U.S. patent application number 09/819514 was filed with the patent office on 2001-10-11 for method of forming an eccentrically expanded pipe and eccentrically pipe-expanding device.
Invention is credited to Kido, Tsuguo, Nakada, Yuji, Omori, Tetsuji, Yamamoto, Seiji.
Application Number | 20010027675 09/819514 |
Document ID | / |
Family ID | 18606949 |
Filed Date | 2001-10-11 |
United States Patent
Application |
20010027675 |
Kind Code |
A1 |
Kido, Tsuguo ; et
al. |
October 11, 2001 |
Method of forming an eccentrically expanded pipe and eccentrically
pipe-expanding device
Abstract
In forming a fuel inlet pipe FP, (1) a portion of a base pipe is
expanded by use of an expander punch to form a processed pipe
comprising a neck portion, of which the diameter is the same as
that of the base pipe, a tapering portion, and an expanded portion,
all of these portions being connected in coaxial relation to one
another (coaxially expanding process); and (2) a central axis of
the neck portion and a central axis of the expanded portion are
decentered relative to each other, and the expanded portion of the
processed pipe is further expanded by use of an expander punch
having a diameter larger than that of the expander punch used in
the coaxially expanding process, thereby forming the fuel inlet
pipe FP (eccentrically expanding process). The coaxially expanding
process is performed one time or a plurality of times, while the
eccentrically expanding process is performed only one time.
Inventors: |
Kido, Tsuguo; (Okazaki-shi,
JP) ; Omori, Tetsuji; (Okazaki-shi, JP) ;
Yamamoto, Seiji; (Okazaki-shi, JP) ; Nakada,
Yuji; (Okazaki-shi, JP) |
Correspondence
Address: |
DAVIS & BUJOLD, P.L.L.C.
500 NORTH COMMERCIAL STREET
FOURTH FLOOR
MANCHESTER
NH
03101
US
|
Family ID: |
18606949 |
Appl. No.: |
09/819514 |
Filed: |
March 27, 2001 |
Current U.S.
Class: |
72/370.06 |
Current CPC
Class: |
B21D 41/02 20130101 |
Class at
Publication: |
72/370.06 |
International
Class: |
B21D 039/08 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 29, 2000 |
JP |
2000-91493 |
Claims
Wherefore, we claim:
1. A method of forming an eccentrically expanded pipe, the method
comprising the steps of: coaxially expanding a portion of a base
pipe by use of a first expander punch to form an expanded portion,
an intermediate tapering portion and a neck portion having a
diameter the same as that of the base pipe, all of said portions
being contiguously coaxially connected about a central axis;
decentering the expanded portion and the neck portion relative to
one another to form a secondary axis spaced from the central axis
by use of a second expander punch having a diameter larger than
that of the first expander punch, thereby forming an eccentrically
expanded pipe, and coaxially expanding the base pipe at least one
time, while the decentering step is performed only one time.
2. The method of forming an eccentrically expanded pipe according
to claim 1, wherein the method further comprises a step of
coaxially expanding the portion of the base pipe a plurality of
times using expander punches of various diameters.
3. The method of forming an eccentrically expanded pipe according
to claim 1, wherein the method further comprises a step of
coaxially expanding the portion of the base pipe a plurality of
times using expander punches of increasing diameter.
4. The method of forming an eccentrically expanded pipe according
to claim 1, wherein the method further comprises the steps of
coaxially expanding the expanded portion of the processed pipe at a
ratio of between about 70 to 80% relative to the base pipe, and
further expanding the expanded portion during decentering at a
ratio of at least 90% relative to the base pipe.
5. The method of forming an eccentrically expanded pipe according
to claim 1, wherein the eccentrically expanded pipe formed by the
method is a fuel inlet pipe.
6. The method of forming an eccentrically expanded pipe according
to claim 5, wherein the base pipe is initially formed having HAZ
portions, and during decentering the HAZ portions are disposed
between a range of about 45 to 135 degrees relative to a direction
of eccentricity defined by the central and secondary axis.
