Piezoelectric revolving motors applicable for future purpose

The principle of a battery driven and IC-controlled m-watt ultrasonic motor called the Kumada motor, and its applications are outlined. The Kumada motor is based on a stator consisting of a piezoelectric revolving resonator. Its center of mass rotates around the geometric center drawing a circle a few micrometers in radius, at a very high speed of about several million revolutions per minute. The revolving motion is excited with a four-phase rotating voltage with a frequency of several tens of kilohertz. The stator of the motor has several kinds of shapes. An advantage offered by this motor is the concept of direct drive. As an example a novel type of clock is described with minute and hour hands driven independently and directly by two stators without gears and pivots