US3333457A

US3333457A - Hydraulic ram assembly for a forging press

Info

Publication number: US3333457A
Application number: US436255A
Authority: US
Inventors: Allen Herbert
Original assignee: Cameron Iron Works Inc
Current assignee: Cooper Industries LLC
Priority date: 1965-03-01
Filing date: 1965-03-01
Publication date: 1967-08-01
Anticipated expiration: 1984-08-01

Description

H. ALLEN HYDRAULIC RAM ASSEMBLY FOR A FORGING PRESS Aug. 1, 1967 2 Sheets-Sheet 1 Filed March 1, 1965 Hererz /4//e/7 INVENTOR.

v Afro/WW5 VJ Aug. 1, 1967 H. ALLEN 3,333,457

HYDRAULIC RAM ASSEMBLY FOR A FORGING PRESS Filed March 1, 1965 2 Sheets-Sheet 2 J/l I I N VEN TOR.

United States Patent 3,333,457 HYDRAULIC RAM ASSEIVIBLY FOR A FORGING PRESS Herbert Allen, Houston, Tex., assignor to Cameron Iron Works, Inc., Houston, Tex. Filed Mar. 1, 1965, Ser. No. 436,255 6 Claims. (Cl. 72453) This invention relates to an improved hydraulic ram assembly for aforging press.

A hydraulically operated forging press may employ one or more hydraulic ram assemblies. Usually, they are located between a fixed platen and a moving platen that carries the movable portion of the die that forms the work piece into the desired shape. Each hydraulic ram assembly includes at least one piston and cylinder combination. The force that the press can exert on the work piece depends on the pressure of the hydraulic fluid supplied to the ram assembly and the total effective area of the piston or pistons against which it acts. Usually, it is easier to increase the output force of a hydraulic press by increasing the piston area against which the hydraulic fluid acts than to increase the'pressure of the fluid. This is done by increasing the effective piston area of each hydraulic ram assembly or by increasing the number of such assemblies that are used. Increasing the number of ram assemblies is preferred for this also gives some flexibility to the press by allowing the output force of the press to be varied by varying the number of ram assemblies that are supplied with hydraulic fluid.

As the number of ram assemblies increases, the areas of the platens between which they are located also increase. In very large forging presses this is the limiting factor that determines the size press that can be built since there is a practical limit to the size of platens that can be used.

Tandem piston and cylinder combinations can be used in each ram assembly to increase its force output without increasing the area of the platens. Where the stroke of the ram, i.e., the distance through which the movable platen is moved by the ram, remains the same for the tandem piston ram as for the single piston, the height of the press is increased which is undesirable, for there is a practical limit to the height of the rams that can be used.

Therefore, it is an object of this invention to provide a hydraulic ram assembly for a forging press that provides a substantially greater available piston area than a conventional single piston and cylinder combination of the same outside diameter and overall height.

It is another object of this invention to provide a hydraulic ram assembly for a forging press that provides a total area against which the pressure fluid can act that is substantially greater than the pressure area available in a single piston and cylinder combination of the same diameter and height, and which has substantially the same stroke.

It is yet another object of this invention to provide a hydraulic ram assembly having two pistons in which the effective stroke of the ram is substantially equal to that of a single piston ram of the same overall physical size and in which the force, which the ram assembly can produce, is greater than that of each single piston ram by an amount equal to the area of the second piston less the area of the piston rod to which it is connected, times the pressure of the available hydraulic fluid.

It is yet another object of this invention to provide a hydraulic ram for a forging press having two piston and cylinder combinations, either or both of which can be used to operate the press, that are so arranged that the height of the ram assembly is substantially equal to that of a single piston and cylinder combination having the same stroke.

It is a further object of this invention to provide a hydraulic ram assembly that is so constructed that it will be held in engagement with the two platens, between which it is located by hydraulic pressure, making it unnecessary to fix the ram to either platen.

Often forging presses are used to produce forgings that do not require all of the force the press is capable of providing. The output force of a press can be reduced, of course, by reducing the pressure of the hydraulic fluid used. Usually, this is inconvenient to do since the same pressure system likely is being used to operate other presses that require the higher pressure. If the press has more than one ram assembly, the number used can be reduced. If the press has only one conventional ram assembly comprising one piston in a cylinder this cannot be done, so the die sets must be designed to take the total output force of the press. This increasesthe cost of the dies.

