GB573571A - Improvements in or relating to the mounting of electrodes in electric discharge tubes - Google Patents

Abstract

573,571. Discharge apparatus. FERRANTI, Ltd., CHILCOT, A. L., and MILLER, J. L. April 18, 1942, No. 5202. [Class 39 (i)] In the manufacture of discharge tubes, the spacing of two electrodes, one of which is ring- shaped and surrounds a circular raised portion on the other, is effected, during their mounting in the envelope, by a tubular jig which fits over the raised portion of the one electrode and has a shouldered external surface on which the ring electrode is positioned. The invention may be applied to the manufacture of valves having two, three or more electrodes, and gas-filled or evacuated, but is described as applied to a triode, Fig. 3, in which the cathode a is a nickel-iron cup with a raised centre portion b and the ring-shaped electrode e is the control grid. The cathode is carried on three wires, one of which c<1> is extended to form the external lead, sealed through the closed end of a tube h forming part of the envelope. The ring is carried by a lead f sealed through a hole in the side of the tube. During sealing, the electrodes are spaced relatively to each other by the jig i, which is a tubular member fitting closely in the tube h and over the part b of the cathode ; the ring e lies against a shoulder j on the external surface of the jig. The tube is closed by a header carrying the anode and an exhaust tube, and may be exhausted and activated by the means described in Specification 573,570. The cathode may be of the cold activated or thermionic type.