Schraubenfestziehvorrichtung

摘要

A screw tightening apparaus of type including an electric screwdriver the bit shaft of which is arranged to carry a male screw engaged therewith to be threaded into a mounting hole of a workpiece and a drive mechanism arranged to move the screwdriver toward and away from the mounting hole of the workpiece, wherein the screwdriver and drive mechanism are controlled in such a manner that the bit shaft is driven at a low speed and applied with a small thrust force at an initial stage during which the male screw is located to be engaged with the mounting hole, that the bit shaft is driven at a higher speed than that at the initial stage and applied with a larger thrust force than that at the initial stage at an interim stage during which the male screw is threaded into the mounting hole and that the bit shaft is driven at a lower speed than that at the initial stage and applied with a larger thrust force than that at the interim stage at a final stage during which the male screw is tightened and seated on the workpiece.