CA3015246A1

CA3015246A1 - Drainage foil for use in an installation for producing a paper web with a fabric belt, which can be moved over a multiplicity of drainage foils oriented transversely to its direction of movement

Info

Publication number: CA3015246A1
Application number: CA3015246A
Authority: CA
Inventors: Klaus Bartelmuss
Original assignee: Individual
Current assignee: Individual
Priority date: 2017-08-28
Filing date: 2018-08-24
Publication date: 2019-02-28
Also published as: TW201920805A; AT519874A4; AT519874B1; RU2018130836A; JP2019039125A; EP3450625A1; US20190062995A1; BR102018016901A2; CN109423912A

Abstract

A drainage foil (3) for use in an installation for producing a paper web with a fabric belt (1), which can be moved over a multiplicity of drainage foils (3) oriented transversely to its direction of movement, characterized in that the surface of the drainage foil (3) is formed with a defined profiling, which has elevations (42) and/or depressions (43), wherein the vertical extent of the profiling is at least 0.1 mm.

Description

DRAINAGE FOIL FOR USE IN AN INSTALLATION FOR PRODUCING A
PAPER WEB WITH A FABRIC BELT, WHICH CAN BE MOVED OVER A
MULTIPLICITY OF DRAINAGE FOILS ORIENTED TRANSVERSELY
TO ITS DIRECTION OF MOVEMENT
The actual invention relates to a drainage foil for use in an installation for producing a paper web with a fabric belt, which can be moved over a multiplicity of drainage foils oriented transversely to its direction of movement.
The actual invention further relates to a kit and an installation for producing a paper web.
Known installations for producing a paper web have a closed loop fabric belt which is kept circulating by means of transport rolls and onto which, at the start of the installation, a fibrous stock is sprayed. In a first region of the installation, the fabric belt is moved over drainage foils and over suction boxes formed with drainage foils, by which liquid that has emerged from the fibrous stock is stripped off and sucked away. In further regions of the installation, the paper web produced on the fabric belt is dried by means of felt belts.
The drainage foils found in such an installation, which are oriented transversely to the direction of movement of the fabric belt, are foils produced from metal or from plastic which, on their upper side which faces the fabric belt in the operating position, can be provided with an overlay of a wear-resistant material, in particular of plane-ground ceramic plates. The ceramic plates consist in particular of Al oxide, of Zr oxide, of Si nitride and of Si carbide. The fabric belt is moved over the drainage foils at a speed of 1 m/s to 40 m/s. By means of the drainage foils, firstly the fabric belt is supported. Secondly, the drainage foils serve to strip off from the fabric belt liquid that has escaped from the fibrous stock and is found on the underside of the fabric belt. By means of an oblique position of a first group of drainage foils with respect to the fabric belt, wedge-shaped interspaces can be in this case formed between the surfaces of the drainage foils and the fabric belt, which interspaces enlarge in the direction of movement of the fabric belt, which means that, because of the movement of the fabric belt, a suction action is exerted on the fibrous stock found on the latter, by means of which liquid found in the

2 fibrous stock is sucked away. Underneath a second group of drainage foils there are suction boxes, by means of which a suction action is likewise exerted on the fibrous stock found on the fabric belt. The liquid that has escaped from the fibrous stock as a result is led away through the suction boxes.
During the movement of the fabric belt over the drainage foils, the fabric belt rests on the surfaces of the drainage foils or on the ceramic plates found on the latter, as a result of which high frictional resistances are caused, which have to be overcome by the transport rolls. In addition, as a result the surfaces of the drainage foils and the fabric belt are subjected to high wear, for which reason the drainage foils and the fabric belt have only short service lives.
The actual invention is based on the object of devising a drainage foil by means of which, during operation of such a fabric belt installation, the frictional resistances occurring between the fabric belt and the individual drainage foils are reduced.
According to the invention, this object is achieved in that the surface of the drainage foils is formed with a defined profiling, which has elevations and/or depressions, wherein the vertical extent of the profiling is at least 0.1 mm.
Within the scope of the invention, the elevations and the depressions can be implemented and/or distributed randomly or in a non-concretely defined manner. However, in the invention it is preferred if the elevations and the depressions have a defined profiling and/or are distributed in a defined manner on the surface, since more specific influencing of the friction is therefore possible. Preferably but not necessarily, the drainage foil is formed on its surface assigned to the fabric belt in the operating position with a multiplicity of ceramic plates located beside one another which, on their surface, are formed with defined profiling in the form of elevations and/or of depressions, wherein the vertical extent of the profiling is at least 0.1 mm.
According to a preferred embodiment of the invention, the vertical extent is up to

3 mm, preferably up to 2.5 mm or up to 1.6 mm, in particular 0.2 mm up to 0.8 mm.
The surface of the drainage foil can be formed with profiling oriented in the longitudinal extent of the drainage foil or enclosing an acute angle with the latter.

