Patent ID: 8328551
Filing Date: 2012-12-11
Classification: B23K,F27B,F27D

Abstract:
1. A convection furnace comprising: a heating chamber having a plurality of heat zones, each of the heat zones having at least one heating assembly for providing heated gas to a product conveyed through the furnace, each of the heating assemblies including an electrical heater within a plenum box having an orifice plate containing an array of openings from which jets of heated gas impinge on the product; a controller in communication with the heating chamber and coupled to the heating assemblies to control the heating assemblies to provide a thermal profile along the heat zones of the furnace, the thermal profile comprising a preheat interval, a soak cycle, and a spike cycle; a cooling chamber at the exit end of the heating chamber having at least one cooling assembly including a plenum box for providing jets of cooled gas to a product conveyed through the cooling chamber; a conveyor comprising a movable support surface extending through the heating chamber and the cooling chamber of the furnace for conveying a product through the heating chamber and the cooling chamber of the furnace; a gas path from the cooling chamber to at least one of the heat zones of the furnace chamber, the gas path comprising a conduit, the conduit including an entrance opening and at least one exit opening, the conduit connected to the cooling chamber at a location to introduce cooled gas provided by the cooling assembly into the conduit through the entrance opening, the entrance opening of the conduit spaced a distance away from the heat zones, and the conduit connected to at least one plenum box in the heating chamber at the at least one exit opening to introduce cooled gas in the conduit provided by the cooling assembly in the cooling chamber into the at least one of the heat zones of the heating chamber in addition to and to mix with the heated gas in the at least one plenum box provided by the heating assembly within the heat zone; and means for controlling the volume of cooled gas flowing in the gas path from the cooling chamber to the at least one of the heat zones to provide an intended temperature in the at least one of the heat zones below a temperature provided by the heating assembly.