GB641922A - Improvements in or relating to electric cables - Google Patents

Abstract

641,922. Screened cables; couplings. LIVERPOOL ELECTRIC CABLE CO., Ltd. June 2, 1948, No. 14841. [Classes 36 and 38 (i)] A conductor a having rubber-like insulation b is provided with a flexible screen c of conducting rubber in which are embedded one or more metallic conductors d, each of which forms an open helix about the cable core. A multicore cable may have the individual cores screened in this manner, or they may be collectively screened as in Fig. 3. The insulated conductors a, b, and bare earth conductor g are assembled in a rubber-like cracore f, which may also be conductive, and then enclosed in the screen c, d, and an outer protective sheath e. The screening layer may be built up on the cable core by applying a lapped or extruded layer of conducting rubber, over which the metal conductors are wound and a further conducting rubber layer applied, the layers being bonded together by vulcanizing under pressure. Alternatively the screen may be preformed, either by laying the wires between sheets of conducting rubber and nailing the sheets by pressure, or by extruding a covering of conducting rubber around suitably spaced wires. This composite screen is applied to the cable core by lapping on. Such preformed screens may be cut into tapes and used for repairing damaged screens when required. Specification 526,895 is referred to.