An
actuator device (2) includes a piezoelectric or electro-strictive
solid state
actuator element (6) that is elongated upon application of an electric
voltage thereto, and a transmission mechanism (8) that amplifies the
stroke displacement of the
actuator element. The transmission mechanism (8) includes a plurality of
rigid frame members (12), including unitary frame members (12.1, 12.2) and divided frame members (12.3), and elastically flexible joints (10) that respectively interconnect the frame members. Each one of the divided frame members (12.3) is made up of a plurality of separate parallel link rods (16). Each flexible joint (10) is made up of a plurality of individual parallel hinge members (18) that respectively connect an end of each one of the link rods (16) to the adjacent unitary frame member (12.1, 12.2). By this division of the flexible joints and of the divided frame members into parallel sub-components, the cross-sectional thickness of each individual hinge member is reduced, and thereby the
bending stiffness and the outer
fiber strain of the material of the hinge members is significantly reduced while providing the same total tensile strength and tensile stiffness. The link rods of each divided frame member effectively form a
parallelogram linkage for moving and guiding the output members (12.1) in a parallel manner.