High-efficiency, large angle, variable displacement hydraulic pump/motor

A variable displacement hydraulic pump/motor comprising:

• a yoke comprising a pair of shafts aligned to define a yoke pivot axis, a pair of arms having first ends on said pivot axis and respectively fixed to said shafts, said arms extending perpendicular from said shafts to said second ends, and a valve plate connected to and extending between said second ends, said valve plate presenting a valve plate surface having intake and discharge apertures;
• a cylinder barrel mounted for rotation about a longitudinal axis and having a plurality of piston cylinders formed therein in a circle centered on said longitudinal axis, each piston cylinder being open at one end of said cylinder barrel to receive a piston head reciprocably mounted therein and having a cylinder opening at a second end of said cylinder barrel, said second end of said cylinder barrel mating with said valve plate surface whereby said cylinder openings come into communication alternately with said intake and discharge apertures as said cylinder barrel rotates;
• a drive block mounted on an end of an input/output shaft for rotation about a central axis of rotation inclined at an angle of inclination relative to said longitudinal axis;
• a plurality of piston rods, each piston rod connected at a first end to one of said pistons and pivotally connected at a second end to said drive block, said second ends being connected to said drive block in a circular array centered on said axis of rotation;
• drive means for engaging at least one of said first ends of said arms to pivot said yoke to change angle of inclination;
• and
• a universal joint comprising a central member presenting convex spherical surfaces at opposing ends thereof, a first guidance member fixed to said drive block and having a flat or concave surface mating with a first of said convex spherical surfaces and a second guidance member fixed to said cylinder barrel and having a flat or concave surface mating with a second of said convex, spherical surfaces, said central member and said guidance member serving to guide and center the relative movement among the input/output shaft, central member and cylinder barrel.

A variable displacement hydraulic pump/motor comprising:

• a yoke comprising a pair of axially-aligned shafts defining a pivot axis for said yoke and a valve plate connected to and intermediate said shafts and axially offset relative to said shafts, said valve plate presenting a valve plate surface having intake and discharge apertures;
• a cylinder barrel rotatable about a longitudinal axis and having a plurality of piston cylinders formed therein in a circle centered on said longitudinal axis, each piston cylinder being open at one end of said cylinder barrel to receive a piston reciprocably mounted therein and opening at a second end of said cylinder barrel through a fluid port, said second end of said cylinder barrel mating with said valve plate surface for intake of fluid from the arc-shaped intake aperture to a fluid port in communication with one of said piston cylinders and discharge of fluid from another of said piston cylinders through its fluid port and the arc-shaped discharge aperture;
• a drive block mounted on an end of an input/output shaft for rotation about a central axis of rotation inclined at an angle of inclination relative to said longitudinal axis;
• a plurality of piston rods, each piston rod connected at a first end to one of said pistons and pivotally connected at a second end to said drive block, said second ends being connected to said drive block in a circular array centered on said axis of rotation;
• and
• a universal joint comprising a drive block shaft fixed to said drive block, a first torque disc rotatably mounted in an end of said drive block shaft, a cylinder barrel shaft fixed to said cylinder barrel, a second torque disc rotatably mounted in an end of said cylinder barrel shaft and a pair of pivotally connected coupling halves, each of said coupling halves having a recess receiving one of said torque discs.