FI76140B - ANORDNING FOER BORTTAGANDE AV VATTEN FRAON PAPPERSMASSAN PAO EN PAPPERSMASKINS VIRAVAEVNAD. - Google Patents

Description

ANNOUNCEMENT ISSUE

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SUOMI FINLAND

(Fl) (21) Patent application - Patentansökning 1213/7 ** (22) Application date - Ansökningsdag 22.0¾.7 **

National Board of Patents and Registration (23) Start date - Giltighetsdag 22.04.7¾

Patent- och registerstyrelsen (41) Familiar to the public - BHvit offentiig 11.03.75 (44) Date of display and publication - 31.05.88

Ansökan utlagd och utl.skriften publicerad (86) Kv. application - Int. ansökan (32) (33) (31) Privilege claimed - Begärd priority 10.09.73 USA (US) 395 ^ 60 (71) Inotech Process Limited, 6 ^ 20 Victoria Avenue, Suite 8, Montreal,

Quebec, Canada-Canada (CA) (72) Wavell Frederick Cowan, Montreal West, Quebec, Canada-Canada (CA) (7¾) Oy Kolster Ab (5¾) Device for removing water from the pulp in the wire cloth of a paper machine - Anordning för borttagande av vatten frln pappersmassan pä en pappersmaskins viravävnad

The present invention relates to papermaking and in particular to the dewatering step in the papermaking process. More specifically, the invention relates to a device for removing water from a pulp on a paper machine's wire web, wherein the wire rests directly on a front surface of a dewatering strip including a lower surface behind it, with a surface between these surfaces inclined at an angle to the support surface and a suction box. extending transversely to the direction of movement of the wire fabric, a plurality of drainage strips extending in the longitudinal direction of the suction box are arranged at a distance from each other.

In Pourdrinier machines, the pulp is unloaded onto a moving, endless sieve. In the drying stage, the wire screen carrying the pulp is passed over several table rolls, each of which provides suction and removal of water on the web. After the table rollers, several suction boxes connected to a vacuum source are normally used. It is well known 2 76140 that table rollers have a water-removing effect because a suction force is generated between the different surfaces of the roll and the wire screen. Table rollers have yet another function in that they cause the wire screen to oscillate somewhat, thus keeping the fibers and pulp in motion, preventing them from concentrating too much on certain areas, which could result in paper of uneven density. Fourdrinier vii screens can be made of metal, plastic and the like.

One problem with the use of table rolls is that there is no means of controlling the amount of suction force generated by the rollers, nor is there a means of adjusting the movement of the wire according to varying requirements.

Recently, solutions have been developed in which table rolls have been replaced by removable, fixed foil strips connected to a suction box, e.g. in accordance with U.S. Patent No. 2,928,465. The divergence angle provided by such foil strips is designed to be equivalent to the different surface of the table roll to absorb water from the pulp on the wire screen. However, such drying parts meet only one of the requirements and thus do not completely replace the table roll. As shown in said patent publication, these drying parts do not provide the wire movement required to wave the screens. In addition, in said suction boxes with membranes according to the above-mentioned patent, there is a risk of an over-concentrated vacuum area over a short distance of the movement of the wire screen, which causes other detrimental effects.

It is an object of the present invention to provide a derivative device with a suction box with wings, which has the advantages of easily replaceable foil strips and the advantages offered by table rollers.

The device according to the invention is characterized in that it comprises a combination of the following features: a) the angle between the plane of the support surface and the inclined surface is greater than 5 °, b) the lower surface is 3 / 5-4 / 5 of the effective span of the wire at one end of the foil strip; between the leading edge of the next foil strip, c) the length of the lower surface is greater than the width of its preceding support surface, the surface being so much lower than the surface that the free-hanging portion of the wire does not touch the lower surface and both surfaces are substantially horizontal, and (d) the length of the lower surface is selected such that the distance between the lowest point of the freely suspended portion of the wire and the surface forms a water trap.

The depth of the concavity of each strip is such that when the wire screen moves supported by the flat guide surfaces of successive strips, the concave portion does not support it effectively. The distance between the unsupported span compression point of the wire screen, i. however, the critical distance between the wire screen and the concave surface shall not exceed the critical distance between the wire screen and the concave surface, so that the effective suction area applied to the wire screen and the pulp is limited to the space between the compression point and the leading edge of the downstream strip.

The wire screen passing over the described structure is supported by the front plane surfaces of successive strips and bends between the front plane surfaces, providing a certain amount of movement of the wire screen. Since the distance between the wire screen and the concave surface of the wings is not large enough to allow water to flow, little or no suction force would be applied to most of the concave portion of the wings to the point where the downwardly bent wire is closest to the bottom of the recess. The suction force at this squeezing point and the remaining distance to the leading edge of the wing provides the required drying.

A preferred embodiment of the invention will now be described in more detail, by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a schematic view of a suction box with wings spaced apart; and Figure 2 shows an enlarged view of the wing of Figure 1. The figures show the wire screen indicated by the general number 10 and the suction box indicated by the number 12. The series strips or wings 14 extend laterally with respect to the movement of the wire screen but in the longitudinal direction of the suction box. The wings 14 are supported by a suction box in a known manner, e.g. according to U.S. Patent 3,629,058. A series of elongate portions 28 are e.g. welded at the ends to the end walls of the suction box and the wings have a half dovetail rib 30 76140 4 designed to fit into the dovetail groove 32 of the portion 28.

Transversely separated support members (not shown) could be used under sections 28. As shown in Figure 2, each wing has a flat supported guide surface 16 and a lower concave surface 18 below.

