Abstract:
A through air dryer (TAD) fabric having a composite configuration whereby side fabric portions made of a more resistant material are woven to the main body portion of the fabric. Side fabric portions that are not protected from the paper web, and therefore exposed to harsher environmental conditions than the portion of the fabric covered by the paper web, deteriorate faster. By replacing the side portions that are exposed to harsher environment with more resistant material, the TAD fabric will last longer.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   The present application claims priority under 35 U.S.C. §119 of U.S. patent application No. 60/721,321 filed 27 Sep. 2005, the disclosure of which is expressly incorporated by reference herein in its entirety. 

   STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not applicable. 
   REFERENCE TO A COMPACT DISK APPENDIX 
   Not applicable. 
   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The invention relates to through air dryer (TAD) fabrics, and more particularly, to TAD fabrics have a composite whereby side fabric portions are woven to the main body portion of the fabric. 
   2. Background of the Invention 
   There is continuing need to improve the fabrics used in TAD applications. For typical dryers such as non-TAD, there is a need to alternate standard and, for example, PPS yarns, to prevent tension variation during the heat-setting process. Still further, PPC is used in some fabrics across the entire width of the fabric, and this is very expensive. PPS does not have the same level of tenacity as PET, so a combination is better. 
   In many TAD machines, the paper that is produced is trimmed at the forming section prior to being transferred to the TAD fabric. At the TAD section, as depicted in  FIG. 1 , hot air is blown going through the paper  100  and passing through the fabric  102  and drum  104 . However, as the paper was previously trimmed, there is an area of the fabric  106  that received more air flow at higher temperatures. 
   The result is that the fabric that is not in contact or otherwise protected by the paper web is exposed to the harsher paper machine running conditions than if the fabric was protected by the web. This result in premature wear or other destruction of the fabric. 
   Accordingly, a need exists for a TAD fabric having the ability to survive under the harsh environments longer by postponing the wear at the exposed sides of the fabric. 
   BRIEF SUMMARY OF THE INVENTION 
   A TAD fabric meeting the needs discussed above is achieved using a composite fabric for through air drying having a fabric body fabricated from a first material and having a first side portion and a second side portion, wherein the first side portion is fabricated from a second material. Similarly, the second side portion can be fabricated using a third material, or the second material and the third material can be the same material. 
   In prior art TAD applications, part of the fabric is not protected by the paper web. More specifically, the edge portions of the, the edge portions of the fabric, when not in contact or otherwise covered by the web, is exposed to the harsher environment of the paper machine running conditions. 
   In the present invention, a new edge material is added to the main portion of the fabric. That is, a main central portion of the fabric running in the machine direction has additional side panels added. The paper web generally covers the main middle portion, and overlays, or extends to cover a portion of the side portions. 
   In the composite fabric, the first side portion is woven to the fabric body along one side edge. The second side portion is woven to the fabric body along a second side edge. The second side edge is opposite the first side edge. The first and second side portions can be woven to the fabric body on the same loom. 
   Likewise, the first and second portions can have the same weave pattern as the fabric body. 
   Still further, the first and second side portions can be subjected to the same processing as the fabric body, for example, heat setting, stretching, coating, and the like. When a coating is utilized, the coating, when compared to the composite fabric, has at least one of enhanced release properties, enhanced wear properties and enhanced thermal stability. 
   The material used for the body of the composite fabric is at least one of polyester and polyethylenepterathalate (PET). 
   The material used for the first side portion is at least one of polyphenylenesulfide (PPS), polyetheretherketone (PEEK), high temperature and hydrolysis resistant polymers, blends using PPS, blends using PEEK, alloys of PPS, alloys of PEEK, and high temperature nylon. The high temperature nylon is at least one of a variant of nylon  66  and an aromatic nylon. 
   Additionally, the diameter of the material used for the first side portion can be substantially the same as the diameter of the first material. 
   When the first side portion is woven to the fabric body, it is preferably woven in the same plane. 
   It is also preferred that the fabric body and the first side portion have substantially the same CFM throughput. However, depending on the design parameters, the CFM throughput of the first side portion can be different from the fabric body, or may be different from the second side portion. 
   Additionally, it is preferred that there is a smooth transition between the main portion of the fabric and the side portions. 
