The present invention relates to paper and board machines, in particular to cal¬ enders. The present invention relates more specifically to a method in a calender according to the preambles of claims 1 and 9 and a multiroll calender according to the preamble of claim 10, 14 and 15.

The invention relates further to a method for loading a calender roll of a multiroll calender according to the preamble of claim 18 and a multiroll calender according to the preamble of claim 27 for carrying out the method.

Calendering is generally carried out in order to improve the properties, like smoothness and gloss, of a web-like material such as a paper or board web. In calendering the web is passed into a nip, i.e. calendering nip, formed between rolls that are pressed against each other, in which nip the web becomes deformed as by the action of temperature, moisture and nip pressure. In the calender the nips are formed between a smooth-surfaced press roll such as a metal roll and a roll coated with resilient material such as a polymer roll. The resilient-surfaced roll adjusts itself to the forms of the web surface and presses the opposite side of the web evenly against the smooth-surfaced press roll. In this connection the term calender rolls refers to rolls that form the calendering nip, upper roll refers to the uppermost roll in a stack of rolls, upper nip refers to the uppermost calendering nip, formed between the upper roll and the calender roll below the upper roll, lower roll refers to the lowest roll in a stack of rolls and lower nip refers to the lowest calendering nip in a stack of rolls, which lowest calendering nip is formed between the lower roll and the calender roll above the lower roll. Intermediate nips refer to calendering nips formed by means of calender rolls between the up- per nip and the lower nip of a calender.

The line between paper and board is flexible and they can be divided according to their basis weight into two categories: papers, which are single-layer and have a basis weight of 25-300 g/m and boards, which are manufactured using multilayer technique and have a basis weight of 150-600 g/m ³ . As can be seen, the line be- tween paper and board is flexible, since boards having the smallest basis weight are lighter than papers with the highest basis weight. Paper is generally used for printing and board for packing.

The following descriptions are examples of fibrous web values in use at present, and considerable variations from the given values are possible.

Wood-containing printing papers i.e. printing papers made of mechanical pulp, comprise newsprint, uncoated magazine paper and coated magazine paper.

Newsprint is either entirely composed of mechanical pulp or it may contain only a small amount of bleached softwood pulp (0 - 15%) and/or some of the mechanical pulp can be substituted with recycled fibre. The following can be considered as common values for newsprint: basis weight 40 - 48,8 g/m ² , ash content 0 - 20%, PPS SlO roughness 3.0 - 4.5 μm, Brendsten roughness 100 - 200 ml/min, density 600 - 750 kg/m ³ , brightness 57 - 63% and opacity 90 - 96%.

Uncoated magazine paper (SC - supercalendered) usually comprises 50 - 70 % of mechanical pulp, 10 - 25 % of bleached softwood pulp and 15 - 30 % of fillers. Typical values for calendered SC paper (including e.g. SC-C, SC-B and SC- AJA+) are: basis weight 40 - 60 g/m ² , ash content 0 - 35 %, Hunter gloss <20 - 50 %, PPS SlO roughness 1.0 - 2.5 μm, density 700 - 1250 kg/m ³ , brightness 62 - 70 % and opacity 90 - 95 %.

Coated magazine paper (LWC = light weight coated) comprises 40 - 60 % of me- chanical pulp, 25 - 40 % of bleached softwood pulp and 20 - 35 % of fillers and coatings. The following can be considered as usual values for LWC paper: basis

weight 40 - 70 g/m ² , Hunter gloss 50 - 65 %, PPS SlO roughness 0.8 - 1.5 μm (offset) and 0.6 - 1.0 μm (roto), density 1100 - 1250 kg/m ³ , brightness 70 - 75 % and opacity 89 - 94 %.

The following can be considered as usual values for MFC paper (machine finished coated): basis weight 50 - 70 g/m ² , Hunter gloss 25 - 70 %, PPS SlO roughness 2.2 - 2.8 μm, density 900 - 950 kg/m ³ , brightness 70 - 75 % and opacity 91 - 95%.

The following can be considered as usual values for FCO paper (film coated off¬ set): basis weight 40 - 70 g/m ² , Hunter gloss 45 - 55 %, PPS SlO roughness 1.5 - 2.0 μm, density 1000 - 1050 kg/m ³ , brightness 70 - 75 % and opacity 91 - 95 %.

The following can be considered as usual values for MWC paper (medium weight coated): basis weight 70 - 90 g/m ² , Hunter gloss 65 - 75 %, PPS SlO roughness 0.6 - 1.0 μm, density 1150 - 1250 kg/m ³ , brightness 70 - 75 % and opacity 89 - 94 %.

HWC (heavy weight coated) has a basis weight of 100 - 135 g/m ² and it can be coated even more than twice.

Woodfree printing papers made out of pulp i.e. fine papers comprise coated - and uncoated pulp-based printing papers having a mechanical pulp content of less than 10%.

Uncoated pulp-based printing papers (WFU) contain 55 - 80% of bleached birch pulp, 0 - 30 % of bleached softwood pulp and 10 - 30 % of fillers. The values of WFU vary considerably: basis weight 50 - 90 g/m ² (up to 240 g/m ² ), Bendtsen roughness 250 - 400 ml/min, brightness 86 - 92 % and opacity 83 - 98 %.