7. A pipe-expanding device for eccentrically expanding a processed
pipe having an expanded portion, an intermediate tapering portion,
and a neck portion, all of said portions being contiguously
coaxially connected about a central axis, the pipe-expanding device
comprising: neck-portion holding means moveable in a predetermined
radial direction for holding a periphery of the neck portion of the
processed pipe; neck-portion moving means for moving the
neck-portion holding means in the predetermined radial direction to
facilitate displacement of the neck portion and the expanded
portion in eccentric relation to each other; and an axially
moveable expander punch for axial insertion into an opening end of
the expanded portion of the processed pipe held by the neck-portion
holding means to facilitate further expansion of the expanded
portion.
8. The pipe-expanding device for eccentrically expanding a
processed pipe as set forth in claim 7, wherein the axially
moveable expander punch further comprises a cylindraceous body
having an insertion tip, the body defining a substantially constant
diameter about the central axis and wherein the insertion tip has
an upper portion having a slope defined by a radially decreasing
diameter from the constant diameter towards an end of the tip.
9. The pipe-expanding device for eccentrically expanding a
processed pipe as set forth in claim 8, further comprising an
expanded portion holding means having a displaceable pipe holding
means for accommodating the further expansion of the expanded
portion of the pipe.
10. The pipe-expanding device for eccentrically expanding a
processed pipe as set forth in claim 9, wherein the neck portion
holding means has a displaceable neck portion holding means for
accommodating the eccentric displacement of the neck portion
relative to the central axis caused by the neck portion moving
means.
11. The pipe-expanding device for eccentrically expanding a
processed pipe as set forth in claim 10, wherein the eccentric
displacement of the neck portion relative to the central axis
creates the secondary axis about which the neck portion is
substantially defined.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method of forming an
eccentrically expanded pipe and an eccentrically pipe-expanding
device suitable for use in the method.
BACKGROUND OF THE INVENTION
[0002] As shown in FIG. 6, a fuel inlet pipe FP comprises a
large-diameter portion FPa, a gradually changing portion FPb, and a
small-diameter portion FPc, in which a central axis of the
large-diameter portion FPa and that of the small-diameter portion
FPc are in eccentric relation to each other. In the fuel inlet pipe
FP, the diameter of the large-diameter portion FPa is 1.9 or more
times greater than that of the small-diameter portion FPc.
Moreover, as mentioned above, the central axis of the
small-diameter portion FPc is in eccentric relation to that of the
large-diameter portion FPa. For these reasons, it has been
difficult to produce the fuel inlet pipe FP by a pipe-expanding
method, and it has been usual to produce it by welding three parts,
i.e., the large-diameter portion FPa, gradually changing portion
FPb, and small-diameter portion FPc.
[0003] Now, in order to integrally form such a fuel inlet pipe FP
by use of the pipe-expanding method, the following procedure is
undertaken.
[0004] In general, if a pipe is expanded to such an extent that a
limit of expandability of its material is exceeded, an expanded
portion of the pipe is cracked or a base pipe portion (non-expanded
portion) of the pipe is buckled and, therefore, it is impossible to
highly expand the pipe in one process. Accordingly, a fuel inlet
pipe to be expanded at a high expansion ratio, such as the fuel
inlet pipe FP as shown in FIG. 6, is gradually expanded through a
plurality of pipe-expanding operations. Also, in order to place the
large-diameter portion FPa and the small-diameter portion FPc in
eccentric relation, the small-diameter portion FPc is decentered
little by little relative to the large-diameter portion FPa, while
the pipe is expanded in stages.
[0005] However, in cases where a pipe is eccentrically expanded,
the pipe is partially expanded in a large degree because of
decentering, and an expansion ratio becomes substantially high in
such a portion where the pipe is highly expanded. As a result, even
if the pipe is eccentrically expanded little by little in stages,
there is still a strong possibility that the pipe is cracked in the
portion where it is highly expanded.
SUMMARY OF THE INVENTION
[0006] The present invention was made to solve the aforementioned
problem. More specifically, an object of the invention is to
provide a method of eccentrically expanding a pipe in which
formation of cracks or the like is prevented even if a desired
expansion ratio is high, and in which an eccentrically expanded
pipe can be integrally formed. Also, another object of the
invention is to provide an eccentrically pipe-expanding device
which is suitable for use in the method.
