Method for the shaftless winding of a web

Method for shaftless winding of a web of material

It is known to affect the hardness of a roll supported on two mutually parallel carrier rolls during winding by distributing the load of the roll on the carrier rollers. For this purpose, carrier rollers of similar diameters are adapted to different horizontal planes or carrier rollers of different diameters are used. It is also known that when winding on a carrier with a smaller diameter, a harder winding is obtained than when winding on a carrier with a larger diameter.

Despite these decades of known influences, no fully satisfactory winding technique has been found so far. An attempt has been made to prevent the disadvantage that, as the diameter of the roll increases, the outer region compresses the inner region of the roll radially and deforms in a star shape by introducing a higher roll hardness. However, this type of winding resulted in too much hardness of the roll in the outermost region. Wrinkles, tears and cracks were formed. To avoid this drawback, smaller roll diameters have been satisfied, so that the winding hardness was also below the acceptable limit in the outermost region. Furthermore, it turned out that in connection with the winding of the web of material, the processing of the web of material at a station arranged behind the calendar brought with it accuracy problems. In the case of the cross cutter, the specified shape could not be accurately maintained. It was found that this effect could be deduced from the silent tension of the material web. Measurements of the winding hardness of the roll diameter showed that the winding hardness fluctuated strongly around the average value.

The object of the invention is to provide a method for the shaftless winding of a web of material on two carrier rolls, by which method better winding results are obtained. In particular, the winding hardness should be uniform in diameter and star formation should be avoided.

9 81 8

This task is solved by a method of axially winding a web of material on two carrier rollers of different diameters, in particular with a diameter ratio> 1.5, of which the smaller carrier roll with axes is located horizontally above or below the horizontal plane where the axis of the larger carrier roll is located. between the vertical planes of the axes of the rollers, which method is characterized by that, depending on the desired maximum coil diameter D ^ max, the maximum pivot angle of the small carrier roll with respect to the large carrier roll is set to

a) to provide a soft winding (Figure 1) ⁼ + ('X - £) and max max ^J

b) to provide hard winding (Figure 2) ¹ = - arctan \ -------- ^ tan max

[d_i + 2a + D₂ | cosp (D. + D max) 'max 1 o

<img file="FI69818C_D0001.tif" />

<img file="FI69818C_D0002.tif" />

at least where max • 4 max at the beginning of the winding event, when

<td rowspan="2">= 80 ° - 90 ° = arccos (1</td><td>A</td><td>- D max · BP</td>

<td>C</td><td>+ D max · E P</td>

<td>A - 2 · a (a</td><td>+ D₂</td><td> )</td>

<td>B = 2 (a +</td><td>d₂)</td><td></td>

<td>C = (O_χ +</td><td>2a +</td><td> °₂)</td>

<td>E = D₁ + 2a</td><td>+ D</td><td></td>

<td colspan="2">a = carrier rollers</td><td>gap.</td>

The method of both windings according to the invention provides a roll whose winding hardness increases less sharply in diameter as measured from the inside to the outside than in the case of conventional winding methods. This means a reduction in the overall hardness level and thus a lower load on the material web. There is a risk that hard winding on the outside and soft winding on the inside will form on the inside

6981 8 star formations, practically no longer exist. The invention creates the condition that rollers with a larger diameter can be produced without exceeding the maximum permissible winding hardness. Accordingly, the hardness level of the winding can be raised or lowered to improve the quality of the roll and to prevent damage to the web of material during winding as needed.

In connection with winding, in order to make the conditions as independent as possible from the tensile stress of the material web, it has been proposed that in connection with the winding of softer rolls, the material web is wound around a larger diameter carrier roll.

Since both carrier rollers were used in connection with the calenders used in practice, in order to increase the winding hardness of the roll around which the web of material was not wound, it is not necessary to use both carrier rolls when the other carrier roll is loaded with a larger part of the roll weight. In this case, it is sufficient to use a heavily loaded carrier roller.

In the following, the invention will be explained in more detail in connection with the drawing.

In detail, Fig. 1 shows the calender as a schematic representation adjusted for soft winding and Fig. 2 shows the calender as a schematic representation adjusted for hard winding.

When installing the calender, the gap a of the carrier rollers is first determined. The minimum diameter D2 of the smaller carrier roll depends on the load on this carrier roll. The requirements for this carrier roll are: low deflection under roller tension, adequate fracture toughness under static and dynamic loading, no critical torsion and deflection frequencies.

There is already a choice of a larger roll diameter

6981 8 take into account the desired winding result. Larger diameter carrier rollers can provide softer winding than smaller diameter carrier rollers.

With a given ratio of diameters, the turning angle can then be calculated according to the above formula as a function of the desired final diameter of the roll. As, for safety reasons, it does not wind up to the top of the carrier in the usual way, is accepted^{/; s &lt;}_max for a value less than 90. Good results are obtained at an angle of Ά = 85 °.

It was found that soft winding is obtained above all when the nip-induced winding tension is produced mainly by means of a nip and mainly by a carrier roll 11a with a larger diameter. These conditions are obtained when the roll axis passes only a small angle around the axis of the larger diameter carrier roll during the winding operation and the starting turning angle / is large. This can be accomplished with respect to large diameters in the ^ 1 ^ 2 connection. At the same time, a more uniform winding hardness for the roll diameter is thus obtained. A diameter ratio of 1.7 has proven to be suitable.