The invention relates to a dewatering device for a paper machine.

From the prior art a device arrangement is known in which dewatering takes place by means of a so-called blade shoe (for example, US patent 6,372, 091). The blade shoe is a ceramic structure placed transversely across the width of a suction box.

A flow passage for the water to be removed from a pulp web is formed between adjacent blade shoes. In the prior-art arrangements, the area of the load-bearing surface of the structure is substantially larger than the so-called free surface through which liquid is removed out of connection with the structure. This application discloses a totally novel dewatering device. The blade shoes are replaced in this application with pieces which are each separately attached to their base. The cross-section of the pieces is advantageously, for example, a circular cross-section, and the pieces are attached to their base such that the free space remaining between them forms a certain hole pattern. By selecting the grouping of the pieces and the free spaces between them, i. e. the so-called"hole pattern", in a suitable manner, the marking of the web is prevented and, hence, said selections have an important role in the manufacture of paper. Small button-like, preferably ceramic pieces are attached, in one embodiment of the invention, detachably to their base, for example, with screw means, and they can be placed in a precise position such that the outer surfaces of the pieces allow a desired web run to be formed as a straight run or with a certain radius of curvature M.

In the prior-art arrangement, dewatering passages, for example, grooves have been formed by working a ceramic structure and by removing material. In this application, this is not done, but pieces manufactured to be of a certain size are assembled into groups on the frame of the dewatering device using attachment means, and by means of them a dewatering pattern of a desired size and shape is

formed. In other words, the so-called free space remaining between the pieces can be made as desired in shape and in size by attaching the pieces to form a group of a certain configuration with respect to their base and one another.

In blade-gap formers in particular there is a very great need to provide symmetric initial dewatering where pulsating is minimized.

In this application it is proposed that the first chamber of the blade shoe be replaced with a straight or a slightly curved dewatering zone in which the carrier surfaces in contact with a wire are constituted by small separate pieces.

Advantageously, the pieces are ceramic pieces. Said ceramic pieces are placed such that they form a certain pattern that corresponds, for example, to a drilling pattern of a prior-art forming roll. In one embodiment of the invention, on both sides of the dewatering zone there is the same pattern formed by pieces, however, such that there is a phase shift between the patterns formed by the different sides.

Because of the phase shift, in said dewatering zone, a situation cannot arise where opposing pieces are placed against each other. An open volume is formed in the gaps formed between said pieces, preferably ceramic pieces, along which volume the water being drained is conducted away and, when needed, fine-tuning of the two-sidedness of the web is carried out by adjusting the dewatering process by means of suction.

The carrier surface of the dewatering area is formed such that the wires can be kept in shape with a sufficient number of pieces and with wire tension.

In accordance with the invention, the equipment is particularly suitable as a dewatering unit in connection with a former, so that the pieces define a surface against which a wire Hl, H2 is placed, stock W passing between the wires Hl and H2 and water being removed on two sides by means of a first dewatering unit of a dewatering box and, in one embodiment, by means of a second dewatering unit situated on the opposite side of the wire run. The pieces are arranged in such a

pattern configuration that a desired free space A2 is provided between the pieces 15ai, 15a2..., so that in the arrangement in accordance with the invention, in each suction zone, the ratio of the total area A2 of the free space to the area SA1 of the total surface defined by the pieces is selected as follows. The area A2 of the free space is larger than the area LA1 of the total support surface of the pieces in contact with the wire. The total area A2 of the free space remaining between the pieces 15al, 15a2... in the device is in a range of from 50 % to 90 % of the sum of the area LA1 of the total support surface of the pieces 15al, 15a2... and the total area A2 of the free space. The pieces are arranged into a suitable pattern, thereby avoiding the marking of the web, and the pattern may correspond, for example, to hole patterns of a forming roll. Each piece is attached to a frame R, for example, with a screw or with another attachment means in a detachable manner.

