GB822441A - Improvements in or relating to sodium vapour electric discharge lamps - Google Patents

Abstract

822,441. Discharge lamps. GENERAL ELECTRIC CO. Ltd. Oct. 29, 1956 [Nov. 11, 1955], No. 32340/55. Addition to 815,893. Class 39(1). A low-pressure sodium vapour discharge lamp as claimed in the parent Specification having mounted, or arranged for mounting, within an outer single-walled or Dewar jacket 5 a discharge envelope 1 including one or more axially straight parts 2 formed with one or more regions 3 of appreciably reduced area of cross-section and short axial length to prevent migration of sodium, has at least one straight part 2 surrounded by a closely fitting sleeve 16 of transparent heat-insulating material as described in Specifications 801,482 and 816,043 there being provided for each said sleeve at least one metal spring member 17 which is positioned at a region 3 between the straight part 2 and the sleeve 16 to prevent transverse and longitudinal movement of the sleeve. Each region of reduced cross-section can be formed as an annular depression in a straight part 2 and each spring member 17 can be in the form of a resilient metal wire bent into polygonal form or wave form. Each spring member 17 can be of steel or " Iconel " (Registered Trade Mark). The envelope 1 can be of U-shape and filled with sodium at a pressure of less than 1 mm., preferably about 0À01 mm., and neon containing 0À5% by volume of argon at a total pressure of about 10 mms. The inner surface of the envelope 1 can be of sodium resistant glass. The envelope 1 is supported within the jacket 5 by a mica disc 23 and a spring clip device 13 having two arms 14 which clip over the end of the envelope and two arms 15 extending radially at right angles to the arms 14 into curved abutment with the jacket as described in Specification 815,782. A getter element 20 is provided in the jacket 5. Each sleeve 16 is surrounded by an auxiliary starting wire 18 extending between one of the electrode lead mounting wires 9 and a mica tag 19 secured to one of the arms of the spring clip 13.