This invention relates to a device for joining filter bags, in particular a device for joining filter bags applied to automatic machines for the production of filter bags for infusion products, such as, for example, tea, coffee, camomile and the like.

Joining devices are known which comprise two operating units, each having a sealing head for sealing (usually, but not necessarily, of the hot- melt type) bottom and/or top ends of filter bags of various types, such as, for example, traditional singie-lobed bags, two-lobed bags, bags of tetrahedrai shape, etc.

It should be noted that the joining devices are used on machines comprising stations (operating, preferably, but not necessarily, continuously) which are able to form continuous strips of filter material with a tubular shape feeding along a feed direction (horizontal or vertical) into which, at predetermined intervals, a dose of infusion product is placed. Some examples of prior art joining devices are illustrated in patent documents JP S63 96003, DE 101 26 202, DE 296 07 449 U1 and EP 2 644 514.

These joining devices join a portion of tubular strip which defines a top of a filter bag being formed and a bottom of a next filter bag. More in detail, the sealing heads of the joining devices cyclically move towards each other until coming into contact with the portion of tubular strip and move away until detaching from the tubular strip, performing seals transversal to the tubular strip arranged at regular intervals. The sealing heads are located on opposite sides and transversaiiy to the tubular strip of filter material being fed.

Each sealing head is connected to a supporting body which, in turn, is constrained to a kinematic unit; the kinematic unit moves the supporting body and the sealing head.

Each kinematic unit comprises two axes of rotary movement (of which at least one is motor driven and synchronised with the movement for feeding the tubular strip of filter material), usually arranged side by side with respect to a horizontal plane or a vertical plane, for each supporting body- sealing head unit.

On each of the axes of rotary movement is keyed an eccentric rotary system consisting of a circular plate having a protruding shaft positioned outside the geometrical centre of the circular plate to form a crank system. Each supporting member is articulated to the eccentric rotary system in such a way as to rotate about the two axes of rotary movement according to a circular trajectory (clockwise or anti-clockwise) and able to move the joining head with an alternating motion towards and away from the continuous strip of filter material at least between an operating position in contact with the tubular strip of filter material and a non-operating position away from the strip of filter material.

As may be noted in Figure 1 , the circular trajectories Ta and Tb of the two supporting body - sealing head units CT define a point of contact PC (which corresponds to a transversal joining zone of the continuous tubular strip of filter material) at the point of tangency of the trajectories of movement Ta and Tb.

However, the joining devices described above have a disadvantage: the sealing heads remain in contact with the continuous tubular strip of filter material for a very short sealing time.

In effect, the sealing heads are effectively in operational contact with the continuous tubular strip of filter material at a single point of contact PC (corresponding to the point of tangency of the circular trajectories Ta and

Tb) for a reduced time and this may determine joins defective or insufficient joins / seals in particular on machines having high production speeds.

Disclosure of the invention

The aim of this invention is therefore to provide a device for joining filter bags for infusion products which is able to overcome the above-mentioned drawbacks.

More specifically, the aim of this invention is to provide a device for joining filter bags for infusion products which is able to operate with high flexibility, at a high operating speed and with a high level of reliability.

A further aim of this invention is to provide a device for joining filter bags for infusion products which is capable of obtaining high quality joins on the strip of filter material.

These aims are achieved by a device for joining filter bags for infusion products according to claim 1 . Preferred embodiments of the invention are covered by the dependent claims.

A device for joining filter bags according to the invention comprises two operating units located on opposite sides of a continuous tubular strip of filter material movable along a feed direction.

Each operating unit comprises a supporting body and a sealing head, connected to the supporting body.

The joining device according to the invention comprises two kinematic units equipped with a corresponding eccentric rotary system. Each kinematic unit is connected to a respective supporting body. The eccentric rotary system is able to move the respective supporting body along a first trajectory to move the sealing head between a position of contact with the strip and a position away from the strip.

Each operating unit also comprises a carriage associated with the sealing head and slidabiy connected to the supporting body. The carriage is configured to be able to translate in both directions relative to the supporting body along a second rectilinear trajectory, advantageously perpendicular to the feed direction.

Each operating unit also comprises a second kinematic unit articulated to a third axis of movement and to the carriage for moving the carriage in a synchronised fashion with the supporting body, thus obtaining a third trajectory of the sealing head resultant from the combination of the first trajectory and the second rectilinear trajectory. According to the invention, the third trajectory comprises a rectilinear stretch which is parallel to the feed direction at the position of contact of the sealing head.

