阅读说明：本技术 用于制作用于浸泡产品的过滤袋的机器 (Machine for making filter bags for infusion products ) 是由 S·里沃拉 S·巴迪尼 F·波维切利 于 2018-07-03 设计创作，主要内容包括：一种用于制作用于浸泡产品的过滤袋(1)的机器，所述机器包括：第一旋转传送器(2)，第一旋转传送器(2)连续旋转并具有沿其定位的多个第一操作工位(4)；每个操作工位被构造成在对应的过滤材料的件(1a)上操作，以进一步获得并排并且竖立定位的两个腔室(1b、1c)；机器包括第二旋转传送器(6)，第二旋转传送器与第一旋转传送器并排放置并且连续旋转；第二旋转传送器具有沿其定位的多个结合元件(7)；每个结合元件连接到对应的控制设备(8、9)，以用于致动结合元件的一系列运动，以截取定位在操作工位上的竖立的过滤材料的件的自由端，并将这些自由端朝向包含一剂产品的两个腔室中的一个结合。(A machine for making filter bags (1) for infusion products, comprising: a first rotary conveyor (2), the first rotary conveyor (2) being continuously rotating and having a plurality of first operating stations (4) positioned therealong; each operating station is configured to operate on a corresponding piece (1a) of filter material to further obtain two chambers (1b, 1c) positioned side by side and upright; the machine comprises a second rotary conveyor (6) placed side by side with the first and rotating continuously; the second rotary transmitter has a plurality of coupling elements (7) positioned therealong; each engaging element is connected to a corresponding control device (8, 9) for actuating a series of movements of the engaging element to intercept the free ends of the pieces of filter material standing upright positioned on the operating station and to engage these free ends towards one of the two chambers containing a dose of product.)

1. A machine for making filter bags (1) for infusion products, starting from pieces (1a) of filter material each having two free ends (1d, 1e) and an intermediate portion (1f), between each of said free ends (1d, 1e) and said intermediate portion (1f) there being two chambers (1b, 1c) containing a corresponding dose of product, respectively; the piece (1) advances along a feed line (A) of the machine, which comprises:

-a first rotary conveyor (2), said first rotary conveyor (2) being in continuous rotary motion about a first axis of rotation (2X) and having at least a plurality of first operating stations (4), said plurality of first operating stations (4) being positioned along the first rotary conveyor (2) and being continuously movable with said first rotary conveyor (2), each first operating station (4) being configured to hold and operate on a respective piece (1a) of filter material fed along at least a predetermined section of rotation angle of said first rotary conveyor (2) in order to raise at least said two chambers (1b, 1c) to a side-by-side and upright position, i.e. positioned radially with respect to said first axis of rotation (2X);

it is characterized by also comprising:

-a second movement carousel (6), said second movement carousel (6) being placed side by side with the first carousel (2) and rotating continuously about a second rotation axis (6X) parallel to the first rotation axis (2X); -the second rotary conveyor (6) has a plurality of coupling elements (7), said plurality of coupling elements (7) being positioned along said second rotary conveyor (6) and being continuously movable with said second rotary conveyor (6); each joining element (7) is connected to a corresponding control device (8, 9), said control devices (8, 9) being configured to actuate a series of movements of said joining element (7) in a manner synchronized with the corresponding rotation of said first rotary conveyor (2) and of said second rotary conveyor (6) and at least along a predetermined curved path, so as to intercept said free end (1d, 1e) of the piece (1) of filter material standing up positioned on the operating station (4) and join said free end (1d, 1e) towards one of the two chambers (1b, 1c) containing a dose of product.

2. Machine according to claim 1, wherein said second rotary conveyor (6) has a plurality of said coupling elements (7), the number of said coupling elements (7) being smaller than the number of operating stations (4) present on said first rotary conveyor (2).

3. Machine according to claim 1 or 2, characterized in that said second rotary conveyor (6) rotates at a speed different from and constant to the speed of rotation of said first rotary conveyor (2) and has a direction of rotation (V6) opposite to the direction of rotation (V2) of said first rotary conveyor (2).