The amounts of coating vary considerably in coated pulp-based printing papers (WFC) according to the requirements and intended use. The following are typical values for pulp-based single and double coated printing papers: single coated ba¬ sis weight 90 g/m ² , Hunter gloss 65 - 80 %, PPS SlO roughness 0.75 - 2.2 μm, brightness 80 - 88 % and opacity 91 - 94 % and for double coated basis weight 130 g/m ² , Hunter gloss 70 - 80 %, PPS SlO roughness 0.65 - 0.95 μm, brightness 83 - 90 % and opacity 95 - 97 %.

Release paper, having a basis weight that varies between 25 and 150 g/m ² .

Other fine papers include, for example, sackkraft paper, tissue and wallpaper.

Pulp, mechanical pulp and/or recycled fibre pulp is used in the manufacture of board. Boards can be divided e.g. in the following main categories according to their intended use:

Corrugated board with a liner and fluting.

Box board is used for the manufacture of boxes, cartons, e.g. packaging boards for liquids (FBB, WLC, SBS).

Finnish patent specification no 96334 is cited as prior art, which document dis¬ closes a method for calendering a paper or an equivalent web material in a calen¬ der. In the method the web material to be calendered is passed through nips formed by a deflection-compensated upper roll and a deflection-compensated lower roll, and by two or more intermediate rolls arranged between the upper and lower roll. The rolls are arranged as a substantially vertical stack of rolls. Rolls in which the form of the natural deflection line produced by their own gravity is sub¬ stantially equal are used as intermediate rolls. The nip load produced by the masses of the intermediate rolls and the auxiliary equipment related to the inter¬ mediate rolls is substantially completely relieved in the method and an adjustable

load is applied to the calendering nips by means of the deflection-compensated upper or lower roll and/or by means of an external load applied to the upper or lower roll.

Pressing is typically provided in a multiroll calender by anchoring the upper or lower roll of a stack of rolls to its place and pressing the stack of rolls against the anchored roll, which may be an upper roll, a lower roll or an intermediate roll/some intermediate rolls. Alternatively, both the upper roll and the lower roll are pressed against each other either such that none of the intermediate rolls is fixedly locked to its place or such that at least one of the intermediate rolls is fix¬ edly locked to its place. It is possible to compensate for the deflections of the rolls by means of equipment for compensating for deflections usually located in the upper and lower rolls, for example such that the roll nips acquire a linear form.

The centre shafts of the calender rolls in a stack of rolls of a multiroll calender have, as is known in the art, been parallel. The centre shafts of the calender rolls have been in crosswise CD direction relative to the running direction of the web. In such a situation there is always a nip calendering the web between the adjacent calender rolls, these rolls forming a pair of calender rolls, the pressing plane of the nip being parallel to the centre shafts of the calender rolls of the pair of calender rolls.

The calendering technique of choice is more and more often online-calendering, because higher and higher running speeds are required from paper machines. MuI- tinip on-line calendering is calendering in a calendering unit, in which the nips are formed between an intercalated smooth-surfaced press roll such as a metal roll and a roll coated with resilient material such as a polymer roll. The linear load increases in multinip calenders from the upper nip to the lower nip due to gravita¬ tion, unless roll relief systems are used. In multinip calenders presently in use roll relief that compensates for gravitation and that is carried out by means of a cylin¬ der and lever mechanism is used for eliminating downwards-increasing linear

load, for controlling the deflection line of the roll and also for rapid opening of a set of rolls. Such a roll relief system is used in the applicant's multiroll calenders known by the brands OptiLoad and TwinLine.

From prior art multiroll calenders are known, the set of rolls of which is formed of two sets of rolls, each set of rolls comprising at least two calender rolls, for exam¬ ple one comprising five and the other six rolls. As paper machine running speeds and the need for online calendering increase, a possibility to carry out various types of calendering by means of a calendering machine is also needed, which can be carried out e.g. by means of running with fewer than all nips known as such, in which the web is passed through a calender such that during calendering the web is being calendered only in some of the possible nips of the calender. In runs with fewer than all nips it has been known, for example, to lock the levers of the calen¬ der by means of hydraulics during runs with fewer than all nips. A problem re- lated to this arrangement is that it cannot be easily applied in efficient production machinery, because in an arrangement like this the forces directed to the bearings of the calender grow to a substantial magnitude.

As is known from prior art, for example from publications FI 96334 and EP 732444, the calender rolls forming the nip of a multiroll calender are mounted by means of roller bearings, which has caused certain problems, the solving of which has required special arrangements.

In some cases multiroll calenders are run with linear loads that bring about a very small load, even a so-called zero load, on the roller bearings of the calender roll. This is very problematic in view of the roller bearings, since, in a zero load situa¬ tion, the rolling members of a roller bearing are enabled, instead of rolling, to slide considerably relative to the bearing frames, resulting in speedy wear and break down of the bearing. In a zero load situation of the roller bearing the point of contact between the rolling elements of the roller bearing and the rolling sur¬ faces of the bearing frames is unadvantageously vague and unsteady, since the

rolling frames of the bearing do not press the rolling elements between themselves steadily from any direction with sufficient force.

In calendering a known calender definition is so-called calendering work, which refers to work that can be done by means of a calender and is determined by the term kN/m x number of nips in a calender. It is known from calendering theory that the number of nips is not completely replaceable through increase in the lin¬ ear load. The combination of the number of nips and linear load constitutes thus a criterion in estimating the suitability of a calender for a particular paper grade.

