The invention relates to a method according to the preamble of claim 1.

The invention also relates to a method according to the preamble of claim 12.

The invention further relates to an apparatus according to the preamble of claim 23.

The invention also relates to an apparatus according to the preamble of claim 25.

Many types of manufacturing methods of paper and board web, and paper and board machine lines are known from prior art. One example is published interna- tional patent application WO00/70144, which describes a method for manufactur- ing paper, and a paper machine line.

In arrangements known from prior art, especially in connection with finishing devices like calenders, coating machines and slitters, it is sometimes advantageous to vary the running speed instead of using constant speed, for example to avoid vibration problems and harmful effects caused by them, e. g. the barring phenome- non of coated rolls. For example, during a longer period of calendering at constant speed the roll vibrations at constant frequency tend to mark or even damage, e. g. cause dents in polymer-coated rolls. As a consequence, still greater vibration im- pulses are generated in the process and the barring problem gets worse. Due to this, particularly in off-line calendering, the running speed is sometimes varied slightly, and to avoid marking problems of the roll even a minimal speed variation is often enough. To avoid vibration problems the speed may, if necessary, also be

varied in the coating machine, winders, size press, and other devices with similar problems.

In the machines of a paper and board manufacturing line there are also other situa- tions in which it is advantageous to temporarily change the running speed. It may, for example, be advantageous to carry out grade change in a paper or board ma- chine or splicing, threading, or reeling drum exchange at a temporarily lowered speed. By this means the intended operation, e. g. splicing or threading, can be carried out more successfully and more reliably.

A speed change on an entire paper or board manufacturing line while maintaining production is, however, very difficult, because every device and sub process of the line must naturally be controlled individually according to the changed situa- tion. The operation of each sub process and the paper quality produced in that sub process usually depend greatly on the speed. To compensate for the effects the speed changes have on quality is complex even on the sub process level. The sub processes may also involve rather long stabilization delays. Due to this the con- trolling of an entire line is difficult, and in connection with speed changes part of the output is often lost.

A first object of the invention is to provide a method and an apparatus for manu- facturing paper and board, with which method and apparatus it is possible to change the running speed of one or more devices or sub processes of the manufac- turing line without disturbing the operation of the rest of the line.

To achieve this object it is a goal of the invention to provide a method and an ap- paratus suited for changing the running speed, e. g. to prevent vibration problems, particularly in connection with the finishing devices, such as calenders, coating machines, slitters and winders, used in the manufacture of paper and board.

A second object of the invention is to provide a method and an apparatus for use in the manufacture of paper and board, with which method and apparatus it is pos- sible to change the running time of the paper web between one or more devices or sub processes of the manufacturing line.

To achieve this second object it is a goal of the invention to provide a method and an apparatus suited for use in a paper manufacturing line for changing the running time of the paper web between the devices of the manufacturing line. The method and apparatus are particularly well suited for use in connection with finishing de- vices, for example for changing the length (and thus running speed) of the web between the drying section and the calender/coating device, when it is desired to change the length of free draw, for example in order to control the cooling of the paper. The method and apparatus may further be used especially, for example, to change the delay between a moisturizing device (or a steaming device or the like) and a calender nip or between a calender and a windup. Or to any other entity ob- vious to a person skilled in the art.

To achieve the afore-mentioned objects and those objects that will come out later the method according to the invention is mainly characterized in what is presented in the characterizing part of claim 1. A second main application of the method according to the invention is, in turn, mainly characterized in what is presented in the characterizing part of claim 12.

Further, the apparatus according to the invention is mainly characterized in what is presented in the characterizing part of claim 23. A second main application of the apparatus according to the invention is, in turn, mainly characterized in what is presented in the characterizing part of claim 25.

With the help of the invention the following basic applications can be achieved: 1. continuous speed oscillation (dynamic mode of operation)

2. temporary change of speed on a section of a paper or board manufacturing line (within the limits permitted by the capacity of the buffer stock) for a short pe- riod of time (dynamic mode of operation) 3. adjusting the running time of the web between actuating means (static mode of operation) 4. adjusting the moisturizing/heating/cooling time of the web in a controlled at- mosphere chamber or in free air volume.

