INCLINED-WIRE FORMER AND METHOD OF PRODUCING A FIBROUS WEB

Abstract

An inclined-wire former for producing a fibrous web, in particular a long-fibered paper or wet-laid nonwoven web, includes a wire that runs over a breast roll, subsequently runs inclined at an angle with respect to the horizontal, before it is deflected at a deflection point into a substantially horizontal direction. A headbox in the inclined section of the wire applies a fibrous suspension to the top side of the wire. At least one dewatering element is arranged on the bottom side. The headbox has a front wall which defines, together with the wire, an outlet gap for the at least one fibrous suspension. The front wall of the headbox extends in the wire running direction beyond the deflection point of the wire, such that the outlet gap is arranged above the substantially horizontally extending portion of the wire.

Claims

1. An inclined-wire former for producing a fibrous web from at least one fibrous suspension, the inclined-wire former comprising: a wire disposed to run over a breast roll and, subsequently in a wire running direction, to run in an inclined section of said wire that is inclined relative to a horizontal before said wire is deflected at a deflection point into a substantially horizontally extending section of said wire; at least one headbox disposed at the inclined section of said wire and configured to apply at least one portion of the at least one fibrous suspension to a top side of said wire; said headbox having a front wall which, together with said wire, defines an outlet gap for the at least one fibrous suspension, said front wall extending in the wire running direction beyond said deflection point of said wire and forming said outlet gap above said substantially horizontally extending section of said wire; and at least one dewatering element disposed at a bottom side of said wire for dewatering the at least one portion of the at least one fibrous suspension applied to said wire.

2. The inclined-wire former according to claim 1, wherein said at least one dewatering element is arranged on the bottom side of said inclined section of said wire, extends in the wire running direction beyond said deflection point of said wire, and ends below said substantially horizontally extending section of said wire.

3. The inclined-wire former according to claim 1, wherein said front wall of said headbox has, in the region of the deflection point of said wire, a curvature or a bend, which causes a spacing between said front wall and said wire to narrow in the wire running direction.

4. The inclined-wire former according to claim 3, wherein said spacing between said front wall and said wire tapers continuously in the wire running direction.

5. The inclined-wire former according to claim 1, further comprising a fixing suction device underneath said substantially horizontally extending section of said wire, said fixing suction device being usable for determining a position of a water line of the at least one fibrous suspension on said substantially horizontally extending section of said wire.

6. The inclined-wire former according to claim 5, further comprising at least one further dewatering element disposed downstream of said fixing suction device, underneath said substantially horizontally extending section of said wire, and configured to further dewater the fibrous web.

7. The inclined-wire former according to claim 6, wherein said at least one further dewatering element is a suction box.

8. The inclined-wire former according to claim 1, further comprising at least one steam blower box arranged above said substantially horizontally extending section of said wire.

9. The inclined-wire former according to claim 1, further comprising at least one top wire arranged above said substantially horizontally extending section of said wire.

10. The inclined-wire former according to claim 1, wherein said wire has at least one of a low air permeability of less than 410 CFM or a high retention value of more than 100 FSI.

11. The inclined-wire former according to claim 1, further comprising edge limiters disposed to laterally surround said substantially horizontally extending section of said wire, at least in certain portions thereof.

12. The inclined-wire former according to claim 1 configured for producing a long-fibered paper web or a wet-laid nonwoven web from the at least one fibrous suspension.

13. A method, comprising: providing the inclined-wire former according to claim 1; and producing a long-fibered paper web or wet-laid nonwoven web with the inclined-wire former.

14. The method according to claim 13, which comprises forming a web selected from the group consisting of a battery separator paper web, an aramid paper web, and a capacitor paper web.

15. The method according to claim 13, which comprises operating the inclined-wire former to form a water line of the at least one fibrous suspension on the substantially horizontally extending section of the wire.

16. The method according to claim 13, which comprises setting a consistency of the at least one fibrous suspension to less than 0.3%.

17. The method according to claim 16, which comprises setting the consistency of the at least one fibrous suspension to lower than 0.02%.

18. The method according to claim 13, wherein the long-fibered paper or wet-laid nonwoven web has a grammage of less than 20 g/m.sup.2.

