The present invention relates to paper and board machines or to similar fibrous web machines, in particular to multiroll calenders. The invention is directed to a method for calendering a fibrous web in a multiroll calender according to the preamble of claim 1.

The invention is also directed to a multiroll calender according to the preamble of claim 13.

The state of the art in the calendering of a fibrous web is described in FI application publication 20030002, in which the invention relates to a multiroll calender comprising roll stacks placed one on top of another and/or next to one another. The state of the art is also described in FI application publication

20030003, in which the invention relates to a method for calendering a fibrous web in a calender comprising at least two roll stacks, and in which publication the invention also relates to a calender. With respect to the state of the art, reference may also be made to DE patent 196 31 056, which discloses a calender in which there are movable rolls arranged at the bottom and top ends of a roll stack. This known arrangement, however, has the problem that when the grade of the fibrous web is changed, the web must be passed along a new path, which slows down grade change. This known arrangement also does not allow several nips to be used for matte qualities.

In calendering, attempts are made to generally improve properties, such as smoothness, gloss and oil adsorptivity, of a web-like material, such as a paper or board web. 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 nips in the calender 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. 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 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 in a multiroll calender by fixing the top roll or the bottom roll in place and by pressing the roll stack against the roll fixed in place, which roll fixed in place can be a top roll, a bottom roll or one/some of the intermediate rolls. Alternatively, both the top roll and the bottom roll are both pressed against each other either such that none of the intermediate rolls is fixedly locked in place or such that at least one of the intermediate rolls is fixedly locked in place. The deflections of the rolls can be compensated for by means of deflection-compensation devices generally provided in the top and bottom rolls such that the roll nips obtain a rectilinear form.

In the calendering technology, online 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. Linear load increases in multinip calenders from the top nip to the bottom nip because of the force of gravity if no roll relief systems are used. To eliminate the

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. This kind of roll relief system is used in multiroll calenders known under the applicant's trademarks OptiLoad and TwinLine.

Great demands are made on the modern calender with respect to the mode of calendering. The several quality classes of different paper grades call for alternative ways of loading the calender roll stack, as well as different calendering modes. This has helped the introduction of different load-adjustable nips and roll covers of different types into calenders. In particular, the introduction of polymer covers in calender rolls has allowed high temperatures and high linear loads in calendering, which makes it possible to also produce more demanding fibrous web qualities on the same calender. In calendering, high temperature and high linear load help create high gloss in the end product.

Today, it is required that the calender shall have a structure that enables a 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 printing paper, i.e. matte paper.

In this description, operation with fewer than all nips refers to a running mode in which at least one nip of a roll stack in a multiroll calender is open, i.e. a nip that does not calender a fibrous web, and the fibrous web is calendered in at least one nip.

In a multiroll calender it is also required today that the calendering process shall allow operation with fewer than all nips in one or several nip positions in order that in a multiroll calender comprising only one roll stack it might be possible to produce several paper grades and different paper qualities of these paper grades, such as, for example, both heavily calendered glossy grades and matte and tissue grades. The human eye sees paper as matte when the gloss of paper is under 35 gloss % Hunter. Typically, when matte paper is calendered, the number of calendering nips is small and calendering temperature is low. For producing matte quality, on the one hand, soft calendering is known in an online soft calender provided with a nip comprising two soft rolls and, on the other hand, offline supercalendering is known in which a fibrous web is passed into a nip formed by soft rolls using a special web run where a number of nips are bypassed.

The state-of-the-art multiroll calenders provided with relief lever mechanisms have lacked a method of providing the roll stack with a matte nip, i.e. a nip in which there are two soft, covered rolls against each other and by means of which sufficiently high linear loads would be achieved. Attempts have been made to solve this problem by dimensioning the intermediate rolls of the calender so that they are overdimensioned, thereby allowing linear load to be raised for matte qualities. Sufficiently high linear load levels have not been achieved by the overdimensioning of the intermediate rolls because the strength of the roll suspension arrangements used is not sufficient, and the higher frictions caused by growing masses reduce the control accuracy of roll stack relief and, in addition, the acquisition costs of the roll have increased because of larger diameters. Furthermore, a nip with alternating hard and soft nips is poorly suitable for paper grades coated with a blade method because of the risk of mottling. Also, today's matte nip arrangements have made it necessary for spare rolls to be an integral part of the machine, which means that the maintainability and efficiency of the machine deteriorates, and the change of a spare roll becomes slower, for instance, when the shell of a deflection-compensated roll has to be changed onto a fixed spare roll. In addition, the known separate matte nip arrangements have required a

separate drive for the spare rolls, with the result that the investment and operation costs of the known arrangements have been high. In some known arrangements it has been contemplated that spare rolls of a precalender would be used as changeable rolls with a multiroll calender, but these have not been changeable in respect of matte nips because the mode of attachment can be different or a roll with a drive has been required or the difference in roll diameter has not allowed changeability. In the state-of-the-art multiroll calenders comprising two roll stacks, the use of a matte nip in situations where a matte nip is formed between two separate roll stacks, in which connection the deflection-compensated rolls (2 rolls) of both roll stacks have participated in calendering and it has not been possible to make use of the rest of the roll stack, has prevented the use of both separate roll stacks simultaneously with the matte nip, and in known multiroll calenders with two roll stacks it has not been possible to make use of, for example, thermo rolls of the calender in order to arrange a heatable hard/soft nip because the deflection-compensated rolls and the thermo rolls have not been compatible or interchangeable in respect of their modes of attachment, for example, with the thermo roll of the precalender.

An object of the present invention is to provide a method and a calender in which the above-noted problems and drawbacks of the state-of-the-art methods and calenders are eliminated or at least minimized.

An object of the present invention is to provide a new and inventive method that enables the calendering process to be accomplished in a multiroll calender in a better and more versatile manner than previously.

In addition, an object of the present invention is to enable the calendering of several fibrous web grades and different qualities of these fibrous web grades in a multiroll calender, in particular the calendering of both heavily calendered glossy qualities and matte and tissue qualities.