The profiling preferably has the shape of ribs that are triangular in cross section, rectangular foils or wave-like foils, other profilings also being possible in the context of the invention, however. Furthermore, the profilings of ceramic plates located beside one another can be offset with respect to one another both in and also transversely to the longitudinal direction of the drainage foil and/or different.
In addition, the longitudinal extent of the elevations and/or the depressions can enclose an angle of 0 to 80 with the longitudinal direction of the drainage foil.
Furthermore, the profiling can be formed by depressions located at a distance from one another, in particular by cut-outs that are concave in cross section or cylindrical holes.
According to the invention, the surface of the drainage foils can also have a convex curvature in the section transverse to the longitudinal extent of the drainage foil, wherein, in the invention, it is preferred for the curvature to have a radius of 100 mm to 500 mm, preferably of 200 mm to 350 mm.
Finally, it is preferred in the invention if the side edges of the surface of the drainage foil are rounded in cross section with a radius of 0.5 mm to 5 mm, preferably of 1 mm to 3 mm.
In known drainage foils, the surfaces that face the fabric belt in the operating position, which, in particular, are coated with ceramic plates, are plane-ground, having surface roughness values Ra of 0.15 pm to 0.7 pm. Because of the plane grinding of the surfaces of the ceramic plates and the low roughness values achieved hereby, according to the known prior art the frictional resistances occurring between the surfaces of the drainage foils, in particular the surfaces of the ceramic plates, and the fabric belt moved over the latter should be minimized.
By contrast, the actual invention is based on the finding that, with a substantially intensified profiling of the surfaces with defined elevations and depressions, bow waves occur in the liquid which is located in the depressions as a result of the fabric belt moved over the drainage foils, by means of which waves the fabric belt in the regions of the elevations is raised above the latter, there being a layer of liquid between the fabric belt and the elevations, by means of which the frictional

4 resistances occurring between the fabric belt and the elevations are reduced significantly.
Further preferred embodiments of the invention are the subject matter of the remaining subclaims.
Further features and advantages of the invention are gathered from the following description of preferred exemplary embodiments of the invention, not restricting the protective scope, with reference to the attached drawings, in which:
FIG.1 shows a section of an installation for producing a paper web with a fabric belt, which is moved over drainage foils and a suction box located underneath, in a section located in the longitudinal direction of the movement of the fabric belt, FIG.1A shows the detail X from FIG.1, on a scale highly enlarged with respect to FIG.1, FIG.2 shows a first embodiment of a drainage foil according to the invention in an axonometric illustration, FIG.3 shows the drainage foil according to FIG.2 in a cross section, on a scale highly enlarged with respect to FIG. 2, FIG.3A shows an illustration corresponding to FIG.1A to explain the mode of action of the drainage foil according to FIG.3, on a scale highly enlarged with respect to FIG.3, FIG.4, FIG.4A and FIG.4B show three further embodiments of a drainage foil according to the invention, each in cross sections, FIG.5 and FIG.5A show a further embodiment of a drainage foil according to the invention in plan view and in section according to the line V-V from FIG.5, FIG.6, FIG.6A and FIG.6C show two further embodiments of a drainage foil according to the invention in plan view and in sections according to the line VI-VI from FIG.6, FIG.7 shows design variants of the drainage foil according to the invention according to FIG.2, in a cross section and on a scale enlarged with respect to FIG.2,

