. 11 consists of fig. 11A, 11B and 11C and illustrates features of one embodiment of a shaped article having a peelable liner sheet attached to a face of the article.

FIG. 11A is a cross-sectional view of an edge of an article comprising a relatively thick thermoformable base sheet 101 and a relatively thin flexible liner sheet 500 attached to a face thereof; and illustrates the configuration of the deflectable flange 160 of the article prior to undergoing the flipping operation described herein, including the potentially sharp or rough peripheral edge 110 of the deflectable flange at an accessible location. Fig. 11B is a cross-sectional view of the same edge of the article after its peripheral edge has been turned over as described herein. The peripheral edge 111 of the base sheet 101 has been folded sufficiently so that it points "backwards" into the main body of the article, and in this view the peripheral edge 511 of the liner sheet 500 has been detached from (or peeled away from) the peripheral edge 111 of the base sheet. In fig. 11C, lidding sheet 600 contacts liner sheet 500 at the extended portion 50 of the deflectable flange, while the peripheral edge 610 of the lid is positioned outside the periphery of the article. The lid 600 and the liner sheet 500 may be attached to each other at the locations indicated by the hollow arrows by inserting an adhesive between them, or by pressing them against each other (e.g., while applying heat sufficient to bond or melt them together). If so adhered to the liner sheet 500, the lid 600 may be removed from the base sheet 101 of the article simultaneously with the liner sheet 500 by grasping the liner sheet at or near the liner sheet peripheral edge 511 and peeling the liner sheet 500 (with the lid 600 still attached) away from the base sheet 101.

Detailed Description

The subject matter disclosed herein relates to the formation of shaped thermoplastic articles, and more particularly to articles formed such that one or more edges of the article have a configuration in which the peripheral edge of the thermoplastic sheet forming the article is turned away from the face of the article, and preferably away from the periphery of the article, such that frangible material (e.g., flesh or a thin flexible plastic sheet) applied on the face or periphery does not contact the edge of the sheet. Because such sheet edges can be sharp, especially when the edges are cut or broken, directing the edges away from the face and/or periphery of the article can prevent damage to fragile materials in contact with the face or periphery. The subject matter disclosed herein is particularly useful for forming containers that are to be sealed with a frangible plastic film applied to the face of the container or wrapped therein. In preferred embodiments disclosed herein, the peripheral edge of the thermoplastic sheet forming the article is turned away from the periphery of the article to such an extent that the resulting article is suitable for any or all of the OW, VSP and MAP sealing techniques. The shaped articles described herein are considered to be the first packages that can be sealed using virtually all three of these techniques. Optimally, thermoformable and moldable plastics tend to be widely accepted in recycling programs, and articles made from the plastics are more easily recycled than, for example, foam articles.

Briefly, the basic method described herein for forming a shaped thermoplastic article having smooth edges involves forming a deflectable flange at the periphery of the article. The deflectable flange includes a potentially sharp or rough peripheral edge of the thermoplastic material forming the article. The deflectable flange is softened (i.e., raised to a temperature at or above the glass transition temperature of the material forming the flange, and preferably less than the melting point of the material) at one or more portions thereof such that when the deflectable flange is deflected toward the body of the article (preferably with the peripheral edge "hidden" between the deflected portion and the extension, body, or both of the deflectable flange), the peripheral edge is directed away from the periphery of the article. Cooling (i.e., tempering) the softened and deflected deflectable flange below its glass transition temperature may "lock" the peripheral edge in this position, reducing the likelihood that material (e.g., flesh or film) contacting the outer periphery of the article will be damaged by the sharpness or roughness of the peripheral edge.

The presence of the deflectable flange formed at the periphery enables the peripheral edge (and particularly the curved edges and corners of the peripheral edge) to be "flipped" to create a smooth periphery. In previous pallets that included an outer flange (e.g., a pallet having a periphery as shown in fig. 1A, no bend region 150, spacers 140, bends 130, and outer peripheral flange 120, and having a peripheral edge 110 at the periphery of extension 50), the outer flange may have bent or rolled along a straight edge, but bending or rolling the curved edges and corners of such outer flange may not have caused the material in the flange to buckle or buckle, which creates an undesirable non-smooth edge. The presence of the smooth, bent regions 150 of the deflectable flange and the spacers 140 described herein enables the peripheral edge 110 to deflect away from the periphery of the article without causing such buckling or wrinkling, thereby creating a smooth periphery. As can be seen in fig. 1, 4, 5, 7, and 8, the buckling, flexing, and curling experienced by the deflectable flanges may be induced in any one or more of the extensions 50, the buckling regions 150, the spacers 140, the bends 130, the peripheral flanges 120, and even at the peripheral edges 110. Regardless of which one or more of these elements is bent or deflected to achieve this effect, the resulting arrangement of the potentially sharp peripheral edge 110 away from the periphery of the article, and preferably not reasonably close at its periphery from outside the article, results in an article having a smooth periphery that is suitable for contact with fragile membranes, tissues or other surfaces.

In one embodiment, the deflectable flange comprises a peripheral flange that protrudes from the article in a peripheral direction and is attached to the spacer portion by a bend (e.g., a 90 degree turn, or by some other offset angle, such as a turn of one of 60 degrees to 120 degrees) in the thermoplastic material forming the article. The main body of the article is attached to the spacer by a fold region that defines an angle (angle a in fig. 1A; preferably a substantially right angle) between the spacer and a portion of the main body adjacent to the fold region (i.e., the portion is typically an extension for connecting the main body to the fold region). The deflectable flange is inserted inside a cavity in the body (e.g., upper body 200 or impact head 300) such that the peripheral flange is impacted by the walls of the cavity, thereby deflecting the deflectable flange in the direction of the body of the article. In doing so, heat is applied to the bend region in an amount sufficient to soften or melt the thermoplastic material at the bend region such that the deflectable flange remains deflected toward the main body as the bend region cools. Alternatively, the impact head may be inserted into the cavity behind the deflectable flange, and the face of the impact head in contact with the deflected peripheral flange may cause further deflection of the deflectable flange, further displacing the peripheral edge of the article away from the peripheral edge upon cooling. In this way, the smooth, "rolled-over" edge of the thermoplastic material forms the outermost periphery of the article, while the peripheral edge of the thermoplastic material remains within the outermost periphery of the article, in which case the sharpness of the edge is less likely to damage the frangible material in contact with the outermost periphery of the article.

In another embodiment, the deflectable flange is in contact with an impact head that deflects the deflectable flange in a direction that deflects the sharp edge of the thermoplastic sheet away from the periphery of the article. Before, during, or after such deflection, one or more portions of the deflectable flange (e.g., the bend region, the spacer, the bend, the peripheral flange, any portion in contact with the impact head, or a combination of these) are heated sufficiently to soften the thermoplastic material, and then the deflectable flange is cooled to "lock" the deflection. Depending on the degree of deflection, the peripheral edge of the thermoplastic material may simply be turned away from the periphery of the article when softened, turned in a direction generally opposite the periphery, or even "rolled up" with a tight enough radius by deflecting the deflectable flange such that a J-shape, U-shape, or even spiral configuration is achieved (i.e., any shape that produces a substantially smooth peripheral edge) is achieved, wherein the resulting peripheral edge is virtually incapable of damaging flesh or films present at the periphery of the article.

The various elements and aspects of the shaped article and the method of making them will now be described in more detail.

Shaped article

The methods described herein are believed to be applicable to articles having a variety of different shapes and sizes, particularly articles that typically have sharp peripheral edges when manufactured by conventional methods. The motivation for making shaped thermoplastic articles with smooth edges arises in part from the need to make common storage trays (e.g., plastic trays for storing food such as fresh or frozen meat, fruit, or vegetables) with edges that are sufficiently blunt (non-sharp) that the tray can be wrapped in or contacted with plastic films (such as polyvinylidene chloride and polyethylene films) without the film being cut or punctured by the tray edges under normal use conditions. However, once the methods described herein are developed, it is recognized that smooth rounded edges are desirable in various other situations, such as to prevent physical injury to persons gripping trays and other shaped articles and to prevent the film sealing one tray from being damaged by the sharp edges of a second sealed tray (e.g., as in a shipping container containing multiple sealed trays).

For example, a common method of making shaped articles such as meat trays is by thermoforming a thermoplastic sheet. In the thermoforming process, a portion of the long thermoplastic sheet is raised to a temperature at which the thermoplastic softens and can be molded. The softened thermoplastic is applied to the surface of one or more molds (typically with the aid of negative air pressure to ensure that the softened thermoplastic film is in close opposition to the mold surface). When the film cools (e.g., upon contact with a mold surface), the thermoplastic hardens and becomes less deformable, causing the thermoplastic film to acquire and retain the shape imparted thereon by the molding process. In a thermoforming process multiple castings are typically made from the same article in a single sheet of film, and each article is released from the film by cutting (e.g., die cutting) the film around its periphery. This process tends to produce sharp edges at the cut portions of the film, including sharp edges around all or part of the periphery of the article (i.e., where the article is cut from the film).

By way of further example, the thermoplastic material may be melted in an extruder and injected into a mold cavity that defines the shape of the molded article. After cooling, the mold may be opened to release the molded article. In the molding process, thermoplastic material often appears at parts of the finished product where it is not desired to be present, such as "flash" that occurs when molten thermoplastic flows between mold plates or at ports through which molten thermoplastic is fed into a closed mold. These undesirable features may themselves be sharp, and may leave sharp edges when cut from the molded article.

The size and shape of the articles described herein is not critical. Typically, the shaped article will be one in which it is desired to grasp the article or to provide contact between the peripheral edge of the article and the one or more frangible materials. Regardless of the method of producing the article, the edge smoothing methods described herein may remove one or more sharp edges from a thermoplastic article that typically has such sharp edges.