Therefore, it is another object and an important feature of this invention to provide for a forging press a hydraulic ram assembly that has the same height as a conventional single piston and cylinder ram assembly, which can provide, through substantially the same stroke, three different output forces with hydraulic fluid of the same pressure.

Other objects, advantages and features of this invention will be apparent to one skilled in the art upon a consideration of the written specification, the attached claims and the annexed drawings.

In accordance with this invention, a first piston is arranged in a first or outer cylinder that is adapted to be located between a fixed platen and the movable platen of a forging press. A hollow piston rod is connected to the piston and arranged to extend out of the outer cylinder to engage one of the platens. The hollow piston rod, in turn, serves as an inner or second cylinder in which a second piston is located. This second piston is held against movement relative to the first or outer cylinder by a piston rod that extends through the first piston and engages the platen that is engaged by the outer cylinder. With this arrangement, the hydraulic ram assembly can provide two independent forces either of which can be used to operate the press. Also the two independent forces can be combined to provide a third force for operating the press which force is substantially greater than the output force available from a conventional single piston and cylinder arrangement having the same diameter. The first force is obtained by introducing hydraulic pressure in the first or outer cylinder to act against the first piston therein and exert a force on the platens through the hollow piston rod or second cylinder. The second force is obtained by supplying the inner cylinder with hydraulic pressure between the second piston and the platen which the inner cylinder or hollow piston rod engages. As stated above either or both of these forces are available, yet the over-all height of the ram assembly is not greatly increased over a single piston and cylinder combination having the same stroke. Further, in the preferred embodiment of this invention, the outer cylinder is provided with an inwardly extending flange against which the hydraulic pressure therein can act to hold the cylinder in engagement with the platen which it engages thereby making it unnecessary to otherwise attach the cylinder to the platen.

The invention will now :be described in detail in connection with the embodiment of the invention shown in the attached drawings in which:

FIGURE 1 is a view in side elevation of a conventional forging press, the one shown being provided with two hydraulic ram assemblies constructed in accordance with this invention, showing in dotted lines the positionsof the movable platen when the rams are extended;

FIGURE 2 is a vertical sectional view on an enlarged scale of one of the hydraulic ram assemblies of the press of FIGURE 1 when the ram is retracted; and

FIGURE 3 is a view like that of FIGURE 2, with the ram extended.

Forging presses are arranged in various ways. FIGURE 1 shows one common arrangement. The press shown includes a frame having an opening 11. Fixed

platens

12 and 13 are positioned in opening 11 at the top and bottom thereof. Guide rods 14 and 15, which have their opposite ends located in

cylinders

19 and 20, are located parallel to each other on opposite sides of opening 11 to guide movable platen 16, which is attached to the rods, as it moves vertically in opening 11 toward and away from top platen 12. Between moving platen 16 and bottom fixed platen 13 are located

hydraulic ram assemblies

17 and 18, which provide the power to move the movable platen upward with sufficient force for the dies (not shown) located between it and fixed platen 12 to form a work piece to the desired shape. To return the movable platen and the hydraulic rams to their retracted position as shown in FIGURE 1, pressure is applied in hydraulic cylinders 19, forcing the guide rods and movable platen downward. The bottom pistons 20 can be used to lift the movable platen when it is desired to service the hydraulic ram assemblies. 7

In accordance with this invention, a hydraulic ram assembly is provided for use with a forging press, such as the one shown in FIGURE 1, that provides a substantially greater output force than does a conventional ram of the same physical size having a single piston and cylinder combination. An embodiment of such a hydraulic ram assembly, constructed in accordance with this invention, is shown in FIGURES 2 and 3, which are vertical cross sectional views of ram assembly 18 of FIG- URE 1 and a portion of the surrounding press structure. The ram comprises an outer cylinder 21, which has one end 21a in engagement with fixed platen 13. This same end of the cylinder is provided with an inwardly extending flange 22 for purposes which will be explained below. Platen 13 is provided with annular groove 22a to receive the end of outer cylinder 21 to keep the cylinder from moving laterally relative to the platen. Seal 22b is located in the platen to engage flange 22 and prevent the escape of fluid from the outer cylinder through the groove. Located in outer cylinder 21 is first piston 23 which is arranged for longitudinal movement relative to the cylinder. Integrally attached to piston 23 and extending upwardly therefrom to engage movable platen 16 is hollow piston rod or inner cylinder 24. Seal 25 is located adjacent the upper end of the outer cylinder to provide a seal betweenthe outer cylinder and inner cylinder 24 as piston 23 and the inner cylinder move longitudinally relative to the outer cylinder.

