GB1489313A - High-pressure discharge lamp - Google Patents

Abstract

1489313 Metal vapour lamps ITT INDUSTRIES Inc 13 Feb 1975 [20 Feb 1974] 6141/75 Heading H1D A high pressure discharge lamp comprises an inner envelope (burner) 8 inside an elongate main envelope 1 capped 13, 131 at each end with connections 14 to the electrodes 10, 10<SP>1</SP>, with at least one reflector 16 insulated froth the electrodes in the outer envelope near an end 7 of the burner to protect the neighbouring connections and base cap 13. The burner tube 8 of quartz or hard glass contains Hg or Na, with single or mixed rare gases and halogenides such as CsI, Y 2 I 3 , Tl 2 I 3 , and has a main electrode 10, 10<SP>1</SP> at each end together with a starting electrode 11 of thoriated W at one end. Alternatively (Fig. 2, not shown) the main electrodes may be filaments heated for starting. The main envelope 1 of metal-sealable glass, evacuated for thermal insulation and possibly containing a getter, carries electrically insulated reflectors 16, 16<SP>1</SP> and optionally a fluorescent coating on its walls: The construction except for starting electrode 11 is symmetrical about plane AA<SP>1</SP>. For given output the invention allows reduction in overall length.