The invention relates to a device for guiding a moving fabric or web in a paper or board machine according to the preamble of claim 1.

The invention also relates to a method for measuring the tension of a moving fabric in a paper or board machine according to the preamble of claim 11.

Furthermore, the invention relates to a device according to the preamble of claim 14 for measuring the tension of a moving fabric in a paper or board machine according to the preamble of claim 14.

With respect to the prior art, reference may be made to FI patent application 992285 disclosing an apparatus for guiding a fabric in a paper machine, the apparatus comprising an alignment roll which is contact with the fabric and one end of which is movably mounted by means of bearings on the frame of the paper machine to change the axial alignment of the alignment roll, and in which the bearing support of the movable end of the alignment roll is disposed on support of at least one, preferably two bellows members filled with a pressure medium, which bellows members are arranged to carry the weight of the roll, keep the height position of the end of the roll substantially constant, and allow limited lateral of the end of the roll. The alignment apparatus described in the publication also comprises means for measuring fabric tension, the means comprising a pressure measurement member arranged to measure the pressure acting inside the bellows.

With respect to the state of the art, reference may also be made to FI patent application 20000328 disclosing a device for guiding a moving fabric or web in a paper or board machine, in which the fabric or web is passed over an alignment roll, which alignment roll is mounted on the frame structure of the machine by means of bearings, and one end of which alignment roll is movable to change the axial alignment of the alignment roll, and in which the axle journal or an equivalent axle of the movable end of the alignment roll is mounted on the machine frame by means of a sliding bearing, in which said axle journal is supported on a bearing block using hydrostatic sliding bearing elements, which are movable in the bearing block in a direction substantially transverse to the axis of the alignment roll to adjust the axial alignment of the alignment roll.

The control of the fabric alignment roll and the measurement of fabric tension can be easily accomplished in the prior art applications that employ sliding bearing technology. However, these applications involve one annoying feature: the sliding bearing arrangement does not operate without auxiliary systems in an electric power failure situation. From the viewpoint of the bearing arrangement of the alignment roll it would be important, however, that not even during electric power failure does the bearing arrangement cause problems, but, instead, control would stop and yet the lubrication of the bearing arrangement would be taken care of. One problem is also the limitations imposed by the sliding bearing arrangement on the range of alignment movement, which is at present about ±30 mm.

In the prior art applications, information about the tension of a moving fabric, such as a wire, has been calculated based on the pressures of a hydraulic wire tensioning device. In that connection, information on the position of the tensioning device has also been needed and it has been necessary to take into account the weight of the frames of the tensioning device and the weight of the roll in different positions. One problem in these measurements has been that tension information has been inaccurate because frictions of the wire-tensioning hydraulic motor and frictions acting in power transmission have also affected

control and measurement values. Moreover, it has not been possible to calculate wire tension in situations where the tensioning device has been in an extreme position.

An object of the invention is to provide a device for guiding a moving fabric or web in a paper or board machine, in which the problems known from the prior art in connection with problems encountered in electric power failure situations have been solved.

One object of the invention is also to provide a device for guiding a moving fabric or web in a paper or board machine, enabling a wider alignment movement range than the currently known arrangements based on sliding bearing arrangements.

In addition, one object of the invention is to provide a method and a device for measuring the tension of a moving fabric in a paper or board machine in which the drawbacks and problems of the known applications are eliminated or at least minimized.

With a view to achieving the objects described above as well as those coming out later, the device for guiding a moving fabric or web in a paper or board machine according to the invention is mainly characterized by what is stated in the characterizing part of claim 1.

The method for measuring the tension of a moving fabric in a paper or board machine according to the invention is mainly characterized by what is stated in the characterizing part of claim 11.

The device for measuring the tension of a moving fabric in a paper or board machine according to the invention is in turn mainly characterized by what is stated in the characterizing part of claim 14.

In the device of the invention for guiding a moving fabric or web in a paper or board machine, the sliding bearing arrangement in the rotary motion of the roll found in the state-of-the-art application has been dispensed with, and in accordance with the invention it is taken care of by means of roller bearings, and in the device in accordance with the invention a hydrostatic bearing arrangement is adopted as a linear bearing in the direction of the alignment movement of the roll. The moving of the bearing housing is performed using devices known in themselves and used today. In case of electric power failure and when the feed of oil is cut off, the lubricating film disappears but the sliding bearing arrangement remains, as it shall do. The arrangement in accordance with the invention has, in principle, no limitation at all relating to the alignment movement range, but, instead, it can be made as long as desired.

In connection with the invention, the feed of oil in the hydrostatic bearing arrangement is advantageously carried out using a cartridge valve or equivalent known in itself from sliding bearing technology, so that fabric tension can also be calculated directly from a change in pressure measured from under a bearing piston in accordance with an advantageous additional feature of the invention. In connection with the invention, the bearing arrangement can be accomplished either such that the piston, the cartridge valve and the feed of oil are placed in a roller bearing block or in a frame. There can be one or more pistons. In that case, the feed of oil can be through one cartridge valve or each piston may have its own.

