A hydraulic system in a work machine includes a travel operation device provided in a pilot oil path between a hydraulic pump a travel pump and including an operation member and configured to generate a pilot pressure supplied via the pilot oil path and an additional pilot pressure in accordance with an operation amount of the operation member. The travel pump is to control a flow direction of hydraulic oil supplied to a travel motor based on the pilot pressure and the additional pilot pressure. A pressure selection valve is provided in a first coupling oil path to select a selected pressure from the pilot pressure and the additional pilot pressure to apply the selected pressure to the pilot hydraulic oil in the second coupling oil path. A pressure adjustment valve is provided in a second coupling oil path to control the selected pressure to be an adjusted pilot pressure.

A system and method is provided for monitoring a hydraulic power system having at least one light emitter and a button. The method includes powering on the hydraulic power system, receiving an actuation at the button and detecting a release of the button after a first time interval, and entering a diagnostic state. The method further includes retrieving a code and displaying the code by turning on the emitter in a first pattern. In some embodiments, a system and method is provided for regulating a temperature of a hydraulic power system. In some embodiments, a system and method is provided for controlling operation of a hydraulic torque wrench.

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 landing gear lifting/lowering EHA system includes: a hydraulic actuator configured to lift and lower the leg of an aircraft; at least one electrically operated hydraulic pump; a hydraulic path; a pressure sensor attached to the hydraulic actuator or the hydraulic path and configured to output a measurement signal corresponding to hydraulic pressure; and a controller configured to output a control signal to the electrically operated hydraulic pump, wherein, when a state in which the hydraulic pressure exceeds a set pressure continues for a set time, the control unit stops the electrically operated hydraulic pump in operation and resumes the operation of the electrically operated hydraulic pump after the hydraulic pressure drops to or below a second set pressure after the electrically operated hydraulic pump is stopped.

An accumulator includes: a main cylindrical housing having a closed first axial end and a second axial end; a piston arranged in the main cylindrical housing and sealed to an inner surface of the main cylindrical housing, which piston is movable in an axial direction and provides with the main cylindrical housing and the closed first axial end of the main cylindrical housing a variable accumulating space; an urging device arranged between the piston and the second axial end of the main cylindrical housing for urging the piston towards the first axial end of the main cylindrical housing; a fluid supply opening arranged in the first axial end of the main cylindrical housing, which fluid supply opening is in fluid connection with the variable accumulating space; and a protective cylindrical housing having a first and a second axial end, the protective cylindrical housing being arranged concentrically.

A lift arm lifting and lowering mechanism cylinder case provided with a cylinder portion into which oil is fed, a piston slidable inside the cylinder portion to define a hydraulic chamber and receiving hydraulic pressure of the hydraulic chamber on a front surface, a safety valve provided to the piston to discharge the oil inside the hydraulic chamber to the outside when the hydraulic pressure of the hydraulic chamber becomes greater than or equal to a predetermined value, and a lift arm supported by the cylinder case and rotatable in conjunction with movement of the piston, in which the piston includes an oil passage allowing communication between a rear surface of the piston and the front surface, and the oil passage includes a containing portion provided to open on the axially front surface side and capable of containing the safety valve, and a non-containing portion provided on the axially rear surface side relative to the containing portion and incapable of containing the safety valve.

A time-based power boost control system. A fluid source supplies fluid. A relief device relieves pressure of the fluid supplied by the fluid source when the pressure of the fluid exceeds a relief pressure level. A control device controls the relief device. When a boost mode in which at least a first level of pressure and a second level of pressure, higher than the first level of pressure, are allowed to be selectively used as the relief pressure level is active, a length of a boost-on time in which the second level of pressure is used as the relief pressure level is shorter than a preset maximum boost-on time limit, and a length of a succeeding boost-off time succeeding the boost-on time in which the first level of pressure is used as the relief pressure level is equal to or longer than a preset minimum boost-off time limit.

A system for exhausting hazardous stored energy from a pneumatic subsystem of a railcar, comprises: an air supply for delivering air to the pneumatic subsystem of the railcar; and an isolation valve interposed between the air supply and the pneumatic subsystem of the railcar. When the isolation valve is in a normal operating position, a supply port and a delivery port of the isolation valve are in fluid communication with one another, but when the sliding shoe is in the second position, the sliding shoe effectively closes access to the supply port, and the delivery port is in fluid communication with an exhaust port of the isolation valve. The isolation valve further includes a means for locking the sliding shoe in the second position.

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.

An over-pressure protection system includes a main body housing defining a main body chamber configured to receive a fluid therein, wherein the main body housing comprises a spring, the main body housing configurable in a collapsed configuration and an expanded configuration; and a pressure sensor configured to measure a fluid pressure of the fluid, the pressure sensor configurable in an activated mode and a deactivated mode; wherein, in the collapsed configuration, the spring biases main body housing inward at an intermediate point of the main body housing such that the main body housing defines a substantially hourglass shape.