FI104648B - Method and device for modifying the eigen frequency of a roll nip structure in a paper or cardboard machine - Google Patents

Abstract

Method and device for modifying the eigen frequency of a roll nip structure in a paper or cardboard machine. By means of the invention the mass distribution of at least one roll in the roll nip structure is modified in oscillation. This may be done, for example, by shifting plates 13, 14 fitted inside the roll shell 11 and oscillating in respect of the centre of gravity of the roll, the weight distribution of the roll being modified in oscillation, thus also modifying the eigen frequency of the roll in oscillation. <IMAGE>

Description

104648

Method and apparatus for changing the characteristic frequency of a nip roller structure of a paper or board machine 5.

The invention relates to a method as defined in the preamble of claim 1 and to a device as defined in the preamble of claim 4.

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In paper machines and paper finishing machines, vibration is a quite significant problem and vibration problems have become more evident as current systems are constantly striving for higher speeds. There are several possible sources of vibration in paper machines, and some of them more prominent are rollers and cylinders, which comprise a large mass rotating at considerable speed. Naturally, the rolls are designed to be as accurate as possible during manufacture, and the rolls are also balanced to eliminate vibrations.

• ·.}. However, current paper machines and paper finishing equipment increasingly use soft-coated rollers which, when used, can: ·: provide a significant source of vibration. Such rolls are used, for example, in on-line: V and off-line calenders, coating machines, adhesive presses, supercalenders, and • · · v: and the like, wherein said soft-coated roll forms a nip with another roll. A paper web and possibly a felt, wire or the like are passed through the nip.

• ·: .V 25 In such a nip roll solution, when running through the nip, a seam of wire, felt or • · · · · web, significant impurities, or anything else that causes: V: a significant change in the thickness of the web passing through the nip, ** · · · ϊ., .ϊ ground, whereby the coating acts as an oscillating spring. For example, in a glue stick: "· *: in a cross member and in an adhesive press type coating device, the nip is formed by two • ·: · 30 rolls with one nip roll mounted directly on the body of said device while the opposite roll is mounted on its bearing nipple . In this case, especially the roller mounted on the 2 104648 load arms starts to vibrate, whereby the coating of the soft-surface roller is modified, as a result of which the vibration is intensified and the roll begins to resonate.

One common technique in the art for eliminating such vibrations is to change the speed of the machine 5 so that at that speed the vibration is no longer amplified but begins to damp. Vibration problems have thus limited machine speed.

Applicant FI Patent 94458 discloses a method and apparatus for adjusting the critical roll speed to prevent vibrations. The critical roll speed may be varied by varying the roll mass and / or stiffness of the roll support and / or the axial position of the roll support point and / or the spring bearing constant of the roll bearing and / or by supporting the roll with a movable support roll.

Applicant FI Patent Application 971864 discloses a method for damping vibrations in a paper machine or paper finishing device by means of a dynamic dampener comprising an additional weight suspended by a spring on the vibrating object. . '. ·. The method measures continuously the vibration frequencies of a vibrating object with one or more vibration sensors. The measurement signals provided by the vibration sensor are amplified by an amplifier and fed to a vibration analyzer which detects the problematic excitation frequency and converts that problematic excitation frequency into a control signal. The control signal is applied to a control device for changing the spring constant of the dynamic attenuator spring a and V 1 and / or the mass of the dynamic attenuator to characterize the dynamic attenuator to substantially equal the problematic excitation frequency. The dynamic · · .. · damper may consist of, for example, a substantially horizontal bar mounted on a roller bearing housing with an additional weight mounted on the bar, which can be displaced • ·:::.

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The main features of the method according to the invention will be apparent from the characterizing part of claim 1 and the main features 30 of the device according to the invention will be apparent from the characterizing part of claim 4.

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The method and apparatus of the invention are well suited for use in a nip roll construction in which a roll nip is formed between a soft surface and a hard surface roll. In such structures, the soft-roll roll coating may result in rapidly growing vibrations that need to be controlled.

This is done in the invention by changing the characteristic frequency of the nip roll before the deformation has reached too far, so that the vibration level can be controlled. In the solution according to the invention, the mass distribution of the roll is changed oscillatingly, whereby the specific frequency of the roll is also oscillating.

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The invention will now be described with reference to the figures in the accompanying drawings, in which details, however, are not intended to be limited solely.

Figure 1 is a schematic view of a roll according to the invention having movable masses within the roll 15.