Thus, these components combine to provide a pressure chamber 26 in which hydraulic fluid can be provided to exert a force on piston 23 and through inner cylinder 24 on moving platen 16 urging it upwardly away from fixed platen 13. To supply chamber 26 with hydraulic fluid platen 13 is provided with an opening 27. Hydraulic hose 27a connects the'opening to a supply of hydraulicv fluid.

To increase the output force of the hydraulic ram assembly over that of a conventional single piston and cylinder arrangement having substantially the same physical dimensions, second piston 28 is located in inner cylinder 24 between the first piston and movable platen 16 to provide a second pressure chamber 34. Seal 29 carried by the second piston to sealingly engage the inner cylinder and seal 38 located between the end of inner cylinder 24 and movable platen 16, prevent the escape of fluid from 'the chamber. Integrally connected to second piston 28 is piston rod 30 which'extends downwardly from the second piston through first piston 23. Means are provided to hold the rod and the second piston against downward movement relative to the outer cylinder toward the fixed platen.

In the embodiment shown, the rod engages the fixed platen directly which prevents it and the second piston' hydraulic fluid. Seal 36 is located between the first piston and the rod to prevent fluid from escaping from pressure chamber 26 into chamber 37 formed in inner cylinder 24 between the two pistons.

Thus, with this arrangement, not only can hydraulic fluid under pressure be supplied to pressure chamber 26 to provide a force to move movable platen 16 away from the fixed platen, but a second force can be obtained by supplying hydraulic fluid under pressure to chamber 34. The amount of the first force will depend on the efiective area of the first piston and the pressure of the hydraulic fluid. The eflective area of the first piston is the annular area encompassed by its outer periphery less the crosssectional area of piston rod 30 including opening 33. The amount of the second force is equal to the cross-sectional area of the inner cylinder times the pressure of the hydraulic fluid. Either or both of these forces are available depending upon which chamber is supplied with hydraulic pressure.

As set out above, it was one of the objects of this invention to provide a hydraulic ram assembly wherein the over-all physical dimensions of the assembly were not increased over that of a conventional single piston and cylinder ram assembly but which provided a substantial increase in output force without substantially decreasing the stroke or distance through which this force can be applied. The maximum stroke of the ram assembly shown in FIGURES 2 and 3 is the distance S between the two pistons.

As a practical matter, however, the ram stroke used to design the dies for the press usually will be a distance S (FIG. 3), such that the dies will close before the end of first piston 23 approaches too close to the upper end of outer cylinder 21 and before it contacts the second piston. The length of seal 25 can vary, however, usually the distance S will be such that the piston does not pass the lower end of the seal, or if the seal is carried by the piston and piston rod assembly, such that the seal does not pass beyond the upper end of the outer cylinder.

A conventional single piston and cylinder ram assembly would have an outer cylinder, such as outer cylinder 21, and a piston, like piston 23, which would exert its force on the movable ram through a rod such as inner cylinder 24. With this arrangement, the eflective area of the piston against which the hydraulic pressure can act is the total area encompassed by the outer periphery of thepiston. Also the stroke of such a ram assembly would be S the same as for the embodiment shown, for the same reasons given above. Therefore, a hydraulic ram assem- V bly constructed in accordance with this invention having the same outside dimensions as a conventional assembly can have a stroke that is substantially equal to that of the conventional assembly, while providing a substantial increase in the available output force of the hydraulic ram assembly, and adding flexibility to the press by allowing three diflerent output forces to be obtained from the ram. The increase in output force of the ram is the ratio of the effective area of the second piston, less the cross-sectional area of the portion of the rod that .extends through the first piston,.to the effective area the first piston would have if the rod did not extend through it. In one ram designed in accordance with this invention, about a 50% increase in output force was obtained over a conventional single piston ram of the same outside dimensions.

As first piston 23 moves upwardly toward the second piston, when the ram assembly is in operation, means must be provided to vent chamber 37 between the two pistons to prevent a fluid lock from existing in the chamber which would resist the movement of the two pistons toward each other. In the embodiment shown, passageway 40 is located in the wall of inner cylinder 24 and has one end connected to chamber 37 adjacent the first piston and its other end connected to the ambient atmosphere of the ram assembly. Thus, as the two pistons move toward and away from each other, air can enter and leave the chamber through passageway 40 as required.

