GB385340A - Improvements relating to vacuum electric tube devices - Google Patents

Abstract

385,340. Thermionic valves. ROBINSON, E. Y., Garvary, Dryden Road, Bush Hill Park, Enfield, Middlesex, and ASSOCIATED ELECTRICAL INDUSTRIES, Ltd., Crown House, Aldwych, London. July 6, 1931, No. 19457. [Class 39 (i).] In valves having a flattened tubular grid surrounding a filament, an end of the filament is fixed between two metal strips arranged face to face, separate strips 20, 23, Fig. 6, being used or one strip having its end bent over around the filament as at 20, Fig. 5. The strips form a support or lead for the filament 7 and are registered, near the point at which the filament is attached, by slidably engaging a rectangular slot 21 in an insulating crosspiece 11 itself slidably engaging grid supports 10 to position the filament centrally of the grid with the strip 20 parallel to the flat sides of the grid. Both ends of a hairpin or W-shaped filament may be so supported and hairpin filaments may be joined by such supports. The central bight of a W-shaped filament may be supported by such supports or by a wire hook 22a. The filament may have a diameter of 1À5-2 mils. The upper bends of the filament are supported by spring hooks 14, Fig. 1, from the grid wires 10, the hooks being coated with insulation or a glass bead interposed. In assembling the electrodes on supports 3 .. 6, 22 previously secured in the pinch 1, the flat strips 20 are secured to the wires 5, 6, the filament 7 is secured to the strips 20, the mica cross-piece 11 is added and held to the anode supports 3 by clips 13, the grid 9 with the hooks 14 is assembled and moved endwise to tension the filament before securing the wires 10 to the supports 4, and a two-part anode 8 and upper mica cross-piece 12 are finally added.