| 摘要 |
A ratchet wrench having a self-shifting transmission apparatus having a rotational drive and a rotational output spindle with a ratchet driven by the output spindle. A first transmission gear and an overrunning clutch are rotatably connected in series between the rotational drive and the rotational output spindle. A centrifugal clutch is rotatably connected in series between the rotational drive and the rotational output spindle. The centrifugal clutch is rotatably connected to a shaft which rotates in the overrunning clutch such that upon the drive rotating at and above a predetermined rotational speed, the centrifugal clutch engages to rotate the output spindle while rotating the shaft to overrun within the overrunning clutch. Upon the drive rotating below the predetermined rotational speed, the centrifugal clutch disengages thereby permitting the overrunning clutch to engage the shaft and rotate the output spindle through the first transmission gear.
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