[0007] In order to attain the aforementioned objects, there is
provided a method for forming an eccentrically expanded pipe, the
method comprising a coaxially expanding process in which a portion
of a base pipe is expanded by use of an expander punch to form a
processed pipe having a neck portion, of which the diameter is the
same as that of the base pipe, a tapering portion, and an expanded
portion, all of these portions being connected in coaxial relation
to one another; and an eccentrically expanding process in which a
central axis of the neck portion and a central axis of the expanded
portion are decentered relative to each other, and the expanded
portion of the processed pipe is further expanded by use of an
expander punch having a diameter larger than that of the expander
punch used in the coaxially expanding process, thereby forming an
eccentrically expanded pipe. In this method, the coaxially
expanding process is performed one time or a plurality of times,
while the eccentrically expanding process is performed only one
time.
[0008] In the coaxially expanding process according to the
invention, the pipe is coaxially expanded by use of the expander
punch, and decentering is not performed in this process. It is
preferable to expand the portion of the base pipe in a plurality of
stages by use of expander punches of various diameters, in other
words, to perform this coaxially expanding process a plurality of
times, depending on a desired expansion ratio. As an example, the
pipe is preferably expanded at a low expansion ratio (for example,
30 to 55%; specifically, 35 to 50%) in a first coaxially expanding
process, and then expanded at a high expansion ratio (for example,
65 to 85%; specifically, 70 to 80%) in a second coaxially expanding
process. By expanding the pipe in stages in this manner, the pipe
can be safely expanded without being cracked even in cases where
the desired expansion ratio is high. According to the Japanese
Industrial Standards (JIS), the expansion ratio is represented by
the following formula; and in the invention, the expansion ratio is
calculated using the diameter of the base pipe as "D" in the
following formula. 1 Expansion ratio = D1 - D D .times. 100 % [
Formula 1 ]
[0009] D: Outside Diameter of Pipe Before Pipe Expansion
[0010] D1: Outside Diameter of Pipe After Pipe Expansion
[0011] It is preferable that, in the coaxially expanding process,
80% or more of pipe expansion is performed relative to a desired
expansion ratio (that is, an expansion ratio of the expanded
portion of the eccentrically expanded pipe). For example, if the
desired expansion ratio is 90%, an expansion ratio of the expanded
portion of the processed pipe is preferably 70% or more after the
coaxially expanding process.
[0012] Now, in the eccentrically expanding process according to the
invention, the central axis of the neck portion and that of the
expanded portion are decentered relative to each other, and the
expanded portion of the processed pipe after the coaxially
expanding process is further expanded, thereby forming the
eccentrically expanded pipe. This eccentrically expanding process
is performed only one time, without being divided into a plurality
of stages. As mentioned above, the coaxial expansion of the pipe
can be achieved in one stage or in a plurality of stages with
little possibility of formation of cracks or the like. On the other
hand, if the eccentric expansion of the pipe is achieved in a
plurality of stages, there is a possibility that cracks may be
formed on the pipe since an expansion ratio of a portion of the
pipe, which is highly expanded at the time of decentering, becomes
substantially high. For this reason, the eccentrically expanding
process is performed only one time.
[0013] As aforementioned, according to the invention, the
multistage eccentric expansion of the pipe is never performed, and
instead, the coaxial expansion of the pipe is performed in one
stage or in a plurality of stages, and subsequently, the eccentric
expansion is accomplished in one stage. As a result, the
eccentrically expanded pipe can be formed without any cracks or the
like formed thereon.
[0014] The method of the invention for forming an eccentrically
expanded pipe is suitable, particularly, for making a pipe expanded
at a high expansion ratio of 90% or more in its expanded portion.
In this case, the pipe is expanded by a plurality of coaxially
expanding operations such that the expansion ratio of the expanded
portion of the processed pipe becomes 70 to 80% after the coaxially
expanding process. And then, the pipe is further expanded such that
the expansion ratio of the expanded portion of the eccentrically
expanded pipe becomes 90% or more after the eccentrically expanding
process. This is a preferable procedure to surely prevent the
formation of cracks. In this manner, the present invention makes it
possible to integrally form an eccentrically expanded pipe, without
forming any cracks or the like thereon, even in cases where the
expanded portion of the eccentrically expanded pipe is desired to
be expanded at a high expansion ratio such as 90% or more.
