Patent GB-254733-A (GB)
Title: Improvements in or relating to tautening devices for stretched filaments, in electric lamps and discharge tubes
IPC: H01J1/18
Filed: 1926-07-01
Abstract: 254,733. Naamlooze Vennootschap Philips' Gloeilampenfabrieken. July 2, 1925, [Convention date]. Vacuum tubes.-To prevent stretched filaments from sagging when they lengthen upon being heated, a transverse displacement of one or more points of support is produced to keep the filaments taut, by the means of a device that tends auto. maticallv to turn in a determined direction. In the case of a single filament 157, Fig. 16, a point intermediate its ends may be embraced by a spring 161 mounted so as to rotate upon a post 160. Two parallel filaments may be kept taut by the opposite ends of a spring' similarly mounted on a post. In the case of a discharge tube comprising an anode 51, Fig. 7. sealed' to a glass member 52 having re-entrant tubes 53, 54, 55 supporting respectively a conductor 63 connected to the lower end of a cathode 86, a conductor 84 connected to the upper end of the cathode, and a conductor 69 supporting a grid 75, the several parallel filaments of the cathode are engaged by radial arms 94 projecting from a refractory ring 93 rotatable, under the action of a spring 97, on a central tube 57 that conveys a cooling-fluid from the central hollow conductor. The arms 94 are tied together by a wire 96, Fig. 11, to retain their spacing as they move angularly. In this discharge tube, the central tubular conductor 63 is spaced from the surrounding tubes by rings of beads 65 or other insulating projections. The conductor 63 is screwed at its lower end, where it is perforated for the passage of cooling-fluid. into a hood 59 in which radial filament. supporting arms 61 are secured bv screws. The tube 57 is insulated from the hood 59 by a length of glass tube 58 to which both are sealed, the joints being protected from bombardment by a hood 60. To provide for an additional supply of current to point about midway betwen the ends of the filaments, radial conducting arms 89 are welded to the tube 57 and are slit at their ends to clamp the filaments. The outer end of the conductor 84 comprises a tube 82 which is screwed at its lower end into a socket on the cap 80 that seals the end of the glass tube 54, and the lower end of the .conductor 82 is perforated for the flow of cooling-fluid. The lower end of the conductor 84 passes into a ring 85 to which the upper ends of the filaments are secured. A helical wire grid 75 is supported on the rods 73 screwed or tied at both ends to discs 70, 77. To maintain the spacing of the grid wires, wires 76 are wound along the supporting-rods 73. In a modification, the central cooling-tube 57 is composed of several metal sections alternating with glass sections, all welded together, the rotating strainers being mounted directly on the metal .sections of the tube without further insulation. The anode may be provided with plain or screwthreaded flanges 100 by which it may be supported in a vessel containing a cooling-liquid. In the discharge tube shown in Fig. 1 a simple rod 20 ,conveys current to the lower end of the cathode. Collars 30, 31 on this rod provide runways for insulating rollers 29 carrying wire frames 32 provided with eyes 33 through which the several filaments of the cathode pass. When the cathode is heated, the currents in it create a field that tends to rotate the frames 32 and thereby impart a lateral movement to the eyes 33 to keep the filaments taut. This rotarv movement may be assisted by springs. The grid support comprises two U-shaped members 9 crossing at the point 14 where they are tied together. The lower filament-supporting arms 22 are bound by wire to the central conductor and to the filaments. In the filament-straining device shown in Fig. 4a, the wire frame 42, 43 is carried by two widelyspaced insulating rings 37 rotatably mounted on the rod 20, whereby conduction of heat to the rings is reduced. A strainer for U or V-shaped filaments comprises two wire frames insulated from each other and adapted respectively to hold the opposite limbs of the filaments.