CZ9903623A3 - High-pressure press for hydraulic forming - Google Patents

Abstract

Equipment for hydraulic forming of tubular metal the preform has a pressing mechanism (12), a hydraulic source forming fluid, hydraulically driven mechanism (36) for tube end control, hydraulically operated mechanism (110) for increasing the pressure and a single source (22) hydraulic A hydraulically driven actuating mechanism (36) the tube ends seals the opposite ends of the tubular metal a preform (T) in said pressing cavity and can move by longitudinally compressing the tubular metal preform (T). Hydraulic forming fluid flows into the mechanism for controlling the pipe ends from a source of hydraulic forming fluid a has an outlet passage for supplying hydraulic forming the liquid through which the hydraulic forming fluid can to the interior of the tubular metal preform. A hydraulically operated pressure boosting mechanism (110) it can move so as to increase hydraulic forming pressure a liquid contained within a metal tubular preform thereby expanding the diameter of the preform. Single source (22) hydraulic force supplies hydraulic fluid under pressure to said fluid a hydraulically actuated raising mechanism (110) pressure to bring said mechanism (110) to increasing the pressure into motion and thereby increasing the hydraulic pressure a liquid located in the interior of the tubular metal the preform and expanding the diameter of the tubular metal preform until its outer surface takes on the shape of said inner pressing surface. A single hydraulic power source (22) supplies said hydraulic fluid under pressure to said fluid a hydraulically driven end control mechanism (36) tubes to move said mechanism (36) for I control the tube ends during longitudinal compression of the tube a metal preform and thereby performing metal reordering the material of the tubular preform to undergo expansion diameter, longitudinally inward for refilling the wall thickness of the tubular preform being undergoing expanding the diameter, and maintaining the thickness of its wall in advance range.

Description

High pressure press for hydraulic forming

Technical field i

The present invention is directed to a hydraulic forming apparatus that requires less operating cost in performing high pressure hydraulic forming of tubular parts. In particular, the present invention is directed to the replacement of a conventional, single "multiplier" press system for generating high internal pressures in an expanded tubular parison.

BACKGROUND OF THE INVENTION

Conventional hydroforming utilizes low pressure (e.g., by gravity) supply of hydraulic hydroforming fluid from a reservoir serving to supply hydraulic hydroforming fluid to the quick, initial filling of the tubular parison after closing the cavities of the press around the chest, but before actuating the axial cylinders and cavity press. As a result, it is necessary for a separate multiplier to push the tubular parison into the cavity of the press.

SUMMARY OF THE INVENTION

Disadvantages of the prior art can be overcome by developing a device that uses a hydraulic forming fluid from a tank by a method of supplying relatively less water to increase the pressure in the tubular parison after sealing, when such a tubular parison is ready to expand. This smaller amount of water is fed into the dual function cylinder which is used to push the tubular parison into the press cavity as well as to increase the liquid pressure inside the press cavity from one side of the tool. Replacing the previously used multipliers with a dual function cylinder, which performs hydraulic injection of the tubular parison into the cavity of the press and increases the internal pressure of the liquid for molding purposes, significantly reduces the cost of equipment.

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According to the present invention, water is supplied under relatively low pressure to the lateral piston and cylinder hydraulic assemblies used to expand the tubular parison. The piston and cylinder hydraulic assemblies utilize the same source of hydraulic force to exert the pressures required to expand the tube as well as the pressure required to push the opposite ends of the tube inward to maintain the desired wall thickness of the resulting product. Therefore, no separate multiplier is required.

The present invention also advantageously utilizes the same source of hydraulic force to exert downward pressure on the upper structure of the press when the upper structure hsu is in its lowered position to face the pressure of the inner cavity of the press during pressure increase in the tube.

It is another object of the present invention to provide an apparatus for hydroforming a tubular metal preform, the apparatus comprising a pressing mechanism, a fluid source for hydraulic pressing, a hydraulically driven mechanism for controlling pipe ends, a hydraulically operated pressure boosting mechanism, and a single source of hydraulic force. A hydraulically driven end-of-pipe mechanism seals the opposite ends of the tubular metal preform in said press cavity and can move longitudinally as the tubular metal preform is compressed. The tube end control mechanism enters a hydraulic forming fluid of said source of hydraulic forming fluid, and the tube end controlling mechanism has an outlet opening for supplying said liquid through which the hydraulic forming fluid can be fed into a metal tube preform. The hydraulically operated pressure boosting mechanism may move, thereby increasing the pressure of the hydraulic forming fluid located within the tubular metal preform, followed by increasing the diameter of said preform. A single source of hydraulic power supplies hydraulic fluid under pressure to said hydraulically operated pressure boosting mechanism to actuate the pressure boosting mechanism, compressing the hydraulic forming fluid located within the tubular metal parison and expanding the diameter of the tubular metal parison to the extent until its outer surface abuts the inner pressing surface. A single source of hydraulic power also supplies hydraulic fluid under pressure to a hydraulically driven tube end control mechanism, whereby this hydraulically driven tube end control mechanism longitudinally compresses said tubular metal parison so that the metal material advances inwardly as the tubular parison expands to add thickness

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The wall of the expanded tubular metal preform and maintaining its wall thickness within a predetermined range.

Another object of the present invention is also to provide an apparatus for hydroforming a tubular metal preform, the apparatus comprising a press mechanism, a fluid source for hydraulic press, a hydraulically driven end-of-pipe mechanism, and a hydraulically operated pressure-boosting mechanism. The pressing mechanism has an internal pressing surface that defines a pressing cavity. The mold cavity has a structural design and arrangement such that a tubular metal preform can enter it. The hydroforming fluid source is positioned higher than the press cavity and its design and arrangement allows the hydroforming fluid to be introduced into the interior of the tubular metal preform by the action of gravity. A hydraulically driven end-of-pipe mechanism controls and effectively seals opposite ends of the tubular metal blank in the press cavity. The pipe end controlling mechanism may be moved to longitudinally compress the tubular metal preform. The tube end control mechanism enters a hydraulic forming fluid from said source of hydraulic forming fluid, and the tube end controlling mechanism has an outlet opening for supplying said liquid through which the hydraulic forming fluid can be fed into the metal tube preform. The hydraulically operated pressure boosting mechanism can move in response to hydraulic fluid pressure, and consequently can compress the hydroforming fluid located inside the tubular metal blank to expand the diameter of the tubular metal blank until its outer surface is generally adjacent. to the inner pressing surface. The hydraulically driven tube end control mechanism may move in response to changes in hydraulic fluid pressure, whereby the hydraulically driven tube end control mechanism may longitudinally compress said tubular metal blank so that as the diameter of the tubular blank is expanded, the metal material may advance inward to replenish the wall thickness of the expanded tubular metal preform and maintain its wall thickness within a predetermined range.

