FI122761B - Method and apparatus for adjusting the position of a roll in a calender - Google Patents

Description

Method and apparatus for adjusting the position of a roll in a calender

Field of the Invention 5

The invention relates to a method for adjusting the position of a roll in a calender. The invention also relates to an apparatus for adjusting the position of a roll in a calender.

Background of the Invention

During papermaking, after the paper web has been dried, the web is calendered as a normal finishing operation. There are several calendering methods, but all of them have in common the passing of a rib through one or more nips formed between two surfaces, usually rotating roll surfaces. The purpose of calendering is to improve the quality of the paper by squeezing it to a certain constant end thickness, affecting the density of the paper and smoothing its surface to obtain the desired gloss and / or smoothness of the paper. Ts. kalante-20 rotation affects both the visual and structural properties of the paper.

The calendering roll may be a hard-surface, heated thermo roll, a soft-surface deflection-compensated roll, a soft polymer roll, or a 25-soft long nip roll. In a soft calender, at least one of the rolls forming the calender nip has a soft surface. Generally, one of the rolls forming the calender nip ™ is a hard surface thermal roll and the other is one of the soft rolls mentioned above.

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g 30 There are many types of Soft Calendars depending on the application. The single-ring construction is a calender with two rolls and thus only one 55 nip. Generally, the rolls are superimposed and the other roll is mounted LT) firmly on the calender body. The second roll is provided with loading cylinders arranged at the ends of the respective roll. Closing the calender nip and adjusting the line load is performed externally by lifting 2 rollers with load cylinders against the fixed roll by means of the load cylinders.

Calenders are also used which have an endless belt loop extending around the guide rollers and a counter element arranged outside the belt, usually a roll. The belt and roll are arranged in contact with each other so that a nip is formed between them, through which the web is passed. Such a belt calender is disclosed, for example, in WO 03/064761. The tension of the belt and its position on the surface of the guide rollers and the counter element 10 with respect to their length are controlled by moving the guide rollers. Movement of the guide rollers is accomplished by means of loading cylinders arranged at both ends thereof.

The problem with these calendars is that small changes in position-15 of the rolls are extremely difficult, if not impossible, to be accomplished with the pressure control methods currently in use. In addition, in single-nip soft calendars it has been almost impossible to drive with low line loads, i.e. line loads of less than 50 kN / m. This has been a problem especially for thin paper grades. There have also been 20 problems with nipple closing. This is due to the fact that the adjustment methods based on pressure control cannot drive the nip evenly, but when the lower limit of adjustment has been reached, the roller controlled by hydraulic cylinders has "" jumped "onto the counter roll, thereby causing errors in the calenderable web.

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Also, the small changes in the position of the guide rollers required to position the belt calender belt have also been difficult to accomplish by the adjustment methods currently available. Similarly, fine adjustment of the belt tension has been difficult to accomplish.

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BRIEF DESCRIPTION OF THE INVENTION The object of the present invention is thus to provide a novel solution for adjusting the position of a roll in a calender.

To accomplish this object, the method according to the invention is essentially characterized in what is set forth in the characterizing part of independent claim 1.

The apparatus according to the invention, in turn, is essentially characterized by what is disclosed in the characterizing part of independent claim 5.

Other dependent claims disclose some preferred embodiments of the invention.

The invention is based on the idea of adjusting the position of the roll in the calender by using a hydraulic cylinder connected to the end of the roll and supplied with a pressure medium by means of a valve 15 which controls both the flow of pressure medium to the piston rod chamber of the hydraulic cylinder. and flow of pressure medium to the piston side chamber.

20 For control of the valve, the force F exerted by the hydraulic cylinder at the end of the roll is measured by a first measuring device, such as a force transducer. The first gauge is provided with a feedback valve that controls the flow of pressure medium to the hydraulic cylinder piston rod chamber based on the measured force. Sa-25 is currently monitoring the position of the roll by measuring the flow of pressure medium Q into the piston-side chamber of the hydraulic cylinder ^

™ with another measuring device. The measured flow rate is also directed to the valve 9, which then controls the flow of pressure medium to the piston side chamber. Thus, both sides of the hydraulic cylinder g 30 are constantly under active control.

