US3126096A

US3126096A - Hydrostatic extrusion system

Info

Publication number: US3126096A
Authority: US
Publication date: 1964-03-24
Anticipated expiration: 1981-03-24

Description

March 24, 1964 G. GERARD ETAL 3,126,096

HYDROSTA'IIC EXTRUSION SYSTEM Filed May 4, 1961 3 Sheets-Sheet 1 FIG their gram/5Z3 March 24, 1964 Y s. GERARD ETAL 3 ,126,096

HYDROSTATIC EXTRUSION SYSTEM 3 Sheets-Sheet 2 Filed May 4, 1961 mmvgoxs. GERARD a RAYMAN GEORGE FIG 4 their AT T OR/VE Y5 March 24, 1964 ca. GERARD ETAL 3,126,096

' HYDROSTATIC EXTRUSION SYSTEM Filed May 4, 1961 3 Sheets-Sheet 3 FIG 3 INV EN TORS.

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B y 6 I Fl glMQ iheir ATTORNEYS United States Patent 3,126,896 HYDROSTATIC EXTRUSION SYSTEM George Gerard, Yonkers, and Jacob Brayman, Staten Island, N.Y., assignors to Barogenics, Inc., a corporation of New York Filed May 4, 1961, Ser. No. 107,836 11 Claims. (Cl. 207-6) This invention relates generally to methods and apparatus for extruding material such as ferrous and nonferrous metals, plastics, stone, or the like. More particularly, this invention relates to methods and apparatus in which hydrostatic pressure is used to extrude such material.

In present day commercial practice, materials such as brass, aluminum, mild steel, and other low strength materials are extruded in a manner as follows. A cylindrical billet of the material is placed within a close fitting tubular container having an open rear end and having at its front end a stationary extrusion die. For so called hot extrusion, the billet as placed in the container is at an elevated temperature to promote the extrusion thereof through the die. Moreover, to the end of reducing friction between the billet and the container wall, the billet is usually coated with a lubricant.

Extrusion is effected by inserting a ram into the container behind the billet, and by driving the ram inwardly under great force until the pressure within the billet builds up to the point where the material therein becomes sufficiently plastic to flow through the die.

While the above-described conventional extrusion technique is the best hitherto known to the art for commercial use, it has numerous disadvantages as follows. First, in spite of the use of a solid or viscous lubricant around the billet, during most of the extrusion an appreciable amount of friction will exist between the billet and the container wall for the reason among others that, early during the extrusion the pressure of the ram causes the billet to bulge radially to squeeze out through the die most of the lubricant interposed between the billet and the container wall. Therefore, a great amount of the tonnage used in forcing the billet forward must be expended merely in overcoming the substantial frictional eifect around the billet circumference.

Second, because of the described friction between the billet and the container wall, in most of the billet the radial distribution of pressure is not truly hydrostatic. Instead, except at its rear end where the billet is flatly contacted by the ram, the radial pressure distribution in the billet is such as to peak in the center and to fall off towards the outer edges where the billet is able to sustain shear stresses because of its contact with the wall of the stationary container. As a result of this uneven radial pressure distribution, it is necessary to supply energy to the ram which is substantially in excess of the theoretical amount of energy needed to extrude the billet.

Another factor necessitating a ram pressure much in excess of that theoretically needed, is that, due to the described friction between the billet and the container wall, and due, further, to radial bulging of the billet under the pressure applied thereto and to consequent radial bulging of the container, the axial distribution of the pressure within the billet is not uniform. Specifically, over the length of the billet the pressure therein drops from a maximum pressure at the billet-ram interface toa front end pressure which may be, say, only about one tenth of such maximum pressure when the billet is of its original length. It follows that, to build up the pressure in the front end of the billet to the critical value required at such front end to produce flow of the billet material through 3,126,096 Patented Mar. 24, 1964 the die it is necessary to exert a much larger pressure on the rear end of the billet.

Fourth, the ram pressure required at the rear end of the billet to produce extrusion thereof is a pressure which is a function of the unextruded length of the billet. That is, as, during extrusion, the unextruded length of the billet progressively decreases, the ram pressure required first drags and then climbs again. The result of this phenomenon is that at the beginning and towards the end of the extrusion, greater pressures are required to be exerted by the ram than would normally be expected from the maximum shear stress properties of the billet material. In fact, the ram pressure required for extrusion finally increases so much that it virtually becomes impossible to extrude the entire billet. Therefore, the extrusion usually terminates with a butt of the billet being left in the container and requiring removal before the next extrusion cycle.

Fifth, although at the beginning of the extrusion cycle, the die is coated with a solid or other lubricant, during the early part of the extrusion, this lubricant is, as stated, washed out with the extruded material, so as soon to leave the die bare. Thereafter, the passage of the billet material through the unlubricated \die exposes it to high abrasive and frictional forces which materially reduce the life of the die.

In an attempt to overcome the above-noted disadvantages accompanying conventional extrusion, experimental efforts have been made to produce extrusion of a billet through a die in stationary relation to the billet container by employing a hydraulic fluid disposed in the container around the billet to generate the extruding pressure.

