Stock material or miscellaneous articles – Structurally defined web or sheet – Edge feature
Reexamination Certificate
2000-07-26
2003-01-07
Cole, Elizabeth M. (Department: 1771)
Stock material or miscellaneous articles
Structurally defined web or sheet
Edge feature
C442S181000, C442S239000, 16
Reexamination Certificate
active
06503602
ABSTRACT:
BACKGROUND
1. Field of the Invention
The present invention generally relates to a woven fabric for use on a papermaking machine. More particularly it relates to a fabric for use in drying the paper web. Most particularly, it relates to a dryer fabric having reinforced edges.
2. Description of the Related Art
Fabrics used in papermaking machines are used as endless belts for carrying the paper through various stages of manufacture. The fabrics are either joined endless by a seam or woven endless. In either case, the fabrics must be durable to minimize the down time and loss of production associated with a fabric change. Because the edges are subject to damage and wear due to repeated contact with machine parts and guide rails, edge protection has been a concern. Recurrent problems found in papermaking fabrics include premature edge wear and unraveling at the edges. Unprotected edges also lead to reduced fabric stability. Sealing the fabric edges helps to prevent yarn shifting throughout the body of the fabric. Paper machine guide system suppliers have long advocated increasing the mass of the fabric edge as a means to prolong the life of the fabric selvage.
Typically, the fabric edges have been protected by application of an edge sealant. Popular sealants include polyurethane and epoxy urethanes. Ultraviolet light curable silicone and radiation curable coatings also have been used to protect fabric edges. Problems associated with these sealants include long drying times, cost and application problems. Additionally, these types of sealants do not fuse the threads at the fabric edge. Therefore, the fabric may suffer from stray threads or unraveling.
In the past, rather than sealing the edge with a coating, the belt edge has been reinforced by stitching additional, more durable material along the edge or weaving special threads into the edge. The latter technique is the common approach in papermaking fabrics. In some cases, stranded, more flexible warp yarns have been used in the fabric selvage to reduce the danger of edge cracking. In other instances, special yarns have been woven into the edge for treatment with heat or chemicals. When exposed to the appropriate element, the special yarns fuse or bond together to create a more stable finished selvage. One such method uses solvents to partially dissolve the edge fibers and cause them to fuse together. Similarly, ultrasonic welding has been used to fuse a substitute thermoplastic warp thread to edge yarns where a standard warp thread has been removed. In other applications, ultrasonic bonding has been improved by the addition of a thermoplastic web between two material layers. Thermoplastic webs have more traditionally been heat fused between a base fabric and batt material to reduce compaction between the two layers.
Papermaking machines continually improve, becoming faster and demanding better, more durable fabrics. The papermaking art demands constant evolution of papermaking fabrics and will benefit from reinforcement of the papermaking fabric edge according to the present invention.
SUMMARY OF THE INVENTION
The present invention concerns a papermaking fabric having edges reinforced with a webbing which is bonded to the papermaking surface or the machine surface or both. Longitudinal machine direction edges, as well as the cross machine direction seam edges of a flat woven fabric, may be reinforced by application of the webbing.
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AstenJohnson, Inc.
Cole Elizabeth M.
Volpe and Koenig P.C.
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