Hydraulic cushion for die pads in presses

Claim 1

IN A RAM TYPE PRESS WHEREIN A DIE PAD ENGAGES THE WORK AND IS RETRACTED UPON THE CLOSING OF THE PRESS RAM, A HYDRAULIC CYLINDER AND PISTON REACTING ON SAID DIE PAD TO RESIST SUCH MOVEMENT AND TO RETURN THE DIE PAD TO ITS EXTENDED POSITION AFTER OPENING OF THE PRESS RAM, A TANK OF HYDRAULIC FLUID UNDER RELATIVELY LOW PRESSURE, HYDRAULIC FLUID FLOW AND PRESSURE TRANSMITTING CONNECTIONS BETWEEN SAID TANK AND CYLINDER FOR SUPPLYING HYDRAULIC FLUID UNDER TANK PRESSURE TO THE CYLINDER WHEN THE TANK PRESSURE EXCEEDS THAT OF THE CYLINDER, AND NORMALLY CLOSED VALVE MEANS DISPOSED IN SAID HYDRAULIC CONNECTIONS SO AS TO PROVIDE A HIGH PRESSURE RESISTANCE TO THE DISCHARGE OF HYDRAULIC FLUID FROM SAID CYLINDER DURING CLOSING OF THE PRESS RAM, SAID VALVE MEANS COMPRISING A NORMALLY CLOSED COMBINED CHECK AND PRESSURE RELIEF VALVE HAVING HYDRAULIC PRESSURE RESPONSIVE SURFACES EXPOSED TO THE HYDRAULIC FLUID IN SAID CONNECTIONS, SAID HYDRAULIC CONNECTIONS INCLUDING A FLUID PORT FORMING A SEAT ON WHICH SAID VALVE SEATS IN ITS CLOSED POSITION, A SPRING BIASING SAID VALVE TOWARD ITS SEAT, SAID VALVE BEING CONSTRUCTED SO AS TO OPEN BY MOVEMENT IN ONE DIRECTION ONLY WHEN THE EFFECTIVE PRESSURE ACTING THE VALVE SURFACE EXPOSED TO FLUID PRESSURE ON THE TANK SIDE OF THE VALVE EXCEEDS THE EFFECTIVE PRESSURE ON THE OPPOSITE SIDE OF THE VALVE EXPOSED TO FLUID PRESSURE ON THE CYLINDER SIDE OF THE VALVE AND MEANS OPERABLE IN RESPONSE TO AN INCREASE IN THE PRESSURE ON THE HYDRAULIC CYLINDER SIDE OF SAID VALVE SUBSTANTIALLY ABOVE TANK PRESSURE FOR SUDDENLY REDUCING THE PRESSURE ON AT LEAST ONE OF SAID VALVE SURFACES EXPOSED TO THE PRESSURE ON THE CYLINDER SIDE OF SAID VALVE SO THAT RESULTANT PRESSURE ON SAID VALVE SURFACES WILL CAUSE SAID VALVE TO OPEN AND PERMIT THE FLOW OF HYDRAULIC FLUID FROM THE HYDRAULIC CYLINDER SIDE OF THE VALVE THROUGH SAID CONNECTIONS AND VALVE TOWARD SAID TANK.