MACHINE FOR FORMING FILTER BAGS FOR INFUSION PRODUCTS Technical field

This invention relates to a machine for forming filter bags for infusion products, such as tea, coffee, camomile (in powder, granular or leaf form).

Background art

The term filter bags is used to indicate at least two types of filter bag: the single-chamber filter bags, comprising, in a minimum configuration, a piece of filtering material forming a chamber containing a dose of infusion product; and the double-chamber filter bags, again comprising a single piece of filter paper, but forming two separate chambers. Each chamber contains a dose of infusion product. The two chambers are folded towards each other forming a single upper end (in the shape of an upturned "V") and a bottom end in the shape of a "W".

The single-chamber and double-chamber filter bags can also be equipped with a tag and a tie string connecting the tag to the filter bag.

Lastly, an overwrap envelope may be added to the above mentioned filter bags for wrapping and closing the single filter bag, in a hermetic or non- hermetic manner.

A type of machine, used for making filter bags of the type called two-lobed, is known from patent documents EP762973, EP762974 and EP765274 (all in the name of the same Applicant).

The machine extends along a forming and feeding line on which are positioned:

- a station for feeding a web of filtering material along a feed surface;

- a station for feeding doses of product on the web of filtering material at predetermined distances;

- a tabularisation station for folding the strip on itself, wrapping the doses of product and, subsequently, longitudinally joining the strip;

- a station for folding individual pieces of filtering material with double chamber;

- a carousel, equipped with radially protruding grippers, positioned beneath the folding station and configured to receive individual pieces of folded filtering material; the carousel, moved stepwise about a horizontal axis, rotates each piece of filter paper to the operating stations, arranged one after another and stationary relative to a frame of the machine, to associate to the piece of filtering material a string, suitably wrapped around the piece of filter paper, and a tag in turn connected to the string. In some machine solutions, depending on the type of filter bag to be formed, there may be (alternatively):

- a station for folding the open ends of the two chambers of the piece along the path of the carousel with their retaining by the knotting of the string on the same piece; or

- a further station for transversal closing of the ends of the piece before or at the same time as the separation from the remaining film.

The machine may also comprise a station for applying a sheet of overwrapping material for each filter bag positioned along the path of the carousel, or at a further carousel.

The machine structured as described above operates intermittently, that is to say, stepwise for all the stations present along the feed line.

The stepwise operation places a limit on the productivity of the machine. Disclosure of the invention

The aim of this invention is to provide a machine for forming filter bags for infusion products with a productivity greater than the productivity of the prior art machines, maintaining a high quality of the filter bag.

More specifically, the aim of this invention to provide a machine for forming filter bags for infusion products with reduced dimensions and high flexibility. These aims are fully achieved by a machine for forming filter bags for infusion products according to the appended claims.

Brief description of the drawings

The invention will be described with reference to the accompanying drawings, provided by way of example only and without limiting the scope of the invention, in which:

- Figure 1 is a schematic front view, with some parts cut away to better illustrate others, of a machine for forming filter bags for infusion products according to this invention;

- Figure 2 is a perspective view of a piece of filtering material configured at the outlet from a first folding carousel of the machine of Figure 1 ;

- Figure 3 is a perspective view, with some parts cut away in order to better illustrate others, of a first transfer wheel of the machine of Figure 1 ; - Figure 4 illustrates a perspective exploded view of the first wheel of Figure 3;

- Figures 5, 6 and 7 illustrate, respectively, front perspective view, rear perspective view and perspective view from above of a receiving unit forming part of the first transfer wheel of Figure 4;

- Figure 8 illustrates a perspective view, with some parts exploded to illustrate others, of a front part of the receiving unit;

- Figure 9 illustrates a perspective view, with some parts cut away, of a station for feeding a tag to the first transfer wheel forming part of the machine of Figure 1 ;

- Figures 10 to 15 illustrate front views, with some parts schematic and others cut away, of corresponding operating positions of a receiving unit of the first wheel.

