Machine for assembling filter bags for infusion products

Abstract

A machine for consolidating filter bags (1) for infusion products is described, said machine comprising a moving wheel (2) rotatable about a first axis of rotation (X2), a transfer wheel (3) rotating synchronously with the moving wheel (2) about a second axis of rotation (X3), a device (4) for collecting the filter bags (1), a number of gripping elements (5) arranged along the circumference of the transfer wheel (3) and movable together with the transfer wheel (3) between a pick-up arrangement for picking up the filter bags (1) from the moving wheel (2) in a first angular position and a release arrangement for releasing the filter bags (1) to the collecting device (4) in a second angular position after an angular section of rotation (TA) has been moved along the feed direction (A), and a device for collecting defective filter bags (1). , sensor means (7) configured to detect possible defects in the filter bag (1) so as to identify it before it reaches the second angular position in which the collecting device (4) is arranged, and a rejection area (8) configured to receive a defective filter bag (1D), the rejection area (8) being arranged downstream of the collecting device (4) and upstream of the first angular position with respect to the feed direction (A), the machine also comprising lock control means (9) configured to control said gripping elements (5) to prevent release of the filter bag (1D) in the second angular position when the gripped filter bag (1D) is detected as defective by the sensor means (7).

Description

[Technical field]

[0001] The present invention relates to a machine for assembling filter bags for infusion products such as tea (in powder, granule or leaf form), coffee, chamomile, etc. [Background technology]

[0002] The term filter bag is used to indicate at least two types of filter bags: single-chamber filter bags, which in a minimal configuration comprise a piece of filter material forming a chamber that contains a dose of infused product, and double-chamber filter bags, which also comprise a single piece of filter paper, but in which the piece of filter paper forms two separate chambers, each chamber containing a dose of infused product. The two chambers are folded towards each other to form a single upper end (in the shape of an upward facing "V") and a lower end in the shape of a "W".

[0003] The single and dual chamber filter bags may also include a tag and a tie string connecting the tag to the filter bag.

[0004] Finally, an overwrap packaging material may be added to the filter bag to encase and close the single filter bag in an airtight or non-airtight manner.

[0005] A machine for manufacturing filter bags for infusion products of this kind is known from patent document WO 2017 / 145044.

[0006] The machine is continuously movable, which allows a higher productivity than that of stepped machines while maintaining a high quality of the filter bags.

[0007] The machine of this solution comprises at least a continuously rotating carousel having on its circumferential surface a plurality of first gripping elements for holding respective pieces of filter material being formed, and a plurality of stations associated with corresponding first gripping units and configured to act on the pieces of filter material to partially or completely form a filter bag along at least one predetermined angular section of the rotation of the moving carousel.

[0008] The basic concept of the machine is therefore that it comprises a number of working units, all performing the same operation on the pieces of filter material, and all working units are driven independently of each other and continuously about their axes of rotation.

[0009] Once work on a piece of filter material is completed, the gripping unit corresponding to each work station arrives at the outfeed area of ​​the moving carousel and releases it so that the piece can be transferred to a subsequent processing step / station, e.g. a further moving carousel.

[0010] As mentioned above, depending on the type of filter bag being formed, a single carousel defining the machine, or several carousels successive to one another and having a structure similar to that described above, defining the entire machine, result in the definitive formation of filter bags, the latter of which must then be transferred to a collection or stacking area, or, in case of defects, released to a collection area for defective products different from the previous area.

[0011] For this reason, there is a need to provide an operational unit that can operate at the same high speeds as the carousel present in the machine to pick up filter bags from the carousel, and at the same time, can eject defective filter bags and release them into a collection or stacking area.

[0012] A solution of a working unit for releasing filter bags is known from patent document WO 2019 / 087012, which describes a transfer wheel rotating in a continuous motion with a plurality of gripping devices arranged along the transfer wheel and each configured to receive a filter bag from a corresponding working station and to release the filter bag to an area for collecting the filter bag, each gripping device being movable between a first working position for receiving a filter bag from a preceding carousel or releasing the filter bag to a collection area, and a second working position for holding the filter bag.

[0013] There is also a control unit configured to measure defects in the filter bags formed on the preceding carousel, and an auxiliary control device disposed on the transport wheel and connected to the control unit.

[0014] The auxiliary device enables the selected gripping device to release the defective filter bag at a signal from the control unit into an unloading area arranged in front of the collection area relative to the direction of rotation of the wheel.

