US2984980A - Hydraulic press apparatus - Google Patents

Description

y 1961 R. v. ROWLES ET AL 2,984,980

HYDRAULIC PRESS APPARATUS Filed June 23, 1952 4 Sheets-Sheet l INVENTORS' REGINALD v. ROWLES BY ROBERT MADELEY May 23, 1961 R. V. ROWLES ET AL HYDRAULIC PRESS APPARATUS 4 Sheets-Sheet 2 Filed June 23, 1952 INVENTORS REGINALD V. ROWLES ATTORNEYS y 1961 R. v. ROWLES ET AL 2,984,980

HYDRAULIC PRESS APPARATUS 4 Sheets-Sheet 3 Filed June 23, 1952 8 m V 3 9 5 a 1 w 4 A MU: N m .4. I A D 3 ll! \&\ v0 w w i w L 4 Q INVENTORS REGINALD v. ROWLES ROBERT MADELEY Fla. 5

y 1961 R. v. ROWLES ET AL 2,984,980

HYDRAULIC PRESS APPARATUS Filed June 23. 1952 4 Sheets-Sheet 4 Fla. 6.

INVENTORS REGINALD V. ROWLES' ROBERT MADELEY w mwnwn r l United States Patent HYDRAULIC PRESS APPARATUS Reginald V. Rowles and Robert Madeley, Gloucester,

England, assignors, by mesne assignments, to Anglo- American Extrusion Company, Wilmington, Del., a "corporation of Delaware Filed June 23, 1952, Ser. No. 295,097 Claims priority, application Great Britain July 5, 1951 2 Claims. (Cl. 60-51) This invention relates to hydraulic presses and control arrangements for hydraulic piston or rams of such presses, and while it has particular application to the control of rams used in extrusion presses, in pressure forging and upsetting processes for example, it will be seen to be capable of wide application.

In the case of mechanically powered impact extrusion presses of the crank operated type, it is recognized that the duration of the power stroke is quite short and that there is no uniform power follow-up. In such presses there is also a rapid increase of power which frequently leads to the overloading of the tools which under normal working conditions are already highly stressed and such over-stressing may lead at times to fracture of the press frame.

According to the present invention, a hydraulic press apparatus comprising a piston means or ram and cylinder means therefor and a source of stored fluid pressure is so constructed that the power available from said source is released to the piston means or ram instantaneously or substantially instantaneously. It follows that a velocity is imparted to the ram greatly in excess of that which would result from relatively slow release of the power available and, in contradistinction to a mechanically powered ram, a hydraulic ram operated in accordance with the invention maintains a substantially constant level of power throughout its working stroke.

The source of fluid pressure preferably is constituted by a gas loaded hydraulic accumulator and the loading is pre-set in accordance with the power required to perform any particular operation.

Apparatus embodying the invention is usable advantageously for performing various operations, such as the working of materials including metals, the full hydraulic power required to effect an operation on a piece of material being released to the ram instantaneously or substantially so. Press apparatus embodying the present invention may be employed, for example, for the extrusion of cold metal billets by the percussion or impact extrusion method disclosed in the application of Archibald Claude Bridge, Serial No. 212,728, filed February 26, 1951, now'United States Patent No. 2,753,994, dated July 10, 1956. The piston structure may be so adjusted that immediately prior to the effective application of the full accumulator power to the piston structure the extrusion ram or thrust member rests in contact with a billet to be extruded so that extrusion commences immediately on release of said power. Alternatively in the case of metal working processes or extrusion processes, the work engaging ram or thrust member is adjusted so that immediately prior to the application of hydraulic power thereto, it is spaced from the work and the full power required to elfect a complete or partial operation on the material is released instantaneously or substantially instantaneously, the space between the work engaging ram and the work being such that before impact, the ram acquires a desired kinetic energy, which is imparted to the work.

Patented May 23, 1961 According to a further feature of the invention, the hydraulic piston means or ram is restrained from movement by means which may quickly be released so as to enable the ram instantaneously or substantially instantaneously to perform its working stroke. Preferably, a hydraulic piston or ram means is arranged to oppose the main hydraulic piston area or ram and to hold it until the cylinder of the holding piston area or ram means is opened to exhaust. In carrying out the invention as applied to extrusion processes, either the indirect or the direct process of extrusion may be employed.

According to a still further feature of the invention the functions of the main and the holding piston areas or rams are performed by a common piston means or ram assembly formed with opposed pressure surface areas selected to provide an area differential such that the liquid pressure load applied from a common source to the opposed surfaces simultaneously, will maintain the piston or ram assembly in a predetermined position.

