FI117567B - Process for compensating nip load changes caused by mold defects of the sheath of a roller - Google Patents

Description

117567

The present invention relates to a method according to the preamble of claim 1 for compensating for nipple loading changes in a calender caused by deformations of a rotating roll. This type of calender comprises a first roll and a second roll forming a nip through which the web to be calendered is passed and loading means for changing the loading of the nip.

10 The purpose of calendering is to increase the smoothness and gloss of paper or cardboard and to enhance other printing surface properties. When calendering a paper or board web, i is pressed in a nip formed by two mutually arranged and rotating rolls.

The calender roll diaper shapes have very tight tolerances in shape because the roll diaper shapes cause variations in nip load. In turn, variation in nip load 15 causes a detrimental thickness variation to the calendered web. For this reason, it is sought to make the cylinders of the rolls as cylindrical as possible.

However, ideally completely cylindrical roll diapers are difficult to fabricate, but always have some roughness. In addition, the roll diapers are deformed during calender operation, for example as a result of wear.

It is an object of the present invention to provide a solution for compensating for changes in nip load caused by the deformation of the roll shell.

The invention is based on determining the shape profile of the nip forming roll shell and the nip loading devices are controlled according to the shell shape profile and the roll rotation angle of the roll due to deformation of the nipple. to compensate for the changes.

More particularly, the method of the invention is characterized by * * t. ***. 30 which is disclosed in the characterizing part of claim 1.

* * * '·.? · * · • · • ·! **. The invention provides considerable advantages.

· · • * 2 117567

The changes in nip load caused by the unevenness of the rolls, i.e. changes in the compression pressure on the web in the nip, are reduced, thus also reducing the thickness variation of the calendered web and improving the quality of the end product. The solution of the invention is able to compensate especially for load changes of long wavelength. In addition, the premature wear of the rolls due to load changes is reduced.

The invention will now be described in more detail with reference to the accompanying drawings.

Figure 1 is a side view of a two-roll calender.

10

Figure 2 is a schematic view of an embodiment of the invention in the calender of Figure 1.

Figure 3 is a side elevational view of a multi-roll calender with suspension rollers for the intermediate rolls provided with relief cylinders.

15 \

Figures 1 and 2 show a soft calender 1 comprising a lower roll 3 and an upper roll 2 which are arranged in a nip contact with one another during travel of the calender. Thereby, between the rotating rolls 2, 3, there is a nip N of a compression length, through which the web 9 to be calendered is passed and where the compression force is applied to the web 9.

20 * »* * *

The top roll 2 is a deflection compensated roll of type N adjusting the web 9

• · · · · ·, applied purge pressure or nip load in the transverse direction of the web 9. Or, the bump-compensated roller 3 can adjust the transverse thickness and gloss profile of the web 9. The deflection-compensated roller 3 comprises a stationary shaft which is • surrounded. t • · · ·. · * ·. The 25 rails are provided with a tubular, rotating roll mantle. The roller sheath is mounted on both ends of the shaft by means of bearings. The sheath is usually cast iron and it is. coated with a coating, preferably a flexible polymer coating. The shaft is • · ·; *** · mounted at both ends in the bearing housings 4. The bearing housings 4, in turn, are fixed • · · 'attached to the calender body 5.

. »·! 30: • · * · ·

Between the roll casing of the deflection compensated upper roll 2 and the shaft 19, hydraulic load elements 11 are provided which act on the inner surface of the roll shell in the nip plane N. The load elements 11 are supported on the roll shaft 19. The load element 11 rests 3 117567. a sliding shoe 12 arranged against the inner surface of the roll shell and a pressure chamber 13 having a pressurized medium. hydraulically oil.

Typically, the deflection compensated roll 2 has 20-60 axially spaced loading elements 11 in the longitudinal direction of the shaft 19. The number of loading elements 11 depends on the width of the deflection compensated roll 10. The distance between the centers of adjacent loading elements in the longitudinal direction of the shaft is typically 100 to 250 mm. The pressure medium is supplied to the pressure chambers 13 of the loading elements via the feed channels in the shaft 19. The feed ducts are arranged so that the load elements can be controlled individually or in zones comprising two or more load elements.

15 Typically, there are 6-8 zones that are independently controlled.

The calender lower roll 3 is a hard roll type thermo roll. The shaft of the lower roller 3 is mounted at both ends in the bearing housings 6. Each bearing housing 6 is provided with a lever arm 7 which is pivotally mounted on the calender body 5. Each of the lever arms. At the hinge 20 there is a loading cylinder 8 mounted on the calender body 5 with a piston! "·· i acts on the lever arm 7. The loading rollers 8 press the lower roller 3 against the upper roller 2 and thereby adjust the nipple load over the entire width of the nipper. The sheath of the thermal roller 3« * * · is usually made of cast iron or steel. • · heated inside by recyclable heat transfer fluid or by heating the roll • inductively indoors or externally.

• · ·; Shape defects in the jacket of the thermal roller 3, i.e., points where the roller jacket is rounded, cause the roll to rotate to nipple loading. Nippikuormituk-, ···. its changes, in turn, cause thickness variations in the calendered web 9. Kek-I · · f ', ·.' ', * ··. The solution of the present invention first determines the locations * in the jacket of the thermal roller 3 where the deformation occurs and the magnitude of the deformation. Based on these, the attribute * · e · V '. The profile of the roll mantle.

* «· • * 4 117567

The roll diaper deflections can be determined indirectly, for example, by measuring the thickness variation occurring in the calendered web 9 after the nip. From the measurement results, the shape profile of the roll shell can be determined. The thickness variation of the web 9 is measured, for example, by a suitable electromechanical device which contacts the web 5 on one or both sides or is intact on the web 9.

The roll shell deformation can also be indirectly determined by measuring the pressure variation of the hydraulic fluid in the hydraulic circuits 13 of the load elements 12 of the deflection compensated upper roll 2. In turn, based on the pressure variation and the rotation angle of the thermal roll, the shape profile of the thermal roll can be determined.

i

Roll deflection errors can be determined directly by measuring the shape of the sheath, for example, during grinding. From the measurement results, the shape profile of the roll shell can be determined.

15

Once the shape profile of the roll of the thermal roller is determined, the profile information is stored in a database 17.

The valves 14,15 of the load circuits 11 of the deflection compensated roller 2 are provided with valves 14,15, by means of which the pressure prevailing in the hydraulic circuits and thus the load exerted by the load elements 12 on the roll shell 18 can be adjusted. If * · * - * *. the load elements 11 are individually controlled, the hydraulic elements of each load element 11 being ·· * ·· • ·. two valves are connected to the circuit. The first valve 14 is connected to the hydraulic fluid supply duct and by opening the valve, the pressure of the hydraulic fluid in the pressure chamber 13 of the loading element 11 can be increased, thereby increasing the load applied by the loading element 11 to the roll shell 18. At the same time, the nipple load increases with the load- »···. ** ·. 11 in the sphere of influence. The second valve 15 is connected to the hydraulic fluid outlet duct * · · .1. but by opening it, the pressure of the hydraulic fluid in the pressure chamber 13 of the loading element 11 can be lowered, thereby reducing the load applied by the loading element 11 to the roll shell 18 • · · φ 30. At the same time, the nip load decreases on the load element «·» · ***. sphere of influence.

5, 117567

If the loading elements 11 are controlled by zones, similar valves 14, 15 are connected to the hydraulic circuit of each zone by which the loading of the loading elements of the zone to the roll shell 18 can be varied. At the same time, the nip load changes in the area of influence of the zone load elements.

5

The valves 14,15 of the hydraulic circuits of the deflection compensated roll 2 are controlled based on the rotation angle of the thermal roll and the shape profile information of the roll mantle in the database 17. The valves are controlled by the control circuit 16. From the rotational angle of the thermal roll 3 and the corresponding profile profile information of the roll shell, it can be deduced how the load on the nip-10 changes as the roll 3 rotates. The rotation speed and rotation angle of the thermal roller 3 are measured with a suitable measuring device.

The regulator 16 controls the valves 14, 15 so that the nip load is varied by the loading elements 11 in the opposite direction compared to the nipple load due to them due to the shape of the shell 15 of the thermal roll 3. If the nip load increases as a result of the deformation, the nip load is reduced by the load elements 11.

Correspondingly, if the nip load decreases as a result of a deformation, the nip load is increased by the load elements 11. For example, if there is a protrusion on the surface of the thermo roll 3, the load on the load elements 11 is changed so that the nipple load

* M

* ··. ·, 3 the surface of the diaper has a well, the load of the load elements 11 is modified so that the nip load increases at the well when it is in the nip plane N. The change in the nip load caused by the load elements 11 is sought to be substantial. • n · · ·. ***. 25 but in the opposite direction.

In another embodiment of the invention, as illustrated in Figure 3, nipple loading changes due to roll deformation are compensated in a multi-roll calender with nip loading caused by the mass of intermediate rolls 25-32 and associated auxiliaries. 30 are lightened by lightening devices fitted to the calender 20. Multi-roll fish • · · .1. the blade comprises a roll stack mounted on the calender body having deflection compensated top roll 23 and deflection compensated bottom roll 24 and intermediate rolls 25-32 arranged between the top and bottom roll. There are two or more intermediate rollers. The rolls of the roll stack are imitated 6117567 so as to form nipples through which the calendering web 21 is passed. The web 21 is first directed to the nip Nj formed by the upper roll 23 and the upper intermediate roll 25, and further through the other nips to the lower nip N9 formed by the lower roll 24 and the lower intermediate roll 32. Between the nips N N-Ng, the web 21 is taken off the surface of the rolls 5 by means of the take-up rolls 22. The structure and operation of the deflection compensated top 23 and the lower roll 24 are similar to the deflection compensated roll 2 shown in the embodiment of Figures 1 and 2.

The shaft of the upper roller 23 is mounted at both ends in the bearing housings 33 slidably attached to the vertical guides 35 mounted on the calender 34 body. The bearing housings 23 may be displaced vertically along the rails 35 by the loading cylinders 36.

15

The shaft of the lower roller 24 is mounted at both ends in bearing housings 37, which are further slidably attached to vertical guides attached to the calender body 34. Each bearing housing 37 of the lower roller 24 has a loading cylinder 38 attached to the calender body 34, by means of which the lower roller 24 can be moved .. 20 vertically.

• · · •. ·> '

• · · 'V

The intermediate rollers 25-32 are either of the hard-surface type thermal rollers or of soft-coated rolls, preferably of polymeric coating. Intermediate rollers 25-32 are cooled in a roll stack so that at least one of each roll of each nip is provided with a soft ·· «*. ***. 25 coatings. In the swivel nipple N5, both nip forming rollers 28,29 are fitted with a ··· soft coating. The shafts of the intermediate rollers 25-32 are mounted at both ends Λ • rotatably in the bearing housings 39. The bearing housings 39 are fitted with base members 40 which are • ♦ ·: '** · pivotally mounted on the calender body 34. ··. with means 20 for reducing the nip load caused by the mass of the intermediate rolls.

• · ·. ···. In the embodiment of Fig. 3, the lightening devices are pressure-medium driven lightening cylinders 20. The first end of the lightening cylinder 20 is fixed to a base • 1 * *. part 40 and the other end to calender body 34. For example, hydraulic fluid or compressed air is used as the pressure medium for the relief cylinders 20.

: -> Ϊ! 7 117567

By means of the relief cylinders 20, a relief force is applied to the base portions 40 of the intermediate rolls 25-32 to compensate, in whole or in part, for the weight of the intermediate rolls 25-32 and the auxiliary devices attached thereto.

5

In the calender of Fig. 3, changes in the nip low load due to deformations of the intermediate roll or rolls are compensated by changing the load on the relief rollers 20. In a preferred embodiment of the invention, changes in nip load caused by deformations of hard surface thermo rolls are compensated. In the solution of the invention, the locations of the outer surface of the desired intermediate roll sheath where defects occur and the magnitude of the defects which determine the shape of the outer surface of the roll sheath are first determined.

The roll diaper deformation can be determined indirectly, for example, by measuring the thickness variation in the fish-15 sharpened web 21 after the nip for which the load variation is to be compensated. Based on the measurement results, the shape profile of the roll mantle can be determined. The thickness variation of the web can be measured, for example, by means of a suitable electromechanical measuring device which contacts the web on one or both sides or is intact on the web.

The deformations of the roll diapers of the upper intermediate roll 25 and the lower intermediate roll 32 can be determined by measuring the pressure variation in the hydraulic circuits of the deflection compensated upper roll 23 and lower roll 24. In turn, the shape profile of the intermediate roll 25, 32 can be determined from the pressure variation and the rotation angle of the intermediate roll 25.32.

• ·; The shape profile of the intermediate roll can also be determined by measuring the shape of the roll shell as an example when grinding. > # * * * · · * · · * ·· * 30 After defining the shape profiles of the desired rollers, the profile data is stored in a database. Shape errors a-V 'of the upper intermediate roll 23 and the lower intermediate roll 32. 1 · 2, that is, by varying the pressures of the hydraulic circuits of the flexural roller loading elements 117567 8 ^ "according to the shape profile and rotation angle of the intermediate rolls. Then the pressure of the hydraulic fluid in the hydraulic circuits of the relief circuits of one of the rollers 20 and the nip load is altered based on the roll profile information and the angle of rotation. and 15 in the embodiment of Figures 1 and 2. The control circuit controls the valves based on the shape profile and rotation angle in the database. The speed of rotation and the angle of rotation of the roll shall be measured by means of a suitable measuring device.

The control circuit controls the valves of the relief cylinders 20 in a manner similar to that of the embodiment of Figures 1 and 2, i.e. the nip load is changed by the relief cylinders in the opposite direction relative to the nipple /? load change. If the nip load increases as a result of a deformation, the nip load is reduced with the relief cylinders. Similarly, if the nipple «« ί. "20 The load decreases as a result of a deformation, increasing the nip load on the relief • · · *, * cylinders. For example, if there is a protrusion on the surface of the roll casing, the load on the nipple cylinders is modified so that the nipple load is reduced. .¾ in the nip plane If there is a hole in the surface of the thermo roll sheath, the load on the relief rollers will be adjusted to increase the nip load at the pit to f ♦ · ··· at 25 pp. The change in the load caused by the relief rollers nipple load change due to deformation, but in the opposite direction., • · 7} φ · • «« ♦ ♦ ♦ ♦ · ♦ ♦ ♦

Claims (6)

A method for compensating nip load variations caused by mold defects in men of a roller in a calender, comprising a first rotating roller (3; 25-32) and a second rotating roller (2; 23-32), wherein the web ( 9; 21) which are calendered through the nip (N; Ni-N9) which also form, and load means (11; 20) for changing the nip load, characterized by defining a molding profile of the first roller (3; 25-32), the first roller ( 3; 25-32) rotation angle is measured and the load devices (11; 20) are controlled on the basis of the shape profile of the first roller (3; 25-32) and rotation angle to compensate for the nip load variations caused by the shape error of the first roller (3; ; 25-32) mantle. Method according to claim 1, characterized in that the shape profile of the roller sheath is defined indirectly on the basis of variations in the thickness of the calendered web (9, 21). 15 Method according to claim 1, characterized in that the shape profile of the roller sheath is indirectly defined on the basis of the change in pressure in the load; ***; the pressure medium of the device (11). The method according to claim 1, characterized in that the shape profile of the roller sheath ·· is defined directly by measuring the shape of the roller sheath. * * * · • · · • * · 20 Method according to any of the preceding claims, characterized in that the second roll consists of a bending-compensated roll (2; * 23: 24), wherein the nip load is changed by means of load elements (11) arranged therein. for compensating nip load variations caused by the shape defect of the sheath of the first roller (3; 25, 32). * · * * • ·· • * • · 25 6. A method according to any of the preceding claims, characterized in that the at least second nip forming roller (25-32) is formed; hanging devices (40) are provided with relief devices (20) to reduce the nip load caused by the weight of the roller, the nip load being changed by the relief devices (20) to compensate for the nip load variations caused by the shape errors of the first roller. ·· · * · ♦ · ♦ # · · • · · • · * · • · 1 • · ·. • · • · • 1 1 1 · * ···· • 1 · ··· 1 • · 1 • · ··· • 1 1 ··· ··· · 1 · * · • · ··.;. ··· • · 1 ·· 1 «• · · • · • · · 2 ·» »• · ····. ···: · · · 2