[0015] It has been noted that the location of the defective filter bag unloading area relative to the collection area is along a section of reduced rotation angle, which may result in a delayed response of the auxiliary devices to carry the defective bag beyond the unloading area or even to the collection area at high production speeds of the machine. Summary of the Invention

[0016] It is therefore an object of the present invention to provide a machine for assembling filter bags for infusion products in a continuous motion, which can complete the cycle for forming the filter bags in a fast and accurate manner and which allows the filter bags to be safely stored.

[0017] More specifically, the object of the present invention is to provide a machine for assembling filter bags for infusion products, which is capable of selecting and rejecting unsuitable filter bags with high safety, while maintaining a high flexibility and reduced size at high operating speeds of the machine.

[0018] Said object is fully achieved by a machine for forming filter bags for infusion products as claimed in the appended claims. [Brief description of the drawings]

[0019] The present invention will be described with reference to the accompanying drawings, which are provided as examples only and not as limiting the scope of the invention. [Figure 1-3] 1 shows schematic front views of a transfer wheel forming part of a machine for assembling filter bags for infusion products according to the invention, in three corresponding different working configurations; [Figure 4] FIG. 2 is a perspective view from below of the device for collecting the filter bags of the previous figures; [Diagram 5] FIG. 5 is a partial perspective view from above of the collection device of FIG. 4. [Figure 6] FIG. 4 is a perspective view of an extraction body forming part of the exclusion area of ​​the machine of FIGS. 1 to 3; [Figure 7] FIG. 4 is a perspective view, with parts cut away to better illustrate other parts, of details of a gripping element forming part of the transfer wheel of FIGS. 1 to 3; [Figure 8] FIG. 2 is a perspective view, partly cut away to better illustrate other parts, of the gripping device of the transport wheel of the previous figure, connected to the first and second control means; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] With reference to the accompanying drawings, and in particular to Figures 1 to 3, the machine according to the invention, generally labelled 100, is used to manufacture and pack filter bags 1 containing infusion products such as tea, coffee, chamomile, etc., dosed in powder, granule or leaf form.

[0021] The term "filter bag" may be used to refer to at least two types of filter bags.

[0022] The first type, known as single chamber, comprises a piece of filter material forming a single chamber which contains a dose of the infused product.

[0023] The second type of filter bag, known as a double chamber, comprises a single piece of filter material forming two separate chambers, each containing a single dose of infusion product. The two chambers are folded towards each other to form a single upper end (in the shape of an upward facing "V") and a lower end in the shape of a "W".

[0024] These two types of filter bags may be equipped with a grip tag and a tie string that connects the tag to the formed filter bag 1 .

[0025] An outer overwrap packaging material may also be added to enclose each single filter bag 1 formed.

[0026] The machine 100 according to the invention starts from the concept that various types of filter bags, including those mentioned above, can be obtained (from the simpler single-chamber filter bags to the more complex double-chamber bags with tie strings and tags in the overwrap packaging material) and, if necessary, adds work stations designed to carry out the required operations on the pieces of filter material or filter bags (such as folding and / or applying tie strings and tags and / or applying an outer overwrap packaging material) while maintaining a continuous process of the machine.

[0027] The machine 100 for forming and assembling filter bags 1 for infusion products (starting from pieces of filter material each having at least one dose of infusion product) comprises a moving wheel 2 which can be operated in rotation (preferably in continuous motion) about a first axis of rotation X2.

[0028] The machine 100 also comprises a transfer wheel 3 which can be operated in rotation about a second axis of rotation X3 parallel to the first axis of rotation X2 in synchronism with the moving wheel 2 (preferably in a continuous movement).

[0029] In the illustrated configuration, the moving wheels 2 are at a lower level than the transfer wheels 3. The machine 100 also comprises a device 4 for collecting the filter bags 1 (in this case the formed filter bags), arranged in close proximity to the transfer wheels 3 and configured to receive the filter bags 1.

[0030] The machine also comprises a number of gripping elements 5 (here only one is shown by way of example) arranged along the circumference of the transport wheel 3 and movable therewith.

[0031] Each gripping element 5 is configured to pick up a filter bag 1 from the moving wheel 2 in a first angular position and to release the filter bag 1 to the collection device 4 in a second angular position after an angular section of rotation TA has been moved along the feed direction A.

