DE29611251U1 - Device for winding or unwinding a fibrous web - Google Patents

Description

Voith Sulzer Paper Machines «ämbä! r · ··**; · '"tgUcfce: PA10180 G D-89509 Heidenheim ·!·· "'*·^# * ** "\51anzfreier

Wrap"

Device for winding or unwinding a fibrous web Description

The invention relates to a device for winding or unwinding a fibrous web, e.g. paper web. It deals with the problems that arise when the web is wound up in its full width onto a winding roller, called a tambour, at the end of the web production process or at the end of a post-treatment process. As is known, such a tambour rests at both ends by means of a bearing on a support device (machine frame, pivot lever or the like). The invention also deals with the problems that arise during unwinding, i.e. when the web is unwound again in its full width from the said tambour, e.g. in order to reroll the web or to process it further.

According to publication DE 44 22 877, the presence of a "contact roller", also called a carrier drum, is required when winding up the web, whereby the roll and the contact roller are pressed horizontally against each other. One problem is seen in the fact that different deflections of the contact roller on the one hand and the roll on the other lead to an uneven contact pressure profile across the width of the web, with the result that crepe folds and bursts occur in the edge areas of the winding. The aforementioned publication suggests exerting a flat relief force on the roll that counteracts the deflection of the roll.

pep 2781 DSh EM 00200 26.06.96 Jank (2909P2/1)

This well-known method may well be suitable for avoiding crepe folds and bursts in the edge areas of the winding. However, in many cases another problem occurs:

It is observed from time to time that when the paper web is unwound, it has areas of high gloss in some places, unevenly distributed over the paper surface. In other words: the surface of the paper web gives a spotty impression, so that it is not usable for some applications. The invention is therefore based on the task of remedying this.

This object is achieved by the features specified in claim 1. Further embodiments of the invention are mentioned in the subclaims.

The invention is based on the knowledge that the irregular shiny spots mentioned are caused by the fact that during winding and/or unwinding - as a result of the sometimes enormous weight of the roll - individual adjacent paper layers slide back and forth on each other. Under the weight of the roll, vertical shear stresses arise within the roll. These can also occur if the reel does not bend or only slightly, e.g. if it has a particularly large diameter. The shear stresses are greatest in the area of the horizontal reel center plane. It is important to recognize that these vertical shear stresses reverse their direction with every half revolution of the reel. One must imagine an "outer" surface area of a paper layer located inside the roll and an adjacent "inner" surface area of a layer located further inside. Due to the winding's own weight and its constant rotation, the outer surface piece, relative to the inner surface piece, wants to lead when running from top to bottom, but lag behind when running from bottom to top.

pep 2781 DSh EM 00200 26.06.96 Jank (2909P2/2)

If the coefficient of friction between the surface pieces is relatively

■i

is low, one surface area slides against the other. This sliding process causes the shiny spots mentioned. In extreme cases, the circumstances described can also lead to the paper web tearing.

With the device according to the invention, the surface relief force can now be specifically measured in such a way that the shear stresses mentioned are reduced and that sliding back and forth of adjacent paper layers is prevented. The previously feared uneven gloss spots no longer occur, so that a much higher percentage of each individual roll is available as saleable paper than before.

It is important that a planar relief force is exerted on the winding; because a linear relief force would not be able to reduce the shear stresses mentioned.

Some winding devices according to the invention are shown schematically in the attached drawing (Figs. 1 to 3).

The essential parts of the winding device shown in Fig. 1 are:

9 incoming paper web.

10 carrying drum.

11 drums.

12 Wraps (the paper web wound on the reel).

13 Longitudinal rails to support the tambour with the winding.

14 Endless belt for direct support of the roll. It is preferred to use a single machine-width belt.

DCD 2781 DSh EM 00200 26.06.96 Jank (2909P2/3)

15, 16, 17 Belt guide rollers; one of these (15) is rigidly mounted and can be driven, the others rest on pivot levers (18), the guide roller (16) can be moved on the pivot lever to tension the belt. 19 Lifting device for lifting the pivot lever and thus for pressing the belt 14 from below onto the roll 12. When the roll is full, it is removed from the carrier drum 10 on the longitudinal rails 13 (to the right); for this purpose, the pivot lever 18 and guide roller 16 are pivoted away. If desired, the belt 14 only comes into contact with the roll 12 when the latter has reached a certain size.

In Figure 2, the carrier drum (10) takes over the function of the drivable belt guide roller (15) from Figure 1. An additional tension roller 19 for the belt 14 can be moved approximately vertically.

Here, the direction of action of the surface relief force can be selected in such a way that it results in a line force between the winding 12 and the carrier drum 10. In this case, the line force and thus the winding hardness can be influenced by varying the relief force. The line force can be influenced by varying the height and/or the direction of action of the relief force. What all of these different methods have in common is that the line force is significantly more uniform across the web width than when the line force is generated by means of lifting devices that act on the ends of the drum 11.

Figure 3 is a variant of Figure 1. The belt guide roller 16 can be pivoted far upwards so that the belt 14 - if necessary - supports the roll 12 from the beginning and presses the roll against the carrier drum 10.

nn 9781 nsh FM 002OO 26.06.96 Jank (2909P2/4)

Claims (10)

Voith Sulzer Papiermaschinen GmbH File: PA10180 G D-89509 Heidenheim "Gloss-free winding" Protection claims 1) Device for winding or unwinding a fibrous web, e.g. paper web, whereby the web is wound onto a reel in its full web width or unwound from a reel and wherein the reel is supported at both ends, further comprising a relief device which, during the winding process, exerts a planar relief force directly on the reel which counteracts its own weight in order to reduce the vertical shear stresses resulting from the reel's own weight, characterized in that at least one endless belt (14) circulating over guide rollers (15, 16, 17) is provided as the relief device, the longitudinal tension of which is variable. 2) Device according to claim 1, characterized in that at least one (16, 17) of the guide rollers rests in movable bearings in order to adapt the travel path of the belt (14) to the increasing winding diameter, e.g. by arranging the bearings on pivoting levers (18). 3) Device according to claim 1 or 2, characterized in that at least one (16 or 19) of the guide rollers is designed as a belt tensioning roller with which the level of the relief force can be controlled. nrn 9781 RSh FMn(IJOiI 26.06.96 Jank (2909P2/5) 4) Device according to claim 1, 2 or 3, characterized in that the relief device supports the roll only by means of an area of the belt that is free from the guide rollers. 5) Device according to claim 1, characterized in that the relief device comprises a compressed air cushion. 6) Device according to claim 1, 2 or 3, in which the web is guided over a support drum during winding, which is arranged in the direction of web travel immediately in front of the roll, characterized in that the endless belt (14) is also guided over the support drum (10). 7) Device according to one of claims 1 to 6, characterized in that the relief device acts uniformly on the roll over the web width. 8) Device according to one of claims 1 to 6, characterized in that the relief device is divided into zones over the web width (e.g. in order to set a higher relief force in the edge zones). 9) Device according to claim 8, characterized in that the relief force is a pressure cushion divided into zones, which acts directly on the roll or on a belt that relieves the roll. 10) Device according to claim 8, characterized in that the relief device has a plurality of belts distributed over the web width and differently tensionable. pep 2781 DSh EM 00200 26.06.96 Jank (2909P2/6)