EP4306466A1 - Method for wrapping a sheet of material and wrapping device - Google Patents

Abstract

The invention relates to a method for winding a material web (1), in particular a plastic film, by means of a winding device (2), wherein the material web (1) moves from at least one first roller (3) to at least one second roller (4). Conveying direction (R) is guided, with at least one cutting device (5) being arranged between the first roller (3) and the second roller (4), which cuts the material web (1) into at least two partial webs (la, 1b, 1c), wherein the partial webs (la, 1b, 1c) are each wound into a roll in the conveying direction (R) behind the second roller (4). In order to ensure that inexpensively wound rolls can be produced in a simple manner and without a lot of technical effort, the invention provides that the at least one first roller (3) and the at least one second roller (4) are each driven by a drive are driven so that the tensile stress in the material web (1) or in the partial webs (1a, 1b, 1c) changes over time in the conveying direction (R) of the material web (1). The invention further relates to a winding device.

Description

The invention relates to a method for winding up a material web, in particular a plastic film, by means of a winding device, wherein the material web is guided from at least one first roller to at least one second roller in a conveying direction, with at least one between the first roller and the second roller Cutting device is arranged, which cuts the material web into at least two partial webs, the partial webs being wound into a roll in the conveying direction behind the second roller. The invention further relates to a winding device.

When winding up partial webs that have been cut out of a material web (film web), this typically occurs due to the recipe used, the conveying speed of the material web, the tension in the film and the blades (knives) used when trimming the material web, in particular the Film, in the conveying direction (production direction) leads to changes in the material and therefore damage to the cut edge. If the cut edge is always wound in the same place when winding, problems arise, so that the finished one Roll may become unusable, that is, in particular, it can no longer be unrolled without damage.

From the US 2014/0208905 A1 and the US 10 494 215 B2 To avoid this problem, it is known that a relative oscillatory movement is provided between the cutting knife and the film to be cut, after which the film is trimmed by knives that oscillate transversely to the conveying direction of the film. The US 5,967,437 For this purpose, the wound roll itself oscillates relative to the knife transversely to the conveying direction. This sees a similar solution US 8,100,356 B2 in which a roller is moved in an oscillatory manner before winding.

All of the solutions mentioned require special connecting elements, drives, eccentrics, cylinders, etc. As a result, the effort required in terms of device technology is correspondingly high and the systems used are relatively expensive.

The invention is therefore based on the object of providing a method and a device of the type mentioned at the outset, with which it is possible to ensure that inexpensively wound rolls can be produced in a simple manner and without high expenditure on equipment. in which the above-mentioned problems do not occur.

The solution to this problem by the invention is characterized according to the method in that the at least one first roller and the at least one second roller are each driven by a drive in such a way that the tensile stress in the material web or in the partial webs changes over time in the conveying direction of the material web.

The at least one first roller and the at least one second roller can each be driven by their drive in such a way that the tensile stress in the material web or in the partial webs changes periodically. It is particularly preferred that the at least one first roller and the at least one second roller are each driven by their drive in such a way that the tensile stress in the material web or in the partial webs changes essentially sinusoidally around an average value. The time-variable tensile stress can be achieved by controlling or regulating the rotational speed of at least one of the roller drives in a time-variable manner (and in particular on the basis of a superimposed sine function).

In this respect, it has proven useful if it is provided that the maximum tensile stress applied to the material web or to the partial webs changes in such a way that the maximum value of the tensile stress increases by at least 0.1%, preferably by at least 1.5% and particularly preferably by at least 5.0% higher than the minimum value of the tensile stress.

According to a preferred embodiment, the at least one first roller cooperates with a further roller in order to be able to build up a tensile stress in the material web or in the partial webs. Accordingly, it can also be provided that the at least one second roller cooperates with another roller in order to be able to build up a tensile stress in the material web or in the partial webs.

It is preferably provided that the at least one first roller is driven at a constant rotational speed and the at least one second roller is driven at a rotational speed that changes over time is driven. With regard to the rotational speed that changes over time, the procedure is preferably such that this change occurs in such a way that the maximum value of the rotational speed is at least 0.1%, preferably at least 1.5% and particularly preferably at least 5.0% higher than that Minimum value of rotation speed. For the change in the rotational speed, a periodically changing course and in particular a sine-like course is preferably specified.

