US20070272386A1

US20070272386A1 - Machine for producing a material web

Info

Publication number: US20070272386A1
Application number: US11/678,303
Authority: US
Inventors: Thomas Scherb; Hubert Walkenhaus; Luiz Silva
Original assignee: Voith Patent GmbH
Current assignee: Voith Patent GmbH
Priority date: 2004-10-26
Filing date: 2007-02-23
Publication date: 2007-11-29
Also published as: BRPI0516431A; WO2006045689A1; EP1817454A1; DE102004052157A1

Abstract

The present invention provides a method and a press in a machine for producing or processing a material web, in particular a fibrous web, the press including a roller whose outer jacket is jointly enwrapped, at least in one wrap zone, respectively by at least a press belt, a support belt and a belt for dispersing water from the material web. The water-dispersing belt is located on the inside in contact with the outer jacket of the roller, the press belt on the outside and the support belt between the press belt and the water-dispersing belt. The material web is guided between the support belt and the water-dispersing belt through the wrap zone. At the end of the wrap zone, first the press belt is lifted off the support belt and then the support belt with the material web is lifted off the water dispersing belt.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of PCT application No. PCT/EP2005/055049, entitled “MACHINE FOR PRODUCING A MATERIAL WEB”, filed Oct. 6, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention
The present invention relates to a press in a machine for producing or processing a material web, in particular a fibrous web. Furthermore, this invention relates to a method for producing a material web, in particular a fibrous web.
2. Description of the Related Art
In particular for the production of tissue paper with a high density and a high water absorption capacity, so-called bulky tissue, it is necessary for the tissue web to be optimally dewatered in each stage of production, meaning that in the press section for example an optimum press pressure must be applied to said tissue web at the correct moment for the necessary length of time and the tissue web must be separated at the correct moment from the paper machine covering or the respectively interacting paper machine coverings.
What is needed in the art is a press and a method which are respectively optimized in particular for the production of bulky tissue products.