In accordance with the invention, it is also possible to use a frame R that is flexible and formed, for instance, such that the frame R is attached, as flexible, to a deformable hose, so that the hose forms a flexible support surface for the web run Hl, W, H2.

In accordance with the invention, the pieces are attached detachably with one central attachment means, preferably with a screw, to their base, such as a rail or a frame plate. Within the scope of the invention, an embodiment is also feasible in which preferably ceramic pieces are shaped so as to comprise a mating attachment shape; a profile shape to be placed in a mating attachment means of a rail, preferably in a groove. Advantageously, the number of pieces is in a range of from 100 pieces/m2 to 500 pieces/m2.

The pieces can be attached either to a rail (as shown in Fig. 5) or they can be attached to a base plate, a so-called frame plate, which is advantageously provided with elongated openings through which a vacuum is applied to a space between the frame plate and the wire run H1 or H2. Desired dewatering is achieved by

adjusting the length and the position of the openings, which also has the effect that there will be no marking in the web.

The dewatering device for a paper machine or equivalent according to the invention is characterized by what is stated in the claims.

In the following, the invention will be described with reference to some preferred embodiments of the invention shown in the figures of the appended drawings, but the invention is not meant to be exclusively limited to them.

Figure 1A is a side view of a piece according to the invention attached to a base.

Figure 1B is an illustrative and axonometric view of a structure according to the invention.

Figure 2A shows how pieces according to the invention are applied in a gap former arrangement, so that they form the surface of a dewatering unit against which a wire H1, H2 is placed.

Figure 2B is a cross-sectional view of the arrangement of Figure 2A in a machine direction and in more detail.

Figure 2C shows another advantageous embodiment of the dewatering device according to the invention. The equipment is in connection with a headbox and the illustration is a side view.

Figure 2D shows the area Xi in Figure 2C, and Figure 2E shows the device arrangement of Figure 2D viewed in the direction of the arrow Kl, and the web run Hi, W, H2 is not depicted to show structures.

Figure 3A illustrates the attachment of pieces to a frame plate comprising elongated openings for applying suction to a space between a wire and the frame plate as desired.

Figure 3B is an illustrative axonometric and partial view of the structure shown in Figure 3A.

Figure 4A shows another embodiment in which a frame plate is provided with elongated openings obliquely with respect to the running direction of the web.

Figure 4B is an axonometric and illustrative partial view of the structure of Figure 4A.

Figure 5 shows the attachment of pieces to a loading hose, to a flexible frame part on the loading hose.

Figure 6A shows another advantageous structure of the piece.

Figure 6B shows pieces of Fig. 6A attached to attachment frames R, R2, R3..., which in the embodiment of the figure are elongated, rib-like rail structures, the ceramic pieces 15ai, 15a2... being placed in grooves T in the rail structures, so that a respective mating piece joint formed in the ceramic piece will be situated in a mating attachment means provided in the attachment frame. The attachment can be, for example, a dovetail attachment.

Figure 6C is a partial sectional view of the position of a ceramic piece in a frame Rl, which is a rail-shaped and rib-like elongated structure comprising a groove T.

Figure 7 shows a curved frame Ri to which pieces 15ai, 15a2 are attached. Figure 7 shows the curvature of the frame Ri, whereby the support surface of the ceramic

pieces can also be made curved, and a certain tension is imparted to the wire H1, H2, which further affects the removal of water from a pulp web W.

