DEWATERING BAR ON A PAPERMAKING MACHINE AND WIRE SECTION OF A PAPERMAKING MACHINE

Abstract

A dewatering bar on a papermaking machine includes a main body with a longitudinal direction aligned transversely to the direction of movement of a screen belt. The main body has at least one chamber closed in a pressure tight manner, which extends in the longitudinal direction of the dewatering bar. The chamber has a connection to a pressure line, a wall having a surface facing the screen belt of the papermaking machine, and side walls connected to the wall. The position of the wall of the chamber is variable, and a device for detecting the change in position of the wall due to changes in the pressure is disposed in the chamber. A wire section of a papermaking machine is also provided.

Claims

1. A dewatering bar for a papermaking machine, the dewatering bar comprising: a main body having a longitudinal direction aligned transversely to a direction of movement of a screen belt of the papermaking machine, said main body having at least one chamber being closed in a pressure tight manner; said at least one chamber extending in a longitudinal direction of the dewatering bar, and said at least one chamber having a connection for a pressure line; said at least one chamber having a wall and side walls connected to said wall, said wall having a surface facing the screen belt and said wall having a variable position; and a device for detecting a change in position of said wall due to changes in pressure in said chamber.

2. The dewatering bar according to claim 1, wherein said wall is deformable.

3. The dewatering bar according to claim 1, wherein said device for detecting a change in the position of said wall is a sensor.

4. The dewatering bar according to claim 3, wherein said sensor is a tilt sensor or a displacement sensor.

5. The dewatering bar according to claim 1, wherein said device for detecting a changed in the position of said wall is disposed in said chamber.

6. The dewatering bar according to claim 2, wherein said wall is made deformable by having regions with different bending stiffness values.

7. The dewatering bar according to claim 6, wherein said wall includes a region having a lower bending stiffness than an adjoining region, and said region having a lower bending stiffness runs in the longitudinal direction of the dewatering bar or obliquely to the longitudinal direction of the dewatering bar.

8. The dewatering bar according to claim 1, wherein said wall includes a region having a lower bending stiffness than adjoining regions of a respectively adjoining one of said side walls, and said region having a lower bending stiffness is disposed in a region of transition from at least one of said side walls to said wall.

9. The dewatering bar according to claim 1, wherein at least one of said side walls has regions with different bending stiffness values.

10. The dewatering bar according to claim 5, wherein said wall includes a region having a lower bending stiffness than at least one adjoining region of at least one of said wall or at least one of said side walls, and said region of lower bending stiffness has a groove formed therein.

11. The dewatering bar according to claim 10, wherein said groove is inwardly open toward said chamber.

12. The dewatering bar according to claim 1, wherein said chamber is one of at least two chambers being closed in a pressure tight manner, said at least two chambers extending in the longitudinal direction of the dewatering bar and being disposed side-by-side, and each of said at least two chambers has a separate connection to a pressure line.

13. The dewatering bar according to claim 12, wherein each of said at least two chambers is associated with a portion of said variable-position wall having a portion of said surface facing the screen belt of the papermaking machine, and said device for detecting the change in position of said wall is one of at least two devices each being associated with a respective one of said at least two chambers.

14. The dewatering bar according to claim 1, wherein said surface facing the screen belt has a first surface segment enclosing a first acute angle with the screen belt, and said first acute angle opens in the direction of movement of the screen belt.

15. The dewatering bar according to claim 14, wherein: said surface facing the screen belt has a second surface segment disposed after said first surface segment in the direction of movement of the screen belt; said second surface segment encloses a second acute angle with the screen belt and said second acute angle closes in the direction of movement of the screen belt; and said surface facing the screen belt has at least one further surface segment running parallel to the screen belt.

16. The dewatering bar according to claim 15, wherein said at least one further surface segment is disposed between said first surface segment and said second surface segment.

17. The dewatering bar according to claim 1, wherein said wall is in contact with the screen belt and said wall is produced from a wear-resistant material, at least in some segment or segments.

18. The dewatering bar according to claim 1, which further comprises at least one of a leading edge or a trailing edge as viewed in the direction of movement of the screen belt, and a strip of wear-resistant material disposed on at least one of said leading edge or said trailing edge.

19. The dewatering bar according to claim 18, wherein said wear-resistant material is a ceramic.

20. The dewatering bar according to claim 18, wherein said strip is secured releasably on said main body at least at one of said leading edge or said trailing edge.

