Improved sealing valve assembly

Claim 1

A REMOVABLE DRILL COLLAR FOR A STRING OF DRILLING CASING COMPRISING A TUBULAR MEMBER ADAPTED TO FIT SLIDABLY WITHIN SAID CASING, AN INVERTED FRUSTO-CONICAL VALVE SEAT OF FLEXIBLE RESILIENT MATERIAL POSITIONED WITHIN AND FASTENED TO SAID TUBULAR MEMBER, SAID VALVE SEAT HAVING A CENTRAL OPENING AT ITS LOWER END, A PLURALITY OF CIRCUMFERENTIALLY ARRANGED RIGID RIBS EMBEDDED IN SAID VALVE SEAT MATERIAL, THE UPPER END OF EACH OF SAID RIBS BEING PIVOTALLY FASTENED TO SAID TUBULAR MEMBER, A BALL SHAPED VALVE ELEMENT FREELY MOVABLE WITHIN SAID TUBULAR MEMBER, SAID VALVE ELEMENT HAVING A DIAMETER GREATER THAN THE OPENING OF SAID VALVE SEAT WHEREBY SAID RIBS WILL MOVE OUTWARD TO ENLARGE SAID OPENING SUFFICIENTLY TO PASS SAID ELEMENT WHEN A DOWNWARD FORCE IS EXERTED THEREON, BUT WILL MOVE INWARDLY TO PREVENT UPWARD RETURN OF SAID ELEMENT WHEN AN UPWARD FORCE EXERTED ON SAID ELEMENT PLACES SAID ELEMENT IN SEALING ENGAGEMENT TO PREVENT SEAT, A STOP MEMBER POSITIONED WITHIN SAID TUBULAR MEMBER BELOW SAID VALVE SEAT AND ARRANGED TO PREVENT FURTHER DOWNWARD TRAVEL OF SAID VALVE ELEMENT AFTER IT HAS PASSED THROUGH SAID OPENING, AND AT LEAST ONE RESILIENT SEAL FIXED TO THE