United States Patent (19) (11) Patent Number: 4,815,299 Bryant (45) Date of Patent: Mar
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United States Patent (19) (11) Patent Number: 4,815,299 Bryant (45) Date of Patent: Mar. 28, 1989 (54) KNITTED FABRICHAVING IMPROVED 56) References Cited ELECTRICAL CHARGE DSSPATION PROPERTIES U.S. PATENT DOCUMENTS 3,699,590 10/1972 Webber et al. ........................... 2/73 3,806,959 4/1974 Gross ................ 66/192 X 75 Inventor: Kenneth G. Bryant, Charlotte, N.C. 4,335,589 6/1982 Flasher .................................. 66/202 FOREIGN PATENT DOCUMENTS 73) Assignee: Conductex, Inc., Charlotte, N.C. 61-27085 2/1986 Japan ..................................... 66/202 Primary Examiner-Ronald Feldbaum (21) Appl. No.: 940,864 Attorney, Agent, or Firm-Kenyon & Kenyon 57 ABSTRACT (22 Filed: Dec. 12, 1986 A knitted fabric having improved electrical charge dissipation properties, constructed so as to form a con 51 Int. Cl* ............................................... D04B 7/16 ductive matrix capable of discharging an electrical 52 U.S. Cl.......................................... 66/202; 66/195 charge along any direction of the course and wale of the 58 Field of Search ................. 66/202, 190, 192, 193, fabric. 66/195; 139/425R, 425 D; 428/242; 57/901; 361/220; 174/117 M 7 Claims, 3 Drawing Sheets O d o d O C O O d O O X 0 O O O O O X 0 0 0 8 7 6 5 U.S. Patent Mar. 28, 1989 Sheet 1 of 3 4,815,299 U.S. Patent Mar. 28, 1989 Sheet 2 of 3 4,815,299 U.S. Patent Mar. 28, 1989 Sheet 3 of 3 4,815,299 Fis. O X 0 O O O O O X O 8 7 4,815,299 1. 2 with electrically conducting carbon particles, the warp KNITTED FABRIC HAVING IMPROVED and filler being woven in an open mesh configuration. ELECTRICAL CHARGE DSSPATION U.S. Pat. No. 4,422,483, issued to Zins, discloses a PROPERTIES multiplicity of elongated filaments which are essentially parallel to each other and which form a single ply of a BACKGROUND OF THE INVENTION conductive thread for woven fabrics. The elongated 1. Field of the Invention filaments in Zins are non-textured continuous, non-con This invention relates to a new and improved knitted ductive filaments or warp threads which are combined fabric having improved electrical charge dissipation together with conductive filaments or fill threads to properties. More specifically, this invention relates to a 10 form a conductive woven fabric. readily manufactured knitted fabric comprised of non Neither Sanders, Rheaume, Blalock or Zins disclose a conductive yarn that extends along the wale and com conductive knitted fabric. While U.S. Pat. Nos. bined with conductive fibers that form overlaps and 4,443,515, issued to Atlas, and its divisional 4,484,926, underlaps within the nonconductive knit to such an disclose that conductive fibers comprised of synthetic extent so as to form a combined stitch construction, e.g., 15 polymers may be incorporated into knitted fabrics, a modified "Queen's Cord' construction, providing an those references do not disclose a pattern whereby such electrically conductive matrix capable of quickly dissi conductive fibers can be economically incorporated pating charge along any direction of both the course into a knitted fabric so as to dissipate static electricity in and wale. any direction along the course and wale directions of 2. Description of the Prior Art 20 the fabric. Electrostatic charge accumulates on clothing as the wearer moves his or her arms and legs and as he or she U.S. Pat. No. 4,398,277, issued to Christiansen et al., walks on non-conductive floor surfaces. The accumula does disclose a pattern whereby insulative yarn and tion of such static charge poses a special problem in electrically conductive yarn are knitted together on two tight-fitting garments such as hosiery and sporting ap 25 levels The insulative yarn in Christiansen et al. forms a parel in which static charge causes adjacent garments to series of interlocking loops on both the technical face cling to one another. This static cling causes both dis and back of the fabric in a tricot construction, while the comfort for the wearer and unpleasant shocks. Such electrically conductive yarn forms a series of chain charge accumulation can also create significant prob stitches on only the technical face. Christiansen et al. lems where the wearer works in an environment in 30 disclose that when their fabric is knitted in such a two which any static charge is undesirable or dangerous. layer construction, one of the surfaces (i.e., the techni A need exists, therefore, for a means to control elec cal face) will be relatively nonconductive. Electrical trostatic charge accumulation on fabric, particularly charge dissipation in such a construction, therefore, is fabric used in clothing worn by individuals who occupy limited to the wale direction of the technical face of the or handle materials in areas in which