21. The dewatering bar according to claim 18, which further comprises a carrier body disposed releasably on said main body, said strip being secured on said carrier body at least at one of said leading edge or said trailing edge.

22. The dewatering bar according to claim 21, wherein said carrier body is made of glass fiber-reinforced plastic.

23. The dewatering bar according to claim 1, wherein said main body is made of plastic.

24. The dewatering bar according to claim 23, wherein said plastic is polyethylene.

25. The dewatering bar according to claim 1, wherein said main body is formed of at least a bottom part for securing said main body on a carrier bar and a top part having said wall of said chamber.

26. A wire section of a papermaking machine, the wire section comprising: at least one dewatering bar according to claim 1; and a screen belt configured to move over the dewatering bar transversely to the longitudinal extent of the dewatering bar.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0036] FIG. 1 is a diagrammatic, perspective view of an embodiment of a dewatering bar according to the invention;

[0037] FIG. 2 is a sectional view of a first embodiment of the dewatering bar according to the invention in a one-piece configuration;

[0038] FIG. 3 is a sectional view of a second embodiment of the dewatering bar according to the invention in a 2-piece configuration;

[0039] FIG. 4 is a sectional view of a third embodiment of the dewatering bar according to the invention in a 3-piece configuration;

[0040] FIG. 5 is a sectional view of a fourth embodiment of the dewatering bar according to the invention in another 3-piece configuration;

[0041] FIG. 6 is a sectional view of a fifth embodiment of the dewatering bar according to the invention in a 4-piece configuration;

[0042] FIG. 7 is a sectional view of a sixth embodiment of the dewatering bar according to the invention in a 3-piece configuration;

[0043] FIG. 8 is a fragmentary, sectional view of the dewatering bar according to FIG. 4 in the unpressurized state together with a screen belt;

[0044] FIG. 9 is a fragmentary, sectional view of the dewatering bar as in FIG. 8 but with a vacuum in the chamber of the bar;

[0045] FIG. 10 is a sectional view of a seventh embodiment of the dewatering bar according to the invention having two chambers with sensors;

[0046] FIG. 11 is a sectional view of an eighth embodiment of the dewatering bar according to the invention in the unpressurized state; and

[0047] FIG. 12 is a sectional view of the embodiment of FIG. 11 in the state in which there is a vacuum in the chamber.

DETAILED DESCRIPTION OF THE INVENTION

[0048] The drawings illustrate embodiments of dewatering bars according to the invention which are only illustrative and, apart from the features according to the invention, as defined in the claims, may also be embodied differently in respect of many components within the scope of the present invention without the need for special mention below. In particular, components and features described in the various embodiments of the invention may be combined in any desired manner without this being explicitly mentioned in each possible case.

[0049] Referring now to the Figs. of the drawings in detail and first, particularly, to FIG. 1 thereof, there is seen a dewatering bar 1 of the kind that can be used for the wire section of a papermaking machine, for example. The dewatering bar 1 has a longitudinal direction (arrow 2), wherein the screen belt 3 illustrated in FIGS. 8 and 9 is moved over the dewatering bar 1 transversely to the longitudinal direction 2 in the direction of arrow 4. The dewatering bar 1 has a main body 5, in which a strip 6 made of a wear-resistant material, such as ceramic, is disposed.

[0050] FIG. 2 illustrates a first embodiment of a dewatering bar 1 according to the invention with a one-piece main body 5. The main body 5 has a chamber 7, which is closed in a pressure tight manner with respect to the surroundings. Lines 8, 9 are connected to the chamber 7. One line 8 of these two lines 8, 9 is a pressure line, via which the pressure in the chamber 7 can be changed. A vacuum is preferably produced in the chamber 7 via the pressure line 8. A gas, e.g. air, or a liquid, e.g. oil, can be used as a pressure medium, for example.

[0051] The main body 5 has a top part 20 and a bottom part 15. The top part 20 has a deformable wall 11 having a surface 12 facing the screen belt 3 and has two side walls 13 and 14. The deformable wall 11, the side walls 13, 14 and the bottom part 15 delimit the chamber 7 in the circumferential direction. In addition, the chamber 7 is delimited at the ends of the dewatering bar 1 by end walls 16. The lines 8, 9 lead through one of the two end walls 16 into the chamber 7. If the dewatering bar has chambers divided in the longitudinal direction 2, lines 8, 9 can also lead through both end walls 16 into the chambers 7.

