GB1034333A - Improvements in or relating to the manufacture of flat glass - Google Patents

Abstract

In the manufacture of flat glass, particularly in ribbon form, in which the glass is advanced over a bath of molten metal, a gas which is chemically inert to the molten metal is bubbled through the latter to remove impurities. A ribbon of glass 22 (Fig. 3, not shown), is advanced over a bath of molten tin 12 contained within a tank 13, 14, 15. A roof structure bridges the bath and consists of a roof 17, end walls 18, 19, side walls 20, and also an intermediate wall 27 situated near the end of the bath. A protective gaseous atmosphere is fed into the headspaces above the glass by ducts 20a, 20b, 20c. Inlet passages 32 extend through the floor of the tank in the regions of the delivery and take out of the glass ribbon to and from the tank. The tank side walls have formed therein a series of pockets 38, (Fig. 4, not shown), each of which provides a gas injection means 39, exhausts 41 being incorporated in equivalent pockets 40 in the superstructure and the depth of metal in the pockets being greater than in the bath. A gas which is chemically inert to the molten metal is bubbled through the latter via passages 32, 39, and is preferably a mixture of four parts nitrogen to one part hydrogen, thus accelerating the vaporization of impurities in the molten metal. The passage of the gas through the molten metal is so chosen that the gas does not come into contact with the glass ribbon. The composition of the protective gas and of the gas bubbled through the molten metal may be the same as that disclosed in Specification 1,034,332.