Importance

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Abstract

A multizone convection furnace is provided in which gas from a cooling chamber of the furnace is directed into one or more heat zones of the furnace for the purpose of providing a specified thermal profile. The gas introduced from the cooling chamber into the one or more heat zones is of the same type of gas present in the heat zones, and typically is nitrogen. In a preferred embodiment, the convection furnaces comprises a heating chamber composed of a plurality of adjacent heat zones and a cooling chamber at the exit end of the heating chamber. A conveyer extends through the furnace for movement of a product through the heat zones and cooling chamber of the furnace. The cooling chamber is coupled to one or more of the heat zones such that cooled gas from the cooling chamber can be introduced into selected heat zones. In one version, a cooled gas path is provided to all of the heat zones and cooled gas is introduced into intended zones by opening associated valves. Alternatively, cooled gas paths can be provided to only predetermined zones where cooled gas introduction is desired.

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First Claim