FI114413B - Method for determining and equalizing pinch force between two rotating rollers - Google Patents

Description

METHOD FOR DETERMINING NIPPING POWER AND EVALUATING NIPPING POWER

WHY BETWEEN TWO ROTATED ROLLS 11441? The invention relates to the determination of the nip force between two rotating rolls pressed against each other both by calculation and by means of measurements. It is an object of the invention to provide a calculation model for calculating the stresses in a second roll caused by uniformly distributed nip force on said roll. The method according to the invention calculates the stresses from a second roll at a point where they can also be measured.

A prior art method for determining the distribution of nip force is the examination of a product passed through a roll, whereby its cross-sectional properties determine the uniformity of compression between the rolls. The disadvantage of such a compression force distribution observed in the final product is that the cross-sectional profile of the final product depends on many other factors than the distribution of the nip force. It is difficult to find a more even distribution of the distribution, because the cross-sectional view does not yet solve, for example, the required change in roll bombing.

In addition, a prior art method is a static nip paper test, whereby the distribution of the compression force is interpreted from the paper pressed between the rolls. Also, this experiment gives I · t · '* only a direction for the change in bombing, is difficult to implement and ignores the effect of the rolls * · ·' rotation on the nip force distribution.

• · »* · · * ♦ *; · * 25 There are known formulas for determining the bombing form required for a roll, for which;,. * factors due to roller bearing support and deflection are included. However, the evenness of the nip force distribution · '' 'could not be verified in the actual situation, ie the web was led. . between rotating rollers. As a result, there is! / Approved the bombardment that is applied to the roll according to the values given in the calculation. .

30 * ;;; The compressive force of the roll at nip contact with one roll is previously adjusted by the roll '; * by means of sliding shoes which are spaced apart by means of: V printed on the inside of the roll by the nipple of the roll. When different types of sliding shoes are provided: ... · the thrust distribution can be adjusted. The disadvantage of this is that only after examining the cross sectional profile of the 114413 2 end product, the distribution of the Liu shoe's thrust force could be corrected with great delay and thus affect the distribution of the nip force.

The method according to the invention solves the above problems and achieves a significant improvement in finding out the nip force distribution and also in correcting the distribution more evenly, as well as its real-time adjustment. The invention is characterized by what is stated in the claims.

An advantage of the method according to the invention is that the control of the nip force or line load is significantly improved because the corresponding stress distribution caused by the uniform nip force distribution on the second roll in the web width direction is represented by a formula and the corresponding stresses on said roll are also measured. When the stress surface is selected as the inner surface of the cylinder shell of the roll to be measured, it can be measured by means of stress strain strips e.g.

15 tensions in axial and radial directions. The stresses on the corresponding inner surface are also computationally acceptable to be determined when the cylinder roll is loaded with bending, deflection at nip contact, and flattening due to nip force.

The process of the invention improves the papermaking process, whereby the quality of the paper is made more uniform over the entire width of the web. Roller bombardment shapes can be better matched to the need and more accurate echo bombardment can be determined. If the roll has an active load of, for example, sliding shoes ... 1, which determines the nip force, the method according to the invention provides t ·:: real-time adjustment when a continuous stress measurement is provided on the counter roll.

1 · '25 • · •': In the following, the invention will be explained in more detail with reference to the accompanying drawing, in which * "·" Figure 1 is a side view of a pair of rollers.

Figure 2 is a sectional view of a pair of rollers having a second roller having a sliding shoe arrangement for adjusting the nip force distribution.

Figure 3 shows the longitudinal stress distribution of the roll.

* • · · ...: Figure 4 shows the nip force distribution of a pair of rollers.

> ·

Figure 5 shows the bombardment mode of a roll.

V Figure 6 shows the force distribution of the force.

3, 114412

Fig. 1 shows a pair of rotatable rollers 1,2 of a papermaking machine supported by a frame 4 such that the bearing of at least one roller is vertically movable in the frame 4. By means of the forces applied to the bearing, the rolls 1,2 can be pressed against each other, whereby a nip contact is formed between the rolls 5. The rolls are cylindrical rolls of length L. The tension stretch tabs 3 are attached to the inner surface of the second cylinder roll, which provides information on the inner surface tension space at a selected pitch in the longitudinal direction of the roll. In this invention, stresses are desired at the outlet which represent stresses exerted on the inner surface of the roll at the nip contact. As the roll 2 rotates, the desired stress values are obtained cyclically 10 only once per revolution. However, the stresses are at their maximum at the nip contact point so that their peak values can be easily distinguished from the information obtained from the strain gauges 3.

Fig. 2 shows a solution in which a second roll 1 (= nip load roller) is thus provided with a non-rotatable shaft 6, at a distance from which are mounted hydraulic pressers 7 which, by means of sliding shoes 8, press the shell 1 against the roll 2. The roller 1 is rotatably supported on the shaft 5. The roll 2 has a strain gauge sensor 3 attached at one of its periphery, preferably at each press 7.8 in the width direction of the roll.

; 20

If the roller 1 has a known bombardment and it is assumed that the nip force is uniformly distributed between the rolls 1,2 and the roller structure and bearings of both rollers and the stiffening effects of the roll ends are known, the invention takes advantage of this situation; . i: a basis-based calculation model which gives the result of the calculation of the inner surface of the second roll 2, «i * ,,. * 25 nanosampler stress values for strain gauge strips 3 with nip line locations.

t «*. 't Assuming that the nip force is evenly distributed on the line contact, the calculation model for solving the stress values on the inside surface of the counter roll is relatively accurate and sufficient for the intended purpose.

