US3379043A

US3379043A - Pressure vessel for forming apparatus

Info

Publication number: US3379043A
Application number: US436128A
Authority: US
Inventors: Francis J Fuchs
Original assignee: Western Electric Co Inc
Current assignee: AT&T Corp
Priority date: 1965-03-01
Filing date: 1965-03-01
Publication date: 1968-04-23
Anticipated expiration: 1985-04-23
Also published as: DE1298880B; GB1139364A; SE348956B; SE319445B

Description

April 23, 1968 F. J. FUCHS, JR

PRESSURE VESSEL FOR FORMING APPARATUS 5 Sheets-Sheet 1 Filed March 1, 1965 INVENTOR fhrzalaz'lkc/s; Jr; l /4W ATTORNEY April 23, 1968 F, J, FUC JR 3,379,043

A ril 23, 1968 Filed March 1, 1965 P. J. FUCHS, JR

PRESSURE VESSEL FOR FORMING APPARATUS 5 Sheets-Sheet 5 April 23, 1968 F. J. FUCHS, JR

PRESSURE VESSEL FOR FORMING APPARATUS 5 Sheets-Sheet 4 Filed March 1, 1965 April 23, 1968 F. J. FUCHS, JR 3,379,043

PRESSURE VESSEL FOR FORMING APPARATUS Filed March 1; 1965 5 Sheets-Sheet 5 &

United States Patent 3,379,043 PRESSURE VESSEL FOR FORMING APPARATUS Francis J. Fuchs, Princeton Junction, N.J., assignor to Western Electric Company, Incorporated, New York, N.Y., a corporation of New York Filed Mar. 1, 1965, Ser. No. 436,128 Claims. (CI. 7256) ABSTRACT OF THE DISCLOSURE A pressure vessel including a forming cylinder for containing fluid which is pressurized by a piston movable into the cylinder. The forming cylinder is expandable in response to a predetermined fluid pressure to allow a portion of the pressurized fluid to flow out of the cylinder, past the piston, into another cylinder, or succession of cylinders, spaced from and surrounding the forming cylinder. The pressurized fluid in the surrounding cylinder, or cylinders, exerts inward forces on forming cylinder counteracting the radial forces generated by the piston acting on the fluid contained in the forming cylinder.

This invention relates to an ultra-high pressure metal forming apparatus and more particularly to a forming apparatus having facilities responsive to the generation of ultra-high pressures within a forming cylinder for applying opposing or restraining forces to the outside of the cylinder.

The ductility of metals such as steel, brass, aluminum, molybdenum, and copper increases tremendously when a high hydrostatic pressure is applied to the metal. Due to this increased ductility, operations such as deep drawing or metal forming are considerably facilitated if accomplished with high fluid pressures acting on the metal within a forming cylinder. Present forming presses are not readily adapted to withstand the internal pressures required to utilize this principle of increased metal ductility at high pressure.

Difliculties involving the design of a piston-cylinder apparatus to withstand high pressures are considerable. The primary limitation on high pressure apparatus is the strength of the materials used in construction. At prescut, the maximum fatigue strength available in steel is 130,000 psi. for unlimited cycles, to a maximum practical value of 150,000 psi. for about 100,000 cycles. Even by using a series of shrink-fitted cylinders, the useful strength levels can be boosted only to 300,000 p.s.i. a value still short of desired high pressures in excess of 500,000 p.s.i. which can be utilized to take advantage of the increased ductility of metals encountered at high forming pressures.

Attempts have been made in the past to attain high pressures by using a multi-stage apparatus whereby a forming cylinder is surrounded by a first pressure vessel which is surrounded by a second pressure vessel, etc. In this type of apparatus, pressurized fluids are introduced into the forming cylinder and the pressure vessels by separate external pressure sources. If any of the external pressure sources should fail for any reason, such as a faulty valve, failure of the forming cylinder or pressure vessel immediately results.

Some multi-stage apparatus directly pass pressurized fluid from the forming cylinder into surrounding vessels. However, it is very difiicult to generate high pressures using this apparatus.

Furthermore, when multi-staging is used, opposing radial forces acting on the forming cylinder wall result in a pinch-off effect in which the metal of the cylinder wall tends to flow longitudinally away from the area being subjected to the opposing radial forces. In practice,

multi-staging is extremely difiicult to utilize and difficulty increases when more than two stages are used.

It is an object of this invention to provide a new and improved ultra-high pressure metal-forming press.

Another object of the invention resides in a press for generating and withstanding ultra-high pressures of over 500,000 p.s.i.

A further object of the invention is to provide a forming cylinder having facilities responsive to internally generated pressures for applying balancing forces to the outer surface to compensate for ultra-high pressures generated within the cylinder.

Another object of the invention resides in the utilization of the elastic deformation of a forming cylinder to vent high-pressure fluid out to an annular chamber surrounding the cylinder to provide counter-acting forces against the outer surface of the cylinder.

Another object of this invention is to provide a forming press having facilities to counteract the longitudinal forces generated in the forming cylinder by the opposing radial forces acting on the forming cylinder.

An additional object of the invention resides in the use of a series of cylinders having facilities to pass fluid from the inner cylinder to the outer cylinders successively, each cylinder being spaced apart from the other and having facilities for confining fluid under pressure in each of these spaces so that the pressure within the inner cylinders will be counteracted by the decreasing pressures within the successive outer cylinders.

Another object of this invention is the provision of a forming press wherein longitudinal or pinch-off forces generated within a forming cylinder Wall are counteracted by opposing forces generated in response to the forces generated within the cylinder.

A further object of this invention is to provide a forming press utilizing a series of concentric cylinders with pressure equalization facilities responsive to a decrease in pressure within an inner cylinder.

With these and other objects in view, the present invention contemplates a deep drawing ultra-high pressure metal forming press having facilities responsive to the forces generated within the press for generating compens'ating forces to overcome the deleterious eifedts of the internal force's on the components of the press. More particularly, a metal blank is placed within a high-pressure forming cylinder. Fluid is introduced into the cylinder, and a piston is moved to act on the fluid to generate high pressures against the metal blank. The forming cylinder w all elastically expands when a predetermined pressure is reached allowing pressurized fluid to flow past the piston into another cylinder or succession of cylinders spaced from and surrounding the forming cylinder. The pressurized fluid acting within the surrounding cylinder exerts inward forces on the forming cylinder, counteracting the radial forces generated by the piston acting on the fluid. These counteracting forces decrease the differential pressure across the forming cylinder wall, thereby decreasing the stresses therein. Furthermore, facilities are provided to exert longitudinal forces on the forming cylinder to counteract those longitudinal forces generated by the opposing radial forces. By using such apparatus as described, it is possible to exert ultra-high pressures in the nature of 500,000 p.s.i. or greater on a metal blank, and to consequently draw the metal blank through a forming die.

Other objects and advantages of the present invention will be apparent from the following detailed description when considered in conjunction with the accompanying drawings, wherein:

FIG. 1 is a front view partially in section of a highpressure forming apparatus embodying the principles of the present invention;

FIG. 2 is a sectional view taken along line 2--2 of FIG. 1 showing the metal blank positioned in a forming cylinder secured by a threaded ring, and a segmented cylinder surrounding the forming cylinder;

FIG. 3 is an exploded front sectional view showing the elements comprising a limited diameter seal on a highpre'ssure piston;

FIG. 4 is a cross-sectional front view of an alternative embodiment of a high-pressure forming apparatus;

FIG. 5 is a front view partially in section of another alternative embodiment of a high-pressure forming appara'tus;

FIG. 6 is a partial enlarged view of an end restraining member and intermediate cylinder taken from FIG. 5 and panticul'arly showing the forces acting on the member and cylinder;

FIG. 7 is a cross-sectional front view of a further embodiment of a high pressure forming apparatus;

FIG. 8 is a partial view taken from FIG. 7 showing the forces acting on a wear-resistant sleeve;

FIG. 9 is a partial view taken from FIG. 7 showing a wear-resistant sleeve forced off a piston into a forming cylinder;

'FIG. 10 is a front view partially in section of another alternative embodiment of a high-pressure forming apparatus; and

FIG. 11 is a detailed front sectional view of a drawing and extrusion die shown in FIG. 5.