In order that the invention may be clearly understood, certain forms of apparatus, representative rather than definitive of the invention, and constructed and arranged for operation in accordance therewith will now be described in greater detail by way of example with reference to the accompanying drawings in which:

Fig. 1 is an explanatory diagram illustrating one method of operating a hydraulic piston or ram,

Fig. 2 is an explanatory fragmentary diagram of an alternative arrangement,

Fig. 3 illustrates the application of a hydraulic press embodying the invention to an extrusion operation, the parts being shown in the positions they occupy immediately prior to the application of power to the main piston area or ram,

Fig. 4 shows a part of the press of Fig. 3 at a stage following commencement of extrusion,

Fig. 5 shows a press in which the functions of the holding piston areas or rams and main piston area or ram are combined in a single piston means or ram assembly, and

Fig. 6 shows an extrusion press embodying the invention in which provision is made for raising and lowering the billet container.

Referring to Fig. 1 of the drawings, the main ram or pressure applying element 1 of a hydraulic press has its enclosing cylinder 2 continuously connected through a needle valve 2a to an expansive gas loaded hydraulic accumulator 3. The permanent fluid column between the accumulator and the cylinder maintains the ram element constantly subjected to fluid pressure tending to effect a working stroke and of suflicient magnitude to cause the ram element to perform the required operation, e.g. an extrusion operation. The constant communication between the accumulator and the cylinder also provides a cushion effect in the application of power through the pressure medium and safeguards from shock stresses any tools acted upon by the piston or ram means. The accumulator is also connected through pipes 4 and 5 via a three-way valve 6 with the enclosing cylinders 7 and 8 of two other rams 9 and 10 which, for convenience, will be termed the holding rams and which are mounted so that in the pressure position of the three-way valve as shown, the holding rams will be subjected to hydraulic pressure directly from the accumulator 3 at the same unit pressure as is applied to the main ram 1 and will drive the main ram into its cylinder through the medium of a cross-head 11, against the action of the gas loaded accumulator 3.

In the construction shown in Fig. 1, the rams 1, 9 and 10, connected by the cross-head 11, constitute a piston means in which the upper end of the ram 1 provides a main working .area and the lower ends of the rams 9 and 10 together provide an aggregate holding area greater than the main working area. Thus, the holding rams, when subjected to a fluid column extending from the accumulator to the cylinders 7 and 8, are capable of restraining the main ram in its cylinder against the pressure applied to it from the hydraulic accumulator, the hold being maintained until the three-way valve is placed in the exhaust position to put the cylinders 7 and 8 in communication with the exhaust pipe line 12. When the three-way valve is so operated, the restraint on the ram is suddenly released and the full power of the hydraulic accumulator is applied extremely rapidly to the main ram which is thus driven with considerable velocity to impact the work, the holding rams retracting freely against exhaust. The capacity of the hydraulic accumulator in relation to the enclosing cylinder 2 of the main ram 1 is such that, after initial release of the ram, the applied power is maintained at a steady high level throughout the working stroke of the ram. A pipe 3: may be provided for supplying make-up hydraulic fluid from a pump, not shown.

The purpose of the needle valve 2a is variably to restrict the flow of pressure fluid to the cylinder 2 and thus to control the velocity of the ram 1 and it is preset to adjust the velocity in accordance with the operation to be performed by the ram. The provision of the needle valve is not essential in cases where the facility of adjustment is not desired, but it will be understood that the velocity of the ram in such cases, assuming a given pressure loading of the hydraulic accumulator, will be determined by the diameter of the pipe connecting the hydraulic accumulator and the cylinder 2, or by the rela tive freedom with which fluid may be discharged from the cylinders 7 and 8, determined by the size of the pipe 5 and the flow opening provided by the valve means associated with the pipe 5.

In an alternative control arrangement illustrated by the fragmentary diagram, Fig. 2, the enclosing cylinder 2 of the main ram 1 is connected through a three-way valve 13 to the gas loaded hydraulic accumulator 3. In one, the pressure position of the valve, the cylinder 2 is connected directly with the hydraulic accumulator, the valve being sufficiently large to permit rapid entry of the pressure fluid to the cylinder. The second position of the three-way valve as shown in Fig. 2 is the normal exhaust position in which the cylinder 2 is in communication with the exhaust pipe line 14.

