Abstract: A low breakout power transfer unit for transferring power between first and second hydraulic systems includes first and second pump/motor units to allow fluid flow between the first and second pump/motor units and the first and second hydraulic systems, respectively. The transfer unit includes a detection device for sensing fluid flow demand in the hydraulic systems and values for automatically isolating the pump/motor units from the hydraulic systems when the detection means senses substantially no fluid flow demands in a hydraulic system. The transfer unit includes a bypass device for each pump/motor unit for recirculating pumped fluid in excess of fluid flow demand.

Abstract: A hydraulic axial piston motor or pump (8) of the type in which a rotor (10) has an odd-numbered plurality of cylinder ports (30) with which the arcuate ports (40,42) of a port plate (36) successively register. The port plate (36) is provided with fluid exchange ports (44,46) through which cylinders (16) communicate with a hydraulic capacitance system (81,82,84,86,93). The capacitance system (81,82,84,86,93) urges fluid into each cylinder (16) of the rotor (10) through an exchange port (44) after the associated cylinder port (30) has departed from registration with one arcuate port (40) but before the associated piston (14) has reached its bottom-dead-center position (72), and receives fluid from each cylinder through an exchange port (46) after the associated piston has begun its compression stroke but before the cylinder port has begun to register with a second arcuate port (42).

Abstract: A bidirectional hydraulic servomotor system includes a variable-displacement motor which may impel or brake movement of a load member that either resists or assits movement by the servomotor, respectively. The direction of load movement is under control of a directional control valve with motor displacement and function (impelling or braking) being effected automatically to achieve controlled load movemement with minimal consumption of hydraulic fluid.