Thus, in volume 1, No. 11 of the Russian publication, Journal of Engineering and Physics, the article at pages. -109 thereat reports on a hydrostatic extrusion apparatus of the sort just described in which a pump is employed to pressurize fluid which is thereafter introduced through a small pipeline into the billet container behind the billet. Such arrangement is not, however, adapted for practical use because known pumps are incapable of generating the high hydrostatic pressures required for extrusion of most materials, and because, once the extrusion starts, it proceeds with considerable speed, and the small diameter pipeline connecting the pump with the billet container cannot supply sufiicient liquid to keep the hydrostatic pressure at a constant level.

In another proposal for hydrostatic extrusion made by T. W. Bridgman, on pages 177-179 of his text Large Plastic Flow and Fracture (published by McGraw-Hill in 1952), the hydraulic fluid in the billet container is pressurized by the inward driving of a ram inserted into the bore of the container at the end thereof away from the stationary die. This latter proposal is, like the earlier discussed Russian one, not adapted for commercial use because the Bridgman apparatus cannot be scaled up to accommodate billets of commercial size and because of various other considerations.

It is accordingly an object of the invention to provide hydrostatic extrusion methods and apparatuses which are free of the above-described disadvantages accompanying conventional extrusion, and which are free, also, of the above described limitations of the experimental efforts hitherto made in hydrostatic extrusion.

Other objects of the invention are to eliminate billetwall interface friction, to increase die life, and to permit the use of much greater energy in extruding the billet.

Another object of the invention is to provide extrusion methods or apparatuses, hydrostatic or otherwise, in which the extrusion of billet material is reverse in the sense that the direction of extrusion of the material is opposite to that in which the ram or other exterior agency acts to produce the extrusion.

Still another object of the invention is to provide extrusion apparatus, hydrostatic or otherwise, in the form of a compact unit which is self-containing of the forces generated during the extrusion process.

These and other objects are realized according to the invention by employing a tubular billet container in which the bore is closed at one end and is plugged at the other end by an extrusion die means disposed inside the bore and adapted to be forced therein towards the closed end thereof. Such die means and the part of the bore inward of such die means form a chamber for containing a billet and, preferably, also, a hydrostatic pressure transmitting medium filling an interspace formed between the billet and the bounding wall surface of the bore of the container. To produce extrusion, the die means inside the bore is driven under extreme force towards the closed end of the bore so as to cause to be developed in the billet an internal pressure sufiicient to produce flow of the billet material through the opening of the die means in a direction the reverse of that in which the die means is driven.

For a better understanding of the invention, reference is made to the following description of an exemplary embodiment thereof, and to the accompanying drawings wherein:

FIGURE 1 is an isometric view in vertical cross-section of the mentioned embodiment;

FIGURE 2 is an enlarged view in vertical cross-section of a portion of the embodiment of FIGURE 1;

FIGURE 3 is a view in vertical cross-section of a modification of the embodiment of FIGURE 1; and

FIGURE 4 shows some exemplary working dimensions for the various elements of the FIGURE 1 embodiment.

Referring now to FIGURE 1, a pressure containing vessel has at its lower front end a flange 11 encircling a bore 12 formed in the vessel to be open at the lower end of the vessel, and to extend upwardly from that open end. The word bore is used herein as descriptive of the structure of the central hollow space of vessel 10 rather than as descriptive of its origin. Thus, the bore 12 need not be a hole formed by boring, but, instead, may be formed, say, by machining out the interior of a cast hollow vessel 10.

As shown in FIGURE 1, the bore 12 extends upwardly only partway through vessel 10 so that the top 13 of the bore is closed off by an end portion 14 of vessel 10 which is integral with the rest of the vessel. If desired, however, the pressure containing vessel may be of a type in which the interior bore extends through the vessel from end to end thereof and in which the top of the bore is closed off by a removable end closure. Thus, for example, the bore 12 may be closed at its top by a closure means similar to one of those disclosed in our copending application, Serial No. 833,420, filed August 13, 1959, now U. S. Patent No. 3,063,594 issued on November 13, 1962.

The flange 11 of vessel 10 registers with a flange 15 disposed at the upper end of and forming an integral part of a piston housing 16. Such housing contains hydraulic cylinder 17 co-axial with and of greater diameter than the bore 12. As shown, the cylinder 17 extends upwardly in housing 15 towards bore 12 from a cylinder bottom 18 formed by an end portion 19 of the housing 16 integral with the rest of the housing. An adapter tube 20 with a hollow axial core 21 extends upwardly through the end portion 19 to project into cylinder 17 beyond the bottom 18 thereof.

Received with a sliding fit in cylinder 17 is an annular piston 25 having a central cylindrical hollow space 26 in which the adapter tube 20 is in turn received with a sliding fit. The piston 25 has formed in the exterior circumference thereof an annular groove 27 in which there is an O ring 28 providing a pressure seal between the piston and the wall of cylinder 17. In like manner, the piston 25 has formed in the interior circumference thereof an annular groove 29 in which there is an O ring 38 providing a pressure seal between the piston and the wall of tube 20. A conduit 31 passing through the bottom portion 19 of housing 16 permits injection of pressurized hydraulic fluid into cylinder 17 behind piston 25'.

