GB431763A - Improvements in and relating to electric discharge devices - Google Patents

Abstract

431,763. Discharge apparatus. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London.-(Assignees of Foulke, T. E. ; 30, Evelyn Place, Nutley, New Jersey, U.S.A.) Oct. 10, 1933, No. 27923. Void [Abridged as open to inspection under Sect. 91 of the Acts, April 12, 1934]. [Class 39 (i)] In a gas discharge device for use as a relay, sputtering of cathode material on the envelope is prevented by means of a shield or by forming the electrodes to act as shields. As shown, a shielding disc 7 of mica or glass is secured to the anode 6 by wires 8, and a smaller mica disc 9 spaces the anode from the envelope. A cathode 4 and an anode 5 for producing a starting discharge are of semicircular shape, and are mounted on leads 2, 3. The distance between the electrodes 4, 6 is greater than the distance between either electrode and the envelope. The back of the electrodes 4, 5 is coated with aluminium powder as described in Specification 397,107 so as to confine the glow to the front of the electrodes. The electrode 4 is coated with alkaline or alkaline earth metal by spraying a mixture of barium or strontium carbonates or nitrates mixed with a binder such as nitrocellulose and cellulose acetate. The envelope is evacuated and heated to 450‹ C. to drive off occluded gas. The electrodes are heated to 1300‹ C. by a highfrequency magnetic field to reduce the carbonates &c. to oxide and the binder to carbon. A filling of neon with one half per cent of argon at a pressure of 50 mms. is introduced and a high-frequency discharge with a steep wave front is passed between the electrodes 4, 5 so as to break up a part of the barium oxide, leaving barium cemented by oxygen and barium oxide. Any oxygen evolved is cleaned up by the aluminium coating. For use with alternating current the electrode 5 is similarly coated. The electrodes 4, 5 are connected with the secondary of a transformer 16 through a battery 15 and a resistance 17. A resistance 20 and contacts 21, normally open but arranged to be closed by a magnet 19, are connected between the anode 4 and the output which includes a battery 18. The auxiliary discharge between the electrodes 4, 5 starts a discharge between the anode 6 and cathode 4, the discharge being broken by the insertion of the resistance 20 through the contacts 21. In a modification, Fig. 2, (not shown), the electrode 5 is omitted and the anode 6 consists of a nickel or iron disc ; the magnet 19, contacts 21, the transformer secondary, and the load battery 18 are connected in series between the two electrodes.