FI84281B - Method during pulling a drying wire of a paper machine, and multicylinder dryer for a paper machine - Google Patents

Description

84281

Method for paper machine drying wire operation and paper machine multi-cylinder dryer The method of dragging the tumble dryer from the paper machine 5 and the game cylinder for the paper machine

The invention relates to a method and an apparatus for using the guide rollers of a drying machine of a paper machine.

When the rollers and cylinders of the drying section are rotated, the so-called with wire drawing using only one or a few application points, each drying group has a wire tension and thus also its elongation and speed at different points in the wire rotation. This is due to the different resistances caused by the cylinders and rollers. The farther the point between the groups, the greater the speed difference caused by the tension differences. Although the speeds of the groups are adjustable, it is difficult to control the situation between the groups because the change in the length of the wire is vague and even variable along the path of the wire 20 turns. Thus, in the prior art solution, it has been very difficult to precisely adjust the speed of the wires, especially at the group spacing. However, it would be important for the operation of the entire drying section to be able to ensure a smooth and stepless transition from one group to another on the paper web.

25

According to the invention, the adjustment in the group spacing is made possible by placing a torque- or speed-adjustable drive on the wire guide roll specifically in connection with the group spacing. Thus, the maximum / minimum-speed differences can be reduced and thus the wire speeds in the track transfer line-30 between the groups can be better controlled. On the other hand, the additional use also reduces the wire tension / speed differences within the group and thus reduces the tendency of the web to loosen.

The method of using the drying wire line of the drying section of the paper machine dryer according to the invention is mainly characterized in that the method adjusts the tension of the drying wire and thus its elongation and speed with an auxiliary drive device In the method, the auxiliary drive device adjusts the torque and / or speed of the wire guide roll near the group gap, preferably with a torque-adjustable motor, whereby adjusting the auxiliary drive torque to the desired tension of the wire and its speed on the wire.

The drying section according to the invention is mainly characterized in that the multi-cylinder dryer comprises an apparatus, preferably a torque-adjustable drive roller, with which the wire tension and at the same time its elongation and speed can be adjusted and that the drive roller is arranged close to the group gap. the same or the speed difference 15 just desired near the group spacing.

The invention will now be described with reference to some preferred embodiments of the invention shown in the figures of the accompanying drawings, to which, however, the invention is not intended to be exclusively limited.

20

Figure 1 schematically shows a drying section according to the invention, comprising equipment arranged and used according to the invention in the vicinity of a group gap.

Fig. 2 shows an axonometric view of the wire tension adjustment apparatus of Fig. 1 in connection with a group spacing.

Figure 1 shows a multi-cylinder dryer according to the invention provided with a single wire outlet. The drying section comprises, as shown in the figure, two consecutive wire groups R1 and R2. The various drying groups have steam-heated drying cylinders 10 and cylinders 11 with a perforated and grooved jacket 12 inside which a vacuum prevails. As shown in Fig. 1, the paper web Win is introduced from the press section to the drying wire of the first group Rt for running after its guide roll, and the web 35 is fixed to the drying wire by means of the vacuum provided by the suction cylinders below. The web is conveyed in a loop through the upper 84281 3 steam-heated drying cylinders, and the wire outlet supports the web in connection with the upper drying cylinders and the suction rollers below the drying group. In order to equalize the speed of the wire H, the auxiliary drive 14 according to the invention is adapted to the group spacing, whereby the tension of the wires of the groups Rx and R2 and the speed difference and speed variation due to elongation differences are controlled by the auxiliary drive.

The speed differences between the drying groups according to the prior art are generally 0.1 to 0.5%. The drying wire stretches by about 1% when the tension changes from 0 to 1.5 kN / m. Especially in wire-driven drying sections, the tension of the drying wire can vary from 1 to 1.8 kN / m depending on the position of the measuring point in relation to the applications. Due to the above, the elongation of the wire 15 due to the tension difference varies from 0.67% up to 1.20%, i.e. the difference can be 0.53%, which is large compared to the speed differences of 0.1-0.5% of the groups.

The maximum tension difference for the wire as it crosses the roll is given by the formula: 20 5T - T2 - Tj - T: (e- 1) j where ÄT - tension - lower tension 25 T2 - higher tension μ - coefficient of friction (usually 0.18) a - coverage angle in radians

The power required to achieve the above tension difference is given by 30 formulas:

P - ST x V x S

V - speed (m / s) 35 S - width (m) 4 84281 if: μ - 0,18 α - 90 ° Τχ - 1,5 kN / m 5

The maximum transmission power is thus 9.8 kW / m, with a tension difference of 0.49 kN / m, which corresponds to a change of about 0.3% in the elongation of the wire.

This shows that, in practice, by adjusting the operating torque of the roll, the speed of the drying wire 10 and thus also of the web can be adjusted in an order of magnitude important for paper production. On the other hand, the use of torque control also makes it easier to select the optimum number of actual operating points.

Figure 1 shows a wire Hz turning roller T in the group Rz, from the axis of which the measurement of the wire Hz speed is taken. The rotational speed of the roll T indicates the speed of the wire Hz and the speed information is transmitted along the bus D as a control pulse to the auxiliary drive 14 in the group Rx.

Figure 2 shows axonometrically and partly diagrammatically the use of a wire according to the invention between the groups R: and Rz. The drying wire of the group Rx is shown by Hx and the drying wire of the group Rz is shown in the figure by Hz. The paper path is marked with W. The web W is guided from the roll Tx to the drying wire Hz of the group Rz in connection with the suction loop below it, ensuring the attachment of the web to the surface of the wire. In order to make the speeds of the drying wire H1 and Hz exactly the same or the speed difference just desired at the point where the web differs from the auxiliary drive roller and moves to the second group Rz drying wire Hz, the auxiliary drive 14 is equipped with a torque adjustable motor M. Hi. The drive motor M is connected to the output shaft A of the roller Tx and the motor M is preferably a hydraulic motor shown schematically in the figure. A pneumatic motor with adjustable output torque or an electric motor can also be used.

