GB696850A - Improvements in or relating to the manufacture of glassware - Google Patents

Abstract

696,850. Treating glass. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. April 27, 1951 [June 10, 1950], No. 9907/51. Drawings to Specification. Class 56. [Also in Group XL (a)] Glass, especially for use with fluorescent lamps, is heated with a gaseous fuel which has mixed therewith sulphur dioxide or other sulphur compounds. The sulphur dioxide combines with the alkali in the glass to form alkali sulphite or sulphate which may be removed by water, the resultant surface being rich in silica and slippery is more resistant to nicking and scratching, avoids the chipping of the phosphor when used for making fluorescent lamps, and when used for exhaust tubing prevents the mercury from sticking to the surface. Glass may be so treated with sulphur dioxide before or after the application of a phosphor thereto. The sulphur dioxide gas fuel mixture may be applied to a lamp envelope over the entire inside and/or outside surfaces while the lamp is rotating, or to an area at each end on the outside and/or inside surfaces during the shoulder forming or end sealing operations. The glass is heated at 300-700‹ C., desirably above 450‹ C. The proportion of sulphur dioxide used with a sulphurless heating gas is 0.0025-0.015 pound of sulphur dioxide per 100 cubic feet of gas, the preferred range being 0.005-0.01 pound per 100 cubic feet. 'Instead of adding sulphur dioxide to the heating gas miscible sulphur compounds such as gaseous or readily vaporisable compounds of sulphur, e.g. hydrogen sulphide or carbon bisulphide, may be substituted. The application of the invention to flare making, stem making, lehring, sealing-in, and exhausting in the production of lamps is also described and illustrated.