U.S. patent application number 10/399192 was filed with the patent office on 2005-06-16 for apparatus and method for hydroforming a tubular part.
Invention is credited to Lee, Arthur L..
Application Number | 20050126243 10/399192 |
Document ID | / |
Family ID | 22910302 |
Filed Date | 2005-06-16 |
United States Patent
Application |
20050126243 |
Kind Code |
A1 |
Lee, Arthur L. |
June 16, 2005 |
Apparatus and method for hydroforming a tubular part
Abstract
A method and apparatus for shaping a raw tube into a formed
part. The part can be configured within a die assembly including a
hydroforming die structure and a pair of tube-engaging punches. The
punches are inserted into the ends of the raw tube to shape the
ends into the desired configuration. The middle portion of the raw
tube is shaped into the desired configuration by hydroforming.
Thus, the method and apparatus can shape the raw tube along its
entire length, leaving no remnants of the raw tube that must be
trimmed away.
Inventors: |
Lee, Arthur L.; (Aurora,
CA) |
Correspondence
Address: |
PILLSBURY WINTHROP SHAW PITTMAN, LLP
P.O. BOX 10500
MCLEAN
VA
22102
US
|
Family ID: |
22910302 |
Appl. No.: |
10/399192 |
Filed: |
March 22, 2004 |
PCT Filed: |
October 16, 2001 |
PCT NO: |
PCT/IB01/01946 |
Current U.S.
Class: |
72/61 |
Current CPC
Class: |
B21D 26/045
20130101 |
Class at
Publication: |
072/061 |
International
Class: |
B21D 026/02 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 19, 2000 |
US |
60241337 |
Claims
What is claimed:
1. A hydroforming die assembly 10 for hydroforming a part from a
tubular blank 40, said part having a desired configuration
different from a configuration of said blank and including a
desired cross section at one end thereof, said die assembly 10
including a die structure having interior surfaces defining a die
cavity 52, said die cavity 52 having a cross sectional
configuration conforming generally to the desired exterior shape of
said part, said die assembly 10 further comprising: a pair of
tube-end engaging structures 81 disposed at opposite ends of said
die cavity 52 and constructed and arranged to engage opposite ends
of said tubular blank 40, said tube-end engaging structures 81
being constructed and arranged to seal said opposite ends of said
tubular blank 40 and to pressurize hydroforming fluid within said
tubular blank 40 for expanding said tubular blank 40 into
conformity with said interior surfaces of said die cavity 52, a
first of said tube-end engaging structures 81 having an outer
cross-sectional configuration corresponding to said desired cross
section at said one end of said part, said first of said tube-end
engaging structures 81 being movable into forced engagement with
one end of said tubular blank 40 to conform said one end of said
tubular blank 40 to said outer cross-sectional configuration of
said first of said tube-engaging structures 81 and hence said
predetermined cross section at said one end of said part.
2. A hydroforming die assembly 10 according to claim 1, wherein
said first tube-end engaging structure 81 has an exterior surface
including a beveled portion 82 which is partially inserted into
said one end of said tubular blank 40, said first tube-end engaging
structure 81 being moved further into said one end of said tubular
blank 40 so as to cause inner surface portions of said one end of
said tubular blank 40 to slide in forced relation along said
beveled portion 82 and cause said one end of said tubular blank 40
to be deformed i) over said first tube-end engaging structure 81
and ii) into conformity with said exterior surface of said first
tube-end engaging structure 81, and wherein one end of said die
cavity 52 receives said first tube-engaging structure 81, said
interior surfaces of said die cavity 52 at said one end of said die
cavity 52 having a configuration conforming to an exterior surface
configuration of said part at said one end of said part.
3. A method of producing a hydroformed part using a hydroforming
die assembly 10 for hydroforming a part from a tubular blank 40,
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 10 including a die structure
having interior surfaces defining a die cavity 52, the die cavity
52 having a cross sectional configuration conforming to the desired
cross section of the part, the method comprising the steps of:
providing and a pair of tube-end engaging structures 81 disposed at
opposite ends of the die cavity 52 and constructed and arranged to
engage opposite ends of the tubular blank 40, the tube-end engaging
structures 81 being constructed and arranged to seal the opposite
ends of the tubular blank 40 and to pressurize hydroforming fluid
within the tubular blank 40 for expanding the tubular blank 40 into
conformity with the interior surfaces of the die cavity 52, a first
of the tube-end engaging structures 81 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 81 into forced engagement with one end of
the tubular blank 40 to conform the one end of said tubular blank
40 to the outer cross-sectional configuration of the first of the
tube-engaging structures 81 and hence the predetermined cross
section at the one end of the part; and applying pressure within
the tubular blank 40 to form the tubular blank 40 in to the desired
configuration of the part.