The alternative arrangement is otherwise similar to Fig. 1 and the hydraulic accumulator is also connected through a second three-way valve, as in the case of Fig. 1 with the cylinders of the holding rams. In the pressure position of the second three-way valve the holding rams drive the main ram into its cylinder, the first three-way valve 13 being in the exhaust position. In this case also, the holding rams are capable of retaining the main ram in its cylinder against the power applied to it from the hydraulic accumulator when the first threeway valve 1 3 is operated to the pressure position, the

holding being maintained until the second three-way valve.

is operated to the exhaust position. When the latter valve is so operated, the full power of the hydraulic accumulator is applied to the main ram.

The apparatus may be designed with only one holding piston. area or it may be found desirable to employ more than two holding piston areas as a matter of convenience in design of the apparatus and if, for example, more than two holding piston areas are provided, their cylinders are supplied in parallel from the hydraulic accumulator through the three-way valve.

The press described may find application wherever a high pressure, high velocity piston or ram is required, for example, in pressure forging, upsetting processes or extrusion. In the subsequent description, the invention will be described in its application to extrusion presses, but it will be appreciated that the extrusion application of the invention has been referred to simply by way. of

example and that the presses described may be provided with tools for performing other operations. For this reason no tools have been shown associated with the ram of the press illustrated in Fig. l of the drawings.

Referring now to Fig. 3 of the drawings, the cylinder 2 is shown supported by a cross head 20 forming part of the press frame. In general, the arrangement is similar to that shown in Fig. 1 although, for convenience hydraulic circuit components are omitted. Theymay be as shown in Fig. 1 or as modified by Fig. 2. The holding piston or ram cylinders are mounted in a base plate 21 forming part of the press frame and which is centrally bored as at 22. The billet container 23 is mounted on the base plate 21 and the cross head 11 is provided with a thrust rod 24 and a. mandrel or pilot 25. Assuming it is desired to extrude an extremely thin tube from a cold billet of aluminium, for example in accordance with the Bridge process referred to above, a billet or work piece 26 of annular cross section and shorter than the length of the container bore is placed in the container in the usual manner, the tools employed being those. common to hydraulic extrusion apparatus. The total effort of the ram 1 is applied instantaneously with the result that the whole billet, except for the usual small discard, is impacted and is extremely rapidly extruded. For this purpose the main ram 1 is initially adjusted so that immediately prior to the extrusion operation, the thrust rod is spaced an appropriate distance 18 away from the billet. The distance IS may conveniently be termed the impact stroke.

In effecting the adjustment of the distance IS, it is important that the piston means including the main ram 1 should approach the container sufliciently far to ensure that the thrust rod 24 enters the mouth of the container so as efiectively to close it, otherwise, if a space is left between the thrust rod and the container bore, some of the billet may splash out of the container when the extrusion commences.

Power for the main ram 1 is supplied by a hydraulic accumulator which also supplies the pressure medium to the holding rams 9 and 10 as already described. Rams 9 and 10 hold the main ram 1 against the pressure of the hydraulic accumulator until total exhaust is suddenly opened to the holding ram cylinders in the manner already described, when the full pressure of the hydraulic accumulator acts suddenly on the main working area at the top of the ram 1 and extrusion of the billet is effected. Prior to the actual extrusion operation the fluid pressure system of the press is stressed in readiness for working because the enclosing cylinder of the main working area is already in association with the accumulator. This is an important factor because no power is absorbed by. the press frame when the main ram is released. It will be appreciated that as the'main ram when released, is free to travel unopposed through the distance IS it will acquire a degree of kinetic energy which is imparted to the billet 26.

The tool assembly described will result in extrusion of a tube which will pass downwardly through the bore 22 in the base plate 21, as shown in Fig. 4.

Referring now to Fig. 5 of the drawings, a hydraulic press is shown in which the functions of the main and holding rams are combined in a single ram assembly. For convenience the pressure liquid supply and control means have been omitted from Fig. 5 but it may be assumed that they are similar to those shown in Figs. 1 or 3.

