GB641788A - Improvements in or relating to the manufacture of electric discharge tubes - Google Patents

Abstract

641,788. Electrode materials and processing. PHILIPS LAMPS, Ltd. Oct. 15, 1946, No. 30701. Convention date, Jan. 15, 1943. [Class 39 (i)] A method of manufacturing a discharge tube which contains a thin layer of carbon, i.e. of the order of 0.1 mm. or less in thickness, and in which the active layer of the cathode is obtained by the heating and decomposition of an alkaline earth carbonate, comprises vaporizing a material such as barium simultaneously with the decomposition of the carbonate so as to absorb the carbon dioxide evolved and to prevent it from attacking the carbon layer. The thin carbon layer may comprise a shield or electrode, e.g. the heating element of an indirectly cathode applied on a ceramic body. A second gasabsorbing material may be vaporized after the exhaustion and sealing-off to absorb other residual gases; alternatively, one gas-absorbing material only may be used which is vaporized in two portions. The gas-absorbing material is arranged in a holder secured to a lead-in conductor. The Specification as open to inspection under Sect. 91 states that the gas-absorbing material may be vaporized immediately before the decomposition of the carbonate. The carbon layer when used as a heating element for an indirectly heated cathode may be applied outside or inside a ceramic body. This subjectmatter does not appear in the Specification as accepted.