Abstract: Pre-loaded piezoelectric actuators provide improved work piece displacement, frequency of repetition, accuracy and repeatability. Actuators may use a coil spring providing a compressive force adequate to substantially fully compress a laminated piezoelectric element on a non-destructive basis. Upon activation, a pre-loaded actuator delivers a full workpiece drive stroke because piezoelectric element axial compression has previously occurred. Pre-loading methods and pre-loading to damp out element oscillation are also disclosed.

Abstract: A driving power unit for a piezoactivator is disclosed that utilizes a semiconductor switching device for supplying power to the piezoelement. When the voltage measured across the piezoelement attains a predetermined valve, the semiconductor switching device turns off. Sensing devices cause the switching device to turn on upon the voltage dropping by a predetermined margin and cause the voltage source to turn off when the switching device remains on beyond a predetermined time period. Memory and logic circuitry also control the switching sequence of the switching device.

Abstract: A press is described using piezoelectric actuators to achieve both the hold down of the work piece during the processing operation as well as powering the die used in deforming the work piece. The sub-assembly containing the piezoelectric element is structured to allow convenient removal from the main body of the press thereby facilitating repair operations, as well as coarse and fine adjusting facilities for the position of the piezoelectric element within the actuator assembly.