GB2237584A - Calender for surface treatment of material webs - Google Patents

Abstract

A calender (10) for surface treatment of material webs, wherein in the event of one sided seizure of an intermediate roller (16, 17, 18) the fixed roller (12) not subject to pressure is adjusted in position at one end such that the asymmetrical linear force profile resulting from the seizure is symmetrically adjusted according to the desired condition in order to optimise processing of the material web. Hydraulic fluid operated deflection equalization supports 24 apply differential pressure along a linear force profile in gap 28. Position sensor 20 reports position of roll sleeve 13 to position controller 22 and control of fluid pressure is performed by controller 28 coupled to controller 22. The calender stack may be horizontal. <IMAGE>

Description

Calender for Surface Treatment of Material Webs The present invention

relates to a calender for treating material webs, and to a method of calendering.

Calenders comprising at least one fixed roll rigidly 10 supported in the pressing direction and at least one movable roll which is mounted for free movement in the pressing direction, are fairly well known. In particular, the roll journals are mounted in elongate guides for free movement in the pressing direction, so that they function as movable rolls and are subject to limited movement in these guides.

However, problems arise from the fact that considerable frictional forces can act in these guides which may even give rise to a seizing effect. As a result, for example with a vertical calender, the expected pressing force in the roller gap of the fixed roll can possibly be too high or too low on one side, according to whether an increase or decrease of the pressing force was executed. This leads to pressing forces deviating from the desired value and/or to inclined press force profiles in the roll gap, the latter occurring since the friction forces are not always equally large in the roll guides.

It has already been attempted many times to moderate the effect of these frictional or seizing phenomena by artificial shaking or moving of the entire roll assembly in order to overcome the frictional forces.

1 - 2 Also it has been attempted to provide a remedy by applying, according to circumstances, a greater or smaller additional load by the movable roll until the desired pressing forces are present at the fixed roll.

In this way, it is sometimes achieved that with approximately constant friction, the actual value of the central line force or the central line force profile in the roller gap on the fixed roll, taken as a measure of the smoothing process, is brought to the desired value. In many cases however it has occurred that the friction increased until the guide seized as a direct result of the mentioned techniques. In any case, the line forces in the roll gaps, which are located between the rubbing or seizing roll and the moving roll experiencing the additional loading, are incorrect, which leads to a considerable disturbance of the rolling process.

It is therefore desirable to provide a calender in which the mentioned friction and seizing phenomena are avoided in a simple and reliable manner, or at least in which their disadvantageous effect can be mitigated without for example having to modify an existing calender considerably.

According to the invention, there is provided means for measuring the pressing forces on the fixed roll, means for adjusting the fixed roll in the pressing direction, means for comparing the desired value of the pressing force with the actual measured pressing force on the fixed roll, and a control device for controlling the adjusting means according to the comparison between the actual and desired values for achieving the desired pressing forces on the fixed roll in the roll gap. The desired value of the pressing force on the fixed roll may thus be derived from the components of the weight forces acting in the pressing direction of the supporting parts movable across the fixed roll in the pressing direction as well as the forces impressed on the displaceable rolls.

This solution exploits the concept of making the roll, which is provided as such for operating as a fixed roll, at least selectively movable at the ends in the pressing direction, in dependence upon the supporting forces measured at the fixed roll, which are largely determined by the pressing forces. The principle operates generally both upwardly and also downwardly (vertically extending calender) and also in any other relative position of the rolls, as for example horizontally where the calender is horizontal. In this connection, a supplementary load can be applied both from above and also from below or from either side.

With use of the invention, the disadvantage effect of the frictional forces can be avoided not only on the adjusted fixed roll but also in the roll gaps between the adjusted fixed roll and the roll on which the disturbing frictional force appears.

It is not necessary to know which of the rolls is rubbing or seizing in its guides.

As the smallest unit, one fixed roll can be combined with one movable roller.

Also movable rolls, which exert supplementary forces are conceivable.

- 4 In conjunction with an upright calender, the fixed roll can be provided either as the uppermost or as the lowermost roll.

In conjunction with a horizontal calender, the fixed roll can be provided either as the outermost right hand or the outermost left hand roll.

It is also possible to provide the fixed roll in the intermediate region of the calender.

The fixed roll itself can expediently be constructed as a deflecting equalization roll with fixed lateral bearings of the roll sleeve (socalled NIPCO-K roll).

