Method and apparatus for packaging articles

Abstract

The present invention relates to a method and an apparatus for forming a package that includes an article (A) encapsulated between a first continuous paper sheet material (18) and a second continuous paper sheet material (20), with the edges of the first and second continuous paper sheet materials joined by a heat-activated adhesive, wherein the first continuous paper sheet material (18) and the second continuous paper sheet material (20) are heated while being subjected to a longitudinal tensile force.

Description

Technical Field

[0001] The present invention generally relates to the packaging of articles, particularly flat articles, i.e., articles having a thickness lower than their other dimensions.

[0002] More specifically, the present invention relates to a method and an apparatus for forming a package that includes an article encapsulated between two opposing sheets of paper material, the edges of the paper material being joined by a heat-activated adhesive.

[0003] The development of the present invention has been particularly focused on its application in the field of packaging plasters, such as plasters for covering wounds, pharmaceutical plasters, pain-relieving plasters, and heating plasters with and without drugs.

[0004] In the following description, reference will be made to this specific field, without loss of generality. Background Art

[0005] In the medical field, there are different types of plasters. In many cases, these products are boxed and not wrapped. In some cases, the plasters are individually packaged in envelope-like packages before being boxed.

[0006] The individual packaging of plasters is achieved by encapsulating the individual plasters between two overlapping flexible sheets, which sandwich the respective plasters and are joined together at their edges by an adhesive. Typically, in this field, the adhesives used are heat-activated adhesives, as they ensure the stable fixation of the sheets, thus protecting the article from external factors. Due to these heat-activated adhesives, once the package is opened, it cannot be resealed again, which allows the health and hygiene standards related to the market of plasters or other similar articles to be met. The package can be formed by two sheets of paper material, with a heat-activated adhesive applied on the inner surface of one of the sheets of paper material. The sheet of material provided with the heat-activated adhesive can be a laminated material having the adhesive already provided.

[0007] In the devices according to the prior art, the packaging of plasters between two flexible sheets is carried out by advancing a continuous array of plasters spaced apart from each other in the machine direction and overlapping two continuous sheets of paper on opposite sides of the continuous array of plasters, one of the sheets of paper having a heat-activated adhesive layer, thereby forming a continuous composite strip consisting of two continuous sheets of paper and a continuous array of plasters sandwiched between the two continuous sheets of paper. The packaging is closed by passing the continuous composite strip through at least one pair of pressure rollers.

[0008] The fixation between the two sheets of paper is achieved by activating the heat-activated adhesive, which occurs when the flexible sheets are compressed together along the compression line.

[0009] Subsequently, the package is obtained by transversely cutting a continuous composite strip along the transverse weld between each pair of articles.

[0010] The welding between two paper sheets must meet precise quality requirements stipulated by the plaster manufacturer. The quality specifications are as follows:

[0011] - From the perspective of appearance: The adhesive material must be clearly transferred from one sheet to the other. The welded joint must be complete and clean, free of impurities and obvious damage. The color of the packaging sheet must not change due to the welding process, and the packaging sheet must not be significantly deformed due to the welding process;

[0012] - From the perspective of the seal of the weld: The release force (peel) must be within a precise quantified range, and during the opening of the package, there must be no variation in the release force between one area and another or between different packages;

[0013] - From the perspective of the seal and hygiene standards of the weld: The welding of the package must place the product in an environment where no contaminants can enter from the outside of the package and ensure that no substances leak from the inside (a leak test is conducted by placing a colored liquid inside the package and monitoring any spills).

[0014] One of the main problems with the equipment according to the prior art is that the current maximum speed of the packaging equipment is approximately in the order of 50 - 60 m / min. This speed limitation is due to the fact that as the machine speed increases, the pressure roller cannot give the flexible sheet enough energy to allow the correct transfer of the adhesive material from one sheet to the other, because the contact time between the pressure roller and the sheet decreases proportionally. In this case, increasing the speed of the equipment beyond the limit of 50 - 60 m / min will compromise the quality requirements stipulated by the plaster manufacturer.

