WO2004061222A1

WO2004061222A1 - Multiroll calender

Info

Publication number: WO2004061222A1
Application number: PCT/FI2003/000997
Authority: WO
Inventors: Markku Kyytsönen; Risto Vainio; Olli Tirronen; Eero Suomi
Original assignee: Metso Paper, Inc.
Priority date: 2003-01-02
Filing date: 2003-12-31
Publication date: 2004-07-22
Also published as: AU2003290142A1; DE10394020T5

Abstract

A multiroll calender (10) comprises at least one roll stack (11) in which there are rolls (12, 13, 14, 15, 16) to form at least one intermediate nip (2, 3, N), and at least one thermo roll (13, 15), as well as a top roll (12) and a bottom roll (16) provided with deflection-compensation devices. In the roll stacks (11) the rolls are movable into nip contact with one another to calender a fibrous web (W) in closed nips. An upper thermo roll (13) constituting a roll pair with the top roll (12) is fixedly supported on a roll frame, so that the closing, opening and loading of a top nip (1) is arranged by loading the shell of the top roll (12) from the inside and the closing, opening and loading of a bottom nip (1) is arranged by loading the shell of the bottom roll (16) from the inside. In order to adjust the load of the nip (2, 3, N) between at least one pair of calender rolls (12, 13; 13, 14; 14, 15; 15, 16) in the roll stack, to open said nip or to lock it in an open position, the pair of calender rolls is provided with a nip load-adjustment and/or locking arrangement (20) which acts between bearing housings (9) or bearing housing carriages and/or loading and/or supporting arms (31, 32) of the calender rolls.

Description

Multiroll calender

The present invention concerns paper and board machines, in particular calenders. The invention relates to a multiroll calender comprising roll stacks placed one on top of another and/or next to one another, at least one of which roll stacks comprises at least three rolls and at least one other of which roll stacks comprises at least four rolls to thereby form at least one intermediate nip, so that some of the intermediate nips can be opened by means of relief devices, and in which multiroll calender a top roll and a bottom roll in each roll stack are provided with deflection-compensation devices and at least one thermo roll is fixedly supported on or openably locked to a roll frame and the rolls in the roll stacks are movable into nip contact with one another for calendering a fibrous web in closed nips.

The present invention also relates to a nip load-adjustment and/or locking arrangement for a pair of calender rolls in a roll stack of a multiroll calender and for a nip between the pair of calender rolls, which roll stack comprises, as calender rolls, a top roll and a bottom roll, at least one of which is provided with an elastic cover and functions as a backing roll for a hard- and smooth-surface pressing roll, and at least one intermediate roll between the top roll and the bottom roll, and in which roll stack the centre axes of the calender rolls are parallel and in the cross direction transverse to the running direction of a web such that between adjacent calender rolls that form a pair of calender rolls there is a nip which calenders the web, the pressing line or plane of which nip is parallel to the centre axes of the calender rolls in the pair of calender rolls.

In connection with the glazing of a paper web, the paper web is passed through a calender, which forms a web running path in which the web is treated in nips which are also called "roll gaps". A nip is typically defined between a smooth- surface pressing roll, such as a thermo or metal roll, and a backing roll provided with an elastic cover, such as a polymer roll, between which rolls the web is treated, i.e. calendered by means of pressure, moisture and elevated temperature. The quality of the treatment that takes place in the calender then determines surface properties. Thus, it may be generally stated that with increasing number of nips, the quality of the surface improves. In many cases, however, a high-quality surface is not needed or desired. In that case, it is possible to be content with a smaller number of nips.

In calendering, attempts are made to generally improve the characteristics, such as smoothness and gloss, of a web-like material, such as a paper or board web. In the calender, nips are formed between a smooth-surface pressing roll, such as a metal roll, and a roll covered with an elastic cover, such as a polymer roll. In calendering, a web is passed into a nip defined between rolls pressed against each other, i.e. into a calendering nip, in which the web is deformed due to the effect of temperature, moisture and nip pressure. The elastic-surface roll conforms to the shape of the web surface and presses the opposite side of the web evenly against the smooth-surface pressing roll. In this connection, by calendering rolls are meant rolls that form a calendering nip, by a top roll is meant the uppermost roll of a roll stack, by a top nip is meant the uppermost calendering nip defined between the top roll and a calendering roll located below the top roll, by a bottom roll is meant the lowermost roll of a roll stack, and by a bottom nip is meant the lowermost calendering nip of a roll stack defined between the bottom roll and a calendering roll located above the bottom roll, by an upper thermo roll is meant a thermo roll constituting a roll pair with the top roll and by a lower thermo roll is meant a thermo roll constituting a roll pair with the bottom roll. By intermediate nips are meant calendering nips that are formed by means of calendering rolls between the top nip and the bottom nip of the calender. Typically, compression is provided by attaching the top or the bottom roll in place and by pressing the roll stack against the roll attached in place or, alternatively, both the top roll and the bottom roll are both pressed towards each other. The deflections of the rolls can be compensated for by means of deflection-compensation devices provided in the rolls such that the roll nips obtain a linear form.

By flexible calendering is meant the possibility of changing in the calender during operation the number and load of the nips that calender the web. This means that by means of different combinations of the number of calendering nips and/or of web running paths it is possible to flexibly calender different fibrous webs or continue the production process despite deterioration, failure or damage of a calender roll/calender rolls.

In the calendering technology, on-line calendering is adopted more and more because the running speeds required from paper machines increase. Multinip online calendering is calendering in a calender unit where nips are formed between a smooth-surface pressing roll, such as a metal roll, and a roll covered with an elastic cover, such as a polymer roll, placed alternately one after another. A multinip on-line calender unit typically has, for example, 8 rolls and 7 nips. Linear load increases in multinip calenders from the top nip to the bottom nip because of the force of gravity. To eliminate this downwards increasing linear load, to control the deflection line of the roll and also for quick opening of the roll stack, today's multinip calenders employ roll relief which is accomplished by means of a cylinder and lever arm mechanism and which compensates for the force of gravity. One such roll relief system is in OptiLoad™ calenders.

h multinip on-line calenders there are typically at least two nips and three rolls in each roll stack. In such multiroll calenders, the linear load of the nips transverse to the running direction of the web increases from the top nip to the bottom nip because of the force of gravity. To eliminate the increasing linear load, to control the deflection lines of individual rolls and also to quickly open a nip in the roll stack, a calender arrangement under the trademark OptiLoad is used today; it has been developed by the applicant and it is already now very well-known in the field. In such OptiLoad calenders, cylinder and lever arm mechanisms connected with the bearing housings or bearing housing arms of the calender rolls provide, in addition to roll relief that compensates for the force of gravity, an arrangement by which the load of the nips can be increased and/or relieved, as needed, such that an individual loading profile can be imparted to the roll stack, which loading profile is downwards increasing, continuously even or downwards decreasing. The calendering potential of the calender is considerable because of this kind of loading profile of the calender nips that can be set within wide limits.

Great demands are made on the modern calender with respect to the mode of calendering. The several quality classes of different paper grades require alternative ways of loading the roll stack of the calender, and different calendering modes. This has helped the introduction of different load-adjustable nips and roll covers of different types into calenders.

Today, it is required that the calender has a structure that enables quick grade change to be carried out by guiding the web to run between the nips required by the web grade. It has been problematic to quickly change the mode of calendering a paper web in the manufacture of paper, for example, in the case when by using the same base paper it is possible to manufacture uncoated and coated paper grades, for example, uncoated newsprint, i.e. news paper, and coated matte- surface coated printing paper, i.e. matte paper.

It has also been problematic to continue the calendering process quickly after it has been interrupted, for example, because of breakage of a roll and to replace a roll during the calendering process. Paper is manufactured with increasingly higher quality requirements, so that, for example, mere deterioration or other more serious damage or failure of a roll cover in the calender during calendering causes, for example, replacement of the roll and may lead to a temporary shutdown or interruption of production through lack of an alternative web running path. A calender is known in the art from EP 890 676, in which the roll stack of the calender can be adjusted such that the running path of the web can be accomplished such that it is possible to arrange at least two opened nips between two closed nips. In accordance with the document, the calender is provided with calender rolls which are movable along slides placed on the calender frame to open or close nips.

Based on EP 661 405 it is known to form a calender comprising four rolls and three nips so that its structure is such that it enables operation selectably with three, two or also with only one nip, so that, depending on the number of the nips selected for calendering, the bottom nip or selectable ones of the lowest nips are closed and the remaining upper nips are open. The calender in accordance with the document uses three deflection-adjustable rolls and the order of the nips is such that when the nips are closed, the treatment that takes place in the second nip is followed by a treatment that takes place in the third nip. Thus, the possibilities of varying the calendering of the web are rather limited.