Referring now to FIG. 1, there is shown one embodiment of an ultra-high pressure metal forming apparatus for forming a circular metal blank 100 into a tubular cup-shaped member 10 1 (as shown by the dotted lines). The ultra-high pressure metal forming apparatus includes a forming cylinder 102 having a bore 103 therethrough and a partially threaded counterbore 104, both of which 3 are filled with fluid 105 during the operation of the apparatus.

The forming cylinder 102 has an upper beveled surface 116, a lower beveled surface 117, and an intermediate shoulder 106 formed by the juncture of the bore 103 and the counterbore 104. A forming die 107, having an orifice therethrough, is tightly fitted into the counterbore 104 in abutting relationship with the shoulder 106.

The metal blank 100, having a diameter of a few thousandths of an inch smaller than the diameter of the countenbore 104, is positioned on top of the forming die 107 and is fixedly held by a hollow externally threaded ring 108, the threads of which are interrupted by several axially extending grooves 109 (see FIG. 2) to provide passageways for the fluid 105 contained in counterbore 104.

The purpose of the grooves 109 is to introduce highpress'ure fluid from counterbore 104 into the annular space 110 defined between the periphery of the metal blank .100 and the inner wall of the forming cylinder 102. The high-pressure fluid acts against the peripheral edge of the metal blank 100 to compressively force the material of the blank 100 toward and into the orifice of the forming die 107. This compressive force reduces the tensile force necessary to draw the blank 100 through the forming die 10-7.

A first piston 113 is mounted for movement within the counterbore 104 of the forming cylinder 102. A limited diameter seal generally designated as 1'14 is attached to the lower end of the first piston 113. The seal 114 (see FIG. 3) includes a first, expandable bevelededged annulus 120 which is urged outwardly toward the inside wall of the forming cylinder 102 by an inner beveled-edged disc or spreader 122. An outer disc or limiter 123 is secured against the inner disc 122 by a retaining screw 1'25, and has an axially extending flange 130 on the periphery thereof which limits the di'a'metrical expansion of annulus 120.

A high-pressure ram 118, forming part of a conunerical- 1y available high-pressure press, engages and moves the first piston 113 to generate high fluid pressures within the counterbore 104 and against the upper surface and the periphery of the metal blank 100. A second piston 1 19, mounted for movement Within bore 103 of forming cylinder 102, is independently movable by a ram 121, forming part of a commercially available high-pressure press, to generate a back-up pressure against the lower surface of the metal blank 100. The back-up pressure is sufliciently high so as to increase the ductility of the metal blank 100, but is substantially lower than the pressure in counterbore 104 so that there is a large pressure differential for drawing the metal blank into and through .the forming die 107. For example, the back-up pressure for a molybdenum blank may be approximately 350,000 p.s.i., while the drawing pressure may be 500,000 psi.

The forming cylinder 102 is surrounded by a hollow cylinder 126 made up of a plurality of separate segments 126a, 126b, etc. (see FIG. 2). The segmented cylinder .126 has an inner beveled surface 132 in juxtaposition with the lower beveled surface 117 of the forming cylinder 102. The top portion of the se mented cylinder 126 is internally threaded at 134 to receive a sleeve-like end restraining member having external threads 133 thereon. End restraining member 115 has a bore 135 therethrough in alignment with the counterbore 104 for receiving the first piston .113. Sleeve-like end restraining member 115 has a beveled surface 131 in juxtaposition with the upper beveled surface 116 of the forming cylinder 102. The segmented cylinder 126 is tightly confined within a hollow intermediate cylinder 127, which in turn is enclosed within a casing 129 which is spaced from the intermediate cylinder 127 to provide an annular space 128 (slightly exaggerated) for receiving fluid therebetween.

The casing v129 has a passageway 147 therethrough for passing fluid from the annular space 128 to an overbalance valve 148. The over-balance valve has two chambers 149 and 150 therein for receiving fluid, respectively, from the annular space 128 and the high-pressure ram cylinder which is not shown. A bore 151 connects the two chambers, 149 and 150. A stepped piston 152 is slid'ably mounted within the bore 151 and the chamber 150. The piston 152 moves into chamber 150 upon subjection to a predetermined pressure ratio, permitting the fluid in the chamber 149 and the annular space 128 to pass through a passageway 153 into a reservoir not shown. The valve 148 is utilized to prevent the fluid contained within the annular space 128 from urging the segmented cylinders 126 inwardly upon retraction of the piston 113 from the forming cylinder 102 after the forming operation is completed. To illustrate, when the piston 113 is withdrawn, the pressure in the counterbore 104 drops and the pressure in the high-pressure ram cylinder drops proportionately. Since the pressure of the fluid in the annular space 128 remains the same, the ratio between the pressure in the annular space 123 and the pressure in the high-pressure ram cylinder increases. When this ratio increases above a predetermined value, the over-balance valve 148 opens to vent fluid from the annular space 128 through the passageway 153. The valve 148 closes when sutficient fluid is vented so that the predetermined ratio is again attained.

The casing 129 is internally threaded at a lower portion .133 and an upper portion 139. A first threaded ring having a groove 141 therein to receive an annular seal 142 cooperates with the lower threaded portion 138 of the casing '129 to enclose the bottom of the annular space 128. A second threaded ring 144 having a groove 145 therein to receive an annular seal 146 cooperates with the upper threaded portion 139 of the casing 129 to completely enclose the annular space 128.

To prevent overstressing the ultra-high pressure apparatus, the second threaded ring 144 and the seal 146 are adjustable to permit fluid 105 contained within the enclosed annular space 128 to vent past the seal and threads to the atmosphere if a predetermined pressure is reached therein. It is not contemplated that fluid would vent to the atmosphere during a normal operation, rather it would vent only in the event of malfunction of any of the high pressure equipment.

When the pressure in counterbore 104 is increased to a sufficiently high value, the cylinder 102 elastically expands allowing fluid 105 to escape past the high-pressure seal 114, through the space between the outer surface of the first piston 113 and the inner surfaces of the forming cylinder 102 and the sleeve-like end restraining memher 115 and then into a radial aperture 124. This radial aperture 12 extends through the sleeve-like member 115, a segment of the cylinder 126 and the intermediate cylinder 127 to pass fluid into the annular space 128. High-pressure fluid introduced into the annular space 123 acts on the intermediate cylinder 127, which in turn forces the segmented cylinder 126 inwardly against the forming cylinder 102.

The inward force exerted by the segmented cylinder 126 on the forming cylinder 102 opposes the outward force generated within the counterbore v104 and the bore 102 of the forming cylinder 102. When the inward force of the segmented cylinder 126 increases to a suflicient extent, the forming cylinder 102 contracts and moves against the seal 114 thereby resisting the flow of fluid 105.

Since the outer peripheral area of the intermediate cylinder 127 is substantially greater than the outer peripheral area of the forming cylinder 102, the inward pressure of cylinder 126 against the forming cylinder 102- is substantially greater than the pressure of the fluid within the annular space 128. More particularly, the pressure P1 of the fluid contained within the enclosed annular space 128 multiplied by the peripheral area A1 of the intermediate cylinder 127 equals a force F1 acting on the cylinder 127. The force F1 is transmitted through the intermediate cylinder 127 and the segmented cylinder 126 to act against the forming cylinder 102. However, since the peripheral area A2 of the forming cylinder 102 is substantially smaller than the peripheral area A1 of the intermediate cylinder 127, the pressure P2 on the forming cylinder .102 is greater than the pressure P1 on the intermediate cylinder '127. In other words, F1=P1 A1 and F2=P2 A2. But F1=F2 since the force is transmitted through the

cylinders

120 and 127 so that Pl A2=Pl A1. Since A1 is greater than A2, P2 is greater than P1. Thus, P2=A1/A2 P1.

The pressuirzed fluid contained within the counterbore 104 and the pressurized fluid contained within the annular space 128 generate opposing forces F7 and F2, respectively, on the forming cylinder 102 resulting in a condition known as pinch-off, whereby opposing longitudinal forces F3 are generated in the forming cylinder 102 as shown in FIG. 1. Pinch-off occurs when opposing internal and external forces acting on a cylinder wall are so high that the metal of the cylinder flows longitudinally away from the area subjected to the opposing forces, thereby decreasing the thickness of the cylinder wall until rupture occurs.

