GB1520487A - High pressure electric dicharge lamps - Google Patents

Abstract

1520487 Metal vapour lamps GENERAL ELECTRIC CO Ltd 11 Nov 1976 [12 Nov 1975] 46696/75 Heading H1D In a constricted arc h.p. discharge lamp with Hg plus rare gas filling, possibly with metal and/or metal halide additives, working at a total pressure of at least one atmosphere, comprising a fused silica tubular envelope 1, optionally within an outer glass envelope, temperature uniformity is improved, particularly when operated horizontally or inclined, by a longitudinal strip baffle 10, also of fused SiO 2 , either planar or cylindrically curved to a larger radius than the envelope, lying parallel to the axis along most of the length, sealed along its edges 12, 13 in the uppermost part of the discharge envelope with a planar or convex surface 11 towards the upper wall, and a planar or concave surface towards the axis. The baffle may be cut from a silica tube larger than the envelope. The W coil electrodes 6, 7 with Mo leads 4, 5 entering from the ends should preferably be displaced downwards to centralize them in the space below the baffle. A suitable lamp may contain Hg, Xe or Ar, NaI, ScI 3 . If the lamp is mounted out of the vertical, the holder or holders should be set so that the baffle is uppermost. The outer envelope may be N 2 filled, and its inner walls may be coated with IR reflective film such as SnO 2 or In 2 O 3 .