GB580406A - Improvements relating to electric discharge lamps - Google Patents

Abstract

580,406. Discharge lamps. BRITISH THOMSON-HOUSTON CO., Ltd. March 19, 1943, No. 4481. Convention date, March 26, 1942. [Class 39 (i)] [Also in Group XXXVI] The base of the lamp is formed by a disc 22, Fig. 4, which is sealed directly to the end of the envelope 10, Fig. 6, and is formed with inwardly cupped recesses 25 in which the contact pins 23 are mounted by glass beads 24. The electrode 17, preferably of the straight coiled coil type, with auxiliary anodes extending parallel thereto from the leads 15, 16, is carried on a mount comprising a pinch 14 and flare 13 which is sealed together with the metal disc to close the end of the envelope. Where the mount carries an exhaust tube 19, the disc is provided with an elongated hole, set in a recessed part, to allow the tube to be tipped off inside the disc: Alternatively the disc at one end may form the end closure of the envelope and the electrode is in this case carried directly by the contact pins, Fig. 9 (not shown). The disc is made of a metal that has a matching coefficient of expansion with the glass of the envelope, such as the chrome-iron alloy " Allegheny 55 " metal for soft glass, or the iron-nickel-cobalt alloy known as " Fernico " for hard glass. The cupped recesses 25 may be made separately from, and welded to the disc. The envelope may be coated with a fluorescent material 20, and may have a filling of neon or argon at a pressure of 4 mm. of mercury, and a small quantity of mercury. The metal disc may be strengthened by concentric corrugations such as 36, or by dishing. Specification 537,901 is referred to. The Specification as open to inspection under Sect. 91 describes a lamp in which the metal cap discs forms the closure for the envelope at both ends. This subject-matter does not appear in the Specification as accepted.