To counteract the longitudinal pinch-off forces, the forming cylinder 102 is firmly supported at both ends. The end restraining member 115 is threaded into the segmented cylinder 126 so that the beveled surface 131 thereof abuts against the beveled surface 116 to support the upper end of the forming cylinder 102. As shown by the force diagram in FIG. 1, end restraining member 115 exerts a normal force F4 perpendicular to the beveled surface 116 of the forming cylinder 102. The normal force F4 has component forces F5 and F6 which respectively oppose the longitudinal pinch-off force F3 and the outward force F7 generated by the high-pressure fluid 105 contained within the counterbore 104.

The lower end of the forming cylinder 102 is supported at the beveled surface 117 by the abutting beveled surface 132 of the segmented cylinder 126. As shown by the force diagram in FIG. 1, the segmented cylinder 126 exerts a normal force F4 perpendicular to the beveled surface 117 of the forming cylinder 102. The normal force F4 has component forces F5 and F6 which respectively oppose the longitudinal pinch-off force F3 and the outward force F7 generated by the high-pressure fluid 105 contained within the bore 103.

The end restraining member 115 is under a high compressive load during the forming operation, which tends to shorten it thus decreasing the pitch of the external threads 133 thereon. Meanwhile, the matching threads 1334 on the segmented cylinder 126 are under tension and experience an increase in the pitch of the threads 134. This results in the end threads being loaded more than the intermediate threads. To eliminate this problem and to provide uniform loading of the threads from end to end, the pitch of the threads 133 on the end restraining member 115 is increased by an amount equivalent to the change in length of the end restraining member 115 under the compressive load. Thus, when the end restraining member 115 is under a compressive load during the forming operation, the pitch of the threads 133 will equal the pitch of the threads 134 on the segmented cylinder 126 thereby providing uniform thread loading.

OPERATION In use of the apparatus, the first piston 113 is initially completely withdrawn. The second piston 119 is partially inserted into the bore 103 of the forming cylinder 102 and hydraulic fluid 105 is introduced or poured into the bore 103. The forming die 107 is then placed against the shoulder 106 of the forming cylinder 102, after which the metal blank is placed on the upper surface of the forming die 107, and the ring 108 is threaded into the forming cylinder 102 to fixedly position and hold the metal blank 100 against the forming die 107. Hydraulic fluid is then introduced or poured into the counterbore 104 and the first piston 113 is moved into the counterbore 104.

Next, the independently driven high-pressure ram 118 and back-up ram 121 are actuated to respectively move the first piston 113 and the second piston 119 toward the metal blank 100. As the piston 113 moves, the pressure in counterbore 104 increases until the forming cylinder 102 is strained and elastically expands permitting fluid 105 to escape past the limited diameter seal 114, through the radial aperture 1 4 and into the enclosed annular space 128 between the intermediate cylinder 127 and the casing 129. The pressurized fluid contained within the annular space 123 acts on the intermediate cylinder 127 which in turn forces the segmented cylinder 126 inwardly to support the forming cylinder 102. The inward pressure exerted by the segmented cylinder 126 on the forming cylinder 102 reduces the net pressure across the wall of the forming cylinder 102 so that the forming cylinder 102 contracts sufficiently to again engage the seal 114, thereby restricting the flow of pressurized fluid 105. As the pressure continues to increase within the counterbore 104, the wall of the cylinder 102 alternately expands from the increasing internal pressure, and contracts from the external pressure of the segmented cylinder 126.

The

beveled surfaces

131 and 132 of the end restraining member and the segmented cylinder 126, respectively, support the ends of the forming cylinder 102 to prevent pinch-off or reduction of wall thickness clue to the high opposing radial forces acting on the forming cylinder 102.

The pressure in bore 103, generated by the movement of the second piston 119, is sufficient to increase the ductility throughout the metal blank 100; but is substantially lower than the pressure in counterbore 104, generated by the first piston 113. The ultra-high pressure fluid in counterbore 10 acts perpendicular to the metal blank 100 tending to draw it through the orifice of the forming die 167. Simultaneously, the ultra-high pressure fluid 105 passes through the grooves 109 in the threaded ring 108 into the annular space 110 to force the periphery of the metal blank 100 inwardly tending to extrude the blank through the orifice of the forming die 107. This extruding force reduces the tensile forces necessary to draw the metal blank 1% through the forming die 167. The combination of the drawing pressure and the extruding pressure forces the blank Hi0 through the die 197, aided by the increased duetility resulting from the bacleup pressure, to form a cup shaped member 121 of substantially equal thickness throughout.

After the metal blank 180 is drawn and formed, the first piston 113 is withdrawn, the threaded ring 1G8 is removed, and the newly-formed tubular cup-shaped member 101 is extracted from the forming cylinder 1G2.

ALTERNATIVE EMBODIh lEFT Referring now to FIG. 4, there is shown an alternative embodiment of a high-pressure metal forming apparatus for forming a metal blank 1% into a tubular cup-shaped member 101. The alternative embodiment is similar in many respects to the first embodiment which is described in great detail. Accordingly, repetitious descriptions of similar or identical elements are not included in the following description, and reference for further details should be made to the description of the first embodiment. The alternative embodiment includes a forming cylinder 2422 having a bore 203 therethrough and a counterbore 264, both of which are filled with fluid during the forming operation. The forming cylinder 262 has an upper beveled surface 266 and a lower beveled surface 207'. A forming die 107, as shown in PEG. 1, is tightly fitted into the counterbore 2&4 and a metal blank 1% is fixedly held thereagainst by a hollow threaded ring 168, the threads of which are interrupted by several axially extending grooves, identical to grooves 139 as shown in FIG. 2.

A hollow segmented cylinder 211, having an upper comically-shaped counterbore 222 and a lower conicallyshaped counterbore 213, surrounds the forming cylinder 202. The counterborcs 212 and 213 have internal threads which cooperate respectively with the external threads of an upper eonically-shaped hollow end restraining member 215 and a lower comically-shaped hollow end restraining member 216. The upper end restraining member 215 has a beveled surface 217 which abuts against the upper beveled surface 206 of the forming cylinder 202 to provide support thereto. The lower end restraining member 216 has a beveled surface 218 which abuts against the lower beveled surface 207 of the forming cylinder 292 to provide support thereto.

A hollow intermediate cylinder 221 tightly surrounds the segmented cylinder 211. A casing 222 surrounds and is spaced from the intermediate cylinder 221 to provide an annular space 223 therebetween. Casing 222 has an internally threaded bottom portion for receiving a threaded ring 224. Ring 224 has a groove 226 therein to receive an annular seal 227 which effectively seals the bottom of annular space 223. Casing 222 has an internally threaded top portion for receiving a second threaded ring 228. Ring 228 urges an annular seal 231 against the intermediate cylinder 221 and the casing 222 to effectively seal the top of annular space 223 to prevent hi h-pressure fluid from escaping therefrom. A radial aperture 225 through upper end restraining member 215, segmented cylinder 211., and intermediate cylinder 221, communicates the inside of the end restraining member 215 with the enclosed annular space 223. An over-balance valve, not shown, similar to the valve 143 shown in FIG. 1, is connected to communicate with the annular space 223.

A first stepped piston 234 has an upper portion 235 of one diameter and a lower portion 236 of a smaller diameter. The upper portion 235 is slidably mounted for movement within the upper end restraining member 215 and the lower portion 236 is slidably mounted for movement within counterbore 264 of forming cylinder 202. An annular pressure chamber 237 is defined between the lower portion 236 and the inner surface of the end restraining member 215. The piston 234 has a seal generally designated as 238 attached to the lower end thereof. This seal is substantially similar to the seal shown in FIG. 3 and described in the first embodiment. A seal 239 is positioned at the juncture of the upper portion 235 and the lower portion 236 to retain high-pressure fluid within the annular pressure chamber 237.

A second stepped piston 241 has a lower portion 242 of one diameter and an upper portion 243 of a smaller diameter. The lower portion 242 is slidably mounted for movement within the lower end restraining member 216 while the upper portion 243 is slidably mounted for movement within the bore 263 of forming cylinder 202. An annular pressure chamber 247 is defined between the upper portion 243 and the inner surface of the lower end restraining member 216. A seal 244, substantially similar to seal 238, is attached to the end of the second stepped piston 241. Another seal 246 is positioned at the juncture of lower portion 242 and upper portion 243 of the second stepped piston 241 to retain pressurized fluid within the annular pressure chamber 247. The stepped pistons 234 and 241 are independently movable by commercially available high-pressure presses 248 and 249.

