Textiles: spinning – twisting – and twining – Strand structure – Covered or wrapped
Reexamination Certificate
1999-02-23
2001-04-17
Calvert, John J. (Department: 3765)
Textiles: spinning, twisting, and twining
Strand structure
Covered or wrapped
C057S230000, C428S364000, C428S373000, C428S377000, C428S378000, C428S394000
Reexamination Certificate
active
06216431
ABSTRACT:
BACKGROUND AND SUMMARY OF THE PRESENT INVENTION
The present invention is related to cut-resistant yarns and associated fabrics, cordage, or non-woven products, which may be produced with the yarn. It is also related to static dissipative materials, materials reinforced for strength, and abrasion-resistant materials. Most particularly, the present invention is related to the above products when containment of a core material is required due to the potential for hazard to the employee, product, or environment if the core material is exposed.
There has been significant activity in recent years with regard to the manufacture of yarns and fabrics for cut-resistant protective apparel. Many of these activities deal with the use of stainless steel wire in conjunction with various fibers to attain an optimal balance of cut resistance and flexibility, coupled with cost of production.
U.S. Pat. No. 4,384,449 to Byrnes, Sr., et al. teaches the use of a longitudinally positioned wire strand covered with aramid, and the numerous resulting advantages of such wrapped wire. One advantage is superior cut resistance performance, when compared to gloves formed of pure aramid. Byrnes, Sr. also describes improved knitability on a conventional glove knitting machine, and improved dexterity of a glove knitted from such a wire yarn.
U.S. Pat. No. 4,470,251 to Bettcher extends the teachings of the above-mentioned Byrnes, Sr. patent by illustrating two primary discoveries. First, that two or more smaller wire strands yield greater flexibility than one strand, while allowing a larger quantity of wire to be used, and the use of a longitudinally positioned fibrous strand incorporated with the wire strands further improves flexible movement. Second, Bettcher demonstrates that an outer covering formed of a polyamide, such as nylon, improves the comfort of the glove to the wearer.
Kolmes/Plemmons, in U.S. Pat. Nos. 4,838,017 and 4,777,789, teach the wrapping of annealed stainless steel wire about a core fiber; wrapping the strands of wire in opposing directions and further increasing flexibility of the fabric while maintaining cut protection. Kolmes/Plemmons also documented a broad range of fibers that can be used in the core and outer wraps of the composite yarn.
The established prior art referenced here offers teachings that have improved the state of protective apparel. While each is representative of improvement, the present invention extends far beyond these prior teachings and demonstrates a novel and unique approach which solves a serious and heretofore unaddressed issue related to the manufacture of protective apparel. One previously unrecognized problem is the fact that in the use of wire composite yarns, the wire strands frequently break, puncturing the skin of the wearer, contaminating various manufacturing and production operations, and exposing the wearer to the possibility of disease. Wire will invariably fracture after repeated flexure and will penetrate the surface of any known composite yarn.
The present inventor has discovered that the invention taught herein provides a method of containing wire and other materials such as fiberglass when these materials are used as the yarn core. To date, there has been no serious attempt by the Food and Drug Administration (FDA) or the U.S. Department of Agriculture (USDA) to eliminate the use of such materials as a yarn core, but the issue is volatile and will eventually need to be resolved. The resolution may not be one which industry finds acceptable or even practical.
Wire and fiberglass are known to provide additional cut resistance to composite yarns by microscopically altering the edge of the cutting surface. This is due to exceptional high density and abrasiveness, which dulls the edge of any cutting instrument or device that contacts the material. Wire and fiberglass also add strength to a yarn. The materials are preferred because of the many benefits they add to a composite relative to the cost. However, these same materials are controversial because they cannot be allowed to escape from the composite yarn into the work place for environmental and/or health reasons. The present invention provides a composite yarn and fabric which may selectively incorporate wire and/or fiberglass and/or other necessary but potentially harmful materials into the basic yarn core, but which offers protection to the worker from exposure to the materials, which materials may fragment or splinter and threaten the health of the worker and also damage the end product.
The present invention provides a novel method of forming a containment barrier around a single component or multi-component core of such controversial and potentially contaminating materials, and substantially decreases the risk of these contaminates being released. The foundation of the present invention is a composite yarn which uses melt-fusible thermoplastics or liquid adhesive coatings to encapsulate and thereby isolate one or more core materials which may present a threat of contamination to workers or the environment. This novel yarn is basically comprised of one or more core materials which are covered in thermoplastics or liquid adhesives and additional layers of material which form one or more outer layers. The combination is then heat-set or otherwise cured to form a flexible fiber barrier which surrounds and entraps the unsafe core.
In a first method of manufacture, the barrier which contains the selected core is created by melt fusing a thermoplastic material with other differing fiber products in such a way that these undesirable materials are trapped between a shroud of fused fibers and a fiber core. In other embodiments, materials which are longitudinally positioned to form the core are encapsulated in a continuous fibrous sheath with no adhesion between the sheath and an inner core yarn.
It is preferred to trap wire in a fused-fiber layer having a smooth outer surface which is unlikely to bond with subsequent outer cover layers. Because wire itself has a smooth surface unlikely to bond with thermoplastic, it is important that the core bond to the thermoplastic and isolate the wire therebetween. The combination becomes a highly effective containment vehicle that retains a high level of flexibility. While the end product, such as a glove, may become slightly more rigid after heat-treating to retain shape, the composite yarn is highly flexible and can therefore be easily knitted, woven, braided, or otherwise formed into a glove or other product. There are many different materials and processing methods available to form the composite yarn, depending on the end use desired. Conventional covering or wire-wrapping equipment is most suitable to manufacture this form of the composite yarn. Other equipment may be used as needed to preprocess materials that can later be wrapped or used as wraps. Examples are commingling machines, twisting equipment, and extruding machines.
It has also been discovered that a new group of adhesive coatings can be utilized and do not require the application of heat to fuse the containment fibers together. Most of these adhesive coatings are liquid at room temperature, enabling a method which allows greater freedom in yarn design by eliminating the effect that high temperature curing can have on fibers. With the exception of those compounds, which become thermoplastic when cured, these adhesives are thermostable and normally will not return to their original state. Therefore it is possible to manufacture yarns containing adhesives with cured melting temperatures higher than the associated fibers.
The group of useful adhesives includes, but is not limited to polyurethanes, silicone, natural or synthetic rubber, polysulfide systems, epoxy-polysulfides, vinylidene chloride and blended polymers derived from this group. The novel method eliminates the necessity for in-line curing ovens because curing occurs within the protective outer sheath. As will be described in more detail in the following material, coatings can be applied, covered, and the yarn taken up on the finished
Calvert John J.
Dremann Christopher C.
Welch Gaby L.
World Fibers, Inc.
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