Plunger 41 is attached to the underside of movable platen 16 to enter opening 33 in piston 28 as the movable platen approaches the end of its downward travel. The plunger restricts the flow of fluid out of fluid chamber 34, and thereby slows down the movement of the movable platen as it approaches the end of its travel.

As mentioned above, the outer cylinder is provided with an inwardly extending annular flange 22. By locating seal 22b so there will be a differential pressure across the flange, a downward force is exerted on the flange which will hold the flange and cylinder against fixed platen 13. It is the usual practice to maintain a positive pressure in the pressure chambers of these forging press rams at all times, so there is always a positive force holding the ram against the fixed platen.

The pressure maintained in pressure chamber 26 also exerts a force on piston 23 which urges inner cylinder 24 toward the movable platen. If pressure chamber 34 above the second piston is supplied with the same pressure, it will tend to urge the movable platen away fiom the inner cylinder, so when the ram is retracted, suflicient pressure should be maintained in cylinders 19 to provide a downward force on the movable platen which when combined with the Weight of the platen and the guide rods, is suflicient to overcome the force exerted by the pressure in pressure chamber 34. Of course, inner cylinder 24 also can be provided with an inwardly extending flange, like flange 22, to help hold the cylinder in engagement with the movable platen, or, if desired, either or both cylinders can be attached to the platens they engage.

For the foregoing, it will be seen that this invention is one well adapted to attain all of the ends and objects hereina'bove set forth, together with other advantages which are obvious and which are inherent to the apparatus.

It will be understood that certain features and subcombinations are of utility and may be employed without reference to other features and subcombinations. This is contemplated by and is within the scope of the claims.

As many embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

The invention being described, what is claimed is:

1. A hydraulic ram assembly for a forging press having two relatively movable platens between which the ram assembly can be located to exert a force on the platens, said ram assembly comprising, an outer cylinder adapted to engage one of said platens, a first piston located in the outer cylinder to form a first pressure chamber in the outer cylinder between said piston and said platen, an inner cylinder connected to the outer periphery of the first piston and positioned to engage said other platen, a second piston located in the inner cylinder to form a second pressure chamber in the inner cylinder between the second piston and said other platen, a piston rod extending through the first piston to engage the second piston and the platen engaged by the outer cylinder, to transmit from the second piston to said platen the force exerted on the second piston 'by pressure fluid in said second pressure chamber and means for supplying both the first and second pressure chambers with hydraulic pressure.

2. A hydraulic ram assembly for a forging press, comprising, an outer cylinder, a first piston located in the outer cylinder for reciprocation relative thereto, an inner cylinder attached to the outer periphery of the first piston for movement therewith, a second piston located in the inner cylinder, means for closing the end of the outer cylinder opposite the side of the first piston away from the second piston to form a first pressure chamber, means for holding the second piston against movement toward the end closing means of the outer cylinder, means for closing the end of the inner cylinder opposite the side of the second piston away from the first piston to form a second pressure chamber, means for venting to the ambient atmosphere the space in the second cylinder between the pistons, and means for supplying the first and second pressure chambers with hydraulic fluid selectively.

3. A hydraulic ram assembly for a forging press, having two relatively movable platens between which the ram assembly is located to exert a force on the platens, said ram assembly comprising, an outer cylinder with one end in engagement with one of the platens, said end having an inwardly extending annular flange and seal means to provide a seal between the flange and said platen, said seal being positioned to keep at least a portion of the side of the flange adjacent the platen from being exposed to the pressure acting against the other side to provide a force on the flange urging it toward the platen when pressure fluid is introduced into the outer cylinder, a firstpiston located in said outer cylinder for reciprocal movement along its longitudial axis, an inner cylinder connected to the outer periphery of the first piston with one end in engagement with the other platen, a second piston located in the inner cylinder, and a piston rod connected to the second piston and extending through the first piston, means for holding the rod and the second piston against movement toward the platen engaged by the outer cylinder when fluid under pressure is introduced into the inner cylinder between the second piston and the platen engaged by the inner cylinder to exert a force on the second piston urging it toward the platen engaged by the outer cylinder, and means for selectively introducing pressure fluid into the inner cylinder between the second piston and the platen engaged by the outer cylinder and means for connecting the inner cylinder between the two pistons to the ambient atmosphere of the ram.

