GB1212208A - Method of and apparatus for differentially toughening glass sheets - Google Patents

Abstract

1,212,208. Differentially tempering glass sheets. TRIPLEX SAFETY GLASS CO. Ltd. 10 July, 1968 [10 July, 1967], No. 31614/67. Heading C1M. A method of differentially toughening glass sheets comprises directing a fluid quenching medium from a first source on to the opposite faces of a heated glass sheet in a predetermined region which is to form a vision zone from apertured blowing faces of one or more pairs of auxiliary quenching boxes disposed on opposite sides of the sheet, the auxiliary quenching box or boxes on each side of the sheet defining a number of compartments and the pressure at which the fluid quenching medium is supplied to each compartment being independently controllable, and a fluid quenching medium from a second source, which is separate from and at a different pressure from the first source, on to the opposite faces of the sheet in the remaining regions thereof. A heated bent glass sheet 1 vertically suspended from tongs is located between and equidistant from opposed pairs of complementary shaped blast heads. Each blast head comprises a main quenching box 5 or 6 having apertures 7 and connected to the second and lower pressure source of fluid via conduits 8 or 10, and at least one and preferably three auxiliary quenching boxes 11a-11c or 12a-12c. Each auxiliary box is provided with its own apertured blowing face, e.g. 14a-14c and is connected with a higher pressure fluid supply means 23 through a flexible conduit 19 extending through the main quenching box 5 or 6, each auxiliary box having its own regulating valve 21 to separately and independently control the pressure in each said box. Each auxiliary box is located in the main quenching box 5 or 6 in a fluid-tight seal 17 which allows the auxiliary box to be adjusted towards or away from and/or angled to the main box. Preferably the central box 14b-15b is supplied with air at 8 p.s.i. and boxes 14a, 14c, 15a, 15s with air at 6 p.s.i. The internal cross-sectional area of each base 19 is equal to at least twice the total area of the apertures on the respective auxiliary quenching head. In an alternative embodiment only a single auxiliary quenching box is used on each blast head, but it is subdivided into three separate and independent compartments. During tempering the blast heads may be cyclically oscillated in or out of phase.