Fig. 1A illustrates an arrangement in accordance with the invention, in which there is a dewatering device 13 removing water from stock W in a wire section of a paper machine. The dewatering device 13 comprises separate pieces 15al, 15a2... that support a wire Hl. The pieces 15al, 15a2... are arranged to be attached with screw means 16 to a frame R such that a free space A2 remains between the pieces 15al, 15a2... The dewatering device 13 comprises pieces 15al, 15a2... attached to the frame R; Rl, R2... and grouped to define a backing surface to be placed against the wire H1, H2 such that a free space A2 remains around each ceramic piece 15al, 15a2... The pieces 15al, 15a2... are advantageously ceramic pieces. The ratio of the total area A2 of the free space to the total area LA1 of the support surface of the pieces, A2 : LA1, is selected as follows. The area A2 of the free space is larger than the area 2 ; A1 of the total support surface of the pieces in contact with the wire. The total area A2 of the free space remaining between the pieces 15al, 15a2... in the device is in a range of from 50 % to 90 % of the sum of the area LA1 of the total support surface of the pieces 15al, 15a2... and the total area A2 of the free space. SA1 is then the sum of the areas of support surfaces J of the separate pieces 15al, 15a2... in contact with the wire. The total area A2 of the free space is that area amount of the wire which is in contact with the piece and which is limited merely to a free space D between the pieces 15al, 15a2... Thus, A2 is substantially larger than SA1 or, at one edge of the area, at most equally large as SA1. In this way, water removal passages become sufficiently large for the water sucked out of a pulp web W, and the dewatering process is made more effective. In the figure, the removal of water from the web W is designated with the arrows Li. The paper pulp or stock W travels between the wires H1 and H2.

The free space A2 surrounds each piece 15al, 15a2... on all sides thereof. The running direction of the web run H1, W, H2 is designated by S1.

In accordance with the invention, the pieces 15al, 15a2..., preferably ceramic pieces, are attached with one central attachment means, preferably with a screw 16, in a detachable manner to their base, such as a rail or a frame plate. Within the scope of the invention, an embodiment is also feasible in which the ceramic pieces are shaped so as to comprise a mating attachment shape; a profile shape to be placed in a mating attachment means of a rail, preferably in a groove. The number of pieces 15al, 15a2... is advantageously in a range of from 100 pieces/m2 to 500 pieces/m2, i. e. in a range of from 100 to 500 pieces/m2.

Fig. 1B is an illustrative and axonometric view of a structure according to the invention, with the web run H1, W, H2 not shown. Each piece 15al, 15ag..., preferably ceramic piece, is attached with screws 16 to a frame beam R1, R2... A vacuum is applied to a space D between the pieces 15al, 15a2... and further to the forming wire H1 and further to the pulp web W which is dewatered. The front edge of the piece 15al, 15a2... with respect to the direction Si in which the web run Hi, W, H2 comes to the piece 15al, 15a2... advantageously comprises a wear- resistant tip; a front edge 15b, which prevents wear of the piece 15al, 15a2... The tip 15b can be made of a different material from that of the rest of the piece 15al, 15a2... The surface J of each piece 15al, 15a2..., being the top surface of the piece, is in contact with the wire.

Fig. 2A shows an advantageous site of application of the invention. A dewatering device 13 comprising pieces 15al, 15a2... and dewatering units 13al, 13a2 situated on both sides of the wire and web run Hl, W, H2, is disposed after breast rolls 10au and 1 lal of a former 200. A stock jet W is introduced from a headbox 100 into a narrowing gap K between the wires H1 and H2 and further into the dewatering device 13 in accordance with the invention, to a space between the wires H1 and H2 between the dewatering units 13al and 13a2 of the dewatering device 13. In the former 200, as shown in Fig. 2A, the wire H1 is passed over rolls 10al, lOa2, lOa3, 10a4 and lOa5 and, similarly, the wire H2 is passed over rolls 1 lai, 1 la2, 1 las, 1 la4 and 1 la5. The web W is passed by means of the suction of the suction roll 10a2

into connection with the wire H1 only and, in connection with the wire Hl, onto a pick-up roll 12, whose vacuum is used for passing the web run W further to a press section 300.

Fig. 2B is a cross-sectional and illustrative view of the structure shown in Fig. 2A.

