Air auto shut-off

An automatic shutoff mechanism for a pneumatic torque-applying tool having an air motor with a rotor shaft and a rotational axis, a pressurized airflow path to the motor and a torquing mechanism driven by the motor, the shutoff mechanism comprising:

• a valve member movable between a normal open position permitting pressurized airflow to the motor and a closed position blocking pressurized airflow to the motor;
• bias structure resiliently urging the valve member to its normal open position,
• the valve member having opposite first and second sides such that in the open position only the first side is exposed to pressurized airflow;
• and
• a trip assembly including an inertia member coaxial with the rotor shaft, and
• a helical coupling assembly between the inertia member and the rotor shaft such that at constant velocity the rotor shaft and the inertia member rotate together, while rapid deceleration of the rotor shaft causes the inertia member to move rotatably and axially relative to the rotor shaft to a position spaced from the valve member by a distance inversely proportional to the torque applied,
• the trip assembly being responsive to application of a predetermined torque for moving the inertia member into engagement with the valve member to move the valve member to a trip position in the airflow path spaced from the open position sufficiently that the second side of the valve member is exposed to pressurized airflow for driving the valve member from the trip position to the closed position.

A pneumatic torque-applying tool comprising:

• an air motor;
• a structure defining a pressurized airflow path to the motor;
• torquing mechanism coupled to the motor and driven thereby;
• and
• automatic shutoff mechanism including,
• a valve member movable between a normal open position permitting pressurized airflow to the motor and a closed position blocking pressurized airflow to the motor,
• bias structure resiliently urging the valve member to its normal open position,
• the valve member having opposite first and second sides such that in the open position only the first side is exposed to pressurized airflow, and
• a trip apparatus responsive to application of a predetermined torque by the torquing mechanism for moving the valve member to a trip position in the airflow path spaced from the open position sufficiently that the second side of the valve member is exposed to pressurized airflow for driving the valve member from the trip position to the closed position.

An automatic shutoff mechanism for a pneumatic tool having an air motor, a pressured air flow path to the motor and output mechanism driven by the motor for applying force to a work piece, the shutoff mechanism comprising:

• a valve member movable between a normal open position permitting pressurized airflow to the motor and a closed position blocking pressurized airflow to the motor;
• bias structure resiliently urging the valve member to its normal open position;
• and
• a trip assembly responsive to application of a predetermined reactive force to the output mechanism for moving the valve member to a trip position,
• the trip assembly including a reactive force responsive device responsive to the reactive force on the output mechanism to generate a signal indicative of the reactive force, and
• an actuator assembly responsive to the signal indicative of the predetermined reactive force level for moving the valve member to a trip position in the airflow path spaced from the open position sufficiently that the valve member is exposed to pressured airflow for driving the valve member from the trip position to the closed position.