[0032] Furthermore, the machine 100 comprises sensor means 7 (in this case arranged upstream of the device 4 for collecting the formed filter bag 1, relative to the feed direction A), which is configured to detect possible defects in the filter bag 1 so as to identify a defective filter bag 1D before it reaches the above-mentioned second angular position in which the collecting device 4 is arranged (Figure 1).

[0033] The machine 100 also comprises a rejection area 8 configured to receive defective filter bags 1D.

[0034] With this in mind, the exclusion area 8 is located lower than the collection device 4 .

[0035] As shown, the exclusion area 8 is located downstream of the collection device 4 and upstream of a first angular position relative to the feed direction A.

[0036] As shown again, the machine 100 comprises a lock control means 9 configured to control the gripping element 5 to prevent releasing the filter bag 1D in the second angular position, i.e. to the collection device 4, if the gripped filter bag 1D is detected as defective by the sensor means 7.

[0037] More specifically, the lock control means 9 is configured to control the gripping element 5 gripping the defective filter bag 1D to release it only after it has passed a second angular position along the feed direction A, whereby the defective filter bag 1D is released into the exclusion area 8 downstream of the collection device 4.

[0038] As can again be seen, the collection device 4 is positioned adjacent to the transfer wheel 3 and is provided with a bottom opening 4b sized to pass the gripping element 5 as it passes along said second angular position.

[0039] In other words, the machine is equipped with transport wheels that can quickly, rapidly and accurately move the filter bags to a storage area and at the same time selectively perform the rejection of filter bags that are deemed defective without slowing down the working speed of the machine.

[0040] As described in more detail below, the wheel structure allows the gripping unit to always pass past the collection device even if a defective bag is present, which will be lowered into a rejection area after passing the collection device.

[0041] In short, the basic concept of the machine 100 is that it comprises one or more wheels, each with a working unit that all performs the same operation on the pieces of filter material, all independent of each other and driven continuously about their axis of rotation.

[0042] Such an arrangement makes it possible to obtain intermediate operations or completed filter bags for a large number of pieces of filter material per unit of time in a more reduced space (angular cross section).

[0043] The present invention describes diagrammatically two wheels 2 and 3 forming part of the machine 100, which may be the last working wheels along the feed line A of the machine 100, combined with a single carousel for forming filter bags, or combined with a series of carousels connected in series with each other and rotating to complete the filter bag 1.

[0044] As shown again, the collection device 4 comprises two opposing vertical walls 11 and 12 arranged at a distance D so as to contact opposing sides of the filter bag 1, and a base 13 configured to support the bottom of the filter bag from below.

[0045] In consideration of this, the base 13 is provided with a bottom opening 4b.

[0046] It should be noted that the base 13 of the collection device 4 is arranged horizontally and substantially perpendicular to the spokes of the transport wheel 3 .

[0047] It should be noted that each gripping element comprises a gripper 5 consisting of two jaws 5a, 5b for holding a filter bag 1 and coupled on the transfer wheel 3. Each gripper 5 is connected to gripper control means 6 configured to rotate the two jaws 5a, 5b between a gripping or release position in which the two jaws 5a, 5b are spaced apart from one another (FIGS. 1 and 3) and a position for holding the filter bag 1 in close proximity with the filter bag 1 therebetween, holding the filter bag 1 over time along an angular interval TA of rotation at least between a first and a second angular position (FIG. 2).

[0048] It should be noted that the gripping element 5 is also configured and operable such that, when releasing a filter bag 1 into the collection device 4, the gripping element 5 pushes further filter bags already positioned in the collection device 4 along the accumulation direction (indicated by the arrow in FIG. 2) to create space for the filter bag being released in each case.

[0049] With this in mind, one of the two claws 5a and 5b is configured to push a further filter bag arranged in the collection device 4 along the accumulation direction.

[0050] With this in mind, the angular interval TA of rotation along the feed direction A by each gripping element 5 between the first and second angular positions is less than 180°.

[0051] Preferably, the transfer wheel 3 has a direction of rotation V3 opposite to the direction of rotation V2 of the transfer wheel 2.

[0052] It should be noted that the sensor means 7 comprises at least one sensor (video camera) configured to detect defects in the filter bag picked up by the gripping element 5, and a processing unit 17 connected to the sensor for receiving a signal from the sensor that a defective filter bag 1D has been picked up by the gripping element 5 and to the lock control means 9 for sending a lock activation signal to said lock control means 9 so as to prevent the gripping element 5 from releasing the defective filter bag 1D in the second angular position.