4. A method according to claim 3, further comprising the step of:
incorporating the part into a product without cutting off the one
end of the part formed by the forced engagement of the first of the
tube-engaging structures 81.
5. A assembly according to claim 1, wherein a first of said
tube-engaging structures 81 has a forward end 33 and a lateral
shoulder 88 protruding from a multifaceted portion 84 such that the
first of said tube engaging structures 81 can be inserted into said
tubular blank 40 continuously from the forward end 33 of said
tube-engaging structure to said lateral shoulder 88 along said
multifaceted portion 84 until said lateral shoulder 88 abuts said
tube-engaging structure 81 and halts further insertion of said
first of said tube-engaging structures 81 relative to said tubular
blank 40.
6. A method according to claim 3, wherein the moving of the first
of the tube-engaging structures 81 includes inserting the first of
the tube-engaging structures 81 into the tubular blank 40
continuously from a forward end 33 of the first of the
tube-engaging structures 81, along a multifaceted portion 84 of the
first of the tube-engaging structures 81, and to a lateral shoulder
88 of the first of the tube-engaging structures 81 that protrudes
from the multifaceted portion 84, until the lateral shoulder 88
abuts the end of tubular blank 40 and halts further insertion of
the tube-engaging structure 81 relative to the tubular blank
40.
7. A method according to claim 3, wherein the moving of the first
of the tube-engaging structures 81 into forced engagement with one
end of the tubular blank 40 is a complete insertion of the first of
the tube-engaging structures 81 into the tubular blank 40 and a
complete reconfiguration of the one end of the tubular blank 40
into the final, desired configuration of the part by fully forcing
the one end of the tubular blank 40 to conform to the outer surface
of the first of the tube-engaging structures 81 and to the inner
surface of the die cavity 52.
Description
[0001] 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.
FIELD OF THE INVENTION
[0002] 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.
BACKGROUND OF THE INVENTION
[0003] 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.
[0004] 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.
SUMMARY OF THE INVENTION
[0005] One object of the present invention is to provide an
improved apparatus and method for forming a hollow part.
[0006] 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.
[0007] 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.
[0008] 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.
[0009] 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.
[0010] Other objects, advantages, and features of the invention
will become apparent from the following detailed description,
appended drawings, and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] FIG. 1 is an exploded perspective view showing upper and
lower die structures and box-shaped punches of a hydroforming die
assembly in accordance with the principles of the present
invention;
[0012] FIG. 2 is a longitudinal section view of the hydroforming
die assembly along section line 1-1 in FIG. 1, and including a
tubular blank positioned within the lower die structure, the upper
die structure shown in the raised or fully open position, and
box-shaped punches engaging the ends of the tubular blank;
[0013] FIG. 3 is a longitudinal sectional view of the hydroforming
die assembly, similar to FIG. 2, but showing the upper die
structure in a fully lowered position, with the tubular blank
positioned within the lower die structure, the box-shaped punches
inserted into the ends of the tubular blank, and fluid injected
into the tubular blank;
[0014] FIG. 4 is a cross-section taken through section line 4-4 in
FIG. 3 and showing an unexpanded oval tubular blank disposed within
the hydroforming assembly and filled with hydroforming fluid;
[0015] FIG. 5 is a cross-section taken through line 5-5 in FIG. 9
showing the tubular blank expanded by fluid under pressure within
the expansion region of the cooperating upper and lower
hydroforming dies;
[0016] FIG. 6 is a partial perspective view, partially in
cross-section, of a box-shaped punch engaging a tubular blank;
[0017] FIG. 7 is a longitudinal sectional view taken through line
7-7 in FIG. 6 showing a box-shaped punch;
[0018] FIG. 8 is a cross-sectional view along section line 8-8 in
FIG. 9 showing the end of the tubular blank between upper and lower
clamping structures with a box-shaped punch inserted therein;
[0019] FIG. 9 is a longitudinal section view showing a hydroforming
step wherein the upper die structure is in the fully lowered
position and a tubular blank has been hydroformed into an expanded
configuration by fluid under pressure;
[0020] FIG. 10 is a longitudinal section view showing the use of
hydroforming ram extenders attached to punches to permit a
relatively short blank to be hydroformed in a relatively long
hydroforming die assembly; and
[0021] FIG. 11 is a longitudinal section view of a hydroforming die
assembly with a box-shaped punch and a round punch engaging
opposite ends of a tubular blank.
