Heat treatment apparatus

Claim 1

IN A FURNACE FOR USE IN THE HEAT TREATMENT OF A CONTINUOUSLY MOVING WORK PIECE, A HEAT TREATMENT CHAMBER THROUGH WHICH SAID WORK PIECE TRAVELS DURING THE HEAT TREATMENT THEREOF, A PASSAGEWAY OPEN TO ATMOSPHERE COMMUNICATING WITH SAID CHAMBER AND THROUGH WHICH SAID WORK PIECE PASSES, MEANS FOR INTRODUCING A HEAT TREATMENT ATMOSPHERE INTO SAID HEAT TREATMENT CHAMBER, A VERTICALLY EXTENDING STACK COMMUNICATING WITH SAID PASSAGEWAY AND THROUGH WHITH THE HEAT TREATMENT ATMOSPHERE IS DISCHARGED AND BURNED OFF AFTER CIRCULATION THROUGH SAID HEAT TREATMENT CHAMBER, A CONDUIT LOCATED IN SAID STACK AND PROJECTING DOWNWARDLY THERETHROUGH, SAID CONDUIT TERMINATING DIRECTLY BENEATH SAID STACK AND AND EXTENDING INTO SAID PASSAGEWAY, AND MEANS FOR INTRODUCING AN INERT GAS UNDER PRESSURE INTO SAID CONDUIT FOR PASSAGE THERETHROUGH INTO SAID PASSAGEWAY, SAID CONDUIT DIRECTING THE MAJOR PORTION OF SAID INERT GAS TOWARD THE OPEN END OF SAID PASSAGEWAY TO DEFINE A BARRIER FOR PREVENTING ATMOSPHERIC AIR FROM ENTERING SAID HEAT TREATMENT CHAMBER FROM THE ENTRANCE END OF SAID PASSAGEWAY, A RELATIVELY SMALL PORTION OF THE INERT GAS BEING DIRECTED UPWARDLY FROM THE LOWERMOST END OF SAID CONDUIT INTO SAID STACK FOR REDUCING THE TEMPERATURE OF THE LOWER END OF SAID STACK FOR REDUCPREVENT BURNING OF TREATMENT GAS THEREIN, SAID INERT GAS DIRECTED INTO SAID STACK FURTHER PREVENTING INGRESS OF ATMOSPHERE INTO SAID PASSAGEWAY FROM SAID STACK IN THE EVENT THAT BURN-OUT OF SAID HEAT TREATMENT ATMOSPHERE OCCURS AT THE UPPER END OF SAID STACK.