Mounted coaxially on piston 25 is a ram 35 of lesser diameter than the piston 25, the said ram 35 being comprised of a head 36 and a stem 37. The ram extends upwardly from the piston to have the front end of the ram received with a sliding fit in the open end of the bore 12 of vessel 10. The ram plugs such open end so that the ram cooperates with the part of the bore inwards of the ram to form a billet container chamber 38. Communicating with that chamber is a coaxial passageway 39 extending through the length of ram 35 from a lower juncture with space 26 inside piston 25 to an upper orifice 40 by which the passageway opens into the lower end of chamber 38. The chamber 38 is otherwise rendered pressure tight at its lower end by an O ring 41 seated in an annular groove 42 formed in the head 36 of the ram, the ring 41 bearing against the circumferential wall of bore 12 to form a pressure seal.

While the arm 35 may be made integral with piston 25, preferably the ram merely rests on the piston so that the ram is free to find its natural position within bore 12 during an extrusion operation. Means other than the shown hydraulic cylinder and piston combination may be employed to drive the ram into the bore. Thus, for example, the housing 16, piston 25 and tube 20 may be dispensed with, and the ram 35 may be driven into bore 12 by placing the assembled combination of vessel 10 and ram 35 between the platens of a conventional hydraulic press to allow the ram to be driven into the vessel by the closure towards each other of such platens.

The chamber 38 is shown in FIGURE 1 as containing (1) a lesser sized billet 45 having its lower end seated over orifice 40 in the head 36 of ram 35, and (2) a volume of a hydrostatic pressure transmitting medium 46 filling the interspace in chamber 38 between the billet and the wall surface of bore 12 which bounds chamber 38. Thus, the medium 46 entirely surrounds the billet except the end of the billet which is seated on the ram. For cold extrusion, the medium 46 may be a hydraulic fluid such as water, alcohol, oil or the like. When, however, the billet as contained in chamber 38 is at an elevated temperature (produced either by heating of the billet prior to its insertion in the chamber or by heating the billet in some manner within the chamber itself), the medium 46 is preferably comprised of temperature resistant material such as a metal with a low melting point or a glass with a similar low melting point and in the form of, say, glass fibers packed around the billet. It is not objectionable for the medium 46 to be comprised of a material which is a non-plastic solid at room temperature and atmospheric pressure so long as such material becomes plastic to transmit pressure in a hydrostatic manner under the pressure and temperature conditions employed to produce extrusion of the billet from the chamber 38.

A fluid medium 46 may be introduced through the top of vessel 10 into chamber 38 by a simple valve system as follows. A cylindrical duct 50 of small diameter is formed in vessel 10 to pass upwardly from chamber 38 through the top portion 14 of the vessel into a larger diameter cylindrical well 51 formed in that top portion. Seated in the chamber 38 is a valve head 53 having an annular gasket 54 on its upper side. The head 53 is connected to the bottom of a valve stem 55 which passes with a sliding fit upwardly through duct 50 to project into Well 51 and to there engage threadedly with a nut 56 of greater diameter than duct 50. Formed in stem 55 is a keyway 57 extending lengthwise in that stem from a point just above head 53 to the top of the stem. Thus, the keyway 57 passes through the nut 56.

To inject fluid into chamber 38, the nut 56 is unscrewed to allow the stem 55 and attached head 53 to drop so as to open up a space between the gasket 54 and the top 13 of the chamber 38. Fluid is then poured into well 51 to pass from that well through keyway 57 into chamber 38. When the chamber has been filled with fluid, the nut 56 is retightened to draw the gasket 54 up against the top 13 of the chamber.

The chamber 38 may be filled with the medium 46 in ways other than that just described. Thus, in the event, it is desired to use a medium which is a solid at room temperature and atmospheric pressure, the FIGURE 1 apparatus may be constructed so that it is upside down in relation to its showing in FIGURE 1, a layer of the solid material may be packed in bore 12 against portion 14 of the vessel to a thickness equal to the desired clearance between the upper end of the billet and the end surface 13 of the bore, the billet may then be inserted in the bore to rest in properly centered relation on such layer, more material may be packed into the bore to fill up the space between the cylindrical wall thereof and the billet, and, finally the ram may be inserted in the bore. Moreover, either a solid or a fluid medium may be introduced in the chamber 38 by constructing vessel so that, as described, the bore 12 extends all the way through the vessel, and the top of the bore is plugged in a pressure-tight manner by an end closure which is removable to permit the filling of the chamber 38 from the top. In FIG. 1, the shell formed around bore 12' by vessel 10 evidently acts as a housing for the billet and for the medium which surrounds the billet. I During an extrusion operation, the vessel 10 and the piston housing 16 are clamped together by a split ring clamp formed of two identical semi-circular halves 60 of which one appears in FIGURE 1. To assure that the two halves of the clamp do not become separated, a safety ring 61 is placed around the clamp. The clamp and safety ring may be constructed in accordance with the teachings in our aforementioned US. Patent No. 3,063,594. As alternatives to the use of split ring clamp, the vessel 10 and housing 16 may be bolted, bayoneted or keyed together.

