Metal deforming – By application of fluent medium – or energy field – With actuated tool engaging work
Reexamination Certificate
2000-04-04
2001-05-29
Jones, David (Department: 3725)
Metal deforming
By application of fluent medium, or energy field
With actuated tool engaging work
C072S061000, C072S421000, C029S421100
Reexamination Certificate
active
06237382
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and an apparatus for hydroforming a metallic tube.
2. Description of the Related Art
Metallic tube hydroforming comprises the steps of introducing a hydraulic fluid into a metallic tube serving as a material tube (hereinafter, referred to merely as a metallic tube) and applying an axial force to the tube ends, to thereby form the metallic tube through combined use of hydraulic pressure and the axial force. The hydroforming process provides tubular parts having a variety of cross-sectional profiles.
FIGS.
7
(
a
1
),
7
(
a
2
),
7
(
b
1
),
7
(
b
2
),
7
(
c
1
), and
7
(
c
2
) show a metallic tube and products. FIG.
7
(
a
1
) is a side view showing a metallic tube, and FIG.
7
(
a
2
) is a front view showing the metallic tube. FIGS.
7
(
b
1
) and
7
(
c
1
) are side views of products obtained through tube hydroforming, and FIGS.
7
(
b
2
) and
7
(
c
2
) are front views of the products.
Each of the products includes an expanded portion
2
a
(
3
a
) having a rectangular cross section and end portions
2
b
(
3
b
) having the same outer diameter as a diameter D
0
of a metallic tube
1
. FIGS.
7
(
b
1
) and
7
(
b
2
) show a product
2
in which side lengths D
1
and D
2
of the expanded portion
2
a
are larger than the tube diameter D
0
.
FIGS.
7
(
c
1
) and
7
(
c
2
) show a product
3
in which at least one (in this case, D
1
) of side lengths D
1
and D
2
of the expanded portion
3
a
is smaller than the tube diameter D
0
. Overall lengths L
1
and L
2
of the products
2
and
3
, respectively, are shorter than the length L
0
. of tube
1
First will be described a conventional hydroforming apparatus used for obtaining-the product
2
.
FIGS.
8
(
a
) and
8
(
b
) show a die portion of the conventional hydroforming apparatus. FIG.
8
(
a
) is a longitudinal sectional view showing the die portion. FIG.
8
(
b
) is a sectional view taken along the line C—C of FIG.
8
(
a
).
The die is composed of a lower die
4
and an upper die
5
. The lower die
4
is attached to a bolster
10
of an unillustrated press unit. The bolster
10
is located at a lower portion of the press unit. The upper die
5
is attached to a ram head
11
of the press unit. The ram head
11
is located at an upper portion of the press unit. The ram head
11
is moved vertically by means of an unillustrated hydraulic cylinder so as to press the upper die
5
against the lower die
4
with a predetermined force. Die cavities
4
a
,
5
a
and a tube-holding groove
4
b
,
5
b
for containing a metallic tube therein are formed in the upper and lower die
4
,
5
. When the upper and lower dies
5
and
4
are closed each other, a space defined by the die cavities
4
a
and
5
a
is used for forming the expanded portion
2
a
of a product. The contour of the die cavities is identical to the external contour of the expanded portion
2
a
of a product. When the upper and lower dies
5
and
4
are closed each other, a space defined by the die cavities
4
a
and
5
a
is used for forming the expanded portion
2
a
of a product. The contour of the die cavities is identical to the external contour of the expanded portion
2
a
of a product. When the upper and lower dies
5
and
4
are closed each other, the diameter of the space defined by the tube-holding grooves
4
b
and
5
b
is identical to the outer diameter D
0
of the metallic tube
1
. Left- and right-hand sealing-punch
6
and
7
are attached to unillustrated corresponding horizontal press units. The left- and right-hand sealing-punch
6
and
7
advance toward or retreat from the left- and right-hand tube-holding grooves
4
b
and
5
b
, respectively.
Next will be described a hydroforming process for obtaining the product
2
through use of the above-mentioned conventional hydroforming apparatus.
FIGS.
9
(
a
1
),
9
(
a
2
),
9
(
b
1
),
9
(
b
2
),
9
(
c
), and
9
(
d
) illustrate a conventional hydroforming process. FIG.
