Patent ID: 6470711
Filing Date: 2002-10-29
Classification: C03B,Y10S

Abstract:
A furnace for heat treatment of glass sheets, comprising:a chamber containing a plurality of conveyor rollers, the conveyor rollers supporting a glass sheet being treated for advancement along an advancement direction, said glass sheet having a first surface and an opposite second surface, the second surface being supported in direct, heat transmission contact on said plurality of conveyor rollers; combined irradiation and first convection heating means arranged in said chamber above said glass sheet supported on said plurality of conveyor rollers and comprising radiating panels arranged side by side along said glass sheet advancement direction, the radiating panels being provided with passage holes, overlying heating units, and fan means for conveying air heated by said heating units to said passage holes, with each one of said panels being brought to a preset temperature by a corresponding one of said overlying heating units, said preset temperature being sufficiently high that said glass sheet first surface is simultaneously heated by heat radiation and forced air convection, said passage holes being provided with a flared configuration allowing passage of a hot air flow provided by said fan means at a speed that is adjustable so that the hot air flow striking the glass sheet first surface from exits of said passage holes spreads across the first surface to ensure temperature uniformity all over said first glass sheet surface, particularly at the start of the heat treatment; and second convection heating means arranged in said chamber below said plurality of conveyor rollers and along said advancement direction of the glass sheet and provided with a plurality of nozzles arranged in a configuration such that a first portion of the plurality of nozzles distribute hot air over the glass sheet second surface and at least a second portion of the plurality of nozzles force hot air to directly strike corresponding ones of the conveyor rollers for simultaneously heating said glass sheet second surface by forced air convection and cooling said plurality of conveyor rollers to temperatures to prevent greater expansion of the glass sheet second surface than the glass sheet first surface, due to heat transmission contact with the plurality of rollers.