Patent ID: 8066082

Claim:
An air driver device for tightening screw members at a prescribed tightening force and for shutting off a supply of compressed air when a tightening torque has reached a set torque value, said air driver device comprising: an air motor for receiving the supply of compressed air; a shut-off valve mechanism; and a tightening torque control mechanism for operating said shut-off valve mechanism to shut off the supply of compressed air to said air motor, wherein said tightening torque control mechanism includes: a clutch unit having a first clutch plate and a second clutch plate engaged with said first clutch plate; a driving piston having said first clutch plate formed on a back face thereof so that, when the tightening torque has reached the set torque value, (i) said first clutch plate and said second clutch plate are capable of rotating at different rates with respect to one another and (ii) said driving piston moves in an axial direction; a cylinder for storing said driving piston and having oil filled therein; a check valve linked to said driving piston through the oil filled in the cylinder, said check valve arranged to move in an axial direction in conjunction with said driving piston and for operating said shut-off valve mechanism to shut off the supply of compressed air when the tightening torque has reached the set torque value and said driving piston and said check valve move in an axial direction through the oil filled in said cylinder; and a torque control member for regulating the set torque value.