Smoothing method

The outer periphery of the thermoplastic article, in particular the outer periphery formed by a bent or shaped sheet of thermoplastic material, may be smoothed by a method comprising the steps of: forming a deflectable flange near the outer periphery of the edge to be smoothed; deflecting the bent portion of the flange to displace the edge from the periphery of the article; softening the bent portion at least when the flange is in the deflected position; and re-hardening the bent portion when the flange is in the deflected position. This method is illustrated in fig. 1. The portion of the deflectable flange 160 that can be softened and bent can be the bend region 150, or preferably a portion of the deflectable flange that is distal from the bend region 150 but proximal to the peripheral edge 110. For example, the softening spacer 140 enables the peripheral portions thereof, including the bend 130, the peripheral flange 120 (if both elements are present), and the peripheral edge 110 to bend inward (i.e., toward the body 10 of the article 100) sufficiently to displace the peripheral edge 110 away from the periphery of the article.

Preferably, at least a portion of the spacer 140 is softened and sufficiently bent to "flip over" the peripheral edge 110 such that the peripheral edge 110 is positioned such that the overwrapped article or film covered across the article does not contact the peripheral edge 110 even when pulled taut. More preferably, the deflectable flange 160 is turned sufficiently to visually obscure the peripheral edge 110 by the spacer 140 or the bend region 150 such that the peripheral edge 110 is not visible when the article 100 is viewed horizontally from the outer periphery of the article (i.e., from the outer peripheral side thereof). It is also preferred that the deflectable flange 160 be turned sufficiently that the peripheral edge 110 "points" toward the body 10 or toward the underside of a portion of the deflectable flange 160, meaning that a plane of the deflectable flange at the portion including its peripheral edge 110 intersects the body 10 including the underside 161 (see, e.g., fig. 1B) of the deflectable flange 160. When the plane of the deflectable flange at its edge including the peripheral edge 110 is not directed toward the body 10 (see, e.g., offset angle OA in fig. 8 Bi) or the underside 161 of the deflectable flange 160 (see, e.g., offset angle OA in fig. 8 Ci), then the peripheral edge should at least be displaced sufficiently away from the periphery of the article 100 (see, e.g., offset angle OA in fig. 8 Ai) or flipped over sufficiently to cause the peripheral edge 110 to be obscured by one or more portions of the deflectable flange 160.

Fig. 1A shows a thermoplastic article 100 having a body 10 (having an irregular shape in this figure) and a deflectable flange connected to the body 10. The deflectable flange includes a peripheral flange 120 that includes the peripheral edge 110 of the thermoplastic sheet forming the article 100. The deflectable flange also includes a bend region 150 disposed between the body 10 and the peripheral flange 120 of the article 100. The fold region 150 is spaced from the main body 10 by an extension 50, which extension 50 is, in this embodiment, simply a flat portion of the thermoplastic sheet. In this embodiment, the peripheral flange 120 is similarly spaced from the fold region by a flat portion of the thermoplastic sheet referred to as a spacer 140. The peripheral flange 120 is connected to the remainder of the deflectable flange by a bend 130, which in this embodiment is a portion of the thermoplastic sheet formed at a right angle.

Fig. 1A is a cross-section of such an article 100, wherein the solid black line represents the cross-section of the thermoplastic sheet forming the article. The peripheral edge 110 forms the periphery of the article 100 because no other portion of the article 100 extends further to the right (in this figure), the spacer 140 and other portions of the peripheral flange 120 being closer to the body 10 than the peripheral edge 110 of the sheet. Thus, if an object is pushed against the right side of the article 100 (in fig. 1A), the object will tend to contact the peripheral edge 110, and the sharpness of the peripheral edge 110 may affect the object, such as by cutting, damaging, or damaging the object.

In fig. 1B, the thermoplastic article 100 is inserted into the interior cavity of the upper body 200. The inner surface 202 of the upper body impacts the peripheral flange 120, deflecting the peripheral flange inwardly (i.e., anti-outwardly circumferentially) toward the body 10 of the article 100. In this embodiment, both the peripheral edge 110 of the thermoplastic sheet forming the article 100 and the outermost peripheral portion of the fold region 150 are positioned approximately equidistant around the outer periphery of the body 10. Preferably, the deflectable flange 160 deflects inward far enough that the peripheral edge 110 of the thermoplastic sheet is received within the interior cavity of the upper body 200. In this embodiment, spacer 140 is substantially rigid and substantially all bending occurs within bending region 150. If heat is applied to the bend region 150 (generally at the location identified as "B" in fig. 1B) sufficient to soften the thermoplastic sheet and the sheet is subsequently cooled (preferably below its glass transition temperature), the deflection flange 160 will maintain the configuration shown in fig. 1B (i.e., deflect relative to its initial configuration shown in fig. 1A as a result of the peripheral edge 110 striking the inner surface 202 of the upper body 200) even after the upper body 200 is separated from the article 100. In this deflected configuration, the peripheral edge 110 does not extend peripherally beyond the circular fold region 150, and the resulting article will be more suitable for sealing with a thin plastic film applied over the extension 50 and fold region 150 than the original pre-deformed article shown in fig. 1A (i.e., because the potentially sharp peripheral edge 110 protrudes beyond the periphery of the fold region 150, where the peripheral edge 110 may easily snag, abrade, or cut the film).

Fig. 1C shows an optional but preferred step in which an impact head (ram)300 is inserted into a cavity in upper body 200 behind article 100 (i.e., sandwiching at least deflectable flange 160 between upper body 200 and impact head 300). This step (relative to the embodiment shown in fig. 1B) further deflects the deflectable flange 160 toward the body 10 of the article 100, thereby displacing the (potentially sharp) peripheral edge 110 of the thermoplastic sheet further from the periphery of the article (i.e., further from the inner surface 202 of the upper body 200). The bend region 150 of the deflectable flange 160 is heated sufficiently to at least soften it when it is in the configuration shown in fig. 1C and then cooled below its glass transition temperature, which can "freeze" the deflectable flange 160 in the configuration shown. In this configuration, the sharp peripheral edge 110 of the sheet of material forming the article is "tucked" under other portions of the deflectable flange 160 (e.g., the fold region 150 and the extension 50, if present) and is therefore less accessible to objects in contact with the outer periphery of the article (and less prone to tearing, cutting, or damaging material in contact with the outer periphery of the article). For example, if a thin plastic film is applied to the extension 50 and the fold region 150, the film is even less likely to be snagged, abraded, or cut by the potentially sharp peripheral edge 110 in this embodiment than in the embodiment shown in fig. 1B. From this progression (i.e., greater deflection in fig. 1C than in fig. 1B and 1A), it can be seen that the more the outer periphery of the portion of the peripheral edge 110 away from the article to which the sealing film is applied is deflected, the less likely the edge becomes to damage the film.

Impact head 300 and upper body 200 each serve the purpose of deflecting the deflectable flange by impact (impacting up) or impact (impacting against). Thus, the two items are essentially interchangeable and may each be used alone or in combination with two or more impact heads and upper bodies. In the present invention, the term "impact head" is used to refer to a body that impacts a deflectable flange by being applied to or on it in the direction from the portion of the deflectable flange that is furthest from the body of the shaped article. Similarly, the term "upper body" is used to refer to impacting the deflectable flange by being applied to or over the deflectable flange in approximately opposite directions (see, e.g., fig. 1C and 4).

In the embodiment shown in fig. 1C, the portion of impact head 300 that impinges on peripheral flange 120 of deflectable flange 160 has a wedge-shaped cross-section when an article is received within the cavity in upper body 200. Such an impact head may be useful for guiding the peripheral flange 120 and the peripheral edge 110 anti-peripherally, since the further the impact head is pushed inside the interior in the direction from the peripheral edge 110 towards the bending region 150, the further the peripheral flange 120 and the peripheral edge 110 will deflect in the anti-peripherally direction. However, these portions of the impact head 300 need not be wedge-shaped. Basically, the impact head 300 may use any shape that will deflect the peripheral flange 120 and the peripheral edge 110 anti-peripherally when inserted behind the article 100 in the upper body 200, such as blunt or rounded shapes (raised or recessed at its upper surface 302), or a combination of any of these (e.g., as shown in fig. 5) may be used.

Fig. 8 illustrates an alternative method of turning or otherwise shaping the edges of the article. As can be seen in fig. 8A, the deflectable flange 160 in this embodiment has no bend or peripheral flange, but only includes a spacer portion that terminates at the peripheral edge 110 of the thermoplastic sheet. The deflectable flange is urged against the upper surface 302 of the heated impact head (in the direction indicated by the hollow arrow in fig. 8, regardless of how such urging is achieved, such as by moving one or both of the article 100 or impact head 300). When the direction of travel of the deflectable flange is closely parallel to the configuration of the upper surface (i.e., as shown in fig. 8A), relatively less of the deflectable flange may contact the upper surface and relatively less heat may be transferred from the impact head to the deflectable flange. However, as shown in FIG. 8B, when relative motion of the article and the impact head causes the contact surface between the upper surface of the impact head and the deflectable flange to be larger or closer together, the contact/close interface area may be larger, thereby causing more heat to flow from the impact head to the deflectable flange. Sufficient heat flow will cause the thermoformable material to soften such that the deflectable flange assumes the configuration of the upper surface. As shown in fig. 8C, as the article and impact head undergo further relative movement, more of the deflectable flange will be softened and deflected. As with the embodiment shown in fig. 1B, it can be seen in this embodiment that heat suitable for bending the deflectable flange is applied (at locations B in fig. 8B and 8C); however, in order to "flip over" the portion of the deflectable flange including the peripheral edge, little or no bending occurs at inflection region 150 and no heat is applied (except to a lesser extent as may occur when the outermost peripheral portion of inflection region 150 is proximate heated impact head 300 as shown in FIG. 8C). For the purposes of the methods described herein, it is essentially immaterial which portions of the deflectable flange are softened and bent, provided that the desired results are achieved: the potentially sharp peripheral edge 110 deflects away from the periphery of the article and is preferably hidden (as shown in fig. 8C) where the peripheral edge is less likely to contact any easily damaged film or tissue that is in contact with the periphery of the shaped article. The deflectable flange may be brought into contact with or into close proximity to the impact head in a single smooth motion, advanced in a plurality of discrete increments, or a combination of these to enable portions of the deflectable flange to soften sequentially.

