Patent ID: 7105126

Claim:
A vacuum heat treating furnace comprising: A. a vacuum vessel having a vessel wall; B. a hot zone disposed in said vacuum vessel, said hot zone having a hot zone wall; C. a plenum formed between the vessel wall and the hot zone wall; D. a plurality of gas injection nozzles extending through the hot zone wall to interconnect the plenum and the hot zone; D. a cooling gas system for providing a forced cooling gas into the plenum; and E. a plurality of check valves connected to the gas injection nozzles externally of the hot zone wall, each of said plurality of check valves comprising: i. a valve body having an inlet portion, an outlet portion, and a channel that extends through the valve body between the inlet portion and the outlet portion; ii. a chamber formed in the inlet portion of said valve body, said chamber encompassing the channel and having a recess formed therein adjacent to said channel; and iii. a flap that is pivotally supported in said chamber such that said flap is adapted to swing toward the outlet portion of said valve body, said flap having a closed position whereby the channel is closed to the flow of cooling gas and an open position whereby the channel is open to the flow of cooling gas and said flap is located substantially within the recess in said chamber.