A hydraulic actuator control system includes a secondary manifold that is configured to direct a meter-in flow received from a main directional valve to the actuator and to direct a meter-out flow of fluid received from the actuator directly to a tank without the return flow travelling back through the main directional valve. The hydraulic actuator control system has a separate return flow connection that permits the use of a load-holding valve (such as, e.g., counterbalance valves, motion control valves, pilot-operated check valves, or zero-leakage logic elements) flanged on the machine's actuator (such as, e.g., a linear cylinder, a rotary cylinder, or a hydraulic motor) to create a directional control valve without directing the return flow through the main directional control valve.

A hydraulic system for a machine is disclosed. The system may have a pump and a motor driven by pressurized fluid from the pump. An accumulator is configured to receive fluid discharged from the motor and to discharge fluid to the motor. The system may include a first valve to selectively communicate the higher pressure of conduits coupled between the pump and motor to the accumulator. A second valve and a third valve can be used to facilitate charging and discharging of the accumulator. The system may include a controller configured to implement a plurality of modes of operation, which each mode of operation may include a different combination of motor deceleration and motor acceleration segments during which the accumulator receives and discharges fluid, respectively. An input may be used to determine the segment of the work cycle.

Disclosed herein are various embodiments of a hydraulic actuator that includes one or more check valves having a dynamically varying cracking pressure. In certain embodiments, a hydraulic actuator may be configured to vary the cracking pressure of a check valve based on an operating condition of a pump of the hydraulic actuator. The check valve may be located along a bypass path in the hydraulic actuator, thereby allowing for fluid flow to bypass a pump of the hydraulic actuator by passing through the check valve. The use of such hydraulic actuators is contemplated in, for example, an active suspension system of a vehicle. Additionally, various embodiments of suitable check valves are disclosed. Additionally, methods are disclosed for operation of the check valve and the hydraulic actuator.

A hydraulic closed circuit system using a single rod type hydraulic cylinder prevents the hunting of a flushing valve due to a delay in response of the flushing valve and circuit pressure pulsations, thereby preventing a decrease in operability of the hydraulic cylinder. A single rod type hydraulic cylinder is connected to a hydraulic pump via two hydraulic lines. A flushing valve is connected between the hydraulic lines and a tank; and a control unit is configured to add a predetermined control parameter to a pressure in a lower-pressure hydraulic line of the two hydraulic lines. The magnitude of a pressure in the higher-pressure hydraulic line of the two hydraulic lines is compared with the magnitude of a compensation pressure to which the control parameter has been added, and the flushing valve is switched when the compensation pressure and the higher-pressure hydraulic line pressure are found to be reversed in magnitude.

A hydraulic valve block configured to specifically control an operation of a clam actuator of a face shovel bucket of a face shovel machine is disclosed. The hydraulic valve block comprises a first inlet, a second inlet, a first outlet connected to the first inlet via a first line and a second outlet connected to the second inlet via a second line. The hydraulic valve block further comprises a two port two position directional control valve interconnected between the first line and the second line, a first pressure relief valve interconnected between the first line and the second line and arranged in series with the two port two position directional control valve, and a second pressure relief valve interconnected between the first line and the second line and arranged in parallel to the first pressure relief valve and the two port two position directional control valve.

A valve (18), for a valve assembly (10) for regulating the pressure of a fluid guided in a hydraulic system for supplying pressure to at least one hydraulic consumer (12a, 12b), includes a pilot control stage (48) and a main control stage (38) for at least partially clearing or blocking a fluid path from a supply connection (P) to an outflow connection (T). A relief stage (54) for pressure relief of a fluid chamber is arranged between the pilot control stage (48) and the main control stage (38). The relief stage (54) compares the existing load pressure at load terminal (LS) dedicated to the hydraulic consumer (12a, 12b) with the outflow pressure at the outflow connection (T), clearing the pressure relief if both pressures are approximately the same. The relief stage (54) can be directly connected to the load connection (LS) and can be charged with load pressure.

A mobile machine comprising an object to be driven, an electric storage, an electric motor connected to the electric storage, a hydraulic pump driven by the electric motor, a hydraulic piston assembly hydraulically connected to the pump and comprising a housing having a first chamber, a second chamber, a piston separating the first and second chambers, and an actuating rod connected to the piston and the object to be driven, the hydraulic piston assembly configured to actuate the object to be driven relative to the mobile machine within a range of motion, and wherein actuation of the object to be driven relative to the body portion of the mobile machine within the range of motion is controllable by the electric motor and powered via the electric storage.

A control device of an electric actuator adapted to perform a forward-reverse movement includes a control unit adapted to be operated in a forward direction or a reverse direction in accordance with the forward-reverse movement of the electric actuator. It also includes a pilot circuit, which is connected to the control unit and which generates a forward pilot pressure or a reverse pilot pressure in accordance with the forward operation or the reverse operation of the control unit. The control device has a differential pressure acquiring unit that acquires a differential pressure between a pilot pressure corresponding to an operation direction of the control unit and a pilot pressure, in a direction opposite to the operation direction, and it has a control command generator that generates a control command for controlling the electric actuator based on the differential pressure acquired by the differential pressure acquiring unit. The control device includes a drive controller for controlling a drive of the electric actuator based on the generated control command.

A hydraulic system (1) is provided comprising a supply port arrangement (P, T), a working port arrangement (A, B), and a booster section (7), said supply port arrangement having at least a supply port (P), said booster section (7) being arranged between said supply port arrangement (P, T) and said working port arrangement (A, B). The operational possibilities of such a hydraulic system should be extended. To this end said working port arrangement comprises at least two working ports (A, B), flow direction changing means (9) are provided changing a flow direction through said working port arrangement and inactivating means (16) are provided inactivating or activating said booster section (7) for each flow direction.

A system and method for a hydraulic swing system of a machine to prevent drift without engaging a swing brake is described. The hydraulic swing system includes a pump powered by a motive element such as an engine and provides a swing motor for rotating the chassis of the machine relative to the undercarriage. The swing system includes a control valve on a first path between the pump and the motor and a second control valve on a second path. The swing system further includes a blocking valve to blocking hydraulic fluid flow and thereby preventing drift engaged when the system is in neutral and below a threshold rotation rate.