GB873901A - Electron tube - Google Patents

Abstract

873,901. Thermionic cathode tubes. EITELMcCULLOUGH Inc. Jan. 7, 1958 [Jan. 18, 1957], No. 596/58. Class 39(1). In an electron tube, an electrode e.g. cathode 12, is mounted on a first ceramic cylinder 50 which is in turn mounted on and hermetically sealed to a flat surface of a metallic envelope part 52, the electrode and envelope part being electrically connected by means of a metallic coating 54 on the surface of the ceramic member. A second ceramic cylinder 58 is also sealed to a flat surface of part 52 and may support a second electrode 14 and terminal unit 34. In the manufacture of the tube shown, support rings 62 sealed to heater support rod 60 are press fitted into the previously metallized ceramic member 50, and ceramic ring 58 is press fitted into metal tube 38. Rod 60, terminal 56 and tube 38 are then mounted in concentric grooves in a carbon brazing jig, rings of brazing material, e.g. a copper - silver - eutectic, being interposed between the lower ends of ceramic members 58, 60 -and flange 52 and between the lower ring 62 and member 50. Reinforcing ring 46 and heater post 64 are then placed in position with suitable interpositions of brazing material and held in accurate alignment by means of a further jig, after which the assembled parts are heated in an oven to brazing temperature. After cooling the insulating discs 66, heater 44 and previously assembled cathode 12 and heat dam cylinder 40 are attached in that order. This assembly is then mounted within the remainder of the tube comprising control grid and screen grid supports 34, 30, glass envelope portions 28, 22 and anode 18. The inventionis also applicable to triodes having planar electrodes, or to klystrons or travelling- wave tubes.