Claims
- 1. A conductor with insulation consisting essentially of a first, second and third continuous non-tape superimposed layers having a temperature rating of at least 150.degree. C., said first layer around and in contact with said conductor and consisting essentially of a plastic selected from the group consisting of perfluoroalkoxy, polytetrafluoroethylene, ethlene-tetraflouroethylene copolymer and fluorinated ethylene-propylene resins; said second layer comprising a polyimide resin around and in contact with said first layer; said third layer being around and in contact with said second layer and consisting essentially of a plastic selected from the group consisting of perfluoroalkoxy, ethylene-tetrafluoroethylene copolymer, polyvinylidine fluoride and a substantially non-hydrolizing thermoset polyamide resin.
- 2. A conductor as set forth in claim 1 wherein said first layer and said third layer is perfluoroalkoxy resin and said insulated conductor has a temperature rating of at least 200.degree. C.
- 3. A conductor as set forth in claim 1 wherein the radial thicknesses of said first layer and said third layer are greater than the radial thicknesses of said second layer.
- 4. A conductor as set forth in claim 1 wherein the polyamide resin of said ssecond layer is thermoset.
- 5. A conductor as set forth in claim 1 wherein at least one of said layers is thermoplastic.
- 6. A conductor as set forth in claim 1 wherein said second layer is an extruded layer.
- 7. A conductor as set forth in claim 1 wherein at least one said layer is an extruded layer.
- 8. A conductor as set forth in claim 1 wherein each of said first layer, said second layer and said third layer is an extruded layer.
- 9. A conductor as set forth in claim 1 wherein at least one of said layers is a coated layer.
- 10. A conductor as set forth in claim 1 wherein said first layer is selected from the group consisting of perfluoroalkoxy and polytetrafluoroethylene resins, and said third layer is selected from the group consisting of perfluoroalkoxy, ethylene-tetrafluoroethylene copolymer and polyvinylidine resins.
- 11. A conductor as set forth in claim 1 wherein said third layer is a substantially nonhydrolizing, thermoset polyamide.
- 12. A conductor as set forth in claim 1 wherein said first layer is selected from ethylene-tetrafluoroethylene and fluorinated ethylene-propylene resins and said third layer is a substantially non-hydrolizing, thermoset polyamide.
- 13. A conductor as set forth in claim 1 wherein said second layer consists essentially of polyimide resin.
- 14. A conductor as set forth in claim 10 wherein said first layer is perfluoralkoxy resin.
- 15. A conductor as set forth in claim 10 wherein said first layer is polytetrafluoroethylene.
- 16. A conductor as set forth in claim 14 wherein said third layer is ethylene-tetrafluoroethylene.
- 17. A conductor as set forth in claim 15 wherein said third layer is ethylene-tetrafluoroethylene.
- 18. A conductor as set forth in claim 14 wherein said third layer is polyvinylidine fluoride.
- 19. A conductor as set forth in claim 15 wherein said third layer is polyvinylidine fluoride.
Parent Case Info
This application is a continuation-in-part of my copending application Ser. No. 901,740, filed Aug. 28, 1986 and entitled "Insulated Conductor with Multi-Layer, High Temperature Insulation" and now abandoned, and its divisional application Ser. No. 068,615 filed June 30, 1987 also copending.
This invention relates to an insulated conductor with a plurality of layers of insulation able to withstand relatively high temperatures and mechanical abuse and to the manufacture thereof.
Insulated conductors which have insulation which is satisfactory for use at relatively high temperatures, i.e. 200.degree. C. and higher, are desirable for many applications and particularly for installation in aircraft and missiles. One such insulated conductor is described in Military Specification Sheet MIL-W-81381/7E and comprises a plurality of stranded wires plated with silver or nickel and surrounded by two helical layers of fluorocarbon/polyimide tape, the outer layer of tape being coated with an aromatic polyimide resin. The tape may be a film of the type sold by E .I. DuPont de Nemours & Co., Wilmington, Del., under the trademark KAPTON, such tape being a thermoset polyimide film combined with a fluorinated ethylene-propylene copolymer film for sealing purposes. The polyimide resin coating is used to provide color identification and to smooth and help protect the tapes with respect to the environment.
While the described insulation conductor will meet a 200.degree. C. temperature rating requirement, it has several disadvantages. The main disadvantage is the problem of proper adhesion of the coating to the tape because of its tendency to hydrolize. Other disadvantages are the necessity of winding two layers of opposite hand with proper overlap and the problem of maintaining dimensions at tape splices.
Another insulated conductor has two extruded layers of irradiated, and hence, cross-linked, ethylenetetrafluoroethylene copolymer (ETFE). However, such insulation has had limited success in meeting flammability requirements and is marginal in meeting even a 150.degree. C. temperature rating.
While polyimide, both thermoplastic and thermoset, has good high temperature properties, it is difficult to apply it directly to the conductors because of air in the interstices of the conductors and the polyimide has strong adhesion to the conductors making it difficult to strip the insulation. Polyimide layers are also subject to cracking and hydrolizing unless the cross-linking thereof is substantially perfect, perfection being difficult to obtain under usual manufacturing conditions.
One object of the invention is to provide an insulated conductor which can be temperature rated at at least 200.degree. C.
Another object of the invention is to overcome problems with insulated conductors described hereinbefore.
In accordance with the preferred embodiments of the invention, a first layer of perfluoroalkoxy (PFA) resin compound, a polytetrafluoroethylene (PTFE) resin compound, an ethylene-tetrafluoroethylene (ETFE) resin compound or a fluorinated ethylene-propylene (FEP) resin compound is extruded over and in contact with the conductor or conductors which provides a layer of insulation which can withstand a temperature of at least 250.degree. C. and which makes the multi-layer insulation readily strippable from the conductor or conductors. The outer surface of the first layer is etched in a conventional manner, and therafter, a layer of polyimide in a solvent having a relatively high polyimide content preferably is extruded over the first layer and the solvent is removed by heat to provide a solid second layer of polyimide. Then, a third layer, a layer of PFA compound, an ETFE compound, a polyvinylidenefluoride (PVDF) compound or a non-hydrolizing polyamide compound which thermosets is extruded over the second layer, such third layer protecting the polyimide, second layer from the environment.
Although in the preferred embodiment each of the three layers of insulation is extruded over the conductor, or the conductor with one or more layers of insulation thereon, in an alternative embodiment, one or more, or all, the layers may be applied by conventional coating techniques.
US Referenced Citations (9)
Divisions (1)
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Number |
Date |
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68615 |
Jun 1987 |
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Continuation in Parts (1)
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901740 |
Aug 1986 |
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Patent Grant
4801501