The breast rolls 10ai and l la1 bend the wires H1 and H2 into the narrowing gap K, into which the stock W is introduced as a jet from the headbox 100 and further into the dewatering device 13 in accordance with the invention, which dewatering device comprises the dewatering units 13al, 13a2..., preferably suction boxes, on both sides of the wire-stock-wire run HI, W, H2. Thus, water is removed from the pulp web W through the wires H1 and H2 on two sides by means of the suction produced in a space D by the vacuum of the suction boxes 13al, 13a2. The vacuum in the space D in the suction box 13al, 13a2 is produced through a dewatering and suction duct 14 such that the vacuum is applied to the space D between the pieces 15al and 15a2 and their attachment frames Rl, R2... The removal of water from the pulp web W thus takes place on two sides, and by using pieces 15al, 15a2... in accordance with the invention, the free flow area A2 between the pieces 15al, 15a2... can be maximized to maximize dewatering. The frames Ri, R2... can be curved, thus imparting curvature to the web run HI, W, H2. Suction can be provided in both suction boxes or only in one suction box or in neither suction box. Dewatering can be accomplished by means of the curvature of the web run Hl, W, H2 and, thus, by means of the tension of the wire H1, H2 and/or making use of the centrifugal force acting on the curved web run Hi, W, H2. In addition to these, it is also possible to use a vacuum produced by pumps in the space D, and thus suction. It is advantageous that water can be removed from the pulp web W in both directions, i. e. through both wires H1, H2.

Figs. 2C, 2D and 2E show an embodiment of the invention in which stock W is passed from a headbox 100 into a narrowing gap K between wires Hl and H2 passed via breast rolls 10ai and 1 lai. Further, after the gap K there is a dewatering device 13, which, in accordance with the invention, comprises a frame R which is

formed of a plate and to which pieces 15al, 15a2,15a3... are attached, for example, by gluing or detachably with screws 16. Fig. 2D shows the dewatering device 13 in more detail from the area Xi in Fig. 2C. Fig. 2E shows the structure as viewed in the direction of the arrow K in Fig. 2C. As shown in the above- mentioned figures, the plate R is thus provided with openings or holes Ul, U2..., through which a vacuum is applied to a free space D formed between the wire H1 and the plate R. The cross-section of the holes/openings Ul, U2... is advantageously a circular cross-section. The frame R has a radius of curvature M.

Thus, the web run Hi, W, H2 can be conducted with the radius of curvature M, and the stock W can then be subjected to a centrifugal force to remove water from the pulp web W. In the embodiment of the figure, water is thus moved out of the stock, i. e. the pulp web W, in two directions, into the space D due to the effect of the vacuum produced in the space D and, because of the centrifugal force, in the other direction, in which direction water is removed from the pulp web W through the wire H2. On the other side of the plate R there is a suction duct 14, which is further connected to a pump (not shown), so that the pump is used for applying suction through the holes/openings Ul, U2... of the plate R to the space D and further, through the wire H2, to the stock W. In the structure shown in Figs. 2C, 2C and 2D, the suction duct 14 is connected to an inlet chamber G, which becomes narrower towards its end, i. e. towards that part of the structure to which the web run H1, W, H2 comes first in the dewatering device 13. The entire structure, i. e. the plate frame R and the walls of the chamber G as well as the suction duct 14 can be advantageously made of stainless steel. The pieces 15al, 15a2 can be attached with screws to threaded holes of the frame R or the piece 15al, 15a2... can comprise an attachment arm tl, which is glued into a hole f of the frame R.

Figs. 3A and 3B show one advantageous embodiment of the invention in which pieces 15al, 15a2... are advantageously attached with screw means 16 to a plate- like frame R. It is provided with elongated openings Ul, U2..., the longitudinal axes X of which extend in the embodiment perpendicularly to the running

direction Si of the web and through which openings a vacuum is applied to a space D between the wire H1 and the frame R. By making the openings U1, U2... in a desired manner between the pieces 15al, 15a2..., sufficient space is also obtained for the wire water removed from the pulp web W.

