Patent ID: 8226676

Claim:
An ultrasonic surgical instrument including a surgical unit which generates ultrasonic vibration to conduct a procedure of a site to be operated on and driving means for driving the surgical unit, wherein the driving means comprises: a first actuator provided with a first actuator main body formed of electrostrictive polymer and at least one pair of electrodes which are arranged on the first actuator main body so as to be separated from each other, wherein, when voltage is applied between the electrodes, the electrostrictive polymer is driven in a stretching and shrinking manner; a second actuator provided with a second actuator main body formed of electrostrictive polymer and at least one pair of electrodes which are arranged on the second actuator main body so as to be separated from each other, wherein, when voltage is applied between the electrodes on the second actuator main body, the electrostrictive polymer of the second actuator main body is driven in a stretching and shrinking manner; a fixing member which is coupled to the surgical unit; and power source means for ultrasonically vibrating the surgical unit via the fixing member at a time of driving the first and second actuators, wherein the surgical unit includes a blade which has a longitudinal axis, the fixing member is interposed between the first actuator and the second actuator in a longitudinal axial direction of the blade, and in a first voltage in which the electrostrictive polymer of the first actuator shrinks in a longitudinal axial direction while the electrostrictive polymer of the second actuator stretches in the longitudinal axial direction, and a second voltage in which the electrostrictive polymer of the first actuator stretches in a longitudinal axial direction while the electrostrictive polymer of the second actuator shrinks in the longitudinal axial direction, the power source means being configured to cyclically apply the first voltage and the second voltage alternately on the first actuator and the second actuator to ultrasonically vibrate the surgical unit via the fixing member.