   The size of the first and second side portions is dependent upon the size of the paper web. In the preferred embodiment, the width of the side portions is approximately 20-40 cm when measured in the weft direction. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention is further described in the detailed description which follows, in reference to the noted plurality of drawings by way of non-limiting examples of exemplary embodiments of the present invention, in which like reference numerals represent similar parts throughout the several views of the drawings, and wherein: 
       FIG. 1  is a cross section of the prior art; 
       FIG. 2  is a plan view of paper side of the composite fabric of the invention; 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 2  depicts a plan view of the composite fabric  10  of the present invention. The composite fabric has a central fabric portion  12 , a first fabric side or outer edge portion  14 , and a second fabric side or outer edge portion. MD indicates the machine direction of the composite fabric. 
   It is understood that the first fabric side portion  14  and the second fabric side portion  16  are interchangeable, and reference to one may be interchanged with the other. Stated differently, the plan view of  FIG. 1  may represent either the paper side or the drum side. 
   The central portion  12  can be any woven TAD fabric. The material used for the central portion  12 , also known as the body of the composite fabric, is preferably at least one of polyester and polyethylenepterathalate (PET). 
   The first fabric side portion  14 , or new edge material, is added to the central fabric portion  12 . That is, the central fabric portion of the fabric running in the machine direction has additional side panels  14 ,  16 . The paper web  18  generally covers the central fabric portion  12 , and overlays, or extends to cover a portion of the side portions  14 ,  16  at first and second paper web overlays  20 ,  22 . 
   In the composite fabric, the first side portion  14  is woven to the central fabric portion  12  along a first side edge  24 . The second fabric side portion  16  is woven to the central fabric portion  12  along a second side edge  26 . The second side edge  26  is opposite the first side edge  24 . The first and second fabric side portions  14 ,  16  can be woven to the central fabric body  12 . This weaving of the first and second fabric side portions  14 ,  16  to the central fabric body  12  is preferably performed on the same loom on which the central fabric body was woven. 
   There is no requirement that the first fabric side portion  14  have the same weave pattern as the central fabric portion  12  or the second fabric side portion  16 . In the preferred embodiment, the first and second fabric portions  14 ,  16  have the same weave pattern. Additionally, it is preferable that the first and second fabric portions  14 ,  16  have the same weave pattern as the central fabric portion  12 . 
   Still further, the first and second fabric side portions  14 ,  16  can be subjected to the same processing as the central fabric portion  12 . For example, heat setting, stretching, coating, and the like. When a coating is utilized, the coating, when compared to a composite fabric without the coating, has at least one of enhanced release properties, enhanced wear properties and enhanced thermal stability. 
   The material used for the central fabric portion  12  of the composite fabric  10  is preferably at least one of polyester and polyethylenepterathalate (PET). 
   The material used for the first fabric side portion  14  and/or the second fabric side portion  16  is preferably at least one of polyphenylenesulfide (PPS), polyetheretherketone (PEEK), high temperature and hydrolysis resistant polymers, blends using PPS, blends using PEEK, alloys of PPS, alloys of PEEK, and high temperature nylon. The high temperature nylon is at least one of a variant of nylon  66  and an aromatic nylon. 
   Additionally, the diameter of first fabric side portion fibers  28  used for the first fabric side portion  14 , and the diameter of second fabric side portion fibers  30  used for the second fabric side portion  16  can be substantially the same as the diameter of the central fabric portion fibers  32  used for the central fabric portion  12 . 
   When the first side portion is woven to the fabric body, it is preferably woven in the same plane. 
   It is also preferred that the fabric body and the first side portion have substantially the same CFM throughput. However, depending on the design parameters, the CFM throughput of the first side portion can be different from the fabric body, or may be different from the second side portion. 
   Additionally, it is preferred that there is a smooth transition between the main portion of the fabric and the side portions. 
   The size of the first and second fabric side portions  14 ,  16  is predetermined and can be based upon the size of the paper web. In the preferred embodiment, the width of each of the fabric side portions  14 ,  16  is approximately 10-60 cm when measured in the weft direction, preferably approximately 20-40 cm. 
   It is noted that the foregoing examples have been provided merely for the purpose of explanation and are in no way to be construed as limiting of the present invention. While the present invention has been described with reference to an exemplary embodiment, it is understood that the words which have been used herein are words of description and illustration, rather than words of limitation. Changes may be made, within the purview of the appended claims, as presently stated and as amended, without departing from the scope and spirit of the present invention in its aspects. Although the present invention has been described herein with reference to particular means, materials and embodiments, the present invention is not intended to be limited to the particulars disclosed herein; rather, the present extends to all functionally equivalent structures, methods and uses, such as are within the scope of the appended claims.