5 FIG.8 shows a section of an installation for producing a paper web, formed with drainage foils according to the invention, with a fabric belt moved over the drainage foils and with a further formation of the surfaces of the drainage foils, in cross section, and FIG.8A shows the detail Y from FIG.8, on a scale highly enlarged with respect to FIG.8.
FIG.1 illustrates a section of a fabric belt 1 in an installation for producing a paper web, on which a layer of a fibrous stock 2 is found and which is moved in the direction of the arrow M over a group of drainage foils 3. The fibrous stock 2 is sprayed onto the fabric belt 1 at the start of the latter. The drainage foils 3 are each formed on their upper side with an overlay 4 made of a wear-resistant material. Underneath the drainage foils 3 there is a suction box 5, in the interior 51 of which there is a vacuum of about -2 mbar to -700 mbar. The drainage foils 3 are located on a supporting frame 52, which is detachably fixed to the upper side of the suction box 5.
The fabric belt 1, which extends over a length of up to about 50 m and can have a width of 2 m up to 12 m, is moved over the drainage foils 3 at a speed of, for example, 1 m/s to 40 m/s by means of transport rolls located in the installation.
The drainage foils 3 are usually but not necessarily produced from acid-resistant stainless steel, from a plastic, e.g. from polyethylene, or from a glass fiber reinforced plastic. The suction box 5 is generally likewise produced from acid-resistant stainless steel. The overlays 4 found on the supporting bars 3 are preferably plates made of a ceramic material, e.g. Al oxide (hardness HV 0.5 18,000 N/mm2), Zr oxide (hardness HV 0.5 12,700 N/mm2), Si nitride (hardness HV 0.5 18,800 N/mm2), Si carbide (hardness HV 0.5 28,150 N/mm2).
As a result of the vacuum prevailing in the interior 51 of the suction box 5, a suction force is exerted on the fibrous stock 2, by means of which liquid 6 contained in the latter is extracted. The liquid 6 escaping from the fibrous stock 2 passes through the fabric belt 1 and reaches the underside of the fabric belt 1,

6 from which, during the movement of the fabric belt 1 over the drainage foils 3, it is stripped off the latter and reaches the suction box 5, through which it is led away.
FIG.1A illustrates a drainage foil 3 having a wear-resistant overlay 4 and the fabric belt 1 moved over the latter, on which the fibrous stock 2 is found. As can be seen herefrom, the fabric belt 1, which consists of a fabric, e.g. of polyamide or of polyester, has warp threads la oriented in the longitudinal direction of the fabric belt 1 and weft threads lb oriented in the transverse direction of the fabric belt 1.
During the movement of the fabric belt 1 over the drainage foils 3 in the direction of the arrow M, during which the fabric belt 1 rests on the surface of the overlays 4 of the drainage foils 3, high frictional resistances occur, which have to be overcome by the transport rolls found in the fabric belt installation in order to move the fabric belt 1. In addition, in this case, high wear of the fabric belt 1 and of the drainage foils 3 and of the overlays 4 is caused, which means that the fabric belt 1 and the drainage foils 3 have only short service lives. During the movement of the fabric belt 1 over the drainage foils 3, bow waves 61 are formed in the liquid 6 that has escaped from the fabric belt 1, in front of the weft threads lb resting on the drainage foils 3.
According to the prior art, the drainage foils 3 can be formed on their upper side, facing the fabric belt 1 in the operating position, with a multiplicity of ceramic plates, which have lengths of, for example, 12 mm to 230 mm in the direction of the drainage foils and widths of, for example, 12 mm to 100 mm transverse to the drainage foils, and also heights of, for example, 2 mm to 10 mm. The hardnesses of said ceramic plates are preferably HVO,5 12,700 Nimm2 to HVO,5 28,150 N/ mm2. In order to keep the frictional resistances which occur during the movement of a fabric belt 2 over the drainage foils 3 as low as possible, the surfaces of the drainage foils 3, in particular the ceramic plates 4, are plane-ground according to the prior art, having surface roughness values Ra of 0.15 pm to 0.7 pm.
FIG. 2 shows a drainage foil 3 according to the invention. This drainage foil differs from a drainage foil according to the prior art in the fact that the ceramic

