Patent ID: 7216511

Claim:
A furnace having upper and lower zones within a furnace chamber incorporating different heating methods and adapted for tempering glass panels having a top surface with a lower emissivity than a bottom surface, the furnace comprising: rollers for carrying and supporting the glass panels as the panels traverse through the furnace chamber; the lower heating zone within the chamber including radiative heating elements disposed within the lower heating zone for heating the bottom surface of the glass panel, said radiative heating elements forming a primary source for heating the lower surface of the glass panel; the upper heating zone within the chamber including nozzle assemblies for forcing heated air onto the top surface of the glass panel and heating the top surface of the panel thereby, fan assemblies for circulating air drawn from the chamber to the nozzle assemblies, and radiative heating elements disposed in a return air path between the glass panel and the fan assemblies for heating the air as it is drawn from the chamber by the fan assemblies.