FI123494B - Method for controlling the paper machine's nip rolls and the control device for the paper machine's nip rolls - Google Patents

Description

A method for controlling paper machine nip rolls and a control arrangement for paper machine nip rolls

The present invention relates to a method for controlling nip rolls 5 of a papermaking machine, wherein the nip rolls include at least a first roll and a counter roll for forming a press nip between the first roll and the second nip, the first roll having a stationary shaft; hydraulic actuators disposed on the shaft and 10 on which the telescope can be loaded via the loading shoe belonging to the hydraulic actuator, and at least one bearing element and / or at least one hydraulic actuator provided with a control valve for rapidly releasing and / or releasing the hydraulic load.

The present invention further relates to a control arrangement for nip rolls of a papermaking machine comprising at least a first roll and a counter roll for forming a press nip between the first roll and the second nip, the first roll having a stationary shaft, a roll jacket arranged to rotate about an axis supported by arranged on the shaft and on which the telescopic cam is loaded via the load shoe of the hydraulic actuator and at least one bearing element and / or at least one hydraulic actuator provided with a control valve for releasing and / or releasing the hydraulic load rapidly.

° 25 i o Such arrangements are necessary in particular in the following cases.

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C \ l | Experience in recent years has shown that especially when manufacturing o thick paper grades at high speeds, the Belt Belt can break up to o g 30 at the nipple locally by multiple factors. Specifically, when the end of the web is inserted, the multiplication factor for the broken web at nip N (see Fig. 4) is a common factor for loading the nip and belt 4. In some cases, 2 tissues may also be interrupted for one reason or another or enter the nipple in a rush due to, for example, a tissue defect. This will almost always result in such large local nip pins that damage both the Belt strap and the shoe. In the nip, the belt strap and shoe 5 are more resilient and more susceptible to damage than the high-mass counter-roll 20 and its jacket 22. When a pressure stroke hits any area of the nip, the oil film between the strap 4 and the shoe may locally fail gradually begin to disassemble the strap.

Under the respective pistons 6 and 23 of the two rollers 2 and 20, a common loading pressure (flow path 7) is preferably applied to both. The load is released by relieving the pressure with the control valve. Because the belt roll 2 is inherently slower to discharge than the counter roll due to internal pressure losses, the belt roll unloading speed has been increased with electrically controlled discharge cartridges 8 'mounted inside the roll. The cartridges 8 'are disposed on the web of the shaft 3 at the intermediate outlets of the load pressure bore connecting the load-15 pistons 6. The quick release of the nipple load is based on the prior information that is used to electrically control the discharge rollers inside the Belt roller 8 'by activating the valve. At the same time, the control valve connects the roll load line to the tank line. The nip load can be unloaded in about 1 sec. Preliminary information on the need for quick-20 opening is obtained from several different signal sources e.g. line break detector and pick-up roll control information.

However, the advantage of the present arrangement is that the activation of the quick discharge via the machine control system takes into account the state of the machine more extensively than

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cv 25 for one nip; for example, in a press of two consecutive nips, discharge of the load from only one nip causes problems in handling the web.

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cv point of view. The nip load quick release is performed only by external electronic sig-

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£ on the basis of a bean. This has the disadvantage of not being able to react to all track irregularities. In particular, there is no need for comprehensive monitoring of headache disorders. The current express discharge is slow. The high-speed ° machine should be able to release the load in a few milliseconds instead of the current approx.

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A similar problem can be seen in arrangements where the traditional Hippie loading machine for paper machines is an external hydraulic cylinder. When the paper path is broken, a multi-layer paper web that is thicker than the normal path may be forced into the nip. Foreign hard objects can also drift into the nipple. The points exceeding the normal thickness of the track 5 produce a very sudden force pulse, the duration of which depends on the track speed and the length of the thick part. Impulse can break rollers, nip load mechanics and paper machine frame structures.

