Peristaltic driver apparatus

Abstract

A peristaltic driver, also known as an Inchworm.RTM. actuator using stepping, 'clamp-extend-clamp', action of a piezoelectric actuator device provides motion in high resolution (steps) of an object, such as a probe of a scanning probe microscope or other optical, electrical and computer elements. The actuator device is an integral body made up of successive pusher and clamping sections. The clamping sections selectively clamp to members which are spaced from each other. An object is moved along a path between the members by being coupled to a pusher section which is disposed in symmetrical relationship with pairs of other pusher sections and pairs of clamping sections. Voltages are applied across the various sections and provide clamping action without transferring net forces in directions along which the object is pushed, thus reducing motion discontinuities each time the clamping sections extend or retract. The members along which the actuator moves are biased to apply a constant spring pre-load against the clamping members thereby compensating for dimensional changes due to thermal expansion or contraction of the actuator and mechanical wear. Tensile stresses on the piezoelectric material are minimized in that forces are transferred via the clamping sections when they are under compression. In a preferred embodiment, seven sections are used each made of a multiplicity of layers of piezoelectric, ceramic material which are oriented generally paralleling the surfaces of the members for the clamping sections and generally perpendicular to these surfaces for the pusher sections. These sections are interconnected by ceramic material and form a monolithic, integral body.