[0015] US5613601A discloses a method and apparatus for thermally sealing dispensing packages, which packages include a water-permeable bag formed of two nonwoven webs that encapsulate a predetermined amount of particulate product, such as tea or coffee, which releases flavoring substances in an immersion liquid. The nonwoven webs have a heat-activated type adhesive surface that allows the bag walls to be permanently closed by circumferentially thermally sealing them to each other. The thermal sealing operation is carried out simultaneously with encapsulating a predetermined amount of particulate product between the two nonwoven webs. Summary of the Invention

[0016] The object of the present invention is to provide a method and apparatus for packaging articles, the articles being encapsulated between two opposite flexible sheets that are joined together by a heat-activated type adhesive, the method and apparatus allowing the production speed to be increased without compromising the quality requirements of the package.

[0017] According to the present invention, the above object is achieved by a method and an apparatus for packaging articles. Description of the Drawings

[0018] The present invention will now be described in detail with reference to the drawings given by way of non - limiting example only, in which:

[0019] Figure 1 is a schematic view of an apparatus for packaging articles according to the present invention;

[0020] Figure 2 and Figure 3 are schematic details of a possible embodiment of a tensioning device for the apparatus according to the present invention;

[0021] Figure 4 is Figure 1 a partial perspective view of a heating roller indicated by arrow IV in ; and

[0022] Figure 5 is Figure 1 a perspective view of a compression unit indicated by arrow V in. Detailed Description of the Preferred Embodiments

[0023] Referring to Figure 1 , reference numeral 10 denotes an apparatus for packaging flat articles A in an envelope - shaped package which closes around each article A along the edges of the package.

[0024] The article A can be a wound - covering plaster, a pharmaceutical plaster, an analgesic plaster, a heating plaster, or the like.

[0025] The articles A are aligned and spaced apart from each other in a continuous array which advances in the machine direction X on an inlet conveyor 12.

[0026] The apparatus 10 includes a first feeding assembly 14 and a second feeding assembly 16 which feed a first continuous paper sheet 18 and a second continuous paper sheet 20 to an overlapping unit 22 respectively.

[0027] The first continuous paper sheet 18 and the second continuous paper sheet 20 are unwound from respective reels 19, 21. At least one of the two continuous paper sheets 18, 20 includes a heat - activatable adhesive. One of the two continuous paper sheets 18, 20 can be a laminated material already equipped with a heat - activatable adhesive. In other embodiments, the heat - activatable adhesive can be applied in - line using an adhesive dispenser. The heat - activatable adhesive layer can be applied or already present on the entire surface of the continuous paper sheets 18, 20. The heat - activatable adhesive has no adhesive properties until it is heated above a preset temperature (activation temperature) for a preset time. After pressure is applied, the heat - activatable adhesive fixes its state and typically its state will no longer change even if it is reheated to the activation temperature.

[0028] In a possible embodiment, the first continuous paper sheet 18 may have a specific gravity of 8.3 g / m 2 and may have a layer of heat-activated adhesive over the entire surface, and the second continuous paper sheet 20 may have a specific gravity of 9 g / m 2 and may have a layer of silicone-like smooth material on the surface. The two continuous paper sheets 18, 20 are joined such that the surface of the first continuous paper sheet 18 having the heat-activated adhesive contacts the smooth surface of the second continuous paper sheet 20.

[0029] The overlapping unit 22 may include a pair of joining rollers 24 that are tangent to each other and may rotate in opposite directions about respective axes that are parallel to each other and perpendicular to the machine direction X. The joining rollers 24 may rotate idly about the respective axes of rotation.

[0030] When the two continuous paper sheets 18, 20 advance toward the tangent region of the two joining rollers 24, they remain in contact with the outer surfaces of the respective joining rollers 24. The article A is fed in the X direction between the two continuous paper sheets 18, 20 toward the tangent region between the pair of joining rollers 24. The two continuous paper sheets 18, 20 overlap each other on opposite sides with respect to the article A while passing through the tangent region of the pair of joining rollers 24.