These objects are achieved by the method mentioned at the beginning, the special features characteristic of this method being stated in the characterizing part of the appended independent claim 1.

The calender according to the invention is in turn mainly characterized by what is stated in the characterizing part of claim 13.

With respect to other special features of the invention, reference is made to dependent claims 2-12 and 14-23 of the appended set of claims.

In the method and in the multiroll calender in accordance with the invention, as a running mode it is possible to use operation with fewer than all nips in one or more nip positions. Advantageously, the nip positions are top and bottom nip positions but, in accordance with one advantageous embodiment of the invention, operation with fewer than all nips can also be accomplished in intermediate nips within the limits allowed by roll stiffnesses. The load and stiffnesses of calender rolls, in other words, the outside diameter and the inside diameter and the material of calender rolls are arranged such that the deflections caused by the mass of the rolls and the auxiliary devices of the rolls and by the loading of the rolls do not cause a cross-direction nip load profile error, for example, the profiling accuracy of a deflection-compensated roll ± 0.5 kW/m.

In connection with the invention, in the top position an intermediate roll/intermediate rolls is/are loaded by means of their bearing arrangements and support and loading arms against a fixed or movable-shell deflection-compensated top roll or another sufficiently stiff top roll.

In connection with the invention, in the bottom position the load of a nip defined by one intermediate roll and a bottom roll is in turn produced such that the deflection-compensated bottom roll is loaded with bottom cylinders against the intermediate roll placed above. In the bottom position, the load of the nips defined

by several intermediate rolls and the bottom roll is produced such that the deflection-compensated bottom roll is loaded by means of bottom cylinders against the intermediate roll placed above. The load is transmitted from the intermediate roll loaded with the bottom roll further to the intermediate roll placed above said intermediate roll if there are two operating nips in the bottom position. Since the nip load is typically desired to be higher in the bottom position than the load caused by the mass of an intermediate roll/intermediate rolls and auxiliary devices, the topmost intermediate roll can be locked by means of support and loading arms in its position with respect to the frame of the calender. When an intermediate roll/intermediate rolls is/are loaded with the bottom roll in order to close nips, the weights of the intermediate rolls and the auxiliary devices of the intermediate rolls are taken into account in the determination of load level.

On the multiroll calender, using the method in accordance with the invention it is possible to produce several different fibrous web grades and different qualities of these fibrous web grades, such as, for example, both glossy paper qualities and matte and tissue qualities. Such fibrous web grades can be, among other things, news, SC, MFC, LWC and WFC grades.

In accordance with the invention, an auxiliary frame is arranged in connection with the calender and the rolls of a matte nip are attached to the auxiliary frame. The rolls to be attached are advantageously intermediate rolls or deflection- compensated rolls of the calender. The auxiliary frame is attached to the frame of the calender by means of a lever mechanism, a guide mechanism, a fixed arrangement or equivalent. In connection with the auxiliary frame and an upper roll or a lower roll or with both there is at least one loading cylinder which can be used for loading the roll nip in matte operation. When glossy qualities are calendered, there is no nip contact between the rolls attached to the auxiliary frame, and the prevention of nip contact is accomplished by means of a fixed, detachable or adjustable intermediate piece placed between roll shafts. When glossy grades are calendered, the auxiliary frame can be lifted with a cylinder or

an equivalent actuating member when closing the roll stack, and the at least one loading cylinder arranged in connection with the rolls of the auxiliary frame can be made use of in producing nip load. In accordance with an advantageous application, the upper set of rolls is closed by means of a cylinder, and linear load is produced for the upper set of rolls by means of another cylinder.

The invention makes it possible to arrange a nip, i.e. a matte nip, of two rolls with a polymer surface, i.e. soft rolls, in a set of rolls, i.e. a roll stack, of a multiroll calender by using, for example, deflection-compensated rolls or a shoe roll as a backing roll or a polymer-covered tubular roll as an intermediate roll. The roll suspension arrangement accomplished by means of the auxiliary frame used in connection with the invention makes it possible to achieve a quick change of the running mode in the entire roll stack for matte operation. The roll suspension arrangement used in connection with the invention enables higher linear loads to be used for matte qualities than the roll suspension arrangements previously known from multiroll calenders, and when using the invention, the intermediate rolls of the multiroll calender need not be overdimensioned for matte qualities because of the one-sided loading used because deflection-compensated rolls and shoe rolls are stiffer than the intermediate rolls of the calender, and thus withstand a higher linear load and are capable of adjusting themselves to the deflection of the roll such that the linear load is even across the entire width of the nip.

By means of the roll suspension of the invention it is possible to vary the linear loads of the sets of rolls situated one on top of the other independently of each other and, when calendering matte qualities, the forces caused by linear load are not transmitted to the frame of the calender because the auxiliary frame forms a closed force field between the rolls of the matte nip.

In accordance with the invention, the roll suspension is constituted by an auxiliary frame, to which the rolls of the matte nip are attached. The rolls to be attached are advantageously intermediate rolls or deflection-compensated rolls of the calender.

The auxiliary frame is advantageously attached by means of a guide mechanism to the frame of the calender. In accordance with an advantageous application, the upper set of rolls is closed with a cylinder, and linear load is produced for the upper set of rolls by means of another cylinder. The linear load of the lower set of rolls is produced by means of a third cylinder.

By means of one advantageous application of the invention it is possible to provide a matte nip for a multiroll calender making use of only one spare roll of the calender. The invention allows a situation where one of the two spare rolls included in the scope of delivery of a conventional calender is utilized in the matte operation arrangement and the other spare roll is utilized for maintenance or for storage. The invention also enables intermediate rolls and the top roll to be changed during matte operation. The invention also makes it possible to reduce the number of guide rolls needed for the matte running mode as compared with previous arrangements. The invention further enables the use of hard/soft nips in the upper part of the roll stack while rolls of the matte nip in the lower part of the roll stack are changed. The invention makes it possible to reduce the investment costs and the energy consumption of the matte running mode by excluding one high-power line drive because, for instance, in the matte surface arrangement (cf. FI 20000076U) the spare rolls, 2 rolls, (deflection-compensated rolls) are suspended before the calender and in the online arrangement both rolls have to be driven rolls. In connection with the invention, in the matte nip it is possible to make use of one drive of the roll stack proper and add only one drive for a backing roll.

