This invention relates generally to structural elements. More specifically, the invention relates to reinforcing beams. In particular, the invention relates to reinforcing beams configured and operable to absorb impacts perpendicular to the length thereof.
Reinforcing beams are incorporated into a variety of structures, including motor vehicles, to increase the resistance of those structures to impacts. In particular, reinforcing beams, also referred to as side impact beams, are incorporated into door panels and body panels of motor vehicles so as to increase their strength in side impact collisions. Likewise, such reinforcing beams may be incorporated into bumpers, roof structures, and the like. Also, such beams may be utilized in applications other than motor vehicles such as static structures.
In general, it is desirable that any such reinforcing beams have a high strength to weight ratio, since weight represents loss in efficiency in mobile structures such as motor vehicles, and in any instance, represents material costs. In order to increase the strength, and hence the strength to weight ratio of such beams, various configurations of beam design have been implemented in the prior art. For example, U.S. Pat. No. 6,554,345 discloses a lightweight beam with two flanks that have a cross section that follows the equation y=cos hyp (x). However, the '345 patent results in a beam with an open back side that if closed, must have strips of sheet metal or a sheet steel cover spot welded to the two flanks. Joining the strips of sheet metal or the sheet steel cover to the two flanks, which provides improved rigidity to the beam, requires additional manufacturing steps to cut and/or form the beam and join the sheet material thereto.
As will be explained in detail hereinbelow, the present invention recognizes that beams having a particularly configured cross section will provide a structure having a very high strength to weight ratio. Furthermore, the configuration of the beams of the present invention may be readily fabricated by high speed, relatively simple processes such as roll forming. These and other advantages of the invention will be apparent from the drawings, discussion and description which follow.
A high strength reinforcing beam structure is provided. The beam structure includes an elongated member, with at least a portion of a length of the member having a cross section which defines a first, a second, a third, and a fourth curved segment. Each of the curved segments has a shape that can be defined by a hyperbolic cosine function. In addition to the high strength reinforcing beam structure, a process for making such a structure is provided. The process includes feeding an elongated member at least partially into a roll forming machine, the machine forming at least a first portion of a length of the elongated member such that the cross section has a first, a second, a third, and a fourth curved segment, each of the curved segments defined by a hyperbolic cosine function. In some instances, the process produces a cross section that includes a discontinuity between at least two of the curved segments. In other instances, the curvature of each of the curved segments can be identical or in the alternative the curvatures of the segments can all be different. In yet other instances, the curvature of at least two of the segments can be identical. In addition, the cross section of the elongated member can have two planes of symmetry and/or the cross section can be a closed cross section, or in the alternative an open cross section.
The present invention comprises a high strength reinforcing beam structure. The beams of the present invention are generally elongated members, typically formed from high-strength materials such as steel. The beams are configured so that at least a portion of the length thereof has a particular cross-sectional profile which includes a first, a second, a third and a fourth curved segment, wherein the curvature of each of the segments is defined by a hyperbolic cosine function.
Curves defined by hyperbolic cosine functions are also generally known as catenary curves, and a catenary curve is a mathematical shape defined by a chain or other such flexible body which is supported at each of its ends by supports spaced apart at a distance less than the length of the flexible body, so that the flexible body will hang therebetween. The force of gravity acting on the flexible body will cause it to assume a curved shape referred to as a catenary.
The curves defining the segments of the cross section of the reinforcing beam of the present invention are catenary-type curves, although it is to be understood that these curves need not define a full catenary, but may comprise only a portion of a catenary. In general, the curves of the present invention are defined by a hyperbolic cosine function, and a general formula therefor is:
where k is a constant and e is the base of natural logarithms, namely 2.718 . . . .
It has been found that reinforcing beams which incorporate such curved segments exhibit very high strength to weight ratios. Therefore, the use of such beams in motor vehicles allows for the manufacture of a safe, high strength, collision-resistant vehicle without unduly increasing the weight thereof. The beams of the present invention may be implemented in a variety of configurations, and the principles of the invention will be illustrated with regard to some specific embodiments; although, it is to be understood that various other embodiments may likewise be implemented in accord with the teaching presented herein and within the scope of the present invention.