An objective of the invention is to provide a method in a multiroll calender and a multiroll calender, by means of which method and multiroll calender it is possible to carry out different types of runs i.e. running with fewer than all nips.

An objective of the invention is to provide a method in a multiroll calender and a multiroll calender, by means of which method and multiroll calender the widest possible calendering work area is achieved.

A further objective of the invention is also to provide a calender in which the sup- port of the rolls on the calender frame is as rigid as possible.

An objective of the present invention is to eliminate the above-mentioned prob¬ lems and deficiencies or at least reduce the above-mentioned inconveniences and to prevent a zero load situation of the roller bearings of a calender roll of a multi- roll calender or at least to reduce the linear load zone in which the load of the bearings of the calender roll would be too small.

To achieve the object of the invention the method of the invention is mainly char¬ acterized in what is presented in the characterizing part of claim 1 or 9.

The multiroll calender according to the invention is in turn mainly characterized in what is presented in the characterizing part of claim 10, 14 or 15.

In the method according to the invention, applied in a multiroll calender having two sets of rolls, both sets of rolls comprising at least two rolls, most appropri¬ ately one set of rolls comprising more than three and the other more than five rolls, and the uppermost two rolls of one set of rolls advantageously being ar¬ ranged to form a matte nip between themselves i.e. the rolls forming the nip being soft-surfaced calender rolls, a possibility is provided to carry out different types of calendering by means of a calender for fibrous web being run in the calender by using fewer than all nips in the calender.

According to the invention seven different types of running, for example, can be carried out by means of the sets of rolls. These running types with fewer than all nips in use are carried out such that at least one intermediate roll, advantageously the lowest or second lowest intermediate roll of both sets of rolls is locked by means of a hydraulic cylinder to a lower position, whereby, by loading the rolls above or below the locked roll, a required number of nips can be provided for use. Thus, the run of the web is the same irrespective of the running type. If it is de- sired to use the calender in producing matte-surfaced web, the web is passed only, for instance, through a matte nip formed between the two uppermost rolls of one set of rolls.

In the method in a calender according to the invention and in the multiroll calen- der according to the invention a wide calendering work area is made possible, in which area the loading of the calendering arrangement and the loading system of the calender enable a wide kN/m x number of nips running area, meaning that an extremely versatile calendering method and a calender suitable for many different paper grades are achieved.

In an advantageous embodiment of the invention a roll support point is insight¬ fully positioned in the calender frame as close as possible to the centre of gravity of the roll, resulting in good support rigidity. The support is realized by means of a lever attached to a side panel that is in connection with the calender frame, actu- ating means for carrying out the loading and moving of the roll being arranged in connection with the lever. Also, according to an advantageous further feature sup¬ port is arranged symmetrically on both sides of the calender frame, meaning that stresses are divided evenly. Symmetrical support also enables high loadability required by the load when running with fewer than all nips. Space needed inside the frame for the symmetrical support is provided by narrowing the bearing ar¬ rangement of the flyrolls. The lever used in this embodiment of the invention is advantageously made of spheroidal graphite cast iron. A relief cylinder and hy- draulically lockable support cylinders located on the outwardly facing surfaces of the lever are advantageously used side by side in connection with the support of the rolls. The structure of the lever of the intermediate rolls is determined based on the bearing housing and load of the mode of running with fewer than all nips, and the levers and bearing housings of different roll positions can be adjusted to each other by reducing the roll size. A wider roll can be provided for the lever and bearing housing if the load when running with fewer than all nips is reduced in order to maintain stress of the lever. Support according to this embodiment of the invention makes it possible to increase speed and width, in addition to which the temperature of thermo rolls can be increased to over 300 ⁰ C and possible interme¬ diate moisturizing can be arranged in connection with the calender, thus increas¬ ing calendering capacity.

In the calender according to the invention, when utilizing advantageously load¬ able-shell rolls as the upper and lower rolls of the sets of rolls, frictions are re¬ duced significantly even down to a third compared to conventional applications. When the friction is small, the preciseness of the linear load in the edge areas of the web is also improved.

In the invention it is also possible to increase the rate of motion of a set of rolls to a value of about 15mm/s, meaning that the target running speed and target quality are achieved faster than in calenders known from prior art.

The method according to the invention for loading a bearing of a calender roll of a multiroll calender is mainly characterized in what is presented in the characteriz¬ ing part of claim 18.

The multiroll calender according to the invention is in turn mainly characterized in what is presented in the characterizing part of claim 27.

In connection with the invention it is advantageous that the centre shaft of at least one calender roll is arranged inside or outside a nip plane in a multiroll calender having one or two sets of rolls and, according to one embodiment, the centre shaft of at least one calender roll is arranged fixedly inside or outside the nip plane. The centre shaft of the upper roll in a stack of rolls of a multiroll calender is advanta¬ geously arranged fixedly inside the nip plane to create a horizontal force compo¬ nent on the bearings of the upper roll while the upper roll is in nip contact.

According to an embodiment of the invention the centre shaft of at least one cal¬ ender roll is moved to the inside or outside of the nip plane, in which case the path of travel of the centre shaft may be circular or linear or a combination of these.

The centre shaft of the intermediate roll above the lower roll is advantageously moved aside the nip plane to create a horizontal force component on the bearings of said intermediate roll while the intermediate roll is in nip contact.

