Patent ID: 7669507

Claim:
A tightening tool comprising: a body, a driving motor housed in the body, the driving motor configured to rotate in a normal rotation and a reverse rotation, a driving-side clutch element configured to receive torque of the driving motor both in the normal rotation and in the reverse rotation, an auxiliary clutch element rotated by the driving-side clutch element by the interaction of cam surfaces on the auxiliary clutch element, the cam surfaces on the auxiliary clutch element including first inclined surfaces, first projecting surfaces and first flat holding surfaces for interacting with second inclined surfaces, second projecting surfaces and second flat holding surfaces of the driving-side clutch element such that the auxiliary clutch element is movably provided in the axial direction away from the driving-side clutch element during reverse rotation of the driving-side clutch element, wherein the auxiliary clutch element and the driving-side clutch element are prevented from moving in the circumferential direction with respect to each other by contact between the first and second projecting surfaces, a driven-side clutch element configured to directly releasably engage with both the driving-side clutch element and the auxiliary clutch element so as to receive the torque of the driving-side clutch element to rotate in the normal rotation and directly releasably engage with only the auxiliary clutch element in the reverse rotation, a driven shaft configured to be driven by rotation of the driving-side clutch element, and a tool bit connected to the driven shaft to perform a tightening operation and a loosening operation via rotating torque of the driven shaft, wherein: the driven shaft configured to move in the axial direction with respect to the body together with the driving-side clutch element, during normal rotation of the driving motor, the driven-side clutch element is configured to move in the axial direction by application of a pressing force of the user to the body to engage with the driving-side clutch element, so that the torque of the driving motor in the normal direction is transmitted to the tool bit to perform a tightening operation, and during reverse rotation of the driving motor, the driving-side clutch element and the auxiliary clutch element are configured to move relatively with respect to each other in the axial direction by rotating torque of the driving-side clutch element, and the driving-side clutch element or the auxiliary clutch element is configured to engage with the driven-side clutch element, so that the torque of the driving motor in the reverse direction is transmitted to the tool bit to perform a loosening operation, whereby the engagement of the driven-side clutch element with the driving-side clutch element or the auxiliary clutch element is configured to occur without movement of the driven-side clutch element in the axial direction relative to the body.