Note: Descriptions are shown in the official language in which they were submitted.
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T1TLE: APPARATUS AND METHOD FOR FORNIING SHAPED PARTS
BACKGROUND OF THE INVENTION
(00011 The present invention relates generally to the 6eld of forming tubular
members into
shaped parts using hydraulic pressure and, more particularly, to a method and
apparatus for
forming from a tube a shaped part having at least one bend and a substantially
larger cross
section in at least a portion of the tube between the bend or bends and an end
or ends of the
tube,
[0002] Prior art discloses shaping, for example, metal tubes using hydraulic
presses, For
instance, U.S. Patent No. 2,892,254 to Garvin ("the Garvin Patent") discloses
a hydraulic
press for shaping metal parts. Hydraulic presses such as that disclosed by the
Garvin Patent
generall), have two opposing dies that close to form a cavity. The cavity
defines the desired
resultant shape of the part. To form a shaped part, a tube is placed in the
cavity between the
,lies of a hydraulic press. The dies close and the ends of the tube are
sealed. The tube is
filled with liquid which is then pressurized to expand the tube until it
conforms to the shape
of the cavity defined by the dies of the hydraulic press. In this manner, the
tube is expanded
to form the desired shaped part. It has been found that the expansion of a
tube is limited
because as the tube is expanded the wall thickness of the expanded portion is
progressively
thimied. In practice, it has been found that the cross section of a tube
cannot be expanded by
more than about twenty percent.
[0003] The problem of limited expansion has been overcome by feeding
additional tube
material from both ends into the expanding portion during the expansion
process. For
,xample, U.S. Patent No. 5,481,892 to Roper et al. ("the Roper Patent")
discloses feeding
additional tube material into expansion portions from both ends of a tube. The
system and
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method of the Roper Patent discloses that the cross section of the tube can be
expanded by as
much as one-hundred percent. Although, according to the systeni and method of
the Roper
Patent, frictional constraints typically limit expansion of the cross section
to fifty percent.
100041 One disadvantage of the system and method disclosed by the Roper Patent
is that it is
not possible to feed additional tube material into the expanding portion past
a bend or bends
in the tube when the ends of the tube are in an upright position.
[0005] Some prior art systems and methods have overcome this problem by
separating the
bending and expanding steps. For instance, U.S. Patent No. 5,353,618 to Roper
et al.
discloses pre-bending, for example, metal tubes prior to the expansion step.
It has been found
that it is possible to feed additional tube material into the expanding
portion past a bend or
bends in the tube when the tube is rotated such that the ends are in the same
horizontal plane
as the niain portion of the tube.
[0006] One disadvantage of pre-bending the tube prior to expansion is that it
requires an
additional step in the manufacturing process, which requires additional
tooling and labor and
therefore increases the price per part. For example, the tube first must be
placed in a bender
to create the bend or bends. The tube then must be transferred to the hydrofoi-
ining apparatus
for the expansion step, which increases labor time and may even require
additional laborers.
Because the tube must be placed in the hydroforming apparatus such that the
ends of the tube
are in the same horizontal plane as the main portion of the tube, larger dies
are required to
accommodate the tube, which increases the cost of production. Additionally,
pre-bending the
tube prior to expansion causes thinning in the wall at the bend of the tube.
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[0007] Another disadvantage of pre-bending the tube prior to expansion is that
thin-walled
tubes often split during the expansion step. It has been found that pre-
bending is only
possible with tubes having wall thicknesses of about 0.065 inches and greater.
[0008] Accordingly, there is a need for a method and apparatus that allows for
the greater
expansion of a shaped part having a bend between the expanding portion and the
end of the
tube or having bends on either side of the expanding portion between the
expanding portion
and the ends of the tube.
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SUMMARY OF THE INVENTION
[0009] In accordance with one aspect of the present invention, a method is
provided for
forming fi=om a tube a shaped part having a bend and a substantially larger
cross section than
the original tube in at least a portion of the tube between the bend and an
end. The method
includes the steps of placing the tube into a hydraulic press having upper and
lower dies,
sealing the ends of the tube, filling the tube with a liquid, pressurizing the
liquid to expand a
portion of the tube, bending the tube between the expanding portion and one
end, and axially
pushing on the end of the tube adjacent the bend to feed metal into the
expanding portion
while the tube is being bent. As a result, the cross section of the expanded
poi-tion can be
expanded much more while still maintaining the desired wall thickness.
