MXPA98004804A - High speed bending unit for food product packaging machines that can be seen - Google Patents

Abstract

The present invention relates to a high-speed unit for machines for packaging pourable food products, the unit comprising: a supply station for supplying a succession of packets of a pillow-type container containing food products, each having several portions of bending to be bent and sealed on the respective walls of the package to form a respective container in the form of a parallelepiped, conveyor means for feeding the packages along the formation path extending from the supply station to a supply station to an exit station fold means located along the formation path and cooperating with each package to perform the respective fold operations on the package; heating means acting on the folded portions of each package, to melt and seal the folded portions of the respective walls; final package cooperating with each package to retain the respective bent portions on the respective walls as the bent portions are cooled, the unit is characterized in that the conveying means is continuous, and the folding means and the pressing means comprise several interaction members which interact with the packets, and which are fixed in size and cooperate with the packets by virtue of the movement of the transport medium

Description

HIGH SPEED BENDING UNIT FOR MACHINES EIW? S DORS OF PRODUCT ALTERING THAT YOU CAN V _-_ K.'l? K DESCRIPTION OF THE INVENTION The present invention relates to a high speed bending unit for packaging machines for continuously producing aseptic sealed packages, containing pourable food products, from a tube of packaging material. Many food products that can be poured, such as fruit juices, pasteurized milk or UHT (treated at ultra high temperature), wine, tomato sauce, etc. They are sold in containers made of sterilized packaging material. A typical example of such a container is the parallelepiped-shaped packaging container for liquid or for pourable food products known under the name of Tetra Brik Aseptic (registered trademark), which is formed by folding and sealing a material of packaging rolled into strips. The rolled packaging material comprises layers of fibrous material for example paper, covered on both sides with thermoplastic material, for example, polyethylene. and the side of the packaged material and finally makes contact REF: 27478 with the food product in the package also comprises a layer of barrier material, for example, an aluminum sheet, which in turn is covered with a layer of thermoplastic material. As is known, packages of the above type are produced in fully automatic packaging machines, in which a continuous tube is formed from the packaging material supplied in the form of a strip. The strip of packaging material is sterilized by the packaging machine, for example, by applying a chemical sterilizing agent such as a hydrogen peroxide solution; followed by sterilization, the sterilizing agent, for example heat-vaporized, is removed from the surfaces of the packaged material; and the packaged material strip sterilized in this way is maintained in a closed sterile environment, and is folded and longitudinally sealed to form a tube. The tube is filled with the sterilized or sterile processed food product, and sealed in equally spaced cross sections in which packets are then cut into a pillow form, which are then mechanically folded into parallelepiped-shaped packages . Packaging machines of the above type are known, in which pack pillow-type packages are bent into parallelepiped-shaped packages by bending units substantially comprising a conveyor for feeding the packages in stages along a forming path; several bending devices are located in the formation path; a heating assembly acts on the portions of each container to be folded, to melt and seal the portions on respective walls of the container; and a final pressure device cooperates with each container to retain the heat sealed portions in the respective walls as the portions are cooled. More specifically, the bending devices and the final pressing device comprise several interaction members located along the formation path and which can be moved in stages to and from the conveyor to perform respective forming operations on the traveling containers. on the transporter. A major drawback of the known folding units is the intermittent movement, characterized by successive braking and restarting, to which the conveyor and interaction members are subjected and which, as the speed of performance increases, results in deceleration and acceleration Sudden parts of moving parts, and dynamic problems at and above a given maximum performance speed. An object of the present invention is to provide a reliable high-speed bending unit for pourable food packaging machines., designed to solve the aforementioned drawback typically associated with known bending units. In accordance with the present invention there is provided a high speed bending unit for pourable food packaging machine, the unit comprising: a supply station for supplying a succession of pillow type package containing food products, each has several fold portions to be bent and sealed on the respective walls of the package to form a respective parallelepiped-shaped package; conveyor means for feeding the packages along the formation path that extends from the supply station to an exit station; folding means located along the formation path and cooperating with each package to perform the respective fold operations on the package; heating means acting on