9
(
a
1
) is a longitudinal sectional view showing a metallic tube set in the upper and lower dies. FIG.
9
(
a
2
) is a sectional view taken along the line C—C of FIG.
9
(
a
1
). FIG.
9
(
b
1
) is a longitudinal sectional view showing a final state of hydroforming. FIG.
9
(
b
2
) is a sectional view taken along the line C—C of FIG.
9
(
b
1
). FIG.
9
(
c
) is an enlarged view showing the encircled portion a of FIG.
9
(
b
2
). FIG.
9
(
d
) is a perspective view showing a product ruptured during hydroforming.
As shown in FIGS.
9
(
a
1
) and
9
(
a
2
), first, the metallic tube
1
is set in the tube-holding grooves
4
b
formed in both end portions of the lower die
4
. The ram head
11
is lowered so as to press the upper die
5
against the lower die
4
. The sealing punches
6
and
7
are advanced from their respective sides so that head portions
6
a
and
7
a
of the sealing punches
6
and
7
, respectively, are tightly inserted into both end portions of the metallic tube
1
, thereby the tube ends are sealed during hydroforming. Next, while a hydraulic fluid
8
is introduced into the metallic tube
1
by means of an unillustrated pump through a path
6
b
extending through the left-hand sealing punch
6
, air inside the metallic tube
1
is ejected through a path
7
b
extending through the right-hand sealing punch
7
. An unillustrated valve located on the extension of the path
7
b
is closed after the interior of the metallic tube
1
is filled with the hydraulic fluid
8
.
An example of the hydraulic fluid
8
is an emulsion prepared by dispersing a fat-and-oil component in water in an amount of several percent so as to produce a rust-preventive effect. The pressure of the hydraulic fluid
8
contained in the metallic tube
1
is increased with advancing the sealing-punch
6
and
7
to press the metallic tube axially. Thus, the material of the metallic tube
1
is expanded within the die cavities
4
a
and
5
a
to form the product
2
as shown in FIGS.
9
(
b
1
) and
9
(
b
2
).
The upper and lower dies
5
and
4
are pressed against each other during the hydroforming in order to prevent the upper die
5
from being pressed upward off the lower die
4
when the metallic tube
1
is expanded through the application of fluid pressure and axial force. Axial pressing is performed in order to feed the material of the metallic tube
1
located in the tube-holding grooves
4
b
and
5
b
into the die cavities
4
a
and
5
a
, to thereby minimize the wall thinning of an expanded portion of the product
2
.
Subsequently, the internal fluid pressure of the product
2
is reduced to atmospheric pressure. Then, the upper die
5
is moved upward, and the sealing punches
6
and
7
are retreated, thereby draining the hydraulic fluid
8
from inside the product
2
. The product
2
is ejected from the lower die
4
.
Next will be described a conventional hydroforming process for obtaining the product
3
. FIGS.
10
(
a
1
),
10
(
a
2
),
10
(
b
1
), and
10
(
b
2
) illustrate conventional dies used for obtaining the product
3
through hydroforming. FIG.
10
(
a
1
) is a longitudinal sectional view of a set of lower die
14
and upper die
15
. FIG.
10
(
a
2
) is a sectional view taken along the line C—C of FIG.
10
(
a
1
). FIG.
10
(
b
1
) is a longitudinal sectional view of an another set of lower die
24
and upper die
25
. FIG.
10
(
b
2
) is a sectional view taken along the line C—C of FIG.
10
(
b
1
).
In FIGS.
10
(
a
1
) and
10
(
a
2
), the rectangular cross section of a space defined by die cavities
14
a
and
15
a
of a lower die
14
and an upper die
15
, respectively, is profiled such that a vertical side length D
1
is shorter than a horizontal side length D
2
. In FIGS.
10
(
b
1
) and
10
(
b
2
), the rectangular cross section of a space defined by die cavities
24
a
and
25
a
of a lower die
24
and an upper die
25
, respectively, is profiled such that a horizontal side length D
1
is shorter than a vertical side length D
2
.
In hydroforming with either the die shown in FIG.
10
(
a
1
) or the die shown
Inoue Saburo
Kojima Masayasu
Jones David
Marhoefer Laurence J.
Sumitomo Metal Industries Ltd.
Venable
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