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).

A hydraulic lockout lever failure detection system preferably includes a first analog sensor, a second analog sensor, at least one electronic control module (ECU) and a solenoid valve. The voltage output level of the first and second analog sensors is monitored by the ECU. The solenoid valve controls the flow of hydraulic fluid to operate an excavator or other equipment. The operation of the solenoid valve is controlled by the ECU. However, a second ECU may be used to control the operation of the solenoid valve. A hydraulic lockout lever causes the first and second analog sensors to output either a low voltage to indicate a closed position, or to indicate an open position to the ECU. If the first and second analog sensors output a voltage that is above a low set value or above a high set value, a fault is detected.

Universal control circuitry for an electro-hydraulic valve actuator system includes logic gate circuitry to control one or more of a closing solenoid valve, an opening solenoid valve, an emergency shutdown solenoid valve, and a hydraulic fluid pump motor to route hydraulic fluid through a hydraulic circuit to actuate a valve via a hydraulic actuator according to received commands. The universal control circuitry is configured to control operation for multiple different configurations of a hydraulic valve actuator system including double-acting configurations, single-acting spring-to-open configurations, and single-acting spring-to-close configurations, each with or without an emergency shutdown arrangement (which may be configured to trip based on an external shutdown input alone or in combination with a local system power failure), a hydraulic accumulator, and maintained or momentary input commands.

A power unit with manual override control for a hydraulic system having an initial state and at least one operational state is provided, comprising: a tank for storing hydraulic fluid that moves between a first chamber and a second chamber of a hydraulic cylinder; a pump that routes the hydraulic fluid in and out of the tank; a first relief valve; a first solenoid valve configured to shift between a plurality of positions based on the at least one operational state of the hydraulic system; a first check valve connected to the first solenoid valve; a manual override control unit comprising: a second check valve; and a second solenoid valve configured to shift between a plurality of positions based on activation of a manual override control, wherein the activation of the manual override control returns the hydraulic system from the at least one operational state to the initial state.

A hydraulic circuit includes a pump connected to a tank for supplying hydraulic liquid under pressure to a component via a directional control slide valve provided with a feed port connected to an inlet of the component and with a return port connected to an outlet of the component. The hydraulic circuit further includes a pressure limiter connected to the inlet of the component and the tank, and a feed control system for the hydraulic component including a pressure sensor installed upstream of the hydraulic component downstream of the feed port for supplying information about the pressure of the hydraulic liquid and a setpoint pressure. The feed control system further including an actuator for controlling the movement of the directional control slide valve, and a control unit for generating a control signal for the actuator based on information about the pressure measured at the feed port.

A hydraulic drive system raises and lowers an object by supplying and discharging operating oil to and from each of two ports of an actuator and includes a control device, first to third electromagnetic proportional control valves, a hydraulic pump, a control valve, and a lock valve. When a second pilot pressure is output, the control valve causes the operating oil to be discharged from a first port in order to lower the object. The lock valve is disposed so as to be able to prevent the operating oil from being discharged from the first port by closing a path between the first port and the control valve, and only when a third pilot pressure is output, allows the operating oil to be discharged from the first port by opening the path between the first port and the control valve.

An electrohydraulic system includes an output shaft, a hydraulic piston, and a preload device. The output shaft rotationally drives the valve and extends along a first axis. The hydraulic piston extends along a second axis perpendicular to the first axis, is actuated by a pressure medium, and rotates the output shaft. The preload device stores energy via preloading of an elastic element, which extends along a third axis, by a hydraulic cylinder and to transmit the energy to the output shaft in the event of a fault. The hydraulic piston is guided into first and second cylinder housings, and at least one of the cylinder housings is connected to the hydraulic cylinder. A check valve is arranged between the cylinder housing and the hydraulic cylinder, and is configured to decouple the preload device from the hydraulic piston, the blocking direction going from the hydraulic cylinder to the cylinder housing.

Fail-fixed hydraulic actuator systems for aircraft include a hydraulic actuator having a piston in a housing. The piston separates the housing into a retract cavity and an extend cavity. A sleeve is moveably arranged within the housing and includes a sleeve aperture that is aligned with a piston head during normal operation. A driving mechanism is configured to drive movement of the sleeve to maintain alignment between the sleeve aperture and the piston head. A low pressure cavity is defined between an interior surface of the housing and the sleeve and, when the piston head is offset from the sleeve aperture, the low pressure cavity is hydraulically connected to one of the retract cavity or the extend cavity to cause a pressure differential with the other of the extend cavity and the retract cavity and cause movement of the piston head to align with the sleeve aperture.

In general, techniques are described regarding a rotary servo for actuators. A servo assembly includes a cylindrical outer sleeve including ports, a cylindrical outer spool annularly disposed within the cylindrical outer sleeve, a stepper motor mechanically coupled to the cylindrical outer spool, and an actuator mechanically coupled to compressor variable geometry that controls compression provided by a compressor. The cylindrical outer spool includes channels configured to provide fluidic interconnection between the ports and a cylindrical inner spool, where the cylindrical inner spool is annularly disposed within the cylindrical outer spool, and the cylindrical inner spool includes grooves configured to provide fluidic interconnection through the channels of the cylindrical outer sleeve. The stepper motor is configured to rotate the cylindrical outer spool within the cylindrical outer sleeve to deliver a fluid to and thereby actuate the actuator to control the compressor variable geometry.

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).