Provided is an electrohydrostatic actuation system including an emergency shut-off circuit to be actuated stably with a simple configuration. The electrohydrostatic actuation system includes: a hydraulic cylinder (24) including a piston (25) to which a valve element is connected, a first chamber (24A), and a second chamber (24B); a hydraulic pump (21) configured to supply hydraulic fluid to the first chamber (24A) or the second chamber (24B); a servo motor (M) configured to drive the hydraulic pump (21); a shuttle valve (11) configured to establish communication to a downstream side under a state in which a hydraulic pressure generated by the hydraulic pump (21) is maintained; a solenoid valve (12) configured to receive the hydraulic pressure via the shuttle valve (11) as a pilot pressure; and a logic valve (13) including a first port configured to receive the pilot pressure from the solenoid valve (12), and a second port to be communicated to the first chamber (24A) of the hydraulic cylinder (24). When the solenoid valve (12) is brought to a de-energized state, the pilot pressure of the logic valve (13) is released, and the logic valve (13) causes the hydraulic fluid in the first chamber (24A) communicated to the second port to flow into the second chamber (24B) so that emergency shut-off of the valve element is achieved by a return spring (26).

An example valve includes: a seat member; a spool configured to be seated on the seat member to block fluid flow from a first port to a second port when the valve is in a closed state, wherein fluid at the first port applies a fluid force on the spool; a spring applying a biasing force on the spool toward the seat member, wherein as the fluid force overcomes the biasing force, the spool moves in the proximal direction off the seat member, thereby allowing fluid flow from the first port to the second port through a flow area formed between the spool and the seat member; a turbine configured to rotate as fluid flowing through the flow area flows downstream across the turbine; and an electric generator coupled to the turbine, such that rotation of the turbine causes the electric generator to generate electric power.

An example valve includes: a pressure compensation spool configured to be subjected to a first fluid force of fluid received at a first port acting in a proximal direction; a pressure compensation spring disposed in a pressure compensation chamber and applying a biasing force on the pressure compensation spool in a distal direction; a turbine configured to rotate as fluid flows through the valve; and a flow area configured to throttle fluid flow from the first port to the pressure compensation chamber, wherein fluid in the pressure compensation chamber applies a second fluid force on the pressure compensation spool in the distal direction, such that the pressure compensation spool moves to a particular axial position based on force equilibrium between the first fluid force, the second fluid force, and the biasing force to throttle fluid flow from the pressure compensation chamber to a second port.

Methods can comprise charging a first hydraulic device of a first hydraulic circuit with a first quantity of hydraulic fluid from a hydraulic fluid source. The methods can further comprise pressurizing a control segment and locking the first quantity of hydraulic fluid from exiting the first hydraulic circuit in response to hydraulic pressure within the control segment. The methods can also include unlocking the first quantity of hydraulic fluid to permit exiting of the first quantity of hydraulic fluid from the first hydraulic device in response to dropping the hydraulic pressure within the control segment after a delay. Hydraulic apparatus can comprise a normally open hydraulic pilot operated control valve that can be configured to hydraulically lock a first hydraulic device in response to a hydraulic pressure within a control segment rising to greater than or equal to an actuation pressure.

The present disclosure relates to systems that use a single proportional valve to control raising and lowering of a load. The present disclosure also relates to proportional valves that provide proportional flow control in first and second opposite flow directions through the proportional valve.

A hydraulic system, comprising: a hydraulic pump, a hydraulic load, and an electric machine. The electric machine working as an electric generator and mechanically coupled with said hydraulic pump. A low-pressure fluid tank and a valve assembly comprising one or more valves selectively fluidly connecting the hydraulic load with the low-pressure fluid tank.

A hydraulic system includes a first output fluid tube connecting between a hydraulic pump to output operation fluid and a first operation valve to change a first pilot pressure of the operation fluid, a second output fluid tube connected between the hydraulic pump and a second operation valve to change a second pilot pressure of the operation fluid, a switching valve provided in the second output fluid tube, and a warm-up fluid tube connected between the first operation valve and the switching valve, wherein the switching valve is switched between a first position allowing the operation fluid to be drained through the first output fluid tube, the first operation valve, the warm-up fluid tube and the switching valve, and a second position allowing the operation fluid to be supplied through second output fluid tube to the second operation valve.

There is provided a work machine which can improve accuracy of control of an actuator when a pressure difference between a hydraulic pump and the actuator is large and the demanded flow rate of the actuator is small. An auxiliary flow rate controller is configured such that an opening area of a main valve changes between a maximum opening area and zero according to the opening area of a pilot variable restrictor when the opening area of the pilot variable restrictor is equal to or more than a predetermined opening area and that the opening area of the main valve is zero irrespective of the opening area of the pilot variable restrictor when the opening area of the pilot variable restrictor is less than the predetermined opening area.

A method and control system operable to control movement of a work implement of a work vehicle. The control system includes a reservoir that retains fluid, a pump in fluid communication with the reservoir, and an actuator in fluid communication with the pump. The actuator has a first side and a second side. A control valve is fluidly positioned between the pump and the actuator, a first proportional relief valve is fluidly positioned between the pump and the first side of the actuator, and a second proportional relief valve is fluidly positioned between the pump and the second side of the actuator. The first proportional relief valve is configured to permit flow of fluid from the first side of the actuator to the reservoir when a pressure at the first side of the actuator exceeds a pressure set point.

A balancing valve includes four ports. While the pressures at a pair of balancing ports of a hydraulic balancing valve are equal, the valve maintains two other ports in a closed position. Upon a pressure differential between the balancing ports, fluid communication can occur between one of the balancing ports and either of the other ports based upon the direction of the pressure differential. A hydraulic ride control system utilizes the balancing valve together with other control valves to provide ride control functionality.