[0031] Downstream of the overlapping unit 22, a continuous composite strip 26 is formed, which includes the two continuous paper sheets 18, 20 that overlap each other and a continuous array of articles A that are longitudinally spaced apart from each other and sandwiched between the two continuous paper sheets 18, 20. One of the two continuous paper sheets 18, 20 has a heat-activated adhesive layer on its surface facing the other continuous paper sheet 18, 20.

[0032] The apparatus 10 includes a compression unit 28 that is configured to fix the two continuous paper sheets 18, 20 to each other by compressing the heat-activated adhesive along a sealing line extending around a single article A.

[0033] The overlapping unit 22 and the compression unit 28 are two independent modules independent of each other, so that the steps of overlapping and compressing the two continuous flexible sheets 18, 20 are independent. In particular, when the step of encapsulating the article A between the flexible sheets 18, 20 is completed, the compression step is performed such that when the compression step is performed, the article is completely encapsulated between the flexible sheets 18, 20.

[0034] Refer to Figure 4, the compression unit 28 includes a first compression roller 30 and a second compression roller 32 that cooperate with each other and are configured to compress the continuous composite strip 26 along a series of compression zones 34, each compression zone having a frame-like shape around the corresponding article A. The compression zones 34 are formed on the outer peripheral surface of the first compression roller 30. The compression zones 34 can be defined by two continuous longitudinal compression elements 36 and a plurality of transverse compression elements 38. The compression zones 34 can be made of a soft material, such as silicone resin, to avoid forming marks on the two continuous paper sheets 18, 20. In a possible embodiment, the first compression roller 30 is not heated, while the second compression roller 32 can be heated, for example, by an internal heating resistor.

[0035] The second compression roller 32 can have a smooth outer surface that presses against the longitudinal compression elements 36 and the transverse compression elements 38 of the first compression roller 30.

[0036] Referring to Figure 1 , a first pair of feed rollers 25 can be arranged between the coupling roller 22 and the compression rollers 30, 32, and a second pair of feed rollers 42 can be arranged downstream of the compression rollers 30, 32. The first pair of feed rollers 25 and the second pair of feed rollers 42 are driven at the same circumferential speed, and their purpose is to control the feed speed of the continuous composite strip 26 when it passes through the compression unit 28. The first pair of feed rollers 25 and the second pair of feed rollers 42 can have a recessed central portion to avoid compressing the article A.

[0037] Reference Figure 1 , the apparatus 10 includes a first heating roller 44 and a second heating roller 46 that are configured to heat the corresponding continuous paper sheets 18, 20 upstream of the overlapping unit 22.

[0038] Referring to Figure 5 , each heating roller 44, 46 can be configured to heat the corresponding first continuous paper sheet 18 or second continuous paper sheet 20 along a local heating zone 48 formed on the outer surface of the heating roller 44, 46, each local heating zone having a frame-like shape. In a possible embodiment, the heating zone 48 has the same shape as the compression zone 34. Each heating roller 46, 48 can have the same structure as the compression roller 30 of the compression unit 28. Similar to the compression zone 34, the heating zone 48 can be defined by two continuous longitudinal heating elements 50 and a plurality of transverse heating elements 52, which can be made of a metal such as steel. Each heating zone 48 is surrounded by an insulating portion 54 made of an insulating material such as (Teflon) or formed. A portion 56 of the insulating material can also be arranged laterally outwardly onto the longitudinal heating element 52.

[0039] The heating zones 48 of the heating rollers 44, 46 can be heated by heating elements arranged inside the heating rollers 44, 46. The heating elements can be electric heating elements or fluid heating elements that use a fluid such as oil or air as the heating medium.

