GB354620A - Improvements in or relating to sealing-in bodies for vacuum tubes - Google Patents

Abstract

354,620. Electric incandescent lamps &c. NAAMLOOZE VENNOOTSCHAP PHILIPS' GLOEILAMPENFABRIEKEN, 13D, Emmasingel, Eindhoven, Holland. Oct. 20, 1930, No. 31402. Convention date, Nov. 2, 1929. [Class 39 (ii).] Leading-in wires.-A sealing-in device for a vacuum tube consists of a hollow metal tube 11 which is adapted to be surrounded by the glass envelope or stem 10 of the vacuum tube and has substantially the same coefficient of expansion as the glass, the tube, which is formed by metal applied chemically or electrochemically to a core being closed at one of its ends by a closing member 12 which is connected to a leading-in wire 13 and is constituted by that portion of the core which is left after a portion thereof has been removed. The closing member 12 may be either at the upper or lower end of the tube 11 and preferably should be so located that it is not surrounded by glass. The tube 11 may be made of tungsten with a closing member 12 of molybdenum obtained, for example, by heating a molybednum core to 2000‹ C. in an atmosphere containing tungsten hexachloride vapour, thereby applying a finely crystalline coating of tungsten, after which one end is covered by a glass bead and the whole immersed in a mixture of concentrated sulphuric and nitric acids, the duration of the action being such that the end covered by the bead retains part of the core. The wire 13.may be secured to the membr 12 by soldering with the aid of liquid silver poured into the tube. A clearance between the wire 13 and the inner wall of the tube 11 allows for expansion.