GB517536A - Improvements in and relating to electric lamps - Google Patents

Abstract

517,536. Discharge lamps. BRITISH THOMSON-HOUSTON CO., Ltd. July 26, 1938, No. 22207. Convention date, July 28, 1937. [Class 39 (i)] [Also in Group XXXVI] In the manufacture of an electric lamp comprising a glass stem tube projecting inside the envelope and supporting an electrode and a metal disc applied to the end of the envelope, the ends of the envelope and of the stem tube are arranged in close proximity to each other and to the disc and on the same side of the latter, the disc being then heated to fuse the ends together and to the disc. In a gas discharge lamp, an envelope 10 has at each end a stem tube 13 with flared outer end 14 and an inner end 15 sealed around lead wires 16, 17 to which an electrode 18, is welded ; the electrode preferably comprises a coiled coil of tungsten with a primary coiling mandrel left in, and is coated with an electron emissive material such as barium oxide. One stem tube has an exhaust tube 19. The stem tube is placed on a metal disc 20 with a tubular part 21, and the envelope 10 is pressed against the flare 14, the disc being then heated by a gas flame or a high frequency coil to fuse the parts together. For soft glass the disc may be of chrome-iron alloy known as <11> Allegheny 55," and for hard glass, of an iron-nickel-cobalt alloy known as <11> Fernico." When both ends of the envelope 10 are sealed, it is evacuated through tube 19, current is passed through electrodes 18 to activate them and the envelope filled with neon, argon &c., e.g. at a pressure of 4 mms. of mercury, a small amount of mercury 26 is inserted, and the tube 19 is sealed by a twoflame burner. The lead wire 16 is then spotwelded to the disc 20 and a plug 22 of synthetic resin is placed in the tubular part 21 of the disc 20 and the lead wire 17 is soldered to an eyelet 24 in the plug ; the latter may be held by the lead wire or by indentations 27. In Fig. 4, the disc 201 has an inwardly diverging cavity 28 adapted to receive a holder, and after welding the lead 16 to the disc, sealing, evacuating and filling the envelope, activating the electrodes, and sealing the tube 19, the lead 17 is twisted round the lead 16; in a modification, however, the disc 20<1> at one or each end of the envelope has a plug 22 and eyelet 24 as in Fig. 1 arranged in the cavity 28. The inner surface of the envelope 10 may be provided with fluorescent material such as zinc silicate, calcium tungstate or cadmium silicate or mixtures thereof. Specification 452,191, [Group XXXVI], is referred to.