GB450630A - Improvements in and relating to ceramic bodies forming parts of electric discharge devices - Google Patents

Abstract

450,630. Discharge apparatus. BRITISH THOMSON-HOUSTON CO., Ltd., Crown House, Aldwych, London. Nov. 22, 1935, No. 32444. Convention date, Nov. 24, 1934. [Class 39 (i)] [See also Group V] In electric discharge vessels wherein an envelope wall is of ceramic material, the lead-in to the electrodes &c. is formed by a ceramic body, which owing to its content of metal oxides such as the oxides of cadmium, uranium or titanium-which are reduced during manufacture-is at least in part electrically conductive; electrodes and the envelope may also be made of such material and may be provided with a conductive layer. Quartz, aluminium oxide or silicate are used to mix with the metal oxide. A mixture of magnesium and titanium oxides in the proportion of 2 to 1 is a suitable composition for the material; this mixture may be first sintered in an oxidizing and afterwards in a reducing atmosphere, to reduce the titanium oxide. To increase the conductivity of the body, metal may be deposited thereon either electrolytically or as a paste before burning ; this metal coating is omitted where the body is to be sealed to the envelope ; metal coatings may also be provided where it is intended to secure electrodes to the wall. In one form a rod 1, Fig. 2, as a whole is reduced and fixed in the envelope 2 by a glass or ceramic seal 3 ; a connection 5 is made to the electrodes and if the reducing action is taken only up to the level when this connection is fixed, a support 7 may be attached to the upper part which remains an insulator. Where a hollow body 11, Fig. 5, is used, the inner face 9 only and it may be the exterior of the body are reduced to form one or two conductors ; the inner surface of the envelope may also be reduced to act as a conductive layer. Electrodes, such as a cathode 12, Fig. 6, may be formed with a conducting layer to which electron emitting material is applied ; the layer extends outside the envelope, and the heater 13 is carried by a screwed-in closing plate 14. Water-cooled grids 25, Fig. 8, for controlled arc rectifiers may be formed from the conducting material, the grids passing through the envelope wall. In a thermionic valve, the envelope 16 may be wholly conducting or may have a conducting layer on its interior or exterior ; the leads 17, 18, 19 are fused into the base 15, the envelope acts as the anode which may be hollow for cooling purposes ; bowl form leads as described above mav be used. The rod 17 for the filament cathode is oxidized at its upper end to carry in an insulating manner the cathode support 21. X-ray, cathode ray and photo-electric tubes may have parts constructed as above.