Blasting with abrasive particles

Claim 1

IN A PRESSURE RESPONSIVE MIXING ASSEMBLY FOR FEEDING AND CONTROLLING THE FLOW OF A STREAM OF PARTICLES COMPRISING A PARTICLE SUPPLY CONTAINER, A MIXING CHAMBER FOR RECEIVING SAID PARTICLES FLOWING FROM SAID SUPPLY CONTAINER, AN INLET FOR SAID CHAMBER, AN OUTLET FOR SAID CHAMBER, SAID INLET AND OUTLET SERVING TO PASS A BLAST STREAM OF PRESSURIZED AIR THROUGH THE MIXING CHAMBER WHICH AIR IS MIXED WITH THE PARTICLES RECEIVED BY THE MIXING CHAMBER, A FLOW CONDUIT CONNECTING SAID SUPPLY CONTAINER WITH SAID MIXING CHAMBER FOR PASSING SAID PARTICLES FROM THE CONTAINER TO SAID CHAMBER, AN AXIALLY SLIDABLE TUBE TELESCOPCALLY SUPPORTED WITHIN SAID CONDUIT THROUGH WHICH THE PARTICLES PASS, A VALVE SEAT IN CONDUIT BEYOND THE INNERMOST END OF THE TUBE WITHIN THE CONDUIT, AN IMPRESSION SPRING SUPPORTED AROUND SAID TUBE FOR URGING THE TUBE AGAINST SAID VALVE SEAT, PRESSURE RESPONSIVE DIAPHRAGM MEANS HOLDING THE TUBE IN PLACE, AND A PRESSURE APPLYING CONNECTION FOR VARYING THE PRESSURE ACTING UPON THE DIAPHRAGM MEANS TO LODGE THE TUBE AGAINST AND AWAY FROM THE VALVE SEAT TO CLOSE AND OPEN THE FLOW CONDUIT, THE IMPROVEMENT OF USING A RESILIENT SHUTOFF VALVE ELEMENT FOR OPENING AND CLOSING FLOW THROUGH SAID CONDUIT, AND THE SEATING PORTION OF SAID VALVE ELEMENT BEING A SEGMENT OF A SPHERE.