GB997961A - - Google Patents

Abstract

997,961. Glow discharge lamps. P. J. KAYATT. Aug. 8, 1961 [Aug, 18, 1960], No. 28677/61. Heading H1D. During manufacture of a glow discharge lamp, an assembly of electrodes, at least one of which is coated with barium azide, is mounted within an envelope and heated to decompose the barium azide. At least two evolutions of nitrogen occur, heating and exhausting being terminated after the start of the second gas evolution to leave a small amount of nitrogen within the coating, after which the envelope is filled with an inert gas and sealed. The gas pressure, the amount of nitrogen left in the coating and the spacing of the electrodes are such that in use the lamp exhibits an unstable cathode flow which continually changes its position, and simulates the flickering flame of a candle. The electrodes 1 may be of iron, nickel, ferrous alloy, or preferably of nickel-plated iron, of 5 to 6 mils thickness, and may be cleaned by use of carbon tetrachloride before being mounted on glass stem 3, boiled in an isopropanol solution, rinsed in water and dried in air at 150%. The electrodes are coated with 15% barium azide in water, iron oxide present on the edges also being brushed over the surface, and dried in air at 80‹ to 100‹ C., this process being repeated until four or more coats have been applied. The electrodes are mounted within envelope 4 with a mutual spacing of 0À5 to 2 mm, e.g. 1 mm., at the top and 1 to 4 mm. adjacent stem 3, the envelope being evacuated at room temperature and then at 350‹ to 400‹ C., e.g. 375‹ to 380‹ C., until after the second gas evolution has started, after which pumping is terminated and the envelope is filled with neon and/or helium, with or without 2% hydrogen, at 70 to 120, e.g. 100, mm. of Hg. After sealing, the lamp is operated for a few hours at double the normal current density of 5 to 30 ma./sq. cm. The mounting of one electrode may be such that tapping of the envelope is sufficient to alter the electrode spacing. Wire, rather than plate, electrodes may be used and there may be more than one pair in the envelope. The path of the moving glow may be influenced by use of electrostatic or electromagnetic fields, or by cutouts in, or additions to the electrodes to vary their mutual spacing.