Patent GB-414753-A (GB)
Title: Improvements in and relating to vacuum electric discharge tubes
IPC: H01J19/02
Filed: 1933-02-09
Abstract: 414,753. Discharge apparatus. BURCH, C. R., 12, Derbyshire Lane, Stretford, Manchester, LUDLOW, J. H., 8, Brogden Grove, Brooklands, Cheshire, and ASSOCIATED ELECTRICAL INDUSTRIES, Ltd., Crown House, Aldwych, London. Feb. 9, 1933, No. 4022. [Class 39 (i).] In a screened grid tube, particularly a valve for generating short waves, having electrodes of cylindrical shape, the screening grid supporting member with its terminal portion forms a partition starting from outside the envelope so as to divide the discharge space into two parts, one containing the anode, and the other containing the cathode and control grid, the external screen being conductively continuous with the terminal member around effectively the whole periphery ; the valve may be dismountable. As shown in Fig. 1, a copper tube 45, supporting the screening grid 2, is secured to a terminal ring 16 connected with an external ring 25 ; the partition thus formed is extended to the external screen by annual members 53, 59. The anode 1, fixed upon an evacuating pump, has a fluidcooled channel 5 and extends through a part 8 to a ring 9 forming an accurate fit with a flanged ring 10, the oil or grease seal being protected from bombardment by a flange 14. A quartz ring 13 is mounted between the rings 10, 16. The ends of a filament cathode 4 are supported by rods 41 from lugs 40 on semi-cylindrical members 36<a>, 36b, connected respectively by rings 37, 39 with terminal rings 20, 18. The members 36<a>, 36b are closely spaced from the tube 45. An insulator 42, carried by the lugs 40, supports the bights of the filament. The rings 16, 18, 20 are spaced by quartz rings 17, 19, and the ring 18 is connected with a ring 30. Joints are sealed by bitumen 31. The control grid 3 is connected with a terminal disc 21<a> by a tube 32 which is slotted to allow the passage of the lugs 40. The terminals are provided with fluid cooling channels. Two washers 48, 49, secured to the ring 30, carry two condensers 51, 56, the condenser 51 being connected between the screen grid and the earthed end of the cathode, and the condenser 56 connected across the filament. In a pentode, Fig. 2 (not shown) the suppressor grid is supported by a tube to which one end of the filament is connected. In another valve, Fig. 3 (not shown) filament supporting rods are connected with end discs, and the tubes supporting the control grid and screen grid are connected with flat terminal rings. In the valve shown in Fig. 4, the screen grid 2 is supported at both ends by tubes 45, 45<a>, connected with rings 16, 16<a>, and the control grid 3 is carried by a rod 32<a>. One part 51 of a screen grid condenser is connected between the ring 16 and an external screen 83, and another part 51<a> between the ring 16<a> and a screen 79 connected with an earthed pump 77. In another valve, Fig. 5 (not shown) the anode is arranged on the inside, and the filament on the outside of the grids, and a cylindrical filament condenser is mounted around the filament supporting tube. The length of the valve may be reduced by extending the anode into the main insulating tube, Fig. 6 (not shown). In the permanentlysealed valve shown in Fig. 7, a disc 93, carried by the supporting tube 45 for the screen grid, is connected with an external annular terminal 16 by six or more radial copper strips 94 sealed through a glass tube 89 sealed to the anode 1. The strips may be replaced by a corrugated disc sealed trough the tube 89, Fig. 10 (not shown), or the tube 45 may be sealed between two glass envelope portions, Fig. 8 (not shown), or connected with another tube sealed to those portions, Fig. 9 (not shown). Specifications 382,996 and 389,509 are referred to.