Actuator for an aircraft landing gear assembly

A single acting actuator for an aircraft landing gear assembly, comprising:

• a housing;
• a cavity provided in the housing;
• a piston and a piston rod connected to the piston;
• the piston being mounted in the cavity for relative movement with respect to the housing such that the piston and piston rod are movable relative to the housing between a retracted position and an extended position;
• the piston dividing the cavity into first and second pressure chambers such that the volume of one of the pressure chambers is increased and the volume of the other is decreased as the piston is moved relative to the housing;
• the piston being movable relative to the housing from one of the retracted and extended positions to the other by a resultant force on the piston due to the pressure of actuator fluid in the first and second pressure chambers;
• wherein at least one of the pressure chambers is associated with first and second outlets, with the actuator being arranged such that, in respect of the relative movement in which the pressure chamber is the decreasing volume pressure chamber, in a first stage of the relative movement the first and second outlets are open thereby allowing actuator fluid to flow out of the pressure chamber through the first and second outlets and in a second stage of the relative movement the second outlet is open but the first outlet is closed, thereby acting to slow the relative movement of the piston with respect to the housing, and
• wherein the actuator is sealed with respect to the atmosphere.

A single acting actuator for an aircraft landing gear assembly, the actuator comprising:

• a housing;
• a cavity provided in the housing;
• a piston and a piston rod connected to the piston;
• the piston being mounted in the cavity for relative movement with respect to the housing such that the piston and piston rod are movable relative to the housing between a retracted position and an extended position;
• the piston dividing the cavity into first and second pressure chambers such that the volume of one of the pressure chambers is increased and the volume of the other is decreased as the piston is moved relative to the housing;
• the piston being movable relative to the housing from one of the retracted and extended positions to the other by a resultant force on the piston due to the pressure of actuator fluid in the first and second pressure chambers;
• and
• a connection which connects the first and second pressure chambers such that actuator fluid flows from the decreasing volume pressure chamber to the increasing volume pressure chamber;
• the actuator being arranged such that in respect of the relative movement in which the first and/or second pressure chambers is the decreasing volume pressure chamber, in a second stage of the relative movement the flow of actuator fluid out of the pressure chamber is restricted, relative to a first stage of the relative movement, thereby acting to slow the relative movement.

An actuation system for an aircraft landing gear assembly, the actuation system comprising:

• a single acting actuator comprising a housing, a cavity provided in the housing, and a piston and piston rod connected to the piston;
• a closed system of actuator fluid including an actuator fluid reservoir;
• and a pump;
• wherein
• the piston is mounted in the cavity for relative movement with respect to the housing such that the piston and piston rod are movable relative to the housing between a retracted position and an extended position;
• the piston divides the cavity into first and second pressure chambers such that the volume of one of the pressure chambers is increased and the volume of the other is decreased as the piston is moved relative to the housing;
• the actuation system is arranged such that the pump is operable to pump actuator fluid from the reservoir to the actuator so as to pressurise actuator fluid in at least one of the first and second pressure chambers so as to move the piston relative to the housing from the one of the retracted and extended positions to the other;
• and
• at least one of the pressure chambers is associated with first and second outlets, with the actuator being arranged such that, in respect of the relative movement in which the pressure chamber is the decreasing volume pressure chamber, in a first stage of the relative movement the first and second outlets are open thereby allowing actuator fluid to flow out of the pressure chamber through the first and second outlets and in a second stage of the relative movement the second outlet is open but the first outlet is closed, thereby acting to slow the relative movement of the piston with respect to the housing.

An actuation system for an aircraft landing gear assembly, the actuation system comprising:

• a single acting actuator for an aircraft landing gear assembly, the actuator comprising:
• a housing;
• a cavity provided in the housing;
• a piston and a piston rod connected to the piston;
• an actuator fluid reservoir;
• and
• a pump;
• wherein
• the piston is mounted in the cavity for relative movement with respect to the housing such that the piston and piston rod are movable relative to the housing between a retracted position and an extended position;
• the piston divides the cavity into first and second pressure chambers such that the volume of one of the pressure chambers is increased and the volume of the other is decreased as the piston is moved relative to the housing;
• the piston is movable relative to the housing from one of the retracted and extended positions to the other by a resultant force on the piston due to the pressure of actuator fluid in the first and second pressure chambers,
• at least one of the pressures chambers is associated with first and second outlets, with the actuator being arranged such that, in respect of the relative movement in which the pressure chamber is the decreasing volume pressures chamber, in a first stage of the relative movement the first and second outlets are open thereby allowing actuator fluid to flow out of the pressure chamber through the first and second outlets and in a second stage of the relative movement the second outlet is open but the first outlet is closed, thereby acting to slow the relative movement of the piston with respect to the housing;
• the actuation system is arranged such that the pump is operable to pump actuator fluid from the reservoir to the actuator so as to pressurise actuator fluid in at least one of the first and second pressure chambers so as to move the piston relative to the housing from the one of the retracted and extended positions to the other;
• and
• the actuation system comprises an emergency return line that connects the actuator to the actuator fluid reservoir, for passing actuator fluid from the actuator to the fluid reservoir, and
• a emergency return line flow control that is selectively controllable between an open configuration in which it allows actuator fluid to pass from the actuator to the actuator fluid reservoir and a closed configuration in which it prevents said return flow.