OPERATION In the operation of the high-pressure apparatus, the r rst stepped piston 234 is completely withdrawn and the second stepped piston 241 is partially withdrawn. Hydraulic fluid is then introduced or poured into the lower end restraining member 216, the forming cylinder 202, and the upper end restraining member 215. Next, the forming die 107, metal blank 10%), and ring 1% are inserted into the fluid-filled counterbore 204. The first stepped piston 234 and second stepped piston 241 are then independently moved inwardly toward the metal blank 1%. As the pressure builds up in the counterbore 204, the forming cylinder 202 is increasingly strained until it elastically expands allowing pressurized fluid to pass between the seal 238 and the inner surface of the forming cylinder 2G2 into the annular pressure chamber 237. Similarly, high-pressure fluid expands the lower portion of the forming cylinder 232 to provide a passageway for fluid into the second annular pressure chamber 247.

The pressurized fluid in the first and second pressure chambers 237 and 247 provides radial support for the smaller diameter portions 236 and 243 of the first stepped piston 234 and the second stepped piston 241. This radial support prevents mushrooming of the pistons from the high pressures acting on the ends thereof. Mushrooming occurs when a piston is subjected to a high compressive load which tends to shorten it thereby expanding or mushrooming the diameter.

The pressurized fluid in the first and second pressure chambers 237 and 247 also reduces friction between the first stepped piston 234 and end restraining member 215, and between the second stepped piston 241 and end restraining member 216. If the pressure Within the second annular pressure chamber 247 exceeds a predetermined value, high-pressure fluid vents past the seal 246 to the atmosphere. However, under normal operating conditions this does not occur.

As the pressure in the first annular pressure chamber 237 increases, the upper end restraining member 215 elastically expands permitting fluid to escape past the seal 239, through the radial aperture 225 and into the enclosed annular space 223 between the casing 222 and the intermediate cylinder 221. The pressurized fluid within the enclosed annular space 223 acts against the intermediate eylindcr 221. which in turn forces the segmented cylinder 211 inwardly to support the forming cylinder 202 during the forming operation.

Continued movement of the pistons 234 and 241 increases the pressure of the fluid acting against the metal blank 100 until the blank 100 is drawn and extruded through the forming die 107 as described in the First Embodiment.

ALTERNATIVE EMBODIMENT Referring now to FIG. 5, there is shown an alternative embodiment of a high-pressure forming apparatus for forming a metal blank 100 into a tubular cup-shaped member 101. The alternative embodiment is similar in many respects to the first embodiment which is described in great detail. Accordingly, the detailed descriptions of the similar features are not repeated in the following description, and reference may be made to the description of the first embodiment for more complete details. The alternative embodiment high-pressure apparatus includes a forming cylinder 301 with a bore 332 therethrough which is filled with fluid during the forming operation. The forming cylinder 301 has an upper beveled surface 303 and a lower beveled surface 304. A drawing and extrusion die, generally designated as 600 (see FIG. 11) having a metal blank 100 secured therein is positioned within the bore 392 of the forming cylinder 301. The die 600 is described in greater detail further on under the heading Alternative Die.

A hollow segmented cylinder 306, having an upper conically-shaped counterbore 337 and a lower conicallyshaped counterbore 308, surrounds the forming cylinder 331. An upper conically-shaped hollow end restraining member 309 fits within the counterbore 307 and has a beveled surface 311 abutting against the beveled surface 303 of the forming cylinder 301 to provide support thereto. A lower externally threaded conically-shaped hollow end restraining member 312 fits within the counterbore 393 and has a beveled surface 313 abutting against the lower beveled surface 304 of the forming cylinder 301 to provide support thereto. A hollow intermediate cylinder 314 tightly surrounds the segmented cylinder 306 and has upper and lower conical surfaces in juxtaposition with the upper and lower

end restraining members

309 and 312.

A casing 316 surrounds and is spaced from the intermediate cylinder 314 to provide an annular space 317 therebetween for receiving fluid. The casing 316 has a lower internally threaded portion 318 which cooperates with the threads on the lower end restraining member 312. The casing 316 has a groove 319 therein for receiving an annular seal 321 to effectively enclose the bottom of the annular space 317. Casing 316 has an upper threaded portion 322 for receiving an externally threaded support ring 323 which has a lower surface 324 in juxtaposition with the upper surface of the end restraining member 309.

The end restraining member 309 has an aperture 325 therethrough which permits fluid under pressure to pass from the bore 302 of the forming cylinder 301 into the annular space 317. As shown in FIG. 6, the support ring 323 has a groove 326 therein for receiving an annular seal 327 which prevents pressurized fluid in space 317 from escaping between the support ring 323 and the end restrainin member 309. Another annular seal 328 is positioned below the support ring 323 to prevent highpressure fluid from escaping out the top of annular space 317. An annular seal 330 is positioned between end restraining member 309, intermediate cylinder 314, and casing 316 to prevent high-pressure fluid from entering the space between the segments of cylinder 306. However, if pressurized fluid leaks past the seal 330, the end restraining member 309 is provided with a plurality of equally-spaced passageways 329 which vent fluid trapped between the segments of the cylinder 306 to atmosphere.

A first high-pressure piston 331 is slidably mounted within the bore 302 of the forming cylinder 301 and is movable by a high-pressure ram 332 which could be part of a conventional high-pressure press. Piston 331 has a limited diameter seal 335 attached to the end thereof. A second piston 333 is slidably mounted for movement within the bore 302 opposing the first highpressure piston 331. Piston 333 has a limited diameter seal 336 attached to the end thereof. The second piston 333 is independently driven by a ram 34 which could also be part of a conventional high-pressure press. The seals 335 and 336 are substantially similar to the limited diameter seal shown in FIG. 3. The apparatus includes an over-balance valve, not shown, similar to valve 148 shown in FIG. 1, to vent fluid from the annular space 317.

OPERATION In operation, the first piston 331 is withdrawn and bore 302 of forming cylinder 301 is filled with hydraulic fluid. Then the drawing and extrusion die 600, with a metal blank secured therein, is inserted into the fluid-filled bore 302.

Next, the first piston 331 and the second piston 333 are actuated to move toward the drawing and extruding die 600. As pressure builds up within the upper part of the forming cylinder 301 (the part above the die 600). the cylinder 301 is strained until it elastically expands, allowing high-pressure fluid to escape past the seal 335 and through the aperture 325 of the upper end restraining member 309 into the annular space 317 between the easing 316 and the intermediate cylinder 314. The pressurized fluid within the annular space 317 acts on the intermediate cylinder 314 which in turn forces the segmented cylinder 306 inwardly to support the forming cylinder 301, thereby decreasing the net pressure across the wall of the forming cylinder. In addition, pressurized fluid trapped between the lower surface 324 of the threaded support ring 323 and the upper surface of end restraining member 309, acts on the end restraining memher 309 forcing it inwardly and downwardly (as shown in FIG. 6) to counteract the radial and the longitudinal (pinch-off) forces generated in the forming cylinder 301. As the pressure continues to increase in the forming cylinder 301, the pressure also increases in annular space 317, thereby providing increasing forces against both the end restraining member 309 and the intermediate cylinder 314. The vent passageways 329 in the upper end restraining member 309 provide an escape to the atmosphere for any fluid which leaks into the spaces between the segments of the cylinder 306. Such fluid is forced out the vent passageways 329 when the segments of cylinder 306 are forced inwardly.

As the

pistons

331 and 333 continue further movement, the pressure within the forming cylinder 301 increases until the blank is drawn and extruded into a tubular cup-shaped member 101. During the movement of the pistons toward each other, the wall of the forming cylinder 301 expands under the high internal pressure and contracts under the supporting pressures many times, as previously described, until the necessary drawing and extruding pressure is attained within the forming cylinder 301.

ALTERNATEVE EMBODIMENT Referring now to FIG. 7, there is shown an alternative embodiment of a high-pressure forming apparatus for forming a metal blank 100 into a tubular cup-shaped member 131. The alternative embodiment is similar in many respects to the first embodiment which is described in great detail. Accordingly, repetitious description of similar or identical elements are not included in the following description, and for further details reference should be made to the description of the first embodiment. The alternative embodiment includes a hollow forming cylinder 401 having a top flanged portion 402 which has a bore 407 therethrough for receiving the first step 438 of a multi-stepped piston 409. An inner cylinder 403 is tightly fitted within the bottom of forming cylinder 401 and has a bore 404 therethrough for receiving a piston 496. Step 408 of piston 469 is encompassed by a wear-resistant sleeve 411 which is shorter than the length of the first step 408. The outer diameter of the wearresistant sleeve 411 is substantially equal to the diameter of the bore 407.

