US Patent 7497678 Clamp piston assembly with mold break function

A self-positioning clamp piston assembly (300) provides clamp-up, mold break and position reset function through the provision of distinct clamp-up (329), mold break (366) and reset (368) chambers. A position reference shoulder (337) on a piston front ring (330) fixed into a platen (12), permits positioning of a tie bar (12) to ensure clearance (102) between teeth (100) on the tie bar (12) and teeth (98) on a related but separate locking assembly (94). With the tie bar (12) coupled to a clamp piston (304) through a tie bar end plate (340), movement of the tie bar under clamp pressure displaces an independently moveable reset piston (360) from alignment with the tie bar end plate (340). Pressurization of the mold break chamber (366) causes displacement of the reset piston (360) from the shoulder (337), but re-alignment of the reset piston with the tie bar end plate (340). Finally, actuation of the reset piston (260) through pressurization of the reset chamber (368) restricts movement of the clamp piston (304) but permits the reset piston (360) to be moved back against the shoulder (337) to establish the clearance (102).