DEWATERING DEVICE

Abstract

A dewatering device has a dewatering box and a plurality of dewatering strips. A contour of at least one dewatering strip changes over its length. There is also described a machine for the production of a fibrous web, such as a paper, cardboard or tissue web, with a dewatering device of this kind, and to the use of the latter in a machine of this kind.

Claims

1-13. (canceled)

14. A dewatering device, comprising: a dewatering box forming or delimiting a receiving plane; a multiplicity of dewatering strips disposed on said receiving plane; at least one of said dewatering strips having a longitudinal axis, an underside facing said receiving plane, and an upper side opposite said underside; said at least one dewatering strip being formed, in each case viewed in a section perpendicular to the longitudinal axis of said dewatering strip, with a vertical distance between said upper side of said dewatering strip and said receiving plane of said dewatering box continuously or discontinuously varying, or being variable, along the longitudinal axis of said dewatering strip.

15. The dewatering device according to claim 14, wherein the vertical distance changes from the center in the direction towards respective axial ends of said dewatering strip, viewed along the longitudinal axis.

16. The dewatering device according to claim 15, wherein the vertical distance increases from the center of said dewatering strip toward the axial ends, viewed along the longitudinal direction of said dewatering strip.

17. The dewatering device according to claim 14, wherein said dewatering strip is divided along the longitudinal axis into a multiplicity of segments.

18. The dewatering device according to claim 17, wherein said segments adjoin one another directly.

19. The dewatering device according to claim 14, further comprising at least one actuator configured to change the vertical distance between said upper side and said receiving plane continuously or discontinuously along the longitudinal axis of said dewatering strip.

20. The dewatering device according to claim 19, wherein said at least one actuator acts in a region of the center and/or in a region of at least one axial end of the dewatering strip.

21. A dewatering device, comprising: a dewatering box forming or delimiting a receiving plane; a multiplicity of dewatering strips disposed on said receiving plane; at least one of said dewatering strips having a longitudinal axis, an underside facing said receiving plane, an upper side opposite said underside, and a front side adjoining said upper side and said underside; wherein a leading edge is formed at a transition between said front side and said upper side of said at least one dewatering strip; said at least one dewatering strip being formed, in each case viewed in a section perpendicular to the longitudinal axis of said dewatering strip, with a vertical distance between said leading edge of said dewatering strip and said receiving plane of said dewatering box continuously or discontinuously varying, or being variable, along the longitudinal axis of said dewatering strip.

22. The dewatering device according to claim 21, wherein, viewed in the section perpendicular to the longitudinal axis of said dewatering strip, a smallest angle enclosed by a tangent to an outer contour of said upper side through said leading edge and said receiving plane of said dewatering box with each other lies between 0° in a center of said dewatering strip and 10° at respective axial ends of said dewatering strip.

23. The dewatering device according to claim 22, wherein an angular range lies between 0° in the center and 8° in a region of the axial ends of said dewatering strip.

24. The dewatering device according to claim 21, wherein the vertical distance changes from the center in the direction towards respective axial ends of said dewatering strip, viewed along the longitudinal axis.

25. The dewatering device according to claim 24, wherein the vertical distance increases from the center of said dewatering strip toward the axial ends, viewed along the longitudinal direction of said dewatering strip.

26. The dewatering device according to claim 21, wherein said dewatering strip is divided along the longitudinal axis into a multiplicity of segments.

27. The dewatering device according to claim 26, wherein said segments adjoin one another directly.

28. The dewatering device according to claim 21, further comprising at least one actuator configured to change the vertical distance between said upper side and said receiving plane continuously or discontinuously along the longitudinal axis of said dewatering strip.

29. The dewatering device according to claim 28, wherein said at least one actuator acts in a region of the center and/or in a region of at least one axial end of the dewatering strip.

30. In combination with the dewatering device according to claim 21, a clothing disposed to sweep over said dewatering device along a running direction, and wherein the receiving plane of said dewatering device extends at least partly parallel to said clothing, and the upper side of said dewatering strip faces the clothing.

31. In combination with the dewatering device according to claim 14, a clothing disposed to sweep over said dewatering device along a running direction, and wherein the receiving plane of said dewatering device extends at least partly parallel to said clothing, and the upper side of said dewatering strip faces the clothing.

32. A machine for producing a fibrous web selected from the group consisting of a paper web, a cardboard web, and a tissue web, the machine comprising: a dewatering device according to claim 14, and at least one clothing disposed to sweep over said dewatering device.

33. A machine for producing a fibrous web selected from the group consisting of a paper web, a cardboard web, and a tissue web, the machine comprising: a dewatering device according to claim 21, and at least one clothing disposed to sweep over said dewatering device.

