Note: Descriptions are shown in the official language in which they were submitted.
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Cross-Reference to R -tatpd~ ' atin
The present application claims priority of provisional application Serial
No. 60/061,103, filed October 3, 1997, and titled Protective Bar For Vehicle
Door.
Technical Field
The present invention relates generally to protective bars for vehicles
and more specifically to a roll formed martensitic steel protective bar with
flanges bonded to the protective bar using structural adhesive.
Background of tl~e Invention
Protective bars for vehicles are generally known and are necessary for
protecting vehicle occupants during a crash. A protective bar for a vehicle
must have sufficient strength to adequately protect the passengers of the
vehicle
during the crash. At the same time, it is desirable to design the bar for a
specific yield or failure point so that crash loads can be dynamically
absorbed.
As with all automotive components, it is also desirable that the protective
bar
be low in weight and cost. A typical protective bar consists of a tubular bar
positioned from front to rear in a vehicle door. Brackets for interconnecting
the bar and the door are typically welded to the ends of the tubular bar. Many
prior art tubular steel protective bars suffer from the limitation that they
are
heavy arl~ it is difficult to control the yield or failure point of the bar.
U.S. Patent No. 5,232,261, issued to Kuroda et al., discloses an
example of a door impact beam for an automobile which includes a rectangular
cross sectional shaped and internally hollowed heat treated steel member and
which includes rounded edges. Attachment portions are provided at two
opposite ends of the heat treated steel body and are welded respectively to
the
beam body as well as to the front and rear portions of the door panel.
A further example of a vehicle door intrusion beam is illustrated in
U.S. Patent No. 5,580,120, issued to Nees et al., and which shows a hollow
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cross sectional configuration formed by a single piece of material by roll
forming a tubular blank to a closed I-beam cross-sectional configuration.
First
and second mounting plates are arrayed at the opposite ends of the elongate
beam and are likewise secured by welding.
Summary of the Present Invention
The present invention is a protective bar system for installation within
a vehicle, and most particularly a vehicle door. A protective bar is provided
and is constructed of a roll formed steel material. Martensitic steel is a
desirable material for protective bars due to its high strength. It is
preferable
to form martensitic steel by roll forming; since the process is fast, and does
not
require large, complicated equipment. It has further been determined that hot
stamping of martensitic steel is fairly expensive to accomplish and often
results
in thinning of the material, with adverse structural consequences.
The elongate protective bar exhibits a substantially "U" shaped cross
section and further includes first and second oppositely extending flange
portions extending from the cross sectionally "U" shaped body. Secured to a
first end of the protective bar is a first flange and secured to a second end
of the
protective bar is a second flange. The first and second flanges are likewise
constructed with a substantially "U" shaped cross section and with oppositely
and outwardly extending portions for receiving the ends of the elongate bar in
matingly engaging fashion. The flanges each further include substantially
flattened Cnds for securing to front and rear portions of the door panels.
A structural adhesive secures the first and second flanges to the matingly
engaging ends of the protective bar and is a novel improvement over prior art
welding techniques which often result in the roll formed martensitic steel
deforming when flanges are welded thereto. It has also been found that
welding techniques employed with martensitic steel will result in a delayed
deformation after some time, this causing a resultant deformation of a vehicle
door to which the protective bar has been attached. The substantially
flattened
ends of the first and second flanges may themselves be secured to front and
rear
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portions of the door panel either by welding or by the use of additional
structural adhesives.
Reference will now be made to the attached drawings, when read in
combination with the following specification, wherein like reference numerals
refer to like parts throughout the several views, and in which:
Figure 1 is an environmental view of the protective bar system mounted
within a conventional vehicle door according to the present invention;
Figure 2 is an enlarged view of the protective bar system as illustrated
in Figure 1 according to the present invention;
Figure 3 is a side view of the protective bar system illustrated in Figures
1 and 2 according to the present invention;
Figure 4 is a cross-sectional view of the bar system of Figure 2 taken
along lines 4-4; and
Figure 5 is a cross-sectional view of the bar system of Figure 2 taken
along lines 5-5.
Detailed Descriution of the Drawings
Referring now to the figures, a protective bar system according to the
present invention is generally shown at 10 for use with a conventional vehicle
door 12. The vehicle door 12 is constructed in a conventional manner and
typically includes an outer panel 14, a spaced apart inner panel 16, a front
portion 18~ and a rear portion 20. It is understood however that the
protective
bar system according to the present invention may further be utilized with any
other conventional portion of a vehicle, such as its undercarriage, roof or
rear
side, or with any other type of enclosure in which the provision of an impact
resistant member would be advantageous.
