The invention relates generally to an improved apparatus and method for more efficiently hydroforming a tubular part. More specifically, the invention relates to an apparatus and method that uses a punch to shape each end of the part into the desired configuration and hold the part during hydroforming.
Typically, to form a tubular part by hydroforming, a raw tube is positioned within a hydroforming tool and the tube is secured at its ends. The middle portion of the raw tube is then subjected to hydroforming, leaving a transitional zone between the ends of the raw tube and the hydroformed middle portion. The hydroformed part is then finished by having the two transition zones removed from the tube, leaving only the fully hydroformed middle portion. The ends of the tube can be secured by tip portions being generally wedge-shaped as disclosed in EP 1022073A1. Hydroforming is also disclosed in the U.S. Pat. Nos. 5,987,950 to Horton and U.S. Pat. No. 6,014,950 to Jaekel et al.
Removing the ends of the hydroformed part creates inefficiencies. For example, the cut away ends become wasted raw material. Also, cutting away ends requires additional cutting tools, which complicates the apparatus needed to create the finished part. Further, time is wasted performing the added step of cutting off the transitional zones at each end.
One object of the present invention is to provide an improved apparatus and method for forming a hollow part.
Another object of the present invention is to provide an improved apparatus and method for efficiently and cost effectively shaping a hollow part by mechanically shaping at least one end of the part and by hydroforming a portion of the part.
Still another object of the invention is to provide an apparatus and method for forming a part that uses a punch to secure each end of the part while the punch shapes the end so that each end has the same configuration as a hydroformed, middle portion.
The forgoing objects are basically attained by providing a hydroforming die assembly for hydroforming a part from a tubular blank, the part having a desired configuration different from a configuration of the blank and including a desired cross section at one end thereof, the die assembly comprising: a die structure having interior surfaces defining a die cavity, the die cavity having a cross sectional configuration conforming to the desired cross section of the part; and a pair of tube-end engaging structures disposed at opposite ends of the die cavity and constructed and arranged to engage opposite ends of the tubular blank, the tube-end engaging structures being constructed and arranged to seal the opposite ends of the tubular blank and to pressurize hydroforming fluid within the tubular blank for expanding the tubular blank into conformity with the interior surfaces of the die cavity, a first of the tube-end engaging structures having an outer cross-sectional configuration corresponding to the desired cross section at one end of the part, the first of the tube-engaging structures being movable into forced engagement with one end of the tubular blank to conform the one end of the tubular blank to the outer cross-sectional configuration of the first of the tube-engaging structures and hence the predetermined cross section at the one end of the part.
The forgoing objects are also attained by providing a method of forming a hydroformed part comprising the steps of: providing a hydroforming die assembly for hydroforming a part from a tubular blank, the part having a desired configuration different from a configuration of the blank and including a desired cross section at one end of the part, the die assembly including a die structure having interior surfaces defining a die cavity, the die cavity having a cross sectional configuration conforming to the desired cross section of the part, and a pair of tube-end engaging structures disposed at opposite ends of the die cavity and constructed and arranged to engage opposite ends of the tubular blank, the tube-end engaging structures being constructed and arranged to seal the opposite ends of the tubular blank and to pressurize hydroforming fluid within the tubular blank for expanding the tubular blank into conformity with the interior surfaces of the die cavity, a first of the tube-end engaging structures having an outer cross-sectional configuration corresponding to the desired cross section at one end of the part; moving the first of the tube-engaging structures into forced engagement with one end of the tubular blank to conform the one end of the tubular blank to the outer cross-sectional configuration of the first of the tube-engaging structures and hence the predetermined cross section at the one end of the part; and applying pressure within the tubular blank to form the tubular blank in to the desired configuration of the part.
Other objects, advantages, and features of the invention will become apparent from the following detailed description, appended drawings, and claims.
Shown generally in
As shown in
The lower die structure 14 has similar cradle areas 30 at opposite longitudinal ends thereof which are constructed and arranged to accommodate lower clamping structures 28 in a similar fashion. As shown, the longitudinal ends, indicated at 15, forming cradle area 30 of the lower die structure 14 have a generally U-shaped configuration.
The lower clamping structures 28 each have an upwardly facing surface 34 having a cross-sectional configuration that defines one-half of a multifaceted surface configuration. In the context of the present invention, the term multifaceted means square, rectangular, parallelepiped, polygonal, or any other closed, non-circular or oval configuration. In the illustrated embodiment, surface 34 defines one half of a rectangle.
In the embodiment shown, the upper two clamping structures 26 are substantially identical to the lower clamping structures 28 but are inverted with respect thereto. More particularly, each upper clamping structure 26, has a downwardly facing surface 36 having a cross-sectional configuration that defines a second half of the multifaceted (i.e., rectangular) surface configuration. The surface 36, of each clamping structure 26, cooperates with surface 34, of the respective lower clamping structures 28, to form a multifaceted clamping surface that captures end portions of a tubular blank 40 when the upper die structure 12 is lowered.
As can be appreciated from, for example,
The lower die structure 14 has a central opening 42 extending vertically therethrough, between the U-shaped longitudinal ends 15. The opening 42 receives fixed die structure 16. Interior vertical surfaces 41 in the lower die structure 14 define the aforementioned central opening 42. More particularly, a pair of longitudinally extending side surfaces 41, define the lateral extremities of the opening 42. The surfaces are vertically disposed in parallel facing relationship with one another. The U-shaped end portions 15 of the lower die structure 14 define the longitudinal extremities of the opening 42, and have interior surfaces (not shown) vertically disposed in parallel facing relation to one another.
The fixed base 18 is in the form of a substantially rectangular metal slab. The fixed die structure 16 is affixed to an upper surface 46 of the fixed base 18. The fixed die structure 16 is an elongate structure which extends along a major portion of the length of the upper surface 46 of the fixed base 18, generally along the center of the fixed base 18. The fixed die structure 16 projects upwardly from the fixed base 18 and has substantially vertical side surfaces 48 on opposite longitudinal sides thereof. The fixed die structure 16 is constructed and arranged to extend within the opening 42 in the lower die structure 14, with minimal clearance between the generally vertical side surfaces 48 of the fixed die structure and vertical surfaces 41 of the lower die structure 16. Similarly, there is minimal clearance between the interior transverse side surfaces (not shown) of end portions 15 of the lower die structure 14 and the vertical end surfaces 49 of the fixed die structure 16. The fixed die structure 16, further includes an upwardly facing, generally horizontal and longitudinally extending die surface 50, which is constructed and arranged to extend in spaced facing relation to the longitudinally extending, downwardly facing die surface 44 of the upper die structure 12.
As can best be seen in
After the blank 40 is placed in the lower die structure 14, the upper die structure 12 is lowered to form the die cavity 52. The die cavity may be ultimately smaller than what is illustrated in
The punch 81 is secured to the end of the mounting structure 90 by means of mechanical fasteners 92, such as bolts, extending through counter-bored apertures 94 formed in the punch 81 and into the holder 92. Base 86 preferably has a size and shape that is complementary to the size and shape of the mounting structure 90 so as to form a smooth, uniform transition between the punch 81 and the mounting structure 90.
In the embodiment shown, the beveled portion 82 is preferably formed at an angle θ (see
The forward end 83 of the punch 81 at the free end of the beveled portion 82 has dimensions that are smaller than the multifaceted portion 84, thus permitting the forward end 83 to be inserted into the unexpanded end of the tubular blank 40 as shown in
Thus, when the tube is formed over the punch to fit the finished tube shape it will not be necessary to remove the scrap portion of the blank, this eliminates the need for cut-off tooling, which saves money and time.
While the above description refers to only one punch, it should be appreciated that this discussion may apply to both punches 81 at opposite ends of the tube 40.
The tubular blank 40 may be round (circular cross section). Punches 81 have a similar height and width dimensions as the blank. The blank may be oval for punches that are rectangular or otherwise elongated along a height or width dimension. Hydroforming processes using oval tubular blanks are disclosed in U.S. Pat. No. 5,987,950, the disclosure of which is hereby incorporated by reference, as stated above. 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 conforms more closely to the final cross sectional perimeter of the generally box-shaped (not square) cross-sectional shaped die cavity 52. Thus, less expansion of the blank 40 is required when expanding the blank into conformity with the surfaces forming cavity 52. In addition, the closer conformity of blank 40 and cavity surfaces allows the blank to be more easily expanded into the corners of the cavity 52, where expansion becomes most difficult due to the increasing frictional surface contact between the exterior surface of the blank and cavity surfaces during expansion of the blank 40.
As can be seen in
End portions of the sealed die cavity 52 are generally rectangular in shape as defined by surface portions 54 having generally the same size and shape as the clamping surfaces 34, 36 of the clamping structures 28, 26, respectively. Thus, the portions 54 define areas of the die cavity which have a cross-sectional area that is the same as or only slightly larger than the area defined by the cross-sectional shape of the end portions of the tubular member 40 after the punches 81 have been forced into the ends of the tubular member as illustrated in
The cavity 52 may also include an enlarged portion 56 towards the longitudinally central portions thereof. With the upper die structure 12 closed with respect to the lower die structure 14 and with the punches 81 sealingly inserted into the ends of the blank 40, the fluid F can be pressurized to expand the tubular blank 40 into conformity with the surfaces defining die cavity 52 (see
In accordance with another embodiment, if a significant amount of perimeter expansion is required at one end of the tube part so that substantial wall thickness replenishment is required thereat, it is generally preferred to employ a circular or oval punch, as opposed to a multifaceted punch. This is because material flows more effectively and evenly toward the enlargement area from a rounded end than from a box-shaped end. Such a hydroforming configuration is shown in
At the end of the blank 40′ engaged by the multifaceted punch 81, the die structure (not shown) presents a surface configuration that forms the blank 40′ such that the cross sectional configuration at portion 110 of the blank is expanded only to the extent that the rounded cross section of the blank is converted to a multifaceted cross section. The portion 110 is joined by a gradually tapered segment 108 which extends to an enlarged rectangular-shaped cross sectional portion 106. Conversely, at the end of the blank 40′ engaged by the cylindrical punch 100, the die structure presents a surface configuration that forms a relatively short, non-enlarged cylindrical portion 105 of the blank. The blank then transitions from the rounded perimeter shape at 105 to the rectangular cross section at area 106. The cylindrical punch 100 allows for the relatively large expansion of enlarged area 106 and the abrupt transition region 104 because longitudinal pushing at the end of the tubular member 40′ is more effective for replenishing wall thickness if the punch is round. The cylindrical end portion of the formed member shaped by the cylindrical punch 100 would typically be cut off during a subsequent finishing operation.
The box-shaped end formed by the rectangular-shaped punch 81, on the other hand, can be tailored to the desired final member shape so the end need not be cut off.
As shown in
Thus, the present invention includes a hydroforming die assembly for hydroforming a part from a tubular blank comprising a die structure having interior surfaces defining a die cavity, the die cavity having a cross sectional configuration conforming to the predetermined cross section of the part, the part having a predetermined configuration different from a configuration of the blank and including a predetermined cross section at one end thereof.
It should be appreciated that the foregoing detailed description and accompanying drawings of the preferred embodiments are merely illustrative in nature, and that the present invention includes all other embodiments that are within the spirit and scope of the described embodiments and appended claims.
Number | Date | Country | Kind |
---|---|---|---|
60241337 | Oct 2000 | US | national |
This application claims the benefit of U.S. Provisional Application Ser. No. 60/241,337, filed on Oct. 19, 2000, the entire contents of which are incorporated herein by reference thereto.
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/IB01/01946 | 10/16/2001 | WO |