: Y: Fig. 2 is a schematic view of another roll according to the invention, wherein: the weight distribution of the liquid inside the roll is changed.

Fig. 3 is a schematic diagram of a modification of the embodiment of Fig. 2.

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The roll according to the invention shown in Fig. 1A comprises roll roll 11 and shaft pins 12A, 12B at the ends of roll roll 11 to which roll roll 11 is attached. Thus, the entire roll rotates on the bearing (not shown) of the shaft pins 12A, 12B. Within the roll shell 11 • · · * 25 are two masses 13, 14 which are displaceable in the axial direction of the roll. The masses may consist of substantially cylindrical discs 13, 14 having an internally threaded hole connected to the central axis of the cylinders. The discs 13, 14 are adapted to be internally threaded m! '·]: To register on an external threaded rod 15 which engages the center axis of the roll. , 14 move in the direction S of the roll axis, whereby the mass distribution of the roll and thus also the specific frequency of the roll are changed.

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The discs 13, 14 may be dimensioned such that the outer circumference of the discs is slidably in contact with the inner surface of the roll shell 11 via an oil film or other durable coating. In this case, the discs 13, 14 act as stiffening structures of the roll, thereby reducing the vibration of the roll.

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The discs 13, 14 may also be dimensioned such that the periphery of the discs is spaced from the inner surface of the roll shell 11. In this case, the discs 13, 14 do not stiffen the roll, but moving the mass contained in the discs 13, 14 in the direction S-X of the roll axis changes the specific frequency of the roll.

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Figure 1B shows a solution for moving the discs 13, 14 in the direction of the roll axis. The figure shows a portion of the roll end above the center line X-X of the roll axis. Through channel 33, compressed air is supplied through a roll shaft pin 12A to a pneumatic motor 30 attached to the end portion of the shaft pin 12A. 20 through the roll casing 11.

Figure 1C shows that the disc 13 is locked to the roll shell 11 in the roll shell 11

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20, which engages in a corresponding recess 13a in the disc 13. Thus, the disc 13 can move along the axis of the roll, but the disc 13 cannot rotate at a different speed than the roll casing 11, but the disc 13 always rotates at the same rotational speed as the roll casing 11. Of course, the other disc 14 also has: locked in the roll casing 11.

25 * · · V: The threaded rod 15 can be divided in its longitudinal direction so that one side of · · · V · has a clockwise thread and the other side has a counterclockwise thread. By this arrangement, the first half of the threaded rod 15 *: ·: the disc 13 moves in the other direction and the disc 30 14 in the second half of the threaded rod 15 moves in the opposite direction when the threaded rod 15 is rotated by the pneumatic motor I · · t

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30.

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The discs 13, 14 thus rotate continuously with the diaper 11. When the threaded rod 15 is not rotated by the pneumatic motor 30, the discs 13, 14 remain stationary in the axial direction X-X of the roll. As the threaded rod 15 is rotated by the pneumatic motor 30 with respect to the direction of rotation of the roll, alternately clockwise and anticlockwise, the discs 13, 14 move gently in the axial direction X-X of the roll alternately away from each other and alternately towards each other.

The discs 13, 14 are, of course, arranged to move in the axial direction X-X of the roll symmetrically with respect to the center of gravity of the roll so that the center of gravity of the roll remains constant.

In the situation illustrated in Figure 1, the roll shell 11 rotates with the shaft pins 12A, 12B, but the invention can of course also be applied to the situation where the roll shell 11 is rotatably mounted on the shaft pins 12A, 12B. If the solution shown in Fig. 1B is then used, the threaded rod 15 must be rotated by the motor 30 at the same speed as the roll shell 11 rotates when the discs 13, 14 are to remain stationary 15 in the axial direction X-X of the roll. When the speed of rotation of the threaded rod 15 varies. , flattens so that it momentarily falls below the rotational speed of the roll shell 11 and momentarily exceeds • I · '! the rotational speed discs 13, 14 of the roll mantle 11 move oscillatingly in the axial direction of the roll; X-X alternately away from each other and alternately towards each other.

• I · «• ·. ·. ·. Figure 2 shows another roll structure according to the invention in which the mass distribution of the roll is varied by means of a liquid or the like inside the roll shell 11. This can be accomplished, for example, by installing an inner shaft 40 inside the roll shell 11 surrounded by a flexible bellows inner tube 50. A separate bellows 51 is provided in the central portion of the inner tube 50 to supply compressed air P through 25 bores 41. The ends of the inner tube 50 are secured to the end portions 52 which in turn are attached to the inner shaft 40 at the ends of the roll. However, the end portions 52 are not secured to the end of the roll so that the end portions 52 may bend when subjected to traction. 50. The space 60 between the inner tube 50 and the sheath 11 is filled with liquid.

