GB444830A - Improvements in trunk communication electric cables - Google Patents

Abstract

444,830. Cables. SIEMENS & HALSKE AKT.-GES., Siemensstadt, Berlin. Nov. 16, 1934, No. 33067. Convention date, Nov. 16, 1933. [Class 36] In a trunk communication cable having an extruded waterproof sheath arranged within an armour sheath and in which the cable core is insulated with a dielectric, such as polystyrol or polyvinyl chloride, which is detrimentally affected by heat at the temperature of extrusion of the sheath, the insulated core is surrounded by a thin electrically conductive layer between which and the waterproof sheath is arranged a thicker layer of a material which protects the insulation of the core against heat during the extrusion of the waterproof sheath and which is itself unaffected by said heat. The protective layer may consist of metal wool, spun or plaited metal strands, or other metal structure having a large heat reflecting or dissipating surface ; or a material of low heat conductivity, such as paper, asbestos, or spun glass, may form the protective layer. The thin electrically conductive layer, which serves primarily for restricting the electric field of the core to the heat sensitive dielectric material and which may consist of a metallized impregnated paper strip, may be polished externally and internally. In the construction shown, a cable core 1 having polystyrol insulation 2 is surrounded by a conductive layer 3, consisting of a helically wound metal tape, which has a polished outer surface and over which is applied a layer 4 of closely wound asbestos cord adapted to protect the insulation 2 during the extrusion on the layer 4 of a lead sheath 5. An armouring 6 of round wires, which may be insulated from the sheath 5, completes the cable.