Abstract:
An energy absorbing extruded bumper for a vehicle is disclosed. The extruded bumper is formed from a lightweight metal, preferably aluminum base alloy material. The extruded bumper includes an outer wall, an inner wall, a top wall connecting the outer and inner walls, and a bottom wall connecting the outer and inner walls. Extending between the outer and inner walls are two or more s-curved trigger stiffeners. The trigger stiffeners include an upper s-curved trigger stiffener connecting the outer and inner walls and a lower s-curved trigger stiffener connecting the outer and inner walls. The lower s-curved trigger stiffener is spaced apart from the upper s-curved trigger stiffener.

Description:
TECHNICAL FIELD 
       [0001]    The disclosed invention relates to an extruded aluminum bumper for an automotive vehicle. More particularly, the disclosed invention relates to a lightweight, extruded aluminum bumper with triggers. The extruded aluminum bumper of the disclosed invention provides performance at least equivalent to conventional bumper configurations. 
       BACKGROUND OF THE INVENTION 
       [0002]    Bumpers are mounted at the forward and rearward extremities of a vehicle to protect the chassis of the vehicle from minor impacts. The bumper is mounted to the lower frame rails of the vehicle chassis for support thereof and functions to withstand minor impacts by collapsing to absorb the energy encountered through the impact. 
         [0003]    For conventional bumpers, enhancements to the cross-sectional configuration in the form of reinforcement inserts provide higher energy absorption qualities for those reinforced areas of the bumper, thus achieving some relative improvement in the collapsing of the bumper structure. Such reinforcements are conventionally placed at the attachment points between the bumper structure and the lower frame rails to allow for a greater absorption and dispersion of impact energy by the bumper before being transferred to the lower frame rail into the vehicle chassis. 
         [0004]    A more recent development which has been provided to both reduce weight and cost without compromising crash performance has been the introduction of the extruded aluminum bumper. However, known extruded bumpers generate peak and average crash loads having differences so great that the engineer is prevented from designing an optimum bumper system with a crash energy management level of the same order as that of the longitudinal rail member supporting the bumper. If the average crash load carrying capacity of the bumper beam could be increased to the level of the supporting longitudinal member, the bumper peak crash load would cause the supporting rail to collapse prior to triggering the bumper beam crash. This is an undesirable crash mode because of the non-sequential collapse of the front end structural systems. 
         [0005]    Accordingly, it is desirable to provide a lightweight bumper configuration that would be capable of crash performance characteristics of heavier conventional bumpers that are formed with reinforcement inserts while allowing the bumper to achieve an optimum crash energy level with a crash load equal to that of the supporting longitudinal rails and without the risk of non-sequential collapse. In addition, reducing the weight of the structure without sacrificing performance of the bumper can provide manufacturing cost savings. 
       SUMMARY OF THE INVENTION 
       [0006]    The disclosed invention provides an energy absorbing extruded bumper for a vehicle. The extruded bumper is formed from a lightweight metal, preferably aluminum base alloy material. The extruded bumper includes an outer wall, an inner wall, a top wall connecting the outer and inner walls, and a bottom wall connecting the outer and inner walls. 
         [0007]    Extending between the outer and inner walls are two or more s-curved trigger stiffeners. The trigger stiffeners include an upper s-curved trigger stiffener connecting the outer and inner walls and a lower s-curved trigger stiffener connecting the outer and inner walls. The lower s-curved trigger stiffener is spaced apart from the upper s-curved trigger stiffener. 
         [0008]    Preferably but not necessarily the upper s-curved trigger stiffener is inverted with respect to the lower s-curved trigger stiffener such that the inward-curving sections of the s-curves of each trigger stiffener are in opposition and the outward-curving sections of the s-curves of each trigger stiffener are in opposition. Also preferably but not necessarily the inward-curving sections of the s-curves are adjacent the outer wall and the outward-curving sections of the s-curves are adjacent the inner wall. 
         [0009]    The inward-curving sections of the s-curves have a thickness and the areas of the trigger stiffeners adjacent the inward-curving sections have a thickness. Preferably but not exclusively the thickness of the inward-curving sections of the s-curves is greater than the thickness of the adjacent areas. Similarly and also preferably but not exclusively the outward-curving sections of the s-curves have a thickness and the areas of the trigger stiffeners adjacent the outward-curving sections have a thickness, the thickness of the outward-curving sections of the s-curves being greater than the thickness of the adjacent areas. 
         [0010]    The extruded bumper of the disclosed invention provides a structure that is durable, lightweight, easy to assemble and is inexpensive to make without sacrificing crash performance. 
         [0011]    Because the bumper of the disclosed invention is extruded the cross-sectional configuration of the bumper beam can be uniformly manufactured along the entire length of the bumper beam. 
