US3264858A - Hydraulic control for dies in ram type presses - Google Patents

Description

9, 1966 F. M. WWW mmm HYDRAULIC CONTROL FOR DIES IN RAM TYPE PRESSES Filed June 25, 1963 IN VEN TOR.

HI I I gy h zr/zamm United States Patent M 3,2643% HYDRAULIC CONTROL FDR DIES IN RAM TYPE PRESSES Floyd M. Williamson, Detroit, Mich, assignor to Di-lDro Engineering Company, Detroit, Mich, a corporation of Michigan Filed June 25, 1963, Ser. No. 290,557 7 Claims. (Cl. 72351) This invention relates to a hydraulic control system for die pads in ram type presses and has particular reference to hydraulic cushions for movable die pads in presses and hydraulic control means for providing different resistances to retraction of two or more die pads upon closing of the press.

The present invention is directed to a hydraulic system for one die or set of dies in a press in which resistance to retraction of the die pad is provided by forcing a relatively small quantity of hydraulic fluid through a pressure relief valve while the die pad is returned to its extended position by relatively low pressure hydraulic fluid reacting against a larger area of the reciprocable piston which reacts against the die. Another die or set of dies react against a second piston which is reciprocablewithin a cylinder bore within the first piston and is also connected to the hydraulic fluid source through the pressure relief valve upon closing of the press. With this arrangement, it is possible to select the diameters of the telescoping pistons in such a way as to provide different predetermined resistances to retraction of the several die pads so as to assist in forming operations and return the die pads to their extended positions for stripping the work from the dies. The invention, therefore, provides two or more movable die pads controlled by a single pressure relief valve thereby providing economy in manufacturing costs and a reduction in the size of the control system.

A principal object of the invention is to provide a new and improved hydraulic control system for dies in ram type presses. Another object of the invention is to provide a new and improved hydraulic control system for dies which results in substantial saving in manufacturing costs and in the space required for the control system on the press. Another object of the invention is to provide a hydraulic cushion for two or more dies in which different resistances to the retraction of the dies in provided through a single control valve.

Other and further objects of the invention will be apparent from the following description and claims and may be understood by reference to the accompanying drawings, of which there is one sheet, which by way of illustration shows a preferred embodiment of the invention and what I now consider to be the best mode applying the principles thereof. Other embodiments of the invention may be used without departing from the scope of the present invention as set forth in the appended claims.

As shown in the drawing, a ram .type mechanical press may include a movable die pad 10 and a movable die pad 12 over which the work is to be formed upon closing of the ram (not shown) of the press. The hydraulic control system for the dies 10 and 1 2 includes a tank 14 containing hydraulic fluid under a regulated pressure of, for example, 100 pounds per square inch. A cylinder block 16 is provided with a cylinder bore 18 within which a piston 20 is reciprocable. The piston 20 carries a washer 22 which sealingly engages the cylinder bore 18. A second piston 24 is integral with the piston 21 but is of smaller diameter and carries a washer 26 which sealingly engages a cylinder bore 28 in the cylinder block 16. The piston 20 is provided with a cylinder bore 30 containing a reciprocable piston 32 which is provided at its lower Patented August 9, 1966 ICC end with a washer 34 sealingly engaging the cylinder bore 30. A passage 36 in the piston 24 provides communication between the lower end of the cylinder bore and the cylinder bore 28.

The piston 20 is provided at its upper end with a reduced diameter portion defining a shoulder 40 for supporting a series of rods 42 which are engaged by the movable die pad 10. The lower ends of the rods 42 are secured to a pair of support rings 44, one of which is seated on the shoulder 40 and the other of which is engaged by a retaining Washer 46 to rigidly mount the rods 42 on the upper end of the piston 20. A series of rods 43 are mounted in a similar manner on the upper end of the piston 32 and engage the movable die pad .12.

