Electromechanical translation device comprising an electrostrictive driver of a stacked ceramic capacitor type

Claim 1

An electromechanical translation device for axially moving a shaft in a stepwise manner, said device comprising: a housing defining a hollow space in which said shaft is housed and from which it is extended outwardly of said housing; an electromechanical driver fixed to said housing within said hollow space and having first and second end surfaces, a cylindrical driver having an inner peripheral surface along which said shaft is freely movable and an outer peripheral surface, said driver comprising a pile including a plurality of electrostrictive driver layers which are stacked longitudinally along said driver, with internal driver electodes interposed between said electrostrictive driver layers; first and second controllable electromechanical grippers attached in said hollow space to said first and said second end surfaces, respectively, said grippers having cylindrical gripper inner peripheral surfaces along which said shaft is controllably and slidably movable and having gripper outer peripheral surfaces, each of said first and said second grippers comprising a pile having a plurality of electrostrictive gripper layers stacked transversely of said gripper inner peripheral surface of each of said first and said second grippers with gripper internal electrodes interposed between said electrostrictive gripper layers; power supplying means for controllably supplying electrical power to said driver and to said first and said second grippers to make said driver and said first and said second grippers cooperate for axially moving said shaft in a stepwise manner; driver connecting means for electrically connecting said driver internal electrodes to said power supplying means, said driver connecting means comprising first and second driver external electrodes along said driver outer peripheral surface, said first driver external electrode being electrically connected to alternate ones of said driver internal electrodes, said second driver external electrode being electrically connected to remaining ones of said driver internal electrodes; gripper connecting means for electrically connecting said gripper internal electrodes of each of said first and said second grippers to said power supplying means, said gripper connecting means comprising first and second gripper external electrodes along said gripper outer peripheral surface, said first gripper external electrode being electrically connected to alternate ones of said gripper internal electrodes, said second gripper external electrode being electrically connected to remaining ones of said gripper internal electrodes; and an electrically insulating and vibration damping film formed on said gripper inner peripheral surface of each of said first and said second grippers, wherein said electrostrictive layers of said driver and said first and said second grippers are of a composition described by a chemical formula of (1-X) Pb (Mg 1/3 Nb 2/3) O 3 ·X Pb Ti O 3 ; where X is about 0.35.