GB356745A - - Google Patents

Abstract

356,745. Discharge lamps. CLAUDE NEON LIGHTS, Inc., 41, East 42nd Street, New York, U.S.A.-(Assignees of Beck. L. L. ; 27, Stoncleigh Park, Westfield, New Jersey, U.S.A.) June 5, 1930, No. 17436. Convention date, Nov. 30, 1929. [Class 39 (i).] Discharge l a m p s with thermionic cathodes are filled with helium mixed with not more than 8 per cent of neon and not more than 0À5 per cent of argon, krypton, or xenon, operation at a discharge current of 0À03-1À25 amps. per sq. cm. of tube cross section producing a bright, white light. The mixture depends on the current to be used, the percentage of neon being increased from 3 to 8 as the current increases in the above range. The potential gradient in the gas is reduced by high current densities and by the addition of the argonkrypton, or xenon. The proportion of krypton or xenon used is less than 0À30 and 0À15 per cent respectively. The pressure of the gas mixture in the tube is selected at a value from 8 to 1 mm. for tubes of diameter ranging from 11 to 30 mm. The length of the tube for a given potential drop can be increased by increasing its diameter. Dimensions of a tube and its electrodes are specified for a gas filling containing 7À25 per cent of neon. The electrodes are of copper, nickel, or iron, the cathode being coated with emission material such as oxides of alkaline-earth or rare-earth metals. Suboxides may be formed; for example, a coating of barium peroxide may be heated by a heavy discharge or by high-frequency induction, the gases evolved being exhausted. The cathode may be conical or cylindrical and may be coated with the oxide internally. In operation, the cathode may be heated by ionic bombardment due to the discharge, starting being effected by a high-frequency field. To avoid temperature variations, the cathode 3, Fig. 1, is preferably heated by a filament 14 heated initially by a separate current supply 16 and during operation by flow of the discharge current through it, the connection to the direct-current source 1 and variable resistance 4 being as shown. For alternating current, two anodes are provided, or both electrodes are thermionic and a circuit reactance corrects the power factor. In a modification, Fig. 5, a cylindrical cathode 3 coated externally is heated by a tungsten helix 14, the connections allowing the discharge current or current from a separate source 16 to be passed through the helix. To produce a helix of singlecrystal tungsten rigid at high temperature, the helix is heated to 2800‹ C., the heating taking place in a channel-shaped trough in an inert gas or hydrogen, or in situ with the helix supported on a quartz &c. rod which may be partly vaporized or destroyed during the heating. The Specification as open to inspection under Sect. 91 (3) (a) comprises also the use of cathodes of alkali metal, such as a pool of potassium, sodium or caesium, instead of thermionic cathodes. This subject-matter does not appear in the Specification as accepted.