A second hollow cylinder 413 surrounds and is spaced from the forming cylinder 4E1 to provide an annular space 414 therebetween. The second cylinder 413 has a bottom flanged portion 416 which is threaded or forcefitted against the periphery of the forming cylinder 431 to enclose the bottom of the annular space 414. The second cylinder 413 has a top flanged portion 417 having a bore 418 therethrough for receiving the second step 419 of the stepped piston 409. A wear-resistant sleeve 421 encompasses the second step 419 of piston 469. Sleeve 421 has an aperture 422 through the bottom thereof which is slightly larger than the outer diameter of sleeve 411.

A third hollow cylinder 423 surrounds and is spaced from the second cylinder 413 to provide an annular space 424 therebetwcen. The third cylinder 423 has a bottom flanged portion 426 which is threaded or force-fitted against the outer periphery of the second cylinder 413 to effectively enclose the bottom of annular space 424. The third cylinder 423 has a flanged top portion 428 having a bore 429 theret'nrough for receiving the third step 431 of the piston 409. A wear-resistant sleeve 432 encompasses the third step 431 of piston 469 Sleeve 432 has an aperture 439 through the bottom thereof which is sli htly larger than the outer diameter of sleeve 421.

The top

flanged portions

402, 417, and 428 of cylinders 4G1, 413, and 423, respectively, are provided so that pressurized fluid actin thereagainst generates longitudinal forces downwardly (see FIG. 8) to counteract the longitudinal or pinch-off forces which are generated in the walls of the cylinders by the high opposing radial forces acting thereon.

A casing 433 surrounds and is spaced from the third cylinder 423 to provide an enclosed space 434 therebetween. The casing 433 has a bore 435 therethrough for receiving the fourth step 437 of piston 499 which is encompassed by a wear-resistant sleeve 438. The sleeve 438 has an aperture 440 through the bottom thereof which is slightly larger than the outer diameter of sleeve 432.

The wear-

resistant sleeves

419, 421, 432, and 438 are made of a material, such as chrome plated high carbon steel, which has very good wear characteristics. Each sleeve has an aperture through the bottom thereof which is sufiiciently large to pass over the preceding step and sleeve. This permits any sleeve to be individually and easily replaced when it becomes worn. Furthermore, the replaceable feature of the sleeves prolongs the useful life of the stepped piston and cylinders. In addition, each wear-resistant sleeve is shorter than the length of the step which it encompasses to permit pressurized fluid to act axially against the edge of the sleeve.

Moreover, the depth of each cylinder is slightly greater than the length of each wear-resistant sleeve so that the sleeve may slide off the piston into the cylinder to provide a fluid passageway such as 436, as shown in FIG. 9, between the cylinder and the surrounding annular space.

OPERATION In operation, the stepped piston 4%? is withdrawn, a metal blank 13s is secured between the ring 198 and the die 107, and the forming cylinder 4&1 is filled with hydraulic fluid. Piston tdand stepped piston 339 are then independently moved toward each other. As the pressure increases, forming cylinder 401 is strained and elastically expands allowing fluid to pass between the first wearresistant sleeve 411 and the top flanged portion into the annular space 414. As the stepped piston 409 moves downwardly, the pressure within annular space 414 increases until the second cylinder 413 is strained sufficiently and elastically expands allowing fiuid to pass into the annular space 424. Further downward movement of the 1.2 stepped piston 409 strains the third cylinder .23 so that fluid passes into the annular space 434. Each successive cylinder is supported by the pressurized fluid in the surrounding annular space.

Referring now to FIG. 8, there is shown an enlarged view taken from FIG. 7 of one wear-resistant sleeve and the forces acting thereon. The pressure within the forming cylinder 401 is denoted as P1. The pressure within the annular space 414 is denoted as P2. Pressure P1 acts upwardly forcing the sleeve 411 against the bottom of first step 408 of piston 409. In addition, pressure P1 also acts radially, forcing the portion of sleeve 411, which is in cylinder 4%, inwardly against the step 4-08 of piston 499. The upper portion of the sleeve 41-1 is subjected to radial pressure P2 acting inwardly to force the sleeve 411 against the step 408. There is also an axial force from pressure P2 acting against the edge of sleeve 411 which tends to push sleeve 4-11 downwardly into the forming chamber 401. But, since pressure P1 is greater than pressure P2, the axial force of P2 is effectively opposed and the sleeve 411 remains in contact with the piston 409. However, if pressure Pl drops substantially below pressure P2, the sleeve 411 is forced downwardly into the forming cylinder 481 thereby providing a fluid passageway 436 (as shown in FIG. 9) between annular space 414- and forming cylinder 401 which allows equalization of the pressures (P1 and P2) therebetween. If there is no sleeve on the piston or if the sleeve is not movable, a loss of pressure in cylinder 461 results in an unopposed high pressure acting inwardly which may be great enough to rupture or produce failure in cylinder 401. The wearresistant sleeves prevent this occurrence by effectively acting as pressure-relief valves between successive cylinders.

In normal operation, the stepped piston continues downwardly until sulficient pressure is attained within the forming cylinder 401 to draw and extrude the metal blank into a tubular cup-shaped article 161.

ALTERNATIVE EMBODIMENT Referring now to FIG. 10, there is shown an alternative embodiment of a high-pressure forming apparatus for forming a metal blank 10%) into a tubular cup-shaped member 101 (as shown by the dotted lines). The alternative embodiment is similar in many respects to the first embodiment, which is described in great detail. Accordingly, the detailed description of similar features are not repeated in the following description, and reference should be made to the description of the first embodiment for more complete details. The alternative high-pressure apparatus includes a movable forming cylinder 502 having a bore 503 partially therethrough and a counterbore 504- through one end thereof. A radial aperture 506 extends through the wall of the movable forming cylinder 5632 into bore 563. The forming cylinder 502 has a shoulder 507 formed by the juncture of the bore 503 and the counterbore 504. A forming die "508 is mounted within counterbore 504 in abutting relationship with the shoulder 507. A threaded ring 509 having grooves 511 extending axially through its threads fixedly holds a metal blank 1% against the forming die 5%.

A first cup-shaped cylinder 512 having a tapered top portion and an aperture 513 through its bottom surrounds and is spaced from the movable cylinder 502. A stationary piston 514 having an intermediate tapered portion 516 is force-fitted into the aperture 513 of cylinder 512. Aperture 513 is countersunk from both ends thereof to provide only minimum contact with tapered portion 516. The end of stationary piston 514 extends upward into the counterbore 504 and has a limited diameter seal 517 attached thereto (similar to the seal shown in FIG. 3). An annular seal 518 is held in position by a threaded ring 519 to provide an enclosed annular space 521 between cylinder 512 and cylinder 502. A second cup-shaped cylinder 522 surrounds and encloses the first cup-shaped cylinder 512 to provide an enclosed annular space 523 there- 13 between. A third cup-shaped cylinder 524 surrounds the second cup-shaped cylinder 522 to provide an enclosed annular space 526 therebetween. A casing 527 surrounds the third cup-shaped cylinder 524 to provide an enclosed annular space 52-8 therebetween.

OPERATION In operation, the movable forming cylinder 502 is completely withdrawn and hydraulic fluid is introduced into the first cup-shaped cylinder 512. The forming dies 508 is inserted into counterbore 504 and the metal blank 100 is fixedly positioned thereagainst by the threaded ring 509. The forming cylinder 502 is then moved into the cupshaped cylinder 512 so that the bore 503 and the counterbore 504 fill with fluid.

As the cylinder 502 moves downwardly, the pressure of the fluid in cylinder 512 increases. In addition, the pressure of the fluid within the counterbore 504 increases until the forming cylinder 502 is sufliciently strained to elastically expand allowing fluid to escape past the limited diameter seal 517 into the enclosed space 521.

The pressurized fluid contained within the enclosed space 521 passes through the radial aperture 506 into the bore 503 of the movable forming cylinder 502 to provide a back-up pressure against the metal blank 100. This backup pressure is substantially lower than the pressure within the counterbore 504, but is sufficiently high to increase the ductility of the metal blank 100.