the folded portions of each package, for melting and sealing the folded portions on the respective walls; and a final pressing means cooperating with each package to retain the respective bent portions on the respective walls as the bent portions are cooled; characterized in that the transport means is continuous; and the folding means and the pressing means comprise several interacting members that interact with the packages, and which are of fixed size and cooperate with the packages by virtue of the movement of the transport means. A preferred non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows an exploded perspective view of a high speed bending unit for food product packaging machines which can be poured, according to the present invention; Figure 2 shows a view of the upper side, on a larger scale, in perspective, with parts removed for clarity, of the unit of Figure 1; Figure 3 shows a view of the underside on a larger scale, in perspective, with parts removed for clarity of the unit of Figure 1; Figures 4 to 8 show schematic front views of a preferred sequence made by the unit of Figure 1 for folding a pillow-type package in a parallelepiped-shaped package. The number 1 in Figures 1 to 3 indicates a high-speed folding unit for a packaging machine (not shown) for continuously producing, from a known tube of packaging material (not shown), packages 2 in the form of aseptic and sealed parallelepipeds (figure 8) containing a pourable food product, such as pasteurized milk or UHT, fruit juice, wine, etc. The tube is formed in a known manner upstream from unit 1 by longitudinally bending and sealing a known strip (not shown) of heat-sealed laminate comprising layers of fibrous material, eg, paper, covered on one side which finally forms the outside of the containers 2, with a layer of thermoplastic material, for example polyethylene and, on the side that finally makes contact with the food product, with a layer of thermoplastic material and a layer of barrier material, for example a sheet of aluminum that in turn is covered with thermoplastic material. The tube of packaging material is then filled with the food product for packaging, sealed in equally spaced cross sections and cut along the cross sections into several packs 3 in the form of a pillow-type container (Figure 4), which are subsequently sent to unit 1 where they are mechanically bent to form the respective containers 2. With reference to Figure 4, each package 3 has an axis A, and comprises a main portion 4 in the form of a parallelepiped and in opposite upper and lower end portions 6, 7 tapered from the portion 4 towards the sealing lines 8, 9 respective, perpendicular to the axis A of the package 3. More specifically, the portion 4 of each container is defined laterally by a pair of flat rectangular walls 10 parallel to each other, to the axis A and to the sealing lines 8, 9 and by a pair of flat rectangular walls 11 extending between the walls 10. Each end portion 6, 7 is defined by a pair of walls 12 substantially in the shape of an isosceles trapezium, inclined slightly towards each other with respect to a plane perpendicular to axis A and having shorter edges defined by respective edges of the walls 10 of the portion 4, and longer edges joined together by the respective sealing line 8, 9. Each package 3 also comprises, for each end portion 6, 7, a substantially rectangular and elongated tab 13, projecting from the respective sealing line 8, 9; and a pair of substantially triangular portions 15, 16 projecting laterally from opposite sides of the portion 4 and which are defined by the end portions of the respective walls 12. To form the package 2, the unit 1 comprises end portions 6, 7 of the package 3 towards one another, so that they bend the respective tongues 13, 14 on end portions 6, 7 and fold and seal the portions 15 of the end portion 6 on the respective walls 12, and portions 1 6 of the end portion 7 on the respective walls 11 of the portion 4. With reference to figures 1 to 3, the unit 1 comprises a support frame 20 (FIG. shown exploded in the component elements in Figure 1); a chain conveyor 21 placed in the frame 20 and for continuously feeding the packages 3 along a formation path B from a supply station 22 to an output station 23; several bending devices 24, 25, 26 placed on the frame 20 at fixed positions along the path B and cooperating with the packages 3 to perform the respective bending operations on the packages; and a heating device 27 acting on the portions 15, 16 of the package 3 to be bent, to melt and seal the portions 15, 16 in respective walls 12, 11; and a final pressing device 28 cooperating with each package 3 to retain the portions 15, 16 in the respective walls 12, 11 as the portions 15, 16 are cooled. More specifically, the conveyor 21 comprises at least one mesh, and In the example, a drive gear 29 and a driven gear 30 are shown; and an articulated chain 31 that forms a circuit around and interposed with the gears 29, 30 and which is positioned with several flat rectangular blades 32, each of which projects from the chain 31 and cooperates and pushes a corresponding wall 10 of a respective pack 3 for feeding the packet along the path B. More specifically, the string 31 comprises a horizontal upper branch 33; a lower branch 34 substantially parallel to the branch 33; and two curved C-shaped portions 35, 36, placed with their respective concavities facing each other, connecting the branches 33, 34 and the middle portions of which respectively define the supply station 22 and the exit station 23 .