The arrangement in accordance with one embodiment of the invention is formed of a deflection-compensated roll that serves as the bottom roll of the calender and is attached to the auxiliary frame. A spare roll of the calender is also attached to the same auxiliary frame. The top roll of the calender is interchangeable with the bottom roll and/or the spare roll. The auxiliary frame is attached to the frame of the calender using guides and it is movable by means of a loading cylinder when

the whole roll stack is used. Of the rolls attached to the auxiliary frame, the bottom roll can be fixed and the spare roll movable with respect to the auxiliary frame or vice versa. During matte operation, the nip is closed removing an intermediate piece and moving the spare roll upwards by means of a cylinder or the bottom roll downwards by means of a cylinder depending on which of the rolls is fixed. When operating with the entire roll stack, there is an intermediate piece between the bottom roll and the spare roll preventing nip contact and stiffening the structure. The entire roll stack is closed using a loading cylinder in a manner known per se. When operating with the entire roll stack, the spare roll can be removed for maintenance, if needed, and another intermediate piece can be placed in the empty space. The number of the guide rolls used for guidance of the web is determined based on the height of the machine.

One embodiment of the invention makes it possible to provide the multiroll calender with a hard/soft nip for matte and news qualities. The invention makes it possible to arrange in the lower part of the roll stack a hard/soft nip allowing high linear loads and high temperatures or, alternatively, a cooling cylinder with or without nip contact depending on the position of the centre of the deflection- compensated backing roll. The roll arrangement enabled by the invention and comprising a cooling cylinder makes it possible to cool the calendered web after the roll stack and to thus lower the reeling temperature. The roll arrangement of the matte nip can be accomplished such that a spare thermo roll of the precalender is used as a hard-surface roll, which means that the total number of rolls in a delivery remains the same as in today's deliveries.

The arrangement in accordance with one embodiment of the invention comprises an auxiliary frame, to which the rolls of a matte nip are attached. The upper roll can be a deflection-compensated roll of the multiroll calender or a thermo roll (of the precalender) or a cooling cylinder, and the lower roll can be a spare thermo roll of the precalender or a deflection-compensated spare roll of the multiroll calender or a separate roll dimensioned for this position. The lower roll can be

heated when it is used as a normal thermo roll or it can be cooled when the roll is used as a cooling cylinder. Auxiliary rolls can be attached to the auxiliary frame for different web run alternatives, among other things, it is possible to bypass the roll stack of the multiroll calender and use only the matte nip as cold or as hot, or the web runs through the roll stack but is guided on a roll to the matte nip at the end of the roll stack, which allows the use of the upper nips of the roll stack, but a matte nip is used in the lower part of the roll stack or the web runs through the roll stack all the way down where it is guided on a roll around the thermo roll functioning as a cooling cylinder, in which connection the web runs, in a previously known manner, through the entire roll stack without running through the matte nip any more.

By means of one application example of the invention it is possible to provide the multiroll calender with a hard/soft nip or a soft/soft nip for matte and news qualities. The invention makes it possible to arrange in the upper part of the roll stack a hard/soft nip allowing high linear loads and high temperatures or, alternatively, a cooling cylinder with or without nip contact depending on the running mode. The roll arrangement enabled by the invention and comprising a cooling cylinder makes it possible to cool the uncalendered web and to lower the temperature of the web both with coated and uncoated paper grades and to thus increase the temperature gradient in the nip. The roll arrangement of the matte nip can be accomplished such that a spare thermo roll of the precalender is used as a hard-surface roll, which means the total number of rolls in a delivery remains the same as in today's deliveries.

One advantageous application of the invention comprises matte nip rolls attached to an auxiliary frame. The upper roll is a spare thermo roll of the precalender, a hard- or soft-surface deflection-compensated spare roll of the multiroll calender and the lower roll is a deflection-compensated roll of the multiroll calender. The auxiliary frame is fixedly attached to the frame of the calender. The upper roll can be heated when it is used as a normal thermo roll or it can be cooled when the roll

is used as a cooling cylinder. Auxiliary rolls can be attached to the calender for different web run alternatives, so that, among other things, the matte nip can be used as cold or as hot. The web can run through the entire roll stack or the web is cooled and the web runs around the uppermost roll, in which connection there can be nip contact between the rolls or the rolls are separated from each other depending on the direction of the loading shoes of the deflection-compensated roll. If there is no nip contact between the rolls, the entire roll stack of the multiroll calender can be used. The nip contact of the matte nip can be accomplished by means of cylinders and by removing a detachable intermediate piece from between the shafts of the rolls or by using a movable shell in the deflection-compensated roll.

One advantageous application of the invention makes it possible to provide a multiroll calender comprising two separate roll stacks with one or two soft/soft matte nips or soft/hard matte nips with high linear loads. The invention also enables the operation of a multiroll calender equipped with two roll stacks, such as several soft calender types, for example, soft calenders with one or two nips. The invention allows the two-sidedness of matte qualities to be controlled more cost-efficiently as compared with previous matte nip arrangements. The roll arrangement in the matte nip can be accomplished such that a spare roll of the multiroll calender or a spare roll of the precalender serves as the backing roll. The invention also allows a high capacity to be achieved in the calender using alternative web runs. The invention makes it possible to calender, for example, matte qualities bypassing rolls or roll stacks and at the same time to change rolls of the roll stack not used. The auxiliary frame is situated in the lower part of the first, second or both roll stacks. Of the rolls attached to the auxiliary frame, one is a deflection-compensated roll of the multiroll calender, which roll may also have shell loading. The backing roll can be a deflection-compensated spare roll of the multiroll calender, a spare roll of the precalender or a separate roll dimensioned for this position or a shoe roll. The order of the roll and the backing roll in the auxiliary frame can be changed. The auxiliary frame is attached by means of a

guide mechanism or a link mechanism to the frame of the calender. The backing roll can be heated when it is used as a normal thermo roll in a hard/soft nip or it can also be cooled when the roll is used as a cooling cylinder. Auxiliary rolls can be attached to the auxiliary frame, which auxiliary rolls can also be movable for different web run alternatives. The roll stacks can be closed by means of a cylinder independently of each other when the whole roll stack is used. In matte nip operation, nip contact between rolls is provided by loading the shells of a roll with a movable shell or by removing an intermediate piece from between the shafts of the rolls and by using the cylinders. The operation of the matte nips of the roll stacks can be independent from each other. The roll stacks can be bypassed partly or totally by means of guide rolls.