Compared to formerly known arrangements significant advantages are achieved by means of the invention, the advantages including, among others, the following. Since the centre shaft of the calender roll of a multiroll calender is located or can be located aside the nip plane formed by the centre shafts of the other calender

rolls, a horizontal force component dependent on linear load is directed to the bearings of this calender roll. This horizontal force presses the rolling elements and rolling surfaces of the bearings against each other and prevents the rolling elements from sliding on the rolling surfaces. By means of said horizontal force the linear load area, in which the load on the bearings of the calender roll would be too small, can be essentially reduced. In a calendering nip in a so-called zero load situation the rolling members of a roller bearing do not have the possibility to slide, instead of rolling, relative to the bearing frames, which results in longer service life of the bearing and of the fibrous web machine in general. Thus, runs needed for replacing broken bearings and for cooling down and warming up of heatable calender rolls can be avoided and thus the production capacity of the cal¬ ender is improved. This reduces the need to store that large numbers of bearings in case bearings break down.

Various applications and advantageous additional features of the invention are particularly well suited for fast calenders having a running speed of 1700-1800 m/min and advantageously for calenders having a width of more than 4-5 meters and especially advantageously for calenders operating as online calenders in paper machines.

The invention will now be described with reference to the accompanying draw¬ ings of principle illustrating the method and multiroll calender according to the invention, without, however, confining the invention strictly to what is presented in the drawings.

Figures 1-7 schematically show some embodiments for carrying out the method according to the invention in a multiroll calender having two sets of rolls for real¬ izing various types of runs.

Figure 8 schematically shows an advantageous embodiment for a roll locking ar¬ rangement.

Figure 9 schematically shows an example of a wide calendering work area achieved according to the invention.

Figures 10-15 schematically show some embodiments of running types to be car- ried out in the method and calender according to the invention, in which running types the calendering work area is wide.

Figure 16 shows a stack of rolls of a multiroll calender, the stack of rolls having five rolls and four nips, in which stack of rolls the centre shaft of one calender roll can be located essentially inside a nip plane formed by the centre shafts of the other calender rolls.

Figure 17 shows nip force having an effect in a calendering nip, which nip force is divided into horizontal and vertical components, while the centre shaft of one cal- ender roll is located essentially inside a nip plane formed by the centre shafts of the other calender rolls.

Figure 18 shows a multiroll calender comprising two stacks of rolls.

Figure 19 shows a stack of rolls of a multiroll calender, in which stack of rolls it is possible, by means of a linear motion, to move the centre shaft of a calender roll essentially to the inside and outside of a nip plane formed by the centre shafts of the other calender rolls.

Figure 20 schematically shows a roll support arrangement according to an advan¬ tageous embodiment of the invention.

Figure 21 schematically shows a roll support arrangement according to an advan¬ tageous embodiment of the invention in connection with an upper roll.

Figure 22 schematically shows a calender frame structure used in connection with a support arrangement according to an advantageous embodiment of the inven¬ tion.

In the following Figures 1-22 the same reference numerals and markings have been used for parts and structures mainly corresponding to each other, unless stated otherwise.

Figures 1-7 schematically show some embodiments for carrying out the method according to the invention in a multiroll calender having two sets of rolls for real¬ izing various types of runs. Multiroll calender 150 shown in Figures 1-7 com¬ prises two sets of rolls 2OA and 2OB, a fibrous web W being calendered in the nips between the calender rolls of said sets of rolls. Reference numerals 21B-26B starting from the top refer to the rolls of the set of rolls 2OB and reference mark- ings 21A-25A refer to those of the set of rolls 2OA. In the embodiments presented in the figures rolls 21A, 25 A, 22B, 26B are soft-surfaced (polymer-surfaced) sym- rolls, rolls 22A, 24A, 23B, 25B are steel rolls, either heatable and/or coolable rolls, rolls 23 A, 23B are polymer-surfaced rolls and roll 21B is a polymer- surfaced roll. The running types with fewer than all nips achieved by means of the invention are realized such that the lowest or second lowest intermediate roll of each set of rolls 2OA, 2OB can be locked by means of a hydraulic cylinder to a lower position, whereby, by loading the rolls above or below the locked roll, a required number of nips can be provided for use. In the embodiments disclosed in Figures 1-6 the draw of the web W remains the same irrespective of the type of running. Figure 7 discloses an application for realizing a matte run, in which case the web W is passed, according to the application presented in the figure, only to the set of rolls 2OB through a matte nip 21B, 22B formed by the two uppermost rolls. Figures 1-7 schematically show different types of running. A person skilled in the art will understand, based on the text, which nips are open and which nips are closed (in other words, which nips are used in calendering).

By means of the running type disclosed in Figure 1 a type of running is provided, in which calendering is carried out in both sets of rolls by means of five rolls i.e. in the set of rolls 2OB by means of rolls 22B-26B and in the set of rolls 2OA by means of rolls 21A-25A. The figure discloses a 5+5 running type application and, in the application disclosed in the figure, rolls 24A and 25B are locked. This type of running is especially well suited for SC paper grades, coated paper and board.

Figure 2 discloses a type of running in which five rolls i.e. rolls 22B-26B are used in the set of rolls 2OB and three rolls i.e. rolls 23 A-25A are used in the set of rolls 2OA. The figure discloses a 5+3 running type application and rolls 24A and 25B are locked. This type of running is especially well suited for SC grades.

