GB652225A - Improvements in and relating to electric discharge devices - Google Patents

Abstract

652,225. Electric discharge lamps. BRITISH THOMSON-HOUSTON CO., Ltd. July 3, 1945, No. 16934. Convention date, July 7, 1944. [Class 39 (i)] An electron discharge device, particularly a flash-lamp, comprises a vitreous envelope 2 containing two coaxial electrodes 8 and 11 separated by an insulative covering 9 which projects beyond the discharge ends of the electrodes and is provided with means, namely a shoulder 10 .with which engages the electrode 11, for determining the relative axial position of the electrodes. The envelope 2 may be made of borosilicate glass of the type known under the Registered Trade Mark " Pyrex," and fused seals for the lead-wires 6 and 7 for the electrodes 8 and 11 are made with dome-shaped ferrules 4, 4 which may be made of an iron-nickel alloy or an iron-nickel-cobalt alloy such as is known under the Trade Name "Fernico." The electrode 8 is formed as a tip at the end of the lead-wire 6. The insulative covering 9 includes a radiationtransmitting refractory portion around and adjacent the tip 8 and preferably comprises a quartz glass sleeve. The electrode 11 extends from the shoulder 10 to a point not so far as or about even with the electrode tip 8. The electrode 11, which forms the anode, is of iron or steel, and is welded to the Z-shaped lead-wire 7. The electrode tip 8 forms the emissive cathode and may comprise 87 per cent tungsten, 10 per cent nickel and 3 per cent barium oxide. The envelope may contain argon at 600 mm. pressure and also hydrogen at a partial pressure of 10 mm. or xenon alone at 600 mm. pressure.