MXPA99009432A - High pressure hydroforming press - Google Patents

Abstract

Se describe un aparato para la hidroformación de un primordio metálico tubular que tiene una estructura de troquel (12), una fuente de fluido de hidroformación, una estructura (36) de acoplamiento al extremo del tubo, hidráulicamente accionada, una estructura (110) intensificadora de presión, hidráulicamente accionada, y una fuente de energía hidráulica simple (22). La estructura (36) de acoplamiento al extremo del tubo sella los extremos opuestos del primordio metálico tubular T en la cavidad del troquel, y es movible para comprimir longitudinalmente el primordio metálico tubular T. La estructura de acoplamiento al extremo del tubo recibe el fluido de hidroformación desde la fuente de fluido de hidroformación y tiene una salida de suministro del fluido de hidroformación a través de la cual puede ser proporcionado el fluido de hidroformación hacia el primordio metálico tubular. La estructura (110) intensificadora de presión, hidráulicamente accionada, es movible para presurizar el fluido de hidroformación proporcionado al interior del primordio metálico tubular, y con esto expandir un diámetro del primordio. Una fuente (22) de energía hidráulica simple proporciona el fluido hidráulico bajo presión a la estructura (110) intensificadora de presión, hidráulicamente accionada, con el fin de mover la estructura (110) intensificadora de presión, y con esto presurizar el fluido de hidroformación proporcionado al interior del primordio metálico tubular y expandir el diámetro del primordio metálico tubular, de modo que su superficieexterior se conforma a aquella de la superficie interna del troquel. La fuente de energía hidráulica simple (22) también proporciona el fluido hidráulico bajo presión a la estructura de acoplamiento al extremo del tubo, hidráulicamente accionada, para hacer posible que la estructura (36) de acoplamiento al extremo del tubo comprima longitudinalmente el primordio metálico tubular y provoque que el material metálico del primordio tubular diametralmente expandido fluya longitudinalmente hacia adentro, con el fin de volver a llenar un espesor de pared del primordio metálico tubular diametralmente expandido, y mantenga el espesor de pared del mismo dentro de un intervalo predeterminado.

Description

HIGH PRESSURE HYDROFORMING PRESS FIELD OF THE INVENTION The present invention relates to a hydroforming system that requires less capital investment to achieve hydroforming at high pressure of tubular parts. In particular, the present invention relates to a replacement for the conventional "separator" system, to provide high internal pressures within the tubular blank to be expanded.

BACKGROUND OF THE INVENTION Conventional hydroforming utilizes the low pressure hydroforming fluid (eg, gravity force) fed from a supply tank to supply the hydroforming fluid for rapid pre-filling of the tubular blank after the cavities of the die have been closed on the tube, but before the axial cylinders are coupled and the tubular primordium enters the cavity. As a result, it is necessary for a separate intensifier REF-: 31743 to push the tubular blank into the mold cavity.

BRIEF DESCRIPTION OF THE INVENTION The disadvantages of the prior art can be overcome by providing an apparatus that uses hydroforming fluid from a tank to supply a relatively smaller amount of water to intensify the pressure within the tubular blank after it is sealed, and is ready to be expanded. This smaller amount of water is supplied to a double-function cylinder used to push the tubular blank into the die cavity, as well as the intensification of fluid pressure within the die cavity from one side of the tool. By replacing the current sensors with a double-function cylinder that supplies the hydraulic thrust to the tubular blank and the internal fluid pressure for formation, the full cost of the equipment is substantially reduced. In accordance with the present invention, water is fed under relatively low pressure to the .. ^ - »sfc¿A« fe ^ mounts of gate assemblies or hydraulic lateral tool holders that are used to expand the tubular blank. The side toolholder mounts use the same hydraulic power source to exert the pressures that are required to expand the tube, as well as the pressure that is required to force the opposite ends of the tube in an inward direction to retain the desired wall thickness of the resulting product. In this way, separate intensifier is not required. The present invention also preferably uses the same source of hydraulic power to also apply the downward pressure to an upper die structure, when the upper die structure is in its defending position to oppose the internal pressure of the die cavity during the pressurization of the tube. A further object of the present invention is to provide an apparatus for the hydroforming of a tubular metallic blank comprising a die structure, a hydroforming fluid source, a hydraulically actuated coupling structure to the end of the tube, an intensifying structure of pressure, hydraulically driven, and a simple hydraulic power source. The coupling structure at the end of the tube seals opposite ends of the tubular metal blank in the die cavity, and is movable to longitudinally compress the tubular metal blank. The end tube coupling structure receives the hydroforming fluid from the hydroforming fluid source and has a supply outlet of the hydroforming fluid through which the hydroforming fluid can be provided to the tubular metal core. The hydraulically actuated pressure-intensifying structure is movable to pressurize the hydroforming fluid provided into the interior of the tubular metallic primordium, and with this expand a diameter of the primordium. A simple hydraulic power source provides the hydraulic fluid under pressure to the pressure-intensifying structure, hydraulically actuated, in order to move the pressure-intensifying structure and thereby pressurize the hydroforming fluid provided into the interior of the tubular metallic primordium and expanding the diameter of the tubular metallic blank so that its outer surface conforms to that of the inner surface of the die. The simple hydraulic power source also provides the hydraulic fluid under pressure to the hydraulically operated tubular end coupling structure to enable the coupling structure at the end of the tube to longitudinally compress the metallic tubular blanket and cause the metallic material of the tubular The diametrically expanded tubular blank flows longitudinally in an inward direction in order to fill a wall thickness of the diametrically expanded tubular metal blank and maintain the wall thickness thereof within a predetermined range. Still another object of the present invention is to provide an apparatus for the hydroforming of a tubular metallic blank comprising a die structure, a hydroforming fluid source, a hydraulically actuated coupling structure at the end of the tube, and an intensification structure of hydraulically actuated pressure. The die structure has an internal die surface that defines a die cavity. The die cavity is constructed and accommodated to receive the tubular metal blank. The hydroforming fluid source is positioned higher than the die cavity, and is constructed and accommodated to provide the hydroforming fluid internally to the tubular metallic core under the force of gravity. The hydraulically actuated coupling structure to the end of the tube engages and substantially seals the opposite ends of the tubular metal blank in the die cavity. The coupling structure to the tubular end is movable to longitudinally compress the tubular metal blank. The coupling structure at the end of the tube receives the hydroforming fluid from the hydroforming fluid source and has a hydroforming fluid supply outlet through which the hydroforming fluid can be provided into the tubular metal core. The hydraulically actuated pressure intensifying structure is movable in response to hydraulic fluid pressure, to pressurize the hydroforming fluid provided into the tubular metal blank, and thereby expand a diameter of primordium until an outer surface of the metallic primordium Tubular is generally shaped to that of the inner surface of the die. The hydraulically actuated coupling structure at the end of the tube is movable in response to the pressure of the hydraulic fluid, to enable the coupling structure at the end of the tube to longitudinally compress the tubular metal blank and cause the metallic material of the tubular blank The diametrically expanded fluid flows longitudinally inwardly in order to fill a wall thickness of the diametrically expanded tubular metal blank, and maintain the wall thickness thereof within a predetermined range. The resulting system is much less complex, less troublesome, and less expensive than conventionally known systems.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic view is a hydroforming press apparatus in accordance with the principles of the present invention; Figure 2 is a schematic view similar to that shown in Figure 1, but showing the coupling structures at the end of the tube moved in engagement with the opposite ends of the tube, to be hydroformed; Figure 3 is a schematic, cross-sectional view of the hydraulic side gate or tool assemblies and the die structure, in accordance with the present invention; Figure 4 is a view similar to that shown in Figure 3, but showing the coupling structures at the end of the tube moved in engagement with opposite ends of the tubular blank to be hydroformed; Figure 5 is a view similar to that shown in Figure 4, with the valve open to initiate pressurization of the tube to be hydroformed; Figure 6 is a view similar to that shown in Figure 5, but showing the initial estimate of the tube to be hydroformed, and with the upper die structure in a lowered position; Figure 7 is a view similar to that shown in Figure 6, but showing the complete expansion of the tubular blank and the inward movement of the hydraulic side gate assemblies to maintain the wall thickness of the part that is shape; Figure 8 shows the subsequent step to that of Figure 7, in which the outer gates are returned to their original position within the side gate assemblies after a hydroforming operation; Figure 9 is a schematic, enlarged partial view of a second embodiment of a hydroforming press apparatus according to the principles of the present invention, and showing the press in the open position; Figure 10 is a schematic view of the complete hydroforming press apparatus exemplified partially in Figure 9, and showing the press in the open position; A Figure 11 is a schematic view similar to that shown in Figure 10, but showing the downstream gate of the press and the closed die; Figure 12 is a schematic view similar to that shown in Figure 11, but showing the coupled side cylinders and the rapid filling initiated; Figure 13 is a schematic view similar to that shown in Figure 12, but showing the side cylinders pushing inward over the ends of the tubular blank, as the fluid is being pressurized; Figure 14 is a schematic view similar to that shown in Figure 13, but showing a hydroformed, expanded tube; Figure 15 is a schematic view similar to that shown in Figure 14, but showing the gate of the press up after completion of the hydroforming cycle; and Figure 16 is a longitudinal, enlarged sectional view, generally describing the die halves and the laterally positioned cylinders described in Figure 15.

DETAILED DESCRIPTION OF THE PREFERRED MODALITIES As shown in Figure 1, the hydroforming system 10 includes a hydroforming die structure 12, which includes an upper die portion 14 and a lower die portion 16. The lower die portion 16 is mounted on a rigid base 18. As can be seen from Figure 1, the upper die portion 14 is carried by an upper hydraulic toolholder or gate 20, which controls the vertical movement of the upper die portion 14. More particularly, the tool holder upper 20 is hydraulically actuated to allow the weight of die portion 14 to move upper die portion 14 vertically downwardly in cooperation with lower die portion 16 at the beginning of a hydroforming operation. further, after the upper die portion 14 is lowered, the upper tool holder 20 applies a downward hydraulic force to the portion of the upper punch 14, to maintain the portion of the upper punch 14 in cooperative relationship with the lower punch portion 16, during the high pressure conditions formed within the die cavity, between the upper and lower die portions 14, 16. A hydraulic pump assembly 22 is constructed and accommodated to provide hydraulic fluid under pressure to the upper tool holder 20 via the line of hydraulic fluid 24, to maintain the upper die portion 14 in cooperative relationship with the lower die portion, against the opposing force created by the high pressure conditions in the die cavity, as mentioned above. A servo valve 26 is positioned in the fluid line 24 to regulate the flow of fluid between the hydraulic pump assembly 22 and the upper tool holder 20. The hydraulic pump assembly 22 is also connected with a pair of tool holder assemblies, side 28 and 30 , positioned at opposite longitudinal ends of the die structure 12. The side tool holder mounts 28, 30 include respective tool holder housings 32 and 34, and the respective end tube coupling structures, 36 and 38. The structure 36 of coupling to the end of the tube projects outwardly from the housing 32 of the lateral tool holder, and the coupling structure 38 at the end of the tube projects outwardly from the housing 34 of the lateral tool holder. As shown in Figure 2, the structure 36 for coupling to the end of the tube is movable in an inward direction from the housing 32 of the tool holder, and in engagement and in sealing relationship with one end of a tube T carried by the portion of the tube. lower die 16. The coupling structure 38 at the end of the tube is movable inwardly from the housing 34 of the tool holder, and is constructed and accommodated to engage and seal the opposite end of the tube T. The coupling structure 36 at the end of the tube is will move inwardly and outwardly relative to the housing 32 of the tool holder, based on the hydraulic fluid provided to the mounting 28 of the side toolholder, by the hydraulic pump assembly 22 through three separate hydraulic fluid lines 40, 42 and 44, as shown. The servo valves 46, 48 and 50 are positioned in fluid lines 44, 42 and 40, respectively, to control the flow of fluid between the pump assembly 22 and the side tool holder assembly 28. In a similar manner, the side tool holder assembly 30 is connected to the hydraulic pump assembly 22 for controlled movement of the coupling structure 38 to the end of the tube. The side tool holder assembly 30 is connected to the hydraulic pump assembly 22 via three separate hydraulic fluid lines 52, 54 and 56, as shown. The servo valves 58, 60 and 62 are positioned within the fluid lines 50, 54 and 56, respectively, to control the flow of fluid between the pump assembly 22 and the side tool holder assembly 30. The hydroforming apparatus 10 further includes an upper water tank 80 constructed and accommodated to retain a prescribed amount of water. The water tank 80 is connected via the fluid line 82 to the coupling structure 36 to the end of the tube, of the side tool holder assembly 28. A servo valve 84 is positioned in the fluid line 82 and controls the flow of water within the coupling structure 36 at the end of the tube when it is coupled and sealed with the end of the tube T. The coupling structure 36 at the end of the tube The tube in turn supplies water to the inside of the tube T. The hydroforming apparatus 10 also includes a lower water tank 90, which is connected to the coupling structure 38 at the end of the tube, via the water line 92. A servo valve 94 placed on the water line 92 controls the flow of water from the coupling structure 38 to the end of the tube towards the end of the tube. lower tank 90. After the structures 36, 38 for coupling to the end of the tube are connected to the opposite ends of the tube T as shown in Figure 2, the valve 84 opens, and the water flows from the upper tank 80 , through the structure 36 of coupling to the end of the tube, through the tube T and in the coupling structure 38 to the end of the tube.

A drain line 96 is connected from the lower die portion 16 to the lower tank 90. After a hydroforming operation, a drain line 96 drains any water remaining in the lower die portion 16 within the lower tank 90. A Servovalve 98 is placed in the drain line 96 to control the flow of water to the lower tank 90. After a hydroforming operation, the water captured in the lower tank 90 is returned to the upper water tank 80 through the water line. return 100. A simple positive displacement water pump 102 is placed in the return line 100 to pump water from the lower tank 90 to the upper water tank 80, through the return line 100. A servo valve 104 is positioned on the return line 100 to regulate the flow of fluid from the lower tank 90 to the upper water tank 80. The hydroforming apparatus 10 is As will now be described in more detail in Figure 3. As shown, the tool holder housing 32 of the side tool-holder assembly 28 houses the coupling structure 36 at the end of the tube, and a pressure-enhancing structure 110. As shown, the coupling structure 36 at the end of the tube comprises a similar portion 112 and an end cap 114. More particularly, the main portion includes a tubular sleeve portion 116 and a flange portion 118 extending radially outward from the rear end of the sleeve portion 116. The outer peripheral edge 119 of the flange portion 118 is positioned in a slidably sealed relationship, with a cylindrical internal side surface 120, of the housing 32 of the tool holder. Similarly, an outer cylindrical surface 122 of the sleeve portion 116 is positioned in a sliding and sealed relationship with a cooperating surface 128, which generally defines an opening in the tool holder housing 32 through which the structure is projected. coupling to the end of the tube. The end cap 114 includes an annular flange portion 130 bolted and sealed by virtue of the appropriate fasteners 132 toward the circular distal end of the sleeve portion 116, which is positioned away from the tool holder housing 32. The end cap 114 further includes an elongated tubular portion 134, integrally formed with the flange portion 130 and extending axially in an outward direction with respect to the sleeve portion 116. The tubular portion 134 has an outer surface 136, in cylindrical general, which is constructed and accommodated to form a peripheral seal with a surface portion 138, upper, arcuate punch, of the upper punch portion 14, and a surface 140 of the lower, arcuate punch, of the lower punch portion 16, when the upper die portion 14 is closed. The end cap 114 terminates in a nozzle portion 144, which projects outwardly from the tubular portion 134. The nozzle portion 144 is substantially tubular in shape, and is of reduced external diameter as compared to the tubular portion. 134. A radially extending annular flange portion 146 is positioned at the transition between the tubular portion 134 and the nozzle portion 144. The flange portion 146 is constructed and accommodated to engage in sealed engagement with one end of a tube. T placed in the die structure 12 during a hydroforming operation. The nozzle portion 144 has a cylindrical outer surface 148 constructed and accommodated to be received within one end of the tube T. It may be preferable for the surface 148 to form an interference fit with the inner wall of the tube T at said end. An orifice or longitudinal internal diameter fl 150 extends through the end cap 114, and is constructed and arranged to communicate fluid from within the end tube coupling structure 36 to the inner confines of the tube T. The pressure relief structure 110 has a base portion 160 generally in disc shape having an annular outer periphery positioned in a slidably sealed relationship with the internal surface 120 of the tool holder housing 32. An intermediate, cylindrical, solid block portion 162 is integrally formed with the base portion 160 and decreased in diameter compared to the base portion 160. A solid, cylindrical front portion 164 is integrally formed with the intermediate portion 162 and is of decreased diameter compared to the intermediate portion 162. The front portion 164 is r-HW- »'extends from the intermediate block portion 162 into the inner confines of the sleeve portion 116 of the outer tool holder 36. The outer surface of the front portion 164 has a generally cylindrical outer surface positioned in a slidably sealed relationship with the cooperating, generally cylindrical, inner surface of the sleeve portion 116. At the transition between the leading portion 164 and the intermediate block portion 162 is an annular flange surface 168 that extends radially. The flange surface 168 serves as a back stop for the coupling structure 36 at the end of the tube. In Figure 3, the tube coupling structure 36 and the pressure relief structure 110 are shown in their most rearward positions within the housing 32 of the tool holder. It should be noted that the side tool holder assembly 30 is substantially identical to the side tool holder assembly 28, with the exception of the connections to the lower tank 90 for the tool holder assembly 30, versus the connection to the upper tank 80 for the tool holder assembly 28 Thus, in the figures, similar elements for the two tool holder assemblies 28 and 30 are given with the same reference numerals. The operation of the system will now be described. As shown in Figure 4, after the tube T is placed in the lower die structure 16, the servo valve 46 is opened and the hydraulic fluid under pressure from the hydraulic pump assembly 22 is provided through the line of fluid 44 within an intermediate chamber 170, generally between the flange portion 118 of the coupling structure 36 at the end of the tube and the base portion 160 of the pressure intensification structure 110, in the housing 32. S imilar , the servo valve 62 is opened so that the hydraulic pump assembly 22 can provide the hydraulic fluid through the fluid line 56 within the intermediate chamber 170 in the side tool holder assembly 30. When the fluid is provided to the side tool holder assemblies 28 and 30 in such a manner, the structures 36 and 38 of coupling to the end of the tube are moved in an inward direction towards each other, so that the flange portion 146 of each one is coupled and sealed with the opposite ends of the tube T. Next, as shown in Figure 5, the servo valve 84 is opened to allow the flow of water from the upper water tank 80 through the fluid line 82. within a pressure intensifying chamber 174 positioned within the confines of the coupling structure 36 at the end of the tube, between the innermost end of the pressure intensification structure 110 and the end cap 114. The fluid travels through the orifice 150 of the structure 36 coupling to the end of the tube, inside the tube T, and is subsequently communicated through the hole 150 in the tool holder 38, external, opposite inside the the front chamber 174 of the outer tool holder 38. During this filling process of the tube T, the servo valve 94 is initially opened and therefore allows the flow of fluid to the lower tank 90. With this fluid flow through the tube T, substantially all the air bubbles are purged from the tube T. Subsequently, the servo valve 94 is closed and the tube T is pressurized to a predetermined degree.

As shown in Figure 6, after the tube T is filled with the fluid, the upper die portion 14 is lowered onto the lower die portion 16 to form a closed die cavity 190, which preferably has a transverse shape. boxed, between these. By lowering the upper die portion 14, the servo-valve 84 connected to the coupling structure 36 at the end of the tube and the servo-valve 94 connected to the coupling structure 38 at the end of the tube is closed. Subsequently, the servo valves 48 and 60 are opened, and the hydraulic fluid under pressure is provided by the hydraulic pump assembly 22 through the hydraulic lines 42 and 54, to pressurize the rear chambers 194 positioned with rearward direction of the structures 110. of pressure intensification of the associated assemblies 28 and 30 of lateral tool holders. The fluid provided within the rear chambers 194 causes the movement of the pressure intensification structures 110, in an inward direction toward each other to displace the water within the pressure intensification chambers 174, through the outlets 150 of fluid supply and inside the tube T. As shown, the forced movement of the non-compressible water contained in the pressure intensification chambers 174 inside the tube T, causes an initial diametrical expansion of the tube T. As shown in Figure 7 , the pressure intensification structures 110 continue to be forced inwardly towards each other to displace the water in the pressure intensifying chambers 174 and also diametrically expand the T-tube. The servo valves 46 and 62 remain open to allow the fluid Pressurized hydraulic continues to flow from pump assembly 22 through hydraulic lines 44 and 56, for pressurizing the intermediate chambers 170 of the side tool holder assemblies 28 and 30. The fluid provided under pressure within the intermediate chambers 170 causes the structures 36 and 38 of coupling to the end of the tube to move longitudinally and in an inward direction towards each other, and against the opposite ends of the tube T. The movement of the external tool holders 36 and 38 thus causes the metallic material forming the T-tube (preferably steel) to flow along the length of the tube, so that the diameter of the tube can be expanded in some areas by 10% or more , while the wall thickness of the hydroformed tube T is preferably maintained within ± 10% of the wall thickness of the original tubular blank. More preferably, the fluid pressure between 2,000 and 3,500 atmospheres is used to expand the tube. Depending on the application, it may also be preferable to use pressures between 2,000 and 10,000 atmospheres, although even higher pressures may be used. After the tube T is formed in the desired shape, corresponding to the shape of the die cavity, the pump 22 stops pressurizing the fluid lines 42, 44, 54 and 56. Then the valves 50 and 58 are opened to allow the flow of hydraulic fluid under pressure from the hydraulic pump assembly 22 through the fluid lines 40 and 52. As a result, the hydraulic fluid is provided under pressure to return to the chambers 200 placed forward of the portion of tab 118 of the structures 36 and 38 coupling to the end of the tube, as shown. The pressurization of the return chambers 200 drives the coupling structures 36 and 38 to the end of the tube, with outward direction, inside the respective tool holder housings 32 and 34, to move the coupling structures 36 and 38 to the ends of the tube out of engagement with the opposite ends of the tube T, as shown in Figure 8. As the structures 36 and 38 of coupling to the end of the tube are driven outwardly into the housings 32 and 34 of the tool holder, the flanges 118 engage the flange surfaces 168 facing forward of the pressure intensification structures 110, and actuate the pressure intensification structures 110, with outward direction. Sooner or later the intensification of the pressure and the coupling structures at the end of the tube reach their original positions, as can be seen from a comparison between Figures 3 and 8. During this outward movement of the intensifying structures 110 pressure and the structures 36 and 38 coupling to the end of the tube, the valves 48, 46, 60 and 62 are opened to allow backflow of the hydraulic fluid inside jifera ..- jgsfafc- '. of a reservoir of hydraulic fluid contained in a hydraulic pump assembly 22. After the structures 36 and 38 of coupling to the end of the tube are decoupled with the opposite ends of the tube T, the water remaining in the coupling structures at the end of the tube and in the tube T, is drained through the drain line 96 beyond the open servo valve 98 and into the lower tank 90. The water contained in the lower tank 90 is recycled to the upper tank 80 through the line of return 100, when the water pump 102 is activated. Selling, since the side tool holder assemblies 28 and 30 of the present invention employ pressure intensification structures 110 within the coupling structures 36 and 38 at the end of the tube, there is no need to provide an intensifying system *. costly, separate, to provide high internal pressures to expand the tube Such intensifiers are normally required in high pressure hydroforming systems (eg, hydroforming systems using hydraulic expansion pressures greater than 2,000 atmospheres), and both have been particularly required in high pressure hydroforming operations in which the opposite ends of a tube are engaged and forced inward to effect the flow of the metallic material along the length of the tube, to refill or maintain the thickness of the tube wall during the expansion thereof. Sif icators have been used in conjunction with separate, lateral toolholder members that are used only to push the opposite ends of the tube inward to effect the above-mentioned flow of material. The present invention achieves the same desired function as a hydroforming system having the conventional intensifier, but is of lower cost. In the present invention, the water is fed under relatively low pressure, preferably by gravity (or a simple low pressure circulation pump), to the lateral tool holder assemblies. The side tool-holder assemblies then use the same hydraulic power source (for example hydraulic pump 22) to exert the pressures that are required to expand the tube, as well as the pressures that are required to force the opposite ends of the tube inwardly, to preserve the desired wall thickness. Yet another advantage of the present invention is the use of the same hydraulic pump 22, used as described above, to also apply the downward pressure to the upper punch portion 14, when the upper punch portion 14 is in its lowered position. . The hydraulic pump 22 effects a downward force on the upper die portion 14 to oppose the pressure of the internal cavity of the die during pressurization of the tube, and thereby retain the portion of the upper die 14 in the lowered position. In addition, the final system is less complex and less problematic than the conventional system. Referring now to Figures 9-16, an enlarged partial view of a second embodiment of a hydroforming system is generally indicated at 220, in accordance with the principles of the present invention. The preferred apparatus is comprised of five main assemblies: a frame assembly that generally provides the structural support and generally indicated at 222, a top press assembly generally indicated at 224, a lower press assembly generally indicated at 226, a hydroforming die structure in general ^ indicated at 228, and a hydraulic line assembly generally indicated at 230. With particular reference to FIG. ,9, the frame or frame assembly 222 includes a pair of side structural press members 232, described as elongated, laterally spaced, parallel vertical members, for mounting the upper press assembly fc 224 and the press assembly lower 228. The upper ends of the side structural members 232 have a crown plate 234 mounted through the upper portions thereof. The crown plate 234 serves as the support for the system parts of hydraulic fluid, which will be described later. The upper press assembly 224 is configured as follows. A cylindrical mounting plate 236 is secured at its ends to the side structural members 232 of the press. In general, centrally positioned on the cylinder mounting plate 236, there is a tool cylinder 238 having a piston rod 240 of the tool holder, which extends to through an opening 242 of the piston rod, vertically placed, on the plate 236 of the cylinder assembly. An upper portion of the piston rod 240 has an expanded outer diameter that allows the upper portion of the rod 240 to be placed in sealed sliding engagement with the inner surface of the cylinder 238. A space defined by the upper portion of the rod 240 of the piston and the inner surfaces of the cylinder • 238, define an upper pressure chamber 244. The The diameter of the piston rod below the upper end portion described is slightly reduced and defines a lower pressure chamber 246 between the cylindrical outer surface of the rod 240 and the inner surfaces of the cylinder 238. chamber 246 of lower pressure is defined in its • lower end by a radially inwardly extending portion of the base of the cylinder 238 and at its upper end by the lower annular surface of the upper portion of greater diameter of piston rod 240. Fixedly secured to the lower end of the rod 240 of the piston is a tool holder 248 under pressure. Pressurized tool holder 248 extends horizontally and does not cover much of the lateral space between the two structural members 232.

»,« B ^^. J ^ efi = as-.

The lower press assembly 226 includes a press bed 250, a right cantilevered beam 252 fixedly secured to the bed 250 of the press by a tie bolt 254, and a left cantilevered beam 256 securely secured to the bed 250 of the press, via of another tie bolt 254. The press bed 250 supports a lower die half 260 and provides a base for other assemblies. The lower ends of the side frame members 232 of the press are securely fixed to the bed 250 of the press near the opposite ends of the bed 250. Fixed securely to the lateral ends of the press bed and generally rising in the direction toward up and laterally out of the bed 250 are the right cantilever beam 252 and the left cantilever beam 256 that provide support for the cylinders 274 and 292 of the hydraulically actuated assemblies, which will be described later. With further reference to the hydroforming system 220 exemplified in Figure 9, the die structure 228 (which is enlarged in Figure 16) is comprised of an upper die half 258 and a lower die half 260. The cylinders 274 and 292 are mounted on ^ gs the aforementioned left and right cantilever beams. The die halves 258 and 260 have respective internal surfaces 264 and 270 that cooperate to define a die cavity 262 that defines the size and shape within which the tubular blank will be hydroformed. The upper portion of the upper die half 258 is fixed to the bottom of the press tool holder 248. The lower die half 260 is fixedly mounted on the bed 250 of the press. The lower die half 260 is of the same overall size and shape as the upper die half 258, but its internal die surface 264 is inverted relative to the surface 270 of the cavity of the lower die. Placed in the upper and lower die halves 258 and 260, there are the cavities for upper and lower tool or clamping or clamping structures 266 and 272 cooperating to roundly clamp the outer surface of the tubular blank T near each of its longitudinal ends, and thereby secure the tubular blank inside the die closed. A fluid inlet 273 is placed in one of the lower tool cavities and will be described in more detail below. Placed along the axis of the die cavity and the tool cavities 266 and 272, and mounted beyond the lateral structural press members 232 on the cantilevered beams 252 and 256, are a pair of hydraulically actuated assemblies 274 and 292. , aligned with the tubular shaft and directed towards the ends of the tubular blank T. One of the cylinders 274, mounted on the left cantilevered beam 256, is a lateral thrust cylinder. This cylinder 274 consists of a front member 276 and a rear member 278 which are secured to the upper surface of the left cantilevered beam 256, and a cylindrical wall member 280 secured between the front and rear members 276 and 278. The front member 276 it has a central opening which allows the sealed, sliding movement through it by a structure 282 for coupling to the end of the tube. The rear end 281 of the coupling structure 282 at the end of the tube is positioned inside the cylinder 274 and is of a diameter placed in sealed sliding relationship with the internal surface of the cylindrical wall member 280. The forward portions of the structure 282 of coupling at the end of the tube, they are smaller in diameter than the described rear end portion, creating a lateral cylindrical chamber 284 defined by the outer cylindrical lateral surfaces of the coupling structure 282 at the end of the tube, the cylindrical internal surface of the cylindrical wall member 280 , the annular inward face surface of the rear end 281 of the coupling structure 282 at the end of the tube, and the annular, rearward facing interior surface of the front member 276 of the cylinder 274. A rear pressurization chamber 286 is defined by the forward facing interior surface of the rear member 278 of the cylinder 274, the cylindrical wall member 280 and the rear surface of the rear end portion 281 of the coupling structure 282 at the end of the tube. These chambers 284 and 286 communicate with the hydraulic fluid lines, as will be discussed below. A front end portion of the coupling structure 282 at the end of the tube projecting beyond the front member 276 and the cylinder 274 is of slightly reduced diameter, and at the front end of this front portion of the piston rod is a portion of coupling to the tube in the form of a tapered nose section 288. The tapered nose section 288 is constructed and accommodated to be received within the open end of a T pipe blank that is to be hydroformed. The back portion of the tapered nose section 288 preferably has a radially outwardly extending annular flange (not shown) which bounds against the end edge of the tubular blank T to enable the nose section 288 to apply substantial force against the end of the tube in the longitudinal direction to the tube. A relatively thin perforation defining a fluid outlet 289 is formed through the nose section 288 and extends from an internal chamber 290 within the inwardly extending portion of the coupling structure 282 to the end of the tube, so as to communicating the fluid from the chamber 290 within the tubular blank T, when the nose section 288 is engaged in a sealed relationship with the end of the blank T. On the opposite side of the bed 250 of the hydroforming press and mounted securely to the upper part of the right cantilevered beam 252, is a double cylinder assembly 292, hydraulically actuated. The double cylinder assembly 292 has an inner wall 294 and an outer wall 296, securely fixed to the right cantilevered beam 252. A cylindrical wall member 298 is secured between the inner wall 294 and the outer wall 296 to define a chamber cylindrical Positioned within the interior of the double cylindrical assembly 292 is a hydraulically actuated pressure boosting structure 300, and a hydraulically actuated coupling structure 304 to the end of the tube. The hydraulically actuated pressure intensifying structure 300 has an outer end portion 299 positioned in sliding sealed relationship with an inner surface of the cylindrical wall member 298 and an inwardly extending portion 303 that has a relatively small diameter. The inwardly extending portion 303 of reduced diameter of the pressure build-up 300 passes in a sealed sliding relationship through an opening formed in an annular cylindrical divider 302 positioned approximately halfway along the longitudinal axis of the shaft of the cylindrical wall 298. The hydraulically actuated coupling structure 304 to the tube end within the double cylinder assembly 292 is tubular and positioned in the direction of the cylindrical divider 302. The coupling structure 304 at the end of the tube has a rear end portion 311 movable in a slidably sealed relationship with the inner surface of the cylindrical wall 298. A cylindrical sleeve portion 309, longitudinal, main, having a reduced diameter, extends in an inward direction through and moves in sealed sliding relationship with an opening formed in the inner wall 294. A portion of coupling to the end of the tube in the form of a portion tapered nose 307 is defined on the innermost end of the cylindrical sleeve portion 309. The nose portion has a configuration similar to the nose portion 288, as previously described. The portion 303 extending inward from the pressure-enhancing structure 300, with the high-pressure seals 301 secured to its innermost end, is slidably mounted within the cylindrical sleeve 309 of the tool-holder structure 304. Defined with direction inward of the high-pressure seals 301 of the pressure-building structure 300, and within the tool-holder structure 304, is an intensifier fluid chamber 306. The nose portion 307 has a relatively thin bore defining a fluid outlet 308 formed therethrough, extending in an inward direction from the intensifier chamber 306, and opening through an innermost portion of the tapered nose portion 307. , to enable the chamber 306 to communicate fluidly with the adjacent end of the tubular blank T. A pressurization chamber 310 is defined between the rear end portion 299 of the hydraulically actuated pressure-relief structure 300 and the exterior wall 296 of the double cylinder 292. A return chamber 312 is defined between the inwardly facing annular surface of the outer end portion 299 of the pressure intensification structure 300, and the outward facing surface of the cylindrical divider 302. A chamber 314 under pressure, from the coupling structure to the end of the tube, is formed between the face surface in the cylindrical divider 302 and the outward facing surface of the outer end portion 311 of the hydraulically actuated coupling structure 304 at the end of the tube. A return chamber 316 of the coupling structure at the end of the tube is defined around the cylindrical sleeve portion 309 of the coupling structure 304 at the end of the tube between the outer end portion 311 of the coupling structure 304 at the end of the tube. of the tool holder, and the inner wall 294 of the double cylinder assembly 292. These chambers have openings for the fluid lines, as will be described later. The hydroforming assembly 220 illustrated in Figures 9 to 16 includes a hydraulic line assembly 230 consisting of fluid lines, reservoirs, pumps and valves, as will be described in conjunction with the following operation description of the invention. Figures 9 and 10 show the assembly 228 of the hydroforming die in its open position. With particular reference to Figure 10, in the open position, the press tool holder 248 and the upper die half 258 are raised. The hydroforming fluid 318, which is a combination of tap water and chemicals, is stored in a lower tank filter tank 320. This tank 320 has a float valve 322 that is connected to a water / chemical mixer by means of line 324 provided for evaporation and another fluid loss constitution. Fluid 318 is pumped through line 326 by a tank / water pump motor 328 to a higher gravity feed tank 330, which is mounted on crown plate 234. A tank outlet line 334 upper is connected to tank 330. A total shut-off valve 332 on line 334 is in the closed position in Figures 9 and 10, allowing the upper feed tank by gravity 330 to be filled by means of line 326. The apparatus of hydroforming 220 includes a reservoir 338 of hydraulic fluid that stores the hydraulic fluid 336, preferably oil. A simple source of hydraulic power in the form of a high pressure hydraulic pump 340 pulls hydraulic fluid 336 through line 342, and then pumps fluid 336 through line 344 to a control valve assembly 346, comprised of a plurality of valves (1-8). Valves No. 2 to No. 8 are shown on your .s = AáSL- »closed position in Figure 10. After the fluid 336 passes through the control valve assembly 346, it returns to the hydraulic reservoir 338 through the line 344, allowing the hydraulic pump and 340 motor operate in a freewheel mode. As previously stated, in Figure 10, the press tool holder 248 is in the open or raised position and is supported by the rod 240 of the piston, the cylinder 238 of the tool holder and the mounting plate 236 of the cylinder. The rod 240 of the piston is held in its raised position by the valve No. 1 that opens and the hydraulic fluid 336 that is pumped through the line 348 into the pressurization chamber 246, inside the cylinder 238 of the press tool holder. . With half of the upper die 258 raised, the tubular blank T can be placed over the tool holes 272, lower of the lower die half 260. In Figure 11 it can be seen that the level of hydroforming fluid 350 in the tank 330 has been increased compared to Figure 10, as a result of the fluid being pumped through the 326 line. Sooner or later, the ,. * k £ AIBIA? , - "" * 3a * - float valve 352 in the upper gravity feed tank 330, turns off the water pump and the engine 328 when the hydroforming fluid 350 has reached its proper level. 1 of the control valve assembly 346 is a 3-way valve that closes to the hydraulic fluid flow and opens to depressurize the line 348. Also, the opening valve No. 1 prevents the hydraulic back pressure from being constituted within the chamber 246 during downward movement of piston rod 240 by allowing hydraulic fluid trapped in chamber 246 to be expelled through line 348 and again drained back to hydraulic reservoir 338. Valve No. 2 opens towards line 354 and makes it possible for pump 340 to pressurize the upper chamber 244 of cylinder 238 of the press tool holder.The piston rod 240 of the press tool holder moves in a downward direction and forces the upper punch half 258 to close to grasp or trap the tubular blank T between the die halves 258, 260. The hydraulic pressure in the chamber 244 of the press tool cylinder 238 is maintained for the entire cycle of hydroforming until the tubular primordium T is completely deformed. In Figure 12, the coupling structure 304 at the end of the toolholder tube is activated by the opening of the No. 7 valve to thereby allow the hydraulic fluid to pass inwardly through the line 381 and pressurize the chamber. 314 coupling pressure to the end of the tube. This moves the coupling structure 304 to the end of the tube towards one end of the tubular blank T within the die halves 258 and 260, closed to seal the end of the closed die assembly, while remaining separate from the end of the tubular blank T On the opposite side of the hydroforming system, the coupling structure 282 at the end of the tube is activated by the opening valve No. 4 to allow hydraulic fluid to flow through line 358 and into the pressurization chamber. 286. This forces the coupling structure 282 to the end of the tube, inwardly into the closed die halves 258 and 260, towards the opposite end of the tubular blank T. The coupling structure 282 at the end of the tube moves forwardly to coupling the inner diameter of the tubular blank T with the tapered nose section 288 thereof, and sealing the adjacent end of the tubular blank T. In the upper part At the end of the system, a valve 332 is opened and allows the hydroforming fluid 350 to flow rapidly through line 334 under gravitational force from the gravity tank 330. The hydroforming fluid enters the closed die through an inlet 273 and floods the interior of the tubular primordium Tinternally Subsequently, the coupling structure 304 at the end of the tube moves in an inward direction and the tapered nose portion 307 engages the tubular blank T to seal the hollow interior thereof. The pump and water motor 360 pulls the hydroforming fluid from the upper gravity tank 330 through the line 362, and pumps it through a flexible line 364 and a high pressure shutoff valve 366. The hydroforming fluid It travels inside the intensifying chamber 306 from the shut-off valve 366. It should be appreciated that in another preferred embodiment, the motor and pump 360 is omitted, and the hydroforming fluid travels from the tank 330 to the chamber 306 under the force of gravity. The fluid is forced at low pressure from the chamber 306 into the tube T through the fluid outlet 308 in the nose of the coupling structure 304 at the end of the tube. The high pressure seal 301 prevents the hydroforming fluid 350 from the tank 330 from mixing with the hydraulic fluid 336 from the tank 338. The hydroforming fluid which is forced through the fluid outlet 308, increases the pressure within the tubular blank T. This, in turn, evacuates or purges the air together with the fluid carrying air bubbles within the tubular blank T, through the opening 289 of the coupling structure 282 at the end of the tube. This mixture of fluid and air flows through the inner chamber 290 and into the flexible, high-pressure hose connection sections 370 and 371. The hydroforming fluid then passes through a high pressure shutoff valve 372 and into the lower reservoir 320 of the hydroforming fluid via line 374. Valves Nos. 3 and 8 of the control valve assembly 346 are opened to prevent that any hydraulic back pressure is constituted within the chambers 316 and 284 of the right and left lateral push cylinders, respectively. In Figure 13, the high pressure shutoff valves 366 and 372 close after the air has been evacuated from the interior of the tubular blank T. The valve No. 5 opens to allow the high pressure hydraulic fluid to travel through line 376 within the intensifier chamber 310. This forces the rod 300 of the intensifying piston to extend within the intensifying chamber 306, compressing the hydroforming fluid through the opening 308 in the rod 304. of the piston, lateral, which is coupled to the end of the tube, and inside the tubular primordium T. With the closing valves 366 and 372 at high pressure, closed, the pressure of the hydroforming fluid is increased and begins to force the walls of the primordium tubular T with outward direction, towards surfaces 264 and 270 of the die cavity. The valve No. 7 opens again to supply pressure to the chamber 314, to force forward the rod or rod 304 of the coupling piston to the end of the tube. This forces the material of the tubular blank T into the cavity of the die 262. The coupling structure 282 at the opposite end of the tube moves forward when the valve No. 4 again supplies the pressure to the chamber 286 and forces the structure 282 for coupling to the end of the tube to push the tubular blank material T into the cavity of the die 262. By forcing the ends of the tubular blank T into the cavity of the die 262 the metal material flow is created inwardly, so as to maintain the wall thickness of the tube as it is expanded. The wall thickness of the final part is preferably to remain within ± 10% of the wall thickness of the original blank. As can also be seen in Figure 13, the opposing piston rods 304 and 282 continue to force the tubular blank material into the die cavity 262, while the forward portion 303 of the rod 300 of the intensi fi er piston is further extends within the intensifying chamber 306. This increases the pressure inside the intensifying chamber 306., forcing more hydroforming fluid into the tubular blank T through the opening 308 in the front nose portion 307 of the main piston rod 304. The hydroforming fluid within the primordium S S.?, ^^? Ás .. tubular T reaches a pass greater than 3,515 kg / cm (50,000 psi). With reference to Figure 14, the rod or rod 300 of the intensifying piston continues to move forward until the tubular blank T is completely formed against the surfaces 264 and 270 of the hydroforming die cavity, through a preset pressure. The lateral thrust on the ends of the tubular blank T is maintained until the final shape of the desired part 200 has been reached. Figure 14 shows the intensifying chamber 306 which reaches its pre-set pressure, which means that the cycle of Hydroforming is complete. In Figure 15, the intensifying piston rod 300 is retracted by the closure of the No. 5 valve and the opening of the No. 6 valve which forces the hydraulic fluid into the forward intensifying chamber 312, removing the extreme high pressure. of the hydroforming fluid inside the tube part. The coupling structure 282, opposite, side, is retracted when the No. 3 valve opens, allowing the pump 340 to pressurize the line 378 and the chamber 284 of the push cylinder 274. This causes the tapered nose 288 of the coupling structure 282 at the end of the tube moves outwardly from the end of the tubular blank T. The three-way valve No. 4 opens to depressurize the lines 358 and the chamber 286 during the retraction of the structure 282 coupling to the end of the tube, to allow hydraulic fluid from chamber 286 to drain through line 344 into tank 338. Corresponding events occur at the opposite end of tubular blank T when valve No. 8 opens and pressurizes the line 380 and the chamber 316 of the cylinder 292. This causes the rod 304 of the piston to retract and remove the tapered surface 307 from the forward end of the rod 304 of the piston, from the end of the tubular blank T. The hydroforming fluid is then drained from the tubular blank T out of the die and into the tray 382 of press bed entrapment, where it is returned to the lower reservoir tank 320 through of drain line 374. The three way valve No. 7 is opened to allow chamber 314 and line 381 to depressurize and drain through line 344 into tank 338 during retraction of piston 304. Valve No. 1 is activated to connect pump 340 to chamber 246 along line 348. Chamber 246 is pressurized to retract rod 240 from the press tool cylinder. This raises the press tool holder 248 and opens the upper half of the die 258, allowing the finished part 200 (hydroformed from the tubular blank T) to be removed. The gravity feed valve 332 closes, allowing the hydroforming fluid to be pumped back into the upper gravity feed tank 330 to initiate the next hydroforming cycle. Figure 16 provides an enlarged longitudinal sectional view describing the hydroforming operational stage illustrated in Figure 15, and more clearly shows the parts of die assembly 228. In Figures 15 and 16, part 200 has been formed and the Die has been opened. It should be appreciated that the present invention contemplates that the coupling structure at the end of the tube may comprise only one component that forces the end of the tube, simple, with the opposite coupling component to the end of the tube, which is a fixed component. This is in contrast to the previously described embodiments, where the coupling structures at the end of the tube comprise two movable components that move towards each other. Similarly, the pressure enhancing structure can provide high pressure fluid from only one end or both ends of the tubular part. The invention described above reduces the initial cost to acquire the hydroforming equipment by as much as a third. It also reduces maintenance and operating costs. While the invention has been described and detailed with reference to a limited number of embodiments, it will be apparent that variations or modifications may be made therein without departing from the spirit and scope of the invention. Therefore, it is intended that the following claims cover all modifications, variations and equivalents thereof, in accordance with the principles and advantages noted herein.

It is noted that in relation to this date, the best method known to the applicant to carry out the aforementioned invention, is that which is clear from the present description of the invention.

Claims (14)

CLAIMS Having described the invention as above, the content of the following claims is claimed as property:

1. An apparatus for hydroforming a tubular metal blank, characterized in that it comprises: a die structure having an internal die surface defining a die cavity, the die pocket is constructed and accommodated to receive the tubular metal blank; a source of hydroforming fluid; a hydraulically actuated coupling structure to the end of the tube, constructed and accommodated to substantially engage and seal the opposite ends of the tubular metal blank in the die cavity, the coupling structure at the end of the tube is movable to longitudinally compress the tubular metal blank , the coupling structure at the end of the tube is constructed and accommodated to receive the hydroforming fluid from the hydroformation fluid source and has a supply outlet of the hydroforming fluid. hydroforming fluid through which the hydroforming fluid can be provided into the interior of the tubular metal blank; a hydraulically actuated, pressure-intensifying structure movable to pressurize the hydroforming fluid provided into the tubular metal blank, and thereby expand a diameter of the blank until an outer surface of the tubular metal blank generally conforms to that of the internal surface of the die; and a simple hydraulic power source, constructed and accommodated to supply pressurized hydraulic fluid to the hydraulically actuated pressure-intensifying structure and to the hydraulically operated pipe end coupling structure, said hydraulic power source providing the hydraulic fluid at pressure to the pressure intensifying structure, hydraulically driven, in order to move the pressure intensification structure and thereby pressurize the hydroforming fluid provided into the tubular metal blank and expand the diameter of the tubular metal blank, so that its outer surface conforms to that of the internal surface of the die, the simple hydraulic power source provides the hydraulic fluid under pressure to the coupling structure at the end of the tube, hydraulically driven, to make it possible for the coupling structure to e The end of the tube longitudinally compresses the tubular metal blank and causes the metallic material of the diametrically expanded tubular blank to flow longitudinally in the inward direction, in order to fill a wall thickness of the diametrically expanded tubular metal blank, and maintain the thickness of the wall of it within a predetermined interval.

2. An apparatus according to claim 1, characterized in that the hydraulically actuated tube end coupling structure comprises a pair of movable end coupling members of the tube, positioned on opposite sides of the die structure.

3. An apparatus according to claim 2, characterized in that the members of coupling to the end of the tube each have a longitudinal bore formed therein, and the pressure-enhancing structure comprises a pair of pressure intensifying members positioned on opposite sides of the die structure, each pressure intensifying member is mounted within an associated perforation of the coupling structures at the end of the tube, each of the pressure intensifying members defines a pressure intensifying chamber within those associated with the perforations, the pressure intensifying chambers in fluid communication with the interior of the tubular metal blank in the die cavity through the fluid support outlets when the coupling members at the end of the tube are coupled with the opposite ends of the tubular metal blank, such that the longitudinal inward movement of the pressure intensifying members reduces a volume of each of the pressure intensifying chambers, thereby pressurizing the hydroforming fluid provided into the interior of the tubular metallic blanket, and expanding the diameter of said tubular metallic blank so that its outer configuration conforms to that of the internal surface of the die.

4. An apparatus according to claim 1, characterized in that the coupling structure at the end of the tube comprises a pair of pipe coupling members positioned on opposite sides of the die structure, one of the coupling members at the end of the tube has a perforation or longitudinal orifice formed therein, the simple pressure-enhancing structure comprises a simple pressure-intensifying member placed on one of the opposite sides of the die structure, the simple pressure-intensifying member being mounted within the orifice longitudinally of one of the coupling members at the end of the tube, the simple pressure intensifying member defines a pressure intensifying chamber within the longitudinal hole of the coupling members at the end of the tube, the pressure measuring chamber. it is in fluid communication with the interior of the tubular metallic primordium in the die cavity, through a fluid supply outlet of one of the coupling members to the end of the tube, when the coupling members at the end of the tube are coupled to the opposite ends of the tubular metal blank, such that longitudinal movement inwardly of the simple pressure intensifying member reduces a volume of said pressure intensifying chamber, thereby pressurizing the hydroforming fluid provided to the interior of the tubular metallic blank and expanding the diameter of the tubular metallic blank, so that its outer configuration it conforms to that of the inner surface of the die.

5. An apparatus according to claim 2, characterized in that the die structure comprises a movable upper die portion and a fixed lower die portion, the upper die portion is movable between a closed position to define the die cavity with the portion of lower die, and an open position to allow respectively the tubular metal blank to be placed on and removed from the lower die portion, the simple hydraulic power source provides the hydraulic fluid to the upper die portion, in order to move the upper die portion between the closed and open positions thereof.

6. An apparatus according to claim 1, characterized in that the coupling structure at the end of the tube comprises a tubular coupling member at the end of the tube having an internal cavity, and wherein the pressure intensifying structure comprises a movable member positioned in and movable with respect to the tubular coupling member at the end of the tube.

7. An apparatus according to claim 1, characterized in that the source of hydroforming fluid is placed higher than the coupling structure at the end of the tube, such that the hydroforming fluid is provided to the coupling structure at the end of the tube, under the force of gravity.

8. An apparatus according to claim 2, characterized in that one of the coupling members at the end of the tube comprises an internal cavity, and wherein the pressure-enhancing structure comprises a movable member positioned within one of the end-coupling members. of the tube.

9. An apparatus according to claim 1, characterized in that it further comprises a valve assembly communicating with the hydroforming fluid source and the simple hydraulic power source with the pressure intensifying structure and the coupling structure at the end of the tube. , said valve assembly directs the hydraulic fluid to move the coupling structure to the end of the tube in compression with the opposite ends of the tubular metal blank, and move the pressure intensifying structure to pressurize the hydroforming fluid into the tubular metal blank, to expand said tubular metal blank while maintaining the wall thickness of the tubular metal blank within the predetermined range, the valve assembly is adjustable to direct the hydraulic fluid to move the coupling structure to the end of the tube away from the opposite ends of the tubular metallic blank, and to move the pressure intensifying structure to depressurize the hydroforming fluid after the hydroforming operation.

10. An apparatus according to claim 1, characterized in that the predetermined range is ± 10% of the wall thickness of an original tubular metal blank.

11. An apparatus for hydroforming a tubular metal blank, characterized in that it comprises: a die structure having an internal die surface defining a die cavity, the die pocket is constructed and accommodated to receive the tubular metal blank; a source of hydroforming fluid positioned higher than the die cavity, and constructed and accommodated to provide the hydroforming fluid internally to the tubular metallic core, under the force of gravity; a hydraulically actuated coupling structure to the end of the tube, constructed and accommodated to substantially engage and seal the opposite ends of the tubular metal blank in j¿a £ -e ^. The die cavity, the coupling structure at the end of the tube is movable to longitudinally compress the tubular metal blank, the coupling structure at the end of the tube is constructed and accommodated to receive the hydroforming fluid from the source of hydroforming fluid, and having a supply outlet of the hydroforming fluid, through which the hydroforming fluid can be provided to an inner part of the tubular metal blank; and a pressure-intensifying, hydraulically actuated structure, movable in response to hydraulic fluid pressure, to pressurize the hydroforming fluid provided into the tubular metal blank, and thereby expand a diameter of the blank until an outer surface of the metallic blank In general, tubular conforms to that of the internal surface of the die, the structure of coupling to the end of the tube, hydraulically driven, is movable in response to hydraulic fluid pressure, to make it possible for the coupling structure at the end of the tube to compress longitudinally the tubular metallic blank and cause the metallic material of the diametrically expanded tubular blank to flow longitudinally inward in order to refill a wall thickness of the diametrically expanded tubular metal blank, and maintain the wall thickness thereof within a predetermined interval or.

12. An apparatus according to claim 11, characterized in that the source of hydroforming fluid provides the hydroforming fluid through a first way to fill the tubular metal blank, before coupling the coupling structure to the end of the tube, with the opposite ends of the tubular metallic blank, and wherein the hydroforming fluid source provides the hydroforming fluid through a second path or path different from the first path or path to the coupling structure at the end of the tube, and through the fluid supply outlet within the tubular metal blank, after the coupling structure at the end of the tube engages the opposite ends of the tubular metal blank.

The apparatus according to claim 12, characterized in that the hydroforming fluid is forced through a first path and through the second path under the force of gravity.

14. An apparatus according to claim 13, characterized in that the second way comprises a pump for facilitating the flow of the hydroforming fluid towards the coupling structure at the end of the tube. i ^ ¡^^^ = ¡^^^^^^^^^ ¡¡¡¡¡SUMMARY OF THE INVENTION Disclosed is an apparatus for hydroforming a tubular metal blank having a die structure (12), a hydroforming fluid source, a hydraulically actuated linkage structure (36) to the tube end, an intensified structure (110) pressure grinder, hydraulically driven, and a simple hydraulic power source (22). The coupling structure (36) at the end of the tube seals the opposite ends of the tubular metal blank T in the die cavity, and is movable to longitudinally compress the tubular metal blank T. The coupling structure at the end of the tube receives the fluid from the tube. hydroforming from the hydroforming fluid source and having a hydroforming fluid supply outlet through which the hydroforming fluid can be provided to the tubular metallic core. The hydraulically actuated pressure-enhancing structure 110 is movable to provide the hydroforming fluid provided within the tubular metal blank, and thereby expand a diameter of the blank. A simple hydraulic power source (22) provides the hydraulic fluid under pressure to the hydraulically actuated pressure intensifier structure (110) in order to move the pressure intensifier structure (110) and thereby pressurize the hydroforming fluid provided inside the tubular metal blank and expanding the diameter of the tubular metal blank, so that its outer surface conforms to that of the inner surface of the die. The simple hydraulic power source (22) also provides the hydraulic fluid under pressure to the hydraulically actuated coupling structure at the end of the tube, to enable the coupling structure (36) at the end of the tube to longitudinally compress the tubular metallic primordium. and causing the metallic material of the diametrically expanded tubular blank to flow longitudinally inward, in order to refill a wall thickness of the diametrically expanded tubular metal blank, and maintain the wall thickness thereof within a predetermined range.