Patent ID: 7014429

Claim:
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 a pair of arc-shaped intake and discharge apertures, a radial port formed in each of said shafts and a pair of fluid passages internal to said yoke through which fluid flows perpendicularly to said pivot axis, each fluid passage connecting an arc-shaped aperture with a radial port; 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; and 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.