GB1268280A - Improvements in or relating to coaxial cable and manufacture thereof - Google Patents

Abstract

1,268,280. Coaxial cables. PHELPS DODGE COPPER PRODUCTS CORP. 26 Nov., 1969, No. 57962/69. Heading H1A. A coaxial cable has spacers in the form of discs or a helical spacer 15 of solid plastics insulating material between the inner and outer conductors 11, 13 a layer 16 of solid plastics insulating material surrounding the inner conductor and an insulating foam 17 filling the remainder of the space between the conductors. The layer 16 may or may not be integral with the spacer or spacers. In manufacture the spacer or spacers are applied around the inner conductor to form a core and the core and a metal tape to form a longitudinally seamed outer conductor tube are advanced into a tube forming zone. The foam forming composition is applied in advance either to the core or to the tape and the composition is subsequently expanded in a heating zone. The plastics material for the spacers and for the layer 16 may be a crosslinked or otherwise polyolefin, e.g. polyethylene, polypropylene, polytetrafluoroethylene or polysulphone. The plastics foam may be produced from a thermosetting or a thermoplastic resin, e.g. a urethane, a phenolic, a urea formaldehyde, a vinyl, a polystyrene or a polyolefin. The foam forming composition may be applied to the core or to the metal tape in a mist forming chamber or as a froth. The effective dielectric constant of the cable is less than 1À3.