Abstract: A method and apparatus for heating glass sheets in preparation of tempering. A furnace (1) is provided with upper and lower convection blasting conduits (11, 14) extending lengthwise of the furnace. The furnace is also provided with upper and lower radiation heating elements (12, 16). The convection heating air is pressurized with a compressor (3), cleaned with a filter (4). The upper convection heating air is heated with air discharged from the furnace in a plurality of separate heat exchangers (7), through which the convection heating air is passed into the upper convection blasting conduits (11). The amount of air discharged from the furnace (1) through the heat exchangers (7) is substantially equal to that blasted into the furnace for convection heating.

Abstract: In a method and an apparatus for heating glass panels in a tempering furnace equipped with rollers, glass panels are carried on a conveyor defined by rollers into a tempering furnace for the duration of a heating cycle, followed by carrying the glass panels into a tempering station. The glass panels are heated in the tempering furnace by bottom- and top-heating radiation elements as well as by bottom- and top-heating convection elements through which convection air is supplied to the tempering furnace. The glass panels' bottom side is heated by the bottom-heating convection elements, which are arranged lengthwise along the furnace and define convection heating zones side by side in a lateral direction of the tempering furnace. Thus, convection heating effects of the convection heating zones can be altered relative to each other for profiling the heat transfer coefficient in a lateral direction of the furnace.

Abstract: A method and apparatus for heating glass sheets in preparation of tempering. A furnace (1) is provided with upper and lower convection blasting conduits (11, 14) extending lengthwise of the furnace. The furnace is also provided with upper and lower radiation heating elements (12, 16). The convection heating air is pressurized with a compressor (3), cleaned with a filter (4). The upper convection heating air is heated with air discharged from the furnace in a plurality of separate heat exchangers (7), through which the convection heating air is passed into the upper convection blasting conduits (11). The amount of air discharged from the furnace (1) through the heat exchangers (7) is substantially equal to that blasted into the furnace for convection heating.

Abstract: In a method and an apparatus for heating glass panels in a tempering furnace equipped with rollers, glass panels are carried on a conveyor defined by rollers into a tempering furnace for the duration of a heating cycle, followed by carrying the glass panels into a tempering station. The glass panels are heated in the tempering furnace by bottom-and top-heating radiation elements as well as by bottom-and top-heating convection elements through whcih convection air is supplied to the tempering furnace. The glass panels' bottom side is heated by the bottom-heating convection elements, which are arranged lengthwise along the furnace and define convection heating zones side by side in a lateral direction of the tempering furnace. Thus, convection heating effects of the convection. heating zones can be altered relative to each other for profiling the heat transfer coefficient in a lateral direction of the furnace.

Abstract: The invention relates to a method for heating glass sheets to be tempered or heat-strengthened, in which method glass sheets are heated in a preheating furnace (1) by applying a hot-air blast and convection heating produced thereby to the opposite sides of a glass sheet and the preheated glass sheet is transferred from the preheating furnace (1) into a radiation heating furnace (2) for heating the glass sheet to a tempering temperature. During the convection heating of a glass sheet, the rotating speed of a hot-air fan (5) is increased while adjusting the heating effect of heating resistances (6) so as to maintain the temperature of blasted air substantially constant. Thus, the diminishing temperature difference between glass and air is compensated for by controlling the coefficient of heat transfer.