Patent ID: 7661335

Claim:
A screw tightening apparatus comprising: a motor; an output shaft to which a bit for screw tightening is connected so as to be rotatable integrally with the output shaft and which is axially movable, the output shaft being driven to be rotated by the motor; a spring whose one end contacts a member constituting a main body of the screw tightening apparatus; a spring receiving member which the other end of the spring contacts, the spring receiving member transmitting a biasing force of the spring to the output shaft; a conductive member which contacts the output shaft and the spring receiving member; and a gear box that includes a first gear to which a rotation of the motor is transmitted, and a second gear provided on the output shaft, engaged with the first gear, and configured to move in an axial direction of the output shaft together with the output shaft relative to the first gear.