ROTATIONAL ULTRASONIC MOTOR

A rotary ultrasonic motor includes an ultrasonic actuator, a driven element, an inner casing member and an outer casing member. A piezoelectric or electrostrictive or magnetostrictive material is arranged between an excitation electrode and at least one general electrode. The ultrasonic actuator is between the inner and outer casing members of a casing, and is directly or indirectly in contact with the element to be driven, so that periodic deformations generated in the ultrasonic actuator by electrical excitation are transferable to the drive element. The ultrasonic actuator is mounted by a retaining device arranged on the casing with at least one retaining section which engages in a recess associated with a respective retaining section.