[0053] In the accompanying drawings the sensors are shown merely as an example on the moving wheel 2 and may also be located on a carousel forming part of the machine or on a leading working wheel.

[0054] 7 and 8 show a single gripping element 5, gripper control means 6 and lock control means 9.

[0055] The gripper control means 6 is a first kinematic unit 18 comprising at least two cam follower rollers 18a configured for the movement (rotation) of one of the two jaws 5a of the gripper 5 and movable along a corresponding track 18c having a cam profile (visible in FIG. 8 ); a second kinematic unit 19 comprising at least one cam follower roller 19a configured for the movement (rotation) of the other jaw 5b of the gripper 5 and movable along a corresponding track 19c having a cam profile; a third kinematic unit 20 configured for a radial movement of the gripper 5 relative to the axis of rotation X3 of the transfer wheel 3 and comprising a pair of cam follower rollers 20a movable along a corresponding track 20c having a cam profile; and a fourth kinematic unit 21 configured to enable tensioning of at least the second kinematic unit 19 and comprising a movable cam follower roller 21a in a track having a cam profile (not shown) having an opposite path to the cam profile of the second kinematic unit 19.

[0056] The first three kinematic units 19, 20, 21 are connected to the jaws 5a, 5b via a connecting rod system 22 which allows to obtain a mixed rotational-translational movement of the jaws 5a, 5b while the gripper 5 performs an angular movement along its circular trajectory.

[0057] As shown in Figures 7 and 8, the second kinematic unit 19 comprises a further cam follower roller 19b arranged at a different height along the rotation axis of the first roller 19a.

[0058] This further cam follower roller 19b slides along a similar cam track section (not shown) to the track followed by the first cam follower roller 19a when the correct filter bag 1 is present in the gripper 5.

[0059] In case of a defective filter bag 1D picked up by the gripper 5, the sensor 7 sends a signal to the processing unit 17, which activates the second control means 9. The second control means 9: a kinematically connected control device 23; and a sector 24 of the auxiliary cam track which is tiltable or rotatable and configured to interrupt a further cam follower roller 19b of the second kinematic unit 19 so as to nullify the movement imparted by the first cam follower roller 19a and prevent the opening movement of the jaws 5b of the gripper 5 at least during an angle lock interval TAB starting from the second angular position.

[0060] The sector 24 of the auxiliary cam track has a limited deployment and deactivates the first roller 19a over an angular section of a path of several degrees and then releases the first cam follower roller 19a again, allowing the gripper 5 to return to normal operation.

[0061] Essentially, the position of the grippers 5 along the circumference of the transport wheel 3 can be summarised thus, with reference to FIG.

[0062] The position of the gripper 5 with the correct filter bag 1 is From the pick-up position (first angular position) to the release position (second angular position), i.e. in the angular section TA, the gripper 5 is in a position for holding the filter bag, From the second angular position (unloading the filter bag 1) to the third angular position, the gripper 5 is in an open position (angular section TA1) for passing through the collecting device 4 and releasing the filter bag 1, From the time the third angular position is reached until the fourth angular position (close to the exclusion area 8), the gripper 5 returns to the closed holding position (section TA2), but can also remain in the open position; Close to the exclusion area 8, i.e. at the end of the angular interval TA2 (fourth angular position), the gripper 5 performs a claw opening movement for the angular interval TA3, which again ends at the first angular position, in order to pick up a new filter bag 1.

[0063] The position of the gripper 1 with the defective filter bag 1D is From the pick-up position (first angular position) to the release position (second angular position), i.e. in the angular section TA, the gripper 5 is in a position for holding the defective filter bag 1D, activating the control means 9 for locking the opening of the gripper 5 (locking the defective filter bag 1D to the gripper 5) from the second angular position during an angle locking interval TAB, which ends after the angle interval TA1, so as to completely lock the opening of the gripper 5 even during the passage through the collecting device 4; reactivating the path of the gripper 5 from the end of the angular locking position to a fourth angular position (close to the exclusion area 8), the gripper 5 remaining in a closed holding position (part of section TA2); Close to the exclusion area 8, i.e. at the end of the angular interval TA2 (fourth angular position), the gripper 5 performs an opening movement of the claws 5a, 5b with the release of the defective filter bag 1D into the exclusion area 8, and then continues over the angular interval TA3 which ends again at the first angular position for picking up a new filter bag.