It is important that the divergence angle of the interface 26 between the plane surface 16 and the concave surface 18 is greater than 5 °, and in this case it is 90 °, as shown in step 20. If the angle is less than 5 °, then the suction feature of the previous patents would reduce the efficiency of the wings of the present invention.

The depth of the concave surface 18 from the planar surface 16 is indicated in Fig. 2 by the symbol x. According to the present invention, it has been found that the size of this recess is preferably 0.127-3.048 mm with the length of the surface 18 being about 25.4-101.6 mm. The drainage length or space between the trailing edge 22 and the leading edge 24 of the downstream wing would be 6.35-50.8 mm. 4-9 blades would normally be used in each suction box 14.

In the tests performed, the length of the concave portion 18 has been changed with respect to the dewatering length and dimensioned with respect to a predetermined effective span length. All of the following information relates to suction boxes that can be used in accordance with the terms of this invention.

In a Fourdrinier machine using a bronze wire at 365-426 m / min in an application, a suction box with 9 wings would have the following dimensions:

Effective span, 57.15 mm; recess length 42.92 mm; dewatering length 14.22 mm; the depth of the recess is 0.762 mm.

In another example, using the same wire on the same machine, a suction box with 7 wings would have the following dimensions: Effective span 80.52 mm; recess length 64.51 mm; dewatering length 16 mm; the recess depth is 11.43 and 15.24 mm.

In a third example using the same wire and machine, a suction box with only 5 wings would have the following dimensions: Effective span 127 mm; recess length 101.6 mm; dewatering length 25.4 mm; the depth of the recess is 1.143 mm.

The following table provides information for the intended use of the wings.

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The length of the recess in Embodiment I is 65% of the effective span, but in Embodiment II it is 70%. In Embodiment III it is 75% and in Embodiment IV 80%. It appears that the best power is obtained when the length of the recess is 75-80% of the effective span.

The depth of the recess depends on the type of wire used, the normal speed of the machine and the nature of the raw material. When using, for example, a bronze wire, a suitable depth of concavity was found to be 0.127-1.14 mm, with the best value being 0.76-1.14 mm. When using a plastic wire, a suitable range of 0.76-3.048 mm and a preferred range of 1.14-2.28 mm are considered.

As the wire screen 10 passes over the suction box 12, it is supported by the planar surfaces 16 of the wings 14. However, it is unsupported across the effective span between successive planar surfaces 16, as shown in Figure 1. The normal shape of the wire screen 10 is approximately as shown by the dashed lines in Figure 2. After passing over successive wings, the screen would have a desirable wire movement. However, it is preferred in the present invention that the suction area is not too large or too centralized, and it is therefore important that the dewatering property important in previous solutions, e.g., U.S. Patent 2,928,465, does not exist or only to a very small extent. in the wings of the invention.

The depth of the concave portion 18 of the wing should therefore be such that when the wire screen passes over the concave portion by bending, as shown in Figure 2, the distance between the wire screen and the trailing edge of the concave portion is not large enough to allow water to flow normally, with negligible suction in this area of the concave portion 18. . It is desirable that the suction force exists only between the compression point and the leading edge of the successive wings.

Claims (9)

An apparatus for removing water from a pulp on a paper machine's wire web, wherein the wire rests directly on a front surface of a dewatering strip including a lower surface behind it, therebetween a surface extending at an angle to the plane of the support surface and a suction box extending transversely with respect to the direction of movement of the wire fabric, a plurality of longitudinal drainage strips are arranged spaced apart from each other, characterized by a combination of the following features: a) the angle between the plane of the support surface (16) and the inclined surface (26) is greater than 5 °; 18) the length is 3/5 to 4/5 of the effective span of the wire between the end of one foil strip and the leading edge of the next foil strip, c) the length of the lower surface (18) is greater than the width of its preceding support surface (16), whereby the surface (18) ) is so much lower than the surface (16) that the freely suspended portion of the wire does not contact the lower surface and both surfaces (16, 18) are substantially horizontal, parallel planes; and d) the length of the lower surface (18) is selected such that the distance between the lowest point and the surface of the freely suspended portion of the wire (10) is the water trap. Device according to Claim 1, characterized in that the angle between the plane of the support surface (16) and the inclined surface (26) is 90 °. Device according to Claim 1, characterized in that the effective span is 49.53 to 127 mm, the gap between the successive wings (14), the suction gap, is 6.35 to 50.8 mm and the height of the intermediate surface (26) is 0.127 to 127 mm. 3.048 mm and the length of the back surface (18) is about 25.4 to 101.6 mm. Device according to Claim 3, characterized in that the suction box (12) has nine vanes (14) and an effective span of the vanes of 57.15 mm, a length of the rear surface (18) of 42.92 mm and a length of the suction gap of 14.22 mm and an intermediate surface. (26) height 0.762 mm. 7 614 0 p Device according to Claim 3, characterized in that the suction box (12) has seven strips (14) and an effective span of the strips of 80.52 mm, a length of the rear surface (18) of 64.51 mm, a length of the suction gap of 16.0 mm and an intermediate surface ( 26) height 1.14 mm and 1.52 mm. Device according to Claim 3, characterized in that the suction box (12) has five strips (14), an effective span of the strips of 127 mm, a length of the rear surface (18) of 101.6 mm, a length of the suction gap of 25.4 mm and an intermediate surface (26). ) height is 1.14 mm. Device according to Claim 1, characterized in that the height of the intermediate surface (26) is 0.762 to 2.28 mm. 7 76140 Device according to Claim 7, characterized in that the height of the intermediate surface (26) is 1.14 to 1.52 mm. 9 76140