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Preferably, the valve used is a proportional valve. Proportional valves are characterized by controlled movement of the valve slide, which can be achieved by a plurality of control signals. The controlled movement of the slider 35 avoids pressure shocks and provides a smooth movement of the hydraulic actuator throughout the adjustment range. In this way, the hydraulic actuator, i.e. the hydraulic cylinder, can be controlled evenly over a wide pressure range, from low to high pressures. Furthermore, the proportional valve can be easily controlled, which control is either centrally or decentrally controlled by a control system integrated in or near the valve itself.

According to the invention, each end of the roll is provided with its own hydraulic cylinders, each with its own control system and valve.

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The invention makes it possible to precisely and quickly adjust the position of the roll included in the calender. The force measurement is an accurate measurement and gives an accurate feedback signal for valve control. The proportional valve is a sensitive valve capable of rapidly providing the control responses indicated by the measurement results and required for adjustment. The control device can achieve control speeds of up to 2-3 ms, which is a very fast adjustment and a significant improvement over the prior art controllers.

When applied to single-nip calendars, the invention enables the same calender to be driven over a wider line loading range of the calender nip, since it is possible to run from small line loads up to about 0 kN / m to large line loads. With the invention, it is possible to drive the calender with line loads of less than 50 kN / m. With the calender nipper closed, your drive is static, allowing the adjustment system to correct the position of the roll in a small area. The invention ™ makes it possible to calender both thin and thicker paper grades with the same single nip calender. The paper quality also improves 8 because it is possible to close the nip without causing it to flow iin 30 into the paper.

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The invention also enables the belt calender belt to be accurately positioned on the surface of the guide rollers and the counter element.

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BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be explained in more detail with reference to the accompanying figures, in which: FIG. 1 schematically shows a side view of a calender to which the method and system according to the invention can be applied; FIG. 2 schematically shows a side belt calender where the method and system according to the invention a control system that can be applied to adjust the position of the 15 calender rolls.

DETAILED DESCRIPTION OF THE INVENTION

Figure 1 shows a single nip soft calender, wherein the calender nip N1 N1 is formed between two rolls 1 and 2. The roll 1 is a hard surface, heated thermo roll and is supported at its ends firmly on the calender body 3. The roll 2 is a soft surface roll which is also supported at each end by means of supporting members 4 therein. The position of the roll 2 relative to the roll 3 can be changed by means of hydraulic loading cylinders 11 in communication with the supporting members 4 25. The peeling cylinders 11 move the roller 2 mainly vertically. Also, opening and closing the calendering nip in a threading situation

9 is performed by means of the loading cylinders 11. Calenderable web W

8 is guided into the nip of the web N1 from the previous manufacturing step or open ϊ the winding device 30 according to the arrow A. After the calender, the web is directed to the next processing step or rewinder. By adjusting the weapon 55 of the roller, one can influence the prevailing condition of the calendering nipple N1

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1 Although the roller movable by means of the loading cylinders is shown to be a soft surface roll, it may also be a hard surface 6 heated roller. Likewise, the movable roll may also be positioned at the top of the calender nip, so-called. the upper roll.

Fig. 2 shows a belt calender in which the calendering nip N1 is arranged by means of a calender belt 6 and a counter element thereof, i.e. a roll 7, which is in contact therewith. The calender belt is a belt in the form of 6 endless loops shown in dotted lines in the figure. The calender belt 6 passes through and is guided by guide rollers 8. At least one guide roller 8 is arranged to be movable horizontally and vertically 10 to adjust a suitable tension of the belt 6 and the position of the roller. So, at most, all the guide rollers are movable. By moving the guide rollers 8, the position of the belt 6 on the surface of the guide rollers and the roll 7 is also adjusted, i.e. its position with respect to the length of the said rolls. The belt should not only be kept in an optimum position on the guide rollers, but also be positioned so that the web to be calendered is on the belt during calendering. The guide rollers are moved by moving their ends by means of loading cylinders 11 arranged at each end. The figure shows for clarity only provided one control roll 8 with a loading cylinder 11. The calendered web 20 W, which in Figure 2 is shown in a solid line, is guided into the nip N1 in accordance with the previous web making step or the unwind direction of arrow A. After the calender, the web is directed to the next processing step or rewinder.

