阅读说明：本技术 一种旋转压紧式抓取机构 (Rotary pressing type grabbing mechanism ) 是由 钟世权 陈军校 刘红佳 于 2021-08-16 设计创作，主要内容包括：本申请提供一种旋转压紧式抓取机构,被抓取的工件顶面具有凹槽,凹槽的截面为T型槽或燕尾槽结构。抓取机构包括：连接杆、压紧套以及拉杆。连接杆下段加工有圆柱孔。压紧套呈管状结构,滑动设于圆柱孔内,压紧套与圆柱孔底面之间设有弹簧。拉杆设于连接杆下段,并同轴为于圆柱孔内,拉杆下段穿过压紧套的底部,拉杆穿过弹簧；拉杆底部垂直穿设有可拆卸的横杆。利用纯机械结构实现对工件的夹持及松开,结构简单,夹紧及松开均十分便捷,且夹持稳定可靠。(The application provides a mechanism is snatched to rotatory pressing mode, and the work piece top surface of snatching has the recess, and the cross-section of recess is T type groove or dovetail structure. Snatch the mechanism and include: connecting rod, compress tightly cover and pull rod. The lower section of the connecting rod is provided with a cylindrical hole. The compressing sleeve is of a tubular structure and is arranged in the cylindrical hole in a sliding manner, and a spring is arranged between the compressing sleeve and the bottom surface of the cylindrical hole. The pull rod is arranged on the lower section of the connecting rod and is coaxial in the cylindrical hole, the lower section of the pull rod penetrates through the bottom of the pressing sleeve, and the pull rod penetrates through the spring; the bottom of the pull rod vertically penetrates through a detachable cross rod. The clamping and loosening of the workpiece are realized by utilizing a pure mechanical structure, the structure is simple, the clamping and loosening are both very convenient, and the clamping is stable and reliable.)

1. The utility model provides a rotatory pressing mode snatchs mechanism, the work piece top surface of snatching has the recess, and the cross-section of recess is T type groove or dovetail structure, its characterized in that includes:

the lower section of the connecting rod (10) is provided with a cylindrical hole (101);

the pressing sleeve (20) is of a tubular structure and is arranged in the cylindrical hole (101) in a sliding mode, and a spring (21) is arranged between the pressing sleeve (20) and the bottom surface of the cylindrical hole (101);

the pull rod (30) is arranged at the lower section of the connecting rod (10) and is coaxially arranged in the cylindrical hole (101), the lower section of the pull rod (30) penetrates through the bottom of the pressing sleeve (20), and the pull rod (30) penetrates through the spring (21); the bottom of the pull rod (30) is vertically provided with a detachable cross rod (31) in a penetrating way.

2. The rotary compression type grabbing mechanism is characterized in that an adjusting screw hole (102) is formed in the middle section of the connecting rod (10), the adjusting screw hole (102) is coaxial and communicated with the cylindrical hole (101), a screw rod portion (301) is arranged on the upper section of the pull rod (30), and the screw rod portion (301) is connected with the adjusting screw hole (102) in a matched mode.

3. The rotary compression type grabbing mechanism is characterized in that a pair of side baffles (22) is arranged on the outer side of the compression sleeve (20), the distance between the side baffles (22) is adjusted according to the outer size of a grabbed workpiece, and the side baffles (22) are positioned at openings at two ends of a workpiece groove when the workpiece is grabbed.

4. The rotary compression type grabbing mechanism is characterized in that a circular ring (23) is sleeved on the periphery of a compression sleeve (20), the circular ring (23) is movably arranged along the axis of the compression sleeve (20), a limiting groove (201) is formed in the outer wall of the compression sleeve (20) along the axis direction, a limiting screw (24) penetrates through the circular ring (23), and the front end of the limiting screw (24) is embedded in the limiting groove (201); the circular ring (23) is provided with a pair of adjusting plates (231) along the normal line outwards, and the side baffles (22) are respectively arranged on the adjusting plates (231) in a sliding manner; the side baffle (22) is arranged below the adjusting plate (231), the top of the side baffle (22) is upwards provided with a rectangular groove (221), and the adjusting plate (231) penetrates through the rectangular groove (221).