Each operating unit therefore is equipped with a combination of two different components movable in a synchronised fashion with each other, through the agency of a kinematic mechanism, which is able to generate a cyclical movement of the sealing head resulting from the interaction of the two individual trajectories performed by the supporting body and by the carriage: this allows the sealing heads to remain in contact with the continuous tubular strip of filter material (following each other) for sufficient time to perform a correct joining on the continuous tubular strip.

Further features of the invention will become more apparent from the following detailed description of a preferred, non-limiting embodiment of it, with reference to the accompanying drawings, in which:

- Figure 1 shows an operational diagram of a joining device for filter bags of known type;

- Figure 2 shows a schematic front view of a kinematic diagram of the device for joining filter bags for infusion products according to this invention;

- Figure 3 shows a scaied-up schematic front view of an operating diagram of sealing heads referred to Figure 2;

- Figure 4 shows a perspective view of the device for joining filter bags with infusion products according to the invention;

- Figure 5 shows an exploded perspective view of an operating unit forming part of the joining device referred to Figure 4;

- Figures 6 to 9 show front views, with some parts cut away in order to better illustrate others, of successive operating steps of the joining device. Detailed description of preferred embodiments of the invention

With reference to the accompanying drawings, a joining device according to the invention, labelled 100 in its entirety, is used on machines for packaging filter bags 1 for infusion products, such as, for example, tea, coffee, camomile and the like.

In this specification, the joining device acts on a continuous tubular strip of filter material from which, through further operating steps, are formed the filter bags, for example of the single-lobed, doubie-iobed, tetrahedral types etc.

In this case, and purely by way of non-limiting example, the joining device 100 is illustrated during a step of joining a continuous tubular strip S of filter materia! for joining a stretch of it which defines a top of a filter bag being formed and a bottom of a next filter bag.

As illustrated in Figures 2 to 9, the device 100 for joining filter bags 1 for infusion products comprises at least two operating units 2, 3 positioned on opposite sides of the continuous tubular strip S which feeds along a direction A,

Each operating unit 2, 3 comprises a sealing head 4 (for example hot) positioned facing the continuous tubular strip S and a supporting body 5, which supports the sealing head 4.

Moreover, each operating unit comprises two first kinematic units 6 and 6', each having an eccentric rotary system 7, 8, 9, 7', 8', 9 ^" .

Each of the two first kinematic units 6 and 6' is connected to a corresponding first X1 and second X2 axis of movement, of which at least one (for example, the first X1 ) is motor-driven. The first X1 and the second X2 axis of movement are movable in rotation and in a synchronised fashion with the continuous tubular strip S. The two first kinematic units 6, 6' are articulated to the supporting body 5 to move the supporting body 5 along a first trajectory T1 which is able to move the sealing head 4 at least between an operating end position in contact with the continuous tubular strip S and a non-operating end position, away from the continuous tubular strip S. Advantageously, as described in more detail below, the first trajectory T1 is substantially circular.

Again as illustrated, the joining device 100 comprises, for each operating unit 2, 3, a carriage 10 associated with the sealing head 4.

The carriage 10 is slidably housed in the supporting body 5 and configured in such a way as to translate, in both directions, relative to the supporting body 5. The carriage 10 is configured to translate in both directions relative to the supporting body 5 along a second trajectory T2 transversal to the feed direction A. Advantageously, as described in more detail below, the second trajectory T2 is substantially rectilinear. Moreover, the second trajectory T2 is substantially perpendicular to the feed direction A.

Each operating unit 2, 3 also comprises a second kinematic unit 1 1 articulated, at a first end, to a third axis X3 of movement, and at a second end, to the carriage 10.

The second kinematic unit 1 1 is configured for moving the carriage 10 along the second trajectory T2 in a synchronised fashion with the supporting body 5 which is movable along the first trajectory T1 , so as to obtain a movement of the sealing head 4 along a third trajectory T3, resultant from the combination of the first trajectory T1 of the supporting body 5 and of the second trajectory T2 of the sealing head 4 relative to the supporting body 5. The third trajectory T3 comprises at least one rectilinear stretch which is parallel to the feed direction A of the continuous tubular strip S at the operating end position of contact with the sealing head 4.

In other words, the operating units are equipped with two different components movable in a synchronised fashion with each other, through the agency of a kinematic mechanism, which are able to generate a cyclical movement of the sealing head resultant from the combination of the two individual trajectories performed by the supporting body and by the carriage which allows the sealing head to remain in contact with the 5 continuous tubular strip of filter material (following each other) for sufficient time to perform a correct joining on the continuous tubular strip S.

