GB700494A - Improvements in or relating to gas-pressure electric cables - Google Patents

Abstract

700,494. Cables. PIRELLI SOC. PER AZIONI. March 31, 1952 [April 18, 1951], No. 8099/52. Class 36 The gas distributing tubes of single or multicore gas pressure cables are provided with perforations which, of themselves or in co-operation with an auxiliary member, act as valves, allowing the free flow of gas outwardly from the tube, but preventing the flow of insulating compound or gas in the reverse direction. In a multicore cable having impregnated paper filling 12 in the spaces between the cores, one or more of these spaces also includes a metal helix 4 enclosing an elastic tube 5 which may have an internal metal helix 6. The tube 5 is provided with small apertures 14 made by puncturing with a needle or thin blade and spaced so that they are not obstructed by the turns of the helix 4. Internal pressure opens the apertures, but external pressure holds them tightly closed. The tube 5 may be replaced by a metal tube having perforations of finite diameter. An elastic tape is tightly wound on this tube so as to close the perforations but allow the escape of gas under pressure from within the tube. The cable may also include a signalling cable 7 and an unperforated tube 8 to convey gas through a length of the cable without permitting its distribution. In a single core cable the helix 4 forms an axial passage within the hollow stranded conductor and embraces either the elastic or metallic tube above described.