A rotatable piston assembly for a reciprocating piston type hydraulic machine includes a rotatable piston configured for a controlled rotation and configured to reciprocate within a cylinder bore of the reciprocating piston type hydraulic machine.

A hydrostatic axial piston machine includes a double-acting actuating cylinder configured to adjust the piston displacement. The actuating cylinder has two actuating chambers that are connected to two spatially separated cartridge valves. The two cartridge valves are inserted obliquely into a wall section of the axial piston machine. The wall section on the one hand forms a wall of the housing of the axial piston machine and on the other hand forms a wall of the actuating cylinder.

A hydrostatic axial piston machine includes a housing and a pivot cradle. At least one slide bearing of the pivot cradle on a high-pressure side is hydrostatically relieved. The slide bearing includes one or two pairs of relief grooves. A relief pressure field develops about and between the one or two pairs of relief grooves as the grooves are supplied with relief pressure medium on one side and are closed at their outer ends. An optional slide bearing on a low-pressure side has one or two limiting grooves which delimit the relief pressure field there, as the limiting grooves are open at their outer ends.

An energy recovery system includes cylinders that articulate a hydraulic tool in a pump mode to provide potential energy and in a motor mode to recover the potential energy. The energy recovery system includes a tank that stores a hydraulic fluid for the cylinders and an open circuit variable displacement pump that circulates the hydraulic fluid in the pump mode from the tank to the cylinders and in the motor mode from the cylinders to the tank. The open circuit variable displacement pump includes a swashplate articulable between a positive position and a negative position. In the positive position, the hydraulic fluid circulates in the pump mode and in the negative position the hydraulic fluid circulates in the motor mode. The open circuit variable displacement pump includes an actuator that articulates the swashplate and a bias system that maintains the swashplate in a positive position when the hydraulic fluid is not in circulation.

A hydraulic motor apparatus includes a motor housing engaged to an end cap having a first porting system and an adapter connected to an external surface of the end cap and having a second porting system. A filter may be attached to the adapter and connected to the second porting system and a pressure reducing valve in the adapter is connected to the second porting system. The assembly may also include a controller operatively connected to the pressure reducing valve and system sensors measuring parameters affected by the output of the hydraulic motor apparatus, whereby the pressure reducing valve is operatively controlled by the controller in response to input from the system sensors.

A hydraulic unit includes a driving mechanism whose displacement volume is adjustable to two operational states by means of a position-able adjustment element. The adjustment element can be positioned by a servo piston of a servo unit into a first, initial position and a second, operative position. A first front face and a second front face of the servo piston, which are opposing each other, can be pressurized individually with pressurized hydraulic fluid in order to position the servo piston at either end position of a servo cylinder of the servo unit. The servo piston is of a stepped design thereby forming a ring-shaped damping surface opposing the first front face. In the servo cylinder a ring-shaped shoulder surface is formed opposing the damping surface such that a damping volume is formed in the servo cylinder by the damping surface, the shoulder surface and the servo cylinder.

A fluid delivery system for an engine is disclosed. The fluid delivery system comprises a pump, a valve module, a motor, and a displacement control module. The pump is operatively coupled with an engine and is adapted to provide a flow of a fluid. The valve module is provided in fluidic communication with the pump to control the flow of the fluid. The motor is provided in fluidic communication with the valve module to receive the flow of the fluid and generate mechanical power. The displacement control module is provided in fluidic communication with the pump and the valve module and is provided downstream of the pump and upstream of the valve module. The displacement control module controls a displacement of the pump for maintaining a constant flow rate of the fluid from the pump based, at least in part, on an engine speed regardless of compressor load.

A method teaches a control function, preferably a characteristic curve, of a hydrostatic motor of a traction drive of a work machine when in drive mode. The traction drive is provided with the hydrostatic motor and a hydrostatic pump, which is hydraulically connected to the hydrostatic motor. The method includes setting a pivot angle of the hydrostatic motor while taking into account a desired velocity of the work machine when in the drive mode, and checking whether predefined conditions are met. If the predefined conditions are met and a current velocity differs from the desired velocity, the method includes correcting the control function of the hydrostatic motor by taking into account a difference between the desired velocity and the current velocity. At least one value of the corrected control function of the hydrostatic motor is taught during the correcting.

A method for driving a tilt rotor between vertical and horizontal using a variable displacement motor controlled in response to a swash angle of the motor measured in a feedback loop. The loop includes an algorithm configured to monitor change in swash angle as the motor speed reduces and the actual tilt position of the rotor pylon approaches the second position and, based on the change and actual tilt position, to limit change in swash angle to be within a predetermined range as a percentage of the operating load.

An energy recovery system includes cylinders that articulate a hydraulic tool in a pump mode to provide potential energy and in a motor mode to recover the potential energy. The energy recovery system includes a tank that stores a hydraulic fluid for the cylinders and an open circuit variable displacement pump that circulates the hydraulic fluid in the pump mode from the tank to the cylinders and in the motor mode from the cylinders to the tank. The open circuit variable displacement pump includes a swashplate articulable between a positive position and a negative position. In the positive position, the hydraulic fluid circulates in the pump mode and in the negative position the hydraulic fluid circulates in the motor mode. The open circuit variable displacement pump includes an actuator that articulates the swashplate and a bias system that maintains the swashplate in a positive position when the hydraulic fluid is not in circulation.