GB818423A - Electric discharge lamp - Google Patents

Abstract

818,423. Fluorescent discharge lamps. SYLVANIA ELECTRIC PRODUCTS Inc. Oct. 25, 1956 [March 13, 1956], No. 32607/56. Class 39(1). A high pressure mercury vapour lamp comprises an inner discharge tube 4 surrounded by a light-transmitting outer jacket 2 coated on the inside with a phosphor 1 which, in operation, absorbs light from the mercury discharge and is stimulated thereby to emit yellow light and also light of shorter wavelengths, and coated on the outside with a yellow filtercoating 9 adapted to transmit the yellow light and to absorb the light of shorter wavelengths. The discharge tube 4 contains a high pressure filling of an inert gas and a quantity of mercury and has two main electrodes 6, 8 sealed into it. The filter coating may be formed by spray-coating the envelope 2 with a paste containing copper sulphide, iron sulphide and clay, firing to allow the copper and iron to enter the glass and then removing the excess paste leaving the bulb stained a greenish yellow. Alternatively a yellow ceramic glaze may be formed en the envelope by coating it with a mixture of 90 parts of low melting glass and 10 parts of cadmium sulphide and then heating it to a temperature high enough to fuse the low melting glass. The phosphor coating may have a molecular composition of 2À65 SrO, 0À20ZnO, 1À00P 2 O 5 and 0À06SnO. The tube 4 is supported by means of collars 22, 24 on a U-shaped wire 20 which is supported in envelope 2 by means of resilient metal fingers 28, 30, 32. An auxiliary electrode 10 is provided and connected through a resistor 34 to support wire 20.