EP patent EP 822 289 discloses partial nip operation in a multinip calender through one nip. i the calender, a top roll or a bottom roll is arranged in a carriage movable in vertical slides of the calender frame. An additional roll above the top roll or, correspondingly, an additional roll below the bottom roll is arranged on the same carriage. By this means, the top roll and the additional roll above it and, correspondingly, the bottom roll and the additional roll below it form pairs of rolls provided with their own rotary drives. In accordance with the document, this pair of rolls is movable out of contact with an intermediate roll of the calender, so that the additional roll is movable into contact with the top roll or, correspondingly, to the bottom roll with a view to enabling partial nip operation in the calender. Alternatively, the additional roll is movable out of contact with the top roll or, correspondingly, with the bottom roll, which enables the normal operation of the calender, i.e. passing the web along the normal running path through all calender nips. hi some prior art calenders of this type there occurs problematic roll and nip vibration during running, which vibration is accentuated, among other things, because of the combined effect of the support of some height- and load-adjustable rolls and the required high linear load, and/or because of non-homogeneous web material.

An object of the present invention is to provide a new and inventive calender which makes it possible to solve or at least reduce the above-mentioned problems and drawbacks and which enables different types of fibrous web grades to be calendered in a flexible manner.

In this patent application, the flexibility of calendering of different types of fibrous web grades refers to the possibility of changing the arrangement of the calendering nips and the running path of the fibrous web in a multiroll calender, so that by making use of different combinations of nip arrangements and/or web running paths it becomes possible to flexibly calender different fibrous web grades and it becomes possible to flexibly continue production and bypass obstacles causing interruptions, such as a damaged or worn roll cover, or replace a roll.

The invention is generally characterized in that an upper thermo roll constituting a roll pair with a top roll is fixedly supported on or openably locked to a roll frame, so that when the upper thermo roll is fixedly supported or locked, the closing, opening and loading of a top nip is arranged by loading the shell of the top roll from the inside, and so that when the locking or support arrangement of the upper thermo roll is open, the closing, opening and loading of the top nip is arranged by loading a bottom roll or the shell of the bottom roll from the inside, and that, selectably, the closing, opening and loading of a bottom nip is arranged by loading the bottom roll and/or the shell of the bottom roll. It is advantageously characteristic of one embodiment of the invention that the upper thermo roll constituting a roll pair with the top roll is fixedly supported on the roll frame, that the closing, opening and loading of the top nip is arranged by loading the shell of the top roll from the inside, and that the closing, opening and loading of the bottom nip is arranged by loading the shell of the bottom roll from the inside.

It is in accordance with one embodiment of the invention that the roll stack has at least four rolls, that a lower thermo roll constituting a roll pair with the bottom roll is provided with a support arrangement which is connected with the roll frame and allows an upward and downward movement whose downward movement distance can be limited, and which support arrangement comprises a locking mechanism which is closed to lock the support arrangement in a fixed position or which is open.

In accordance with one embodiment of the invention, for closing and loading the bottom nip and for keeping each intermediate nip above the bottom nip and below the top nip open, the lower thermo roll constituting a roll pair with the bottom roll is locked in a fixed position.

Further, in accordance with one embodiment of the invention, the closing and opening as well as the load level of the top nip can be controlled independently.

Further, in accordance with one embodiment of the invention, the closing and opening as well as the load level of the bottom nip can be controlled independently.

In accordance with one embodiment of the invention, the closing of each intermediate nip above the bottom nip and below the top nip can be arranged by loading the shell of the bottom roll from the inside. In accordance with one embodiment of the invention, the intermediate roll above the lower thermo roll is provided with a support arrangement connected with the roll frame and allowing an upward and downward movement.

In accordance with one embodiment of the invention, the downward movement distance of the support arrangement of the intermediate roll above the lower thermo roll is arranged to be limited.

In accordance with one embodiment of the invention, the load of each intermediate nip above the bottom nip and below the top nip can be arranged by loading the shell of the bottom roll from the inside.

In accordance with one embodiment of the invention, for closing and loading each intermediate nip above the bottom nip and below the top nip by means of the bottom roll, the locking mechanism of the support arrangement of the lower thermo roll constituting a roll pair with the bottom roll is open.

In accordance with one embodiment of the invention, the upper thermo roll is provided with a support arrangement connected with the roll frame and allowing an upward and downward movement.

The invention provides several advantages over the state of the art, some of which advantages are mentioned below, hi the roll stack of the multiroll calender in accordance with the invention there are at least two independently adjustable nips, and in the multiroll calender which is formed of such roll stacks placed one on top of another and or next to one another, at least one of which roll stacks comprises at least two nips and at least one other of which roll stacks comprises at least three nips, the nip arrangement and the running path of the web can be varied, while at least one nip is closed to calender a fibrous web. The structure of the multiroll calender in accordance with the invention is such that by changing the nip arrangement used for calendering as required by a fibrous web grade it also becomes possible to carry out grade change without changing the running path of the fibrous web by opening and closing nips, hi this description, by the calendering nip arrangement, or more briefly by the nip arrangement, is meant those nips of the multiroll calender in question which take part in the calendering of the fibrous web as closed nips at any given moment of calendering. The calender in accordance with the invention is favourably suitable to serve as a multigrade calender. If in a nip essential to the calendering mode required by a given web grade there occurs damage that interrupts production or substantially lowers quality, for example, damage to a roll cover or breakage of a bearing, such an obstacle to production can also be bypassed by changing the nip arrangement. A further advantage is that by changing the running path, the fibrous web can be guided to run in the calender along an alternative path that produces the same or a different calendering result, hi accordance with one embodiment of the invention, the structure of the calender enables roll replacements during calendering without interrupting the calendering process. Interruptions in production caused by grade change and breakages can thus be avoided and the continuation of calendering assured using alternative substitute nip arrangements and/or web running paths. The independently loadable nips allowed by the invention help to provide a desired linear load distribution. The other advantages and characteristic features of the invention come out from the following detailed description of the invention.

Generally, an object of the present invention is to eliminate or at least reduce the calendering problems, limitations and weaknesses associated with the prior art and improve and widen the web calendering potential and the flexibility of calendering, i.e. the possibilities of producing different paper grades using one multinip calender, in which the loads in the nips can be adjusted and/or optimized and which enables opening or closing of the nips.

One special object of the invention is to enable the load of at least one individual nip to be adjusted or limited independently of the load of the other nips of the roll stack. Another special object of the invention is to enable at least one individual nip to be opened and locked in an open position independently of the load of the other nips of the roll stack.

These objects are achieved by the present invention, which, according to a second aspect of the invention, is characterized in that in order to adjust the load of a nip between at least one pair of calender rolls in a roll stack, to open said nip or to lock it in an open position, the pair of calender rolls is provided with a nip load- adjustment and/or locking arrangement which acts between bearing housings or bearing housing arms and/or loading and/or supporting arms of the calender rolls.

In accordance with a first embodiment of the second aspect of the invention, the nip load-adjustment and/or locking arrangement includes a pair of nip load- adjustment and locking elements acting between the bearing housings or bearing housing arms of the calender rolls of a pair of calender rolls, that connection, it is advantageous that the nip load-adjustment and locking elements are constituted by power means which act against each other and which are each provided with a loading shoe, so that the mating surfaces of the loading shoes of the power means are shaped to conform to each other. To take account of the movement path of the supporting or loading arms moving in a lever-like manner and to assure that the adjustment and/or locking elements are maintained against each other, it is particularly recommended that one of the mating surfaces shall be convex, advantageously a convex spherical surface, and that the other one of the mating surfaces shall be concave, advantageously a concave spherical surface.

In accordance with a second embodiment of the second aspect of the invention, the nip load-adjustment and/or locking arrangement includes a nip load- adjustment and/or locking element that acts between the supporting or loading arms of the calender rolls of a pair of calender rolls and which is a power means whose one end is attached to the supporting or loading arm of one calender roll of the pair of calender rolls and whose other end is attached to the supporting or loading arm of the other calender roll of the pair of calender rolls.

hi accordance with a third embodiment of the second aspect of the invention, the nip load-adjustment and/or locking arrangement includes a nip load-adjύstment and/or locking element acting between the bearing housings or bearing housing carriages of the calender rolls of a pair of calender rolls and movable by means of a power means, which nip load-adjustment and/or locking element is a wedge-like or spherical element that is movable in a direction transverse to the centre axes of the pair of rolls.

In addition, in accordance with the second aspect, it is generally characteristic of the invention that the drive of the power means for loading and/or moving a nip load-adjustment and/or locking element or nip load-adjustment and/or locking elements is advantageously hydraulic, pneumatic, electromechanical and/or mechanical or another drive that provides an equivalent function. Among other things, a hydraulic power cylinder, a pneumatic power cylinder, an electric motor, a manual drive can be mentioned as examples of the drives.

hi accordance with the second aspect, it is also generally characteristic of the invention that increasing of the load of the nip load-adjustment and/or locking arrangement has the effect of reducing nip load and that reducing of the load of the nip load-adjustment and/or locking arrangement has the effect of increasing nip load.