The invention will be described in the following with reference to the accompanying figures, however, not limiting the invention exclusively to the illustration of the figures.

Figures 1 and 2 show a multiroll calender comprising only one roll stack in which a fibrous web runs through all calendering nips.

Figures 3, 4 and 5 show a multiroll calender comprising only one roll stack in which a fibrous web runs through five calendering nips.

Figure 6 shows illustrations of linear load levels in closed nips of a roll stack.

Figures 7-12 show advantageous application examples of the invention for roll suspension arrangements for use in a calender.

When the rolls- in a multiroll calender are movable with respect to one another, operation with fewer than all nips and more conventional operation with all nips can be used as the running mode of the calender. The multiroll calenders of Figs.

1-5 are shown during operation with fewer than all nips. In the method of the

invention, a top roll of the multiroll calender can be either fixed with respect to a frame F or fixed with respect to the frame F and provided with a movable shell. In the multiroll calenders 100, 200 all intermediate rolls and a bottom roll are movable. The bottom rolls 20 are movable and loadable from below with loading cylinders 22. The movability of the bottom rolls 20 is depicted by a vertical double-headed arrow symbol. Support and loading arms 24 provided with loading devices 23 are mounted by means of bearings on the frame F of the multiroll calenders 100, 200, said kind of arms being used in the multiroll calenders known under the trademarks OptiLoad and TwinLine. The loading devices 23 are mounted between the lever-like support and loading arms 24 and the frame F. Intermediate rolls 12-19 are journalled at their end areas on the support and loading arms 24. For the sake of clarity, only the parts essential in each particular case from the viewpoint of the description are shown of the support and loading arms 24 and of the loading devices 23.

The multiroll calenders of Figs. 1-5 are equipped with ten calender rolls, but the number of the calender rolls can be 3-14, advantageously 8-14, for example, eight, nine or twelve. The invention relates to a method of calendering a fibrous web in a multiroll calender provided with only one roll stack comprising two or more calendering nips. The nips in the multiroll calenders of Figs. 1-5 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, alternately following one another. The top roll 11, 11' and the bottom roll 20 are advantageously rolls covered with an elastic cover. In Figs. 1-5, the number of the rolls in the roll stack of the multiroll calender is even, so that the centremost soft-surface intermediate rolls form an intermediate nip called a reversing nip between themselves.

By operation with fewer than all nips is meant in this description a running mode in which at least one nip of the roll stack 100, 200 is open, i.e. a nip that does not calender a fibrous web W, and the fibrous web is calendered in at least one nip.

In operation with fewer than all nips, the web run of the fibrous web W can be complete, as in Figs. 1 and 2, in which the fibrous web W is passed through all nips of the roll stack of the calender 100. In Figs. 1 and 2, at least one nip functions as a closed nip, i.e. as a calendering nip that calenders. In Fig. 1, two nips are closed, namely a top nip 1 and an intermediate nip 2 located underneath the top nip. In Fig. 2, one nip is closed, i.e. the uppermost intermediate nip 2.

In operation with fewer than all nips, one advantageous web run of the fibrous web comprises the running of the fibrous web through all nips of the roll stack, so that the running mode can be readily changed from operation with fewer than all nips to operation with all nips without needing to perform a new threading process.

The fibrous web is calendered in the calender using operation with all nips when the web run of the fibrous web comprises the running of the fibrous web through all nips of the roll stack, and all nips of the roll stack of the calender are closed.

Another advantageous way of accomplishing operation with fewer than all nips is to arrange at least one closed nip both above and below the reversing nip in the roll stack 10, 101 of the multiroll calender 100, 200, in which connection it is possible to affect the two-sided quality properties of the fibrous web W, such as gloss, smoothness and oil absorption.

In those roll stacks 10, 101 of Figs. 1-5 comprising ten calender rolls in which the top roll 11, 11' has a soft surface and soft-surface and hard-surface calender rolls alternate in the roll stack from above downwards and in which roll stacks the bottom roll 20 has a soft surface and soft-surface and hard-surface calender rolls alternate in the roll stack from below upwards, the reversing nip 5 is in the middle of the roll stack. Soft intermediate rolls 15 and 16 form the reversing nip 5 between themselves. The web runs shown in Figs. 1-5 thus allow both the top side

Y and the bottom side A of the fibrous web W to be calendered, when desired,

using operation with fewer than all nips, for example, in one nip located above the reversing nip 5 and in one nip located below the reversing nip 5, thereby making it possible to advantageously affect the two-sided quality properties of the fibrous web W, such as gloss, smoothness and oil absorption, in a desired manner.

In the multiroll calender 100 shown in Figs. 1 and 2, the top roll 11 is fixed with respect to the frame F of the calender and provided with a movable shell. In the method of the invention, the multiroll calender of Figs. 1 and 2 provided with a complete web run of the fibrous web W can naturally also comprise a top roll that is fixed with respect to the frame F of the calender but provided with a non- movable shell.