The change in the tensile stress in the material web or in the partial webs is preferably carried out in such a way that the width of the material web or the partial webs changes by a value of +/- 0.1 mm to +/- 5 mm around the mean value of the width. The mean value is to be understood as the arithmetic mean value of the corresponding path, which here changes periodically by the dimensions mentioned.

The proposed winding device for winding a material web, in particular a plastic film, has at least one first roller and at least one second roller with which the material web can be guided in a conveying direction, the first roller and the second roller each being connected to a drive are, with which the rollers can be rotated, furthermore at least one cutting device which is arranged between the first roller and the second roller in order to be able to cut the material web into at least two partial webs, and at least one winder for winding up the partial webs, the winder is arranged behind the second roller in the conveying direction. According to the invention it is provided that the drives of the first roller and the second roller are connected to a control device, the Control device is designed to drive one of the rollers at a non-uniform rotational speed.

The control device is preferably designed to drive one of the rollers in a periodically variable manner, in particular in such a way that the rotational speed of the roller changes substantially sinusoidally around an average value.

In order to produce sufficient adhesion between the film and the roller, it can be provided that the at least one first roller cooperates with a further roller and/or that the at least one second roller cooperates with a further roller.

At least one of the rollers is preferably provided with a profiling on the roller surface.

In the procedure proposed according to the invention, the material web, in particular the plastic film, is specifically stretched or relaxed by changing the tensile stress in the material between two rollers and in particular by the targeted acceleration or braking of rollers, so that the material web is stretched by a different degree of Constriction changed in width.

After the tensile stress in the material has been reduced, the cut edge of the partial web is no longer straight, but rather wavy and, in particular, “sinusoidal”.

The proposed method is used in particular after the film has been trimmed.

The change in the width of the material web or the partial webs, preferably in a range between +/- 0.1 mm to +/- 5 mm, results in the subsequent winding of the partial webs that the cut edge is not always wound in the same place.

This makes it possible to produce the partial webs of the film without errors, i.e. H. especially without edge welds, defects and undevelopable areas.

The proposed procedure therefore ensures that the cut edge of the film for the individual partial webs is not always in the same place during winding, which means that the winding problems mentioned above can be prevented.

Advantageously, this is made possible in a very cost-effective manner according to the present invention, since no additional device parts (for carrying out oscillatory movements transversely to the conveying direction of the material web) need to be provided.

Furthermore, the proposed procedure can be activated and deactivated in the process so that there is no impairment of production. In the previously discussed solutions with the oscillation of the knives, when the production conditions change, the system has to be stopped, which creates waste.

The proposed method can still be used advantageously regardless of the width of the rolls. The width of the partial benefits can be adjusted, and in particular the number of partial benefits or rolls can be flexibly selected.

Figur 1

zeigt schematisch in der Seitenansicht eine Wickelvorrichtung zum Aufwickeln einer in Teilbahnen geschnittenen Folienbahn gemäß einer ersten Ausführungsform der Erfindung,

Figur 2

zeigt eine zu Figur 1 alternative Ausgestaltung der Wickelvorrichtung,

Figur 3

zeigt schematisch drei Teilbahnen, die aus der Folienbahn ausgeschnitten wurden, wobei die Veränderung der Breite durch Aufbringen unterschiedlicher Zugspannungen illustriert ist, und

Figur 4

zeigt die zur Rolle aufgewickelte Teilbahnen nach Abschluss des Wickelprozesses.

Exemplary embodiments of the invention are shown in the drawings.

Figure 1

shows a schematic side view of a winding device for winding a film web cut into partial webs according to a first embodiment of the invention,

Figure 2

shows one too Figure 1 alternative design of the winding device,

Figure 3

shows schematically three partial webs that were cut out of the film web, with the change in width being illustrated by applying different tensile stresses, and

Figure 4

shows the partial webs wound into a roll after the winding process has been completed.

In the Figures 1 and 2 Two very similar embodiments of a winding device 2 are shown, with which a material web 1 in the form of a plastic film is cut into partial webs 1a, 1b, 1c and the latter are then wound up into finished film rolls 15.

Essential elements of the winding device 2 are a first roller 3, which is preferably designed as a driven fixed-point roller, and a second roller 4, which is preferably designed as a lower cutting roller. In the conveying direction R of the material web 1 between the two rollers 3 and 4 there is a cutting device 5 with which the material web 1 is cut into the partial webs 1a, 1b, 1c.

Drives with which the first roller 3 and the second roller 4 are rotationally driven are not shown. Also not shown is a control device with which the drives of the rollers are controlled.

The central aspect of the proposed concept is that the tensile stress in the material web 1 or in the partial webs 1a, 1b, 1c (after the cut) varies over time. Although the first roller 3 is driven at a constant rotational speed set for the production process, the second roller 4 is driven at a non-constant rotational speed. A sinusoidal curve is preferably superimposed on a basic rotational speed of the second roller 4, so that the rotational speed of the second roller 4 changes accordingly.

The result of this is that the material web 1 or the partial webs 1a, 1b, 1c between the two rollers 3 and 4 are exposed to a variable tensile stress, which in Figure 3 is illustrated. At the points marked with the arrows are in Figure 3 Those sections are marked where the material web was exposed to increased tensile stress. Accordingly, the material web 1 or the partial webs 1a, 1b, 1c cut out from it are as in Figure 3 shown constricted.

If the partial webs cut in this way are wound, film rolls 15 result, as shown in Figure 4 are sketched. The cutting edges 9 do not all lie on top of each other, but are variable, which facilitates the unwinding of the film from the film rolls 15.

In the Figures 1 and 2 Some elements are also entered, some of which are advantageous for the present invention, but some of which are also well known in the prior art.

Worth mentioning is the further roller 6, which interacts with the first roller 3 and which is designed as a driven fixed-point roller.

In Figure 1 There is no provision for the second roller 4 to interact with another roller. However, this is in Figure 2 illustrated, for which reference is made to the further roller 7, which acts as a pressure roller.

In the conveying direction R behind the second roller 4 there is a winder 8 with several winding stations on which the finished film rolls 15 are wound.

In the Figures 1 and 2 an upper cutting roller 10, a strip deflection roller 11, a tension measuring roller 12, a satellite roller 13 and a contact roller 14 are also shown, which are useful for the perfect production process.

The tension prevailing in the material web 1 or the partial webs 1a, 1b, 1c can be measured in the longitudinal direction via the tension measuring roller 12. In terms of control technology, this makes it possible, for example, to specify a sine curve for the tension in the material and to regulate it accordingly.

The material web, ie the film, is stretched in the conveying direction (longitudinal direction) by the proposed variable tensile stress in the material, which changes the width of the film (see. Figure 3 ).

As a result, the cut edge does not always meet in the same place when winding up the partial web, as in Figure 4 is shown.

The first and second rollers 3 and 4 and, if applicable, the additional rollers 6 and 7 that interact with these rollers can have a profiled, in particular spiralized and/or roughened surface, so that the corresponding tension in the material web can be reliably built up between the rollers.

In general, the rollers between which the tensile stress is built up (as a result of targeted acceleration or braking of the rollers) are one or more rollers before the cut and one or more rollers after the cut, with the first roller 3 and the second roller 4 can be: the upper cutting roller and the lower cutting roller; the fixed point roller and the tension measuring roller or the satellite roller; the fixed point roller and the contact roller.

If the adhesion to the surface of the roller is not sufficient to build up the required tension in the material web between the first and second rollers 3, 4, a pressure roller (as in Figure 2 shown), which in this exemplary embodiment is placed at the lower cutting roller and interacts with it.

Preferably, the roller or rollers before the cut (in the exemplary embodiment, the first roller 3 together with the further roller 6) are used as a "fixed point", ie these rollers move at a constant rotational speed or speed. The roller or rollers after the cut (in the exemplary embodiment the second roller 4 together with the further roller 7) rotate at a non-uniform speed or speed driven, so that the material web between the first and the second roller is periodically accelerated or braked by changing the rotational speed or the speed of these rollers.

As in Figure 3 shown, this changes the width of the slide; the cut edges 9 are not wound in the same place during winding.

According to a preferred embodiment of the invention, the rotational speed of one roller (e.g. roller 4) is periodically changed in such a way that, starting from a nominal value of 100%, the roller rotates for a period of e.g. B. is accelerated for 1 s, with the acceleration achieving an increased rotational speed of 101.5%. The roller is then braked for approximately the same period of time (e.g. 1.1 s) until the nominal rotation speed of 100% is reached again. This process is repeated periodically in order to achieve the described effect of changing the width of the web.

List of reference symbols:

1

material web

1a

Partial track

1b

Partial track

1c

Partial track

2

winding device

3

first roller (driven fixed point roller)

4

second roller (lower cutting roller)

5

Cutting device

6

further roller (cooperating with the first roller; driven fixed point roller)

7

another roller (cooperating with the second roller; pressure roller)

8th

Winder

9

cutting edge

10

upper cutting roller

11

Strip deflector roller

12

Tension measuring roller

13

Satellite roller

14

contact roller

15

ready-wrapped roll of foil

R

Direction of conveyance

Claims (12)

Method for winding a material web (1), in particular a plastic film, by means of a winding device (2), wherein the material web (1) is guided from at least one first roller (3) to at least one second roller (4) in a conveying direction (R), wherein at least one cutting device (5) is arranged between the first roller (3) and the second roller (4), which cuts the material web (1) into at least two partial webs (1a, 1b, 1c), wherein the partial webs (1a, 1b, 1c) are each wound into a roll in the conveying direction (R) behind the second roller (4), characterized, that the at least one first roller (3) and the at least one second roller (4) are each driven by a drive in such a way that the tensile stress in the material web (1) or in the partial webs (1a, 1b, 1c) in the conveying direction ( R) the material web (1) changes over time. Method according to claim 1, characterized in that the at least one first roller (3) and the at least one second roller (4) are each driven by their drive in such a way that the tensile stress in the material web (1) or in the partial webs (1a , 1b, 1c) changed periodically. Method according to claim 2, characterized in that the at least one first roller (3) and the at least one second roller (4) are each driven by their drive in such a way that the tensile stress in the material web (1) or in the partial webs (1a , 1b, 1c) changed essentially sinusoidally around an average value. Method according to one of claims 1 to 3, characterized in that the maximum tensile stress applied to the material web (1) or to the partial webs (1a, 1b, 1c) changes such that the maximum value of the tensile stress increases by at least 0.1%, is preferably at least 1.5% and particularly preferably at least 5.0% higher than the minimum value of the tensile stress. Method according to one of claims 1 to 4, characterized in that the at least one first roller (3) cooperates with a further roller (6) in order to create a tensile stress in the material web (1) or in the partial webs (1a, 1b, 1c). to be able to build. Method according to one of claims 1 to 5, characterized in that the at least one second roller (4) cooperates with a further roller (7) in order to create a tensile stress in the material web (1) or in the partial webs (1a, 1b, 1c). to be able to build. Method according to one of claims 1 to 6, characterized in that the at least one first roller (3) is driven at a constant rotational speed and the at least one second roller (4) is driven at a time-changing rotational speed. Method according to claim 7, characterized in that the time-changing rotational speed is changed so that the maximum value of the rotational speed is at least 0.1%, preferably at least 1.5% and particularly preferably at least 5.0% higher than that Minimum value of rotation speed. Method according to one of claims 1 to 8, characterized in that the change in the tensile stress in the material web (1) or in the partial webs (1a, 1b, 1c) takes place in such a way that the width of the material web (1) or the partial webs ( 1a, 1b, 1c) changed by a value of +/-0.1 mm to +/- 5 mm around the mean value of the width. Winding device (2) for winding a material web (1), in particular a plastic film, which has: - at least one first roller (3) and at least one second roller (4), with which the material web (1) can be guided in a conveying direction (R), the first roller (3) and the second roller (4) each being included are connected to a drive with which the rollers can be rotated, - at least one cutting device (5) which is arranged between the first roller (3) and the second roller (4) in order to be able to cut the material web (1) into at least two partial webs (1a, 1b, 1c), - at least one winder (8) for winding the partial webs (1a, 1b, 1c), the winder (8) being arranged behind the second roller (4) in the conveying direction (R), characterized,
that the drives of the first roller (3) and the second roller (4) are connected to a control device, the control device being designed to drive one of the rollers (4) at a non-uniform rotational speed. Winding device according to claim 10, characterized in that the control device is designed to drive one of the rollers (4) in a periodically variable manner, in particular in such a way that the rotation speed the roller (4) changes essentially sinusoidally around an average value. Winding device according to one of claims 10 or 11, characterized in that the at least one first roller (3) cooperates with a further roller (6) and/or that the at least one second roller (4) cooperates with a further roller (7), wherein preferably at least one of the rollers (3, 4, 6, 7) is provided with a profiling on the roller surface.

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