GB864303A - Improvements in or relating to electric discharge tubes - Google Patents

Abstract

864,303. Thermionic valves. SIEMENS & HALSKE A.G. Sept. 30, 1959 [Sept. 30, 1958], No. 33214/59. Class 39(1). In a discharge tube including a grid assembly sealed into the tube envelope, the grid extends in a plane across an aperture in a supporting frame to which it is attached and a metal ring is bonded to the grid in such a way that its unbonded surface is parallel to the plane of the grid. As shown, a grid comprising a plane mesh of crossed wires is gold or copper soldered to a supporting frame and a malleable metal ring 5, e.g. of copper, gold or silver, is pressure bonded in a jig on to the soldered grid mesh to form a cold weld, the malleable metal filling all the cavities which were created by soldering the grid mesh to the frame 4. The jig has a non-deformable distance piece which maintains the desired dimension between the unbonded surfaces of the frame 4 and ring 5 and ensures that these surfaces are parallel to each other and to the grid mesh so that the grid-cathode distance can be accurately determined. The grid assembly together with a metal foil 3 and the ceramic wall portions are then pressed together and heated, thus producing a diffusion weld between ring 5 and foil 3, whilst annular metallic members 6 and 7, previously secured to the ceramic wall portions, are soldered together.