GB340516A - Improvements in grid electrodes of vacuum electric tube devices - Google Patents

Abstract

340,516. Thermionic valves. ROBINSON, E. Y., Gavary, Dryden Road, Bush Hill Park, Enfield, Middlesex, and ASSOCIATED ELECTRICAL INDUSTRIES, Ltd., Bush House, Aldwych, London. Sept. 21, 1929, No. 28690. [Class 39 (i).] Helical grids are shaped to provide, in cross-section, a tunnel or active portion 6, Fig. 1, completely enclosing a cathode element 1 electrically, and extensions 7 between the tunnel 6 and one or more backbones 5. The anode 4 in one or more parts is shaped to correspond to the tunnel 6 and extends around the tunnel for over 180‹. The extensions 7 may project through openings in, and the backbones 5 be outside, the anode 4 to facilitate radiation of heat, and the cathode 1 may be equipotential and shaped in cross-section similarly to the tunnel 6. In a modification, Fig. 4, the backbones form part of the tunnel 6a and the extensions 7a project beyond the backbones. In another modification, Fig. 5, the wire between two backbones is formed into two tunnels 6b joined by straight parts 10 of the helical wire and each enclosing a straight cathode element. In other modifications, the helical wire has extensions 11, Fig. 9, on one or both sides of a single backbone 5d, to a tunnel 6d, the anode being an open-sided tube or an indented flattened tube. The grids are made by winding a wire about the backbones on a mandrel to form an oval helix, welding the wire to each backbone along two lines of contact as described in Specification 231,225, [Class 39 (i), Electric lamps, Arc &c.], and then pressing the sides of the helix together to form the tunnels. Specifications 261,915 and 276,783, [both in Class 39 (i), Electric lamps, Arc &c.], also are referred to. Reference has been directed by the Comptroller to Specification 321,553, [Class 39 (i), Electric lamps, Arc &c.].