[00101 In accordance with another aspect of the present invention, an
apparatus is provided
for fonning fi-om a tube a shaped part having a bend and a substantially
larger cross section in
at least a portion of the tube between the bend and an end. The apparatus
includes a hydraulic
press having upper and lower dies, at least one sealing mechanism configured
to seal the ends
of the tube, a fluid control device for pressurizing liquid within the tube,
and an assembly
configured to ride on and follow the end of the tube as the tube is being bent
while coaxially
pressing on the end of the tube to feed material from the portion between the
bend and the
end into the portion that is being expanded. As a result, the cross section of
the expanded
portion can be enlarged by as much as sixty-five percent of the original cross
section while
maintaining the adequate thickiiess.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0011] While the specification concludes with claims particularly pointing out
and distinctly
claiming the present invention, it is believed the same will be better
understood from the
following description taken in conjunction with the accompanying drawings,
wliich illustrate,
in a non-linliting fashion, the best mode presently contemplated for canying
out the present
invention, and in which like reference numerals designate like parts
throughout the Figures,
wherein:
[0012] Fig 1 is a partial perspective view of a portion of the prefeiTed
embodiment of the
present invention, as shown in the open position;
[0013] Fig. 2 is a partial perspective view of a portion of the preferred
embodiment of the
present invention, as shown in the closed position;
[0014] Fig. 3 is a side elevational view of the preferred embodiment of the
present invention,
as shown in the open position;
[0015] Fig. 4 is a side elevational view of the preferred embodiment of the
present invention,
as shown in the closed position;
[0016] Fig. 5 is a cross sectional view of the prefeiTed embodiment of the
present invention,
as taken about Line A-A of Fig. 2.
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DETAILED DESCRIPTION OF THE INVENTION
[0017] The present invention is directed towards an apparatus and method for
forming fiom a
tube a shaped part having a bend and a substantially larger cross section in
at least a portion
of the tube between the bend and an end.
[0018] The tube may be comprised of any material that perniits the formation
of a bend and a
substantially larger cross section in at least a portion of the tube between
the bend and an end.
Preferably, the tube is comprised of metal. The present invention works
especially well with
common steel grades, such as SAE 1008 or 1018. The present invention also may
be used
with difficult-to-form metals such as Stainless Steel 304L or 409 or aluminum.
[0019] The wall thickness of the tube depends upon the diameter of the tube
and the type of
material used. For example, for a tube composed of SAE 1008 or 1018 steel and
having a
diameter of one inch, the present invention works best for wall thicknesses in
the range of
0.028 to 0.031 inches. As another exan7ple, for a tube composed of Stainless
Steel 304L and
having a diameter of one inch, the present invention works best for wall
thicknesses of 0.049
inches and greater.
[0020] The tube is expanded with any type of liquid that provides for the
expansion of the
tube upon pressurization. For example, the liquid may comprise water.
Alternatively, the
liquid may comprise a mixttu=e or may include additives. For example, the
liquid may include
a lubricant and/or a rust iiihibitor. Preferably, the liquid is comprised of
approximately 95%
water and 5% additives, including a lubricant and a nist inhibitor.
[0021] The present invention uses a hydraulic press for bending the tube and
forming the
shaped part. The hydraulic press has first and second dies that move between a
first or open
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position and a second or closed position. In the first or open position, the
dies are spaced
apart, either vertically or horizontally, such that the tube may be placed in
between the dies.
Preferably, the dies are configured such that the first die is above the
second die. The first or
upper die moves vertically downward from the first or open position to the
second or closed
position. Alternatively, both dies move towards each other from the first or
open position to
the second or closed position.
[0022] In the second or closed position, the dies engage one another, thereby
enclosing on the
tube. Preferably, the upper die moves vertically downward to engage the lower
die, thereby
enclosing on the tube. Alternatively, the dies are configured such that either
the first die or
the second die move. For example, the first die travels vertically upward
towards the second
die, or both dies move towards one another to enclose on the tube.
