Metal deforming – By use of non-deforming work-gripping clamp and relatively... – By individually non-deforming clamps
Reexamination Certificate
2001-03-27
2002-09-24
Larson, Lowell A. (Department: 3725)
Metal deforming
By use of non-deforming work-gripping clamp and relatively...
By individually non-deforming clamps
C072S370040, C072S370060
Reexamination Certificate
active
06453714
ABSTRACT:
FIELD OF THE INVENTION
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
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.
Now, in order to integrally form such a fuel inlet pipe FP by use of the pipe-expanding method, the following procedure is undertaken.
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.
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
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 expansion 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.
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.
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.
Expansion ratio
=
D1
-
D
D
×
100
%
[
Formula
1
]
D: Outside Diameter of Pipe Before Pipe Expansion
D
1
: Outside Diameter of Pipe After Pipe Expansion
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.
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.
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.
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.
The method of the invention for forming an eccentrically expanded pipe is suitable, particularly, for making a fuel inlet pipe. In recent y
Kido Tsuguo
Nakada Yuji
Omori Tetsuji
Yamamoto Seiji
Davis & Bujold P.L.L.C.
Futaba Industrial Co. Ltd.
Larson Lowell A.
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