Detailed description of preferred embodiments of the invention

With reference to the accompanying drawings, and in particular to Figure 1 , a machine according to the invention, labelled 1 00 in its entirety in Figures 1 , is used for forming filter bags containing infusion products, such as tea, coffee, camomile dosed in powder, granular or leaf form.

The expression "filter bags" may refer both to single-chamber filter bags and double-chamber filter bags without thereby limiting the scope of protection of this invention.

The first type of filter bag (single-chamber) comprises a single piece of filtering material having at least two free ends defining, respectively, a head and a bottom between which there is a chamber containing a dose of product.

The second type of filter bag, which for simplicity of description will be referred to in this invention, always comprises a single piece 1 a of filtering material, which forms two separate chambers 1 b, 1 c. Each chamber 1 b, 1 c contains a dose of infusion product. The two chambers 1 b, 1 c are folded towards each other forming a single upper end (in the shape of an upturned "V") and a bottom end in the shape of a "W".

Both types of filter bag (single-chamber or double-chamber) may be equipped with a gripping tag 1 t and a tie string connecting the tag to the filter bag formed (the string is not illustrated).

An outer overwrapping envelope may also be added to wrap around and enclose each single filter bag formed (the bag is also not illustrated).

Reference will be made below to a double chamber filter bag merely for the purpose of simplifying the description of the machine.

The main aim of the machine 100 according to the invention is to at least form, through a suitable handling, the basic geometrical shape of the filter bag with a double chamber starting from a piece 1 a of filtering material and folding it and then passing the piece to subsequent stations for the adding to or the completion of the filter bag.

The machine 100 according to the invention is a complex machine with operating stations designed to perform the requested operation on the piece of filtering material or on the filter bag (applying tie string and tag, and/or applying outer overwrapping envelope, etc), whilst maintaining a continuous operation of the machine.

The machine 100 forms filter bags for infusion products starting from pieces 1 a of filtering material (see Figure 2) each having two free ends 1 d, 1 e and an intermediate portion 1 f (designed to shape the bottom in the form of a "W").

Between each free end 1 d, 1 e and the intermediate portion 1 f there are, respectively, two chambers 1 b, 1 c containing a corresponding dose of product.

Each piece 1 a is fed along a feed line A.

As illustrated in Figure 1 , the machine 100 comprises a first carousel 2 for continuous rotary movement about a first axis 2X of rotation and with direction V2.

The machine 100 also comprises a plurality of first operating stations 3 (illustrated schematically) positioned along, and movable continuously with, the first movement carousel 2.

Each first station is associated with corresponding gripping elements 3a positioned along, and continuously movable with, the first movement carousel 2.

Each pickup unit 3a is configured for holding a respective piece 1 a of filtering material being formed.

Each first operating station 3 is configured to operate on the piece 1 a of filtering material in order to form, at least partly, a filter bag along at least one predetermined angular stretch of rotation of the first movement carousel 2.

Advantageously, the first operating station 3 acts in conjunction with the corresponding gripping means 3 for retaining the respective piece 1 a of filtering material being formed.

The machine 100 also comprises a plurality of first translation devices (not illustrated), associated with the first movement carousel 2 and configured for translating, mutually, the first operating stations 3 and the corresponding gripping means 3a along a direction parallel to the axis 2X of rotation.

In short, the basic concept of the machine 100 is that it comprises a multiplicity of operating units, all operating a same operation on the piece of filtering material, all independent of each other and driven continuously about an axis of rotation.

This configuration allows an intermediate operation of the filter bag to be obtained on a large number of pieces of filtering material per unit of time and in a reduced space (angular section).

In the case illustrated, pieces of filtering material in a tubular shape are fed to the first movement carousel 2 and the operating stations are folding designed to fold, that is to say, erect, the piece for making a filter bag still without the tie string and tag.

Therefore, each first operating station 3 may be configured to perform intermediate operations on the piece 1 a of filtering material (in this case folding and erection of the piece).

