A hydraulic system (e.g., of an aircraft or other vehicle) includes a pump, a pressure line coupled to the pump and configured to distribute pressurized hydraulic fluid, and a return line configured to return hydraulic fluid to a reservoir. The hydraulic system also includes an auxiliary leakage valve coupled to the pressure line, to the return line, and to an actuator. The auxiliary leakage valve is configured to receive a control signal and, based on the control signal, selectively open a restricted fluid path. The restricted fluid path couples the pressure line to the return line to allow a restricted amount of the hydraulic fluid to flow from the pressure line to the return line.

An air dryer control method may include a cold mode in which a controller performs a winter season condition control in which air temperature is lowered to freezing temperature if an engine starting is detected, and performs a winter season thawing control in which compressed air introduced into a valve control of an air dryer warms a purge valve of the air dryer.

A hydraulic propulsion system converts heat or thermal energy into hydraulic energy, and such hydraulic energy into mechanical work. The hydraulic propulsion system includes a thermal unit, a hydraulic cylinder with pistons and springs mounted therein, one or more hydraulic motors, one or more hydraulic accumulators, and one or more electrical energy generators, as well as a plurality of flow control valves to control the flow of hydraulic fluid between the various components. The hydraulic propulsion system may be enhanced by a sonic transmission unit including a sonic wave generator.

A hydraulic system for a working machine includes a hydraulic actuator having a first fluid chamber and a second fluid chamber, an accumulator, an outputting fluid tube to output an operation fluid, and a switching valve to be switched between a first position and a second position. The first position allows the first fluid chamber and the second fluid chamber to be communicated with the outputting fluid tube and thereby allowing a floating operation. The second position allows the first fluid chamber and the accumulator to be communicated with each other, allows the second fluid chamber and the outputting fluid tube to be communicated with each other, and thereby allows an anti-vibration operation.

A hydraulic system for a working machine includes a hydraulic actuator having a first fluid chamber and a second fluid chamber, an accumulator, an outputting fluid tube to output an operation fluid, and a switching valve to be switched between a first position and a second position. The first position allows the first fluid chamber and the second fluid chamber to be communicated with the outputting fluid tube and thereby allowing a floating operation. The second position allows the first fluid chamber and the accumulator to be communicated with each other, allows the second fluid chamber and the outputting fluid tube to be communicated with each other, and thereby allows an anti-vibration operation.

An unmanned underwater vehicle (UUV) with a hydraulic system (100) for use in cold surroundings and method of controlling such hydraulic system. The hydraulic system (100) comprises a hydraulic circuit (10). One or more tools (21,22) may be hydraulically operable via the hydraulic circuit (10). A pump (32) is configured to pressurize a flow of hydraulic fluid (F) via the hydraulic circuit (10) e.g. for actuating the tools (21,22). A valve system (40) comprises control valves (41,42,43) disposed in the hydraulic circuit (10) for controlling the flow of hydraulic fluid (F) through the hydraulic circuit (10). A controller (50) is configured to control one or more of the control valves (43) as a function of a temperature (T) of the hydraulic fluid (F).

A method of flushing a hydraulic system including a fluid circuit and an in-service fluid flowing therein includes fluidly coupling a kidney loop to the fluid circuit such that at least a portion of the in-service fluid may flow therethrough, the kidney loop including a depth media filter and a micro-glass filter arranged in a parallel flow pattern and introducing a solvent cleaner into the in-service fluid at a concentration level between approximately 2.5% and approximately 6%, the solvent cleaner including at least one hydrocarbon group V fluid. The method further includes maintaining a temperature of the in-service fluid between approximately 100 degrees Fahrenheit and approximately 155 degrees Fahrenheit and controlling the flow of the in-service fluid at a flow rate between approximately 3 gallons per minute and approximately 6.8 gallons per minute.

A work machine is provided. The work machine includes a changeover valve capable of disabling area limiting control by bypassing an area limiting control solenoid proportional valve disposed in a pilot line through which pilot pressure generated by a hydraulic pilot type operation device is guided to a directional control valve and the work machine can perform the area limiting control while ensuring response of a work implement. When a first fluid temperature T1 is higher than a first predetermined temperature Ta and a control changeover switch 66 specifies disabling of the area limiting control, a controller brings a plurality of changeover valves into a bypass position. When the first fluid temperature T1 is equal to or lower than the first predetermined temperature Ta, the controller brings the changeover valves into a communication position and places the solenoid proportional valves in a fully open position.

Provided is an electric work vehicle having a simple configuration, yet allowing a hydraulic cylinder to function appropriately even in a low-temperature environment. An electric work vehicle includes a first hydraulic cylinder, a second hydraulic cylinder and a third hydraulic cylinder and includes also a hydraulic system for feeding work oil to these hydraulic cylinders and a traveling motor. The hydraulic system includes an oil heating circuit for heating the work oil using heat generated from the traveling motor.

Provided is an electric work vehicle having a simple configuration, yet allowing a hydraulic cylinder to function appropriately even in a low-temperature environment. An electric work vehicle includes a first hydraulic cylinder, a second hydraulic cylinder and a third hydraulic cylinder and includes also a hydraulic system for feeding work oil to these hydraulic cylinders and a traveling motor. The hydraulic system includes an oil heating circuit for heating the work oil using heat generated from the traveling motor.