Two-stage hydraulic cushions for dies

Claim 1

IN A HIGH SPEED CRANK TYPE PRESS WHEREIN A DIE PAD REACTS ON THE WORK UPON THE CLOSING OF THE PRESS RAM AND THE RAM DECELERATES AS IT APPROACHES ITS CLOSED POSITION, A HYDRAULIC CUSHION ARRANGED TO RESIST MOVEMENT OF SAID DIE PAD UPON CLOSING OF THE PRESS RAM AND TO RETURN THE DIE PAD TO ITS EXTENDED POSITION UPON OPENING OF THE PRESS, SAID HYDRAULIC CUSHION COMPRISING A HYDRAULIC SYSTEM WHICH INCLUDES A HYDRAULIC WORK CYLINDER AND PISTON REACTING AGAINST SAID DIE PAD AND DISCHARGING HYDRAULIC FLUID THEREFROM AT A DECREASING RATE AS THE RAM CLOSES, A TANK OF HYDRAULIC FLUID UNDER PRESSURE, HYDRAULIC FLUID FLOW AND PRESSURE TRANSMITTING CONNECTIONS BETWEEN SAID TANK AND CYLINDER FOR SUPPLYING HYDRAULIC FLUID TO THE LATTER UNDER TANK PRESSURE AND NORMALLY CLOSED HYDRAULIC FLUID PRESSURE RELIEF VALVE MEANS ASSOCIATED WITH SAID HYDRAULIC CONNECTIONS SO AS TO CREATE A VARYING RESISTANCE TO THE DISCHARGE OF HYDRAULIC FLUID FROM SAID WORK CYLINDER UPON AND DURING CLOSING OF THE PRESS RAM, SAID RELIEF MEANS BEING CONSTRUCTED AND ARRANGED TO OPEN DIRECTLY IN RESPONSE TO A PREDETERMINED PRESSURE OF THE HYDRAULIC FLUID DISCHARGED FROM SAID WORK CYLINDER, THAT IMPROVEMENT WHEREIN SAID PRESSURE RELIEF VALVE MEANS COMPRISES TWO PRESSURE RELIEF VALVES OF DIFFERENT PRESSURE SETTINGS DISPOSED IN PARALLEL FLUID FLOW RELATION WITH RESPECT TO THE DISCHARGE OF HYDRAULIC FLUID FROM SAID WORK CYLINDER, THE LOW PRESSURE RELIEF VALVE BEING OF INSUFFICIENT CAPACITY AT THE PRESSURE FOR WHICH IT IS SET TO PASS THE AMOUNT OF HYDRAULIC FLUID DISCHARGED FROM SAID CYLINDER DURING THE RELATIVELY FAST MOVEMENT OF THE DIE PAD WHICH OCCURS IN THE FIRST PORTION OF THE DIE PAD MOVEMENT DURING CLOSING OF THE PRESS RAM WHEREBY THE LOW AND HIGH PRESSURE RELIEF VALVES OPEN DURING SAID FIRST PORTION OF DIE PAD MOVEMENT SO AS TO PERMIT THE RESULTING DISCHARGE OF HYDRAULIC FLUID FROM SAID WORK CYLINDER UNDER A PRESSURE AS DETERMINED BY THE HIGH AND LOW PRESSURE RELIEF VALVES, SAID LOW PRESSURE RELIEF VALVE HAVING SUFFICIENT CAPACITY TO ACCOMMODATE THE DISCHARGE OF HYDRAULIC FLUID FROM SAID WORK CYLINDER AT A DECREASED RATE DURING THE SUCCEEDING RELATIVELY SLOWER CLOSING MOVEMENT OF THE PRESS RAM WHEREBY AS THE RATE OF DISCHARGE OF HYDRAULIC FLUID FROM THE WORK CYLINDER DROPS TO SUCH DECREASED RATE, THE HIGH PRESSURE RELIEF VALVE CLOSES AND THE LOW PRESSURE RELIEF VALVE REMAINS OPEN TO PERMIT THE RESULTING DISCHARGE OF HYDRAULIC FLUID FROM THE WORK CYLINDER.