Patent Application
20100299953
1. Field of the Invention
The invention relates to a support band and the use of a support band for a drying arrangement for drying one of a paper, a board, a tissue or an other fibrous web in a machine for one of producing and finishing the same.
2. Description of the Related Art
In drying arrangements the steam arising as a result of the heating of the fibrous web during the contact with the heated drying cylinder passes into water-absorbing bands surrounding the fibrous web as it wraps around the drying cylinder. In these bands, condensation and storage of the condensate occur. Following the wrapping, the bands are led away from the fibrous web, cleaned and dried again.
On the bands, a sealing band wraps around the drying cylinder and prevents steam from escaping. This sealing band is normally cooled, so as to intensify the temperature gradient toward the heated drying cylinder, to predefine the direction of the evaporation from the fibrous web and to intensify the condensation of the steam.
Drying arrangements of this type are relatively complicated and expensive, in particular because of the large number of bands and their guidance.
What is needed in the art is a simplified drying arrangement that reduces the expenditure for the bands.
According to one embodiment of the present invention there is claimed a method of using a support band in a drying arrangement for a fibrous web. The method including the steps of wrapping the support band around a drying cylinder and cooling a water-impermeable sealing layer located on an outside of the support band. The fibrous web is located between the drying cylinder and the support band. The support band includes a water-impermeable sealing layer and at least one water-absorbing storage layer adjacent the water-impermeable sealing layer. The water-impermeable sealing layer and/or the water-absorbing storage layer being made at least partially of a highly thermally conductive material. The highly thermally conductive material is a metal fabric. The metal fabric being both a part of the water-impermeable sealing layer and a part of the water-absorbing storage layer.
Since the support band not only acts in a sealing manner, but is also able to absorb the steam escaping from the fibrous web as a result of the heating and the condensate forming, the number of necessary bands is reduced. This also leads to a simplification of the structure.
The highly thermally conductive material of the sealing layer permits the formation of a relatively large temperature gradient between the heated drying cylinder and the sealing layer. This applies in particular if the sealing layer of the support band, located on the outside as it wraps around the drying cylinder, is cooled. This temperature gradient predefines the evaporation direction from the fibrous web, the cooling promoting the condensation of the steam in the storage layer. This is further assisted by the fact that the storage layer also consists, at least partially, of a highly thermally conductive material.
A further accomplishment is achieved if the sealing layer and/or the storage layer consists completely of a highly thermally conductive material, preferably metal.
In order, on the one hand, to ensure the stability of a metal band, in particular on account of the tensile forces occurring during the wrapping, but on the other hand, also to permit adequate flexibility of the metal band, the thickness of the metal band should preferably be between 0.05 and 2 mm.
The metal band can overall form the sealing layer. However, it may also be advantageous if the metal band has a profiled surface on one side, which forms at least part of the storage layer, and the sealing layer is formed by the other part of the metal band. The profiling of the metal band can be implemented by way of spark erosion, compression molding or laser removal. This embodiment of the support band is very simple in construction.
However, the support band can advantageously also include a metal fabric, which forms the sealing layer and at least part of the storage layer. To this end, the part provided for the sealing layer can be fused, in a sealing manner, on one side of the metal fabric. However, it may also be advantageous to fill the metal fabric with a filling material of plastic or metal in order to form a sealing layer on the appropriate side. In both cases, the porous region of the metal fabric should form at least part of the storage layer. This combining of functions contributes substantially to the simplification.
If the storage layer of the metal band or metal fabric does not have sufficient storage capacity, then, on the side facing away from the sealing layer, the metal band or the metal fabric is joined to at least one water-absorbing storage band, in at least some zones, in order to form or expand the storage layer. In order to avoid indentations on the fibrous web, the outer storage band should be as smooth and fine as possible on the side facing the fibrous web.
Depending on the loading and the requirement on the thermal conductivity, the storage band should be formed by a fabric made of metal and/or plastic. A connection between the metal band or the metal fabric and the adjacent storage band and, if appropriate, also between the storage bands, can be accomplished by adhesive bonding, welding, riveting, soldering or the like.
