Apparatus and method for bending glass sheets

Abstract

Sheet glass is heated during conveyance within a furance housing having a fixed roof and vertically movable side doors that define side slots through which ends of conveyor rolls project outwardly to be supported and frictionally driven by continuous drive loops slidably driven over external support surfaces that extend alongside the side slots. A vacuum holder of the apparatus is positioned within the furnace housing above the conveyor and has a downwardly facing surface with spaced openings in which a vacuum is drawn to receive a glass sheet from the conveyor and support the sheet above the conveyor. The holder surface is disclosed as being both planar and curved and as having a porous cover of ceramic fibers so as to distribute the vacuum and prevent marring of the glass as it is supported. A greater vacuum is drawn to initially support the glass and a lesser vacuum is subsequently drawn to prevent glass deformation at the spaced openings. Vertically movable auxiliary lifters positioned between the rolls or vertical movement of the vacuum holder facilitates glass pickup. Sensing of the glass position along the conveyor and operation of a locator cooperatively provide accurate positioning of the glass on the holder surface without requiring the conveyor to be stopped prior to the holder operation. A carrier mold ring moves under the supported glass and the vacuum is then terminated so the glass drops onto the ring and bends under the bias of gravity in a manner that allows thin glass to be accurately bent. Subsequently the mold ring is moved from the furnace to a quench unit between upper and lower blastheads that temper the bent glass. Increased air is then supplied to the lower blasthead relative to the upper blasthead to lift the glass sheet off the ring and allow return of the ring to the furnace.