5. The rotary compression type grabbing mechanism according to claim 1, wherein lubricating discs (25) are arranged at the upper end and the lower end of the spring (21), the lubricating discs (25) are sleeved on the outer peripheral side of the pull rod (30), annular grooves are formed in the surface, in contact with the bottom surface of the cylindrical hole (101), of the lubricating disc (25) at the upper end and the contact surface, between the lubricating disc (25) at the lower end and the compression sleeve (20), of the lubricating disc (25) at the lower end, and grease lubricating oil is filled in the annular grooves.

6. The rotary pressing type grabbing mechanism is characterized in that a pressing screw (32) penetrates through the bottom of the pull rod (30), and a positioning hole (311) is formed in the bottom surface of the cross rod (31).

7. The rotary compression type grabbing mechanism is characterized in that the cross rod (31) is provided with a through hole (312), and the bottom of the through hole (312) is provided with a counter bore (313); the through hole (312) and the counter bore (313) are coaxial with the pull rod (30); the cross bar (31) is connected to the pull rod (30) through a connecting bolt (33); the connecting bolt (33) penetrates through the solid part of the pull rod (30) below the cross rod (31); a screw rod of the connecting bolt (33) penetrates through a through hole (312) of the cross rod (31) and a counter bore (313), and the screw rod part of the connecting bolt (33) is connected to a solid part of the pull rod (30) above the cross rod (31); the head of the connecting bolt (33) is located in the counterbore (313).

8. A rotary compression type gripping mechanism according to claim 2, wherein the upper section of the connecting rod (10) is provided with a connecting screw hole (103) for mounting the operating rod or connecting the gripping mechanism to the driving device through the connecting screw hole (103); at least one locking screw (11) penetrates through the side wall of the connecting rod (10) corresponding to the connecting screw hole (103) and the adjusting screw hole (102).

Technical Field

The invention belongs to the technical field of mechanical grabbing structures, and particularly relates to a rotary pressing type grabbing mechanism.

Background

In mechanical production, grooves with different structures are machined on the tops of a plurality of workpieces or parts, and when the workpieces or the parts are transferred, the existing clamps usually connect and grab the workpieces or the parts by means of the groove structures. However, the existing structure of the clamp for directly contacting with the workpiece or the part usually adopts automatic control, for example, a cylinder or a motor is used for driving a clamping block to realize the clamping of the workpiece or the part. Although the structure is convenient for clamping and loosening workpieces or parts, the structure has excessive electric elements, the structure is complicated, the manufacturing and maintenance cost is high, and more importantly, the structure has large size and is inconvenient to assemble and arrange.

Disclosure of Invention

In order to solve the defects of the prior art, the invention provides a rotary compression type grabbing mechanism which is simple in structure, convenient and fast to clamp and loosen and stable and reliable in clamping, and workpieces are clamped and loosened by using a pure mechanical structure.

In order to realize the purpose of the invention, the following scheme is adopted:

a rotary pressing type grabbing mechanism is characterized in that a groove is formed in the top surface of a grabbed workpiece, and the section of the groove is of a T-shaped groove or dovetail groove structure. Snatch the mechanism and include: connecting rod, compress tightly cover and pull rod.

The lower section of the connecting rod is provided with a cylindrical hole.

The compressing sleeve is of a tubular structure and is arranged in the cylindrical hole in a sliding manner, and a spring is arranged between the compressing sleeve and the bottom surface of the cylindrical hole.

The pull rod is arranged on the lower section of the connecting rod and is coaxial in the cylindrical hole, the lower section of the pull rod penetrates through the bottom of the pressing sleeve, and the pull rod penetrates through the spring; the bottom of the pull rod vertically penetrates through a detachable cross rod.

Furthermore, the middle section of the connecting rod is provided with an adjusting screw hole which is coaxial and communicated with the cylindrical hole, the upper section of the pull rod is provided with a screw rod part, and the screw rod part is matched and connected with the adjusting screw hole.

Furthermore, a pair of side baffles is arranged on the outer side of the pressing sleeve, the distance between the side baffles is adjusted according to the size of the outer side of a workpiece to be grabbed, and the side baffles are positioned at openings at two ends of a workpiece groove when the workpiece is grabbed.

