WO2007054624A2

WO2007054624A2 - Loading bearings of a calender roll of a multi-roll calender

Info

Publication number: WO2007054624A2
Application number: PCT/FI2006/050492
Authority: WO
Inventors: Markku Kojo; Hannu Pullinen; Jari J. MÄKELÄ; Juha Linja
Original assignee: Metso Paper, Inc.
Priority date: 2005-11-14
Filing date: 2006-11-13
Publication date: 2007-05-18
Also published as: FI117903B; WO2007054624A3; DE112006003131B4; FI20055604A0; AT505215A1; AT505215B1; DE112006003131T5

Abstract

This publication described a method for loading the bearings of an intermediate roll (13,14) of a multi-roll calender (100) and a multi-roll calender (100). The multi-roll calender comprises one or more sets of rolls (10) in which in at least one set of rolls the centre shafts (C14, C15) of at least two calender rolls form a nip plane (P), whereby for normal calendering a bottom roll (15) is loaded on the nip plane (P) by first load means, such as bottom cylinders (16). For partial nip run, in said at least one set of rolls (10) of the multi-roll calender (100) the centre shaft (C15) of the bottom roll (15) is transferred, without detaching from the multi-roll calender (100), aside from the plane (V14) passing via the centre shaft (C14) of the intermediate roll (14) above the bottom roll (15), and the bottom roll (15) is loaded against the intermediate roll (14) above it by second load means (18) at an angle α of 15-25°, advantageously at an angle α of about 22°, in relation to the vertical plane.

Description

Loading bearings of a calender roll of a multi-roll calender

The present invention relates to paper and board machines, especially to calenders.

In more detail, the present invention relates to a method for loading the bearings of an intermediate roll of a multi-roll calender, the multi-roll calender comprising one or more sets of rolls in which in at least one set of rolls the centre shafts of at least two calender rolls form a nip plane, whereby for normal calendering the bottom roll is loaded on the nip plane by first load means, such as bottom cylinders.

Furthermore, the invention relates to a multi-roll calender which has one or more sets of rolls of which in at least one set of rolls the centre shafts of at least two calender rolls form a nip plane, and in which there are first load means, such as bottom cylinders, for loading the bottom roll on the nip plane for normal calendering.

Calendering is generally carried out in order to improve the properties, such as smoothness and gloss, of a web-like material, such as a paper or board web. In calendering, the web is passed into a nip, i.e. calendering nip, formed between rolls being pressed against each other, in which nip the web becomes deformed from the effect of temperature, moisture and nip pressure. In this context, calender rolls refer to rolls forming a calendering nip, a top roll refers to the uppermost roll of a set of rolls, a bottom roll refers to the undermost roll of a set of rolls, and a bottom nip refers to the undermost calendering nip of a set of rolls which nip is formed between the bottom roll and the calender roll above the bottom roll. Intermediate nips refer to calendering nips being formed by means of calender rolls between the top nip and the bottom nip of the calender. Intermediate rolls refer to calender rolls being between the top and bottom roll in the set of rolls. In this context, the term nip plane refers to a plane formed by the centre shafts of the calender rolls, which plane in some contexts is also referred to as a nip line or a line of a set of rolls.

Finnish patent specification 96334 is cited as prior art which document discloses a method for calendering a paper or an equivalent web material in a calender. In the method, the web material to be calendered is passed through nips formed by a deflection-compensated top roll and a deflection-compensated bottom roll and by two or more intermediate rolls arranged between the top and bottom rolls. The rolls are arranged as a substantially vertical set of rolls. Such rolls in which the form of the natural deflection line produced by their dead weight is substantially equal are used as intermediate rolls. The nip load produced by the masses of the intermediate rolls and the auxiliary devices related to them is substantially completely relieved in the method, and an adjustable load is applied to the calendering nips by means of the deflection-compensated top or bottom roll and/or by means of an external load applying to the top or bottom roll.

Pressing is typically provided in a multi-roll calender by fastening the top or bottom roll of the set of rolls to its place and by pressing the set of rolls against the fastened roll which roll can be an top roll, a bottom roll or an intermediate roll/some intermediate rolls. Alternatively, both the top and the bottom roll are pressed against each other either so that none of the intermediate rolls is fixedly locked to its place or so that at least one of the intermediate rolls is fixedly locked to its place. It is possible to compensate for the deflections of the rolls by means of deflection-compensating devices usually located in the top and bottom rolls e.g. so that the roll nips acquire a linear form, as is described in Finnish patent specification 96334.

