GB714842A - Improvements in or relating to electric discharge lamps and electrodes therefor - Google Patents

Abstract

714,842. Discharge lamps; electrode materials. GENERAL ELECTRIC CO., Ltd., and RIGDEN, S. A. R. Feb. 22, 1952 [May 17, 1951], No. 11593/51. Class 39(1) A high pressure constricted arc discharge lamp for operation on A.C. contains a pair of main electrodes at least one of which consists of a solid block of tungsten or molybdenum having its terminal surface formed with a plurality of intersecting slots recessed into the terminal surface, which slots are filled with a solid sintered mixture of the powders of two or more refractory materials, at least one of the materials constituting an activating material for the electrode. The mixture of refractory powders can be sintered in a reducing atmosphere to form a solid mass whilst contained within the slots and before mounting the electrodes in the lamp envelope. The activating material can be thoria and the material with which it is sintered may consist of tungsten and/or molybdenum, the weight of the thoria being substantially half of the total weight of the mixture. The mixture can be applied to the slots as a paste with distilled water with several applications. In the construction shown in Figs. 1 and 2 of the drawings accompanying the Provisional Specification the terminal surfaces 4, 5 of the tungsten rod electrodes 2, 3 of diameter 0.6 cm. contained in the spheroidal quartz bulb 1 are formed with a plurality of regularly spaced parallel slots 10, 11 intersected at rightangles by a further plurality of regularly spaced parallel slots, one set 12 of these further slots being shown in Fig. 2. Each slot is approximately 0.75 mm. deep and 0.375 mm. wide extending across the terminal surface of 'the electrode. The terminal surfaces of the electrodes are diametrically opposite and spaced approximately 15 mm. apart about the centre of the bulb which has a longer internal diameter of 61 mm. and a shorter internal diameter of 56 mm.