Abstract: A rotary impact tool including a generally tubular cage rotated by a motor about a central longitudinal axis of the cage. The cage has an internal wall with axially extending guide channels formed in it for receiving hammer pins capable of moving axially in the guide channels. The hammer pins have a generally flat striking surface. An output shaft mounted generally coaxially with the cage for rotation relative to the cage has radially outwardly projecting anvils having generally flat impact surfaces. A clutch mechanism intermittently moves the hammer pins to an extended position in which the striking surfaces of the hammer pins are in registration with the impact surfaces of the anvils. The striking surfaces of the hammer pins strike the impact surfaces of the anvils upon further rotation of the cage for delivering an impact to the output shaft, and then withdrawn by the clutch mechanism to regain momentum.

Abstract: By transferring the power fed from a motor to a ratchet mechanism through means of an impact clutch mechanism, a relatively large torque is obtained by the impact clutch mechanism. In addition when a torque greater than a predetermined level is applied to the ratchet mechanism, reaction is never given to the operator's hand because the impact clutch mechanism does not transfer a force greater than the present torque to the ratchet mechanism, thus permitting safe operation. With the ratchet mechanism, moreover, it becomes possible to effect such operation as first loosening and removing by the operator's force such members as bolts and nuts which have been additionally tightened independently or strongly tightened to a level in excess of a certain torque preset for the device.