GB445738A - Improvements in and relating to electron discharge devices - Google Patents

Abstract

445,738. Discharge apparatus. ROGERS RADIO TUBES, Ltd., 100, Sterling Road, Toronto, Canada. April 4, 1935, No. 10462. Convention date, April 4, 1934. [Class 39 (i)] A vacuum discharge device has a cathode, a rodlike anode and a control grid disposed externally to the cathode and anode and formed with reentrant or constricted portions located in the region between the cathode and the anode. More than one anode may be provided with a re-entrant portion of the grid between each anode and the cathode. As shown in Fig. 2, the indirectlyheated cathode 11 and the anodes 12, 13 are surrounded by the helically wound control grid 15 and spaced apart by preferably ceramic members 17, 18. A further mica spacer 20 may be rectangular in shape with a central aperture, for positioning the electrode assembly in the envelope. The grid 15, Fig. 3, is constricted between the cathode and each anode and the ratio of the distance d between the constrictions to that between the cathode and anode is preferably 10 per cent and not more than 33 per cent. A large amplification factor is obtained and the grid may be designed to give a " variable-mu " effect. A directlyheated filamentary cathode may be employed. The anode rods may be of tungsten, molybdenum or nickel, and are operated at white heat. In a modification the anode rods are electrically connected within the valve. A metal coating on the envelope is preferably connected to the cathode and reduces ill effects of wall charges.