GB733853A - Improvements in or relating to electrodes for gaseous discharge lamps - Google Patents

Abstract

733,853. Discharge lamps. KREFFT, H. E. April 18, 1951 [Dec. 18, 1950], No. 9064/51. Class 39 (1). An activated electrode of the self-heating and storage type for gaseous electric discharge lamps, particularly high-pressure and superhigh-pressure lamps containing one or more metal vapours, e.g. mercury, and rare gases, e.g krypton and xenon, comprises a coil assembly, Figs. 1 and 2, formed by a plurality of metallic wires 1, 2, 3, 4 of high melting point so arranged as to enclose a channel 7, a tungsten wire coil 5 which is helically wound about and firmly connected on the core so as to leave channels 6 between the core and the coil, the individual convolutions of the coil being closely adjacent to one another, with narrow spaces therebetween, to form a protecting wall, and a store of activating material arranged inside the coil in the channels 7, 6 formed between the wires of the core and between the core and the coil. The core can be composed of a plurality of wires 1, 2, 3, 4, Fig. 4, twisted with respect to the axis of the core and the coil can be in the form of a coiled coil 10 as shown in Figs. 5 and 6. The core 1, 2, 3, 4 is composed of tungsten, molybdenum, tantalum or thorium wires or of a combination of wires of these metals, preferably three tungsten wires and one tantalum or thorium wire. A centrally located gas absorbing core wire 9, Fig. 3, of tantalum or thorium may be added. The activating material 8 can be composed of the oxides of barium, calcium, strontium or thorium or of zirconium dioxide or of mixtures of these materials. In the construction shown in Fig. 5, the coiled-coil 10 fits accurately around a wire or rod 11 of tungsten, tantalum or molybdenum and which may form the inner lead of the lead wire contained in the seals of the lamp. The rod 11 may be composed of a plurality of wires forming a secondary core which has the same structure as the primary core. In the construction shown in Fig. 6 the coiled-coil electrode structure is self-supporting.