DEVICE AND METHOD FOR THE MANUFACTURING OF HOLLOW TUBES

Description

[0001] The invention relates to a device for producing hollow tubes, in particular drinking straws or products of the tobacco processing industry, comprising a formatting device which is designed to form a first material strip and a second material strip into a two-layer hollow tube during conveyance through the formatting device, wherein a material strip feed device is provided which is designed to feed the first material strip and the second material strip to the formatting device, wherein a cutting device is provided for longitudinally axially cutting a base material strip into the first material strip and into the second material strip.

[0002] The invention further relates to a method for producing hollow tubes, in particular drinking straws or products of the tobacco processing industry, comprising the following method steps: Conveying a base material strip in the longitudinal axial conveying direction, cutting the base material strip longitudinally axially into a first material strip with a first width and a second material strip with a second width, feeding the first material strip and the second material strip to a formatting device, forming the first material strip and the second material strip in the formatting device into a hollow tube.

[0003] When manufacturing hollow tubes, for example to produce straws or recessed filters or heat-not-burn products in the tobacco processing industry, it is important to produce hollow tubes with cross-sections that are as consistent as possible in order to ensure the most consistent quality possible of the hollow tubes.

[0004] EP 3 033 952 A2 discloses a device and a method for producing hollow tubes from which small tubes are cut to length at the end. The device comprises a material strip feed device and a cutting device for longitudinally cutting a base material strip into a first material strip with a first width and a second material strip with a second width, a gluing device by means of which the first and / or second material strips can be glued, a joining device by means of which the first and second material strips are brought together for gluing such that the first and second material strips lie offset from one another, and a formatting device in which a tubular strand is produced from the joined first and second material strips.In this process, two first and second strips of material cut from the base material are placed offset from one another and joined together to create butted edges in the resulting hollow tube. Paper webs, for example, are suitable as material strips. The base material strip is usually drawn from a reel.

[0005] EP 3 332 655 A1 discloses a similar device and a similar method, wherein size specifications for the material strip thicknesses, widths and the amount of adhesive are given.

[0006] WO 2021 / 185486 A1 also discloses a device for producing hollow tubes, in which a first formatting device is provided, which is designed to convey a first material strip longitudinally axially and to form it into a first hollow tube during conveyance, wherein a second formatting device is provided, which is arranged downstream of the first formatting device in the conveying direction and is designed to wrap a second material strip around the first material strip during longitudinal axial conveyance of the second material strip, so that a double-layer hollow tube is formed, which has the first hollow tube on the inside and the second material strip on the outside. This improves the quality of the produced hollow tubes, in particular drinking straws, wherein in particular hollow tubes or drinking straws free of corrugations or smooth hollow tubes or drinking straws can be produced.In this case, the first formatting device for forming has a formatting chamber which does not require a formatting belt, so that inner hollow tubes which have a constant diameter are formed reliably over very long periods of operation of the device.

[0007] Due to wear on the formatting belt used in the formatting device, the diameters of the produced hollow tubes can change over time. Wear is relatively high in the production of hollow tubes due to the relatively high slippage between the formatting belt and the material strip or hollow tube.

[0008] The object of the present invention is to provide a device and a method for producing hollow tubes, in particular drinking straws or products of the tobacco processing industry, which enable a highly stable manufacturing process for hollow tubes, particularly enabling reliable operation during the formation of the hollow tubes from first and second material strips. In particular, reliable production of hollow tubes should also be enabled in the case where a connection point is present in the material strip.

[0009] This object is achieved by a device for producing hollow tubes, in particular drinking straws or products of the tobacco processing industry, comprising a formatting device which is designed to form a first material strip and a second material strip into a two-layer hollow tube during conveyance through the formatting device, wherein a material strip feed device is provided which is designed to feed the first material strip and the second material strip to the formatting device, wherein a first web tensioning device is provided for the first material strip and a second web tensioning device is provided for the second material strip, wherein upstream of the first web tensioning device and the second web tensioning device there is provided a cutting device for longitudinally axially cutting a base material strip into the first material strip and into the second material strip.

