Abstract: A pre-stressed, sandwich-type, ultrasonic transducer assembly includes front and rear mass members having stacked therebetween alternating piezoelectric members and electrode members, with each of the members having surfaces which are substantially flat except for minute surface irregularities. Thin, soft, aluminum foil washers are respectively disposed between the facing surfaces of adjacent members of the stack. At least one bolt joins the front and rear mass members to subject it to a compressive pre-load, under which load the washers deform to follow the surface irregularities of the adjacent member surfaces and thereby fill inter-element voids created by such irregularities.

Abstract: A high power ultrasonic generator for driving a transducer/horn assembly includes a transistor bridge inverter power output circuit connected to a DC source for producing an alternating output current. A pulse generating circuit produces a bipolar train of pulses for controlling the switching of the transistors in the bridge inverter circuit. The pulse widths are adjusted to provide a dead time therebetween at least equal to the storage time of the inverter transistors to prevent any overlap in the conduction of the opposite legs thereof. Overload control means reduces the widths of the pulses when the output current exceeds predetermined levels, thereby to reduce the output current. A starting circuit in the pulse generator gradually increases the pulse widths during start-up of the generator, and other circuitry protects against unduly high current loads in the power supply during AC turn-on of the system.