| 摘要 |
PURPOSE:To rotate a screw without applying an extra force to the screw, by providing a universal joint at a part of a driver bit to restrict movement on an axis of the driver bit until an engagement portion of the driver bit engages a head portion of the screw, and also providing a bit restriction releasing mechanism for releasing the restriction after the engagement is reached. CONSTITUTION:When a driver bit 11 is lowered to urge a lower end of a guide cylinder 14 against a head portion of a screw 13, the screw 13 is guided into the guide cylinder 14 by a recess 14a, and simultaneously slippage of axes of the bit 11 and the screw 13 is absorbed. Further lowering of the bit 11 causes compression of a coil spring 17 to urge an engagement portion 12 against the head portion of the screw 13. Then, the lowering of the bit 11 is stopped, and a rotating shaft 3 is rotated by a pulse motor 5 to thereby rotate the bit 11 through a ball spline nut 7, a ball spline shaft 8 and a universal joint 10. As a result, the lower end of the engagement portion 12 is engaged with a groove of the head portion of the screw 13. Accordingly, the screw 13 can be rotated without applying an extra external force thereto.
|
