Patent ID: 6814152
Filing Date: 2004-11-09
Classification: B25B

Abstract:
A power wrench for tightening a screw joint to a predetermined target torque level, comprising:a housing; a motor; a power source; a control unit connected between the motor and the power source; an output shaft; an override type release clutch that couples the motor to the output shaft at torque levels below the target torque level and releases the motor from the output shaft upon attainment of the target torque level, wherein the clutch generates a characteristic clutch release sound when releasing the motor; and a microphone arranged to generate a signal indicative of the clutch release sound; wherein the control unit comprises a signal identifying device arranged to identify the clutch release sound indicative signal generated by the microphone; and wherein the control unit delivers a shut-off signal to the motor in response to identification of the clutch release sound indicative signal.