[0064] As shown in Figures 4 and 5 and described above, the two opposing vertical walls 11 and 12 and the base 13 of the collection device 4 define a C-shaped channel.

[0065] The collection device 4 is configured and sized to be passed by the gripping element 5 when the gripping element 5 passes along the second angular position described above.

[0066] With this in mind, the collection device 4 comprises a head end having a front inlet portion 4a configured for the front inlet of the filter bag 1 transported by the gripping element 5, and a bottom opening 4b configured for the downward outfeed of the gripping element 5 which may be in a released position or may be locked in a second holding position if a defective filter bag 1D is present.

[0067] It should be noted that the two opposing vertical walls 11, 12 each have a tab 14 that projects towards the bottom opening 4b. The tabs 14 have a sloped profile (so as to define an inlet where the retained filter bag 1 enters the channel C) and are configured to interfere with and temporarily fold the outer edge or side of the filter bag 1 that enters the device 4 (see FIG. 5).

[0068] Furthermore, the collection device 4 has a bottom opening 4b formed in the bottom of the channel C.

[0069] The above-mentioned base 13 of the collection device 4 is formed by a pair of spaced apart flat elements with a bottom opening 4b therebetween, each of which extends from one of the two vertical walls 11 and 12 in a mirror L-shape with respect to each other.

[0070] With this in mind, the base 13 is provided with separation teeth 15 protruding horizontally into the bottom opening 4b and configured to fold the defective filter bag 1D while it is being directed towards the exclusion area 8 so as to avoid contact between the defective filter bag 1D and a filter bag 1 previously placed on the base 13.

[0071] As shown in FIG. 6, the rejection area 8 of defective filter bags 1D comprises a body 16 for guiding, transporting and releasing defective filter bags 1D arranged adjacent to the transfer wheel 3.

[0072] The body 16 has a first curved surface 16a having a profile that is substantially parallel to the trajectory of the gripping elements 3 and matches the trajectory of the gripping elements 5 along a limited angular interval.

[0073] The guiding body 16 also comprises at least one vertical channel 16b configured for the free passage of the gripping elements 5, ie the claws 5a and 5b, separating the gripping elements 5 and the defective filter bag 1D.

[0074] With this in mind, the guide body 16 is provided with two vertical channels 16b which allow the free passage of the gripping elements 5 and the simultaneous separation of the defective filter bag 1D from the gripping elements 5.

[0075] The guiding body 16 also comprises a second surface 16c opposite the first curved surface 16a, which is configured to guide the separation and guided falling of a defective filter bag 1D, if present.

[0076] The released defective filter bags 1D are then to be collected in a suitable container, not shown.

[0077] The invention also provides a method for assembling a filter bag 1 for an infusion product.

[0078] The method comprises: - actuating a transfer wheel 3 in synchronism with the moving wheel 2, the transfer wheel 3 comprising a plurality of gripping elements 5 arranged along a circumference; - picking up the filter bag 1 from the moving wheel 2 by one of the gripping elements 5 in a first angular position; releasing the filter bag 1 picked up by the gripping element 5 in a second angular position to a collecting device 4 arranged close to the transport wheel 3 after an angular section TA of rotation has been moved along the feed direction A; - detecting possible defects in the filter bags 1 by means of sensor means 7, identifying defective filter bags 1D before they reach a second angular position in which the collection device 4 is located; activating the control means 9 to prevent the gripping element 5 from releasing the filter bag 1D into the second angular position, i.e. into the collection device 4, when the gripped filter bag 1D is detected as defective by the sensor means 7; Releasing the defective filter bag 1D in an exclusion zone 8 located lower than the collection device 4, the exclusion zone 8 being located downstream of the collection device 4 and upstream of a first angular position relative to the feed direction A, When the gripping element 5 passes along the second angular position, it passes through a bottom opening 4 b of the collection device 4 which is located close to the transport wheel 3 .

[0079] Furthermore, each time a filter bag 1 is released into the collection device 4, the gripping elements 5 push further filter bags already positioned in the collection device 4 along the accumulation direction to create space for the filter bag that is released in each case.

[0080] The preset objectives are fully achieved with the above mechanical structure.

