Valve control for discharge of finely divided material from vacuum to atmosphere

Claim 1

DISCHARGE VALVE STRUCTURE FOR HANDLING FINELY DIVIDED DRY MATERIAL HAVING A RESERVOIR CHAMBER UNDER VACUUM AND BELOW IT A SURGE CHAMBER OF CONSTANT VOLUME COMPRISING RIGID WALLS FORMING AN AIR-TIGHT PASSAGEWAY HAVING AN INLET OPENING AT ITS UPPER END FOR ATTACHMENT TO SAID RESERVOIR CHAMBER AND HAVING AN OUTLET OPENING AT ITS LOWER END, A FIRST VALVE AND A SECOND VALVE EACH CONTROLLABLE BY DIFFERENTIAL PRESSURES ON THE UPSTREAM AND DOWNSTREAM SIDES THEREOF, EACH OF SAID VALVES COMPRISING COACTING LIPS OF FLEXIBLE RUBBERLIKE MATERIAL EXTENDING FROM A SLEEVE WITH A SMOOTH THROUGH OPENING, SAID LIPS BEING SUFFICIENTLY SOFT AND FLEXIBLE TO SEAL AROUND ANY FINELY DIVIDED MATERIAL CAUGHT BETWEEN THEM, COACTING PAIRS OF SAID LIPS HAVING PLANAR TERMINAL PORTIONS ENGAGING TO COMPLETELY CLOSE SAID VALVE, SAID LIPS ADAPTED TO BE CLOSED AND OPENED BY A DIFFERENTIAL PRESSURE EFFECTIVE WHEN GREATER EXTERNALLY OF THE VALVE TO PRESS SAID LIPS TOGETHER IN CLOSE RELATIONSHIP, AND EFFECTIVE WHEN GREATER INTERNALLY OF THE VALVE TO PART SAID LIPS, SAID FIRST VALVE HAVING ITS UPSTREAM SIDE INTERNALLY IN COMMUNICATION WITH SAID INLET OPENING AND HAVING ITS DOWNSTREAM SIDE EXTERNALLY EXPOSED IN SAID SURGE CHAMBER PASSAGEWAY, SAID SECOND VALVE HAVING ITS UPSTREAM SIDE INTERNALLY IN COMMUNICATION WITH SAID SURGE CHAMBER PASSAGEWAY AT SAID OUTLET OPENING AND ITS DOWNSTREAM SIDE EXTERNALLY IN A DISCHARGE ZONE, AND THE SOLE OPERATING MEANS FOR SAID