GB821465A - Improved electric incandescent lamps - Google Patents

Abstract

821,465. Electric incandescent lamps. UNION CARBIDE CORPORATION. Jan. 15, 1957 [Jan. 16, 1956], No. 1443/57. Drawings to Specification. Class 39(2) An electric incandescent lamp has a filament consisting essentially of tantalumcarbide in an atmosphere or gaseous filling comprising, at operating temperatures, a halogen, hydrogen and vaporized carbon, said atmosphere being substantially free of oxygen. The gaseous pressure within the bulb or envelope during operation is maintained at, or near, the highest level that the bulb can withstand, an inert gas such as argon being included to attain such pressure if necessary. In an example a sealed beam automobile lamp has a tantalum carbide filament in an atmosphere.. at operating temperature, of hydrogen, chlorine, and volatilized carbon, together with argon. The components of the atmosphere may be provided by introducing hexachlorobenzene before the bulb is sealed. The filament may be carried between tantalum carbide leads which are, in turn, attached to nickel leading-in wires. The envelope, which is of about 270 c.c. capacity, has a filling comprising about 2.75 m.g. hexachlorobenzene and 20 c.c. of hydrogen at atmospheric pressure and room temperature, along with sufficient argon to bring the total pressure within the bulb at least to slightly less than one atmosphere. The inner surface of the bulb is preferably provided with a protective coating, e.g. by evaporating calcium fluoride upon it before the lamp is assembled. The filament may be straight, coiled, crimped or otherwise shaped and may be converted from tantalum to tantalum carbide, after the bulb has been assembled, by baking the bulb at about 300‹C. for about 15 minutes, with sufficient current passing through the filament to yield a filament temperature of about 3100‹C. Alternative materials for providing the necessary atmosphere comprise ethylenediamine hydrochloride oimethylamine hydrochloride, or a combination of materials such as ethylene or another hydrocarbon and hydrogen chloride gas, or a combination of hydrogen chlorine, and a volatile hydrocarbon. Other inert gases, such as xenon or krypton may be used instead of argon. The parts of the leads within the bulb may be rods of carbon, tungsten, or gold plated nickel.