[0052] The one-piece embodiment illustrated in FIG. 2 is formed of plastic, e.g. polyethylene, in which wear-resistant particles can be embedded in the deformable wall 11 when required in order to increase the wear resistance of the deformable wall 11.

[0053] A device 17 for detecting the deformation and thus change in the position of the wall 11 is disposed on the inner surface 41 of the deformable wall 11. This device 17 is, for example, a tilt sensor, which detects the tilt of the deformable wall 11 relative to the horizontal. Alternatively, however, the device 17 could also be, for example, a measuring device which measures the distance from the opposite bottom surface 18 of the bottom part 15 or a change in this distance or some other distance.

[0054] The device 17 is connected to line 9, which can be an electric line or an optical waveguide, for example. Wireless transmission of the measurement results from the device 17 to a controller is of course likewise possible.

[0055] In an embodiment that is not illustrated in the drawings, the deformable wall 11 can have a substantially constant wall thickness and can be deformed substantially continuously when excess pressure or a vacuum is applied in the chamber 7.

[0056] In the case of the invention, however, it is preferred if the wall 11 has regions of different bending stiffness. In the embodiments illustrated in the drawings, the wall 11 has a region 19 which has a lower bending stiffness than the adjoining or adjacent regions 21, 22. In the embodiments illustrated in the drawings, the region 19 of lower bending stiffness is formed by a groove 23, which lies between the regions 21, 22 of the wall 11, which have a substantially constant wall thickness and a higher bending stiffness than the region 19 weakened by the groove 23.

[0057] In addition or alternatively to the region 19 of lower bending stiffness in the wall 11, a further region 24 of lower bending stiffness can be disposed in the region of transition from the wall 11 to the side wall 14, that region 24 likewise being formed by a groove 25 in the corner between the wall 11 and the side wall 14 in the embodiment illustrated.

[0058] In addition or alternatively, a further region 26 of lower bending stiffness can also be disposed in a side wall 13, that region likewise being formed by a groove 27 in the embodiment illustrated.

[0059] According to the invention, it is not necessary for all the regions 19, 24 and 26 of lower bending stiffness to be present. It is also possible for none of these regions to be present or for just one or two of the three regions 19, 24 and 26 to be present. Each of these three regions 19, 24 and 26 may thus also be omitted, depending on the respective requirements. It is also possible for more than three regions to be provided or else for one or more regions of lower bending stiffness to be disposed at different locations.

[0060] The advantage of the embodiments with one, two or three regions 19, 24 and 26 of lower bending stiffness is that the device 17 can be mounted on a part of the wall 11 which is not deformed because, overall, the wall 11 is deformed only in the region or regions 19, 24 and 26 of lower bending stiffness when an excess pressure or a vacuum is applied in the chamber 7.

[0061] Theoretically, it would also be possible in the invention to create regions of lower bending stiffness by using, in some segment or segments, materials of lower strength, which have a lower bending stiffness.

[0062] In addition, as known per se from the prior art, the dewatering bar 1 illustrated in FIG. 1 has a wedge-shaped leading edge 28, on which or over which the screen belt 3 runs onto the dewatering bar 1. As likewise known per se from the prior art, an approximately T-shaped groove 29 is disposed in the bottom part 15 for the purpose of mounting the dewatering bar 1 on a carrier bar of the papermaking machine. However, the specific shape of the leading edge 28 and that of the groove 29 are not of significance for the present invention and may also be replaced by alternative geometries or entirely omitted and, where the groove 29 is concerned, may be replaced by alternative fastening methods.

[0063] FIG. 3 illustrates an alternative embodiment of a dewatering bar 1 according to the invention, which, where the main body 5 is concerned, can be embodied substantially in the same way as the dewatering bar 1 of FIG. 2.

[0064] However, the embodiment of FIG. 3 differs from the embodiment of FIG. 2 in that the leading edge 28, which is exposed to the greatest wear, is not formed directly on the main body 5 but on a wearing part 31, which is connected to the main body 5 by way of a wedge-shaped slot and key joint 32. The advantage of this embodiment resides in that the wearing part 31 can be connected to the main body 5 and also released again from the latter without problems when the wear becomes too great, and it is not necessary, as in the embodiment of FIG. 2, for the technically more complex main body 5 with the device 17 to be entirely replaced. The wearing part 31 can be produced from a material that is different from and, in particular, more wear-resistant than the main body 5, which must have different properties.