FIGURE 2 shows the details of the head 36 of ram 35. This head is, in fact, a die means or die assembly comprised of an upper annular primary die 70, a lower annular secondary die 71, and an annular die holder 72 disposed below die 70 and around die 71. To relate the presently described assembly to come of the previously described features of Vessel 10, it is the central opening through primary die 70 which forms the orifice 40 by which the passageway 39 in ram 35 opens into the billet container chamber 38. Moreover, it is the die holder 72 which acts as the carrier for the previously described groove-and-

ring pressure seal

41, 42 by which fluid is prevented from leaking out of chamber 38 through the circumferential interface between the die assembly and the cylindrical wall of bore 12. The elements 763-72 of the die assembly are fastened together and to the stem 37 of the ram 35 by conventional securing means (not shown) as, say, bolts. The secondary die 71-needs no particular securing means since such die is entirely constrained by the primary die 70, the die holder 72 and the ram stem 37. If desired, the die assembly need include only a single die instead of the two dies '70 and 71.

The bottom face 80 of the billet 45 and the top face 81 of the primary die 70 are matched incontour to make flat contact with each other over an annular area disposed radially outward of the orifice 40. This annular area of contact forms -a seal which prevents hydraulic fluid 46 in the interspace around the billet from leaking underneath the billet into orifice '40 and thence out passageway 39. The integrity of such seal depends, of course, upon the contact pressure between the billet and the primary die. While the weight of the billet is, alone, enough to maintain the integrity of the seal, the tightness of the seal is further increased when the hydraulic fluid 46 is pressurized in the course of effecting an extrusion of the billet. This is so, because of the following. As shown, the annular area of contact between the billet and the primary die 70 is less than the area (FIG. 1) of the top of the billet. Hence, when the fluid 46 becomes pressurized, should any of this fluid leak into the interface between the billet and the primary die, the greatest force which such fluid can exert upwardly on the billet is equal to the fluid pressure times the area of contact between the billet and the primary die. On the other hand, the downward force simultaneously exerted on the top of the billet is equal to the same fluid pressure times the area of the billet top. The latter area is, however, evidently greater than the mentioned area of contact. Accordingly, when the fluid 46 is pressurized, such fluid exerts on the billet a net downward force which increases as the pressure increases. Thus, the seal provided ,by the contact .between the billet and the primary die is one which is characterized by a self-tightening effect.

As shown, the billet 45 has formed at the front end thereof a cylindrical stub which projects, into the orifice 40. This stub serves both to center the billet in relation to the die assembly in the course of setting up the apparatus and to provide a leader into the die during the extrusion process.

The FIGURE 1 apparatus is set up for cold extrusion in the following manner. With the safety ring 61, the split ring clamp 60 and the vessel 10 being removed from the housing 16, with the piston 25 being at the bottom of the hydraulic cylinder '17, and with the ram 35 upstanding from the piston as shown, a billet 45 of material to be extruded is seated in centered relation on the ram 35. The vessel 10 is then placed over the housing 15 so that the flange 11 of the vessel and the flange 15 of the housing are in registration, and so that the ram and the billet thereon slip into the bore 12 of the vessel. Next, the ring clamp is assembled to lock together the flanges 11, 15 and thesafety ring 61 is placed around the assembled ring clamp. Finally, the chamber 38 within bore 12r is filled with hydrostatic fluid in the manner heretofore described through the valve system at the top of the vessel. The apparatus is now ready to operate.

The extrusion operation is initiated by injecting hydraulic fluid through conduit 31 into cylinder 17 behind piston 25 so as to drive the piston upwardly. The pressure of the fluid injected behind the piston may be of the same order as that commonly used in the present day hydraulic art, i.e., between 10,000 p.s.i. and 50,000 psi. In the view, however, that the face area of piston 25 is greater by, say, tenfold than the face area of ram 35, the driving pressure behind the piston is converted by a pressure multiplying action into a much higher pressure exerted by the head of the ram 35 on the fluid 46 in the chamber 38. Thus, the pressure ultimately developed in fluid 46 by the ram may be on the order of from 100,000 p.s.i. to 500,000'p.s'.i.

As the ram 35 is driven by piston 25 into the bore 12, the ram automatically compacts the fluid 46 to build up the hydrostatic pressure therein to the critical value required to initiate extrusion of billet material through the die assembly 36. During this build up of hydrostatic pressure, the forward movement of the ram lifts the billet so that the top thereof moves towards the valve head 53. Suflicient clearance is, however, provided between the top of the billet and the valve head so that the critical hydrostatic pressure value is reached well before the top of the billet strikes the valve head. Thus, it will be seen that the ram does not at any time exert any direct pressure on the billet.

' The critical hydrostatic pressure value is reached when the pressure exerted on the billet by the fluid 46 renders the billet material sufficiently plastic to start to flow into the die assembly and thereafter, through, in order, the rest of passageway 39, the space 26 inside piston and the hollow core 21 of adapter tube 20 to be finally ejected from the apparatus. Once this critical pressure has been reached, and extrusion of the billet material begins, the further advancement of ram into bore 12 merely maintains the pressure in fluid 46 at this critical value, and the extrusion of the billet material is continuous until all of the billet has been extruded. Once the billet has been fully extruded, the fluid 46 escapes from chamber 38 through passageway 39 the pressure of the fluid in chamber 38 drops to a negligible value, and the extrusion run is terminated.