The pressurized fluid within the enclosed space 521 exerts an inward pressure on the movable forming cylinder 502 counteracting the pressure within the counterbore 504 so that the forming cylinder 502 contracts and cuts off the flow o-f fluid past the limited diameter seal 517. As the movable forming cylinder 502 continues downwardly, the pressure in the enclosed annular space 521 increases until the first cup-shaped cylinder 512 is strained sufficiently to elastically expand. At this time, pressurzied fluid passes between the first cup-shaped cylinder 512 and the tapered portion 516 of stationary piston 514 into the enclosed annular space 523. Then the pres- 1 surized fluid within the enclosed annular space 523 acts on the first cup shaped cylinder 512 forcing it inwardly against the tapered portion 516, thereby counteracting the pressure of the fluid in enclosed space 521.

As the movable forming cylinder 502 continues downwardly, the pressure of the fluid within the enclosed annular space 523 increases and strains the second cupshaped cylinder 522 until it elastically expands allowing fluid to pass into the enclosed annular space 526. As the pressure increases within the enclosed annular space 526-, the third cup-shaped cylinder 524 is strained and elastically expands allowing fluid to pass between the third cup-shaped cylinder 524 and the tapered top portion of the first cup shaped cylinder 512 into the annular space 528. If a predetermined pressure is reached within annular space 528, the casing 526 expands allowing fluid to vent to the atmosphere to prevent overload of the apparatus. However, this predetermined pressure is not normally attained during operation of the apparatus.

Cylinder 502 moves downwardly until the pressure within counterbore 504 is sufficiently high to draw and extrude the metal blank 100 through the forming die 508.

The enclosed annular spaces 521, 523, 526, and 528 contain fluid of successively decreasing pressures which are utilized to counteract the pressures in the forming cylinder 502. Hence, ultra-high forming pressures can be generated within the counterbore 504 without rupture or failure of the forming cylinder 502.

ALTERNATIVE DIE Referring now to FIG. 11, there is shown an alternative drawing and extrusion die 600 which can be used with any embodiment of the high-pressure metal forming apparatus shown in the preceding drawings. The drawing and extrusion die 600 includes a cylindrical upper die member 601 having a bore 602 therethrough for receiving a draw punch 617. Die member 601 has an internally threaded counterbore 603 with a plurality of axially extending grooves 605 formed in the threaded surface.

A cylindrical lower die member 604 is externally threaded to engage with the internal threads in counterbore 603 of the upper die member 601 to secure a metal blank 100 the-rebetween. The metal blank 100 is slightly smaller in diameter than the counterbore 603 so that an annular space 613 is defined between the periphery of the metal blank 100 and the counterbore 603. The lower die member 604 has a plurality of axially extending grooves 612 formed in the threaded surface comunicating with the annular space 613. Grooves 605 may be unnecessary providing grooves 612 are deeper than the threads of the lower die member 604. The lower die member 604 has an axial bore 606 therethrough aligned with the bore 602 of the upper die member 601. An annular bore 607 for receiving a hollow cup-shaped piston 609, extends partially upward from the bottom of the lower die member 604, concentric with the axial bore 607. An annular counterbore 610 in the lower die member 604 receives annular seals 618 and 619 and seal

retainers

620 and 621 to eflectively prevent high-pressure fluid contained within the anular bore 607 from escaping past the hollow piston 609. A plurality of radial apertures 608 connect the annular bore 607 with the

axially extending grooves

605 and 612 in the threads of the upper and lower die

members

601 and 604.

Seals

622 and 623 are provided to prevent fluid from passing between the forming cylinder 614 and the upper and lower die

members

601 and 604.

OPERATION In operation, a cylindrical metal blank 10 is placed between the upper die member 601 and the lower die member 604 and the die members are threaded securely together. The die members and the metal blank are then completely immersed in a fluid-filled forming cylinder 614. The draw punch 617 is inserted into bore 602 of the upper die member 601 and abuts against the upper face of the metal blank 100.

A first piston 616 and a second piston 611 are independently moved toward each other, by facilities such as the rams of conventional high-pressure hydraulic presses, to increase the pressure within the forming cylinder 614. The pressure of the fluid in the enclosed space between the first piston 616 and the upper die member 601 will hereinafter be referred to as P1. The pressure of the fluid in the enclosed space between the second piston 611 and the lower die member 604- will hereinafter be referred to as P2. The pressure of the fluid within the annular bore 607 will hereinafter be referred to as P3. Pressures P1, P2 and P3 are equal until the hollow cup-shaped piston 609 enters the fluid-filled annular bore 607. At this time, the pressure P3 increases and the pressurized fluid passes through the aperture 608 and

grooves

605 and 612 to act against the peripheral edge of the metal blank 100. The high pressure P3 generated by the piston 609 tends to extrude the metal blank through the axial bore 606 of the lower die member 604. As pressure P3 rises, pressure P1 rises and becomes larger than pressure P2 thus providing a pressure diflerential of Pit-P2 across the metal lank 100. However, pressure P2 is still suificiently high to increase the ductility of the metal blank 100. Any increase in pressure P2 over a predetermined value will expand the wall of the forming cylinder 614 and allow fluid to vent past piston 611 to the atmosphere. The draw punch 617 tends to force the metal blank 100 down into the lower die member 604 while the fluid in the annular space 613 under pressure P3 simultaneously acts on the periphery of the blank 100. The combination of pressures P1 and P3 draw and extrude the 'metal blank 100 into a tubular cup-shaped article 101. By balancing the extrusion pressure P3 and the drawing punch pressure P1, very deep cup-shaped articles can be formed.

The forming cylinder 614 is supported against the high pressures generated within by utilizing the elastic deformation of the forming cylinder to vent support fluid to an enclosed annular space surrounding the forming cylinder as hereinbefore described.

It is to be understood that the above-described embodiments of the invention are merely illustrative and that numerous modifications may be made within the spirit and scope of the invention.

What is claimed is:

1. A high-pressure press comprising:

an expandable hollow cylinder closed at one end for receiving fluid,

a piston movable within said cylinder,

means for moving said piston with sufficient force to pressurize said fluid sufliciently to expand the wall of said cylinder away from said piston to pass fluid out of said cylinder between said cylinder and said piston, and

casing means, providing an enclosed space around said cylinder for receiving the passed fluid.

2. A pressure vessel comprising:

a cylinder having an axial bore through one end for receiving fluid, said cylinder constructed to elastically expand upon the received fluid being pressurized to a predetermined pressure,

a piston movable within the bore of said cylinder to pressurize said fluid,

means for moving said piston against said fluid with suflicient force to generate said predetermined pressure to radially expand said cylinder away from said piston to provide a fluid passageway through which the pressurized fluid can be forced, and

easing means spaced from the surrounding said cylinder for receiving said pressurized fluid forced through said passageway and confining said pressurized fluid to exert inward supporting forces against said cylinder.

3. A high-pressure press comprising:

a casing,

an expandable hollow cylinder closed at one end for receiving fluid mounted within and spaced from said casing,

a piston mounted for movement within said cylinder,

means for sealing said casing to said piston to provide an confined space between said casing and said cylinder, and

means for moving said piston within said cylinder with sutficient force to act on and force the fluid to expand said cylinder and pass fluid between said piston and said cylinder into said confined space to generate fluid forces to act inwardly against said cylinder.

. A pressure vessel, comprising:

a series of concentrically spaced hollow cylinders for receiving fluid, said cylinders constructed to elastically expand upon subjection to predetermined internal pressures,

means for sequentially generating said predetermined pressures within said cylinders from the innermost cylinder successively outwardly to expand each succeeding cylinder to pass fluid to the surrounding cylinder, and

means for confining said fluid between said cylinders to counteract the pressures within the inner cylinders by the pressures within each succeeding outer cylinder.

5. A pressure vessel, comprising:

means for sequentially generating said predetermined pressures within said cylinders from the innermost cylinders successively outwardly to radially expand each succeeding cylinder to pass fluid to the surrounding cylinder,

means for confining said fluid between said cylinders within the innermost cylinders by the pressures within each succeeding outer cylinder, and

means responsive to the generation of said predetermined pressures for generating longitudinal forces against said cylinders to counteract the longitudinal forces generated by the opposing radial pressures acting on each succeeding cylinder.