A hydraulic fluid connection 50 leads from the lower end of tank 14 to a fitting 52 on the cylinder block 16. A passage 54 provides communication between the lower end of cylinder 18 and the hydraulic line 50. A hydraulic fluid line 56 also leads from the tank 14 to a valve unit 58 which includes a pressure relief valve 60 and a ball check valve 62. Cylinder block '16 is provided with a passage 64 providing communication between the lower end of the cylinder 28 and a line as communicating with the interior of the valve unit 58.

When the press is opened, hydraulic fluid under pressure in the tank 14 will be forced through line 50 and passage 54 into the lower end of the cylinder 18 to react against the underside of the piston 28. The hydraulic fluid under tank pressure will also flow through line 56 into passage 68 in the valve 58 past check valve 62 and through passage 70, line 66, and passage 64 into the lower end of the cylinder 28 to react against the underside of the piston 24 and through passage 36 into the lower end of the cylinder 30 to react against the underside of the piston 32. The pistons 20, 24 and 32 will thus all be forced upwardly by hydraulic fluid under tank pressure to move the die pads 1d and 12 to their extended positions shown in the drawing.

When the press closes, hydraulic fluid in the cylinder 30 and the cylinder 28 is trapped by the check valve '62 and then returned to the tank 14 only by forcing open the pressure relief valve 60 which may be set by an adjusting screw 72 to open .at a predetermined pressure. The hydraulic fluid in the cylinder 18 is returned directly to the tank 14 through passage 54 and the connection 50. The pistons 24 and 32 are :both subjected to the same pressures which resist retraction of the pistons and retraction of both pistons 24 and 32 is controlled by the single pressure relief valve 611. However, by selecting different diameters for the pistons 24 and 32, or different areas exposed to the pressure fluid resisting their retraction, different predetermined resistances to movement of the die pads is provided. The differences in the areas of the pistons may also be utilized to assist in stripping the work from the dies.

The control system described not only has the advantage of providing for control of two or more sets of dies through a single control valve but also provides a relatively large area reacted upon by hydraulic fluid under tank pressure to return the dies to their extended positions while only a relatively small area reacts against the high pressure fluid which is trapped by the pressure relief valve upon closing of the press. This latter feature is disclosed in my co-pending application Serial No. 114,264, filed June 1, 1961, for Hydraulic Control for Die Pads in Presses, now U.S. Patent No. 3,124,340 and in my co-pending application Serial No. 145,297, filed October 16, 196 1, [for Hydraulic Control lfor Dies in Ram Type Presses, the present application being a continuation in part of such prior co-pending applications.

While I have illustrated and described a preferred embodiment of my invention, it is understood that this is capable of modification, and I therefore do not wish to be limited to the precise details set forth but desire to avail myself of such changes and alterations as fall within the purview of the following claims.

I claim:

1. In a press having a pair of dies each movable from an extended to a retracted position upon closing of the press, a hydraulic cushion reacting on said dies so as to resist retraction thereof, said hydraulic cushion comprising a tank of hydraulic fluid under pressure, a cylinder having two bores, a piston reciprocable in each bore and reacting on one of said dies so as to be retracted as said one die moves toward its retracted position, a hydraulic circuit including fluid flow connections between said tank and said cylinder bores through which hydraulic fluid under tank pressure is supplied to each cylinder bore when the press opens so as to cause said pistons to bias said one die toward its extended position, said fluid flow connections providing for hydraulic fluid flow from said cylinder bores toward said tank upon the retraction of said pistons, a pressure relief valve in the connection between one of said bores and said tank so as to provide a resistance substantially greater than tank pressure to the retraction of the piston in said one bore, said pistons being integral and being provided with a cylinder bore communicating with said one cylinder bore, a third pistonin said cylinder bore in said pistons, the other of said dies being arranged to react on said third piston to provide a resistance substantially greater than tank pressure to the retraction of said third piston in its cylinder bore, said pistons having different diameters so as to provide different predetermined resistances to retraction of said dies upon closing of the press.

