GB655568A - Improvements in or relating to the manufacture of thermionic valves - Google Patents

Abstract

655,568. Thermionic valves. HIVAC, Ltd. Nov. 20, 1947, No. 30856. [Class 39 (i)] A method of manufacturing a thermionic valve of the type described in Specification 619,771, having a series of generally planar electrodes disposed in stacked relation with interleaved planar spacing-members of sheet insulating material includes the step of so shaping at least one of said spacing members that it co-operates with at least one of the electrodes during the stacking assembly of the valve elements so as to ensure correct location of said spacing member with respect to said valve electrodes in both transverse and longitudinal directions of the plane of said spacing member, as well as effecting the requisite spacing of the electrode from another electrode. The jig employed in the assembly of the valve elements consists of a flat base-plate upon which are mounted four L-section pillars c, Fig. 3(i), projecting upwardly and defining a rectangle, and two blades d. An anode part 10 having side portions 12 bent upwardly at right-angles is first placed between the blades d, followed by a mica spacing frame 13, grid electrode 17, of the type described in Specification 619,770, [Group XXII], spacing frame 21, and filament subassembly 23 of the kind described in detail in Specification 655,567. Elements 13, 17 and 21 each have four corners which fit snugly into the pillars c. Further elements 21, 17 and 13 are then added, in that order, followed by a second anode part 28. The completed stack is then compressed and the upper ends of the side portions 12 bent over the anode part 28, and preferably welded to the latter to hold the assembly in clamped relation. During the compression of the various parts, the filament wire 25 becomes drawn into the notches 22 of the adjacent spacing frame to provide exact location of the filament and to damp it against vibration. The aperture 14 of each spacing frame 13 is made longer than the adjacent anode zone to provide openings for the removal of occluded gases from the active electrode region. The outwardly-projecting lugs 15 on spacing- member 16 serve as resilient fingers, engaging with an positioning the assembly within the valve envelope, which may be circular, oval, or rectangular in section. If desired, all the spacing members may be similar to the frame 13. The second anode part 28 may be omitted and the two bent-over portions 12 of the first anode part 10 arranged to meet edge-to-edge to form the second anode zone. A tetrode, pentode, or valve having a greater number of electrodes may be constructed by suitable addition to the number of grid electrodes and interposed spacing frames.