GB476187A - Improvements in and relating to thermionic power valves - Google Patents

Abstract

476,187. Thermionic valves. LUDLOW, J. H., and METROPOLITAN-VICKERS ELECTRICAL CO., Ltd. June 19, 1936. No. 17144. [Class 39 (i)] A continuously evacuable high power thermionic valve, adapted to form, together with a continuously evacuable condenser, part of a high frequency circuit, is arranged with the condenser within a common envelope so that the valve and condenser can be evacuated in series. The valve, which may be a screen grid vacuum tube as disclosed in Specification 414,753, which is referred to, comprises a tubular anode 1, a tubular screen grid 2 carried by a metal tube 5, supported on but insulated from the anode 1, a filament cathode 4 similarly carried bv a tube 8 and supported on the tube 5, and a control grid 3, carried by a metal tube 10 which is supported on the tube 8 and is fixed to the terminal 11, serving to close the upper end of the valve. The valve is mounted directly on the inner tubular electrode 14 of a condenser, the anode 1 being in metallic connection therewith, and the other electrode 16 of the condenser surrounds the electrode 14 and is in turn supported by an evacuating pump through an insulating tube 18. The structure is dismountable, the junctions between the metallic and insulating envelope portions being rendered vacuum tight by low vapour pressure grease or bitumen. The structure may be incorporated in a transmitter, the anode circuit extending through the condenser 14, 16 and inductance 19 to one set of plates 20 of a condenser, whose other set of plates 21 is connected to the cathode 4 through the tube 8 and also to the screen grid 2 through the tube 5, while the control grid circuit extends from terminal 11 through inductance 22 and grid condenser 23 to the condenser plates 21. In a modification, a triode valve comprises a similar arrangement of tubular anode and control grid and a filament cathode, supported on the anode which is in turn supported by an insulating tube on the, evacuating pump. The condenser consists of two coaxial tubular members, of which the outer one is mounted upon and in direct metallic contact with a perforated terminal disc which forms the upper end of the valve and supports through a metal tube the cathode of the valve. The inner member of the condenser is supported on the outer member by an insulating tube.