Flextensional metal-ceramic composite transducer

DETAILED DESCRIPTION OF THE INVENTION Referring to FIG.
1, a first embodiment of the transducer of the invention includes a piezoelectric or electrostrictive ceramic annulus 10 with conductive electrodes bonded 12 and 14 bonded to opposed surfaces of annulus 10.
A pair of formed sheet metal end caps 16 and 18 take the shape of opposed truncated cones and include rims that are bonded to respective electrodes 12 and 14.
The cones are positioned such that they respectively extend into hollowed out area 20 within ceramic annulus 10.
To prevent electrical contact between end caps 16 and 18, insulating layers 22 may be placed on the opposed surfaces thereof.
Hereafter, the transducer configuration of FIG.
1 will be referred to as the inverted cymbal transducer to distinguish it from the standard cymbal transducer shown in U.
S.
Pat.
No.
5,729,077.
Each end cap is preferably produced by a stamping process wherein a metal sheet is both cut and shaped to a "cymbal" form in a stamping action.
The metal sheet preferably exhibits a relatively constant thickness dimension that is thin in relation to the overall surface area of the end cap structure.
The thickness of the metal sheet is dependent upon the actuation pressure required and will, as a result, be thicker when higher actuation pressures are needed.
Ceramic annulus 10 is preferably poled across its thickness dimension (i.
e.
, along the direction shown by arrow 24).
It is to be understood however, that ceramic annulus 10 can be poled in a radial direction.
A sensor 26 is coupled to conductive electrodes 12 and 14 and is adapted to measure a voltage thereacross that enables pressure-induced changes in polarization to be sensed.
If the transducer of FIG.
1 is subjected to a pressure wave P, end caps 16 and 18 are caused to move towards each other and as a result create radially inward-directed stresses on ceramic annulus 10, causing compressive forces thereon.
The arrangement of end caps 16 and 18 enables them to withstand substantially higher pressures than the arrangement of the cymbal transducer of U