Study of a recessless screw and a piezo electric screwdriver

Screw´s are very widely used in a variety of machines because of their ease of use and very high joint force. However, the cross- or minus- shaped recess on the head of a screw causes a lot of problems. First, the recess can make a machine less aesthetically pleasing. Second, many screwdrivers of different diameter have to be available. Third, if the recess is damaged by a screwdriver, it becomes difficult or impossible to tighten or loosen the screw. In order to solve these problems, this paper proposes the recessless screws. The proposed screwdriver uses piezo electric cells to rotate recessless screws. The piezo-electric cells vibrate at ultrasonic frequency, and the vibration generates tightening torque. The principle of the proposed screwdriver is examined by experiments.