The path B comprises a straight main portion Bx defined by the branch 33 of the chain 31; and two end portions B2, B3 of supply and output, respectively, defined by the respective upper portions 35a, 36a of the portions 35, 36 of the chain 31 that extend between the corresponding stations 22, 23 and the branch 33. The branch 33 and the portions 35a, 36a of the portions 35, 36, therefore define a conveyor branch of the chain 31 to feed packages 3 from the station 22 to station 23; while the branch 34 and the remaining portions 35b, 36b of the portions 35, 36 define a return branch of the chain 31 to feed the blades 32 from the station 23 to the station 22. The chain 31 comprises several articulated links 40 by flat rectangular plates from which the cutters extend perpendicularly 32 respective. More specifically, each blade 32 extends asymmetrically from the respective link 40, and divides the link 40 into two rectangular portions 41, 42 of different lengths along the path B and located respectively upstream and downstream of the blade 32 a along path B. More specifically, portion 41 is larger than portion 42 along path B.

Each link 40 is also slightly separated with respect to the adjacent links 40, with which they define respective spaces 43 for the purpose described later. By virtue of the structure of the conveyor 21, the blades 32 are placed vertically along the portion Bx of the path B, and horizontally at the stations 22, 23. Each package 3 is placed on the conveyor 21 with the portion 7 of end in contact with the conveyor branch of the chain 31, with one of the walls 10 resting on the respective blade 32 and with the axis A parallel to the blade 32, so that the portions 15, 16 of each package 3 extend transversely to the trajectory B. The packages 3 are also fed to the conveyor 21 in a horizontal entry position, where the end portion 7 makes contact with the portions 42, 41 of adjacent links 40 and a tongue 14 is loosely inserted. within the respective space 43. Similarly, each finished container 2 moves from the conveyor 21 in a horizontal exit position. The bending device 24 comprises an elongated guide member 44 placed on the frame 20 in a fixed position facing and on the conveyor branch of the chain 31, which extends in the connection portion of the portions Bx and B2 of the trajectory B and defining, toward the chain 31, a concave contrast surface S converging towards the conveyor branch and cooperating in a sliding manner with the end portion of each package 3 for compressing and flattening the end portion 6 towards the chain 31. The guide member 44 comprises several elongated and parallel curved sections 45 rigidly connected to each other by a connecting element 46 transverse to the sections 45; and the sections 45 extend at lateral ends of the guide member 44 comprising portions The respective end 47 projecting longitudinally towards the station 23 with respect to the other sections 45. The bending device 25 comprises a pair of contrast elements 50 defined by parallel elongated sections, placed on the frame 20 adjacent to the opposite side edge 51. respective of the branch 33 of the chain 31, and cooperating slidably with the end portion 7 of each package 3 to bend the tongue 14 on the respective walls 12, and the portions 16 on the respective walls 11 of the portion 4 of the package 3. More specifically, each contrast element 50 comprises a straight intermediate portion 52, parallel to the branch 33 of the chain 31; an upstream curved portion 53 extending toward the branch 33 from the intermediate portion 52; and a downstream curved portion 54 extending from the intermediate portion 52 toward the guide member 55 of the bending device 26, positioned on the bending device 25. The portions 53 upstream of the contrast elements 50 slidely cooperate with the end portion 7 of each package 3 to bend the portions 16 towards the respective walls 11 of the package 3, after first folding the tongue 14 onto the walls 12. respective by means of the elements 90; the intermediate portions 52 of the contrast elements 50 cooperate slidably with the portions 16 of each package 3 to keep the portions 16 oriented towards the respective walls 11 of the package 3; and the downstream portions 54 slidely cooperate with the portions 16 to bring them into contact with the walls 11. A guide member 55 is defined by a substantially U-shaped elongated section that is placed in the frame 20 in a confronting position. and on the branch 33 of the chain 31, which extends downstream from the guide member 44, along the path B and which cooperates with the portions 15 of the end portion 6 of the package 3 to fold it over the walls 12 respective.