[0010] The invention is based on the idea that by providing two web tensioning devices, each of which is provided for a cut material strip, even with different friction differences in the paths of the two material strips, fewer conveying problems occur than when guiding the two material strips via a common web tensioning device.

[0011] Preferably, the second web tensioning device comprises a pneumatically deflectable deflection device. The pneumatically deflectable deflection device enables a sufficiently high, but not excessive, tension in the material strip guided around the pneumatically deflectable deflection device. This is particularly advantageous when the other material strip experiences high friction during forming in the formatting device, so that very little tension is transferred to the associated web tensioning device via this material strip.

[0012] The pneumatically deflectable deflection device allows a maximum tensile stress to be set. A minimum tensile stress can also be set. The pneumatically deflectable deflection device is preferably provided for the second material strip and, during operation, results in a deflection or movement of the deflection device, which changes the conveying path or the length of the conveying path of the second material strip. For example, if the tensile stress in the second material strip drops too significantly, the conveying path can be extended, resulting in a higher tensile stress.

[0013] The second web tensioning device preferably has a deflection roller arranged on a pneumatic cylinder. The deflection roller serves to deflect the second material strip. By changing the position of the deflection roller using the pneumatic cylinder, preferably by linearly deflecting the pneumatic cylinder, the deflection roller can be moved into a predetermined position, by means of which a length of the conveying path of the second material strip is specified.

[0014] Preferably, the length of the conveying path or the conveying path is varied, controlled, regulated and / or adjusted by means of the pneumatically deflectable deflection device depending on the stability of the first and / or second material strip.

[0015] Alternatively or in addition to varying the distance or length of the conveying path of a feed path of the second material strip, the pressure in the pneumatically deflectable deflection device can also be changed.

[0016] Preferably, the pressure in the compressed air cylinder is varied depending on the stability of the second material strip.

[0017] Preferably, the web tension devices are web tension control and / or regulation devices. The first web tension device can be a dancer. Such dancers are known in the tobacco processing industry, for example, from EP 2 702 881 A1, EP 3 434 406 B1, and WO 2019 / 211157 A1.

[0018] The pneumatic cylinder is preferably linearly deflectable. The deflectability can preferably be between 40 mm and 120 mm, particularly preferably between 60 mm and 100 mm, and especially preferably between 70 mm and 90 mm. This allows for a deflection of the second material strip by up to 180°, which can be used to extend the path of the second material strip by twice the distance.

[0019] Preferably, the pressure in the compressed air cylinder is varied, particularly preferably depending on the stability of the second material strip. Thus, the overpressure in the compressed air cylinder can be between 0.5 bar and 10 bar, preferably up to 8 bar, and particularly preferably up to 6 bar.

[0020] If, for example, a strip of material is pulled off a reel and the paper is further processed from this reel, the pressure in the compressed air cylinder can be at the upper value, for example 6 bar. This moves the deflection roller into a position which serves to maximally extend the length of the conveying path of the second strip of material. If a reel is changed, i.e. a strip of material from a first reel is joined to the strip of material from a second reel, the tensile stability of this joint is not as high as the tensile stability of the material strip itself. In this case, the pressure in the compressed air cylinder is preferably reduced in order to keep the tensile stress in the strip of material low until the joint has run through the format device. For example, the overpressure in the compressed air cylinder can then be 0.5 bar.Preferably, the lower value is a value which is less than 1 bar, in particular less than 0.8 bar, in particular less than or equal to 0.6 bar and preferably greater than 0.2 bar, preferably greater than 0.4 bar.

[0021] Preferably, the first web tensioning device is a material strip tension control and / or regulation device comprising a pivotable deflection roller, as disclosed in the above-mentioned prior art. The pivoting can be spring-biased or can be provided by means of an electric motor.

