Patent ID: 7550903

Claim:
A method for polarizing a piezoelectric first actuator, comprising the steps of: providing the first actuator consisting of a number of piezoelectric layers which are arranged between two end surfaces, wherein each layer being arranged between two electrodes, applying changing voltage values for polarizing the layers to the electrodes of the layers, wherein the first actuator being arranged during polarization between two retaining elements providing a second actuator in series with the first actuator, wherein the second actuator comprises two end surfaces, wherein an end surface of the first actuator having an effective connection to an end surface of the second actuator, applying a compressive stress to the first and second actuators via the outer end surfaces through the retaining elements, supplying the first and the second actuator for polarization with a first or with a second changing voltage, defining, after a start phase, the voltages which are applied to the two actuators in a manner whereby the sum of the two voltages is approximately constant over time, so that the total length of the two actuators, despite the changes in length of the first and the second actuator generated by the voltages are kept approximately constant over time.