The guide member 55 comprises a pair of elongated contrast arms 56 extending substantially over the respective contrast elements 50 and over the respective lateral edges 51 of the branch 33 of the chain 31; and a portion 57 of transverse connection to a path B and connecting the respective current ends of the arms 56. The bending device 26 also comprises a forming roll 58 having an axis perpendicular to the path B, loosely attached to the frame 20 between the arms 56 and a guide member 55, and having opposite circular end surfaces 59 facing the arms 56 and defining, with the arms 56, respective seats in which the portions 15 of each pack 3 slide. The arms 56 comprise, along the path B, first guide portions 60 that diverge with respect to the branch 33 of the chain 31, and which converge with each other to rotate the portions 15 of each package 3 toward each other; second guide portions 61 parallel to each other and to the branch 33, and positioned facing the respective end surfaces 59 of the roller 58 to retain the portions 15 in contact with end surfaces 59; third guide portions 62 parallel to the branch 33 and converging towards each other to bend the portions 15 towards the end portion 6 of the package 3, and fourth guide portions 63 parallel to each other and to the branch 33, and to maintain the portions 15 in the assumed position at the exit of the third guide portions 62. Finally, the portion 57 of the guide member 55 cooperates slidably with the portions 15 of each package 3 to bring them into contact with the end portion 6 of the package 3. With reference to Figures 2 and 3, the frame 20 comprises a pair of fixed sides 64 (only one is shown) to laterally retain the packages 3 along the path B, located on opposite sides of the conveyor branch of the chain 31 and extending between the station 22 and the device 28 of final pressing, which is located immediately downstream of the bending devices 25, 26 along the path B. With reference to figures 1 to 3, the heating device 27 comprises an air heating assembly 65 placed on the frame 20; a pair of first nozzles 66 connected to the assembly 65 and located between the guide portions 63 of the arms 56 for directing hot air over portions 15 of each package 3 before the portions 15 reach the portion 57 of the guide member 55; and a pair of second nozzles 67 connected to the assembly 65 and located between intermediate portions 52 of contrast elements 50 for directing hot air over portions 16 of each package 3 before the portions 16 reach portions 54 downstream of the elements 50 of contrast. The final pressing device 28 comprises three endless bands 70, 71, 72, which are placed in respective pairs of pulleys 73 which in turn are loosely placed on the frame 20 and placed 90 ° to each other and define, between them, and together with the branch 33 of the chain 31, a forming duct (indicated as Pl in Figure 8) having a constant rectangular section and defining the outer contour of the finished packages 2 leaving the unit 1. In the example shown, the bands 70, 71, 72 and the respective pulleys 73 are placed in an upper portion of the frame 20, but alternatively they can be placed in the lower portion of the frame 20. More specifically, two bands are located ( 70, 71) on opposite sides of the branch 33 of the chain 31 and comprise respective regular active branches 74, 75 facing each other, perpendicular to the branch 33 and extending substantially along extensions of the respective sides 64. The band 72 is located on the blades 32, and comprises an active branch 76 parallel to the branch 33 of the conveyor 21 and perpendicular to the active branches 74, 75 of the bands 70, 71. On the outside, the band 72 comprises several projections 77 evenly spaced, shaped and cooperating slidably with the portions 15 of each pack 3 to compress portions 15 over the now portion 6 of the flat end of the package 3. On the outside, the band 72 also compresses several elongated projections 78 perpendicular to the path B interposed between the shaped projections 77 and which, as the conveyor 21 advances, coincide with respective elongated openings 79 formed in the same direction. the free end edges of the respective blades 32 to synchronize the movement of the band 72 with the chain 31. Alternatively, the bands 70, 71 can be formed in the same manner as the band 72, with projections similar to the projections 77, 78. As will be apparent from the foregoing description, in accordance with an important feature of the present invention, the guide members 44, 45, the contrast elements 50, the roller 58 and the bands 70, 71 and 72 are all of fixed size and cooperate with the packages 3 under the movement of the conveyor 21. Now the operation of the unit 1 will be described with reference to a package 3, and from the at which time the package 3 is fed onto the respective blade 32 of the conveyor 21 in the horizontal entry position with the tongue 14 of the end portion 7 engaging the respective space 43. By virtue of the movement and the momentum exerted by the blade 32, the package 3 is inclined along the portion B2 of the trajectory B and finally ends at the upper end on a vertical position at the beginning of the portion B of the trajectory B; movement during which the end portion 6 of the package 3 slidably cooperates with the guide member 44 which, as described, has a patient converging towards the chain 31 and thus compresses and flattens the end portion 6 (figure 5). As soon as or shortly after the end portion 6 of the package 3 approaches the end portions 47 of the sections 45, the end portion 7 of the package 3 contacts the upstream portions 53 of the elements 50 of contrast; as the package 3 slides against the element 90, the tongue 14 is bent over the end portion 7, and the end portion 7 is flattened; and as the package 3 slides along the portions 53 of the contrast elements 50, the portions 16 are rotated towards the respective walls 11 of the package 3 (Figure 6).