In the multiroll calender 100 of Fig. 1, which comprises only one roll stack 10, the fibrous web W runs through all calendering nips of the roll stack. In the roll stack 10 there are ten calender rolls 11-20 placed one on top of another. During calendering, the fibrous web W is passed to a calendering nip formed between rolls pressed against each other or to calendering nips formed between rolls pressed against one another, the web run of the fibrous web W in the roll stack 10 of Fig. 1 comprising nine calendering nips in succession. During operation with fewer than all nips, at least one nip of the calendering nips 1-9 is open, i.e. a nip that does not calender the fibrous web W, and the fibrous web is calendered in at least one nip. The nips can be closed and opened. Take-out rolls 21 are shown of the rolls not taking part in the forming of the nips 1-9.

The top nip 1 is formed between the top roll 11, in this case a roll covered with an elastic cover, advantageously a roll with a polymer surface, and the uppermost intermediate roll 12, which is a pressing roll with a smooth surface, advantageously an upper thermo roll. In Figs. 1 and 2, the top roll 11 is a roll with a movable shell, advantageously a deflection-compensated roll. The movability of the shell of the top roll 11 is depicted with a vertical double-headed arrow symbol.

Some other sufficiently stiff top roll not provided with deflection-compensation equipment may also be applied.

By the above-mentioned sufficient stiffness is meant in this connection a property required of the top roll 11 that the intermediate roll 12 or intermediate rolls located underneath the top roll 11 and loaded in the direction of the top roll 11 in operation with fewer than all nips are not able to cause in the top roll 11 such a deflection that would give rise to a cross-direction nip load profile error. Thus, the top roll 11, which is not a deflection-compensated roll and which in operation with fewer than all nips receives the load caused by the intermediate roll 12 situated underneath or receives the load caused, for example, by two intermediate rolls 12, 13 situated underneath if in operation with fewer than all nips there are two nips 1, 2 in an upper position as shown in Fig. 1, shall be so stiff that no cross-direction nip load profile error is caused by the mass and load of the roll /rolls. In that case, the load profiles of the calendering nip/calendering nips are straight in the cross direction.

The deflection-compensated top roll 11 can be used for compensating for the cross-direction nip load profile error caused by the mass and load of the loadable rolls participating in operation with fewer than all nips in such a way that the load profiles of the calendering nip/nips are straight in the cross direction.

Naturally, the multiroll calender 100 of Fig. 1 can use, as a running mode, operation with fewer than all nips only in the top nip 1, in which case the nip 2 below the top nip 1 is kept open.

The running mode used in the multiroll calender 100 of Fig. 2 is operation with fewer than all nips. In other respects, the multiroll calender of Fig. 2 corresponds to the multiroll calender of Fig. 1 but the number of closed nips differs from that of the illustration of Fig. 1. The intermediate nip 2 below the top nip is closed, in which case the top nip 1 is kept open and the loading of the intermediate nip 2 is

accomplished by means of the loading devices 23 of the intermediate rolls 12 and 13 and using the support and loading arms 24 fixed to the frame F. Similar operation with fewer than all nips only in an intermediate nip can also be accomplished in other intermediate nips 3-8 of the multiroll calender 100 in which the stiffnesses of the intermediate rolls 13-19 allow a nip to be formed between two intermediate rolls. It is recommended that to enable operation with fewer than all nips in an intermediate nip/intermediate nips, the stiffness of the respective intermediate rolls 12-19, in other words, the outside diameter and the inside diameter and the material, be arranged such that the deflections arising from the mass and load of the rolls do not cause a cross-direction nip load profile error.

By the loading devices 23 are meant, for example, hydraulic power cylinders, which in some cases can also be used for accomplishing the locking of the support and loading arms 24 with respect to the frame F of the calender.

The method of the invention can also be applied only in the lower nip positions in the multiroll calender 100 shown in Figs. 1 and 2. In that case, the upper nip positions, such as, for example, the top nip 1 and the topmost intermediate nip 2 are open and operation with fewer than all nips is carried out in a closed lower nip position/closed lower nip positions, such as, for example, in a closed bottom nip 9 and/or in a closed intermediate nip 8 above the bottom nip. Similar operation with fewer than all nips performed in a lower nip position is described further in connection with the multiroll calender 200 of Fig. 3.

The method of the invention can be applied in both positions, both in an upper nip position and in a lower nip position, in the multiroll calender 100 shown in Figs. 1 and 2, in which connection it is possible to calender bypassing the reversing nip 5 in the manner described earlier in this description. In that case, one of the upper nip positions is closed and one of the lower nip positions is closed, so that operation with fewer than all nips is performed in the closed upper and lower nip positions and it is possible to affect the two-sided quality properties of the fibrous

web W, such as gloss, smoothness and oil absorption. One example of operation with fewer than all nips applied both in an upper nip position and in a lower nip position is illustrated by means of the multiroll calender 200 of Fig. 5.

In operation with fewer than all nips, the web run of the fibrous web W can also be partial, so that the fibrous web W is passed through some nips of the roll stack 101 of the calender 200, as in Figs. 3-5. The fibrous web W can be guided to outside the roll stack 101 of the multiroll calender 200 to bypass some calendering nips, so that during operation with fewer than all nips at least one nip functions as a closed nip, i.e. as a calendering nip that calenders. In that case, one advantageous way of performing operation with fewer than all nips is to arrange at least one closed nip both above and below the reversing nip 5 in the roll stack 101 of the multiroll calender 200, thus making it possible to affect the two-sided quality properties of the fibrous web W, such as gloss, smoothness and oil absorption.

In the multiroll calender 200 shown in Figs. 3-5, the top roll 11' of the roll stack 101 is fixed with respect to the frame F of the calender. The multiroll calender of Figs. 3-5 provided with a partial web run of the fibrous web W can naturally also comprise, in the method of the invention, a top roll that is fixed with respect to the frame F of the calender and provided with a movable shell.

In the multiroll calender 200 of Figs. 3-5, which comprises only one roll stack 101. In the roll stack 101 there are ten calender rolls 11', 12-20, one on top of another, and nine nips 1-9. Take-out rolls 21 are shown of the rolls not participating in the forming of the nips 1-9. The fibrous web W is shown to run through five calendering nips 1, 2, 7, 8, 9 of the roll stack 101. In operation with fewer than all nips, at least one nip of the calendering nips 1, 2, 7, 8, 9 is open, i.e. a nip that does not calender the fibrous web W, and the fibrous web is calendered in at least one nip. The nips can be closed and opened.