The strap 6 may be a metal strap, or a steel-reinforced rubber strap, a dusty sea strap, or a coated metal, rubber or polymer strap. The strap may also be coated with various coatings. If the strap 6 is made of metal, means may be provided in the calender for heating the strap 8 (not shown). The counter roll 7 may be a hard surface, heatable roll or a soft surface roll. The materials of the belt and the counter roll are selected according to the product to be calendered and the desired process equipment configuration such that the calendering nip is exposed on one side to a heated hard surface and on the other to a soft surface. I.e. the calendering belt and the counter roll have different characteristics.

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In the above calendars, the position of the at least one calender roll or calender belt guide roll is adjusted by moving said calender. roll by means of loading cylinders at both ends of the roll. Figure 3 shows a system for adjusting the position of the roll 10 in the calender. The roll 10 may be a calender roll forming a calender nip or a guide roll which guides the belt calender belt.

In other words, one hydro roll cylinder 11 is connected to each end 10a and 10b of roll 10, that is, the position of roll 10 is controlled by two hyd roll rolls 11, one connected to end 10a of roll 10 and the other to end 10b of roll 10. In the control of both hydraulic cylinders, the same means and devices are used, and in order to illustrate this, the corresponding devices are denoted by the same numerals. In the following description, only the movement of the head-15 dyn 10b of the roll 10 is described. The end 10a of the roll 10 is moved in a similar manner.

The piston rod 12 of the hydraulic cylinder 11 communicates with the roll end 10b through a loop 13 mounted thereon. In Figure 3, loops 13 are shown schematically for clarity. The position change of the roll 10 is accomplished by supplying a pressure medium to the hydraulic cylinder 11 which causes the cylinder piston and piston rod 12 attached thereto to move and the associated roll end 10b to move.

The amount of pressure medium to be fed to the hydraulic cylinder 11, such as the hydraulic fluid, is controlled by the valve 14. Valve 14 is a proportional 9 valve arranged to supply pressure medium both to the piston rod chamber 11a of the hydraulic cylinder piston through line 15g 30 and to the piston side chamber 11b of the hydraulic cylinder through the line 16b. The valve is controlled by an associated control system 55, which may be either a control system integrated into or near the valve LT). The proportional valve control system and the valve control are known per se to the person skilled in the art and are not further described herein.

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The force F exerted by the hydraulic cylinder 11 on the roll ends 10a and 10b is monitored by a first force measuring device, i.e., a force transducer 17 connected to the loops 13 provided on the roll ends. The first measuring device 17 is feedback to the valve 14.

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The position of the roll 10 is monitored by means of a second measuring device 18. For example, the second gauge 18 may be a linear sensor, such as an LVDT sensor, mounted on a line 16 transferring a proportional valve 14 pressure medium to the piston side chamber 11b of the hydraulic cylinder.

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A discharge valve 19 is provided in a line 16 conveying pressure medium 14 from valve 14 to piston side chamber 11b of hydraulic cylinder 11. The discharge valve 19 acts as a safety valve that stops the operation of the system and the position of the roller in the event of a problem. In addition, a pressure difference valve 20 is provided in the line 15 which conveys the pressure medium from the valve 14 to the piston rod chamber 11a of the hydraulic cylinder 11 for the purpose of monitoring the possible differential pressure between the ends of the roll. In particular, when closing the nip, the pressure should be the same throughout the nip length to prevent damage to the roller coatings.

The following describes how to adjust the position of the roll 10 using, for example, moving the end 10b of the roll 10. The other end 10a of the roll is moved accordingly.

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The first measuring sensor 17 measures the force F caused by the hydraulic cylinder 11 at the roll end 11b. The measurement result is fed through line 21 9 to the valve 14. The valve control system (not shown) 8 adjusts the flow of pressure medium to the chamber 11a on the hydraulic cylinder piston rod. This Q_ causes the roll position to change.

