Hydraulic couplings

Claim 1

A HYDRAULIC COUPLING COMPRISING IN COMBINATION A ROTATABLE DRIVING MEMBER PROVIDED WITH A PLURALITY OF BORES WHICH EXTEND INWARDLY FROM AN OUTER PERIPHERAL SURFACE OF SAID DRIVING MEMBER TOWARDS THE AXIS THEREOF, A ROTATABLE DRIVEN MEMBER WHICH IS MOUNTED COAXIALLY WITH SAID DRIVING MEMBER, AN ANNULAR MEMBER UNITED WITH SAID DRIVEN MEMBER, AND PROVIDED WITH AN INTERNAL CAM SURFACE WHICH IS SITUATED AROUND, AND ADJACENT TO, THE OUTER ENDS OF SAID BORES, A PLURALITY OF DRIVING ELEMENTS WHICH ARE MOUNTED RESPECTIVELY WITHIN, AND MOVABLE ALONG, SAID BORES, AND WHICH ARE IN CONSTANT SEALING ENGAGEMENT RESPECTIVELY WITH THE PERIPHERIES OF SAID BORES, A PLURALITY OF PORTS WHICH COMMUNICATE RESPECTIVELY WITH THE INNER ENDS OF SAID BORES, AND THROUGH WHICH HYDRAULIC FLUID IS ADMISSIBLE TO, AND DISCHARGEABLE FROM, SAID BORES, AND VALVE MEANS FOR CLOSING SAID PORTS TO PREVENT DISCHARGE OF HYDRAULIC FLUID FROM SAID BORES WHEN IT IS DESIRED TO TRANSMIT MOVEMENT FROM SAID DRIVING MEMBER TO SAID DRIVEN MEMBER, SAID BORES BEING ARRANGED SO THAT WHEN SAID DRIVING MEMBER IS ROTATED SAID DRIVING ELEMENTS ARE URGED BY CENTRIFUGAL FORCES TO EXTREME POSITIONS IN WHICH THEY PROJECT FROM THE OUTER ENDS OF SAID BORES INTO ENGAGEMENT WITH SAID CAM SURFACE, AND ARE HELD IN SAID EXTREME POSITIONS BY THE HYDRAULIC FLUID IN SAID BORES WHEN SAID PORTS ARE CLOSED BY SAID VALVE MEANS TO PREVENT DISCHARGE OF HYDRAULIC FLUID FROM SAID BORES, SO THAT SAID DRIVING MEMBER IS DRIVINGLY COUPLED TO SAID DRIVEN MEMBER BY THE ENGAGEMENT OF SAID DRIVING ELEMENTS WITH SAID CAM SURFACE.