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).

An aircraft assembly having: a first part; a second part, the second part being movably mounted with respect to the first part; an electro-hydraulic actuator coupled between the second part and a first anchor point, the actuator comprising a cylinder defining a bore and a piston and rod assembly slidably mounted within the bore and an active chamber within which an increase in fluid pressure causes the actuator to change during a first phase between first and second extension states to move the second part relative to the first part. The electro-hydraulic actuator further includes a hydraulic fluid supply circuit comprising a piezo-electric pump operable to supply pressurised fluid to the active chamber to change the actuator between first and second extension states.

A shovel includes a hydraulic pump, multiple hydraulic actuators, a center bypass oil passage supplied with hydraulic oil discharged from the hydraulic pump, multiple directional control valves, and a bleed-off valve. The directional control valves are arranged in tandem in the center bypass oil passage and configured to supply the hydraulic actuators with the hydraulic oil from the center bypass oil passage. At least a directional control valve other than the most downstream directional control valve in the center bypass oil passage among the directional control valves opens the center bypass oil passage. The bleed-off valve is connected to part of the center bypass oil passage upstream of at least one of the directional control valves.

A compressed air supply installation for operation of an air spring installation of a vehicle includes an air feed with an air compressor configured to supply a compressed air feed with compressed air, a pneumatic main line with an air dryer and a compressed air connection for supplying the pneumatic installation with compressed air, a purge line branching from the pneumatic main line to the compressed air feed and comprising a purge valve connected in the purge line and a purge connection for releasing air to the environment, wherein the purge valve is part of a controllable valve assembly. The controllable valve assembly with the purge valve can be pneumatically loaded with a control pressure derived from the air compressor.

According to an embodiment, a variable pressure device includes a channel constituting unit and a switch valve mechanism. The channel constituting unit constitutes a channel including a first regulator and second regulators that are arranged in series to the first regulator and are in parallel to one another. The switch valve mechanism selectively connects the second regulators to the first regulator. Opening areas of the second regulators are different from one another.

Provided is a construction machine capable of detecting a stuck-open state of a surplus flow control valve in real time during operation without involving a reduction in the operational speed. The construction machine is equipped with: a surplus flow control valve control section configured to output a closing command to a first surplus flow control valve at the operation start when an operation amount signal of an operation lever device is detected; a pump delivery control section configured to output a delivery flow rate command to an adjustment section of an open circuit pump; an assist valve control section configured to continue to output a closing command from before to an assist valve; a sticking detection determination section configured to compare a pressure signal with a previously set threshold value and determining that the surplus flow control valve is in a stuck-open state when the pressure signal is less than the threshold value and determining that the surplus flow control valve is normal when the pressure signal exceeds the threshold value; and a stop signal generating section configured to input therein a sticking determination signal, output in the case of a stuck-open state a control signal maintaining a closed state of the assist valve to the assist valve control section, and output in the case of a normal state a control signal causing the assist valve to perform an opening operation to the assist valve control section.

A compressed-air feed system for operating a pneumatic system includes a compressed-air supply, a compressed-air connection to the pneumatic system, at least one ventilation connection to surroundings, and a pneumatic main line between the compressed-air supply and the compressed-air connection. The pneumatic main line has an air dryer and a regeneration throttle. The compressed-air feed system further includes a first ventilation line between the pneumatic main line and the at least one ventilation connection. The first ventilation line has a first ventilation valve and a ventilation throttle. The compressed-air feed system additionally includes a second ventilation line between the compressed-air connection and the at least one ventilation connection. The second ventilation line has a second ventilation valve formed as a 2/2 directional valve. The compressed-air feed system is designed to provide an operating mode in which the second ventilation valve is open over a predetermined time period.

A hydraulic switching assembly for a motor vehicle, having a hydraulic pump (1) which guides a hydraulic medium from a reservoir (2) via hydraulic lines (3) and at least one magnetic valve assembly (4) including a magnetically actuatable switching valve (5), to a switching element (6) in order to hydraulically actuate the switching element (6) between two switching positions. A pressure accumulator (7) and a first check valve (8a) are mounted in a supply line (3a) upstream of the switching valve (5) in order to realize a reliable temporary supply of oil pressure to the switching element (6).

A valve block arrangement configured as a closed center system includes at least one main spool for controlling a hydraulic consumer. The main spool is configured to open and close at least one pressure medium connection between a hydraulic pump and the consumer in controlled, continuous fashion and, in at least one embodiment, is electrically activated. A bypass flow path with a cut valve branches off between the adjustable, hydraulic pump and the main spool. The cut valve is configured to open and close a pressure medium connection between the hydraulic pump and a tank in controlled, continuous fashion. The cut valve is electrically activatable.

A hydraulic unit includes an oil tank, a hydraulic pump, a first return pipe, and a first heat exchanger. The oil tank stores a hydraulic oil. The hydraulic pump supplies the hydraulic oil in the oil tank to an actuator. The first return pipe returns the hydraulic oil from a flow path between a discharge port of the hydraulic pump and the actuator to the oil tank. The first heat exchanger causes a coolant to exchange heat with the hydraulic oil returning to the oil tank through the first return pipe.