In the development of miniature opening and closing mechanism, piezoelectric element has been used as its actuator. This mechanism, however, tends to become larger and complicated as it needs a mechanism for displacement enlargement because of the infinitesimal output displacement. Therefore, an attempt applying buckling phenomenon of long column to the opening and closing mechanism has been made. An elastic member with a long strip shape was bent in the shape of M character, both ends fixed and the V-shaped common portion at the centre constituted to do reciprocating and translational drive. As a result, a simple miniature gripper with large rate of bending displacement at the finger tip to a translational displacement at the centre, namely the enlargement rate of the displacement G, has been developed.
In this study, in addition to the development of element technologies for product, increasing of the rate of gripping force F to driving tensile force P on the finger, that is, gripping efficiency Z was aimed. The results obtained are as follows.
(1) Hinge joints on supporting portions at both ends or the mid common portion of the ringers decrease initial load P-0 beginning to grip. They, however, little contribute to the improvement of Z. Reduction of P-0 is advantageous in energy.
(2) Crossing an operating member at the centre in the shape of X character so as to enlarge an angle of the operating members to the finger increases Z. G, however, decreases, so that the angle should be decided based on the object.
(3) Free support of an intermediate portion on a lateral surface of the finger allows the change of Z. When bending deformation outside at the centre in length of the finger is restrained, Z increases by about 2 times.