[0040] Referring Figure 1 , the first feeding assembly 14 and the second feeding assembly 16 feed the corresponding first continuous paper sheet 18 and the second continuous paper sheet 20 on the outer surfaces of the corresponding heating rollers 44, 46. The first continuous paper sheet 18 and the second continuous paper sheet 20 are wound around the outer surfaces of the corresponding heating rollers 44, 46 at an angle of approximately 280°. The winding angles of the first continuous paper sheet 18 and the second continuous paper sheet 20 on the outer surfaces of the corresponding heating rollers 44, 46 depend on the diameters of the heating rollers 44, 46 and the feeding speeds of the first continuous paper sheet 18 and the second continuous paper sheet 20. When the feeding speeds of the first continuous paper sheet 18 and the second continuous paper sheet 20 are approximately 200 m / min, the first continuous paper sheet 18 and the second continuous paper sheet 20 should remain in contact with the outer surfaces of the corresponding heating rollers 44, 46 along corresponding arcs having a range of 800 - 1000 mm. When the feeding speeds of the first continuous paper sheet 18 and the second continuous paper sheet 20 are approximately 100 m / min, the first continuous paper sheet 18 and the second continuous paper sheet 20 are sufficient to remain in contact with the outer surfaces of the corresponding heating rollers 44, 46 along arcs having a range of approximately 505 mm.

[0041] The heating rollers 44, 46 can be configured to heat the continuous paper sheets 18, 20 along the heating zone 48 at a temperature between 100 - 200 °C, preferably between 160 - 180 °C.

[0042] Heating the first continuous paper sheet 18 and the second continuous paper sheet 20 on the first heating roller 44 and the second heating roller 46 may not fully activate the heat - activated adhesive, such that the first continuous paper sheet 18 and the second continuous paper sheet 20 cannot be bonded to each other in the overlapping unit 22. In this case, the full activation of the heat - activated adhesive is carried out in the compression unit 28. In a possible embodiment, heating the continuous paper sheets 18, 20 on the heating rollers 44, 46 can fully activate the heat - activated adhesive, such that the heat - activated adhesive is fully activated before reaching the compression unit 28.

[0043] The pressure roller 30 of the compression unit 28 and the heating rollers 44, 46 are controlled by an electronic control unit 78, which drives the heating rollers 44, 46 and the compression roller 30 around their respective axes at the same speed and keeps the heating zone 48 and the compression zone 34 in phase with each other, such that the continuous composite strip 26 is compressed in the compression zone 34 that overlaps with the heating zone 48 of the first continuous paper sheet 18 and the second continuous paper sheet 20.

[0044] The continuous flexible sheets 18, 20 are preheated on the heating rollers 44, 46 to allow the continuous composite strip to have a greater speed during its passage through the compression unit 28. It has been found that by heating the continuous flexible sheets 18, 20 to a temperature in the order of about 160 - 180 °C, the continuous composite strip 26 can be advanced through the compression unit 28 at a speed of about 200 m / min. The flexible sheets 18, 20 can be advanced through the compression unit 28 at a speed of 150 - 250 m / min, especially 180 - 210 m / min. Even at very high manufacturing speeds, the preheating ensures that the final packaging meets all the quality requirements specified by the plaster manufacturer, in particular the uniform transfer of the heat - activated adhesive onto the non - adhesive layer sheet, the optimal sealing of the welds, the uniform release force, and the guarantee of no leakage.

[0045] According to the features of the present invention, the first feeding assembly 14 and the second feeding assembly 16 are configured to feed the first continuous paper sheet 18 and the second continuous paper sheet 20 along the respective longitudinal directions with a longitudinal pulling force between 50 and 200 N. The optimal pulling force is about 100 N. This pulling force is maintained along the path of the first continuous paper sheet 18 and the second continuous paper sheet 20 from the respective feeding assemblies 14, 16 until the compression unit 28. In a possible embodiment, the pulling force of the first continuous paper sheet 18 and the second continuous paper sheet 20 is maintained until the second pair of feeding rollers arranged downstream of the compression unit 28.