Furthermore, a circular ring is sleeved on the periphery of the compression sleeve and movably arranged along the axis of the compression sleeve, a limiting groove is formed in the outer wall of the compression sleeve along the axis direction, a limiting screw penetrates through the circular ring, and the front end of the limiting screw is embedded in the limiting groove; the circular ring is provided with a pair of adjusting plates outwards along the normal line, and the side baffles are respectively arranged on the adjusting plates in a sliding manner; the side baffle is arranged below the adjusting plate, a rectangular groove is formed in the top of the side baffle upwards, and the adjusting plate penetrates through the rectangular groove.

Furthermore, the upper end and the lower end of the spring are respectively provided with a lubricating disc, the lubricating discs are sleeved on the periphery of the pull rod, annular grooves are formed in one surface of the upper end of the lubricating disc, which is contacted with the bottom surface of the cylindrical hole, and in the contact surface between the lower end of the lubricating disc and the pressing sleeve, and the annular grooves are filled with lipid lubricating oil.

Furthermore, a compression screw penetrates through the bottom of the pull rod, and a positioning hole is formed in the bottom surface of the cross rod.

Furthermore, the cross rod is provided with a through hole, and the bottom of the through hole is provided with a counter bore; the through hole and the counter bore are coaxial with the pull rod; the cross rod is connected to the pull rod through a connecting bolt; the connecting bolt penetrates through the solid part of the pull rod below the cross rod; a screw rod of the connecting bolt penetrates through the through hole and the counter bore of the cross rod, and the screw rod part of the connecting bolt is connected to the solid part of the pull rod above the cross rod; the head of the connecting bolt is positioned in the counter bore.

Furthermore, a connecting screw hole is processed at the upper section of the connecting rod and used for installing the operating rod or connecting the grabbing mechanism with the driving device through the connecting screw hole; at least one locking screw penetrates through the side wall of the connecting rod corresponding to the connecting screw hole and the adjusting screw hole.

The invention has the beneficial effects that:

1. the structure is simple, various electrical elements are not used, and the clamping and the loosening of the workpiece or the part with the groove are realized by a pure mechanical structure; the cross bars can be replaced to connect grooves of different cross sections.

2. The device has wide application range, can be connected with various devices for use, and is more convenient to arrange due to small and exquisite structure; and can be used as a manual tool.

3. The clamping of the workpiece or the part is stable and reliable, and the workpiece or the part is firstly connected with the groove of the workpiece through the cross rod, so that the primary connection can be realized, and the workpiece or the part is lifted or slowly moved; secondly, the workpiece is compressed by the compression sleeve, so that the workpiece is prevented from shaking, the stability of clamping the workpiece is further improved, and the workpiece or parts can be moved relatively quickly; utilize the side shield to carry on spacingly to the work piece at last, prevent the horizontal pole landing simultaneously, not only more stable to the centre gripping of work piece or spare part this moment, also further promote the security when the operation is held to the centre gripping moreover.

Drawings

The drawings described herein are for illustrative purposes only of selected embodiments and not all possible implementations, and are not intended to limit the scope of the present disclosure.

FIG. 1 illustrates an overall cross-sectional view of one embodiment of the present application.

FIG. 2 is a block diagram illustrating an embodiment of the present application before use.

FIG. 3 shows a block diagram of an embodiment of the present application in grabbing a workpiece.

Fig. 4 shows the structure of the side dams.

Fig. 5 shows the structure and positional relationship of the spring and the lubricating disk.

Fig. 6 shows a cross-sectional view of one connection of the cross bar to the tie rod.

Figure 7 shows a side view of a preferred connection of the cross bar to the tie rod.

Figure 8 shows a cross-sectional view of a preferred cross bar to tie rod connection.

Fig. 9 shows a conventional connection structure of a cross bar and a tie bar.

Fig. 10 illustrates one embodiment of use of the grasping mechanism.

Fig. 11 shows another embodiment of the use of the gripping mechanism.

The labels in the figure are: the device comprises a rotary cylinder-1, a lifting cylinder-2, a handle-3, a connecting rod-10, a cylindrical hole-101, an adjusting screw hole-102, a locking screw-11, a pressing sleeve-20, a limiting groove-201, a spring-21, a side baffle-22, a rectangular groove-221, a circular ring-23, a limiting screw-24, a lubricating disc-25, an adjusting plate-231, a pull rod-30, a screw rod-301, a cross rod-31, a positioning hole-311, a through hole-312, a counter bore-313, a pressing screw-32 and a connecting bolt-33.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the following detailed description of the embodiments of the present invention is provided with reference to the accompanying drawings, but the described embodiments of the present invention are a part of the embodiments of the present invention, not all of the embodiments of the present invention.

It should be noted that: like reference numbers and letters refer to like items in the following figures, and thus, once an item is defined in one figure, it need not be further defined and explained in subsequent figures.

In the description of the present invention, it should be noted that the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings or orientations or positional relationships that the products of the present invention are usually placed in when used, and are only for convenience of describing the present invention and simplifying the description. The terms "first," "second," and the like are used solely to distinguish one from another and are not to be construed as indicating or implying relative importance. The terms "parallel", "perpendicular", etc. do not require that the components be absolutely parallel or perpendicular, but may be slightly inclined.

In the description of the present invention, it should also be noted that, unless otherwise explicitly specified or limited, the terms "disposed," "mounted," "connected," and "connected" are to be construed broadly, e.g., as meaning either a fixed connection, a removable connection, or an integral connection; either directly or indirectly through intervening media, or through both elements. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

A rotary pressing type grabbing mechanism is provided, the top surface of a grabbed workpiece is provided with a groove, and the section of the groove is of a T-shaped groove structure shown in fig. 11 or a dovetail groove structure shown in fig. 10.

As shown in fig. 1 to 3, a rotary press-type grasping mechanism includes: connecting rod 10, clamping sleeve 20 and pull rod 30.

Specifically, a cylindrical hole 101 is formed in the lower section of the connecting rod 10.

Specifically, the compression sleeve 20 is of a tubular structure and is slidably arranged in the cylindrical hole 101, the bottom of the cylindrical hole 101 is provided with a limiting ring, the upper end of the compression sleeve 20 is provided with a flange, and the limiting ring and the flange are used for limiting so as to prevent the compression sleeve 20 from falling off from the cylindrical hole 101. A spring 21 is arranged between the pressing sleeve 20 and the bottom surface of the cylindrical hole 101.

Specifically, the pull rod 30 is arranged at the lower section of the connecting rod 10 and is coaxial in the cylindrical hole 101, the lower section of the pull rod 30 penetrates through the bottom of the pressing sleeve 20, and the pull rod 30 penetrates through the spring 21; the bottom of the pull rod 30 is vertically provided with a detachable cross rod 31 in a penetrating way, so that the cross rod 31 with different structures can be conveniently replaced to adapt to grooves with different sections of workpieces.

Preferably, as shown in fig. 1, an adjusting screw hole 102 is processed in the middle section of the connecting rod 10, the adjusting screw hole 102 is coaxial and communicated with the cylindrical hole 101, the upper section of the pull rod 30 is provided with a screw portion 301, the screw portion 301 is in fit connection with the adjusting screw hole 102, and the protruding length of the pull rod 30 relative to the connecting rod 10 is adjusted by adjusting the fit length of the screw portion 301 and the adjusting screw hole 102, so as to adapt to grooves with different depths of workpieces. Meanwhile, the clamping device has the function of adjusting the pressure of the pressing sleeve 20, and the distance between the bottom surfaces of the pressing sleeves 20 of the cross rods 31 can be changed by adjusting the matching length of the screw rod parts 301 and the adjusting screw holes 102, so that the pressing force of the pressing sleeves 20 on workpieces is adjusted. The principle is that when the workpiece is pressed to a certain thickness, the smaller the distance between the cross bar 31 and the bottom surface of the pressing sleeve 20 in the natural state of the spring 21, the longer the stroke of the pressing sleeve 20 moving when pressing the workpiece, the greater the amount of compression of the spring 21, and therefore the greater the pressure, and thus the greater the pressing force applied to the workpiece by the pressing sleeve 20.

Preferably, as shown in fig. 2, 3, 10 and 11, a pair of side guards 22 are provided outside the pressing sleeve 20, the distance between the side guards 22 is adjusted according to the outside size of the workpiece to be gripped, the side guards 22 are located at the openings at the two ends of the workpiece groove when the workpiece is gripped, and the side guards 22 are used to limit the position of the workpiece relative to the pull rod 30, so as to prevent the cross bar 31 from sliding off from the two ends of the workpiece groove.

Further preferably, as shown in fig. 2 and 3, the outer periphery of the pressing sleeve 20 is sleeved with a circular ring 23, the circular ring 23 is movably disposed along the axis of the pressing sleeve 20, the outer wall of the pressing sleeve 20 is provided with a limiting groove 201 along the axis direction, the circular ring 23 is provided with a limiting screw 24 in a penetrating manner, the front end of the limiting screw 24 is embedded in the limiting groove 201, and the circular ring 23 is prevented from rotating relative to the pressing sleeve 20 through the matching of the limiting screw 24 and the limiting groove 201 so as to keep the relative position fixed. The ring 23 is provided with a pair of adjusting plates 231 along the normal line, the adjusting plates 231 are located on the same straight line, and the side baffles 22 are respectively slidably arranged on the adjusting plates 231, so as to realize the purpose of adjusting the distance between the side baffles 22. The height position of the side baffle 22 is controlled according to the structural shape of a workpiece or a part by adjusting the position of the ring 23 along the axis of the pressing sleeve 20.

More specifically, as shown in fig. 2 to 4, the side guard 22 is disposed below the adjusting plate 231, the top of the side guard 22 is upwardly opened with a rectangular slot 221, and the adjusting plate 231 passes through the rectangular slot 221, so as to improve the stability of the connection structure between the side guard 22 and the adjusting plate 231 and prevent the side guard 22 from rotating and shifting relative to the adjusting plate 231.

Preferably, as shown in fig. 1 and 5, the upper end and the lower end of the spring 21 are both provided with a lubricating disc 25, the lubricating disc 25 is sleeved on the outer periphery of the pull rod 30, the surface of the upper end of the lubricating disc 25, which is in contact with the bottom surface of the cylindrical hole 101, and the contact surface between the lower end of the lubricating disc 25 and the pressing sleeve 20 are both provided with annular grooves, and the annular grooves are filled with grease lubricating oil. So as to reduce the friction force between the spring 21 and the connecting rod 10 and the pressing sleeve 20, and make the relative rotation between the connecting rod 10 and the pressing sleeve 20 smoother. Thereby prevent to compress tightly that cover 20 from producing the rotation relative to the work piece to guarantee to compress tightly that the relative position between cover 20 and the work piece is more stable, still can effectively avoid fish tail work piece surface. On the other hand, the side baffle plates 22 can be always positioned at two ends of the workpiece groove, and the position of the side baffle plates 22 is prevented from moving.

As shown in fig. 6, in an embodiment in which the cross bar 31 is connected to the pull rod 30, a pressing screw 32 is disposed at the bottom of the pull rod 30, a positioning hole 311 is disposed at the bottom of the cross bar 31, and the pressing screw 32 presses the positioning hole 311, so that the cross bar 31 is fixed to the pull rod 30, and the purpose of facilitating the detachment is achieved.

In a further preferred embodiment, the cross bar 31 is connected with the pull rod 30, as shown in fig. 7 and 8, the cross bar 31 is provided with a through hole 312, and the bottom of the through hole 312 is provided with a counter bore 313; the through hole 312 and the counter bore 313 are coaxial with the pull rod 30; the cross bar 31 is connected to the pull rod 30 through a connecting bolt 33; the connecting bolt 33 penetrates through the solid part of the pull rod 30 below the cross rod 31; the screw of the connecting bolt 33 passes through the through hole 312 of the cross bar 31 and the counter bore 313, and the screw part of the connecting bolt 33 is connected with the solid part of the pull rod 30 above the cross bar 31; the head of the connecting bolt 33 is located in the counterbore 313. this design avoids any structure on the outside of the bottom surface of the tie rod 30, which reduces the overall size below the cross bar 31, making the cross bar 31 easier to insert into a groove having a smaller depth in the workpiece. The conventional connection method of the cross bar 31 and the pull rod 30 is shown in fig. 9, which can also reduce the structural size below the cross bar 31, but like the scheme shown in fig. 9, the cross bar 31 is connected only by bolts, the tensile force borne by the cross bar 31 is ensured only by the tensile strength of the bolts, the bolts have the risk of breaking, and therefore, the cross bar 31 also has the risk of falling. In the structure of the present invention, besides the pulling force provided by the connecting bolt 33, the solid portion of the pull rod 30 below the cross bar 31 as shown in fig. 8 can be used as a support, so that the connecting structure of the cross bar 31 is more stable and reliable. The connection shown in fig. 9 does not completely prevent the crossbar 31 from rotating with respect to the axis of the tie rod 30. In the application, the cross rod 31 penetrates through the pull rod 30, and the cross rod 31 is limited by the connecting hole of the pull rod 30 for penetrating the cross rod 31, so that the cross rod 31 can be completely prevented from rotating relative to the axis of the pull rod 30.

Preferably, as shown in fig. 1, the upper section of the connecting rod 10 is processed with a connecting screw hole 103 for installing the operating rod or connecting the grasping mechanism to the driving device through the connecting screw hole 103; at least one locking screw 11 is arranged on the side wall of the connecting rod 10 corresponding to the connecting screw hole 103 and the adjusting screw hole 102 in a penetrating manner and used for locking and connecting part structures connected in the screw hole 103 or the adjusting screw hole 102.

The specific implementation mode is as follows:

the working principle is as follows: before the grabbing mechanism is used, as shown in fig. 2, the axis of the cross rod 31 is consistent with the sliding direction of the side baffle 22, at the moment, the opening direction of the cross rod 31 is parallel to the groove at the top of the workpiece, so that the cross rod 31 is placed in the groove at the top of the workpiece, and the diameter of the pull rod 30 is smaller than the opening size of the groove at the top of the workpiece, so that the pull rod can be smoothly inserted into the groove. The spacing between the side guards 22 is adjusted according to the dimension between the ends of the groove. In use, the cross bar 31 is inserted into the recess so that the side guards are outside the ends of the recess as shown in figure 10. Before the cross bar 31 is completely inserted into the groove, the bottom surface of the pressing sleeve 20 is contacted with the top surface of the workpiece, the spring 21 is gradually compressed during the process that the cross bar 31 is continuously inserted into the groove, and the elastic force generated by the compression of the spring 21 is provided for the pressing sleeve 20, so that the pressing sleeve 20 is pressed on the surface of the workpiece. Then the connecting rod 10 is rotated to enable the cross rod 31 to be perpendicular to the groove at the top of the workpiece, the cross rod 31 is clamped in the groove, the connection between the grabbing mechanism and the workpiece is achieved, and then the workpiece can be transferred. At this time, because the pressing sleeve 20 has a larger friction force with the workpiece, the friction force among the spring 21, the connecting rod 10 and the pressing sleeve 20 is reduced by the lubricating disc 25; thereby making the relative rotation between the connecting rod 10 and the pressing sleeve 20 smoother and preventing the relative rotation between the pressing sleeve 20 and the workpiece. The operation is very simple and only the connecting rod 10 needs to be pressed and rotated.

When the workpiece needs to be loosened, the connecting rod 10 only needs to be rotated, the transverse rod 31 is parallel to the groove in the top of the workpiece in the opening direction, and at the moment, under the action of the elastic force of the spring 21, the transverse rod 31 is automatically separated from the groove in the top of the workpiece, so that the operation is very convenient and smooth.

As shown in fig. 10, the rotary pressing type grabbing mechanism of the present application is connected to an automation device for use, and is connected to a rotating shaft of a rotary cylinder 1 through a connecting rod 10, the rotary cylinder 1 drives the connecting rod 10 to rotate, and finally, a cross rod 31 is rotated to connect and separate a workpiece or a part. The rotary cylinder 1 is connected to a push rod of the lifting device 2, the lifting device 2 is used for controlling the lifting of the grabbing mechanism, and the rotary cylinder is not only used for descending a lifting machine for workpieces or parts, but also used for pushing the pressing sleeve 20 to press the workpieces.

As shown in FIG. 11, when the tool is used as a hand tool, a handle 3 can be installed above the connecting rod 10, the handle 3 can be used for controlling the connecting rod 10 to rotate, and the pressing sleeve 20 can be pushed.

The foregoing is only a preferred embodiment of the present invention and is not intended to be exhaustive or to limit the invention. It will be understood by those skilled in the art that various changes may be made and equivalents may be substituted without departing from the scope of the invention.