| 摘要 |
A rotary stepper actuator having a rotatable output shaft provided with a cam portion fixedly secured thereto and engaged by a plurality of pairs of oppositely acting fluid pressure responsive pistons wherein each pair of pistons is movable along an axis intersecting the axis of the shaft. Preferably, the pistons are arranged in circumferentially spaced apart formation around the shaft and provided with roller elements adapted to bear against the cam portion the periphery of which takes the general form of an ellipse having opposite depressed mid portions. The applied piston forces acting through the rollers against the peripheral edge of the crank portion produce a force couple tending to rotate the shaft to the extent that the rollers become engaged with the opposite depressed mid portions whereupon the couple becomes reversed preventing further rotation of the shaft. By sequential pressurization of the plurality of pairs of pistons, the cam portion and thus the shaft connected thereto is made to rotate in one or more discrete steps or stepping motion. If desired, the plurality of pairs of pistons may be arranged in so-called "pancake" formation in which case the shaft is provided with a plurality of axially spaced apart cam portions corresponding to the plurality of pairs of pistons. |