SUMMARY OF THE INVENTION

The present invention provides a press in a machine for producing or processing a material web, in particular a fibrous web, the press including a roller whose outer jacket is jointly enwrapped, at least in one wrap zone, respectively by at least a press belt, a support belt and a belt for dispersing water from the material web, wherein the water-dispersing belt is located on the inside in contact with the outer jacket of the roller, the press belt on the outside and the support belt between the press belt and the water-dispersing belt, and wherein the material web is guided between the support belt and the water-dispersing belt through the wrap zone. At the end of the wrap zone, first the press belt is lifted off the support belt and then the support belt with the material web is lifted off the water dispersing belt.
According to the present invention, first the press pressure is removed from the material web, in particular the fibrous web, which is being guided on the support belt. The actual dewatering, which takes place essentially in the direction of the water-dispersing belt, is thus ended. Then the support belt with the material web is lifted off the water-dispersing belt in order to prevent rewetting of the material web by the water-dispersing belt.
Variations for constructing the water-dispersing belt are possible. On the one hand the water-dispersing belt can be permeable for water and gas such that water from the material web can be dispersed through the water-dispersing belt by way of an air flow or an air through-flow for example. In addition or alternatively to this, the water-dispersing belt can have a water absorption capacity. For example, it is possible to use a press felt, a mesh or a mesh with a fine pore structure as the water-dispersing belt.
According to another embodiment of the present invention, the roller has a suction zone and the end of the wrap zone is in the region of the end of the suction zone in the web running direction. On the one hand the dewatering of the fibrous web in the direction of the water-dispersing belt is increased as a result of the suction zone, which is arranged on the side of the water-dispersing belt facing away from the fibrous web. On the other hand the rewetting of the fibrous web by the water-dispersing belt is prevented as the result of the suction zone being arranged at least in the region of the end of the wrap zone in that the fibrous web is separated from the water-dispersing belt.
The fibrous web can be exposed to an air through-flow which passes first through the press belt, then the support belt, then the fibrous web and finally the water-dispersing belt.
According to another embodiment of the present invention, the press belt is lifted off the support belt by between 0° and 15°, preferably 0° and 10°, in particular preferably 2° and 6°, before the support belt and the material web are lifted off. Advantage is drawn in this case from the fact that two mutually conflicting effects have to be taken into account: (1) on the one hand the dry content of the fibrous web upon leaving the press should be as large as possible. This is achieved by simultaneous pressing by the press belt and sucking by the vacuum zone up to near the end of the vacuum zone; and (2) on the other hand the press belt has to be lifted off the fibrous web early enough to prevent rewetting of the fibrous web and belated separation of the fibrous web from the press belt.
The present invention provides an optimum of the mutually conflicting effects.
To prevent any rewetting of the material web, in particular the fibrous web, by the belt dispersing the water from the material web, it is necessary to lift off the fibrous web from the belt dispersing the water from the material web ahead of, or at the latest at, the end of the suction zone in order to ensure that the fibrous web is in contact with the belt dispersing the water from the material web only as long as dewatering from the fibrous web in the direction of the belt dispersing the water from the material web is guaranteed by the suction effect of the suction zone. Hence the support belt with the material web should be lifted off ahead of the end of the suction zone.
If, on the other hand, the lifting off of the support belt takes place too early, this can lead to separation of the fibrous web from the support belt and to tearing of the fibrous web.
Tests have shown that an optimum of the previously described mutually conflicting effects is found when the support belt with the material web is lifted off the belt dispersing the water from the material web in an arc angle range, in relation to the end of the suction zone, of between>0° and <10°, preferably between >0° and 6°, in particular preferably between 2° and 6°.
The belt dispersing the water from the material web can be lifted off the outer jacket of the roller at the end of the suction zone or thereafter. This ensures that the belt dispersing water from the material web is in contact with the suction zone for as long as possible, which, if the belt is a press felt and has a high water absorption capacity for example, results in water being drawn out of the belt over as long a section as possible.
In particular for the production of tissue papers it is necessary to press the tissue web only on a zone basis in order to obtain regions in the tissue web which were not compressed and which therefore have a low density and hence a high water absorption capacity. A structured mesh, in particular a TAD (through air drying) mesh, or a structured membrane is ideal for this purpose because it has a structure with elevations and pockets. En route through the press the tissue web is only slightly compressed in the region of the pockets as compared with the other regions. An embodiment of the present invention provides accordingly for the support belt to be a structured membrane or a structured mesh, in particular a TAD mesh.
To increase runability it makes sense to transfer the fibrous web in the still wet state as little as possible from one covering to another covering. An embodiment of the invention thus provides for the fibrous web to be formed on the support belt.
For the production of bulky tissue papers it makes sense for the tissue web to be formed on a support belt with zonal pockets in order to create regions with a high fiber mass. Another embodiment of the invention thus provides for the fibrous web to be formed on the TAD mesh.
The produced fibrous web can have a gsm substance (grams per square meter substance weight or basis weight) of less than 42 g/cm²and in particular is a tissue paper.
Furthermore, the fibrous web has a specific bulk of over 10 g/cm³, preferably over 14 g/cm³, in particular preferably over 16 g/cm³.
In addition the fibrous web has a water absorption capacity of more than 10 g water per g (gram) fibrous web, preferably more than 14 g water per g fibrous web, in particular preferably more than 16 g water per g fibrous web.
The invention relates also to a method for producing a material web, in particular a fibrous web, with which the material web is passed through a press nip, said press nip being formed by wrapping at least one press belt around the outer jacket of a roller, wherein the material web, positioned between a support belt and a water-dispersing belt, is passed through the press nip, and wherein the water-dispersing belt is located on the inside in contact with the outer jacket of the roller, and wherein at the end of the wrap zone first the press belt is lifted off the support belt and then the support belt with the material web off the water-dispersing belt.