During calendering, the fibrous web W is passed into a calendering nip formed between rolls pressed against each other or into calendering nips formed between rolls pressed against one another, the web run of the fibrous web W in the roll stack 101 of Figs. 3-5 comprising nine calendering nips in succession. In the roll stack 101 the fibrous web W is arranged to run through two upper nip positions and through three lower nip positions. In the web run depicted, after the intermediate nip 2, the fibrous web W is taken out to outside the roll stack 101 onto the topmost take-out roll 21 on the left side in the figures and passed back to the roll stack 101 in the intermediate nip 7 after the fibrous web W has bypassed four intermediate nips 3, 4, 5 and 6 of the roll stack 101 on the left side while guided by three take-out rolls 21. The bypassing of the calendering nips illustrated by means of the roll stack 101 is meant to be an example of a web run of the fibrous web W in which operation with fewer than all nips can be performed in an upper nip position or in a lower nip position of the multiroll calender or in both positions both in an upper position and in a lower position without threading through all calendering nips. In Figs. 3-5, there are five closable and openable nips 1, 2, 7, 8, 9 in succession in the running direction of the fibrous web W.

The bottom nip 9 is formed between the bottom roll 20, in this case a roll covered with an elastic cover, advantageously a polymer-surface roll, and the lowermost intermediate roll 19, which is a smooth-surface pressing roll, advantageously a lower thermo roll. In Figs. 3-5 the bottom roll 20 is advantageously a deflection- compensated roll, which is loaded and moved by means of a bottom cylinder 22. The movability of the bottom roll 20 is depicted by a vertical double-headed arrow symbol. The lowermost intermediate roll 19 can be locked with respect to the frame F of the calender by means of a support and loading arm 24 provided with a loading device 23.

By means of the deflection-compensated bottom roll 20 it is possible to compensate for the cross-direction nip load profile error caused by the mass and

load of the intermediate rolls taking part in operation with fewer than all nips such that the load profiles of the calendering nip/nips are straight in the cross direction.

In Fig. 3, operation with fewer than all nips is carried out only in the bottom nip 9, the top nip 1 and the topmost intermediate nip 2 of the roll stack 101 being open. The lowermost intermediate roll 19, i.e. advantageously a lower thermo roll, is locked with respect to the frame F of the calender by means of the support and loading arms 24 provided with the loading device 23, and the deflection- compensated bottom roll 20 is loaded with the bottom cylinders 22 against the locked lowermost intermediate roll 19.

In Fig. 4, operation with fewer than all nips is carried out in two lower nip positions, that is, in the bottom nip 9 and in the lowermost intermediate nip 8, the top nip 1 and the uppermost intermediate nip 2 being open. The intermediate roll 18 above the lowermost intermediate roll 19 is locked with respect to the frame F of the calender by means of the support and loading arms 24 provided with the loading device 23, and the bottom roll 20 is loaded upwards against the lowermost intermediate roll 19 and the intermediate roll 18.

In Fig. 5, operation with fewer than all nips is carried out in both nip positions, both in an upper nip position and in a lower nip position, in the roll stack 101 of the multiroll calender 200, the closed nips being the top nip 1 and the bottom nip 9. The other calendering nips of the roll stack 101 are open. The uppermost intermediate roll 12 is loaded against the fixed top roll 11' and the bottom roll 20 is loaded against the locked lowermost intermediate roll 19. In Fig. 5, the method of the invention is applied by calendering the fibrous web W bypassing the reversing nip 5, so that by suitably selecting the load levels of the nips and other process parameters, such as, for example, running speed, temperature and moisture, the two-sided quality properties of the fibrous web W, such as gloss, smoothness and oil absorption, are affected in the closed upper and lower nips during operation with fewer than all nips.

With the web run of the fibrous web W shown in Figs. 3-5 it is also possible to perform operation with fewer than all nips in an intermediate nip position in which a calendering nip is formed between two intermediate rolls. Such intermediate nip position operation with fewer than all nips could be, for example, operation with fewer than all nips in the uppermost intermediate nip 2 in a manner similar to that of Fig. 2 or operation with fewer than all nips in the lowermost intermediate nip 8.

It is recommended that to enable operation with fewer than all nips in an intermediate nip/intermediate nips, the outside diameter and the inside diameter and the material of the respective intermediate rolls 12-13, 17-19 be arranged such that the deflections arising from the mass and load of the rolls do not cause a cross-direction nip load profile error.

On the multiroll calender 100, 200 comprising only one roll stack, using the method of the invention, it is possible to produce several different fibrous web grades and different qualities of these fibrous web grades, such as, for example, both glossy paper qualities and matte and tissue qualities. The fibrous web grades may include, among other things, news, SC, MFC, LWC and WFC grades.

By means of the method of the invention it is possible to produce, by loading two or three calender rolls against one another, linear load levels of 100-300 kN/m substantially providing matte qualities.

In the invention, all nips of the calender can be loaded with a desired load, which can be equal in all closed nips. This is achieved by eliminating the nip load caused by the masses of the calender rolls 12-19 of the roll stack 10, 101 as well as by the masses of the bearing housings of the rolls and the auxiliary devices attached to them. The loads in the calendering nips 1-9 are adjusted to be as desired either by individually over- or under-relieving the masses of each intermediate roll 12-19

and the auxiliary devices associated with it by means of the support and loading arms 24 provided with the loading devices 23.

By the method according to the invention, using one and the same multiroll calender 100, 200, it is possible to achieve a substantially larger range of runnable paper grades than that achieved by conventional arrangements. In addition to constant linear loads, it also possible to run the multiroll calender with increasing linear loads or the other way round, i.e. with decreasing linear loads. Control is carried out in that connection making use of the control of the relief forces of the loading devices 23.

