GB476488A - Improvements in the sealing of electric conductors into quartz envelopes - Google Patents

Abstract

476,488. Sealing electric conductors into quartz envelopes. GENERAL ELECTRIC CO., Ltd., FRANCIS, V. J., HARRIS, N. L., and RYDE, J. W. June 5, 1936, Nos. 15765 /36, 23436/36, and 9888/37. [Class 36] The manufacture, and sealing, of leading-in conductors for high pressure mercury vapour discharge lamps, comprises the following steps in the following order : (1) attaching to each end of a strip 1 of molybdenum or tungsten not more than 20Á thick a stouter lead 7 which is preferably also of tungsten or molybdenum ; (2) placing the body formed in step (1) within a quartz tube 6 separate from the final envelope, evacuating from the tube all gas chemically reactive to the metal strip, and collapsing the tube on to the strip by externally applied heat to form a gas-tight seal between the strip and quartz ; (3) fusing the quartz part of the seal to the sides of an aperture in the envelope while the envelope is evacuated or filled with a gas chemically neutral to an electrode which is either secured to or formed on the end of the inner lead-in wire. A number of sealed foil units may be produced together by placing within a quartz tube 3 a chain consisting of foil strips 1 connected by wires 2 of tungsten or molybdenum, and evacuating the tube 3 through its upper end before collapsing it on to the strips 1, the lowest strip being sealed first and the process carried upwardly. The tube 3 is not collapsed along the whole lengths of the wires 2, so that the separate units with projecting end wires 7 can be obtained by severing the tube at the points 4. Alternatively, a number of foil strips with attached end wires are arranged separately along a quartz tube, with their end wires overlapping, these overlapping parts being left clear when the tube is collapsed, and providing free end portions at which the tube is severed. The quartz part of a sealed unit is fused to the main part of the envelope either by a butt-weld to an open neck, or by placing it within a tubular extension of the envelope which is collapsed by heating. The envelope may be filled with nitrogen during the sealing. British Specifications 18255/03, [Class 39 (ii)], 396,103, 418,906, [both in Group XI], and U.S.A. Specification 1,271,245 are referred to. Reference has been directed by the Comptroller to Specification 465,475.