In the specific case illustrated here, the machine 100 according to the invention is designed for making (as mentioned above) double chamber filter bags starting from a continuous tubular strip of filtering material containing doses of product arranged in succession.

More specifically, the first carousel 2 of the machine 100 illustrated serves to form the two-lobed pieces 1 a of filtering material and to fold them in the upright form with the ends joined and with the bottom already in the form of a "W".

It should be noted that the first movement carousel 2 rotates continuously in a clockwise direction (direction V2).

As illustrated, each operating station 3 (synchronised with the gripping means and the transfer devices) is configured to retain and operate on a corresponding piece 1 a of filtering material fed along at least one predetermined angular stretch of rotation of the first movement carousel 2, to obtain at least a lifting of the two chambers 1 b, 1 c to a position alongside and erect, that is to say, positioned radially relative to the first axis 2X of rotation, and with the corresponding free ends 1 d, 1 e joined to one another and arranged spaced apart relative to the first carousel 2. The machine also comprises transfer means 4 designed to transfer the pieces 1 a of filtering material (folded) from the first movement carousel 2 to a second movement carousel 5 rotating continuously about a second axis 5X Parallel to the first axis 2X of rotation (see Figures 1 to 4).

The transfer means 4 comprise a first wheel 6, rotatable continuously about a third axis 6X of rotation parallel to the first 2X and to the second 5X axis of rotation, and actuated in a synchronised fashion with the first 2 and the second 5 movement carousels.

Again as illustrated, the first wheel 6 is equipped (along its circumference) with a plurality of receiving units 7 for receiving from the corresponding first operating stations 3 of the first movement carousel 2, and releasing on the second movement carousel 5, a corresponding piece 1 a of filtering material being formed after its predetermined arc of rotation.

Each receiving unit 7 is equipped with corresponding first gripping and stabilising means 8 and 13 to retain the piece 1 a of filtering material upright and positioned with its free ends 1 d, 1 e (head) joined facing towards the third axis of rotation 6X.

Again as illustrated, the first gripping and stabilising means 8, 13 comprise a unit 8 for the stabilising the piece 1 a of filtering material in an upright position when receiving of the piece 1 a of filtering material.

The first stabilising means 8 of each receiving unit 7 comprises a first gripper consisting of two fork-shaped claws 8a, 8b for retaining the piece 1 a of filtering material and articulated on the receiving unit 7.

Each first gripper is connected to a first control device 14 configured for rotating the two claws 8a, 8b between an open operating position for gripping or releasing the piece 1 a of filtering material, wherein the two claws 8a, 8b are spaced apart from each other, and a closed operating position for retaining the piece 1 a of filtering material, wherein the two claws 8a, 8b are moved towards each other. It should be noted that each receiving unit 7 comprises the corresponding first gripping and stabilising means divided into two separate components: an element 13 for gripping the piece 1 a of filtering material for retaining the joined head ends 1 d, 1 e, and the above-mentioned stabilising means 8 for keeping in an upright position the piece 1 a of filtering material retained by the joined free head ends 1 d, 1 e at the receiving of the piece 1 a of filtering material, (see also in particular Figure 7).

As mentioned above (see in particular Figures 5 to 8), each stabilising means 8 of each receiving unit 7 comprises a first gripper consisting of two fork-shaped claws 8a, 8b for retaining the piece 1 a of filtering material, which are articulated on the receiving unit 7.

In light of this, each first gripper is connected to a first control device 14 configured for rotating the two claws 8a, 8b between an open operating position for gripping or releasing the piece 1 a of filtering material, wherein the two claws 8a, 8b are spaced apart from each other (see Figures 10 and 15), and a closed operating position for retaining the piece 1 a of filtering material, wherein the two claws 8a, 8b are moved towards each other (see Figures 1 1 -14).

