EP1907147A1

EP1907147A1 - Apparatus and method for forming shaped parts

Info

Publication number: EP1907147A1
Application number: EP05775704A
Authority: EP
Inventors: Gary A. Webb; James H. Brown
Original assignee: Aquaform Inc
Current assignee: Aquaform Inc
Priority date: 2005-07-26
Filing date: 2005-07-26
Publication date: 2008-04-09
Also published as: JP2009502511A; WO2007018499A1; MX2007016408A; CA2616550A1; EP1907147A4

Abstract

An apparatus and method are provided for forming a shaped part from a tube (14) having an end and at least one bend, the shaped part having an enlarger portion between the bend and the end. The shaped part is formed by applying pressure fluid within the tube (14) while maintaining pressure on the end of the tube to cause expansion of the tube between the bend and the end. The shaped part is formed on a hydraulic press (10) having upper (18) and lower dies (16). The apparatus (10) includes at least one side assembly (22) pivotally mounted to the lower die (16) with a cylinder (28) for applying pressure to at least one end of the tube (14). The apparatus further includes seals (34) for sealing ends of the tube (14) and a fluid control device (36) for pressurizing the fluid within the tube.

Description

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) ÷ (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

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

invention are intended to be included within the scope of the claims.

Claims

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

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.