Abstract: Shock caused to a clutch mechanism of an electric screw driver is minimized by bearing members, adjacent to upper and lower clutch members, which are provided with bearing distal ends which contact one another when one of the clutch members moves toward the other clutch member by means of the biasing force of an adjustment coil spring. The bearing distal ends prevents the clutch members from impacting with one another. Resilient convex discs which bulge in opposite directions are provided adjacent to one of the bearing member to absorb shock caused to the bearing members. Limitedly movable engaging members are provided in the clutch members to minimize localized wear of the engaging members.

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.

Abstract: An electric screwdriver with an improved automatic turn-off device has a novel clutch mechanism with a upper clutch member and a lower clutch member, a switch device for controlling the driving means according to the tightness of a screw or nut on a workpiece and a switch device supporting means with a force absorbing spring, wherein said upper clutch member has two bottom substantial triangular cam protrusions, each of which has two arcs with different curvature and the lower clutch member has a flange portion with two holes and ball members whereby they are arranged and assembled in a simple mechanism for the user to use conveniently and effectively.