4. A hydraulic ram assembly for positioning between a fixed platen and a movable platen of a forging press, said ram comprising, an outer cylinder having one end in engagement with the fixed platen, an inwardly extending flange connected to said end, and seal means between the flange and the platen to keep at least a portion of the side of the flange adjacent the fixed platen from being exposed to the hydraulic pressure in the outer cylinder so the hydraulic pressure will exert a force on the flange holding it against the fixed platen, a first piston in the outer cylinder for reciprocal movement along the longitudinal axis of the cylinder, an inner cylinder located in the outer cylinder with one end connected to the first piston and with its other end in sealing engagement with the movable platen, a second piston located in the inner cylinder, a piston rod connected to the second piston extending through the first piston into engagement with the fixed platen, means for connecting the outer cylinder, between the fixed platen and the first piston, and the inner cylinder, between the sec-ond piston and the movable platen, to a source of hydraulic fluid, and means for connecting the inner cylinder between the pistons to the ambient atmosphere.

5. A hydraulic ram assembly for a forging press having two relatively movable platens between which the ram -assembly can be located to exert a force on the platens, said ram assembly comprising, an outer cylinder adapted to engage one of said platens, an inner cylinder located in the outer cylinder in sliding and sealing engagement therewith and in engagement with the other platen, said inner cylinder having inwardly extending flanges to provide a'first piston to form a first pressure chamber in the outer cylinder between said first piston and said platen, a second piston located in the inner cylinder to form a second pressure chamber between the second piston and said other platen, a piston rod extending through the first piston to engage the second piston and the platen engaged 'by the outer cylinder to transmit from the second piston to said platen the force exerted on the second piston by pressure fluid in said second pressure chamber, and means for supplying both the first'and second pressure chambers with hydraulic pressure.

6. A hydraulic forging press having a fixed platen and a movable platen and a plurality of hydraulic ram assemblies for moving the movable platen toward the fixed platen and for exerting a forging force on a workpiece located between the platens, each of said hydraulic ram assemblies comprising, an outer cylinder adapted to engage one of said platens, an inner cylinder located in the 8 outer cylinder in sliding and sealing engagement therewith and in engagement with the other platen, said inner cylinder having an inwardly extending flange to provide a first piston to form a first pressure chamber in the outer cylinder between said first piston and said platen, a second piston located in the inner cylinder to form a second pressure chamber between the second piston and said other platen, a piston rod extending through the first piston to engage the second piston and the platen engaged by the outer cylinder to transmit from the second piston to said platen the force exerted on the second piston by pressure fluid in said second pressure chamber, and means for supplying both the first and and second pressure chambers with hydraulic pressure.

References Cited UNITED STATES PATENTS 788,876 5/1905 Beche 72-453 1,268,270 6/1918 Nazel 72453 WILLIAM W. DYER, JR., Primary Examiner.

GERALD A. DOST Examiner.

Claims

1. A HYDRAULIC RAM ASSEMBLY FOR A FORGING PRESS HAVING TWO RELATIVELY MOVABLE PLATENS BETWEEN WHICH THE RAM ASSEMBLY CAN BE LOCATED TO EXERT A FORCE ON THE PLATENS, SAID RAM ASSEMBLY COMPRISING, AN OUTER CYLINDER ADAPTED TO ENGAGE ONE OF SAID PLATENS, A FIRST PISTON LOCATED IN THE OUTER CYLINDER TO FORM A FIRST PRESSURE CHAMBER IN THE OUTER CYLINDER BETWEEN SAID PISTON AND SAID PLATEN, AN INNER CYLINDER CONNECTED TO THE OUTER PERIPHERY OF THE FIRST PISTON AND POSITIONED TO ENGAGE SAID OTHER PLATEN, A SECOND PISTON LOCATED IN THE INNER CYLINDER TO FORM A SECOND PRESSURE CHAMBER IN THE INNER CYLINDER BETWEEN THE SECOND PISTON AND SAID OTHER PLATEN, A PISTON ROD EXTENDING THROUGH THE FIRST PISTON TO ENGAGE THE SECOND PISTON AND THE ENGAGED BY THE OUTER CYLINDER, TO TRANSMIT FROM THE SECOND PISTON TO SAID PLATEN THE FORCE EXERTED ON THE SECOND PISTON BY PRESSURE FLUID IN SAID SECOND PRESSURE CHAMBER AND MEANS FOR SUPPLYING BOTH THE FIRST AND SECOND PRESSURE CHAMBERS WITH HYDRAULIC PRESSURE.