Preferably, each receiving unit 7 comprises a base 15 for supporting the first gripper connected to a second control device 16 configured for moving the supporting base 15 tangentially in both directions relative to the third axis 6X of rotation between a first advanced position (with a radial movement relative to the third axis 6X of rotation), where the supporting base 15 is away from the third axis 6x of rotation, at least at:

- the passage of the piece 1 a of filtering material from the first movement carousel 2 to the receiving unit 7 (Figures 10 and 1 1 );

- the picking up of the tag 11 (Figure 13); and

- the release of the piece 1 a of filtering material with the tag 1 t (positioned alongside) to the second movement carousel 5 (Figure 15),

and a withdrawn position, wherein the supporting base 15 is moved close to the third axis of rotation 6X at the intermediate transits of the receiving unit 7 between the above-mentioned pick-up and release positions (Figure 14).

Each receiving unit 7 has second gripping means 9 for positioning and retaining a tag 1 t on the piece 1 a of filtering material, fed by a corresponding feeding station 10, in such a way as to release to the second carousel 5 the piece 1 a of filtering material with a corresponding tag 1 t placed alongside the joined free ends 1 d, 1 e of the piece 1 a of filtering material.

Preferably (see figure 9), the station 10 for feeding the tags 1 t has means 1 1 of unwinding and separating the tags 1 t and a device 12 for picking up the individual tags 1 t (from the means 1 1 ) and for feeding the individual tags 11 to the receiving units 7 in transit.

Preferably, the second means 9 for gripping an individual tag 1 t, independent of the first gripping and stabilising means 8, 13, are configured for picking up and positioning the individual tag 1 t in contact with the joined free ends 1 d and 1 e of the piece 1 a of filtering material at least prior to the passage of the piece 1 a of filtering material with the tag 1 t to the second movement carousel 5.

Preferably, the second gripping means 9 comprise a second gripper for gripping the tag 1 t consisting of two claws 9a, 9b articulated on the receiving unit 7.

It should be noted that the second gripper is positioned upstream relative to the first gripper with reference to a direction V6 of rotation of the first wheel 6 (in this case anticlockwise).

In light of this, the second gripper is connected to a third control device 17 configured for moving at least one claw 9a or 9b relative to the other claw 9b or 9a between an open operating position for the gripping or releasing of the tag 1 t (see Figures 12 and 15), wherein the two claws 9a, 9b are spaced far apart, and a closed operating position for retaining the tag 1 t, wherein the two claws 9a, 9b are close together (see Figures 13 and 14). It should also be noted that the second gripper is connected to a fourth control device 18, in a synchronised fashion with the second control device 16 and the third control device 17 (as described in detail below), configured at least for rotating the two claws 9a, 9b between a first standby position (Figures 10 and 13), wherein the two claws 9a, 9b are spaced apart from the first gripper, and a second operating position (Figures 14 and 15), wherein the two claws 9a, 9b are moved towards the first gripper for bringing the tag 1 t alongside the piece 1 a of filtering material.

Preferably, the gipping means 13 (see figure 7) comprise a third gripper 19 articulated on the receiving unit 7 downstream of the first gripper with reference to the direction V6 of rotation of the first wheel 6.

In light of this, the third gripper 19 is connected to a kinematic unit 20 of levers articulated on the receiving unit 7 and connected to a fifth control device 21 configured for rotating the third gripper 19 between a first non- operating position (dashed line in Figure 7), wherein the third gripper 19 is moved away from the first gripper, and a second operating position (continuous line in Figure 7), wherein the third gripper 19 is moved close to the first gripper and in contact with the joined free head ends 1 d and 1 e of the piece 1 a of filtering material with contact on a portion of the bottom 15. It should be noted, as shown in Figure 2, that in the case illustrated for this type of solution the piece 1 a of filtering material is picked up by the first wheel 6 with the ends 1 d, 1 e facing towards the centre of the piece 1 a to form a fold obtained in two successive steps during the path carried by the first wheel and by means of folding means not illustrated.

