FI108058B - Process for checking the web tension of paper or equivalent web material in a roll stack and device for applying the process - Google Patents

Abstract

The invention relates to a process for checking the tension in a web material W of paper or equivalent on roll surfaces 1, for example a calender, which roll stack 1 comprises a top roll or first roll 4, a bottom roll or last roll 5 and intermediate rolls 2, 3. The intermediate rolls are arranged between the top roll or first roll 4 and the bottom roll or last roll 5, which rolls 2,3 form the roll stack 1. The web material W is guided through the nips n formed by the roll stack 1. After each nip n, the web material W is released from the surface of the roll 2, 3, 4, 5 by means of the drawing roll 6. The desired tension of the web material W is maintained and/or adjusted by adjustment, on the basis of the comparison between the determined tension level and the reference tension level, of the torques for the operation 9 of the rollers 2, 3, 4, 5, or by adjustment, on the basis of the comparison between the determined web speed differential and the reference web speed differential level, of the torques for the operation 9 of the rollers 2, 3, 4, 5. The invention also relates to devices for applying the process. <IMAGE>

Description

108058

A method for controlling the tension of a paper or similar wood material by a roll stack and a device applying the method

The present invention relates to a method and apparatus for controlling the tension of paper or similar web material by a roll stack, e.g., a calender comprising a top roll or a first roll, a lower roll or a last roll, pickings arranged between the top roll or first roll and the lower roll or last roll. which rolls form the roll stack, and that the web material is passed through nip formed by the roll stack, and that after each nip, the web material 10 is removed from the surface of the roll by means of an output roll.

JP 3158315 discloses a method for controlling the web tension in a calender. The method is based on information from a single measuring point sensor corresponding to the deflection of the web. The brake device voltage is varied according to the information obtained from the measuring point, providing a suitable web tension and eliminating web deflection.

A problem with the above method is that the measuring point is located after the first calendering nip at a point where the web passes through the upper roll and 20 soft surface rolls below it. Thereby, it is likely that, at calendars available at ever higher speeds, the tension of the web at the lowest rolls of the roll stack has become unfavorable compared to the tension set at the top roll by the t-brake mechanism.

25 96334, for its part, discloses a paper web calendering method in which rolls with their own weight are used as intermediate rolls. caused by the natural deflection line is essentially similar in shape.

An adjustable load is applied to the calendering nipples by an external load applied to the upper and / or lower roller.

It is an object of the present invention to provide a method for controlling paper or the like web material by a roll stack, such as calendars, which controls the tension of the web material as it proceeds through the nip formed by the roll stack.

To accomplish this, the method according to the invention is characterized in that the desired tension of the web material (W) is maintained and / or adjusted by: 1) determining the tension level of the web material at a defining point in the roll stack, 2) comparing the determined tension level of the web material by adjusting the moments of the drives of the rollers based on the result of the comparison.

The method according to another aspect of the invention is characterized in that the desired tension of the web material is maintained and / or adjusted by: 1) determining the slip level of the web material by measuring the web speed based on the resulting track speed ratio, 25 drive moments of the rollers to keep the track speed ratio within the desired range.

A further embodiment of the device applying the method according to the invention is characterized in that the device for maintaining and / or adjusting the desired tension of the web material comprises: 1) measuring sensors for determining the tension level of the web material at a point of determination; suction for comparing the determined tension level of the web material with the comparative tension level of the web material, and 3) adjusting means for adjusting the moments of drive of the rolls based on the result of comparison 5.

In addition, another embodiment of the device applying the method according to the invention is characterized in that, for maintaining and / or adjusting the desired tension of the web material, the device comprises: 1) gauges for determining the slip level of the web material, 2) means for determining the web speed difference; and (4) adjusting means for adjusting the moments of operation of the rolls on the basis of the resulting web speed ratio.

20

Preferred embodiments of the invention are disclosed in the dependent claims. . contracts.

Advantages of the invention may be mentioned that by adjusting the tension and slip of the web material 25, it is possible to stabilize the optimum tension / slip distribution over the entire roll stack at high speeds. Further, the quality of the web material can be better considered. For example, the paper web may have formed entire web-wide "ridges" of which the roll stack is known to propagate. The "ridges" may then equalize the paper web tension and / or slip '30 by adjusting the torque / slip ratios and the torque ratios This change substantially reduces the so-called barring effect of telapinol, which is particularly applicable to calendars and generally to sequences of multiple or successive rolls.