[0022] Preferably, the cutting device for longitudinally cutting a base material strip into the first material strip and the second material strip is provided directly upstream of the first web tensioning device and the second web tensioning device. The cutting device preferably comprises a tension cutting roller and a cutting blade acting thereon.

[0023] Typically, the first material strip has a slightly different width after cutting than the second material strip, since the first material strip preferably serves to form an inner tube and the second material strip preferably serves to form an outer tube of the two-layer hollow tube. To produce both tubes butt-jointed, the width of the material strip of the inner tube is necessarily smaller than the width of the material strip of the outer tube.

[0024] Preferably, the first web tensioning device is designed to control and / or regulate a conveying speed of the base material strip. A base conveying speed is preferably specified by a machine control system, which preferably depends on the conveying speed of the hollow tube to be produced. The first web tensioning device can then be used to change the base conveying speed, particularly depending on the tension in the first material strip. This allows consistently high-quality hollow tubes to be produced.

[0025] The formatting device is preferably free of a formatting belt. A formatting device that is free of a formatting belt and serves to form a two-layer hollow tube has its own inventive content. The use of a formatting device that is free of a formatting belt for producing hollow tubes from a first material strip and a second material strip has the advantage that the diameter of the produced hollow tube remains constant. This means that wear on an otherwise used formatting belt does not affect the diameter of the hollow tube, which would be the case when using a formatting belt to form the hollow tubes in a formatting device. The hollow tube is formed entirely from the two material strips in the formatting device.

[0026] Preferably, a pulling formatting device with a formatting belt is provided for conveying the material strips. This pulling formatting device is arranged downstream of the formatting device in the conveying direction. The pulling formatting device then pulls the hollow tube produced in two layers.

[0027] The formatting device preferably has a heating device. Since the formatting device is free of a formatting belt, it is possible to provide a heating device at this point. In particular, a heating device is provided from below in a sub-format. This allows the adhesive used to bond the material strips to cure quickly and quickly.

[0028] To reduce the friction of the material strips in the formatting device, an air flow is admitted from the outside to the inside of a formatting chamber of the formatting device. This creates an air cushion between the inner wall of the formatting chamber of the formatting device and the material strip, thus reducing friction. For this purpose, one or more bores can be provided in the formatting device, particularly through the cover strip. In addition, a compressed air supply device can be provided that conveys compressed air through the bore or bores. The compressed air supply device can also be a compressed air reservoir. Alternatively, a pump can be provided.

[0029] The formatting device preferably comprises a first formatting chamber and a second formatting chamber, wherein the first formatting chamber is designed to convey the first material strip longitudinally axially and to form it into a hollow tube during conveying, wherein the second formatting chamber is arranged behind the first formatting chamber in the conveying direction and is designed to wind the second material strip around the first material strip in a longitudinally axial conveying manner, so that a double-layered hollow tube is formed which has the hollow tube on the inside and the second material strip on the outside. This is a configuration that essentially corresponds to that of WO 2021 / 185486 A1. Here, the second formatting chamber can be provided with a formatting belt or, preferably, without a formatting belt. Preferably, the first and second formatting chambers are free of formatting belts. The first formatting chamber and the second formatting chamber are part of the formatting device.

[0030] The object is further achieved by a method for producing hollow tubes, in particular drinking straws or products of the tobacco processing industry, with the following process steps: Conveying a base material strip in the longitudinal axial conveying direction, cutting the base material strip longitudinally axially into a first material strip with a first width and a second material strip with a second width, feeding the first material strip via a first web tensioning device and the second material strip via a second web tensioning device to a formatting device, forming the first material strip and the second material strip in the formatting device into a hollow tube.

[0031] Preferably, the first material strip and the second material strip are in direct or immediate contact with each other at least in the format device.

[0032] Preferably, a conveying path of the second material strip is changed by means of the second web tensioning device depending on the stability of the first and / or second material strip.

