GB777127A - Improvements relating to electric discharge lamps - Google Patents

Abstract

777,127. Discharge lamps. SIEMENS BROS. & CO., Ltd. Sept. 9, 1955 [Aug. 6, 1954], No. 22981/54. Class 39(1). A high pressure mercury vapour lamp, which may include other metals, of the compact source type has a filling including xenon, wherein the cold filling pressure of the xenon exceeds 1 atmosphere and wherein in operation the partial pressure due to the mercury vapour exceeds that due to the xenon. In operation the partial pressure of the xenon may be more than 20 per cent, e.g., 29 per cent, of the total pressure. In a particular example the filling consists of about 1'1 1 grs. of mercury and xenon at a cold filling pressure of about 2 atmospheres giving when in operation a partial pressure due to mercury vapour of about 15 atmospheres and due to xenon of about 6 atmospheres. In the construction shown in Fig. 1 the quartz bulb 12 of diameter about 55 mms., contains electrodes 1 and 2 of thoriated tungsten about 6 mms. apart, the bottom of the electrode 1 being roughly at the centre of the bulb. Each electrode and leading- ing structure includes a tungsten electrode coil 3, a tungsten supporting rod 4, a wrapping 14 of molybdenum ribbon around the rod 4, molybdenum tape leads 5, molybdenum sealing foil 6, and a metallic terminal member in the form of a brass cap 7, 8. Each brass cap has a tapped hole 10 for connection to a screw-ended flexible lead. The lower and cooler portion of the bulb 12 has an external silver coating 13.