Subsequently, the portions 15 of the end portion 6 of the package 3 reach the guide portions 60 of the arms 56, where they are rotated upwards to a vertical position parallel to one another; at which point the portions 15 are fed between the guide portions 61 of the arms 56 and the end surfaces 59 of the forming roller 58 and are further bent towards the walls 12 of the end portion 6 by guide portions 62 arms 56 (figure 7). As package 3 travels between the portions 63 of the arms 56 and between the intermediate portions 52 of the contrast elements 50, the nozzles 66, 67 direct hot air to the respective portions 15, 16 to partially and locally melt the layer of thermoplastic material covering the portions 15 and 16. , 16; and as the package 3 slides below the portion 57 of the guide member 55 and between the portions 54 downstream of the contrast elements 50, the portions 15, 16 are finally folded into the respective walls 12, 11. Finally, the package 3 is pushed by the movement of the conveyor 21 through the conduit Pl defined by the branch 33 of the conveyor 21 and by the active branches 74, 75 and 76 of the badas 70, 71 and 72, within which the portions 15, 16 are cooled and sealed, by virtue of the pressure exerted on them, to the respective walls 12, 11 to form in finished container 2 (figure 8). The advantages of unit 1 according to the present invention will be apparent from the description that follows. In particular, the continuous operation of unit 1 solves the dynamic problems caused by the sudden acceleration and deceleration to which the moving parts of step-operated systems are subjected., and therefore provides the ability to obtain high throughput speeds (eg 8000-24000 containers per hour). In addition, unlike the known bending units, unit 1 has as its feature only one activated member, i.e., conveyor 21 which, therefore, is simplified and provides greater reliability of the control system of unit 1 , and therefore the packaging machine in which the unit 1 is installed. Finally, unit 1 is highly compact by virtue of the members that interact with the package 3 (44, 50, 55, 58, 70, 71, 72) which are all placed substantially on the conveyor 21. Clearly, changes can be made to the unit 1 as described and illustrated herein, however, without departing from the scope of the claims.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates. Having described the invention as above, property is claimed as contained in the following:

Claims (16)

I ^ Iv NDICATIONS

1. A high-speed bending unit for machines for packaging pourable food products, the unit comprises: a supply station for supplying a succession of pillow-type packets containing food products, each having several fold portions to be bent and sealed on the respective walls of the package to form a respective container in the form of a parallelepiped; conveyor means for feeding the packages along the formation path that extends from the supply station to an exit station; folding means located along the formation path and cooperating with each package to perform the respective fold operations on the package; - heating means acting on the folded portions of each package, for melting and sealing the folded portions on the respective walls, - and final pressing means cooperating with each package to retain the respective folded portions on the respective walls as they are cooled the folded portions; the unit is characterized because the means of transport is continuous; and the folding means and the pressing means comprise several interacting members that interact with the packages, and which are of fixed size and cooperate with the packages by virtue of the movement of the transport means.

The unit according to claim 1, characterized in that the conveyor means comprises an endless conveyor, which in turn comprises several pusher elements for respective packages, a conveyor to feed the pusher elements and the packages along of the training path, and a return branch to feed the pushing elements from the exit station to the supply station.

The unit according to claim 2, for folding pillow-type packets, each comprising a main portion substantially in the form of a parallelepiped, a first end portion tapered from the main portion towards the respective sealing line and placed in contact with the conveyor branch, and a second opposite end portion also tapered from the main portion towards a respective sealing line; each package comprises, for each end portion, a pair of bent portions projecting laterally from opposite sides of the main portion and transversely to the formation path, the unit is characterized in that the interaction members of the bending means comprise a first elongated guide member facing the conveyor branch extending to an upstream portion of the forming path and defining a contrast surface converging toward the conveyor branch and cooperating slidably with the second end portion of each package to flatten the second end portion.

The unit according to claim 3, characterized in that the first guide member comprises several elongated, parallel and fixed elements that extend in the same direction as the formation path.