At the same time, the flow of pressure medium introduced by the valve 14 into the manna chamber of the hydraulic cylinder is measured by means of another measuring device 18. The measurement result is fed through line 22 to valve 14. The valve control system determines the position 9 of the roll from the measurement result and adjusts the pressure medium flow to the piston chamber of the hydraulic cylinder to obtain the desired position of the roll.

By means of the invention, it is possible to precisely adjust the position of the roller while driving while the nip is closed. The force measurement is more accurate compared to, for example, pressure measurements, which, together with the sensitive proportional valve, allows precise adjustment. Precise force measurement also allows the soft calender to be driven with 1 - 50 kN / m line loads.

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The position of the calender roll can be adjusted as described above, both horizontally and vertically. For example, the position of the calendering roller 2 shown in Figure 1 is adjusted mainly vertically to adjust the line pressure of the calendering nip at low line pressures. The position of the guide rollers 8 shown in Fig. 15 2 can be adjusted both horizontally and vertically to adjust the position of the belt calender belt.

The invention is not intended to be limited to the exemplary embodiments set forth above, but is intended to be extensively applied within the scope of the inventive idea defined by the following claims.

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Claims (10)

A method for adjusting the position of a roll in a calender, wherein the method comprises adjusting the position of the roll by at least one hydraulic cylinder (11) communicating with one end (10a, 10b), to which the flow of pressure fluid is fed to the hydraulic cylinder (11) in the method, the valve (14) controls both the flow of pressure medium to the piston rod chamber (11a) of the hydraulic cylinder (11) and the flow of pressure medium to the piston side chamber (11b), characterized by measuring the roll end (10a) of the hydraulic cylinder (11) 10b) and adjusting the flow of pressure medium to the piston rod chamber 15 (11a) of the hydraulic cylinder (11) based on the force measurement result and measuring and adjusting the pressure medium flow to the piston chamber (11b) of the hydraulic cylinder (11) the pressure of the medium the flow of pressure medium to the piston side chamber (11b) on the basis of the flow. 20 Method according to Claim 1, characterized in that the position of the roll (10) is determined on the basis of the pressure medium flowing into the piston-side chamber (11b) of the hydraulic cylinder (11). Method according to claim 1, characterized in that the roll is a calender roll (2) of a soft calender or a guide roll (8) of a belt calender belt ™. sj- o Method according to claim 1, characterized in that the g (30) valve is a proportional valve. CL O σ> Apparatus for adjusting the position of a roll in the calender, wherein g has a ° - hydraulic cylinder (11) having a piston rod-side chamber 35 (11a) and a piston-side chamber (11b), and the hydraulic cylinder communicating with at least one end of the roll (10a) , 10b), and - a valve (14) for controlling the flow of pressure medium to the hydraulic cylinder, and in which apparatus - the valve (14) is arranged to regulate the pressure medium supplied to both the piston rod chamber (11a) and the piston side chamber (11b) of the hydraulic cylinder (11) flow, characterized in that the apparatus comprises: - a first measuring device (17) for measuring the force (F) exerted by the hydraulic cylinder (14) on the end (10a, 10b) of the roll, which is connected to the valve (14) on the piston side of the hydraulic cylinder (11); for controlling the flow of pressure medium to the chamber (11a), and - a second measuring device (18) for measuring the flow of pressure medium (Q) 15 to the piston side chamber (11b) of the hydraulic cylinder (11), and the result of the flow measurement is arranged to be supplied to a valve (14) for controlling the flow of pressure medium to the piston side chamber (11b) of the hydraulic cylinder. Apparatus according to claim 5, characterized in that a pressure medium flow (Q) into the piston-side chamber (11a) of the hydraulic cylinder (11) is arranged to determine the position of the roll (10). Apparatus according to claim 5, characterized in that the roll is a calender roll (2) of a soft calender or a guide roll (8) of a belt calender belt ™. sj- o Apparatus according to claim 5, characterized in that the brick (14) of the valve 30 is a proportional valve. CL O Apparatus according to Claim 5, characterized in that the system comprises a load lowering valve (16). o (M Apparatus according to Claim 5, characterized in that the apparatus comprises a differential pressure valve (20).