[0081] In effect, the machine according to the invention is extremely flexible, configurable depending on the filter bags to be produced, and highly productive.

[0082] A transport wheel structured in this way is extremely accurate and has a high degree of operational flexibility, regardless of the number of carousels present in the machine or the position in which it is applied to the machine.

[0083] The presence of the sensor means in combination with the first and second control means provides an accurate and rapid system for selecting and removing defective filter bags, even when operating at high speeds. [Prior art documents] [Patent documents]

[0084] [Patent Document 1] WO2017 / 145044 [Patent Document 2] WO2019 / 087012

Claims

1. A machine for assembling filter bags (1) for infusion products, comprising: a moving wheel (2) rotatable about a first axis of rotation (X2); a transfer wheel (3) that can be operated in rotation about a second axis of rotation (X3) parallel to the first axis of rotation (X2) in synchronization with the moving wheel (2); a collection device (4) for collecting the filter bags (1), arranged in the vicinity of the transfer wheel (3), and adapted to receive the filter bags (1); a plurality of gripping elements (5) arranged along the circumference of the transfer wheel (3) and movable together with the transfer wheel (3) between a pick-up arrangement for picking up the filter bag (1) from the moving wheel (2) in a first angular position and a release arrangement for releasing the filter bag (1) to the collecting device (4) in a second angular position after an angular section (TA) of rotation has traveled along the feed direction (A); sensor means (7) configured to detect possible defects in the filter bag (1) so as to identify a defective filter bag (1) before it reaches the second angular position in which the collection device (4) is positioned; a rejection area (8) configured to receive the defective filter bag (1D), the rejection area (8) being lower than the collection device (4); the rejection area (8) is arranged downstream of the collecting device (4) and upstream of the first angular position relative to the feed direction (A), the machine also comprising lock control means (9) configured to control the gripping elements (5) to prevent the filter bag (1D) from being released at the second angular position, i.e. at the collecting device (4), when the gripped filter bag (1D) is detected as defective by the sensor means (7), the collecting device (4) being located close to the transfer wheel (3) and comprising a bottom opening (4b) sized to allow the gripping elements (5) to pass through when they pass along the second angular position.

2. 2. The machine according to claim 1, wherein the collecting device (4) comprises two opposing vertical walls (11, 12) arranged at a distance (D) so as to contact opposing sides of the filter bag (1), and a base (13) configured to support the bottom of the filter bag from below, the base (13) comprising the bottom opening (4b).

3. 3. The machine according to claim 2, wherein the two opposing vertical walls (11, 12) each comprise a tab (14) protruding towards the bottom opening (4b), the tab (4) having an inclined profile and configured to obstruct and temporarily fold the side of the filter bag (1) entering the collection device (4).

4. 4. A machine according to claim 2 or 3, wherein the base (13) of the collecting device (4) is formed by a pair of flat elements spaced apart from each other with the bottom opening (4b) between them, each flat element extending from one of the two vertical walls (11, 12) in a mirrored L-shape relative to each other.

5. 4. The machine according to claim 2 or 3, wherein the base (13) comprises separating teeth (15) protruding horizontally into the bottom opening (4 b) and configured to fold the defective filter bag (1D) while directing the defective filter bag (1D) towards the exclusion area (8) in a manner that prevents contact between the defective filter bag (1D) and a filter bag (1) previously placed on the base (13).

6. 3. A machine according to claim 2, wherein the base (13) of the collection device (4) is arranged horizontally and substantially perpendicular to the spokes of the transfer wheel (3).

7. 4. A machine according to any one of claims 1 to 3, wherein the angular interval (TA) of rotation travelled by each gripping element (5) along the feed direction (A) between the first and second angular positions is less than 180°.

8. 4. The machine according to claim 1, wherein the rejection area (8) for the defective filter bags (1D) comprises a body (16) for guiding and transporting the defective filter bags (1D), the body being arranged in the vicinity of the transfer wheel (3) and comprising at least one channel (16b) configured to allow the free passage of the gripping elements (5) and the separation of the defective filter bags (1D) from the gripping elements (5).

9. 9. The machine according to claim 8, wherein the body (16) for guiding and transporting the defective filter bag (1D) comprises a first curved surface (16a) having a profile substantially parallel to the trajectory of the gripping elements (5) and a second surface (16c) opposite the first curved surface (16a) and configured to guide the released defective filter bag (1D).

