Patent GB-565949-A (GB)
Title: Improvements in and relating to the manufacture of grid-like electrodes for electricdischarge tubes
IPC: H01J19/00
Filed: 1943-04-02
Abstract: 565,949. Making grid electrodes. MULLARD RADIO VALVE CO., Ltd., and MYERS, L. M. April 2, 1943, No. 5337. [Classes 83 (ii), 83 (iii) and 83 (iv)] Coiling; soldering; jointing by forging ; screwing.-Hollow grid electrodes with longitudinal wires for electric discharge tubes are made by winding the wires about one axis, attaching strips of softer metal thereto parallel to the winding axis by applying pressure so that the grid wires are at least partially embedded in the strips and bending the assembly about an axis at right angles to the winding axis. In one form, a nickel wire 29, Fig. 5, is coiled on a standard grid winding machine over a pair of backbone wires 30 and cut to remove one set of wires, whereupon the other set with the backbone wires are placed in a groove 22 in a jig containing a pair of pins 23 round which a copper ring strip, at this stage in wire form 31, is wound and secured by screws 25. -The upper jig member 26, which has a rib 27 to fit between the backbone wires 30 and a pair of holes to fit the pins 23, is now placed over the pins and pressed down so as to flatten the ring wire into strip form and to embed the grid wires therein. The backbone wires 30 are then removed and the sections cut to size and then bent to convert the strips 32 into ring form. The grid wires may project at one end so that they may be inserted into a tubular metal support 34. The wires may be soldered to the rings and to the support and the ends of the rings soldered by winding solder wire round the parts and heating by eddy currents in a reducing atmosphere. The parts are held in position during soldering by a binding wire 33 wound round the grid wires. In another form, the wire is fed from a spool round a tension pulley 48 and guide rollers and over a lead screw 44 geared to a helically grooved mandrel which is driven by a motor 50. The mandrel consists of a hard steel central part 53 and two outer steel or copper parts 54 urged outwards by springs on dowel pins 57, but normally held contracted by bolts 56. The central section carries pairs of posts 58 on which the wire 59 to form the strips is wound as in the previous form, the ends of the wire being secured to a spring- pressed collar 60 to keep it taut. After the grid wire is wound on the mandrel, the bolts 56 are removed to allow the mandrel to expand and hold the wires taut and the ring 60 and spring 61 are then removed and jig plates 62, Fig. 15, applied to the posts 58 and the parts assembled in a press so a,s to flatten the strip wires and unite them to the grid wires. The assembly is then bent as in the previous form. The lead screw and also the mandrel may have the screw-thread applied thereto by winding thereon a wire 71 of diameter equal to the desired pitch with the consecutive turns in contact. This wire may be of tungsten or molybdenum and may be brazed in position. The strip and grid wire assemblies may be stoved in a vacuum oven for degassing. The wires may be copper plated. Specification 470,618 is referred to.