High temperature damper

Claim 1

A multiple hearth furnace including: a plurality of vertically aligned hearths defining hearth chambers therebetween; means defining breeching ports in selected hearth chambers; an elongated, rotatable shaft extending up through the center of the furnace and passing thrugh the floor of each hearth; means for moving material to be processed in the furnace downwardly to successively adjacent hearth chambers upon rotation of said shaft; means external of said furnace for generating high temperature gases to be conducted to selected hearth chambers for treating therein the material to be processed; conduit means connecting said high temperature gas generating means to said breeching ports; a blade of high temperature ceramic material formed with a bore along an axis thereof, said blade selectively adjusting the cross-sectional area of said conduit means; a hollow shaft mounted transversely of said conduit and extending into said bore and keyed to said blade to impart rotary movement to said blade about said axis upon rotation of said shaft, whereby said blade selectively adjusts the cross-sectional area of said conduit means; means for directing a flow of cooling medium through said shaft; and an insulating sleeve disposed between said shaft and the surface of said bore for restricting the transfer of heat from said blade to said shaft.