         [0012]    In addition, the s-curved trigger stiffeners can have thicker areas such as at the inward-curving sections and outward-curving sections while the adjacent areas are thinner, thus providing appropriate thickness only at the locations where such material thickness is needed without requiring the utilization of reinforcement inserts. 
         [0013]    While exemplary embodiments in accordance with the invention are illustrated and disclosed, such disclosure should not be construed to limit the claims. It is anticipated that various modifications and alternative designs may be made without departing from the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]    For a more complete understanding of this invention, reference should now be made to the embodiments illustrated in greater detail in the accompanying drawings and described below by way of examples of the invention wherein: 
           [0015]      FIG. 1  is a perspective fragmentary view of a portion of a prior art extruded bumper in its initial, pre-impact condition shown in partial cross-section; 
           [0016]      FIG. 2  is the same view as  FIG. 1  but illustrating early stage deformation of the prior art bumper when a load is applied; 
           [0017]      FIG. 3  is the same view as  FIG. 2  but illustrating late stage deformation of the prior art bumper when a load is applied; 
           [0018]      FIG. 4  is a graph illustrating the results of impact studies showing load vs. displacement characteristics of a prior art extruded bumper and of the extruded bumper of the disclosed invention. 
           [0019]      FIG. 5  is a perspective fragmentary view of a portion of a first preferred embodiment of the extruded bumper of the disclosed invention in its initial, pre-impact condition shown in partial cross-section; 
           [0020]      FIG. 6  is the same view as  FIG. 5  but illustrating early stage deformation of the bumper of the disclosed invention when a load is applied; 
           [0021]      FIG. 7  is the same view as  FIG. 6  but illustrating late stage deformation of the bumper of the disclosed invention when a load is applied; and 
           [0022]      FIG. 8  is a perspective fragmentary view of a portion of a second preferred embodiment of the extruded bumper of the disclosed invention in its initial, pre-impact condition shown in partial cross-section. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0023]    In the following figures, the same reference numerals will be used to refer to the same components. In the following description, various operating parameters and components are described for different constructed embodiments. These specific parameters and components are included as examples and are not meant to be limiting. 
         [0024]    With respect to  FIG. 1 , a perspective fragmentary view of a portion of a prior art extruded bumper, generally illustrated as  10 , is shown. The bumper  10 , shown in partial cross-section, is illustrated in its initial, pre-impact condition. 
         [0025]    As is known in the art, the extruded bumper  10  is attached to a vehicle (not shown) by a pair of supporting longitudinal rails of which one, longitudinal rail  12 , is illustrated. 
         [0026]    According to known design, the bumper  10  includes a top wall  14 , a bottom wall  16 , a front wall  18 , and a rear wall  20 . Extending between the front wall  18  and the rear wall  20  is an upper stiffener  22  and a lower stiffener  24 . As is known in the art the upper stiffener  22  and the lower stiffener  24  have no trigger area. 
         [0027]    The difficulty with known approaches to extruded bumpers having stiffeners but no trigger area is apparent with reference to  FIGS. 2 and 3  which illustrate the results of an impacting force on the bumper. With reference first to  FIG. 2 , an impacting force, illustrated as F, is shown acting upon the extruded bumper  10 . The deformation shown in  FIG. 2  illustrates how the bumper would appear about 17 msec after the impact of the force F. As can be seen, the upper stiffener  22  and the lower stiffener  24  are beginning to deform. 
         [0028]    In  FIG. 3  the impacting force F is shown having acted further upon the extruded bumper  10 . The deformation shown in  FIG. 3  illustrates how the bumper would appear about 34 msec after the impact of the force F. As can be seen, the upper stiffener  22  and the lower stiffener  24  have substantially deformed. 
         [0029]    The prior art bumper set forth in  FIGS. 1 through 3  illustrates the challenges inherent in such designs. As illustrated in  FIG. 4 , the peak crashing load of the non-triggered, extruded bumper  10  (a typical extruded aluminum bumper), illustrated as broken line  26 , is approximately 90% higher than its average crash load. (Peak and average crash loads are taken at front rails centerlines.) As illustrated, load (in Klbf) is shown on the y-axis and displacement (in inches) is shown on the x-axis. 
         [0030]    The extruded bumper of disclosed invention overcomes the problems of known extruded bumpers by providing an extruded aluminum bumper having dual triggering. A first preferred embodiment of the extruded bumper of the disclosed invention is set forth in  FIGS. 5 through 8 . It is to be noted that the bumper illustrated in these figures is intended as being exemplary and is not intended as being limiting as variations of the disclosed bumper may be formulated without deviating from either the spirit or the scope of the disclosed invention. 
