Controlling high-pressure wells while drilling

Claim 1

APPARATUS FOR CONTROLLING A DRILLING WELL IN WHICH A HIGH-PRESSUR FLUID ENTERS THE WELL FROM DRILLED FORMATIONS, SAID APPARATUS COMPRISING: A CASING EXTENDING INTO SAID WELL, A DRILL PIPE EXTENDING INTO SAID WELL THROUGH SAID CASING, A SEAL BETWEEN SAID CASING AND SAID DRILL PIPE NEAR THE TOP OF SAID WELL, A CONDUIT EXTENDING THROUGH THE WALL OF SAID CASING AT A LEVEL BELOW SAID SEAL, A PINCH VALVE ON SAID CONDUIT, SAID PINCH VALVE INCLUDING A FLEXIBLE SLEEVE THROUGH WHICH DRILLING FLUID CONTAINING LARGE BIT CUTTINGS AND LOST CIRCULATION MATERIAL CAN FLOW FROM SAID CONDUIT, AND A HIGH -PRESSURE HOUSING SURROUNDING SAID SLEEVE, THE INTERNAL DIMENSIONS OF SAID HOUSING BEING SUFFICIENTLY GREATER THAN THE EXTERNAL DIAMETER OF SAID SLEEVE TO PROVIDE A CHAMBER INTO WHICH GAS CAN BE INTRODUCED AROUND SAID SLEEVE, HIGH PRESSURE FLUID TO BE APPLIED TO THE OUTSIDE OF THE SLEEVE OF SAID PINCH VALVE, AND MEANS FOR REGULATING THE PRESSURE OF THE FLUID APPLIED TO THE OUTSIDE OF THE SLEEVE OF SAID PINCH VALVE,