[0015] The method of the invention for forming an eccentrically
expanded pipe is suitable, particularly, for making a fuel inlet
pipe. In recent years, a type of fuel inlet pipe called one-inch
eccentrically expanded fuel inlet has been developed. The one-inch
eccentrically expanded fuel inlet has an expansion ratio of over
90% in its large-diameter portion, and moreover, its small-diameter
portion and large-diameter portion are in eccentric relation to
each other (see FIG. 6) Therefore, it has been considered to be
impossible to integrally form this type of fuel inlet pipe so far;
however, it was made possible for the first time by use of the
forming method of the invention.
[0016] In cases where the method of the invention for forming an
eccentrically expanded pipe is applied to the making of the fuel
inlet pipe, it is preferable, in the eccentrically expanding
process, to dispose HAZ portions in the range of 45 to 135 degrees
relative to a direction of eccentricity, seen in section of the
pipe. A HAZ portion means a weld heat affected zone (referred to as
a HAZ in general). More specifically, it is a portion formed on the
periphery of weld metal when flux and part of base metal are fused
by heat energy such as an arc.
[0017] Since the HAZ portions are different from the other portions
in expanding properties, it is not preferable to dispose the HAZ
portions in an area where the pipe is highly expanded at the time
of decentering, that is, in an upper part of the fuel inlet pipe.
This is because there is a possibility that the pipe might be
cracked if the HAZ portions are disposed in such an area. On the
contrary, it is preferable to dispose the HAZ portions in an area
where the pipe is not so highly expanded at the time of
decentering, that is, in a lower part of the fuel inlet pipe.
However, the HAZ portions are easily cracked by a shock, such as an
automobile collision, and therefore, if the HAZ portions are
disposed in the lower part of the fuel inlet pipe, fuel leaks may
be caused in the case of formation of cracks in the HAZ portions.
Consequently, it is preferable to dispose the HAZ portions in the
range of 45 to 136 degrees relative to the direction of
eccentricity, seen in section of the pipe, such that the HAZ
portions can be prevented from being cracked at the time of
decentering, and such that even in the event that the HAZ portions
are cracked by the automobile collision or the like, fuel leakage
from the cracked portions can be prevented.
[0018] When the eccentrically expanding process according to the
invention is implemented, the following device is preferably used.
That is, an eccentrically pipe-expanding device comprising:
[0019] neck-portion holding means moveable in a predetermined
radial direction while holding a periphery of the neck portion of
the processed pipe;
[0020] neck-portion moving means for moving the neck-portion
holding means in the predetermined radial direction, thereby
placing the neck portion and the expanded portion in eccentric
relation to each other; and
[0021] an expander punch for being pressed, from the expanded
portion of the processed pipe held by the neck-portion holding
means, into the expanded portion in an axial direction thereof. Use
of the eccentrically pipe-expanding device facilitates the
eccentrically expanding process of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The invention will now be described, by way of example, with
reference to the accompanying drawings, in which:
[0023] FIGS. 1A and 1B are explanatory views showing a first
process according to an embodiment of the invention;
[0024] FIGS. 2A and 2B are explanatory views showing a second
process according to the embodiment;
[0025] FIGS. 3A, 3B and 3C are explanatory views showing a third
process according to the embodiment as well as schematic diagrams
showing an eccentrically pipe-expanding device to be used
therein;
[0026] FIG. 4 is an explanatory view showing arrangement of HAZ
portions according to the embodiment;
[0027] FIG. 5 is a schematic diagram showing an eccentrically
pipe-expanding device according to another embodiment of the
invention; and
[0028] FIG. 6 is a sectional view of a fuel inlet pipe.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0029] In this embodiment, the making of a fuel inlet pipe FP (see
FIG. 6) as an eccentrically expanded pipe is taken as an example.
The fabrication procedure is divided into three processes, i.e., a
first process (a first coaxially expanding process), a second
process (a second coaxially expanding process), and a third process
(an eccentrically expanding process), each of which is described
below.
[0030] (1) First Process (First Coaxially Expanding Process)
[0031] FIG. 1A is an explanatory view showing a state prior to the
first process, and FIG. 1B is an explanatory view showing a state
during the first process.
[0032] First of all, a one-inch straight pipe (of which the outside
diameter is 25.4 mm) is prepared as a base pipe P0, and a first
expander punch 11 is pressed into the base pipe P0, with one end of
the base pipe P0 thrust against a stopper 10, from an opening at
the other end of the base pipe P0. The first expander punch 11
comprises a first punch body 11a of cylindrical shape, a first
conical top 11b formed at an end of the first punch body 11a in
coaxial relation thereto, and a first pedestal 11c attached to a
base end of the first punch body 11a. The outside diameter of a tip
of the first conical top 11b is approximately equal to the inside
diameter of the base pipe P0. Also, the first punch body 11a is
inserted in a first ring 11d, which is coupled, via first springs
11e, to the first pedestal 11c.
