Digital torque-responsive pneumatic tool

A torque-responsive, automatically torque-controlling pneumatic impact-type torque tool of portable character, comprising:

• a portable housing for hand-held use;
• a pneumatic motor within the housing for being powered by a source of pressurized gas, an output shaft from the motor, and a coupling at a forward portion of the output shaft for coupling torque from the output shaft to a workpiece to which it is desired to apply torque to a predetermined torque value by rotation of the output shaft;
• an impact mechanism for coupling torque from the output shaft to the workpiece;
• a motor control within the housing having a trigger for permitting an operator to selectively supply gas from a source to the motor for its operation;
• a magnetorestrictive torque sensor within the housing and associated with the output shaft for systematically measuring the amount of torque being applied by the shaft as it supplies torque to the workpiece via the impact mechanism, the torque sensor comprising
• (a) multiple magnetic permeability regions in the form a pair of bands of magnetostrictive material exhibiting magnetic permeability, the bands being carried coaxially by the output shaft and spaced along a length of the output shaft, magnetic field-producing means for producing an external magnetic field around these regions, said regions providing respectively different magnetic responses when the shaft is delivering torque to the workpiece, each band of magnetostrictive material being constituted by at least a single wrap of film material wrapped coaxially about the output shaft;
• and
• (b) magnetic sensing means for magnetically sensing the different magnetic responses to indicate thereby the torque delivered to the workpiece, the magnetic permeability of the bands differentially varying in response to the torque delivered to the workpiece, the magnetic sensing means magnetically sensing the differential varying of the magnetic of the bands;
• a torque control input carried by the housing permitting the operator to select a predetermined torque value to be delivered to the workpiece;
• a torque control circuit interconnected with the torque control input and the torque sensor operating to compare the torque being applied to the output shaft with the predetermined torque value;
• and an air control within the housing operating to prevent pressurized gas from being supplied to the motor by the motor control and thus shutting off the motor to prevent application of further torque to the workpiece when the torque supplied to the shaft reaches the predetermined torque value as torque is being applied to the workpiece;
• whereby the tool applies to the workpiece torque at substantially no more than the predetermined level.