As is known in the art, the centre shafts of the calender rolls in a set of rolls of a multi-roll calender have been parallel. The centre shafts of the calender rolls have been in crosswise CD direction in relation to the run direction of the web. Then, there is always a nip calendering the web between the adjacent calender rolls, these rolls forming a calender roll pair, the pressing plane of which nip is parallel to the centre shafts of the calender rolls of the calender roll pair. The nip plane P according to Fig. 1 can also be at a certain angle in relation to the horizontal plane so that a set of rolls of a calender is formed between the rolls 11-15.

The calendering technique of choice is more and more often on-line calendering, because higher run speeds are required of paper machines. Multi-nip on-line calendering is calendering in a calendering unit in which nips are formed between a smooth-surfaced press roll, such as a metal roll, and a roll coated with flexible cover, such as a polymer roll, alternately following each other and/or a reversing nip. Linear load increases in multi-nip calenders from the top nip to the bottom nip due to gravitation, if no roll relief systems are used. In multi-nip calenders presently in use, roll relief which compensates for gravitation and is carried out by a cylinder and lever mechanism is used for eliminating downwards-increasing linear load, for controlling the deflection line of the roll and also for rapid opening of the set of rolls. Such a roll relief system is used in the applicant's multi-roll calenders known by trademarks OptiLoad and TwinLine.

From prior-art are known multi-roll calenders the set of rolls of which is formed of two sets of rolls, each set of rolls including at least two calender rolls, e.g. one including five rolls and the other six rolls. As run speeds of paper machines and the need for on-line calendering increase, a possibility to carry out various types of calendering by means of the calender is also required which can be carried out e.g. by means of partial nip run known as such, in which the web is passed through a calender so that, during calendering, the web is being calendered only in some of the possible nips of the calender. In partial nip runs, it has been known to lock the levers of the calender by hydraulics during partial nip run. As known of prior art, e.g. publication FI 96334, the calender rolls forming the nip of a multi-roll calender are bearing-mounted by roller bearings, which has caused certain problems, the solving of which has required special arrangements.

In some cases, e.g. in partial nip run, multi-roll calenders are run with such linear loads which bring a very small load, even a so-called zero load, on the roller bearings of the calender roll. This is very problematic from the viewpoint of roller bearings since, in a zero-load situation, the rolling elements of a roller bearing are able, instead of rolling, to slide in a significant amount in relation to bearing frames, resulting in a speedy breakdown of the bearing. In a zero-load situation of a roller bearing, the point of contact between the rolling elements of the roller bearing and the rolling surfaces of the bearing frames is disadvantageously vague and unsteady, because the rolling frames of the bearing do not press the rolling elements between themselves steadily from any direction with sufficient force.

If the set of rolls of a multi-roll calender is almost vertical, gravitation is parallel to the linear load and the motion of the set of rolls. When the linear load difference upwards between the roll nips reaches the dead mass of the roll, the roll bearing falls to a zero-load zone. The bearing load should generally be at least about 2% of the maximum load of the bearing. When using the bottom nip of a multi-roll calender, the upper roll falls easily to the zero-load zone, whereby the linear-load zone in the use of the calender decreases. When running e.g. such partial nip run in which the fibre web is calendered in the two lowest nips of the set of rolls of the multi-roll calender, whereby the three lowest rolls of said set of rolls take part in the calendering, the zero-load problem applies especially to the middle and the upmost roll of these rolls.

An object of the present invention is to eliminate above-mentioned problems and defects or at least decrease above-mentioned disadvantages and to prevent a zero- load situation of the roller bearing of the calender roll of the multi-roll calender or at least decrease the linear load zone in which the load of the bearings of the calender roll would be too small.

An object of the invention is to create a method in a multi-roll calender and a multi-roll calender, by which it is possible to obtain better calendering potential in the multi-roll calender, especially an object is to increase the linear load zone of the multi-roll calender in partial nip run to the load zone in which the zero-load problem has known to have occurred.

