WO2007118930A1

WO2007118930A1 - A suction device equipped with an overpressure apparatus, and an overpressure apparatus

Info

Publication number: WO2007118930A1
Application number: PCT/FI2007/050150
Authority: WO
Inventors: Olavi Savolainen
Original assignee: Effcom Oy
Priority date: 2006-04-13
Filing date: 2007-03-20
Publication date: 2007-10-25
Also published as: FI118693B; FI20065236A; FI20065236A0

Abstract

An apparatus for removing a liquid, dusty or solid substance from a moving fabric or web (3, 16, 17, 28), the device comprising at least: a surface (1 a, 2b), against which the fabric or web is pressed by the effect of negative pressure; and one or more openings, gaps or perforations in the surface (1 a, 2a), through which the negative pressure is effective on the fabric or web travelling past said surface (1 a, 2a); a pressure box (19), through which an overpressure is effective on the fabric or web travelling past said surface (1 a, 2a). In one embodiment of the apparatus, the pressure box (19) is arranged to follow the transverse movement of the fabric or web. In one embodiment, the apparatus comprises at least one carriage moving on the surface (1a, 2a), the pressure box (19) being coupled to the carriage.

Description

A SUCTION DEVICE EQUIPPED WITH AN OVERPRESSURE APPARATUS, AND AN OVERPRESSURE APPARATUS

Field of the invention

The invention relates to an apparatus for removing a liquid, dusty or solid substance from a moving fabric or web. The invention also relates to a method for removing liquid from a wire moving in a paper machine and from a web placed on the same. Furthermore, the invention relates to the use of an apparatus for cleaning a moving wire, felt or another fabric.

Background of the invention

The conventional function of the wet end of a paper machine is based on, for example, the so-called Fourdrinier principle, by which an endless rotating wire is covered with pulp which consists of a liquid and the fibres required for paper manufacture and which is herein also called a web. Water is removed from the web at several different steps by means of devices placed under the wire and including, for example, foils and various suction boxes.

One suction box is presented in EP 0 639 667 A1. Said suction box comprises a roll rotating with the wire and having a jacket that is, for example, meshed. The roll is placed in the box under a negative pressure. Air flows through the wire and the jacket of the roll. The document also presents the use of overpressure to make the removal of liquid more efficient. A device for producing suction in the suction box is presented in WO 99/64667 A1. WO 95/07387 A1 discloses a device used for controlling a felt and a web supported on it, applying a rotating roll whose perforated jacket is permeable to air. Other rolls are also known which are provided with a perforated jacket and equipped with suction by means of a separate device. One device is disclosed in US 5,347,728.

A suction device according to Fig. 1 is also known, by which it is possible to support a moving wire so that the friction is reduced when compared with, for example, foils. In an opening in the upper surface of the device, against the wire, a perforated rotating roll is provided, through which a negative pressure is effective on the wire. The device is used to provide a sufficient suction effect and high-capacity dewatering, wherein it can also be applied on wires with a high speed. In particular, the device can be used to replace suction boxes of prior art. The device is suitable for the removal of liquid as well as solids, for example dust, from a wire, a felt or various other fabrics which are used, for example, in a paper machine.

The device of Fig. 1 is also applicable for the removal of dust developed during the manufacturing process of various fabrics or the like, or for the removal of liquid, dust and solids accumulated during their cleaning. Consequently, the device can be used as a cleaning device or a dewatering device for removing liquid or solids from moving pulp, a web or a fabric, for example from a wire and a felt, which are sufficiently permeable to air or liquid.

Summary of the invention

The aim of the invention is to eliminate the above-presented drawbacks of prior art. Another aim of the invention is to make the operation of the suction device more efficient, particularly by affecting the removal of liquid.

The apparatus according to the invention is presented in claim 1. The method according to the invention is presented in claim 14. The use according to the invention is presented in claim 15. Another apparatus according to the invention is presented in claim 16. The other claims present some embodiments of the invention.

