GB928868A - Method of drawing sheet glass - Google Patents

Abstract

928,868. Sheet glass manufacture. G.B.D., SOC. ANON HOLDING. Oct. 23, 1961 [Nov. 17, 1960], No. 37954/61. Class 56. Sheet glass is drawn out to a thinner sheet by progressing a continuous, fire-polished sheet 1 of uniform thickness over the surface 5 of a molten metal bath 2 while maintaining a non- oxidizing atmosphere 6 over the bath, re-heating as at 7 the moving sheet over a transverselyextending strip-like zone at a position where the viscosity exceeds 10<9> C.G.S. units and such that the marginal edges 13 of the sheet are excluded from the re-heating so as to retain substantially the initial viscosity and the strip is raised above softening temperature whereby the viscosity thereof is less than 10<7> C.G.S. units, drawing the strip horizontally in contact with the molten metal bath in the direction of the longitudinal axis of the initial continuous sheet to produce a continuous sheet 9 of uniform thickness less than that of the initial sheet save at the excluded edge 13, which are of substantially the original thickness, and two intermediate portions 14 of narrow width whereat the thickness varies, progressively cooling the sheet 9 on the surface of the molten metal bath in the non-oxidizing atmosphere to re-establish thermal homogeneity throughout the width of the sheet 9, and passing the sheet 9 into a tunnel kiln with horizontal carrying rolls to cool the sheet slowly. As shown in Fig. 3b, the re-heating is by tubes 16 of ceramic material carrying coils 17 of resistance wire extending from inwardly of the edges 13 of the sheet 1. Screens 18 may also be used to shield the edges 13 from the heating. As shown in Fig. 4a a heating plate 19 forms the base of a trough 22 of refractory material set into the superstructure 4 and covered by a refractory slab 23 with two outlet openings 24 and a central opening for a burner 20 fed by a gas-air mixture from two pipes 21. A screen 18 at each side may be provided. Reference has been directed by the Comptroller to Specification 769,692.