GB789216A - Improvements relating to electric discharge lamps - Google Patents

Abstract

789,216. Discharge lamps. BRITISH THOMSON-HOUSTON CO., Ltd. Dec. 29, 1954 [Jan. 5, 1954], No. 285/54. Class 39(1). A high pressure mercury vapour electric discharge tube 1 is enclosed in an outer envelope 2 filled with an oxidizing gas and has molybdenum leads 6, which pass from the electrodes 7 through the wall of the tube 1 into the interior of the outer envelope 2, provided with a coating of silicides of molybdenum so as to prevent oxidation. The coating consists of a series of layers of the silicides which can be formed by passing a volatile halide of silicon, e.g. silicon tetrachloride, over the molybdenum while it is heated as described in Specification 730,855 [Group XXXVI]. The conductors connected to the molybdenum leads 6 and extending therefrom to copper coated nickel-iron leads sealed through the stem of the outer soft glass envelope 2 may be of nickel or nickel-iron alloy. The tube 1 is supported within the outer envelope 2 by a framework 4 which engages the tube 1 at its ends and contacts the inner periphery of the envelope 2. The ends of the tube 1 are provided with a reflective metallic coating. The tube 1 is formed of hard alumino-silicate glass and is filled with a rare gas such as argon at a few mms. pressure and mercury producing an operating pressure of above 1 atmosphere. According to the Provisional Specification the leads 6 can be provided with a coating of a molybdenumchromium alloy which can vary in composition throughout the coating, and the tube 1 can be supported within the outer envelope 2 by a framework as described in Specification 434,720 [Group XL].