Figs. 4A and 4B show an embodiment corresponding to that of Figs. 3A and 3B except that in the embodiment the longitudinal axes X of the openings Ul, U2... are arranged obliquely with respect to the running direction Si of the web. In this way, a desired arrangement of openings can be formed in the space D for different dewatering needs, thus achieving desired dewatering. The marking of the web can also be avoided by directing the opening Ul, U2... and, in the embodiment comprising an upper suction box 13al and a lower suction box 13a2, by placing the pieces in staggered relationship with respect to the upper suction box 13au and the lower suction box 13a2. In that case, the pieces 15al, 15a2... of the upper suction box 13al and the lower suction box 13a2 are not in opposed relationship.

Fig. 5 shows an embodiment of the invention in which a frame Ru comprises in its connection a pneumatic hose 40 that forms a flexible base for pieces 15al, 15a2...

In this embodiment, the rib-like frame Ru, to which the pieces 15al, 15a2... are attached by means of screws 16, is also a flexible structure, which is, for instance, glued to the surface of the hose 40.

In the embodiments of the invention, it is advantageous that the pieces 15al, 15a2... are attached with attachment means 16, preferably with screws, to the frame R, i. e. to their base. A desired piece pattern can thus be selected for different papermaking runs and the desired pieces can be attached to the frame R.

If a piece 15al, 15a2... is damaged, its replacement is also simple because a new piece 15al, 15a2... can be attached in place of a damaged one with an attachment means, such as a screw 16.

Figs. 6A and 6B show an advantageous embodiment of the invention in which pieces 15al, 15a2 are attached to a frame R formed of rails Ri, R2... Fig. 6A is a side view of a ceramic piece 15al. Fig. 6B shows ceramic pieces 15al, 15a2... according to Fig. 6A as attached to the frames Rl, R2, which are rails. Each ceramic piece 15al, 15a2... is passed, as shown in Fig. 6B, to its rail Ri and placed at a certain distance with respect to one another and attached to the rail with an attachment means, such as a screw 16. The rail Rl, R2... comprises a groove 160 in which a mating attachment means i. e. an attachment profile 161 of the piece 15al is placed. The screw 16 serving as the attachment means proper is passed through the piece 15al, 15a2... such that each piece 15ai, 15a2... can be attached to a desired point in the rail Rl, R2... when it has first been brought in a guide 160 (in Fig. 6C) to a certain position in the rail Rl, R2... A surface J of the piece 15al, 15a2... in contact with and against the wire is curved in the embodiment of the figure and corresponds, for instance, to the curvature of the web run H1, W, Ho.

The surface J may also be a straight surface.

As shown in Figs. 6A and 6B, the piece 15al, 15a2... comprises a curved front edge 150 which is placed against the running direction Si of the web and by means of which the water being removed from the stock and further from the wire Hl, H2 is guided.

Fig. 6C illustrates the position of the piece 15al in a guide-shaped frame Ri, the upper edges of a groove T of the frame Ri being shaped into attachment means 160 into which a dovetail edge i. e. the mating attachment means 161 of the piece 15al is positioned. Thus, the pieces 15ai, 15a2... can be placed into the guide- shaped frames R1 from the end of the frames and, as shown in the figure, they can be attached to a desired position with the attachment means 16, preferably with a screw, which is passed, for instance, into a hole el which is situated in the bottom P of the frame Ri and which comprises an edge into which the screw thread of the screw 16 is positioned. The centre axis of symmetry is designated by the reference letter Y. Fig. 6C is a partial sectional view.

Fig. 7 shows a curved frame Ri with pieces 15al, 15a2... placed on it. The frame comprises a guide to which the pieces are passed and attached in a desired position with an attachment means 16. By making the frame curved, the surface defined by the pieces 15al, 15a2... can also be made curved in a desired manner.

As shown in Fig. 7, the frame Ri comprises a curvature M, so that the joint support surface defined by the pieces 15al, 15a2... for the web run Hl, W, H2 will also comprise said curvature M.

By a paper machine or equivalent is also meant board, soft tissue and pulp drying machines.