When the thermoformable material is moved out of contact with the impact head (either by disengaging both, or as shown in fig. 8C, when a portion of the deflectable flange moves beyond the upper surface of the impact head), the thermoformable material may cool and the deflection caused upon cooling will remain. As shown in fig. 9B and 9E, the disengagement of the article and the impact head produces an inverted edge of the article that has a smooth outer perimeter and is suitable for gripping and/or contact with the frangible plastic film. While the degree of deflection of no peripheral edge 110 may be unambiguously identified as a "minimum" amount of deflection sufficient to prevent contact between the edge and the fragile tissue or membrane in all possible edge configurations, it can be said that, in general, if the bent portion of the deflectable flange is sufficiently bent such that the peripheral edge is "pointed" (i.e., intersects a plane tangent to the thermoplastic sheet at the peripheral edge and extending through the peripheral edge) any portion of the deflectable flange (including, for example, an extension, bent portion, spacer, or bent portion), such a configuration should generally hide the peripheral edge sufficiently to prevent the edge from contacting the fragile tissue or membrane at or near the periphery of the article (see, for example, fig. 8C, 8G, and 9B). Alternatively, the deflectable flange may be deflected sufficiently that the peripheral edge 110 is in close opposition to the side wall of the recessed portion (see, e.g., fig. 8C, 8K, and 9B) or closer to the extension 50 than the bent portion that is further from the extension (as shown in fig. 8B, 8D, 8F, and 8J) to enable such concealment. Preferably, the peripheral edge 110 is "contained" within a compartment defined by the upturned portion of the deflectable flange and the side walls of the recess (including, for example, as shown in fig. 8K) or a portion of the deflectable flange that completely surrounds the periphery of the article so that it is substantially free of sharp edges that could damage delicate tissues and fragile plastic films adjacent to the article. In another embodiment, the flat bottom tray has a generally planar peripheral edge, the plane of the edge being substantially parallel to the bottom (e.g., in standard MAP trays and other trays); for such flat-bottomed trays, the rolled-up peripheral edge is preferably rolled up sufficiently that the peripheral edge is directed "rearwardly" towards the tray cavity (i.e. parallel to the two planes, but oriented in the direction of the tray cavity) or rolled up further (e.g. sufficiently that the peripheral edge is directed at the rim towards the underside of the extension or the underside of the bend).

In fig. 8A-8C, the deflectable flanges are depicted without the elbow 130 and the peripheral flange 120 shown in fig. 1A for simplicity of illustration. Although deflectable flanges may be produced without bends and peripheral flanges (e.g., by mechanically or laser cutting the deflectable flanges at spacers 140 shown in fig. 1), such production may be difficult and costly and, therefore, have limited utility in mass production operations. For this reason, shaped articles 100 processed as described herein, such as those intended for use as food packaging trays, will typically have both bends and peripheral flanges as shown in fig. 1A. As shown in fig. 8E-8K, a formed article with a bend and peripheral flange can still be processed using the methods and apparatus described herein.

Fig. 8E-8G illustrate the processing of the shaped article 100 with the deflectable flange 160 including the peripheral flange 120 and the bend 130 described herein, and the processing illustrated in these figures is substantially similar to the processing illustrated in fig. 8A-8C. In fig. 8E, the outer peripheral edge of deflectable flange 120 directly contacts upper surface 302 of impact head 300. As the impact head is heated, the heat is conducted directly to the peripheral edge in contact with the impact head and by radiating from closely opposed portions of the spacer. By controlling the heat flow from the impact head and the dwell time of the article 100 in the position shown in fig. 8E, the operator can cause softening of portions of the deflectable flange, particularly including portions at the peripheral edge of the deflectable flange and at portions of the spacer adjacent the peripheral edge. The softening of these portions helps the deflectable flange to bend at the softened portion, such as by pushing the article further against the impact head, such that when more of the outer peripheral portion of the deflectable flange is driven against this curved portion of the upper surface by less of the outer peripheral portion (which transmits the force applied to the article) as shown in fig. 8F, the curved portion of the upper surface will cause bending. As shown in fig. 8G, the article is pushed further against the impact head such that the portion of the bendable flange in contact with the upper surface of the impact head slides across the upper surface. As the material is driven beyond the point where it contacts the upper surface, it may remain softened for a short period of time (and tend to bend further), or it may cool and become only deflectable (rather than bendable or moldable). Whether cooled by moving over the heated portion of the impact head or by moving the article out of contact with the impact head (or even by applying a cold flow, such as by directing cold air at the shaped portion, by using a cooled plug element within the body of the article, or by other means), cooling of the deflectable flange below its glass transition temperature can "set" or "lock" the configuration of the material during this transition period. Thus, by shaping the deflectable flange to have the configuration shown in fig. 8G and cooling it below its glass transition temperature, the edges of the article may be smoothed (because its bend region 150 is smooth and because of its spacers 140, including its peripheral edge 110 has been turned to have a configuration that does not have rough or sharp edges at the outer periphery of the article).

As shown in fig. 8F, the peripheral flange 120 may be partially deflected during the formation of the deflectable flange; in this article, the peripheral edge is preferably "directed" toward the underside of the main body or deflectable flange. As shown in fig. 8G, the shaping of the deflectable flange sometimes causes the peripheral flange and the bend disposed between the peripheral flange and the remainder of the spacer to disappear. This may occur because the material in the peripheral flange "melts" into the spacer or simply because the offset angle of the bend becomes about 180 degrees. However, as can be seen in fig. 8J, for example, the peripheral flange 120 may deflect in a direction that may still be distinguished from the rest of the spacer, possibly forming a hook-like structure. Because such a configuration may position a potentially sharp or rough peripheral edge at or near the outer periphery of the article, it is preferable to deflect the deflectable flange sufficiently to accommodate any such hook-like structure within the upturned edge (relative to the article outer periphery) as shown in fig. 8K.

In the method illustrated in fig. 1 and 8, the impact of the upper body 200, the impact head 300, or both, on the deflectable flange 160 can cause the walls of the shaped article to deflect inward. For example, compression induced in the deflectable flange upon impact on the flange of the sidewall of the upper body (compare the locations of the spacers 140 in fig. 1A and 1B) will create an inward force on the extension 50 (i.e., away from the sidewall of the upper body and toward the shaped body 10 of the article 100) that will be transferred to the shaped body, possibly causing a portion of the body to bend or deflect. Similarly, the impact of the impact head against the peripheral flange portion 120 of the deflectable flange will also generate an inward force on the extension and thus the forming body. By way of further example, the inward force exerted on the deflectable flange in the embodiment shown in fig. 7 and 8 may also be transferred to the shaped body of the article. The transfer of force from the deflectable flange to the forming body may be undesirable for at least two reasons. First, deflection of the forming body can change the orientation of the deflectable flange and the portion bent as described herein, making it difficult to control the final shape of the article (and its edges). Second, the force transmitted from the deflectable flange to the body generally does not drive the deflectable flange against the impact head and/or upper body, meaning that the force does not cause the deflectable flange described herein to buckle and deflect, at least to the extent desired. Accordingly, it is desirable to limit the transmission of force from the deflectable flange, the deflection of the shaped body by such force, or both, in order to direct the force into the deflection of the deflectable flange.

Essentially, any apparatus or method for preventing or reducing the transfer of force from the deflectable flange to the body, reducing or preventing deflection of the shaped body, or both, may be employed. An example of such a device and how it may be used is shown in figure 8D. Fig. 8D illustrates the shaping of the deflectable flange 160 in the shaped article 100 by the application of a downward force (open arrows) (as shown in fig. 8B). In contrast to fig. 8B, the shaped article shown in fig. 8D is coupled with three objects 401, 402, and 403. Here shown in cross-section, each of the three objects is a solid body (e.g., a rounded metal bar) having a rounded square profile. The object 401 abuts a portion of the shaped article 100 to which an inward force (smaller horizontal solid arrows) is applied when a downward force causes the deflectable flange 160 to impact on the upper surface 302 of the impact head 300. The object 403 abuts the extension 50 of the deflectable flange and transmits a downward force to the deflectable flange. Object 402 is connected (rigidly, in this embodiment, but not necessarily) to object 401 and object 402. One or more of the three objects may be cooled to prevent heat (e.g., from the heated impact head 300) from softening the plastic at the body or extension of the article.

In fig. 8D, when a downward force (open arrow) is applied to the object 403, the force is transferred to the deflectable flange. The impact of the deflectable flange on the impact head 300 opposes the downward force. In the absence of the object 401, this force may be transmitted to the shaped body of the article 100 through the deflectable flange (i.e., through the extension 50). However, because the object 401 is present and remains sufficiently in place to prevent deflection of the portion of the article it abuts. The downward force exerted on the deflectable flange is not dissipated by the deflection of the shaped body (i.e., in the direction indicated by the small horizontal black arrow in fig. 8D, as the object 401 prevents such deflection). And this force is in turn applied along the deflectable flange in the direction indicated by the large black arrow in fig. 8D. This force drives the deflectable flange (particularly its peripheral edge, the peripheral flange (if present), and the portion of the spacer closest to the peripheral edge) against impact head 300 and causes deflection of the deflectable flange, the configuration of the portion of the deflectable flange against upper surface 302 of the impact head (particularly when the heat provided by the impact head is sufficient to soften these portions), and the displacement of the deflectable flange across the surface of the impact head. As shown, the contour of the upper surface of the impact head may thus be imparted to the outermost peripheral portions of the deflectable flange, thereby smoothly bending these portions (assuming the upper surface of the impact head has a smooth contour) and displacing (or even "curling" the peripheral edge of the deflectable flange back out of the body of the article, e.g., as shown in fig. 8C).

The shape, size, arrangement, attachment (if any) of the objects 401, 402, and 403 is not important. Also, not all three of these objects must be used together; one, two or all three may be used. In one embodiment, three objects are secured together to form a "lid" or "stopper" for a container as shown in FIG. 6, such that the portion of the lid/stopper corresponding to object 401 may substantially fill the interior of the container (i.e., press against all walls, including in particular the four long straight walls of the container; see, e.g., stopper P in FIGS. 8Di and 8 Dii). The portion of the cover/plug corresponding to object 403 forms a ring that may be applied around the interior of the container over the entire rim of the container, and the portion of the cover/plug corresponding to object 402 may be any material or structure that connects objects 401 and 403. For example, such a lid/plug may be formed from a single piece of material (e.g., a "plug" that fills the entire interior and overlaps the rim around the interior). One or more of the objects may be cooled to reduce heating of the shaped article (other than at the desired location of the portion of the deflectable flange) and thereby prevent undesired deformation of the shaped article during processing.