The arrangement according to the invention for making the operation of the suction device more efficient comprises an apparatus, by means of which overpressure is effective on the opposite side of the wire when compared with the effect of negative pressure. The overpressure makes, for example, the removal of liquid from the web path and the operation of the suction device more efficient. The overpressure moves liquid from the web path to an area subjected to negative pressure, and the negative pressure removes the liquid further from the web path. The arrangement is applied particularly by providing a web path with two wires and the web therebetween. A suction device and an overpressure apparatus implemented by means of a pressure box are provided on opposite sides of the web path.

In the arrangement according to the invention, overpressure is effective on an area that is also subjected to the negative pressure of the suction device. In one embodiment of the invention, the sealing between the overpressure apparatus and the suction device is provided by defining the area which is subjected to the overpressure and in which the friction between the web path and the sealing is as low as possible. The structures of the suction device are taken into account in the sealing solutions.

In one embodiment of the invention, the pressures and amounts of air in the overpressure apparatus and the suction device are set so as to minimize the spurting and splashing of liquid between the overpressure apparatus and the web path, or the sealing and the web path. The settings are selected so as to direct the air flow in said locations towards the inside of the configuration formed by the suction device and the overpressure apparatus, or to minimize said air flow.

The arrangement according to one embodiment of the invention comprises, for the suction device, a sealing device that is capable of following the transverse movement of a fabric, for example a wire. The function can be described as being active, because the sealing device follows the movement of the fabric in different situations. The sealing device is capable of keeping the ends of the opening of the suction device closed and sealed even if the fabric moved in the transverse direction. The sealing device is placed onto the ends of the opening and glides above the roll. Using the sealing device, the openings can be made so long that they cover the full width of the fabric, irrespective of even large movements of the fabric. According to one example, the suction device is coupled to the sealing device, with which the overpressure apparatus moves. The sealing device utilizes a movable carriage which can also be utilized for moving the overpressure apparatus as such, without properties relating to the sealing. Brief description of the drawings

In the following, the invention will be described in more detail with reference to the appended drawings, in which:

Fig. 1 illustrates the principle of a suction device according to prior art, the suction device comprising a rotating roll against a moving fabric,

Figs. 2, 3, 4, and 5 illustrate suction devices according to the invention, equipped with overpressure apparatuses,

Figs. 6, 7, 9, and 10 illustrate pressure boxes and sealings in cross-sectional views, and

Fig. 8 illustrates the pressure box and the sealing of Fig. 9, seen from below.

Detailed description of the invention

As shown in Fig. 1 , the dewatering suction device comprises a box-like and sealed chamber 1 used as a basin, in which a rotating roll 2 has been placed. The upper surface 1 a of the box, on and against which a fabric 3 is placed, is substantially flat and typically horizontal. The upper surface 1 a may also form a very gently sloping angle, the roll 2 being placed in the angular point. The chamber 1 is elongated and extends preferably underneath the fabric 3, substantially over its whole length. The chamber 1 is placed crosswise, primarily transversely to the travel direction of the fabric 3, in the same way as the opening 1 b in the upper surface 1a of the chamber 1. The opening 1 b is uniform and continuous and extends over the full width of the fabric 3. The chamber 1 is closed with end parts 1c.

A roll 2 is placed inside the chamber 1 and is allowed to rotate with the fabric 3. The opening 1b exposes at least part of the outer jacket 2a of the roll 2 in such a way that the moving fabric 3 or web that is tangential to the chamber 1 can be supported to the outer jacket 2a. Preferably, the roll 2 extends slightly higher than the upper surface 1 a and causes a gently sloping ridge in the fabric 3, when the wire is placed or aspirated against the outer jacket 2a. The roll 2 and the upper surface 1 a form a surface, against which the fabric 3 is pressed by the effect of the suction. This part of the outer jacket 2a covers a sector-like part limited by beams 4 and 5 at the front and back edges of the opening 1b. The exposed sector-like part encompasses about a quarter or less of the outer jacket 2a shown in Fig. 1. In the presented embodiment, said beams 4 and 5, at the same time, constitute the upper surface 1 a and are placed as close to the roll 2 as possible. The beams 4 and 5 are connected to the upper part of the chamber 1 or to supporting structures above the chamber 1.

