US Patent 7987668 Electro hydrostatic actuator with swash plate pump

A fluid pressure actuator includes an output cylinder, a fluid pressure pump, an electric motor, a first output cylinder passage, a second output cylinder passage, a return passage and a swash plate control cylinder. The output cylinder includes a first output cylinder chamber, a second output cylinder chamber and an output piston arranged between the first output cylinder chamber and the second output cylinder chamber. The fluid pressure pump includes a first supply and discharge port, a second supply and discharge port and a swash plate for changing displacement of the fluid pressure pump. The electric motor drives the fluid pressure pump. The first output cylinder passage connects the first output cylinder chamber and the first supply and discharge port. The second output cylinder passage connects the second output cylinder chamber and the second supply and discharge port.