US 3066556 A
Description (OCR text may contain errors)
Dec. 4, 1962 F, T. JASKOWIAK METHOD AND APPARATUS FOR ESTABLISHING HIGH FLUID PRESSURE Filed July 2, 195a INVEN TOR. FRANK T. JASKUWIAK -77 tfornegs 4 H w i111 :WW// 7 2 v w. W MHIWYH 1i! 1. G I r nfl Q F M 7 2 W1 /w/ w w 4 4 a w m 1 3 m PU. m\o F M m 2 E l 9 :r..\& Q
3,%,55h Fatenterl Dec. 4, 1962 3,066,55 METHOD AND APPARATUS FGR ESTABLISHHNG HTGH FLUID PRESSURE Frank T. .laskowiair, Milwaukee, Wis., assignor to A. O.
Smith Corporation, Milwaukee, Wis, a corporation of New York Filed duly 2, 1958, Ser. No. 746,283 1 Claim. (CI. 78-61) This invention relates to a method and apparatus for establishing high fluid pressure and is particularly adapted to the extrusion of high strength steel and other high strength metal alloys by the use of high extruding forces.
Presently partial extrusion of cold steel and other similar cold metals wherein the metal is simultaneously extruded and stretched requires the use of low tensile strength metals in order to provide the required softness in the metal necessary to insure plastic flow of the metal.
For example, in automotive control arms a flanged hub member is formed by partial extrusion and forming of a central portion of an apertured disc. In the extrusion and forming process, the metal immediately adjacent the aperture is moved laterally of the blank to form the hub or neck portion of the member. Although highly satisfactory hub members are formed by this process, the steel employed must be of a relatively soft characteristic and consequently of a low tensile strength. In the formation of the member, the metal has a tendency to he carried along with the punch and substantial radii are formed at the junction of the neck and the flange.
Further, in order to prevent fracturing or tearing of the neck portion from the flange portion during the extruding operation, the portion of the neck immediately adjacent the flange is substantially enlarged and tapers down to a final neck thickness.
In accordance with the present invention a fluid backing is provided in the cavity into which the punch and the extruded and formed portion of the metal blank moves.
'The punch engages the extruded and formed portion of the metal blank under a pressure which loads the extruded portion to the bearing strength yield point and higher. This pressure effectively seals the die opening and prevents escape of the backing fluid. The backing fluid is water or some other similar substance which has a low coefficient of compressibility. Consequently, very small movement into the cavity establishes relatively large back or reaction pressures which act uniformly on the metal blank moving into the cavity. This back pressure establishes stresses in the metal which tend to overcome or alleviate the tensile stresses which are set up within the extruded portion of the metal blank and thereby maintains relatively plastic flow of the metal even with extremely high tensile strength metals.
The movement of the punch into engagement with the blank and the subsequent extrusion into the cavity establishes a positive hermetic seal of the cavity ope.- ing. Consequently, as the punch moves into the cavity, the water or other fluid is compressed and establishes pressures, which by suitable selection of fluid and size of the die and punch components can create exceedingly high pressures. Thus, the present invention can be used as a high pressure pump to establish any pressure desired as well as in the extrusion of cold members.
The present invention provides a rugged and reliable method and apparatus for extruding members which will yield under pressure, and particularly metal members having high strength and low ductility such as steel.
The drawing furnished herewith illustrates the best mode presently contemplated by the inventor for carrying out the invention.
In the drawing:
FIGURE 1 is a view partly in elevation and partly in section of an extruded hub member;
FIGURE 2 is a perspective View of a metal blank from which the hub is to be formed by cold extrusion;
FIGURE 3 is a cross-sectional view of a die and punch assembly constructed in accordance with the present invention; and
FIGURE 4 is an enlarged fragmentary view of a portion of the die and punch assembly of FIGURE 3 showing a metal blank in the process of being extruded.
Referring to the drawing and particularly FIGURES 1 and 2, an annular member l is shown comprising a tubular neck 2 of slightly reduced thickness integrally joined with an encircling radial flange 3. The member 1 is formed from a suitable metal disc blank l, as shown in FIGURE 2, having a small central aperture 5 by extruding a portion of the metal immediately adjacent the aperture 5 in a direction transversely of the plane of the metal blank.
Referring to FIGURES 3 and 4, a die and punch assembly is shown adapted to form the tubular neck 2 in the blank 4. The assembly includes a lower die member 6 having a smooth upper surface '7 from which extends a central cylindrical cavity 8 which is adapted to receive a punch 9.
The diameter of cavity '8 corresponds to the outer diameter of neck 2 while the length of cavity 8 is substantially longer than the length of the neck 2. A plurality of pressure adjusting slugs it are disposed within the cavity 8 to selectively vary the quantity of a fluid 11 necessary to fill the cavity 8. The adjusting slugs lit) may be formed of any relatively non-compressible material such as mild steel or the like.
The fluid ll is water or some other similar fluid having a relatively low coeflicient of compressibility. Consequently, as more fully set forth hereinafter, movement of the punch 9 into cavity 8 establishes high reaction pressures.