DETAILED DESCRIPTION OF THE DRAWINGS
[0022] Shown generally in FIG. 1 is an exploded perspective view of
a hydroforming die assembly generally indicated at 10 in accordance
with the present invention. The hydroforming die assembly 10
includes a movable upper die structure 12, a movable lower die
structure 14, a fixed die structure 16, and a fixed base 18 on
which the fixed die structure 16 is mounted. A plurality of
pneumatic or nitrogen spring cylinders 20 mount the lower die
structure 14 for movement on the fixed base 18. The upper die
structure 12, lower die structure 14, and fixed die structure 16
cooperate to define a longitudinal die cavity therebetween, having
a substantially boxed-shaped or multifaceted cross section as will
be described herein. Preferably, the upper die structure 12, lower
die structure 14, fixed die structure 16, and fixed base 18 are
each made of an appropriate steel material such as P-20 steel
and/or 2714 steel.
[0023] As shown in FIG. 1, the upper die structure 12 defines a
pair of cradle areas 22 at opposite longitudinal ends thereof. The
cradle areas 22 are shaped and arranged to receive and accommodate
upper clamping structures 26, at opposite longitudinal ends of the
upper die structure 12. Particularly, the clamping structures 26
are each connected to the upper die structure 12 at the respective
cradle areas 22, by a plurality of pneumatic or nitrogen spring
cylinders 24 which permit relative vertical movement between the
clamping structures 26 and the upper die structure 12.
[0024] 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.
[0025] 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.
[0026] 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.
[0027] As can be appreciated from, for example, FIGS. 2, 3, and 4,
the upper die structure 12 defines a longitudinal channel 38 having
a substantially inverted U-shaped cross section. The channel 38 is
defined by a downwardly facing, generally horizontal longitudinally
extending surface 44, and a pair of spaced, longitudinally
extending vertical side surfaces 43, which extend parallel to one
another from opposite sides of surface 44.
[0028] 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.
[0029] 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.
[0030] As can best be seen in FIGS. 4 and 5, the aforementioned
side surfaces 41, the upwardly facing surface 50, the side surfaces
43 and downwardly facing surface 44 cooperate to define a die
cavity 52, having a multifaceted cross sectional configuration
substantially throughout its longitudinal extent. The die cavity
surfaces define the desired shape of a part to be hydroformed from
a circular or oval blank tube.
[0031] FIG. 2 shows the upper die structure 12 in an opened or
raised position. In this position the hydroforming die assembly 10
enables the tubular blank 40 to be placed within the lower die
structure 14.
[0032] 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 FIG. 4 to effect a slight crushing of the tubular blank 40
before the blank 40 is expanded in the hydroforming operation, as
disclosed in U.S. Pat. No. 5,987,950 to Horton, which is
incorporated herein by reference. With the tubular blank 40
positioned between the closed upper die structure 12 and lower die
structure 14, hydroforming rams 80 having punches 81 attached to
mounting structures 90 are advanced from opposite sides of the
hydroforming die assembly 10 to engage opposite ends of the tubular
blank 40. As shown most clearly in FIGS. 6 and 7, each punch 81
includes an initial beveled portion 82 which transitions into a
multifaceted, here rectangular, portion 84. A base 86 forming a
lateral shoulder 88 is formed at one end of the multifaceted
portion 84 opposite the initial beveled portion 82.
[0033] 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.
[0034] In the embodiment shown, the beveled portion 82 is
preferably formed at an angle .theta. (see FIG. 7) of between about
13-17.degree., and most preferably, about 15.degree. with respect
to the sides of the box-shaped portion 84. The multifaceted portion
84 preferably has straight sides so as to have a perimeter that
defines a multifaceted shape, such as a polygon, square rectangle,
skewed parallelogram, etc. The perimeter shape of the box-shaped
portion 84 corresponds substantially to the shape of the clamping
surface formed by the upwardly facing surface 34 of the lower
clamping structure 28 and the downwardly facing surface 36 of the
upper clamping structure 26. Also, the size of the multifaceted
portion 84 is defined so as to provide a sealing interference fit
with the wall of the tubular blank 40, with the clamping surfaces
providing external support for blank 40.
[0035] 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 FIG. 2. With the forward end 83 of the punch 81 engaged with the
end of the blank 40, the hydroforming ram can be further advanced
under the force of hydraulic pressure, thus forcing the punch 81
into the end of the tubular blank 40 after the upper die structure
12 is lowered, as shown in FIG. 3. The beveled portion 82 of the
punch 81 gradually forms the end of the blank 40 until the
multifaceted portion 84 is fully inserted into the end of the blank
40. During this process, the end portions of blank 40 may be
stretched outwardly as they are conformed to the multifaceted
portion 84 and hence, the adjacent clamping surfaces 34, 36, as
best shown in FIGS. 3 and 8. The width of the lateral shoulder 88
is preferably substantially the same as the thickness of the
tubular blank 40 so that the outer surface of the tubular blank 40
transitions smoothly with the outer surfaces of the base 86 and the
holder 90.
[0036] 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.
[0037] 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.
[0038] 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.
[0039] As can be seen in FIG. 3, when the blank 40 is substantially
rigidly held in place between die structures 12 and 14 and the
hydroforming cylinders or rams 80 are telescopically and sealingly
inserted into both opposite ends of the blank 40, so that beveled
surfaces 82 engage the opposite edges of blank 40. The rams 80 are
forced inwardly to cause the opposing edges of blank 40 to ride
down surface 82 until it engages surface 88 and thus converts the
end portions of the blank into the exterior shape of portion 84 of
punch 81. The hydroforming cylinders then preferably pre-fill, but
do not pressurize to any large extent, the tubular blank 40 with
hydroforming fluid (preferably water) as indicated by reference
character F. The hydraulic fluid is injected through a channel 87
formed in one or both punches 81 which communicates with a channel
97 formed in the corresponding mounting structure 90. Although the
pre-filling operation is preferred to reduce cycle times, and to
achieve a more smoothly contoured part, for some applications the
upper die structure 12, may be fully lowered before any fluid is
provided internally to tubular blank 40.
[0040] 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 FIG. 6. Otherwise stated, the
portions 54 of the die cavity 52 define areas of the die cavity
which are used to expand the tubular blank 40 during the
hydroforming process only to the extent required to convert the
shape of the blank from a round or oval cross section to a
multifaceted (here rectangular) cross sectional configuration.
Because the end portions of the blank 40 fitted with punches 81 (as
illustrated in FIG. 6) will form the shape desired for the final
part to be hydroformed, and will not constitute an unexpanded
portion that must be cut off after the hydroforming process so that
the remaining uncut portions of the tube correspond to the desired
part, substantial scrap material is saved. Each unexpanded surface
portion 54 of the die structure defines a shape consistent with the
shape of the portions 84 and 86 of the punch 81.
[0041] 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 FIGS. 5 and 9). The tubular blank 40 is expanded into the
non-round, multifaceted (e.g., rectangular) of the die cavity 52.
If the hydroforming assembly includes a die cavity with an enlarged
portion 56, the blank 40 will be enlarged in that area. Because the
portions 54 of die cavity 52 define shapes that are consistent with
the shape of the multifaceted portion 84 of the punches 81, the
hydroformed member has a consistent shape out to its ends, and it
is not necessary to cut the end portions off. If a portion of the
blank is to be significantly enlarged in its cross-sectional
perimeter (e.g., greater than 5% relative to the original blank
perimeter), it may be preferred that the longitudinal ends of the
blank be pushed inwardly toward one another to replenish wall
thickness as the blank is expanded. If the blank is not to be
enlarged, but is only expanded into conformity with a multifaceted
die cavity, longitudinal movement of the ends during expansion of
the blank may not be necessary. More particulars on the preferred
hydroforming process are disclosed in U.S. Pat. No. 6,014,879 to
Jaekel et al., the disclosure of which is hereby incorporated by
reference.
[0042] 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 FIG. 11, in which the surrounding die
structures are not shown for clarity of the illustration. The
arrangement shown includes one hydroforming ram 80 having a
beveled, rectangular-shaped punch 81 and a rectangular-shaped
mounting structure 90, as shown and described previously. The
arrangement also includes a second hydroforming ram 100 that
includes a cylindrical base portion 112 and a smaller cylindrical
portion 102 with an insertion bevel 116 formed at the end. A
circular, annular sealing shoulder 114 that engages the end of the
tubular blank 40' is defined between base portion 112 and
cylindrical portion 102.
[0043] 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.
[0044] 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.
[0045] As shown in FIG. 10, one or more ram extenders 120 can be
installed between the punch 81 and the holder 90. The extenders 120
have a rectangular-shaped cross sectional configuration that
conforms with the rectangular-shaped cross sections of the mounting
structure 90 and the base 86 of the punch 81. Accordingly, the
hydroforming rams 80' can extend further into the relatively an
enlarged portions 54 of the die cavity 52 to accommodate
hydroforming of shorter tubular blanks 40' within the same die
cavity 52. Of course, the extended hydroforming blanks 80' cannot
extend to an enlarged area 56 of the hydroforming cavity 52 or the
seal between the end of the tubular blank 40' and the shoulder 88
of the punch 81 will be lost as the tubular blank expands into the
enlarged area 56.
[0046] 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.
[0047] 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.
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