Because, during extrusion, the fluid 46 exerts pressure on the billet on all sides excepting at the front end thereof, throughout the volume of the billet the pressure therein is substantially hydrostatic and uniform. Hence, at substantially 'all points in the billet the material thereof is characterized to the same degree by that desired condition of full plasticity which is required for the billet material to flow through the opening of the die assembly. With all the material of the billet thus being in this fully plastic condition, the combination of the pressure exerted by fluid 46 downward on the billet and the pressure exerted by such fluid inwardly on the billet, particularly all around its base but also all around the rest of the circumference of the billet, the pressurize fluid has on the billet material an ideal guiding or channeling affect whereby, throughout the extrusion run, the billet material flows freely and in the path of least resistance towards the opening of the die assembly. Two desirable consequences of such actions by the pressurized fluid 46 of rendering the billet material fully and uniformly plasticized and of channeling such material to so flow towards the die assembly opening are (1) the entire billet may be extruded so that no butt is left over at the end of the run, (2) the billet may be of substantially greater diameter than the die assembly opening.

Some other advantages of the described hydrostatic extrusion method are as follows.

Because the billet is separated at all times by fluid 46 from the wall of bore 12, there is no billet-wall interface friction whatever. Moreover, fluid 46 provides an excellent lubricant for the billet. This is so, because as the billet material passes through the die assembly, there is carried with such material a thin film of fluid which clings to the material being extruded to act as a lubricant between it and the die faces. There is always more than enough fluid 46 in the chamber 33 to provide such fluid lubricating film. Accordingly, the die assembly'is effectively lubricated throughout the whole extrusion run, and the life of the die assembly is thereby maximized.

In conventional extrusion (l) the diameter of the ram must be approximately the same as that of the billet, 2) the length of the ram must be short enough in relation to its diameter to avoid buckling of the ram under the force applied thereto to effect extrusion of the billet, (3) the maximum stroke of the ram is limited by its length, (4-) the volume of billet material which can be extruded by the ram is limited by its stroke and is roughly equal to such stroke times the ram (or billet) diameter. Therefore, in conventional extrusion, as the diameter of the billet decreases, the volume of extruclable billet material decreases as the square of such diameter.

In the above described hydrostatic extrusion method, on the other hand, after the hydrostatic pressure in the chamber 38 has reached the value at which extrusion begins to take place, all that is required to fully extrude a billet of given diameter is that the volumetric displacement of the chamber be decreased in an amount equal to the volume of the billet. Such decrease in the volumetric displacement of chamber 38 need not, however, be obtained by a ram stroke approximating the length of the billet. Instead, it can be obtained by using a chamber substantially greater in diameter than the billet, and by using a ram which is substantially shorter than the billet length and which, therefore has a stroke substantially shorter than that length. Thus, the described hydrostatic method permits the use of a ram which is stubby relative to the length of the billet to be extruded, and which, because of its stubbiness, is capable, without buckling, of extruding a much greater volume of billet material than if the diameter and length of the ram had to be proportioned to respectively, the diameter and length of the billet.

To state what has just been said in another way, in the described hydrostatic method the critical factor is the value of hydrostatic pressure required for extrusion, since such value determines the ratio of ram diameter to ram length which must be used to assure that the ram will not buckle in the course of building up the hydrostatic pressure in the billet containing chamber to that required value. Further, assuming a certain required value of hydrostatic pressure and a ram having a diameter length ratio determined by such value, and having a given diameter and length which are in accordance with such ratio, evidently (in order to fit into the chamber) the billet must be of less diameter than the ram, and, also, (if full extrusion of the billet is desired), the total volume of the billet must be less than the product of the rams diameter and stroke. Subject, however, to the limitations just enumerated on the maximum diameter and volume of the billet, the ram and associated chamber (when the latter is of suitable shape) are capable of extruding a billet of any diameter and volume whatever less than the limiting diameter and volume, whereas this is not true of the ram and chamber employed in conventional extrusion.

In the described apparatus, while the pressurizing of fluid 4s tends to produce radial bulging of the circumferential wall of bore 12, any resulting tendency of the pressure seal provided by the 0 ring 41 to open up is largely counteracted by the thick flange 11 around the mouth of the bore. Such tendency to open up is further counteracted during extrusion by the extruded material which, as it passes through the die assembly, is highly compressed to exert on the interior of the assembly a force directed radially outward and tending to expand the assembly to more firmly seat the ring 41 against the wall of the bore.

As will be noted, the die assembly is fully supported during extrusion by the ram stem 37. Because of the excellent support so provided for the die assembly on the side thereof opposite the high pressure generated in chamber 3, there can be eliminated from the FIGURE 1 apparatus the extra element of the massive stationary support which is usually needed in conventional extrusion apparatus to assure that the die assembly does not fail under such pressure. Moreover, inasmuch as the ram stem is driven by the piston 25 to provide a dynamic type of support for the die assembly, any deflection of deformation of such assembly under pressure is much reduced compared to what it would be if such pressure were to be opposed only by the passive support action of a stationary support.

