Rotary hydraulic actuator with hydraulically controlled position limits

A rotary hydraulic actuator apparatus, comprising:

• a housing including:
• a peripheral wall and an end wall which cooperatively define a generally cylindrical internal chamber, where a first boss extends radially inward from the peripheral wall;
• and
• a port block defining a cylindrical bore communicating with the end wall, the port block further including a rotor supply port and a rotor drain port communicating with the bore, and a stator port communicating with the internal chamber through a stator hole in the boss;
• a rotor mounted for rotation in the internal chamber about an axis of rotation, the rotor including:
• a body with an arm extending laterally-outward therefrom;
• a first stub shaft which is received in the bore of the housing, the first stub shaft including base slots passing laterally therethrough;
• a first rotor port which is disposed in the arm in communication with the internal chamber, and oriented in a tangential direction relative to the axis of rotation;
• and
• internal passages which interconnect the rotor base slots and the first rotor port;
• and
• passages in the port block communicating with the bore and configured to interconnect the rotor supply port and the rotor drain port through the rotor base slots, at a preselected first angular position of the rotor relative to the housing.