The diameter of punch 9 corresponds to the inner diameter of the tubular neck 2 such that as the punch moves into the cavity 8 a space exists between the Wall of the cavity 8 and the punch 9 which corresponds to a predetermined thickness for the neck 2. which thickness is less than the thickness of the blank 4. The outer surface of the punch 9 and the wall of the cavity 3 are parallel to each other to provide a neck of uniform thickness.
Referring particularly to FTGURE 4, the lower end of the punch 9 is relieved by a small conical recess 12 to provide an initial relatively annular blunt edge contact of the punch 9 and blank 4.
An annular blank-restraining member 13 is shown removably attached to the upper end of the die 6 by a plurality of cap screws 14 and includes a central opening somewhat larger than the diameter of the punch 9 and less than the diameter of the cavity 8. The member 13 s accurately aligned with the punch 9 and cavity 8 to allow relative movement of tne punch and the die. The metal blank 4 is disposed between the upper surface of die 6 and the restraining member 13 and when the cap screws 14 are tightly drawn up, the blank 4 is rigidly clamped between the upper surface 7 of die 6 and member 13. The blank 4 is rigidly held against movement except for that portion overlying the cavity 8. The restraining member 13 also initially seals the joint between the blank 4 and the upper surface 7 of the die 6. Consequently, as the punch 9 moves into the cavity 8, the fluid lll cannot escape along the upper surface of the die member 6.
A lower mounting plate 15 carries the die member 6 and also a plurality of upwardly extending spacing memaccesses bers 16, which are rigidly secured thereto by a plurality of cap screws 17. The spacing members 16 protrude slightly above the upper level of the restraining members 13 and are adapted to be engaged by a punch plate 18 to which the punch 9 is rigidly attached. The punch plate it; limits the downward movement of the punch 9.
The punch 9 is located within a center recess in the punch plate 18 and is rigidly secured thereto by a plurality of cap screws 19 which extend through suitable openings in the punch plate and thread into correspondingly tapped openings in an enlarged head portion 2d of the punch 9. Suitable pressure means, not shown but schematically illustrated and referred to by a plurality of arrows 2-1, are provided to vertically move the plate and attached punch a. In this manner the punch 9 is selectively forced into and withdrawn from the cavity 8.
A small purge plunger 22 threads into a correspondingly tapped opening in the center of the lower end of the punch 9. The purge plunger 22- passes freely through the aperture 5 in the blank i during the extruding operation and eliminates all air from within the cavity 8 during initial downward movement of the punch.
The operation of the punch and die assembly is as follows:
With the punch 9 withdrawn and retainer 13 removed or disassembled from the die 6, the blank 4 is positioned upon the upper surface of die 6 with the aperture 5 centrally located with respect to the cavity 8. The retainer 13 is then attached to die a? by drawing up on the cap screws 14 to rigidly clamp the blank 4 in position and prevent movement of the flange portion of the blank 4. lressure is then applied to the punch plate 18 to move the punch 9 downwardly into the cavity 8. The lower end of the punch '5 first engages the blank 4, as shown in phantom outline in FEGURE 4, with a relatively blunt edge Contact due to the conical relief recess 12. As the punch 53 moves downwardly into the cavity 3, the portion of the metal blank 4 overlying the cavity is forced into the cavity within the space between the punch 9 and the wall of cavity 8. The space between the punch 9 and the wall of cavity 8 is less than the thickness of the metal blank Consequently, the metal in the blank 4 is extruded.
As an incident of this extrusion, high frictional forces are established between the cooperating surfaces of the die, punch and blank and a positive hermetic seal is established between the punch 9 and the blank 4. Consequently, the cavity 8 is sealed against fluid leakage and the fluid is trapped in the cavity 3. The seal established in this manner allows high pressures to be established in the trapped fluid.
The plastic flow equation for metal members being deformed is as follows:
Where particularly as applied to any elemental cube or portion in the extruded portion of the member:
5, is equal to the axial tensile stress in the metal;
S is a circumferential tensile stress in the metal;
S is the compressive stress in the metal; and
S is the yield stress in tension of the particular metal.
The above equation is the standard equation generally found in the Standard Handbook for Engineers, and is specifically set forth at page 400, th ed., 1951 of Marks Mechanical Engineers Handbook.
In the illustrated embodiment of the invention, the stresses are related to the principal stresses referred to in the above text reference as follows:
S is a stress in the axial direction in the extruded tubular portion of the disc-like member as it is being formed. S is a stress acting upon the cube perpendicularly to S and generally in a circumferential direction as viewed in the tubular portion. And, S is a compressive stress acting in a direction perpendicular to the plane containing the stresses S and S and thus perpendicularly i.- of both stresses of S and S The stresses 5,, S and S are thus principal stresses which are normal to the principal axis of the other stresses.
in order to prevent fracturing of the metal, the various stresses established within the metal, namely, 3,, S and S must be maintained at such a level that the above equation remains in balance.
In tubular extrusion of metal such as in the formation of the neck 2, the compressive stres S is usually the limiting factor which normally requires the use of a relatively soft and low tensile strength material in order to maintain S within permissible limits.