Generally, the object 401 is simply a mass for preventing the sides of the shaped article from flexing during deflection of the deflectable flange. Such objects may substantially fill all portions of the interior of the shaped article (e.g., the entire interior of the container shown in fig. 6D). Alternatively, one or more objects 401 may be used to support portions of the shaped article that deflect more easily than other portions (e.g., the long straight sides of the container shown in fig. 6D).

Object 403 may be any object capable of pushing the deflectable flange against the impact head. Multiple objects may be used to push the deflectable flange against one or more impact heads at different locations on the article, or a single object 403 may be used that contacts the article at or near all portions of the deflectable flange. In one embodiment, the object 403 is the upper body 200 described herein, for example in the form of a completely surrounding container rim as shown in fig. 6D. Object 403 may be a frame designed to fit snugly over the entire rim of the interior recessed compartment of the container surrounding the chamber, so as to simultaneously push a deflectable flange completely around the rim against the impact head in the manner described herein. In one embodiment, the object 403 may be intentionally cooled (e.g., by directing a cooling fluid, such as chilled water, chilled oil, or ambient air, to or through the object, particularly where the object is made of a good thermal conductor, such as metal) in order to reduce, inhibit, or prevent heating of the body of the shaped article during processing (e.g., as shown in fig. 8D). The object 403 may be rigidly or movably connected with the object 401 such that the deflection-resistant object 401 may apply a force to the deflectable flange of the shaped article through the object 403 while being applied to the interior of the shaped article.

The object 402 (when present) may be an object that connects the object 403 to the force source, an object that holds the object 401 in place within the recessed portion of the shaped article 100 during deflection of the deflectable flange 160, or a combination of these.

Another advantage of the upturned edge formed by this method, as shown in fig. 9C and 9E, is that the upturned edge can be used in place of a conventional stacking lug (i.e., a thermoformed portion of the article that is contoured to limit how tightly the article can nest within another identically shaped formed article of another shape). In order to perform its required anti-nesting function, such known stacking lugs must also be narrower at their upper ends than at their lower ends (see fig. 9D as an example) in order to prevent nesting of the stacking lugs of adjacent trays. This "narrower top" configuration is known to present difficulties in demolding the tray during thermoforming because the narrower "top" portions of the lugs must be stretched or deformed over the larger "bottom" portions of the lug molds in order to remove the thermoformed tray from the molds. The rollover edge shown in fig. 8 and 9 (i.e., manufactured as described herein) avoids this difficulty while still preventing unduly tight nesting of adjacent trays. Trays having a rollover edge as described herein can be separated using conventional de-nesting equipment, such as screw-and finger-based machines (screw-and finger-based machines) for separating adjacent nested/stacked trays, and as shown in fig. 9E, so that the trays can be stacked more densely than using trays with formed stacking lugs.

Fig. 9F illustrates an alternative embodiment of the rollover edge described herein that also affects the stacking characteristics of a shaped article having a rollover edge. On the right side of fig. 9F, three stacked trays with the rollover edges described herein are shown, the rollover edges being substantially the same (including in height) around the entire periphery of the tray. Three other stacked trays are shown on the left side of fig. 9F, with the trays also having a turned edge around their entire periphery as described herein. However, the rolled edge of the tray on the left side is not uniform around its entire periphery, as compared to the tray on the right side of the figure. As shown at one corner in the figures, the portion of the deflectable flange that flips over at the corner of the trays is smaller than the portion of the deflectable flange that flips over along other portions of its edge. Thus, the tray is provided with a circular stacking extension 180 at its corners. As with the stacked trays shown on the right side of fig. 9F, the trays on the left side of the figure nest within each other and sink until the lower surface of the rolled edge of the tray contacts and rests on the upper surface of the rolled edge of the second tray in which the tray is nested. However, because the stack extension 180 of the trays on the left side of the figure has a higher height than the remaining majority of the rollover edge of those trays, the trays on the left side will nest such that the lower surface of the stack extension 180 rests on the upper surface of the rollover edge of the tray below that tray, bringing the lower surface of the majority of the rollover edge of the upper tray out of contact with the tray below it, creating a gap between the nested trays (compare the gap represented by the large brackets on the left side of fig. 9F to the gap represented by the small brackets on the right side of fig. 9F). When the shaped article 100 is given a turned edge that includes a stack extension 180 as described herein, the degree and manner in which the deflectable flange is deflected should be selected to position the peripheral edge 110 at the stack extension 180 such that it is unlikely to contact a film or other material at the periphery of the article 100 as described herein.

Yet another advantage of the "rollover edge" depicted in fig. 8 and 9 is the mechanical strength imparted to the formed article by this edge configuration. Plastic films tend to be highly flexible, and articles formed from such films may have "weak" edges that are easily deformed when handled or manipulated (e.g., during sealing or wrapping with the film). For the same reason, hollow tubes or round materials tend to be stronger and stiffer than planar sheets of the same type and thickness of material, and the curved or rolled edges described herein give the shaped articles described herein greater edge strength and edge rigidity than corresponding articles lacking such edges. Such rim strength and rim stiffness enables the lid to be formed on the shaped article described herein or enables a separately manufactured lid to be joined with the shaped article. Thus, in addition to shaped articles that can be sealed with a film using OW, VSP or MAP techniques, the enhanced rim strength of the shaped articles described herein enables them to be sealed with snap-fit type lids or other conventional sealing techniques. The edge strength and edge stiffness imparted to the shaped article also prevents tension-induced deflection in the film used to overwrap or seal the article (e.g., so-called "buckle-like" because recessed articles can exhibit closure phenomena on their depressions when wrapped or sealed), or for withstanding the stresses imposed by gripping-container equipment, such as de-nesting equipment used to separate individual containers from a stack of nested containers (or the stresses necessary to operate the equipment).

As noted above, the edge strength and edge stiffness observed in shaped articles (e.g., trays for wrapping or sealing with a film) manufactured as described herein is derived from the geometry and materials present in the edges of the article. These geometries and materials, in turn, are derived from the geometries and materials selected for the deflectable flanges described herein. Although many of the following features are believed to be readily apparent to those skilled in the art, these features are discussed in the context of their selection to affect edge strength and edge stiffness. One such feature is the thickness of the thermoplastic used to form the edge. Thicker polymer sheets tend to be more difficult to bend or deform than thinner polymer sheets, all other things being equal; thus, by using a thicker thermoplastic-by thermoforming a thicker initial sheet or by thickening the thermoplastic during edge rollover (e.g., by in-plane compressing the sheet in its softened state or simply by maintaining the sheet in its softened state for a longer period of time), the edge strength and edge stiffness of the articles described herein can be increased. The radius of curvature of the bend region of the shaped article may also affect edge strength and edge stiffness, with smaller radii generally yielding greater edge strength and edge stiffness. The degree to which the peripheral edge 110 and adjacent portions (e.g., spacer 120) of the deflectable flange rotate or roll over also affects the edge strength and edge stiffness. For example, rolling the edge into a substantially full circle (i.e., rolling it about 360 degrees so that the peripheral edge 110 contacts the inward side 161 of the spacer 120) will produce much greater strength and stiffness than an edge that is rolled about 180 degrees (e.g., as shown in fig. 9B). The rim strength and rim stiffness may also be increased by increasing the width of the area of the extension 50 surrounding the recessed portion or by forming the side walls of the recessed portion to resist deflection (see, for example, "ribs" (ribs) formed in the side walls of the container as shown in fig. 6C and 6D).

In one embodiment, a standard size tray suitable for MAP sealing was manufactured as described herein (i.e., by having it with a flip edge) and compared to a similar tray made of the same material but lacking a flip edge. The edge strength/stiffness of the two trays was measured by evaluating the compressive force required to achieve an 1/4 inch deflection when each tray was compressed at the midpoint of the opposing long edges in the tray. It was found that the tray with the rollover edge described herein required (the force required to rollover the edge tray was about 5.5 pounds, and the non-rollover edge tray required about 2.3 pounds of force), which shows an embodiment with a substantial increase in edge strength. While it is impractical to describe every possible combination of configuration, dimensions, and material selection that will result in the desired edge strength or stiffness, one skilled in the art can use the information provided herein to design an edge of an article having a variety of different strengths and stiffnesses that are superior to the strength and stiffness of the article lacking a deflecting edge described herein. The edge strength and edge stiffness of the articles described herein are important to resist compressive forces generated when the package is sealed, when the interior of the recessed portion is pressurized or evacuated during packaging, and combinations thereof. Thus, this edge enhancement represents a significant advance in packaging functionality.

It is important in these methods that the potentially sharp peripheral edge 110 of the thermoplastic sheet forming the article 100 should be deflected away from the periphery of the article and "frozen" in place by heating-softening and cooling a portion of the sheet that is bent when the sheet is so deflected (typically including substantially only those portions of the deflectable flange). The heated, bent and cooled portions preferably include at least the bending region 150 of the deflectable flange 160, as this region is designed to bend smoothly and create a smooth outer perimeter for the container. Softening, bending, and hardening of other portions of the deflectable flange (e.g., the extension 50, the spacer 140, the bend 130, and/or the peripheral flange 120) may also (or alternatively) be performed and may contribute to the smoothness of the outer periphery of the article.

Alternatively, any of these portions of the pliable flange 160 may simply be bent without heating, so long as sufficient bending force is applied such that the thermoplastic material irreversibly bends at the location of the bend (rather than merely reversibly deflecting upon removal of pressure). However, bending methods based on non-heating and softening will tend to leave relatively sharp (or at least less smooth) edges where the bend is applied, and therefore such methods are not favored unless care is taken (e.g., by bending the material around a circular "die" member) to ensure that such a bend is smooth. The deflectable flange 160 disclosed herein provides a convenient structure for practicing the method.