[0065] FIG. 4 illustrates yet another, three-piece embodiment of a dewatering bar 1 according to the invention, where the bottom part 15 of the main body 5 is a separate part, which is releasably or non-releasably connected to the side walls 13 and 14 of the main body 5. The advantage of this embodiment is that the bottom part 15, on the one hand, and the side walls 13, 14 and the deformable wall 11, on the other hand, can, should or must once again have different strength properties. In particular, the side walls 13, 14 and the deformable wall 11 should have elastic and possibly wear-resistant properties that are not required for the bottom part 15, which is only present for connection to a carrier bar.

[0066] FIG. 5 illustrates an embodiment of the invention in which the leading edge 28 is formed by a wear-resistant strip 33 being formed, for example, of ceramic material, which is secured, e.g. adhesively bonded, on a carrier body 34. The carrier body 34 is connected to the main body 5 by way of a slot and key joint 32, which is T-shaped in the illustrative embodiment and is situated in the region of the side wall 14 and of the bottom part 15.

[0067] The advantage of this embodiment is that the strip 33, which can also be formed, for example, of ceramic segments such as those which can be produced in a manner known per se from the prior art because they do not have to be connected directly to the main body 5 of the dewatering bar 1 but can be connected in a conventional way to the carrier body 34, which for its part is connected to the main body 5.

[0068] In the embodiment of FIG. 6, the embodiments of FIGS. 3 to 5 are combined. That is to say that a main body 5 having a deformable wall 11 and side walls 13, 14 with a separate bottom part 15 is connected to a carrier body 34 by way of a slot and key joint 32 on the side wall 14, wherein the wear-resistant strip 33 is once again connected to the carrier body 34.

[0069] FIG. 7 illustrates an embodiment of a dewatering bar 1 according to the invention which is similar to the embodiment of FIG. 5. In order to connect the carrier body 34 to the main body 5, however, a screwed joint 35 is provided, not a slot and key joint.

[0070] The functioning of the deformable wall 11 according to the invention in conjunction with a changed pressure in the chamber 7 can be seen from FIGS. 8 and 9.

[0071] If the screen belt 3 with the stock mixture 36 situated thereon moves over the dewatering bar 1 in the direction of arrow 4 and rests with its underside on the dewatering bar 1, liquid 37 that has passed through the screen belt 3 is scraped off by the leading edge 28.

[0072] When ambient pressure or a slight excess pressure prevails in the chamber 7, for example, the surface 12 facing the screen belt 3 can be straight or level in the illustrated embodiment, as illustrated in FIG. 8. The sensor 17 will send a corresponding signal to the controller.

[0073] If, however, a vacuum is produced in the chamber 7 via line 8, the deformable wall 11 is pulled inward into the chamber 7 by the vacuum, as illustrated in FIG. 9. The wall 11 is kinked somewhat in the central region 19 with the lower bending stiffness, wherein the region of transition 24 to the side wall 14, which likewise has a lower bending stiffness, is deformed somewhat. The region 26 of lower bending stiffness in the other side wall 13 is likewise deformed, but less so. Of course, the degree of deformation of the respective regions 19, 24 and 26 depends on the degree of weakening and also on the specific arrangement of the respective region on the main body 5.

[0074] Since there are regions 21 and 22 of higher bending stiffness between the regions 19, 24 and 26 of lower bending stiffness, these regions are not deformed and they form surface segments 38, 39 which remain substantially level. These surface segments 38, 39 enclose acute angles with the screen belt 3, wherein the angle between the first surface segment 38 and the screen belt 3 opens in the direction of movement 4 of the screen belt 3, with the result that a suction force is exerted on the screen belt 3 and on the liquid emerging from the stock mixture 36. Adjoining the second surface segment 39, there is, in contrast, the angle between the surface segment 39 and the screen belt 3 in the direction of movement 4 of the screen belt 3, as a result of which once again a pressure is exerted on the screen belt 3 and on the liquid emerging from the stock mixture 36. By selective setting of the angles and , turbulence may be produced in the fiber suspension 36 on the screen belt 3, affecting the fiber orientation, thereby enabling the formation of the stock mixture 36 to be influenced.

[0075] An exact knowledge of the shape and position of the surface 12 with the surface segments 38, 39 is crucial here because not only the pressure in the chamber 7 but also the screen belt 3 with the stock mixture 36 situated thereon exert a force on the deformable wall 11. By the direct detection of the position or deformation of the wall 11 by using the device 17, it is always exactly possible to adjust the angles and exactly, even when conditions change during operation.