35 5 84281

As shown in the figure, the motor M is operated via the control valve 15. Valve 15 is a three-position valve, whereby when the central block Cr is connected to the hydraulic lines 16, 16b, 18 there is a valve and the whole system in the locked state and the hydraulic motor M is not used. Correspondingly, when the block C2 of the valve 15 is on, the hydraulic oil is transferred from the pressure source, e.g. from the oil pump P, through the valve 15 to the pressure line 16 and further to the engine M, whereby the return line 17 is connected via a pressure relief valve 23 to the tank. Between lines 16 and 17 there is a connecting line 20 provided with a non-return valve 19. The valve 15 is preferably a proportional valve, the opening of which also controls the oil flow to the engine M and the engine torque. The valve 15 is preferably controlled electrically via the control card 21.

When the valve block C3 is on, the motor M can be operated in the opposite direction of rotation. Line 22 is connected to an oil pressure source P, so pressure lines flow to lines M through lines 22 and 17. The purpose of the valve 23 of the line 17 is to direct the oil flow from the engine M directly to the tank E when flowing from line 16 to line 17 (valve 15 operating position C2). there is no pre-control-20 and when block C3 in the main control valve 15 is affected and in its operating position the flow from line 2 through valve 23 to line 17 and to motor M and further from motor M via line 16 to main control valve 15 and on to tank E.

The control system preferably comprises feedback 24 from the control line 16 to the control board 21, whereby the setpoint given to the control board 21 keeps the PI controller at the desired constant torque M, thus ensuring that the operating torque remains at the desired value and the desired wire tension near the group spacing.

30

According to the invention, the torque of the motor M is adjusted by limiting the pressure to a certain value on the control board 25. The set value is also set for the oil flow and thus for the rotational speed of the motor. However, the pressure acts as the primary torque limiter. This is the so-called P / Q control, where 35 the motor M torque and the volume flow Q are adjusted and the valve 15 acts as a pressure compensator.

Claims (8)

A method of pulling the drying wire of a paper machine, in which method of pulling the drying wire in a multi-cylinder dryer with several wire groups (RX, R2) one after the other, each of which is preferably two rows of cylinders and the drying wire in the form of a closed link from the drying cylinder to a drum, advantageously a suction drum and further to a drying cylinder, characterized in that in the process the voltage of the drying wire is regulated and also its elongation and velocity with an auxiliary drive device in connection with the group space. R2), where the velocities of the wires in adjacent groups (Rx-R2) are equal or the speed difference is just desired when transferring the web from the group (Rx) to the group (R2), whereby in the process the torque and / or velocity are controlled. By means of auxiliary drive device, advantageously a motor (M) with d adjustable torque, whereby by controlling the torque of the auxiliary drive to the desired size, the voltage on the wire and at the same time its speed on the wire (Hx) becomes equal to the wire (H2) in the following drying cylinder group or a speed difference of just the desired size. 2. A method according to claim 1, characterized in that in the process, the wireline conduit is driven by a hydraulic motor (14), by regulating the driving pressure (Px) the torque mediated by the hydraulic motor (M) in the desired size and thus a desired wire tension in conjunction with the group gap. 3. A method according to the preceding claim, characterized in that in the process the valve is controlled with a control device, in which the desired setpoint for the torque is set and the torque value is maintained in the desired size with a feedback produced from the pressure line with the control pressure and / or the regulatory information obtained from this. 35 Method according to any of the preceding claims, characterized in that in the process both the motor (M) torque and the volume flow son through it are controlled, at least the momentum transmitted by the motor (M) to the roller coupled to this desired value. ίο 84281 5 5. A method according to any of the preceding claims, characterized in that in the process the speed of the wire (Hz) is measured and a control pulse is produced from the wire speed of the motor (14) in order to control the motor (14) in such a way, that the wire rates of the wires in the group (Ra) and the group (Rz) fA are substantially equal in connection with the group space (R1-R2). 6. Multi-cylinder dryer for a paper machine consisting mainly of single-wire cylinder groups (R1, RZ ...) having mainly such cylinder groups which most suitably have Angled-heated drying cylinders in the upper row, break cylinders, most preferably suction cylinders, , wherein the web (W) is guided through its drying portion substantially as a closed feature, characterized in that the multi-cylinder dryer comprises a plant, advantageously a drive roller with adjustable torque with which the tension on the wire (H) and on the seam increase its elongation and velocity. can be regulated and the respective driving rollers are arranged to be in contact with the group gap (R1-Rz), whereby the speed of the rolling torque (HltHz) in adjacent groups is controlled so that they are equal or so that the speed difference becomes desired in contact with the group space. 25 7. A multi-cylinder dryer according to the preceding claim, characterized in that the drive system comprises a hydraulic motor (M) controlled by a hydraulic pressure, the plant comprising pressure lines conducted to the hydraulic motor (M), whereby a valve is arranged in one pressure line. which acts as a directional valve and pressure control valve, whereby by regulating the opening of the control spindle, the pressure produced to the motor (M) is also regulated and thus the torque of the motor (M) is regulated. 8. A multi-cylinder dryer according to the preceding claim, characterized in that the plant comprises a control card in which one can n 84281 set the desired setpoint to produce a desired torque for the winding which is driven by the motor (M) and that the in the control board and thereby the valve can also enter pressure data as Feedback from the pressure line preceding the motor, whereby the torque on the motor can be maintained at the desired preset value by means of control data obtained as a Feedback.