Figure 3 discloses a type of running where three rolls i.e. rolls 24B-26B are used in the set of rolls 2OB and all five rolls i.e. rolls 21 A-25A are used in the set of rolls 2OA. The figure thus discloses a 3+5 running type application and rolls 24 A and 25B are locked. This type of running is especially well suited for SC grades.

Figure 4 discloses an embodiment in which, in the running type, in both sets of rolls 2OA, 2OB the three lowest rolls, i.e. rolls 24B-26B and 23A-25A are used. The figure illustrates a 3+3 running type application and rolls 24 A and 25B are locked. This type of running is especially well suited for SC grades, particularly for SC-B paper grade.

Figure 5 shows a calender 150 arranged as a two-nip soft calender, i.e. utilizing the lowest two rolls 25B-26B and 24A-25A of both sets of rolls 2OB, 2OA. The running type application shown in the figure is typically suited for a running type of an Optisoft-type calender, when a two-nip calender is in question, and the locked rolls are rolls 24 A and 25B. This type of running is especially well suited for a calender for uncoated board and for newsprints.

Figure 6 shows a type of running in which a calender 150 is arranged to corre¬ spond, as to its running type, to a one-nip soft calender, in which case the lowest two rolls i.e. rolls 25B-26B of the set of rolls 2OB are used. The running type ap¬ plication illustrated in the figure corresponds in a way to the running type of a one-nip Optisoft-type calender, roll 25B being the locked roll. This type of run¬ ning is advantageous when running uncoated board and newsprints.

Figure 7 shows an embodiment providing a matte type of running, in which case soft-surfaced rolls 2 IB, 22B, arranged as the two uppermost rolls of the set of rolls 2OB, are used. The running type application shown in the figure corresponds in a way to the running type of an Optisoft-type calender intended for matte grades. This type of running is thus suited for use in the manufacture of matte- surfaced paper grades, especially when running coated paper grades such as LWC, MWC and WFC.

As can be seen from Figures 1-7, the web can, according to the invention, be passed freely first to the upper or lower nip according to the layout and the re¬ quirements of the production line.

Figure 8 schematically shows an example for a locking arrangement of a lockable roll, in which arrangement a hydraulically lockable relief cylinder is used. Refer¬ ence numeral 42 refers to the hydraulic locking arrangement and reference nu¬ meral 43 to the relief cylinder.

Figure 9 shows an example of a" wide calendering work area achieved according to the invention. The application of the figure is shown in connection with a 10-nip calender having two sets of rolls, by means of which calender a calendering work area i.e. a loading area according to the figure is achieved. In the figure the verti¬ cal axis illustrates the type of running, shown as the total number of nips and in parentheses by means of a value, e.g. in the form 1 nip (1/0), illustrating the num¬ ber of nips each set of rolls has in use. The horizontal axis demonstrates in turn

calendering work kN/m X nip. As can be seen from the figure, any kN/m x num¬ ber of nips running value is achieved by means of the calender according to the example. When running the entire set of rolls, the minimum linear load of the cal¬ ender is selected such that its product with the number of nips is the same as the corresponding value of four nips performing running with fewer than all nips (The minimum linear load for the entire set of rolls is, for example, 50 kN/mm and 4/4 running type is compared with 2/2 running type). As can be seen from the figure, running types 0/4; 1/4 and 2/4 produce one-sided paper. The figure assumes that the loads when running with fewer than all nips can be 0 kN/m and, on the other hand, possible zero load areas of the bearings have, in practice, also to be taken into consideration. It can thus be seen from Figure 9 that zero load does not cause problems when running several different paper grades with one calender. With a running type (1/0) - (4/4) the load is between about 0 kN/m - about 3100 kN/m.

In the running type applications shown in Figures 10-11 lower draw is used in the calenders, i.e. the web W is passed from below from a first set of rolls 2OA to a second set of rolls 2OB. Corresponding running types can also be carried out by means of upper draw, i.e. passing the web above the sets of rolls from a first set of rolls to the second. In the calenders 250 according to Figures 10-11 the first set of rolls 2OA has three rolls 2 IA, 22 A, 23 A and the second set of rolls has five rolls 21B, 22B, 23B, 24B, 25B. In the application shown in Figures 12-15 both sets of rolls 2OA and 2OB both sets of rolls have five rolls i.e. the first set of rolls 2OA comprises rolls 21 A, 22 A, 23 A, 24 A, 25 A and the second set of rolls 2OB com¬ prises the rolls 21B, 22B, 23B, 24B, 25B. In the figure the letters inside the roll refer to the type of roll: SYM = loadable roll with a movable or fixed shell, e.g. a similar roll to the one marketed by the applicant by the name SymRoll, P = poly¬ mer-coated roll and T = heatable, metal-surfaced roll i.e. a so-called thermo roll. The minimum linear load of the set of rolls is indicated in the rectangular boxes in the figures. Fixedly positioned rolls of the calender are shown in the figure pro- vided with locking means 251.

Figure 10 shows a running type in normal calendering, in which type two nips are in use in the first set of rolls 2OA and four nips in the second set of rolls 2OB. By means of the calender 250 according to the figure 2/0 running type can also be carried out, whereby the second set of rolls is bypassed, or 0/4 running type can be used, whereby the first set of rolls is bypassed.