BRIEF DESCRIPTION OF THE DRAWINGS

The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein:
FIG. 1 shows a side view of a press according to the present invention; and
FIG. 2 shows a detail of the press in FIG. 1.
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate one embodiment of the invention, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, and more particularly to FIG. 1, there is shown a press 1 on which a fibrous web 2 is dewatered in a press nip 3.
The press 1 has a tensioned press belt 4, a support belt 5, a water-dispersing belt 6 and a roller 7 with outer jacket 8. The outer jacket 8 of the roller 7 is enwrapped by the press belt 4, the support belt 5 and the water-dispersing belt 6 in a joint wrap zone 9.
In the embodiment in question the press belt 4 is constructed as a spiral mesh 4 from plastic or metal.
In the embodiment in question the support belt 5 is constructed as a TAD mesh.
In the embodiment in question the water-dispersing belt 6 is constructed as a press felt 6.
Outside the wrap region 9 the spiral mesh 4 is passed over a multiplicity of rollers 18, 19, 20, 21 and 22, with the roller 18 serving as a tensioning roller.
Also outside the wrap zone 9 the press felt 6 is passed over a multiplicity of rollers 23 to 28, the fibrous web 2 being brought together with the press felt 6 in the region of the roller 28.
Likewise outside the wrap zone the press felt 6 is cleaned by a cleaning device 29 and subsequently dried by a suction box 30 and a dryer 31.
The wrap zone has a beginning 10 and an end 11.
As is evident from FIG. 1, the press felt 6 makes contact, on a side 12, with the outer jacket 8 of the roller 7. The spiral mesh 4 is arranged on the outside and the TAD mesh 5 is arranged between the spiral mesh 4 and the press felt 6.
The fibrous web 2 is guided between the TAD mesh 5 and the press felt 6 through the wrap zone 9. By way of this arrangement a press force is exerted by the spiral mesh 4 via the TAD mesh 5 onto the fibrous web 2.
The wrap zone 9 accordingly forms the press nip 3.
In the region of the end 11 of the wrap zone 9, first the spiral mesh 4 is lifted off the TAD mesh 5 and then the TAD mesh 5 with the fibrous web 2 is lifted off the press felt 6.
The roller 7 has a suction zone 13 with an end 14.
As is evident from FIG. 1, the end 11 of the wrap zone 9 is arranged in the region of the suction zone 13 but ahead of the end of the suction zone 13 in the web running direction 15.
Arranged above the roller 7 in the region of the suction zone 13 is a blast box 16 which forces compressed air or steam 17 successively through the spiral mesh 4, the TAD mesh 5, the fibrous web 2 and the press felt 6. Hence on the one hand the dewatering of the fibrous web is promoted by the action of force in the direction of the suction zone 13 and on the other hand the fibrous web 2 is pre-dried by a through-flow of air.
FIG. 2 shows a detail in the region of the end 11 of the wrap zone 9. As is evident from FIG. 2, the spiral mesh 4 is lifted off the TAD mesh 5 at an arc angle α_Bof 4° before the TAD mesh 5 and the fibrous web 2 are lifted off.
Furthermore, the TAD mesh 5 guiding the fibrous web 2 is lifted off the press felt 6 at an arc angle α_Wof 2° in relation to the end 14 of the suction zone 13.
In addition, the press felt 6 is lifted off the outer jacket 8 of the roller 7 after the end 14 of the suction zone 13.
In the concrete embodiment the fibrous web 2 guided through the press 1 is a web with a gsm substance (grams per square meter substance weight or basis weight) of less than 42 g/cm², meaning in particular tissue paper with a high specific bulk in the range of 16 g/cm³and with a water absorption capacity of 16 g water per g (gram) fibrous web.
While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.

