Center bolt design
In a piezoelectric transducer, a design where a single stack bolt runs through a center hole in the ceramics. When this bolt 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 bolt). Details ...
Also see —
Center stud design
Peripheral bolt design