Metal deforming – Process – Tube making or reshaping
Reexamination Certificate
1999-10-25
2001-07-17
Larson, Lowell A. (Department: 3725)
Metal deforming
Process
Tube making or reshaping
C072S318000
Reexamination Certificate
active
06260401
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of forming a highly flared portion on an end of a pipe, which is of a diameter about twice the diameter of the blank pipe, and a highly flared pipe.
BACKGROUND ART
Heretofore, it has been attempted to flare an end of a pipe, e.g., a beam member or a frame member in the form of a metallic pipe as a vehicular indoor component or the like, for increasing the mounting strength of the pipe. According to one known machining process for flaring a pipe end, the outer circumferential surface of a blank pipe is clamped in place by clamp dies and a tapered flaring punch is pressed into an end of the pipe hole thereby to flare the pipe end.
When the flaring punch is pressed into the pipe end to flare the same according to the above machining process, the flared pipe end is elongated with a resultant reduction in its thickness. When the elongation limit of the pipe material is reached, the pipe starts being ruptured from the flared end. Ordinary steel pipes can be flared up to diameters that are about 1.4 times those of blank pipes, and cannot further be machined beyond that limit.
When the flaring punch is pressed into an end of a blank pipe, the centers of the blank pipe and the flaring punch may be positioned out of alignment with each other for thereby producing a pipe with an eccentric flared end. According to this process, the produced pipe includes a region which is more elongated than a pipe with a concentric flared end depending on the amount of eccentricity, resulting in large thickness variations of the pipe. Generally, it is more difficult to produce pipes with eccentric flared ends than pipes with concentric flared ends.
FIG. 11
shows measured thicknesses of a pipe with an eccentric flared end which has been machined from a blank pipe having a wall thickness of 1 mm according to the conventional process. The measured thicknesses indicate that the thickness of a pipe region where the wall thickness is reduced to a maximum, among regions in circumferential and axial directions, is reduced to about 50% of the wall thickness of the blank pipe.
Pipes with concentric flared ends and pipes with eccentric flared ends are employed in different spots in vehicles, and some flared ends are attached to vehicle bodies and parts are mounted on other flared ends. Since pipes with ends flared to diameters that are about 1.4 times those of blank pipes suffer insufficient mechanical strength and generally have reduced thickness, they need to be reinforced by separate stiffeners. However, if those pipes are incorporated in vehicles, then use of the stiffeners is disadvantageous because they increase the weight of the vehicles.
DISCLOSURE OF THE INVENTION
The present invention has been made in an effort to solve the above problems. It is an object of the present invention to provide a machining technique of flaring at least an end of a pipe to produce a concentric or eccentric flared end which is of a diameter about twice the diameter of a blank pipe without rupturing the end, and a highly flared pipe.
To achieve the above object, there is provided in accordance with the present invention, as defined in claim
1
, a method of forming a highly flared pipe by pressing a flaring punch into a pipe from its hole to form a concentric or eccentric flared portion, characterized by the steps of applying axial compressive forces to the pipe material where the flaring punch is pressed in to allow the flared portion to maintain a wall thickness which is at least 70% of the wall thickness of the blank pipe and to have a diameter which is about twice the diameter of the blank pipe.
Specifically, the pipe is flared while compressive forces are being applied axially (in the direction in which the flaring punch is pressed) to the pipe material where the flaring punch is pressed in to allow the flared portion to maintain a wall thickness which is at least 70% of the wall thickness of the blank pipe. Even if the pipe is flared to a diameter which is about twice the diameter of the blank pipe, the pipe is prevented from being ruptured or otherwise damaged at the end.
According to the present invention, the compressive forces applied axially to the pipe material where the flaring punch is pressed in are adjusted by adjusting the taper angle of the flaring punch.
If the taper angle were excessively large, then only tensile forces would be radially applied to the pipe material where the flaring punch is pressed in, and axial compressive forces would not effectively be applied thereto. If the taper angle were excessively small, then, similarly, compressive forces would not effectively be applied to the pipe material where the flaring punch is pressed in, and the efficiency with which to form the flared portion would be low.
If the taper angle is appropriately established, then the pipe portion where the flaring punch is pressed in can maintain a wall thickness which is at least 70% of the wall thickness of the blank pipe. Thus, even if the pipe is flared to a diameter which is about twice the diameter of the blank pipe, the pipe is prevented from being ruptured or otherwise damaged.
According to the present invention, furthermore, the flared portion is formed by pressing flaring punches having different maximum diameters in a plurality of stages.
When the flaring punches having the different maximum diameters are pressed in the plural stages, pipe regions where the elongation of the pipe material is maximum are axially distributed, but prevented from being localized in a certain area.
Those flaring punches have the same taper angle.
If the pipe is a seam-welded pipe and the flared portion is eccentric, then a seam-welded region is aligned with the direction in which the amount of eccentricity is maximum.
With the eccentric highly flared pipe, the direction in which the amount of eccentricity is maximum represents a region where the tensile forces are maximum and the material elongation is largest. With the seam-welded pipe, the seam-welded region is harder than other regions of the pipe. Consequently, the seam-welded region is aligned with the region where the maximum tensile forces are imposed, for thereby preventing that region from being ruptured.
According to the present invention, moreover, a highly flared pipe has a flared portion having a diameter which is about twice the diameter of a blank pipe, produced by pressing a flaring punch into the blank pipe from its hole, the flared portion having a wall thickness which is at least 70% of the wall thickness of the blank pipe. According to claim
6
, if the pipe is a seam-welded pipe, then a seam-welded region is aligned with the direction in which the amount of eccentricity is maximum.
The above highly flared pipe can be produced by the above forming method.
According to the present invention, furthermore, the end of the flared portion is flanged.
If the end of the flared portion is flanged, then it can be used as a mounting member of increased rigidity.
REFERENCES:
patent: 2506657 (1950-05-01), Webster
patent: 2739376 (1956-03-01), Peet
patent: 4450329 (1984-05-01), Arimoto et al.
patent: 4732030 (1988-03-01), Tanaka
patent: 4901557 (1990-02-01), Schmidt
patent: 49-65974 (1974-06-01), None
patent: 54-52664 (1979-04-01), None
patent: 57-39049 (1982-03-01), None
Bestex Kyoei Co., Ltd.
Larson Lowell A.
Merchant & Gould P.C.
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