For achieving the object of the invention, the method for loading the bearing of the calender roll of the multi-roll calender is mainly characterised by what is presented in the characterising part of claim 1.

Also, the multi-roll calender according to the invention is mainly characterised by what is presented in the characterising part of claim 5.

Compared to formerly known arrangements, significant advantages are achieved by means of the invention, the advantages including, inter alia, the following. As the bottom roll of the multi-roll calender and, according to a second embodiment of the invention, also the intermediate roll above the bottom roll can be located for partial nip run away from the line of the set of rolls in which the intermediate roll above the bottom roll is in normal calendering and the bottom roll can be loaded away from the line of the set of rolls, to the bearings of the intermediate roll above the bottom roll can be applied a horizontal force component dependent on the linear load. According to the second embodiment of the invention, correspondingly also to the bearings of a second intermediate roll counting from under can be applied a horizontal force component dependent on the linear load. Such a horizontal force is able to press the rolling elements and rolling surfaces of the bearings of the intermediate roll against each other and to prevent the rolling elements from sliding on the rolling surfaces. Utilising said horizontal force, the linear load zone, in which the load of the bearings of the calender roll would be too small, can be substantially decreased especially for partial nip ran. Thus, it is possible to increase the calendering potential i.e. linear load zone in which the fibre web can be calendered, without the bearing of roll taking part in the calendering nip suffering from the zero-load problem.

In partial nip run, many times a fibre web of matte grade is calendered. When running matte grade as one does not wish to press the fibre web too much, a small load is chosen for calendering. Especially then the decreasing of the zero-load zone is a significant advantage.

In the calendering nip in the so-called zero-load situation, the rolling elements of the roller bearing are not able to slide, instead of rolling, in relation to bearing frames, whereby the result is the increase of the lifetime of the bearing and generally of the lifetime of the fibre-web machine. Thus, it is possible to avoid change times of broken bearings and the cooling and heating times of heatable calender rolls and more time can be used for the actual calendering process. There is also no need to store the bearings in such large numbers for bearing failure situations.

The invention enables the transfer of the bottom roll of the multi-roll calender also for roll change. Then, no special tool is required for the transfer or lift of the bottom roll and e.g. common lifting bands can be used for lifting and transferring.

The invention will next be described by referring to enclosed figures showing the principal of the invention with which figures the method and the multi-roll calender according to the invention have been illustrated, without limiting the invention solely to what is shown in the figures.

Fig. 1 shows a set of rolls of a multi-roll calender in which in normal calendering a fibre web is calendered in all nips between the calender rolls, all nips closed. Fig. 2 shows a set of rolls of a multi-roll calender in which for partial nip run two lowest rolls are used, whereby the web is calendered in one nip.

Fig. 3 shows a set of rolls of a multi-roll calender in which for partial nip run three lowest rolls are used, whereby the web is calendered in two nips.

Fig. 4 shows a support solution of the bottom roll of a multi-roll calender.

Figs. 1-4 schematically show a multi-roll calender 100. Especially, the figures show a set of rolls 10 of a multi-roll calender which set includes a top roll 11 and a bottom roll 15 and three intermediate rolls 12, 13 and 14 arranged between the top and the bottom roll, whereby the top, bottom and intermediate rolls form the calender rolls 11-15 of each set of rolls. The fibre web being calendered in the multi-roll calender is not shown in the figures. The intermediate rolls are bearing- mounted to the frame of the multi-roll calender e.g. by means of support and load arms rotating around a pivot, which pivots and arms are not shown in detail. The frame of the multi-roll calender is referred to in the figures by a dash-and-dot line designated by F.

In Fig. 1, the set of rolls 10 of the multi-roll calender 100 is in a full nip run position which is called a normal calendering position. In Figs. 2 and 3, the sets of rolls 10 are shown in a partial nip run position.

In the sets of rolls, adjacent calender rolls 11, 12; 12, 13; 13, 14 and 14, 15 form calender roll pairs in which the calender rolls can form a nip 1, 2, 3 and 4 calendering the fibre web between them with designations of Figs. 1-3 from the top downwards. In this context, the invention has been described by using a five- roll and four-nip set of rolls as an example, but any other number of rolls and nips of the set of rolls is also possible. It is possible to apply the set of rolls 10 described in connection with the multi-roll calender 100 with one set of rolls of the invention also in a multi-roll calender with two or more sets of rolls. Thus, the multi-roll calender can comprise e.g. two five-roll sets of rolls.

