Hydraulic control system for die pads in presses

Claim 1

IN A PRESS HAVING A MOVABLE DIE PAD ENGAGED BY THE WORK UPON CLOSING OF THE PRESS AND A HYDRAULIC CUSHION FOR SAID DIE PAD TO MOVE SAID PAD TO ITS EXTENDED POSITION AND TO PROVIDE A PREDETERMINED RESISTANCE TO MOVEMENT OF SAID PAD TO ITS RETRACTED POSITION UPON CLOSING OF THE PRESS, SAID HYDRAULIC CUSHION COMPRISING A CYLINDER HAVING A PISTON THEREIN REACTING AGAINST SAID PAD, A SOURCE OF FLUID UNDER PRESSURE, A FLUID CONNECTION BETWEEN SAID FLUID PRESSURE SOURCE AND SAID CYLINDER THROUGH WHICH PRESSURE FLUID IS SUPPLIED TO SAID CYLINDER TO MOVE SAID PAD TO SAID EXTENDED POSITION, A CHECK VALVE IN SAID CONNECTION TO PREVENT RETURN FLOW THERETHROUGH, A PAIR OF RETURN LINES CONNECTING SAID CYLINDER TO SAID FLUID PRESSURE SOURCE THROUGH WHICH FLUID IS RETURNED TO SAID SOURCE AS SAID PAD IS RETRACTED UPON CLOSING OF THE PRESS, A NORMALLY CLOSED PRESSURE RELIEF VALVE IN EACH OF SAID RETURN LINES, SAID RELIEF VALVES BEING DISPOSED IN PARALLEL RELATION TO EACH OTHER AND SET TO OPEN AT DIFFERENT PREDETERMINED PRESSURES, TIMING MEANS INTERPOSED IN THE RETURN LINE THROUGH THE PRESSURE RELIEF VALVE WHICH IS SET TO OPEN AT THE LOWER PRESSURE, SAID TIMING MEANS INCLUDING A VALVE MEMBER ADAPTED IN ONE POSITION THEREOF TO BLOCK SAID ONE RETURN LINE AND IN ANOTHER POSITION THEREOF TO OPEN SAID RETURN LINE, AND MEANS RESPONSIVE TO THE HYDRAULIC PRESSURE GENERATED IN SAID CYLINDER DURING CLOSING OF THE PRESS TO SHIFT SAID VALVE MEMBER FROM ONE OF SAID POSITIONS TO THE OTHER AT A PREDETERMINED RATE TO EFFECT DISCHARGE OF FLUID THROUGH EACH PRESSURE RELIEF VALVE DURING A PREDETERMINED PORTION OF THE WORKING STROKE OF THE PRESS.