The press frame 40 is provided with a platform 41 for mounting a billet container 42, the platform and the container being centrally, bored as at 43 and 44 respectively to permit exit from beneath of thev product of extrusion of a billet 26. The upper end of the frame supports a cylinder member 45 and the lower portion is formed with guide surfaces 46 for a guide cross-head 47 of a composite ram member, the piston rod-48 passing into the cylinder 45 and carrying a piston 49 which operates in the cylinder. The piston rod extends beyond the piston 49 and the extended portion 50 will be referred to as the tail rod. A pipe 51 for conveying pressure liquid to the cylinder 45 is connected to it at the upper end and the second pipe 52 for conveying pressure liquid to the cylinder, or for connecting the latter to exhaust through a three-way valve not shown, is connected to the cylinder at its lower end. The lower face of the guide cross-head 47 carries a thrust rod 24, which, in the pre-extrusion position just enters the billet container in contact with a billet 26. In some cases it may be desirable to provide a tool or thrust rod carrier which is not integral with the guide cross head so that the latter does not itself have to transmit the power stroke, the ram assembly in this case acting directly on the tool carrier.

In the present case again, the press is constructed to extrude tubing and the billet 26 is therefore made hollow to receive a mandrel 25 which projects from the face of the thrust rod through the billet and beyond to define, with the central bore 44 of the container, an annular gap which determines the thickness of the tube to be extruded.

For convenience of explanation, the cross sectional area of the cylinder 45 will be referred to as area A, that of the tail rod 50 as area C and that of the piston rod 48 as area D. The area C is made larger than the area D by a difierential which will be referred to as X. The piston 49, piston rod 48 and tail rod 50 constitute a unitary piston means having a main working area provided by the top surface of the piston 49 and a holding area provided by the bottom surface of the piston 49, the holding area being larger than the main working area because the tail rod 50 is of larger cross sectional area than the piston rod 48.

In operation of the press, pressure liquid from an air or gas loaded hydraulic accumulator not shown is supplied to the cylinder 45 through the supply pipes 51 and 52. The pressure on the holding area provided by the lower annular face of the piston 49, that is to say area A less area D, is greater than that on the main working area provided by the upper annular face, that is to say A less area C and the ram assembly is restrained from thrusting downwardly. To effect extrusion, the threeway valve, not shown, in the pipe 52 supplying the lower end of the cylinder is suddenly opened to exhaust so that the full pressure of the supply is effective on the ram assembly which descends instantaneously. To return the ram assembly to its initial position, the three-way valve referred to is closed to exhaust and the pressure liquid again enters the lower end of the cylinder, forcing the ram assembly upwardly under the pressure differential X previously referred to.

In the extrusion presses so far described, the billet containers have been assumed to be fixed in position so that the presses operate to effect extrusion with the direct mode of flow of the extruded product. However, the indirect or inverted mode of flow can be used or the two types of flow mixed or combined.

A press provided with a movable container for the purpose indicated is shown in Fig. 6 in which most of the parts are as described with reference to Fig. 5 although the hydraulic circuit components have been added ineluding a pipe 70 for connection to a fluid pressure make-up pump, not shown. The billet container 71 is, however, carried by rams or pistons 72, 73 operating in cylinders 74, 75 formed in the base 76 of the press frame. Further, a main supply pipe 77 from the hydraulic accumulator 3 is connected through a variable control valve 78 to pipes 79, 80 connected respectively to the upper ends of the cylinders 74, 75 and a branch pipe 81 is connected through a valve 82 to pipes 83, 84 connected respectively to the lower ends of the cylinders 74, 75. The pipes 79, 80 are supplied through a valve 85, this valve being constructed to permit controlled passage of pressure fluid from pipe 77 to the cylinders 6 74, 75, or to connect the upper ends of these cylinders to exhaust.

In operation of the press, the main piston or ram assembly 47, 48, 49 and 50, subjected constantly to primary fluid pressure, is driven as described with reference to Fig. 5. Prior to the extrusion stroke, the container 71 is raised to its maximum height by actuating the valve 82 to allow secondary pressure fluid to enter the lower ends of the cylinders 74 and 75, the valve 85 being turned to the exhaust position, and thus allowing the pistons or rams 72 and 73 to rise. The valves 78, 82, and 85 are then set in position and their actuation synchronized by electrical or mechanical interlocking with that of the valve 6 so that when the latter is opened to exhaust to allow the main piston or ram assembly to effect the extrusion stroke, the rate of descent of the container will be such as to produce a desired resistance opposing downward movement of the container under the influence of the force exerted by the main or extruding ram. The downward travel of the container can be assisted by any desired degree of pressure control by the valve 85 and the setting of valve 82 to a slow or rapid exhaust position.

