Calender

Details Calender Calender

1999-05-04

2000-11-21

Cuda, Irene

Roll or roller

With antideflection means

Rotatable relative to supporting shaft

492 16, B29C 4346

Patent

active

061495638

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a calender.
2. Description of the Prior Art
In the rollers described in the preamble, the bearing pockets rest against the inside circumference of the hollow cylinder with an edge which is sealed all around. The edge forms essentially sealed hydrostatic pressure chambers. The pressure of the chambers acts against the inside circumference of the hollow cylinder and produces the linear force in the roll nip. The pressure fluid is supplied via a first feed line and constantly flows to the outside over the edge of the bearing pockets, causing a bearing fluid film to form between the edge and the inside circumference of the hollow cylinder, preventing metal-to-metal contact. In order for the bearing pockets to be sealed and for pressure to build up in the pockets, the edge has to be pressed against the inside circumference of the hollow cylinder with a certain force. This is accomplished with the pressure in the sealed cylinder space. The sealed cylinder space is structured as a piston/cylinder unit in the supporting element, the force of which presses the supporting element and therefore the edge against the inside circumference of the hollow cylinder. The pressure fluid which acts on the cylinder space is supplied via a second feed line. The bearing pockets have pressure fluid at different pressures applied to them, individually or in various groups, in order to be able to adjust a linear force profile of the desired type along the roll nip. In practice the cylinder spaces are generally connected with a common feed line at a single pressure, which feed line is dimensioned so as to maintain sufficient contact.
A roller with two feed lines to the supporting elements is known from German Patent 38 20 974 A1. Such a roller has already been used in a calender, which thereby represents the state of the art. An important characteristic of the roller according to German Patent 38 20 974 C2 is that the bearing pockets are connected with the first feed line without a throttle, i.e. that the pressure fluid can pass over into the bearing pockets from the space under the supporting element, through the inner channels which are present in the supporting element, and have a cross-section which does not cause any significant pressure drop in normal operation.
The rollers of the prior art are also used in calenders with plastic-coated roller mantles. The plastic coatings are significantly more sensitive, mechanically and thermally, than a metal roller surface. If web problems occur, such a soft roller coating is therefore easily damaged. A web problem is, for example, a break in the web, which has the result that a roller with a plastic coating suddenly comes into contact with a hot counter-roller, something that the plastic cannot tolerate. In normal operation, the roller surface is protected from the hot counter-roller by the cooler web, for example the paper web. Doubling of the web can also damage the surface of the plastic coating, if the linear forces are high, by pressing the web into the coating.
In the case of such web problems, rapid opening of the roll nip due to the danger of damage to the roller coating is absolutely necessary.
During normal production of the calender, the cross-head of the roller is deflected away from the roll nip, due to the forces of the supporting elements which support the roller mantle. In the case of calanders with a large width, the amount of deflection is several centimeters in the center. The change in distance between the cross-head and the inside circumference of the roller mantle is overcome by moving the supporting elements out in a direction perpendicular to the cross-head. The volume of pressure fluid enclosed under the supporting element is increased by the amount which corresponds to this movement path.
This also holds true for calenders with deflection-controlled rollers with a so-called inside stroke. Here, to adjust the contact with a counter-roller, rather than moving the position of the

REFERENCES:
patent: 5534117 (1996-07-01), Roerig
patent: 5628717 (1997-05-01), Van Haag
patent: 5919121 (1999-07-01), Kusters et al.
patent: 5980438 (1999-11-01), Van Haag et al.

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