4. Machine according to claim 1 or 2, characterized in that said second rotary conveyor (6) rotates at a speed different and variable from the speed of rotation of said first rotary conveyor (2) and has a direction of rotation (V6) opposite to the direction of rotation (V2) of said first rotary conveyor (2).

5. The machine according to any one of the preceding claims, wherein each of the joining elements (7) comprises a gripper for folding the free end (1d, 1e) of a piece (1) of filter material, consisting of two independent first (7a) and second (7b) jaws, the first (7a) and second (7b) jaws being hinged along respective independently rotating axes (X7a, X7b), the axes (X7a, X7b) being parallel to each other and to the second axis of rotation (2X); each of said first and second jaws (7a, 7b) being connected to a corresponding first and second control device (8, 9), said first and second control devices (8, 9) each having at least a first and a second motion-transmission shaft (8a, 9a) connected by a kinematic mechanism to corresponding cam means (10, 11), said cam means (10, 11) being positioned inside said second rotary conveyor (6) so as to allow a synchronous movement of the two jaws (7a, 7b) between at least one inoperative position, in which said two jaws (7a, 7b) are spaced apart, and an operative position for folding/joining the free end (1d, 1e) of the piece (1a) of filter material, the two jaws (7a, 7b) are in contact with each other and project radially from the second rotary transmitter (6).

6. Machine according to claim 5, characterized in that between said first control device (8) and said second control device (9) and said first jaw (7a) and said second jaw (7b) there are interposed corresponding kinematic motion units (23, 24; 28, 29) to allow, at the end of the coupling of the free ends (1d, 1e) of said piece of filter material (1a), the rotation of said first jaw (7a) and said second jaw (7b) away in a rotation direction opposite to the rotation direction (V6) of said second rotary conveyor (6).

7. The machine according to claim 5 or 6, characterized by comprising an operating plate (12), said operating plate (12) being interposed between said second movement carousel (6) and each gripper positioned on said second movement carousel (6); each plate (12) is hinged along an axis (X12) parallel to the second rotation axis (2X); each plate (12) being connected to a corresponding third control device (13), said third control devices (13) having a third shaft (13a) for transmitting dynamic movements connected to cam means (14), the cam means (14) being positioned inside the second rotary transmitter (6), to allow the plate (12) to move at least in sections of its opposite predetermined curved path, rotating between several operating positions along a section of the curved path in a manner synchronized with the rotation of the gripper and of the second rotary conveyor (6), wherein the plate (12) rotates in a direction (V12) opposite to the direction of rotation (V6) of the second rotary conveyor (6), to keep the gripper rotation axis (X7a) at a constant distance from the first rotation axis (2X), at least in the folding operating position of the gripper.

8. Machine according to any one of claims 5 to 7, characterized in that said first jaw (7a) is hinged to an operating plate 12 and has a hinge axis (X7a), and in that said second jaw (7b) has a first hinge point coinciding with the hinge axis (X7a) of said first jaw (7a) and a second hinge point (X7b) spaced at a distance from said first hinge point and connected to a corresponding second control device (9) positioned on said second rotary transmitter (6).

9. Machine according to any one of claims 5 to 8, characterized in that each gripper has the first jaw (7a) with an operating head (15), the operating head (15) having a plate of triangular cross section, the vertex of which is directed towards the second jaw (7b), and in that the second jaw (7b) has an operating head (16), the operating head (16) being shaped so as to define two halves of an intermediate channel (17), the intermediate channel (17) being shaped so as to allow, when approaching a triangular sheet and cooperating therewith, at least a first folding of the portion of piece of filter material (1a) towards the inside of the same piece (1a) with respect to the side edges of the flaps of the superposed free ends (1d, 1 e).

10. The machine according to any one of the preceding claims, comprising a curved contact guide (18), the guide (18) being positioned close to the first rotary conveyor (2), at a predetermined distance (D) from the first rotary conveyor (2), and along its operating path in at least predetermined sections; the guide (18) is positioned close to the area of the free end (1d, 1e) of the piece (1a) of filter material with respect to the first end for intercepting and joining by the joining element (7) so that the formed end of the piece (1a) of filter material is joined until the piece (1a) is released from the first rotary conveyor (2).

