U.S. patent application number 11/063362 was filed with the patent office on 2005-06-30 for method of elongated bumper bar with sections twisted rotationally about the axis of elongation.
Invention is credited to Bladow, Jeff, Fleeger, Jereme, Jaeger, Walter.
Application Number | 20050138812 11/063362 |
Document ID | / |
Family ID | 32912158 |
Filed Date | 2005-06-30 |
United States Patent
Application |
20050138812 |
Kind Code |
A1 |
Bladow, Jeff ; et
al. |
June 30, 2005 |
Method of elongated bumper bar with sections twisted rotationally
about the axis of elongation
Abstract
A bumper system for an automotive vehicle includes a rolled
steel tube having a box or C-shaped cross section fixed to the
forward ends of the side rails of the vehicle so as to extend
transversely to the vehicle's longitudinal axis. The forward
surface of the vehicle is formed by a plastic fascia which may have
sloped surfaces for styling or aerodynamic reasons. The space
between the forward end of the bumper bar and the fascia is filled
with foam intended to absorb energy in an impact. To better match
the sloped sections of the fascia, certain sections of the bumper
bar are twisted about the longitudinal axis of the bar to create
surfaces inclined relative to the vertical. The bars are formed by
roll forming a steel web into an elongated member having generally
vertical opposed faces. A section of the rolled member is heated
above a metallurgical transition temperature. Then sections to be
inclined are twisted about the longitudinal axis of the bumper bar
in a die forming station and are then quenched to form a hardened
steel member.
Inventors: |
Bladow, Jeff; (West
Bloomfield, MI) ; Jaeger, Walter; (Lake Angleus,
MI) ; Fleeger, Jereme; (Wayne, MI) |
Correspondence
Address: |
GIFFORD, KRASS, GROH, SPRINKLE & CITKOWSKI, P.C
PO BOX 7021
TROY
MI
48007-7021
US
|
Family ID: |
32912158 |
Appl. No.: |
11/063362 |
Filed: |
February 23, 2005 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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11063362 |
Feb 23, 2005 |
|
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10745194 |
Dec 22, 2003 |
|
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60435410 |
Dec 20, 2002 |
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Current U.S.
Class: |
29/897.2 |
Current CPC
Class: |
Y10T 29/49622 20150115;
B60R 2019/1873 20130101; B60R 19/18 20130101; B60R 2019/1813
20130101; B60R 2019/1886 20130101 |
Class at
Publication: |
029/897.2 |
International
Class: |
B60R 019/03 |
Claims
I claim:
1. The method of forming a bumper bar for use in a bumper system
for a vehicle having a frame with forward projecting side members
which are secured to the rear face of the bumper bar, and a fascia
extending forward of the bumper bar and having certain sections
inclined forwardly and downwardly relative to the central section
of the vehicle, comprising: roll forming sheet steel into a section
having generally vertical opposed sidewalls; heating at least
certain portions of said rolled section above a metallurgical
transition temperature; twisting at least certain portions of said
roll formed heated section to provide at least the forward section
of the bumper bar with a forward and downward inclination at said
twisted section; and quenching the bumper bar.
2. The method of claim 1, wherein the roll formed section is formed
as a box section, further including the step of joining the
proximate edges of the box section to form a closed box
section.
3. The method of claim 1, wherein the sheet steel is rolled as a
"C" section.
4. The method of claim 1, wherein the metallurgical transition
temperature constitutes its austenizing temperature.
5. The method of claim 1, including the step of bending the bar
about its longitudinal axis while it is heated above its
metallurgical transition temperature, to provide a sweep to the
bumper.
6. The method of claim 1, wherein the step of twisting at least
certain portions of said rolled section about an elongated axis of
the bumper bar to provide at least the forward section of the
bumper bar with a forward and downward inclination at said twisted
section comprises engaging the bar, while heated above its
metallurgical transition temperature, with a forming tool which
engages the selected sections of the bar and twists the selected
sections about the longitudinal axis of the bar.
7. The method of claim 6, wherein the forming tool additionally
bends the bar about the longitudinal axis to provide it with a
sweep to accommodate the fascia.
