GB245146A - Improved manufacture of oxide cathode discharge tubes - Google Patents

Abstract

245,146. Naamlooze Vennootschap Philips' Gloeilampenfabrieken. Dec. 24, 1924, [Convention date]. Drawings to Specification. Vacuum tubes; R÷ntgen-ray tubes.-A process of making an oxide-cathode discharge tube consists in mounting in a discharge tube a metal core having its surface partly or wholly oxidized, and one or more electrodes carrying one or more compounds, such as the azide, of one or more alkaline earth metals, heating the electrodes by currents induced by a high-frequency magnetic field to decompose the azide and precipitate on the core the alkaline earth metal, which is subsequently oxidized. The core may consist of a wire or other body of nickel or a noble metal, or of platinum-rhodium with or without a coating of copper. Barium azide, dissolved in water, is trickled on the inside of one or more anodes, and the water evaporated before mounting the anode in the tube. After the preliminary evacuation the anode is brought to incandescence by induced currents so as to decompose the azide, and deposit barium on the core. Oxidation of the layer of barium may be effected by the oxidized surface of the core, or by admitting oxygen to the tube. Gas is removed from the grid by electron bombardment from the anode, the grid being maintained at a positive potential and the tube connected with the exhaust pump. During this operation the cathode may be protected from bombardment by maintaining it at the same potential as the anode, and by heating slightly. Any barium deposited on the tube serves to improve the vacuum or to remove impurities from the gas filling. Specification 214,262 is referred to.