In accordance with the present invention, as the punch 9 moves into the cavity 8, the trapped water 11 is compressed and establishes a reaction force which acts upon the metal being extruded into the recess, as shown in FIGURE 4. This reaction pressure acts in all directions upon the metal within the cavity and tends to compress the metal. In so doing, compressive stresses are established within the metal within the cavity which maintains the previous equation in balance.
Water and other similar materials have such a low coefiicient of compression that they are normally considered incompressible. Consequently, a very low amplitude of compression results in substantial pressure and very limited movement of the punch establishes sufficient pressure on the extruded metal to establish compressive stresses which maintains the plastic flow equation in balance.
The compressive forces established on the metal within the cavity are such that cracks normally created in the edge of the aperture 5 during the drilling thereof are actually stopped from increasing and under predetermined condition made to disappear by the extrusion process.
The degree or amount of reaction force is readily adjusted by insertion and removal of the filler slugs 10 which changes the volume of the water within the cavity 8. The smaller the amount of the water or the like, the greater is the reaction force per unit of movement of the punch 9.
The completed annular member 1 extruded and formed in accordance with the present invention is provided with an integrally formed neck 2 having relatively sharp corners at the integral junction between the neck 2 and the flange 3 to provide a substantially smooth upper surface.
During the initial movement of the extrusion opera tion, the neck portion of the blank 4 appears to pull in to the cavity 8 and establish a radius 23 at the upper junction of the neck 2 and flange 3. However, as the extrusion process continues, some of the metal within the space between the punch 9 and cavity 8 moves outwardly and fills in the radius 23 to form a square corner if the compressive pressure is increased sufficiently high.
The walls of the neck 2 are of a constant thickness and of a height directly proportioned to the total material available for formation of the hub.
Further, the present extrusion method and apparatus completely and fully work hardens the material in the neck 2 and correspondingly improves the physical characteristic of the metal.
Extruded members are therefore entirely formed of a high strength metal in a simple and relatively inexpensive process in accordance with the present invention.
Although particularly described with respect to metal forming by extrusion, the method and apparatus is more broadly applicable to the creation of extremely highfiuid pressure by means of sealing a fluid within a cavity by partial extrusion of a member between a punch means and a fluid opening.
Although particularly applicable to metal extrusion, Lucite and any other material which yields under bearing pressure can be extruded in accordance with the present invention.
Various modes of carrying out the invention are contemplated as being within the scope of the following claim particularly pointing out and distinctly claiming the subject matter which is regarded as the invention.
Apparatus for forming a tubular collar on an apertured plate, which comprises a femal die having a planar outer die surface and a die cavity open to said surface through a passage leading from said cavity with the outer surface of the die being adapted to receive the plate to be formed and with the aperture thereof overlying said passage, and said die cavity and passage being imperforate and adapted to confine a fluid capable of developing extremely high pressures when the fluid is compressed by the apparatus in operation, a restraining member clamping said plate to said die surface, a male die disposed to engage the portion of said plate that overlies said passage and surrounds said aperture, the clearance between the wall of the female die and said male die is less than the thickness of said portion of the plate to be formed to provide said portion as a seal between said dies against escape of the fluid in the die cavity when said portion is being formed by said dies, an aperture in said restraining member closely receiving said male die, and means to urge said male die into engagement with the portion of the plate and into the female die a sufficient distance to thereby force said portion of the plate into the female die to form an open ended tubular collar, and suflicient fluid confined and sealed in the die cavity by the dies and said portion, so that the movement of the male die will compress the fiuid confined in the die cavity to develop an extremely high pressure exerting a counteracting force against said portion of the plate exposed to said fluid to create a forming force on said collar in reverse to the 6 action of said male die to compress the metal of said collar and reverse the metal thereof to form a right angular corner between the surface of said plate opposite said collar and the inside of said collar.
References Cited in the file of this patent UNITED STATES PATENTS 1,464,146 Begot Aug. 7, 1923 1,493,516 Bohle May 13, 1924 1,613,961 Schwartz Jan. 11, 1927 1,819,254 Mantle Aug. 18, 1931 2,157,354 Sherman May 9, 1939 2,292,799 Romann et a1 Aug. 11, 1942 2,305,610 Ernst Dec. 22, 1942 2,308,953 Brown Jan. 19, 1943 2,558,035 Bridgman June 26, 1951 2,615,411 Clevenger et al. Oct. 28, 1952 2,783,728 Hoffman Mar. 5, 1957 2,870,907 Creutz Jan. 27, 1959 2,898,788 Baxa Aug. 11, 1959 FOREIGN PATENTS 9,025 Great Britain AD. 1906 698,366 Germany Nov. 8, 1940 OTHER REFERENCES University Physics-Mechanics, Heat, and Sound, by 'Francis Weston Sears and Mark W. Zemansky, 2nd ed., Addison-Wesley Pub. Co., Inc., Cambridge 42, Mass, 1955, p. 187.
Introduction to the Theory of Plasticity for Engineers, Oscar Hofiman and George Sachs, McGraW-Hill Book Co., Inc., New York, 1953, pp. 7 and 38-40.