Hydraulic pumps and motors with multiple cylinders of the barrel or swashplate type

Claim 1

A PUMP COMPRISING A GENERALLY CYLINDRICAL CASING HAVING SPACED ENDS ONE OF WHICH IS PROVIDED WITH SPACED INLET AND OUTLET PORTS, A HOLLOW SHAFT IN AND EXTENDING PARTLY THROUGH SAID CASING IN AXIAL ALIGNMENT TOWARS THE OTHER OF SAID ENDS, SAID SHAFT HAVING AN INTERNAL BORE COUPLED TO SAID INLET PORT AND EXTENDING THROUGH SAID SHAFT TO OPEN TOWARDS SAID OTHER END OF THE CASING, A BARREL ENCIRCLING SAID SHAFT, A RING BETWEEN SAID BARREL AND SHAFT AND DEFINING A PASSAGE THEREBETWEEN, SAID BARREL INCLUDING A PORTION EXTENDING BEYOND SAID SHAFT TOWARDS SAID OTHER END OF THE CASING, PUMP MEANS ON SAID PORTION SPACED FROM THE END OF THE SHAFT TO DEFINE THEREWITH A SECOND PASSAGE COMMUNICATING SAID BORE WITH THE FIRST SAID PASSAGE, A DRIVE SHAFT EXTENDING INTO SAID OTHER END OF SAID CASING AND INTO SAID PORTION OF SAID BARREL, SAID PORTION AND DRIVE SHAFT INCLUDING INTERENGAGED TEETH FOR THE DRIVING OF SAID BARREL, SAID PUMP MEANS AND BARREL PORTION INCLUDING INTERENGAGED TEETH FOR THE DRIVING OF SAID PUMP MEANS, SAID BARREL INCLUDING AXIALLY ALIGNED CYLINDER MEANS ADAPTED FOR BEING ROTATED INTO SEQUENTIAL ALIGNMENT WITH SAID PORTS, PISTON DISPLACEABLE IN SAID CYLINDER MEANS, AND A CONTROL RING MOUNTED ON SAID BARREL PORTION TO CONTROL THE MAGNITUDE OF DISPLACEMENT OF SAID PISTONS, SAID BARREL BEING PROVIDED WITH PASSAGES CONNECTING SAID FIRST AND SECOND PASSAGES WITH SAID CYLINDER MEANS AT SPACED POSITIONS IN THE LATTER, SAID CASING DEFINING WITH SAID BARREL AN ANNULAR SPACE AND INCLUDING A DISCHARGE PORT CONNECTED THERETO, SAID BARREL BEING PROVIDED WITH A FURTHER PASSAGE EXTENDING BETWEEN SAID ANNULAR PASSAGE AND SAID FIRST PASSAGE.