Center stud design
In a piezoelectric transducer, a design where a single stud runs through a center hole in the ceramics. This stud may be a separate component that threads into the front driver or it may be an integral part of the front driver. The portion of the stud that extends beyond the rear ceramic is threaded to accept a nut, which is often the back driver. When this nut is tightened, the ceramics are compressed between the back driver and front driver, thereby applying the required prestress to the ceramics.
In this design, the axis of the bolt coincides with the axis of the transducer and the ceramics are shaped like washers (i.e., with a center hole that provides clearance for the stud). Details ...
Also see —
Center bolt design
Peripheral bolt design