Patent ID: 7448232

Claim:
A convection furnace for a tempered glass sheet, comprising: a hauling rack along which the glass sheet is directed into the furnace, heating resistances which heat air to be blasted against the glass sheet, a blast apparatus including blast channelling for blasting the heated air against the glass sheet, wherein the blast channelling comprises elongated air channels disposed in the glass sheet direction or at right angles to the glass sheet direction, wherein inside of each said air channel there is at least a part of a said blast heating resistance, wherein each said elongate air channel includes a narrowest portion in which the at least a part of said heating resistance is located for effecting heat transfer by convection from each heating resistance to the blast air, wherein each said air channel has downstream of the narrowest portion a broadening portion, said broadening portion including a bottom part furnished with blast holes through which the heated air is directed onto the glass sheet, and wherein said bottom part is made of a thin plate which, due to a strong convection blast of the air and/or a surface quality chosen for said thin plate, transmits substantially little thermal radiation to the adjacent glass sheet.