| 摘要 |
A screw joint tightening power tool including a torque limiting device and a rotation motor which via a planetary reduction gear (13) is arranged to deliver a torque to an output spindle (14). A torque responsive release clutch (22, 26, 27) is associated with the planetary gear (13) in order to maximize the output torque of the tool. The ring gear (20) of the planetary reduction gear (13) is rotatably as well as axially movable in the housing (10) and forms together with the housing (10) a torque responsive release clutch which is arranged to transfer a reaction torque from the planetary gear (13) to the housing up to a level determined by the axial bias force provided by a spring (28) acting on the ring gear (20). The release clutch comprises a cam (22, 26) for axially displacing the ring gear (20) against the action of said spring (28) upon rotation of the ring gear (20) relative to said housing (10) as a certain reaction torque level is exceeded. A sensor (33) is coupled to the ring gear (20) to detect axial displacement of the latter and cause deactivation of the power supply of the motor. |
