| 摘要 |
A device comprises a housing having a planetary gear reduction mechanism accommodated therein and a handle projecting therefrom, an electric motor or like rotation source attached to the housing for inputting power to the reduction mechanism, an outer socket coupled to an internal gear of the reduction mechanism and engageable with a nut, an inner socket coupled to a planetary gear support frame of the reduction mechanism and engageable with a bolt tip, and a torque detecting control mechanism for detecting a nut tightening force to discontinue supply of power to the rotation source upon the tightening force reaching a predetermined value. A friction ring is provided between the housing and the support frame coupled to the inner socket to effect frictional engagement therebetween. A definite axial tension is available by rotating the outer socket, i.e., the nut, with the inner socket in a fixed state. Even if the bolt should rotate about its axis, the support frame slips, whereby the tightening device is prevented from turning around in its entirety.
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