Fig. 6 shows linear load level illustrations in closed calendering nips that participate in operation with fewer than all nips in the roll stack 10, 101. The effect of friction has been eliminated from the load illustrations. The horizontal axis of the quadrangles drawn adjacent to the roll stacks 10, 101 represents the linear load in the closed nips formed by the calender rolls which participate in operation with fewer than all nips in the roll stack 10, 101 which is parallel to the vertical axis. The illustration I is a simplified schematic example of a linear load distribution which is increases linearly from above downwards, and can be achieved by means of the method of the invention. The range shown in the illustration I represents a linear load distribution in which nip load is substantially linearly increasing from the first nip to the last nip. This kind of linear load distribution is generally attained when the effect of the masses of rolls and auxiliary devices is not compensated for by means of relief devices.

Because the weights of the intermediate rolls and the auxiliary devices associated with them can be over- or under-relieved in a desired manner, the entire calendering potential of the calendering nips participating in operation with fewer than all nips can be utilized in a desired manner. In the illustration II of Fig. 6, the shaded-in area represents a linear load distribution that is linearly constant from above downwards, which shaded-in area simultaneously represents the entire

calendering potential. Lines extending at different angles across the area are drawn to the shaded-in area in an attempt to illustrate the fact that, in addition to constant linear loads of different levels, all linear increasing and decreasing load alternatives are available when the loads of the nips participating in operation with fewer than all nips are selected in a suitable manner. The illustration III of Fig. 6 shows separately a linear load distribution that decreases linearly from above downwards.

The relief devices 23 are used for producing a relief force for the support and loading arms 24 of the intermediate rolls participating in operation of rolls with fewer than all nips, by means of which relief force it is possible to partly or totally compensate for the loads caused by the weight of the rolls and the auxiliary devices attached to the rolls. The weights of the rolls and auxiliary devices can thus be partly or totally caused to have no increasing effect on the nip loads. In that connection, the linear load in each nip 1-9 can be made unequal or equal, when desired, the profiles of the linear loads being like those shown in Fig. 6.

In the following, embodiments of the invention are described in which operation with fewer than all nips in a multiroll calender, in particular matte nip operation, is provided in a calender which is provided, by means of an auxiliary frame and a roll suspension arrangement associated with said frame, with an option of a matte nip in connection with a roll stack as an alternative roll stack for the paper grade produced by normal operation. Figs. 7-12 show different application examples of this embodiment, and in the figures the same reference numerals corresponding to those of Figs. 1-5 are mainly used of parts corresponding to one another, and the structures correspond to one another unless otherwise mentioned.

In the application examples shown in Figs. 7-12, a roll stack 10, i.e. a set of rolls,

(or sets of rolls 1OA, 10B) of a calender 300, 400 comprises an auxiliary frame 301, to which rolls 303 and 304 are attached between which a matte nip MN can be formed. When running with the matte nip MN, the matte nip MN between the

rolls 303, 304 is closed with cylinders 305, and when in turn running glossy web grades with the roll stack/roll stacks 10; 1OA, 1OB of the calender 300, 400, an intermediate piece 306 is used for preventing nip contact between the rolls 303, 304, which intermediate piece can be fixed, variable in height and/or detachable. In the arrangement shown in Fig. 7, the auxiliary frame 301 is attached by means of lever arms 302 to a frame F of the calender and in the applications shown in Figs. 8-12 the auxiliary frame 301 is attached to the frame F of the calender by means of a guide mechanism 314 or it is attached to the frame fixedly. The following figures also show application examples for web run arrangements WA- WE of different runs with fewer than all nips.

Fig. 7 shows a calender in accordance with one advantageous application example of the invention, the roll stack 10 of the calender comprising an auxiliary frame 301, to which rolls 303, 304 forming a matte nip MN are attached. The rolls 303, 304 to be attached can be intermediate rolls or deflection-compensated rolls of the calender. The auxiliary frame 301 is attached by means of a lever mechanism 302 to a frame F of the calender 300. Between the auxiliary frame 301 and the upper roll 303 or the lower roll 304 or in both there is a loading cylinder 305, by means of which the roll nip MN can be loaded during matte operation. When calendering glossy qualities, there is no nip contact between the rolls 303, 304 and calendering is carried out by means of other rolls 11-14 and 17-20 of the roll stack 10. Nip contact can be prevented with a fixed intermediate piece 306 between the shafts of the rolls 303, 304. When glossy qualities are calendered, the auxiliary frame 301 can be lifted with a cylinder 307 when closing the roll stack 10.

Fig. 8 shows a multiroll calender 300 in accordance with one advantageous application example of the invention, which calender comprises an auxiliary frame 301, to which matte nip rolls 303, 304 are attached. The rolls 303, 304 to be attached can be intermediate rolls or deflection-compensated rolls of the calender. The auxiliary frame 301 is attached by means of a guide mechanism 314 to the frame F of the calender. Below and above the upper roll 303 attached to the

auxiliary frame 301 there are loading cylinders 305, by means of which the roll nip MN can be loaded during matte operation. The upper set of rolls A is closed by means of a cylinder 307, and linear load is produced in the upper set of rolls A by means of a cylinder 305 situated above the roll 303. The linear load of the lower set of rolls B is produced by means of a cylinder 22. When calendering glossy qualities, there is no nip contact between the rolls 303, 304. Nip contact in the nip MN can be prevented with a changeable intermediate piece 306 between the shafts of the rolls 303, 304. When matte qualities are calendered, the intermediate piece 306 can be made lower to provide nip contact in the nip MN and linear load can be produced with the cylinders 305.

Fig. 9 shows one advantageous application example of the calender in accordance with the invention, in which example the calender 300 comprises a deflection- compensated roll 303 which serves as the bottom roll of the calender and is attached to an auxiliary frame 301. A spare roll 304 of the calender is also attached to the same auxiliary frame 301. The top roll 11 of the calender is interchangeable with the bottom roll 303 and the spare roll 304. The auxiliary frame 301 is attached to a frame F of the calender by means of guides 314 and can be moved with a loading cylinder 22 when running with the entire roll stack. Of the rolls attached to the auxiliary frame 301 the bottom roll 303 is fixed and the spare roll 304 is movable with respect to the auxiliary frame 301 or vice versa.