Figure 11 shows matte calendering applications in a calender according to Figure 10, which calender enables running types 1+1/1+1; 1/1; 1/0; 1+1/0; 0/1+1 and 0/1. In the Figure rolls 22A, 22B and 24B are fixedly locked to their position by means of locking means 251 for achieving the running type applications. Roll 23B may roll at crawl speed during calendering.

Figure 12 shows matte calendering applications in which running types 1+1/1+1; 1/1; 1/0; 1+1/0; 0/1+1 and 0/1 are realizable. As can be seen from the figure, this arrangement makes it possible to achieve versatile running possibilities for differ¬ ent matte grades, meaning that a soft calender is not necessarily needed.

Figure 13 in turn shows normal calendering applications for running types 4/4; 4/0 and 0/4.

Figure 14 schematically shows bypassing of the second set of rolls 2OB, for ex¬ ample when changing a roll in the second set of rolls 2OB. Running types 4/0; 1+1/0 (running with fewer than all nips) are thus enabled. It is also possible to replace the second thermo roll of the first set of rolls 2OA with a polymer-coated roll.

Figure 15 in turn shows schematically bypassing of the second set of rolls 2OA for roll change, thereby enabling running types 0/4; 0/1+1 (running with fewer than all nips); 0/1+0. (running with fewer than all nips); 0/0+1 (running with fewer than all nips) and 0/0 (the web being run past both sets of rolls).

In connection with Figures 16-19 the term nip plane refers to a plane formed by the centre shafts of calender rolls, which plane in some connections is also re¬ ferred to as nip line. The definition inside a nip plane refers in this connection to a location on the side of the nip plane situated on the side of the frame of a multiroll calender.

Figures 16-19 schematically show multiroll calenders 100 and Figure 18 sche¬ matically shows a multiroll calender 200. The figures particularly show stacks of rolls 10a, 10b, 10c, 1Od comprising an upper roll 11 and a lower roll 15 as well as three intermediate rolls 12, 13 and 14 arranged between the upper and the lower roll, whereby the upper, lower and intermediate rolls form the calender rolls 11-15 of each stack of rolls. A fibrous web being calendered in the multiroll calender is not shown. In the stacks of rolls adjacent calender rolls 11,12; 12,13; 13,14 and 14,15 form calender nip pairs, in which the calender rolls form in each occasion between themselves a nip 1, 2, 3 and 4 calendering the fibrous web as shown by the reference numerals of Figures 16-19 from the top down. The invention has been described in this connection by using a five-roll, four-nip stack of rolls as an example in each case, but another number of rolls and nips in a stack of rolls may as well be used. It is also possible to apply the stack of rolls shown, in each occa- sion, in connection with the one-stack multiroll calender 100 of the invention in a multiroll calender comprising two or more stacks and to apply the stack of rolls shown in connection with the two-stack multiroll calender 200 in a multiroll cal¬ ender comprising one or more stacks.

Pressing of a fibrous web can be provided in a multiroll calender either by anchor¬ ing the upper roll 11, lower roll 15 or any one of the intermediate rolls 12, 13, 14 in the stack of rolls to its place relative to the frame of the calender, which frame is illustrated by means of a dot-and-dash line with the reference marking F, and by pressing a stack of rolls/a single roll against a roll anchored to its place relative to the frame F, which anchored roll may be the upper roll 11, lower roll 15 or, for example, one or some of the intermediate rolls 12, 13, 14. Alternatively, both the

upper and lower roll are pressed against each other either such that none of the intermediate rolls is fixedly locked to its place or such that at least one intermedi¬ ate roll is fixedly locked to its place. The pressing forces of the upper roll 11 and/or lower roll 15 can in many arrangements be adjusted independently of each other. In a multiroll calender an upper roll and/or lower roll may be provided with a loading apparatus arranged inside the shell and/or the upper roll may be loaded by means of a superjacent loading cylinder and/or the lower roll may be loaded by means of a subjacent loading cylinder 16. Roll deflections can be compensated for by means of equipment for compensating for deflections residing in the rolls, for example such that the deflection lines of the rolls have almost the same form. Equipment for compensating for deflections typically resides in the upper and/or lower roll, but one of the intermediate rolls may also be provided with equipment for compensating for deflections.

Figures 16-19 shows stacks of rolls of multiroll calenders 100, 200 in a position where an upper nip 1 and an intermediate nip 2 are closed, an intermediate nip 3 is open and a lower nip 4 is closed, in which case the fibrous web is calendered in the closed nips 1, 2 and 4.

In Figures 16-18 the lowest intermediate roll 14, especially the centre shaft C ₁₄ of the intermediate roll 14 is arranged to be movable along a circular path T. The mid point of the circular path T is a joint 17 located in the frame F of the multiroll calender. For example, the intermediate roll 14 is mounted by means of bearings on the frame F of the multiroll calender by means of a supporting and loading lever turning around the joint 17, the lever not being illustrated in more detail. The lowest intermediate roll 14 may also be brought into contact with a superja¬ cent intermediate roll 13, as illustrated by means of a position 14' of the interme¬ diate roll 14, the position 14' being presented by means of dashed lines.

The centre shafts of the calender rolls in the stacks of rolls of the multiroll cal¬ enders 100, 200 are in the same direction. According to the invention the centre

shaft of at least one calender roll either is or may be arranged to be located on the inside or outside of a nip plane formed by the centre shafts of other calender rolls when said at least one calender roll is in nip contact. The centre shafts of the cal¬ ender rolls are marked by means of the reference marking C and by means of a subindex corresponding to the reference numeral of a particular roll.

