Electrohydraulic actuator for aircraft control surfaces

An improved electrohydraulic actuator for use aboard an aircraft, said actuator being of a type including a balanced, double-acting hydraulic ram connectable between a support and a member to be moved relative to said support, such ram having a cylinder and a movable piston received within the cylinder, said piston dividing the cylinder into first and second chambers, one on each side of said piston, said actuator further comprising:

• a fixed displacement pump, the operative rotation of which is reversible, and having a pair of ports, said pump being characterized in that one of said ports acts as a pump outlet and the other of said ports acts as a pump inlet, and vice versa, depending on the direction of rotation of said pump, wherein said port acting as an outlet outputs hydraulic fluid at a certain outlet pressure;
• a reversible variable drive electric motor drivingly connected to said pump;
• a first conduit unobstructedly connecting one of said pump ports to one of said cylinder chambers, for providing an uninterrupted fluid flow path between said one port and said one chamber;
• a second conduit unobstructedly connecting the other of said pump ports to the other of said cylinder chambers, for providing an uninterrupted fluid flow path between said other port and said other chamber;
• a third conduit interconnecting said first and second conduits;
• an accumulator means, connected to said third conduit, for delivering pressurized hydraulic fluid thereto, at a pressure less than said pump outlet pressure;
• and
• valve means, positioned in said third conduit, for blocking pump outlet flow in one of said first and second conduits from flowing into the other of said first and second conduits, and for at the same time permitting hydraulic fluid flow from said accumulator means to be communicated into said other conduit.