Referring now to
Referring now to
As further illustrated in
In the beam of
In the illustration of
Yet other embodiments of cross-sectional profiles may be utilized to fabricate the reinforcing beams. For example,
Referring now to
As discussed above, a single beam may be fabricated to have different cross-sectional profiles along its length, provided that at least a portion of the length of the beam has a profile comprised of four curved segments as discussed above. The remainder of the beam may have the very same profile, or it may be otherwise profiled. In some instances the beam may have two length segments each having a different cross-sectional profile, each of the profiles including four curved segments each defined by a hyperbolic cosine function, while in other instances a portion of the beam may be otherwise configured. For example, such other portions of the beam may include less than four curved segments defined by hyperbolic cosine functions.
The beams of the present invention may be fabricated from a variety of materials; although, for reasons of strength and weight, metals are one specifically preferred group of materials for their fabrication. Steel comprises one specific material which may be utilized for the fabrication of the beams, and such steels may comprise hardened or hardenable steels. In other instances, other metals such as aluminum and various alloys may likewise be employed, as may be composite materials such as reinforced polymers, carbon-carbon composites, metal matrix composites and the like.
A variety of processes may be utilized to fabricate the beams of the present invention. Roll forming is one process having particular utility in the fabrication of these beams, since roll forming may be readily implemented to form complex profiles in a high-speed process. Other forming techniques including stamping, pressing, bending and the like may be likewise employed as may be multi-step processes.
It has been found that beams fabricated in accord with the foregoing provide very good strength when subjected to loading in a direction perpendicular, or in an angled relationship, to their length and hence may be advantageously employed to increase the side impact resistance of motor vehicles. Likewise, the beams may be utilized as bumper bars or as reinforcements for roofs and other portions of a vehicular body. Beams fabricated in accord with the foregoing may also be incorporated into aircraft and watercraft as well as static building structures.
As an example, and for illustrative purposes only, testing of side impact door beams for motor vehicles made in accordance with an embodiment disclosed herein was compared with testing of prior art side impact door beams. The results the testing are shown in Table 1 below wherein the thickness of the sheet material used to make a given beam, the overall mass of the beam tested and the energy required to deform a door beam with a particular cross-sectional profile a distance of 6 inches was recorded. The cross-sectional profile for each beam is shown in
As shown in the table above, door beams 5A-5E were beams having a prior art structure while door beams 5F and 5G had a structure in accord with the present invention, i.e. the cross section of beams 5F and 5G were defined by a first, a second, a third, and a fourth curved segment with each of the curved segments having a shape defined by a hyperbolic cosine function.
Regarding the prior art beam structures, door beam 5A was made from sheet steel having a thickness of 2.200 millimeters (mm) with an overall weight of 1.676 kilograms (Kg). Door beam 5A was also the strongest of the prior art beam structures requiring a specific energy of 1433 joules per kilogram (J/Kg) to deform 6 inches. In comparison, door beam 5F had a cross section in accord with the embodiment shown in
Referring now to the data shown for beam 5G, which also had a cross section in accord with the embodiment shown in
Also disclosed herein is a method or process for making reinforcing beams having cross sections as taught above. Turning now to
The foregoing has described some specific embodiments of the beams of the present invention but is not meant to be a limitation upon the practice thereof. Numerous modifications and variations of the foregoing will be readily apparent to those of skill in the art. It is the following claims, including all equivalents, which define the scope of the invention.
This application claims priority of U.S. Provisional Patent Application Ser. No. 60/889,308 filed Feb. 12, 2007, entitled “Reinforcing Beam Structure” which is incorporated herein by reference.
Number | Date | Country | |
---|---|---|---|
60889308 | Feb 2007 | US |