GB937310A - Improvements in and relating to electric incandescent lamps - Google Patents

Abstract

937,310. Incandescent electric lamps. UNION CARBIDE CORPORATION. Jan. 21, 1961, No. 2497/61. Drawings to Specification. Class 39 (2). An incandescent lamp with a filament a major portion of which is tantalum carbide contains a gas filling comprising carbon or a source of carbon and nitrogen or a source of nitrogen, the major portion of the source of nitrogen being distinct from the source of carbon. The filling may also include at least one source of hydrogen, an inert gas of low heat conductivity such as argon and at least one source of halogen. The filament leads may be of tantalum carbide or rods of carbon, nickel, tungsten, platinum, palladium, rhodium or molybdenum or of metals coated with platinum, palladium or rhodium may be used. The filament may be produced in situ by combustion of a filament of pure tantalum by passing a current therethrough to produce a temperature of 3100‹ C. in a carburizing atmosphere, e.g. of a volatile hydrocarbon, A source of carbon such as methane, propane, butane, acetylene, ethylene or carbon tetrachloride may be used with nitrogen gas. Part of the nitrogen may be derived from cyanogen, nitriles, such as succinonitrile, adiponitrile or glutaronitrile, cyanamide, dicyanamide, aniline, ethylene diamines or phenylhydrazine. Halogens may be provided in uncombined form or a compound such as methyl chloride, trichloroiodomethane, benzene hexachloride, tetrachloroethane, chloroform or carbon tetrachloride. Halides of cyanogen or cyanamide may also be used. The filling must be free from water and oxygen. A sealed beam headlamp having an aluminized, silvered or other reflecting surface through which the leads to the filament pass is described. Where halogen is present in the filling, the glass of the headlamp may be protected by a coating of calcium fluoride evaporated thereon.