According to the invention, a"buffer stock"for web is provided between the de- sired two devices of a paper or board manufacturing line. The buffer stock com- prises an upper set of rolls and a lower set of rolls situated on different sides of the web. The terms"upper"and"lower"are used in a non-restrictive sense, primarily to differentiate the sets of rolls and, of course, to illustrate that the sets of rolls have been placed on different sides of the web, i. e. above and below the web. In both sets of rolls the rolls have been placed in the running direction of the web at a distance from each other such that when it is desired to change the speed, the rolls of the upper set of rolls are lowered and the rolls of the lower set of rolls are raised or the rolls of one set of rolls are moved while the rolls of the other set of rolls remain stationary such that the web runs in a meandering fashion, whereby the web in a way folds between the rolls of the upper set of rolls and the lower set of rolls. In this situation the vertical distance between the upper set of rolls and the lower set of rolls is altered to adjust the length of the web as desired so as to pro- vide the required change of speed. The web runs meanderingly e. g. from the first roll of the upper set of rolls to the first roll of the lower set of rolls, and from there further to the second roll of the upper set of rolls, etc.

According to the invention, the web is fed into the buffer stock in order to de- crease the speed by increasing the distance between the upper and lower sets of rolls so that the length of the web running via the sets of rolls increases or that the web is discharged from the buffer stock formed by moving the upper and lower sets of rolls towards the position of a normal situation. When the distance between

the sets of rolls is altered at a certain rate of change and the speed at which the web enters the buffer stock remains constant, the speed at which the web exits the buffer stock depends on the rate of change. This provides the desired change of speed.

The method and the apparatus according to the invention may be applied in connection with the manufacture of a paper or board web at a desired location where a change of running speed/capacity is needed. The invention is applicable in connection with both off-line and on-line finishing devices. The invention is particularly well suited for use in connection with finishing devices, e. g. cal- enders, of on-line manufacturing lines. The only prerequisite is that the web withstands tensile stress, at least 50ON/m-800N/m, to which tensile stress the web is subjected, when the distance between the upper and lower sets of rolls is increased, and that the web withstands the air currents of free draw.

With the help of the invention it is possible to temporarily change the speed, for example in order to pass resonance vibration points, whereby the shocks occurring during vibration in the steady state do not hit the same point of the roll, since the running speed has been changed, whereby the frequency of the vibration changes.

The invention may also be applied in the adjustment of the dwell time in connec- tion with actuating devices, for example so that an upper and a lower set of rolls forming a buffer stock are placed between devices of the manufacturing line, which sets of rolls are situated in connection with an actuating means, e. g. in con- nection with a coating station or a water moisturizing station, whereby, when changing the distance between the upper and lower sets of rolls of the roll ar- rangement provided in connection with the actuating means, the dwell time of the web before an actuating means/the next device of the manufacturing line can be changed, whereby, for example after water moisturizing, the moisturizing time can be prolonged or shortened according to what is necessary or, for example,

more dwell time can be provided before the next device/treatment phase in order for the coating colour to dry.

The invention can also be used for ventilating, e. g. cooling the web, whereby ad- ditional evaporation area can be created by moving the upper set of rolls and the lower set of rolls to a desired distance from each other. In addition, due to a big enough buffer stock it is possible to temporarily lower the running speed of the calender, even to temporarily halt it, for example to carry out threading more suc- cessfully, e. g. in connection with a web-break or a similar situation or in connec- tion with roll change or roll splicing, particularly in applications in which the speed of an actuator of the paper machine is low.

The method according to the invention can also be applied in web threading and/or in connection with web threading, in which web threading is carried out either as a partial-width web, e. g. as a lead-in strip, or as full-width threading.

By placing the modifiable run of the web according to the invention e. g. in an air- conditioned chamber, in a"hood", or an equivalent space, it is also possible to heat and/or moisturize the web in a controlled and, above all, adjustable manner.

This application of the invention is based, inversely according to the inventive idea, on the fact that the evaporation/heating/adsorption area can be modified in a controlled manner, when the distance between the upper and lower sets of rolls is altered. That is to say that the heating or adsorption time changes, when the run- ning time of the web changes without the running speed needing to be changed.

The rolls of the upper and lower sets of rolls used in the buffer stock may be freely rotating rolls or even non-rotating rods or supporting structures, against which the web slides. The invention can be used in connection with various paper and board webs, i. e. with various fibrous webs including tissue paper webs. When the invention is being used, for example in connection with fibrous webs weaker

in strength (tissue and other similar webs) a support wire or another suitable sup- port fabric is used, if necessary.