10 Loading nipples outside the nipples are traditionally equipped with small n.

With 1 liter pressure accumulators. The precharging pressure of the batteries is about 10 ... 20% higher than the maximum load pressure, whereby the load system remains rigid under normal driving conditions. The battery next to the cylinder is the best of the traditional methods for counteracting sudden pressure shocks. Another method of counteracting the unfavorable effects of track unevenness 15 has been to provide the cylinder with a fast, direct-controlled pressure relief valve. The weakness of the pressure relief valve is the slowness of the operation. The response of commercial valves (spindle movement from space to open) is in the order of 50 ... 100 ms depending on valve size.

Such rollers with pressure accumulators, as mentioned above, are known from, for example, Finnish Patent Publication FI 120409, in addition, one solution is disclosed in EP 1155190 B1.

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The arrangement according to EN 120409 is functional as such, i.e., it eliminates vibrations in rolls due to misalignment of the material web.

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^ flatness and receives the sudden load caused by head-throwing | its a change. The problem with such an arrangement is that adding such a feature (pressure accumulator) to an old roll, for example, would require transporting the entire roll to its suitable workshop (service station) and disassembling the shaft, additional machining, reassembly, etc., which are expensive measures. .

In addition, the problem of the arrangement mentioned below is its uncertain operation. The pressure peak may dampen in the ductwork and never reach the membrane of the battery. Even at its best, a state-of-the-art battery pack responds slowly.

It is an object of the present invention to eliminate or at least substantially reduce the above-mentioned drawbacks.

To achieve the purpose of the above invention, the method of the present invention is characterized by providing actuators 10 which are automatically responsive to the rate of change of the load pressure.

Further, to achieve the object of the above invention, a control arrangement employing the method of the present invention is characterized in that actuators are provided on the control valve which automatically react to the rate of change of the load pressure.

The roller according to the present invention avoids the above disadvantages of the prior art.

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Preferred embodiments of the present invention are set forth in the dependent claims.

Next, the control arrangement of the present invention will be described in more detail with reference to the accompanying drawings, in which:

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Fig. 1 is a schematic cross-sectional view of the present invention a control arrangement of nip rolls according to one embodiment and hydraulic actuators therein provided with a regulating valve, δ c \ j 5

Figure 2a is a schematic cross-sectional view of the control valve according to the present invention,

Figure 2b is a schematic cross-sectional view of the control valve according to the present invention, open;

Fig. 2c is a schematic cross-sectional view of the control valve of the present invention provided with additional features;

Figure 3 is a schematic cross-sectional view of a nip roll control arrangement according to a third embodiment, and

Figure 4 shows a prior art control arrangement of nip rolls.

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Thus, Fig. 1 is a schematic cross-sectional view of a nip roll guide arrangement according to the invention, designated herein by reference numeral 1. Here, the guide arrangement 1 includes at least a first roll designated by reference numeral 2 and a counter roll 20 denoted by reference numeral 20. Material web W (paper) the orbit formed by it is arranged to pass through nip N in a manner known per se.

The first roll 2 is a belt roll. The belt roll 2 comprises a stationary shaft 3c and a roll shell 4, the structure and material of which are preferably known per se from known Belt rolls. The roll jacket 4 is arranged to rotate, supported by the hydraulic actuators 5 and 6 arranged on the shaft 3,

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cv 3 around. The hydraulic actuators 6 are preferably in the radial direction of the nip | At N, the load elements 6 are arranged in a row on the shaft 3, which are also loaded in the radial direction also in a manner known per se, e.g. by means of a hydraulic pressure medium supplied to the elements 6 via a flow path 7 formed in the shaft. In addition, an elongate loading shoe 5 is provided in the space between the load element row and the inner surface of the roll shell 4.

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The load shoe 5 is a beam extending across all load elements 6 in the transverse direction of the machine, which receives the nip load and at the same time acts as a sliding element. Lubricant (oil) is supplied between the support surfaces of the shoe 5 and the inner surface of the shoe 4 via the lubricant supply channels 10 formed on the shoe 5 and the shaft 3 5. The corresponding prior art loading of the loading roller of the counter roll 20, i.e. under the loading elements 23, is exerted by a common loading pressure obtained by supplying a hydraulic pressure medium along a flow path 7 to the loading elements 23 for loading the inner surface of the roll shell 22.