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In Fig. 2A, the inner tube 50 is in its home position, with the liquid between the inner tube 50 and the roll shell 11 being uniformly distributed over the longitudinal direction of the roll. In Fig. 2B, compressed air P is introduced into the bellows 51 in the central portion of the inner tube 50, whereby the bellows 51 expands toward the inner surface of the roll shell 11. As the bellows 51 expands toward the inner surface of the roll shell 11, the inner tube 50 also expands from its central portion and exerts an attraction on the end portions 52, which bend and position in the position shown in Figure 2B. In the situation of Figure 2B, the liquid distribution is changed such that more liquid is present at the ends of the roll than at the center of the roll. By releasing the compressed air P from the bellows 51, the central portion of the inner tube 50 is contracted and the end portions 52 raised, thereby again achieving the condition shown in Figure 2A. The weight distribution of the roll can thus be oscillated between the situation shown in Figure 2A and Figure 2B.

Naturally, the dimension of the inner tube 50 and its associated portions must be such that the total volume 15 of the space 60 between the inner tube 50 and the roll shell 11 remains constant throughout the transition from Figure 2A to Figure 2B.

In Fig. 2C, the end portion 52 is enlarged in the position corresponding to Fig. 2A and in Fig. 2D the end portion 52 is enlarged in the position corresponding to Fig. 2B.

Thus, the end portion 52 is a resilient material which returns to the position of Figure 2C when the tube

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20 50 the attraction F applied to it is sufficiently diminished. At the inner edge of the end portion 52, butter

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I ', be, for example, a saw blade pattern 52a fitted with a spring load. The spring load then performs the resetting of the end member 52 to the position of Fig. 2C as the traction force F decreases.

Figure 3 shows a modification of the roll structure of Figure 2. In this embodiment, the interior space of the roll 25 is divided into three separate fluid spaces 60j, 602, 603 by partitions 100, · · v! 101. Each fluid space 60 ^ 602, 603 may have an inner tube 50j, 502, 503 which

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A: The diameter can be changed. To each space 611, 612, 613 between the inner tube 501 (502, 503 and the inner shaft 40) a bore 41j, 412, 413 is made to the inner shaft 40 through which compressed air can be supplied to each of said spaces 61j, 612, 613.

The fluid may be transferred between fluid spaces 60j, 602, 605 in partitions 100, 101

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via valves 100a, 101a near the inner surface of the shell 11.

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In the situation of Figure 3A, the fluid between the inner tubes 50j, 5 (> 2.5, 3) and roll shell 11 is uniformly distributed over the longitudinal direction of the roll. In each case, the inner tubes 50j, 502? 50 ^ have the same diameter. which increases the diameter of the middle inner tube 50j, while opening the valves 100a and 101a, whereby fluid flows from the first liquid state 61j to the second 6I2 and third 6I3 fluid states, while the fluid flowing into the second 6I2 and third 6I3 fluid spaces 5 This results in the situation shown in Figure 3B in which the diameter of the first inner tube 50j has expanded to the inner surface of the roll shell 11 and the diameter of the second inner tubes 5Ο2 and 10 to the outer surface 40 of the third shaft 5 .3.

By switching off the pressure Pj and switching off the pressures P2 and P3 and opening the valves 100a, 101a in the opposite direction, the liquid can be transferred from the second liquid state 6Ο2 and the third liquid state 6Ο3 to the first liquid state 60j, thereby returning to FIG.

. . The weight distribution of the roll can thus be oscillated between the situation in Fig. 3A and Fig. 3B.

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In situations where the roll rotates at a relatively high speed, the inner tubes 50j, 502, 5Ο3 may not be needed at all, and the fluid will then be uniformly circumferred by the roll shell 11 ;; on the inner surface. In start-up and shut-down situations, of course, care must be taken to ensure that the roll is not unbalanced. This can be done, for example, by filling the roll with: V fluid only when it is rotating at a sufficiently high speed and accordingly emptying the roll prior to stopping it.