The fabric 3 travels along the upper surface 1a, and the negative pressure effective on the fabric 3 removes, for example, liquid from the fabric 3 further into the chamber 1. The roll 2 is perforated, and the suction prevailing inside it pulls the fabric 3 against the outer jacket 2a of the roll and the liquid to the inside of the roll 2 and into the chamber 1. The roll 2 is arranged to rotate around a rotation axis X, and the rotation axis X is parallel with the longitudinal axis of the roll 2 and also with the opening 1 b. The width of the opening 1 b is a fraction of the length of the roll 2 and the opening 1 b. The longitudinal axis is parallel with the chamber 1 and transverse to the travel direction of the fabric 3. The roll 2 rotates or is rotated at a speed that corresponds to the speed of the fabric 3.

The roll 2 comprises the structure of a shaft 6, for example a solid shaft, appropriately mounted with bearings at its ends. In the presented embodiment, the ends of the shaft 6 protrude from both ends of the chamber 1 , wherein the bearings can be easily arranged outside the chamber 1. The gap between the end of the chamber 1 and the shaft 6 is sealed with appropriate sealings. At least one end of the shaft 6 may be connected to a separate rotating device, typically an electric motor, to rotate the roll 2 via the shaft 6.

The roll 2 comprises an outer jacket 2a with a circular cross-section. The outer jacket 2a can be made of a sheet or, for example, as a wire-cloth that is permeable to liquid and air. In a way known as such, the outer jacket 2a may be perforated or equipped with holes or openings, through which the suction is effective on the moving fabric 3. Through the outer jacket 2a, the liquid or air flow can enter the inside of the roll 2. The air flow effected by the suction and passing through the fabric 3 and the web carries liquid, dust and possibly other solids that can penetrate the fabric 3 and the outer jacket 2a.

The ends of the upper surface 1a of the chamber 1 are provided with inclined sealing surfaces 8 which are placed partly underneath the fabric 3. The fabric 3 rises from the upper surface 1a onto the sealing surface 8. The sealing surfaces 8 are placed onto the roll 2, and simultaneously they cover the ends of the opening 1 b. The sealing surface 8 is connected to the chamber 1 or to the beams 4 and 5. The sealing surface 8 is formed in a part, whose lower side conforms to the shape of the roll 2 at the opening 1 b. In Fig. 1 , said part is connected next to a cover 7 fixed on the end part 1c to close the opening 1 b. The sealing surface 8 and the cover 7 may also constitute a single integrated element.

The chamber 1 is coupled, for example by means of a connection 9, to a separate suction system to provide a suction effect. The pressure difference causes a liquid or air flow through the outer jacket 2a and simultaneously through the fabric 3 or web into the chamber 1.

The beams 4 and 5 as well as the sealing surfaces 8 define a suction area, that is, the area subjected to negative pressure, having a length Y1 and a width X1. The suction area is placed at the opening 1b. Similarly, in the example of Fig. 3, the beams 4 and 5 and the carriages 11 define the suction area. The suction area may also be shorter than the distance between the two sealing surfaces 8 or the carriage 11 , because the length Y1 of the suction area is also confined to that area of the outer jacket 2a of the roll 2 which is provided with holes, openings or gaps.

In the example of Fig. 2, the overpressure apparatus is installed as a pair to the suction device of Fig. 1 , on the opposite side of the web. The overpressure apparatus comprises a box or a hood that is also called a pressure box 19 in this description, wherein the web is placed between the pressure box and the roll 2. The pressure box 19 is placed at the suction area defined by the suction device, and the size of the pressure box is selected so that the pressure is effective on the suction area (X1 , Y1). The pressure box is coupled, for example by means of a connection 20, to a separate suction system to provide a pressure effect. The pressure box can be constructed in a variety of ways and of various materials. The pressure box can be constructed, for example, of metal or plastic, or the pressure box is made of a fabric and a frame supporting it.

In this example, the web path consists of two fabrics 18 and 16, a web 17 being placed therebetween. The pressure box is compressed against the fabric 16, and the roll 2 is compressed against the fabric 18. The pressure box is installed at a distance from the suction device, and it is supported by structures whose construction may vary. The pressure box is supported, for example, to structures on top of the web, or structures placed on each side of the web.