[0046] In the solutions of the prior art, the typical working pulling force of the continuous paper sheets is usually in the range from a few N to 20 - 30 N. It has been found that with the pulling force used in the prior art methods, at a feeding speed of the continuous paper sheets of about 200 m per minute, there is poor glue transfer at the center of the transverse seal section. It has also been found that as the pulling force of the first continuous paper sheet 18 and the second continuous paper sheet 20 at the heating rollers 44, 46 increases, the sealing quality between the first continuous paper sheet 18 and the second continuous paper sheet 20 at the center of the transverse seal section improves.

[0047] The reason for the improvement in the sealing quality as the pulling force increases is that the high pulling force of the continuous paper sheets 18, 20 on the heating rollers 44, 46 ensures more uniform contact of the paper sheets with the heating rollers 44, 46 in the transverse direction.

[0048] It has been found that by gradually increasing the feeding pulling force of the continuous paper sheets 18, 20, the problem of the reduction of the sealing connection at the center of the transverse seal gradually decreases.

[0049] Tests conducted by the applicant have shown that a feeding pulling force of about 100 N for the continuous paper sheets 18, 20 eliminates the defects in the central part of the transverse seal.

[0050] With a higher feed tension, the sealing quality at the center of the lateral seal can be further improved. The upper limit of the feed tension can be close to the breaking limit of the paper sheet material (about 200 N for paper sheet materials with a heat-activated adhesive layer and about 150 N for paper sheet materials without a heat-activated adhesive layer). The lower limit of the feed tension is in the range of 50 - 60 N. It should be noted that these tension values are very different from the feed tension of the nonwoven web, which is typically in the range of 1 - 10 N. In the solution according to the present invention, a high feed tension is possible because paper is a material with very little deformability and can withstand a tension close to the breaking limit under a relatively small stretch.

[0051] When the first continuous paper sheet 18 and the second continuous paper sheet 20 pass in contact with the heating rollers 44, 46, various methods can be used to tension them.

[0052] Reference Figure 1 , in one possible embodiment, the first feed assembly 14 and the second feed assembly 16 can include respective feed rollers 60, 58, which can be driven at a circumferential speed lower than the circumferential speed of the feed rollers 25, 42.

[0053] In a possible embodiment, the heating rollers 44, 46, the feed rollers 25, 42, and the compression rollers 30, 32 are all driven at the same circumferential speed, so that the longitudinal tension of the first continuous paper sheet 18 and the second continuous paper sheet 20 remains constant in the respective paths extending from the heating rollers 44, 46 until the feed roller 42 located downstream of the compression rollers 30, 32. In some cases, the circumferential speeds of the compression rollers 30, 32 and the heating rollers 44, 46 may be slightly different from the circumferential speed of the feed rollers 25, 42. Under these conditions, there is a slight slip between the first continuous paper sheet 18 and the second continuous paper sheet 20 and the compression rollers 30, 32 and the heating rollers 44, 46.

[0054] The electronic control unit 78 can control the circumferential speed of the feed rollers 60, 58 based on the signals provided by the tension measuring devices 64, 66, which measure the longitudinal tension of the respective first continuous paper sheet 18 and the second continuous paper sheet 20. Each tension measuring device 64, 66 can include a force measuring sensor 68 formed by an idler roller around which the first continuous paper sheet 18 or the second continuous paper sheet 22 is wound. The force measuring sensor 68 sends a signal to the electronic control unit 78 indicating the longitudinal tension of the first continuous paper sheet 18 and the second continuous paper sheet 22. If for any reason the longitudinal tension of the first continuous paper sheet 18 and the second continuous paper sheet 20 changes relative to a preset value, the electronic control unit 78 changes the speed of the feed rollers 58, 60 to maintain the tension of the first continuous paper sheet 18 and the second continuous paper sheet 22 at the preset value.

[0055] Reference Figure 2 Referring to Figure 2 , in a possible embodiment, each of the first feed assembly 14 and the second feed assembly 16 may include a tensioning device 70 that applies a lateral force to the respective first continuous paper sheet 18 or second continuous paper sheet 20 when the first continuous paper sheet 18 or the second continuous paper sheet 20 moves towards the corresponding heating rollers 44, 46. The tensioning device 70 may include a tensioning roller 72 that engages with the respective continuous paper sheets 18, 20 and is movable in a direction transverse to the respective continuous paper sheets 18, 20.

