Piezoelectrically driven ultrasonic generator

Claim 2

A transducer assembly comprising in combination: an ultrasonic generator which includes a pair of piezoelectric ceramic wafers having substantially parallel opposite major surfaces comprising electrode means interposed between the internal major surfaces of said wafers and on the two external surfaces thereof, said generator designed to vibrate in the direction of the longitudinal axis of said transducer assembly in a principal resonant-thickness mode of vibration. a cylindrical backing element having a pair of substantially flat end surfaces, means interposed between one said end surface of said cylindrical backing element and one of the opposite surfaces of said generator for bonding said backing element to said one face, a solid transforming member formed to include at its opposite ends a pair of substantially circular parallel disks coaxial with said ultrasonic generator each having a diameter slightly exceeding the diameter of said generator, said disks spaced apart along the axis thereof by a connecting portion symmetrical about the said axis and declining therebetween to a minimum diameter not exceeding about one-third the diameter of said disks, one of said disks being bonded in acoustical transfer relation to the other face of said generator, and the other said disk being free to function as an ultrasonic radiator.

Claim 3

The combination in accordance with claim 1 wherein the flat major surfaces of said cylindrical backing element and of said solid transforming member each have engraved thereon a series of concentric grooves, and said bonding means includes an epoxy cement interposed between said grooves in the one face of said backing element and one of the outer surface of said piezoelectric generator, and means including an epoxy cement interposed between said grooves in the major face of said transforming member and the outer surface of said piezoelectric generator.

Claim 4

The combination in accordance with claim 2 wherein said electrode means interposed between the major surfaces of said generator wafers and on the external surfaces thereof comprises electrically conducting epoxy.

Claim 5

The combination in accordance with claim 2 wherein the axial length of said transducer assembly from a plane bisecting the thickness of said radiator plate to the other end surface of said backing element approximates an integral number of quarter-wavelengths in the principal vibrating frequency of said transducer, and wherein the diameter of said disks approximates a half-wavelength in said vibrating frequency.

Claim 6

The combination in accordance with claim 2 wherein the ratio between the mass of said backing element and the mass of said transforming member including said radiator plate is at least about 1:1.

Claim 7

The combination in accordance with claim 1 wherein said transducer assembly is enclosed in a tubular inner housing, the end of the cavity of said housing containing the backing element of said asembly being partially closed by a plug having a central bore for accommodating a pair of energizing leads Connected across terminals on the electrode means of said ultrasonic generator, said end plug terminating in an annular flange, an externally screw-threaded hollow cylindrical outer housing having an enlarged cylindrical inner chamber constructed to accommodate the flanged end of said tubular inner housing, means comprising a series of o-rings of elastomer material constructed to fit between said tubular inner housing and the inner chamber of said outer housing for acoustically isolating said innner housing from said outer housing, said outer housing having a coaxially disposed extension, an electrical coaxial connector containing a solid insulating shell between a pair of conductors comprising a central conductor and an outer coaxial shell accommodated in the extension of said housing, said outer shell being in electrical contact with the said external housing, means for connecting one of the electrode terminals of said ultrasonic generator to the said central conductor, and means for providing an electrical conducting path between the other electrode terminal of said ultrasonic generator and said external housing.

Claim 8

the combination in accordance with claim 6 wherein said means for providing an electrical conducting path between the other electrode terminal of said ultrasonic generator and said external housing comprises a conducting strap interposed therebetween.

Claim 9

The combination in accordance with claim 6 wherein said means for providing an electrical conducting path between the other electrode terminal of said ultrasonic generator and said external housing includes conducting material interposed into said o-rings.