A method for manufacturing an at least sectionally spherical-cap-shaped recess on a drive shaft for a hydrostatic axial piston machine includes whirling of the recess and heat treatment of the recess to form a wear layer. A drive shaft for a hydrostatic axial piston machine includes at least one recess manufactured according to the method. A hydrostatic axial piston machine includes a drive shaft with at least one recess manufactured according to the method.

A rotary fluid pump-motor includes first and second rotor assemblies and a bent cylinder sleeve. The first rotor assembly includes a first rotor, a piston cylinder, and a flange ring with an inclined guide surface. The second rotor assembly includes a second rotor and a piston. The first and second rotors are rotatably movable about inclined first and second rotor axes, respectively. The bent cylinder sleeve receives the piston cylinder and the piston therein through respective sleeve openings to define a piston chamber therebetween. The bent cylinder sleeve is in at least intermittent contacting relationship with the flange ring's inclined guide surface and rotatably movable about the first rotor axis with respect to the inclined guide surface such that the bent cylinder sleeve moves along the first rotor axis relative to the piston cylinder based upon its circumferential position along the inclined guide surface to correspondingly vary the piston chamber's volume.

A hydraulic device comprises an outer surface of a rotor rotating and facing an outer surface of a port member. The rotor has a plurality of cylinders disposed about an axis and cooperating pistons. The cylinders communicate with respective open ends at the rotor outer surface. Each open end alternatingly communicates with high and low pressure ports. Each two successive cylinders are interconnected via a fluid displacement member having first and second openings communicating with each respective cylinder and a closure element that obstructs either the first or second opening if the pressure in the cylinder that communicates with the second opening is higher or lower than the pressure in the cylinder that communicates with the first opening, respectively. The first opening and the second opening of each two fluid displacement members which communicate with one cylinder are fluidly connected with that cylinder at opposite sides of a flow resistance.

A hydraulic device comprises a housing and a shaft with a flange extending perpendicularly to a first axis of rotation. A plurality of pistons are fixed to the flange and move each in a sleeve supported by and rotatable with a barrel plate. The barrel plate is provided with a plurality of actuators for exerting counter forces (Fa) on the respective sleeves in a direction and at a location such that at least when one of the pistons is at bottom dead center under operating conditions the counter force on the cooperating sleeve acts along a line at a distance from the center point of the piston head and causes a counter torque about the center point of the piston head against the tilting torque, wherein the actuators are controlled such that the counter forces increase with increasing rotational speed of the barrel plate about the second axis of rotation.

A hydraulic device comprises a housing and a shaft with a flange extending perpendicularly to a first axis of rotation. A plurality of pistons are fixed to the flange and move each in a sleeve supported by and rotatable with a barrel plate. The barrel plate is provided with a plurality of actuators for exerting counter forces (Fa) on the respective sleeves in a direction and at a location such that at least when one of the pistons is at bottom dead center under operating conditions the counter force on the cooperating sleeve acts along a line at a distance from the center point of the piston head and causes a counter torque about the center point of the piston head against the tilting torque, wherein the actuators are controlled such that the counter forces increase with increasing rotational speed of the barrel plate about the second axis of rotation.