[0033] The first expander punch 11 is shifted in an axial direction
of the base pipe P0 such that the tip of the first conical top 11b
is pressed into the base pipe P0 from the opening at the other end
thereof. Then, the base pipe P0 is expanded to conform to the shape
of the first expander punch 11 as the first expander punch 11 is
pressed thereinto, since the base pipe P0 is thrust, at its one
end, against the stopper 10.
[0034] Even after the first ring 11d externally attached to the
first punch body 11a comes into contact with the other end of the
base pipe P0, the first expander punch 11 is further pressed into
the base pipe P0 against the urging force of the first springs lie
Once the first expander punch 11 is pressed in up to a place where
it can no longer proceed in a pressing direction, the first
expander punch 11 is then shifted in the reverse direction, that
is, in a drawing direction.
[0035] As a result, the base pipe P0 is formed into a first
processed pipe P1 by plasticity. The first processed pipe P1
comprises a first expanded portion P1a expanded by the first punch
body 11a of the first expander punch 11, a first tapering portion
P1b shaped in conformity with the shape of the first conical top
11b of the first expander punch 11, and a first neck portion P1c,
having the original diameter of the base pipe P0, into which the
first expander punch 11 was not inserted. These portions P1a to P1c
are formed in coaxial relation to one another. In this example, the
outside diameter of the first expanded portion P1a is 36.2 mm, and
the expansion ratio thereof is 42.5% relative to the base pipe
P0.
[0036] (2) Second Process (Second Coaxially Expanding Process)
[0037] FIG. 2A is an explanatory view showing a state prior to the
second process, and FIG. 2B is an explanatory view showing a state
during the second process.
[0038] First of all, a second expander punch 21 is pressed into the
first processed pipe P1 resulting from the first process, with one
end of the first processed pipe P1 thrust against a stopper 20,
from an opening at the other end of the first processed pipe
P1.
[0039] The second expander punch 21 comprises a second punch body
21a of cylindrical shape, a second conical top 21b formed at an end
of the second punch body 21a in coaxial relation thereto, and a
second pedestal 21c attached to a base end of the second punch body
21a. The outside diameter of a tip of the second conical top 21b is
approximately equal to the inside diameter of the first neck
portion P1c of the first processed pipe P1. Also, the second punch
body 21a is inserted in a second ring 21d, which is coupled, via
second springs 21e, to the second pedestal 21c. The diameter of the
second punch body 21a is larger than that of the first punch body
11a.
[0040] The second expander punch 21 is shifted in an axial
direction of the first processed pipe P1 such that the tip of the
second conical top 21b is pressed into the first processed pipe P1
from the opening at the other end thereof (i.e., at an end of the
first expanded portion P1a). Then, the first processed pipe P1 is
expanded to conform to the shape of the second expander punch 21 as
the second expander punch 21 is pressed thereinto, since the first
processed pipe P1 is thrust, at its one end (i.e., at an end of the
first neck portion P1c), against the stopper 20.
[0041] Even after the second ring 21d externally attached to the
second punch body 21a comes into contact with the other end of the
first processed pipe P1, the second expander punch 21 is further
pressed into the first processed pipe P1 against the urging force
of the second springs 21e. Once the second expander punch 21 is
pressed in up to a place where it can no longer proceed in a
pressing direction, the second expander punch 21 is then shifted in
the reversed direction, that is, in a drawing direction.
[0042] As a result, the first processed pipe P1 is formed into a
second processed pipe P2 by plasticity. The second processed pipe
P2 comprises a second expanded portion P2a expanded by the second
punch body 21a of the second expander punch 21, a second tapering
portion P2b shaped in conformity with the shape of the second
conical top 21b of the second expander punch 21, and a second neck
portion P2c, having the original diameter of the base pipe P0, into
which the second expander punch 21 was not inserted. These portions
P2a to P2c are formed in coaxial relation to one another. In this
example, the outside diameter of the second expanded portion P2a is
45.0 mm, and the expansion ratio thereof is 77.2% relative to the
base pipe P0.