[0033] Alternatively or additionally, instead of changing the conveying path or the length of the conveying path, the tensile stress of the second material strip is controlled or regulated.

[0034] Preferably, the first web tensioning device controls or regulates a feed of the base material strip or a conveying speed of the base material strip.

[0035] If the change in the conveying path or the length of the conveying path of the second material strip is preferably carried out by means of a pneumatic deflection of a deflection device of the second web tensioning device, a very safe process can be enabled, wherein on the one hand a sufficient tensile stress is provided in the second material strip and on the other hand this tensile stress can be sufficiently reduced when changing the reel.

[0036] Preferably, the pneumatic pressure is changed if the stability of the first material strip and / or the second material strip changes. This is particularly the case when the splice is conveyed through the material strip path during a reel change.

[0037] Preferably, the forming of the first material strip and the second material strip in the formatting device takes place without a formatting belt. This allows the diameter of the produced hollow tube to be kept very constant. Preferably, a pulling formatting device with a formatting belt is provided for conveying the material strips, which is arranged downstream of the formatting device in the conveying direction.

[0038] Preferably, the material strips are heated in the formatting device.

[0039] Furthermore, in order to reduce the friction between the material strip and the inner surface of the format chamber or the format chambers of the format device, an air cushion is preferably created between the first material strip and / or the second material strip of at least one inner wall of the format device.

[0040] Preferably, the first material strip and the second material strip are brought together offset from one another in front of the formatting device so that they are placed on top of one another, or the first material strip is conveyed longitudinally axially through a first formatting chamber of the formatting device, whereby a first hollow tube is formed from the first material strip and then the second material strip of a second formatting chamber of the formatting device is wound around the first hollow tube to form a two-layer hollow tube.Thus, two alternative processes are preferably carried out, namely in the first process that the two material strips are brought together offset from one another before forming into the hollow tube, wherein an adhesive is then applied between the two material strips in order to then be conveyed together through the formatting device in order to thus produce the hollow tube or as a second variant, first forming the inner tube in a first formatting chamber of the formatting device in order to then wrap the second material strip around the outside, wherein here too an adhesive was applied to connect the two material strips before wrapping.

[0041] They show: Fig. 1 is a schematic representation of a material strip run according to the invention, Fig. 2 is a schematic representation of a format device according to the invention in a first embodiment and Fig. 3 is a schematic representation of a format device according to the invention in a second embodiment.

[0042] Within the scope of the invention, features marked with "in particular" or "preferably" are to be understood as optional features.

[0043] In the drawings, identical or similar elements and / or parts are provided with the same reference numbers, so that a repeated presentation is omitted.

[0044] Fig. 1shows a schematic representation of a material strip path for producing two-layer hollow tubes 10 in a material strip feed device 23 according to the invention. A base material strip 20, for example made of paper, is drawn from a reel 19 by a cutting device 37. The cutting device 37 can be a tensile cutting device. In the prior art, for example in EP 3 332 655 A1, the first material strip 21 and the second material strip 22, which is cut from the base material strip 20, are deflected via a common dancer, and later the material strips 21, 22 are conveyed via other paths. The dancer serves to control the tensile tension of the material strip webs.However, if excessive friction loss occurs in one of the two material strips 21, 22 during the formation of the hollow tubes 10, it may be that this material strip alone determines or co-determines the propulsion of the base material strip 20, so that the tensile stress in the other material strip is greatly reduced, which may lead to problems in production.

[0045] The invention now provides in particular for the two material strips 21 and 22 to run over two separate web tensioning devices 31 and 32. In the embodiment of the Fig. 1the first material strip 21 is made to run over a first web tensioning device 31, for example a dancer, i.e. over the deflectable, in particular pivotable, deflection roller 36, and the second web tensioning device 32 is made to run over a deflection device 33, comprising a deflection roller 35, which is arranged on a compressed air cylinder 34. The deflection device 33 can thus, as the arrows indicate, be moved over a distance. As a result, a sufficiently high or low force or tensile stress can be maintained in the second material strip 22. This is done by moving the compressed air cylinder 34 and / or the deflection roller 35, which is arranged on the compressed air cylinder 34, in a direction that lengthens or shortens the path of the second material strip 22.