Also the fixed roll can be constructed as a deflecting equalization roll with a roll sleeve movable in the pressing direction over its entire length, which sleeve can be fixed by a distance measuring arrangement at a selectable position for operation in the pressing direction (so-called NIPCO-F roll with position control).

The movable roll, which can apply supplementary forces, is advantageously conceivable as a deflecting equalization roll with a roll sleeve movable in the pressing direction.

For measuring the load on the rolls, load cells can be employed or also hydraulic or pneumatic pressures can be derived from the loading systems of the rolls.

For changing the position ofthe front ends of the respective fixed roll, jacking devices, piston systems or other mechanical arrangements can be used.

i In conjunction with a fixed roll as deflecting equalization roll with a roll sleeve movable in the pressing direction over the entire length, which sleeve can be fixed by means of a distance measuring arrangement at a selectable position for operating in the pressing direction, the said adjustment can be performed by modifying the selectable position, e.g. by appropriate inputs into a controller fixing the position of the roll sleeve, or by modifying the 10 position of the entire deflecting equalization roll. Another possible technique is to reduce artificially the clearance at the distance measuring arrangement and thus to initiate readjustment.

Readjustment of the position of the fixed roll towards or away from the rubbing or seizing roll can be separately automated at both roll ends in dependence upon the actual-desired pressure force difference between the fixed and movable rolls.

The invention will now be described in the following in more detail on the basis of exemplary embodiments illustrated purely schematically in the drawings, in which:

Fig. la shows a schematic view of a calender; Fig. lb shows a schematic side view of the calender according to Fig. la; Figs. 2a to 2e show various upright calenders and a horizontal calender; and Figs. 3a and 3b show a two roll construction in longitudinal and transverse section.

- 6 consists of a plurality of rolls arranged another to form a roll gap or nip therebetween, through which passes the paper web to be smoothed. With an upright calender according to Figs. la and lb, a lower roll 12 and an upper roll 14 are provided with intermediate rolls 16, 17 and 18 arranged therebetween. A portion of the intermediate rolls is not illustrated in Fig. la. Although either the upper or the lower roll or even an intermediate roll can be provided as a so-called fixed roll, in the example illustrated in Fig. la, the lower roll 12 is constructed as a so-called NIPCO roll having a roll sleeve 13 and a yoke 15. This roll here represents a so-called fixed roll. These NIPCO ro 'c can be constructed in various ways. To form a so-called NIPCO-K roll, the roll sleeve 12 is itself mounted laterally and bending equalization of the sleeve takes place by means of intermediate supports which can be loaded using hydraulic fluid. With the so-called NIPCO-F roll, the roll sleeve is no longer laterally supported, but instead the support is provided only over the length of the roll sleeve on the yoke. Such a NIPCO roll is a known deflection equalization roll.

A calender behind one On the roll sleeve 13 or on the yoke 15 is located a position sensor 20 which is coupled to' a position controller 22. The deflection equalization supports represented by the arrows 24 are supplied with hydraulic fluid in order to apply differential pressure along a linear force profile in the roll gap 26 between the intermediate roll 18 and the lower fixed roll 12 across the length of the roll. The control of the hydraulic fluid pressure is performed by means of a fluid pressure controller 28 coupled to J 4 the position controller. The fluid pressure at various positions of the roll gap can be displayed graphically on a monitor via lines 30.

The position sensor 20 reports the actual position of the NIPCO roll sleeve 13 to the position controller 22 which continuously corrects the fluid pressure of all zones in such a manner that the NIPCO roll sleeve 13, and thus the entire roll assembly assumes a definite horizontal height position and maintains it. The entire roll assembly floats as it were within quite narrow limits.

The rollers are guided by lateral journals 32 is engaging in vertical guides. The rolls normally lie on one another in the vertical calender as a result of their own weight. However, also according to the arrows 34, a supplementary pressure can be applied laterally to the upper roll 14. In this connection, the upper roll 14 can likewise be a NIPCO roll.