an electrostatic 35 fabric. discharge could be hazardous to the individual or could Attempts have been made to develop a knitware damage material which is being handled by the wearer, pattern that can be economically manufactured, which e.g., in operating rooms where potentially explosive require the use of a relatively small amount of conduc gases are present or in "clean rooms' where electrically tive fiber and which possess electrical conductivity sensitive microcircuits are manufactured. along both the course and wale directions and on both The utilization of fibers possessing electrical conduc the technical face and back of a two layer knitted fabric. tivity (e.g., metal fibers, fibers coated with electrically A knitted fabric in which conductive yarn is knitted in conductive material, or metal laminate filaments) in an argyle pattern together with nonconductive yarn, combination with common natural and manmade fibers resulting in a fabric having electrical conductivity along to produce a woven, knitted, netted, tufted, or other 45 the course and wale directions on both the technical wise fabricated structure, which readily dissipates static face and back, has been constructed. charge as it is generated is well known. The argyle construction suffers from several disad In U.S. Pat. No. 3,823,035, issued to Sanders, an elec vantages. Such a construction requires that the conduc trically-conductive textile fiber is disclosed in which tive fiber be stitched simultaneously along both the finely-divided electrically conductive particles are uni 50 course and wale directions to form a saw-tooth pattern formly suffused in a filamentary polymer substrate. known as an "Atlas stitch' which, when joined to a Sanders discloses the interweaving of such electrically similar adjacent stitch, forms the argyle pattern. Such conductive fibers with ordinary threads made from simultaneous horizontal and vertical movement of fiber natural fibers such as cotton or wool in an amount suffi requires that the argyle knit be manufactured on a knit cient to render the electrical resistance of the fabric to a 55 ting machine having at least two separate guidebars value of 109 ohms/cm. dedicated to the argyle construction. Further, the ar U.S. Pat. No. 4,312,913, issued to Rheaume, discloses gyle construction requires the use of a substantial a heat-conductive woven fabric comprising a plurality amount of conductive yarn, which is a significant disad of fill layers of weavable yarns, each yarn comprising a vantage given that such yarn is currently more than plurality of fibers that are metallic or are coated with an 60 about thirty-six times as expensive as nonconductive effective amount of a metallic, heat conducting mate yarn. An additional significant disadvantage of this rial. An angle weave pattern is woven through the conductive argyle construction is that it can only be layers of fill yarns in Rheaume, and this angle woven fabricated by a relatively complex warp knitting ma pattern extends from the top to the bottom of several chine, i.e., one having two or more dedicated guidebars layers of fill yarns. 65 as mentioned above. Similarly, U.S. Pat. No. 4,296,855, issued to Blalock, A need exists, therefore, for a relatively inexpensive also discloses a woven pattern of filler and warp yarns easily knitted fabric capable of rapidly and effectively comprised of an electrically insulating material suffused discharging static electricity. Further, the need exists 4,815,299 3 4. for such a knitted fabric which is capable of discharging static electricity along the course and the wale direc DETALED DESCRIPTION tions of the fabric and on the technical back and/or face Referring to FIG. 1 and FIG. 2, the illustrated se of the fabric. Further, there is also a need for such an quence of chain stitches may be formed on a knitting antistatic knitted fabric which can be manufactured on machine of the type well known in the art. See, e.g., a conventional knitting machine that is not as mechani "An Introduction the Stitch Formations in Warp Knit cally complex as those required for complex knits, e.g., ting” $1.3, pp. 27-42 (Employees Assoc. Karl Mayer E. double argyle, presently used in the industry. V., West Germany 1966) (hereinafter "Stitch Forma Accordingly it is an object of the present invention to tions”) the entirety of which is incorporated herein by 10 reference. A significant advantage of the present inven provide a knitted fabric having improved electrical tion is that a knitting machine containing only one dedi charge dissipation properties. cated guide bar may be employed to fabricate the de It is a further object of the present invention to pro sired pattern of stitches of nonconductive fiber inter vide such a knitted fabric in which an electrostatic laced with conductive fiber 1. charge can be dissipated both along the course direction 15 As illustrated in FIG.