Mechanical air classifier

Claim 1

IN AND FOR A CLASSIFIER OF THE CENTRIFUGAL TYPE FOR PARTICULATE MATERIAL AND COMPRISING A CASING; A FIRST ROTARY TABLE ROTATABLE ABOUT AN AXIS CENTRAL IN SAID CASING; FEED MEANS FOR DELIVERING PARTICULATE MATERIAL SUBSTANTIALLY AXIALLY ON TO SAID ROTARY TABLE FOR SUBSEQUENT EJECTION THEREFROM AT THE PERIPHERY OF SAID FIRST TABLE UNDER CENTRIFUGAL FORCE; CENTRIFUGAL FAN MEANS ABOVE SAID FIRST ROTARY TABLE FOR CAUSING A FLOW OF AIR PAST THE PERIPHERY OF SAID FIRST ROTARY TABLE, THE EJECTED PARTICULATE MATERIAL BEING ENTRAINED IN SAID FLOW OF AIR ADJACENT THE PERIPHERY OF SAID FIRST TABLE; A ROTOR COMPRISING A SECOND ROTARY TABLE ROTATABLE ABOUT SAID AXIS AND LOCATED ABOVE SAID FIRST ROTARY TABLE AND BELOW THE CENTRIFUGAL FAN MEANS, WALLS ON SAID SECOND TABLE HAVING ONE END SUBSTANTIALLY AT THE PERIPHERY OF SAID SECOND TABLE AND EXTENDING A SUBSTANTIAL DISTANCE FROM THE PERIPHERY THEREOF TOWARD THE AXIS THEREOF, AND A SHROUD PLATE AXIALLY SPACED ABOVE THE SURFACE OF THE SECOND TABLE TO FORM A CLASSIFYING ZONE THEREBETWEEN FOR SAID AIR AND ENTRAINED PARTICULATE MATERIAL TO FLOW THERETHROUGH IN A CENTRIPETAL DIRECTION AND TO BE ROTATED BY SAID WALLS, SAID SHROUD PLATE BEING OF CONTINUOUS ANNULAR CONSTRUCTION TO PROVIDE A PERIPHERAL OPENING SERVING AS AN INLET TO SAID CLASSIFYING ZONE FOR SAID FLOW OF AIR WITH ENTRAINED PARTICULATE MATERIAL, AND AS AN OUTLET FOR PARTICLES REJECTED UNDER CENTRIFUGAL FORCE, AND TO PROVIDE A CENTRAL OUTLET FOR AIR AND ENTRAINED PARTICULATE MATERIAL, SAID SECOND TABLE AND SAID SHROUD PLATE BEING SHAPED TO PROVIDE A FLOW CROSS-SECTION INCREASING TOWARD SAID CENTRAL OUTLET AT A RATE SUCH THAT FOR A PARTICLE OF GIVEN SIZE THE RATIO OF THE INWARD RADIAL AERODYNAMIC DRAG FORCE TO THE CENTRIFUGAL FORCE IS SUBSTANTIALLY THE SAME THROUGHOUT SAID CLASSIFYING ZONE, AND A GUARD RING AT LEAST PART OF WHICH SURROUNDS THE CLASSIFYING ZONE AND IS SUBSTANTIALLY CYLINDRICAL AND COAXIAL WITH THE SECOND TABLE TO CAUSE AIR AND ENTRAINED PARTICULATE MATERIAL TO ENTER THE PERIPHERY OF THE CLASSIFYING ZONE WITH DIFFERENT INWARD RADIAL COMPONENTS OF VELOCITY OVER THE DEPTH OF SAID PERIPHERAL INLET OPENING.