Digital fluid stepping motor

A digital command stepping motor comprising:

• a cam mounted for rotation about an axis, said cam having a circular peripheral portion presenting a radially outwardly directed, smoothly undulating cam surface, defined by alternating peak and valley regions;
• a set of three linear actuators disposed radially outwardly from said cam surface, each said actuator comprising a radially extending push rod having an end portion in contact with said cam surface, means for forcibly driving its push rod endwise against said cam surface, and means for removing the drive force from its push rod;
• and
• said actuators being spaced relative to said cam surface such that when the push rod of any one actuator is fully extended and in contact with the bottom of a valley region, the push rod of the second actuator is in a partially extended position against a sloping surface between a peak and a valley, and the push rod of the third actuator is in a partially extended position against an oppositely sloping surface between a peak and a valley, so that the cam wheel can be rotated in position in either direction, by operating the actuators to drive the push rod which is in contact with the sloping surface which trails the direction of desired rotation while removing any radially inwardly directed force on the push rods of the other two actuators;
• and
• wherein said actuators are linear fluid motors having wall means defining a cylinder and, a piston slidably received in said cylinder to which the push rod is connected, said wall means and said piston defining an expansible chamber on the side of the piston opposite the push rod and said stepping motor further comprising means for delivering a driving fluid into and out from said expansible chamber.