Branson Ultrasonics Corporation

Allan J Roberts

James F Sheehan

An electroacoustic converter is disclosed for converting electrical energy into mechanical vibrations at a predetermined frequency. The converter is supplied with alternating electrical power from a power supply. The converter has a metal front driver mass, a metal back driver mass, a front ceramic stack, a back ceramic stack, a spacer between said front and back ceramic stacks, and a fastener extending axially of the converter coupling the front and back drivers masses to clamp the ceramic stacks and the spacer between the front and back drivers. The front and back ceramic stacks are of a suitable piezoelectric ceramic material such that when energized with alternating electrical power from the power supply the piezoelectric material renders the converter resonant at the predetermined frequency. The spacer, back driver, and front driver masses are provided with fins to radiate heat from the converter. The converter exhibits substantially even temperatures and a vibrational node within the spacer.

Electroacoustic converter

An ultrasonic apparatus useable for welding metal by vibrations in the ultrasonic frequency range, employs a horn dimensioned to be resonant as a full wavelength resonator for vibrations of a predetermined frequency traveling longitudinally therethrough. To increase the energy available, the horn is coupled to a pair of transducers, one transducer coupled to each of the radially disposed end surfaces of the horn. During operation, one transducer must be in its longitudinal expansion mode when the other transducer is in its longitudinal contraction mode and vice versa. In order to accomplish this, two substantially identical transducers are used, but the orientation of the piezoelectric disc or discs in one of the transducers is reversed with respect to the orientation of the disc or discs in the other transducer.

Ultrasonic apparatus

In an ultrasonic apparatus a plurality of piezoelectric electroacoustic transducers (10, 12) are mechanically coupled to a horn (14) for providing ultrasonic vibrations thereto, and the transducers are energized in parallel from a common electrical power supply (28). In order to avoid the presence of circulating currents among the transducers, transformer balancing units (30) are connected in circuit with each of the transducers. Since the use of parallel connected piezoelectric transducers increases the total circuit capacitance, series connected capacitors (32, 34) are provided to restore the circuit capacitance to a value required for the resonant circuit condition.

An ultrasonic power supply for driving a piezoelectric transducer at its parallel resonant frequency includes a clamped-mode resonant converter for converting direct current to alternating current and a demodulator, a loop filter and a voltage controlled oscillator in a phase locked loop configuration. The power supply also includes a control circuit for adjustably setting and controlling the amplitude of vibration of the transducer, and providing during start-up a ramp start. The power supply, further, includes a control circuit for limiting the maximum permissible current flow to the transducer and the reverse current flow from the transducer resulting from stored mechanical energy. Both control circuits provide feedback signals which control the pulse width modulated operation of the clamped-mode resonant converter and thereby control the voltage amplitude of the alternating current output from the converter. The phase locked loop circuit causes the frequency of the alternating current output from the converter to track the parallel resonant frequency of the transducer.

Growing community of inventors

Poughquag, NY, United States of America

Allan J Roberts