In Figure 16 the centre shaft C ₁₄ of the intermediate roll 14 can be arranged to be located inside a nip plane P formed by the centre shafts C ₁₁ , C ₁₂ , C ₁₃ and C ₁₅ of the other calender rolls 11, 12, 13 and 15 of the stack of rolls 10a, intermediate roll 14 being in nip contact with a superjacent intermediate roll 13, e.g. in position 14', the centre shaft being marked with C ₁₄ -. The centre shaft C ₁₄ of the intermedi¬ ate roll 14 is arranged to be movable along a circular path T. The centre shaft C ₁₄ of the intermediate roll 14 can also be arranged to be located inside the nip plane P, the intermediate roll 14 being at the same time in nip contact with the superja- cent intermediate roll 13 and a subjacent lower roll 15. The centre shaft C ₁₄ of the intermediate roll 14 can be arranged to be located inside the nip plane P, while the intermediate roll 14 is in nip contact with the lower roll 15 only.

For the nip contact of the intermediate roll 14 it is also possible to arrange the centre shaft C ₁₄ of the intermediate roll 14 in the same nip plane P as the centre shafts of the other calender rolls. According to Figure 16, the curved path T of the centre shaft C ₁₄ of the intermediate roll 14 runs past the nip plane P when the cen¬ tre shaft C ₁₄ is at the same height with joint 17.

It is possible to affect in various ways the path T of the centre shaft of a calender roll arranged to be moved to the outside or inside of the nip plane P such as by selecting the location of the joint 17 in the frame F, the distance of the centre shaft C ₁₄ from the joint 17 and the angular position of said lever relative to the frame F appropriately. The path of the centre shaft C ₁₄ does not need to be circular as illus- trated in Figure 16 but it is essential for the path T to have a geometry that makes it possible to arrange the centre shaft C ₁₄ on the outside or inside of the nip plane

P for the nip contact of the intermediate roll 14. The linear path of the centre shaft of a calender roll is illustrated by means of Figure 12 and the description relating to it.

The curved path T of a calender roll and its centre shaft may of course also be defined to be such as that illustrated in Figure 17, in which case the highest point of the path T is a point of contact and intersection with the nip plane P and the, for example, circular path T continues below said intersection point. Then, in an ar¬ rangement according to Figure 17 it is possible to arrange a nip contact of an in- termediate roll 14' with a superjacent intermediate roll 13 on the nip plane P, the centre shaft C ₁₄ of the intermediate roll 14 being on the same horizontal plane as a joint 17, and it is also possible to arrange the nip contact of the intermediate roll 14' with a lower roll 15 on the nip plane P.

Figure 17 illustrates nip force FN acting especially in a calendering nip, which nip force is divided into a horizontal force component FH and a vertical force compo¬ nent Fv, the calender roll being located substantially aside relative to a nip plane P formed by the centre shafts of the other calender rolls of the stack of rolls. In Fig¬ ure 17 particularly the centre shaft C ₁₄ of an intermediate roll 14 is arranged essen- tially inside the nip plane P formed by the centre shafts C ₁₁ , C ₁₂ , C ₁₃ and C ₁₅ of the other calender rolls 11, 12, 13, 15 of the stack of rolls 10b.

By means of the method and multiroll calender of the invention a zero load situa¬ tion of the roller bearings of the intermediate roll 14 can be prevented, a situation that might occur when it is desired to run linear loads bringing about a very small load on the roller bearings. In a zero load situation the rolling members of the rol¬ ler bearing would be enabled to slide, instead of roll, relative to bearing frames resulting in speedy wear and break down of the bearing. The force effect on the calendering nip caused by acceleration of gravitation and the mass of the interme- diate roll 14 can, as is known, be relieved by means of actuators such as cylinder actuators acting, for example, between the frame and supporting and loading lev-

ers of the multiroll calender. A horizontal force component F _H dependent on the linear load is directed to the bearings of the intermediate roll 14 due to the way of locating the intermediate roll 14 disclosed in Figure 17. By means of the method and multiroll calender of the invention the linear load area in which the loading of the roller bearings of the intermediate roll 14 would be too small can be reduced.

Figure 18 shows a multiroll calender 200 comprising two stacks of rolls. The stack of rolls 10a on the left has already been described previously in this descrip¬ tion in connection with Figure 16. The right-hand-side stack of rolls 10c of a two- stack multiroll calender 200 comprises one calender roll whose centre shaft is arranged essentially inside a nip plane P formed by the centre shafts of three cal¬ ender rolls of the stack of rolls 10c and another calender roll whose centre shaft can be arranged essentially inside and also outside a nip plane P formed by the centre shafts of three other calender rolls of the stack of rolls 10c.

The centre shaft Cn of the uppermost calender roll 11 of the right-hand-side stack of rolls 10c of a multiroll calender 200 is arranged essentially inside a nip plane P formed by the centre shafts C ₁₂ , C ₁₃ and C ₁₅ of three calender rolls 12, 13, 15 of the stack of rolls 10c. The uppermost calender roll is a fixed upper roll 11 fixedly attached to the frame F of the multiroll calender, for example at its bearing hous¬ ing 18. Alternatively, the centre shaft C ₁₁ may be located outside the nip plane P. Because the centre shaft C ₁₁ is located aside the nip plane P, a horizontal force component dependent on the linear load is directed to the bearings of the upper roll 11. The linear load area in which the loading of the roller bearings of the up- per roll 11 would be too small can be reduced taking said horizontal force compo¬ nent into consideration and thus a situation is enabled where the rolling members of the roller bearing are able to roll, relative to the bearing frames, instead of slide, which sliding would cause speedy break down of the bearing.