Preferably (see Figure 5), each first kinematic unit 6 and 6' for moving the supporting body 5 comprises a shaft 7, 7' equipped with a crank 8, 8' with the pin 9, 9' which is eccentric relative to the axis of rotation of the shaft 7, i o T.

!t should be noted that each shaft 7, T is connected to the corresponding first X1 and second X2 axis of movement (as described in more detail below).

Hereafter, for simplicity of description, only the operating unit 2 is 15 described, since the structure and the components of the operating unit 3 are substantially the same as the operating unit 2, Any differences of the operating unit 3 relative to the operating unit 2 will be described.

Preferably, the second kinematic unit 1 1 comprises a shaft 12 connected to the third axis X3 of movement.

20 The shaft 12 is equipped with a crank 13 with a pin 14 is eccentric relative to the third axis X3 of movement.

The second kinematic unit 1 1 also comprises a connecting rod 15 articulated, at a first end, to the eccentric pin 14 and, at a second end (in P15), to the carriage 10 associated with the sealing head 4.

25 The second kinematic unit 1 1 uses a crank - connecting rod system for the independent movement, rectilinear and in both directions, of the carriage 10 relative to the supporting body 5.

The extension of the movement of the carriage 10 depends on the size of the crank 13 and the distance of the pin 14 from the centre of rotation of

30 the crank 13 and also on the length of the connecting rod 15.

In light of this, the third axis X3 of movement is connected by a kinematic mechanism to the first X1 and second X2 axes of movement and configured to rotate the shaft 12 with a direction of rotation V12 (for example, in a clockwise direction for the operating unit 2 and anticlockwise for the operating unit 3).

In the embodiment illustrated, the shaft 12 rotates in the opposite direction to the directions V7 of rotation of the eccentric rotary systems 7, 8, 9, 7', 8', 9' of the corresponding first X1 and second X2 axis of movement, so as to obtain the third trajectory T3 of the sealing head 4 configured as a "slot". In alternative embodiments not illustrated, the shaft 12 is not connected in a kinematic fashion to the first X1 and to the second X2 axis of movement, but has autonomous operation and can be rotated in the same direction as the directions V7 of rotation of the eccentric rotary systems 7, 8, 9, 7', 8', 9' of the corresponding first X1 and second X2 axis of movement

Describing in more detail the combination of the first trajectory T1 and the second trajectory T2 (see Figures 2 and 3), the first trajectory T1 of substantially circular movement of the supporting body 5 tends to move the sealing head 4 towards (and away from) the continuous tubular strip S, whilst the translationai movement of the carriage 10 contrasts the moving towards of the sealing head 4 to the continuous tubular strip S, thus obtaining a stretch of trajectory which is rectilinear and parallel to the feed direction A of the continuous tubular strip S. In other words, the combination of the first trajectory T1 and the second trajectory T2 allows the sealing heads 4 to follow and simultaneously come into contact with the continuous tubular strip S for a sufficient time to provide a high quality sealing.

In short, the third trajectory T3 comprises at least one active rectilinear stretch parallel to the feed direction A of the continuous tubular strip S, wherein the sealing heads 4 are in contact with the continuous tubular strip S. Advantageously, the third trajectory T3 comprises at least two rectilinear stretches, of which one active, parallel to the feed direction A of the continuous tubular strip S, wherein the sealing heads 4 are in contact with the continuous tubular strip S, and one inactive, parallel to the feed direction A of the continuous tubular strip S of filter material, wherein the sealing heads 4 are spaced apart from the continuous tubular strip S of filter material.

Preferably, the third axis X3 of movement is interposed between the first X1 and the second X2 axis of movement (see Figures 2 and 5).

!n light of this, each of the axes X1 , X2, X3 of movement is equipped with a respective gear wheel 18, 17, 18. More specifically, the first axis X1 is equipped with a first gear wheel 16 and the second axis X2 is equipped with a second gear wheel 17, keyed to a respective shaft (7, 7') of the eccentric rotary systems (7, 8, 9 and 7\ 8', 9'). Moreover, the third axis X3 is equipped with a third gear wheel 18 keyed to the shaft 12 of the second articulated kinematic unit 1 1 . Advantageously, the third gear wheel 18 is interposed between, and engaged with, the first gear wheel 16 and the second gear wheel 17.

