GB845617A - Improvements in or relating to sodium vapour electric discharge lamps - Google Patents

Abstract

845,617. Electric discharge tubes. GENERAL ELECTRIC CO. Ltd. May 1, 1959 [May 2, 1958], No. 14065/59. Drawings to Specification. Class 39(1). A sodium vapour electric discharge lamp of the positive column type comprises two gas filled similar U-shaped discharge tubes mounted side-by-side in a common outer jacket (which may be double-walled) and the inner surface of the jacket is sealed after the jacket has been evacuated. The U-tubes are mounted closely adjacent to one another with the axes of their limbs parallel and located at the corners of a rectangle located in the plane perpendicular to the axes. The spacing between adjacent limbs of the two discharge tubes is preferably less than or equal to the spacing between the limbs of the individual tubes. The discharge tubes are preferably supported by a pair of flexible discs located at each end of the jacket and provided with holes through which project various parts of the discharge tubes; the disc fits closely against the inner surface of the jacket and the holes in the disc are so shaped that they grip the respective regions of the tubes and thereby resiliently support them. The gas filling may be of neon containing 0À8% argon at a total pressure of 10 mms., and the U-tubes have an internal coating of sodium resistant glass. The jacket or U-tubes may be provided with closely fitting heat insulating sleeves. One end of the jacket is domed and the other is sealed into a mounting in a conventional manner and leads pass through it. The space between the inner jacket wall and the U-tubes is provided with gettering means, and the lamp may be mounted in a holder which is fitted with reflectors.