GB713926A - Improvements in and relating to electric discharge lamps - Google Patents

Abstract

713,926. Discharge lamps. BRITISH THOMSON-HOUSTON CO., Ltd. Sept. 29, 1952 [Sept. 28, 1951], No. 24344/52. Class 39(1) A lamp unit comprises a double-ended tubular electric discharge lamp 4 having stems 5 protruding from the ends of its envelope, a light transmitting tubular jacket 1 around the lamp, and bases 3 at the ends of the unit holding the lamp and jacket in predetermined spaced relation, each of the bases comprising a stiff metal protective sleeve 13 around the end portion of the lamp envelope and extending around and beyond the protruding stem 5, and an annular inelastic insulator 16 around the sleeve and tightly secured thereto between the ends thereof by a metal skirt 20 tightly secured to the peripheral portion of the insulator 16 and clamped around the end portion of the jacket 1 whereby the unit is capable of accurate mounting by the sleeves 13, the stems 5 being protected by the sleeves. Each of the end portions of the envelope 4 has a rib 15 extending longitudinally thereon and each of the metal protective sleeves 13 has a slot 14 engaging a rib. The annular insulator 16 of porcelain or lava is held in fixed position on the sleeve 13 by the roll flange 17 on the sleeve wall against which the insulator 16 is held by the metal snap ring 18 forced against the insulator by four protuberances 19 in the sleeve 13 and spaced apart an angular distance of 90 degrees. The metal skirt 20 is tightly secured to the periphery of the insulator 16 by an inwardly extending flange 21 thereof engaging one side of the insulator and by a snap ring 22 inside the skirt 20 and forced against the other side of the insulator by the four indentations 23 spaced 90 degrees apart in the wall of the skirt 20. Each base 3 is secured to the end of the jacket 1 by the portion 24 of the skirt 20 overlapping the end portion of the jacket 1 and clamped thereto by the metal clamping band 25. The portion 24 is provided with longitudinally extending slits 26. A strip 27 of asbestos paper moistened with a solution of sodium silicate is wrapped around the end portion of the jacket 1 before the slit portion 24 of the skirt 20 is slipped over the end of the jacket 1. The envelope 4 is of quartz and the stem 5 comprises a quartz stem tube 6 hermetically united with the envelope 4 and a current conductor extending through the stem and consisting of two stiff wires 7 and 8 of tungsten or molybdenum attached to a thin molybdenum foil strip 9 to which the stem tube 6 is hermetically united. The wire 8 extends into the neck 10 of the envelope 4 to support the electrode 11. The wire 7 is provided with a flexible metal wire 12 attached to the inner surface of the sleeve 13 by silver soldering. The envelope 4 is provided with a starting gas such as argon at a pressure of about 9 to 25 mms. and an amount of mercury sufficient to produce a high pressure unsaturated vapour atmosphere.