In practice, it has been found that particularly the position of new wires in relation to the suction device varies from several millimeters to even several centimeters; that is, the wire "wanders" in the direction transverse to the travel direction of the web path. The variation of the web path may have a negative effect on the quality of the web, particularly at the edge of the web and the wire. For example, the suction device of Fig. 1 has an opening 1 b, through which the suction is effective on the wire and the web which is narrower than the wire. If the wire and the web move vigorously in the cross direction, the ends of the opening 1 b are covered to a varying extent, which will affect the negative pressure maintained inside the apparatus and makes it more difficult to maintain a uniform suction. If the opening 1 b is not sealed under the wire, the suction becomes weaker.

According to one example, the web path, for example the fabric 3, moves the sealing device which comprises parts placed at both edges of the fabric 3 and coupled to each other for a synchronized movement.

Figure 3 shows in more detail a suction device according to one embodiment of the invention, equipped with a moving sealing device and an overpressure apparatus. The principle of operation of the suction device of Fig. 3 corresponds primarily to the operation of the suction device of Fig. 1. Figure 3 shows one of two carriages 11 detached from a coupling 13 and apart from a bearing part 10, for better illustration and to expose the bearing part 10. As in Fig. 2, the overpressure apparatus is installed as a pair to the suction device, comprising a pressure box placed between the carriages 11 and at the suction area defined by the suction device.

The bearing parts 10 close the ends of the openings 1b, being placed at the edges of the beams 4 and 5, and they are connected e.g. on top of the end parts 1c. The bearing parts 10 are also placed as close as possible to the ends of the roll 2. The shape of the upper surface of the bearing parts 10 corresponds to the joint shape of the upper surface 1a and the outer jacket 2a of the roll 2. For the bearing, the upper surface of the bearing part 10 is provided with a cut grooving 12, to which a liquid is supplied, for example pressurized water, to carry the carriage 11 and to act as a bearing between the bearing part 10 and the moving carriage 11 , and also between the carriage 1 1 and the beams 4, 5. The water also seals the gap between the bearing part 10 and the carriage 11 , so that no suction into the roll 2 takes place via said gap, and variations of negative pressure are avoided. The liquid is supplied, for example, via an inlet at the end of the bearing part 10. From the inlet, a channel extends inside the bearing part to the grooving 12.

Figure 4 shows an example in which the suction device of Fig. 3 is used, but the pressure box is supported on top of the carriages 11. In one example, two carriages are provided at the same end of the roll 2, the first carriage moving with the fabric 3 and taking care of the sealing, and the second carriage supporting the pressure box. The second carriage is stationary and is moved, if necessary, for example by actuators.

The single carriage 11 can be utilized for sealing independently of the pressure box, as shown in Fig. 3, or solely by moving the pressure box supported on top of the carriage 11 , or jointly for both sealing and moving of the pressure box. The pressure box can also be arranged to be movable in another way, for example, for monitoring the transverse movement of the carriage 11 or the web path. With reference to Fig. 3, the shape of the lower surface of the moving carriage 11 , in turn, corresponds to the joint shape of the upper surface 1a and the outer surface 2a of the roll 2 so that the carriage 11 can be placed sealingly on top of them. Because the shapes are the same, the carriage 11 can glide on the bearing part 10 and the beams 4, 5. In the example shown in Fig. 4, the carriage 11 has a substantially vertical surface, against which the moving edge of the fabric 3 is sealed. When the fabric 3 moves in the cross direction, it simultaneously also pushes aside the carriage 11 , wherein no gap can be formed between the fabric 3 and the carriage 1 1. The end of the roll 2, as well as the gap between the roll 2 and the bearing part 10, are placed underneath the carriage 11. The roll 2 is wider than the fabric 3, so that the suction effect remains equal over the full width of the fabric 3, even if the fabric 3 moved in the lateral direction.

The other carriage 11 on the other side of the fabric 3 is coupled to the carriage 11 that the fabric 3 forces to move. Thanks to a coupling 13, the carriages 11 follow each other's movements, wherein no gap is formed between said second carriage 11 and the fabric 3 either. The coupling 13 is, for example, mechanical, comprising two bars coupled to both sides of the carriage 11 and to both carriages 11. The coupling 13 is placed so that it will not be hit by the fabric 3. For example, the coupling 13 may have a control function, by means of which the distance between the carriages 11 can be changed as desired. The coupling 13 can also be placed underneath the beams 4 and 5 or inside channels formed therein. The pressure box coupled on top of the two carriages 11 can be used as a corresponding coupling.