6. In an ultra-high pressure forming apparatus:

means for sequentially generating said predetermined pressures within said cylinders from the innermost cylinder successively outwardly to radially expand each succeeding cylinder to pass fluid to the surrounding cylinder,

means for confining said fluid between said cylinders to counteract the pressures within the inner cylinders by the pressure within each succeeding outer cylinder, and

means responsive to a decrease in pressure in the innermost cylinder for equalizing the pressures in succeeding cylinders.

7. In an ultra-high pressure forming apparatus:

a series of concentrically spaced hollow cylinders for receiving fluid, said cylinders constructed of material that elastically expands upon subjection to predetermined internal pressures,

means for generating said predetermined pressures within said cylinders from the innermost cylinder successively outwardly to radially expand each succeeding cylinder to pass fluid to the surrounding cylinder,

means for confining said fluid between said cylinders to counteract the pressures within the inner cylinders by the decreasing pressures within each succeeding outer cylinder,

means responsive to the generation of said predetermined pressures for generating longitudinal forces against said cylinders to counteract the longitudinal forces generated by the opposing radial pressures acting on each succeeding cylinder, and

pressure relief means actuated by the reversal in pressure differential within an inner cylinder and the next succeeding outer cylinder for reducing said pressure differential.

8. A pressure vessel, comprising:

a forming cylinder having an axial bore through one end for receiving fluid, said cylinder constructed to elastically expand upon subjection to a predetermined internal pressure,

a piston movable within the bore of said cylinder,

means for moving said piston against said fluid with sufficient force to generate said predetermined pressure in said bore to radially expand said cylinder away from said piston to provide a fluid passageway,

a casing spaced from and surrounding said cylinder to provide a confined space for receiving said fluid forced through said passageway which confined fluid provides support to said forming cylinder, and

means mounted on said piston and moved in response to a decrease in pressure within said bore for equalizing the pressures within said forming cylinder and said casing.

9. A metal forming press comprising:

an expandable hollow cylinder closed at one end for receiving fluid and having an inwardly formed flange on the other end to provide an aperture therethrough,

a piston movable within said aperture,

a cup-shaped sleeve movably mounted on said piston and having a length less than the distance from the bottom of the flange to the bottom of the cylinder,

means for moving said piston with suflicient force to radially expand said hollow cylinder to pass fluid between said flange and said sleeve, and

a casing surrounding said cylinder and engaging said piston for receiving said passed fluid to support said cylinder and to apply a force to move said cupshaped sleeve into said cylinder in response to a decrease in the pressure of the fluid within said cylinder whereby a fluid passageway is provided between said piston and said flange for equalizing the pressures within said casing and said cylinder.

10. In a high-pressure press:

an elastically expandable forming cylinder having a bore through one end thereof for receiving fluid,

a piston mounted for movement in said bore,

casing means surrounding said forming cylinder and engaging said piston to provide a confined space between said forming cylinder and said casing,

means for moving said piston with sufiicient force to increase the pressure of the fluid in said bore to elastically expand said forming cylinder to pass fluid into said confined space to support said forming cylinder, and

a cup-shaped sleeve movably mounted on the end of said piston and having a length less than the depth of said bore, said sleeve having the upper end thereof exposed to the fluid within said confined space and having forces acting thereon to move said sleeve into said forming cylinder in response to a decrease in pressure in said bore.

11. A high-pressure press comprising:

a casing,

a hollow cylinder closed at one end for receiving fluid mounted within and spaced from, said casing,

a piston mounted for movement within said cylinder,

means for sealing said casing to said piston to provide a confined space between said casing and said cylinder,

means for moving said piston with suflicient force to increase the pressure of said fluid within said cylinder and elastically expand said cylinder to pass fluid between said piston and said cylinder into said confined space wherein said fluid generates radial forces acting inwardly against said cylinder to oppose the outwardly acting radial forces within said cylinder, whereupon said opposing inward and outward radial forces generate longitudinal pinch-off forces in said cylinder, and

means responsive to said forces generated within said confined space for opposing said longitudinal forces.

12. In a high-pressure press:

a cylinder having a bore extending therein for receiving fluid,

a casing surrounding said cylinder to provide a confined space therebetween,

said cylinder having a passageway communicating said bore with said confined space,

a piston movably mounted within said bore to cover said passageway,

means for moving said piston within said bore with sufiicient force to increase the pressure of the fluid therein to elastically expand said cylinder to pass fluid between said piston and said cylinder through said passageway into said confined space to generate forces therein which act inwardly to support said cylinder, whereupon said inward forces act in conjunction with the outward forces generated within the bore to generate longitudinally extending pinchoff forces in said cylinder, and

means responsive to the forces generated in said confined space for applying forces to said cylinder to oppose the longitudinally extending pinch-oif forces.

13. A high-pressure press comprising:

a hollow cylinder for receiving fluid,

a first piston mounted for movement within said cylinder,

a second piston mounted for movement within said cylinder opposing said first piston,

means for moving said first piston and said second piston relative to each other with sufiicient force to increase the pressure of said fluid to elastically expand said cylinder and provide a fluid passageway between said cylinder and said pistons, and

easing means surrounding said cylinder to provide an enclosed space therebetween for receiving the fluid passing through said passageway.

14. A high-pressure metal forming press comprising:

a hollow cylinder for receiving fluid,

-a die having an orifice therethrough mounted within said cylinder for receiving a metal blank thereon,

a first piston mounted for movement within one end of said cylinder,

a second piston mounted for movement within the other end of said cylinder opposing said first piston, means for moving said second piston with suflicient force to increase the pressure of the fluid to a predetermined value to increase the ductility of said metal blank,

means for moving said first piston with sufficient force to increase the pressure of said fluid to (a) elastically expand said cylinder to pass fluid between said first piston and said cylinder and (b) draw said metal blank through said die, and

a casing surrounding said cylinder to provide an enclosed space therebetween for receiving the fluid passing from said cylinder.

15. A pressure vessel, comprising:

a casing,

a hollow intermediate cylinder mounted within and spaced from said casing,

means for sealing the ends of said casing to the ends of said intermediate cylinder to provide an enclosed annular space therebetween,

a segmented cylinder having a bore therethrough mounted within said intermediate cylinder,

said segmented cylinder having an upper threaded coun-terbore,

an elastically expandable forming cylinder mounted within the bore of said segmented cylinder having a bore extending from the top thereof for receiving fluid,

said forming cylinder having a beveled top surface,

a hollow end restraining member threaded into said upper counterbore of said segmented cylinder having a beveled bottom surface abutting against the beveled top surface of said forming cylinder, said end restraining member having an internal bottom section extending inwardly to the diameter of the bore of said forming cylinder,

said end restraining member, segmented cylinder and intermediate cylinder having a radial passageway therethrough communicating the internal surface of said upper end restraining member with said enclosed annular space,

a stepped piston having a first diameter portion movable within said bore of said forming cylinder and a second diameter portion movable Within said end restraining member to cover said radial passageway and provide an annular pressure chamber between said end restraining member and said first diameter portion of said stepped piston, and

means for moving said stepped piston with suflicient force to increase the pressure of the fluid in said bore of said forming cylinder to elastically expand said forming cylinder to pass fluid into said annular pressure chamber to radially support said first diameter portion, said moving means increasing the pressure in said annular pressure chamber to elastically expand said end restraining member to pass fluid 19 through said radial aperture into said enclosed annular space.

16. A pressure vessel, comprising:

an elastically expandable hollow cylinder for receiving fluid,

a first piston spaced from and movable within an end of said cylinder, said piston having a recess extending from one end for receiving fluid,

a seal between said first piston and the top of said cylinder,

a stepped piston having a first diameter section force fitted within the other end of said cylinder and a second diameter section projecting within said recess,

means for moving said first piston with suflicient force to act on the fluid (a) within said recess to elastically expand said first piston to pass fluid between said first pis ton and said second section of said stepped piston into the space between said first piston and said cylinder and (b) within said space to elastically expand said cylinder to pass fluid between said cylinder and said first section of said stepped piston, and

a casing surounding said cylinder to provide an enclosed space for receiving fluid passing between said cylinder and said first section of said stepped piston and confining said fluid to exert inward supporting forces against said cylinder.

