GB569651A - Improvements in or relating to electric discharge lamps - Google Patents

Abstract

569,651. Discharge lamps. SIEMENS ELECTRIC LAMPS & SUPPLIES, Ltd., ALDINGTON, J. N., and CREASY, W. G. Jan 27, 1939, No. 2903. [Class 39 (i)] In mercury vapour lamps operating at pressures over 5 atmospheres, the electrodes 3 are formed of solid blocks of thoriated tungsten and are used both for starting and running purposes. Starting is facilitated by the addition of an inert gas such as argon or neon, or a mixture of such gases, at a pressure of the order of 50 m.m. of mercury. The thoriated tungsten may be made by making a paste of thorium nitrate and tungsten trioxide, drying, igniting to decompose the nitrate and reducing by heating in hydrogen. In one arrangement, the electrodes 3 are in the form of rods of uniform diameter up to the point at which they are sealed into the bulb 1. In another arrangement, the electrode comprises a head and a shank around which is a closelywound helix of heavy tungsten wire. Three or more electrodes may be used to produce several coalescing are discharges. The bulb is of quartz and may be enclosed in a sealed outer jacket which may be evacuated or have a filling of gas of good thermal conductivity. Alternatively the surrounding jacket may be in the form of an open cylinder. The sealing of the leading-in conductors may be made as described in Specifications 512.941 and 512,974, [both in Group XXXVI].