When the corresponding stress values of the counter roll 2 can also be measured in accordance with the invention, the accuracy of the calculation model is determined by practical experiments. The calculation model provides, in a highly useful application in the other direction, a nip force distribution of known: "'rolls in linear contact when the voltage values measured in the counter roll 2 are fed to the calculation model.

114413 4

From the measured tension values of the back roll 2, the calculation model can further determine the shape of the required bombardment in order to distribute the nip force evenly.

In the case of the solution of FIG. 2 having a nip force zone control by means of the hydraulic pressers 7,8 located within the roll, it is possible to obtain an adjustment for each press 7 individually by means of the measured tension values of the counter roll 2 and thereby obtain active control and nip force control. The aim of the adjustment is to obtain a result where the stress values at the strain gauges 3 are the same as those calculated at 10 at these points under the assumption that the nip force is uniformly distributed. When the stress values are continuously received from the strain gauges 3 and the computational model algorithms can be quickly solved by means of a computer, the control system is able to control the pressures 7 in real time. Because there are several presses and adjusting one affects the operation of adjacent ones, the adjusting system will need to perform a few adjustment turns to achieve a sufficient accuracy.

Figure 3 shows schematically the stresses measured in the axial direction 5a and radially 5r along the length L of the roll by means of the strain gauges 3. The stress values at the corresponding points are also determined using a calculation model.

20th Figure 4 shows the distribution of the nip force Fn over the length of the roll. Each nip force value »· ,,, corresponds to certain stress values in Figure 3 and vice versa when looking at the same pair of rollers.

Fig. 5 illustrates one form of bombardment on the outer surface of a roll.

• | *; Figure 6 is a schematic representation of the distribution of the thrust Fp.

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If the calculation model applied to a known pair of rolls gives a reliable result and the rolls, ·,: bending, bending, and flattening can be controlled in one embodiment, the constraint. ''. only measure the tension in the center of the roll so that, by knowing the properties of the roll from the tensile values of the center of the roll, other residuals affecting the length of the roll can be determined.

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Claims (9)

A method for defining evenness of a nip force (Fn) acting in line contact area of two rotating rollers (1,2) and for smoothing existing uneven line load, in which method the quantities described by the viewing roll pair are placed into counts. model shape having the shape of the corresponding pair of rolls and through the shape are determined the strenuous shell stress conditions which represent evenly distributed pinch force (Fn), which said shell gives calculated to exist at least on the inner surface of another roll (2) in the seed grain. Nip points, which are in synthesis in the nip contact line, characterized in that it is measured at least from inside the second roller (2) from the inner surface shell stresses caused by the cylinder at the nip point, whereby in the method the line load of the nip contact is equalized by second roll or bombing when the matte stresses sufficiently correspond to the calculated stress values. 15 A method for defining the uniformity of a nip force (Fn) acting in the line contact area of two rotating rollers (1,2) in which method the quantities described by the viewing roll pair are placed in a calculated model form which has been formed by the corresponding roll pairs and the shape determines the strenuous shell stress ratios representing evenly distributed pinch force (Fn), which said shells provide to be thought to exist at least on the inner ,,,,; the surface of another roller (2) at the saturated points of the mantle, which in turn lies in the nip contact line, characterized in that it is measured in the process at least from within the other »· in t; , *. the roller (2) from the inner surface shell voltages of the cylinders caused to the cylinder in the new point, I * »·, '" whereby, due to the difference between the calculated and measured voltages, the pinch force j' · "(Fn) is uniform in the line contact area. t I t> · t I Method according to claim 1 or 2, characterized in that it is taken into account; · As the quantities into the calculation form from the inspecting roll pair (1,2) at least support: the ends of the roll, stiffness and bearing support, mantle bombardment, mantle bending stiffness,:. '. 30 mantle flow and mantle plate on the basis of nip power. I I I · • I · I I I 4. A method according to claim 1, characterized in that nip contact force is smoothed by the full casing eating at least in the second roll (1) by means of loading means (7, 8) spaced apart into the men of said roll. with the help of each organ, regulated load force (Fp) is caused to men who are at the nip contact point. 5. Method according to Claim 1 or 2, characterized in that the measured and calculated shear stress values are defined as optimal shape for the bombing. 6. A method according to claim 1 or 2, characterized in that the shell stresses on the inner surface of the roll caused by the even distribution of the nip force existing between the pair of rollers (1,2) are calculated calculatively on the length (L) of the roll and the shell stress. from within the roll in the center of the roll at the point of nip, the other stress measurements are not performed from within the roll and they are defined calculatively from the mat's scaling stress value of the roll. 15 7. A method according to claim 1 or 2, characterized in that the scale voltage values from the inner surface of the rotating roller (2) are measured by using an extension strip sensor (3) and the signals are transmitted wirelessly to an unrotating receiver. Method according to Claim 1 or 2, characterized in that pressing between the rollers (1,2) is caused by the whole bearing system eating at least in another roll. i · 9. A method according to claim 1 or 2, characterized in that pressing between the rollers (1, 2) is caused by the whole bearing system eating at least in another roller and / or,. integrate another roller (1) by means of a printing arrangement (7, 8) into it. 25 t · »» *> t • · r · * 1 1 t t I 1 I> • 1 I I>:! ·. 30 •! »» I <1 * t • I t 1 »» I · <I I · t I «» I · I ·