GB1446413A - Molding glass articles - Google Patents

Abstract

1446413 Moulding glass PILKINGTON BROS Ltd E COEN E J PARRY and R C STEERE 18 Oct 1973 [20 Oct 1972 16 May 1973] 48446/72 Heading C1M A glass article, e.g. a lens blank 19 (Fig. 1), is prepared by supplying a gob of molten glass to an open press mould, closing the mould to shape the gob, regulating the mould temperature and time of closure so that, on completion of moulding, the glass at the surface of the article has a viscosity of at most 10<SP>10.5</SP> poises and the glass at the centre of the article has a viscosity of at most 10<SP>8</SP> poises, opening the mould, and rapidly transferring the thermally inhomogenous moulded article from the mould, without deforming the shaped article, while the surface viscosity remains not above 10<SP>10.5</SP> poises, directly into a cooling medium in which the glass is rapidly cooled to a temperature at which the surface viscosity is at least 10<SP>12.5</SP> poises. In one embodiment (Fig. 1) molten glass gobs are supplied from shears 42 (Fig. 4, not shown) alternately to bottom mould parts 3, 23 via shoots 35, 36. The glass is shaped by pneumatically operated plungers 4, 24. Sensing and control means are provided to facilitate heating or cooling of the bottoms and sides of the lower mould parts 3, 23. Control and timing means may also be provided to synchronize the glass feeding, glass moulding and ejection of the moulded article (Fig. 7, not shown). After withdrawal of the plungers 4, 24, the lower mould parts 3, 23 are rotated (by means of tables 5, 25, on which the parts 3, 23 are mounted) about horizontal axles 6, 26, allowing the moulded products 19 to fall into cooling fluid 17 maintained, at a desired temperature, in tank 16, so that the glass is tempered. The cooling fluid may be an oil of flash point above 300‹ C., or molten inorganic salt. The tempered product, e.g. lens blanks 19, may be removed from tank 16 by conveyer 18, and may subsequently be annealed. In an alternative embodiment, Fig. 13, the moulded product (e.g. lens blank A) may be ejected from lower mould part 3 by a jet of compressed air from nozzle 250 (e.g. at a pressure of 0À7-4 kg./cm.<SP>2</SP>), and allowed to fall, through trajectory B, into tank 16. In either of the above embodiments the quenching may be carried out by one or more gas streams.