US Patent 11165369 Pre-loaded piezoelectric stack actuator

A pre-loaded piezoelectric stack actuator comprising a stack of piezoelectric material. Caps are coupled at opposed ends of the stack. Each of the caps includes projecting fingers. Insulating plates are stacked between the ends of the stack and the caps. A pair of pre-loaded spring plates are coupled to the stack. The spring plates define slots. The fingers on the caps extend through respective ones of the slots at respective ends of the spring plates for coupling the spring plates to the stack. A method of pre-loading the piezoelectric stack actuator includes the step of mounting the stack, the caps, the insulating plates, and the spring plates in a pre-load tool that applies a pre-load tensile stretching force to the spring plates. The pre-load tensile force is subsequently released and the actuator is removed from the tool.