[0043] (3) Third Process (Eccentrically Expanding Process)
[0044] FIG. 3A is an explanatory view showing a state prior to the
third process, and FIGS. 3B and 3C are explanatory views each
showing a state during the third process.
[0045] Prior to the description of the third process, composition
of an eccentrically pipe-expanding device 50 is first described.
The eccentrically pipe-expanding device 50 comprises a movable body
51, a neck-portion holder 52, a third expander punch 56, and an
expanded-portion holder 57, and it is set up on a working bench
60.
[0046] The movable body 51 can be moved, by an actuator (not shown)
such as a hydraulic cylinder or the like, in a vertical direction
relative to the working bench 60.
[0047] The neck-portion holder 52 is composed of a lower
neck-portion holding member 53 being capable of moving up and down
via a plurality of springs 53a provided on the working bench 60,
and an upper neck-portion holding member 54 fixed on a bottom face
of the movable body 51. Both the members 53 and 54 pinch and hold
the second neck portion P2c of the second processed pipe P2 from
its upper and lower sides to prevent the second processed pipe P2
from moving in its axial direction (specifically, in a direction in
which the third expander punch 56 is inserted, or in the right
direction in FIGS. 3A to 3C).
[0048] The third expander punch 56 comprises a cylindrically-shaped
third punch body 56a and a tip 56b. The third, punch body 56a and
the tip 56b correspond to the large-diameter portion FPa and the
gradually changing portion FPb, respectively, of the fuel inlet
pipe FP as shown in FIG. 6. The diameter of the third punch body
56a is larger than that of the second punch body 21a. The tip 56b
of the third expander punch 56 is formed in such a manner that an
upper portion thereof slopes downward, forming a curve toward an
end of the tip 56b.
[0049] The expanded-portion holder 57 is composed of a lower
expanded-portion holding member 58 fixed on the working bench 60,
and an upper expanded-portion holding member 59 being capable of
moving up and down via a plurality of springs 59a provided on the
bottom face of the movable body 51. Both the members 58 and 59
pinch and hold the second expanded portion P2a of the second
processed pipe P2 from its upper and lower sides.
[0050] Now, the procedure of eccentrically expanding the second
processed pipe P2 by use of the eccentrically pipe-expanding device
50 is described. First of all, as shown in FIG. 3A, the movable
body 51 is set above the working bench 60, being greatly apart
therefrom. In this state, the second neck portion P2c and the
second expanded portion P2a of the second processed pipe P2 are
placed, respectively, on the lower neck-portion holding member 53
and the lower expanded-portion holding member 58.
[0051] If the second processed pipe P2 has a beaded portion (weld
metal portion) B and HAZ (heat affected zone) portions H as shown
in FIG. 4, the second processed pipe P2 is disposed in such a
manner that the beaded portion B as well as the HAZ portions H are
located in the range of 45 (.theta.1) to 135 (.theta.2) degrees
(preferably, at an angle of approximately 90 degrees) relative to a
direction of eccentricity (E), i.e., the vertical direction.
[0052] Subsequently, as shown in FIG. 3B, the movable body 51 is
moved toward the working bench 60. Then, the second neck portion
P2c and the second expanded portion P2a of the second processed
pipe P2 are pinched and held, respectively, between the upper and
lower neck-portion holding members 54, 53 and between the upper and
lower expanded-portion holding members 59, 58. In this state, the
second neck portion P2c is decentered relative to the second
expanded portion P2a.
[0053] More specifically, with a downward movement of the movable
body 51, the second neck portion P2c of the second processed pipe
P2 is also moved downward by the upper neck-portion holding member
54, while the springs 53a provided between the lower neck-portion
holding member 53 and the working bench 60 are compressed.
Accordingly, a central axis of the second neck portion P2c is
lowered after the movable body 51 is moved downward. On the other
hand, even after the movable body 51 is moved downward, a central
axis of the second expanded portion P2a is maintained at the same
height as before the movable body 51 is moved downward, since the
springs 59a provided between the movable body 51 and the upper
expanded-portion holding member 59 are compressed. The amount of
the downward movement of the movable body 51 is determined
depending on a desired slippage between the central axis of the
small-diameter portion FPc of the fuel inlet pipe FP and that of
the large-diameter portion FPa thereof.
