METHOD OF SECURING FASTENER

摘要

A method for automatically tightening a tapped member such as a nut is disclosed. A socket of an open end air wrench mounted on a nut tightening robot is coupled with the tapped member. The robot rotates the socket in a first direction, i.e., a tightening direction, to a first relatively small torque, and subsequently rotates the socket in a second direction opposite to the first direction to a predetermined position, i.e., a central receptive position after the socket being disengaged from the tapped member. A rotary encoder is provided to generate pulses in response to the rotation of the socket in the second rotational direction. An angle of rotation of this rotation of the socket in the second direction is detected by counting the number of pulses generated by the encoder. In response to the detected angle of rotation a torque wrench is coupled with the tapped member and the robot rotates the torque wrench in the tightening direction to a second relatively great torque.