GB442417A - Improvements in and relating to glass-to-metal seals - Google Patents

Abstract

442,417. Discharge apparatus. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London. Sept. 2, 1935, No. 24483. Convention date, Sept. 1, 1934. [Class 39 (i)] [See also Group XI] In sealing a leading-in conductor through the metal envelope of a vacuum tube, for example a two-electrode rectifier of the all metal type, the conductor 5, Fig. 3, is threaded through a glass tube or vitreous member 7 which is heated until the glass adheres to the conductor after which the combined conductor and glass are placed in a vertical position within a hollow metal cone 6, Fig. 4, forming part of the envelope, whereupon the coned member is heated to melt the glass which settles solely by gravity towards the smaller end of the cone to form an insulating seal. In the example a filamentary cathode 4, Fig. 1, is supported by two leading-in conductors 5 which are sealed within the conical members 6 comprising part of a metal discharge vessel 1 formed by two flanged portions which may be welded together at the abutting flanges after sealing the leading-in conductors 5 in position. The vessel is exhausted through a tube 2, which is made of a metal having a small coefficient of expansion, soldered or otherwise secured in an opening in the upper portion, a glass extension tube 3 being fused to the upper end of the tube 2 to provide a fusible seal. An inert gas or a source of vapour may be introduced into the vessel before sealing. As shown in Fig. 4 the lower part of the discharge vessel with the combined glass and conductor members placed in the coned portions 6 is supported upon a heavy base 9 of metal or graphite which may be placed in an oven and heated until the glass melts.