Improvements in or relating to electrode structures for thermionic valves

789,215. Thermionic-cathode tubes. ELECTRIC & MUSICAL INDUSTRIES, Ltd. Dec. 10, 1954 [Dec. 24, 1953], No. 35838/53. Class 39(1). An insulating electrode support comprises two oppositely disposed surfaces, with at least two electrodes extending between them, with their ends resting on and secured to said surfaces, the electrodes having deformed or " loop " portions to accommodate longitudinal expansion. In the drawing, the supporting surfaces 6 and 7 are formed by ceramic members 2, 3 which may be integral with a valve base 1. The cathode is a hollow box 8, the grid a frame-like construction of two pressed parts placed together, Fig. 2 (not shown), and the anode 10 similarly of two flat parts placed together. The electrodes may thus be nested one within the other before being finally placed on the supports. The flat ends of the electrodes rest on the surfaces 6, 7, which have been previously metallized, and are brazed thereto. The inter-electrode spacing is thus accurately referenced from the surfaces 6, 7. The insulators may be slotted between the electrodes, as at 22, to reduce leakage. Metallized portions 26, 27 connect the electrodes to the leads. Valves with two or three grids may be similarly constructed. Specification 730,483 is referred to in the Provisional Specification.