The bar system includes an elongate and roll formed steel bar 22 which,
viewed in cross section, has a substantially modified "U" shaped or hat shaped
configuration with a flat base 24, a first upwardly extending side 26, a
second
upwardly extending side 28, a first flange portion 30 extending from an upper
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edge of the first upwardly extending side 26 and a second flange portion 32
extending in opposite fashion from the first flange portion 30 and from an
upper edge of the second upwardly extending side 26. The first and second
flange portions 30 and 32 preferably extend in substantially perpendicular
fashion from the upwardly extending sides 26 and 28 and in parallel fashion
relative to the flat base 24, however it is understood that cross sectional
shape
of the bar 22 can be modified to a substantially "V" shape or other
configuration according to strength requirements and without departing from
the scope of the invention. The bar is preferably formed of a martensitic
steel
preferably of a grade between 190 to 220 and a thickness of 2.0 mils and such
is available from the Inland Steel Company among others. Within the context
of this disclosure, it is to be understood that martensitic steel is a high
strength
roll formable steel which includes martensitic therein. It is further
understood
that other types of high strength steel may also be utilized in the protective
bar
system according to the present invention.
A first flange 34 is adhesively bonded to one end and a second flange
36 adhesively bonded to the other end of the bar 22. The first and second
flanges 34 and 36 are shaped to nest with the ends of the steel bar 22 as best
shown in Figure 4. Specifically, referring again to Figure 4, which is the
cutaway view showing first flange 34 in nesting arrangement with associated
end of steel bar 22, first flange 34 includes a mating flat base 38, a first
side
40, a second side 42, a first outwardly extending flange portion 44 and a
second outwardly extending flange portion 46. The flat base 38, first and
second sides 40 and 42 and first and second outwardly extending flange
portions 44 and 46 are matingly engaged with the corresponding surfaces 24,
26, 28, 30 and 32 of the steel bar 22 as viewed in cross section. The first
flange 34 further includes first and second downwardly extending end portions
48 and 50 which extend from the first and second outwardly extending flange
portions 44 and 46, respectively, and cover the terminating edges of the
opposite extending flange portions 30 and 32 when viewed from the side. The
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second flange 36 is constructed identically to the first flange 34 such that
it will
matingly engage with the opposite end of the steel bar 22.
The flanges 34 and 36 are preferably stamped steel and are shaped, at
corresponding flattened ends 52 and 54, to conform to mounting surfaces on the
5 front and rear portions 18 and 20 of the vehicle door 12. Different brackets
14
and 16 may also be used depending upon the application. The steel bar 22 has
a uniform cross-section and therefore by using the steel bar 22 in combination
with a variety of flanges 34 and 36, the steel bar 22 can mate with a variety
of
vehicle surfaces.
The flanges are adhesively bonded to the steel bar 22 using a layer of
structural adhesive 56. Within the context of this disclosure, structural
adhesives are understood to include high strength adhesives having a yield
strength in a shear of at least 2000 pounds per square inch. Preferably, the
structural adhesive 56 is a two part epoxy with a yield strength in shear of
at
least 2067 pounds per square inch according to specified requirements and
typically of a value greater than 3000 pounds per square inch. Such adhesives
are available from The 3-M Corporation and an example is the two part epoxy
adhesive 5047 which is formulated for hem flange bonding applications on
aluminum, steel or the like.
To form the bar 22, martensitic steel is roll formed into the substantially
"U" shaped configuration with first and second flange portions 30 and 32
extending'~thherefrom. This cross-sectional shape provides high strength and
the
additional mating surface area of the flange portions 30 and 32 provide a
large
bonding region for the structural adhesive layer 56 as best shown in Figure 4.
Roll forming is generally limited to forming pieces without closed sections.
Therefore, an open hat channel or "U" shaped configuration is easily formed.
After the flanges 34 and 36 are attached through the use of the structural
adhesive, curing is accomplished by moderate heating of the adhesive,
typically to a temperature of less than 350°F. Such temperatures will
not
deform the martensitic bar since they do not reach the higher temperatures
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otherwise accomplished by conventional welding techniques or the like.
Heating may be accomplished by baking the unit in an oven, or by passing an
electrical current through the adhesive so as to cause resistive heating in
the
area of the adhesive. In some instances, room temperature curing adhesives
may be employed. It is also envisioned that the flattened ends 52 and 54 of
the
flanges 34 and 36 may also be secured to the front and rear portions 18 and 20
through use of a structural adhesive as well as being secured by conventional
mounting techniques such as welding or the like.
In view of the teaching presented herein, other modifications and
variations of the present inventions will be readily apparent to those of
skill in
the art. The foregoing drawings, discussion and description are illustrative
of
several embodiments of the present invention; but are not meant to be
limitations on the practice thereof. It is the following claims, including all
equivalents, which define the scope of the invention.
I claim:
