EP0300238A1 - Method and device for winding elastically extensible thin strips - Google Patents

Abstract

In the winding of great lengths of elastically extensible thin strips (18), instability of the package occurs particularly in the end region (28) of the bobbins or the package can become detached or collapse in the end region. The method and the device are intended to make it possible for thin and elastically extensible film web to be wound in great lengths to form compact bobbins which are stable in the region of their ends and can accordingly also be unwound again satisfactorily. During the winding method, pressure is applied locally over the entire length of the bobbin during winding thereof. The winding roll (10) has a flexible, adaptable surface in the contact region with the bobbin (16) or of the package (27) situated thereon. <IMAGE>

Description

The invention relates to a method for winding elastically stretchable, thin film tapes, for example made of polyurethane, in which tape material is continuously fed to a rotating spool and wound onto this spool under a certain longitudinal tension. In addition, the invention relates to a device for performing this method, which has a guide for the incoming strip material or foil strip, a rotatably mounted, drivable winding roller and a slide which is adjustable relative to the winding roller and on which the spool to be wound can be freely rotated and exchangeably arranged.

Elastic, stretchable film tapes, in particular film tapes consisting of polyurethane, are used, for example, as an elastic pad for diapers and, when stretched, are glued to the diapers so that these tapes ripple the diapers in the edge area when they are relaxed. Such foil tapes are extremely thin and flexible. They are about 25 µm thick and tend to wrinkle. It is therefore difficult to wind up such foil tapes on spools.

For an economical mechanical manufacture of diapers, however, it is necessary to provide such film tapes in large lengths on spools, since each spool change causes uneconomical production interruptions. The production of diapers with glued-in elastic stretchable film tapes therefore requires spools that hold at least 25,000 meters of film tape. It is therefore necessary to apply a relatively thick wrap from the extremely thin and flexible film strip to each spool.

It has always been difficult to wind coils with such difficult-to-handle foil strip material because the foil strip material itself can make little contribution to the stability of the winding and air pockets have formed in the winding, which contribute to the instability of the winding, especially in the end region of the coils. However, if an exact winding cannot be achieved, such a bobbin cannot be used without problems for the further processing of the film strip material, because unwinding errors can hardly be avoided in machine operation.

In order to avoid the problems when winding thin and elastic film tape, which is slippery and difficult to handle during winding, but in particular to avoid that when winding longer lengths of such film tape on a spool in the end region of the winding there are instabilities or the winding can dissolve or collapse in the forehead area, it is known (EP 0 086 096 A 1) to wind the film strip in the form of individual disc-shaped windings on a spool, so that the film strip is wound up in a stepwise manner in superimposed layers and only at the transition points from one makes a cross connection to the next winding disc. In this way, a stable winding is obtained even when winding up longer lengths of the film strip material, since no air pockets can settle between the individual layers of the spiral wound film strip, because air located between the individual layers of the wound film material can escape to both end faces of the respective winding discs . The disadvantage of such a winding, however, is that a very precise step-by-step control is required to produce the individual winding disks and a distance, albeit a small one, should remain between the disks, which affects the winding capacity.

There is also the problem that there is an inaccurate and non-uniform distance between the individual wound disks, which leads to mutual contact. In particular, the band is curled in the edge zones, which can lead to adhesion of the individual band layers in the manner of a weld. The consequence of this is that the strip material can tear off the spool during unwinding, which causes the processing machine to come to an undesirable standstill at the further processor.

The invention has for its object to be able to mechanically and economically wind thin and elastically stretchable film tape in great lengths of at least 25,000 meters into compact spools which are stable in the area of their ends and can accordingly also be unwound again.

This object is achieved according to the invention with a method which has the features of patent claim 1. In addition, this object is achieved with a device which is the subject of claim 3.

Advantageous embodiments of the method and the device according to the invention are the subject of the dependent claims.

The invention makes it possible to wind up thin and inherently less dimensionally stable film tapes, even in greater lengths, to form a compact roll which can also be unwound or unwound reliably and without problems. This wrap also has sufficient strength in the end areas, without the exact position of the individual winding layers having to be maintained. Rather, it is possible to continuously wind the film strip helically on the spool without having to pay attention to an exact position of the film strip or the individual winding layers. At the front ends of the winding, the winding is preferably continuously shortened slightly, so that the front ends are designed like a relatively steep cone or cone, which effectively prevents instabilities. Since the foil tape is wound helically with overlap, the edges of the tape do not lie on one another in the individual winding layers, so that they cannot hook into one another or connect in any other way and there is no risk of mutual "welding".

It is crucial for the invention that the film strip is wound in a kind of tangled position helically and in an overlapping arrangement on the spool or the winding located thereon without the risk of air pockets.

Since during the winding process the winding roller with its soft elastic surface always has a pressing effect on the entire length of the winding, air pockets in the winding are effectively prevented, irrespective of the point at which the elastic foil strip just runs onto the spool. The film strip, similar to that known for winding textile threads in textile machines, can be wound helically back and forth on the surface of the winding or the bobbin. Accordingly, the winding process is easier to control. The shortening of the individual successive winding layers can be preprogrammed and thus controlled in a simple manner.

Foil tape wraps made according to the invention are stable in both manufacture, handling and unwinding, i.e. there is no risk of the winding collapsing, not even in the area of its ends, although the film strip material is wound onto the spool in a helical manner and not, as previously known, spirally.

During the winding process, the film strip material can run in with an axial tension or tensile stress of up to 4% and preferably up to 2%, i.e. with an axial tension, which causes an elongation of 4 or 2%. The film strip material thus lies on the roll under a certain longitudinal tension, which, however, is less than the longitudinal tension or elongation with which the film strip is to be processed later.

Although the invention is particularly suitable for processing elastically stretchable film tape made of polyurethane, other films with comparable properties or made of other plastics can also be processed or wound into compact windings of great lengths of 25,000 meters and more.

• Fig. 1 eine Seitenansicht dieser Vorrichtung, die in drei Ebenen übereinander Aufwickelstationen aufweist, und
• Fig. 2 eine Draufsicht auf eine Aufwickelstation in gegenüber Fig. 1 vergrößertem Maßstab.

In the drawing, an embodiment of a device according to the invention for winding or winding elastic thin film tape is shown schematically, namely shows

• Fig. 1 is a side view of this device, which has winding stations in three levels one above the other, and
• Fig. 2 is a plan view of a winding station on an enlarged scale compared to Fig. 1.

The winding device (1) contains in a frame (2) one above the other a total of three winding stations (3, 4 and 5), which in turn can have several winding devices next to each other, so that a large number of film strips can be wound or wound onto a spool at the same time. Since all winding stations are of the same design and work in the same way, only one of these winding stations (3 to 5) is explained in detail here.

Each winding station (3 to 5) has drive rollers (8) which are supported on a crossbar (6) fixed in the frame (2) via pillow block bearings (7) and which are arranged in a rotationally fixed manner on a shaft (9) not shown. In addition, a winding roller (10) is rotatably mounted on the crossmember (6) and can be set in rotation by the drive rollers (8). This winding roller (10) is held on pivotably mounted arms (11), which are each pivotably supported on a further pillow block (12) attached to the crossmember (6).

Furthermore, a carriage (13) which is displaceable perpendicularly to the crossmember (6) and thus to the drive rollers (8) and the winding roller (10) is provided and is slidably seated on a rail guide (14). A spool (16) can be freely rotated in this carriage (13) between the end stand (15).

By means of a pressure cylinder (17), the carriage (13) can be pressed in the direction of the crossmember (6) and thus towards the winding roller (10), so that the spool mounted in the carriage (13) is pressed against the winding roller (10). Since the winding roller (10) is in turn resiliently mounted, it is then pressed against the rigidly mounted drive rollers (8) which set the winding roller (10) in rotation. The winding roller (10) transmits its rotary movements to the spool pressed against it, so that the spool (16) is then also rotated if the shaft (9) is driven.

As shown in Fig. 1, the centers of the shaft (9), the winding roller (10) and the spool (16) are practically in one plane (30), so that an effective drive is ensured.

A guide arm (19) is provided for guiding the film strip (18) to be wound onto the reel (16) and is fastened on an axis (20) which can be moved in an oscillating manner so that the guide arm (19) between the drive rollers (8 ) can be moved back and forth parallel to the axis of rotation of the winding roller (10) in order to wind the film strip (18) helically on the spool (16).

At the front end or infeed end of the guide arm (19) there is a pair of rollers (21 and 22) which can be rotated about vertical axes and around which the incoming film strip (18) is wound. On the relevant side of the guide arm (19) there is also a fixed rod (23) over which the film strip (18) is guided in order to bring it into a horizontal position, and a rotatable guide roller (24) which has a roughened surface and guides the film strip (18) onto the winding roller (10). The rod (23) made of thick wire not only directs the film strip (18) onto the guide roller (24), but also exerts a certain braking effect on the film strip (18), which is so strong that the film strip is tensioned during the winding process elongation of about 1%. A further elongation of 1 to about 3 to 4% is experienced by the film strip (18) as a result of the tension which arises when it is fed to the winding station and during winding.

The rotatably mounted winding roller (10) has a rigid roller body (25) and a coating (26) made of elastically resilient soft material such as foam rubber in the angular region or middle region. The surface of the coating (26) is designed to be low-abrasion.

Since the coil (16) presses against the winding roller (10) during operation, the coating (26) hugs the surface of the coil (16) or the coil (27) formed on it due to its soft elastic properties. This prevents that under the on the winding (27) emerging foil tape (18) can form air pockets. Rather, the film strip (18) is allowed to run onto the winding (27) with sufficient pressure in order to push out the air underneath and to prevent any air pockets. Although the film strip (18) is wound helically in continuous layers on the spool (16) or the winding (27), a compact, firm winding is produced in this way.

The front ends (28) of the winding (27) are conical, for example at a cone angle of 20 ° to 40 ° and preferably about 30 °, so that the front ends (28) of the winding (27) are compact and the winding is not here can collapse.

This is achieved, for example, by, after winding up a length of between 200 and 1800 m of the film strip, preferably a length of between 300 and 900 m, the width of the random layer roll being shortened by between 3 and 18 mm, preferably between 4 and 8 mm . The width of the film strip is between 6 and 27 mm, preferably at least 12 mm and at most 20 mm.

The invention is suitable for very thin tapes of less than 100 μm, preferably less than 60 μm and particularly preferably less than 40 μm. The invention is even applicable to extremely thin tapes less than 30 microns thick, and the art has been found to be extremely advantageous in the art for winding tapes approximately 25 microns thick. These are extremely thin ribbons, and on an industrial scale this is now the lower limit for the thickness of ribbons that can be manufactured on an industrial scale. Even thinner ribbons can also be produced, and the invention can also be applied to them; however, the large-scale production of such tapes still presents certain problems. The lower limit for the thickness of the ribbons is determined solely by the possibility of being able to produce them properly on an industrial scale. As mentioned, today it is around 25 µm or 20 µm in large-scale production. Of course, even thinner tapes can be produced on a pilot plant scale and wound according to the invention.

The film strips generally consist of thermoplastic elastomers, for example polyurethane, but also polyester amide or polyether ester amide.

According to a preferred practical embodiment, the film strip (18) has a width of approximately 17 mm. The feed of the guide arm (19) is then, for example, 5 mm per revolution of the winding roller (10) in order to ensure the desired overlap of the foil tape coil on the winding (27). To ensure this, the feed must always be sufficiently smaller than the respective width of the film strip (18).

The pressure between the coil (16) or winding (27) and the winding roller (10) must be sufficiently high to exclude air pockets between the individual helical layers of the wound film strip (18). For this purpose, pressure medium such as compressed air with a pressure of 2 to 10 bar, preferably 2.5 to 6 bar, is fed into the pressure cylinder (17).

The winding roller (10) expediently has a diameter of approximately 10 to 50 cm, the diameter preferably being less than 40 cm and particularly preferably less than 30 cm. A diameter in the range of approximately 15 to 25 cm has proven to be particularly advantageous. The soft, elastic, conformable surface (26) suitably consists of so-called cellular rubber (closed-cell blown cellular rubber). The thickness of this surface (26) is advantageously in the range from about 5 mm to about 50 mm. The minimum thickness is expediently about 10 mm, while the upper limit is expediently about 40 mm, preferably about 30 mm and particularly preferably about 25 mm. The most preferred range is about 15 to 20 mm thick.

According to the invention, very high winding and thus peripheral speeds of the soft, elastic, conformable surface (26) can be achieved, namely up to about 250 m / min. However, this circumferential speed of the winding roller (10) should expediently be below 200 m / min and advantageously below approximately 150 m / min. The minimum peripheral speed is about 50 m / min, preferably about 100 m / min.

The following physical properties have proven to be expedient for the soft-elastic, conformable surface (26):
Degree of hardness according to ASTM: RE about 41 to 43, advantageously about 42.
Compression hardness according to ASTM: about 20 to 80, preferably about 30 to 70 kPa.
Compression set: about 12 to 20, preferably about 15 to 19, particularly preferably about 16 to 18%.

Since the wound film strips can be extremely thin, it is expedient that the longitudinal or tensile stress during winding is extremely low. It has proven to be particularly expedient that the winding takes place almost without tension.

The local pressure during winding should also be as low as possible, expediently below 5 bar, preferably below 3 bar and particularly preferably below 1 bar. Surprisingly, this extremely low pressure is sufficient to exclude air pockets between the individual helical layers of the wound film strip (18).

For the winding, sleeves are used which advantageously have a diameter of approximately 5 to 30 cm, preferably approximately 10 to 25 cm and particularly preferably approximately 15 to 20 cm.

Claims (5)

1. Method for winding elastically stretchable, thin film tapes, for example made of polyurethane, in which tape material is continuously fed to a rotating spool and wound onto it under a certain longitudinal tension.
characterized in that a pressure is exerted locally on the coil over its entire length when it is wound. 2. The method according to claim 1, characterized in that the tape material over the length of the spool back and forth or iridescent this is fed and the individual layers of the helically overlapping tape roll are continuously shorter, so that the tape roll has a conical end under one Receives angles from about 20 ° to 45 °. 3. Device for performing the method according to claim 1 or 2 and for winding elastic thin film strip or the like. on spools, with a guide for the incoming film strip, a rotatably mounted, drivable winding roller and a slide that is adjustable relative to the winding roller, on which the spool to be wound can be freely rotated and exchangeably arranged,
characterized in that the carriage (13) is displaceable radially with respect to the winding roller (10) and can be pressed against it, and in that the winding roller (10) has a soft, elastic fit in the contact area with the coil (16) or the winding (27) located thereon Surface (26). 4. The device according to claim 3, characterized in that the soft elastic surface (26) of the winding roller (10) consists of compressible foam rubber and has a low-abrasion surface. 5. Apparatus according to claim 3 or 4, characterized in that the winding roller (10) has a solid surface (25) in its end regions and a coating (26) made of foam rubber in the central region.

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