According to a preferred solution, the fork-shaped claws 8a, 8b of the first gripper have corresponding pairs of end heads 22, 23 each having a transversal tab 24 for retaining the lateral edges of the piece 1 a of filtering material and configured for defining a free central zone from the bottom 1 f to the joined head ends 1 and 1 e of the piece 1 a of filtering material.

This architecture of the claws 8a, 8b makes it possible to retain and stabilise correctly the piece 1 a of filtering material and, at the same time, define a free zone both for the placing the tag 1 t alongside the piece 1 a and for gripping the piece 1 a with the tag by a corresponding station 5a of the second carousel 5. Figure 15 illustrates, only by way of non-limiting example, a gripper 5p of one of the stations 5a of the second carousel 5 for gripping and positioning the piece 1 a with the tag 1 t in the relative operating station 5a.

In other words, the second movement carousel 5 is substantially alongside the first transfer wheel 6.

The second carousel comprises a plurality of grippers 5p positioned along, and movable continuously with, the second movement carousel 5.

Each gripper 5p is configured to receive and retain a piece 1 a of filtering material with tag 1 t being formed.

Each gripper 5p is linked to a corresponding operating station 5a positioned along, and movable continuously with, the second movement carousel 5.

Each operating station 5a is configured to operate on the piece 1 a of filtering material with the tag 1 t in order to further form, at least partly, a filter bag along at least one predetermined angular stretch of rotation of the second movement carousel 5 which, in this case may be the application of a tie string (not illustrated) to the joined ends 1 d and 1 e and to the tag 11.

It should be noted that the first carousel 2 and the second carousel 5 have corresponding directions V2, V5 of rotation concordant with each other (clockwise direction), whilst the first transfer wheel 6 has a direction V6 of rotation opposite to the directions V2, V5 of rotation of the two carousels 2, 5 (anticlockwise direction).

More in detail of the functional components of each receiving unit 7, the first device 14 for controlling the first stabilising means 8 comprises (Figures 5 to 8):

- a first connecting rod 27 articulated to a flange extension 28 of the first claw 8a: - a first lever 29 articulated at the other end of the first connecting rod 27;

- a first shaft 30 for transmitting the motion on which is articulated the first lever 29; the first shaft 30 is rotatably housed inside the first wheel 6 with its axis of extension parallel to the third axis 6X; the first shaft 30 has a series of cam follower rollers 31 , located on its innermost end, and positioned in contact with a cam profile made on the inner part of the first wheel 6.

It should be noted that the cam profiles which are referred to in the description and which are present in the first wheel 6 are not indicated in detail, but each of them is configured, in terms of the profile, for implementing the illustrated movements of each control device described in this invention.

It should be noted that the first control device 14 is connected to a single claw, 8a, therefore in order to obtain a coordinated movement between the two claws 8a, 8b there is a kinematic system positioned inside the supporting base 15 of the receiving unit 7.

The kinematic system (see Figure 8) comprises two pins 32 and 33 keyed to the corresponding claws 8a, 8b in such a way as to define the articulation points on the receiving unit 7. Each pin 32 and 33 has a zone with greater thickness 34 and 35 on which there is a toothed sector 36 and 37 meshed with the toothed sector 37 and 36 from the other zone 34 and 35.

Thanks to this kinematic connection, the rotary movement actuated by the first claw 8a, on the command of the first control device 14 described above, is transmitted, with inverted directions of movement, to the second claw 8b in such a way as to allow the moving away or towards each other of the two claws 8a and 8b.

The second control device 16 (Figures 5 to 8) of the supporting base 15, which, as described in more detail below, is directly correlated in the movement of the receiving unit 7 with the fourth control device 18, comprises: - a second connecting rod 38 articulated to a flange 39 of the support base 15:

- a second lever 40 articulated at the other end of the second connecting rod 38;

- a second shaft 41 for transmitting the motion on which is articulated the second lever 40; the second shaft 41 is rotatably housed inside the first wheel 6 with its axis of extension parallel to the third axis 6X; the second shaft 41 is coaxially positioned on the first shaft 30 and its axis coincides with the axis of the first shaft 30.

