GB536385A - Improvements in or relating to electric gaseous discharge tubes and methods of manufacture thereof - Google Patents

Abstract

536,385. Discharge lamp envelopes. ARNOLD, J. C. (Plastic Lights, Inc.). Dec. 8, 1939, No. 31796. Drawings to Specification. [Class 39 (i)] (Also in Group XXIII] In an electric discharge lamp the envelope is formed from plain lead glass coated with a ceramic material which will enable the lamp to be seen in the daytime with the current off ; the coating is translucent and has a melting point substantially the same as the lead glass. Suitable compositions for the coating are as follows, parts being given by weight:-(i) Borax 6.9, feldspar 3.9, quartz 20.7, fluorspar 9.1, lead oxide 55.3. (ii) Borax 34.4, boric acid 4.3, feldspar 34.6, quartz 19.1, aluminium oxide 3.2, fluorspar 3.5. (iii) Borax 38.2, feldspar 28.2, quartz 20.3, soda ash 10.2, cryolite 2.2. (iv) Borax 34.9, feldspar 28.9, quartz 12.0, soda ash 5.3, nitre cake 13.2, aluminium oxide 2.6, sodium silico fluoride 3.0. (v) Borax 32.0, feldspar 33.2, fluorspar 2.12, cryolite 2.12, flint 30.5, tin oxide 7.0. (vi) Borax 29.64, feldspar 30.78, fluorspar 3.0, cryolite 2.0, flint 28.22, sodium carbonate 2.38, zinc oxide 5.0. (vii) A ceramic enamel including molybdic acid, low lead flux and lead molybdate. The coating is fused on the lead glass and may have a different colour from the colour given by the luminous gas. The tube when used as an advertising sign may be divided into luminous parts by opaque sections. The tube during its heat treatment may be supported in pans containing as a bedding plaster of Paris ground asbestos, talc, mica or finely divided quartz or silica. The black coatings may be fused on before the other coatings.