2. In a press having a pair of dies each movable from an extended to a retracted position upon closing of the press, a hydraulic cushion reacting on said dies so as to resist retraction thereof, said hydraulic cushion comprising a tank of hydraulic fluid under pressure, a cylinder having two bores, a piston reciprocable in each bore and reacting on one of said dies so as to be retracted as said one die moves toward its retracted position, a hydraulic circuit including fluid flow connections between said tank and said cylinder bores through which hydraulic fluid under tank pressure is supplied to each cylinder bore when the press opens so as to cause said pistons to bias said one die toward its extended position, said fluid flow connections providing for hydraulic fluid flow from said cylinder bores toward said tank upon the retraction of said pistons, a pressure relief valve in the connection between one of said bores and said tank so as to provide a resistance substantially greater than tank pressure to the retraction of the piston in said one bore, said pistons being integral and being provided with a cylinder bore communicating with said one cylinder bore, a third piston in said cylinder bore in said pistons, the other of said dies being arranged to react on said third piston to provide a resistance substantially greater than tank pressure to the retraction of said third piston in its cylinder bore, the piston in said one bore and said third piston having different areas exposed to the hydraulic fluid in their respective cylinder bores so as to provide different predetermined resistances to retraction of said dies upon closing of the press.

3. In a press having a pair of dies each movable from an extended to a retracted position upon closing of the press, a hydraulic cushion reacting on said dies so as to resist retraction thereof, said hydraulic cushion comprising a tank of hydraulic fluid under pressure, a cylinder, a piston reciprocable in said cylinder and reacting on one of said dies so as to be retracted as said one die moves toward its retracted position, a hydraulic circuit including fluid flow connections between said tank and said cylinder through which hydraulic fluid under tank pressure is supplied to said cylinder when the press opens 80 as to cause said piston to bias said one die toward its extended position, said fluid flow connections providing for hydraulic fluid flow from said cylinder toward said tank upon the retraction of said piston, a pressure relief valve in the connection between said cylinder and said tank so as to provide a resistance substantially greater than tank pressure to the retraction of said piston, said piston being provided with a cylinder bore communicating with said cylinder, a second piston in said cylinder bore, the other of said dies being arranged to react on said second piston to provide a resistance substantially greater than tank pressure to the retraction of said second piston in its cylinder bore, said pistons having different areas exposed to the hydraulic fluid in their respective cylinder bores so as to provide different predetermined resistances to retraction of said dies upon closing of the press.

4. In a press according to claim 3, a third cylinder having a piston therein reacting against one of said dies and a fluid flow connection between said tank and said third cylinder through which hydraulic fluid under tank pressure is supplied to said third cylinder when the press opens to assist in biasing said one die toward its extended position,

5. In a press according to claim 4, said piston in said third cylinder and said first mentioned piston being integral.

6. In a press having a pair of dies each movable from an extended to a retracted position upon closing of the press, a hydraulic cushion reacting on said dies so as to resist retraction thereof, said hydraulic cushion comprising a tank of hydraulic fluid under pressure, a cylinder, a piston reciprocable in said cylinder bore and reacting on one of said dies so as to be retracted as said one die moves toward its retracted position, said piston having a cylinder bore therein, a second piston in said last mentioned cylinder bore and reacting on the other of said dies so as to be retracted as said other die moves to its retracted position, a hydraulic circuit including fluid flow connections between said tank and said cylinder bores through which hydraulic fluid under tank pressure is supplied to each cylinder bore when the press opens so as to cause said pistons to bias said dies toward their extended positions, said fluid flow connections providing for hydraulic fluid flow from said cylinder bores toward said tank upon the retraction of said pistons, a pressure relief valve in the connections between said bores and said tank so as to provide a resistance subtantially greater than tank pressure to the retraction of said pistons, said pistons having different areas exposed to the hydraulic fluid in their respective cylinder bores so as to provide different predetermined resistances to retraction of said dies upon closing of the press.