The second shaft 41 has a series of cam follower rollers 42, located on its innermost end and positioned in contact with a corresponding cam profile made on the inner part of the first wheel 6 to allow the tangential movement in both directions of the supporting base 15.

The third control device 17 (Figures 5-8) of the second gripping means 9 comprises a third shaft 43 for transmitting the motion on which is articulated a claw 9a of the second gripping means 9.

The third shaft 43 is rotatably housed inside a fourth shaft 44 for transmitting the motion (which forms part of the fourth control device 18) and both are positioned inside the first wheel 6 with the axis of extension parallel to the third axis 6X.

The third shaft 43 protrudes from the fourth shaft 44 and is equipped with a link-rod 45 equipped with a cam follower roller 46 designed to follow a front cam profile present on the first wheel 6 to allow a rotation of the claw 9a towards and away from the other claw 9b.

The second claw 9b of the second gripping means 9 is associated stably with the fourth control device 18 which interacts with the second 16 and third 17 control device.

The fourth control device 18 (Figures 5-8) comprises the above-mentioned fourth shaft 44 for transmitting the motion (inside of which is housed, freely rotatable, the third shaft 43) comprising at the outer end a relative front portion configured in the form of a cradle and defined also by a cover 48 integral with the fourth shaft 44 and carrying the centre of rotation of the supporting base 15.

On the front portion of the fourth shaft 44 is associated the second claw 9b of the second gripping means 9.

The fourth shaft 44 has on its inner end housed in the first wheel 6 cam follower rollers 49 in contact with a corresponding cam profile so as to rotate about its axis and allow the movement towards and away from the claws 9a, 9b of the second gripping means 9 of the first gripping means 8. These movements are coordinated and in phase with the lifting and lowering movement of the support base 15 also by means of the second control device 16.

The fifth control device 21 of the stabilising element 13 comprises:

- the above-mentioned kinematic unit of levers 20 configured to connect the gripper 19 (positioned in front of the piece 1 a of filtering material and upstream of the first gripping means 8 relative to the direction V6 of rotation of the first wheel 6) to a fifth shaft 50 for transmitting the motion positioned downstream of the first gripping means 8 again relative to the direction V6 of rotation of the first wheel 6.

The fifth shaft 50 is housed, freely rotatable, inside the fourth shaft 44 and parallel to the third shaft 43.

The fifth shaft 50 protrudes from the fourth shaft 44 and is provided with a link-rod 51 equipped with a cam follower roller 52 designed to follow a front cam profile present on the first wheel 6 to allow the movement from the first non-operating position (a dashed line in Figure 7), wherein the third gripper 19 is moved away from the first gripper, and a second operating position (continuous line of Figure 7), wherein the third gripper 19 is moved close to the first gripper and in contact with the joined free ends 1 d and 1 e of the piece 1 a of filtering material.

This movement is in phase with the movement of the second, third and fourth shaft for transmitting the motion.

Preferably, (Figures 1 and 9), the above-mentioned device 12 for picking up the individual tags 1 t and for feeding the individual tags 1 t to the receiving units 7 in transit is configured for feeding the tags 1 t according to a direction radial to the first transfer wheel 6.

In light of this, the device 12 for picking up the individual tags 1 t and for feeding the individual tags 1 t is positioned alongside the first wheel 6 and in a position in the path of the first wheel 6 between the pick-up zone of the piece 1 a of filtering material from the first movement carousel 2 and the release zone of the piece 1 a of filtering material with the tag 1 t to the second movement carousel 5.

In an alternative embodiment (not illustrated), the device 12 for picking up the individual tags 1 t and for feeding the individual tags 1 t is again positioned alongside the first wheel 6, but in a position in the path of the first wheel 6 between the zone for releasing the piece 1 a of filtering material with the tag 1 t to the second movement carousel 5 and the zone for picking up the piece 1 a of filtering material from the first movement carousel 2. In other words, the tag 1 t could be fed to the receiving unit 7 before picking up the piece 1 a of filtering material from the first movement carousel 2. It should be noted that the above-mentioned means 1 1 for unwinding the tags 1 t comprise a reel 1 1 b of tags 1 t in a continuous strip which is fed towards the device 12 for feeding the individual tags 1 t from a pair of motor-driven rollers 1 1 c, 1 1 d.

Between the pair of rollers 1 1 c and 1 1 d and the device 12 there is a cutting unit l i t designed for separating the individual tags 1 t before their picking up.

The movement of the pair of rollers 1 1 c and 1 1 d and of the cutting unit 1 11 is of the alternating type.

Preferably, the pick-up device 12 comprises two independent drums 12a and 12b side by side and rotating about a fourth axis 12X of rotation which is shared and parallel to the third axis 6X of rotation of the first transfer wheel 6.

Each drum 12a, 12b has a plurality of grippers 25a, 25b for picking up and transporting a corresponding single tag 17 from the unwinding and separating means 1 1 to the first transfer wheel 6.

Each gripper 25a or 25b is configured in the shape of an '"L" in such a way as to position itself along a circular trajectory shared between the two drums 12a and 12b coinciding with the points for picking up and releasing the tags 1 t.

Each drum 12a, 12b is moved, in a discontinuous manner, by movement means 26 configured to allow an alternating rotation of the drums 12a, 12b in such a way as to position the corresponding grippers 25a, 25b of each drum 12a, 12b with a reciprocal angular displacement, between preceding and successive grippers 25a, 25b, so as to constantly maintain a gripper 25a, 25b with the tag 1 t of one of the drums 12a, 12b in the proximity of the corresponding receiving units 7 in transit with continuous movement. In short, each receiving unit 7 operates during the continuous rotation of the first wheel 6 in the manner illustrated in Figures 10 to 15.

The receiving unit 7 arrives in the proximity of the first carousel 2 (approximately at 12 o'clock position - Figure 10) and with a radial lifting movement of the first gripper in the open position picks up the piece 1 a of filtering material from a corresponding first station 3 of the first carousel 2, closing on the same piece 1 a.

Subsequently, whilst the first wheel 6 continuous its rotation, the first closed gripper is lowered whilst the third gripper 19 rotates so as to lock and stabilise the piece 1 a (Figure 1 1 - 1 1 o'clock position).

Subsequently (Figure 12 - 10 o'clock position), the first gripper starts a new lifting whilst the second gripper is brought to the open position and away from the first gripper.

At the intercepting of the feed drums 12a and 12b the second gripper picks up a tag 11 from a gripper 25a or 25b of a drum 12a or 12b.

After this operation, the first gripper with the piece 1 a is lowered whilst the second gripper with the tag 1 t is brought into contact with the piece 1 a (Figure 14 - 8 o'clock position). At this point the receiving unit 7, arriving in the proximity of the release zone of the piece 1 a with the tag 1 t, prepares to raise the first gripper with consequent opening of the first gripper 8, the third gripper 19, and the second gripper at the intercepting of a gripper 5p of the second carousel 5 (Figure 15 - 5 o'clock position).

The preset aims are fully achieved with the machine structure just described.

In effect, a machine according to the invention is extremely flexible, configurable as a function of the filter bag to be made, and with a high productivity.

It should be noted that each individual operation on the piece of filtering material, or on the filter bag, is no longer linked to the pause time (as in the machines with step-mode operation) and has a duration independent from one another. It is therefore possible to lengthen or shorten, as necessary, the time of execution of an operation (in this case, for example, preparing the piece of filtering material with free ends closed with a tag already positioned) simply by using a longer or shorter stretch of rotation of the movement carousel.

Each unit may operate on the piece of filtering material along an extremely short arcuate stretch of the carousel and with the possibility of starting the operations immediately, reducing the down times and the dimensions of the machine.