Additionally, the dies may
be configured such that the dies travel in a horizontal path as opposed to a
vertical path.
[0023] The dies have matching or corresponding cavities that hold the tube. In
this
an=angement, when the dies engage one another, the cavities define the desired
shape of the
tube following expansion.
[0024] An assembly retains at least one end of the tube during the bending and
expansion
steps. The assembly is configured to follow the end of the tube as the tube is
being bent. The
assembly also applies pressure to the end of the tube while the tube is being
bent.
Additionally, the assembly maintains pressure on the end of the tube during
the expansion
step to cause expansion of the tube between the bend and the end. The assembly
is pivotally
mounted to one of the dies. Preferably, the assembly is mounted to the lower
die.
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[0025] The assembly pivots or moves from a first or downward position to a
second or
upward position. The assembly begins in the first or downward position. The
tube is placed
between the open dies such that an end of the tube is received by the
assembly. Preferably,
the tube is received by a bore in the assembly, which retains the end of the
tube.
[0026] As the tube is bent, the assembly pivots towards the second or upward
position in
order to ride on and follow the end of the tube. Preferably, the assembly
pivots about a pin,
which is aligned with the bore. The assembly pivots about the pin to the
second or upward
position. In this maimer, the assembly retains the ends of tube as it is being
bent.
[0027] The assembly includes a cylinder that pushes on the end of the tube
while the tube is
being bent. Preferably, the cylinder exerts force on a locking block, which
retains the end of
the tube, via a piston rod. As the assembly pivots upward, the cylinder
continues to exert
force on the end of the tube. By pushing on the tube, the cylinder forces the
tube into the
cavity between the dies. Additionally, the force exerted by the cylinder on
the end of the tube
causes expansion of the tube. Preferably, the cylinder is a hydraulic
cylinder. Alteniatively,
the cylinder can be electric or pneumatic.
[0028] The cylinder exerts a specific force on the tube depending upon the
type of material
comprising the tube.
[0029] The present invention includes a sealing mechanism to seal the ends of
the tube. The
sealing mechanism extends over or into the ends of the tube, thereby sealing
the tube and
allowing the tube to be pressurized by a fluid control device. Preferably, the
sealing
mechanism is a seal cone having tapered walls that is substantially similar to
that disclosed in
U.S. Patent No. 6,502,822 to Brown, which is incorporated by reference herein.
The sealing
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mechanism is preferably composed of a hardened steel such as D2 Steel, which
is a hardened
tool steel.
[0030] To form the shaped part, the tube is placed between the upper and lower
dies of the
hydraulic press. The ends of the tube are sealed by the sealing mechanism, and
the tube is
filled with the hydroforming liquid. The tube is bent, and the liquid inside
the tube is
pressurized by the fluid control device. The assembly presses on the ends of
the tube during
the bending process to feed tube material into the expanding portion between
the bend and the
end to maintain a desired thickness of the expanded portion during the bending
and
expanding steps.
[003,1.] While the tube is being bent, the liquid inside the tube is
pressurized by the fluid
control device. The pressurized liquid serves as a mandrel to prevent the tube
from
defoi-ining. The liquid is pressurized to a specific pressure or pressure
range depending upon
the type of mater-ial comprising the tube. For most metals, the liquid
initially is pressurized to
about 500 pounds per square inch and then is brouglit up to about 3,000 pounds
per square
inch during the course of the bending step.
[0032] While the tube is being expanded, the liquid inside the tube is
pressurized by the fluid
control device to be within the pressure range of 3,000 to 60,000 pounds per
square inch. In
order to cause expansion of the tube, the pressure of the liquid must be above
the yield point
of the tube. Additionally, the pressurized liquid must be below the lesser of
either a pressure
at which the dies separate or a bursting pressure of the tube. The bursting
pressure, PU,,,=S1, is
defined as:
[0033] PU,,,=St = (2 x th x TS) =(2 x f)
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[0034] where th is the wall thickness of the tube, r is the radius of the
tube, and TS is the
tensile strength of the material comprising the tube.
