Abstract: An automatic overload release and power stoppage device consisted of a central control mechanism, a power switching mechanism, a power output mechanism, a torque control mechanism, and a release control mechanism, whereby the central control rod of the central control mechanism is moved upwards to trigger the power switch of the power switching mechanism in turning the main shaft thereof and the output shaft as the output shaft of the power output mechanism; the central control rod is moved downwards by the release control ring of the release control mechanism to cut off power source as the torsional force surpasses the critical level set by a torque control mechanism.

Abstract: A turn-on and turn-off control apparatus for electric screw-drivers including: a disk seat member with a plurality of tabs and blocks for making connections therewith; an arresting mechanism retractably disposed in the blocks, a positioning device fixed on the tabs in opposite direction; a turn-on switch matched with a first follower member and a second follower member connected to the positioning device; a turn-off switch matched with a braking follower member movably arranged on one side of the positioning device; and a linking-up device movably connected between the positioning device and a clutch and driving mechanism of an electric screw-driver, which is installed in a body structure together with the turn-on and turn-off control apparatus; thereby, turn-on and turn-off of the electric screw-driver can be effectively performed in screw tightening and loosing operations.