11. The machine according to any one of the preceding claims, wherein the first moving rotary conveyor (2) comprises a plurality of gripping elements (3) positioned along the first moving rotary conveyor (2) and moving in succession with the first moving rotary conveyor (2), each first gripping element (3) being configured for holding a respective piece (1a) of filter material being formed; each gripping element (3) is associated with a corresponding first operating station (4).

12. Machine according to any one of the preceding claims, wherein said first moving rotary conveyor comprises a plurality of translation devices (5), said translation devices (5) being associated with said first moving rotary conveyor (2) and being configured for translating a corresponding clamping element (3) along a direction parallel to the first rotation axis (2X) of said first moving rotary conveyor (2) to bring said corresponding clamping element (3) to each piece (1a) of filter material at least on one section of a feed line (A).

Technical Field

The present invention relates to a machine for making filter bags for infusion products such as tea, coffee, chamomile (in powder, granular or leaf form).

The term filter bag can relate to at least two types of filter bags: a single-chamber filter bag comprising, in a minimum configuration, a piece of filter material forming a chamber containing a dose of infusion product; and dual chamber filter bags, which also comprise a single piece of filter paper, but are formed as two separate chambers. Each chamber contains a dose of infusion product. The two chambers are folded towards each other, forming a single top end (in the shape of an inverted "V") and a bottom end in the shape of a "W".

Single and dual chamber filter bags may also be provided with a tag and a string connecting the tag to the filter bag.

Finally, the filter bags described may be provided with a packaging wrap which encloses and closes the individual filter bags hermetically or non-hermetically.

Machines of this type for forming filter bags of the double flap type are known from patent documents EP762973, EP762974 and EP765274 (all of which are filed by the present applicant).

WO 2016/029987 describes a machine according to the preamble of claim 1.

The machine extends along a forming and feeding line comprising:

-a feed station for a strip of filter material advancing along a feed plane;

-a feeding station for affixing a dose of product to the strip of filter material at a predetermined distance;

-a tube station for folding the strip onto itself, wrapping a dose of product and subsequently joining the strip along the longitudinal sides;

-a folding station of a single piece of filter material with double chambers;

-a rotary conveyor with radially extending grippers, the rotary conveyor being positioned below the folding station and configured to receive a single piece of folded filter material; the rotary conveyor rotates in steps about a horizontal axis, rotating each piece of filter material at an operating station, placed and fixed in sequence (series) with respect to the frame of the machine, to attach a rope to the piece of filter material, conveniently wound around the same piece of filter material, and then attaching the labels to the rope in turn.

In some solutions, depending on the type of filter bag to be formed, the machine may (alternatively) have:

-a folding station for holding the open ends of the two chambers of the piece along the path of the rotary conveyor by tying a thread to the piece itself; or

-a further transverse closing station for closing the ends of the closure before or at the same time as the separation of the remaining portion of the strip.

The machine may also comprise an application station for applying a wrapping wrapper to each filter bag placed along the path of the rotary conveyor or at an additional rotary conveyor.

The machine organized in this way operates with discontinuous motion, i.e. with only one step for all stations along the forward line.

This step operation limits the productivity of the machine.

Disclosure of Invention

The aim of the present invention is to provide a machine for forming filter bags for infusion products which has a higher productivity than the machines of the prior art and which maintains a high quality level of the filter bags.

More specifically, the object of the present invention is to provide a machine for forming filter bags for infusion products which takes up less space and has greater flexibility.

These aims are fully achieved by a machine for forming filter bags for infusion products according to the following claims.

Drawings

The invention will now be described with reference to the accompanying drawings, provided as non-limiting examples, in which:

figure 1 shows, in a schematic front view, a machine for forming filter bags for infusion products according to the present invention, with some parts removed so as to highlight other parts;

figures 2 to 5 each show the machine of figure 1 in a corresponding different operating position, all in elevation with some parts removed so as to highlight other parts;

figure 6 shows, in an exploded perspective view, the combined rotary conveyor of a part of the machine of the previous figures;

figure 7 shows an enlarged view of a detail of figure 6;

figure 8 shows a perspective view of a series of control devices of the folding station shown in figures 2 to 7, in combination with a rotary conveyor;

figure 9 shows a perspective view of the filter bag formed by the machine of the previous figures.

