GB616808A - Improvements in or relating to electric high-pressure metal-vapour discharge tubes - Google Patents

Abstract

616,808. Metal-vapour lamps. PHILIPS LAMPS, Ltd. Nov. 24, 1945, No. 31761. Convention date, Aug. 10, 1940. [Class 39 (i)] In high-pressure discharge tubes of the type in which one electrode at least projects from the body of vaporisable metal, such as mercury, which provides the vapour pressure, the electrode has a part of reduced thermal conductivity between its end and the body of vapourproducing 'metal, and near the level of the metal. The part of reduced thermal conductivity may be provided by forming the electrode 3, with a reduced cross-section by contracting it as at 8, or by making it hollow at the region where it emerges from a pool of mercury 7. Alternatively, the electrode may be formed of an operating part of tungsten and a base part of graphite. In the construction shown, the electrode 3 is supported by a ring 4 carried by a lead 5'. The cathode is supported by a lead and ring 9, surrounded by a helically wound tungsten wire 11 in the space between the cathode and the seal. The envelope is of quartz and the seals for the leads 5 and 9 are formed by a layer 6, 10 of an intermediate glass. A filling or argon at a pressure of about 65 mm. may be provided, and in operation the tube is surrounded by a glass cylinder through which cooling water is passed. The subjectmatter is identical with that of Specification 549,727.