GB795146A - Improvements in and relating to thermionic valves - Google Patents

Abstract

795,146. Thermionic valves. GENERAL ELECTRIC CO. April 1, 1955 [April 12, 1954], No. 10716/54. Class 39(1). A multiple electrode structure for a thermionic valve consists of an integral combination of a cathode electrode 8, Fig. 1, and another electrode 4 for example a control grid, in the form of interconnected areas deposited on a common support 1. In one form the grid is deposited on the top of a number of ridges 2 standing up from the insulating or semi-conducting support 1 and connected at one end in the form of a comb, Fig. 2. A metal layer 7 covers the bottoms of the grooves between the ridges, where it is coated with thermionically emissive material, and also the sides of the support. The upright walls of the grooves, which may be undercut for focusing effect, Fig. 6 (not shown), are coated with a resistive layer 10 to prevent charging. The whole structure is mounted with anode 18, Fig. 4, to form a vacuum or gas-filled disc-sealed valve. The heater 22 may be inside the valve, Fig. 3 (not shown), outside in mere juxtaposition to the cathode, as shown, or wound around an external projection from support 1. The grid is connected to the centre disc 11 by spring contact. The support need not be ridged, the interleaved cathode set 8, Fig. 7, and grid set 6 being then in the same plane. In another form the support is a conductor 34, Fig. 8, on which rests an insulating member 2 carrying the grid 4, the cathode 8 being deposited in the spaces left. The member 2 may be comb-shaped or a plate with a number of spaced apertures, Fig. 12 (not shown). In a multiple valve two or more grids may be simultaneously supported, and the anodes may be mounted in the same way as the grids especially where there is a diode section. The insulating support may be glass or ceramic or an intermediate such as " Photo-Caram " and the grooves may be made by cutting or moulding or, in the latter case, by photo-etching permitting reduction in groove dimensions to the order of 1 mil. The coatings may be applied by stencilling, photo-printing or evaporation, and once deposited may be thickened electrolytically. The Provisional Specification gives further details of the photo-etching and photoprinting processes.