The beams 4 and 5, the bearing parts 10 and the carriages 11 are made of, for example, a plastic material having good sliding properties to reduce friction.

According to another embodiment of the invention, an inclined sealing surface 8 according to Fig. 1 can be placed next to the carriage 11 , underneath the fabric 3, the fabric 3 rising above the sealing surface 8, which is connected to the carriage 11. The fabric 3 pushes and moves the carriage 11 , being pressed against the sealing surface 8. The carriages 11 slide on the suction device, crosswise to the fabric 1 , and the web path is placed therebetween. The above-presented principles can also be applied when the upper surface 1a is substantially flat throughout and it does not comprise a roll. Even in such a case, the shape of the upper surface of the bearing part conforms to the upper surface 1 a, and the lower surface of the carriage 11 conforms to the shape of the upper surface of the bearing part and the upper surface 1 a. The carriage 11 covers those openings, gaps or holes in the upper surface 1a, which are not placed underneath the fabric 3.

Figure 4 shows an example in which the suction device of Fig. 3 is used, but the pressure box is supported on top of the carriages 11. When the carriages 11 move, the pressure box moves as well. The advantage is that the moving pressure box is always in the same position in relation to the web path which moves in the transverse direction. The suction area defined by the carriages 11 moves with the web path, and thanks to the arrangement, the pressure is always effective in the suction area followed by the pressure box 19.

Figure 5 shows an example in which the suction device of Fig. 2 is used, but the pressure box is supported on top of the covers 7. Alternatively, the pressure box is supported on top of the bearing part 10 or the end 1 c, in a movable or stationary manner.

Figures 6, 7, 8, 9, and 10 illustrate, in more detail, examples of the sealing structures used for sealing the pressure box. The sealing structures seal the pressure box and particularly the gap against the wire, to enable a more accurate control of the overpressure and the negative pressure. The sealing structures define the area subjected to the overpressure and covering the suction area, for example the suction area X1 , Y1 of Fig. 1. The sealing structure defines, for example, a width X2, X3 or X4 and, for example, a length Y2 for said area. The area subjected to the overpressure is preferably equal to or slightly larger than the suction area. Figure 9 shows the sealing structure of Fig. 8 seen from below. Figure 6, 7, 8, and 10 show cross- sectional views of the pressure box, seen from the end of the pressure box.

Figure 6 shows a sealing 21 fixed to the lower edge of the pressure box, at least on the long sides of the pressure box, and also at the ends, if necessary, wherein it is suitable for suction devices of both Figs. 1 and 2 and Figs 4 and 5. For example, the sealing 21 has four straight parts placed at the four edges of the pressure box. The sealing 21 comprises a flexible skirt, whose first edge is attached to the pressure box and the second edge is freely movable but is placed against the wire. The sealing is made of a suitable flexible material, for example rubber or plastic. The contact points between the sealing 21 and the wire define the area X2, inside which the suction area is placed. The skirt is directed towards the inside of the pressure box, wherein the overpressure of the pressure box tends to press them against the wire, improving the sealing.

Figure 7 shows a sealing 22 fitted at the lower edge of the pressure box, at least on the long sides of the pressure box. The sealing 22 has a circular or oval cross-section, and it may also be hollow, wherein pressure is maintained inside it. The overpressure of the pressure box tends to press the sealing 22 against the wire, improving the sealing. The sealing 22 is such that it can move towards the wire which is touched by the sealing 22 on its convex surface. The contact points between the sealing 22 and the wire define the area X3, inside which the suction area is placed.

