GB913468A - Improvements in or relating to sodium vapour electric discharge lamps - Google Patents

Abstract

913,468. Discharge lamps. GENERAL ELECTRIC CO. Ltd. March 1, 1961 [March 10, 1960], No. 8487/60. Class 39 (1). A low-pressure sodium vapour-rare gasdischarge lamp having the discharge envelope 1 sealed within an evacuated outer jacket 7 has within the outer jacket a pair of auxiliary electrodes 17, 18, each connected to one of the lead-in conductors 9, 8 to the main electrodes 3 for producing at least a partial ionization of any residual gas present within the outer jacket in the region of the electrodes. The auxiliary electrode 17 can be a length of 0.07 mm. diameter tungsten wire with a layer of electron-emissive material and the auxiliary electrode 18 can be a nickel gauze cylinder of 2 cms. diameter surrounding the electrode 17. The envelope 1 can be of straight or U-shape surrounded by a sleeve of transparent heatinsulating material or by a sleeve 6 on each limb as described in Specification 801,482. A getter element 15 of the barium-aluminium type is mounted on a wire 16 within the outer jacket 7 and can be eddy-current heated to form a layer of getter material on the wall of the jacket. The rare gas part of the filling can consist of neon with about 0.75% argon at a total pressure of 10 mms. The discharge envelope 2 is supported within the outer jacket 7 by a mica disc 14 and a spring clip device on the end 19 of the discharge envelope.