Generally, pressing of the fibre web is provided in the multi-roll calender either by fastening the top roll 11, the bottom roll 15 or one of the intermediate rolls 12, 13, 14 of the set of rolls to its place in relation to the frame F of the calender and by pressing several rolls as a roll stack or a single roll in relation to the frame F to its place against the roll fastened to its place, which roll fastened to its place can be the top roll 11, the bottom roll 15 or one/some of intermediate rolls 12, 13, 14. Alternatively, both the top and the bottom roll can be pressed against each other either so that none of the intermediate rolls is fixedly locked to its place or so that at least one of the intermediate rolls is fixedly locked to its place. The pressing forces of the top roll 11 and/or the bottom roll 15 can be adjusted irrespective of each other in many arrangements. In the multi-roll calender, the top roll and/or the bottom roll can be provided with a load apparatus arranged inside the shell and/or the top roll can be loaded by the top load cylinder and/or the bottom roll can be loaded by the bottom load cylinder 16. The deflections of the rolls can be compensated by deflection-compensating devices in the rolls e.g. so that the deflection lines of the rolls are of the same form. There are deflection- compensating devices typically in the top and/or bottom roll, but also one of the intermediate rolls can be provided with deflection-compensating devices.

By means of Figs. 1-4, the invention was schematically illustrated in a multi-roll calender with one set of rolls for achieving different run modes. For implementing partial nip run, the lowest or the second lowest intermediate roll of the set of rolls 10 can be locked whereby, by loading the rolls above or below the locked roll, a required number of nips is obtained. Figs. 2 and 3 show how especially below the locked intermediate roll it is possible to obtain one or two nips for partial nip run taking place in the lower position of the calender. In Fig. 1, the set of rolls 10 of the multi-roll calender 100 is shown in such a position in which all calendering nips, the top nip 1, the intermediate nip 2, the intermediate nip 3 and the bottom nip 4 are closed in normal calendering, whereby the fibre web is calendered in four closed nips 1-4. By the arrangement shown in Fig. 1, a run mode is achieved in which the calendering is performed in the set of rolls 10 by five rolls 11-15. Then, the centre shafts of the calender rolls 11, 12, 13, 14 and 15 of the set of rolls 10 in the corresponding order C₁₁, C₁₂, C₁₃, C₁₄ and C₁₅ form a nip plane P.

Fig. 2 shows a run mode in which in the set of rolls 10 the two lowest rolls, i.e. the rolls 14 and 15, are used, whereby the bottom nip 4 is available for partial nip run. Then for partial nip run, in at least one set of rolls 10 of the multi-roll calender 100 the centre shaft C₁₅ of the bottom roll 15 is transferred, without detaching from the multi-roll calender 100, aside from the plane V₁₄ passing via the centre shaft C₁₄ of the intermediate roll 14 above the bottom roll 15, which plane V₁₄ is in the situation shown in Fig. 2 congruent with the nip plane P when the nip plane P is vertical. The bottom roll 15 is loaded against the above intermediate roll 14 by second load means 18 at an angle α of 15-25°, more advantageously at the angle α of about 22°, in relation to the vertical plane. Fig. 2 shows that the bottom roll 15 has been transferred in partial nip run outside the nip plane P as viewed from the direction of the frame F of the multi-roll calender 100. In this partial nip ran situation, the web (not shown in figures) is calendered in the bottom nip 4 of the set of rolls 10 of the multi-roll calender 100 which nip is formed by the bottom roll 15 and the intermediate roll 14 above the bottom roll between them being loaded against each other at a significantly oblique angle α. It should be noted that, in this context, the term above intermediate roll means the position of a certain intermediate roll 13; 14 in the set of rolls/roll stack as the next upper calendering roll, even though this intermediate roll is not in the vertical direction exactly above the next calendering roll 14; 15 located lower, but these calendering rolls can be brought to a nip contact to be under loading against each other in a way described by the invention at a significantly oblique angle in relation to the vertical plane.

