GB866466A - Improvements in or relating to electric discharge lamps - Google Patents

Abstract

866,466. Discharge lamps. SYLVANIA ELECTRIC PRODUCTS Inc. June 3, 1959 [June 18, 1958(2)], No. 19049/59. Class 39(1). A fluorescent electric discharge lamp includes two lead-in wires which support between them a coiled refractory wire electrode the central region of which has an electronemissive coating and the regions between this coating and the supports are coated with an insulating, refractory, firmly adhering material. The lead-in wires, of the preferred embodiment, support in addition to the cathode auxiliary anodes and a nickel shielding member, the latter being disposed between the coiled electrode and a stem press in the end of a glass envelope. The dimensions of the various elements are fully discussed. The electrode may be of the coiled-coiled-coil type, at least at its central portion. Suitable coatings of the oxides of strontium, calcium and barium with a small proportion of zirconium oxide are placed on the central portion 12, of the electrode, the parts 10, 11 being coated with insulating material such as the oxides of aluminium or titanium. The emissive layer preferably partially overlaps the insulating layer. The support rods may be housed in ceramic tubes except at the points when the rods are joined to the various electrodes. The tube may have a gas filling of 80% neon and 20% Argon, at about 1 mm. of mercury total pressure and the tube may contain sufficient mercury to yield an operating partial pressure of at least 10 microns, or the filling may comprise 15% helium and 85% argon. The electrode may be used in a purely Argon filled lamp, which does not have the auxiliary anodes, and the gas pressure may be 1 mm. of Hg. The alumina or titania is coated on to electrode by sintering at 1100‹C. or 1700‹C. respectively or by a cataphoretic method that part of the coil in which the coating is not required being temporarily coated in wax. The wax is removed and the emissive layer is then applied. Specification 863,724 and U.S.A. Specification 2,771,589 are referred to.