| 摘要 |
A power screw driver for tightening self-tapping screws comprises a housing (10), a rotation motor, an output shaft (12), a torque limiting release clutch (11) having torque transferring cam means (17, 19) and a spring biassed thrust element (20) exerting an engagement force on the cam means (17, 19) and yielding axially to a release position as a desired output torque is reached, and a screw bed (32) engaging contact member (31) coupled to an activation means (42) and arranged to be axially displaced to shift by means of the activation means (42) a lock means (36, 39) from a thrust element (20) locking position during the thread forming phase of the tightening process to a thrust element (20) unlocking position during the final pretensioning phase. <IMAGE> |
