ACTIVE SEALING OF A SUCTION 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. 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 apparatus. One apparatus is disclosed in US 5,347,728.

A suction apparatus 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 appa-

ratus 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 apparatus can be used to replace suction boxes of prior art. The apparatus 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 apparatus 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 apparatus 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.

In practice, however, it has been found that particularly the position of new wires in relation to the suction apparatus varies from several millimeters to even several centimeters; that is, the wire "wanders" in the direction transverse to the travel direction of the web. The variation of the web 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 apparatus of Fig. 1 has an opening, 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 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 is not sealed under the wire, the suction becomes weaker. If the suction is not constant but varies, it may have a harmful effect e.g. on those areas of the web which are located at the edges of the wire.

Summary of the invention

The aim of the invention is to eliminate the above-presented drawbacks of prior art.

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.

The arrangement according to the invention comprises, for the suction apparatus, a sealing device that is capable of following the movement of a fabric, for example a wire, in the cross direction. 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 apparatus closed and sealed even if the fabric moved in the cross direction. In one embodiment of the invention, the sealing device is placed on the ends of the opening and glides above a roll. By means of the invention, 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 fabric moves the sealing device which comprises parts placed at both edges of the fabric and coupled to each other for a synchronized movement. Thanks to the invention, the full width of the fabric can be utilized more closely, wherein e.g. the web on the wire can be made wider and the quality of the web is also better than before in the edge areas, because the suction effect no longer varies.

In one embodiment of the invention, the edge of the fabric is sealed against a vertical wall in the sealing device. An advantage to the example of Fig. 1 is not using an inclined sealing surface under the edge of the wire. In the invention, the edge of the wire remains straight, wherein the full width of the wire can be utilized, and the inclined position does not affect the quality of the web, even if the wire moved in the cross direction.

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 apparatus according to prior art, the suction apparatus comprising a rotating roll against a moving fabric,

Fig. 2 illustrates the principle of the suction apparatus according to the invention, the suction apparatus comprising a rotating roll against a moving fabric,

Fig. 3 illustrates the principle of one end part of the sealing device according to Fig. 2, and

Fig. 4 illustrates the operating principle of the sealing device according to Fig. 2, seen from the side.

Detailed description of the invention

As shown in Fig. 1 , the dewatering suction apparatus comprises a box-., like and sealed chamber 1 used as a basin, in which a rotating roll 2 has been placed. The upper surface 1a 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 1a 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 1a 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 1a 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, water 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 2a. The width of the opening 2a is a fraction of the length of the roll 2 and the opening 2a. 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 and the web 3 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 1b. 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 1b. The sealing surface 8 and the cover 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.

Alternatively, it is also possible to use a suction apparatus comprising an upper surface 1a that is uniformly flat or has a gently sloping angle but which suction apparatus does not comprise a roll placed in an opening. The fabric 3 remains straight and flat against the upper surface 1a. The upper surface 1a comprises one or more gaps or openings covering the full width of the fabric 3. Alternatively, the upper surface 1a is provided with a dense perforation covering the full width of the fabric 3. Even in this case, suction is arranged inside the chamber 1 , effective on the fabric 3 through openings, gaps or holes, to remove liquid from the by-passing fabric 3.

Figure 2 shows in more detail a suction apparatus equipped with a moving sealing device according to one embodiment of the invention. The numbering of the elements corresponds to the numbering in Fig. 1 , because the operating principle of the suction device of Fig. 2 corresponds primarily to the operation of the suction device of Fig. 1 ;

furthermore, the same reference numerals are used for the same parts. Figure 2 shows one of two sealing carriages 11 detached from a coupling 13 and apart from a bearing part 10, for better illustration and to expose the bearing part 10. In the following description, reference will be made to Figs. 2, 3 and 4.

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 18 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 sealing carriage 11 and to act as a bearing between the bearing part 10 and the moving sealing carriage 11 , and also between the sealing carriage 11 and the beams 4, 5. The water also seals the gap between the bearing part 10 and the. sealing carriage 11 , so that no suction into the roll 2 takes place via said _^ gap, and variations of underpressure are avoided. The liquid is supplied, for example, via an inlet 14 at the end of the bearing part 10. From the inlet 14, a channel 16 extends inside the bearing part to the grooving 12.

The shape of the lower surface 17 of the moving sealing 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 sealing carriage 11 can be placed sealingly onto them. Because the shapes are the same, the sealing carriage 11 can glide on the bearing part 10 and the beams 4, 5. In the example shown in Fig. 4, the sealing 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 sealing carriage 11 , wherein no gap can be formed between the fabric 3 and the sealing carriage 11. The end of the roll 2, as well as the gap between the roll 2 and the bearing part 10, are placed underneath the sealing 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 though the fabric 3 moved in the lateral direction.

The sealing carriage 11 of Figs. 2, 3 and 4 moves under the guidance of the fabric 3, without external control or monitoring, so that, for moving the sealing carriage 11 , it will not be necessary to employ actuators for moving the sealing carriage 11 and sensors for monitoring the lateral movements of the fabric 3 and for controlling the actuators via a control unit. Because the fabric 3 can move in the lateral direction without having a negative effect on the suction, it is also unnecessary to guide the fabric 3 by preventing its lateral movement by any device preceding the suction apparatus.

The other sealing carriage 11 on the other side of the fabric 3 is coupled to the sealing carriage 11 that the fabric 3 forces to move. Thanks to a coupling 13, the sealing carriages 11 follow each other's movements, wherein no gap is formed between said second sealing carriage 11 and the fabric 3 either.. The coupling 13 is, for example, mechanical, comprising two bars coupled on both sides of the sealing carriage 11 and to both sealing 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 sealing 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 beams 4 and 5, the bearing parts 10 and the sealing 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 sealing carriage 11 , underneath the fabric 3, the fabric 3 rising above the sealing surface 8, which is connected to the sealing carriage 11. The fabric 3 pushes and moves the sealing carriage 11 , being pressed against the sealing surface 8. However, the embodiment of Fig. 4 is more preferable, because the suction can be directed over the full width of the fabric 3.

The sealing carriage 11 can also be guided on the bearing part 10 and the beams 4, 5 so that the sealing carriage 11 extends over the flanks of the bearing part 10 and further underneath the bearing part 10. Thus, the movement of the sealing carriage 11 is limited both in the vertical direction and in the cross direction, and the clearance between said parts can be limited as desired. However, the sealing carriages 11 can slide freely on the suction apparatus, crosswise to the fabric 1 , and the fabric 3 is placed therebetween.

The above-presented principle of the invention 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 16 conforms to the upper surface 1a, and the lower surface 17 conforms to the shape of the upper surface 16 and the upper surface 1a. The sealing carriage 11 covers those openings, gaps or holes in the upper surface 1a, which are not placed underneath the fabric 3.

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