Curved elongate member of closed sectional shape and method...

Vehicle fenders – Buffer or bumper type – Composite bumper

Reexamination Certificate

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C293S122000, C052S749100, C052S749100, C052S749100

Reexamination Certificate

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06296287

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to curved elongate members of a closed sectional shape which are particularly suitable for use as bumper beams reinforcing automotive vehicle bumpers, as well as methods and apparatus for fabricating such closedsectional curved elongate members.
2. Related Prior Art
As bumper-reinforcing beams (bumper beams) for automotive vehicles and the like, there have been used elongate tubular members which have a sectional shape of, for example, a closed rectangle and are curved along a longitudinal direction thereof. These elongate tubular members will hereinafter be referred to as “closed-sectional curved elongate members”. Such closed-sectional curved elongate members are generally fabricated by pressing or rolling; in recent years, the rolling has been used more popularly than the pressing because it achieves higher productivity than the pressing. Examples of the known methods of fabricating the closedsectional curved elongate members using the rolling include a “method of fabricating a reinforcing member for a vehicle bumper” disclosed in Japanese Patent Laid-open Publication No. HEI-9-141329.
According to the disclosure in the No. HEI-9-141329 publication, closed-sectional curved elongate members are formed of a continuous plastic sheet or strip (typically a metal strip) sequentially supplied from an uncoiler disposed at an upstream end of a fabricating apparatus. More specifically, the disclosed fabricating method comprises a first roll-bending step, a laser welding step, a second roll-bending step and a cutting step.
In the first roll-bending step, the plastic strip supplied from the uncoiler is bent widthwise into a semifinished tubular structure having a substantially closed section by means of a roll-bending machine which includes a series of roller pairs, each made up of upper and lower rollers, disposed along a traveling direction of the strip (i.e., in an upstream-to-downstream direction). Also, as the strip sequentially passes through the roller pairs, it is progressively curved along the traveling direction, i.e., along its length.
Then, in the laser welding step, opposite longitudinal edge portions of the plastic strip, which have been caused to substantially butt against each other through the bending in the first roll-bending step, are welded together by a laser welding machine disposed downstream of the roll-bending machine, to thereby provide a finished tubular structure with a welded joint section.
Next, in the second roll-bending step, the finished tubular structure is further curved by means of a three-point roll-curving machine having three rollers disposed downstream of the laser welding machine. Finally, in the cutting step, the finished tubular structure with the welded joint section, transferred from the second roll-bending step, is cut into a predetermined length to provide the bumper-reinforcing member.
Because the bumper-reinforcing member fabricated by the method disclosed in the No. HEI-9-141329 publication is in the form of a closed-sectional curved elongate member, it has great rigidity against bending and twisting forces and great robustness against impacts as compared to the traditional open-sectional curved elongate member having its opposite longitudinal edge portions left unjointed.
However, because the method discussed in the No. HEI-9-141329 publication uses the expensive laser welding machine to butt-weld the opposite longitudinal edge portions of the semifinished tubular structure, it would require complicated manufacturing lines and increased costs. Further, if a high-tensile steel sheet is used as the strip, the butt-welded joint section would become more brittle (i.e., would have a reduced strength), so that there would arise a need for an extra step of locally annealing the butt-welded joint section.
SUMMARY OF THE INVENTION
It is accordingly an object of the present invention to provide a closed-sectional curved elongate member which can be fabricated in quantity at low costs in a greatly simplified manner.
It is another object of the present invention to provide method and apparatus capable of fabricating a closed-sectional curved elongate member in quantity at low costs in a greatly simplified manner.
According to an aspect of the present invention, there is provided a closed-sectional curved elongate member which includes a crimped joint section that is formed on any one of a plurality of wall surfaces of the elongate member defining a closed section of the elongate member, the crimped joint section extending along a length of the elongate member, and which is curved along a longitudinal direction thereof.
The crimped joint section thus formed along the length of the elongate member can function as a rib reinforcing the elongate member, so that the closed-sectional curved elongate member of the present invention has rigidity equal to or greater than that of the conventional closed-sectional curved elongate member having the welded joint section.
The crimped joint section may be provided on either the outside or the inside of the elongate member. However, it is more preferable that the crimped joint section be provided inside the closed section of the elongate member, because the crimped joint section thus provided will not interfere with other components already placed or to be placed near the elongate member.
Further, it is preferable that the crimped joint section have gatherings that will achieve an increased strength of the joint.
According another aspect of the present invention, there is provided a method of fabricating a closed-sectional curved elongate member, which comprises: a step of bending a plastic strip, such as a metal strip, widthwise into a closed sectional shape by means of a series of bending rollers disposed along a longitudinal direction of the strip; a step of crimping together opposite longitudinal edge portions of the strip that are caused to substantially butt against each other through the bending by the step of bending, by means of crimping rollers, to thereby provide a closed-sectional elongate member with a crimped joint section; and a step of curving the closed-sectional elongate member along a length of the closed-sectional elongate member, by means of a series of curving rollers, as the closed-sectional elongate member is transferred in a predetermined traveling direction.
The step of curving may be initiated either after completion of the step of bending or during the step of crimping. However, performing the step of curving during the step of crimping is more preferable in that the curving step can be done concurrently with the crimping step and thus the overall necessary time for the fabrication can be significantly reduced.
According still another aspect of the present invention, there is provided an apparatus for fabricating a closed-sectional curved elongate member, which comprises: a roll-bending unit including a series of bending rollers disposed along a traveling direction of a plastic strip for bending the strip widthwise into a semifinished closed sectional shape; a rolling unit for rolling a bottom portion of the strip bent via the roll-bending unit, to thereby curve the strip along the traveling direction; a crimping-roll unit for sequentially crimping together opposite longitudinal edge portions of the strip that are caused to substantially butt against each other through the rolling by the rolling unit, to thereby provide a closed-sectional elongate member with a crimped joint section; and a roll-curving unit including a series of curving rollers for further curving the closed-sectional elongate member along the traveling direction.
The apparatus of the present invention can sequentially crimp together the substantially butting opposite longitudinal edge portions of the strip by means of the crimping-roll unit and can perform the crimping and curving of the elongate member in succession. Thus, the inventive apparatus can fabricate the closed-sectional curved elongate member in a greatly simplified manner

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