10. 9. The machine according to claim 8, wherein the guide body (16) comprises two vertical channels (16b) that allow the free passage of the gripping elements (5) and the simultaneous separation of the defective filter bag (1D) from the gripping elements (5).

11. 4. The machine according to claim 1, wherein the sensor means (7) comprises at least one sensor configured to detect defects in the filter bag picked up by the gripping element (5), and a processing unit (17) connected to the sensor for receiving a signal from the sensor that a defective filter bag (1D) has been picked up by the gripping element (5) and connected to a lock control means (9) for sending a lock activation signal to prevent the gripping unit (5) from releasing the defective filter bag (1D) in the second angular position.

12. 4. The machine according to claim 1, wherein the gripping elements (5) are also configured and operable, when releasing the filter bag (1) into the collection device (4), to push further filter bags already placed in the collection device (4) along the accumulation direction to create spaces each time a filter bag is released.

13. 4. The machine according to claim 1, wherein each gripping element comprises a gripper (5) with two claws (5 a, 5 b) for holding the filter bag (1), the two claws (5 a, 5 b) being coupled on the transfer wheel (3), and each gripper (5) is connected to gripper control means (6) configured to rotate the two claws (5 a, 5 b) between a gripping or release position in which the two claws (5 a, 5 b) are spaced apart from each other and a holding position for the filter bag (1), in which the two claws (5 a, 5 b) approach each other with the filter bag (1) interposed therebetween in order to hold the filter bag (1) over time at least along an angular interval (TA) of rotation between the first angular position and the second angular position.

14. The gripping element (5) is also configured and operable such that, when releasing the filter bag (1) into the collection device (4), the gripping element (5) pushes further filter bags already placed in the collection device (4) along the accumulation direction to form a space each time a filter bag is released; 14. The machine according to claim 13, wherein one of the two claws (5a, 5b) is configured to push the further filter bag placed in the collection device (4) along the accumulation direction.

15. 14. The machine according to claim 13, wherein the gripper control means (6) comprises at least a first kinematic unit (18) configured to move one of the two jaws (5a) of the gripper (5) and comprising a cam follower roller (18a) movable along a corresponding track (18c) having a cam profile enabling the gripping position or the release position and the holding position.

16. 16. The machine according to claim 15, wherein the gripper control means (6) also comprises a second kinematic unit (19) with a further cam follower roller (19b), and the lock control means (9) comprises a control device (23) actuable in the presence of a defective filter bag (1D), the control device (23) being kinematically connected to an auxiliary sector (24) of a rotatable cam track and configured to block the further cam follower roller (19b) of the second kinematic unit (19) so as to lock the opening movement of the two jaws (5a, 5b) of the gripper (5) over at least one angular locking interval (TAB).

17. 4. A machine according to any one of claims 1 to 3, wherein the moving wheels (2) are lower than the transfer wheels (3).

18. A method for assembling a filter bag (1) for an infusion product, comprising: - actuating a transfer wheel (3) in synchronism with the moving wheel (2), said transfer wheel (3) comprising a plurality of gripping elements (5) arranged along its circumference; picking up the filter bag (1) from the moving wheel (2) at a first angular position using one of the plurality of gripping elements (5); releasing the filter bag (1) picked up by the gripping element (5) to a collecting device (4) arranged close to the transfer wheel (3) in a second angular position after an angular section (TA) of rotation has been moved along the feed direction (A); detecting possible defects in said filter bag (1) by means of sensor means (7) so as to identify a defective filter bag (1D) before it reaches said second angular position in which said collection device (4) is located; activating a lock control means (9) for preventing the gripping element (5) from releasing the filter bag (1D) in the second angular position, i.e., into the collection device (4), if the gripped filter bag (1D) is detected as defective by the sensor means (7); releasing the defective filter bag (1D) into an exclusion zone (8) located lower than the collection device (4), the exclusion zone (8) being located downstream of the collection device (4) and upstream of the first angular position relative to the feed direction (A), When passing along the second angular position, the gripping element (5) passes through a bottom opening (4b) of the collection device (4) arranged adjacent to the transfer wheel (3).

19. 19. The method according to claim 18, wherein each time a filter bag (1) is released into the collecting device (4), the gripping elements (5) push further filter bags already arranged in the collecting device (4) along the accumulation direction to make space for the respectively released filter bag.

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