MACHINE FOR FORMING FILTER BAGS FOR INFUSION PRODUCTS

Technical field

This invention relates to a machine for making filter bags for infusion products, such as tea.

The filter bag for infusion products such as tea comprises a filtering body of the single- or double-lobed type containing the dose(s) of the infusion product, which is equipped with a thread for connecting the filtering body with a tag.

Background art

There are prior art machines for forming these filter-bags basically comprising a plurality of operating stations (positioned along a protected operating path) for forming the filter bag.

One of these stations is a rotary carousel equipped with a plurality of grippers on each of which is positioned a filter bag containing the dose(s) of the product to which to apply a stretch of thread and a respective tag connected to the thread during the stepwise rotating movement of the carousel.

On these machines, each component forming the filter bag (filter paper, product, thread and tag) has a corresponding feed station, including a station for feeding strips of tags of particular interest in this invention.

This feed station comprises a first and a second reel, each with a respective first and second continuous strip of tags.

A first reel feeds its first strip of tags to the wheel along a predetermined path up to the carrousel for forming the filter bags, whilst the other is waiting to be used when the first strip of tags is nearly finished. The condition of each reel of being nearly empty is controlled by respective sensors.

The second strip has a relative free end positioned close to a zone of the predetermined path for feeding tags on the carousel. The free end of the strip waiting is provided with an adhesive joining piece.

In the same zone there are two rollers for conveying the first strip, one having a fixed axis of rotation and one having a axis of rotation movable in such a way that it can move towards and away from the other fixed roller.

When the first roll is finished, a unit is activated for moving the second strip and connecting it to the first strip by bilateral pressure, whilst the movable roller moves away from the fixed roller to allow entry of the second strip along the predetermined path.

The pressure joint, with the machine operating and therefore with the first strip moving, must occur between the head of the first tag of the second strip and the tail of a tag of the first strip nearly empty in such a way that the two parts are coplanar with each other and in step between a final tag (first strip) and an initial tag (second strip).

Once the two strips have been joined, the movable roller moves towards the fixed roller and continues with the feeding of the second strip along the predetermined path.

At the same time, a cutting element separates the last stretch of the first strip of tags remaining, upstream of the pair of rollers.

This type of operation must therefore be carried out in a very precise manner, since each tag, having a shape and a print on its surface, must be separated individually from the strip, according to a predetermined feed step, and associated with the portion of thread of a filter bag.

If the joining between the two strips is not performed in a correct fashion, that is to say, not in a stepwise fashion, the successive tags fed to the carousel are offset and therefore with incorrect size and/or wording.

The presence of the tags on the carousel is controlled by a sensor present close to the carousel.

This photocell also detects whether the tag has the correct size and wording. If this photocell detects incorrect tags it starts to send signals corresponding to a command for rejecting the respective filter bags. After a predetermined or consecutive number of rejects the machine is stopped for suitable checks and the retiming up of the operating stations.

This type of prior art system therefore has a drawback due to the limited safety in the system for changing the strip of tags due to the emptying of the reels, as it is necessary to join two different strips when the machine is operating, that is to say, with the operating strip in movement.

This limited safety in the joint, as mentioned, can result in frequent machine stoppages.

Aim of the invention

The aim of the invention is to provide a machine for making filter bags for infusion products, such as tea, which overcomes the above-mentioned drawbacks of the prior art.

In particular, the aim of the invention is to provide a machine for making filter bags for infusion products, such as tea, which is able to guarantee a change of strips of tags being fed which is extremely precise, safe and without affecting the operating parts of the machine.

A further aim of the invention is to propose a method for changing strips of tags which is simple, safe and with a reduction in the time for changing strips as well as a reduction in the waste of the strips of the empty reels.

Said aims are fully achieved by a machine for making filter bags for infusion products, such as tea, according to the invention and by a method for changing strips of tags, as characterised in the appended claims.