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Fig. 3C shows a solution for providing a diameter-changing inner tube 50. The intermediate plate 100 is provided with a spiral groove 110 fitted with a · · chain-shaped tube 50. The chain-shaped tube consists of blocks 51 and connecting them t of the hinges 52. The chain 50 may be moved in a helical groove 110, whereby the diameter of the tube 50 30 may be enlarged and reduced. The outer space of the chain 50 and the intermediate part of the chain portion thereof is sealed by a seal 53. Suitable means can be provided on the inner surface 8104648 of the chain 50 for the shaft 40, which can be subjected to a compressed air jet for moving the chain 50.

Fig. 3D shows another solution for providing an inner tube 50 for changing the diameter 5, which is a rolled sheet whose ends extend in sealed overlap for some distance. When compressed air is introduced into the interior of the inner tube 50, the ends of the plate slide relative to one another so that the diameter R of the inner tube 50 increases. Further, between the inner tube 50 and the inner axis 40, there is a need for centering seats 70 which allow the inner tube 50 to be centered relative to the inner axis 40. When the pressure is lowered inside the inner tube 50, the spring force of the plate slides the ends of the plate so that the diameter R of the inner tube 50 again decreases.

The claims which follow, within the scope of the inventive idea as defined, may differ from the above only by way of example only.

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Claims (8)

A method of changing the intrinsic frequency of a nip roller construction in a paper or cardboard machine, characterized in that the mass distribution of the at least one nip roller structure is oscillating, and the intrinsic frequency of the roller is also oscillating. 2. A method according to claim 1, characterized in that at least one mass (13, 14. mounted within the roller sheath (11) of at least one roller in the nip roller structure 10 is moved in oscillating motion in the axial direction of said roller. Method according to claim 1, characterized in that two masses (13, 14) mounted within the roller sheath (11) of at least one roller in the nip roller structure are moved in oscillatory motion in the axial direction of said roller. 15 4. A roller in a nip roll construction in a paper or cardboard machine, said roller comprising a roller sheath (11) and shaft pins (12A, 12B) at the ends of the roller sheath (11), characterized in that the roller further comprises at least one within the roller sheath ( 11) mounted mass (13, 14, 60), by means of which the mass distribution of the roll can be changed oscillatingly. I I I 5. A roller according to claim 4, characterized in that the roller comprises two within * m. . the roller sheath (11) mounted mass concentrations (13, 14) which can be set in motion in the axial direction of the roller to change the mass distribution of the roller. • m · 25 6. A roller according to claim 4, characterized in that the roller further comprises a * · 1 · inside the roller located (40), whose center axis coincides with the center axis of the roller, and around which the inner axis (40) is mounted. at least one inner tube (40), the shape of which is <II *! '. may be changed, and the space (41) between the inner tube (40) and the roller sheath (11) is filled with a liquid, the liquid distribution in the space (41) between the inner tube (40); and the roller sheath (11) is changed by changing the shape of the inner tube (40), wherein the mass distribution of the roller is also changed and thus the intrinsic frequency of the roller is also changed. 7. A roller according to claim 6, characterized in that an inner tube (50) extending over the entire length of the roller (5) is mounted around the inner shaft (50), a separate bellows being arranged at the middle part of the inner tube (50). (51) on the inner shaft (40), to which bellows (51) can be passed compressed air (P) by mediating a bore (41) received in the inner shaft (40), that the inner tube (50) with its ends is fixed to end portions (52) attached to the inner shaft (40), whereby an increase in the volume of bellows (51) increases the volume of the middle portion of the inner tube (50) and decreases the volume of the end portions of the inner tube. (50) and thus cause a change in the mass distribution of the liquid between the inner tube (50) and the roller sheath (11). Roll according to claim 6, characterized in that the inner space of the roll is divided into three parts with two intersections (100, 101) mounted between the inner shaft (40) and the roller sheath (11), which have valves (100a, 101a) in the immediate vicinity of the inner surface of the roller sheath (11), that in each part is mounted around the inner shaft (40) an inner tube (50j, 502 »5Ο3), the shape of which can be changed so that compressed air can be conducted to each pressure space (612, 6I2, 6I3) between the inner tube (50j, 502, 50j) and the inner shaft (40) by mediating the respective bores (41 j, 4 4, 4 13) accommodated in the inner shaft (40), whereby through pressure changes in the pressure spaces (61 j, 6I2, 6I3): "and with the help of the valves (100a, 101a) in the fluid walls (100, 101) I / can be moved between the fluid spaces (606Ο2, 6Ο3) between the the inner tubes (50j, 502 »5Ο3) and the roll casing (11) for changing the mass distribution of the roll. · 25 • · «• • · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · ·