GB1309515A - Electric resistance heating cable - Google Patents

Abstract

1309515 Resistance heating cables PHILIPS ELECTRONIC & ASSOCIATED INDUSTRIES Ltd 19 April 1971 [13 Feb 1970] 21456/71 Heading H5H In an electric resistance heating cable of the type comprising a flexible insulating core 4, a heating wire 5 wound helically around the core and extending throughout the length of the cable and an insulating covering 6, the cable consisting of a plurality of groups of alternating sectors extending in the longitudinal direction of the cable, which sectors assume mutually different temperatures during use of the cable, the heating wire 5 consists of sections having a comparatively high resistance per unit length separated by sections having a comparatively low resistance per unit length. The wire 5 has a resistant core 1 provided at regular distances with short-circuiting " envelopes " 2 of comparatively low resistance, and preferably with an oxidation resistant enveloping layer 3. Core 1 and layer 3 are, e.g. nickel, whilst envelopes 2 are, e.g. copper. The flexible insulating core 4 may be of single or composite structure, and comprise polyvinylchloride, silicone rubber, nylon, glass fibre, asbestos fibre, polytetrafluoroethylene and polyfluoroethylene propylene. A central conductor may be present in the core 4 and connected to wire 5 at one end. The outer covering 6 may be an extruded synthetic resin or the core 4 and wire 5 may be wound and/or pleated with glass or asbestos fibres or rayon or cotton to provide the covering 6. Alternatively the covering 6 may be ceramic beads. The covering 6 bears markings to identify the sectors of different temperature. Applications to heating hair curlers, heating refrigerator defrosters, clothing, coffee-makers and rooms are mentioned. Several ways of providing the " envelopes " 2 on wire core 1 are described, including swaging and drawing cylinders 2 thereon, etching, electrolysis, and coating by deposition from a liquid or vapour phase. Instead of " envelopes " 2, the heating wire 5 may have sections of the same material of alternately small and large diameter, or have sections of different conductivity joined by welding or soldering. Specification 1,284,385 is referred to.