CA2290558A1

CA2290558A1 - Calendar arrangement

Info

Publication number: CA2290558A1
Application number: CA002290558A
Authority: CA
Inventors: Bernhard Brendel; Peter Svenka
Original assignee: Individual
Current assignee: Eduard Kuesters Maschinenfabrik GmbH and Co KG
Priority date: 1998-03-17
Filing date: 1999-03-04
Publication date: 1999-09-23
Also published as: JP4575476B2; DE19811474A1; ATE239825T1; JP2001526747A; EP0990070A1; DE59905425D1; WO1999047750A1; JP2008285806A; EP0990070B1

Abstract

The invention relates to a vertical calendar arrangement, comprising a bendcontrolled upper roller (12) and a bend-controlled lower roller (20) as well as intermediate rollers (14, 16, 18) located between them. The upper roller (12) and the lower roller (20) are each provided with a power drive mechanism.

Description

Calender arrangement s The invention relates to a calender arrangement.
In vertical calenders having a plurality of rolls, one of the intermediate rolls is provided with a main drive and transmits the torques to all the other rolls frictionally, by means of tangential forces, from one roll to the next and via the web to be treated and the roll covers. This leads to undesired horizontal deflections, to that is to say to deformations of the intermediate rolls. In addition, the web structure and the roll covers are impaired. Fig. 1 shows a schematic side view of a known off-line calender, in which an intermediate roll 2, that is the drive roll with a main drive, is driven.
In an on-line calender, before the paper web is threaded, and with the 15 nips open, all the rolls in contact with the paper web are accelerated by their auxiliary drives, and the drive roll with the main drive is accelerated to a rotational speed at which the respective circumferential speed corresponds to the web speed of the paper, which can be 1000 m per minute and much higher. After the nips have been closed, power is introduced only by the main drive of a single 2 o drive roll. This is illustrated schematically in Fig. 2, in which the main drive 4 is represented by a large drive symbol and the auxiliary drives 6 are represented by a small drive symbol. In Figs. 1 and 2, the horizontal deflections at the centre of the roll are drawn schematically as a centre offset.
In modern calenders, the top roll and the bottom roll of the roll stack are 2 s designed as controllable-deflection rolls. Because of their internal frictional losses, necessitated by their functioning, these two rolls need a greater drive force than the remaining calender rolls. In addition, the most extreme deformation of the paper web takes place in the first nip. In conventional calenders having a main drive, these two power components have to be dragged through the entire roll 3 o stack and, in so doing, stress the paper web and the roll covers in a damaging way as a result of frictional transmission of the tangential forces. This results in increased wear of the roll surfaces and a reduction in the service life of the rolls.
According to an earlier proposal in DE-196 50 576.3, all the rolls are provided with their own (power) drives, and the powers of the individual drives are coordinated with one another in such a way that the horizontal roll deformations are minimized.
The object of the invention is to provide a calender whose roll drive is designed such that the outlined disadvantages of the prior art are avoided cost s effectively.
The achievement of this object in accordance with the invention is defined in Patent Claim 1.
According to the invention, the controllable-deflection rolls are each provided with their own power drive. In one configuration of the invention, a i o controllable-deflection top roll and bottom roll can be driven with drive powers matched to each other. It is preferred to register the horizontal deformation of an intermediate roll and to control or regulate the power distribution to the two drives in such a way that this deformation at least remains below an amount which is still permissible. It has been shown that this requirement can be met if the top roll and 15 bottom roll are driven with essentially the same power.
Two embodiments of the calender arrangement according to the invention are reproduced schematically in side view in the appended Figures 3 and 4. Here, Fig. 3 shows a calender arrangement analogous to Fig. 1, while Fig.

4 represents a calender arrangement analogous to Fig. 2. The symbols for the 2 o power drive and auxiliary drive in Fig. 3 and Fig. 4 correspond to the symbols for the main drive and auxiliary drive in Figs. 1 and 2.
After the nips have been closed, the calender rolls have the predefined line load applied to them, at which predefined pressure stresses are developed in the nips. At the same time, the calendering forces corresponding to the loading 2 s are provided by the two power drives of the top and bottom rolls. An intermediate roll is expediently provided with sensors for the horizontal deformations, and the distribution of the drive power to the top and bottom roll is carried out in such a way that these horizontal deformations are minimized. Alternatively, it is also possible for the horizontal forces acting on an intermediate roll to be measured 3 o and minimized.
In the embodiments according to the invention according to Figs. 3 and 4, the paper web 10 runs firstly into the nip formed between the upper controllable-deflection roll 12 and the first intermediate roll 14, which is a heatable hard roll. After this, the paper web passes into the nip formed between the latter 3 s roll and a central intermediate roll 16; roll 16 is provided with a resilient cover. On the side facing away from roll 14, roll 16 forms, with a second heatable hard roll 18, the next nip through which the paper web 10 passes. A last nip is formed between roll 18 and the bottom controllable-deflection roll 20. The rolls 12 and 20 are equipped with power drives. The intermediate rolls 14, 16 and 18 are mounted s in a manner known per se in lever arms 22, via which forces from operating cylinders 24 can be introduced, in particular in order to compensate for the so-called overhung loads. Hydraulic units 26 are used to close the nips; instead of this, the inner stroke of the roll 20 could also be used for this purpose, while the upper controllable-deflection roll 12 is mounted in a fixed location in the frame.
1 o On one of the intermediate rolls 14, 16, 18, transverse forces which occur can be measured via sensing elements (not illustrated) and, depending on the measurement result, the power distribution of the drives for the top roll 12 and the bottom roll 20 can be adjusted, in order that these transverse forces do not exceed a predefined value. Alternatively, possible deformations of the 15 intermediate rolls 14, 16, 18, in particular at their roll centre, can be measured by means of measuring elements. This measurement result can be included in the power distribution of the drives for the top roll 12 and the bottom roll 20, in order also to minimize these deformations.
It should further be noted that the concept according to the invention is 2 o particularly suitable for re-equipping existing calenders, in which there is often a lack of space, or for narrower machines having a relatively low drive power and relatively stiff intermediate rolls.

Claims

1. Vertical calender arrangement, comprising a controllable-deflection top roll, a controllable-deflection bottom roll and intermediate rolls arranged between the top and bottom rolls, characterized in that the top roll (12) is provided with a power drive and the bottom roll (20) is likewise provided with a power drive.

2. Calender arrangement according to Claim 1, characterized in that the top roll (12) and the bottom roll (20) can be driven with drive powers matched to each other.

3. Calender arrangement according to Claim 1 or 2, characterized in that one of the intermediate rolls (14, 16, 18) is provided with a measuring device for its horizontal deflection, and the drive power of the two driven rolls (12, 20) can be distributed in such a way that the horizontal deflection of the intermediate roll (14, 16, 18) provided with the measuring device is less than a predetermined amount.

4. Calender arrangement according to Claims 1 to 3, characterized in that the intermediate rolls (14, 16, 18) are provided with measuring elements for measuring the horizontal forces on the same, and the drive power of the two driven rolls (12, 20) can be adjusted in such a way that the horizontal forces on the intermediate rolls (14, 16, 18) can be minimized.

5. Calender arrangement according to one of Claims 1 to 4, characterized in that all the rolls in contact with the paper web, except the top roll (12) and the bottom roll (20) are provided with an auxiliary drive.