[0056] The tensioning roller 72 may be carried by a pivot arm hinged about an axis parallel to the axis of rotation of the tensioning roller 72. A counterweight may be provided on the pivot arm to adjust the force applied by the tensioning roller 72 to the respective continuous paper sheets 18, 20.

[0057] Referencing Figure 3 Referring to Figure 3 , in a possible embodiment, the tensioning device 70 may include an actuator 74 that laterally moves the tensioning roller 72 towards the respective continuous paper sheets 18, 20.

[0058] The longitudinal tension of the first continuous paper sheet 18 and the second continuous paper sheet 20 is equal to half of the force applied by the tensioning roller 74 to the respective continuous paper sheets 18, 20.

[0059] Feeding the first continuous paper sheet 18 and the second continuous paper sheet 20 at a high longitudinal tension solves the problem of poor sealing quality at high speeds, but problems occur when the device stops. If the paper sheets 18, 20 remain in stationary contact with the heating rollers 44, 46 at a high longitudinal tension for a period of time (about 30 minutes), they will burn or be damaged to the extent that they will break when the device is restarted. To solve this problem, the first feed unit 14 and the second feed unit 16 are configured to reduce the longitudinal tension of the respective first continuous paper sheet 18 and second continuous paper sheet 20 when the feeding of the first continuous paper sheet 18 and the second continuous paper sheet 20 stops. When the device stops, the longitudinal tension of the respective first continuous paper sheet 18 and second continuous paper sheet 20 can be reduced to 0 - 30 N. In Figure 1 the embodiment of, the reduction of the longitudinal tension of the first continuous paper sheet 18 and the second continuous paper sheet 20 can be achieved by increasing the speed of the feed rollers 58, 60 before the device 10 stops or by driving the feed rollers 58, 60 for a short time after the device 10 stops.

[0060] In Figure 2 and Figure 3 the embodiment of, the reduction of the longitudinal tension of the first continuous paper sheet 18 and the second continuous paper sheet 20 can be achieved by raising the tensioning roller 72, thereby reducing or eliminating the force applied by the tensioning roller 72 to the first continuous paper sheet 18 and the second continuous paper sheet 20.

[0061] Of course, without prejudice to the principles of the present invention, the details of the construction and embodiments may be widely varied relative to those described and shown, and thus do not depart from the scope of the present invention as defined by the appended claims.

Claims

1. A method for packaging an article, the method comprising: - Feed a first continuous paper sheet and a second continuous paper sheet in a respective longitudinal direction, wherein at least one of the continuous paper sheets has a heat-activated adhesive on one surface, - Tension the first continuous paper sheet and the second continuous paper sheet along the respective longitudinal direction using a longitudinal tension force between 50 and 200 N to improve the retention of the heat-activated adhesive, - While tensioned in the longitudinal direction, heat the first continuous paper sheet and the second continuous paper sheet on respective heating rollers so as to heat the first continuous paper sheet and the second continuous paper sheet without activating the heat-activated adhesive such that the heated first continuous paper sheet and second continuous paper sheet do not adhere to each other when overlapped, - Feed a product stream between the first continuous paper sheet and the second continuous paper sheet, - Overlap the heated and tensioned first continuous paper sheet and second continuous paper sheet via respective joining rollers independent of the heating rollers on opposite sides of the product stream, wherein the first continuous paper sheet and the second continuous paper sheet do not adhere to each other during the overlap, and - Compress and further heat the first continuous paper sheet and the second continuous paper sheet around the product to activate the heat-activated adhesive for bonding and fix the first continuous paper sheet and the second continuous paper sheet to each other by the heat-activated adhesive, the compression and further heating being performed by a pair of cooperating compression rollers independent of the heating rollers and the joining rollers.

2. The method according to claim 1, wherein, The first continuous paper sheet and the second continuous paper sheet remain tensioned from upstream of the heating rollers until the compression step.