Detailed Description

With reference to the figures, a machine according to the invention, generally designated by the numeral 100 in figures 1 to 5, is used for the formation of filter bags 1, the filter bags 1 containing an infusion product such as tea, coffee, camomile in the form of a number of doses of powder, granules or leaves.

In the present description, the term filter bag 1 is intended to denote a so-called double chamber filter bag.

This type of filter bag 1 comprises a single piece 1a of filter material, which defines two separate chambers 1b, 1 c. Each chamber 1b, 1c contains a dose of infusion product. The two chambers 1b, 1c are folded towards each other, forming a single top end (in the shape of an inverted "V") and a bottom end in the shape of a "W".

This type of filter bag may be provided with a gripping tag and a string connecting the tag to the folded filter bag 1 (tag and string are not shown).

An outer wrapping wrap may be added which encloses and encloses each separate folded filter bag 1.

The main purpose of the machine 100 of the invention is to form the geometry of at least the double-chambered filter bag 1 by leaving the piece 1a of filter material and treating it as required.

The machine 100 concerned can be used independently or as part of a more complex set of machines, if necessary with additional operating stations that perform the requested operations (application of ropes and labels, and/or application of outer wrapping, etc.) on pieces or filter bags of filter material, while the machine remains running continuously.

The machine 100 for forming filter bags 1 for infusion products operates on the basis of pieces 1a of filter material, each piece 1a of filter material having two free ends 1d, 1e and one intermediate portion 1f (which will eventually form the bottom end of a "W").

Between each free end 1d, 1e and the intermediate portion there are respectively two chambers 1b, 1c containing respective doses of product.

Each piece 1a moves forward along the forward line a.

As shown, the machine 100 comprises a first rotary conveyor 2 with continuous rotary motion about a first axis of rotation 2X.

The machine 100 comprises a plurality of first gripping elements 3, the plurality of first gripping elements 3 being positioned along the first moving rotary conveyor 2 and being continuously movable therewith.

Each clamping element 3 is configured for holding a respective piece 1a of filter material being formed.

The machine 100 also comprises a plurality of first operating stations 4, these first operating stations 4 being positioned along the first moving rotary conveyor 2 and being continuously movable therewith.

Each first operating station 4 is associated with a corresponding first gripping element 3.

Each first operating station 4 is configured to operate on a piece 1a of filter material so as to at least partially form a filter bag 1 along a predetermined angular section of the first moving rotary conveyor 2.

Advantageously, the first operating station 4 cooperates with the corresponding first clamping element 3 to hold the respective piece 1a of filter material being formed.

The machine 100 further comprises a plurality of translation devices 5, the translation devices 5 being associated with the first moving rotary conveyor 2 and configured for translating the first operating stations 4 and the corresponding first gripping elements 3 with respect to each other along a direction parallel to the rotation axis 2X (the first stations 4 schematically shown herein, depicted in fig. 2-5).

In essence, the basic concept of the machine 100 is that it comprises a plurality of operating units, all of which perform the same operation on pieces of filter material, independently of each other and in continuous motion about an axis of rotation.

With this configuration, a large number of pieces of filter material can be intermediately operated on the filter bag in a short period of time and in a reduced space (angular section).

Positioned on the first rotary conveyor 2 are a plurality of first operating stations 4, a corresponding plurality of gripping elements 3 and a plurality of translation devices 5.

In the example shown, a piece of tubular filter material is fed to the first moving rotary conveyor 2 and the operating station is a folding station for folding, i.e. erecting, the piece to form a filter bag, still free of cords and tags.

Thus, the first operating station 4 can be configured to rotate at least a predetermined rotation angle section of the conveyor 2 along the first movement, to perform intermediate operations on the piece 1a of filter material (folding and erecting the piece), or alternatively to perform finishing operations on the basis of one piece of filter material and to form a complete filter bag 1 (applying strings and labels to the folded and closed piece).

From these examples it can be seen that the proposed solution has the feature of high operational flexibility combined with high productivity.

Due to the structure of the units, each unit is composed of gripping elements, operating stations and translation devices distributed along the rotary conveyor, whereby it is possible to simplify the actuators and the control groups and preferably bring them together in the vicinity of the rotation axis, thus reducing the bulk of the machine while maintaining a high operating precision.

