BROWN JAMES H (US)
US6502822B1 | 2003-01-07 | |||
US5979201A | 1999-11-09 | |||
US5396786A | 1995-03-14 | |||
DE4428564A1 | 1995-06-22 |
CLAIMS We claim:
1. A method for forming a shaped part from a tube including 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, bending the tube, and pressurizing the liquid to expand at least a
portion of said tube, characterized in that: applying force to an end of the tube during the step of bending 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.
2. The method of claim 1 wherein said tube comprises metal.
3. The method of claim 1 wherein said tube comprises stainless steel.
4. The method of claim 1 wherein said tube comprises aluminum.
5. The method of claim 1 wherein the pressure inside the tube during bending is in a
range of 500 to 3,000 pounds per square inch.
6. The method of claim 2 wherein the pressure to expand the tube is in a pressure range
above a yield point of said tube and below a pressure at which said upper die and said lower die separate.
7. The method of claim 2 wherein the pressure to expand said tube is a pressure range of
3,000 to 60,000 pounds per square inch.
8. The method of claim 1 wherein the cross section of the expanding portion of tube
expands by as much as sixty-five percent.
9. The method of claim 1 wherein said liquid comprises water.
10. The method of claim 1 wherein said liquid comprises water, a lubricant, and a rust inhibitor.
11. An apparatus for forming a shaped part from a tube, the apparatus having a hydraulic
press having upper and lower dies, at least one sealing mechanism configured to seal the ends
of the tube, and a fluid control device for pressurizing liquid within the tube, characterized in that:
an assembly configured to follow the end of the tube as the tube is being bent, the
assembly also configured to apply force to the end of the tube to feed tube material into the
expanding portion between the bend and the end to maintain a desired thickness of the
expanded portion.
12. The apparatus of claim 11 wherein the assembly comprises a hydraulic cylinder.
13. The apparatus of claim 12 wherein the cylinder is pivotally mounted to the lower die.
14. The apparatus of claim 11 wherein said tube comprises a metal.
15. The apparatus of claim 11 wherein said tube comprises stainless steel.
16. The apparatus of claim 11 wherein said tube comprises aluminum.
17. < The apparatus of claim 11 wherein the pressure inside the tube during bending is in a
range of 500 to 3,000 pounds per square inch.
18. The apparatus of claim 14 wherein the pressure to expand the tube is in a pressure
range above a yield point of said tube and below a pressure at which said upper die and said
lower die separate.
19. The apparatus of claim 14 wherein the pressure to expand said tube is a pressure range
of 3,000 to 60,000 pounds per square inch.
20. The apparatus of claim 11 wherein the cross section of the expanding portion of tube
expands by as much as sixty-five percent.
21. The apparatus of claim 11 wherein said liquid comprises water.
22. The apparatus of claim 11 wherein said liquid comprises water, a lubricant, and a rust
inhibitor.
23. The apparatus of claim 11 wherein the sealing mechanism comprises a seal cone
adapted to extend into the ends of the tube to seal and to allow the tube to be pressurized. |
TITLE: APPARATUS .4ND METHOD FOR FORMING SHAPED PARTS
BACKGROUND OF THE INVENTION
[0001 ] The present invention relates generally to the field 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 generally 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 dies 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 thinned In practice, it has been found that the cross section of a tube cannot be expanded by more than about twenty percent
[0003J The problem of limited expansion has been overcome by feeding additional tube matenal from both ends into the expanding portion duπng the expansion process For example, 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
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 system and method of the Roper
Patent, frictional constraints typically limit expansion of the cross section to fifty percent.
[0004] 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 main 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 hydroforming 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.
[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.
SUMMARY OF THE INVENTION
[0009] In accordance with one aspect of the present invention, a method is provided for
forming from 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 portion can be
expanded much more while still maintaining the desired wall thickness.
[0010] In accordance with another aspect of the present invention, an apparatus is provided
for forming from 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 thickness.
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, which illustrate,
in a non-limiting fashion, the best mode presently contemplated for carrying 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 preferred 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 preferred embodiment of the present invention,
as taken about Line A-A of Fig. 2.
DETAILED DESCRIPTION OF THE INVENTION
[0017] The present invention is directed towards an apparatus and method for forming from 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 permits 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 example, 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 mixture or may include additives. For example, the liquid may include
a lubricant and/or a rust inhibitor. Preferably, the liquid is comprised of approximately 95%
water and 5% additives, including a lubricant and a rust 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
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
arrangement, 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.
[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 manner, 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. Alternatively,
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
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.
[0031] 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
deforming. The liquid is pressurized to a specific pressure or pressure range depending upon
the type of material comprising the tube. 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.
[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, P burst, is defined as:
[0033] P burst = (2 x th x TS) í (2 x r)
[0034] where th is the wall thickness of the tube, / • 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.
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 many different forms and should not be
construed as being limited to the embodiment set forth herein.
[0039] Refening now to the drawings, wherein like reference numerals designate identical or
corresponding parts throughout the several views, Fig. 1 is a perspective view of the rotating hydro forming apparatus 10. The present invention is used in connection with a hydraulic
press 12 for bending a tube 14 and forming the shaped part.
[0040] With reference to Figs. 1 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 arrangement, 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.
[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, IS 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,
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 necessary 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 manner, assembly 22 retains the ends of tube 14 as it is being bent.
[0048] Referring 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 incorporated 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
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
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.
[0051] While the tube 14 is being bent, the liquid inside the tube is pressurized by the fluid
control device 26. The pressurized 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, IS.
[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
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 inhibitor, as the specific applications may require. Preferably, the
liquid is comprised of approximately 95% water and 5% additives, including a lubricant and a
rust 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.
Next Patent: APPARATUS AND METHOD FOR LIFE ENHANCEMENT OF A PRINT BLANKET IN ELECTROSTATIC PRINTING