The situation shown in Fig. 2 can be implemented by a transferable support arrangement of the bottom roll 15 shown in Fig. 4 in which support arrangement there is no need to detach the bottom roll for transfer from the multi-roll calender 100. In normal calendering, the bottom roll 15 is located to an almost vertically line with the other rolls of the set of rolls 10 i.e. the nip plane P, as is shown in Fig. 1.

When in the multi-roll calender 100 one transfers from the normal calendering run mode to calendering the fibre web by partial nip run, the bottom roll 15 of the multi-roll calender 100 is transferred away from the line of the set of rolls 10 so far that the bottom roll 15 can be loaded against the above intermediate roll 14 at a significantly oblique angle α. The significantly oblique angle α in relation to the vertical plane is suitably 15-25°, more advantageously the angle α is about 22°. Generally in paper-machine lines, the roll masses and the linear-load zones are such that the zero load of the bearings can be eliminated significantly almost totally, if the bottom roll is at an angle of 15-25°, advantageously at an angle of about 22° in relation to the line of the vertical set of rolls. The presented angle is affected by the mass, width and used linear load of used rolls. By generally used roll masses, roll widths and linear loads, about 37% from the nip load is obtained for a horizontal force F_H applied to the bearings of the roll at the angle of 22°, and said angles are suitable also from the viewpoint of using the bottom nip 4 and the intermediate nip 3 above the bottom nip in partial nip run.

By means of Figs. 2 and 3, nip forces FN prevailing in the partial nips have been illustrated by arrows which force is divided to a horizontal force component FH and a vertical force component Fy. The designations are provided in Fig. 3 by indexing corresponding the designation of the nip. In Fig. 2, an oblique nip load FN creates a horizontal force component FH to the bearings of the intermediate roll 14 which prevents the bearing to fall to a zero load. The horizontal force component F_H of the bottom nip 4 deflects the intermediate roll 14 above the bottom roll 15 horizontally, but the effect of the deflection is insignificant with used linear loads of partial nip run e.g. 5-100 kN/m by which most matte and news grades calendered by partial nip run are covered.

Fig. 3 shows the partial nip run mode according to an advantageous additional embodiment of the invention, whereby in the set of rolls 10 the three lowest rolls are used, i.e. the upper intermediate roll 13, the lower intermediate roll 14 and the bottom roll 15, whereby two nips, the bottom nip and the intermediate nip above it, are available for partial nip run. In the description of Fig. 3, the descriptions and designations related to Fig. 2 can be applied to an appropriate extent. A difference to the description of Fig. 2 is that the use of the intermediate nip 3 above the bottom nip 4 in partial nip run is shown in Fig. 3, whereby also the centre shaft C₁₄ of the intermediate roll 14 above the bottom roll 15 is transferred aside from the nip plane P to the same direction as the centre shaft C₁₅ of the bottom roll 15. Thus, of these three rolls the middle roll i.e. the lower intermediate roll 14 has been transferred in partial nip run outside the nip plane P as viewed from the direction of the frame F of the multi-roll calender 100. Then, the intermediate roll 13, i.e. the upper intermediate roll, above this intermediate roll 14 is loaded by the bottom roll 15, in addition to the intermediate roll 14, via its above intermediate roll 14 at an angle α of 15-25°, more advantageously at the angle α of about 22°, in relation to the vertical plane. Naturally, also the relief of the nip load caused by the masses of intermediate rolls and auxiliary devices related to them is used.

Fig. 4 shows how the bottom roll 15 is transferred, without detaching from the multi-roll calender 100, aside from the plane V₁₄ passing via the centre shaft C₁₄ of the intermediate roll 14 above the bottom roll 15. A bottom roll 15' shown by dash-and-dot lines shows the bottom roll 15 in the partial nip run position. A bottom roll 15" shown by dash-and-dot lines shows the bottom roll 15 in the roll change position.

According to an embodiment of the invention, the normal linear load of the bottom roll 15 is made by first load means, such as bottom cylinders 16, which are large hydraulic cylinders and which are not used in the loading of partial nip run. Then, the bottom roll is in Fig. 4 in a position shown by designation 15 on the nip plane P of the set of rolls 10 bearing-mounted to bearing housings 19 which have been installed to load arms 20 in the horizontal position.