Regarding the advantages of the invention, it may be mentioned that by keeping the support arrangement of the calender roll forming a pair with the bottom roll of the roll stack locked, it is possible to accomplish independently both the closing, opening and/or loading of the bottom nip of the roll stack independently and the opening, keeping closed and/or loading of the nip above the bottom nip of each roll stack, that by keeping the support arrangement of the calender roll forming a pair with the top roll of the roll stack locked, it is possible to accomplish independently both the closing, opening and/or loading of the top nip of the roll stack independently and the opening, keeping closed and/or loading of the nip below the top nip of each roll stack, and the loading, opening and/or closing of all nips of the roll stack can be controlled and/or adjusted independently, and that the magnitude of the force between the rolls is individually adjustable in accordance with the invention, so that the force producing the load of an individual nip is determined by the desired load distribution in the nip. It is typically desired that the load or linear load of an individual nip might be lowered or increased, i.e. regulated in a range of 0 + 50 MPa. Feed of power taking place in the opposite phase eliminates loading disturbances and increases damping.

To enable the nips of the roll stack to be independently opened, closed and/or loaded, it is recommended that each pair of rolls shall have at least one calender roll supported on the roll frame by means of a support arrangement that allows vertical movement. Such a support arrangement is, for example, a mechanism that comprises loading and/or supporting arms movable in a lever-like manner and bearing block carriages associated with the bearing blocks of the calender roll. With a view to applying the invention, it is also recommended that the top roll and/or the bottom roll of the roll stack be deflection compensated.

Regarding the other advantages and details of the invention, reference is made to the following special part of the description of the present invention.

In the following, the invention will be described with reference to the appended figures, by means of which the multiroll calender in accordance with the invention is illustrated, yet not limiting the invention exclusively to the illustration in the figures. Figure 1 shows a roll stack of a multiroll calender in accordance with one embodiment of the invention, which roll stack has five rolls and four nips, of which two nips can be adjusted independently of one another, when desired.

Figure 2 shows one web running path in a two-stack multiroll calender formed in accordance with one embodiment of the invention.

Figure 3 shows an alternative calendering nip arrangement offered by the web running path shown in Fig. 2 in the two-stack multiroll calender formed in accordance with one embodiment of the invention.

Figure 4 shows three ways of forming a two-stack multiroll calender out of roll stacks.

Figure 5 also shows three ways of forming a two-stack multiroll calender out of roll stacks.

FIG. 6 illustrates a first embodiment of a second aspect of the invention.

FIG. 6a illustrates a detail of Fig. 6.

FIG. 7 illustrates a second embodiment of the second aspect of the invention.

FIG. 8 illustrates a third embodiment of the second aspect of the invention.

The invention is described below by means of some of its advantageous embodiments with reference to Figs. 1 - 5 and 6 - 8. In multiroll calenders 10 shown in Figs. 1 - 5 there are roll stacks 11, 111, 112, 113 placed one on top of another and/or next to one another, at least one of which roll stacks comprises at least three rolls and at least one other of which roll stacks comprises at least four rolls to thereby form at least one intermediate nip 2, 3, 2 3', and a top roll 12, 121, 122, 123 and a bottom roll 16, 161, 162, 163 of each roll stack in the multiroll calenders are provided with deflection-compensation devices. An upper thermo roll 13, 131, 132, 133 of each roll stack is fixedly supported on or openably locked to a not shown roll frame, advantageously the upper thermo roll is fixedly supported on the not shown roll frame, and in the roll stacks the rolls can be arranged into nip contact with one another for calendering a fibrous web W in closed nips.

In Figs. 1 - 3 the invention is illustrated using, as an example, five-roll roll stacks 11, 111 in accordance with one embodiment of the multiroll calender 10. The top roll 12, 121 and the bottom roll 16, 161 of each roll stack 11, 111 in the multiroll calenders 10 shown in Figs. 1 - 3 are provided with deflection-compensation devices. In Figs. 1 - 3, in accordance with an advantageous embodiment of the invention, the upper thermo roll 13, 131 is fixedly supported on a roll frame not shown in the figures, and in the roll stacks the rolls can be arranged into nip contact with one another for calendering the fibrous web W in closed nips.

Fig. 1 shows a roll stack 11 of the multiroll calender 10 in which there are five calendering rolls 12, 13, 14, 15 and 16, placed one on top of another, and four nips 1, 2, 3, 4. Of rolls not participating in the forming of nips 1, 2, 3, 4, Figs. 1 -

3 show two take-out rolls 5 and one take-out roll 6. In calendering, the fibrous web W is passed into a nip formed between rolls pressed against each other; in the roll stack 11 of Fig. 1 there are four nips in succession in the running direction of the fibrous web W. The nips can be closed and opened. A top nip 1 is formed between the top roll 12, in this case a deflection-compensated roll covered with an elastic cover, advantageously a polymer-surface roll, and a smooth-surface pressing roll, advantageously the upper thermo roll 13. In Fig. 1, the thermo roll

13 forming a roll pair with the top roll 12 is fixedly supported on the roll frame in accordance with the invention. From the outlet of the top nip 1 the web W is passed over a take-out roll 5 following after the roll pair 12, 13 to an intermediate nip 2 below the top nip 1, which intermediate nip 2 is formed, as a roll pair, by the upper thermo roll 13 and an intermediate roll 14, in this example, a roll covered with an elastic cover, advantageously a polymer roll. After the intermediate nip 2, the web W is passed over a take-out roll 6 into an intermediate nip 3, which is formed between the intermediate roll 14 and, in this case, a smooth-surface pressing roll, advantageously a lower thermo roll 15, from between which rolls the web W is passed, over a take-out roll 5 following after the roll pair 14, 15, into a bottom nip 4. The bottom nip 4 is formed between the thermo roll 15 and the bottom roll 16, i.e. a deflection-compensated roll covered with an elastic cover, advantageously a polymer-surface roll. From the outlet of the bottom nip 4, the web W is passed over at least a not shown take-out roll or equivalent to another roll stack of the multiroll calender 10 or, alternatively, past another roll stack/other roll stacks to reeling or to another finishing device.

In Fig. 1, the closing, opening and loading of the top nip 1 of the roll stack 11 is arranged by loading the shell of the top roll 12 from the inside and the closing, opening and loading of the bottom nip 4 is arranged by loading the shell of the bottom roll 16 from the inside, which is illustrated in each Fig. 1 - 3 by arrow symbols placed inside the top and bottom rolls, said arrow symbols being parallel to the nip plane and being directed to said nips. In the case where the shell is loaded, the arrow symbol is in contact with the inner surface of the shell and the nip participates in calendering. Similarly, in a situation in which the shell of the top or bottom roll is not loaded and the nip does not participate in calendering, the arrow symbol is shown to be spaced from the inner surface of the shell.

Loading devices placed inside the top roll 12 are used for closing, opening and loading the top nip 1, by means of which loading devices the shell of the top roll 12 can be displaced in the direction of the nip plane with respect to the shaft of the top roll 12. h that case, it is possible to dispense with the known arrangement of using a top cylinder in connection with the top roll 12 for closing and/or loading of the top nip. The load of the top nip 1 can be controlled independently in the roll stack 11 of Fig. 1 ; in other words, the closing and opening as well as the load level of the top nip 1 can be controlled independently.

To close, open and load the bottom nip 4, it is possible to use, as in Fig. 1, loading devices which are placed inside the bottom roll 16 and by means of which the shell of the bottom roll 16 can be displaced in the direction of the nip plane with respect to the shaft of the bottom roll 16 or, alternatively, it is possible to use loading cylinders 17 which act on the bottom roll 16 and are shown with a broken line. In the roll stack 11 of Fig. 1, the bottom nip 4 can be controlled independently; in other words, the closing and opening as well as the load level of the bottom nip 4 can be controlled independently. When the closing distance of the bottom nip 4 is minimized, no lower cylinders 17 are needed at all for moving the bottom roll 16 and for subjecting the bottom nip 4 to a load from below. The closing distance of the top nip 1 can be arranged to be structurally such that the movement distance of the shell of the top roll 12 is sufficient to close the top nip 1 and to accomplish deflection control. The closing distance of the bottom nip 4 can be arranged to be structurally such that the movement distance of the shell of the bottom roll 16 is sufficient to close the bottom nip 4 and to accomplish deflection control. When the roll stack 11 includes at least four rolls, as in the case of Figs. 1 - 3, the lower thermo roll 15 forming a roll pair with the bottom roll 16 is supported on the roll frame so that it is movable and lockable into a fixed position. The locking mechanism of the support arrangement provided for the lower thermo roll 15 and allowing the lower thermo roll 15 to move upwards and downwards is open or closed. To make an open bottom nip 4 possible, the downward movement distance of the support arrangement of the lower thermo roll 15 can be limited and the support arrangement of the lower thermo roll 15 can be locked, so that when the bottom roll 16 or the shell of the bottom roll 16 is at an adequate distance from the lower thermo roll 15, the bottom nip 4 is open. Merely for closing the bottom nip 4 and for keeping each intermediate nip 2, 3 above the bottom nip 4 and below the top nip 1 open, the locking mechanism of the support arrangement of the lower thermo roll 15 is closed, which is illustrated in Fig. 1 with a closed lock symbol. The intermediate roll 14 is provided with a support arrangement that enables the opening and closing of the intermediate nip 2 and the upward and downward movement of the intermediate roll 14, the movement distance of which support arrangement is limited downwards to make an open intermediate nip 3 possible.

