US Patent 7647862 Linear actuator

A dual-acting linear actuator including a hollow body and a stationary hollow rod. The stationary hollow rod includes a first rod segment separated from a second rod segment by a separator plate, the stationary hollow rod extending through the hollow body such that the separator plate forms a first chamber and a second chamber within the hollow body, wherein the first rod segment is configured to transmit a power medium to the first chamber to cause the hollow body to move along the stationary hollow rod toward the first rod segment and the second rod segment is configured to transmit the power medium to the second chamber to cause the hollow body to move along the stationary hollow rod toward the second rod segment.