Partial nip run load is made by separate second load means 18 which are e.g. hydraulic cylinders smaller than bottom cylinders 16. An advantage of this is the speed and sensitivity of positioning provided by smaller cylinders. The bottom roll 15 is transferred to a position 15' corresponding the partial nip run position aside supported by its bearings housings 19 by means of transfer means 17, such as guide surfaces formed by horizontal guides and the lower surfaces of bearing housings, and further in lateral transfer e.g. electro-mechanical or hydraulic actuators known as such can be used as aids. The new support arrangement of the bottom roll 15 is in the embodiment of Fig. 4 arranged into connection with the load arms 20 supporting the bearing housings 19 of the bottom roll 15. For partial nip run, the bearing housings 19 of the bottom roll 15 are transferred in the lateral direction by transfer means 17 which are arranged to the load arms 20, and the bearing housings 19 of the bottom roll 15 are lifted supported by the load arms 20 by second load means 18 affecting the load arms 20. The second load means 18 are installed between the load arms 20 and the frame F. The load arms supporting the bearing housings 19 are arranged to the frame F of the multi-roll calender 100 both movable in the vertical direction and inclinable to a position diverging from the horizontal direction. The load arms 20 are in normal calendering loadable by the bottom cylinders 16 and in partial nip run loadable by the second load means 18. The vertical transfer motion of the load arms 20 in the frame F is implemented by vertical carriages 22 movable along the slide guides 21 of the frame F. This transfer motion is used when loading the bottom roll 15 by the bottom cylinders 16 and when finding the load arms 20 a suitable starting position of height in order to be able to lift the bottom roll 15 to the partial nip run position 15' without inclining the load arms 20. For inclining to a position diverging from the horizontal direction and for moving the bottom roll 15 to a nip contact and loading, the load arms 20 are pivotedly fastened inclinable in relation to pivots 23 to the vertical carriages 22 in the frame F. The load arms 20 are locked in a horizontal position in their place to the vertical carriages 22 using removable locking pins 24 in normal calendering, when using the bottom cylinders 16. For partial nip run, the load arms 20 are fastened by means of removable fastening means, such as removable cylinder fasteners 25, to the second load means 18, after which the locking pins 24 are opened for inclining the load arms 20 around the pivots 23 and for lifting the bottom roll to the partial nip run position 15' loaded by the load means 18.

The fastening of the bottom roll 15 is made such that the transfer of the bottom roll 15 sidewards and further to the load position 15' against the above intermediate roll 14 can be done during the grade change of a fibre web, such as paper, in less than 5 minutes.

In Fig. 4, the bottom roll 15 is shown by dash-and-dot lines in the roll change position 15". It is possible to move the bottom roll 15 by the transfer means 17 to a vertical lifting line L, whereby e.g. common lifting bands can be used for the lifting and transferring. Then, there is no need for a special tool for the transfer or lifting of the bottom roll 15. Such known special tools are, inter alia, special hooks for lifting the roll and a transfer device enabling the roll change of the bottom roll. By means of the method and the multi-roll calender of the invention, it is possible to prevent the zero-load situation of the roller bearing of the intermediate roll/intermediate rolls which kind of situation can occur in partial nip run, when one wishes to run with such linear loads which cause a very small load to the roller bearings. In the zero-load situation, the rolling elements of the roller bearing would be able to move in relation to bearing frames instead of rolling, whereby the result was a quite speedy breakdown of the bearing. The force effect caused by the acceleration of the mass of the intermediate roll/intermediate rolls and the gravitation to the calendering nip can be relieved in a known way by actuators, such as cylinder actuators, which affect e.g. between the frame of the multi-roll calender and the support and load arms supporting the roll. Because of the location of the bottom roll 15 and its centre shaft C₁₅ aside from the plane V₁₄ passing via the centre shaft C₁₄ of the intermediate roll 14 above the bottom roll 15 shown in Fig. 2, a horizontal force component F_H dependent on the linear load is applied to the bearings of the intermediate roll 14. Correspondingly in connection with the embodiment of Fig. 3, the horizontal force components F_R3 and F_H4 are applied to the bearings of two intermediate rolls above the bottom roll. By means of the method and the multi-roll calender of the invention, it is possible to decrease the linear load zone on which the load of the roller bearings of the intermediate roll/intermediate rolls 13; 14 would be too small and thus enabling a situation in which the rolling elements of the roller bearing are able to roll in relation to the bearing frames instead of sliding, the result of which sliding would be quite a speedy breakdown of the bearing.