[0035] For most metals, the liquid initially is pressurized to be about 3,000
pounds per square
inch. During expansion of the tube, the pressure of the liquid is increased to
about 60,000
pounds per square inch to cause the tube material to completely fill the
cavity between the
dies.
[0036] During expansion of the tube, tube material is fed into the expanding
portion of the
tube, which allows for substantial expansion of the cross section of the tube.
Preferably, with
a tube composed of Stainless Steel Type 304L, the tube material fed into the
expanding
portion of the -tube causes the cross section to expand by as much as sixty-
five percent.
[0037] Many changes and modifications will occur to those skilled in the art
upon studying
this description. All such changes and modifications which are within the
spirit of the
invention are intended to be included within the scope of the claims.
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DESCRIPTION OF THE PREFERRED EMBODIMENT
[0038] The present invention will now be described more fully with reference
to the Figures
in which the preferred embodiment of the present invention is shown. The
subject matter of
this disclosure may, however, be embodied in inany different forms and should
not be
construed as being limited to the embodiment set forth herein.
[0039] Referring now to the drawings, wherein like reference numerals
designate identical or
coiTesponding parts tliroughout the several views, Fig. 1 is a perspective
view of the rotating
hydrofoi-ming apparatus 10. The present invention is used in connection with a
hydraulic
press 12 for bending a tube 14 and foiniing the shaped part.
[0040] With reference to Figs. l and 3, the hydraulic press 12 has first and
second dies 16, 18
that are shown in a first position. In the first or open position, the dies
16, 18 are spaced
apart, either vertically or horizontally, such that the tube 14 may be placed
in between the
dies. For example, as shown in Fig. 3, dies 16, 18 are disposed in parallel
spaced relation to
one another such that second or upper die 18 is disposed above first or lower
die 16. Upper
die 18 moves vertically downward from the first or open position shown in Fig.
3 to a second
or closed position shown in Figs. 2 and 4.
[0041] First die 16 includes a cavity 20 that holds the tube 14 and defines a
portion of the
desired shape of the tube following expansion, as described hereafter.
Similarly, second die
18 includes a cavity (not shown) that corresponds with cavity 20. In this
aiTangement, when
the dies 16, 18 engage one another, as shown in Fig. 4, the cavities define
the desired shape of
the tube 14 following expansion, as described hereafter.
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[0042] An assembly 22 is pivotally mounted to one of the dies 16, 18.
Preferably, assembly
22 is mounted to the first or lower die 16. Alternatively, assembly 22 may be
mounted to the
second or upper die 18. Assembly 22 is configured to follow the end of the
tube 14 as the
tube is being bent. Additionally, assembly 22 pushes on the end of the tube
14, as described
hereafter.
[0043] Assembly 22 is shown in a first or downward position in Figs. 1 and 3.
In this
manner, the tube 14 may be placed between the dies 16, 18 such that an end of
the tube is
received by assembly 22. Preferably, the tube 14 is received by a bore 24,
which retains the
end of the tube.
[0044] A cylinder 28 pushes on the end of the tube 14 while the tube is being
bent. As shown
in Figs. 1 and 3, cylinder 28 exerts force on locking block 30 via a piston
rod 32, which
retains the end of the tube 14. As the assembly 22 pivots upward, as shown in
Figs. 2 and 4,
cylinder 28 continues to exert force on the end of the tube 14. By pushing on
the tube 14, the
cylinder 28 forces the tube into the cavity 20. Additionally, the force
exerted by cylinder 28
on the end of the tube 14 controls the expansion of the tube, as described
hereafter. Cylinder
28 may be hydraulic or pneumatic. Preferably, cylinder 28 is a hydraulic
cylinder.
[0045] The cylinder 28 exerts a specific force on the tube 14 depending upon
the type of
material comprising the tube.
[0046] Referring now to Figs. 2 and 4, the dies 16, 18 of the hydraulic press
12 are shown in
a second position. In the second or closed position, the dies 16, 18 engage
one another,
thereby enclosing on the tube 14. Preferably, as shown in Fig. 4, upper die 18
moves
vertically downward to engage lower die 16, thereby enclosing on the tube 14.
