GB409410A - Improvements in and relating to electrical discharge devices for production of luminous effects - Google Patents

Abstract

409,410. Discharge lamps. FREEDMAN, P., 6, Hillside Gardens, Highgate, London. Nov. 7, 1932, No. 31367. [Class 39 (i).] A lamp is provided with one or more main electrodes through which is adapted to pass the whole or the greater part of the discharge current, the main electrodes extending individually or in conjunction with others over substantially the entire tube length and closely adherent, over substantially half their surface, to the inner glass walls of the tube. The lamp may be provided with semi-cylindrical electrodes 6, Fig. 1, separated by a gap 8 and each of which extends over half the length of the tube, or with electrodes 10, Fig. 3, which extend over the entire length of the tube and are separated by a gap 12, or with an electrode 16, Fig. 4, which extends over the entire length of the tube and between cylindrical electrodes 14 which are of the same polarity and consist of nickel or iron containing the metal or oxide of strontium or barium. The electrodes may be formed by depositing a silver film on to the glass walls by precipitating silver from ammoniated silver nitrate by means of Rochelle salt, or by wetting the walls with a solution of platinum chloride which is heated to form a platinum film. The metallic films may be coated electrolytically with metal, such as silver, and subsequently coated with one or more of the oxides of calcium, barium and strontium, e.g. by coating electrolytically with the carbonate of the metal and heating to form the oxide. Alternatively one or more of the metals sodium, potassium, lithium, rubidium, and caesium may be introduced into the tube to form a film on the electrode surfaces. The lamp may be filled with one or more of the gases neon, argon, helium with or without a metallic vapour such as mercury, and may be bent to form letters or other designs.