GB147817A - Improvements in and relating to enclosed electric arc devices - Google Patents

Abstract

147,817. British Thomson - Houston Co., (Assignees of Clough, J. H.). Oct. 30, 1915, [Convention date]. Arc lamps; vacuum tubes. -A sealed envelope contains a refractory cathode 2 operating at incandescence, a rare gas at a pressure high enough to prevent electrical disintegration of the cathode, and an anode 3 wholly or partly consisting of a metal chemically active towards impurities in the gas. Alkaline-earth metals, magnesium, and titanium are suitable for this purpose. The gas pressure may range from several mm. of mercury to about an atmosphere. Argon at 5-12 cm. of mercury, or neon at about a quarter of an atmosphere, are suitable fillings for devices with calcium anodes. Low electric pressures are sufficient, especially after working ior some time. In a rectifier, the voltage peak at the beginning of each half-wave for which the device is conductive is lower than the voltage at the middle of this half-wave. The cathode 2 of tungsten, tantalum, carbon, &c. may be provided with an enlarged arcing end. The envelope may be of low-expansion sodium-magnesium boro-silicate glass. Specifications 152,694 and 157,041 are referred to.