Claims

1. A press in a machine for one of producing and processing a material web, said press comprising:

a press belt;

a support belt;

a water-dispersing belt for dispersing water from the material web; and

a roller including an outer jacket, the press defining a wrap zone, said outer jacket being jointly enwrapped, at least in one said wrap zone, respectively by at least said press belt, said support belt, and said water-dispersing belt, said water-dispersing belt being located on an inside in contact with said outer jacket of said roller, said press belt being located on an outside, said support belt being between said press belt and said water-dispersing belt, said support belt and said water-dispersing belt configured for guiding the material web therebetween through said wrap zone, at an end of said wrap zone said press belt being configured for being lifted off said support belt and said support belt being configured for being lifted off said water-dispersing belt, with the material web, after said press belt is lifted off said support belt.

2. The press according to claim 1, said roller includes at least one suction zone including an end in a web running direction, said end of said wrap zone being in a region of said end of said suction zone in said web running direction.

3. The press according to claim 2, wherein said support belt is configured for being lifted off said water-dispersing belt, with the material web, in an arc angle range, relative to said end of said suction zone, of between >0° and <10°.

4. The press according to claim 2, wherein said support belt is configured for being lifted off said water-dispersing belt, with the material web, in an arc angle range, relative to said end of said suction zone, of between >0° and 6°.

5. The press according to claim 2, wherein said support belt is configured for being lifted off said water-dispersing belt, with the material web, in an arc angle range, relative to said end of said suction zone, of between 2° and 6°.

6. The press according to claim 2, wherein said water-dispersing belt is configured for being lifted off said outer jacket of said roller one of at said end of said suction zone and thereafter.

7. The press according to claim 1, wherein the material web is configured for being exposed to an air through-flow, said press belt, said support belt, the material web, and said water-dispersing belt configured for passing said air through-flow first through said press belt, then said support belt, then the material web, and then through said water-dispersing belt.

8. The press according to claim 1, said press belt is configured for being lifted off said support belt by between 0° and 15° before said support belt and the material web are lifted off.

9. The press according to claim 1, said press belt is configured for being lifted off said support belt by between 0° and 10° before said support belt and the material web are lifted off.

10. The press according to claim 1, said press belt is configured for being lifted off said support belt by between 2° and 6° before said support belt and the material web are lifted off.

11. The press according to claim 1, wherein said support belt includes one of a structured membrane and a structured mesh.

12. The press according to claim 11, wherein the material web includes a fibrous web, said support belt configured for being a structure on which the fibrous web is formed.

13. The press according to claim 11, wherein the material web includes a fibrous web, the fibrous web having a gsm substance of less than 42 g/cm².

14. The press according to claim 13, wherein the material web includes a fibrous web, the fibrous web being a tissue paper.

15. The press according to claim 1, wherein said support belt includes a through air drying mesh.

16. The press according to claim 15, wherein the material web includes a fibrous web, said through air drying mesh configured for being a structure on which the fibrous web is formed.

17. The press according to claim 1, wherein said water-dispersing belt is configured for at least one of being permeable for a fluid and having a water absorption capacity.

18. The press according to claim 1, wherein the produced material web is a fibrous web.

19. The press according to claim 18, wherein the fibrous web has a specific bulk of over 10 g/cm³.

20. The press according to claim 18, wherein the fibrous web has a specific bulk of over 14 g/cm³.

21. The press according to claim 18, wherein the fibrous web has a specific bulk of over 16 g/cm³.

22. The press according to claim 18, wherein the fibrous web has a water absorption capacity of more than 10 g water per gram fibrous web.

23. The press according to claim 18, wherein the fibrous web has a water absorption capacity of more than 14 g water per gram fibrous web.

24. The press according to claim 18, wherein the fibrous web has a water absorption capacity of more than 16 g water per gram fibrous web.

25. A method for producing a material web, said method comprising the steps of:

forming a press nip by wrapping at least one press belt around an outer jacket of a roller;

passing the material web through said press nip, the material web being positioned between a support belt and a water-dispersing belt, said water-dispersing belt being located on an inside in contact with said outer jacket of said roller; and

at an end of a wrap zone, first lifting said press belt off said support belt and then lifting said support belt with the material web off said water-dispersing belt.