As shown in Fig. 1, the upward movability of the support arrangement of the lower thermo roll 15 makes it possible to close, open and load each nip above the bottom nip 4 and each nip below the top nip 1 from below by means of the bottom roll 16. The locking mechanism of the support arrangement of the lower thermo roll 15 is open for closing, opening and loading the bottom nip 4 and, at the same time, the intermediate nip 3 above the bottom nip 4 and the intermediate nip 2 below the top nip 1, and the roll stack comprising the bottom roll 16, the lower thermo roll 15 and the intermediate roll 14 can be driven by means of the bottom roll 16 into contact with and against the upper thermo roll 13 fixedly supported on the roll frame, while the bottom nip 4, the intermediate nip 3 above the bottom nip 4 and the intermediate nip 2 below the top nip 1 are closed in said order, the opening of said nips 2, 3 and 4 taking place by reducing the load inside the shell of the bottom roll 16 and by displacing the shell of the bottom roll 16 downwards in the direction of the nip plane. The intermediate nip 2 opens as the first nip in opening order when the intermediate roll 14 moves downwards while supported by its support arrangement that allows movement. The intermediate nip 3 opens as next in order after the intermediate nip 14 has reached the lower limit of its movement path. When the bottom roll 16 or the shell of the bottom roll 16 moves further downwards in the direction of the nip plane, the lower thermo roll 15 reaches the lower limit of its support arrangement that allows movement or the locking mechanism of the support arrangement of the lower thermo roll 15 allowing movement is locked, so that the bottom nip 4 opens. It may be emphasized that the opening, closing and especially loading of the intermediate nips 2, 3 can comprise features that differ from the foregoing, in particular when using means for affecting the load and/or quick-opening between the calendering nips. The closing and/or opening of the intermediate nips 2 and 3 can also be arranged such that the lower thermo roll 15 and the intermediate roll 14 above the bottom roll 16 are driven against the upper thermo roll 13 by means of the bottom roll 16 provided with lower cylinders 17 or, alternatively, the closing of the intermediate nips 2 and 3 of the five-roll roll stack 11 can also be advantageously arranged without the loading cylinders 17 shown with broken lines in Fig. 1, which is also illustrated in Figs. 2 and 3 such that the bottom roll 16 is not provided with any lower cylinders, but the lower thermo roll 15 and the intermediate roll 14 above the bottom roll 16 are caused to move upwards against the upper thermo roll 13 by loading the shell of the bottom roll 16 from the inside, whereby the load of the bottom roll 16 is made full use of. When the movement paths of the rolls 14 and 15 are minimized, no lower cylinders 17 are needed at all for moving the bottom roll 16 as well as the lower thermo roll 15 and the intermediate roll 14 and for producing a load from below in the bottom nip 4, in the intermediate nip 3 above the bottom nip 4 and in the intermediate nip 2 below the top nip 1.

When in the five-roll roll stack 11 of the multiroll calender 10 in accordance with one embodiment of the invention the closing movement distance of the roll stack foπning the bottom nip 4, the intermediate nip 3 above the bottom nip 4 and the intermediate nip 2 below the top nip 1 is minimized, the lower cylinders can be dispensed with in opening, closing and loading of the nips 4, 3 and 2. In that case, the vibration situation in the calender can also be kept better under control.

An advantage of supporting the upper thermo roll 13 fixedly on the roll frame is that the vibrations of the calender 10 during running are reduced as compared with a situation in which a possibly openably lockable lever arm, which makes the structure more complicated and allows the movement of the upper thermo roll 13, would provide the support of the roll. The fixed support arrangement of the upper thermo roll 13 is also inexpensive to accomplish. When the roll stack 11 includes at least four calendering rolls, the lower thermo roll 15 forming a roll pair with the bottom roll 16 is supported on the roll frame so that it is movable and can be locked in a fixed position, which locking is open or closed, in which case there are at least two independently closable and openable nips, the top nip 1 and the bottom nip 4, in at least one roll stack 11 of the multiroll calender 10.

When, as shown in the example of Fig. 5, three rolls, a top roll 12, a thermo roll 13 and a bottom roll 16, are arranged in a roll stack 11 of the multiroll calender 10 in accordance with one embodiment of the invention, which rolls form two independently closable and openable nips, a top nip and a bottom nip, the adjustment of the load in these nips can be accomplished independently by means of the top roll 12 and the bottom roll 16, while the thermo roll 13 is fixedly supported on the roll frame, but the regulation of temperature must be accomplished by means of the thermo roll 13 which is common to the top and bottom nips and which is between the top roll 12 and the bottom roll 16 of the roll stack 11.

When four rolls, a top roll 12, an upper thermo roll 13, a lower thermo roll 15 and a bottom roll 16, and three nips are arranged in a roll stack 11 of the multiroll calender 10 in accordance with one embodiment of the invention, of which nips the outermost nips, a top nip and a bottom nip, are independently closable and openable nips, the adjustment of their load and heating can be accomplished independently in a manner similar to that of Fig. 1 while the upper thermo roll 13 is fixedly supported on the roll frame. In this case, in the roll stack 11 of four rolls there is no intermediate roll, so that the middle nip is an intermediate nip which is thus formed between two thermo rolls, the upper thermo roll 13 and the lower thermo roll 15.

hi Figs. 2 arid 3, the multiroll calender 10 in accordance with the invention is formed of two roll stacks 11 and 111 such that it is possible to calender the fibrous web W using different alternative nip arrangements and/or web running paths.

Figs. 2 and 3 show one example of the running path of the web W. In the first roll stack 11 of the multiroll calender 10 there are five rolls placed one on top of another, a top roll 12, an upper thermo roll 13, an intermediate roll 14, a lower thermo roll 15 and a bottom roll 16, and four nips 1, 2, 3, 4. In the second roll stack 111 there are, in a corresponding manner, five rolls placed one on top of another, a top roll 121, an upper thermo roll 131, an intermediate roll 141, a lower thermo roll 151 and a bottom roll 161, and four nips 1', 2', 3', 4'. The tension of the web W is controlled using a not shown tension measuring roll placed between the first roll stack 11 and the second roll stack 111.

The independently loadable top nip 1 and bottom nip 4 of the roll stack 11 in accordance with the invention help to produce a desired linear load distribution in the multiroll calender 10, so that in the exemplifying embodiment of the invention shown in Figs. 1 - 3 it is possible to set the linear load distribution of the roll stack 11 as desired by means of the load of the independent top nip 1 and the load of the independent bottom nip 4. It is possible, for example, that the top nip 1 can be open or closed, that the bottom nip 4 can be open or closed, that the load in the bottom nip 4 can be, according to the desired linear load level, higher than, equal to or lower than that of the top nip 1, that the intermediate nip 3 above the bottom nip 4 and the intermediate nip 2 below the top nip 1, said intermediate nips being dependent on the load of the bottom nip 4, can be open while the bottom nip 4 is open or closed, and it is possible that the intermediate nip 3 above the bottom nip 4 and the intermediate nip 2 below the top nip 1, said intermediate nips being dependent on the load of the bottom nip 4, can be closed while the bottom nip 4 is closed.

When the locking mechanism of the support arrangement of the lower thermo roll 15 in the roll stack 11 is open, the loads of the nips 2, 3 and 4 below the top nip 1 depend on one another such that the linear load increases from the intermediate nip 2 below the top nip 1 to the bottom nip 4 because of the force of gravity if for eliminating the downwards increasing linear load and for controlling the deflection line of the roll, for example, roll relief devices known in themselves are not used in connection with the rolls forming said nips, which roll relief devices are accomplished by means of a cylinder and lever arm mechanism and compensate for the force of gravity, and which roll relief devices can also be used for quick-opening of the roll stack.

In the multiroll calender 10 in accordance with one embodiment of the invention, both the linear load distribution within the roll stacks 11 and 111 and the load between the roll stacks 11 and 111 can be varied to optimize the paper quality, for example, with respect to the following properties: gloss/density, smoothness/density, loss of bulk, load/elongation history, etc. The linear load distribution of the nips can be adjusted to be continuous/discontinuous and/or linear/non-linear. For example, in the top nip 1 of the first roll stack 11, the web W can be subjected to a nip load equal to a linear load of 100 kN/m, and while running in the nip 2 below the top nip 1 and in the nip 3 above the bottom nip 4 as well as in the bottom nip 4, the web W is subjected to a linearly increasing nip load, the linear load maximum of which in the bottom nip 4 is 100 kN/m, and the nips of the other roll stack 111 are kept open. In accordance with one alternative linear load example, the linear load in the top nip 1 of the first roll stack 11 is half of the linear load of the other nips 2, 3 and 4 kept linear by means of relief devices, while the nips of the other roll stack 111 are open.

