This hydraulic system is provided with: a hydraulic pump; a pilot-type control valve; an electromagnetic proportional valve; a controller; and a pilot pressure switching unit which is capable of switching the electromagnetic proportional valve supply pressure to a first pressure during a normal operation, or to a second pressure lower than the first pressure. The control valve is provided with a bleed-off passage, and is capable of controlling the operating oil pressure supplied to the actuator, according to the opening area thereof. During an emergency operation, the electromagnetic proportional valve supply pressure is switched from the first pressure to the second pressure, the electromagnetic proportional valve is brought into a fully opened state, and the operating oil discharge amount from the hydraulic pump increases and decreases, and the operating oil pressure increases and decreases, and thus the operating speed of the actuator is controlled.

An apparatus for controlling a hydraulic machine, for example a turbine, pump or pump turbine, using variable-speed driven fixed displacement pumps. The apparatus includes a device for carrying out an emergency shut-off that is characterized by low energy consumption and high efficiency while guaranteeing all the operation-relevant and safety-relevant requirements of a hydraulic machine.

In a control unit of an electromagnetic valve system, a safety circuit includes a first switch and a second switch for switching, by control from a control circuit supply and shutdown of power from a drive power supply to an electromagnetic valve drive circuit. A common line extends to a plurality of electromagnetic valve units and is connected to one end of a plurality of solenoids. A plurality of power lines are connected to the other end of each of the plurality of solenoids. The electromagnetic valve drive circuit includes a plurality of open/close switches for switching, by control from the control circuit, supply and shutdown of power to the plurality of solenoids.

A dual spool valve and methods of controlling hydraulic fluid that is moved to a hydraulic actuator of an aircraft. The dual spool valve may include ports to receive and discharge hydraulic fluid. The dual spool valve may also include first and second valve sections that are selectively positionable to control the flow of hydraulic fluid into and out of the actuator. One position provides for hydraulic fluid to move through closure lines. Method of controlling the dual spool valve may provide for selectively positioning the valve sections to control the flow of hydraulic fluid, and to position the valve sections to move hydraulic fluid through a closure line during certain circumstances.

An electric motor-driven, rolling element screw linear actuator is presented which work in cooperation with an hydraulic actuator and share several components. This is achieved through the integration of a screw-driven integrated nut piston assembly. Combining the use of an electric screw driven actuator can also reduce the need for a redundant hydraulic system, resulting in the elimination of 50% of connections, valves, piping, pumps, filters etc., while still being 100% redundant. An additional advantage is that the two drive systems are technologically independent, and therefore will not both fail because of an identical component flaw or failure point. The systems may also be used at the same time if conditions require force in excess of that generated by the hydraulic actuator alone.

An actuator control arrangement comprising: a hydraulic actuator having a housing and a piston rod axially moveable within the housing between a neutral position, a retracted position and an extended position with respect to the housing in response to application of pressure to the piston rod; the arrangement further comprising a check valve moveable between a first position providing a flow path between a pressure source and the actuator, and a second position in which the flow path is closed off; and characterised by a mechanical link between the piston rod and the check valve, actuated in response to the piston rod passing a predetermined retracted position in a negative stroke direction, to set the check valve to the first position.

A hydraulic system of a construction machine includes: a pump that supplies hydraulic oil to a hydraulic actuator; a control valve on a center bypass line extending from the pump to a tank, the control valve including a bypass passage; an unloading valve on the center bypass line downstream of the control valve; and a controller that controls the unloading valve. The control valve is configured such that an opening area of the bypass passage is greater than an opening area of the unloading valve while an operation signal outputted from an operation device increases from a predetermined value to a first setting value, and such that the opening area of the bypass passage is less than or equal to of a maximum opening area of the bypass passage when the operation signal is greater than or equal to a second setting value greater than the first setting value.

Distributed trailing edge wing flap systems are described. An example wing flap system for an aircraft includes a flap and an actuator. The flap is movable between a deployed position and a retracted position relative to a fixed trailing edge of a wing of the aircraft. The actuator is to move the flap relative to the fixed trailing edge. The actuator is hydraulically drivable via first pressurized hydraulic fluid to be supplied by a hydraulic system of the aircraft. The actuator is also hydraulically drivable via second pressurized hydraulic fluid to be supplied by a local power unit. The local power unit is selectively connectable to an electrical system of the aircraft. The electrical system is to power the local power unit to supply the second pressurized hydraulic fluid.

A system for detecting and controlling the position of a spoiler of an aircraft wing is described herein comprising: a hydraulic actuator having a piston rod operably connected to the spoiler, the piston rod being moveable between a retracted position, a neutral position and an extended position; and means for providing power to said hydraulic actuator; and a mechanical device for detecting whether the piston rod is in the retracted position, the neutral position or the extended position; and means, operatively connected to the mechanical device, that is configured to provide a change in a load applied to said hydraulic actuator, wherein said means is configured to change said load based on whether said piston rod is detected as being in said retracted position or said extended position.

Provided is a joint device which can be connected by quick and simple operation while being subjected to high-pressure high-flow-rate pressurized operating oil. The present invention comprises: a closed chamber 27 provided in a hydraulic circuit on which pressurized fluid acts, the pressurized fluid circuit having an upstream side and a downstream side, which are closed by an upstream-side stop valve 211 and a downstream-side stop valve 212; a male joint 30 provided at a position in communication with the closed chamber 27; and a female joint 40 connectable to the male joint 30 and provided in an emergency hydraulic circuit connected to the hydraulic circuit. The present invention is configured so that the female joint 40 is connected to the male joint 30 while the closed chamber 27 is closed by the upstream-side stop valve 211 and the downstream-side stop valve 212.