GB663854A - Electric discharge tube - Google Patents

Abstract

663,854. Discharge apparatus. SYLVANIA ELECTRIC PRODUCTS, Inc. Feb. 27, 1948 [Aug. 23, 1945], No. 6187/48. Class 39 (i). A cold - cathode gas - filled electric discharge tube comprises a cathode, a graphite electrode, and a lead-in wire extending into, but spaced and insulated from, said graphite electrode to act as an anode, the graphite electrode extending beyond the lead-in wire in a direction towards the cathode. In the tube 12, Fig. 2, the anode 14 is a tantalum wire attached to a metal cap 13 and supported by a glass tube 15 from which it is separated over the greater part of its length by an air-space 16, to prevent cracking due to heat. A graphite electrode 17, which may function as a control grid; is sealed to the glass tube 15 by heating the graphite to the softening point of glass and then pushing the glass tube into the graphite electrode, at the same time keeping the glass tube open by means of a mandrel. The graphite electrode is also. supported by a metal strip 18 attached to wires 19 supported in glass sleeves 20 from the press 29. The cathode (Fig. 3) comprises a " pill " 21 of caesium chloride and aluminium in a highly compressed form held in a nickel cup 22 insulated by a ceramic cup 24 'supporting an annular metal disc 25 which prevents sputtering of the cathode material and is provided with a lead-in wire 31 so that it may act as a keepalive electrode when necessary. A metal strap 27 masks the hole in the disc 25 to further prevent sputtered material from reaching the carbon electrode 17. A getter 28 is mounted on each side of the press 29. The filling may comprise helium at 7 to 20 mm. pressure, or any inert gas.