The invention will now be described in more detail with reference to the figures of the accompanying drawing, to the details of which the invention is, however, by no means intended to be narrowly confined.

Figures 1A-1B schematically show the operation of a buffer stock according to the invention in connection with an application of the invention, in which applica- tion the sets of rolls of the buffer stock are in dynamic motion, Figure 2 schematically shows an application of the invention, in which application an actuating means has been placed between two buffer stocks and in which ap- plication the second set of rolls of the buffer stock is in a stable position, Figure 3 schematically shows an application of the invention, in which application a support wire is used for supporting the web, Figure 4 schematically shows a special variation of the invention, and Figure 5 schematically shows an application of the invention, in which application the web is heated and/or moisturized in a controlled and adjustable manner.

In the following description the directions upwards/downwards are used to refer to the direction that can be seen in the figures. The real moving direction of the sets of rolls of the buffer stock naturally depends on the principal substantial run- ning direction of the web in the application area in question.

In Figures 1A-1B a first device is marked with reference number 10 and a sec- ond device with reference number 20. From the device 10 a web W runs to the device 20. In a normal running situation according to Figure 1A an upper set of

rolls 12 comprising rolls 11 is situated above the web W and a lower set of rolls 14 comprising rolls 13 below the web W. The upper and lower sets of rolls 12,14 form together with the run of the web a buffer stock 15. In the normal running situation shown in Figure 1A the web W runs via the upper and lower sets of rolls 12,14 so that by increasing the distance d between the upper and lower sets of rolls 12,14 it is possible to later decrease the speed of the device 20 and corre- spondingly by decreasing the distance between the upper and lower sets of rolls 12,14 it is possible to increase the speed of the device 20. In the situation shown in Figure 1B the distance d between the upper set of rolls 12 and the lower set of rolls 14 has been increased by augmenting the amount of the web W gathered in the buffer stock 15. By increasing the distance d between the upper and lower sets of rolls in a controlled manner in a continuous operation it is possible to lower the speed of the device 20 in a controlled manner. By carrying out the phases shown in Figures 1A-1B in a reverse order (i. e. 1B, 1A) it is possible to accelerate the speed of the device 20 by discharging web W from the buffer stock 15.

In the exemplifying embodiment shown in Figures 1A-1B the upper set of rolls 12 comprises rotating rolls 11 and the lower set of rolls 14 correspondingly com- prises rotating rolls 13. Instead of the rotating rolls 11, 13, non-rotating rolls or non-rotating rods may also be used. The rolls/rods may be either eatable or coolable as needed.

In Figures 1A-1B the web W, e. g. a paper web, comes from the device 10, e. g. a drying section, at a constant speed vl. When it is desired to change the running speed of the next device 20, e. g. a calender, the device is operated so that when the speed of the device 20 is decreased, the rolls 11 of the upper set of rolls 12 are moved downwards or they remain stationary, and the rolls 13 of the lower set of rolls 14 are moved upwards, and in the position caused by the rolls 11,14, which position makes the web W run in a meandering way, the distance d between the upper set of rolls 12 and the lower set of rolls 14 is increased at a rate of change v3, whereby the buffer stock 15 formed on the runs of the web W between the

rolls 11,13 of the upper and lower sets of rolls 12,14 collects the excess amount of the web W which otherwise would have run through the device 20 at a greater speed. When it is desired to accelerate the latter device 20, the buffer stock 15 formed on the runs of the web W between the rolls 11,13 of the upper and lower sets of rolls 12,14 is discharged by correspondingly decreasing the distance d between the sets of rolls 12,14 as desired by driving the rolls 11 of the upper set of rolls 12 upwards and the rolls 13 of the lower set of rolls 14 downwards to- wards the normal running position (FIG. 1B) at a rate required by the desired change of speed, while the sets of rolls 12,14 of the buffer stock 15 are in dy- namic motion. By repeating these phases (Figures 1A, 1B) in a controlled manner and by choosing the rate of change V3 at which the distance d between the upper and lower sets of rolls 12,14 changes so that it is, for example, harmonically os- cillating, it is possible to vary the running speed of the next device 20 within cer- tain limits allowed by the size of the buffer stock 15. If the speed of the web is 1500 m/min, the oscillating speed may be, for example, 50 m/min, and if the web is"looped", for example ten times in a set of rolls, the necessary speed of motion V3 of the rolls is approximately 5 m/min maximum.

