GB1462955A - Discharge lamp - Google Patents

Abstract

1462955 Metal-vapour lamps; electrode materials IWASAKI DENKI KK 2 May 1974 [10 May 1973] 19281/74 Heading H1D In a discharge lamp having an arc tube 10 comprising a radiation transmitting sealed tubular body 12, a pair of electrodes 14 and 16 arranged oppositely at both ends of said body, a pair of lead-out conductors 18 and 20 connected electrically to the electrodes, and a filling including mercury, a rare gas, at least one kind of luminous metal other than mercury, and at least one halogen in the form of element or metal halide, said electrodes include at least one rare earth metal oxide, and the filling includes a substance which reacts with the halogen to form a compound which then reacts with said rareearth metal oxide during operation of the lamp to form a halide of said rare earth metal. Specific rare earth metal oxides mentioned are oxides of Sc, Y and Dy. The reacting substance may be Th, Al or Si or a mixture, e.g. Th-Al, Th-Si, Th-Al-Si, or Al-Si. The invention is stated to reduce a loss of transparency of the lamp envelope and a wearing of the electrode tips in known lamps having electrodes containing thorium oxide and a filling containing Sc. Lagging members 26 and 28 are mounted on the end parts of the body 12.