GB1246181A - Incandescent electric lamps - Google Patents

Abstract

1,246,181. Incandescent lamps. USHIO ELECTRIC Inc. 20 Aug., 1969 [9 May, 1969], No. 41637/69. Heading H1F. The gas filling in a tungsten-filament lamp comprises chlorine, hydrogen and an inert gas such as argon or krypton, the chlorine being present in an amount between 2À5 : 10<SP>-7</SP> gm. atoms/cm.<SP>3</SP> and 2À5 : 10<SP>-6</SP> gm. atom/cm.<SP>3</SP>, and the atomic ratio of chlorine to hydrogen falling between 4: 10 and 4 : 5. The presence of hydrogen causes rapid heating of the walls of the envelope during switching-on of the lamp so reducing the'possibility of blackening; the wall temperature during operation should not however exceed 300‹ C. The hydrogen and chlorine may be introduced into the envelope in elemental form, as hydrogen chloride and hydrogen, as a chloride of carbon and hydrogen or as a chlorinated hydrocarbon with added hydrogen as necessary. In the latter two cases the carbon produced on decomposition of thechloride or hydrocarbon serves as a getter with respect to any free oxygen contained in the envelope as an impurity. In the example illustrated in Fig. 2, portions of the filament 2 are rendered non-operative by means of shortcircuiting rods 6 in order to achieve the uniformity of illumination in an axial direction required for copying machines. The filament is held by supports 4 and connected to molybdenum seals 3. The envelope is made of quartz. In an alternative embodiment, Fig. 1 (not shown), the shorting rods are omitted.