If for example seizure occurs on the right hand side in the vertical guide of intermediate roller 17, this results in upward deflection of the roll sleeve 13 (NIPCO sleeve) so that the position sensor 20 on the right hand side in Fig. 1 detects movement in the vertical direction between the associated sensor components. Thus, on the seizing side the position sensor registers the reduced loading as a small upward movement of the sleeve and thus controls a correspondingly reduced fluid pressure on this side. The linear forces now applied by the self-loading NIPCO roll uniformly increase from the side where seizing occurs up to full loading on the opposite side which is displayed as an inclined linear force - 8 profile on the monitor via the lines 30. linear nrofile is illustrated bv the A differing arrows of differing length in the region of the NIPCO roll in Fig. la. According to the invention, the lower roll 12 arranged as a fixed roll on the right hand side, i.e. on the side of the seizure, is now moved upwardly in such manner that again a uniform linear force profile across the length of the roller is set according to the desired values. This means that the actual fixed roll is adjustable in the direction of the remaining rolls for re-regulation at least at the ends.

It should also be mentioned that in the event of seizure on the right hand side of the intermediate roll 17 the conditions above this roll remain satisfactory, as indicated by the arrows at that point in Fig. la. The conditions beneath the seizure are brought back to the desired condition by regulation across the entire length of the rolls.

Fig. 2 shows in schematic representation vertical calenders in Figs. 2a to 2d and a horizontal calender in Fig. 2e. In Fig. 2a, the rolls 14 and 16 are movable rolls which are guided by means of guide components 17 in vertical guides 19. The lower roll 12 is here a fixed roll.

In Fig. 2b, the upper roll 14 is fixed in just the same way as the lower roll 12, which however can here be moved by a jacking unit 21 for active pressure force application. Also this movement can be subject to seizure.

In Fig. 2c, the lower roll 12 is fixed, the upper roll 14 being movable vertically by a jacking unit 21 for pressure force application.

1 - 9 Fig. 2d shows how the calender in Fig. 2b may have a lower roller 12 movable by a jacking unit 21 as well as a fixed intermediate roll 1411.

In the horizontal calender of Fig. 2e, the outer right hand outer roll 141 is fixed and the outer left hand roll 121 is movable by a jacking unit 211. The intermediate rolls 161 are likewise movable with guide components 121 in a guide 191.

In order to simplify this system, a measurement can be performed separately at both ends of the fixed roll. In this connection, it is irrelevant whether the loading is applied by the self weight and an additional load above in the vertical calender or is applied by force application below. In each case it has to be ensured that, taking account of the desired loading, the actual loading appearing in the event of seizure possibly also on one side, is eliminated and brought back to the desired value by slight movement of the fixed roll at the corresponding end. The hydraulic or pneumatic pressures of the pressure application system may for example of the loadings.

serve as measures The possibility also exists of determining the respective actual value in the region of the support of the fixed roller using load cells and then performing regulation to the desired value. For position change of the respective fixed roll, jacking devices, piston systems or other mechanical arrangements are suitable.

Also measuring and positioning systems can occur in combination, as for example the so-called "floating stack principle,, with position sensors in combination with self-loading NIPCO rolls.

Readjustment of the position of the fixed roll towards or away from the rubbing roll can be automated in dependence upon the difference between the desired pressure deviation of the two extreme superimposed roll gaps, separately at both roll ends. For the system, it is not necessary to know which of the rolls is rubbing or seizing in its guides.

Figs. 3a and 3b show a two roll system. This includes two so-called NIPCOF rolls. The roll sleeve 13 is supported via pressure rams 42 on the yoke 15, where these pressure rams can be selectively activated via a chamber 43 and an oil conduit 44, as shown by the arrows in Fig. 3a in the region of the pressure rams. The outer edge of the roll sleeve 13 is supported via a bearing 40 on a connecting member 38. This connecting member is movable vertically on a guide of the yoke 15, as indicated by the arrow in Fig. 3b. Thus it can be moved vertically relative to the yoke 15 in dependence upon the pressure force exerted by the pressure rams on the applied pressing force, along the corresponding vertical guide surfaces 50. The mentionded seizing can occur there as a result of the increased friction. The movement of the roll sleeve 13 relative to the yoke 15 can be determined by a displacement transducer 46. Here, the possibility exists of compensating disharmony of the pressing forces in the event of seizure occurring solely by use of simple software control.

i, W? - 1 1 - 4

Claims (28)

Claims:

1. A calender comprising: at least one fixed roll which in operation is substantially rigidly supported in the pressing direction; at least one movable roll which is mounted for free movement in the pressing direction; means for measuring pressing forces on the fixed roll; means for adjusting the fixed roll in the pressing direction; means for comparing a desired pressing force with actual measured pressing force on the fixed roll; and control means for controlling the adjusting means according to the comparison between the actual and desired values of force for achieving the desired pressing forces on the fixed roll in the roll gap.

for treating material webs,

2. A calender according to claim 1 wherein one fixed roll and one movable roll are provided.

3. A calender according to claim 1 or 2 wherein the fixed roll is provided as the uppermost roll in a vertical arrangement.

