GB285784A - Improvements in or relating to vacuum electric tube devices - Google Patents

Abstract

285,784. Robinson, E. Y., and Metropolitan-Vickers Electrical Co., Ltd. Nov. 9, 1926. Vacuumtubes.-Cathodes comprise several filaments electrically in parallel with their ends secured between superposed metal members fixed together and constituting part of a closed rigid framework the remainder of which consists at least eventually of the foot or seal or other insulating parts. The framework may be mounted on the foot before or after or simultaneously with mounting the other electrodes on the foot. The anode may be in portions fitted together. Very thin filaments may be used and may have a metallic sheath removed after mounting on the framework as described in Specification 285,538. After being mounted on the framework or on the foot, the filaments may be coated as described in Specification 285,538 with oxide or with a metal or compound subsequently converted to oxide or may be otherwise treated to reduce the work function, for example, thoriated tungsten filaments may be treated with a reducing agent such as carbon. During such treatment, the framework may be treated by current. The oxide coating may be applied as described in Specification 221,851, and grids of the kind described in Specification 231,225 may be used. The ends of the filaments 30, Fig. 5, are held between pairs of metal strips 32 held apart at one end by a steatite or other insulator or bead 33 and at the other end by a metallic cross-piece which, after the framework has been mounted on the foot 1, Fig. 1, by securing the parts 32 to filament leads 4, 5, is removed or cut through at 16. Wires 7, 9 held respectively in the foot 1 and in a tube 3 in the foot support an anode and grid and may be welded at their upper ends to wires fixed into the bead 33. In mounting the filaments in the parts 32, a filament may be wound about pegs 31, Fig. 4, the loops around the pegs being finally cut off if desired. Specification 273,394 also is referred to. The Provisional Specification describes modifications with filaments having series-connected legs.