Patent ID: 7208861

Claim:
Electromechanical drive element comprising: volumes of electromechanical material; electrodes for exciting said volumes; a drive pad attached at a middle portion of said electromechanical drive element; said electromechanical drive element, when being strapped at two pivot supports at respective outer portions of said electromechanical drive element, having a vibration s-mode with a first resonance frequency f 1 ; said electromechanical drive element, when being strapped at said drive pad and at said two pivot supports at respective outer portions of said electromechanical drive element, having a vibration distorted s-mode with a second resonance frequency f 2 ; said s-mode being a vibration mode having three nodes, of which one is situated at said middle portion; said electromechanical drive element, when being strapped at said drive pad and at said two pivot supports, having a vibration ε-mode with a third resonance frequency f 3 ; said ε-mode being a vibration mode having one node at each side outside said middle portion and where said middle portion has a stroke amplitude that is smaller than a stroke amplitude at portions between said middle portion and said nodes; whereby f 3 differs from an average of f 1 and f 2 by less than 25%.