In a vibration driven motor, a rotatable member is brought into frictional contact with a vibration member having an electro-mechanical energy conversion element and by the application of an AC electric field to the electro-mechanical energy conversion element, a driving vibration is excited in the vibration...http://www.google.com.au/patents/US5633553?utm_source=gb-gplus-sharePatent US5633553 - Vibration driven motor
