GB817100A - Improvements in or relating to electric discharge lamps - Google Patents

Abstract

817,100. Metal-vapour lamps. GENERAL ELECTRIC CO. Ltd. Dec. 21, 1956 [Dec. 22, 1955], No. 36804/55. Class 39(1). A U-shaped discharge lamp 1 enclosed in an outer jacket 4, and having a filling comprising an alkali metal vapour, has the envelope wall on the outer part of each limb of the U deformed outwardly in a series of grooves. As shown, the grooves 23 may extend circumferentially. Alternatively they may be inclined to the axis of each limb 2, or may run parallel to the axis. In any case the grooves are confined to the outer part of each limb, so that the spacing between the limbs may be kept very small. They are preferably arranged symmetrically with respect to the plane containing the axes of the two limbs, and the depth and width of the grooves should be small compared with the diameter of the U-tube. The metal filling tends to collect in the grooves, which are cooler than the remainder of the envelope, and which, being uniformly distributed along the lamp, thus maintain a more uniform distribution of metal vapour. A typical application is a sodiumvapour lamp containing a neon-argon filling at about 10 mm. and having an inner coating of sodium-resistant glass. Some suitable dimensions are given. Each limb may have a closefitting insulating sleeve 13, as described in Specifications 801,482 and 816,043. and the bend of the U is supported by a spring clip as described in Specification 815,782. Starting wires 18 attached to the electrode lead wires 7 may be wound round each limb.