Patent GB-294125-A (GB)
Title: Improvements in vacuum electric tube devices
IPC: H01J19/02
Filed: 1927-03-10
Abstract: 294,125. Robinson, E. Y., and Metropolitan-Vickers Electrical Co., Ltd. March 10, 1927, Vacuum tubes.-A valve has a cathode, a control grid, a shielding grid and an anode, all extending upwards and supported from a single reentrant part of the envelope, and the control grid or anode is supported at both ends through one or more insulating members solely and directly from the shielding grid or cathode, or from supports connected thereto. Several arrangements of shielding grids and shielding members are described. As shown in Fig. 1, the anode 6 is supported at both ends through glass beads 23 from a rod 11 carrying the shielding grid 7. The control grid 5 is mounted on a rod 12 carrying a glass bead supporting the loop of the filament 4. The rods and filament are mounted on a reentrant stem 3 having internal and external screens 38, 14. The shielding grid is formed of a helix of fine pitch and the end is closed by a metal cap 13. The anode lead 28 is taken to a contact on the top of the envelope. An external metal shield is provided with a terminal. The grids may be of the kind described in Specification 231,225. In the valve shown in Fig. 5, the shielding grid 7 consists of wire or mesh supported on channel members, and a block 55 of insulating material such as steatite or porcelain is mounted on the supports 49 for the shielding grid, and serves to space and support the control grid and filament, which is of the kind described in Specification 285,536. The anode 6 is mounted on the supports 49, at one end through glass beads 66, and at the other by means of an insulator 63 secured by tabs 64 to the supports 49. In the valve shown in Fig. 8, the spring supports 75 for a double hairpin filament 4 are mounted on the supports 74 for a control grid, which are secured at the lower ends to the supports 80 for the screening grid by washers 76, and at the upper ends through glass beads 78 and wire supports. The anode 6 is mounted directly on the stem. A flanged shield 81 is mounted on the beads 78, a shield 85 is mounted around the supports 80, a plate shield 86 is mounted on the stem, and an external shield 84 is provided. In a modification, the supports 74 are secured at both ends by washers. In a further arrangement, the shielding and control grids and the cathode are spaced at both ends by rings or by perforated discs secured to the supports for the screening grid, and the anode may be spaced by rings around the shielding grid. In the valve shown in Fig. 14, the anode 6 is supported through porcelain washers 110 on a U-shaped frame 115 mounted on the pinch and carrying springs 113 supporting the filament, the control and shielding grids being supported independently on the stem. In a modification, the control grid is supported in a similar way on the filament frame, and the shielding grid and the anode are mounted on the stem. The axis of the electrodes may be inclined at an angle of 45‹ to the vertical. The external metal shield may consist of a slit tube fitting on the envelope. The internal shield may be in the form of a helical wire or mesh mounted around the electrodes and a conical shield may be used. Another form of shield consists of a central ring with two sets of segments extending in two layers, the segments of one layer covering gaps in the other layer. Specification 285,537 also is referred to. Reference has been directed by the Comptroller to Specifications 134,542, 145,421, 166,241, 230,011, and 255,441.