Patent attributes
A hydraulic machine arrangement includes at least one hydraulic machine having a plurality of pistons reciprocating within corresponding cylinders. The pistons can be driven by a cam to operate the hydraulic machine as a pump, and they can drive the cam to operate the hydraulic machine as a motor. The hydraulic machine can be configured to selectively disengage a certain piston or pistons from the cam to operate at less than full displacement. Controlling the pressure in the cylinders corresponding to the disengaged pistons can be accomplished by a number of mechanisms, including selectively exhausting fluid from the cylinders, or using a jet pump to siphon off some of the fluid from a high pressure side of the hydraulic machine. Two of the hydraulic machines can be mounted together to help balance axial forces and eliminate the need for an expensive high capacity thrust bearing.