7 plates 41 found on its upper side are formed with elevations and/or depressions on their upper side facing the fabric belt 1 in an installation for producing a paper web, wherein the height difference of the elevations with respect to the depressions is 0.1 mm to 1.6 mm. Said elevations and depressions in embodiments of the invention that are particularly preferred and described below in various variants have a profiling with a defined cross-sectional shape and distribution over the surface of the ceramic plates 4. The dimensions and the material of the ceramic plates 41 are preferably those according to the above-described known prior art.
FIG.3 illustrates a first embodiment of a ceramic plate 41 found on a drainage foil 3 according to the invention, which is formed with a profiling on its surface.
This ceramic plate 41, which in the direction of movement M of the fabric belt 1 has a width B of, for example, 8 mm to 70 mm, preferably of 12 mm to 25 mm, and a height of, for example, 2 mm to 10 mm, is provided on its surface with ribs 42 extending in the longitudinal direction of the drainage foil 3, triangular or saw-tooth-like in cross section and having upper edges 45, wherein depressions 43 are found in the regions of the flanks located between the edges 45. The width B1 of a rib 42 is, for example, 1 mm to 16 mm, preferably 2 mm to 6 mm, and the height difference T between the edges 45 of the ribs 42 and the bottom of the depressions 43 is at least 0.1 mm, preferably up to 1.6 mm, particularly preferably 0.2 mm to 0.8 mm. The lateral regions 44 of said ceramic plate 41, which have a width A
of, for example, 1 mm to 8 mm, preferably of 2 mm to 6 mm, are likewise formed flatly. Thus, the surface of said ceramic plate 41 is formed with a defined profiling according to the invention, consisting of elevations and depressions, wherein the ribs 42 that are saw-tooth-like in cross section form the elevations with the edges 45, and the regions of the flanks of the saw-tooth-like ribs 42 located between the edges 45 form the depressions 43.
The described formation of the surface of the drainage foils 3, in particular of the surfaces of the ceramic plates 41, particularly preferably but not necessarily with a defined profiled surface, is based on the finding that, as a result of the relatively large elevations and depressions formed according to the invention, the frictional resistances occurring during the movement of the fabric belt 1 over the drainage foils are reduced down to about 50%, which means firstly that a significant

8 reduction in the drive power for the fabric belt 1 can be achieved and secondly the service lives of the fabric belt 1 and of the drainage foils 3 are substantially prolonged.
As can be seen from FIG. 3A, which corresponds to the illustration of FIG. 1A, this action is achieved in that firstly the fabric belt 1 in the regions of the depressions 43 does not rest on the surface of the drainage foil 3 or the surfaces of the ceramic plates 41, which means that no frictional resistances occur in these regions, and that, secondly, because of the movement of the fabric belt 1, bow waves 61 occur in the liquid 6 found in the depressions 43, by means of which the fabric belt 1 in the regions of the elevations 42, in particular the edges 45, is lifted over the latter, and by means of which liquid gets between the elevations and the fabric belt 1, by means of which the frictional resistances between the elevations and the fabric belt 1 are reduced highly.
FIG. 4 illustrates a further embodiment of a ceramic plate 41a profiled in a defined manner according to the invention and having a width B, in which, between the lateral regions 44a which form the elevations and which have a width A of, for example, 1 mm to 8 mm, preferably of 2 mm to 6 mm, there is a depression 43a, the depth of which with respect to the lateral regions 44a is at least 0.1 mm to preferably 2.5 mm, particularly preferably 0.2 mm to 0.8 mm.
In the further embodiment, illustrated in FIG. 4A, of a ceramic plate 4 lb according to the invention having a width B, elevations in the form of ribs 42b of rectangular cross section and depressions in the form of rectangular grooves 43b, which have widths B2 and B3 of, for example, 1 mm to 10 mm, preferably 2 mm to 8 mm, are located between the lateral regions 44b having a width A, wherein the height difference T2 between the elevations formed by the ribs 42b and the depressions formed by the grooves 43b is at least 0.1 mm to preferably 3.0 mm, particularly preferably 0.2 mm to 0.8 mm.
In the further embodiment, illustrated in FIG. 4B, of a ceramic plate 41c according to the invention having a width B, there is a wave-like profiling with ribs 42c and depressions 43c that are concave in cross section located in between two lateral