Although earlier in this specification, reference was made to extrusion of a cold billet, it is to be understood that such reference was merely to indicate the capabilities of a press constructed and arranged to operate in accordance with the invention. The disclosure of several modified embodiments of the invention makes it apparent that the term piston means as used herein applies to press constructions having holding rams or piston elements separate from but connected to main ram or piston elements as in the embodiments shown in Figs. 1 to 4; and also applies to constructions having unitary difierential pistons as shown in Figs. 5 and 6, and that presses and associated equipment constructed or arranged in accordance with the invention may be used for the extrusion of preheated billets.

We claim:

1. Hydraulic press apparatus comprising cylinder enclosed piston means having a main piston area and a holding piston area opposed to and greater in effective pressure area than said main piston area, a gas loaded hydraulic accumulator having a capacity compared to the capacity of the enclosing cylinder of said main piston area sufiicient to supply substantially steady high level power throughout a substantially instantaneous full working stroke of said piston means when the accumulator pressure is applied to said main piston area, a first conduit means connected at one end to said accumulator and at the other end to said enclosing cylinder of the main piston area for applying to said main piston area hydraulic pressure directly from said accumulator from the inception of and throughout said working stroke and having the capacity to transmit said power for said substantially instantaneous full working stroke of said piston means, a second conduit means connected at one end to said accumulator and at the other end to the enclosing cylinder of the holding piston for normally subjecting said holding piston area to hydraulic pressure directly from the same accumulator to move said piston means to and to hold it in retracted position against the accumulator pressure exerted on said main piston area, and an exhaust means for the holding pressure operable substantially instantaneously and having the capacity for sudden substantially total exhaust of said holding pressure, whereby the said substantially instantaneous full working stroke of said piston means may take place under the said steady high level power.

2. Hydraulic pressure apparatus comprising cylinder enclosed piston means having a main piston area and a holding piston area opposed to and greater in effective pressure area than said main piston area, a gas loaded hydraulic accumulator having a capacity compared to the capacity of the enclosing cylinder of said main piston area suflicient to supply substantially steady high level power throughout a substantially instantaneous full working stroke of said piston means when the accumulator pressure is applied to said main piston area, a first conduit means connected at one end to said accumulator and at the other end to said enclosing cylinder of the main piston area for applying to said main piston area hydraulic pressure directly from said accumulator from the inception of and throughout said working stroke and having the capacity to transmit said steady high level power for said substantially instantaneous full Working stroke of said piston means, a second conduit means connected at one end to said accumulator and at the other end to the enclosing cylinder of the holding piston for normally subjecting said holding piston area to hydraulic pressure directly from the same accumulator to move said piston means to and to hold it in retracted position against the accumulator pressure exerted on said main piston area, and valved controlmeans for said second conduit means having a first setting in which both said main and holding piston areas are maintained under pressure from said accumulator and a working stroke setting in which the main piston area is continued under said accumulator pressure while the holding piston area is open to exhaust, said valved control means being actuatable directly from said first setting to said working stroke setting and which valved. control means has the capacity for sudden substantially total exhaust of said holding pressure, whereby the said substantially instantaneous full working stroke of said piston means may take place under the said steady high level power and the total efiort of said piston means may be instantaneously realized.

References Cited in the file of this patent UNITED STATES PATENTS 495,499 List Apr. 18, 1893 523,419 Thorpe July 24, 1894 1,317,238 Summey Sept. 30, 1919 1,826,363 Miedbrodt Oct. 6, 1931 2,088,134 Haessler July 27, 1937 2,132,974 Sentance et a1. Oct. 11, 1938 2,142,628 Ballert Jan. 3, 1939 2,410,581 Hess et al Nov. 5, 1946 2,465,580 Ernst et a1. Mar. 29, 1949 FOREIGN PATENTS 613,588 Germany May 22, 1935 21,805 Great Britain Nov. 9, 1904 534,401 Great Britain Mar. 6, 1941 UNITED STATES IATENT oEEIGE CERTIFICATE OF CORRECTION Patent No. 2,984,980 May 23, 1961 Reginald V; Rowles et a1. a

It is hereby certified that error: appears in the above numbered patent requiring correction and that the said Letters Patent. should read as "corrected below. I

Column 4., line 59, after "Fig. 4," insert the following paragraph: Instead of setting the thrust rod initially that is 'to say immediately prior to the extrusion stroke, so that it is spaced apart from the billet, it may actually rest in contact with the billet so that immediately upon release of the main ram extrusion of the billet commences. column 6, line 55, after "said" first occurrence, insert steady high level Signed and sealed this 21st day of November 1961.

(SEA L) Attest:

ERNEST w. SWIDER DAVID L. LADD Attesting Officer Commissioner of Patents USCOMM-DC

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