The location in the FIGURE 1 apparatus of the die assembly at the same end of the container vessel as the ram allows tire vessel and the hydraulic cylinder and piston assembly or other ram drive means to be joined together, in say, the manner shown without requiring the use to effect such joinder of any tie rods of like extraneous structural elements prone to mechanical failure. The vessel and ram drive means as so joined together form a compact structural unit in which all forces generated in the unit during extrusion are contained therewithin instead of being communicated to an exterior bed or frame.

Referring now to FIGURE 3, the elements of the modification shown therein which are counterparts of those of the FIGURE 1 embodiment are each designated by the same reference numeral as the corresponding FIG- URE 1 element but are further designated by a prime sufiix. The differences between the FIGURE 1 embodiment and the FIGURE 3 modification are as follows. In the modification, a bore 12. is formed in a piston 25' so that the element 25 acts as the billet container vessel as well as the piston. Further, a ram 35' is turned upside down to have its head 35 inserted in the upper end of the bore, and the flanged element 16 is replaced by a similarly flanged ram housing 90 having an upper transverse portion 91 adapted to act as a stop for the back end of the ram stem 37'. Formed in this portion 91 coaxial with a passageway 39' in the ram is a hole 92 permitting escape to the exterior of housing 90 of billet material extruded through such passageway.

The FIGURE 3 apparatus is set up as follows for an extrusion operation. With the safety ring 61', shown split ring clamp 60, housing 90, and ram 35 being removed, a billet 45 is placed in bore 12' so that a guide rod 95 upstanding coaxially from the bottom of the bore is slidably received within a matching guide hole 96 formed in the bottom of the billet. A compression spring 97 encircling rod 95 maintains the billet an appropriate distance from the bottom of the bore. After the billet has so been placed in the bore, hydrostatic fluid 46 is introduced into the bore until the surface of the fluid is level with or slightly higher than the upper end of the billet. Next, the ram 35 is fitted into bore 12 and advanced therein until the head of the ram makes, as earlier described, a fluid sealing contact with the rear end of the billet. During such advancement but before such sealing contact is made, any excess of fluid in bore 12' will be forced around the billet into passageway 39. The assembly of the apparatus is completed by adding housing 90, split ring clamp 60 and safety ring 61'. As shown in FIGURE 3, the spring 97 in bore 12' is of a size and resiliency to position the billet and ram so that, statically, there is a slight clearance between the upper end of ram stem 37 and the underside of portion 91 of housing 90.

In the operation of the FIGURE 3 apparatus, hydraulic fluid is injected through conduit 31' to advance the piston 25' to bring the upper end of ram stem 37 into contact with the stop portion 91 of housing 90. Thereafter, the operation of the FIGURE 3 apparatus is essentially the same as the previously described operation of the FIG- URE 1 apparatus.

The FIGURE 3 apparatus has the same advantages as those of the FIGURE 1 apparatus. Moreover the FIG- URE 3 apparatus has the additional advantage that the pressure of the piston-driving fluid in the interstitial space below ring 28 between piston 25' and the wall of cylinder 17 exerts on the piston a pressure adapted to reduce radial bulging of the circumferential wall of bore 12' in the manner taught in our copending application Serial No. 35,933 of 1960 filed June 14, 1960, now U.S. Patent No. 3,049,756 issued on August 21, 1962.

In the FIGURE 1 apparatus, the

elements

10, 16 and 60 may be made of alloy steel, the

elements

25 and 61 may be made of carbon steel and the die assembly 7G 72 may be made of tool steel. Like elements of the FIGURE 3 apparatus may be likewise constructed. Some exemplary working dimensions for the FIGURE 1 apparatus are shown in FIGURE 4. The FIGURE 3 apparatus may be constructed to the same scale.

The above described apparatus of FIGURE 1 and of FIGURE 3 being exemplary only, it will be understood that additions, omissions and modifications thereto may be made without departing from the spirit of the invention, and that the invention hereof comprehends embodiments diifering in form and/or detail from those which have been specifically described. Thus, for example, V type packings may be used in place of the 0 rings which have been disclosed. Accordingly, the in vention is not to be considered as limited save as is consonant with the recitals of the following claims.

-We claim: a

1. Apparatus comprising, a pressure containing vessel with an interior bore operably open only at one end of said vessel, a single inwardly movable ram projecting into said bore to have a sliding fit therewith and to plug the open end thereof so as to form with the part of said bore inwards of said ram a chamber adapted to contain a billet in abutting relation with said ram and in spaced relation from the wall surface of said bore, and adapted to contain also a hydrostatic pressure transmitting medium filling the interspace between said wall surface and billet, said ram having extending lengthwise therethrough a passageway characterized at its chamber end by an orifice over which said billet is adapted to be seated, means to drive said ram into said bore so as to develop in said medium a hydrostatic pressure producing extrusion through said passageway of billet material, die means forming part of said ram and disposed around said pas sageway to shape the extruded billet material, and annular sealing means disposed around said ram in the interspace between the exterior circumferential surface of said ram and the surrounding wall of said bore to provide in said interspace a seal obstructing leakage of said medium past said ram out of the open end of said bore.