In order to reduce the effort needed for this purpose, it is sufficient if the corresponding storage band is connected to the metal band or the metal fabric only in the edge regions. This applies in particular because of the increased loading by the drive in the edge regions. For this reason, it may also be advantageous if the metal fabric or the metal band has a higher strength in the edge regions. The higher strength may be accomplished in many ways including, but not limited to the use of higher strength materials in the edge regions, the use of more material in the edge regions, or the use of a different mix of materials in the edge regions.
On the side facing away from the storage layer, the support band should be smooth. This makes it easier to seal with respect to a cooling unit for cooling the sealing layer with blown air or water. In addition, the thickness of the support band should lie between 0.6 and 7 mm in order to ensure adequate flexibility and an adequate storage volume for the steam and the condensate. The thickness of the support band should preferably be less than 5 mm, in particular less than 3 mm.
For the application of the support band in drying arrangements for fibrous webs, it is sufficient if the storage volume of the support band lies between 200 and 3000 cm3/m2.
In order to take care of the joint between the metal band or metal fabric and the adjacent support band as a consequence of alternating bending loading, the neutral fiber of the support band should deviate by at most 50% of the thickness of the metal band or metal fabric from the connecting region between the metal fabric or metal band and the adjacent storage band. In order to minimize the bending loading, it is additionally advantageous if, outside the wrap region of the drying cylinder, the support band is led over guide rolls whose diameter is greater than 200 times, preferably greater than 500 times and in particular greater than 800 times the thickness of the support band.
If the storage volume of the support band should not be sufficient and/or the surface of the support band leads to markings, then it is advantageous if the drying cylinder is wrapped around by at least one further porous band, which is arranged between the fibrous web and the support band.
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 embodiments of the invention taken in conjunction with the accompanying drawings, wherein:
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate embodiments of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner.
Referring now to the drawings, and more particularly to
Now, additionally referring to
As a result of the contact of fibrous web 1 with the hot circumferential surface of drying cylinder 3, evaporation into porous storage layer 12 of the support band 2 occurs, where the formation of condensate also occurs.
The thermal conductivity of sealing layer 11 is relatively high, since it is made, at least partly, of metal. This is necessary since sealing layer 11 is cooled in the wrap region of drying cylinder 3 originating from a hood 4 with the aid of water.
The temperature gradient between sealing layer 11 and drying cylinder 3, produced by the cooling, assists the condensation considerably. It is also advantageous if the thermal transfer coefficient α on both sides of sealing layer 11 is as high as possible.
The steam and the condensate are picked up by storage layer 12 and can be removed again after support band 2 has been led away from fibrous web 1. It is therefore also advantageous if the open structure of storage layer 12 has a dirt-repellent surface, which may be made of a PTFE coating. Cleaning can be carried out by blowing out, throwing out or sucking out.
In order to be able to seal sealing layer 11 as well as possible with respect to hood 4, the outer surface of sealing layer 11 should be as smooth as possible.
The thickness of support band 2 lies between 1.5 and 4 mm, sealing layer 11 having less than 40% of the thickness of support band 2.
In order to configure the drying arrangement together with band guidance as simply as possible, support band 2 includes sealing layer 11 and storage layer 12. This also reduces the expenditure for the bands of the drying arrangement overall.
According to
Since the contact area of storage layer 12 with fibrous web 1 should be as smooth and fine as possible in order to avoid markings, a further fabric layer 9, which is woven with metal fabric 6, adjoins metal fabric 6 on the side opposite of sealing layer 11.
Another embodiment of a support band 2 of the present invention is illustrated in
Outside the wrap region of drying cylinder 3, support band 2 is led over guide rolls 5, whose diameter is greater than 800 times the thickness of support band 2, in order to minimize the bending loading of support band 2.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2005 000 793.7 | Jan 2005 | DE | national |
This is a division of U.S. patent application Ser. No. 11/773,605, entitled “SUPPORT BAND”, filed Jul. 5, 2007, which is a continuation of PCT application No. PCT/EP2005/056146, entitled “SUPPORT BAND”, filed Nov. 22, 2005, which is incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 11773605 | Jul 2007 | US |
| Child | 12851104 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP2005/056146 | Nov 2005 | US |
| Child | 11773605 | US |