In the particular case illustrated here, the machine 100 according to the invention is capable of producing (as described above) dual-chambered filter bags based on a continuous tubular strip of filtering material containing a dose of product placed in series.

In particular, the task of the machine 100 shown here is to define double-lobed pieces and fold them into an upright shape, in which the top end is joined and the bottom end is already "W" shaped.

According to what is shown in figure 1, a continuous strip of tubular filter material with a sequence of doses of infusion product, placed at a distance from each other, is fed to the first rotary conveyor 2.

The continuous strip advances in a continuous manner along an advancement line a in an advancement direction V2 towards a first rotary conveyor (which has a rotation direction V2).

The machine 100 may include a plurality of cutting elements 70, the plurality of cutting elements 70 being positioned on the first motion rotary conveyor 2 and being rotationally movable therewith. Each cutting element 70 is positioned between and associated with the first operating station 4 and a corresponding first clamping element 3 (here shown schematically in figures 2-5).

The cutting element 70 is configured for separating a continuous strip of filter material, so as to obtain a single piece 1a of filter material, the piece 1a of filter material having two free end portions 1d and 1e and an intermediate portion 1f (as previously mentioned, the intermediate portion 1f will become the bottom of the filter bag 1 being formed). Between each free end 1d and 1e and the intermediate portion 1f there are two respective chambers 1b, 1c containing respective doses of product.

It should be noted that the first motion rotary conveyor 2 rotates in a continuous clockwise motion (direction V2).

According to the illustrations, each operating station 4 (in phase coordination with the gripping elements 3 and the translation device 5) is configured to hold and operate on a respective piece 1a of filter material fed along at least a predetermined rotation angle section of the first moving rotary conveyor 2, so as to raise at least the two chambers 1b, 1c to a side-by-side and upright position, i.e. positioned radially with respect to the first rotation axis 2X, and with the respective free ends 1d, 1e positioned alongside one another and away from the first rotary conveyor 2.

Each first station 4 comprises a raising element 21 to raise the piece 1a of filter material.

According to the illustration, the machine 100 comprises a second motion carousel 6, the second motion carousel 6 being positioned side by side with the first motion carousel 2 and rotating continuously about a second rotation axis 6X parallel to the first rotation axis 2X.

The second rotary conveyor 6 has a plurality of coupling elements 7, the plurality of coupling elements 7 being positioned along the second rotary conveyor 6 and being continuously movable therewith.

Each joining element 7 is connected to a respective control device 8 and 9, the control devices 8 and 9 being configured to provide a series of movements of the joining element 7, in a manner synchronized with the respective rotation of the first rotary conveyor 2 and the second rotary conveyor 6 and at least along a predetermined curved section, so as to intercept the free ends 1d, 1e of the piece 1a of filter material standing upright positioned on the operating station 4 and join the free ends 1d, 1e towards one of the two chambers 1b, 1c containing a dose of product.

Essentially, the machine 100 comprises at least two rotary conveyors positioned side by side and in succession and in synchronous movement with each other: the first rotary conveyor takes up and confines the piece of filter material and then raises it to a position radially projecting from the first rotary conveyor; the second rotary conveyor intercepts the single piece during rotation and carries out the coupling of the free ends of the two chambers with the dose.

As will be shown in the following description, the term "coupling" is defined as the operation by corresponding elements allowing temporary or permanent closure of the chamber (by operating on the open free end), ensuring that the chamber containing the dose remains sealed during the subsequent steps of transferring and manipulating the above-mentioned pieces.

More specifically, in the present description, the term "bonding" refers in particular to a step in which the free end is folded so as to ensure the closure of the chamber, but this does not exclude that the operation obtained by the solution that is the subject of the invention can be obtained by another type of bonding.

Preferably, the second rotary conveyor 6 has a plurality of coupling elements 7, the number of coupling elements 7 being smaller than the number of operating stations 4 present on the first rotary conveyor 2 (see fig. 1).

Preferably, the second rotary conveyor 6 rotates at a different (preferably higher) and constant speed with respect to the rotation speed of the first rotary conveyor 2, and its direction of rotation V6 is opposite (counter-clockwise) to the direction of rotation V2 of the first rotary conveyor 2.