5, the invention will now be described by way of example with reference to the accompanying drawings, in which:

Figure 1 shows a calender.

Figure 2A shows a partial enlargement of Figure 1 according to one embodiment.

Figure 2B shows a partial enlargement of Figure 1 according to another embodiment.

15

Figure 1 thus shows a calender in which the method according to the invention is applied. The basic structure of the calendar is known in the prior art, for example, from FI 96334. Herein, a schematic structure illustrating the operation of the principle is shown. The calendar includes a plurality of rolls 4 and 5 arranged on top of the calender 20 body (not shown), forming a vertical roll stack 1. The roll stack comprises a top roll 4 and a lower roll 5. Between these is a log; a plurality of spacer rollers 2, 3, each adjacent spacer roller 2, 3 forming nip contact n with each other. The intermediate rolls 2 are hard surface rolls 2 and the intermediate rolls 3 are soft surface rolls. The roll stack may be arranged horizontally, with the intermediate rolls 2,3 being arranged between the first and last rolls instead of the top and bottom rolls. In most cases, the roll stack has intermediate rolls 2, 3 of 9 to 12, but of course the number may vary depending on the application. Preferably, each spacer roll 2a, 2b, 2c, 2d, 3a, 3b, 3c, 3d is provided with its own drive 9a, 9b, 9c, 9d, 9e, 9f, 9g, 9h, which rotates the corresponding roll 30. The drive is preferably a motor that senses position and torque (torque). Such motors include stepper motors or servo motors.

* 5 108058

In the vicinity of the top roll 4 and each intermediate roll there are disposed rollers 6a, 6b, 6c, 6d, 6e, 6f, 6g, 6h and 6i arranged in the calender body. The web material W is guided through the upper take-out roll 6a to the upper node formed by the upper roll 4 and the lower intermediate roll 2a! and detaching from the roll 2a to the second take-up roll 6a by means of the second take-up roll 6b on the opposite side of the nip n. The web material VV is similarly passed through all the nipples n2, n3, n4, n5 n6, n7, n8 and finally through the nip n9 formed by the lower roll 5 and the upper intermediate roll 2d.

Figures 2A and 2B show, by way of example, embodiments applying the method of the invention to control the tension of the web material W, for example paper, by means of a supercalender. The method can also be applied to other multi-nip roll arrangements as mentioned above. The optimal paper web path is denoted by the reference numeral W0. The differences between lines W and W0 have been exaggerated for the sake of clarity.

Fig. 2A shows a method of controlling the web material W based on a direct tension measurement and tension information by means of a roll stack. The measurement of the tension itself is known in the art. Briefly, it can be mentioned that the recesses-20 in the vicinity of the roller 6b have a a measuring transducer 7b is provided at the determination point for determining the direction of tension of the paper web W. In this case, the gauge sensor 7b determines the tension of the web material over the distance between the nipples n1 and n2. The gauge sensor 7b is, for example, a pneumatic sensor for determining the tension of the advancing web W based on a pneumatic signal applied to the web and reflected to the sensor 7b.

Figure 2A shows that the paper web W is tensioned before nip n2 and loosened between nips n2 and n3 or is at least looser than the tension of web W before nip n2. There are many reasons for this change in tension. For example, the rolls 2a and 3a forming the nip n2 30 have different diaper diameters, which causes the rolls 2a and 3a to "slip" relative to one another. Thus, the feed rate of web W at nip n2 changes, resulting in changes in web tension. The roll resistance of the rolls and the quality of the web material also influence the change in tension.

6 108058

The sensor 7b detects this change in the tension of the web VV and transmits information about the specified web tension level to the transmission path S! along the reference members 20. The reference members 20 include a memory in which at least the minimum and maximum limit information of paper tension VV can be stored. The minimum and maximum limit data form 5 reference tension levels within which the tension is desired to be maintained. Further, the reference members 20 include a logic or similar control unit that processes and compares the determined tension level of the web material VV with the reference reference plane. A communication bus s2 is provided from the comparator teams 20 to a drive 9b preferably on a roll 2a and a communication bus s3 preferably to the 10 drives 9d on the roller 2b As a result of the comparison, the communication teams 20 are transmitted to the drives 9b and 9d In this case, in order to adjust the tension of the paper web VV in the area of nipples n2 and n3 to the desired optimum tension W0, the torque of the motor 9b must be appropriately reduced and the torque 15 of the motor 9d appropriately increased or adjusted. By adjusting the torques, the web speed VV on both sides of nip n2 is substantially the same. Suitable torque changes in motors 9b and 9d cause the portion of web W under consideration, i.e. the portion between nipples n, and n3, to adjust to the optimal level W0.