The unit according to claim 3 or 4, characterized in that the interaction members of the bending means comprise: a pair of first fixed contrast elements defined by elongated sections, located downstream from the first guide member as length of the formation path, spaced apart from the conveyor branch and oriented to respective opposite lateral edges of the conveyor branch; and a pair of second fixed contrast elements defined by elongated and located sections adjacent to the respective lateral edges of the conveyor branch; the first and second contrast elements cooperate respectively slidably with the second end portion and the first end portion of each package to bend the respective bending portions.

The unit according to claim 5, characterized in that the first contrast elements define respective arms of a second substantially U-shaped guide member comprising a connection portion transverse to the formation path and connecting the respective ends downstream of the first contrast elements; the interaction members of the bending means comprise a forming roller interposed between the first contrast elements having an axis perpendicular to the formation path and having opposite end surfaces oriented towards the first contrast elements and defining, with the first contrast elements, respective seats in which the respective folded portions of each package slide.

7. The unit according to claim 6, characterized in that the first contrast elements comprise, along the formation path, first guide portions that diverge with respect to the conveyor branch and that converge to each other to rotate the portions respectively bent from each package towards each other; according to the parallel guide portions between and to the conveyor branch and oriented respectively to the end surfaces of the forming roll to retain the bent portions on the end surfaces; third guide portions parallel to the conveyor branch and converging to fold the bent portions towards the second end portion of the package; and fourth guide portions parallel to each other and the conveyor to retain the bent portions in the assumed position at the exit of the third guide portions; the connecting portion of the second guide member slidably cooperates with the respective fold portions of each package to bring the fold portions into contact with the second end portion of the package.

The unit according to any of the preceding claims 5 to 7, characterized in that the second contact elements are parallel to each other, and each one comprises a straight intermediate portion parallel to the conveyor branch; a curved upstream portion extending toward the conveyor branch from the intermediate portion; and a curved downstream portion extending toward the second guide member from the intermediate portion; the upstream portions of the second contrast elements cooperably slidable with the first end portion of each package to rotate the respective fold portions towards the respective opposite walls of the main portion of the package; and the downstream portions of the second contrast elements cooperate in a slidable manner with the respective fold portions of each package to bring the fold portions in contact with the respective walls of the main portion of the package.

The unit according to any of the preceding claims, from 2 to 8, characterized in that it comprises a pair of fixed sides for laterally retaining the packages located on opposite sides of the conveyor and extending between the supply station and the final pressing medium.

The unit according to claim 8 or 9, characterized in that the heating means comprises an air heating assembly; a pair of first nozzles connected to the heating assembly and located between the fourth guide portions of the first contrast elements to direct hot air over the respective fold portions of each package before the fold portions reach the connecting portion of the package. second guide member; and a pair of second nozzles connected to the heating assembly and located between the intermediate portions of the second contrast elements to direct hot air over the respective fold portions of each package before the fold portions reach the downstream portions of the packages. second contrast elements.

The unit according to any of the preceding claims, from 2 to 10, characterized in that the interaction members of the final pressure medium comprise three endless bands placed 90 ° with respect to each other and defining, between them and together with the conveyor branch, a forming duct having a constant rectangular section that defines the outer contour of the packaging finish.

The unit according to claim 11, characterized in that each of the bands is placed in a respective pair of free pulleys.

The unit according to claim 11 or 12, characterized in that the first and second of the bands are placed on opposite sides of the conveyor branch and comprise respective active branches facing the conveyor branch; and wherein the third of the bands comprises an active branch perpendicular to the active branches of the first and second bands and oriented parallel to the conveyor branch.

The unit according to claim 13, characterized in that at least one of the strips comprises several first coupling elements equally spaced to which, as the conveyor advances, they releasably couple the second of the coupling elements on the conveyor. the respective push elements to synchronize the movement of the band with the conveyor branch of the conveyor.

The unit according to claim 14, characterized in that the first coupling elements comprise respective elongate projections, transverse to the formation path and projecting from the third band; and wherein the second coupling elements comprise respective elongate openings formed in the free end edges of the respective push elements.

16. The unit according to any of the preceding claims, from 13 to 15, characterized in that the third band comprises, externally, several shaped projections cooperating in a sliding manner with the respective fold portions of each package to compress the fold portions on the second end portion of the package and defining a respective substantially flat or concave wall of the finished package.