GB323888A - Improvements in or relating to vacuum electric tube devices - Google Patents

Abstract

323,888. Robinson, E. Y., Hubbard, E. J. E., and Associated Electrical Industries, Ltd. Dec. 8, 1928. Vacuum tubes.-An indirectly heated cathode consists of a heater enclosed in insulating- material and surrounded by a separately formed cathode tube which, after being assembled, is distorted or deformed so as to make contact with the insulating-material at one or more points. In one example, a straight tungsten heater wire 1; coated with porcelain 2 as described in Specification 278,787, is inserted into a straight nickel tube 3 which is then pressed into the form shown in Fig. 2 so as to make contact at a number of points 4. If desired, the bending may be so effected that the insulator is deformed so that, if the tungsten core be held in tension, considerable pressure is exerted between the insulator and the surrounding metal tube. Instead of being corrugated, the tube 3 may be given a slight curvature, or two heater members 15 may be placed side by side and the surrounding metal tube 16, Fig. 5, crimped at 17 at the ends and middle or at points between the ends. The insulator may be provided with depressions which interlock with the tube when this is deformed. Fig. 4 shows an arrangement wherein two curved cathode elements 7 having their heater wires 5 joined at 8 are assembled within a flattened grid formed of support wires 12 round which a wire 13 is wound. The wires 5 are connected to leadin wires 9, 10 which may be arranged in parallel.