Alternatively,
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dies 16, 18 are configured such that either first die 16 or second die 18
move. For example,
first die 16 may travel vertically upward towards second die 18, or both dies
16, 18 may move
towards one another to enclose on the tube 14. Additionally, dies 16, 18 may
be configured
such that the dies 16, 18 travel in a horizontal path as opposed to the
vertical path shown in
Fig. 4.
[0047] The dies 16, 18 bend the tube 14 as the dies move into the second or
closed position.
As the tube 14 is bent, assembly 22 pivots in a manner necessaiy to follow the
end of the
tube. Preferably, assembly 22 pivots about a pin 26, which is aligned with
bore 24, as shown
in Fig. 1. Assembly 22 pivots about pin 26 to a second or upward position, as
shown in Figs.
2 and 4. In this mamler, assembly 22 retains the ends of tube 14 as it is
being bent.
[0048] Refeiring now to Fig. 5, a sealing mechanism 34 is configured to seal
the ends of the
tube. The sealing mechanism extends into the ends of the tube, thereby sealing
the tube and
allowing the tube to be pressurized by a fluid control device 36. Preferably,
the sealing
mechanism 34 is a seal cone having tapered walls that is substantially similar
to that disclosed
in U.S. Patent No. 6,502,822 to Brown, which is incoiporated by reference
herein. The
sealing mechanism 34 is preferably composed of a hardened steel such as D2
Steel, which is a
hardened tool steel.
[0049] To form a shaped part, the tube 14 is placed between the dies 16, 18 of
the hydraulic
press 12. The ends of the tube 14 are sealed by the sealing mechanism 34, and
the tube is
filled with a liquid. The tube is bent, and the liquid inside the tube is
pressurized by the fluid
control device 36. The assembly 22 presses on the ends of the tube 14 during
the bending
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process to feed tube material into the expanding portion between the bend and
the end to
maintain a desired thickness of the expanded portion during the bending and
expanding steps.
[0050] The tube 14 may be comprised of any material having a yield point to
permit the
foi-mation of a bend and a substantially larger cross section in at least a
portion of the tube
between the bend and an end. Preferably, the tube is comprised of metal. The
present
invention works especially well with conunon steel grades, such as SAE 1008 or
1018. The
present invention also may be used with difficult-to-foi-in metals such as
Stainless Steel 304L
or 409.
[0051 ] While the tube 14 is being bent, the liquid iiiside the tube is
pressurized by the fluid
control device 26. The pressiu-ized liquid serves as a mandrel to prevent the
tube 14 from
deforming. The liquid is pressurized to a specific pressure or pressure range
depending upon
the type of material comprising the tube 14. For most metals, the liquid
initially is
pressurized to about 500 pounds per square inch and then is brought up to
about 3,000 pounds
per square inch during the course of the bending step.
[0052] While the tube 14 is being expanded, the liquid inside the tube is
pressurized by the
fluid control device 36 to be within a range above a yield point of the tube
and below a
pressure at which the dies 16, 18 separate. For most metals, the liquid
initially is pressurized
to be to be about 3,000 pounds per square inch. During expansion of the tube,
the pressure of
the liquid is increased to about 60,000 pounds per square inch to cause the
tube material to
completely fill the cavity between the dies 16, 1 S.
[0053] During expansion of the tube 14, tube material is fed into the
expanding portion of the
tube, which allows for substantial expansion of the cross section of the tube.
Preferably, with
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a tube composed of Stainless Steel Type 304L, the tube material fed into the
expanding
portion of the tube causes the cross section to expand by as much as sixty-
five percent.
[0054] The tube 14 may be expanded with any type of liquid that provides for
the expansion
of the tube upon pressurization. For example, the liquid may comprise water.
Alternatively,
the liquid may comprise a mixture or may include additives. For example, the
liquid may
include a lubricant or a rust inllibitor, as the specific applications may
require. Preferably, the
liquid is comprised of approximately 95% water and 5% additives, including a
lubricant and a
i-ust inhibitor.
[0055] Many changes and modifications will occur to those skilled in the art
upon studying
this description. All such changes and modifications which are within the
spirit of the
invention are intended to be included within the scope of the claims.