The resulting device is far less complex, less cumbersome, and less expensive than prior art devices that exist in the art.

Overview of the drawings

The present invention will now be described with reference to the drawings, in which:

Fig. 1 is a block diagram of a hydraulic forming die according to the principles of the present invention;

ohr. 2 is a block diagram similar to that shown in FIG. 1, except that it illustrates the mechanisms for controlling the ends of the tube after being moved into contact with the opposite ends of the tube for hydraulic forming;

FIG. 3 is a schematic cross-sectional view of the hydraulic piston and die assembly of the present invention. 4 is a cross-sectional view of the hydraulic piston and die assembly similar to FIG. 3, but showing the end-of-pipe control mechanisms after being moved into contact with opposite ends of the pipe for hydraulic forming;

FIG. 5 is a cross-sectional view of a hydraulic piston-like press assembly similar to FIG. 4, but showing the opening of the valve upon initial increase of the internal pressure in the tube for hydraulic forming;

FIG. 6 is a cross-sectional view of a hydraulic piston-like press assembly similar to FIG. 5, except that it illustrates an initial increase in the internal pressure in a tube for hydraulic forming when the upper pressing mechanism is in the lowered position;

Fig. 7 is a cross-sectional view of the hydraulic piston assemblies and the press mechanism similar to Fig. 6, but showing the complete expansion of the tubular parison and the inward movement of the hydraulic piston assemblies to maintain the wall thickness of the molded part;

Fig. 8 shows a step that follows for the situation shown in Fig. 7, during which the outer pistons return to their original position in the respective hydraulic piston assemblies after the hydraulic forming operation has been performed;

FIG. 9 is an enlarged, schematic view of a portion of a second embodiment of a hydraulic forming die according to the principles of the present invention showing the press in the open position;

-5def. 10 is a block diagram of a complete hydraulic forming die part of which is shown in FIG. 9 showing the press in the open position;

Fig. 11 is a block diagram similar to that shown in Fig. 10, but showing the state that the piston is down and the press is closed;

Fig. 12 is a block diagram similar to that shown in Fig. 11, except that the side rollers are in operation and rapid loading begins;

Fig. 13 is a block diagram similar to that shown in Fig. 12, except that the side rollers are inward towards the ends of the tubular preforms and the fluid pressure is increased;

Fig. 14 is a block diagram similar to that shown in Fig. 13, but showing the expansion of the hydraulically formed tube;

Fig. 15 is a block diagram similar to that shown in Fig. 13, except that it illustrates a press piston upon completion of a hydraulic forming cycle; and Fig. 16 is an enlarged cross-sectional view taken in longitudinal shift and generally showing the press halves and the side rollers illustrated in Fig. 15.

DETAILED DESCRIPTION OF THE INVENTION

It can be seen in FIG. 1 that the hydraulic forming apparatus 10 comprises a hydraulic forming pressing mechanism 12 having an upper pressing portion 14 and a lower pressing portion 16. The lower draw portion 16 is disposed on a fixed support 18.

It can be seen from Fig. 1 that the upper hydraulic piston 20 carries the upper press part 14 and thereby controls the movement of the upper press part 14. More specifically, the hydraulic actuation of the upper piston 20 allows the weight of the upper press part 14 to be moved vertically downward to cooperate with by the lower press part 16 at the beginning of the hydraulic forming operation. Upon displacement of the upper press portion 14 downward, the upper piston 20 exerts a hydraulic force acting on said upper press portion 14 thereby maintaining the upper press portion 14 in relationship with the lower press portion 16 during the high pressure conditions generated by the press. a cavity between the upper press portion 14 and the lower press portion 16.

The hydraulic pressure pump assembly 22 has a structure that delivers hydraulic fluid under pressure to the upper piston 20 via a hydraulic fluid line 24 to maintain the upper press portion 14 in association with the lower press portion 16 against the opposing forces occurring during the existence of said pressurized piston. conditions of high pressure in the press cavity. An auxiliary valve 26 is provided on the fluid line 24 to regulate the fluid flow between the hook hydraulic pump assembly 22 and the upper piston 20.

The hydraulic pressure ram assembly 22 is also coupled to a pair of lateral piston assemblies 28 and 30, which are located at opposite, longitudinal ends of the press mechanism 12. The lateral piston assemblies 28, 30 have piston caps designated by reference numerals 32 and 34, respectively, and respective mechanisms 36, respectively. and 38 for controlling the ends of the spout. The pipe end control mechanism 36 extends outwardly from the side piston housing 32 and the pipe end control mechanism 38 extends outwardly from the side piston housing 34 ·

Referring to FIG. 2, the tube end control mechanism 36 is displaced inwardly from the piston housing 32 and in contact with the seal relationship with one end of the tube T supported by the lower press portion 16. The tube end control mechanism 38 is displaced inwardly. from piston housing 34 and its design is adapted to handle and seal the opposite end of tube T. Mechanism 36 will move in and out with respect to piston housing 32 based on the efficiency of the hydraulic fluid supplied to the side piston assembly 28 from the hydraulic pressure pump assembly. 22, by means of (FIG. 2) three separate hydraulic fluid lines 40, 42 and 44. On these fluid lines 40, 42 and 44, respective auxiliary valves 46, 48 and 50 are provided for adjusting the fluid flow between the hydraulic pressure pump assembly 22 and the side piston assembly 28.

The side piston assembly 30 is coupled to the hydraulic pressure pump assembly 22, which in a similar manner controls the movement of the pipe end control mechanism 38. The side piston assembly 30 is connected to the hydraulic pressure pump assembly 22 by means of (Fig. 2) three separate hydraulic fluid lines 52, 54 and 56. On these fluid lines 52, 54 and 56, respective auxiliary adjustment valves 58, 60 and 62 are provided for adjustment. fluid flow between the hydraulic pressure pump assembly 22 and the side piston assembly 30.

R r r r r r r * * * * * * * * * r r r r r r r r r r ·

The hydraulic forming apparatus 10 further comprises an upper water tank 80, the design of which allows a predetermined amount of water to be maintained. The water tank 80 is connected via the fluid line 82 to the pipe end control mechanism 36 of the piston assembly 28. The auxiliary valve 84 is located on the fluid line 82 that adjusts the flow of water to the pipe end control mechanism 36 when it is the pipe end control mechanism 36 in sealing engagement with the pipe end T. In addition, the pipe end control mechanism 36 supplies water to the interior of the pipe T.

The hydraulic forming apparatus 10 further comprises a lower water tank 90 which is connected via a fluid line 92 to a pipe end control mechanism 38. An auxiliary valve 94 is located on the fluid line 92 to adjust the flow of water from the pipe end control mechanism 38 to the lower tank 90.

Once the tube end control mechanisms 36, 38 have contacted the opposite ends of the tube T as shown in Fig. 2, the valve 84 opens and water flows from the upper tank 80 through the tube end control mechanism 36 and further through the tube T into the mechanism 38 for controlling the end of the tube.

The lower press part 16 communicates with the lower tank 90 via the drain line 96. After the hydraulic forming operation, the drain line 96 drains any remaining water from the lower press part 16 to the lower tank 90. An auxiliary valve 98 is provided on the drain line 96 to adjust flow water to the lower tank 90.

After the hydraulic forming operation, the water collected in the lower tank 90 is returned to the upper water tank 80 via the return line 100. A simple water positive displacement pump 102 is disposed on the return line 100 which pumps water from the lower tank 90 to the upper water tank 80 via the return line. 100. An auxiliary valve 104 is provided on the return line 100 to adjust the water flow from the lower tank 90 to the upper water tank 80.

Referring to FIG. 3, a more detailed description of the hydraulic forming apparatus 10 will be provided. 3 it can be seen that in the piston housing 32 of the side piston assembly 28, a pipe end control mechanism 36 and a pressure increase mechanism 110 are disposed. It can be seen that the tube end control mechanism 36 comprises a main portion 112 and an end cap 114. More specifically, the main portion comprises a tubular housing portion 116 and a transverse, outwardly facing flange portion 118 that extends transversely outwardly from the rear. The outer peripheral edge 119 of the flange portion 118 is in slidably sealed relationship with the cylindrical, inner, side surface 120 of the piston housing 32. The outer cylindrical surface 122 of the housing portion 116 is similarly disposed with the sliding seal with the cooperating surface 128, which generally defines a bore in the piston flat from which a pipe end control mechanism 36 projects.

End cap 114 includes an annular flange portion 130 that is bolted and sealed by respective fasteners 132 to the distal circular end of the housing portion 116 that is located outside the piston cover 32. The end cap 114 further comprises an elongate tubular portion 134 which is integral with the flange. The tubular portion 134 has a generally cylindrical inner surface 136 that is designed and arranged to form a peripheral seal with an arcuate surface 138 of the upper press portion 14 and an arcuate surface 140 of the lower press portion. 16 when the upper press part is closed.

The end cap 114 terminates in the nozzle section 144 which extends outwardly from the tubular portion 134. The nozzle section 144 is substantially tubular in shape and has a reduced outer diameter compared to the tubular portion 134. The transversely extending circular flange portion 146 is located at the transition between the tubular portion 134 and the nozzle section 144. The flange portion 146 is designed and arranged to enter into a sealing relationship with one end of the tube T found in the press mechanism 12 during the hydraulic forming operation. . The nozzle section 144 has a cylindrical outer surface 148 that is designed and arranged to fit into one end of the tube T. It may be preferred that the surface 148 abuts the inner wall of the tube T at said one end.

A longitudinal ISO passage is formed in the end cap 114, the design of which allows fluid to flow from inside the tube end control mechanism 36 to the inner, enclosed space of the tube T.

The pressure boosting mechanism 110 comprises a base portion 160 that generally resembles a disc and has an outer circular periphery adapted to slidably engage the inner surface 120 of the piston housing 32. The rigid, cylindrical, intermediate block portion 162 is integral with the base portion 160 and has a a smaller diameter compared to said base portion 160. The rigid, cylindrical, front portion 164 is integral with the middle portion 162 and has a smaller diameter compared to said intermediate portion 162. The front portion 164 projects from the middle block portion 162. ·················································

The outer surface of the front portion 164 is generally cylindrical in shape and is slidably sealed to the generally cylindrical, cooperating inner surface of the housing portion 116.

At the transition between the front portion 146 and the intermediate block portion 162, there is a transverse, circular, flange surface 168. The flange surface 168 serves as a rear stop of the tube end control mechanism 36.

In Fig. 3, the tube end control mechanism 36 and the pressure increase mechanism 110 are shown in their rearmost positions within the piston housing 32.

It should be appreciated that the side piston assembly 30 is substantially the same as the side piston assembly 28 except for connecting the lower tank 90 to the piston assembly 30 as opposed to connecting the upper tank 80 to the piston assembly 28. Therefore, in the drawings, similar components have both piston assemblies 28 and 28. 30 assigned the same reference numbers.

The operation of the device will now be described. It can be clearly seen in FIG. 4 that after placing the tube T in the lower press mechanism 16, the auxiliary valve 46 opens and the hydraulic fluid flows under pressure from the hydraulic pressure pump assembly 22 through the fluid conduit 44 into the intermediate chamber 170 which is generally located 32. Similarly, the auxiliary valve 62 also opens so that the hydraulic pressure pump 22 can supply hydraulic fluid via fluid line 56 to the middle chamber 170 in the side piston assembly 30. When the liquid is supplied to the side piston assemblies 28, 30 in such a manner, the tube end control mechanisms 36 and 38 are moved inwardly so that their flange portions 146 come into contact with the opposite ends of the tube T and these ends sealed.

Then, as shown in Fig. 5, the auxiliary valve 84 opens and allows the supply of water from the upper tank 80 through the fluid conduit 82 to the pressure boosting chamber 174 located within the interior of the pipe end control mechanism 36 between the extreme inner end of the mechanism 110 The fluid flows through the passage 150 of the tube end control mechanism 36 to the tube preform T and then continues through the passage 150 in the opposite outer piston 38 to the front chamber 174 of the tube end control mechanism 38. When performing the filling step of the tube T, the auxiliary valve opens first to allow liquid to flow into the lower tank 90. Such liquid flow through the fluid reservoir 90 is provided.

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Subsequently, the auxiliary valve 94 closes and the pressure in the tube T gradually increases to a predetermined range.

It can be seen in FIG. 6 that after the tube T has been filled with liquid, the upper press portion 14 is lowered onto the lower press portion 16, thereby forming a closed press cavity 190 having a fully closed cross-sectional shape between said portions 14 and 16.

Upon lowering of the upper press part 14, the auxiliary valve 84 on the line goes to the pipe end control mechanism 36, and the auxiliary valve 94 on the line goes to the pipe end control mechanism 38. Subsequently, the auxiliary valves 48 and 60 are opened and the hydraulic fluid flows under pressure from the hydraulic pressure pump assembly 22 through the hydraulic lines 42 and 54 to the rear chambers 194 of the pressure booster mechanisms 110 of the respective side piston assemblies 28, 30, . The fluid supplied to the rear chambers 194 causes the pressure boosting mechanism 110 to move inwardly towards each other so that it transfers the water present in the pressure boosting chambers 174 through the liquid supply passages 150 into the tube T.

FIG. 7 illustrates how the pressure boosting mechanisms 110 continue to press inwardly toward each other, thereby moving water from the pressure boosting chambers 174 to the tube T and further expanding the tube T with respect to its diameter. The auxiliary valves 46 and 62 remain open to continue to allow the supply of pressurized hydraulic fluid from the hydraulic pressure pump assembly 22 via hydraulic lines 44 and 56 to the intermediate chambers 170 of the side piston assemblies 28 and 30, in which the pressure is gradually increased. The fluid supplied to the intermediate chambers 170 pressurizes the end-of-pipe control mechanisms 36 and 38 as they move towards and against the opposite ends of the tube T. The movement of the outer pistons 36a 38 in this way causes a rearrangement of the metal material of which the tube is T is made (preferably of steel) along the length of the tube so that it is possible to increase the diameter of the tube in some regions by 10% or more, while the wall thickness of the hydroformed tube T is preferably maintained ± 10% of the wall thickness of the original tubular blank.

For the expansion of the pipe, the use of a pressure of 2000 to 3500 atmospheres seems to be most advantageous. Depending on the particular operating conditions, it may also be advantageous to use pressures from 2000 to 10,000 atmospheres, although it is even possible to use higher pressures.

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After the step of forming the tube T into the desired shape corresponding to the shape of the press cavity, the pump 22 terminates pressure build-up in the fluid lines 42. 44. 54 and 56. Valves 50 and 58 then open to allow the hydraulic fluid under the hook to flow into the fluid lines. As a result, hydraulic fluid flows under the hook into the return chambers 200 located, as seen in Fig. 7, in front of the flange portion 118 of the tube end control mechanisms 36 and 38. Increasing the pressure in the return chambers 200 causes the mechanisms 36 and 38 to move outwardly in respective piston housings 32 and 34 so as to move the mechanisms 36 and 38 away from the opposite ends of the tube T, as illustrated in FIG. 8.

During the withdrawal of the tube end control mechanisms 36 and 38 in the piston housings 32 and 34, the flanges 118 come into contact with the front flange surfaces 168 of the pressure boosting mechanisms 110 and push these pressure boosting mechanisms 110 outward. In the present example, the pressure boosting mechanisms 110 assume their original positions, as can be seen by comparing FIG. 3 with FIG. 8.

During this depressure, as a result of which the pressure boosting mechanisms 110 and the tube end controlling mechanisms 36 and 38 are moved outwardly, the valves 48, 46, 60 and 62 are opened and allow the hydraulic fluid to return to the hydraulic fluid reservoir which is part of the hydraulic pressure pump assembly 22.

After disconnecting the pipe end control mechanisms 36 and 38 from opposite ends of the pipe T, the rest of the water contained in these pipe end control mechanisms is discharged through the drain line 96 and the open auxiliary valve 98 to the tank 90. The water contained in the lower tank 90 is pumped into the upper the tank 80 via the return line 100 by actuating the water pump 100.

Since the side piston assemblies 28 and 30 of the present invention preferably employ pressure boosting mechanisms 110 located in the tube end control mechanisms 36 and 38, there is no need to create a separate, costly "multiplier" mechanism for generating high internal expansion pressures sponges. The application of such multipliers is normally required in high pressure, hydraulic forming machines (i.e., hydraulic forming machines that use hydraulic expansion pressures above 2000 atmospheres), and therefore these devices are particularly required in high pressure, hydraulic forming operations where opposite ends of the pipe Manageable

The pressure pushes inwards to regroup metal material along the length of the tube to replenish or maintain the wall thickness of the tube during expansion. The multipliers are conventionally used in conjunction with separate piston components which only serve to push the opposite ends of the tube inwards to provide said material regrouping.

The present invention performs the same desired functions as a hydraulic forming apparatus having a conventional multiplier, but operating the apparatus of the present invention is far more cost effective. In the present invention, water is preferably fed to the side piston assemblies under relatively low pressure due to the force of gravity (or with the aid of a simple, low pressure, circulating shaft). The side piston assemblies then utilize the same source of hydraulic force (i.e., the hydraulic pressure pump 22) to exert the pressures required to expand the tube as well as pressures required to push the opposite ends of the tubes inward to maintain the desired wall thickness.

Another advantageous feature of the present invention is that, in addition to the above-mentioned operations, the same hydraulic pump 22 is also used to exert a downward pressure by the upper press portion 14 when the upper press portion 14 is in its lower position. The hydraulic pump 22 exerts a downward force on the upper press portion 14 that faces the pressure of the inner press cavity during a gradual increase in pressure in the tube, thereby keeping the upper press portion 14 in a lowered position. In addition, the final embodiment of the inventive device is less complex and less cumbersome than a conventional device.

Referring to Figs. 9 to 16, attention will be directed to an enlarged view of a portion of a second embodiment of a hydraulic forming apparatus according to the principles of the present invention, generally designated by reference numeral 220. This preferred apparatus comprises five main assemblies, including the assembly. a frame that generally forms a structural support and is generally designated by reference numeral 222, a top press assembly generally designated by reference number 224, a bottom press assembly generally designated by reference number 226, a hydraulic forming press mechanism generally designated by reference number 228, and a hydraulic line assembly generally designated 230.

In Fig. 9, it is particularly seen that the frame assembly 222 includes a pair of side frame members 232 of the press that are drawn to clearly show that they are parallel, spaced apart, vertical components for attaching the upper assembly 224 press

-13 ·· · ··· and lower press assembly 228. The upper ends of the side frame members 232 have a crown plate 234 that is located at their apexes. The crown plate 234 serves as a support for other components of the hydraulic fluid system, which will be described below.

The upper press assembly 224 has the following construction. The roller support ram 236 is attached at its ends to the side frame members 232 of the press. Overall, in the center of the cylindrical support ram 236 is a ram cylinder 238 having a ram piston rod 240 that extends through a vertically extending piston rod hole 242 formed in the cylindrical support ram 236. The upper portion of the piston rod 240 has an enlarged outer diameter, thereby providing the possibility a portion of the rod 240 with the inner surface of the cylinder 238 in sliding, sealed contact. The space defined by the upper portion of the piston rod 240 and the inner surfaces of the cylinder 238 forms the upper pressure chamber 244. The diameter of the piston rod below the described upper end portion is somewhat reduced and defines the lower pressure chamber 246 between the cylindrical, outer surface of the rod 240 and the inner surfaces of the cylinder 238. the chamber is defined at its lower end by a radially outwardly directed portion of the base of the cylinder 238 and at its upper end by a circular, lower surface of the upper portion of the piston rod 240 having a larger diameter. A pressure piston 248 is permanently attached to the lower end of the piston rod 240. The hook piston 248 is positioned horizontally and does not completely fill the foam space between the two frame members 232.

The press lower assembly 226 includes a press bed 250, a right boom arm 252 that is permanently attached to the press bed 250 with a tightening screw 254. and a left boom arm 256 that is permanently attached to the press bed 250 with an additional tightening screw 254. Press bed 250 supports the lower press half 260 and forms a base support for further assemblies. The lower ends of the side frame members 232 of the press are permanently attached to the press bed 250 near opposite ends of the bed 250. The two (right and left) boom arms 252 and 256 are permanently attached to the side ends of the Usu bed. a carrier for hydraulic cylinder assemblies 274 and 292, the construction of which will be described hereinafter.

Referring to the hydraulic forming apparatus 220 shown in FIG. 9, the press mechanism 228 (which is shown to a larger extent in FIG. 16) comprises an upper press half 258 and a lower press half 260. The cylinders 274 and 292 are according to

-14 · • · • přísluš nosti přísluš ovány přísluš namont namont namont namont nosti nosti namont namont ovány namont namont namont namont namont namont namont ovány namont ovány namont namont namont namont namont namont namont ovány ovány namont namont ovány. the mold halves 258 and 260 have respective inner surfaces 264 and 270 which cooperate to define a mold cavity 262 that determines the size and dimension of the hydroformed tubular parison. The upper portion of the upper press half 258 is permanently attached to the bottom of the press piston 248. The lower press half 260 is permanently attached to the press loa 250.

The lower press half 260 is generally the same size and shape as the upper press half 258, but with the difference that its inner press surface 264 is inverted relative to the lower press surface 270 of the press cavity. Upper and lower halves 258 and 260 are provided with upper and lower tool blocks or clamping structures designated by reference numerals 266 and 272, respectively, which cooperate to surrounding the clamping of the outer surface of the tubular parison near its longitudinal ends to secure the tubular parison in a closed press. . A liquid inlet opening 273 is provided in one of the lower tool blocks, which will be described in detail below. Depending on the guiding of the die cavity axis and the tool blocks 266 and 272 and behind the side frame components 232 of the press, a pair of hydraulically actuated assemblies 274 and 292 are disposed on the boom arms 252 and 256, aligningly with said tube axis and pointing towards the ends of the tubular blank .

One of the pair of rollers, the roller 274 mounted on the left boom arm 256, is a side push roller. This cylinder 274 comprises a front member 276 and a rear member 278. both of these members 276 and 278 are attached to the upper surface of the left boom arm 256, and a cylindrical wall member 280 that is secured between the front member 276 and the rear member 278. Front member 276 has a central bore allowing sliding, sealed, through movement of the tube end control mechanism 282. The rear end 281 of the tube end control mechanism 282 is located in the cylinder 274 and has a diameter that forms a slidably sealed relationship with the inner surface of the cylindrical wall member 280. The portions of the tube end control mechanism 282 that advance further toward the tube T have a smaller diameter than said rear end portion, thereby forming a side cylindrical chamber 284 delimited by the outer, cylindrical side surfaces of the tube end control mechanism 282, the cylindrical inner surface of the cylindrical wall member 280, the circular inwardly facing surface of the rear end 281 and a circular, rearwardly facing, inner surface of the front member 276 of the cylinder 274. The rear pressure chamber 286 is

Is defined by a forward facing, inner surface of the rear member 278 of the cylinder 274, a cylindrical wall member 280, and a rear surface of the rear end portion 281 of the tube end control mechanism 282. Hydraulic fluid lines are connected to these chambers 284 and 286 as will be explained later. The front end portion of the tube end control mechanism 282 that projects beyond the front member 276 of the cylinder 274 is somewhat smaller in diameter, and at the front end of the front portion of the piston rod is a portion for contacting the tube having the shape of a conical tip 288. the section 288 is structurally configured to enter the open opening of the tubular blank T for hydraulic forming. Advantageously, the rear portion of the conical tip section 288 has a radially outwardly extending circular flange (not shown) that abuts against an end edge in the longitudinal direction of the tube. A relatively accurate passage is formed in the tip section 288 that defines a fluid outlet orifice 289 and extends from the inner chamber 290 located in the forward facing portion of the tube end control mechanism 282 to deliver liquid from the chamber 290 to the tubular blank T at a time. wherein the tip portion 288 controls the end of the preform T in relation to the seal.

On the opposite side of the hydraulic forming press bed 250 is a hydraulically operated duplex cylindrical assembly 292 that is permanently attached to the right leg arm 252. The duplex cylindrical assembly 292 has an inner wall 294 and an outer wall 296, both walls 294 and 296 being permanently mounted. The cylindrical wall member 298 is mounted between the inner wall 294 and the outer wall 296, thereby defining a cylindrical chamber. Inside the duplex cylindrical assembly 292 is a hydraulically operated pressure boosting mechanism 300 and a hydraulically driven tube end controlling mechanism 304. The hydraulically operated pressure boosting mechanism 300 has an outer end portion 299 that is in relation to the sliding seal with the inner surface of the cylindrical wall member 298 and the inwardly directed portion 303 having a relatively reduced diameter. The reduced diameter of the inwardly directed portion 303 of the pressure boosting mechanism 300 allows the sliding passage of this portion 303 in a sealing relationship through an opening formed in a circular cylindrical distributor 302 that is located approximately midway along the longitudinal axis of the cylindrical wall member 298. located in the duplex cylindrical assembly 292 has a tubular form and is located within the cylindrical distributor 302. The pipe end control mechanism 304 has a rear end portion 311 which can slid relative to each other.

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Φ Φ Φ

The main, longitudinal, cylindrical, housing part 309 having a reduced diameter extends inwardly and moves in relation to the seal with the opening formed in the inner wall 294. The end of the cylindrical housing part 309 which is located most inside, it is configured in the form of a conical tip portion 307 and has a portion for controlling the end of the tube. This prong portion has a similar design to the prong portion 288. The inwardly directed portion 303 of the pressure boosting mechanism 300, together with the high-pressure seals 301 attached to its inner end, is slidably disposed in the cylindrical housing 309 of the piston structure 304. a pressure fluid chamber 306 is defined in the piston structure 304 in which the fluid pressure is gradually increased during the hydraulic forming operation.

The tip section 307 has a relatively accurate passage defining a fluid outlet opening 308 that extends inwardly from the hook chamber 306 and terminates on the inner portion of the conical tip section to allow fluid to be supplied from chamber 306 to the downstream end of the tubular blank T.

A pressure chamber 310 is defined between the rear end portion 299 of the hydraulically actuated pressure boosting mechanism 300 and the outer wall 296 of the duplex cylinder 292. The return chamber 312 is defined between the circular inwardly facing surface of the outer end portion 299 of the pressure boosting mechanism 300 and the outwardly cylindrical surface. The pressure chamber 314 of the tube end control mechanism is located between the inwardly facing surface of the cylindrical distributor 302 and the outwardly facing surface of the outer end portion 311 of the hydraulically actuated tube end control mechanism 304. The end of the tube end control mechanism 316 is defined around the cylindrical, housing end 309 of the tube end control mechanism 304 between the outer end portion 311 of the piston end actuation mechanism 304 and the inner wall 294 of the duplex cylinder assembly 292. which will be described in more detail below.

The hydraulic forming apparatus 220 shown in Figures 9 to 16 includes a hydraulic distribution system 230 including fluid lines, reservoirs, pumps and valves, the purpose of which will be described in connection with the following description of the operation of the present invention.

Giant. 9 and 10 show the press assembly 228 for hydraulic forming in its open position. With particular reference to Fig. 10, the ram 248 and the upper press half 258 are raised in their open position. Hydraulic forming liquid 318 which is a mixture

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The tank 320 has a float valve 322 that controls the supply of hydraulic fluid from the water mixer and chemicals (not shown) through line 324 in the event of replenishment of hydraulic fluid losses due to evaporation, or other causes. The liquid 318 is pumped by the operation of the storage motor / water pump via line 326 to an upper downflow tank 330 which is mounted on the crown plate 234 and which supplies hydraulic fluid under the action of gravitational force. An upper discharge conduit 334 is connected to the reservoir 330. The shut-off valve 332 on the conduit 334 is in the closed position in Figs. 9 and 10, and it is therefore possible to refill the reservoir 330 via the conduit 326 in this situation.

The hydraulic forming apparatus 220 comprises a reservoir 338 containing a hydraulic fluid, which is preferably oil. A single source of hydraulic power in the form of a high pressure hydraulic pump 340 draws hydraulic fluid 336 from line 342 and then pumps the fluid 336 through line 344 to a control valve assembly 346 containing a plurality of valves (1-8). Both valve # 2 and valve # 4 are shown in their closed position in FIG. After passing through the control valve assembly 346, fluid 336 returns via line 344 to the hydraulic reservoir 338, and in this situation the hydraulic pump and motor 340 can operate in free circulation.

As already mentioned, Fig. 10 shows the pressure piston 248 in an open or raised position in which the pressure piston 248 is held by the piston rod 240, the ram roller 238 and the roller backing ram 236. Open valve 1 keeps the piston rod in its raised position and the hydraulic fluid flows under pressure through line 348 to the pressure chamber 246 in the ram ram 238. While the upper press half 259 is in the raised position, the tubular parison may be positioned on the lower tool blocks 272 of the lower press half 260.

It can be seen from FIG. 11 that the level of the hydraulic forming fluid 350 in the tank 330 has increased compared to FIG. 10 as a result of the fluid being drawn over line 326.

If the hydraulic forming fluid 350 reaches the required level, a float valve 352 in the downflow reservoir 330 utilizing gravity to disengage the fluid may disengage the water pump and motor 328. Hydraulic valve 1 of control valve assembly 346 is a three-way shutoff valve hydraulic fluid and opens the pressure relief line 348. Opening valve number 1 also prevents build-up • ·

-18 hydraulic backpressure in chamber 246 during movement of the piston rod in a direction allowing flow of hydraulic fluid trapped in chamber 244 back through line 348 and drain to hydraulic reservoir 338. Valve number 2 opens flow in line 354 and allows a gradual increase in pressure in the upper chamber 244 of the ram roller 238 of the press. The piston rod 240 of the press plunger moves downward and puts the upper press half 258 into the position of tightly clamping the tubular blank T between the press halves 258 and 260. The hydraulic pressure is maintained in the press roller chamber 238 of the press ram throughout the hydraulic forming cycle. During the course of the process, a complete change of the shape of the tubular preform T is performed.

It can be seen in FIG. 12 that the tube end control mechanism 304 is actuated by opening valve number 7, which allows hydraulic fluid to flow through line 381 and gradually raise the duct in the tube end control chamber 314. As a result, the tube end control mechanism 304 moves to one end of the tubular blank T located within the closed press halves 258 and 260 to the extent that the end of the closed press assembly is sealed but remains some distance from the end The introduction of the tube end control mechanism 282 on the opposite side of the hydraulic forming apparatus is accomplished by opening valve number 4, which allows hydraulic fluid to flow through line 358 into the pressure chamber 286. This pushes the tube end control mechanism 282 inwards into closed end halves 258 and 260 and opposite ends of the sponge blank T. The tube end control mechanism 282 moves forward until its tapered tip section 288 contacts the inner diameter of the tubular blank T and seals the respective Then, the valve 332 located on top of the device opens and allows the hydraulic forming fluid 350 to flow through the reservoir 330 into the conduit 334 under the action of gravity. Hydraulic forming fluid flows into the closed press through the inlet opening 273 and fills the interior of the tubular parison T. Subsequently, the tube end control mechanism 304 moves inwardly and presses its conical tip tip 307 onto the tubular parison T and seals the interior of the tubular parison T.

The water pump and motor 360 suck hydraulic fluid from the top reservoir 330 utilizing gravity mesh to supply the fluid through line 362 and pump this liquid to the flexible line 364 and through the high pressure shut-off valve 366. Hydraulic Forming •

Liquid flows into the pressure chamber 306 from the shut-off valve 366. It should be noted that in another preferred embodiment, the pump and motor 360 are omitted and hydraulic forming fluid flows from the top reservoir 330 to the chamber 306 under the force of gravity. The fluid flows from the chamber 306 into the tube T under low flake conditions through the outlet passage 308 at the tip of the tube end control mechanism 304. The high pressure seal 301 prevents the mixing of the hydraulic forming fluid 350 supplied from the tank 330 with the hydraulic fluid 336 supplied from the tank 338. The hydraulic forming fluid flowing through the propeller passage 308 increases the pressure within the tubular parison T. with a liquid containing air bubbles and located within the tubular parison T through the opening 289 of the tube end control mechanism 282. This mixture of liquid and air flows through the inner chamber 290 into the flexible, interconnecting sections 370 and 371 of the high pressure hose. The hydraulic forming fluid then flows through the high pressure shut-off valve 372 and the duct 374 to the lower tank 320 containing the hydraulic forming fluid. Valve number 3 and valve number 8 of control valve assembly 346 are opened to prevent the possible build-up of hydraulic back pressure in the respective chambers 316 and 284 of the right and left side push cylinders.

It can be seen in FIG. 13 that the high-pressure shut-off valves 366 and 372 close after the expulsion of air from inside the tubular blank T. Opening valve number 5 allows the flow of hydraulic fluid under high pressure conditions via line 376 into pressure chamber 310. As a result, the piston rod 300 is pushed into the pressure chamber 306 and subsequently discharged hydraulic forming fluid through the passage 308 in the side piston rod 304 for controlling the end of the tube into the interior of the tubular parison T. Under the condition of closing the high-pressure shut-off valves 366 and 372, the pressure of the hydraulic forming fluid increases and begins to expand the walls of the tubular parison T outwardly toward the die cavity surfaces 264 and 270. Valve number 7 opens again and pressurizes chamber 314 to push the piston rod 304 to control the end of the pipe forward. This presses the tubular blank T into the press cavity 262. The opposite tube end control mechanism 282 moves forward upon reopening of valve number 4, thereby increasing the pressure in the chamber 286 that presses the tubular blank material through the tube end control mechanism 282. T into the press cavity 262. Pressing the ends of the tubular blank T into the press cavity 262 causes the metal material to rearrange inwardly, thereby maintaining

-20 wall thickness during expansion of the pipe. The wall thickness of the finished part preferably remains within ± 10% of the wall thickness of the original preform.

It can also be seen from Fig. 13 that the opposite piston rods 304 and 282 continue to push the tubular parison material T into the press cavity 262, while the front portion 303 of the piston rod 300 increases pressure further into the pressure chamber 306. This raises the Hook inside pressure chamber and extrudes additional hydraulic forming fluid into the interior of the tubular blank T through the passage 308 in the front tip section 307 of the main piston rod 304. The hydraulic forming fluid present in the tubular blank T reaches pressures greater than 50,000 psi (i.e. 344 75 MPa).

Referring to FIG. 14, the pressure boost piston rod 300 continues to move forward until the forming of the tubular parison T is complete with respect to the surfaces 264 and 270 of the hydraulic mold cavity under predetermined pressure conditions. The lateral pressing of the ends of the tubular blank T is maintained until the desired shape of the desired part 200 is reached. 14 shows the pressure chamber in a situation of reaching a predetermined pressure, which means completion of the hydraulic forming cycle.

Referring to FIG. 15, the pressure boost piston rod 300 is withdrawn due to the closure of valve number 5 and the opening of valve number 6, which admits hydraulic fluid to the front pressure boost chamber 312, thereby reducing the extremely high pressure of the hydraulic forming fluid in the tubular part. The opposite side end control mechanism 282 retracts due to the opening of valve number 3, which allows the pump 340 to increase the pressure in the conduit 378 and the chamber 284 of the pressure cylinder 274. As a result, the conical tip point 288 of the end control mechanism 282 Opening the three-way valve No. 4 reduces the pressure in line 358 and chamber 286 during withdrawal of the pipe end control mechanism 282, since it allows the hydraulic fluid from chamber 286 to be drained via line 344 to tank 338. The corresponding procedure also takes place at the opposite end of the tubular blank T when the valve number 8 is opened, which increases the pressure in the guide 380 and the chamber 316 of the cylinder 292. This results in pulling the piston rod 304 and subsequently moving away 282 to control the end of the tubing from the end of the tubular blank. trub Opening the three-way valve 7 decreases the pressure in chamber 314 and line 381 and allows the piston 304 to be withdrawn while the piston 304 is being withdrawn. 4

The removal of hydraulic fluid through line 344 to tank 338. Actuation of valve number 1 connects pump 340 to chamber 246 via line 348. The increase in pressure in chamber 246 results in retraction of the piston rod 240 of the press cylinder. The ram 248 Hsu is raised and opens the upper press half 258 thereby allowing the finished piece 200 (produced by hydraulic forming from the tubular blank T) to be removed. The fluid guiding valve 332 closes by gravity, allowing the hydraulic forming fluid to be pumped back into the upper liquid delivery tank 330 under the force of gravity in preparation for initiating the next hydraulic forming cycle.

Giant. Fig. 16 is a cross-sectional view in the longitudinal direction showing, on a larger scale, the same phase of the hydraulic forming cycle shown in Fig. 15. 16 shows more clearly the components of the press assembly 228. FIG. 15 and FIG. 16 show the opening of the press while showing the molded part 200.

It should be noted that the present invention includes such an embodiment in which the tube end control mechanism has only a single tube end control component while the opposite tube end control component is permanently stationary. This is different from the above-described embodiments in which the tube end control mechanisms utilize two moving parts that move towards each other.

Similarly, the pressure boosting mechanism can increase the fluid pressure from only one end or both ends of the tubular member.

The invention described above reduces the investment costs for purchasing hydraulic forming equipment up to one third of the total cost. It also reduces the cost of operation and maintenance.

While the present invention has been explained and described with reference to a limited number of embodiments, it should be understood that various changes and modifications can be made therein without departing from the spirit or scope of the invention. Accordingly, there is an intention to cover all such changes, modifications, and replacements with the following claims, including the above principles and advantages.

Claims (14)

PATENT CLAIMS Claims 1. An apparatus for hydroforming a tubular metal preform, comprising a press mechanism having an inner press surface defining a press cavity, wherein said press cavity is designed and arranged to receive the tubular metal preform, a source of hydraulic forming fluid, a hydraulically driven mechanism for actuating a pipe end which is designed and arranged to engage and seal the opposite ends of the tubular metal preform in said press cavity, wherein said pipe end control mechanism may be moved to longitudinally compress the tubular metal preform, wherein said pipe end control mechanism is designed and arranged to supply hydraulic forming fluid from said source of hydraulic forming fluid and having an outlet passage for supplying hydraulic forming fluid through to the hydraulic forming fluid is supplied to the interior of the tubular metal preform, a hydraulically operated pressure-boosting mechanism which in turn increases the pressure of the hydraulic forming fluid within the tubular metal preform by its movement capability and thereby expands the diameter of the preform until the outer surface of the tubular metal preform overall, it adopts the shape of said inner press surface, and a single source of hydraulic force that is designed and arranged to supply hydraulic fluid under pressure to said hydraulically operated pressure boosting mechanism and said hydraulically driven end-of-pipe mechanism, wherein said single hydraulic source providing said hydraulic fluid under pressure to said hydraulically operated pressure boosting mechanism to introduce said pressure boosting mechanism moving and thereby gradually increasing the pressure of the hydraulic fluid present in the interior of the tubular metal preform and expanding the diameter of the tubular metal preform until its outer surface adopts the shape of said inner press surface, and wherein said single source of hydraulic force supplies said hydraulic fluid under pressure to said a hydraulically driven pipe end control mechanism so that said pipe end control mechanism can be Move the longitudinally compressing the tubular metal preform and thereby rearrange the metal material of the tubular preform undergoing a diameter longitudinally inward to replenish the wall thickness of the tubular metal preform undergoing a diameter and maintain its wall thickness within a predetermined range. 2. The apparatus for hydroforming a tubular metal preform according to claim 1, wherein said hydraulically driven end-of-pipe mechanism comprises two movable end-of-mouth parts which are opposed on opposite sides of said pressing mechanism. The apparatus for hydroforming a tubular metal preform according to claim 2, wherein each of said end-of-mouth components has a longitudinal passageway therethrough, and wherein said pressure-boosting mechanism comprises two pressure-boosting components disposed opposite to each other. on opposite sides of said press mechanism, each of said pressure boosting components being respectively located in one of said passages formed in said pipe end controlling components and wherein each of said pressure boosting components defines a chamber for increasing the pressure in one of said passageways respectively wherein said pressure boosting chambers are in fluid communication with the interior of a tubular metal preform located in said press cavity by said calf passage for fluid flow when said tube end control components are in contact with opposite ends of the tubular metal blank so that the longitudinal inward movement of said pressure boosting components decreases the volume of each of said pressure boosting chambers and thereby increases the pressure of the hydraulic forming fluid contained therein a tubular metal preform and expands the diameter of said tubular metal preform until its outer surface adopts the shape of said inner press surface. 4. The apparatus for hydraulic forming of a tubular metal preform according to claim 1, wherein said pipe end control mechanism comprises two pipe end control components located opposite each other on opposite sides. Said pressing mechanism, wherein one of said pipe end controlling components has a longitudinal passage formed therein, and wherein said single pressure boosting mechanism comprises a single pressure boosting component disposed on one of said opposite sides of said pressing mechanism wherein said single flap-raising component is located in said longitudinal passage of one of the end-of-chest control components and wherein said single pressure-increasing component defines a chamber for increasing pressure in said longitudinal passage of one of the end-of-pipe components; the pressure increase is in fluid communication with the interior of the tubular metal preform located in said press cavity by said fluid delivery passageway of one of the tube end control components t Also, when said chest end control components are in contact with opposite ends of the tubular metal preform, so that the longitudinal inward movement of said single pressure boosting component decreases the volume of said pressure boosting chamber and thereby increases the pressure of the hydraulic forming fluid located within the tubular metal and expands the diameter of said tubular metal preform until its outer surface adopts the shape of said inner press surface. 5. The apparatus for hydraulic forming of a tubular metal preform according to claim 2, wherein said press mechanism comprises a movable upper press portion and a permanently stationary, lower press portion, wherein said upper press portion can move between a closed position in which cooperating with said lower press part defines said press cavity, and an open position in which it appropriately allows placing the tubular metal blank or removing the tubular metal blank from said lower press part, and that a single source of hydraulic power supplies said hydraulic fluid to said upper press part so that the upper press part can move between its closed and open positions. The apparatus for hydroforming a tubular metal preform according to claim 1, wherein said tube end control component comprises a tubular portion for controlling the end of a chest having an inner cavity and said mechanism for: ·· ··· The pressure build-up comprises a movable member that is disposed in said tubular member for controlling the end of the tube and which is movable with respect to said tubular member for controlling the end of the tube. 7. The apparatus for hydraulic forming of a tubular metal preform according to claim 1, wherein said source of hydraulic forming fluid is located higher than said mechanism for controlling the ends of the tube so that hydraulic forming fluid can flow into said mechanism for controlling the ends of the tube under force. gravitation. 8. The apparatus for hydroforming a tubular metal preform according to claim 2, wherein one of said end-of-pipe components comprises an internal cavity, and wherein said pressure-boosting mechanism comprises a movable member disposed in said one of said actuating components. pipe ends. 9. The apparatus for hydraulic forming of a tubular metal blank of claim 1, further comprising a valve assembly connecting said source of hydraulic forming fluid and said single source of hydraulic force to said pressure boosting mechanism and said pipe end controlling mechanism, the valve assembly controls the flow of hydraulic fluid by moving said end-of-pipe mechanism into pressurized contact with said opposite ends of said tubular metal preform and moving said pressure-boosting mechanism causing such pressure increase in said tubular metal preform which expands said tubular metal preform simultaneously maintaining the wall thickness of said metal preform within a predetermined range, wherein said valve assembly may be adjusted to control requesting the flow of said hydraulic fluid while moving said end-of-pipe mechanism from said opposite ends of the finished sponge metal blank and moving said pressure-raising mechanism as the pressure of said hydraulic forming fluid decreases upon completion of said hydraulic forming operation. -26 · 999 999 9 · 10. The apparatus for hydroforming a tubular metal preform according to claim 1, wherein said predetermined range is ± 10% of the wall thickness of the original tubular metal preform. An apparatus for hydroforming a tubular metal preform, comprising a press mechanism having an inner press surface defining a press cavity, the press cavity being designed and arranged to receive the tubular metal preform, a source of a hydraulic forming fluid located higher than said press cavity and being designed and arranged to supply hydraulic forming fluid to the interior of said tubular metal preform by force of gravity, a hydraulically driven tube end control mechanism designed and arranged to contact and totally seal opposite ends of the tubular metal preform in said press a cavity, wherein said mechanism for controlling the ends of the tube can move to lengthwise compress the tubular metal preform, and wherein said mechanism for controlling the ends of the tru It is designed and arranged to supply hydraulic forming fluid from said hydraulic forming fluid source and has an outlet passage for supplying hydraulic forming fluid through which the hydraulic forming fluid is introduced into the interior of the tubular metal preform, and a hydraulically actuated flap raising mechanism as disclosed. moving in response to an increase in pressure of the hydraulic forming fluid within the sponge metal preform, thereby expanding the diameter of the parison until the outer surface of the tubular metal preform has generally assumed the shape of said inner press surface, said hydraulically driven end-of-pipe mechanism moving in response to the pressure of the hydraulic fluid so that said end-of-pipe control mechanism can longitudinally compress the tubular metal preform and thereby perform rearranging the metal material of the tubular preform undergoing diameter expansion longitudinally inward to replenish the wall thickness of the tubular metal preform undergoing diameter expansion and keeping its wall thickness within a predetermined range. • · 4 444 ♦ ·· -Π 12. The apparatus for hydroforming a sponge metal blank according to claim 11, wherein said source of hydraulic forming fluid supplies said hydraulic fluid to a first path for filling the tubular metal blank before said pipe end control mechanism. contacting the opposite ends of said tubular metal preform, and wherein said source of hydraulic forming fluid supplies said hydraulic fluid to a second path different from said first path, to said pipe end control mechanism and through said outlet passage for delivering a hydraulic blank liquid into said tubular metal preform after said pipe end control mechanism has contacted opposite ends of said tubular metal preform. 13. The apparatus for hydroforming tubular metal preforms of claim 12 wherein said hydraulic forming fluid flows into said first path and said second path under the action of a force of gravity. 14. The apparatus for hydroforming tubular metal preforms of claim 13, wherein said second path comprises a pump for facilitating the flow of hydraulic forming fluid into said tube end control mechanism.