GB501865A - Process of making glass articles having optically accurate surfaces and articles produced thereby - Google Patents

Abstract

501,865. Glass manufacture. CORNING GLASS WORKS. Jan. 31, 1938, No. 2991. Convention date, Feb. 5, 1937. [Class 56] A process for pressing glass articles having optically accurate surfaces consists in arranging for those parts of the mould which shape the optically important surfaces of the glass to be cooler than the other portions, so that the glass is caused to stiffen first at the opticany important surfaces and any shrinkage which may occur is confined to the optically unimportant areas. A mould for pressing a headlamp reflector comprises an outer shell 11, Fig. 2, with an insert 12 which is preferably formed of metal of a comparatively low conductivity and is separated from the wall of the shell by an air space 13. The plunger 17, which forms the optically important surface of the reflector, is cooled by circulating water. Reflectors of the kind shown in Fig. 4 may be made in a mould formed with shaping- cavities 26, Fig. 5, the ends of which form the optically important surfaces. These ends are formed by insets 27, 31 of material having a higher heat conductivity than the mould body. Openings 28 are drilled in the mould body close to the cavities 26 to form a relatively thin wall at the parts which shape the optically unimportant areas of the reflectors.