High pressure hydraulic pumps or motors

Claim 1

IN COMBINATION, A PAIR OF MEMBERS MOUNTED FOR RELATIVE ROTATION, ONE OF SAID MEMBERS HAVING A WALLED RECESS THEREIN AND THE OTHER OF SAID MEMBERS HAVING AN ABUTMENT PORTION THEREOF DISPOSED COAXIALLY IN THE RECESS AND DIVIDING IT INTO TWO CHAMBERS COMMUNICATING WITH ONE ANOTHER BETWEEN THE RELATIVELY ROTATING SURFACES OF THE ABUTMENT PORTION AND THE WALL OF THE RECESS, AN ANNULAR SEALING ELEMENT ARRANGED IN THE RECESS COAXIALLY ADJACENT THE ABUTMENT PORTION AND HAVING ONE END FACE THEREOF OPENING INTO ONE OF THE CHAMBERS, AND MEANS OPERATIVELY FEEDING HIGH PRESSURE FLUID INTO SAID ONE CHAMBER TO APPLY AXIAL FORCE ON SAID ONE END FACE OF THE ANNULAR SEALING ELEMENT, SAID ANNULAR SEALING ELEMENT HAVING A CYLINDRICAL SEATING ALONG ONE PERIPHERY THEREOF AND THE OTHER END FACE THEREOF RECESSED TO FORM AN ANNULAR SEATING THEREON, SAID CYLINDRICAL SEATING HAVING A RADIUS ABOUT THE AXIS OF THE SEALING ELEMENT INTERMEDIATE THE INNER AND OUTER RADII OF SAID ANNULAR SEATING AND BEING IN FLUID TIGHT ENGAGEMENT WITH A CORRESPONDING SEATING DEFINED BY ONE OF SAID ABUTMENT PORTION AND SAID RECESS WALL, SAID ANNULAR SEATING BEING SO OPERATIVELY SPACED FROM A CORRESPONDING SEATING DEFINED BY THE OTHER OF SAID ABUTMENT PORTION AND SAID RECESS WALL AS TO FORM A NARROW CLEARANCE FOR SMALL LEAKAGE FLOW BETWEEN THE TWO CHAMBERS, AND SAID SEALING ELEMENT DEFINING AN AXIALLYEXTENDING RESTRICTED FLOW PASSAGE BETWEEN THE END FACES THEREOF COMMUNICATING WITH THE CLEARANCE TO REGULATE LEAKAGE FLOW THERETHROUGH BY RESPONSIVELY VARYING THE PRESSURE DROP ACROSS THE SEALING ELEMENT AND THEREFORE THE PRESSURE GRADIENT IN THE CLEARANCE BALANCING SAID AXIAL FORCE.