GB688910A - Thermionic valves - Google Patents

Abstract

688,910. Thermionic valves. SONOTONE CORPORATION. Jan. 17, 1950 [Jan. 26, 1949], No. 1251/50. Class 39(i) A thermionic valve, particularly of the subminiature type, having an assembly of electrodes which extend parallel with a common axis and are enclosed within a coaxial hermetically sealed envelope formed with a flat end wall of insulating material, is provided with at least five leads sealed through the end wall to provide external connections for the electrodes, at least three of the leads being aligned in a plane and the remaining leads being offset from the plane to increase the insulating spacing between the leads. The valve may be a beam tetrode comprising a filamentary cathode 21, a control grid 22, a screen grid 23, a pair of beam-forming plates 25, 26 and an anode 24. The electrodes may be assembled between two spaces 31, 32 provided with apertures for the grid support rods and the lugs 37 of the beam-forming plates, with triangular apertures for the cathode, and with recesses 33 to receive the anode tongues. The cathode is welded at one end to a tensioning spring 54 supported on a U-shaped member welded to the lug 37 of one of the beam-forming plates 26; at the other end it is welded to an L-shaped member 46 which is welded to a lug of the other beam-forming plate. The getter support 61 may be welded to an anode tongue 35, or alternatively the anode itself may be provided on its exterior surface with a pocket for the getter material. Leadin conductors 13, 15 may be welded to the control and screen and support rods and conductors 16 to the anode. Lead-in conductors 12 and 14 are bent over internally and connected to the support rods 17 and 18 which are welded to the lugs of the beam-forming plates and thus serve as connections to the cathode and the beam-forming plates. Conductors 12, 14 and 16 lies in a plane, conductors 13 and 15 being staggered from the plane to increase the spacing. The anode may be provided with arcuate channels 55 to increase its stiffness and the beam-forming plates may be provided with longitudinal channels 48, Fig. 2, for the same purpose. A tube with a distance of 0.315" between spaces 31, 32 operating with a plate and screen voltage of 22.5 and a plate current of 200 ÁA may have a transductance of 100 microhms and a plate resistance of 1 M#. A similar tube with 0.6" between the spaces using the same potentials may have a transductance of 400 microhms and a plate resistance of 170,000 ohms. In assembly the upper spaces 31 is placed in a jig, the grids and anode inserted in the spaces, and the lower spaces is put in position. The cathode is then inserted and the getter strip welded in position. The electrode assembly is then welded to the support and leading-in rods. Specification 324,175, [Class 39(i)], is referred to.