[0076] The angles and can be set using the magnitude of the vacuum in the chamber 7, wherein the ratio of these angles can be influenced through the geometry of the main body and, in particular, the choice and arrangement of the regions 19, 24 and 26 of lower bending stiffness.

[0077] In the illustrated embodiment, the angle is half the angle , for example, because the region 19 of lower bending stiffness is disposed off-center in the wall 11. However, other angle ratios are of course likewise possible, depending on the desired result, since the regions 19, 24 and 26 of lower bending stiffness can be positioned in an appropriately different way or may also be selectively omitted.

[0078] With regard to the size of the maximum angles and that can be set, these can be set to from 0 to 1, 2, 3, 4, 5, 6 or more, for example.

[0079] FIG. 10 illustrates an embodiment of the invention with two mutually adjacent chambers 7, which can be subjected to pressure (excess pressure or a vacuum) independently of one another. Disposed in each of the two chambers 7 is a device 17 for detecting the deformation and thus changing the position of the wall 11 due to changes in the pressure in the chambers 7.

[0080] This embodiment of the invention also illustrates the fact that the surface 12 facing the screen belt 3 can also be corrugated, thereby making it possible to produce additional turbulence in the fiber suspension.

[0081] FIGS. 11 and 12 illustrate an embodiment of the invention in which the wall 11 itself is substantially non-deformable. In order to enable a change in the position of the wall 11, a region of lower bending stiffness is provided in the region of transition 24 to the side wall 14. In addition, regions 26, 42, 43 of lower bending stiffness are disposed in the region of the other side wall 13. The regions 26, 42, 43 of lower bending stiffness have grooves 44, 45 in the edge regions of the wall 13 and a groove 27 in the central region of the wall 13. If the wall 13 has the straight shape illustrated in FIG. 11 in the unpressurized state (ambient pressure) of the chamber 7, the wall 11 is also straight and lies with its surface 12 parallel to the screen belt 3. If, in contrast, there is a vacuum in the chamber 7, the side wall 13 bends inward, as a result of which the deformable wall 11 can pivot about the region 24 of lower bending stiffness, as in the case of a joint, and tilts downward on the same side as the side wall 13, and the surface 12 of the wall 11 encloses an angle >0 with the screen belt.

[0082] In another embodiment of the invention, which is not illustrated in the drawings, the region 24 of lower bending stiffness could also be disposed at some other location, embodied in a different way or omitted entirely if the wall 11 were sufficiently elastic, i.e. flexible, to enable the desired change in position in the region of the right-hand wall 13.

[0083] It is self-evident (as with all other embodiments illustrated) that the shape of the dewatering bar 1 illustrated in FIG. 12 could also represent the state in which the chamber 7 is unpressurized and the dewatering bar 1 can assume the shape illustrated in FIG. 11 when the chamber 7 is put under pressure. It is likewise possible for the dewatering bar 1 to assume a shape between the shapes illustrated in FIGS. 11 and 12 in the unpressurized state, the shape illustrated in FIG. 11 under excess pressure, and the shape illustrated in FIG. 12 under a vacuum.

[0084] The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention: [0085] 1 dewatering bar [0086] 2 longitudinal direction, arrow [0087] 3 screen belt [0088] 4 arrow [0089] 5 main body [0090] 6 strip [0091] 7 chamber [0092] 8 pressure line [0093] 9 line [0094] 11 deformable wall [0095] 12 surface [0096] 13 side wall [0097] 14 side wall [0098] 15 bottom part [0099] 16 end wall [0100] 17 device [0101] 18 bottom surface [0102] 19 region of lower bending stiffness [0103] 20 top part [0104] 21 region of higher bending stiffness [0105] 22 region of higher bending stiffness [0106] 23 groove [0107] 24 region of lower bending stiffness [0108] 25 groove [0109] 26 region of lower bending stiffness [0110] 27 groove [0111] 28 leading edge [0112] 29 groove [0113] 30 trailing edge [0114] 31 wearing part [0115] 32 slot and key joint [0116] 33 strip [0117] 34 carrier body [0118] 35 screwed joint [0119] 36 stock mixture [0120] 37 liquid [0121] 38 surface segment [0122] 39 surface segment [0123] 41 inner surface [0124] 42 region of lower bending stiffness [0125] 43 region of lower bending stiffness [0126] 44 groove [0127] 45 groove