8. The method of forming a bumper bar, comprising: roll forming
steel into a section having generally vertical opposed sidewalls
and generally horizontal top and bottom walls; heating at least
portions of said roll formed section above its metallurgical
transition temperature; engaging certain portions of the heated
section with a forming tool, which twists said certain sections
about the longitudinal axis of the bar, to provide at least certain
portions of the forward section of the bumper bar with a forward
and downward inclination relative to the vertical and horizontal
surfaces of the bar; and quenching the section.
9. The method of claim 8, wherein the metallurgical transition
temperature comprises the austenitic temperature of the metal.
10. The method of claim 8 wherein the twisted section constitutes
the center of the bar, leaving the two ends with substantially
vertical forward walls.
11. The method of claim 8, wherein the twisted section has forward
and rear walls inclined relative to the vertical.
12. The method of claim 8, wherein the twisted section has forward
walls inclined relative to the vertical.
Description
RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 10/745,194 filed Dec. 22, 2003, which claims
priority of U.S. Provisional Patent Application Ser. No. 60/435,410
filed Dec. 20, 2002.
BACKGROUND OF THE INVENTION
[0002] I. Field of the Invention
[0003] This invention relates to bumper systems for vehicles and
more particularly to a unique bumper bar and method for making the
same for use in a bumper system including an exterior fascia having
inclined sections, a bumper bar secured to extending frame sections
of the vehicle, and plastic foam between the bumper bar and the
fascia.
[0004] II. Description of the Prior Art
[0005] Modern automotive vehicles typically employ bumper systems
which include a bumper bar secured to the frame of the vehicle at
either the forward or rear end, so as to extend transversely to the
center line of the vehicle. The outer face of the bar is covered
with a plastic fascia that is designed based on primarily aesthetic
and aerodynamic considerations. The fascia may have surfaces
inclined relative to the vertical, typically sloping downward and
forward. Some or all of the space between the facing surfaces of
the bumper bar and fascia may be filled with material such as a
foam that absorbs energy between the two.
[0006] The system is intended to absorb as much impact energy as
possible in the shortest distance possible for purposes of keeping
the package size of the bumper at a minimum. Additionally, the mass
of the system should be minimized to minimize the energy required
to drive the vehicle and thus the vehicle emissions.
[0007] In order to achieve these criteria, the distance between the
opposed surfaces of the bumper bar and the fascia should be
minimized. However, the goal of employing a bumper bar with a
conventional boxlike configuration with opposed vertical sidewalls,
one connected to the frame and the other to the fascia, and with
fascias employing non-vertical surfaces, is difficult to attain.
This compromises the design goal of maintaining the bumper bar edge
as close as possible to the vehicle exterior surface in order to
meet, distribute and dissipate the energy that is absorbed during
the collision.
SUMMARY OF THE PRESENT INVENTION
[0008] To improve this situation, the present invention
contemplates a box-shaped or C-shaped bumper bar, made by a
conventional rolling process, which has certain of its sections
twisted about the longitudinal axis of the bar so that the forward
faces of the bar at these twisted sections are inclined relative to
the vertical to more closely match the mating surfaces of fascias
with inclined surfaces. These twists may be made at the center
section of the bumper bar, at the ends or other sections. A bumper
system employing this novel bumper bar will have a smaller
dimension along the longitudinal axis of the vehicle, give improved
impact performance, and minimize weight relative to a conventional
bumper design.
[0009] The bumper bars of the present invention may be manufactured
by a variety of processes, but the present invention further
relates to an improved method of manufacture of such bars. The
method involves roll forming the bar in a conventional manner to
achieve a box-shaped or C-shaped frame, welding the longitudinal
seam to join the edges in a closed shape, if necessary and desired,
heating the bar above the transition temperature, preferably to its
austenizing temperature, and placing it in a forming tool which
twists the selected sections about the longitudinal axis of the bar
and bends the bar about the horizontal axis to provide it with the
necessary sweep to accommodate the fascia which often has the
rearward sweep away from the center. After the shaping, and
preferably while in the same forming tool, the bumper beam is
quenched.
[0010] The bumper bar of the present invention provides enhanced
energy absorption performance because energy of impact is absorbed
both in translation and in twisting of the inclined beam surfaces
back toward the vertical.
[0011] Other objects, advantages and applications of the present
invention will be made apparent by the following detailed
description of a preferred embodiment of the invention. The
description makes reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] Reference will now be made to the attached drawings, when
read in combination with the following detailed description,
wherein like reference numerals refer to like parts throughout the
several views, and in which:
[0013] FIG. 1 is a cross section through a conventional bumper
system showing a bumper bar, attached to the forward end of the
vehicle frame, and a fascia covering the forward end of the bumper
bar with foam plastic between the interior surface of the fascia
and the forward surface of the bumper bar;
[0014] FIG. 2 is a perspective view of the bumper bar of FIG. 1
illustrating the sweep of the bar in the horizontal plane so that
the ends are rearwardly of the center section;
[0015] FIG. 3 is a top view of the bumper bar of the present
invention;
[0016] FIG. 4 is a cross section through the bar of FIG. 3 at the
center section showing the contour of the fascia at that section
and showing the untwisted position of the bumper bar in dotted
line;
[0017] FIG. 5 is a cross section through the bumper bar of FIG. 3
adjacent the end of the bumper bar and showing the cross section of
the fascia as it lies at that section showing the untwisted section
of the bumper bar in dotted line;
[0018] FIG. 6 is a schematic diagram illustrating the method of
processing the rolled bumper bar of the present invention; and
[0019] FIG. 7 is a cross section of the die forming part of FIG. 6
showing the manner of twisting the bar at the center section.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT OF THE INVENTION
[0020] The present invention is directed toward a bumper bar system
of the general type commonly used in automobiles and light trucks
and illustrated in FIG. 1. These systems employ a bumper bar 10
which is usually produced by rolling sheet steel to form a
generally box-like configuration which is elongated in the
direction normal to the plane of the drawing. The box may be
completely closed, as illustrated in FIG. 1, which is usually
achieved by securing the free edges of the box as at 12 by welding,
seaming or a similar process. Alternatively, the edges may be left
unsecured, achieving a generally "C" cross section.
[0021] The bumper bar 10 is typically secured to the vehicle by
attaching it to a pair of side rails 14 of the vehicle frame (only
one of which is shown in FIG. 1) by bolts 16 or other attachment
means, at a pair of spaced points inwardly from the ends of the
bumper bar 10. The forward side of the bumper system is covered by
a plastic fascia 18 which forms the outer visible portion of the
bumper system. This fascia is typically nonrectangular and its
contour is determined by both aesthetic and aerodynamic
considerations. The space between the rearward surface of the
fascia and the forward surface of the bumper bar 10 may be filled
with plastic foam 20. The foam may be formed integrally with the
fascia, using a dual durometer system, or they may be separate
components.
[0022] The fascia has a sweep rearwardly from its center section
toward its sides and the bumper bar generally indicated at 10,
illustrated in perspective in FIG. 2, is similarly swept, either in
the rolling process or preferably in a post-rolling pressing
operation.
[0023] The bumper bars 10 of the prior art employ a variety of
cross sections which may vary along the length of the bar and may
include indentations, strengthening ribs and the like. Typical
bumper bars for use in bumper systems of the type contemplated by
this invention are disclosed, for example, in U.S. Pat. Nos.
5,080,410; 6,325,431; 6,343,820; 6,349,521 and 6,352,257. While
each of these bars differs from one another in configuration, all
generally employ the rectangular cross section, with a top 22, a
bottom 24, a forward side 26, and a rearward side 28. The forward
and rearward sides are aligned generally vertically, at right
angles to the top and bottom. As a result, as illustrated in FIG.
1, the spacing between the fascia 18 and the forward surface 26 of
the bumper bar will vary along its height and contour resulting in
different thicknesses of foam 20 positioned between the two.
[0024] These bumper systems are driven by the need to absorb as
much impact energy as possible in the shortest distance for
purposes of minimizing bumper system package size and minimizing
the mass so as not to adversely affect the vehicle's fuel
consumption and emissions. The present invention is directed toward
the goal of providing a bumper bar forward edge which closely
approximates the contour of the fascia so as to minimize the
distance between the two and the need for excessive use of foam or
other material to fill the gaps between the bumper beam and the
fascia.