Description

BRIEF DESCRIPTION OF THE FIGURES

[0030] FIG. 1 shows a diagrammatic side view of an inclined-wire former according to the prior art; and

[0031] FIG. 2 shows an embodiment of the inclined-wire former according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

[0032] Referring now to the figures of the drawing in detail, FIG. 1 shows a diagrammatic illustration of an inclined-wire former 10 which is known from the prior art. The device 10 comprises a headbox 20 and a wire 30. During the intended operation, the wire 30 in the form of an endless loop moves counter-clockwise over a series of rolls. One of these rolls is in the form of a breast roll 32. In the wire running direction, the wire 30 moves from the breast roll 32 upward inclined at an angle with respect to the horizontal direction. In this inclined wire portion, the headbox 20 applies a fibrous suspension to the top side of the wire 30. For the dewatering of the fibrous suspension, a dewatering element 40 is arranged on the bottom side in the inclined wire portion.

[0033] The headbox 20 comprises a front wall 22 which defines, together with the wire 30, an outlet gap 24 for the fibrous suspension. Located downstream of the dewatering element 40 is a fixing suction device 50 which can be used to set the water line of the fibrous suspension. Here, the outlet gap 24, the dewatering element 40 and the fixing suction device 50 are arranged in the inclined section of the wire 30. Only thereafter is the wire 30 deflected in a substantially horizontal direction by means of a first deflection roll 34. In the wire running direction, in a region between the first deflection roll 34 and a second deflection roll 36, the wire 30 moving substantially in the horizontal direction in said region. Further dewatering elements 60 are arranged underneath the wire 30 in order to further dewater the fibrous web.

[0034] Referring now to FIG. 2, there is shown a diagrammatic view of an embodiment of an inclined-wire former 10 according to the invention. Here, components which are similar or identical to those shown in FIG. 1 and described above are provided with the same reference designations, but without an apostrophe. In the following we will primarily discuss the differences between the two embodiments and reference will otherwise be made to the explanations appearing above with reference to FIG. 1.

[0035] The inclined-wire former 10 according to the invention is distinguished in particular by the fact that the outlet gap 24 is already arranged above the substantially horizontally extending portion of the wire 30. In this respect, the front wall 22 of the headbox 20 extends beyond a deflection point at which the wire 30 transitions from an inclined wire portion to the substantially horizontally extending wire portion. It is thus possible to reliably avoid a portion of the fibrous suspension exiting the outlet gap being able to flow back on the wire 30, which is detrimental to the quality of the fibrous web to be produced. In this case, the front wall 22 is bent in the region of the deflection point in such a way that its spacing to the wire 30 narrows in the wire running direction. That is, the spacing tapers, preferably continuously, in the wire running direction.

[0036] The dewatering element 40 arranged underneath the wire 30 also extends beyond the deflection point to under the substantially horizontally extending wire portion. By virtue of the top side of the dewatering element 40 being of curved form, it guides the wire 30 and defines the deflection point. It is therefore possible to dispense with a deflection roll here.

[0037] Here, the fixing suction device 50, which follows the dewatering element 40 in the wire running direction, is thus arranged underneath the substantially horizontally extending portion of the wire 30. Consequently, the water line of the fibrous suspension exiting the outlet gap 24 is also located on the substantially horizontally extending portion of the wire 30. The wire 30 is preferably delimited laterally, at least in the region between the outlet gap 24 and the water line, by edge limiters (not illustrated in FIG. 2) which prevent the fibrous suspension from running laterally down from the wire 30.

[0038] It is optionally possible for a steam blower box 70 and/or a top wire 80 to be arranged above the substantially horizontal wire portion. In this way, downstream of the water line, the dehumidification of the fibrous web can be effected efficiently, or the structural length of the inclined-wire former 10 that is required in order to be able to transfer the fibrous web with a predetermined dry content to a production machine section adjoining the inclined-wire former 10 can be reduced. Preferably, further dewatering elements 60 are arranged under the wire in the region of the steam blower box 70 and/or the top wire 80.

[0039] The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention: [0040] 10, 10 Inclined-wire former [0041] 20, 20 Headbox [0042] 22, 22 Front wall [0043] 24, 24 Outlet gap [0044] 30, 30 Wire [0045] 32, 32 Breast roll [0046] 34 First deflection roll [0047] 36, 36 Second deflection roll [0048] 40, 40 Dewatering element [0049] 50, 50 Fixing suction device [0050] 60, 60 Further dewatering elements [0051] 70 Steam blower box [0052] 80 Top wire