3. The method according to claim 1, wherein, Tension the first continuous paper sheet and the second continuous paper sheet by controlling respective feed speeds upstream of the heating rollers.

4. The method according to claim 3, comprising measuring the longitudinal tensile forces of the first continuous paper sheet and the second continuous paper sheet, and controlling the feed speed based on the measured tensile forces.

5. The method according to claim 1, wherein, Tension the first continuous paper sheet and the second continuous paper sheet by applying a lateral tension force to the first continuous paper sheet and the second continuous paper sheet by means of respective tensioning rollers.

6. The method according to claim 1, wherein, When the feeding of the first continuous paper sheet and the second continuous paper sheet stops, the longitudinal tension force decreases.

7. The method according to claim 1, wherein, Heat the first continuous paper sheet and the second continuous paper sheet along a heating zone, each heating zone having a frame-like shape.

8. The method according to claim 7, wherein, Compress the first continuous paper sheet and the second continuous paper sheet along a compression zone surrounding the respective product, each compression zone having a frame-like shape and overlapping the respective heating zone.

9. The method according to claim 7, wherein, During the compression step, heat the first continuous paper sheet and the second continuous paper sheet along the compression zone.

10. An apparatus for packaging an article, the apparatus comprising: - A first feeding assembly and a second feeding assembly configured to feed a first continuous paper sheet and a second continuous paper sheet in a respective longitudinal direction, wherein at least one of the continuous paper sheets has a heat-activated adhesive on one surface, the first feeding assembly and the second feeding assembly being configured to feed the first continuous paper sheet and the second continuous paper sheet using a longitudinal tension force between 50 and 200 N to improve the retention of the heat-activated adhesive, - A first heating roller and a second heating roller, the first heating roller and the second heating roller being configured to heat the first continuous paper sheet and the second continuous paper sheet while being tensioned in the longitudinal direction, so as to heat the first continuous paper sheet and the second continuous paper sheet without activating a heat-activated adhesive for bonding the first continuous paper sheet and the second continuous paper sheet to each other, - An inlet conveyor configured to feed a product stream between the first continuous paper sheet and the second continuous paper sheet, - An overlapping unit configured to overlap the heated and tensioned first continuous paper sheet and the second continuous paper sheet with each other on opposite sides of the product stream via respective coupling rollers of the overlapping unit, the coupling rollers being independent of the first heating roller and the second heating roller, wherein the first continuous paper sheet and the second continuous paper sheet do not bond to each other during the overlapping, and - A compression unit configured to compress and further heat the first continuous paper sheet and the second continuous paper sheet around the product to activate the heat-activated adhesive for bonding and fix the first continuous paper sheet and the second continuous paper sheet to each other through the heat-activated adhesive, the compression and further heating being performed by a pair of cooperating compression rollers independent of the first heating roller, the second heating roller, and the coupling rollers.

11. The apparatus according to claim 10, wherein, The first feeding assembly and the second feeding assembly are configured to control the longitudinal tension of the first continuous paper sheet and the second continuous paper sheet by controlling the respective feeding speeds.

12. The apparatus according to claim 10, wherein, The first feeding assembly and the second feeding assembly include respective tensioning rollers configured to apply a lateral tension force to the respective first continuous paper sheet and the second continuous paper sheet.

13. The apparatus according to claim 10, wherein, The first feeding assembly and the second feeding assembly are configured to reduce the longitudinal tension of the first continuous paper sheet and the second continuous paper sheet when the feeding of the first continuous paper sheet and the second continuous paper sheet stops.

14. The apparatus according to claim 10, wherein, Each of the first heating roller and the second heating roller has a plurality of heating zones, each heating zone having a frame-like shape and being surrounded by a heat-insulating material.

15. The apparatus according to claim 14, wherein, The compression unit includes a compression roller having a plurality of compression zones, each compression zone having a frame-like shape, the compression zones being in phase with the heating zones of the first heating roller and the second heating roller.

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