17. A high-pressure press comprising:

an elastically expandable forming cylinder having a bore through one end thereof for receiving fluid, said cylinder having a top beveled surface,

a cylinder divided into segments surrounding said forming cylinder, said segmented cylinder having an axial bore therethrough with a threaded upper portion therein and a radial aperture extending into said threaded portion,

an end restraining member threaded into said upper portion of said segmented cylinder and having a lower beveled surface in juxtaposition with said top beveled surface of said cylinder, said member having an axial bore therethrough in alignment with said bore of said forming cylinder and having a radial aperture extending therethrough in alignment with the radial aperture in said segmented cylinder,

a hollow intermediate cylinder surounding said segmented cylinder and having a radial aperture therethrough in alignment with the radial aperture in said segmented cylinder,

a casing spaced from and surrounding said intermediate cylinder,

means for sealing said casing to said intermediate cylinder to provide an enclosed annular space therebetween,

a piston movable within said bore of said forming cylinder, and

means for moving said piston with sufficient force to increase the pressure of the fluid in said bore to elastically expand said forming cylinder to pass fluid between said piston and said cylinder, through said radial apertures into said enclosed space to generate fluid forces acting inwardly to support said forming cylinder.

18. A pressure vessel, comprising:

a casing,

an intermediate cylinder mounted within and spaced from said casing,

means for sealing said intermediate cylinder to said casing to provide an enclosed space therebetween,

a hollow segmented cylinder mounted within said intermediate cylinder and having an upper internally threaded portion,

an elastically expandable forming cylinder mounted within said segmented cylinder, said forming cylinder having a bore through one end thereof for receiving fluid and having a beveled top surface, an end restraining member having external threads thereon for cooperating with said upper threaded portion of said segmented cylinder, said external threads having a predetermined greater pitch than the threads of said segmented cylinder for uniformly distributing the load on the threads during the forming operation, said end restraining member having (a) a lower beveled surface in juxtaposition with said beveled top surface of said forming cylinder, and (b) a bore therethrough in alignment with said bore of said forming cylinder, a piston mounted for movement within said bore of said forming cylinder, said end restraining member, segmented cylinder and intermediate cylinder having aligned radial passageways extending therethrough into said enclosed space, and means for moving said piston with suflicient force to increase the pressure of the fluid to elastically expand said forming cylinder to pass fluid between said piston and said forming cylinder through said radial passageway into said enclosed space, wherein the fluid exerts inward forces to support said forming cylinder. 19. In a press for forming metal blanks under ultrahigh fluid pressure:

a forming cylinder having a bore therethrough for receiving fluid,

a die member having an orifice therethrough mounted within said bore for supporting a circular metal blank having a diameter smaller than the diameter of said bore to provide an annular space between said blank and said forming cylinder for receiving fluid,

a ring member mounted within said bore to hold said blank against said die, said ring member having axial grooves in the periphery thereof to pass fluid into said annular space to act against the periphery of said blank,

means for increasing the pressure of the fluid acting on the bottom of said blank to a predetermined value to increase the ductility of said blank,

means for increasing the pressure of the fluid acting against the periphery and the top of said metal blank to elastically expand said cylinder to pass fluid therefrom and to force said blank through the orifice of said die member, and

means for confining said escaping fluid to exert inward supporting forces against said cylinder.

20. In a high-pressure forming press:

a piston mounted for movement in said bore,

a seal attached to the end of said piston,

casing means surrounding said forming cylinder and engaging said piston to provide an enclosed space between said forming cylinder and said casing,

means for moving said piston with suflicient force to increase the pressure of the fluid within said bore to elastically expand said forming cylinder away from said seal and pass fluid into said enclosed space to generate support forces acting inwardly against said forming cylinder, and

means for limiting the diametrical expansion of said seal with respect to said cylinder.

21. In a high-pressure press:

a cylinder having an axial bore through one end for receiving fluid, said cylinder constructed to elastically expand upon subjection to a predetermined pressure,

a piston movable within said bore of said cylinder,

a seal assembly attached to the end of said piston to retain fluid within said bore, said seal including an expandable beveled edged member and a limiter disc having an axially extending beveled flange on the periphery thereof partially surrounding said expandable member to limit the diametrical expansion of said member,

means for moving said piston with suflicient force to generate said predetermined pressure to expand said cylinder away from said seal to provide a fluid passageway therebetween, and

a casing spaced from and surrounding said cylinder for receiving the fluid passing through said passageway and confining said fluid to exert inward supporting forces against said cylinder.

22. In a high-pressure forming press:

a fluid-filled forming cylinder having a beveled end,

an array of segmented sections surrounding said cylinder, having a frusto-conical recess formed in one end thereof,

double-walled casing means surrounding said segments,

a hollow conical plug secured to said casing means and extending into said frusto-conical recess, said plug having a conical recess formed in the end thereof to accommodate the beveled end of said cylinder,

a piston mounted for movement within said cylinder,

means for moving the piston within said cylinder to force the fluid to elastically expand the cylinder wall and pass fluid between said piston and cylinder, and

said plug having a passageway therethrough to conduct said passed fluid to said casing means whereupon said passed fluid acts against said plug and segments.

23. In a high-pressure press:

a fluid-filled forming cylinder having a beveled end,

casing means surrounding and spaced from said cylinder and having an inwardly projecting flange,

said flange having an inner surface beveled toward the inner wall of said casing,

an end restraining member interposed between said beveled end and said beveled flange surface,

a piston mounted for movement in said cylinder,

means for moving said piston to increase the pressure of said fluid to elastically expand said forming cylinder to pass the fluid between the piston and the cylinder wall,

said end restraining member having a passageway therethrough for conducting said passed fluid to the juncture of said beveled flange and said end restraining member, whereupon said passed fluid forces the end restraining member against the beveled end of said cylinder, and

means responsive to the fluid passed through said juncture for applying forces against said forming cylinder;

24. A pressure vessel comprising:

expandable means for providing a first fluid chamber for receiving fluid to be pressurized;

means for providing a second fluid chamber around said expandable means;

means for pressurizing fluid in said first fluid chamber;

said expandable means, in response to pressurized fluid received therein, being expandable to communicate said first fluid chamber with said second fluid chamber to permit a portion of the pressurized fluid received in said first chamber to pass into said second chamber and provide support to said expandable means.

25. A pressure vessel, comprising:

expandable means for providing a first fluid chamber for containing pressurized fluid;

means for providing a second fluid chamber surrounding said expandable means and for containing fluid for providing support to said expandable means;

said expandable means, upon the occurrence of a predetermined pressure diflerential between the pressurized fluid in the first chamber and the pressurized fluid in the second chamber, being expandable to communicate said chambers to relieve a portion of the pressurized fluid from said first chamber into said second chamber whereupon said relieved pressurized fluid further supports said expandable means in containing the pressurized fluid contained in said first chamber.

References Cited UNITED STATES PATENTS 316,967 5/1885 Heber 138148 667,525 2/1901 Huber 7260 2,558,035 6/1951 Bridgman 726O 2,937,606 5/1960 Paulton 7257 3,030,776 4/1962 Kustusch 6054.5 3,060,507 10/1962 Knowles 726O 3,099,993 8/1963 Smith 138148 3,123,862 3/1964 Levey 1816 3,132,569 5/1964 Shepherd 92-193 3,224,042 10/1965 Meissner 1816 3,255,490 6/1966 Sturm 18-16 CHARLES W. LANHAM, Primary Examiner.

A. RUDERMAN, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3 ,379 ,043 April 23, 1968 Francis J. Fuchs, Jr.

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 5, line 48, "Pl A2=Pl Al" should read P2 A2=Pl Al line 50, "pressuirzed" should read pressurized Column 9, line 72, after "to" insert the Column 10, line 23, "600)." should read 600), Column 13, line 10, "dies" should read die line 38, "pressurzied" should read pressurized Column 14, line 13, comunicating" should read communicating line 34, "blank 10'' should read blank 100 Column 15, line 20, "means," should read means line 34, "the" should read and line 46, "an" should read a Column 16 lines 4 and 5, "within the innermost cylinders by the pressures within each succeeding outer cylinder, and" should read to counteract the pressures within the inner cylinders by the pressures within each succeeding outer cylinder, and line 23, "pressure" should read pressures line 47, "the" should read a Column 19, line 24, "surounding" should read surrounding line 45, "surounding" should read surrounding Signed and sealed this 9th day of September 19.6

(SEAL) Attest EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR. Attesting Officer Commissioner of Patents