During matte operation, a nip MN is closed by removing an intermediate piece 306 and by moving the spare roll 304 upwards using a lower cylinder 305 or the bottom roll 303 upwards using an upper cylinder 305 depending on which of the rolls 303; 304 is fixed. When running with the entire roll stack 10, the intermediate piece 306 is between the bottom roll 303 and the spare roll 304 for preventing nip contact MN and for making the structure stiffer. The whole roll stack is closed in a previously known manner by means of the loading cylinder 22. When running with the entire roll stack, the spare roll 304 can be removed for maintenance, if needed, and another intermediate piece can be placed in the empty

space. A web run WA is employed when operating with the whole roll stack and a web run WB is employed when using the matte nip MN. The number of guide rolls 312 used for guiding the web is determined based on the height of the machine.

Fig. 10 shows one advantageous application example of the invention, in which a

1 calender 300 comprises an auxiliary frame 301, to which rolls 303, 304 of a matte nip MN are attached. The upper roll 303 attached to the auxiliary frame 301 is a deflection-compensated roll of the multiroll calender. The lower roll 304 can be a spare thermo roll of the precalender or a deflection-compensated spare roll of the multiroll calender or a separate roll dimensioned for this position or a shoe roll. The auxiliary frame 301 is attached to a frame F of the calender using a guide mechanism 314. The lower roll 304 can be heated when it is employed as a normal thermo roll or it can be cooled when the roll 304 is employed as a cooling cylinder.

Auxiliary rolls 325, 326 can be attached to the auxiliary frame 301 for different web run alternatives WB, WC, WD, WA. Using the web run alternative WB it is possible to bypass the roll stack 10 of the multiroll calender and use only the matte nip MN as cold or as hot. With the alternative WC, the web runs through the roll stack 10 but is guided on the roll 325 to the matte nip MN at the end of the roll stack 10. This alternative enables the use of the upper nips of the roll stack 101 but the matte nip MN is used at the lower part of the roll stack 10. With the alternative WD, the web runs through the roll stack 10 all the way down where it is guided on the roll 326 around the thermo roll 304 functioning as a cooling cylinder. With the alternative WA, the web runs, in a previously known manner, through the entire roll stack without running through the matte nip any more.

Nip contact in the matte nip MN can be accomplished by means of cylinders 305 and by removing a detachable intermediate piece 306 from between the shafts of the rolls 303, 304. When calendering with the entire roll stack 10 or when using

the lowermost roll 304 as a cooling cylinder, nip contact between the lowermost two rolls 303, 304 is prevented by means of the intermediate piece 306. The roll stack 10 is closed and the entire auxiliary nip is moved using the loading cylinder 22.

Fig. 11 shows one application example of the invention, in which a calender comprises an auxiliary frame 301, to which rolls 303, 304 of a matte nip MN are attached. The upper roll 303 attached to the auxiliary frame 301 is a spare thermo roll of the precalender, a hard or soft-surface deflection-compensated spare roll of the multiroll calender or a separate roll dimensioned for this position. The lower roll 304 is a deflection-compensated roll of the multiroll calender. The auxiliary frame is fixedly attached to a frame F of the calender. The upper roll 303 can be heated when it is used as a normal thermo roll or it can be cooled when the roll 303 is used as a cooling cylinder.

Auxiliary rolls 325, 326 can be attached to the calender for different web run alternatives WB, WA, WC. The web run alternative WB makes it possible to use the matte nip MN as cold or as hot. With the alternative WA the web runs through the entire roll stack along a path that is already previously known. With the alternative WA the web is cooled and the web runs around the topmost roll 303. In this alternative there can be nip contact between the rolls 303, 304 or the rolls 303, 304 are separated from each other depending on the direction of the loading shoes of the deflection-compensated roll 304. If there is no nip contact between the rolls 303, 304, the entire roll stack 10 of the multiroll calender can be used in the alternative WC.

The nip contact of the matte nip MN can be accomplished by means of cylinders

305 and by removing a detachable intermediate piece 306 from between the shafts of the rolls 303, 304 or by using a movable shell in the deflection-compensated roll 304. When calendering with the entire roll stack or when using the topmost

roll 303 as a cooling cylinder, between the rolls 303, 304 is prevented by means of the intermediate piece 306.

Fig. 12 shows one advantageous application example of the invention, in which a calender comprises an auxiliary frame 301 situated in the lower part of a first 1OA roll stack, a second 1OB roll stack or both roll stacks 1OA, 1OB. One of the rolls attached to the auxiliary frame 301 is a deflection-compensated roll 303 of the multiroll calender, which roll may also have shell loading. A backing roll 304 can be a deflection-compensated spare roll of the multiroll calender, a spare roll of the precalender or a separate roll dimensioned for this position or a shoe roll. The order of the roll 303 and the backing roll 304 in the auxiliary frame 301 can be changed. The auxiliary frame 301 is attached by means of a guide mechanism 314 to a frame of the calender. The backing roll 304 can be heated when it is used as a normal thermo roll in a hard/soft nip or it can also be cooled when the roll 304 is used as a cooling cylinder. Auxiliary rolls 325, 326 can be attached to the auxiliary frame 301, which auxiliary rolls can also be movable for different web run alternatives.

The roll stacks 1OA, 1OB can be closed by means of a cylinder 22 independently of each other when the entire roll stack is used. In matte nip operation, nip contact between the rolls 303, 304 is provided by loading the shells of the roll having a movable shell or by removing an intermediate piece 306 from between the shafts of the rolls and by using cylinders 305. The operation of the matte nips of the roll stacks 1OA, 1OB can be independent of each other. The roll stacks 1OA, 1OB can be bypassed partly or totally using guide rolls 413.

The invention has been described above by way of example with reference to the figures of the appended drawings. However, the invention is not exclusively limited to the illustration of the figures but the different embodiments of the invention can vary within the inventive idea defined in the appended claims.