GB587894A - Electron discharge devices - Google Patents

Abstract

587,894. Thermionic valves. STANDARD TELEPHONES & CABLES, Ltd. July 21, 1944, No. 14021. Convention date, July 9, 1943. [Class 39 (i)] In an electron discharge device the anode comprises a metallic mass 18, Fig. 1, provided with a cylindrical bore 22 enclosing the grid and cathode and a frusto-conical outer surface 24 terminating in an extension 26 sealed to a part 14 of the insulating envelope. The mass 18 may have a relatively large hollow core 20 with which the bore 22 communicates. The grid is supported by an inverted frustocoiiical metal member 32 passing through the envelope and preferably forming an angle of about 90 degrees with the surface 24. The grid support and the anode extension 26 may carry connector rings 44, 28 respectively. As shown, the grid support is made in two parts having inward flanges secured to a ring 38 ; the lower part of the grid support is provided with apertures 42 to permit access to the securing screws 40. In a modification, the upper and lower parts of the grid support overlap, flanges being dispensed with, and are secured to a conical ring. The envelope is preferably bell-shaped and its upper and lower parts 12, 14 are joined by a metal ring 16 preferably having a coefficient of expansion the same as the envelope, e.g. a chromium iron alloy ; sealing may be effected by highfrequency heating. A cooling fin structure may be attached to the anode by screwing to a threaded bore 30 or by soldering or brazing. The cathode, to which is connected one end of the heating coil 56, is supported by a member 48 secured to a frusto-conical member 60 sealed through the envelope and secured externally to a threaded connector tube 54. The other end of the heating coil is connected to a threaded member 60 sealed to the upper part of the envelope by an annular knife-edge 62. The member 60 is sealed by knife-edge 64 to a tube 66 through which access to the cathode cormection at 70 may be made before evacuation and sealing. In a modification, the tube 66 is sealed to a knife-edge extending upwardly from a reduced upward extension of the member 60. In a further modification, Fig. 4, the cathode connection is made to a toroidal metal member 360 having inner and outer annular knife-edges 362, 364 sealed to the envelope 12 and the tube 366 respectively, a threaded recess 380 being provided for an external connection. In a modification, the toroidal member is less thick and the cathode lead extends through it.