Brief description of the drawings

The main features of the invention will become more apparent from the following detailed description of a preferred, non-limiting embodiment, illustrated purely by way of example in the accompanying drawings, in which:

- Figure 1 illustrates a part of the machine for forming filter bags for infusion products according to the invention;

- Figure 2 illustrates an enlarged detail A referred to Figure 1 ; Figure 3 illustrates a top plan view of an enlarged detail B referred to Figure 1 ;

- Figure 4 illustrates a schematic top view of a different configuration of a joining unit of Figure 3.

Detailed description of preferred embodiments of the invention

With reference to the accompanying drawings, and in particular with reference to Figure 1 , the machine according to the invention, labelled 100 in its entirety, is used for forming filter bags S for infusion products.

In the case illustrated, the filter bags S may contain tea and each have at least one filtering chamber, a thread and a tag 4.

This specification illustrates only the portion of the machine 100 of particular interest.

The machine 100 comprises a carousel 1 rotating in a stepwise fashion about an axis X of rotation (horizontal).

The carousel 1 has a plurality of grippers 2 (radial) arranged circumferentially and configured for holding respective filtering chambers provided with a thread (applied during a series of steps in previous operating stations).

Each gripper 2 is configured to bring, again with a stepwise rotation, each filtering chamber to a pickup zone 3 (in particular, a single tag 4 to be joined to the thread).

The machine 100 also comprises a first reel 5 of a first continuous strip 6 (from which to cut tags) to be fed to the pickup zone 3 and a second reel 8 of a second strip 9 (of tags to be cut) to be fed to the pickup zone 3, as an alternative to the first strip 6.

The two reels 5 and 6 are rotatably keyed on the frame of the machine 100 about respective axes X5 and X8.

As illustrated, the machine 100 comprises a selector device 10 comprising a first channel 12 engaged by the first strip 6 arriving from the first reel 5.

The selector device 10 comprises a second channel 13 engaged by the second strip 9 of tags arriving from the second reel 8.

Again as illustrated, the selector device 10 has a shared outfeed 10a at the pickup zone 3.

Again as illustrated, the machine 100 comprises first 14 and second 15 movement means, positioned, respectively, along the first 12 and the second 13 channel and configured for feeding, respectively, the first strip 6 and the second strip 9.

These first 14 and second 15 movement means are operated selectively in such a way as to feed alternately the first 6 or the second 9 strip of tags.

These first 14 and second 15 movement means are actuated selectively in such a way as to feed alternately:

- the first strip 6, when it is detected that the second strip 9 is running out, or

- the second strip 9, when it is detected that the first strip 6 is running out, in such a way as to guarantee continuity of operation.

Again as illustrated, the machine 100 comprises a tag cutting unit 11 positioned close to the shared outfeed 10a of the selector device 10.

The cutting unit is configured to cut a single tag 4 at a time from the first strip 6, when the first strip 6 is fed, or from the second strip 9, when the second strip 9 is fed, in such a way that the single tag 4 is associated with the thread of the filtering chamber carried to the pickup zone 3 by the gripper 2.

The machine 100 also comprises a first 17 and a second 18 joining unit, respectively for the first 6 and the second 9 strips, positioned between the respective first 5 and second 8 reels and the respective first 14 and second 15 movement means, along a corresponding first P6 and second P9 path of the first 6 and second 9 strips.

The first joining unit 17 is configured to join a final end of the first strip 6, when it is not fed by the first movement means 14, with an initial end of a new first strip coming from a new first reel.

The second joining unit 18 is designed to join a final end of the second strip 9, when it is not fed by the second movement means 15, with an initial end of a new second strip coming from a new second reel.

As illustrated, the machine 100 also comprises a dividing wall 26 positioned in such a way as to separate the first 17 and the second 18 joining units from the carousel 1 .

In light of this, the dividing wall 26 is provided with a first 26a and second 26b slit to allow the passage, respectively, of the first 6 and second 9 strips, in such a way as to not interrupt the above-mentioned first P6 and second P9 paths.

It should be noted that the dividing wall 26 also separates the first 17 and the second 18 joining units from the selector device 10 (as clearly shown in Figure 1 ).

In light of this, the dividing wall 26 is part of a protective guard 30 which encloses the carousel 1 and the subsequent stations of the machine 100 designed for forming the filter bags S.

It should be noted that the dividing wall 26 lies on a plane parallel to the axis X of rotation of the carousel 1 .

In other words, the machine 100 comprises two zones separated from the guard 30, the first zone, open, where the reels for feeding the materials for forming the filter bags (filter papers, tags, joining thread, distributors of the product to be packaged) are positioned, whilst the second zone, protected by the guard, comprises all the stations for forming the filter bag.

It should be noted that, thanks to the position of the joining units positioned outside the protective guard of the machine, all the operations necessary for changing the empty reel and the joining of the new strip with the portion of strip remaining occur in a zone outside the operating zone protected by the guard, without affecting, therefore, the normal operation of the bag forming stations which can continue their operation safely.

It should be noted that the first 14 and second 15 movement means are connected to a shared control unit 7 (connected to the general control unit of the machine) configured to allow, selectively, a synchronised feeding with stepwise motion of the first strip 6 to the cutting unit 1 1 and at the same time keeping the second strip 9 stationary, or keeping the first strip 6 of tags stationary and at the same time synchronised feeding with stepwise motion of the second strip 9 to the cutting unit 11 .

As illustrated in detail in Figure 2, the selector device 10 comprises a wedge- shaped element 16 with vertex close to the cutting unit 1 1 (vertex which defines the shared outfeed 10a for the tags of both the strips, when fed).

The body 16 has two opposite surfaces on which are made, respectively, the first and second channels 12 and 13.

Each surface of the wedge-shaped body 16 is covered by a respective covering guard 16a and 16b; each guard 16a and 16b has an extension greater than the extension of the relative surface of the wedge-shaped body 15 in such a way as to protrude relative to the vertex of the wedge and define a slit defining the shared outfeed 10a in such a way as to allow a controlled outfeed of the tags towards the pickup zone 3.

The first 14 and the second 15 movement means each comprise a pair of rollers 14a and 15a opposite each other for the respective first 6 and second 9 strips.

Each pair of rollers 14a and 15a is provided with a corresponding drive unit connected to the control unit 7 to allow a synchronised feeding of the first strip 6 of tags to the pickup zone 3 and keep stationary awaiting the second strip 9 of tags and, when the first reel 5 is finished, locking and moving away from the pickup zone 3 the first strip 6 of tags, by withdrawing the remaining portion of the first strip 6 of tags along the first path P6 with simultaneous activation of the synchronised feeding of the second strip 9 to the pickup zone, and vice versa.

As illustrated in Figures 1 , 3 and 4, the machine 100 comprises the above- mentioned first 17 and second 18 joining units, respectively for the first 6 and the second 9 strips of tags.

The first 17 and the second 18 connecting units are positioned between the respective first 5 and second 8 reels and the respective first 14 and second 15 movement means, along the corresponding first P6 or second P9 paths of the strips 6, 9.

It should be noted that each of the first 17 and second 18 joining units is configured to align, in a synchronised fashion, a final end of a respective first 6 and second 9 strip, when the corresponding strip 6 or 9 is kept stationary by the respective movement means 14 and 15, with the initial end of a respective new first and second strip from a respective new first and second reel.

In other words, whilst one of the strips 6 or 9 feeds the carousel 1 , the other strip 9 or 6 is stationary and may be replaced and aligned in a synchronised fashion with a new strip which will be joined to the part of the old strip still present along the path P9 or P6.

In light of this, as shown in Figures 3 and 4, each of the first 17 and second 18 joining units comprises a respective supporting plate 19 positioned, respectively, along the first P6 and the second P9 path on which the first 6 and the second 9 strip slide, respectively.

On each supporting plate 19 there is at least one visual reference RV1 which can be aligned with visual references RV2 printed on the strips 6, 9 in such a way as to allow a precise joining (synchronised with the strip being used up, which is no longer fed to the pickup zone 3, with the new strip).

It should be noted that on each supporting plate 19 there are articulated a first locking lever 20 configured for locking on the supporting plate 19, in a predetermined position, the first or second strip 6 or 9 which does not advance (running out), and a second locking lever 21 configured for locking on the supporting plate 19 the new strip, in a predetermined position.

The supporting plate 19 also comprises a grooved track 22 positioned between the first 20 and the second 21 locking lever and configured to be engageable by a web cutting element 23 (for example, a slidable blade). Moreover, the supporting plate 19 is equipped with a supporting lever 24 configured to be positioned close the grooved track 22 in such a way as to allow the web cutting element 23 to slide along the grooved track 22 remaining resting on the supporting lever 24.

In other words, the new strip (see also Figure 4) is joined to the end portion of the finished strip by:

- locking, in a synchronised fashion (that is to say, with the visual references RV1 and RV2 coincident), the end portion of the reel nearly empty with the first lever 20;

- cutting with the web cutting element 23 the connecting part between the empty reel and the remaining end portion along the path P6 or P9, in such a way as to have the cut edge at the grooved track 22;

- replacing the empty reel with a new reel and unwinding the new strip along the path;

- positioning and locking, in a synchronised fashion (that is to say, with the visual references RV1 and RV2 coincident) the new strip on the plate 19 with the second lever 21 ;

- cutting, again with the web cutting unit 23, a part of the new strip in such a way as to have the cut edge at the grooved track 22 and in front contact with the edge of the end portion;

- joining the two edges in front contact of the end portion and the new strip with a joining web 25 (adhesive).

The invention provides a method for selective feeding of strips of tags 4 to a machine 100 for forming filter bags S for infusion products, such as tea.

The method comprises the following steps:

- preparing a carousel 1 rotating in a stepwise fashion about an axis X of rotation having a plurality of grippers 2 arranged circumferentially and configured for retaining respective filtering chambers provided with a thread; each gripper 2 moving the filtering chamber to a pickup zone 3;

- preparing a first reel 5 of a first strip 6;

- preparing a second reel 8 of a second strip 9;

- stopping the feeding of the first strip 6 of tags when it is nearly finished, by first movement means 14; and synchronously

- activating the feeding of the second strip 9 by second movement means 15;

- cutting a single tag 4 at a time from the first strip 6, when the first strip 6 is fed, or from the second strip 9, when the second strip 9 is fed, in such a way that the single tag 4 is associated with the thread of the filtering chamber in the pickup zone 3, the cut being performed by a tag cutting unit 1 1 positioned close to the pickup zone 3;

- preparing a first 17 and a second 18 joining unit, respectively for the first 6 and the second 9 strip, positioned between the respective first 5 and second 8 reel and the respective first 14 and second 15 movement means, along a corresponding first P6 and second P9 path of the first 6 and second 9 strip; the first joining unit 17 is configured to join a final end of the first strip 6, when it is not fed by the first movement means 14, with an initial end of a new first strip coming from a new first reel, and the second joining unit 18 is configured to join a final end of the second strip 9, when it is not fed by the second movement means 15, with an initial end of a new second strip coming from a new second reel;

- preparing a dividing wall 26 which separates the first 17 and the second 18 joining units from the carousel 1 ; the dividing wall 26 being provided with a first 26a and second 26b slit to allow the passage, respectively, of the first 6 and second 9 strips, in such a way as to not interrupt the first P6 and the second P9 paths.

Preferably, the step of stopping the first strip 6 also comprises a step of moving away, that is, withdrawing, the first strip 6 from the tag cutting unit 1 1.

The method also comprises, after stopping the first strip 6, that there are the following steps with the first reel 5 of the first strip 6 stationary:

- separating an end portion of the first strip 6 from the first reel 5 which is running out;

- disassembling the first empty reel 5;

- assembling a new first reel of a new first strip;

- locking the end portion on a supporting plate 19 using a first locking lever 20;

- positioning an initial portion of the new first strip on the supporting plate 19 superposed on the end portion, in such a way that indicator elements RV2 respectively of the end portion and on the initial portion correspond with a visual reference RV1 present on the supporting plate 19;

- locking the initial portion on the supporting plate 19 by means of a second locking lever 21 ;

- cutting the end portion and the initial portion;

- applying a joining web 25 for joining the end portion and the initial portion; - freeing the end portion and the initial portion from the supporting plate 19 releasing, respectively, the first 20 and the second 21 locking levers, in such a way that the new first strip 6 can be fed to the tag cutting unit 1 1 .