Textiles: weaving – Special-type looms – Multiple-shed
Reexamination Certificate
2000-08-24
2001-09-18
Calvert, John J. (Department: 3741)
Textiles: weaving
Special-type looms
Multiple-shed
C139S42500R, C139S116100, C139S450000, C139S42000D
Reexamination Certificate
active
06289939
ABSTRACT:
BACKGROUND AND FIELD OF THE INVENTION
The present invention is directed to a high conductivity grounding tape used in connection with garments worn in so-called “clean rooms”.
It is well recognized in the industry that in the manufacture of certain sensitive electronic components i.e. “chips”, that even low voltage charges can permanently damage the chips at certain stages of their manufacture. By way of example, operators of manufacturing equipment can produce several hundred volts of static electricity merely by minor movements of their arms.
In order to dissipate voltages as low as those noted, it is imperative that the grounding, voltage dissipating conductor have a high conductivity factor.
While a pure wire conductor will provide the requisite low resistance, it is desirable, and in most instances imperative that the grounding conductor exhibit the “hand” or feel of a conventional fabric.
Numerous attempts have been made to create a fabric-like tape which will exhibit the necessary high conductivity and “hand” demanded by industry and which also will maintain these characteristic through multiple laundering cycles. By way of example, clean room, static dissipating garments are expected to be capable of withstanding a hundred or more washings in deionized and hence highly reactive water, without material increase in the resistance of the grounding tape.
Attempts to provide a tape having the above desired characteristics have included incorporating in the fabric metal clad polymer yarns i.e. yarns coated with silver, copper, etc. The tapes fabricated from clad yarns fail to satisfy the laundering requirements since the ohmic resistance exhibited increases progressively from washing to washing.
Tapes have been formed of yarns impregnated with conductive materials such as carbon. However, carbon filled yarns possess an electrical resistance thousands of times greater than that required in many “clean room” environments.
PRIOR ART
Without conceding the relevance thereof to the instant invention, there is cited below patent references located in the course of studies.
U.S. Pat. No. 4,664,158 assigned to the applicant herein is directed to a grounding fabric for a wrist strap wherein conductive components are raised from the surface of the fabric. A similar disclosure is embodied in 4,577,256.
U.S. Pat. No. 4,557,968 discloses an electrostatic dissipating fabric for making into garments, the conductivity being afforded by carbon doped yarns.
U.S. Pat. No. 3,288,175 discloses a textile material incorporated conductive yarn ends.
U.S. Pat. No. 3,422,460 disclosures a static inhibiting cloth which avoids clinging to the wearer.
U.S. Pat. No. 3,479,565 discloses a circuit board for electronic components made of a woven matrix.
U.S. Pat. No. 3,586,597 discloses a cloth for use in garments employing a conductive fiber having finely divided articles of conductive material therein.
U.S. Pat. No. 3,706,195 teaches a synthetic yarn having conductive carbon which is longitudinally extendible to a high degree before breaking.
U.S. Pat. No. 3,851,456 is directed to anti-static yarn comprised of a mixture of metallic and non-metallic fibers, the metallic fibers including stainless steel.
U.S. Pat. No. 3,882,667 is directed to a composite textile yarn formed of non-metallic yarns and a blended yarn plied with non-metallic yarns, the blended yarn being formed of metallic and non-metallic fibers.
U.S. Pat. No. 3,971,202 is directed to an anti-static yarn particularly useful to form carpets, the yarn being obtained by cobulking non-conductive and conductive yarns.
U.S. Pat. No. 3,986,530 is directed to a knitted or woven cloth having anti static properties including electrically conductive threads composed of metal plated natural or synthetic fibers and metallic filaments.
U.S. Pat. No. 4,045,949 is directed to an integral electrically conductive textile filament including a multiplicity of electrically conducting longitudinally directed strata of fiber-forming polymer material. Conductivity is provided by carbon black.
U.S. Pat. No. 4,064,075 is directed to a highly conductive extrudable material embodying electrically conductive carbon black.
U.S. Pat. No. 4,145,473 relates to an anti-static filament having a polymeric sheath and a conductive polymer core.
U.S. Pat. No. 4,332,082 relates to an anti-electrostatically grounded suiting material. Conductivity is provided by carbon black coated monofiliment fibers.
U.S. Pat. No. 4,296,855 is directed to a conductive fabric especially adapted for use as a controlling antenna on a conveyor belt. Carbon particles provide conductivity.
U.S. Pat. No. 4,357,390 is directed to an anti static polyester fiber, the fiber being hollow.
SUMMARY OF THE INVENTION
The present invention may be summarized as directed to a method of manufacturing a tape and to the resulting tape characterized in that the tape has a low ohmic resistance, e.g. less than 2 ohms per inch, exhibits the “hand” or feel of a conventional textile, and which may be subjected to a multiplicity of washings (well over 100) without any significant loss in conductivity.
It is noted that attempts have been made by applicant on an experimental basis to weave tapes comprised of polymeric yarns and continuous filiments of metal i.e., stainless steel. Initial such attempts have proven to be failures. More particularly, the ohmic resistance of the tape would increase dramatically in the course of handling and washing.
We have discovered, that the loss of conductivity of conventionally woven tapes comprised of polymeric yarn ends and stainless ends is a result of a rupture of the stainless ends, the rupture being occasioned by a differential shrinkage of the polymer and stainless yarns. More particularly, microscopic examination of such tapes reveal the formation of a multiplicity of kinks in stainless yarns. We have theorized that the kinking results from the fact that polymer yarns stretch by a factor of 40 or more times the stretch exhibited by stainless yarns when the yarns are woven together under normal tension parameters.
We have discovered that the kinking with consequent loss of conductivity can be avoided by a unique departure from conventional weaving procedures, namely the polymer and stainless yarns are woven under tension and are removed from the loom while still under tension. The tension in the yarns is continuously maintained after weaving and is maintained until the tape is subjected to a heat setting procedure during which the tendency of the polymer yarns to shorten is removed. The resulting tape evinces the hand or feel of comparable tapes woven entirely of polymer yarns. The tape has been subjected to well over 100 cycles of washing with no significant loss of conductivity. In this connection it is noted that clean room garments are washed in deionized water. This material is more reactive as respects silver or copper clad yarn ends and accounts for the rapid loss of conductivity observed in grounding tapes employing clad yarns. It is noted that conventional weaving procedure is essentially the opposite of the practice described in patents such as U.S. Pat. No. 4,664,158 wherein conductive yarns are woven together with distended elastic yarns. Upon release of tension the conductive yarns are deflected away from the surface of the woven tape to ensure contact with the skin of the user as a result of foreshortening of the elastic yarns.
It is accordingly an object of the invention to provide a highly conductive tape having the “hand” of a conventional tape, the tape being susceptible of a multiplicity of laundering cycles without material increase in the ohmic resistance of the tape.
A further object of the invention is the provision of a method of manufacturing a conductive tape having the above described characteristics.
REFERENCES:
patent: 3288175 (1966-11-01), Valko
patent: 3422460 (1969-01-01), Burke et al.
patent: 3586597 (1971-06-01), Okuhashi
patent: 3722440 (1973-03-01), Igarashi et al.
patent: 3851456 (1974-12-01), Hamada et al.
patent: 3882667 (1975-05-01), Barry
patent:
Fryer Russell
Mortensen John A.
C. M. Offray & Son, Inc.
Calvert John J.
Magidoff Barry G.
Muromoto Jr. Robert H.
Sutton Paul J.
LandOfFree
High conductivity launder resistant grounding tape does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with High conductivity launder resistant grounding tape, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and High conductivity launder resistant grounding tape will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2447972