7. In a press having a pair of dies each movable from an extended to a retracted position upon closing of the press, a hydraulic cushion reacting on said dies so as to resist retraction thereof, said hydraulic cushion comprising a tank of hydraulic fluid under pressure, a cylinder bore, a piston reciprocable in said cylinder bore and reacting on one of said dies so as to be retracted as said one die moves toward its retracted position, said piston having a cylinder bore therein, a second piston reciprocable in said last-mentioned cylinder bore and reacting on the other of said dies so as to [be retracted as said other die moves to its retracted position, a hydraulic circuit including fluid flow connections between said tank and said cylinder bores through which hydraulic fluid under tank pressure is supplied to each cylinder bore when the press opens so as to cause said pistons to bias said dies toward their extended positions, said fluid flow connections providing for hydraulic fluid flow from said cylinder bores toward said tank upon the retraction of said pistons, a pressure relief valve in the connection between one of said bores and said tank so as to provide a resistance substantially greater than tank pressure to the retraction of the piston in said one bore,

different areas exposed to the hydraulic fluid in their 5 respective cylinder bores so as to provide difierent predetermined resistances to retraction of said dies upon closing of the press.

References Cited by the Examiner UNITED STATES PATENTS Hothersall 72351 Gaudreau 72351 Williamson 267-1 Williamson 2671 CHARLES W. LANHAM, Primary Examiner. R. J. HERBST, Assistant Examiner.

Claims (1)

1. IN A PRESS HAVING A PAIR OF DIES EACH MOVABLE FROM AN EXTENDED TO A RETRACTED POSITION UPON CLOSING OF THE PRESS, A HYDRAULIC CUSHION REACTING ON SAID DIES SO AS TO RESIST RETRACTION THEREOF, SAID HYDRAULIC CUSHION COMPRISING A TANK OF HYDRAULIC FLUID UNDER PRESSURE, A CYLINDER HAVING TWO BORES, A PISTON RECIPROCABLE IN EACH BORE AND REACTING ON ONE OF SAID DIES SO AS TO BE RETRACTED AS SAID ONE DIE MOVES TOWARD ITS RETRACTED POSITION, A HYDRAULIC CIRCUIT INCLUDING FLUID FLOW CONNECTIONS BETWEEN SAID TANK AND SAID CYLINDER BORES THROUGH WHICH HYDRAULIC FLUID UNDER TANK PRESSURE IS SUPPLIED TO EACH CYLINDER BORE WHEN THE PRESS OPENS SO AS TO CAUSE SAID PISTONS TO BIAS SAID ONE DIE TOWARD ITS EXTENDED POSITION, SAID FLUID FLOW CONNECTIONS PROVIDING FOR HYDRAULIC FLUID FLOW FROM SAID CYLINDER BORES TOWARD SAID TANK UPON THE RETRACTION OF SAID PISTONS, A PRESSURE RELIEF VALVE IN THE CONNECTION BETWEEN ONE OF SAID BORES AND SAID TANK SO AS TO PROVIDE A RESISTANCE SUBSTANTIALLY GREATER THAN TANK PRESSURE TO THE RETRACTION OF THE PISTON IN SAID ONE BORE, SAID PISTONS BEING INTEGRAL AND BEING PROVIDED WITH A CYLINDER BORE COMMUNICATING WITH SAID ONE CYLINDER BORE, A THIRD PISTON IN SAID CYLINDER BORE IN SAID PISTONS, THE OTHER OF SAID DIES BEING ARRANGED TO REACT ON SAID THIRD PISTON TO PROVIDE A RESISTANCE SUBSTANTIALLY GREATER THAN TANK PRESSURE TO THE RETRACTION OF SAID THIRD PISTON IN ITS CYLINDER BORE, SAID PISTONS HAVING DIFFERENT DIAMETERS SO AS TO PROVIDE DIFFERENT PREDETERMINED RESISTANCES TO RETRACTION OF SAID DIES UPON CLOSING OF THE PRESS.

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