GB481760A - Improvements in or relating to gas-tight joints suitable for electric discharge devices - Google Patents

Abstract

481,760. Sealing metal to insulating - materials. STANDARD TELEPHONES & CABLES, Ltd. Oct. 30, 1936, No. 29556. Convention date, Jan. 17. [Class 36] In a gas-tight joint between a metal member forming part of a low-pressure container and electric insulation material moulded thereon, the metal member is so shaped that gas leaking through or over the surface of the insulation material reaches the surface of a _portion of the metal member projecting into the insulation material and passes over said surface to a chamber intermediate the high and low pressure sides of the joint from which chamber the gas can be exhausted. In the construction shown in Fig. 1, an insulator for carrying a conductor 35 into a discharge tube comprises metal rings A, B connected in gastight manner respectively to the conductor 35 and the body of the discharge tube and separated by a moulded mass of vitreous or other insulating material. The rings A, B are formed with pairs 2, 3 and 12, 13 of coaxial projections embedded in the insulating material, annular chambers 7, 17, free of insulating material, being'formed between the pairs of projections by rings 8, 18 which are shrunk on the inner projections and are of such external diameter as to leave small channels 10, 20 between them and the inner walls of the projections 2, 12. The chambers 7, 17 are continuously exhausted through apertures 23, 24 to remove gas which may leak into the insulation, such gas traversing the surfaces of the projections to reach the chambers 7, 17. To increase the leakage path the projections are grooved. In modified constructions the exhausting chambers are formed within the projections. Fig. 5 shows such a construction, the exhaust chambers 7, 17 being formed within the projections 2, 12 which are built up from a number of superposed grooved rings having spaces such as 45, 44 between their outer edges through which leakage gas may pass to the exhaust chambers. The superposed rings may be so formed that spaces between them occur at the inner edges 'of the rings also.