Self-tightening drill chuck

A drill chuck comprising:

• a chuck body centered on and rotatable about an axis;
• a jaw holder rotatable on the body and formed with a plurality of angularly spaced guides;
• a sleeve surrounding the holder and body;
• respective jaws in the guides between the sleeve and the body;
• means for shifting the jaws in the guides forward and together on rotation of the holder in a tightening direction relative to the body and for opposite shifting of the jaws on rotation of the holder relative to the body in an opposite loosening direction;
• interengaging first and second stops on the body engageable with the sleeve and limiting relative angular movement of the sleeve on the body between respective angularly offset first and second end positions;
• an annular array of teeth rotationally fixed to the chuck body;
• a first pawl angularly fixed on the holder and engageable with the teeth, the pawl and the array of teeth being oriented such that when the pawl is in a locking position engaged with the array of teeth the holder can rotate relative to the body in the tightening direction but not in the loosening direction and when in a freeing position disengaged from the teeth the holder can rotate freely in either direction relative to the body;
• a second pawl angularly fixed on the holder and engageable with the teeth, the second pawl and the array of teeth being oriented such that when the second pawl is in a locking position engaged with the array of teeth the holder can rotate relative to the body in the loosening direction but not in the tightening direction and when in a freeing position disengaged from the teeth the holder can rotate freely in either direction relative to the body;
• respective first and second spring means for urging the first and second pawls into the locking positions;
• and
• means between the sleeve and the pawls for
• in the first end position displacing the first pawl into the locking position and the second pawl into the freeing position,
• in a middle position between the end positions displacing the second pawl into the locking position and the first pawl into the freeing position, and
• in the second end position displacing both the pawls into the respective freeing positions.