| 摘要 |
PROBLEM TO BE SOLVED: To stabilize the unfastened quantity of a screw in comparatively low priced constitution by providing a beginning sensor detecting the position of a bit fitted into the cross recess of a screw, a completing sensor detecting that the screw is unfastened to fixed height, and an operating lever mechanism to make the sensors on or off. SOLUTION: After positioning the bit 5 of a motor 6 with a brake on the screw 2 of a work 1, an elevatable device 4 with floating function is brought down. Since the extreme end of the bit 5 is fitted into the cross recess of the screw 2, the bit 5 is brought down by the height to make a beginning sensor 10 on. Namely, an operating lever supporting shaft 9 is brought down, and because the sliding projection 14a moves in a slotted groove 11a, the operating lever 11 is rotationally moved to make a begging sensor 10 on. When the rotation is continued to unfasten the screw up to a fixed quantity, the screw 2 advances in the axial direction to elevate the bit 5, to make a completing sensor 12 on. Namely, accompanying with the elevation of the operating lever supporting shaft 9, another level 13 rotatably supported therewith is rotationally moved to make the completing sensor 12 on.
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