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Figure 1 shows the control valves 8 of the control arrangement 1 according to the invention, the structure of which will be described in more detail below with reference to Figures 2a and 2b.

Fig. 2a is a schematic cross-sectional view of a control valve 8 in a control arrangement. 12 through. In addition, the slide 82 is formed at a distance from the end face 89 by a guide edge 88, the operation of which will be described below. A central hole 83 is provided in the slide 82, which is provided with a choke 83a. Thus, the same pressure acts through the center spindle hole 83 and its choke 83a co in the space 84 on the opposite side of the slider 82 and thus also on the second surface 90 formed by the slider 82. The second surface 90 io of the slider 82 extends into the space 84 so where

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cv also the pressure medium through the central bore 83 comes. Skid 82 is loaded into the space 84 provided by a force member 85 such as a spring whose spring force exerted by the slider 82 presses the seat 91 against the counter surface or edge 30 of the bore 86 and the space 84, δ C \ 17

Valve 8 and / or its connection also includes tank connections 13 and 14 through which the loading pressure can be discharged into tank T. This operation will be described below. Figure 2a shows the so-called. the normal state (with the valve closed), whereby the surface 89 of the slide 82 is subjected to the same pressure as the other surface 90 of the slide 82. In addition, the force of the spring thus holds the slide 82 in the closed position. As the pressure acting on the first surface 89 increases (e.g. due to the unevenness of the track W), the pressure also increases in state 84, but with a delay. The magnitude of the delay is determined by the size of the choke 83a and the volume of the space 84. The choke 83a restricts the flow to the space 84 and the size of the choke 83a determines a setpoint for the 10 pressure rise rate. When the pressure differences between the first surface 89 and the second surface 90 exceed the spring force value, the slide 82 begins to move upward (in the figure), whereby the slide 82 seat 91 in state 84 is released from the counter surface and rapidly discharged (released) Then, the skid 82 starts at high acceleration upward (in the direction of 15) and moves rapidly to the upper position, whereupon the control edge 88 formed as a damping means in the skid 82 begins to close the connection between the space 84 and the tank carriage 13. This property automatically dampens (slows down) the movement speed of the slider 82 before colliding with the slider at the end of the space 84, thereby acting as the end suppressor of the slider 82. At the same time, the second tank connection 14 20 opens into the supply channel 12 as the slide 82 moves from the closing position of the tank connection 14, i.e. the slide 82 moves upwardly from the tank connection 14 in Fig. 2a to ensure the above pressure release. The position of the slide 82 with valve 8 open is illustrated in Figure 2b. co The valve 8 is returned to normal (closed) by releasing the load pressure ™ 25 in the feed line 7, whereby the spring force pushes the slide 82 to its normal position.

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c \ i In Fig. 2c, valve 8 is supplemented with additional features. Control valve 8 | a valve VI is provided in the connection for controlling the supply pressure to the other surface 90 of the slide, whereby the control valve 8 remains closed. When the closing pressure acts on the volume 30 at 84, oil flows through the skid center hole 83 and the choke 83a from the space 84 g through the flow path 12 to the loading cylinder which is removed from the system by the pressure control valve 40. A valve 8 V2 can be provided in connection with the control valve 8, which can be used for electrically discharging the cylinder pressures. With the help of the pilot valve V3, the valve also functions as a normal pressure relief valve. When the pressure level in the space 84 exceeds the set pressure of the pilot control valve V3, the oil begins to flow through the choke 83a and a differential pressure is created between the first pin 89 and the second surface 90 to release the slide 82 and thereby release the seat control 91 from the closed slot. 82 opens quickly. Thus, valve 8 functions as both an electronically controlled quick discharge arrangement known per se and an automatically reactive discharge valve 10 which operates at a very high speed. Depending on the application, the load release occurs at the fastest speed in a few milliseconds and at most in less than 100 milliseconds, which is considerably faster than in prior art solutions.

