High-frequency ultrasonic generators

Claim 1

A PIEZOELECTRIC GENERATOR COMPRISING IN COMBINATION: A PIEZOELECTRIC CRYSTAL ELEMENT HAVING A CIRCULAR CROSS SECTIONAL DIMENSION POLED TO VIBRATE IN A THICKNESS MODE OF VIBRATIONS, SAID ELEMENT HAVING A THICKNESS WHICH IS SUBSTANTIALLY A HALF-WAVELENGTH IN THE FREQUENCY OF SAID VIBRATIONS, A MOUNTING DISK HAVING A THICKNESS SUBSTANTIALLY EQUAL TO A HALF-WAVELENGTH IN SAID FREQUENCY AND A DIAMETER WHICH EXCEEDS THE DIAMETER OF SAID CRYSTAL ELEMENT, MEANS FOR BONDING A MAJOR SURFACE OF SAID CRYSTAL ELEMENT IN AXIALLY CONCENTRIC RELATION TO A MAJOR SURFACE OF SAID DISK AND IN ACOUSTIC COUPLING CONTACT THEREWITH, SAID DISK HAVING IN THE UPPER AND LOWER FACES THEREOF A PAIR OF ANNULAR GROOVES BETWEEN THE PERIPHERY OF SAID DISK AND THE PERIPHERY OF SAID ELEMENT, SAID GROOVES EACH HAVING A SUBSTANTIALLY RECTANGULAR CROSS-SECTION AND FORMING BETWEEN THEIR BASES A THIN ANNULAR RING CONTACTING THE INNER PORTION OF SAID MOUNTING DISK AT A NODAL PLANE IN SAID VIBRATIONS, A SHALLOW CYLINDRICAL CUP HAVING A BOTTOM WALL, THE PERIPHERAL PORTION OF SAID DISK BEYOND SAID GROOVES DISPOSED TO CLOSE SAID CUP IN A LIQUID-TIGHT SEAL, SAID CRYSTAL ELEMENT BEING DIRECTED INWARDLY AND HAVING ITS INNER FACE SPACED FROM THE BOTTOM WALL OF THE CUP TO DEFINE AN AIR CHAMBER BETWEEN THE INNER FACE OF THE CRYSTAL ELEMENT AND THE BOTTOM WALL, WHEREBY THE INNER FACE VIBRATES FREELY IN SAID AIR CHAMBER, ELECTRODE MEANS APPLIED TO OPPOSING SURFACES OF SAID CRYSTAL ELEMENT, AND MEANS COMPRISING LEAD WIRES CONNECTED TO SAID ELECTRODE MEANS AND ADAPTED FOR CONNECTION THROUGH A LIQUID-TIGHT SEAL TO AN EXTERNAL SOURCE OF ELECTRICAL OSCILLATIONS.