The linear bearing used in connection with the invention can also be inclined from the horizontal plane up to the vertical plane, but in that case a constant force is needed for pressing the roll against the base in order that lubrication and tension measurement shall operate.

In the method according to the invention for measuring the tension of a moving fabric, tension is measured apart from the fabric tensioning device such that in the

method a pressure measurement arrangement is arranged in connection with the support of the bearing housing of the roll for measuring the pressure in a chamber under a piston arranged in connection with the support of the roll, that fabric tension is determined by calculation based on the measured pressure. In that connection, the oil flow amounts needed in the tensioning device are small, and therefore only a small hydraulic unit is needed or the required pressure can be taken from some already existing machine unit of the paper or board machine, for example, from a circulation lubrication system. Moreover, the same unit could be used for measuring the tension of several moving fabrics.

In connection with an advantageous application of the device according to the invention, the support of the bearing housing of the roll is articulated at one edge and pressure measurement means are arranged at the other edge. A rod in connection with the piston is advantageously used for pressure measurement, which rod controls with its movement a small spindle of a pressure reduction valve. The required movement of the piston has been set small, advantageously 0 - 0.5 mm, so that it does not cause problems in the operation of the moving fabric. The pressure produced under the piston is proportional to a force - i.e. the tension of the moving fabric - acting according to a given formula that takes into account the masses of the roll and the fabric as well as the wrap angle of the fabric. The formula comprises mass calibration and the lever ratios at the measurement point. Wire tension is obtained from the following formula:

p • A + r • m - g T = + C ₁ r • (cosα + cosβ)

Where

P = measured pressure A = piston area r = lever ratio of the support m = mass of the roll and bearings

α = wire angle from the horizontal plane, inlet side β = wire angle from the horizontal plane, outlet side g = constant, normal acceleration of gravity, 9.80665 m/s ² C ₁ = correction factor

In the following, the invention will be described with reference to the figures in the appended drawing, but the invention is by no means meant to be narrowly limited to the details of the figures.

Figure 1 is a schematic view of one application of the device in accordance with the invention, viewed perpendicularly from the end of the roll.

Figure 2 is a schematic view of another application of the invention, viewed perpendicularly from the end of the roll.

Figure 3 is a schematic view of an application of the invention using several pistons.

Figure 4 is a schematic view of another application of the invention using several pistons.

Figure 5 schematically shows a longitudinal illustration.

Figure 6 shows one application for an inclined device.

Figure 7 schematically shows another application for an inclined device.

Figure 8 is a sectional view along the line A-A in Fig. 7.

Figure 9 is a schematic view of one application for measuring the tension of a moving fabric.

In Figs. 1-8, the same reference numerals are used, in applicable parts, of the parts corresponding to one another unless otherwise specifically mentioned.

In the figures of the drawing, an alignment roll is denoted with the reference numeral 1, and a fabric or a web running over the roll is denoted with the reference numeral 3. If it is a fabric 3, it can be, for example, a wire, a felt, a drying wire or equivalent. In the case of a web, it can be a paper or board web. The alignment roll 1 is mounted transversely to the running direction R of the fabric 3. The alignment roll 1 is provided at its ends with axle journals 2 or, in a corresponding manner, with an axle, by which axle/axle journals the alignment roll 1 is rotatably mounted by means of roller or other similar bearings 9 placed in bearing housings 5. In accordance with the invention, the bearing housing 5 of one end of the alignment roll 1 in the direction of an alignment movement A is mounted by means of a hydrostatic bearing arrangement 7 on a machine frame 4. The bearing arrangement 7 of the first end of the alignment roll 1, i.e. the end shown in Figs. 1-4 and 6-8, is in accordance with the invention, while a bearing housing 6 of an opposite end of the roll 1 is fixedly attached to the frame 4. The bearing 9 allows the turning of the axial direction of the roll 1 with respect to the bearing point in question inside the bearing housing 6. In that connection, for example, a spherical roller bearing can be used as the bearing 9.

The movable end of the roll 1 shown in the figures is supported in the bearing housing 5 resting on support of the hydrostatic sliding bearing 7. The bearing arrangement 7 supporting the movable end of the roll carries the weight of the roll 1 together with support members of the opposite end of the roll.

The position of the fabric 3 on the roll 1 is monitored in a manner known in itself by means of a monitoring device, which instructs an actuating device 8 to move the end of the roll in either of the movement directions indicated by the arrow A.

