MXPA00000500A - Hydroforming of a tubular blank having an oval cross section and hydroforming apparatus - Google Patents

Abstract

The present invention relates to a method and apparatus for forming an elongated tubular metal member from a tubular metal blank. The method comprises:i) placing a tubular metal blank having a generally oval cross section into a die cavity and orienting the tubular metal blank such that a relatively larger cross-sectional dimension of the generally oval cross section extends generally in a direction of the relatively larger cross-sectional dimension of the die cavity and such that a relatively small cross-sectional dimension of the generally oval cross section extends generally in a direction of the relatively small cross-sectional dimension of the die cavity;ii) engaging and sealing opposite ends of the tubular metal blank;and iii) injecting fluid under pressure into the tubular metal blank so as to expand the tubular metal blank into conformity with the surfaces defining the die cavity and thereby transform the tubular metal blank into the elongated tubular metal member.

Description

HYDROFORMATION OF A PIECE IN TUBULAR TOSCO THAT HAS AN OVAL TRANSVERSE SECTION AND APPARATUS OF HYDROFORMATION Field of the Invention The present invention relates in general to hydroforming methods and die or die assemblies, and more particularly to a method of hydroforming and mounting die or die for hydroforming a piece in tubular metal coarse in a manner that avoids the need for Pre-grinding operation for the insertion of the blank in the die cavity.

Background of the Invention Hydroforming methods are already known as a means for forming a tubular metal coarse piece having a circular cross section in a tubular component having a predetermined desired configuration. In particular, a typical hydroforming operation involves the placement of a piece in tubular metal coarse having a circular cross-section within a cavity of the die or Ref.088892 matrix of a hydroforming assembly and providing a high pressure fluid in the interior of the blank to cause it to expand outwardly to conform to the surfaces that define the cavity of the die or die. More particularly, the opposite longitudinal ends of the tubular metal blank are sealed by hydraulic rams, and the high pressure hydroforming fluid is provided through an opening formed in one of the rams to expand the tubular blank. Typically, as described in US Pat. No. 5,561,902, the tubular blank having the circular cross section is formed in roll form from the metal sheet in its initial configuration. The roll-shaped tubular blank should then be placed in the cavity of the hydroforming die, which typically has a box-shaped, rectangular, or irregular cross-section. Because the circumference of a circular tubular blank that could easily fit into the cavity of the die or die is significantly less than the circumference or perimeter of the cross section of the surfaces defining the mold or die cavity, a Significant expansion of the blank piece may be necessary to shape the blank into the cavity of the die or die. Such significant expansion can cause a significant thinning of the wall, so that a blank with a substantial initial wall thickness could be required. In addition, if such significant expansion is required, it may become more difficult for the blank to conform at the corners within the cavity of the die or die. In order to minimize the amount of expansion required and to provide a tubular blank having a circumference that is initially more closely conformed to the perimeter of the cross section of the die or die cavity, it has been a conventional practice to provide a blank. coarse tubular having a diameter of circular cross-section that is greater than the width of the cavity of the die or die and crushing the tube diametrically in a pre-crushing station to enable the tube to be initially placed in the cavity of the relatively narrow die or die. The pre-crushing operation, however, is expensive because it requires dedicated machinery and is time consuming. U.S. Patent No. 5,170,557 discloses a method of forming a double wall outlet duct component having a truncated oval configuration. A piece in oval metallic coarse is placed in the cavity of the mold or die and is spaced from the surfaces of the die or internal matrix. The length of the perimeter of the blank is substantially less than the length of the perimeter of the surfaces of the internal die or die. Therefore, the tubular blank is subjected to substantial thinning during expansion. It is an object of the present invention, therefore, to eliminate the need for an expensive pre-crushing operation while using a tubular blank that better conforms to the contours of the cavity of the die or die. This object is achieved in accordance with the principles of the present invention by providing a method of forming an elongated tubular metal element. The method uses a die or die assembly having first and second die or die structures movable with each other between an open position and a closed position. The structures of the die or die define a cavity of the die or die having a quadrilateral cross section having a first cross sectional dimension which is larger than a second dimension of the cross section generally orthogonal thereto.The method comprises i) providing a tubular metal coarse piece having an oval cross section including a major axis along a larger diameter thereof and a minor axis along a smaller diameter thereof; Major and minor axes are generally orthogonal to each other, placing the piece in tubular metal coarse in the second die or die structure such that the major axis of the oval cross section thereof generally extends in the same direction as the first the cross-sectional dimension and the minor axis of the oval cross-section thereof extend generally in the same direction as the second dimension of the cross-section; ii) move the structures of the die or die to the closed position; iii) coupling the opposite ends of the tubular metal blank with the structures that couple the end of the tube so that they substantially seal the opposite ends of the tubular metal blank; iv) injecting fluid under pressure into the tubular metal coarse part to expand the tubular metal coarse part in accordance with the cavity of the die or die. The piece in tubular metal coarse has a diameter along the minor axis that approaches the second dimension of the cross section of the cavity of the die or die and a circumference conforming to the length of the perimeter of the section shape of the cavity of the die or die, thereby allowing the structures of the die or die to move to the closed position without distorting the oval cross-sectional configuration of the tubular metal blank placed therein. According to another aspect of the invention, the second structure of the die or die includes a fixed structure of the die or die, and a movable structure of the die or die. The lower structure of the movable die or die has an opening and the fixed structure of the die or die is received within the opening. The first structure of the die or die moves in engagement with the movable structure of the die or die to close the cavity of the die or die and then closes the cavity of the die or die, the movement of the movable structure of the die or die. die or die with respect to the fixed structure of the die or die progressively reduces the cross-sectional area of the cavity of the die or die. The method further comprises the step of progressively reducing the cross-sectional area of the mold or die cavity after the cavity of the mold or die is closed, thereby deforming the oval cross section of the tubular metal blank. inside the cavity of the die or die. An object according to the principles of the present invention is also achieved by an apparatus for forming a tubular metal blank into an elongated tubular metal element having a substantially box-shaped cross-section along an extension thereof. The apparatus comprises a die or die assembly comprising a structure of the movable upper die and a second die or die structure. The structures of the die or die cooperate to define a cavity of the die or die having a substantially quadrilateral surface configuration. The securing structures are placed on opposite ends of the cavity of the die or die and securely secure the portions spaced away from the tubular metal blank. The securing structures have securing surfaces that define a generally oval surface configuration, which generally conforms to a generally oval external peripheral surface of the tubular metal blank. The coupling structure of the end of the pipe coupling and substantially sealing the opposite ends of the tubular metal blank. The second structure of the die or die has a movable lower die structure or die and a fixed die or die structure. The structure of the movable lower die or die has an opening and the structure of the fixed die is received within the opening. Relative movement between the structure of the upper die or movable die in engagement with the second die or matrix structure closes the cavity of the die or die, and after it is closed, the movement of the movable upper die structure with respect to the structure of the fixed die or die progressively reduces the cross-sectional area of the cavity of the die or die to deform the cross section oval of the tubular metal coarse piece.

Brief Description of the Drawings Figure 1 is an exploded perspective view showing the structures of the upper and lower die or die of a die mounting or hydroforming die in accordance with the principles of the present invention; Figure 2 is a side plan view showing the longitudinal end of a hydroforming die or die assembly according to the present invention, with an oval tubular blank placed between the structure of the lower die or die and the structure of the die or upper die in the raised or open position; Figure 3 is a plan view similar to that of Figure 2 showing the mounting of the hydroforming die or die of the present invention with a tubular blank placed in the structure of the lower die or die and the structure of the upper die or die in a lowered or closed position; Figure 4 is a cross-sectional view through the middle pof the die or die assembly, and a tubular oval-shaped blank positioned within the structure of the lower die or die and the structure of the die or upper die in the raised or fully open position; Figure 5A is a longitudinal sectional view of the hydroforming die or die assembly, according to the present invention, showing the structure of the upper die or die in a fully elevated position, a tubular oval blank placed therein; of the structure of the lower die or die, and hydroforming cylinders seated sealingly at opposite ends of the oval tubular blank; Figure 5B is a longitudinal sectional view of the mounting of the hydroforming die or die, according to the present invention, showing the structure of the upper die or die in a totally reduced position, a tubular oval blank placed within the cavity of the die or die defined by the structures of the upper and lower die or die and the structure of the fixed die or die, and the fluid injected into the interior space of the tubular oval blank; Figure 6 is a sectional view showing the next step in the hydroforming process according to the present invention, wherein the structure of the upper die or die is in the fully lowered position and a tubular blank piece of oval shape placed within the structure of the lower die or die; Figure 7 is a sectional view showing the next hydroforming step wherein the structure of the upper die or die is in the fully lowered position and an oval shaped tubular blank that is to be hydroformed is slightly deformed or crushed by the relative movement of the structures of the die or die; and Figure 8 is a sectional view showing a subsequent hydroforming step in which fluid under pressure expands the tubular blank according to the cavity of the die or die.

Detailed description of the invention Generally shown in Figure 1 is a perspective view of a hydroforming die assembly generally indicated at 10 in accordance with the present invention. The hydroforming die assembly 10 includes first and second die or die structures. More pcularly, the first structure of the die or die comprises a structure 12 of the movable upper die or die, while the second structure of the die or die comprises a structure 14 of the movable lower die or die and a structure 16 of the fixed die or die. The die or die assembly further comprises a fixed base 18 on which the structure 16 of the fi xed die or die is mounted. A plurality of pneumatic or nitrogen driven spring cylinders 20 are mounted to the structure 14 of the lower die or die for movement on the fixed base 18. The structure 12 of the die or upper die, the structure 14 of the lower die or die, and the structure 16 of the fixed die or matrix cooperate to define a cavity of the longitudinal die or die therebetween, having a substantially box-shaped cross-section as will be described herein. . Preferably, the structure 12 of the upper die or die, the structure 14 of the lower die or die, the structure 16 of the fixed die or die, and the fixed base 18 are each made of a suitable steel material such as steel P-20. As shown in Figure 1, the structure 12 of the upper die or die defines a pair of support or support areas 22 at the longitudinal ends thereof. The support or support areas 22 are shaped and arranged to receive and accommodate the upper anchoring structures 26, at the opposite longitudinal ends of the structure of the upper die or die 12. Particularly, the securing structures 26 are each connected to each other. the structure 12 of the upper die or die in the respective bearing or support areas 22, by a plurality of pneumatically actuated springs 24 which allow relative vertical movement between the securing structures 26 and the structure 12 of the die or die higher. The structure 14 of the lower die or die has similar support or support areas 30 at the opposite longitudinal ends thereof which are constructed and arranged to accommodate the lower securing structures 28 in a similar manner. As shown, the longitudinal ends, indicated at 15, forming the support or bearing area 30 of the structure 14 of the lower die or die, have a generally U-shaped configuration. The lower securing structures 28 each have an upward facing surface 34 generally parabolic, arched. More particularly, each surface 34 has a cross-sectional configuration defining one half of an oval. The surfaces 34 are constructed and arranged to engage and support the underside of a tubular blank 40 (see Figure 2) having an oval cross-section and placed in the structure of the lower die or die. Each of the arcuate surfaces 34 of the lower securing structures 28 extends longitudinally inward toward the central portions of the mounting of the hydroforming die or die 10 when they have a gradual transition to a boxed U-shaped surface configuration or substantially rectangular 35. The two upper securing structures 26 are substantially identical to the lower securing structures 28 but are inverted with respect thereto. More particularly, each upper securing structure 26 has a generally parabolic, arcuate downward facing surface 36 which has a transition to an inverted box U-shaped surface configuration 37. The arcuate surfaces 36 each have a cross-sectional configuration that defines the other half of an oval. As shown in Figure 2, the arcuate surface 36 of each securing structure 26 cooperates with the arcuate surface 34 of the respective lower securing structures 28 to form an oval anchorage surface that captively seals and engages the ends of the tubular oval blank part 40 when the structure of the upper die or die 12 'is lowered initially. As can be seen from Figures 4 and 5A, the structure of the upper die or die 12 defines a longitudinal channel 38 having a substantially inverted U-shaped cross section. The channel 38 is defined by a longitudinally extending surface 44, generally horizontally facing downwardly, and a pair of longitudinally extending, longitudinally extending side surfaces 43 which extend parallel to each other from opposite sides. of the surface 44. The structure 14 of the lower die or die has a central opening 42 extending vertically therethrough, between the U-shaped longitudinal ends 15. The inner vertical surfaces 41 in the structure of the matrix or lower die 14 define the central opening 42 mentioned above. More particularly, a pair of longitudinally extending side surfaces 41 define the lateral ends of the opening 42. The surfaces are positioned vertically in a parallel facing relation to each other. The U-shaped end portions 15 of the structure of the lower die or die 14, define the longitudinal ends of the opening 42, and have interior surfaces (not shown) positioned vertically in a parallel facing relationship with each other. The fixed base 18 is in the form of a substantially rectangular metal plate. The structure 16 of the fixed die or die is fixed to an upper surface 46 of the fixed base 18. The structure 16 of the fixed die or die is an elongated structure which extends along a greater portion of the length of the upper surface 46 of the fixed base 18, generally along the transverse center of the fixed base 18. The structure 16 of the fixed die or die projects upwards from the fixed base 18 and has lateral surfaces 48 substantially vertical on the opposite longitudinal sides of the same. The structure 16 of the fixed die or die is constructed and arranged to extend within the aperture 42 in the structure of the lower die or die 14, with minimal spacing between the generally vertical surfaces 48 of the die structure or fixed die. and the vertical surfaces 41 of the structure 16 of the lower die or die. Similarly, there is a minimum spacing between the interior transverse side surface of the end portions 15 of the structure of the lower die or die 14 and the vertical end surfaces 49 of the structure of the fixed die or die 16. The structure of the fixed die or die 16, further includes a surface 50 of the horizontal, generally arcuate, facing upward and longitudinally extending die, which is constructed and arranged to extend in a spaced apart relationship with respect to the surface 44 of the die or longitudinally extending die of the structure 12 of the die or upper die. As can be seen better in Figure 6, the lateral surfaces 41 mentioned above, the facing surface 50, the lateral surfaces 43 and the surfaces 44 facing downwards, cooperate to provide a cavity 52 of the die or die, having a cross-sectional configuration with a generally rectangular shape from beginning to end of its longitudinal extension. This cavity of the mold or die will form a hydroformed part having a substantially closed box-shaped cross-sectional configuration. The closed box cross section configuration is preferably a quadrilateral, such as a generally rectangular configuration, but may be some other closed, continuous combination of flat and / or curved surface facets.

Figure 4 shows the structure of the upper die or die 12 in an open or raised position with respect to the structure 14 of the lower die or die and the fixed base 18. In this position the mounting of the hydroforming die or die 10 it makes it possible for the oval tubular blank piece 40 to be placed within the structure 14 of the lower die or die. It can be seen from Figure 5A that the oval tubular blank 40 to be hydroformed is suspended at opposite ends thereof by the lower securing structures 28 to extend slightly above the upper surface 50 of the structure 16 of the fixed die or die when the tubular blank 40 is first placed in the mounting of the hydroforming die or die 10. When the blank is placed in the structure 14 of the lower die or die, the opposite ends of the die blank 40 rest on the respective surfaces 34 of the lower securing structures 28 at the opposite ends of the structure 14 of the lower die or die. Preferably, the surfaces 34 are constructed and arranged to form an interference fit with the lower portion of the respective opposite ends of the tubular blank 4.

Subsequently, the structure of the upper die or die 12 is lowered so that the upper securing structures 26 which are initially maintained in the position extended by the pneumatic cylinders as shown in Figure 2, are lowered as shown in FIG. Figure 3 so that the surface 36 forms an interference fit with the upper portion of the respective opposite ends of the tubular blank 40. At this point, both opposite ends of the tubular blank are captured between the parts of the tubular blank. securing 26 and 28 before the structure 12 of the upper die or die is lowered to its closed position. According to the method and apparatus of the present invention, the tubular blank 40 is provided with an oval cross section configuration by a conventional roll or cylinder forming operation. More particularly, the metal sheet is rolled up until the longitudinal edges of the metal sheet come together to provide an oval configuration. The edges that are joined are then sealed by dots to complete the piece in tubular coarse. Providing a tubular blank having an oval cross section is advantageous in comparison with the conventional circular cross section because it provides a circumference that more closely conforms to the perimeter of the final cross section of the die cavity 52. or die with a generally rectangular cross section shape (not square). As shown in the cross section of Figure 4, the diameter of the oval tube 40 along its minor axis closely approximates the distance between the side surfaces 41 of the cavity of the die or die. Accordingly, a smaller expansion of the blank 40 is required when it is expanded in accordance with the forming cavity 52 of the surfaces. It will be appreciated by those skilled in the art that the narrower conformity of the tube 40 and the surfaces of the cavity allows the tube to be expanded more easily at the corners of the cavity 52, where expansion becomes more difficult due to contact surface increasingly friction between the outer surface of the tube and the surfaces of the cavity during the expansion of the tube 40. In conventional practice it has been possible to provide a tubular blank with a circular cross-section with a perimeter of the cross section that is shaped more closely to the cross-sectional perimeter of the cavity of the die or die providing a diameter of the circular cross-section that is greater than the width of the cavity 52 of the die or die and crushing the tube laterally in a pre-crushing station to make it possible for the tube to fit or fit into the structure of the lower die or die. Nevertheless, the pre-crushing operation is expensive because it requires dedicated machinery and consumes time. The use of a tubular blank makes it possible for the blank to fit or fit into the lower die or die assembly, while providing a sufficient amount of metal in the die or die cavity without the need for a pre-crushing operation. The tubular metal coarse piece 40 in the form of a roll or cylinder is to be hydroformed into an elongated tubular metal element (see reference number 76 in Figure 8) so as to have a cross sectional configuration such that it includes a first cross-sectional dimension (e.g., the distance between the horizontal walls of element 76 in Figure 8) which is greater than a second dimension of the cross section (e.g., the distance between the vertical walls of element 76 in the Figure 8) orthogonal to the first dimension of the cross section along a predetermined longitudinal extension thereof. This results from the fact that the first structure 12 of the die or die and the second structure 14, 16 of the die or die have cooperative surfaces that define a cavity 52 of the die or die having a first cross-sectional dimension (e.g. , a vertical dimension of a length between the surfaces 44 and 50) which is greater than a second dimension of the cross section (eg, a horizontal dimension of a relatively shorter length between the surfaces 41, or between the surfaces 43) generally orthogonal to the first dimension of the cross section. As is inherent with any oval, the oval cross section of the tubular blank includes a major axis along a larger diameter thereof and a minor axis along a smaller diameter thereof, the major and minor are generally orthogonal to each other. As shown in Figure 4, the tubular metal blank part 40 is placed in the second structure 14, 16 of the die or die. As also shown, the second structure 14, 16 of the die or die is constructed and arranged to receive the tubular metal blank 40 without distorting the tubular metal blank from its oval cross-section. As shown in Figure 6, the tubular metal blank piece 40 is placed in the second structure 14, 16 of the die or die in such a way that the major axis of the oval cross-section thereof extends generally therein. direction that the first dimension of the longest cross-section (extending for example between the surfaces 44 and 50) when the first structure 12 of the die or die and the second structure 14, 16 of the die or die cooperate to form the cavity 52 of the die or die, and such that the minor axis of the oval cross-section thereof extends generally in the same direction as the second shorter cross-sectional dimension (which extends for example between the opposing surfaces 41) of the cavity 52 of the die or die when the first and second structures of the die or die cooperate to form the cavity of the die or die. Now as can be seen in Figure 5A, the oval blank part 40 is held substantially rigidly instead of allowing the structures to be coupled to the end of the tube, such that the hydroforming rams or cylinders R, are telescopic inserts and sealing sealant at both opposite ends of the tube 40. The rams R preferably have an outer oval surface configuration that conforms to the inner peripheral surface of the blank 40. The hydroforming cylinders preferably pre-fill, but do not pressurize to any high grade oval rough piece 40, with hydraulic fluid (preferably water) as indicated by reference character F, before or simultaneously with the continuous descent of the structure 12 of the die or upper die. Although the pre-filling operation is preferred to reduce cycle times, and to achieve a more smoothly contoured part, for some applications the structure 12 of the die or upper die can be completely lowered before the fluid is internally provided to the piece of rough oval 40. As shown in Figure 4, the structure 12 of the upper die or die preferably includes a pair of spaced parallel projections 72 projecting down from opposite sides of the cavity 38 of the die or upper die and extending along the length of the structure 12 of the die. matrix or upper die When the structure 12 of the upper die or die is lowered, the projections 72 are brought into engagement with a surface 74 of the upper die or die, of the structure 14 of the lower die or die on the opposite sides of the opening 42 of the die. so as to close and seal the cavity 52 of the die or die as shown in Figure 6. The projections 72 form a sturdy seal that can withstand extremely large cavity pressures above 10,000 atmospheres. As can be seen from Figures 6 and 7, after the initial engagement of the projections 72 with the surface 74 of the die or die, the continuous movement of the structure 12 of the die or upper die down causes the structure 14 of the lower die or die is forced down with it against the force of the pneumatic spring cylinders 20. The rough oval piece 40 is likely to be moved downwardly with the cavity 52 of the die or die. During this continuous downward movement of the structure 12 of the upper die or die and the structure 14 of the lower die or die, the surface 44 of the die of the structure 12 of the die or upper die is moved towards the surface 50 of the die. matrix or die of the structure 16 of the fixed die or die to reduce the size of the cavity 52 of the die or die while maintaining a substantial peripheral seal in the cavity. This arrangement, wherein the cavity of the mold or die is closed and sealed before the size of the cavity 52 of the die or die is reduced to crush the tube in the die or die, prevents perforation of the tube, as can be seen of Patent Application Serial No. 08 / 915,910, incorporated herein by reference. The present invention contemplates, however, that some squashing of the tube may occur prior to the structure 12 of the upper die or die engaging the structure 14 of the lower die or die. When the lower portion of the oval blank 40 engages the surface 50 of the die or die, the continuous downward movement of the structures 12 and 14 of the die or die causes the oval blank 40 to deform. More specifically, when the surface 50 of the lower die or die 44 communicates with the portions of the upper and lower arcuate surface of the oval blank 40, the continuous downward movement of the die and die structures 12 and 14 cause that the surfaces 50 and 44 of the die or die move in toward each other. This forces the arcuate ends of the oval blank 40 to collapse and bend inward causing the oval blank 40 to be lightly ground. This light grinding of the oval blank part 40 is effected to provide a circumference that more closely conforms to the final cross section perimeter of the cavity 52 of the box-shaped die or die. The blank is preformed along its longitudinal extension as shown in Figure 5B. Because the oval blank 40 is preferably prefilled with the hydraulic fluid prior to grinding, the wrinkles in the tube resulting from the grinding are generally avoided and a contoured hydroformed portion can be formed in a generally smooth manner. As shown in Figure 8, with the structures 12 and 14 of the upper and lower die or die in a fully lowered position, the hydraulic fluid within the slightly crushed oval-shaped piece 40 is pressurized by the hydraulic system through the hydraulic system. one of the ends of the oval blank piece 40. During the hydroforming expansion of the oval blank piece 40, the fluid F is pressurized to a sufficient degree to expand the oval blank piece radially outwardly in accordance with the surfaces of the die or die that define the generally box-like cross section of the cavity 52 of the die or die . Preferably, the fluid pressure between approximately 2000 and 3500 atmospheres is used, and the blank is expanded to provide a hydroformed portion having a cross-sectional area which is approximately 10% or greater than that of the oval blank In addition, it is preferred that the longitudinal ends of the tube are pushed inwardly to each other to fill the thickness of the tube wall when it is expanded. It can be seen that by using a tubular, oval, roll-shaped blank for the hydroforming process, instead of a tubular cylindrical piece in the form of a roll, considerable savings are achieved due to the elimination of the step of crushed and the oval tube can be used through the hydroforming steps without any interruption in the process. This reduces the cycle time required because it eliminates the need for a pre-crushing step while providing a sufficient amount of the metal in the cavity of the die or die to form the blank in a desired final configuration. It should be appreciated that the present invention contemplates alternative embodiments wherein the cavity of the die or die can be closed before it is sealed. Stated another way, the cavity of the die or die can be complemented by having a cross section joined together by joining the surfaces, before the structure of the die or upper die makes contact with the structure of the lower die or die. In such an embodiment, for example, the structure of the upper die or die could be provided with a longitudinal projection instead of the channel 38. In addition, the longitudinal channel formed in the structure 14 of the lower die or die within which the part in coarse tubular metal could be deeper, makes it possible for a longitudinal projection to enter the channel and by means of this the cavity of the die or die is closed without the longitudinal projection making contact with the tubular metal coarse piece. The longitudinal projection may optionally after this make contact with the blank, either before or after the structure of the die or upper die makes contact with the structure of the die or lower die. It is also contemplated that the structure of the lower die or die may comprise a fixed unit structure, rather than a combination of a fixed and movable structure as shown. It should be appreciated that the foregoing detailed description and the accompanying drawings of the preferred embodiment are only illustrative in nature, and that the present invention includes all other embodiments that are within the scope of the described embodiment and the appended claims.

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

Having described the invention as above, property is claimed as contained in the following

Claims (10)

1. A method of forming an elongated tubular metal element, the method uses a die or die assembly having first and second die or die structures movable with each other between an open position and a closed position, wherein the structures of the matrix or die defining a mold or die cavity having a closed box-shaped cross-sectional configuration including at least four corners and having a first cross-sectional dimension which is larger than a second generally orthogonal cross-sectional dimension with with respect thereto, the method is characterized in that it comprises: providing a piece of tubular metal coarse that has been shaped into a roll to have an oval cross section, the oval cross section includes a major axis along a larger diameter of the same and a smaller axis along a smaller diameter thereof, the axes larger and smaller are generally orthogonal to each other, placing the piece in tubular metal coarse in the second structure of the die or die so that the major axis of the oval cross section thereof generally extends in the same direction as the first cross sectional dimension and the minor axis of the oval cross section thereof generally extends in the same direction as the second dimension of the cross section; moving the structures of the die or die to the closed position; coupling the opposite ends of the tubular metal blank with the structures that engage the end of the tube to substantially seal the opposite ends of the tubular metal blank; injecting the fluid under pressure into the tubular metal blank to expand the tubular metal blank according to the cavity of the die or die, characterized in that the tubular metal blank has a diameter along the minor axis that it approaches the second dimension of the cross section of the mold or die cavity.

2. The method according to claim 1, characterized in that the second structure of the die or die includes a fixed matrix or die structure, and a movable die structure or die, the structure of the movable lower die or die has a opening and the structure of the fixed die or die is received within the opening, and wherein the first structure of the die or die moves in engagement with the structure of the movable die or die to close the cavity of the die or die and after the cavity of the die or die is closed, the movement of the structure of the movable die or die relative to the structure of the fixed die or die progressively reduces the cross-sectional area of the die cavity or die and the method further comprises the step of progressively reducing the cross-sectional area of the cavity of the die or die after the cavity of the die or die. The die is closed to thereby deform the oval cross-section of the tubular metal blank within the cavity of the die or die.

3. The method according to claim 2, characterized in that the longest cross-sectional dimension of the quadrilateral-shaped cross-sectional configuration of the cavity of the mold or die extends in a generally vertical direction, wherein the dimension of the shorter cross-section of the quadrilateral-shaped cross-sectional configuration of the die or die cavity extends in a generally horizontal direction, and wherein the positioning step further includes: orienting the piece in tubular metal coarse within the cavity of the die or die in such a way that the major axis of the cross section thereof generally extends vertically, and in such a way that the minor axis of the cross section thereof generally extends horizontally.

4. The method according to claim 1, 2, or 3, characterized in that the injection causes the tubular metal blank to expand outwardly in accordance with the cavity of the die or die to provide the elongated tubular metal element formed with a substantially quadrilateral shaped cross section.

5. The method according to claim 4, characterized in that it also comprises; securing the spaced portions away from the tubular metal coarse part with securing structures placed over the opposite ends of the cavity of the die or die, the securing structures having the securing surfaces define substantially oval shaped surface configurations that conform to a Oval external peripheral surface of the tubular metal coarse piece.

6. The method according to claim 5, characterized in that it further comprises: longitudinally compressing the piece in tubular metal coarse to fill a thickness of the wall of the piece in tubular metal coarse when it is expanded.

7. The method according to claims 1 to 6, characterized in that the step of providing a piece in tubular metal coarse includes a step of forming the metal sheet in roll form so that it has an oval cross section.

8. An apparatus for forming a tubular metal blank into an elongated tubular metal element having a substantially box-shaped cross section along an extension thereof, the apparatus is characterized in that it comprises: a die or die assembly comprising a structure of the movable upper die or die, a second structure of the die or die; the structures of the die or die are cooperative to define a mold or die cavity having a closed box-shaped cross-sectional configuration including at least four corners; securing structures placed on the opposite ends of the cavity of the die or die and constructed and arranged to securely secure the portions spaced away from the piece of tubular metal coarse, the securing structures have securing surfaces defining a surface configuration generally oval which conforms to a generally oval external peripheral surface of the tubular metal blank; and a structure that engages the end of the tube, constructed and arranged to substantially engage and seal the opposite ends of the tubular metal blank, the coupling structure of the end of the tube has a generally oval external surface configuration that conforms to a surface generally oval internal peripheral of the tubular metal coarse part, characterized in that the second structure of the die or die comprises a structure of the movable lower die or die and a structure of the fixed die or die, the structure of the lower die or die movable has an opening and the structure of the fixed die or die is received within the opening, whereby the relative movement between the structure of the upper die or movable in engagement with the second structure of the die or die closes the cavity of the die or die, and after the mold or die cavity is closed, the movement of the structure of the movable upper die or die with respect to the structure of the fixed die or die progressively reduces the cross-sectional area of the cavity of the die or die.

9. The apparatus according to claim 8, characterized in that the structure of the movable lower die or die is mounted on a plurality of the compressible spring elements, and the movement of the structure of the upper die or movable die after the closure of the cavity of the die or die, moves the structure of the matrix or movable lower die with it against a deviation of the spring elements.

10. The apparatus according to claim 8 or 9, characterized in that the securing surfaces defining the generally oval surface configuration each have a transition to a boxed U-shaped surface configuration because the securing surfaces extend internally into the cavity of the container. the die or die. SUMMARY OF THE INVENTION The present invention relates to a method and apparatus for forming an elongated tubular metal element from a tubular metal blank. The method comprises: i) placing a tubular metal coarse piece having a generally oval cross-section within a cavity of the die or die and orienting the piece in tubular metal coarse in such a way that a relatively larger cross-sectional dimension of the generally oval cross-section generally extends in a direction of the relatively larger cross-sectional dimension of the cavity of the mold or die and such that a relatively small cross-sectional dimension of the general oval cross-section extends generally in an address of the relatively small cross-sectional dimension of the cavity of the die or die; ii) coupling and sealing the opposite ends of the piece in tubular metal coarse; and iii) injecting the fluid under pressure into the tubular metal coarse piece so that it expands the piece into tubular metal coarse in accordance with the surfaces defining the cavity of the die or die and whereby the piece is transformed into coarse metal tubular in the elongated tubular metal element.