Deflectable flange 160

The deflectable flange includes a bend region 150, a peripheral edge 110, and a spacer 140 disposed therebetween. The fold region forms an angle of less than 180 degrees between the body 10 and the spacer 140 and acts as a flexible "hinge" that can displace the spacer region relative to the body. The angle formed by the fold region (i.e., the angle labeled a in fig. 1A) is preferably about 90 degrees (i.e., is substantially a right angle, meaning no less than 75 degrees, no greater than 105 degrees, more preferably no less than 85 degrees, no greater than 100 degrees, still more preferably no less than 87 degrees, no greater than 93 degrees, and most preferably about 92 degrees). When the angle is less than 90 degrees, it may be difficult to remove the thermoformed article from the thermoforming mold (i.e., because the portion of the mold closest to the extension between the spacer and the main body may be wider than the width between the main body and the spacer closer to the peripheral edge, meaning that the thermoformed article will "grab" the mold and must be pulled or expanded to remove it from the mold). Therefore, it is preferable that the angle formed by the bending region is 90 degrees or more (e.g., 91 degrees, 92 degrees, 93 degrees, 94 degrees, or 95 degrees) to facilitate separation of the thermoformed article and the mold, but the angle may be smaller if, for example, the main body of the article is far from the outer periphery. Less preferably, angles of 110, 115, 120, 125, 130 or 135 degrees may be used, but such an article may require the upper body 200 to be applied first to reduce the angle to approximately 90 degrees before the deflectable flange impacts on the impact head. As this angle increases, the amount of thermoplastic present at the outer corners of the thermoformed precursor article (e.g., the four corners of the tray shown in fig. 6A and 6B) increases and may frustrate bending (i.e., "flipping"). The thermoplastic material may be accommodated at the section where the material is produced, for example by "backing out" (or entering a space built into the upper surface of the impact head) of the spacer above the impact head.

When the spacer is sufficiently displaced, the fold region forms the outer perimeter of the article (i.e., when the spacer is folded "under" the connecting portion of the body, regardless of orientation with respect to gravity). Thus, in one embodiment the fold region will generally form the desired smooth outer perimeter of the article. However, in this embodiment the spacer forms part of the outer periphery of the article (typically the "inner side" of the outer periphery relative to the article 100, with the inner side 161 of the deflectable flange 160 being received within the folded portion of the rollover edge). For this reason, those portions of the spacer (possibly including the bend 130 and the peripheral flange 120) that may reasonably closely approach the membrane or other material pressing on the exterior of the article (e.g., against the underside of its periphery) should preferably also be smooth.

In the formation of the shaped articles having smooth peripheries described herein, deflection of the spacer (and/or other portions) of the deflectable flange causes a bend in the bend region, in the spacer, or both. The angular shape of the bending region controls both the location of the bend and the smoothness of the resulting edge. As shown in fig. 1 and 8, it is beneficial if the angular portions of the bending regions are not formed as sharp (i.e., bilinear) angles, but as flat portions (e.g., the extensions 50 and the spacers 140) arranged at an angle to each other and curved portions (e.g., defined by a radius of curvature, such as a radius of 1, 2, or 3 or more millimeters) connecting the flat portions. The flexing of the curved angled portion will tend to produce a smoother, less film-breaking edge that flexes the sharp angled portion. As shown in fig. 1, 4, 5, 7, and 8, the boundary between inflection region 150 and spacer 140 may be substantially indistinguishable in practice, and in the illustrated embodiment, an inflection of spacer 140 at least in its immediate vicinity of inflection region 150 is contemplated. As shown particularly in fig. 8, the curved state of portions of the spacer 140, including the outermost peripheral portion, may desirably impart a smooth outer periphery to the article prepared as described herein.

In one embodiment (as shown in fig. 1), the deflectable flange 160 includes at least three portions including the inflection region 150, the peripheral flange 120, and the bend 130 positioned therebetween. The fold region 150 is optionally connected to the remainder of the article 100 by an extension 50. The peripheral flange 120 is connected to the inflection region 150 by an elbow 130, optionally with a spacer 140 interposed between the inflection region 150 and the elbow 130. A prototype deflectable flange 160 (attached to the body 10 of the article 100) with each of these portions is shown in fig. 1A.

In this embodiment, the inflection region 150 is disposed anti-peripherally (closer to the main body 10) than at least the outermost peripheral portion of the peripheral flange 120. The function of the bending region 150 is to deflect when the peripheral flange 120 deflects inward (i.e., counter-peripherally, such as by pressing the periphery of the article against a solid object). The deflection of the fold region provides a smooth surface because the peripheral edge 110 of the thermoplastic sheet is not located within the fold region; but rather on the peripheral flange 120. The angle formed by the bend region (e.g., about 90 degrees above the bend region 150 shown in fig. 1A) is not critical and may be selected to facilitate manufacturing. For example, the angle may be obtuse, right, or even acute. When the angle is acute, it can be difficult to remove the thermoformed (pre-flipped) article from its thermoforming mould (since the peripheral portion of the spacer must be deflected to remove the article from the mould), and for this reason the acute angle is undesirable (even if such an article can still be made). The radius of curvature of the bend region 150 is also not critical, but it is preferably substantially greater than the radius of curvature of the bend 130.

As shown in fig. 1A, the fold region 150 preferably has a smoothly curved configuration with a relatively large radius of curvature (e.g., 0.5 mm to several mm or more) such that inward deflection of the deflectable flange 160 creates a smooth outer periphery for the article. However, it is critical that the inflection region 150 not be sharp or pointed; for example, a non-sharp crease is sufficient. The same frangible material contacting a smooth periphery is less likely to be damaged than when the frangible material (such as a plastic film or animal skin) contacts the peripheral edge 110 of the thermoplastic sheet.

The fold region 150 may be connected to the remainder of the article 100 by an extension 50. The extension 50 may be discontinuously discernable from the inflection region 150 (e.g., a flat region distinct from the curved inflection region 150) or substantially indistinguishable (e.g., a slightly curved region indistinguishable from the curvature of the inflection region 150). The size of the extension area is not critical; the dimensions may range from no being present (i.e., the fold region 150 begins at the edge of the body 10 of the article 100) to fractions of a millimeter to several millimeters or more. One function of the extension 50 is to separate the fold region 150 (which in some embodiments applies sheet softening heat) from other portions of the article 100 where potential heat-induced deformation is not desired. Another function of the extension 50 may be to provide the article 100 with a functional surface, such as a surface adjacent to the fold region 150 where a plastic film (that may be pressed against the fold region 150 with little risk of damaging the film) may adhere to the article 100 or bond with the article 100 (e.g., to cover a cavity formed in the article bounded by the deflectable flange 160 of which the extension 50 is a part). The extension 50 may also serve a structural function, such as providing support or rigidity to a section of the article (e.g., by forming a relatively rigid "rim" around the cavity in the container to inhibit flexing of the container when the closure is applied). Yet another function of the extension 50 may be to provide space that the deflectable flange 160 may occupy when the deflectable flange is deflected anti-peripherally. Because extension 50 and peripheral flange 120 are on opposite sides of fold region 150, sufficient flexing of fold region 150 (e.g., upon insertion of article 100 into upper body 200 and insertion of impact head 300 behind the article), spacer 140, or both, may cause peripheral flange 120 (and spacer 140) to approach or even contact extension 50, or to curl or deflect under extension 50 between the periphery of the article and the sidewall of the body of the article (see, e.g., fig. 6E).

In an important embodiment, such as shown in fig. 3A, 3B, and 6E, the bent state of the inflection regions 150, the spacers 140, or both, then cool and harden produces an article in which a gap occurs between the sidewall of the article body and the closest path (i.e., the closest extent) of the inflection portion of the deflectable flange. The size and location of the gap may be selected by selecting the shape of the body, the placement of the impact head 300, the shape of the upper surface 302 of the impact head 300, or a combination thereof. For example, the gap may be selected to extend completely around the periphery of the article such that the article has a turned edge completely around its periphery, with the gap adapted to accommodate a predetermined shape (e.g., a MAP sealing apparatus designed to engage a standard sized tray, such as an industry standard #3 tray, for example). The size and location of this gap is not critical and may be selected, for example, to have a width and location that reflects the width and location of a flat portion of the extension 50 (e.g., a flat sealing surface carried on the extension) or a small portion of the extension. Or a fraction thereof. For example, when the extension 50 carries a flat sealing surface on its upper (opposite recess) face, a turned edge may be formed to leave a gap on the lower face of the extension 50 that is parallel and has a width that is one half or three quarters of the width of the sealing surface on the opposite face. Alternatively, the article and its edge turning or deflecting method may be selected to create a gap of substantially constant width (e.g., 1/8, 1/4, or 1/2 inch gaps) that completely surrounds the side walls of the recessed portion on the underside of the extension 50.

The shaped articles described herein can be made to conform to the shape, size, dimensions, color, and any other characteristics of a tray that is commonly or specifically used with a particular device. Many "industry standard" trays are known, such as, for example, MAP trays such as commonly referred to simply as "No. 2", "No. 3", "No. 4", and "No. 11", and these MAP trays have uniform sizes and shapes that remain substantially consistent throughout the industry. The suitability of the shaped articles described herein to match the size, shape, size, color, and other characteristics of industry standard equipment is generally within the knowledge of one skilled in the art.

In fig. 1A, the peripheral flange 120 comprises the (potentially sharp) peripheral edge 110 of the thermoplastic sheet forming the article. The peripheral flange extends peripherally beyond the fold region 150 so that it will strike the inner surface 202 of the upper body 200 when the article is inserted into the cavity of the upper body 200, as shown in fig. 1B. The peripheral flange extends from the bend 130 to the peripheral edge 110 and in a direction from the bend region 150 or spacer 140 (if present) at an offset angle defined by the bend 130. The function of the peripheral flange 120 is to engage (i.e., strike or be struck by) the inner surface 202 of the upper body 200 when the article is inserted into the cavity of the upper body 200, thereby deflecting the deflectable flange 160 inwardly (counter-peripherally). In addition to displacing the peripheral edge 110 of the sheet anti-peripherally and causing flexing or bending of deflectable flange 160 in its bending region 150, this deflection also positions peripheral flange 120 to be further deflected anti-peripherally when impact head 300 is inserted into the cavity behind article 100. When impact head 300 is so inserted, it impacts peripheral flange 120 and, as the impact head is further advanced into the cavity, causes additional flexing or bending of deflectable flange 160 in its bending region 150, as well as additional anti-peripheral deflection of peripheral edge 110.

