Anti-stall mechanism

A method of selectively transmitting torque from a rotatable stator to a rotatable output shaft positioned in a wellbore, said method comprising:

• providing a drilling assembly including:
• a rotatable housing coupled to a drilling motor positionable in a wellbore and a rotatable output shaft coupled to a rotatable rotor of the drilling motor, said rotatable output shaft having a central longitudinal axis aligned with a central longitudinal axis of the rotatable stator;
• providing a locking clutch including:
• a plurality of slidable locking blocks slidably coupled to the rotatable output shaft, said slidable locking blocks slidable radially inwardly and outwardly with respect to a central longitudinal axis of the rotatable output shaft, said slidable locking blocks spaced apart circumferentially about the rotatable output shaft, each of said locking blocks having a first contacting face and a second contacting face;
• and,
• a plurality of fixed locking blocks coupled to the rotatable stator, said fixed locking blocks positioned radially around the output shaft and spaced apart circumferentially about the interior of the rotatable stator a distance sufficient to receive one of the slidable locking blocks when it moves inwardly toward the central axis of the rotatable output shaft, each said locking block having a first contacting face and a second contacting face;
• positioning the drilling assembly and the locking clutch in the wellbore;
• rotating the rotatable stator at a first rotational speed;
• rotating the rotatable rotor of the drilling motor relative to the rotatable stator at a second rotational speed greater than the first speed;
• and,
• moving the slidable locking blocks outwardly from the central axis of the rotatable output shaft by centrifugal force sufficient to overcome a biasing force applied by a biasing member to the slidable locking blocks.