Figure 8 shows a sealing 14 fixed to the lower edge of the pressure box, at least on the long sides of the pressure box and also at the ends, if necessary, wherein it is suitable for suction devices of both Figs. 1 and 2 and Figs 4 and 5. The sealing 14 comprises a flexible skirt, whose first edge is attached to the pressure box and the second edge is freely movable but is placed against the wire. The contact points between the sealing 14 and the wire define the area X4, inside which the suction area is placed. On that side of the pressure box, where the fabric 3 moves towards the pressure box, the skirt is oriented in the direction of the movement, and on that side where the fabric 3 moves away, the skirt is oriented against the movement. The skirt is directed to the inside of the pressure box, improving the sealing. The sealing 14 has a convex surface touching the wire. The convex surface is provided for example by supporting the free edge of the skirt at a suitable point, for example by means of struts 23.

Figure 9 shows an example of the sealing 14 in more detail. The sealing 14 comprises, for example, a thin uniform material piece with a cut opening 15. The edge of the opening 15 forms the skirt of the sealing 14. Overpressure is effective through the opening 15 on the wire in an area with a width X4 and length Y2. Struts 23 are connected to the edge of the opening 15.

Figure 6 illustrates the use of the sealing structures and the amounts of air moved in the system in more detail. A negative pressure is effective in the suction device, tending to aspirate air through the suction area (amount of air V3). By means of the sealing structure and the setting of the pressures, the situation is controlled so that most of the air is obtained from the pressure box where an overpressure is maintained by supplying air (amount of air V1). The amount of air V1 is fitted to match the amount of air V3, wherein the air flow between the sealing and the wire is as low as possible (amount of air V2). Preferably, the amount of air V2 flows only towards the suction area, wherein the amount of air V3 is equal to or greater than the amount of air V1. The advantage is that the spurting and splashing of liquid between the sealing and the wire are prevented, which can also be monitored to implement the adjustment of pressures.

Figure 10 shows a sealing 24 fixed to the lower edge of the pressure box 19, at least on its long sides, and also at the ends, if necessary, wherein it is suitable for suction devices of both Figs. 1 and 2 and Figs 4 and 5. The shape and the structure of the pressure box 19 may vary, and the sealing 24 can also be applied with other boxes and hoods. The sealing 24 comprises a profile used as a frame 25, inside which a moving lip 26 is placed, partly protruding from the lower edge of the frame 25. The lip 26 is a structure consisting of one or more parts, for example a strip or a beam of a plastic or rubber material. The lower end of the lip 26 is pressed against the fabric, to maintain a pressure p1 inside the pressure box 19. If necessary, the lip 26 can also be provided with a lifting spring or a relief spring.

Figure 10 shows two different examples of the sealing 24. The lip 26 is sealed against the inner part of the frame 25, and a chamber 27 is formed therebetween, which may be supplied with the pressure p1 effective on the upper edge of the lip 26. The lip 26 is used as a piston moved by the pressure p1. The pressure p1 is led into the chamber 27 directly from the inside of the pressure box 19, for example via a gap, so that a separate tubing is not necessary. Even in this case, pushed by the effect of the overpressure in the pressure box 19, the sealing can be pressed, for example, against the wire. The sealing has a surface subjected to the overpressure and providing a force to press the sealing. The sealing is pressed against the fabric from a substantially transverse direction.

The clearance between the lip 26 and the profile 27 may be greater if, for example, a flexible means 28 is placed inside the chamber 27, inside which means the pressure p1 is effective and which is connected to the overpressure effective inside the pressure box 19. Preferably, it is for example a hose or for example a bag or sack connected to the connection 20, a separate connection 29 or a pressure hose 30. By the effect of the overpressure, the member 28 expands and directs a force on the lip 26 which moves.

The invention is not limited solely to the above examples, but it may vary within the scope of the appended claims.

Claims

1. An apparatus for removing a liquid, dusty or solid substance from a moving fabric or web (3, 16, 17, 28), the device comprising at least:

- a surface (1 a, 2a), against which the fabric or web is pressed by the effect of negative pressure, and

- one or more openings, gaps or perforations in the surface (1a, 2a), through which the negative pressure is effective on the fabric or web travelling past said surface (1 a, 2a),

- a pressure box (19) which is placed on the opposite side of the fabric or web with respect to said surface (1a, 2a) and through which the overpressure is effective on the fabric or web travelling past said surface (1a, 2a),

characterized in that:

- the pressure box (19) is arranged to follow the movement of the fabric or web in the transverse direction.