The centre shaft C ₁₄ of the lowest intermediate roll 14 of the stack of rolls 10c of a multiroll calender 200 can be arranged to a position C ₁₄ essentially inside the nip

plane P formed by the centre shafts C ₁₂ , C ₁₃ and C ₁₅ of three calender rolls 12, 13, 15 or to a position C ₁₄ ' outside said plane. In other words, the intermediate roll 14 may be arranged to be in nip contact with the superjacent intermediate roll 13, namely, for example, in a position 14,' aside the nip plane P and the intermediate roll 14 may be arranged to be in nip contact with a subjacent lower roll 15 aside the nip plane P, namely, for example, in position 14. In Figure 18 the path T of the intermediate roll 14 of the stack of rolls 10c differs from calender roll paths dis¬ closed in Figures 16 and 17 such that the curved path T of Figure 11 intersects the nip plane P and continues from the inside of the nip plane P to the outside. Be- cause the centre shaft C ₁₄ of the intermediate roll 14 is located aside the nip plane P, a horizontal force component dependent on the linear load is directed to the bearings of the intermediate roll 14. The linear load area in which the loading of the roller bearings of the intermediate roll 14 would be too small can be reduced taking said horizontal force component into consideration, and thus a situation is enabled where the rolling members of the roller bearing are able to roll, relative to the bearing frames, instead of slide, which sliding would cause speedy break down of the bearing.

Figure 19 shows a stack of rolls 1Od of a multiroll calender, in which stack of rolls a calender roll can be moved by a linear motion such that the centre shaft of the calender roll can be arranged essentially inside or outside a nip plane formed by the centre shafts of the other calender rolls of the stack of rolls 1Od. In the exam¬ ple of Figure 19 the lowest intermediate roll 14 can be moved by a linear motion essentially aside the nip plane formed by the centre shafts Cn, C ₁₂ , C ₁₃ and C ₁₅ of the other calender rolls 11, 12, 13, 15 of the stack of rolls 1Od. Said linear motion may be horizontal according to a path L _H or the linear motion may be inclined relative to the horizontal plane, for example, according to a path LA. What is es¬ sential for the paths L _H , LA is that the centre shaft C ₁₄ of the intermediate roll 14 can be arranged outside or inside the nip plane P for nip contact of the intermedi- ate roll 14. This makes it possible to bring about, via the location of the centre shaft C ₁₄ , a horizontal force component FH dependent on the linear load of the

multiroll calender on the bearings of the intermediate roll 14 and thus avoid a zero load situation or a situation where the loading of the bearings of a calender roll would be too small.

It is of course possible to form combinations of the disclosed curved and linear motions or some other path whose course runs aside the nip plane P, so that the centre shaft of at least one calender roll can be arranged inside or outside the nip plane formed by the centre shafts of other calender rolls in the stack of rolls of a multiroll calender, when said at least one calender roll is in nip contact, in order to cause a horizontal force component on the bearings of said at least one calender roll.

Figure 20 schematically shows an application for a roll support arrangement, in which a roll support point Q is positioned in a calender frame 260 as close as pos- sible to the centre of gravity P of the roll. As can be seen from the figure, the sup¬ port of the roll in the frame is positioned such that distance A is as short as possi¬ ble within the layout requirements of the calender. When distance A is minimized, the moment distance/torque distance of cylinder 261 is determined such that the cylinder does not go down to end position. Distance B marked in the figure is in turn determined based on the height of the set of rolls. The roll is attached to a lever 262 attached to the frame 200, the lever being connected to the cylinder 261. The lever is advantageously made of spheroidal graphite cast iron.

According to Figure 21 a relief cylinder 261 and hydraulically lockable support cylinders 263 i.e. locking cylinders located on the outwardly facing surfaces of the lever 262 are advantageously used side by side in connection with the support of the upper rolls. When a roll is lifted by means of the relief cylinder 261 into nip contact, the relief cylinder carries part of the load. The position of the roll is locked by means of the locking cylinder 263. The support is realized such that the roll descends onto support of frame, whereby the piston of the relief cylinder does

not at any point go down to end position. In addition, hydraulic decelerating throt¬ tling ensures that the roll descends softly against the frame.

According to Figure 22 support is arranged by means of a plate, e.g. a welded plate 265 fixedly connected to a frame 260 or by means of a plate 265 formed directly in the frame. The plate 265 is advantageously continuous and extends over the entire side of the frame 260. The plates are positioned symmetrically on both sides of the calender frame for each set of rolls such that, according to the previous Figures 20-21, the lever 262 can be attached to the frame so that the roll support point in the calender frame 260 as close as possible to the centre of grav¬ ity of the roll. Notches 266 or equivalent projections are formed in the plate in order for the form of the side plate 265 to enable attaching of a relief and locking- hydraulic cylinder for each lever such that the support enables movements of the cylinders and levers.

The invention has been described above by way of example with reference to the figures of the accompanying drawings. However, the invention is not limited only to what is disclosed in the description and figures but different embodiments of the invention may vary within the inventive idea defined in the accompanying claims.