GB901857A - Improvements in or relating to thermionic valves - Google Patents

Abstract

901,857. Thermionic valves. STANDARD TELEPHONES & CABLES Ltd. Jan. 15, 1959, No. 1479/59. Class 39 (1). A miniature thermionic valve includes an indirectly-heated cathode 6, a control grid 3 and an anode 1, each mounted on a metal disc, the grid and cathode discs 5, 10 being annular while the anode disc 2 forms one end of the envelope. Ceramic collars 11, 12, sealed between adjacent pairs of discs, form the envelope wall and the other end of the envelope is closed by a ceramic rod 13, through which a cathodeheater lead is sealed. This rod is of smaller diameter than the cathode disc so that the outer portion of the latter is available for use as a valve seating, and may also be deformed slightly to adjust the grid-cathode spacing of the assembled valve. In the preferred method of assembly of the valve each electrode is welded or brazed to a metal disc which is brazed to a ceramic member. These sub-assemblies are then brazed together on a jig which includes an apertured base-plate providing a seating for the cathode disc and perpendicular rods which press against the ceramic collars, radial slots being provided in the large grid disc to accommodate these rods. In the grounded grid triode valve shown, the large grid disc acts as a screen between anode and cathode circuits, and may also be used to support the valve annular cap-shaped connectors having serrated edge portions being used for making contact with the anode and cathode. In a screen grid valve according to the invention, flexible leads are wrapped around and secured to the electrode discs so that the valve may be suspended in the apparatus wiring, the electrode discs all being of a diameter slightly less than that of the separating ceramic collars.