Description

[0027] The invention is to be explained by way of example by using the figures, in which:

[0028] FIG. 1 shows a schematic, partly longitudinally sectional illustration of a wire section of a machine, shown merely as an extract, for producing a fibrous web;

[0029] FIG. 2 shows a schematic cross-sectional illustration of an embodiment of a dewatering device;

[0030] FIG. 3a shows a schematic side view, not to scale, of the front side of the dewatering strip, in which the leading edge can be viewed, according to a first embodiment;

[0031] FIG. 3b shows a simplified top view of the dewatering strip from FIG. 3a with the indication of the extreme positions of the angle of inclination of the leading edge;

[0032] FIG. 4a shows a schematic side view, not to scale, of the front side of the dewatering strip, in which the leading edge can be viewed, according to a second embodiment;

[0033] FIGS. 4b,4c show a simplified top view of the dewatering strip from FIG. 4a with the indication of the angle of inclination of the leading edge in each sector.

[0034] FIG. 1 shows a schematic, partly longitudinally sectional illustration of a wire section 200 of a machine 100, shown merely as an extract, for producing a fibrous web 2 from at least one fibrous material suspension. The image plane corresponds to the YZ plane described at the beginning. The machine direction L extends from left to right here. The fibrous web 2 can be, in particular, a paper (such as packaging paper), board or tissue web. The fibrous material suspension passes from a headbox onto a fabric, here a wire designed as an endless belt, which circulates relative to the dewatering device 1 such that the fibrous web 2 is transported onward by the fabric in the machine direction L. By means of the fibrous material suspension applied to the upper side of the wire, the fibers for forming the fibrous web are deposited there. The excess water from the fibrous material suspension reaches the dewatering device 1 via the underside of the wire. The fibrous web 2 thus formed on the upper side of the wire is transported onward by means of the same in the machine direction L to the next processing station of the machine.

[0035] The basic structure of a dewatering device 1 is shown in FIG. 2 in the same section as in FIG. 1. The dewatering device 1 can be a constituent part of the wire section 200 of the machine 100 illustrated in FIG. 1.

[0036] The dewatering device 1 can comprise, for example, a box-like main body (dewatering box 4), which can optionally be acted on by a vacuum source 3, indicated dashed and preferably able to be controlled/regulated. Said vacuum source is used to improve the dewatering of the fibrous material suspension, is assigned to the wire section 200 and in the present case is arranged within the dewatering box 4.

[0037] A plurality of dewatering strips 5 extending transversely with respect to the machine direction L (arrow in FIG. 1) and at a distance are arranged on the upper side of the dewatering box 4 that faces the underside of the wire. Here, the upper side of the dewatering box 4, facing the fibrous web or the fabric, forms a receiving plane A. In this receiving plane, the dewatering strips 5 are held, more precisely by their corresponding underside U.

[0038] The dewatering strips 5, viewed in the machine direction L, which corresponds to the running direction of the fibrous web 2 to be produced in the machine, are arranged at a distance from one another. In the present case, these are arranged parallel and at a distance from one another with regard to their longitudinal axes, which extend transversely to the machine direction L into the image plane.

[0039] In each case, two directly adjacent dewatering strips 5 together delimit a dewatering slit 6 at their front sides S, S′ facing each other. If the dewatering strips 5 are arranged as illustrated in FIG. 2, then they preferably form with one another a dewatering surface 5′ that is flat and has multiple dewatering slits 6. Said dewatering surface extends substantially parallel to the wire circulating relative thereto and to the fibrous web 2 to be produced thereon and relative to the receiving plane A of the dewatering box 4.

[0040] Each of the individual dewatering strips 5 can have an upper part 7 facing the wire and a lower part 8 facing the main body 4. The upper part 7 is particularly abrasion-resistant (e.g. produced from a ceramic) and then can be attached, for example, integrally to the lower part 8. However, it is possible that the dewatering strip 5 is also produced in one piece.

[0041] As can be viewed in the present illustration, each of the dewatering strips 5 is designed in such a way that a polygonal cross section of the outer contour results. Thus, each dewatering strip 5 has an upper side O, an underside U and at least one front side S. Front side S and upper side O delimit a leading edge K at their transition. The latter is that edge over which the fabric sweeps first in the machine direction L. As already explained, the underside U of the dewatering strip 5 extends, for example, parallel to or in the receiving plane A. Furthermore, in the embodiment illustrated, the dewatering strip 5 has a second front side S′, which is opposite the front side S and connects the upper side O and the underside U to each other. Also at the transition of the front side S′ to the upper side O, the dewatering strip 5 has an edge, here designated as a trailing edge K′. The trailing edge K′, viewed in the machine direction L, is located downstream of the leading edge K. It would also be possible to say that the liquid of the fibrous material suspension flows firstly over the leading edge K and then over the trailing edge K′.

