Method and apparatus for heat treating articles in a recirculating type furnace

Claim 2

A recirculating system suitable for a furnace for heat treating articles comprising: A. a closed furnace chamber defined by at least one wall of refractory material; B. positioning means within the furnace to position articles to be treated; C. a pressurized system comprising hot gas lines positioned external to the furnace and adjacent the wall; D. a heater including a combustion source connected between the pressurized system and the furnace chamber for providing hot gases and reheating recirculated products of combustion from the furnace chamber; and E. nozzles extending between the hot gas lines and the interior of the furnace for communicating the hot gases and products of combustion from the lines into the furnace for treating the articles, the hot gases and products of combustion entering the furnace chamber at a minimum velocity of about 100 ft./sec. which is sufficient to cause turbulence within the furnace to insure substantial uniformity in temperature within the furnace, said nozzles positioned away from and out of line with the positioning means so as to avoid direct hot gas impingement on said articles.

Claim 3

In a furnace having at least two oppositely disposed walls of refractory material between which articles are positioned by transfer means for heat treating and in which products of combustion are recirculated into the furnace, the improvement in a recirculation system comprising: A. a pressurized system of hot gas lines positioned external of the walls of the furnace; B. a heater including a combustion source connected between the hot gas lines and the furnace for providing hot gases and recirculated products of combustion within the lines; C. nozzles extending from the lines through at least one wall for passing hot gases and recirculated products of combustion into the interior of the furnace, said nozzles positioned away from the out of line of the transfer means so as to avoid direct impingement of the entrants on the articles; and D. fan means associated with the heaTer for forcing the hot gases and recirculated products of combustion through the lines such that the velocity of the entrants leaving the nozzles into the furnace is a minimum of about 100 ft./sec. which is sufficient to cause turbulence within the chamber to insure substantial uniformity of temperature within the furnace.

Claim 4

In a furnace having at least two oppositely disposed walls of refractory material between which articles are positioned by transfer means for heat treating and in which products of combustion are recirculated into the furnace, the improvement in a recirculation system comprising: A. a pressurized system of hot gas lines positioned external of the walls of the furnace; B. a heater including a combustion source connected between the hot gas lines and the furnace for providing hot gases and recirculated products of combustion within the lines; C. nozzles extending from the lines through at least one wall for passing hot gases and recirculated products of combustion into the interior of the furnace, said nozzles positioned away from the out of line of the transfer means so as to avoid direct impingement of the entrants on the articles; and D. fan means associated with the heaTer for forcing the hot gases and recirculated products of combustion through the lines such that the velocity of the entrants leaving the nozzles into the furnace is a minimum of about 100 ft./sec. which is sufficient to cause turbulence within the chamber to insure substantial uniformity of temperature within the furnace.

Claim 5

A recirculating system for a furnace having walls of refractory material within which articles to be treated are moved into and through the furnace by positioning means comprising a pressurized system including hot gas lines external of the walls through which heated products of combustion pass, nozzle means between the lines and the interior of the furnace and positioned in removed relationship from the positioning means for passing products of combustion into the furnace in avoidance of direct article impingement and at a velocity of at least 100 ft./sec. to cause turbulence of the products of combustion within the furnace, removal means connected to the furnace for removing the spent products of combustion and heater means including a combustion source and connected to the removal means and hot gas lines for reheating the spent products and recycling them through the system to the furnace for treating articles therein.

Claim 6

A recirculating system for a furnace having walls of refractory material within which articles to be treated are moved into and through the furnace by positioning means comprising a pressurized system including hot gas lines external of the walls through which heated products of combustion pass, nozzle means between the lines and the interior of the furnace and positioned in removed relationship from the positioning means for passing products of combustion into the furnace in avoidance of direct article impingement and at a velocity of at least 100 ft./sec. to cause turbulence of the products of combustion within the furnace, removal means connected to the furnace for removing the spent products of combustion and heater means including a combustion source and connected to the removal means and hot gas lines for reheating the spent products and recycling them through the system to the furnace for treating articles therein.

Claim 7

In combination, an external pressurized recirculating system connected to at least one radiant tube having an inlet leg and an exhaust leg, the recirculating system comprising a heater including a burner having an air inlet and a fuel inlet, a hot gas line placing the heater in communication with said inlet leg, an exhaust gas line communicating the exhaust leg with the heater for the recirculation of exhaust gases and circulation means associated with one of the hot gas or exhaust lines for causing circulation of the hot gases through the heater and the radiant tube.

Claim 8

In combination, an external pressurized recirculating system connected to at least one radiant tube having an inlet leg and an exhaust leg, the recirculating system comprising a heater including a burner having an air inlet and a fuel inlet, a hot gas line placing the heater in communication with said inlet leg, an exhaust gas line communicating the exhaust leg with the heater for the recirculation of exhaust gases and circulation means associated with one of the hot gas or exhaust lines for causing circulation of the hot gases through the heater and the radiant tube.

Claim 9

The recirculating system of claim 1 wherein each of said nozzles terminates at the furnace wall adjacent the chamber.

Claim 10

The combination of claim 4 including a recuperator positioned between the air inlet of the burner and the exhaust gas line to preheat the air into the burner.