         [0031]    With reference to  FIG. 5 , an extruded bumper, generally illustrated as  30 , is shown. As in the prior art bumper  10  shown in  FIGS. 1 through 3  and discussed in relation thereto, the extruded bumper  30  is attached to a vehicle (not shown) by a pair of supporting longitudinal rails of which one, longitudinal rail  12 , is illustrated. 
         [0032]    The extruded bumper  30  is preferably composed of base alloy aluminum although it is envisioned that the bumper  30  may also be formed from other extrudable, lightweight but strong materials as may be known to those skilled in the art. 
         [0033]    The extruded bumper  30  includes a top wall  32 , a bottom wall  34 , a front wall  36 , and a rear wall  38 . The dual extruded dual triggering mechanism of the disclosed invention is formed from an upper trigger  40  extending between the front wall  36  and the rear wall  38  and a lower trigger  46  extending between the front wall  36  and the rear wall  38 . 
         [0034]    As illustrated in  FIG. 5 , the upper trigger  40  and the lower trigger  46  each has a cross-section generally defined as an s-curve. Particularly, the upper trigger  40  has a inward-curving section  42  and an outward-curving section  44 . The lower trigger  46  has an inward-curving section  48  and an outward-curving section  50 . Preferably but not absolutely the inward-curving sections  42  and  48  may be adjacent the front wall  36  of the bumper  30  and the outward-curving sections  44  and  50  may be adjacent the rear wall  38 . Additional triggers may be incorporated into the illustrated design. 
         [0035]    The favorable results of an impacting a force are shown in  FIGS. 6 and 7 . With reference first to  FIG. 6 , an impacting force, illustrated as F, is shown acting upon the extruded bumper  30 . The deformation shown in  FIG. 6  illustrates how the bumper would appear about 17 msec after the impact of the force F. As can be seen, the upper trigger  40  and the lower trigger  46  are beginning to deform. 
         [0036]    In  FIG. 7  the impacting force F is shown having acted further upon the extruded bumper  30 . The deformation shown in  FIG. 7  illustrates how the bumper  30  would appear about 34 msec after the impact of the force F. The upper trigger  42  and the lower trigger  46  have substantially deformed. 
         [0037]    As a variant to the extruded bumper shown in  FIGS. 5 through 7  and discussed in relation thereto, a second preferred embodiment of the disclosed invention is set forth in  FIG. 8 . With reference thereto, an extruded bumper, illustrated as  30 ′, is shown. According to this alternate embodiment, the extruded bumper  30 ′ includes a top wall  32 ′, a bottom wall  34 ′, a front wall  36 ′, and a rear wall  38 ′. Similar to the first preferred embodiment shown in  FIGS. 5 through 7 , the dual extruded dual triggering mechanism of the second preferred embodiment includes an upper trigger  40 ′ extending between the front wall  36 ′ and the rear wall  38 ′ and a lower trigger  46 ′ extending between the front wall  36 ′ and the rear wall  38 ′. 
         [0038]    As with the first preferred embodiment of the disclosed invention, the upper trigger  40 ′ and the lower trigger  46 ′ of the second preferred embodiment each has a cross-section generally defined as an s-curve. The upper trigger  40 ′ has a inward-curving section  42 ′ and an outward-curving section  44 ′. The lower trigger  46 ′ has an inward-curving section  48 ′ and an outward-curving section  50 ′. One, some or all of the inward-curving sections  42 ′ and  48 ′ and the outward-curving sections  44 ′ and  50 ′ may be thicker than the adjacent area of the curving sections as illustrated in  FIG. 8 . If thicker, the degree of thickness may be varied from one curved section to another or may be constant among the curved sections. 
         [0039]    Regardless of the embodiment, the extruded bumper of the disclosed invention allows the bumper to achieve an optimum crash energy level with a crash load equal to that of the supporting longitudinal rails and without the risk of non-sequential collapse. This outcome is not likely without the embedded dual triggering stiffeners mechanism shown above in  FIGS. 5 through 8  and discussed in relation thereto. As illustrated in  FIG. 4  and referring to the solid line  60 , the average crash load in the bumper of the disclosed invention without the associated crash peak of the non-triggered bumper  10  of the prior art (line  20 ) has a dual benefit. First, the crash load configuration allows the extruded bumper of the disclosed invention to achieve an optimized square stroke in a low speed rigid barrier test. Second, the crash load configuration allows the bumper to manage higher crash energy under high speed, full frontal and offset impacts. 
         [0040]    Accordingly, among the advantages of the disclosed extruded bumper having the dual triggering stiffener mechanism shown in  FIGS. 5 through 8  and described in conjunction therewith are an optimized square stroke under low speed rigid barrier impact, higher crash energy management under high speed impact, and a controlled peak-to-average crash load ratio. 
         [0041]    The foregoing discussion discloses and describes exemplary embodiments of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined by the following claims.