9 regions 44c having a width A, wherein the distance B4 between two depressions 43c is, for example, 1 mm to 20 mm, preferably 2 mm to 8 mm, and the height difference T3 between the upper sides of the ribs 42c and the bottoms of the depressions 43c is at least 0.1 mm to preferably 3.0 mm, particularly preferably 0.2 mm to 0.8 mm.
The elevations 44a, 42b, 42c and depressions 43a, 43b, 43c of the embodiments of the invention illustrated in FIG.4 to FIG.4B are oriented in the longitudinal direction of the drainage foil 3 and preferably extend over the entire length of the ceramic plates 41a, 41b, 41c.
In the further embodiment of a ceramic plate 41d according to the invention, illustrated in FIG.5 and FIG.5A, the defined profiling is formed by elevations in the form of rectangular ribs 42d and depressions located in between in the form of rectangular grooves 43d, which have widths B5 and B6 of, for example, 1 mm to mm, preferably of about 2 mm to 8 mm, and a height difference T4 of at least 0.1 mm to preferably 3.0 mm, particularly preferably of 0.2 mm to 0.8 mm. The longitudinal extent of the ribs 42d and the depressions 43d found in between encloses an angle W1 of 00 to 80 , preferably of 30 to 55 , with the longitudinal extent of the drainage foil 3.
In the further embodiments of two ceramic plates 41e, 41f, according to the invention, illustrated in FIG.6, FIG.6A and FIG.6B, said plates are formed with profilings in the form of concave cut-outs 43e and cylindrical cut-outs 43f located close beside one another on a substantially flat surface, possibly somewhat curved as described below, which are spaced apart from one another. The distances B7 between the centers of two cut-outs 43e and 43f located beside one another are, in this case for example, 1 mm to 20 mm, preferably 2 mm to 12 mm, and the depths T5 of the cut-outs are at least 0.1 mm to preferably 3.0 mm, particularly preferably 0.2 mm to 0.8 mm.
The cut-outs can also have another shape, both in plan view and also in cross section, in particular an elongate or elliptical shape.

10 The ceramic plate 41g according to the invention illustrated in FIG. 7 corresponds to the embodiment according to FIG. 3, having ribs 42g that are saw-tooth-like in cross section and having edges 45g which form the elevations, and depressions 43g in the regions of the flanks of the saw-tooth-like ribs 42g, wherein the lateral regions 44g having a width F of, for example, 1 mm to 20 mm, preferably of 2 mm to 8 mm, are formed so as to fall obliquely toward the outside with an angle of, for example, 2 to 100, preferably of 3 to 6 , and, in addition, the outer edges are rounded with a radius R of, for example, 0.5 mm to 5 mm, preferably of 1 mm to mm.
A further embodiment of a drainage foil according to the invention is explained below:
According to the known prior art, the surfaces of drainage foils are formed flat and the surfaces of drainage foils found on suction boxes are located in a common plane. However, as a result of the fact that a suction action is exerted by the suction boxes on the fabric belt in the interspaces found between the drainage foils, the fabric belt is drawn into the interspaces found between the drainage foils.
In this way, the two lateral regions of the surfaces of the drainage foils, in particular of the overlays of a wear-resistant material found on the latter, for example ceramic plates, are loaded more highly than is the case for the central regions of the surfaces of the drainage foils, located in between.
In order to achieve a uniform pressure distribution over the width of the drainage foils 3a, as can be seen from FIG. 8 and FIG. 8a, the surfaces of the ceramic plates 4a found on the drainage foils 3a have a curvature or are formed convexly in cross section, which means that the fabric belt 1 overall assumes a wave-like course.
The drainage foils 3a are located on a supporting frame 52a, which is detachably fixed to the suction box 5.
As can also be seen from FIG. 8A, the radius R1 of the curved surfaces of convex cross section of the ceramic plates 4a located on the drainage foils 3a is, for example, 100 mm to 500 mm, preferably 200 mm to 350 mm. In addition, the side edges of the drainage foils 3a are rounded, the radius R2 of the rounding of the side edges being, for example, 0.5 mm to 5 mm, preferably 1 mm to 3 mm.

11 By means of such a formation of the surfaces of the drainage foils 3a, in particular of ceramic plates 4a found on the latter, a uniform distribution of the pressure exerted by the fabric belt 1 over the width of the drainage foils 3a is effected, which likewise means firstly that the frictional resistances and secondly the wear of the fabric belt 1 and of the drainage foils 3a are reduced.
This further formation of the drainage foils 3a is in particular combined with the profiling of the surface of the drainage foils, which can be provided with a wear-resistant overlay 4a, e.g. with ceramic plates, as is explained above by using FIG.2 to FIG.7.
The formation of drainage foils according to the invention is in particular advantageous in those drainage foils which are located on a suction box.
The drainage foils can be provided with overlays of ceramic plates. However, the drainage foils can also be produced overall from polyethylene, not being coated with ceramic plates. In addition, the surfaces, in this case, are formed with a profiling in the form of elevations and/or depressions with a vertical extent of at least 0.1 mm to preferably 3.0 mm.
As soon as the elevations have been ground off by the use of the drainage foils, the surfaces are re-machined to the effect that the height differences between the elevations and depressions required for the specified action are reproduced.
All the embodiments described in conjunction with overlays of a wear-resistant material, in particular ceramic, can also be used within the context of the invention in drainage foils which have overlays of another material, in particular materials not having such good wear properties, and likewise in drainage foils which have no overlays, in which the elevations and depressions are applied to or formed directly on the drainage foils.
All the embodiments illustrated and described can be combined wholly or partly with one another and with embodiments which have not actually been illustrated and described.

