GB650425A - Improvements in or relating to concentric conductor electric cables - Google Patents

Abstract

650,425. Concentric conductor cables. STANDARD TELEPHONES & CABLES, Ltd. May 10, 1945, No. 11723. [Class 36] The invention relates to a coaxial cable with a hollow cylindrical inner conductor member the interior of which houses one or more further conductors. The invention in one aspect consists in that the space between the hollow cylindrical inner conductor member and the outer conductor member is filled with solid insulation. In another aspect the invention consists in that the hollow cylindrical inner conductor member comprises a metal tape folded into tube form with the longitudinal edges interengaging by projections thereon and a thin layer of insulating material being extruded over such hollow cylindrical inner conductor member to maintain the tube form. The coaxial cable shown in Fig. 1 has central, intermediate and outer conductors 1, 3, 6, the intermediate conductor 3 being in the form of a hollow cylinder, the other conductors 1, 6 being spaced from it by solid dielectric. The solid copper central conductor 1 has extruded thereover a solid body 2 of a polymer of ethylene over which is applied the inner hollow cylindrical conductor 3 formed from a thin copper tape with butt edges and integral projections as in Specification 476,098, the projections underlying the edges. This tube 3 has extruded thereover a solid body of a polymer of ethylene over which is applied the outer conductor 6, formed from a copper tape or tapes with long lay, a binding 7 of bituminous tape, armouring 8 and an external serving 9 of bituminous tape. The solid central conductor 1 may be replaced by, say, four separately insulated conductors stranded together to form a power or signalling circuit, Fig. 2 (not shown). In an air-space cable, Fig. 3, the inner hollow cylindrical conductor member 3 is carried on spacing washers 14 slotted to fit over the central solid conductor 1. The inner hollow cylindrical conductor member is formed by several copper tapes with long lay, held together by a thin covering 15 of insulation such as a polymer of ethylene which carries similar slotted washers 16 enclosed within an extruded insulating tube 17 over which is formed the outer conductor 6 from copper tapes with a long lay. Windings of steel tape 18 (to form a magnetic shield) and a lead sheath 19 complete the cable. The Provisional Specification states also that the spacing washers may be in halves, cemented or keyed together, the inner conductor may be a multi-telephone cable and the outer conductor may be formed by metallizing the surface of a tube of insulating material, and it refers also to Specifications 458,772, 459,518 and 478,768.