Figure 3 shows another preferred embodiment of the invention. In Fig. 3, the control valve 8 is applied as a pre-control valve which can be located in connection with the load elements 6. The pilot control valve 8 controls the cartridge valve 8 'via a small pilot control line 12' to relieve pressure on all cartridge valves 8 'from a common pilot control line, i.e., activation of one of the pilot control 20 valves 8 relieves shut-off pressure on all cartridge valves 8'. In this case, the uneven position of the track W passing in one transverse direction of the machine causes the pressure to be released (released) from the nip N.

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The present invention is not limited to the embodiments shown, but may be applied in many ways within the scope of the appended claims. For example, Figures 1 and 3 show three control valves 8, | but there may be, for example, 1 to 5 per roll and their number is in principle not limited.

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Claims (8)

A method for controlling a paper machine's nip rolls (2, 20; 2 ', 200, in which method the nip rolls (2, 20; 2', 200) at least have a first roll (2, T) and a support roll (20, 200 for forming the press nip (N) between the first roll (2, 20 and the support roll (20, 200), said first roll (2, 20) having a stationary shaft (3), a roll sheath (4) arranged to rotate about a shaft (3) supported by hydrostatic bearing members, hydraulic means (6) arranged on the shaft (3) and with which the roller sheath (4) is loaded during the transmission of pressure medium, and at least one hydraulic actuator (6) provided with a control valve (8) for quick release and / or relieving the hydraulic load, characterized in that actuators (82, 83, 83a, 84, 85, 89, 90) are arranged on the control valve (8), which automatically responds to the rate of change of the load pressure. Method according to Claim 1, characterized in that the actuating means (82, 83, 83a, 84, 85, 89, 90) of the control valve (8) hears a slide (82) and prevents the slide (82) from impacting the body (81) of the control valve (8) by automatically attenuating the speed of movement of the slide (82) with damping means (88) arranged in conjunction with the slide (82). Method according to claim 1 or 2, characterized in that the control valve (8) is provided with additional actuators (VI, V2, V3) for electrically controlling the co-control valve (8). δ CvJ o Method according to any one of the preceding claims 1-3, characterized in that the nip roller (2, 20; 2, 200 is a flexible roller belt roller) and between which hydraulic actuators (6) and the roller jacket (6). 4) a longitudinally extending unit and load strip (5) extending in the longitudinal direction of the nip selection (2) at least to the press nip (N) is arranged. A guide arrangement (1) for a paper machine's nip rolls (2, 20; 2 ', 200, which arrangement at least comprises a first roll (2, 20 and a support roll (20, 200 to form the press nip) (N) between the first the roller (2, 7) and the supporting roller (20, 200), the first roller (2, 7) having a stationary shaft (3), a roller sheath (4) arranged to rotate about a shaft (3) supported by the hydraulic shaft (3). static bearing elements, hydraulic means (6) arranged on the shaft (3) and with which the roller sheath (4) can be loaded during the transmission of pressure medium, and at least one hydraulic actuator (6) provided with a control valve (8) for quick release and / or relief the hydraulic load, characterized in that the control valve (8) includes actuating means (82, 83, 83a, 84, 85, 89, 90), which are arranged to react automatically to the rate of change of the load pressure. Control arrangement (1) according to claim 5, characterized in that the actuator of the control valve includes a slide (82), in which the damping means (88) are arranged to automatically dampen the movement speed of the slide (82) to preventing the slide (82) from impacting the body (81) of the control valve (8). Control arrangement (1) according to claim 5 or 6, characterized in that the control valve (8) is provided with additional actuators (VI, V2, V3) for electrically controlling the control valve (8). co Steering arrangement according to any of the above-mentioned claims 5-7, characterized in that the nip roll (2) is a belt roll with a flexible sheath and at least one longitudinally extending to the press nip (N) in the longitudinal direction of the nip roll (2). Equivalent uniform load strip (5) arranged between the hydraulic | 5 and the roller sheath (4). o C \ J o m o δ C \ J