The communication paths s1, s2 and s3 are preferably used for electronic, wired and / or wireless communication means known to those skilled in the art.

25

Further, the torques of the motors 9b and 9d can be adjusted by some other external means. based on one half factor. In addition to the minimum and maximum boundary information, the reference bodies 20 are arranged to receive information about changes in the Tainan W, e.g., surface irregularities. This information can be utilized to improve the quality of the web W in the area of the roll stack 1. For example, irregularities in the surfaces of the web W can be measured at some point before the roll stack and fed to the reference members 20. To eliminate or reduce at least v, the torques of the motors 9b and 9d can be adjusted 7108058 between n2 and n3. In this case, the determined web tension may be outside the tension range defined by the minimum and maximum boundary data.

In the previous embodiment, the tension of the web W is determined at a single point 5 (the point of definition can be in conjunction with any of the take-out rollers 6). The tension of the web W can also be determined from a plurality of points. I.e. a measuring transducer 7 may be provided in connection with each take-up roll (defining position) 6a, 6b, 6c, 6d, 6e, 6f, 6g, 6h and 6i of the stack 1, of which sensors 7b, 7c and 7d are shown. Here, the information obtained from the measuring sensor 6a of the first defining point 10a in the forward direction of the web W is compared to the predetermined minimum and maximum limit information of the tension level provided to the comparator members and the necessary tension adjusting operations of the web W are performed. At the same time, the tension level of the first definition point 6a, adjusted according to the above principle, for the area between the minimum and maximum boundary information constitutes a reference level 15, which is compared with the result obtained from the next definition point 6b. Similarly, after any adjustment operation, the result of setting point 6b forms a reference tension level which is compared to the tension level of the next setting point. This adjustment, based on the cascade control principle, is applied at each determination point such that the tension of the web W is controlled over the entire length of the 20 roll stack 1 through all nips n1f n2, n3, n4, n5, n6, n7, n8 and n9 (see Figure 1). Due to the plurality of defining points, and thus multiple adjustment points, the tension of the web W can be adjusted and controlled, even on the basis of an external factor, in the desired region of the roll stack 1 much better and more accurately than before.

25

Figure 2B illustrates another embodiment of the invention. It illustrates a method for controlling the tension of the web material W by means of a roll stack 1 based on various points for measuring the web speed of the web material. The parts shown in Figure 2B are denoted by the same reference numerals as the corresponding parts in Figure 2A.

30

It was mentioned above that the web speeds of the web W are different due to the slip between adjacent rolls 2a and 3a and the web W, e.g. nip n2, for example. On the other side of the nip n2, there are different ratios of the web W of web 10, i.e. 108058. the slip plane for nip n2, is measured by the measuring sensors 8b and 8c provided on the exit studs 6b and 6c. The gauges 8b and 8c are preferably arranged on the shafts of the output rollers 6b and 6c.

The sensors are preferably pulse sensors that produce at least one pulse / revolution. The web speed of web W between the two nip track sections is determined by determining the peripheral speed of the output roll, for example, based on the time taken for one revolution of the output roll when the outer diameters of the roll rolls are known. Preferably, the outer diameters of the outlet rollers are the same.

Thus, according to the example shown in Fig. 2B, the slip level between two measuring points of web W is first determined by pulse encoder 8b measuring circumferential velocity ων of the output roll 6b (first measuring point). Second, the peripheral velocity ω2 of the output roll 6c (second measuring point), which corresponds to the web speed of web W between nip n2 and n3, is measured by pulse encoder 8c. Information about the peripheral velocity ω1 of the sheath roll 6b is transmitted along the transmission path s4 to the determining means, and information about the peripheral velocity ω2 of the sheath roll 6c is transmitted along the transmission path s5 to the determining means preferably arranged with the reference means 20. The measurement means determine the circumferential velocity difference of the diapers from the measurement data, i.e. the web speed difference of web W, thus resulting from slip.

In general, it can be mentioned that the determined track speed difference is compared by means of the reference means 20 to the track speed difference previously given as a reference level. The given web speed difference corresponds to the web speed difference at some other distance W of the roll stack. The result of the comparison is the line speed ratio. This ratio is intended to be kept constant, or in the range of minimum and maximum values, by adjusting the track speed ratio obtained by adjusting the driving moments of the rollers 2,3.

108058 \ 9

In the arrangement of Figure 2B, a communication bus s6 is provided between the reference members 20 and the drive 9b of the roller 2a and a communication bus s7 is provided between the reference members 20 and the drive 9d of the roller 3a. Adjustment information based on the track speed ratio of the desired moments of drives 9b and 9d is transmitted over data paths s6 and s7 to drives 9b and 9d. Hereby, the slip and thus the tension of the web W is maintained at its optimum level W0. Of course, the torques can, if necessary, be adjusted on other grounds as mentioned above so that the track speed ratio deviates from the minimum and maximum values.

The web speed difference ratio may be determined by determining the web speed difference (or slip level) of web W as described above at least at two points on the roll stack 1. Preferably, the web speed difference first determined in web propagation direction is a reference level corresponding to a given reference level. The reference plane is determined, for example, by determining the peripheral speed difference between the ejection rollers 6b and 6f 15, i.e. the slip plane of the web W over the distance between the ejector rollers 6b and 6f (see Figure 1). The track speed ratio is obtained by comparing another determined track speed difference with the reference level. The second track speed difference is determined, for example, by determining the peripheral speed difference between the diapers of the output rollers 6f and 6i. Comparison is performed with reference members 20 (not shown in Figure 1).

20

Preferably, in a preferred embodiment of the invention, a pulse sensor is provided in connection with each output roller 6a, 6b, 6c, 6d, 6e, 6f, 6g, 6h and 6i. In this case, there is only one nip between the two measuring points, the slip of which is defined by the two measuring points mentioned above. In this case, it is advantageous for any of the three consecutive measuring points of the track-1 to determine the track speed difference ratio so that the first and second measuring points determine the reference level of the track speed difference. The second and third measuring points determine the second track speed difference. Comparison of the reference plane and another track speed difference results in the track speed ratio. In this way, by utilizing the cascade-30 control principle, the tension of the web material at the desired position on the roll stack 1 can be better controlled.

• · · 10 108058

Above are two arrangements with preferred variations for maintaining and adjusting the tension of the web material, the first based directly on the determination of the tension and the second based on the determination of changes in web speed. Both arrangements can be utilized simultaneously to determine the tension and slip and, based on this information, to maintain and / or adjust the desired tension.

The invention is not limited to the embodiments shown, but may be varied within the scope of the invention, for example, in terms of structure and positioning of components 10 and methods of measuring stresses and line speeds.

• · «• · i

Claims (12)

