Patent ID: 8365653

Claim:
A hydraulic pump, comprising: a drive shaft rotating on an axis; a circumaxial cam fence formed on the drive shaft and extending radially outwardly therefrom, an outer margin of the fence located at a predetermined radius from the axis, a locus of the outer margin of the fence varying in a direction parallel to the axis and as a function of the angular position of the margin relative to the axis; at least one elongate piston disposed in parallel to and spaced from the axis, the piston having a side wall, a cutout formed in the side wall of the piston and engaging the outer margin of the cam fence, axial displacement of the cam fence as the drive shaft rotates causing axial displacement of the piston; at least one cylinder disposed in parallel to and spaced from the axis, an interior of the cylinder slidably receiving an end of the piston; a side port formed in the cylinder for interruptedly communicating the interior of the cylinder to an inlet reservoir formed radially interiorly of the cylinder, an end port formed in the cylinder to be opposed to the piston end, the end port interruptedly communicating the interior of the cylinder to an output chamber formed around the drive shaft; and a rotary valve operable to periodically open and close the end port of the cylinder, the rotary valve rotating as a unit with the drive shaft and disposed in the output chamber adjacent the cylinder end port.