In an alternative solution, the second rotary conveyor 6 rotates at a speed different and variable from the speed of rotation of the first rotary conveyor 2 and has a direction of rotation V6 opposite (anticlockwise) to the direction of rotation V2 of the first rotary conveyor 2.

In the second case, the acceleration and deceleration of the second rotary conveyor can vary at the tangent and at the contact point where the joining element brings itself close to, joins and separates with respect to the piece of filter material.

In the rest of the present description, an embodiment of the machine will be described in which the second rotary conveyor has a joining element that folds the end of the piece of filter material, but this by no means limits the scope of protection of the invention. Therefore, in the rest of the description, the element 7 will be indicated as folded element 7.

As already mentioned above, the elements present on the second rotary conveyor may have, alone or in combination with the folding elements, joining means (heat or ultrasonic sealing) to join the ends of the piece of filter material.

In the case shown, each coupling element 7 comprises a gripper consisting of two separate first 7a and second 7b jaws, the first 7a and second 7b jaws being hinged along respective independently rotating axes X7a, X7b, the axes X7a, X7b being parallel to each other and to the second axis of rotation 2X.

Thus, each first 7a and second 7b jaw is connected to a corresponding first 8 and second 9 control device.

Each first control device 8 and second control device 9 has at least a first motion transmission shaft 8a and a second motion transmission shaft 9a connected by a kinematic mechanism to corresponding cam means 10 and 11, the cam means 10 and 11 being positioned inside the second rotary conveyor 6 so as to allow a synchronous movement of the two jaws 7a, 7b between at least one inoperative position, in which the two jaws 7a, 7b are spaced apart (fig. 2), and an operative position for engaging the free ends 1d and 1e of the piece 1a of filter material, in which the two jaws 7a, 7b are in contact with each other and project radially from the second rotary conveyor 6 (fig. 3).

It should be noted that the machine 100 comprises an operating plate 12 interposed between the second kinematic rotary conveyor 6 and each gripper positioned on the second kinematic rotary conveyor 6.

Each plate 12 is therefore hinged along an axis X12 parallel to the second rotation axis 6X.

It should be noted that each plate 12 is connected to a corresponding third control device 13, the third control device 13 having a third motion-transmission shaft 13a connected to a cam device 14 by means of a kinematic mechanism, the cam device 14 being placed inside the second rotary conveyor 6 so as to allow the plate 12 to rotate, at least in a section of its opposite predetermined curved path, along a section of the curved path in a synchronized manner with the rotation of the grippers and of the second rotary conveyor 6, between several operating positions, in which the plate 12 rotates in a direction V12 opposite to the direction of rotation V6 of the second rotary conveyor 6, so as to keep the axis of rotation X7a of the grippers at a constant distance from the first axis of rotation 2X, at least in the folded position of the grippers.

In other words, the plate 12 allows to adjust the position of the gripper with respect to the first rotary conveyor 2 (and with respect to the sheet of filter material) during the corresponding rotation and to bring the gripper itself into correct contact with the end to be folded.

It should be noted that each gripper and each operating plate 12 are positioned on staggered vertical planes and parallel to the front surface of the second rotary conveyor 6 so as to protrude therefrom.

Preferably, the first jaw 7a is hinged to the operating plate 12 and has its hinge axis X7 a.

In light of this, the second jaw 7b has a first hinge point coinciding with the hinge axis X7a of the first jaw 7a (so as to allow correct access to the distance between their operative ends and their operative ends) and a second hinge point X7b, X7b distanced from (staggered) the first hinge point, the second hinge point X7b being connected to a corresponding second control device 9 positioned on the second rotary transmitter 6.

This geometry of the jaws 7a and 7b, as will be shown below, allows correct folding of the end of the piece of filter material and quick release/separation of these jaws with respect to the first rotary conveyor once folding is completed.