The length of peripheral flange 120 (bend to peripheral edge) is not critical, but should be selected to facilitate engagement of peripheral flange 120 with impact head 300 and displacement of peripheral flange 120 by impact head 300 as it is advanced within the interior of upper body 200. Typically, the length of the peripheral flange 120 is at least partially affected by the ability to cut the article from the material from which it is formed. The bend 130 can be used, in part, to position the thermoplastic sheet at a location where it can be conveniently cut to release the shaped article from the precursor sheet. Because the peripheral edge 110 formed by such cutting is a source of sharpness or roughness at the outer periphery of the article prior to "flipping" the deflectable flange 160, it is advantageous to cut the sheet as close as possible to the bend 130 (i.e., to make the peripheral flange 120 as small as possible) in order to reduce the volume of thermoplastic material that must be displaced in order to displace the sharp or rough peripheral edge 110 from the outer periphery of the article. As shown, for example, in fig. 8H, the larger peripheral flange also reduces contact (and increases spacing) between the upper surfaces of the impact head impacting the deflectable flange and thus reduces heat transfer from the impact head to the peripheral portion of the deflectable flange. Because the method described herein depends on: heating those portions above their glass transition temperature, deflecting them to a desired configuration, and then cooling those portions below their glass transition temperature, the larger peripheral flange increases the heat input and/or time required for such processing, and is also undesirable for this reason.

A bend 130 is interposed between the bending region 150 and the peripheral flange 120, the function of which is to connect and transfer forces between the bending region and the peripheral flange. That is, the compressive force applied to the peripheral flange 120 by the upper body 200 or impact head 300 impacting the peripheral flange is translated through the bend 130 (and spacer 140, if present) into a torsional force applied to the bending region 150. The conversion of the compressive force to the torsional force ensures that the inflection region 150, the spacer 140, or both flex when the force is applied to the peripheral flange 120. Thus, the force exerted by the upper body 200 and/or the impact head 300 on the peripheral flange 120 deflects the peripheral edge 110 anti-peripherally (i.e., displaces the potentially sharp edge away from the article periphery) and causes the bending of the bend region 150, the spacer 140, or both (i.e., creates a smooth periphery at the article periphery formed by the flexed thermoplastic sheet), thereby creating an article with a smooth periphery, even when the article is formed by a process that creates a sharp peripheral edge at an intermediate step. In effect, the bend creates a force applied to the peripheral flange 120 to "flip" the deflectable flange 160 at the periphery of the article, effectively "hiding" the sharp edge of the thermoplastic sheet from the material at the periphery of the article.

The spacer 140 may be positioned between the bend region 150 and the bend 130. The spacers 140 may be discretely discernable from the inflection regions 150 (e.g., flat regions distinct from the curved inflection regions 150) or substantially indistinguishable (e.g., slightly curved regions indistinguishable from the curvature of the inflection regions 150). The size of the extension area is not critical; the dimensions may range from absent (i.e., bend region 150 begins at bend 130) to fractions of a millimeter to several millimeters or more. One function of the spacer 140 (if present) is to act as a "lever" by which forces applied at the elbow 130 (e.g., by impact between the peripheral flange 120 and one or both of the upper body 200 and the impact head 300) are transferred to the bend region 150. Another function of the spacer 140 (if present) may be to properly position the peripheral flange 120 for engagement with one or both of the upper body 200 and the impact head 300. Yet another function of the spacers 140 (if present) is to increase the distance that the potentially sharp peripheral edge 110 of the thermoplastic sheet can shift anti-peripherally from the periphery of the article when the bending region 150 flexes. Other things being equal, the longer the spacer 140, the further the potentially sharp edge will be from the outer periphery of the article when the article is made as described herein. Deflectable flanges including spacers 140 but lacking the bends 130 and the peripheral flange 120 may be used, for example, as shown in fig. 8A-8D.

The longer spacers 140 facilitate the formation of one or more portions of the "rollover edge" that are higher than other "rollover" portions of the edge, thereby creating a structure that can act as a stacking lug (e.g., to facilitate optional spacing between rollover edges of adjacent nested, stacked articles). In one embodiment, the size of the spacer and the compressive force applied to the spacer (i.e., the force transferred to the spacer from the extended region is balanced by the resistance applied to the spacer due to its impact on the impact head) can cause the spacer to flex outwardly (i.e., peripherally away from the body of the article) forming a smooth protrusion that forms the outer periphery of the article upon cooling.

Whether or not the fold region 150, the spacer 140, or both are folded in the operations described herein, and whether or not the material originally part of the fold region 150, the spacer 140, or both is ultimately formed at the outer periphery of the articles described herein. Importantly, the outer periphery is free of sharp, pointed, rough or abradable edges that could damage plastic film, human tissue or other fragile materials that may contact the outer periphery.

Thermoplastic plastic

The methods and articles described herein can be performed and manufactured with substantially any thermoplastic material. Importantly, at least in the deflectable flange 160 described herein, the material is capable of softening by heat and re-hardening upon cooling. Essentially all thermoplastics exhibit a characteristic temperature above which they soften and become pliable or processable, and below which they become more rigid and retain their shape. The desired thermoplastics for use in the articles and methods described herein retain their shape under normal conditions for the intended end use of the container. It is also desirable to use thermoplastics that soften under conditions readily available in a manufacturing environment. Examples of suitable thermoplastics include Polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), and polyvinyl chloride (PVC). Other suitable thermoplastics will be apparent to those skilled in the art, and essentially any of these thermoplastics may be used. Also useful may be a flexible plastic having a deformable material, such as a metal foil bonded to its surface.

The thermoplastic article comprises a thermoplastic material comprising at least a portion of the article forming and presenting the deflectable flange 160 described herein. The nature of the thermoplastic material is not critical, nor is the presence or absence of non-thermoplastic material. In the presence of a non-thermoplastic material (e.g. in a thermoplastic sheet laminated with a metal foil or paperboard layer), the thermoplastic material in its unsoftened, non-molten state imparts rigidity to the article, preferably sufficient to be able to define the configuration of the article even when the non-thermoplastic material is bent. The article may include one or more peelable layers, for example as described in co-pending U.S. patent application 13/415,781. When one or more peelable layers are present, it is essentially immaterial whether these layers "flip over" at the peripheral edge of the shaped article (rather than the edge of the peelable layer that is peeled from the underlying substrate). For aesthetic reasons and to facilitate sealing, it is preferred that any peelable layer remains adhered. When a peelable layer is present and adhesion is to be promoted, the operating temperature should be selected to be suitable for deflection of the deflectable flange as described herein and for processing the substrate and peelable layer of the shaped article without causing delamination of the peelable layer.

In an important embodiment, the thermoplastic selected for making the shaped article is optically transparent (i.e., transparent, preferably allowing transmission of wavelengths of light in the human visible range > 50%, and preferably allowing such transmission without significant distortion). Transparent packaging materials are preferred for many products that are sold directly to consumers, such as meats and fish, vegetables, and ready-made foods. Transparent packaging enables direct visual inspection of the package contents prior to purchase. Prior to the present invention, it was difficult or impossible to manufacture shaped articles (e.g., trays for holding food products) that were both optically clear and suitable for sealing with films using all three of these OW, VSP and MAP techniques. OW seals are typically used with blunt-edged trays, and the blunting (i.e., not sharp) of the edges is achieved by using a foam material, such as styrofoam. Trays made of transparent material are generally at least not suitable for OW sealing with thin, frangible plastic films. VSP and MAP trays are typically made of polypropylene materials, which are rarely, if ever, optically clear.

For optically transparent shaped articles as described herein, a variety of optically transparent plastics can be used. For example, PET, PVC and polycarbonate are suitable. The shaped article should be optically transparent at least in the recessed portion where the contents are to be stored, and preferably transparent over the entire deflectable flange adjacent the recessed portion, including any bent portion 160 and any portion bent during the operations described herein. For this reason, transparent thermoplastic trays are preferably used, such as those made of PET or PVC, and any heating or bending conditions applied to these trays during manufacture are preferably selected so as not to cause development of opacity in the material (e.g., by heating above the softening temperature prior to flexing the material).

Upper body 200

The upper body 200 performs a number of functions. In general, its function is to contain the deflectable flange described herein within a cavity in the upper body 200 while applying heat to one or more portions of the inflection region 150 of the deflectable flange 160. This containment function may prevent undesired deformation (or direct desired deformation) of the deflectable flange 160 or portions thereof during the peripheral smoothing operations described herein. The shape of the internal cavity of the upper body 200 may also affect the shape of the deflectable flange when it is bent, particularly when it is softened. For example, in fig. 1B, the upper body 200 includes a cavity with an internal right angle into which a portion of the bend region 150 is forced; the right-angled shape of this portion of the cavity will tend to cause the bend region 150 to conform to the right-angled shape, particularly when the bend region 150 softens. For example, the heat source may be a portion of the upper body 200 that is applied to the upper body 200 to conduct heat therethrough. When the peripheral flange 120 of the deflectable flange 160 is inserted into the cavity, the upper body 200 also impacts and is impacted against the peripheral flange. Upper body 200 also serves to prevent deflectable flange 160 from being forced out of the cavity when impact head 300 is in use, and may also limit deflection of bending region 150 when deflectable flange 160 is compressed by impact head 300.

The materials of construction of the upper body are not critical, but these materials should be suitable to withstand the manufacturing conditions described herein. That is, these materials should not melt or degrade at the temperatures used during processing. A variety of different metal, ceramic, stone and polymer materials may be used.

It is important that the shape of the upper body 200 is selected such that when the article 100 described herein is inserted into a cavity in the upper body, impact between the interior of the cavity in the upper body 200 and the peripheral flange 120 will occur. The upper body may have a shape sufficient to simultaneously impact multiple peripheral flanges 120 on the article or to impact most or all of a single peripheral flange 120 present on the article (e.g., one peripheral flange present around the entire peripheral edge of the article). As shown in fig. 2, the upper body 200 may be formed from a solid block of material that covers the entire face of the article while impinging upon the peripheral flange 120 present on one or more portions of the article. For example, the upper body 200 depicted in fig. 2 is designed to impinge on a single peripheral flange 120 that extends completely around the periphery of an article having the shape of a rectangular tray-type container with rounded corners.

