Piston return mechanism

Claim 1

AN AXIAL PISTON HYDRAULIC PUMP OR MOTOR DEVICE COMPRISING A HOUSING, A ROTATABLE CYLINDER BLOCK MOUNTED IN SAID HOUSING, AN ANNULAR SERIES OF AXIALLY DISPOSED CYLINDERS WITHIN SAID BLOCK, A SERIES OF PISTONS HAVING INNER ENDS RECIPROCATING WITHIN SAID CYLINDERS, A DRIVE SHAFT ROTATABLY MOUNTED IN SAID HOUSING EXTENDING THROUGH SAID CYLINDER BOLCK, A TORQUE TUBE IN SAID HOUSING BETWEEN SAID SHAFT AND CYLINDER BLOCK, A FIRST SPLINE CONNECTION BETWEEN THE CYLINDER BLOCK AND TORQUE TUBE, A SECOND SPLINE CONNECTION BETWEEN SAID SHAFT AND TORQUE TUBE, BEARING MEANS IN SAID HOUSING RESTRICTING SAID DRIVE SHAFT AGAINST AXIAL MOVEMENT, A CAM PLATE MOUNTED IN SAID HOUSING AT ONE END OF SAID CYLINDER BLOCK AND HAVING A BEARING FACE INCLINED TO ONE END OF THE CYLINDER BLOCK, SAID PISTONS HAVING SPHERICAL OUTER ENDS, A SERIES OF SHOES UNIVERSALLY MOUNTED ON THE SPHERICAL OUTER ENDS OF THE PISTONS AND HAVING A BEARING FACE ENGAGING THE BEARINGS FACE ON SAID CAM PLATE, PORTS COMMUNICATING THE CYLINDERS WITH THE OPPOSITE END OF SAID CYLINDER BLOCK, A PORT PLATE IN THE HOUSING HAVING INLET AND OUTLET PASSAGES ADJACENT THE OPPOSITE ENDS OF THE CYLINDER BLOCK COMMUNICATING SUCCESSIVELY WITH SAID CYLINDER BLOCK COMMUNICATING THE CYLINDER BLOCK, A HOLD-DOWN RING CARRYING SAID BARING SHOES, A SPHERICAL SURFACE ON SAID TORQUE TUBE ENGAGING THE HOLD-DOWN RING, AN AXIALLY EXPANDABLE CHAMBER GROUNDED ON SAID SHAFT AT ONE END AND BIASING SAID TORQUE TUBE AT THE OTHER END, MEANS FOR SUPPLYING FLUID FOR EXPANDING SAID CHAMBER, AND RESILIENT MEANS GROUNDED ON SAID SHAFT AT ONE END AND BEARING AGAINST SAID CYLINDER BLOCK AT THE OTHER END TO URGE THE BLOCK TOWARD THE PORT PLATE.