A method of controlling the stress in a web material (W) of paper or the like on roll surfaces (1), e.g. a calender, said roll stack (1) comprising a top roll or first roll (4), a bottom roll or a last roll (5), intermediate rolls (2a, 2b, 2c, 2d, 3a, 3b, 3c, 3d), which are arranged between the top roll or the first roll (4) and the bottom roll or the last roll (5), which rolls (2a, 2b, 2c, 2d, 3a, 3b, 3c, 3d, 4, 5) form the roll stack (1), and that the web material (W) is passed through the nip (n) formed by the roll stack (1), and that after each nip (n), the web material (W) is released from the roll (2a, 2b, 2c, 2d, 3a, 3b, 3c), 3d, 4, 5) surface by means of the pull-out roller (6), characterized in that the desired tension of the web material (W) is maintained and / or controlled by: 1. determining the tension level of the web material (W) at a point of determination within the roll stack (1) range, 2. comparing the determined voltage level of the web material (W) with the reference voltage level of the web material (W), and 3) on the basis of the comparison result, regulate the torque of the rollers (2a, 2b, 2c, 2d, 3 a, 3b, 3c, 3d, 4, 5) operation (9a, 9b, 9c, 9d, 9e, 9f, 9g, 9h, 9i, 9j). 2. A method for checking the tension in a web material (W) of paper or the like on roll surfaces (1), e.g. a calender, said roll stack (1) comprising a top roll or first roll (4), a bottom roll or a last roll (5), intermediate rolls (2a, 2b, 2c, 2d, 3a, 3b, 3c, 3d), which are arranged between the top roll or the first roll (4) and the bottom roll or the last roll (5), which rolls (2a, 2b, 2c, 2d, 3a, 3b, 3c, 3d, 4, 5) form the roll stack (1), and that the web material (W) is passed through the nip (n) formed by the roll stack (1), and that after each nip (n) the web material (W) is released from the roll (2a, 2b, 2c, 2d, 3a, 3b, 3c), 3d, 4, 5) surface by means of the pull-out roller (6), characterized in that the desired tension of the web material (W) is maintained and / or controlled by: Determining the sliding level of the web material (W) by measuring the web speed in two measuring points and determining the web speed difference between the measuring points, 2. comparing the web speed determined (W) speed difference with the reference number of web material (W) speed difference, and 3rd reg clay, on the basis of, as a result of the comparison, obtained difference for the web speed, the momentum of the rollers (2a, 2b, 2c, 2d, 3a, 3b, 3c, 3d, 4, 5) (9a, 9b, 9c, 9d, 9e, 9f, 9g, 9h, 9i, 9j) to maintain the difference in web speed within desired ranges. . Method according to Claim 1, characterized in that the reference voltage level is the voltage level at the previous measuring point and / or the reference voltage level is a given voltage level. 15 Method according to claim 2, characterized in that the path speed difference level is the path speed difference between two measurement points and / or reference level is a given path speed level. 20 5. A method according to claim 2, characterized in that the web speed difference of the web material (W) is determined by determining the difference for the peripheral speed between two extension rollers (6). Method according to claim 1 or 2, characterized in that the voltage and the sliding are measured and the desired voltage is maintained and / or controlled simultaneously according to a method according to claims 1 and 2. 7. Device for controlling the tension in a web material (W) of paper or the like on roll surfaces (1), e.g. a calender, said roll stack (1) comprising a 30. top roll or first roll (4), a bottom roll or a last roll (5), intermediate rolls (2a, 2b, 2c, 2d, 3a, 3b, 3c, 3d), which are arranged between the top roll or the first roll (4) and the bottom roll or the last roll (5), which rolls (2a, 2b, 2c, 2d, 3a, 3b, 3c, 3d, 4, 5) support the roll stack (1), and that web material (W) is passed through the nip (n) formed by the roll stack (1), and that after each nip (n), the web material (W) is released from the roll (2a, 2b, 2c, 2d, 3a, 3b). 3c, 3d, 4, 5) surface by means of the pull-out roller (6), characterized in that, in order to maintain the desired tension and / or control of the web material (W), the device comprises: 1. measuring without determining the tension level of the web material (W) in a measuring point within the area of the roller stack (1); controlling the torque of the rollers (2a, 2b, 2c, 2d, 3a, 3b, 3c, 3d, 4, 5) on the base (9a, 9b, 9c, 9d, 9e, 9f, 9g, 9h, 9i, 9j) on the base of the comparison result. 8. Apparatus for controlling the tension in a web material (W) of paper or the like on roll surfaces (1), e.g. a calender, said roll stack (1) comprising a top roll or first roll (4), a bottom roll or a last roll (5), intermediate rolls (2a, 2b, 2c, 2d, 3a, 3b, 3c, 3d) which are arranged between the top roll or the first roll (4) and the bottom roll or the last roll (5), which rolls (2a, 2b, 2c, 2d, 3a, 3b, 3c, 3d, 4, 5) form the roll stack (1), and that the web material (W) is passed through the nip (n) formed by the roll stack (1), and that after each nip (n) the web material (W) is detached from the roll (2a, 2b, 2c, 2d, 3a, 3b, 3c, 3d) 4, 5) surface 25 by means of the pull-out roller (6), characterized in that, in order to maintain the desired tension and / or control of the web material (W), the device comprises: «In 1. measuring probes for determining the sliding level of the web material (W) 2. means for determining the web speed difference on the basis of the measurement results, comparing means for comparing the web material's determined web speed difference with the comparative levels of the web. is the web speed difference of the web material (W), and 4) control means for controlling the operation of the rollers (2a, 2b, 2c, 2d, 3a, 3b, 3c, 3d, 4, 5) (9a, 9b, 9c, 9d, 9e) , 9f, 9g, 9h, 9i, 9j) on the basis of the resulting velocity difference ratio obtained as a result of the comparison. 9. Apparatus according to claim 7, characterized in that the comparator voltage friend is the voltage level of a previous measuring point and / or the comparator voltage level is a given voltage level. 10. Device according to claim 8, characterized in that the path speed difference level consists of the path speed difference between two measuring points and / or the reference level is a given path speed level. 11. Device according to claim 8, characterized in that the web speed difference of the web material (W) is determined by determining the difference for the peripheral speed between two extension rollers (6). 20 Device according to claim 7 or 8, characterized in that the voltage and the sliding are measured and the desired voltage is maintained and / or controlled simultaneously according to a method according to claims 1 and 2.