4. A calender according to claim 1 or 2 wherein the fixed roll is provided as the lowermost roller in a vertical arrangement.

5. A calender according to claim 1 or 2 wherein the fixed roller is provided as the outermost right-hand roll in a horizontal arrangement.

6. A calender according to claim 1 or 2 wherein the fixed roller is provided as the outermost left-hand roll in a horizontal arrangement.

7. A calender according to claim 1 or 2 wherein the fixed roll is provided in the intermediate region of the calender.

8. A calender according to any preceding claim wherein the fixed roli is a deflection equalization roll with fixed lateral rotational mounting of the roll sleeve (so-called NIPCO-K roller).

9. A calender according to any of claims 1 to 7 wherein the fixed roll is a deflection equalization roll with a roll sleeve movable in the pressing direction over its entire length (so-called NIPCO-F roller) which for operation can be set at a selectable position in the pressing direction with the aid of a distance measuring arrangement.

10. A calender according to any preceding claim wherein at least one movable roll is arranged for application of a supplementary load which can be measured.

11. A calender according to any of claims 8 to 10 wherein the measuring means is operable to determine the hydraulic or pneumatic pressures from the loading system of at least one roll.

12. A calender according to any of claims 1 to 10 wherein said measuring means comprises at least one load cell.

-1

13 - t 13. A calender according to any preceding claim wherein said adjusting means comprises a jacking device.

14. A calender according to any preceding claim wherein said adjusting means comprises a hydraulic or pneumatic piston system.

15. A method of calendering comprising: rigidly supporting at least one fixed roll in the pressing direction; mounting at least one movable roll for free movement in the pressing direction; measuring the pressing forces on the fixed roll; adjusting the fixed roll in the pressing direction; comparing the desired pressing force with the measured actual pressing force on the fixed roll; and controlling the adjustment of the fixed roll according to the comparison between the actual and desired value for achieving the desired pressing forces on the fixed roll in the roller gap.

16. A method according to claim 15 in which the fixed roll is provided as the uppermost roll in a vertical calender.

17. A method according to claim 15 in which the fixed roller is provided as the lowermost roll in a vertical calender.

18. A method according to claim 15 in which the fixed roll is provided as the outermost right-hand roll in a horizontal calender.

19. A method according to claim 15 in which the fixed roll is provided as the outermost left-hand roll in a horizontal calender.

20. A method according to any of claims.15 to 19 in which the fixed roll is provided in the intermediate region of the calender.

21. A method according to any one of claims 15 to 20 in which the fixed roller has a roller sleeve movable in the pressing direction over its entire length (so-called NIPCO-F roller) which is fixed at a selectable position in the pressing direction with the aid of a distance measuring arrangement.

22. A method according to claim 15 in which 'a supplementary load is applied by at least one of the movable rollers and this supplementary load is measured.

23. A method according to any of claims which the hydraulic or pneumatic pressures are determined from the loading system of rolls.

to 22 in the roll or

24. A method according to claim 15 in which load cells are employed to measure the pressing forces on the fixed roll.

25. A method according to claim 15 in vihich a jacking device is employed to adjust the fixed roll.

26. A method according to claim 15 in which a hydraulic or pneumatic piston system is employed to adjust the fixed roll.

j

27. A method of calendering substantially as hereinbefore described with reference to Figs. la and lb, any of Figs. 2a to 2e, or Figs. 3a and 3b.

28. A calender substantially as hereinbefore described with reference to Figs. la and lb, any of Figs. 2a to 2e or Figs. 3a and 3b.

Published 1991 at The Patent Office, State House, 66/71 High Holborn, London WC I R4TP. Further copies maybe obtained from Sales Branch, Unit 6. Nine Mile Point- Cvnniclinfach. Cross Keys. Newport. NPI 7HZ. Printed by Multiplex techniques lid, St Mary Cray, Kent