Force-balanced lathe chuck with safety ring

A lathe chuck comprising:

• a chuck body rotatable about a chuck axis;
• a plurality of angularly spaced and radially displaceable jaws on said body each formed with an axially backwardly open jaw recess having at least one side inclined to said axis;
• means including respective jaw actuators axially displaceable in said chuck body and having inclined end portions engageable in said recesses for inward radial displacement of said jaws on displacement of said actuators axially forwardly toward axially advanced positions and for outward radial displacement of said jaws on displacement of said actuators axially backwardly toward partially axially retracted positions, each actuator further being displaceable axially backwardly into an axially fully retracted position out of engagement with the respective jaw, said actuators engaging the respective jaws in and between said advanced and partially retracted positions;
• respective weights radially slidable on said chuck between inner and outer positions and through intermediate positions;
• respective springs urging said weights radially inwardly with respective spring forces greater than the weights of the respective weights but smaller than the normally encountered radially outwardly effective forces of said weights when said chuck is in use;
• means including respective force-transmitting members engaged between said weights and the respective jaws for conversion of radially outwardly effective centrifugal forces of said weights into radially inwardly effective forces on the respective jaws, each force-transmitting member being displaceable between axially advanced and partially retracted positions engageable with the respective jaw and into a fully retracted position unengageable with the respective jaw;
• and
• means including an element operatively engaging said members and actuators and displaceable on said chuck between a jaw-removal position in which said actuators and members can assume the respective fully retracted positions, and a use position for preventing sait actuators and members from moving axially backwardly beyond the respective partially retracted positions into the respective fully retracted positions.