When heat is applied to the bending region 150, the bending region 150 of the articles described herein will generally be located within the cavity of the upper body 200. For this reason, the upper body should be constructed in a manner that facilitates the application of such heat. Upper body 200 may, for example, include a heat source (e.g., an electrically operated heating plate or rod) within, applied to, or fluidly connected to its interior. Alternatively, the upper body 200 may include one or more ports through which heated fluid (e.g., heated gas or liquid) may pass from a source into the interior of a cavity in the upper body. The method selected for transferring heat to the inflection region 150 (and/or other portions of the peripheral flange, such as the spacers 140, the elbow 130, and the peripheral flange 120) is not critical, and any of a variety of well-known heat transfer methods and devices may be used. If upper body 200 is capable of conducting heat and being cooled, the heat present therein during the formation of deflectable flange 160 may flow to upper body 200, and this flow of heat may be used, for example, to cool deflectable flange 160 and thereby stiffen it in its deflected position when compressed between upper body 200 and impact head 300.

As shown in fig. 5 and 8, for example, impact head 300 alone may be used to deflect a deflectable flange with or without upper body 200. The upper body can be used to partially deflect the deflectable flange and apply a force to the article to cause the deflectable flange to impact the impact head. When upper body 200 is not used, alternative means of applying force to the article to cause impact between the impact head and the deflectable flange must be used. For example, in fig. 8D, the alternative instrument is simply depicted as object 403 (optionally in cooperation with object 402). The orientation of these components with respect to gravity is not critical, and the "downward" force (the hollow arrow in FIG. 8D) need only be directed so as to urge deflectable flange 160 against impact head 300 to cause an impact therebetween. It is also immaterial to which of the article and the impact head (or both) the force is applied in order to cause such impact. Importantly, the impact of deflectable flange 160 against impact head 300 (and/or upper body 200, if used) causes the peripheral edge 110 of the deflectable flange to deflect to a position at the periphery of the article where it is not readily accessible. Thus, in one embodiment, the upper body 200 may be a simple flat plate that may be applied to a flat portion of an article (e.g., the extension portion 50 of the deflectable flange 160 depicted in fig. 8D) to drive the deflectable flange in the direction of and ultimately against the impact head.

Impact head 300

The primary function of impact head 300 is to induce deflection in the deflectable flange. The impact head may be used with or without the use of a corresponding upper body 200, but such upper body may be used to contain and control the article as it comes into contact with the impact head. The method and mechanism for imparting relative motion between the article and the impact head is not critical. When an upper body is employed, the impact head is used to impact and apply a compressive force to the peripheral flange 120 of the deflectable flange 160 when the article is disposed in the upper body 200. This compressive force tends to drive the peripheral flange 120 upward and anti-peripherally toward the fold region 150 and extension 50 (if present), thereby moving the potentially sharp peripheral edge 110 of the thermoplastic sheet away from the periphery of the article so formed. Thus, the design of the impact head 300 is not particularly critical as long as such compressive force can be applied. As shown in fig. 1C and 4, an impact head 300 having an angled upper surface 302 will tend to direct the peripheral flange 120 toward a direction along the angle as the peripheral flange 120 is compressed. Accordingly, it may be advantageous to shape upper surface 302 of impact head 300 into a configuration that "deflects" or "pushes" peripheral flange 120 and/or peripheral edge 110 anti-peripherally as compression occurs.

Like upper body 200, the material from which impact head 300 is made is not critical. Metallic, ceramic, stone and polymeric materials capable of withstanding the operating temperatures and pressures are suitable and can be readily selected by the skilled artisan. If impact head 300 is capable of conducting heat and being cooled, the heat present therein during the formation of deflectable flange 160 may flow to impact head 300, and this flow of heat may be used, for example, to cool deflectable flange 160 and thereby stiffen it in its deflected position when compressed between upper body 200 and impact head 300. Heat may also be provided to one or more portions of the deflectable flange by impact head 300 in a conventional manner, such as by using a heated impact head or incorporating a heating element into or onto the impact head.

In the embodiment shown in fig. 2, a single impact head 300 may be configured to impact substantially all of peripheral flange 120 of an article simultaneously. For example, the impact head 300 depicted in fig. 2 is designed to impact and apply a compressive force to a single peripheral flange 120 that extends completely around the periphery of an article having the shape of a rectangular tray-type container with rounded corners.

In an alternative embodiment shown in fig. 5, the deflectable flange 160 of the article is heated to soften and be impacted by the impact head 300 without an upper body 200 of the type described herein. The absence of the upper body 200 may cause the softened portion of the deflectable flange 160 to distort or deflect, at least if other portions (e.g., the extension 50 or portions of the body 10 of the article 100 adjacent the deflectable flange) are not sufficiently rigid to prevent such distortion or deflection. However, if such rigidity is present, or if such distortion or deflection can be tolerated in the final product, the methods described herein can be used without the upper body 200.

Figure 5 also shows the importance of the length of the peripheral flange (measured from elbow to peripheral edge). The peripheral edge is in contact with the impact head. The force exerted on the peripheral edge by impact head face 302 causes deflectable flange 160 to deflect toward body 10 of article 100. As shown in fig. 5A and 5B, when deflectable flange 160 includes peripheral flange 120 offset from spacer portion 140 by 90 ° bend 130, the length of the peripheral flange will affect the degree of deflection of the deflectable flange. Comparing fig. 5C (deflectable flange with zero "length" of the peripheral flange; i.e., deflectable flange lacking the peripheral flange) with fig. 5B, it can be seen that the presence of the peripheral flange causes greater deflection of the deflectable flange in the illustrated configuration. Also, increasing the length of the peripheral flange increases the degree of deflection caused by the impact head, see FIG. 5A. Thus, although the elbow and peripheral flange are optionally absent, their presence enhances deflection and may enhance the "rollover" effect that may be achieved.

FIG. 10 depicts one embodiment of an impact head 300 for inverting an edge of a shaped article having a deflectable flange 160 as described herein. Fig. 10A depicts a striking head 300 having at least two positions for receiving an article 100 having deflectable flanges as described herein. The upper part of the figure shows the position of the load bearing article 100. Because the location shown partially at the bottom right of the figure does not carry an article, this location shows the upper surface 302 that carries the article when present. The location in the figure where the article is carried has the same upper surface 302, but this location is obscured by the spacer 140 and the peripheral flange 120 of the article 100 carried therein. The figure also shows how the extension 50 spaces the body 10 of the article away from the spacer and away from the impact head, this spacing providing a space into which the spacer and peripheral flange can deflect, bend or curl (visible through the transparent material forming the extension).

Fig. 10B and 10C show details of upper surface 302 of impact head 300 including a curved portion (approximately at D in fig. 10C) that will deflect outer peripheral edge 110 of the deflectable flange at the softening temperature when pushed against the curved portion. Fig. 10B is a close-up image of the upper surface, and fig. 10C is a cross-sectional view showing the approximate shape of the upper surface. In operation, the impact head is used in the following manner: by causing the peripheral edge 110 of the deflectable flange to impinge upon the upper surface 302 at any location between position B and position D (from the "downward" direction indicated by the hollow arrow in fig. 10C), yet additional downward force is applied to further drive the peripheral portion of the deflectable flange against the impact head. This additional force causes the peripheral edge to slip, scrape or slide across the upper surface and causes the deflectable flange to deflect inwardly (i.e., toward the body of the article, which in this embodiment is located closer to E than any of a-D). When the deflectable flange is heated above its softening point (i.e., glass transition temperature), if the deflectable flange is subsequently cooled to a temperature below its softening point, the deflection will be inelastic and will be reflected in the shape of the deflectable flange.

The curvature of upper surface 302 of impact head 300 between position C and position E in fig. 10C causes the softened portion of the deflectable flange to curl or bend, and the degree of bending caused is controlled by the degree to which the deflectable flange impacts the impact head. Thus, for example, if the deflectable flange is caused to impact only slightly against the upper surface after softening, only the outermost peripheral portion of the deflectable flange may deflect, if the softened portion of the deflectable flange is impacted to the extent of position D, the peripheral edge will be directed generally toward the body, and if the softened portion of the deflectable flange is impacted to extend beyond position D (e.g., as shown in fig. 8G and 8K), the peripheral edge of the deflectable flange will be effectively "flipped" (i.e., the plane of the deflectable flange at its peripheral edge extends to intersect the underside 161 of the deflectable flange). Depending on the material from which the deflectable flange is made, the deflectable flange may substantially retain its shape when cooled in an "inverted" configuration (e.g., PET and PVC materials do not fall or sag when subjected to the force of gravity in a softened state, whereas PE and PP materials may bend when softened substantially only by gravity). Even if not, such bending is acceptable as long as the peripheral edge of the sagging or descending deflectable flange does not expose the peripheral edge at the outer periphery of the article (e.g., when the rolled edge is sufficiently rolled over such that any sagging occurs in the interior space of the roll).

Sealing film

An important advantage of an article having a periphery treated in the manner described herein is that such treatment renders the article suitable for sealing with a plastic film. Sealing articles with thin plastic films is a well known process, and many suitable films are known (e.g., thin single or multi-layer sheets made of materials such as polyethylene or polyvinylidene chloride, optionally including a polymer layer that inhibits the passage of moisture or certain gases). The article may be sealed with a plastic film, for example, by completely encapsulating the article in the film and sealing the film to itself. Alternatively, the article may be sealed by sealing the film around the periphery of a recess, compartment or other aperture defined by the article, and then trimming those portions of the film beyond the periphery, if desired. All techniques for sealing articles with plastic films are believed to involve at least intermittent contact between the peripheral region of the article and the film used for sealing.

It is therefore advantageous for the articles to be sealed with the plastic film to be free of, or at least substantially free of, sharp, pointed, rough, jagged or abrasive structures, at least at the areas in contact with the film. It is particularly important that such structures are not present on the surface of the article that will have to contact the sealing film, whether during the sealing process, or during further packaging, shipping, unpacking, or retail display of the film-sealed article, and it is highly desirable that such structures also not be present on the surface of the article that may contact the sealing film. Still more preferably, the article to be wrapped with the film is free of such structures at those surfaces where there is a high likelihood of contact between the surface and the film during any of these treatments. Ideally, the article does not have such a surface at any location where a film used for sealing may reasonably be expected to contact the surface location during such treatments.

