Abstract: The invention provides a variable speed hydraulic pump designed to operate at a maximum horsepower throughout its pressure range by adjusting motor speed according to motor load parameters. In particular, the variable speed hydraulic pump includes a hydraulic pump unit coupled to a variable speed electric motor by a drive unit and to a hydraulic fluid tank for pressurizing and pumping hydraulic fluid when operated by the motor. A motor controller is electrically connected to the motor to supply drive signals to the motor based on electrical characteristics of the drive signals which are dependent on the load exerted on the motor. Suction from the load is provided by both the main pump and a bidirectional supercharging pump by reversing the direction of the motor and shifting a 4/3 valve to connect the main pump inlet to the load and its outlet to tank.

Abstract: A piston pump including an inlet manifold, and outlet manifold, and a piston ring sandwiched between the inlet and outlet manifolds. The inlet manifold has a first face and a second face with at least one outlet formed in the second face. The outlet manifold has a first face and a second face, and includes at least one inlet formed in the outlet manifold first face. The piston ring has an inlet face and an exhaust face, wherein the piston ring is sandwiched between said inlet manifold second face and said outlet manifold first face, and has at least one radially extending cylinder formed therein. The piston ring further includes an inlet passageway formed in the piston ring between the inlet face and the cylinder and in fluid communication with the inlet manifold. The piston ring also has an exhaust passageway formed therein between said cylinder and the exhaust face and in fluid communication with the outlet manifold inlet.

Abstract: The invention provides a variable speed hydraulic pump designed to operate at a maximum horsepower throughout its pressure range by adjusting motor speed according to motor load parameters. In particular, the variable speed hydraulic pump includes a hydraulic pump unit coupled to a variable speed electric motor by a drive unit and to a hydraulic fluid tank for pressurizing and pumping hydraulic fluid when operated by the motor. A motor controller is electrically connected to the motor to supply drive signals to the motor based on electrical characteristics of the drive signals which are dependent on the load exerted on the motor. Suction from the load is provided by both the main pump and a bidirectional supercharging pump by reversing the direction of the motor and shifting a 4/3 valve to connect the main pump inlet to the load and its outlet to tank.