[0046] In the usual production case of the hollow tubes 10, for example, a compressed air cylinder 34 can be subjected to a predeterminable pressure, such as 6 bar in this exemplary embodiment. This exerts a force on the second material strip 22 that is greater than the force on the first wrapping material strip 21 caused by the friction losses of the first material strip 21. As a result, the deflection roller 35 reaches the Fig. 1shown upper stop. In the event of a reel change, a connection point is provided in the material strips, which reduces the stability of the first material strip 21 and the second material strip 22. In this case, the pressure in the compressed air cylinder 34 is reduced to 1 bar or lower, whereby the force in the second material strip 22 is reduced, so that the deflection roller 35 moves downwards, as also shown by the downward arrow. As soon as the change point or connection point of the material strips 21, 22 has arrived in the format device 11, the pressure in the compressed air cylinder is increased again to 6 bar, whereby the deflection roller 35 moves upwards again to the end position. In this way, even with high friction losses, seams or change points of material strips 21, 22 can be operated in continuous operation.High friction losses occur in particular when there is a large seam offset, in particular a seam offset greater than 82°, in particular greater than 100°, in particular greater than 110°, in particular greater than 120°, in particular greater than 130°, in particular greater than 140°, in particular greater than 150°, in particular greater than 160°, in particular greater than 170°, in particular with a seam offset of 180°.

[0047] In this exemplary embodiment, the first material strip 21 passes from the first web tensioning device 31 via a deflection roller 17, a flat guide 14, three further deflection rollers 17, another bolt guide 16, by means of which, in particular, the edges of the first material strip 21 are guided, and another deflection roller 17 to the first formatting chamber 51 of the formatting device 11. The hollow tube 10 is formed in the first formatting chamber 51, preferably with the seam at the bottom. The first formatting chamber 51 can comprise a middle finger. Reference is made to WO 2021 / 185486 A1 for this purpose.

[0048] The web of the second material strip 22 runs downstream of the second web tensioning device 32 via a deflection roller 17 past a flat guide 14 and then via further deflection rollers 17 to another flat guide to provide film gluing 15, which provides full-surface or almost full-surface gluing of the second material strip 22. Almost full-surface gluing is considered to be gluing of at least 80% of the surface of the second material strip 22, in particular of at least 90%. The second material strip 22 then moves to another deflection roller 17 to be guided more precisely in the transverse axial position by a bolt guide 16. The bolt guide 16 has, for example, two edges that guide the edges of the second material strip 22.The second material strip 22 then passes via a deflection roller 17 into the second format chamber 52 of the format device 11, in which the second material strip 22 is wound around the inner hollow tube 10 formed from the first material strip 21.

[0049] In Fig. 1 A pulling formatting device 41 is also shown, which has a formatting belt and pulls the produced two-layer hollow tube 10 in the conveying direction 12. At the end, a hollow tube 10 emerges from the pulling formatting device 41, which can be cut to the desired length.

[0050] The guides for the material strips can, of course, also be designed differently. For example, more or fewer guides and / or more or fewer deflection rollers can be provided.

[0051] Fig. 2 shows schematically a format device 11 according to the invention, which has two format chambers 51, 52, wherein the process can be designed as in Fig. 1 Here, an inner tube 10 is first formed from the first material strip 21, and then the second material strip 22 is wound around the formed inner tube 10. To reduce friction in the first format chamber 51, a bore 54 is shown, into which an air stream 55 can be introduced by a compressed air device 53. This is shown very schematically.

[0052] An air flow 55 can also be introduced into the second format chamber 52, or several air flows can be introduced into the format chambers 51, 52. In addition, Fig. 2 schematically shows a heating device 13 which serves to heat the hollow tube 10 formed from two material strips 21, 22 in order to provide early setting of the adhesive or glue.

[0053] A pulling formatting device 41 is connected to the formatting device 11 in the conveying direction 12. The pulling formatting device 41 has a formatting belt 40, which runs as usual in the pulling formatting device 41 and is wound at least partially around the double-layer hollow tube 10 in order to pull it in the conveying direction 12.

[0054] Fig. 3shows schematically another embodiment of a format chamber 11 according to the invention. Here, the first material strip 21 and the second material strip 22 are placed offset from one another and only then introduced into the format device 11. In the format chamber 51 of the format device 11, a double-layered or two-layered hollow tube 10 is then formed. This hollow tube formed there is pulled through the subsequent pulling format device 41 in the conveying direction 12. In this case, too, the pulling format device 41 is provided with a format belt 40, which runs through the pulling format device 41. In both embodiments of the Fig. 2 and 3 The respective format devices 11 are format belt-free. Fig. 3 a heating device 13 is also shown, which heats the material strips 21, 22 from below.

[0055] The provision of a belt-free forming device 11 for forming the two-layer hollow tubes 10 results in very uniformly produced diameters of the hollow tubes 10. If forming belts 40 were used for forming, the diameters of the produced double-layer hollow tubes 10 would continuously increase over the course of use of the forming belts 40, as the forming belts become thinner due to wear. This is prevented by belt-free forming devices 11.

[0056] Preferably, the format chamber 51, 52 or the format chambers 51, 52 of the formatting device 11 are metallic, and in particular, the surfaces that come into contact with the material strips 21, 22 are friction-reduced. This can be achieved by a friction-reducing coating or by very smooth, particularly polished, surfaces. Formatting devices 11 without formatting belts allow the formatting belts 40, which are now only used for conveying, to be used for longer in the pulling formatting device 41, since they only have the function of pulling and no longer of forming. This reduces wear, and also allows the formatting belts 40 to still be used for pulling even if they have become too thin for forming. List of reference symbols

[0057] 10Hollow tube 11Formatting device 12Conveying direction 13Heating device 14Flat guide 15Film gluing 16Bolt guide 17Deflection roller 19Reel 20Base material strip 21First material strip 22Second material strip 23Material strip feed device 31First web tensioning device 32Second web tensioning device 33Deflection device 34Compressed air cylinder 35Deflection roller 36Deflection roller 37Cutting device 40Formatting belt 41Tensioning formatting device 51First formatting chamber 52Second formatting chamber 53Compressed air device 54Opening 55Air flow 56Conveying section

Claims

1. A device for producing hollow tubes (10), in particular drinking straws or products of the tobacco processing industry, comprising a formatting device (11) which is configured to shape a first material strip (21) and a second material strip (22) during the conveying process through the formatting device (11) into a two-layer hollow tube (10), wherein a material strip feed device (23) is provided, which is configured to feed the first material strip (21) and the second material strip (22) to the formatting device (11), wherein a first web tensioning device (31) is provided for the first material strip (21) and a second web tensioning device (32) is provided for the second material strip (22), wherein a cutting device (37) for cutting a base material strip (20) in a longitudinally axial direction into the first material strip (21) and into the second material strip (22) is provided upstream of the first web tensioning device (31) and the second web tensioning device (32).

2. The device according to Claim 1, characterized in that the second web tensioning device (32) comprises a pneumatically redirectable deflecting device, wherein the second web tensioning device (32) in particular has a guide roller (35) arranged on a compressed air cylinder (34), wherein the pressure in the compressed air cylinder (34) is in particular varied as a function of the stability of the second material strip (22).

3. The device according to Claim 1 or 2, characterized in that the first web tensioning device (31) is a material strip traction control and / or regulating device which comprises a pivotable guide roller (17).

4. The device according to Claim 1 or 2, characterized in that the cutting device (32) is arranged immediately upstream of the first web tensioning device (31) and the second web tensioning device (32).

5. The device according to any one of Claims 1 to 4, characterized in that the first web tensioning device is configured to control and / or to regulate a conveying speed of the base material strip.

6. The device according to any one of Claims 1 to 5, characterized in that the formatting device (11) does not have a garniture tape, wherein a traction formatting device (41) having a garniture tape (40) is in particular provided for conveying the material strips (12, 22), which traction formatting device is arranged downstream of the formatting device (11) in the conveying direction (12).

7. The device according to any one of Claims 1 to 6, characterized in that the formatting device (11) has a heating device (13).

8. The device according to any one of Claims 1 to 7, characterized in that an airflow (55) is admitted in a formatting chamber (51, 52) of the formatting device (11) from the outside in.

9. The device according to any one of Claims 1 to 8, characterized in that the formatting device (11) comprises a first formatting chamber (51) and a second formatting chamber (52), wherein the first formatting chamber (51) is configured to convey the first material strip (21) in a longitudinally axial direction and to shape it into a hollow tube (10) during the conveying process, wherein the second formatting chamber (52) is arranged behind the first formatting chamber (51) in the conveying direction (12) and is configured to wind the second material strip (22) around the first material strip (21) in a longitudinally axial conveying process, so that a double-layer hollow tube (10) is formed, which has the hollow tube (10) inside and the second material strip (22) externally.

10. A method for producing hollow tubes (10), in particular drinking straws or products of the tobacco processing industry, having the following method steps: - conveying a base material strip (20) in a longitudinally axial conveying direction (12), - cutting the base material strip (20) in a longitudinally axial direction into a first material strip (21) having a first width and a second material strip (22) having a second width, - feeding the first material strip (21) via a first web tensioning device (31) and the second material strip (22) via a second web tensioning device (32) to a formatting device (11), - shaping the first material strip (21) and the second material strip (22) into a hollow tube (10) in the formatting device (11).

11. The method according to Claim 10, characterized in that a conveying section (56) of the second material strip (22) is altered as a function of the stability of the first and / or second material strip (21, 22) by means of the second web tensioning device (32), wherein the first web tensioning device (31) in particular controls or regulates a feed rate or a conveying speed of the base material strip (20), wherein the conveying section (56) of the second material strip (22) is in particular altered via a pneumatic redirection of a deflecting device (33) of the second web tensioning device (32), wherein the pneumatic pressure is in particular altered provided that the stability of the first material strip (21) and / or of the second material strip (22) changes.

12. The method according to Claim 10 to 11, characterized in that the shaping of the first material strip (21) and of the second material strip (22) in the formatting device (11) takes place without a garniture tape, wherein a traction formatting device (41) having a garniture tape (40) is in particular provided for conveying the material strips (12, 22), which traction formatting device is arranged downstream of the formatting device (11) in the conveying direction (12).

13. The method according to any one of Claims 10 to 12, characterized in that the material strips (21, 22) are heated in the formatting device (11).

14. The method according to any one of Claims 10 to 13, characterized in that an air cushion is generated between the first material strip (21) and / or the second material strip (22) and at least one inner wall of the formatting device (11).

15. The method according to any one of Claims 10 to 14, characterized in that the first material strip (21) and the second material strip (22) are merged offset with respect to one another before the formatting device (11), so that these are placed one above the other, or in that the first material strip (21) is conveyed in a longitudinally axial direction through a first formatting chamber (51) of the formatting device (11), wherein, as a result, a first hollow tube (10) is formed from the first material strip (21) and subsequently the second material strip (22) is wound around the first hollow tube (10) in a second formatting chamber (52) of the formatting device (11), in order to form a two-layer hollow tube (10).