A variety of different plastic films are known for sealing containers, and essentially any of these films can be used to seal the shaped articles (or compartments thereof) described herein. The choice of sealing film (and material used to make shaped articles compatible with such sealing films) is well known in the art, and essentially any known combination of materials can be suitable for use in the shaped articles described herein. For example, when the sealing film is to be removably sealed around a shaped article described herein (e.g., an outer wrapping film that is sealed to itself and not to the wrapped article), the material used to make the shaped article should be selected such that the material does not adhere to the film under the sealing conditions to be used. Conversely, when the sealing film is to be substantially permanently sealed to the shaped article (e.g., around the periphery of the compartment defined by the article), the material used to make the shaped article should be selected so as to form a substantially permanent seal under actual processing conditions. Similarly, the combination of the seal and container materials and the operating conditions to produce a container sealed with a material peelable from the container are known and may be used.

One highly desirable embodiment of the article described herein is a tray-shaped article that is manufactured by thermoforming (and thus has a potentially sharp peripheral edge prior to the edge rollover process described herein) such that the article has a deflectable flange described herein around its entire periphery, and the peripheral edge of the deflectable flange is deflected sufficiently below the extension and behind the spacers and the fold areas of the deflectable flange around the entire periphery of the tray such that the peripheral edge cannot be reached by a human fingertip sliding along the gap between the deflected peripheral flange and the tray body, even if the fingertip slides around the entire periphery of the tray along the gap. In the sealing process, regardless of whether OW, VSP or MAP technology is used, the tray does not have sharp, pointed, rough, jagged or abrasive edges at any point where it is reasonably expected that contact with the sealing membrane will occur. Trays suitable for use with all of these sealing techniques are highly desirable and are considered difficult to obtain prior to the disclosure of the subject matter described herein.

Many plastic films used to seal to articles are flexible and do not thermally cure in the temperature ranges typically employed during sealing and subsequent processing. Flexible membranes sealed to a surface are sometimes difficult to remove from the sealing surface in a monolithic form. For example, when a portion of the film is pulled away from the tray, the flexible film sealed to the flat outer perimeter of the tray may tear or split, thus requiring the user to remove the film in multiple passes or pieces. This difficulty can be particularly acute where the sealing surface is wide, such as in VSP-sealed packages where the sealing film can adhere to or adhere to a relatively large area of the tray on which the article has been sealed between the film and the tray. The techniques described herein may be used to reduce or overcome this difficulty as follows.

Shaped articles described herein (e.g., tray-shaped articles having a smooth outer periphery) can be sealed with a thermoset (i.e., thermoformable) film to produce articles in which the thermoformable sealing film is heated above its glass transition temperature to soften it and applied over the smooth outer periphery of the shaped article. A thermoformable film that is heated above the glass transition temperature of the material from which it is made and subsequently cooled below that temperature will retain any conformation that the film has when the temperature is reduced below its glass transition temperature (e.g., the conformation imposed thereon). Thus, if a thermoplastic film is formed "around" (i.e., extending more than about 90 degrees around) the smooth outer periphery of the article described herein, the film will be retained on the article not only by any attractive or adhesive forces that may exist between the film and the article surface, but also by mechanical forces (i.e., the resistance of the film to deflection around the smooth outer periphery), thereby forming a structure similar to a "snap off" lid.

While softened plastic films can be extremely fragile (e.g., susceptible to damage by sharp, pointed, rough, jagged, or abrasive surfaces), the smooth outer perimeter of the shaped articles described herein allows even such fragile films to be applied thereto. In one embodiment, a shaped article in the form of a tray having a smooth outer periphery can be VSP sealed to wrap the article between the softened thermoplastic sealing film and the tray with little or no gas in the sealed portion. Furthermore, the smooth outer periphery of the articles described herein enables the softened film to be stretched, pressed, or formed around the smooth outer periphery-that is, not only to contact the top portion of the outer periphery (i.e., similar to the extension 50 of the edge of the article depicted in fig. 9B), but also around the bent region 150 of the deflectable flange and along the spacer 140 and any bent or rounded portions thereof (such as to or around the rounded underside 145 of the spacer depicted in fig. 9B); and then fixed by lowering the temperature of the sealing film below its glass transition temperature. Such a seal would form a relatively rigid "cap" and the frictional force or shape of the "cap" (e.g., rotating about the circular underside 145 of the spacer shown in fig. 9B so that the "cap" must be stretched or expanded to disengage it from the inverted peripheral flange 160) would hold the sealing membrane in place on the article in the event that the membrane intersects the article even though the membrane is not adhered or bonded to the shaped article. Furthermore, because the softened thermoset film may be much thicker, and therefore more robust and/or rigid, than the flexible sealing film, the thermoset sealing film may form a seal or "lid" that may tend to be more easily removed in a single piece.

In one embodiment of the shaped article described herein, for example, the article is a tray on which a food product is placed, wherein the thermoset film is covered across the periphery of the food product and tray when the film is in a softened state; the gas between the film and the tray is drawn out to form a VSP-type seal (where the film is in close opposition to the food product and the surface of the tray on which the food product rests); and the film is wrapped around (from top to bottom of the periphery or around the bottom), optionally sealed or adhered to the tray, trimmed around the bottom of the periphery of the tray, and cooled. In the finished tray, the "lid" formed when the film is cooled must be "broken" by stretching the edge of the lid around the periphery of the tray, but once this is done, the entire lid can be removed from the tray in a single piece.

In another embodiment, the shaped articles described herein are sealed (after they have been formed into smooth outer peripheral sides) using a thermoformable plastic film that extends across the compartment defined by the article and extends at least about 90 degrees around the opposite smooth outer peripheral sides of the article (i.e., the opposite ends of the rounded rectangular tray). The film is heated above its glass transition temperature and cooled below that temperature while extending around the opposing smooth outer peripheral sides. If desired, a vacuum or modified atmosphere may be applied to the compartment during such sealing. The resulting article has a thermoset film cover that must be stretched (or "snapped") around at least one peripheral side of the article to remove the film from the article (in addition to any other seals that may be present between the film and the article).

The shaped articles described herein can be used in a manner that is not believed possible using previously known trays. Typically, others have used containers designed and manufactured specifically for each of the various sealing techniques described herein for sealing containers with plastic film (e.g., OW, VSP, and MAP techniques). That is, food trays designed for OW sealing are generally considered unsuitable for VSP and MAP wrapping (e.g., due to the lack of a surface suitable for sealing with VSP technology and/or MAP technology). Similarly, the sharp edges of many containers designed for use with VSP and MAP sealing technologies make these containers unsuitable for overwrapping with frangible polymeric films. The shaped articles described herein may be used to make shaped articles that may suitably be used as containers sealed by any of the OW, VSP and MAP techniques. Because the formed article is thermoformed, container surfaces suitable for VSP and/or MAP sealing can be included in the shape of the article. Any edges of the shaped article (or, alternatively, all edges of the shaped article) that may be at risk of tearing the sealing film can be made to have a smooth configuration using the methods described herein, such as by forming a turned edge or by smoothing the shape of the mold used to thermoform the precursor article. Thus, unlike previously known trays, the shaped articles described herein can be used with substantially any film sealing technique.

Other advantageous uses of the shaped articles described herein relate to the smoothness of the edges thereof. The article can be used in essentially any environment where it is desired or necessary for a solid object to exhibit a smooth edge. For example, instruments used in surgery are often packaged in openable containers (to allow for reuse and sterilization between uses) that are opened by personnel wearing surgical gloves that are prone to tearing during medical surgery. Thermoformed articles (e.g., so-called "clam-shell" type release packages of known design) can be manufactured as described herein, wherein those articles are initially manufactured with a deflectable flange anywhere the articles are cut from a web of thermoformed material, which is then flipped over to produce the smooth edges described herein. Articles manufactured in this manner will present a smooth edge to the user, reducing the likelihood of tearing the surgical glove during surgery by opening such packaging. Similarly, thermoformed packages of known design that can be employed to facilitate handling, deter theft, or for other purposes can be adapted (e.g., by including a deflectable flange in their design and inverting the deflectable flange) to take advantage of the edge smoothing techniques described herein.

System for forming articles

As noted above, the precursors of the shaped articles described herein can be formed by standard thermoforming methods using standard thermoforming equipment. To this end, a precursor article is manufactured using a thermoforming mold by imparting a desired configuration of the finished article to a thermoplastic sheet, except that the deflectable flange described herein is included at the outer peripheral edge where a smooth outer periphery is to be formed. In cutting the precursor article from the web of thermoplastic sheet, the edge smoothing operation described herein may be performed by impacting the deflectable flange on an impact head (optionally with the aid of an upper body).

The newly thermoformed precursor article will tend to emerge from the thermoforming machine at a temperature close to (but below) the glass transition temperature of the thermoplastic. Striking the deflectable flange and the striking head immediately after removing the precursor article from the thermoformer may reduce the amount of thermal energy that must be supplied to one or more portions of the deflectable flange in order to achieve the desired deflection (or "rollover" edge effect) of the deflectable flange described herein. For this reason, it may be desirable to combine the thermoformer, impact head, and impact mechanism into one system or unitary device. Such a system or integrated device should include: i) a thermoformer module capable of forming a precursor article; ii) a cutter for cutting a precursor article from a thermoplastic sheet or web from which the precursor article is formed; iii) a percussion head; and iv) a mechanism for positioning the precursor article on the impact head (i.e. such that the deflectable flange portion is aligned with the respective impact head portion) and impacting the precursor article and the impact head together. The heat required during the deflectable flange-deflecting operation described herein may be provided by the impact head, a cutter (e.g., using a heated cutting knife to heat the peripheral edge and adjacent peripheral portion of the deflectable flange above the softening temperature of the thermoplastic), a separate heater (e.g., a radiant heating element disposed in close opposition to the impact head when the impact head is engaged with the deflectable flange), or a combination of these. The precise selection, orientation, order and configuration of these components of the apparatus is not critical and can be selected by the skilled person according to the requirements and class of processing steps described herein. The system or apparatus may further comprise a plug as described herein for insertion into a void in the precursor article prior to the deflectable flange impacting the impact head.