Abstract: Disclosed is a rotating spindle assembly for a dental handpiece and a hollow cylindrical collet thereof to apply a variable gripping force by which to reliably retain a dental workpiece (e.g., a bur) and thereby prevent the bur from flying out of the collet when the bur is rotated at high speeds during a dental procedure. The collet includes a pair of collet members that are divided (i.e., spaced from one another) by a pair of longitudinally extending slots that are machined into opposite sides of the cylindrical collet. The pair of collet members are pivotally connected to one another at solid pivot junctions that are located in the pairs of slots.

Abstract: A pneumatic-hydraulic proportional valve actuator system is provided having a relatively simple and adjustable means of achieving two stroking speeds by the hydraulic actuator, high speed in normal operation and low speed for small position adjustments and for the final part of any large position adjustments. This prevents overshoot and instability of the actuator.

Abstract: A pneumatic-hydraulic proportional valve actuator system is provided having a relatively simple and adjustable means of achieving two stroking speeds by the hydraulic actuator, high speed in normal operation and low speed for small position adjustments and for the final part of any large position adjustments. This prevents overshoot and instability of the actuator.