2. The apparatus according to claim 1 , characterized in that the apparatus also comprises

- a roll (2) placed transversely to the moving fabric or web and arranged to rotate around a rotation axis (X), and comprising an outer jacket (2a), through which a flow of liquid or air can enter the inside of the roll

(2);

- a chamber (1), inside which said rotating roll (2) is placed, and which comprises an opening (1 b) in the direction of said rotating axis (X), the opening being arranged to expose at least a part of the outer jacket (2a) in such a way that the moving fabric or web, tangential to the chamber (1), can be supported against the outer jacket (2a).

3. The apparatus according to claim 1 or 2, characterized in that the apparatus also comprises a sealing (14, 21 , 22) which is fitted in the pressure box (19) and which defines an area subjected to the overpressure and which, by the effect of the overpressure, is capable of being pressed against the fabric or web (3).

4. The apparatus according to claim 3, characterized in that one or more openings, gaps or perforations provided in the surface (1 a, 2a) define a suction area (X1 , Y1) subjected to the overpressure, wherein the area defined by the sealing (14, 21 , 22) corresponds to said suction area or is greater than said suction area.

5. The apparatus according to any of the claims 1 to 4, characterized in that the apparatus further comprises at least one carriage (11) moving on the surface (1a, 2a) and being placed adjacent to the fabric or web and following the transverse movement of the fabric or web, wherein said carriage (11) is arranged to cover that part of said opening, gap or perforation which is not placed underneath the fabric or web.

6. The apparatus according to claim 5, characterized in that a bearing part (10) is placed underneath the carriage (11), the shape of the upper surface of the bearing part (10) conforming to the shape of the lower surface of the carriage, and that a grooving (12) is provided in said upper surface, through which grooving the liquid used for bearing can be supplied between the carriage (11) and the bearing part (10).

7. The apparatus according to claim 5 or 6, characterized in that the pressure box (19) is arranged to follow the movement of the carriage (11).

8. The apparatus according to any of the claims 1 to 7, characterized in that said apparatus is placed in a part of the paper machine where said fabric (3) consists of two moving wires (16, 18) and where said apparatus is arranged to remove liquid from a web (17) placed between said wires.

9. The apparatus according to claim 3, characterized in that the sealing (14, 21) comprises a flexible skirt which is pressed against the fabric or the web.

10. The apparatus according to claim 9, characterized in that the flexible skirt is supported so that, by the effect of overpressure, a convex form is formed therein and is pressed against the fabric or web (3).

11. The apparatus according to claim 9 or 10, characterized in that on the side of the pressure box (19), where the fabric or web moves towards the pressure box (19), the flexible skirt is oriented in the direction of the movement, and on that side where the fabric or web moves away, the flexible skirt is oriented against the movement.

12. The apparatus according to claim 3, characterized in that the sealing (24) comprises a lip (26) partly placed inside a frame (25) and moving by the effect of overpressure effective inside the frame (25).

13. The apparatus according to claim 12, characterized in that the sealing (24) also comprises a flexible member (28) which expands by the effect of the overpressure and pushes the lip (26) out of the frame (25).

14. A method for removing liquid from a wire moving in a paper machine and from a web placed on it, characterized in that the liquid is removed by means of a device according to any of the claims 1 to 13.

15. The use of an apparatus for cleaning a moving wire, felt or another fabric (3), characterized in that an apparatus according to any of the claims 1 to 13 is used for the cleaning.

16. An apparatus for removing a liquid, dusty or solid substance from a moving fabric or web (3, 16, 17, 28), the device comprising at least:

- one or more openings, gaps or perforations in the surface (1a, 2a), through which the negative pressure is effective on the fabric or web travelling past said surface (1a, 2a),

characterized in that the apparatus also comprises:

- at least one carriage moving on the surface (1a, 2a), the pressure box (19) being coupled to the carriage.

17. The apparatus according to claim 16, characterized in that the carriage (11 ) is placed adjacent to the edge of the fabric or web and follows the transverse movement of the fabric or web, wherein said carriage (11) is also arranged to seal and to cover that part of said opening, gap or perforation which is not placed underneath the fabric or web.