The kinematic system structured in this way makes it possible to obtain simultaneously:

- the movement of the first kinematic units (6, 6') and the second kinematic unit (1 1 ) with a single drive unit (illustrated as a block labelled M in Figure 5);

- the reversal of the direction of rotation of the second kinematic unit (thanks to the third gear wheel 18 acting as idle wheel);

- maintaining in a synchronised fashion the corresponding movements of the supporting body 5 and of the carriage 10 and the feeding of the continuous tubular strip S of filter material, !n short, the sealing heads 4 are stationary relative to the continuous tubular strip S in the active stretch of the third trajectory T3.

In light of this, the first X1 , second X2 and third X3 axes of movement are lying in a same plane positioned parallel with the feed direction A of the continuous tubular strip S of filter material.

It should be noted that, merely by way of an example, the continuous tubular strip S illustrated in the drawings has a trend along a vertical direction, but the invention can be used on a continuous tubular strips S feeding along a horizontal direction, or inclined relative to the vertical direction.

According to the embodiment being described, the carriage 10 has a pair of cylinders 19 slidabie inside corresponding sleeves 20 housed in through seats 21 made on the supporting body 5 for allowing a rectilinear movement, in both directions, of the carriage 10 relative to the supporting body 5, along the second trajectory T2 transversal to the feed direction A of the continuous tubular strip S of filter material.

The through seats 21 made on the supporting body 5 are closed at one end by a cover 25 which, when necessary, may be removed to allow inspections of the through seats 21 or the sleeves 20.

The above-mentioned connecting rod 15 is articulated to the carriage 10 at a point P15 positioned opposite an end of the carriage 10 which supports the sealing head 4.

In a preferred embodiment, the connecting rod 15 is articulated at the end of the carriage 10, outside the supporting body 5, and forming an extension transversal to the supporting zone of the sealing head 4.

In light of this, at least one of the carriages 10 (in the case illustrated and by way of example only, the one present on the unit labelled 2) has a fork 22 in which is articulated an arm 23 for supporting the sealing head 4. The fork 22 has a shaft 26 on which is constrained the arm 23 in order to orient or modifying the position of the sealing head 4 if there were clearances to recover with respect to the opposite head 4, or for adjusting two heads 4 replaced and with different sizes.

The other operating unit 3 has the corresponding arm 23 in a single body with the remaining part of the carriage 10, so that the sealing head 4 of the operating unit 3 defines a fixed contact element for the sealing heads 4 of the operating unit 2.

The supporting body 5 has two end portions 5a and 5b having seats 24 for articulation with the corresponding first kinematic units 8, 6' (in particular the corresponding pins 9, 9') and a central portion 5c for partial siidable housing of the carriage 10.

The structure of the supporting body 5 is substantially C-shaped, wherein the central portion 5c has a middle recess for free passage of the transversal extension of the carriage 10 which can translate freely in both directions supported by the pair of cylinders 19.

The device 100 structured in this way operates according to the steps illustrated in Figures 6 to 9, in which it may be noted that:

- the sealing heads 4 are moved towards the continuous tubular strip S of filter material through a first part of trajectory T1 of the supporting body 5 assisted also by the carriage 10 (curved path), see Figure 6;

- the sealing heads 4 arrive in contact with the continuous tubular strip S of filter material again by means of the movement of the supporting body 5, therefore with first trajectory T1 assisted by the carriage 10, see Figure 7;

- the sealing heads 4 remain in contact with the continuous tubular strip S of filter material under the action of the carriage 10 (second trajectory T2) which allows the contact position to be maintained, whilst there is a lowering and moving away from of the supporting body 5 relative to the tubular strip S of filter material (first trajectory T1 ); the movement of the supporting body 5 allows the sealing heads 4 to follow the continuous tubular strip S of filter material for a stretch sufficient to perform the joining of the strip S (see Figure 8), for the active rectilinear stretch of the third trajectory T3;

- the increase in the withdrawal of the supporting body 5 (trajectory T1 ), together with the re-entry movement of the carriage 10 (trajectory T2) determines the moving away of the sealing heads 4 from the continuous tubular strip S of filter material to perform a new raising and start a new joining cycle (see Figure 9), passing along the inactive rectilinear stretch of the third trajectory T3.

A joining device structured in this way fully achieves the preset aims thanks to the presence of two different components mutually movable and controlled by different kinematic systems which are able to synchronise the movements of the supporting body and of the carriage.

This kinematic combination allows an interaction of two trajectories of movement which are able to maintain the sealing heads in contact with the continuous tubular strip of filter material for a sufficient time to generate a high quality sealing.

This ail achieved without having to increase the dimensions of the operating units and with a high level of operational flexibility of the device, which can maintain high levels of quality even with high operating speeds of the machine on which it is installed.