Patent GB-231225-A (GB)
Title: Improvements in vacuum electric tube devices
IPC: H01J19/02
Filed: 1923-12-18
Abstract: 231,225. Robinson, E. Y. Dec. 18, 1923. Vacuum tubes.- A grid for a thermionic valve comprises a complete tube of wire in coil, mesh, or openwork form, secured along its length to one or more rigid supports, each of which present at least two lines of contact to the turns or meshes, the lines of contact being so spaced apart around the grid that the turns &c. are rendered rigid, and the grid is completely registered with respect to the supports. As shown in Fig. 1, a helical wire 1 is secured in a V- shaped or circular groove 3 in a slab 2 of molvbdenum or other metal by binding wire 4 passed around the slab and between the turns. The slab may be replaced by two strips secured together and having their edges splayed to form the groove, or by a single strip folded around a support and with the edges splayed. As shown in Fig. 5, wire 11 is wound around a plain or grooved slab 2 to form loops 12, and is secured by metal strips 13 welded to the slab. In a modification a helix is mounted between two grooved slabs. As shown in Fig. 11, two helices 6 are carried in a support consisting of stamped plates 16, stapled or riveted together, and formed with splayed edges 19 and arched connecting strips 18. In another arrangement, wire is wound helically on a cylindrical or oval former, pressed to keyhole shape, mounted on a rectangular support, and secured by a channel-shaped member. A grid of the type described is particularly applicable to valves having a short discharge gap, and may be mounted with a filament and anode on a rectangular frame, comprising parallel insulating members connected by metal members, as described in Specification 223,293. Two parallel filaments may be mounted as described in Specifications 222,176 and 228,638. As shown in Fig. 18, the grid comprises two wire helices 1 lashed to splayed strips 5, 6. The anode consists of plates 37 bent as shown to form webs. The strips 5, 6 act as shields to confine the discharge to the active part of the anode, and additional shielding strips 38 may be provided. In the arrangement shown in Figs. 19 and 21, two grids 2 of the type shown in Fig. 1 are mounted inside trough-shaped anodes 40, each formed by two webbed plates. The filaments are registered by means of a perforated plate 46 as described in Specification 222,176, and provided with shortcircuiting strips as described in Specification 228,638. The grids are mounted on a frame 26 by means of plates 53 having keyhole perforations. The anodes are tied together by molybdenum wire 61, and are spaced by plates 58 mounted on the frame. The gap between the sides of the anodes may be reduced so as to increase the screening effect due to the grid supports. In another arrangement, a grid, an anode in the shape of a flattened tube, and a filament with a registering spring, are mounted on supports sealed into a foot at one end, and connected together by a glass bead at the other end. The electrodes may be assembled in a jig consisting of two similar parts, each having a recess 79, Fig. 32, to receive the anode, and grooves 80 to receive the supports, the bead and foot being then sealed to the spaced electrodes. According to the Provisional Specification, the jig containing the electrodes may be heated to 1000 - 1200‹ C. for half-an-hour to an hour in order to remove mechanical strain from the electrodes and supports, and to remove occluded gas. Specification 195,691 also is referred to.