Between the extreme situations 1A, 1B the equation of the change of speed roughly applies to the change of speed brought about by the buffer stock 15: V2-VI = k v3, where k is the number of"folds", at the point marked in Figure 1A k = 4 folds, and vs is the rate at which the upper and lower sets of rolls move relative to each other. The equation can be applied in situations where the web meanders substantially 180° back and forth between the upper and lower sets of rolls.

In Figure 2 corresponding reference numbers and signs are used for parts corre- sponding to those shown in Figures 1A-1B. In Figure 2 the invention is applied in a situation in which it is necessary to adjust the distance or dwell time of an actuating means 30 with respect to a preceding device 10 and a following device 20, at least one set of rolls of the buffer stock being stable. If, for example, the actuating means 30 is a water moisturizer, by adjusting the distance d2 between

the upper and lower sets of rolls it is possible to conveniently control the adsorp- tion time of moisture i. e. dwell time 12 i. e. the distance between the actuating means 30 and the device 20 without the actuating means 30 itself, e. g. a moistur- izer, having to be made movable. This application of the invention is used, for example, when manufacturing paper or board grades that require many different types of water moisturizing. Furthermore, situating the actuating means 30 in connection with the manufacturing line becomes easier. In the application accord- ing to Figure 2 the dwell time 11 before the actuating means 30 and after the device 10 preceding the actuating means 30 is adjusted by means of the distance dl be- tween the upper and lower sets of rolls 12,14 situated before the actuating means 30, and the dwell time 12 after the actuating means 30 before the device 20 follow- ing the actuating means 30 is adjusted by means of the distance d2 between the next upper and lower sets of rolls 12,14. After the actuating means 30 the web W can be heated, cooled, or dried by selecting the rolls 11,13 of the sets of rolls 12, 14 of the latter buffer stock 15 so that they are of the desired type.

In the application according to Figure 2 the distance dl, d2 between the actuating means 30 and the device 10/20 preceding/following it is chosen, for example ac- cording to the paper grade being manufactured. When this application of the in- vention is applied in connection with coating, when changing the amount of coat- ing, it is possible to extend the drying time of the coating by increasing the dis- tance d2 between the upper set of rolls 12 and the lower set of rolls 14 of the buffer stock 15 following the coating device.

Figure 3 shows an application of the invention, in which application a support wire 40 is used in connection with the buffer stock 15. In the figure corresponding reference numbers and reference signs are used for parts corresponding to those of the applications shown in Figures 1A-1B and 2. In the application of Figure 3, to support the run of the web W, a support wire 40 is provided, which runs over the rolls 11,13 of the upper and lower sets of rolls of the buffer stock 15, and which supports the web. The length of the support wire 40 remains constant. This appli-

cation of the invention is suitable for use especially in connection with weaker fibrous webs, e. g. tissue webs. In connection with the support wire 40 guide rolls 41 of the support wire are provided, which rolls can be moved in the direction shown by arrows Sy and SA, and which are shifted, if necessary, when moving the rolls 11,13 of the sets of rolls 12,14 of the buffer stock 15. The support wire 40 can also be situated on both sides of the web W, for example an upper wire placed as shown in Figure 3, said wire running as a mirror image with respect to the sup- port wire. In the running situation according to Figure 1A the web W is passed substantially directly from the device 10 to the device 20. In Figure 4 correspond- ing signs are used for parts corresponding to those shown in Figures 1A-1B, 2 and 3. The application shown in this figure is a special variation of the invention and depicts, for example, a situation where the buffer stock 15 is not yet in use or web threading is carried out through the buffer stock 15.

The invention according to Figures 1A-1B, 2-3 can also be used for ventilating the web, for example for cooling and for control of cooling. This is based on the change in evaporation area.

According to the application shown in Figure 5 by disposing the modifiable run of the web W according to the invention e. g. in an air-conditioned chamber 50, in a "hood", or a similar space, it is also possible to heat or moisturize the web W in a controlled and, above all, adjustable manner. According to the figure the air mass in the chamber 50 has been regulated to a desired temperature/moisture level. The web W tends to set itself in a state of equilibrium. The application of the figure is based, inversely according to the previous idea, on the fact that the evapora- tion/heating/adsorption area can be modified in a controlled manner, when the distance d between the upper and lower sets of rolls 12,14 is altered. That is to say that the heating or adsorption time changes, when the running time of the web W changes without the running speed needing to be changed.