[0054] Further subsequently, as shown in FIG. 3C, the third
expander punch 56 is moved in an axial direction of the second
processed pipe P2 to be pressed into the second processed pipe P2
from an opening at the other end thereof (i.e., at an end of the
second expanded portion P2a). Because the second processed pipe P2
is prevented, by the neck-portion holder 52, from moving in the
axial direction, it is expanded in conformity with the shape of the
third expander punch 56 as the third expander punch 56 is pressed
into the second processed pipe P2.
[0055] At the same time, since the upper expanded-portion holding
member 59 is provided on the bottom face of the movable body 51 via
the springs 59a, if the third expander punch 56 is pressed into the
second processed pipe P2, the third punch body 56a further expands
the second expanded portion P2a, thereby compressing the springs
59a and raising the upper expanded-portion holding member 59.
[0056] As mentioned above, the movable body 51 is moved downward,
and the neck-portion holder 52 gets out of alignment relative to
the expanded-portion holder 57. As a result, the second neck
portion P2c is decentered relative to the second expanded portion
P2a, while the second expanded portion P2a is expanded by the third
expander punch 56 in conformity with the shape thereof.
[0057] Consequently, the second processed pipe P2 is formed into
the fuel inlet pipe FP by plasticity. The fuel inlet pipe FP is, as
shown in FIG. 6, comprised of the large-diameter portion FPa
expanded by the third punch body 56a of the third expander punch
56, the gradually changing portion FPb formed in conformity with
the shape of the tip 56b of the third expander punch 56, and the
small-diameter portion FPc, having the original diameter of the
base pipe P0, into which the third expander punch 56 was not
inserted. The large-diameter portion FPa and the small-diameter
portion FPc are formed in eccentric relation to each other. There
are, of course, no cracks formed on the large-diameter portion FPa
nor on the gradually changing portion FPb, and no buckling caused
to the small-diameter portion FPc. In this example, the outside
diameter of the large-diameter portion FPa is 48.7 to 49.1 mm, and
the expansion ratio thereof is 91.7 to 93.3% relative to the base
pipe P0.
[0058] In these manners, by way of the first through third
processes, the fuel inlet pipe FP can be produced as an
eccentrically expanded pipe without formation of cracks or the like
thereon, even in cases where a desired expansion ratio of the
large-diameter portion FPa is high relative to the base pipe
P0.
[0059] Also, the beaded portion B and the HAZ portions H are
different from the other portions in expanding properties, and it
is, therefore, preferable to dispose these portions to the bottom
of the fuel inlet pipe FP, which is a region where the pipe is not
highly expanded at the time of decentering. However, the beaded
portion B and the HAZ portions H are easily cracked in the event
that any shock is caused to the pipe, for example, in case of
automobile collision, and, therefore, if these portions are
disposed to the bottom of the fuel inlet pipe FP, fuel leaks might
be caused in such an event. For this reason, in the embodiment,
these portions are disposed in the range of 45 to 135 degrees
relative to the direction of eccentricity, as shown in FIG. 4, seen
in section of the pipe, thereby preventing formation of cracks at
the time of decentering as well as preventing fuel from leaking out
even in the event that these portions are cracked by the automobile
collision or the like.
[0060] The present invention is, of course, not restricted to the
above described embodiment, and may be practiced or embodied in
still other ways without departing from the subject matter
thereof.
[0061] For example, in the above embodiment, the coaxially
expanding process is performed twice, but the coaxial expansion of
the pipe may be accomplished in three or more processes. Otherwise,
it may be accomplished in only one process depending on the
expansion ratio desired.
[0062] Also, the eccentrically expanded pipe is not restricted to
the fuel inlet pipe, and other types of pipes of any application
can be produced as well according to the manufacturing method of
the invention.
[0063] Furthermore, in the third process, stoppers for preventing
movement in the axial direction of the second processed pipe P2 may
be incorporated into the neck-portion holder 52. For example, as
shown in FIG. 5, a wall 54b for abutting on the end face of the
second neck portion P2c may be provided on a surface, on which the
second neck portion P2c is placed, of the upper neck-portion
holding member 54, and a wall 53b for abutting on the end face of
the second neck portion P2c may be provided on a surface, on which
the second neck portion P2c is placed, of the lower neck-portion
holding member 53. In this case, the walls 53b and 54b function as
the stoppers.
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