When it is desirable to treat both sides of the web W equally, both sides of the web W shall be subjected to substantially the same nip impulses. In that connection, it is assured by means of the running path of the web W and the arrangement of the nips that along the running path of the web W both sides of the web W are subjected to substantially equal nip impulses in the calendering nips. Thus, in the multiroll calender 10, in which the rolls of the five-roll roll stacks 11 arid 111 are in the position shown in Fig. 2, both the top side and the bottom side of the web W are subjected to substantially equal nip impulses in the top nips 1 and 1'. With the web running path of Fig. 2, the bottom side A of the web W runs in the first roll stack 11 through the closed top nip 1 on the side of the upper thermo roll 13 and in the second roll stack 111 through the closed top nip 1' on the side of the top roll 121, and the top side Y of the web W runs in the first roll stack 11 through the closed top nip 1 on the side of the top roll 12 and in the second roll stack 111 through the closed top nip 1' on the side of the thermo roll 131, while the other nips 2, 3, 4 and 2', 3', 4' of the calender 10 are open. In this example, to calender both sides Y, A of the web W in the multiroll calender 10, both the top side Y and the bottom side A are guided to run through one closed calendering nip 1 on the side of the thermo roll 13 in the first roll stack 11 and through one closed calendering nip 1' on the side of the thermo roll 121 in the second roll stack 111, in which second roll stack 111 the nip impulses applied to the web W are equalized such that, as the end result, the nip impulses received by both sides Y, A of the web W are substantially the same. The arrangement in accordance with the invention also makes it possible that the top side Y and the bottom side A of the web W are subjected to unequal nip impulses.

Each calendering nip has certain properties that affect the calendering result, and not all nips are suitable for the calendering of all fibrous web grades. Thus, a soft roll in particular, such as a polymer-covered top roll and a polymer-covered bottom roll, whose properties significant from the viewpoint of the calendering result include, among other things, hardness, surface quality, temperature resistance and loadability, imposes restrictions on the usability of the nip when calendering, for example, a certain paper grade. Likewise, the properties of a hard roll, such as a thermo roll, for example, surface quality and temperature, affect the calendering result of the calendering nip. Thus, for calendering a certain fibrous web grade, only nips that enable the calendering of this grade and produce the desired calendering result are used. In accordance with one application of the invention, it is possible to advantageously arrange in the multinip calender 10, in place of a nip that produces a certain calendering result, a replacement nip that produces the same calendering result, and it is possible to continue calendering in this replacement nip, for example, when the calendering result of the first- mentioned nip deteriorates or its use is prevented. The structure of the multiroll calender 10 in accordance with one embodiment of the invention is such that by changing the nip arrangement used for calendering as required by a fibrous web grade it becomes possible to carry out grade change quickly without changing the running path of the fibrous web W. The multiroll calender 10 in accordance with the invention is advantageously suitable for use as a multigrade calender, which will be described below by means of Figs. 2 and 3 showing the calendering of the fibrous web W using two different alternative nip arrangements. As shown in Fig. 2, the fibrous web W, which is of a first grade, is calendered in the closed top nip 1 of the first roll stack 11 and in the closed top nip 1' of the second roll stack 111 such that the top side Y of the web W runs through the top nip 1 of the first roll stack 11 on the side of the top roll 12 and through the top nip 1' of the second roll stack 111 on the side of the upper thermo roll 131, and the bottom side A of the web W runs through the top nip 1 of the first roll stack 11 on the side of the upper thermo roll 13 and through the top nip 1' of the second roll stack 111 on the side of the top roll 121. The closing and loading of the top nips 1 and 1' is aπanged by loading the shells of the top rolls 12 and 12' from the inside. The other nips 2, 3 and 4 as well as 2', 3' and 4' of the multiroll calender 10 are open in this nip aπangement and do not participate in calendering. When it is desirable to change the grade of the fibrous web W to be calendered and, thus, the type of calendering, the top nips 1 and 1' are opened and the fibrous web W of a second grade is calendered, as shown in Fig. 3, in the bottom nip 4 of the first roll stack 11 and in the bottom nip 4' of the second roll stack 111 such that the top side Y of the web W runs through the bottom nip 4 of the first roll stack 11 on the side of the bottom roll 16 and through the bottom nip 4' of the second roll stack 111 on the side of the lower thermo roll 151, and the bottom side A of the web W runs through the bottom nip 4 of the first roll stack 11 on the side of the lower thermo roll 15 and through the bottom nip 4' of the second roll stack 111 on the side of the bottom roll 161. The closing and loading of the bottom nips 4 and 4' is arranged by loading the shells of the bottom rolls 16 and 161 from the inside and by locking the locking mechanisms of the support arrangements of the thermo rolls 15 and 151 that allow movement. The other nips 1, 2 and 3 as well as 1', 2' and 3' of the calender 10 are open in this nip arrangement and do not participate in calendering. Grade-specific calendering can be accomplished, for example, as shown in Figs. 2 and 3, by regulating calendering parameters of the top nips 1, 1' and the bottom nips 4, 4', i.e. load, time of action, moisture and temperature or equivalent and by choosing the roll covers of the rolls in the positions in question according to grade.

By using the arrangement described above, it is also possible to bypass, for example, an obstacle to calendering caused by breakage of the roll cover. Thus, for instance, when the polymer cover of the top roll 12 operating in the top nip 1 of the first roll stack 11 of the multiroll calender 10 shown in Figs. 2 and 3 breaks or wears so that its surface quality becomes unsuitable for calendering, the nip arrangement of the multiroll calender 10 can be changed from the arrangement shown in Fig. 2 to that shown in Fig. 3, whereby calendering can be continued producing the same fibrous web grade W.

Calendering that makes it possible to achieve a calendering result that is substantially equal on both sides can also be accomplished such that the web W is guided to bypass some roll stack/roll stacks altogether, so that in the examples of Figs. 2 and 3 it is possible to replace rolls of the first rolls stack 11 or of the second roll stack 111 being bypassed, and calendering can be accomplished in the second roll stock 111 or in the first roll stack 11. The web W can be guided to bypass the first roll stack 11 altogether and the web W can be calendered, for example, in the calendering nips 1' and 4' of the second roll stack 111, so that rolls of the first roll stack 11 can be replaced. Alternatively, the web W can be guided to bypass the second roll stack 111 altogether and the web W can be calendered, for example, in the calendering nips 1 and 4 of the first roll stack 11, so that rolls of the second roll stack 111 can be replaced. The carrying out of calendering only in one roll stack 11 or 111 of the multiroll calender 10 can be, for example, due to the fact that a certain grade-specific calendering roll cover is missing from a roll stack of the calender or to the fact that some grade-specific calendering nip or the roll cover used in a nip or another component, for example, a bearing or a loading device of the roll, has been damaged to the extent that production according to the set quality requirements cannot be run through the nip in question. If the top nip 1, 1' or the bottom nip 2, 2' breaks in the roll stack, it is thus still possible to run production in accordance with set quality requirements. Alternatively, the web W can also be guided past one or more roll stacks to reeling or to another finishing device.

Calendering with some of the nips or 1+1 nip calendering, for example, matte calendering of coated paper, can be accomplished using the multiroll calender 10 in accordance with the invention even though some roll cover or equivalent breaks. To accomplish calendering with some of the nips, both in the first roll stack 11 and in the second roll stack 111 it is possible to close at least one nip at a time independently and the direction of the nips can be changed in the multiroll calender 10. Thus, it is possible to guide the fibrous web W, for example, through the bottom nip 4 of the first roll stack 11 in Fig. 2 or, alternatively, when the bottom nip 4 is not in use, through the top nip 1 ' of the second roll stack 111.

By changing the running path, the fibrous web W can be advantageously guided to run in the calender 10 along an alternative path that produces the same or a different calendering result. In that connection, the running path of the web W is different from that used for running a certain grade in the normal situation, for example, if paper is two-sided. The web W can be guided to run in the first roll stack 11 from above downwards or from below upwards and in the second roll stack 111 from above downwards or from below upwards and/or the direction of the nips can be selected, and the entire two-stack multiroll calender 10 can be set such that the sidedness of the web W can be made as desired. In accordance with one embodiment, the web W is guided to run in the roll stack 11 from below upwards and in the roll stack 111 from above downwards. In that case, an advantage is also a structural or layout improvement, if it is desirable to start calendering from a lower level and finish calendering and perform winding up on the lower level. In accordance with an alternative exemplifying embodiment, calendering can be started from an upper level by guiding the web W as shown in Figs. 2 and 3 and calendering can be finished and winding up can be performed on the upper level. The means for unwinding and winding can also be arranged both on the upper level and on the lower level.

To form the multiroll calender 10 intended for the calendering of the fibrous web W, roll stacks placed one on top of another and/or next to one another are arranged, for example, as shown in Figs. 4 and 5. The roll stacks that form the multiroll calender 10 are selected from these roll stacks placed one on top of another and/or next to one another. Fig. 4 shows by way of example three ways a), b) and c) of forming a two-stack multiroll calender out of roll stacks, and Fig. 5 shows by way of example three different ways a), b) and c) of forming a two- stack multiroll calender out of roll stacks. In the multiroll calender 10 in accordance with one embodiment of the invention there are two roll stacks 11, 111, 112 and 113 placed one on top of another and/or next to one another, as shown by the examples of Figs. 4 and 5. In the multiroll calender 10 shown in Fig. 4, in the first roll stack 11 there are five rolls and in the second roll stack 111, 112, 113 there are five rolls. In the multiroll calender 10 shown in Fig. 5, in the first roll stack 11 there are three rolls and in the second roll stack 111, 112, 113 there are five rolls. The top roll 12, 121, 122, 123 and the bottom roll 16, 161, 162, 163 of each roll stack 11, 111, 112, 113 in the multiroll calenders 10 of Figs. 4 and 5 are provided with deflection-compensation devices.

The two roll stacks of the multiroll calender 10 in the examples of Figs. 4 and 5 are a) the first roll stack 11 and the second roll stack 111, and b) the first roll stack 11 and the second roll stack 112, and c) the first roll stack 11 and the second roll stack 113, in which roll stacks the web W can be guided to run in the roll stack from above downwards or from below upwards and/or the direction of the nip can be selected, and the entire two-stack multiroll calender 10 can be set such that the sidedness of the web W can be made as desired.

Above, the invention has been described by way of example with reference to Figs. 1 - 5 in the appended drawings. However, the invention is not limited solely to the illustration of the figures but the different embodiments of the invention may vary within the inventive idea defined in the appended claims.

Thus, within the inventive idea, in the roll stack of the multiroll calender comprising five rolls and four nips, of which two nips can be controlled independently of each other, when desired, closing and opening and loading of the nips can also be arranged such that the intermediate rolls, by which are here meant the calendering rolls 13, 14, 15 between the top roll 12 and the bottom roll 16 of the calender, are allowed to move freely, i.e. float, within the distance limited by their support arrangements in the nip plane, while the top roll 12 is fixedly supported on the roll frame and the upper thermo roll 13 is supported on the roll frame in a lockable and openable manner, so that the load in the roll stack is produced by loading with the lower cylinders 17, while the support arrangement of the upper thermo roll 13 is open. On the other hand, this same calender makes it possible to lock the upper thermo roll 13 and the lower thermo roll 15 when operating with some of the nips, in which case the top nip 1 can be loaded using the loading devices inside the shell of the top roll 12 and the bottom nip 4 can be loaded with the lower cylinders 17 or using the loading devices inside the shell of the bottom roll 16, and the top and bottom nips can be operated independently of each other in the manner described previously in this description.

Figs. 6 and 7 schematically show a calender 10 that includes one roll stack comprising a top roll 12 and a bottom roll 16 as well as three intermediate rolls 13, 14, 15 arranged between the top and bottom rolls, so that the top, bottom and intermediate rolls form calender rolls 12-16 of the calender 10. The centre axes C of the adjacent calender rolls 12,13; 13,14; 14,15 and 15,16 in the roll stack are parallel and in a cross direction transverse to the running direction of the web (not shown). In that connection, the calender rolls in the pairs of calender rolls formed by the calender rolls 12-16 of the roll stack define between themselves a nip N that calenders the web and whose pressing line or plane is parallel to the centre axes C of the calender rolls in the pairs of calender rolls.

It shall be generally emphasized that the number and/or the orientation of the rolls or roll stacks is/are of no significance to the basic idea of the present invention. Thus, the roll stacks can be composed of roll assemblies having a very different number of rolls and, in addition, the calender may comprise a very different number of roll stacks placed one on top of another and/or side by side. Further, it shall be noted that the orientation of the roll stack can deviate from the vertical and, if the calender has several roll stacks, the orientations of the roll stacks can differ both from one another and from a line vertical to the horizontal machine line of a paper, pulp or other fibre machine, which machine line is typically a lateral line parallel to the floor plane of the fibre machine hall.

The embodiments of Figs. 6 - 7 both show, for the sake of simplicity, only five calender rolls such that the centre axes C of all calender rolls 12-16 are placed in the same vertical plane passing vertically through the nips N and the centre axis C of the calender rolls 12-16. This kind of straight shape of the pressing plane or line passing through the nips N is, of course, not necessary or essential for the invention, but the pressing plane or line of the nips can form a pressing plane or line that is inclined with respect to a zigzagging or horizontal machine line.

With a view to applying the second aspect of the present invention, it is advantageous, although not necessary, that in the roll stack of the calender 10 there is at least one calender roll supported or locked to be unmovable in a vertical direction. This calender roll can be the bottom roll 16, a selectable intermediate roll 13-15 or the top roll 12 of the roll stack. It must be emphasized, however, that the second aspect of the present invention can also be applied equally well in calenders 10 in the roll stack of which all calender rolls are movable in a vertical direction.

Hereafter, the second aspect of the present invention will be described by means of embodiment examples with the lowermost intermediate roll 15 of the roll stack supported or locked to be unmovable in a vertical direction by means of supporting and/or loading anns 31, 32, which lowermost intermediate roll can form a roll pair and, thus, a nip N with the intermediate roll 14 placed above it and with the bottom roll 16.

Generally, in accordance with the second aspect of the present invention, when the aim is to adjust, optimize the load in at least one nip N of the roll stack of the calender 10 and/or to enable at least one nip to be opened or closed, a pair of calender rolls is provided with a nip load-adjustment and/or locking arrangement 20, which acts between bearing housings 9, bearing housing carriages, supporting and/or loading arms 31, 32 of the calender rolls 12-16 of at least one pair of calender rolls 12,13; 13,14; 14,15; 15,16. hi that connection, it is recommended that at least one of the rolls of the pair of calender rolls be movable in its position in a vertical direction, i.e. supported with the supporting and/or loading arms 31, 32 that move in a lever-like manner.

To move the calender rolls in a pair of calender rolls in a vertical direction with respect to each other, in the embodiment of Fig. 6, a nip load-adjustment and/or locking arrangement 20 is arranged between the bearing housings 9 or bearing housing carriages of the calender rolls 12-16 in the pairs of calender rolls

12,13; 13,14; 14,15; 15,16, in the embodiment of Fig. 7, a nip load-adjustment and/or locking arrangement 20 is arranged between the supporting and/or loading arms 31, 32 of the calender rolls 12-16 in the pairs of calender rolls 12,13; 13,14;

14,15; 15,16, and in the embodiment of Fig. 8, a nip load-adjustment and/or locking arrangement 20 is arranged between the bearing housings 9 or bearing housing carriages of the calender rolls 14 and 15 in the pair of calender rolls 14, 15.

To move the supporting and/or loading arms 31, 32, they can be supported on the frame (not shown) of the calender 10 so as to be pivotable around their pivot point, so that the calender rolls can be moved with respect to one another to adjust or optimize nip load or to open the nip N or to close the nip. In moving the calender rolls vertically it is possible to use slides disposed on the frame (not shown) of the calender 10 and enabling the bearing housings or bearing housing carriages to slide along the slides.

In accordance with the invention, improved and individual adjustment or limitation of the load in the nip N between the calender rolls of a generally selectable pair of calender rolls is achieved by this means for the calender 10. Moreover, the invention allows a nip of the calender 10 and/or a nip between two calender rolls to be opened or locked quickly.

Reference is made to the embodiment in accordance with the example shown in Fig. 6. The load-adjustment and/or locking arrangement 20 of the nip N comprises a pair of nip load-adjustment and/or locking elements 101, 102 acting in the pairs of calender rolls 12,13; 13,14; 14,15; 15,16 of the roll stack while placed, in the pair of calender rolls, between the bearing housings 9 or bearing housing carriages of the calender rolls 12-16. hi that connection, by loading the nip load-adjustment and/or locking arrangement 20, the calender rolls in the pairs of calender rolls are able to move with respect to one another to individually increase/reduce the load of the nip N and to open/close nip contact.

Since the load-adjustment and/or locking arrangement 20 of the nip N is placed between the bearing housings 9 or bearing housing carriages of the calender rolls, the distance between the calender rolls associated with the load-adjustment and/or locking arrangement 20 of the nip N can be changed by means of the load- adjustment and/or locking arrangement 20 of the nip N alone, whereby the load of the nip can be limited or the nip can be opened. In the embodiment of Fig. 6, the nip N in the pair of calender rolls 15, 16 has been opened using the nip load- adjustment and/or locking arrangement in accordance with the invention.

Reference is made to Fig. 6a showing an enlarged view of a detail of the embodiment of Fig. 6. The load-adjustment and/or locking arrangement 20 of the nip N comprises a pair of nip load-adjustment and/or locking elements 101, 102, which act between the bearing housings 9 or bearing housing carriages of the calender rolls of a pair of calender rolls. It is typical of this embodiment that the load-adjustment and or locking elements 101, 102 of the nip N both comprise a loading shoe 101 whose mating surfaces 102 conform to each other. Since at least one of the calender rolls in the pair of calender rolls moves by means of the supporting and/or loading arms 31, 32 that move in a lever-like manner, the mating surfaces 102 of the loading shoes 101 are able to move with respect to each other. The magnitude of this relative motion is dependent on the length of the supporting and/or loading arms 31, 32. To compensate for this relative motion and to assure that the loading shoes 101 are maintained against each other, the mating surfaces 102 are shaped such that one mating surface 102 is convex, most advantageously a convex spherical surface, and the other mating surface 102 is concave, most advantageously a concave spherical surface.

It is advantageous that the drive of the nip load-adjustment and/or locking arrangement 20 for loading and/or moving the nip load-adjustment and/or locking elements 101 is hydraulic, pneumatic, electromechanical and/or mechanical or another drive that provides an equivalent function. Among other things, a hydraulic power cylinder, a pneumatic power cylinder, an electric motor, a manual drive can be mentioned as examples of some suitable drives. In this first embodiment of the second aspect of the invention, a pushing force is produced between the calender rolls in the pair of calender rolls by loading the load-adjustment and/or locking elements 101, 102 of the nip N, which pushing force aims to reduce nip load and, when needed, separate the calender rolls in the pair of calender rolls from nip contact. By loading the nip load-adjustment and/or locking arrangement 20, the calender rolls in the pair of calender rolls are able to move with respect to each other in order to individually increase/reduce nip load or to open/close nip contact.

Reference is made to the embodiment in accordance with the example shown in Fig. 7. In this second embodiment of the second aspect of the invention, the load- adjustment and/or locking arrangements 20 of the nip N are arranged between the supporting and/or loading arms 31, 32 of the calender rolls 12-16 of each pair of calender rolls 12,13; 13,14; 14,15; 15,16 in the roll stacks of the calender 10. In this second embodiment, each calender roll in the upper roll stack can be freely movable. Alternatively one calender roll in a pair of calender rolls can be supported or locked to be unmovable in a vertical direction, which means that the use of the nip load-adjustment and/or locking arrangement in this pair of calender rolls has no effect on the load of the nip of the adjacent pair of calender rolls placed below and/or above.

In the embodiment of Fig. 7, the load-adjustment and/or locking arrangement 20 of the nip N comprises a hydraulic power or support element 103, which acts between the loading and/or supporting arms 31, 32 of the calender rolls 12-16 in the calender pairs of the roll stack. The hydraulic power or support element is in itself a hydraulic, pneumatic, electric or electromechanical power or support element 103 which is coupled between the loading and/or supporting arms 31, 32 of the pair of calender rolls and by means of which element power can be transferred between the calender rolls in the pair of calender rolls. As examples of suitable power or support elements 103, among other things, a hydraulic power cylinder, a pneumatic power cylinder, an electric motor, a manual drive, distance measurement, can be mentioned.

In this manner it is possible to adjust nip load and/or open and close the nip between the calender rolls. Such a support or power means 103 in accordance with the second embodiment of the second aspect of the invention makes it possible to produce between the calender rolls a pushing force which aims to reduce nip load and even separate the calender rolls from one another, or a pulling force which aims to increase nip load and return the calender rolls separated from nip contact back into nip contact. By loading the nip load-adjustment and/or locking arrangement 20, the calender rolls in the pair of calender rolls are able to move with respect to each other in order to individually increase/reduce nip load or to open/close nip contact.

With a view to individually adjusting the loads of the nips N, the supporting and/or loading arms 31, 32 of the calender rolls 12-16 comprise two parts 221, 223, so that an articulated joint 222 is arranged between a first arm part 221 and a second arm part 223 of each supporting and/or loading arm. The second arm part 223 is connected to the bearing housing 9 or bearing housing carriage of the calender roll.

Since the load-adjustment and/or locking arrangement 20 of the nip N is placed between the second arms 223 of the supporting or loading arms 31, 32, the angle between the arm parts 223 associated with the load-adjustment and/or locking arrangement 20 of the nip N can be changed by means of the load-adjustment and/or locking arrangement 20 of the nip N and, thus, it is possible both to stiffen the supporting and/or loading arm 31, 32 by means of the intermediate articulated joint 222 and to adjust or limit nip load or to open the nip. In the embodiment of Fig. 7, the nip N in the pair of calender rolls 15, 16 has been opened using the nip load-adjustment and/or locking arrangement in accordance with the invention. Reference is made to the embodiment in accordance with the example shown in Fig. 8. In this third embodiment of the second aspect of the invention, the load- adjustment and/or arrangement 20 of the nip N is arranged between the bearing housings 9 or bearing housing carriages at both ends of the calender rolls in a pair of calender rolls 14, 15 in a roll stack, on support of which bearings housings or bearing housing carriages the calender roll is able to move. In that connection, the load-adjustment and/or locking arrangement 20 of the nip N acts on the bearing housings 9 or bearing housing carriages of the calender rolls 14, 15 in the pair of calender rolls. At least one of the calender rolls in the pair of calender rolls 14, 15 is supported to be movable in a vertical direction, so that the use of the load- adjustment and/or locking arrangement of the nip N, i.e. its movement in a direction transverse to a line passing through the centre axes of the calender rolls 14, 15, does not affect the position of the calender roll that has been supported to be unmovable, but the nip load-adjustment and/or locking arrangement 20 makes it possible to adjust the load of the nip between the calender rolls 14, 15 and the distance between the calender rolls and to open or close the nip N between the pair of calender rolls 14, 15.

In the embodiment of Fig. 8, the nip load-adjustment and or locking arrangement 20 comprises a wedge element 104 that acts on the bearing housings 9 or bearing housing carriages of the calender rolls in the pair of calender rolls, which wedge element can also equally well be a spherical element. Particularly advantageously, the nip load-adjustment and/or locking element 104 in accordance with the embodiment of Fig. 8 is an element supported under the bearing housings 9 or bearing housing carriages of the calender rolls, i.e. in the figure, under the bearing housings or bearing housing carriages of the intermediate rolls 14 and 15, which element can be movable by means of a power means in a direction transverse to the pressing or nip line of the vertical roll stack of the calender 10. By moving the element 104, it is possible, on the one hand, to separate the calender rolls 14, 15 from each other, i.e. open the nip or reduce nip load, or, on the other hand, to allow the calender rolls 14, 15 to move towards each other, i.e. increase nip load or allow normal motion of the calender rolls.

Regarding the invention, it may be generally stated further that the load- adjustment and/or locking arrangement 20 of the nip N in accordance with the second aspect of the invention is typically used for locking the vertical positions of the calender rolls 12-16 of a selectable pair/selectable pairs of rolls 12,13; 13,14; 14,15; 15,16 of the roll stack both with respect to each other and with respect to the positions of other calender rolls. In that case, any selectable nip N can be caused to remain open and, nevertheless, a tail of the web can be threaded or the web can passed through all nips N. Likewise, during on-line operation of the calender 10, the nip N can be opened in case the shell of a calender roll is damaged or when there is a need to change the quality of the fibrous web during the process, i.e. during on-line operation. In that connection, when the nip load- adjustment and/or locking arrangement 20 in accordance with the invention is not in use, i.e. it is out of operation, the nip N closes and its load can be adjusted as normal, and when the nip load-adjustment and/or locking arrangement 20 in accordance with the invention is in use, i.e. it acts between the bearing housings 9, the bearing housing carriages of the calender rolls or between the supporting and/or loading arms 31, 32 of the calender rolls, the nip N does not close or the load of the nip N cannot exceed a certain limit value, but the forces are carried either through the loading and/or supporting arms 31, 32 or through the bearing housings 9 to the next roll.

The invention also makes it possible to keep a different number of different nips closed and form different running paths of the web as needed.

Above, the invention has been described only by means of some of- this embodiments considered to be advantageous. However, this has not been intended to limit the invention in any way and, as is clear to a person skilled in the art, many alternative arrangements and modifications are feasible within the inventive idea and its scope of protection defined in the appended set of claims. Thus, the nip load-adjustment and/or locking arrangement in accordance with the second aspect of the invention can also be disposed between the roll stacks of a calender 10 that comprises two roll stacks. In this case, it becomes possible to combine separate roll stacks, when needed, to form one roll stack. One advantageous embodiment is, for example, such that the nip load-adjustment and/or locking arrangement 20 is disposed in a pair of rolls whose calender rolls are supported to be movable with respect to each other along slides and/or by supporting and/or loading arms 31, 32 moving in a lever-like manner, and whose upper calender roll is the bottom roll of an upper roll stack and whose lower calender roll is the top roll of a lower roll stack. The nip load-adjustment and/or locking means in accordance with the invention also makes it possible to modify, without problems, the roll stack structure of a calender comprising one roll stack into a roll stack structure comprising several roll stacks.

Claims

1. A multiroll calender (10) comprising roll stacks (11) placed one on top of another and/or next to one another, at least one of which roll stacks comprises at least three rolls and at least one other of which roll stacks comprises at least four rolls to thereby form at least one intermediate nip (2, 3), so that some of the intermediate nips can be opened by means of relief devices, and in which multiroll calender a top roll (12) and a bottom roll (16) in each roll stack (11) are provided with deflection-compensation devices and at least one thermo roll is fixedly supported on or openably locked to a roll frame and the rolls in the roll stacks (11, 111) are movable into nip contact with one another for calendering a fibrous web (W) in closed nips, characterized in that an upper thermo roll (13, 131, 132, 133) constituting a roll pair with the top roll (12, 121, 122, 123) is fixedly supported on or openably locked to a roll frame, so that when the upper thermo roll is fixedly supported or locked, the closing, opening and loading of a top nip (1, 1') is arranged by loading the shell of the top roll from the inside, and so that when the locking or support arrangement of the upper thermo roll is open, the closing, opening and loading of the top nip (1, 1') is arranged by loading the bottom roll (16, 161, 162, 163) or the shell of the bottom roll from the inside, and that, selectably, the closing, opening and loading of a bottom nip (4, 4') is arranged by loading the bottom roll (16, 161, 162, 163) and/or the shell of the bottom roll.

2. A multiroll calender as claimed in claim 1, characterized in that the upper thermo roll (13, 131, 132, 133) constituting a roll pair with the top roll (12, 121, 122, 123) is fixedly supported on the roll frame, that the closing, opening and loading of the top nip (1, 1') is arranged by loading the shell of the top roll (12, 121, 122, 123) from the inside, and that the closing, opening and loading of the bottom nip (4, 4') is arranged by loading the shell of the bottom roll (16, 161, 162, 163) from the inside.

3. A multiroll calender as claimed in claim 1 or 2, characterized in that the roll stack (11, 111, 112, 113) has at least four rolls, that a lower thermo roll (15, 151, 152, 153) constituting a roll pair with the bottom roll (16, 161, 162, 163) is provided with a support arrangement which is connected with the roll frame and allows an upward and downward movement whose downward movement distance can be limited, and which support arrangement comprises a locking mechanism which is closed to lock the support arrangement in a fixed position or which is open.

4. A multiroll calender as claimed in claim 3, characterized in that for closing and loading the bottom nip (4, 4') and for keeping each intermediate nip (2, 2'; 3, 3') above the bottom nip (4, 4') and below the top nip (1, 1') open, the lower thermo roll (15, 151, 152, 153) constituting a roll pair with the bottom roll (16, 161, 162, 163) is locked in a fixed position.

5. A multiroll calender as claimed in any one of claims 1 to 4, characterized in that the closing and opening as well as the load level of the top nip (1, 1') can be controlled independently.

6. A multiroll calender as claimed in any one of claims 1 to 5, characterized in that the closing and opening as well as the load level of the bottom nip (4, 4') can be controlled independently.

7. A multiroll calender as claimed in any one of claims 3 to 6, characterized in that the closing of each intermediate nip (2, 2'; 3, 3') above the bottom nip (4, 4') and below the top nip (1, 1') can be arranged by loading the shell of the bottom roll (16, 161, 162, 163) from the inside.

8. A multiroll calender as claimed in claim 7, characterized in that an intermediate roll (14, 141, 142, 143) above the lower thermo roll (15, 151, 152, 153) is provided with a support arrangement connected with the roll frame and allowing an upward and downward movement.

9. A multiroll calender as claimed in claim 8, characterized in that the downward movement distance of the support arrangement of the intermediate roll

(14, 141, 142, 143) above the lower thermo roll (15, 151, 152, 153) is arranged to be limited.

10. A multiroll calender as claimed in any one of claims 3 to 6, characterized in that the load of each intermediate nip (2, 2'; 3, 3') above the bottom nip (4, 4') and below the top nip (1, 1') can be arranged by loading the shell of the bottom roll (16, 161, 162, 163) from the inside.

11. A multiroll calender as claimed in any one of claims 3 to 6, characterized in that for closing and loading each intermediate nip (2, 2'; 3, 3') above the bottom nip (4, 4') and below the top nip (1, 1') by means of the bottom roll (16, 161, 162, 163), the locking mechanism of the support arrangement of the lower thermo roll (15, 151, 152, 153) constituting a roll pair with the bottom roll is open.

12. A multiroll calender as claimed in any one of claims 1 to 11, characterized in that the upper thermo roll (13, 131, 132, 133) is provided with a support arrangement connected with the roll frame and allowing an upward and downward movement.

13. A multiroll calender as claimed in any one of claims 1 to 13, characterized in that the top roll (12, 121, 122, 123) is a polymer roll covered with an elastic cover.

14. A multiroll calender as claimed in any one of claims 1 to 13, characterized in that the bottom roll (16, 161, 162, 163) is a polymer roll covered with an elastic cover.

15. A nip load-adjustment and/or locking arrangement for a pair of calender rolls (12,13; 13,14; 14,15; 15,16) in a roll stack of a multiroll calender and for a nip (N) between the pair of calender rolls, which roll stack (12-16) comprises, as calender rolls, a top roll (12) and a bottom roll (16), at least one of which is provided with an elastic cover and functions as a backing roll for a hard- and smooth-surface pressing roll, and at least one intermediate roll (13, 14, 15) between the top roll and the bottom roll, and in which roll stack the centre axes (C) of the calender rolls are parallel and in the cross direction transverse to the running direction of a web such that between adjacent calender rolls that form a pair of calender rolls there is a nip which calenders the web, the pressing line or plane of which nip is parallel to the centre axes of the calender rolls in the pair of calender rolls, characterized in that in order to adjust the load of the nip (N) between at least one pair of calender rolls (12,13; 13,14; 14,15; 15,16) in the roll stack, to open said nip or to lock it in an open position, the pair of calender rolls is provided with a nip load-adjustment and or locking arrangement (20) which acts between bearing housings (9) or bearing housing arms and/or loading and/or supporting arms (31, 32) of the calender rolls.

16. A nip load-adjustment and/or locking arrangement as claimed in claim 15, characterized in that the load-adjustment and/or locking arrangement (20) of the nip (N) includes a pair of nip load-adjustment and locking means (101, 102) that act between the bearing housings (9) or bearing housing arms of the calender rolls (12-16) of a pair of calender rolls (12,13; 13,14; 14,15; 15,16).

17. A nip load-adjustment and/or locking arrangement as claimed in claim 16, characterized in that the load-adjustment and locking elements of the nip (N) both comprise a loading shoe (101) that is movable by a power means, so that the mating surfaces (102) of the loading shoes placed against each other are shaped to conform to each other.

18. A nip load-adjustment and/or locking arrangement as claimed in claim 17, characterized in that one mating surface of the mating surfaces (102) is convex, advantageously a convex spherical surface, and the other mating surface is concave, advantageously a concave spherical surface.

19. A nip load-adjustment and/or locking arrangement as claimed in claim 15, characterized in that the load-adjustment and/or locking arrangement (20) of the nip (N) includes a nip load-adjustment and/or locking element (103) that acts between the supporting or loading arms (31, 32) of the calender rolls (12-16) of a pair of calender rolls (12,13; 13,14; 14,15; 15,16) and whose one end is attached to the supporting or loading arm of one calender roll in the pair of calender rolls and whose other end is attached to the supporting or loading arm of the other calender roll in the pair of calender rolls.

20. A nip load-adjustment and or locking arrangement as claimed in claim 19, characterized in that the nip load-adjustment and/or locking element (103) is in itself a power means.

21. A nip load-adjustment and/or locking arrangement as claimed in claim 15, characterized in that the load-adjustment and/or locking arrangement (20) of the nip (N) includes a nip load-adjustment and/or locking element (104) that acts between the bearing housings (9) or bearing housing arms of the calender rolls o'f a pair of calender rolls (12,13; 13,14; 14,15; 15,16).

22. A nip load-adjustment and or locking arrangement as claimed in claim 21, characterized in that the nip load-adjustment and/or locking element (104) is a wedge-like or spherical element that is movable by a power means in a direction transverse to the centre axes (C) of the pair of rolls (12,13; 13,14; 14,15; 15,16).

23. A nip load-adjustment and or locking arrangement as claimed in any one of claims 15 to 22, characterized in that the drive of the power means associated with the nip load-adjustment and/or locking arrangement or forming the nip load- adjustment and/or locking arrangement is hydraulic, pneumatic, electric and/or electromechanical.

24. A nip load-adjustment and/or locking arrangement as claimed in any one of claims 15 to 23, characterized in that increasing of the load of the load- adjustment and/or locking arrangement (20) of the nip (N) has the effect of reducing or increasing the load or linear pressure in the nip, and that reducing of the load of the load-adjustment and/or locking arrangement (20) of the nip (N) has the effect of increasing the load in the nip.

25. A nip load-adjustment and/or locking arrangement as claimed in claim 24, characterized in that the effect of reducing or increasing the load or linear pressure in the nip is in a range of 0 ± 50 Mpa.