As the actuating device 8 it is possible to use any electromechanical, pneumatic or

hydraulic actuating device known from similar locations of use. Since the running direction of the fabric 3 remains perpendicular to the axis of the roll 1, a change in the axial direction of the roll causes the fabric 3 to be guided on the roll 1 in a desired direction, and the position of the fabric in the cross direction of the paper machine can be corrected. Because of the linear bearing arrangement 7, the bearing housing 5 moves almost without any friction a desired distance in the direction of action of the movement force produced by the actuating device. Advantageously, the alignment equipment is dimensioned so that the movement of the roll end in the running direction of the fabric 3 is ±60 mm at its maximum.

As shown in the figures, the bearing arrangement of the rotary motion of the roll is provided using roller bearings 9 and the hydrostatic bearing arrangement 7 is used, in the direction of the alignment movement A of the roll, as a linear bearing. The moving of the bearing housing 5 is performed using actuating devices 8 known in themselves and currently in use.

The hydrostatic bearing arrangement 7 is formed by an oil or similar medium film between the bearing housing 5 and the frame 4. The pressure medium of the hydrostatic bearing arrangement 7, for example, oil, is fed along a feeding line 13 into a pressure space under a piston 12 and from there further along capillary lines 17 through the piston 12. Pressure control is accomplished by means of a cartridge valve 11 or equivalent known per se from sliding bearing technology, so that the tension of the fabric 3 can also be calculated directly from a change in pressure measured from under the bearing piston 12. The bearing arrangement 7 can be accomplished such that the piston 12, the (cartridge) valve 11 and the oil feed 13 are placed either in the bearing block 5 or in the frame 4. There can be one or more pistons. Figs. 3 and 4 show an application of the invention using several pistons, the feed of oil being accomplished through one cartridge valve or each piston having its own. In the application shown in Fig. 3, on the left, pressure is controlled by one cartridge valve and oil is passed from under its piston along a separate duct 18 to an adjacent piston. Fig. 4 in turn shows an application in

which both pistons 12 have their own valves 11. For measurement of tension in this kind of application, pressure needs to be measured from under both pistons 12, the total force being obtained from it by calculating.

The linear bearing 7 can also be inclined from the horizontal plane up to the vertical plane, but in that case a constant force is needed for pressing the roll against the base in order that lubrication and tension measurement shall operate, Figs. 6-7.

The slide shoe of the linear bearing arrangement 7 is most preferably mounted in the direction in which the centre of the wrap angle of the fabric 3 indicates, in which case the measurement of tension from the pressure difference is most precise. If the directions differ considerably, measurement accuracy can be increased placing an additional piston 14 at an angle of 90° to the preceding one, and fabric tension can be calculated from the pressure differences of these, Figs. 6-7.

Figs. 6 and 7 show applications in which the location of the alignment roll in the run of the fabric is such that the alignment direction A is not in the horizontal plane. The linear bearing 17 is in that case on an inclined plane. Fig. 6 shows a version in which pistons 12, 14 are at an angle of 90°, and the pressure of each is determined according to load. An additional piston 14 with its valves 11 can be placed either in the bearing block 5 or between the actuating device 8 and the bearing block 5, so that its loading can be against the bearing block 5 or against a backing surface 16 on the side of the actuating device 8. In Fig. 7, second additional pistons 15 are additionally placed in a direction opposite to the bearing 7 to press the bearing block 5 against the frame 4. In the applications shown in Figs. 6 and 7, the actuating device 8 moving the bearing block 5 is situated below the bearing block 5.

Fig. 8 schematically shows a section along the line A-A in Fig. 7, showing an application for providing a support force for the bearing block 5 using second additional pistons 15.

In the example shown in Fig. 9, a support 37 of the bearing housing 5 of the roll 1 is supported at one edge 38 by means of an articulation member 34 and the other edge 5 is provided with a pressure measurement arrangement 30. The pressure measurement arrangement is placed at a rod 21 in connection with a piston 26 arranged at the other edge 35 of the support 37, said rod controlling with its movement a small spindle of a cartridge valve or equivalent 25. A chamber 27 situated under the piston 26 and sealed with a seal 28 arranged in connection with the piston 26 is supplied with pressure oil from below through the cartridge or slide valve 25. The pressure oil feed system also comprises a filter 22, a pump 23 and a bypass circulation 24. The necessary piston movement is set small, advantageously 0 - 0.5 mm, so that it does not cause problems in the operation of the moving fabric. The pressure produced in the chamber 27 under the piston 26 is proportional to the acting force, i.e. to the tension of the moving fabric. The pressure acting in the chamber 27 is measured using a pressure measurement valve 33, and the effective fabric tension is calculated from this taking into account the diameter of the roll, the masses of the roll and the fabric, and the wrap angle of the fabric, as well as the lever ratios of measurement. In the example of the figure, the lever ratio is about ¹ A because the pressure measurement arrangement is placed at one edge of the support. Capillaries 32, 31 are arranged in connection with flow ducts leading from the chamber 27 under the piston 26 to a bleed oil container and to the pressure measurement valve.

Above, the invention has been described only with reference to some of its advantageous exemplifying embodiments, to the details of which the invention is by no means meant to be narrowly limited.