Preferably, each gripper has a first jaw 7a with an operating head 15, the operating head 15 having a plate with a triangular cross-section, the vertex of which is directed towards a second jaw 7b, see fig. 7. In light of this, each second jaw 7b has an operating head 16, the operating head 16 being shaped so as to define two half-parts of an intermediate channel 17, the intermediate channel 17 being shaped so as to allow, when approaching and cooperating with a triangular plate, at least a first folding of the side edges of the flaps (flaps) of the free ends 1d, 1e of the pieces 1a with filter material partially superposed against each other, towards the inside of the same piece 1a (see fig. 9). In particular, the lateral edge is folded towards the outer surface of one of the two chambers of the piece of filter material containing the dose of product.

Again according to the illustration of fig. 7, the second jaw 7b comprises two half-heads 19, the two half-heads 19 presenting a prismatic counter-facing shape along corresponding surfaces inclined and spaced apart from each other, so that the passage 17 is created with the portion of closest reciprocal (reciprocal) approach in the area below the second jaw 7 b.

Preferably, the machine 100 comprises a curved contact guide 18, the guide 18 being positioned close to the first rotary conveyor 2, at a predetermined distance D from the first rotary conveyor 2 and for at least a predetermined section along its operating path.

In light of this, the guide 18 is positioned with its first extremity close to the region for intercepting and joining the free ends 1d and 1e of the piece 1a of filter material by the folding element 7, so that the formed end of the piece 1a of filter material is folded until the piece 1a is released from the first rotary conveyor 2.

Essentially, the guide 18 is positioned downstream (with respect to the direction of rotation V2) of the region in which the end of the piece 1a of filter material is folded and is distanced from the first rotary conveyor 2 by a distance D at least equal to the dimension of the piece of filter material (calculated along the longitudinal section of the erected piece of filter material) for which the end has been folded.

In this way, the folded end of the piece 1a of filter material is retained by the guide 18 during its transit along the section, while the guide 18 is present to prevent the flexible (pliable) end from returning outwards until the piece 1a reaches the area of the first rotary conveyor 2 where the piece 1a is released or further processed.

It should be observed that the presence of the guides 18 determines the necessity of an additional movement of each gripper at the end of the folding step.

In fact, each folding element comprises, between the first control device 8 and the second control device 9 and the first jaw 7a and the second jaw 7b, a corresponding kinematic motion group 23, 24 and 28, 29 to allow the first jaw 7a and the second jaw 7b of the first rotary conveyor to rotate away in a rotation direction opposite to the rotation direction V6 of the second rotary conveyor 6 at the end of the folding (or joining) of the free ends 1d and 1e of the piece 1a of filter material.

As a non-limiting example, fig. 6 and 7 show the control devices 8, 9 and 13 of the pair of claws 7a and 7b and the operation plate 12.

The first control device 8 of the first jaw 7a comprises the jaw 7a to the articulated arm 40 of the operating plate 12 (defining an axis of articulation X7 a).

The arm 40 is fitted to the first gear 22 rotatably supported by the operation plate 12.

The first toothed wheel 22 is part of a set of three toothed wheels 22, 23, 24 (one of which, the intermediate toothed wheel 23, is idle), the three toothed wheels 22, 23, 24 being meshed together and all positioned on the plate 12 to transmit the motion from the shaft 8a to the first jaw 7 a. The configuration of the three-wheel set also allows the first jaw 7a to rotate in the opposite direction to the second wheel 6 with the operating plate 12 fixed.

The third toothed wheel 24 is fitted to the end of the above-mentioned shaft 8a, the shaft 8a passing inside a (tubular) shaft 13a of a part of the control device 13 of the plate 12.

Inside the second rotation transmitter 6, at the end of the shaft 8a there is another fourth toothed wheel 25. The fourth toothed wheel 25 meshes with a first curved toothed segment 26 mounted to a third shaft 27 (having an axis extending parallel to the second rotation axis 6X), and the fourth toothed wheel 25 is positioned inside the second rotary transmitter 6.

The end of the third shaft 27 is provided with a cam follower roller 48, the cam follower roller 48 being in orbital contact with the annular cam 10 of a part of the second rotary conveyor, thereby providing the movement of the first pawl 7 a.

The second control device 9 of the second jaw 7b comprises a crank system with a crank 28 and a rod 29, wherein the crank 28 is articulated with a flange 29a of the second jaw 7 b.

One end of the lever 29 is hinged to the crank 28 and the other end is hinged to the second shaft 9a (the axis of which extends parallel to the second rotation axis 6X), thus determining the effective axis of articulation X7b of the second jaw 7 b.

The second shaft 9a has a fifth toothed wheel 30 fitted at its end inside the second rotary transmitter 6. The fifth toothed wheel 30 meshes with a second curved toothed segment 31 fitted to a third shaft 32, the axis of which extends parallel to the second rotation axis 6X, and is positioned inside the second rotary transmitter 6.

The end of the third shaft 32 is provided with a cam follower roller 33, the cam follower roller 33 being in orbital contact with the other annular cam 11 of a part of the second rotary conveyor 6, thereby providing the movement of the second claw 7 b.

In the above crankshaft system, the second jaw 7a can also rotate in the opposite direction to the second wheel 6, with the operating plate 12 also fixed, and synchronously with the first jaw 7a, for a step separate from the first rotary transmitter 2. The third control device 13 of the plate 12 comprises a shaft 13a, the shaft 13a being firmly attached to the plate 12 and the shaft 13a running inside the second rotary conveyor 6. The tubular shaft 13a has a sixth toothed wheel 34, the sixth toothed wheel 34 being fitted to the inner end of the shaft 13a and being located in the vicinity of the fourth toothed wheel 25 positioned on the shaft 8 a.

The sixth toothed wheel 34 meshes with a third curved toothed segment 35 fitted to a fourth shaft 36 (the axis of which extends parallel to the second rotation axis 6X) and positioned inside the second rotary transmitter 6.

The end of the fourth shaft 36 is provided with a cam follower roller 37, and the cam follower roller 37 is in orbital contact with the annular cam 14 of a part of the second rotary conveyor 6, thereby providing rotation of the operating plate 12.

This configuration of each folding element 7 allows a series of movements (coordinated and always performed during the continuous rotation of the second rotary conveyor and in predetermined sections) which can be summarized as follows, starting from the starting position shown in fig. 2, in which:

the gripper is in the inoperative position, with the first jaw 7a separated from the second jaw 7b, and both jaws projecting from the second rotary conveyor 6 together with a portion of the operating plate 12;

the (continuous) rotation of the second rotary conveyor 6 and the adjusted rotation of the plate 12 bring the ends 1d and 1e of the gripper intercept 1a, more specifically the coordination between the two rotations of the first rotary conveyor 2 and of the second rotary conveyor 6, to bring the second jaw 7b into a position below the ends 1d and 1e and slightly close to the first jaw 7a, while the first jaw 7a moves close to the second jaw 7b to obtain the folding of the ends 1d and 1e according to the series of folding described above and shown in fig. 9 (see fig. 3);

after folding, the two jaws 7a, 7b have an opposite, partial, movement away from each other to allow the folded end of the piece 1a to be released just before reaching the initial extremity of the contact guide 18 (see fig. 4);

after the step of releasing the folded end, the two jaws 7a and 7b are rotated (with the plate 12 fixed) in the direction opposite to the direction of rotation of the second rotary conveyor 6, to avoid contact between the gripper and the guide 18 (see fig. 5) and to facilitate the insertion of the folded end into this guide 18.

During the remaining part of the curved path, the folding elements will be repositioned into their starting configuration, as shown in fig. 2.

The set aims can be fully achieved thanks to the structure of the machine described herein.

In fact, the machine according to the invention will be very flexible, constructable and have a high productivity with respect to the type of filter bag to be made.

It should be noted that each operation on the piece of filter material or filter bag is no longer related to the time during which the machine is stationary (as opposed to a machine operating in steps) and their duration is independent of each other. Thus, the time for performing the operation can be extended or shortened as desired (in this case, for example, folding the piece of filter material and sealing the free end) simply by using a longer or shorter rotary section of the movement rotary conveyor.

Each element can operate on a piece of filter material along a shorter curved path of the rotary conveyor and it is possible to start the operation immediately, thus reducing the fixing time spent and reducing the bulk of the machine.

By this construction, a high operating flexibility is obtained, since the described joining elements can be replaced by or combined with thermal or ultrasonic sealing elements to obtain the sealing of the pieces during each transport thereof.