[0042] FIG. 3a shows a view in the machine direction L of the front side S of a dewatering strip 5 of the dewatering box 4 from FIG. 2. This reveals that the leading edge K does not follow a straight line but a curve deviating therefrom. In other words, the vertical distance to be measured (to the receiving plane A) between the receiving plane A and the leading edge K changes in the longitudinal direction in this view, that is to say along the longitudinal axis 5.1 of the dewatering strip 5. It would also be possible to say that the distance of the upper side O and the underside U and the receiving plane A changes continuously along the longitudinal axis 5.1 of the dewatering strip 5.

[0043] In principle, it would be conceivable for the dewatering strip 5 to be designed in such a way that the course of the non-straight leading edge K is fixed, that is to say non-variable. In such a case, the upper side O could be designed accordingly, for example ground. The upper side O of the dewatering strip would then be convex or crowned.

[0044] However, it would also be conceivable that the non-straight leading edge K does not result permanently but only temporarily. For this purpose, the dewatering strip 5 could initially have a straight leading edge K. This would correspond to an initial position. Starting from this initial position, the entire leading edge would then be intrinsically twisted, for example, in such a way that a leading edge K curved in FIG. 3a results over the length of the dewatering strip 5. Thus, the course of the leading edge K would therefore be caused not to change permanently but only temporarily. After a predefinable time or upon request, this could return to the initial position. The dewatering strip 5 could, for example, be twisted in such a way that the center is rotated about the longitudinal axis 5.1 of the dewatering strip 5 with respect to the firmly held axial ends. The result would likewise be the leading edge K illustrated in FIG. 3a. The dashed line indicates the resultant trailing edge K′ which results when the dewatering strip 5 is twisted, as explained.

[0045] Irrespective of whether the non-straight course of the leading edge K is then fixed permanently or only temporarily, the result toward the axial edges (viewed along the longitudinal axis 5.1) is a rise in the angle of inclination of the leading edge K. This is illustrated schematically in FIG. 3b, which shows a top view of the upper side O of the dewatering strip 5. Thus, the result is an angular change, more precisely an increase in the angle of inclination with respect to the center (here) 0°) toward the axial ends (here: 0.4°). Between the center and the axial ends, the result is a smooth transition of the angle of inclination when a curve of the leading edge K which likewise extends continuously is chosen. In the region of the axial ends, the angle can also be 2°, 4°, 6°, 8° or 10°. In addition, graduations between the aforementioned values are conceivable.

[0046] The embodiment of FIG. 4a shows a modification of the dewatering strip 5 relative to the illustration of FIG. 3a. Here, too, a view in the machine direction L of the front side S of the dewatering strip 5 from FIG. 2 is illustrated. The leading edge K, viewed over its entire length or over the entire length of the dewatering strip 5, does not follow a continuous straight line but is designed in steps. The individual steps result from the fact that the dewatering strip is subdivided into a plurality of segments 5.2 arranged along the longitudinal axis 5.1. The illustration of FIG. 4a implies that the segments 5.2 are designed separately from one another. However, this does not necessarily have to be the case, for example the dewatering strip 5 could also be slit at right angles to the longitudinal axis 5.1 along its length without the individual segments 5.2 being separated from one another. This would consequently still form a single coherent component.

[0047] Here, too, that already stated in relation to FIG. 3a applies: the dewatering strip 5 can be designed in such a way that the dewatering strip 5 has the leading edge K illustrated in FIG. 4a permanently or else that this can be moved reversibly from an initial position, in which the dewatering strip 5 has a straight leading edge K, into a position which is not straight, and back. Of course, combinations of fixed and reversibly rotatable are conceivable, including in the embodiment of FIG. 3a.

[0048] FIGS. 4b and 4c show a schematic top view of the upper side O of the dewatering strip 5 from FIG. 4a, analogously to FIG. 3b. It can be viewed that the angle of inclination of the leading edge K rises from the center (here: 0° or 1°) toward the axial ends—here from segment 5.2 to segment 5.2. Thus, this angle at the segment 5.2 located at the axial end can be 0.4° or 1.4°. Larger angular ranges, as explained with reference to FIG. 3b, can also be conceivable here.

[0049] In principle, the curve of the leading edge K could also extend differently than as shown in FIGS. 3a to 4c, specifically such that the angle of inclination of the latter is greater in the center and decreases toward the axial ends. In principle, the curve can be continuous in the mathematical sense but can also include discontinuities such as steps, particularly in the case of segmented dewatering strips.

[0050] It would also be conceivable to adjust individual or all dewatering strips 5 additionally in height and/or in angle, as explained at the beginning.