Patent GB-389509-A (GB)
Title: Improvements in vacuum electric discharge tubes
IPC: B65G47/14
Filed: 1931-09-17
Abstract: 389,509. Thermionic valves. DAVIS, N. R., 10, Atkinson Road, Sale, Cheshire, BURCH, C. R., 12, Derbyshire Lane, Stretford, Lancashire, LUDLOW, J. H., 8, Bogden Grove, Brooklands, Cheshire, and ASSOCIATED ELECTRICAL INDUSTRIES, Ltd., Millbank, London. Sept. 17, 1931, No. 26087. [Class 39 (i).] A high-power discharge-tube anode which is readily demountable and forms part of the evacuable envelope has two or more active surfaces in the form of similar rectilinear channels arranged parallel or radially, the channels opening into a chamber wherein is disposed a supporting structure for a multiple cathode which has at least one element mounted in each channel and which is insulated from the anode by an insulating member forming a part of the envelope and connected to the anode by a vacuum joint which can be broken and re-made. In one form of construction, Figs. 1 and 3, the cylindrical anode 1 of iron, rustless steel, or copper, formed by machining or a known hot-pressure or quasi-extrusion process, with U-shaped channels 2, has cooling channels 16 spaced about one-eighth of an inch apart and the same distance from the anode active surface and communicating with headers 17, 18, 19. The cooling system is preferably that described in Specification 382,996. The cathode supporting-member 6 has fingers 5 to which the cathode elements 3 are secured by wire eyes 55 mounted on insulating blocks 56. The grid elements 4, of U-shape and stamped from sheet metal, are secured in saw-cuts 49 in angle members 50 bolted to tubes 7 and braced by wires 51, 52. The anode 1 is mounted upon the manifold 10 of the continuously-evacuating pump which is protected by a shield 68 as described in Specification 351,115, through a member 11 of high-grade porcelain. The filaments 3 are held in clamps 22 mounted on guides 20 tensioned by conductors 23. The tube 6 is welded to a tube 25 secured to a disc 14 through which a tube 27 passes to supply cooling water to the member 6. The filaments 3, nine in number, are arranged in groups of three and fed by a threephase supply of which the member 6, preferably earthed, constitutes the star point. The upper ends of each filament group are connected to a bus-bar 29 supported from a disc 31 by watercooled tubes 30 which constitute the phase lead-in of the group. The disc 31 is separated from the disc 14 by a porcelain ring 33. The cathode cooling water passes through the tubes 6 and 25 and then through the three groups of tubes 30 in parallel. The grid supporting tubes 7 are connected at their lower ends to a header 46 and are welded to a copper disc 12 in which appropriate inlet and outlet pipes 45 supply cooling water to the tubes 7. The discs 12, 14 are separated from the anode 1 and from each other by porcelain rings 13, 15. The envelope joints are protected from heat radiated directly from the cathode or indirectly by single or multiple reflection by shields 58 .. 62. An auxiliary ring 63 between the anode 1 and the porcelain ring 13 has a watercooling channel 64, is accurately ground to the anode, and sealed thereto by vacuum grease or oil. A similar ring 66 with a cooling channel 64 is secured to the anode by a grease-sealed joint and to the ring 11 by a semipermanent joint 41. The joints 36 .. 42 are semipermanent, preferably of bitumen braced by rings 43. In a modification, the anode consists of a plane channelled block facing which are insulated metal blocks carrying the upper and lower ends of the filament. In a further modification, Fig. 5, the anode is mounted centrally in the device, and the filaments 3 are supported by members 5 from a ring-shaped tube 82 through which water is circulated. A hydraulic lifting-ram or other constrained lifting-gear may be provided for lifting the cathode and grid portions out of the anode in accurate alignment.