Ultrasonically driven low-speed rotary motor

Abstract

A device using longitudinal ultrasonic vibrations for rotating a shaft at relatively low rotational speeds is particularly useful for rotating a brush-type tooth polisher on an insert for an ultrasonic dental prophylaxis unit. The device has a sleeve which supports the rotatable shaft and a vibrator. A disc is normal to the axis of rotation of the shaft and connected to the shaft for rotation. A transducer at one end of the vibrator responds to excitation for producing longitudinal ultrasonic vibrations in the vibrator, and the other end of the vibrator which is urged against the disc with a constant force converts the longitudinal vibrations into elliptical motion to engage one face of the disc during an arc of the elliptical motion. This imparts substantially only pulses of tangential driving force and normal vibrational forces to rotate the disc and shaft unidirectionally. In one preferred embodiment, the vibrator has a single driving pad urged against the disc. In another, it is forked and has two contact pads (points) to engage the disc alternately on opposite sides of the shaft during opposite directions of the tangential elliptical motion for improved efficiency. In still another, the vibrator is bifurcated to engage opposed faces of the disc simultaneously to cancel the static loading forces acting on the disc whereby bearing wear is virtually eliminated.