When piston 1 is moved to the left by the action of fluid delivered to the right end of its cylinder, helical gear 2, constrained against rotation by key a, moves to the left. This turns helical pinions 3 which mesh with gear 2 and carry jaws 4. As jaws 4 turn outward, they locate and clamp workpiece 5 by its circular recess. Workpiece 5 is released when piston 1 is moved to the right by spring 6.
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