GB844681A - Improvements in electric discharge devices of the liquid cathode type - Google Patents

Abstract

844,681. Metal-vapour discharge apparatus. BRITISH THOMSON-HOUSTON CO. Ltd. June 13, 1957 [June 25, 1956], No. 19605/56. Class 39(1). An electric discharge device comprises a sealed evacuated envelope containing a pool type cathode of electrically conducting liquid, an anode, and an ignitor electrode dipping into said pool type cathode between which and said cathode an initiating arc is adapted to take place means for preventing effective variation in the level of said conducting liquid adjacent said ignitor electrode comprising a plate-like member which is formed of a material wettable by said conducting liquid or which is formed of porous material, which is located parallel to the surface of said pool and in contact with said pool, and which is formed with an aperture or depression to receive the end of said ignitor electrode whereby said initiating arc passes between said ignitor electrode and said cathode through conducting liquid adherent to said plate-like member. In the construction shown a plate 18 of molybdenum treated to render it wettable by mercury is supported by a port 19 and has an aperture 20 into which the tip of the ignitor 12 projects. In an alternative construction, Fig. 2 (not shown), the plate 18 is provided with a central depression and is supported by a metal strap from the wall of the envelope. The ignitor 12 may be made of semi-conductor material or may be an electrically heated member as described in Specification 457,742. The anchoring device 18 may consist of sheet metal or of a composite structure of sheet or wire. Specifications 292,500, 481, 078, 487, 462, 505,474, 530, 073, 536, 932 and 543,072 also are referred to.