GB353624A - - Google Patents

Abstract

353,624. Thermionic valves. LOEWE, S., 10, Wiesenweg, Steglitz, Berlin. June 7, 1930, No. 17717. Convention date, June 7, 1929. [Class 39 (i).] In a method of manufacturing highly emissive cathodes in valves with multiple electrode systems in which the cathodes are coated with emissive substances vaporized by eddy current heating, the coating substances for the several cathodes are arranged in a single system, heating of which vaporizes the substances for the several systems simultaneously. The cathodes are coated with a light metal such as barium produced from a barium reaction compound such as barium acetate or barium oxide and silicon. This compound is enclosed in pockets 5, 9, 10 in the anode 2 of the power stage in a multiple stage valve 1, having two amplification stages 6, 7, 8 and 11, 12, 13 and. a power stage 2, 3, 4. The pockets 5, 9, 10 are arranged so as to open on to the respective cathodes to be coated, i.e. 4, 8, 13 respectively, and on heating the electrodes of the power stage barium is vaporized and deposited on the cathodes of the several systems simultaneously. The reaction compound may be arranged on a carrier coheatable with one of the electrode systems. Cylindrical electrode systems may be used and the vapour passed axially through the systems as in Fig. 3. Metal sieves 17, forming electric screens arranged between the systems, permit the passage of vapour whilst providing efficient screening. A residue of unvaporized metal or compound may be left in the pockets whereby occasional overloading of the power stage or normal operation vaporizes the metal slowly to renew the barium coating on the cathodes.