GB319686A - Improvements relating to electrical discharge devices - Google Patents

Abstract

319,686. British Thomson-Houston Co., Ltd., (Assignees of Charlton, E. E.). Sept. 26, 1928, [Convention date]. Vacuum tubes; low-pressure metallic - vapour apparatus.- Alkali metals are. localized in electric discharge devices by coating the anode or a carrier other than an electrode with a substance absorbing the alkali metal and releasing it on heating. Caesium and rubidium may be localized by a coating of a colloidal suspension of graphite in water. In a half-wave rectifier, Fig, 1, the inner surface of the anode 3 surrounding the filament 6 is coated with this suspension. The tube is evacuated and heated by high-frequency currents to tree metal parts of occluded gases and to liberate caesium from a mixture of caesium chloride and calcium in a nickel casing 10. The caesium cleans up residual gases, and the excess of caesium is absorbed by the coating inside the anode and is liberated during operation of the tube to form a metallic atmosphere. In a 3- electrode valve, the suspension is applied to two carriers secured to the filament leads and extending parallel to the limbs of the hairpin filament, caesium being liberated during operation of the valve. The Specification as open to inspection under Sect. 91 (3) (a) of the Acts states also that the suspension may be applied to the anode or the grid of a three-electrode valve and describes the following :-In a neon lamp for radio transmission of pictures, nickel or iron flat electrodes 22, 23, Fig. 3 (Cancelled), so spaced that the discharge takes place between their outer surfaces have their surfaces coated with the suspension. Caesium or rubidium are freed from a pellet 30 and are absorbed by the suspension and retained thereby during operation of the tube to lower the cathode drop and starting potentials of the tube. In a lamp used as a current or voltage indicator or for illumination, hollow, cylindrical, nickel or iron electrodes mounted side by side are coated externally with the suspension and contain caesium azide or a mixture of caesium or rubidium chloride and calcium, the suspension localizing the alkali metal under all conditions and preventing discoloration of the bulb. This subject-matter does not appear in the Specification as accepted.