[0025] The preferred embodiment of the bumper bar of the present
invention is based on the bumper bar design disclosed in U.S. Pat.
No. 6,352,297 to Sundgren et al. The disclosure of that patent is
incorporated herein by reference. That bar is characterized by the
fact that toward each end of the bar the rear flange surface, i.e.
equivalent to 28 in FIGS. 1 and 2, is formed with a forward
extending center section such that it contacts the forward flange,
i.e. 26, at its midsection. The bar is formed with an array of
grooves along its length and transversely to strengthen the bar and
improve its collision properties. While incorporation of the
improvements in the present invention with the Sundgren et al.
bumper bar provides especially advantageous design, the present
invention can be employed with any form of bumper bar system.
[0026] A bumper bar formed in accordance with the present invention
is illustrated in plan view in FIG. 3. The beam, generally
indicated at 30, is elongated and has a top 32, a rear flange 34, a
forward flange 36, and a bottom flange 38.
[0027] As will be subsequently disclosed, the bumper bar is formed
by a process which first involves rolling a sheet of steel into the
desired cross-sectional configuration. The original cross sections
of the material, before pressing, are illustrated in FIGS. 4 and 5
by the dotted lines of element 31. In this "untwisted" position it
will be noted that the side flanges 34 and 36 are oriented
generally vertically, normally to the end walls 32 and 38. While
these untwisted cross sections include transversely oriented
elements, and in particular the indentation 40 located in the rear
flange 34 of the cross section, adjacent the corners of the
vehicle, the untwisted sections, 31, resemble the prior art bumper
bars. FIGS. 4 and 5 include the cross sections of the fascia at the
centerline of the vehicle, as illustrated at 42 in FIG. 4 and on
the corners of the vehicle as illustrated at 44 in FIG. 5 with the
conventional foam 20 between the forward face of the bar and the
rear face of the fascia. It is important to note that in its
twisted position 30 the forward flange 36 of the bumper bar is
substantially closer to the interior wall of the fascia 42 or 44
than it would be in the untwisted position of 31.
[0028] It should also be noted that in the preferred embodiment of
the invention, the twist has been made about an axis which
corresponds with one upper or lower edge of the twisted shape. In
FIG. 4 the twisted contours and the untwisted contours
substantially match at the forward top corner of the section
indicated by the numeral 48. Similarly, at the corner cross section
of FIG. 5, the twisted section 30 and the untwisted section 38
closely match at the numeral 50. These relatively untwisted points
represent locations at which the cross section is locked during the
twisting operation in the press as will be subsequently
described.
[0029] Referring now to FIG. 6, a schematic illustration is shown
of the method of processing the rolled bumper bar and includes a
first step 52 by which the bar is roll formed the bar in a
conventional manner, and such as in particular to achieve a
box-shaped or C-shaped frame. Succeeding step 54 illustrates the
welding of a longitudinal seam to join the edges in a closed shape,
if necessary and desired.
[0030] Succeeding step 56 illustrates heating the bar above the
transition temperature, preferably to its austenizing temperature.
At step 58, the part is placed in a forming tool which twists the
selected sections about the longitudinal axis of the bar and, at
further step 60, bends the bar about the horizontal axis to provide
it with the necessary sweep to accommodate the fascia, which often
exhibits a rearward sweep away from the center. After the shaping,
and preferably while in the same forming tool, the bumper beam is
quenched at step 62.
[0031] Referring finally to FIG. 7, an illustration is generally
shown of the manner in which a bar is twisted, such as along a
center section thereof. In particular, and as shown, a part 64 is
held between a pair of gripping members 66 and 68, such as
compressible die members. A suitable torsional or twisting force
may be applied, such as generally referenced at 70, and in order to
twist such as a center section location of the bar. Reference is
also made to the cross-sectional view of FIG. 4 and which shows the
center twisted section position of a bar according to the
invention.
[0032] Having described my invention, other and additional
preferred embodiments will become apparent to those skilled in the
art to which it pertains and without deviating from the scope of
the appended claims.
* * * * *