A power transfer unit includes a first hydraulic circuit, a second hydraulic circuit fluidly connected to the first hydraulic circuit, a pump and motor assembly fluidly connected between the first hydraulic circuit and the second hydraulic circuit, an isolation valve arranged along the first hydraulic circuit and fluidly connected to an inlet of the pump and motor assembly. The isolation valve is movable between a closed position and an open position to prevent and enable high-pressure fluid flow to the inlet, respectively. An unloader valve is arranged along the second hydraulic circuit and fluidly connected to an outlet of the pump and motor assembly, and an orifice is arranged along the second hydraulic circuit and fluidly connected to the unloader valve to reduce back pressure in the second hydraulic circuit.

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 elevator may comprise a bidirectional pump that controls up and down motion of an elevator car. A VVVF drive may cause the bidirectional pump to provide working fluid in a controlled manner to a hydraulic jack that supports the elevator car. A control valve may be disposed between the bidirectional pump and the hydraulic jack so that the control valve can be closed when the elevator car needs to be held in place. To avoid pressure waves that propagate when the control valve is opened with disparate pressures on the pump and jack sides of the control valve, the bidirectional pump may adjust the pressure on the pump side of the closed control valve to the pressure on the jack side of the control valve before the control valve is opened.

The disclosure relates to a method of monitoring an electrohydrostatic actuator, wherein the electrohydrostatic actuator comprises a hydraulic pump drivable by an electric motor and a hydraulic activator drivable by means of the hydraulic pump to move a component, in particular an aircraft part. The method include detecting the instantaneous speed of the electric motor; detecting an instantaneous position of the activator; detecting a parameter that relates to an instantaneous operating point of the electrohydrostatic actuator; determining a state variable relating to an efficiency of the electrohydrostatic actuator on the basis of at least the detected speed and the detected position in dependence on the detected parameter; and determining a state of the electrohydrostatic actuator on the basis of the currently determined value.

A hydraulic system of a vehicle includes a first pump for supplying at least one first hydraulic circuit and at least one second pump for supplying at least one second hydraulic circuit with hydraulic medium. The second pump supplies the first hydraulic circuit with hydraulic medium in an emergency mode or when an output pressure of the first pump fails.

The left and right main landing gears on an aircraft are normally controlled by separate hydraulic power packs (HPP). Each HPP is sized for the load of the respective main landing gear. During failure of one of the HPP, a backup valve actuates to allow the other HPP to operate both main landing gears. With the backup valve actuated, the pump of the functioning HPP is coupled to the reservoirs of both HPPs and to the load paths to both main landing gears.

A failure detection apparatus for a hydraulic system, to a hydraulic, failure detection-capable system, and to a method of operating a failure detection apparatus. The failure detection apparatus comprises a monitoring and failure detection unit that receives first and second pressure values from first and second pressure sensors and comprises a failure detection unit that detects a failure of at least one hydraulically operated device when a 2-tuple of a plurality of 2-tuples is within a first and outside a second predetermined tolerance range of relative pressure values, and wherein the failure detection unit 260 detects a failure of the pump when a 2-tuple of the plurality of 2-tuples is outside the first predetermined tolerance range of relative pressure values.

A wheelchair lift system for a vehicle comprises: a platform for accommodating a wheelchair; a lifting arm; a hydraulic circuit including a hydraulic actuator arranged to act on the lifting arm to raise and lower the platform; a barrier mounted on the platform and pivotable between a raised position and a lowered position; a plurality of sensors each arranged to generate a sensor output; a user input device arranged to generate control signals to control operation of the lift; and a control unit. The control unit is arranged to receive the control signals and to receive the sensor output from each of the sensors and to control the hydraulic circuit thereby to control of the lift to perform a number of different operations. The control unit is also operable in a fully operational mode and a safety mode and is arranged to perform a plurality of checks on the sensor outputs, and to record a result of each of the checks, and to switch between the fully operational mode and the safety mode based on the results.

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.