An aircraft (5) including a wing (7) having a wing tip device (1) configurable between: a flight configuration and a ground configuration in which the span of the wing (7) is reduced. The aircraft (5) further includes a lock (13) for locking the wing tip device (1) in the flight configuration, and an actuator (3) for unlocking the lock (13) and for subsequently actuating the wing tip device (1) to the ground configuration. The actuator (3) is a two-stage hydraulic actuator, including a first hydraulic actuator stage (21) arranged to unlock the lock and a second hydraulic actuator stage (23) arranged to actuate the wing tip device (1) to the ground configuration. The first and second hydraulic actuator stages (21, 23) are arranged in series such that the second actuator stage (23) is unable to receive a hydraulic input feed until the first actuator stage (21) unlocks the lock (13).

A control system may be used to control actuators that actuate movement of flight control surfaces of an aircraft. Each actuator is couplable to a flight control surface and includes a motion control assembly having a hydraulic motor and a drive path from the hydraulic motor to the flight control surface. Each hydraulic motor includes an extend port and a retract port. The system includes a hydraulic control module fluidly connected to the extend port and the retract port of each hydraulic motor and a controller operable to output hydraulic power from the hydraulic control module to the motion control assembly to actuate movement of the flight control surfaces. The controller is configured to identify an actuator that positionally leads the other actuators and reduce hydraulic power to the motion control assembly assigned to such actuator.

Apparatus and methods for metering fluid to a fluid actuator. An example apparatus may include a hydraulic actuator, a fluid chamber, and a hydraulic directional control valve. The fluid chamber may include a piston slidably movable between first and second ends of the fluid chamber and dividing the chamber into first and second chamber portions. The hydraulic directional control valve may direct a fluid from a fluid source into the first chamber portion to cause a volume of fluid to be discharged out of the second chamber portion into the hydraulic actuator to actuate the hydraulic actuator by a distance corresponding to the volume of fluid received by the hydraulic actuator.

The present disclosure relates to an adjustment system a method for compensating for temperature variations in a spool valve. The spool valve and adjustment system may be parts in a duplex hydraulic actuator. The adjustment device comprises a spring, a pivot point, and a shape memory alloy (SMA) device. The spring and SMA device are disposed on either side of the pivot point to hold the pivot point in a first position. The SMA device is configured to change size in response to a temperature change so as move the pivot point to a second location. This may eliminate force fight in the duplex hydraulic actuator by preventing asynchronous activation of the spool valves due to thermal expansion within the spool valves.

A hydraulic system for controlling bleed down and retraction of a boom within a safety envelope includes a backup battery power supply, and at least a first boom lift hydraulic cylinder configured to raise and lower the boom. The first boom lift hydraulic cylinder includes a solenoid bleed valve electrically connected to the backup battery power supply. The hydraulic system also includes an input device controllable by an operator of the boom. The input device may, for instance, be used by the operator to initiate bleed down and retraction of the boom from an elevated position. To accommodate independent failsafe features of the system, the input device is configured to selectively actuate the solenoid bleed valve using electrical power supplied from the backup battery power supply.

Apparatus and methods for metering fluid to a fluid actuator. An example apparatus may include a hydraulic actuator, a fluid chamber, and a hydraulic directional control valve. The fluid chamber may include a piston slidably movable between first and second ends of the fluid chamber and dividing the chamber into first and second chamber portions. The hydraulic directional control valve may direct a fluid from a fluid source into the first chamber portion to cause a volume of fluid to be discharged out of the second chamber portion into the hydraulic actuator to actuate the hydraulic actuator by a distance corresponding to the volume of fluid received by the hydraulic actuator.

The present disclosure relates to an adjustment system a method for compensating for temperature variations in a spool valve. The spool valve and adjustment system may be parts in a duplex hydraulic actuator. The adjustment device comprises a spring, a pivot point, and a shape memory alloy (SMA) device. The spring and SMA device are disposed on either side of the pivot point to hold the pivot point in a first position. The SMA device is configured to change size in response to a temperature change so as move the pivot point to a second location. This may eliminate force fight in the duplex hydraulic actuator by preventing asynchronous activation of the spool valves due to thermal expansion within the spool valves.

A hydraulic control circuit operable to selectively hydraulically link first and second hydraulic actuators and to bypass that hydraulic link.

The problem of providing a cylinder/piston unit which can be installed in a relatively space-saving manner, in particular, for use in a master/slave arrangement is solved by virtue of the fact that a first, outer hydraulic cylinder (2) is provided, in which a first piston (6) is mounted sealingly with respect to the cylinder inner wall of the first hydraulic cylinder (2) and longitudinally movable in the latter, and the first piston (6) supports a second, inner hydraulic cylinder (3), in which a second piston (9) is mounted sealingly with respect to the cylinder inner wall of the second hydraulic cylinder (3) and longitudinally movable in the latter. The second, inner hydraulic cylinder (3) supports a piston rod (10), and the piston rod (10) is connected at the end thereof which is remote from the second piston (9) to an end (4) of the outer hydraulic cylinder (2).

A device for automatically adjusting the working width of the first plough body of a plough in accordance with the variable working width of subsequent plough bodies. A first hydraulic cylinder displaces a rear frame section laterally. A second hydraulic cylinder pivots the rear frame section to adjust a transverse spacing of the plough bodies. The first hydraulic cylinder includes a multi-stage cylinder. A first cylinder stage forms a main lateral control, and a second cylinder stage forms an automatic working-width control for the first plough body. The second cylinder stage is in hydraulic-fluid communication with the second hydraulic cylinder in a master-slave configuration. The second cylinder stage is master or the slave depending on a moving direction of the cylinder stage and the second hydraulic cylinder being slave or the master. Piston diameters are matched to provide a correction of a lateral displacement of the front frame section.