It is possible to utilise the invention in calender structures of rebuild type in which existing calenders are improved or repaired, and the invention enables revising of the structure of known calenders to be less limited of their linear load zone.

The invention was described above by way of examples with reference to the figures of enclosed drawings. The invention is not, however, limited to what is presented in the description and figures, but different embodiments of the invention can vary within the scope of the inventive idea presented in the enclosed claims.

Claims

1. A method for loading the bearings of an intermediate roll (13, 14) of a multi- roll calender (100), the multi-roll calender comprising one or more sets of rolls (10) in which in at least one set of rolls the centre shafts (C₁₄, C₁₅) of at least two calender rolls form a nip plane (P), whereby for normal calendering a bottom roll (15) is loaded on the nip plane (P) by first load means, such as bottom cylinders (16), characterised in that for partial nip run in said at least one set of rolls (10) of the multi-roll calender (100) - transferring the centre shaft (C₁₅) of the bottom roll (15), without detaching from the multi-roll calender (100), aside from the plane (V₁₄) passing via the centre shaft (C₁₄) of the intermediate roll (14) above the bottom roll (15), and - loading the bottom roll (15) against the intermediate roll (14) above it by second load means (18) at an angle α of 15-25° in relation to the vertical plane.

2. A method according to claim 1, characterised in that the bottom roll (15) is loaded against the intermediate roll (14) above it at an angle α of about 22° in relation to the vertical plane.

3. A method according to claim 1 or 2, characterised in that the centre shaft (C₁₄) of the intermediate roll (14) above the bottom roll (15) is transferred aside from the nip plane (P) to the same direction as the centre shaft (C₁₅) of the bottom roll (15).

4. A method according to claim 3, characterised in that the intermediate roll (13) above the intermediate roll (14) is loaded via the intermediate roll (14) above the bottom roll (15) at an angle α of 15-25°, more advantageously at the angle α of about 22°, in relation to the vertical plane.

5. A multi-roll calender (100) which includes one or more sets of rolls (10) in which in at least one set of rolls (10) the centre shafts (C₁₄, C₁₅) of at least two calender rolls (14, 15) form a nip plane (P), and in which there is first load means, such as bottom cylinders (16), for loading the bottom roll (15) on the nip plane (P) for normal calendering, characterised in that, for partial nip run, said at least one set of rolls (10) of the multi-roll calender (100) comprising

- transfer means (17) for transferring the centre shaft (C₁₅) of the bottom roll (15), without detaching from the multi-roll calender (100), aside from the plane (Vu) passing via the centre shaft (C₁₄) of the intermediate roll (14) above the bottom roll (15), and

- second load means (18) for loading the bottom roll (15) against the intermediate roll (14) above it, for loading the bottom roll (15) against the intermediate roll (14) above it at an angle α of 15-25° in relation to the vertical plane.

6. A multi-roll calender according to claim 5, characterised in that the bottom roll (15) is arranged to be loaded against the intermediate roll (14) above it at an angle α of about 22° in relation to the vertical plane.

7. A multi-roll calender according to claim 5 or 6, characterised in that the centre shaft (C₁₄) of the intermediate roll (14) above the bottom roll (15) is transferable aside from the nip plane (P) to the same direction as the centre shaft (C₁₅) of the bottom roll (15).

8. A multi-roll calender according to claim 7, characterised in that the intermediate roll (13) above the intermediate roll (14) is arranged to be loaded via the intermediate roll (14) above the bottom roll (15) at an angle α of 15-25°, more advantageously at the angle α of about 22°, in relation to the vertical plane.

9. A multi-roll calender according to any one of claims 5-8, characterised in that it comprises a frame (F) in which are pivotedly (23) fastened load arms (20) which support bearing housing (19) transferable sideways of the bottom roll (15), and that between the load arms (20) and the frame (F) there is arranged the second load means (18) for moving the bottom roll (15) to a nip contact and for loading.

10. A multi-roll calender according to any one of claims 5-9, characterised in that the second load means (18) are hydraulic cylinders smaller than the bottom cylinders (16).