2. Apparatus as in claim 1 further comprising pressurerestraining means in the form of a flange selectively positioned at said end of said vessel and disposed around said end to oppose radial enlargement of the open end of said bore by the pressure of said medium.

3. Apparatus comprising, first housing means having therewithin a bore operably open only at one end of said means, an inwardly movable ram having a stem portion and a head portion of which the latter projects into said bore to plug the open end thereof so as to form with the part of said bore inwards of said ram a billet containing chamber, said ram having extending lengthwise therethrough a passageway for extrusion of billet material from said chamber, second housing means enclosing the stem portion of said ram and disposed opposite said end of said first housing means, threadless coupling means including shoulder means disposed circumferentially about each of said housing means, said threadless means coupling said first and second housing means end to end to provide an enclosure formed or" said two housing means, and means in said enclosure to drive said ram into said bore to produce extrusion of said material through said passageway, said enclosure being self containing of the forces generated therein during said driving of said ram.

4. Apparatus comprising, a pressure containing vessel having flange means at its front end and having an interior bore operably open only at said end, an inwardly movable ram projecting into said bore to plug the open end thereof so as to form with the part of said bore inwards of said ram a billet containing chamber, said ram having extending lengthwise therethrough a passageway for extrusion of billet material from said chamber, a housing disposed opposite said front end of said vessel and having flange means registering with the flange means of said vessel, means in said hon-sing to drive said ram into said bore to produce extrusion of material through said passageway, and ring means clamping said two flange means together to form of said vessel and housing a unit which is self containing of the forces generated therein during said driving of said ram.

5. Apparatus comprising a pressure containing vessel having flange means at its front end and having an interior bore operably open only at said end, an inwardly movable ram projecting into said bore to plug the open end thereof so as to form with the part of said bore in- Wards of said ram a chamber adapted to contain a billet in abutting relation with said ram and in spaced relation from the wall surface of said bore, and adapted to contain also a hydrostatic pressure transmitting medium filling the interspace between said wall surface and billet, sald ram having extending lengthwise therethrough a passageway characterized at its chamber end by an orifice over which said billet is adapted to be seated, a housing disposed opposite said front end of said vessel and having flange means registering with the flange means of said vessel, means in said housing to drive said ram into said bore, to develop in said medium a hydrostatic pressure producing extrusion through said passageway of billet material, die means forming part of said ram and disposed around said passageway to shape the extruded billet material, and ring means clamping said two flange means together so as to form of said vessel and housing a unit which is self containing of the forces generated therein during said driving of said ram.

6. Apparatus comprising a pressure containing vessel with an axially extending interior bore operably open only at one end of said vessel, a housing disposed opposite said end of said vessel and containing a hydraulic cylinder coaxial with and of greater diameter than said bore and opening towards said bore, an adapter tube extending through said housing in coaxial relation with said cylinder to project thereinto beyond the bottom thereof, an annular piston slidably received in said cylinder and having a central space in which said tube is slidably fitted, a ram projecting coaxially from said cylinder into said bore to plug the open end thereof so as to form with the part of said bore inwards of said ram a billet containing chamber, said ram having formed coaxially therethrough a passageway communicating between said chamber and said central space, and means to inject pressurized hydraulic fluid in said cylinder behind said piston to drive said ram into said bore so as to produce extrusion of billet material from said chamber through said passageway, central piston space and adapter tube.

7. The method of extruding a billet comprising the steps of placing said billet in a tubular container with a bore operably closed at one end and open at the other and larger in both longitudinal and cross sectional dimensions than said billet so that said billet is disposed to be everywhere in spaced relation from the wall surface bounding said bore, filling the interspace between said billet and wall surface with a hydrostatic pressure transmitting medium, plugging the open end of said bore by an extrusion die means slidably received in said bore to abut the near end of the billet therein, and forcing said die means towards the closed end of said bore so as to develop in said medium a hydrostatic pressure producing extrusion through said die means of billet material.

8. Apparatus comprising, a housing containing a hydraulic cylinder, a piston slidably received in said cylinder and having formed therein an axial bore of which the end towards the front of the cylinder is open and of which the other end is operably closed, a ram slidably received in said bore to plug the open end thereof so as to form with the part of said bore inwards of said ram a chamber adapted to contain a billet in abutting relation with said ram and in spaced relation from the wall surface of said bore, and to contain also a hydrostatic pressure transmitting medium filling the interspace between said wall surface and billet, said ram having extending lengthwise therethrough a passageway terminated at said chamber end by an end over which said billet is adapted to be seated, means providing a stop behind said ram, means to inject fluid into said cylinder behind said piston to move it forwardly so as to bring said ram in contact with said stop, and, thereafter to drive said ram into said bore so as to develop in said medium a hydrostatic pressure producing extrusion through said passageway of billet material, and die means forming part of said ram and disposed around said passageway to shape the extruded billet material.