Claims

12

1. A drainage foil (3) for use in an installation for producing a paper web with a fabric belt (1), which can be moved over a multiplicity of drainage foils (3) oriented transversely to its direction of movement, characterized in that the surface of the drainage foil (3) is formed with a defined profiling, which has elevations (44a, 42, 42b, 42c, 42d, 42g) and/or depressions (43, 43a, 43b, 43c, 43d, 43e, 43f, 43g), wherein the vertical extent of the profiling is at least 0.1 mm.

2. The drainage foil (3) as claimed in claim 1, characterized in that the elevations (44a, 42, 42b, 42c, 42d, 42g) and the depressions (43, 43a, 43b, 43c, 43d, 43e, 43f, 43g) have a defined profiling and/or are distributed in a defined manner over the surface.

3. The drainage foil (3) as claimed in either of claims 1 and 2, characterized in that it is formed on its surface assigned to the fabric belt (1) in the operating position with ceramic plates (41) located beside one another, and in that the elevations (44a, 42, 42b, 42c, 42d, 42g) and/or the depressions (43, 43a, 43b, 43c, 43d, 43e, 43f, 43g) are formed on the surface of the ceramic plates (41), wherein the vertical extent of the profiling is at least 0.1 mm.

4. The drainage foil (3) as claimed in one of claims 1 to 3, characterized in that the vertical extent of the profiling is up to 3.0 mm, preferably up to 2.5 mm, particularly preferably up to 1.6 mm and in particular 0.2 mm up to 0.8 mm.

5. The drainage foil (3) as claimed in one of claims 1 to 4, characterized in that its surface is formed with a profiling oriented in the longitudinal extent of the drainage foil (3) or enclosing an acute angle with the latter in the form of ribs (42, 42g) that are triangular in cross section.

6. The drainage foil (3) as claimed in one of claims 1 to 5, characterized in that its surface is formed with a profiling oriented in the longitudinal extent of the drainage foil (3) or enclosing an acute angle with the latter in the form of bars (42b, 42d) that are rectangular in cross section and rectangular grooves (43b, 43d).

7. The drainage foil (3) as claimed in one of claims 1 to 6, characterized in that its surface is formed with a profiling oriented in the longitudinal extent of the drainage foil (3) or enclosing an acute angle with the latter in the form of bars (42c) that are wave-like in cross section.

8. The drainage foil (3) as claimed in one of claims 3 to 7, characterized in that the profilings of ceramic plates (41) located beside one another are offset with respect to one another transversely to the longitudinal direction of the drainage foil (3).

9. The drainage foil (3) as claimed in one of claims 6 to 8, characterized in that the longitudinal extent of the elevations (42d) and/or the depressions (43d) enclose an angle (W1) of 0° to 80°, preferably of 30° to 55°, with the longitudinal extent of the drainage foil (3).

10. The drainage foil (3) as claimed in one of claims 1 to 9, characterized in that the profiling is formed by cut-outs (43e) that are concave in cross section and are located at a distance from one another or by cylindrical holes (43f).

11. The drainage foil (3a) as claimed in one of claims 1 to 10, characterized in that its surface has a convex curvature in the section transverse to the longitudinal extent of the drainage foil (3a).

12. The drainage foil (3a) as claimed in claim 11, characterized in that the convex curvature has a radius (R1) of 100 mm to 500 mm, preferably of 200 mm to 350 mm.

13. The drainage foil (3, 3a) as claimed in one of claims 1 to 12, characterized in that the side edges of its surface are rounded in cross section with a radius (R, R2) of 0.5 mm to 5 mm, preferably of 1 mm to 3 mm.

14. A kit for an installation for producing a paper web, comprising drainage foils (3a) located on a supporting frame (52a), the supporting frame (52a) being intended for detachable fncing on a suction box (5) of the installation, characterized in that the drainage foils (3a) are designed as claimed in one of claims 1 to 13.

15. An installation for producing a paper web, having a fabric belt (1) which can be moved over a multiplicity of drainage foils (3, 3a) extending transversely to its direction of movement, characterized in that the drainage foils (3, 3a) are designed as claimed in one of claims 1 to 13.