GB496557A - Improvements in or relating to vacuum tubes - Google Patents

Abstract

496,557. Discharge apparatus ; obtaining high vacua. MARCONI'S WIRELESS TELEGRAPH CO., Ltd. May 31, 1937, No. 14998. Convention date, June 1, 1936. [Class 39 (i)] [Also in Groups XI and XXVIII] A container which is more especially for getter material and is adapted to be mounted within the envelope of a vacuum tube comprises a holder having a chamber adapted to receive a pellet from which a hot vaporous active metal may be evolved by heating, and a narrow channel communicating with the chamber so formed and arranged that the inner surface of the wall of the channel is maintained cooler than the vapour of the active metal which passes through it, whereby the stream of vapour evolved on heating is made to follow a substantially straight line trajectory. The container may be formed of a piece of sheet metal 4 having pressed out recesses 5 and grooves 9. The getter material is placed in the recesses 5 and the sheet is folded over to form the chamber and channel, the edges of the container being sealed by welding. Alternatively, the container may be formed of tubing which is flattened and sealed at its ends. To keep the temperature of the inner surface of the wall of the channel colder than the getter vapour, the inner surface may be coated with a material of low conductivity such as a refractory metal oxide. Alternatively, the channel may be lined with or formed wholly of a tube of ceramic material of low heat-conducting properties, or heat radiating fins may be pressed out of the channel portion of the container, or this portion may be coated with carbon. The container may hold getter material which is directed by the channel on to a part of the envelope of an electron discharge tube away from leads or other insulating members; alternatively, the material may also be used to deposit a pattern of sensitizing material of any desired shape upon a surface in or on the envelope to constitute an electrode. and for this purpose the channel is given a rectangular or other cross-section corresponding to that of the electrode surface to be produced, British Specifications 264,258, and 271,419, [Class 39 (i)], and U.S.A. Specification 1,966,226 are referred to.