9. Apparatus comprising, first housing means having therewithin a bore operably open only at one end of said means, an inwardly movable ram having a stern portion and a head portion of which the latter projects into said bore to plug the open end thereof so as to form with the part of said bore inwards of said ram a billet-containing chamber, said ram having extending lengthwise therethrough a passageway for extrusion of billet material from said chamber, second housing means disposed opposite said end of said first housing means and enclosing said stem portion of said ram, means including a hydraulic cylinder in one of said housing means and a piston in said cylinder for driving said ram into said bore to pro duce extrusion of said material through said passageway, said cylinder and piston being of larger diameter than said ram to convert the hydraulic pressure which actuates said piston into a greater extrusion-inducing pressure exerted on said billet material in said chamber, and means coupling said first and second housing means end to end to provide by said two housing means an enclosure for containing the forces generated therein during said driv ing of said ram.

' 10. The method of extruding a billet comprising placing in the bore of a tubular container both a billet of lesser dimensions than said bore and a hydrostatic pressure-transmitting medium disposed in said bore to render said billet separated by said medium from the wall surface bounding said bore, said bore being operably closed at one end, and being plugged at the other end by an inwardly movable ram of greater diameter than the billet and carrying a die through which extends a passageway continued lengthwise through the ram, and driving said ram into said bore so as to develop in said medium a pressure producing extrusion of the billet material through said passageway and an accompanying shaping of said material by said die.

11. The method of extruding a billet comprising, placing in the bore of a tubular container both a billet of lesser dimensions than said bore and a hydrostatic pressure-transmitting medium disposed in said bore to render said billet separated by said medium from the wall surface bounding said bore, said bore being operably closed at one end, and being plugged at the other end by an inwardly movable ram of greater diameter than said billet and carrying a die supported on the side thereof away from said bore by the body of said ram, and said ram being characterized by a passageway extending lengthwise therethrough and through said die, and driving said ram into said bore so as to develop in said medium a pressure producing extrusion of the billet material through said passageway and an accompanying shaping of said material by said die.

References (Iited in the file of this patent UNITED STATES PATENTS 74,612 Shaw Feb. 18, 1868 1,963,675 Plainevaux et al June 19, 1934 2,558,035 Bridgman June 26, 1951 2,920,760 Genders Jan. 12, 1960 2,962,164 Scribner Nov. 29, 1960 FOREIGN PATENTS 476,793 Canada Sept. 11, 1951 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent NO, 3,126,096 Mareh 24, 1964 George Gerard et a1.

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.

Column 7, line 27, for -"pressurize" read pre -s SuIlZed. column 8, line 49, for "3" read 38 column 9, line 16, strike out "shown" and insert the same after "the" in same line 16, same column 9.

Signed and sealed this 14th day of July 1964.

(SEAL) Attest:

EDWARD J BRENNER Commissioner of Patents ESTON G. JOHNSON Attesting Officer UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 126,096 March 24, 1964 George Gerard et a1.

Column 7, line 27, for "pressurize" read pr-6.3.4:" SUIlZGd column 8 li 49 f n 1" read lumn line Strike Out "shown" and insert the same after "the" in same line 16, same column 9.

Signed and sealed this 14th day of July 1964.

(SEAL) Attest:

ESTON G. JOHNSON EDWARD J. BRENNER Attesting Officer Commissioner of Patents

Claims

1. APPARATUS COMPRISING, A PRESSURE CONTAINING VESSEL WITH AN INTERIOR BORE OPERABLY OPEN ONLY AT ONE END OF SAID VESSEL, A SINGLE INWARDLY MOVABLE RAM PROJECTING INTO SAID BORE TO HAVE A SLIDING FIT THEREWITH AND TO PLUG THE OPEN END THEREOF SO AS TO FORM WITH THE PART OF SAID BORE INWARDS OF SAID RAM A CHAMBER ADAPTED TO CONTAIN A BILLET IN ABUTTING RELATION WITH SAID RAM AND IN SPACED RELATION FROM THE WALL SURFACE OF SAID BORE, AND ADAPTED TO CONTAIN ALSO A HYDROSTATIC PRESSURE TRANSMITTING MEDIUM FILLING THE INTERSPACE BETWEEN SAID WALL SURFACE AND BILLET, SAID RAM HAVING EXTENDING LENGTHWISE THERETHROUGH A PASSAGEWAY CHARACTERIZED AT ITS CHAMBER END BY AN ORIFICE OVER WHICH SAID BILLET IS ADAPTED TO BE SEATED, MEANS TO DRIVE SAID RAM INTO SAID BORE SO AS TO DEVELOP IN SAID MEDIUM A HYDROSTATIC PRESSURE PRODUCING EXTRUSION THROUGH SAID PASSAGEWAY OF BILLET MATERIAL, DIE MEANS FORMING PART OF SAID RAM AND DISPOSED AROUND SAID PASSAGEWAY TO SHAPE THE EXTRUDED BILLET MATERIAL, AND ANNULAR SEALING MEANS DISPOSED AROUND SAID RAM IN THE INTERSPACE BETWEEN THE EXTERIOR CIRCUMFERENTIAL SURFACE OF SAID RAM AND THE SURROUNDING WALL OF SAID BORE TO PROVIDE IN SAID INTERSPACE A SEAL OBSTRUCTING LEAKAGE OF SAID MEDIUM PAST SAID RAM OUT OF THE OPEN END OF SAID BORE.