Abstract:
A vehicle bumper system having a mounting bracket disposed between a vehicle frame and a bumper having angulated walls. The angulated walls are disposed at selected cross-sectional elevations, to avoid parallelograming under impact and provide maximum energy absorption. The mounting bracket includes a first surface and a second surface. The first surface of mounting bracket is adapted to be secured to the vehicle frame. The second surface of the mounting bracket is adapted to be secured to the bumper. The walls of the mounting bracket absorb an impact to the bumper.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority to U.S. Provisional Application 60/574,401, filed on May 26, 2004, which is incorporated herein by reference in its entirety. 
     
    
     TECHNICAL FIELD  
       [0002]     The embodiments described herein relate generally to vehicle bumper systems adapted to provide impact strength and energy absorption. In particular, the embodiments relate to an energy absorbing bumper bracket for attaching a bumper to a vehicle frame.  
       BACKGROUND  
       [0003]     Vehicle bumper systems generally include a bumper beam that is transversely mounted to a vehicle frame using a mounting bracket. Energy absorption is particularly desirable during low speed bumper impacts (i.e., up to about 5 miles per hour), because an important purpose of the bumper system is to absorb energy before the vehicle frame itself begins to undergo damage. A limitation of many bumper beam mounting bracket designs is that they do not adequately absorb impact energy applied to the vehicle bumper system. In many automotive applications, the bumper beam itself, and an optional polymeric foam applied to the face of the bumper beam, generally function as the sole energy absorbing components in the bumper system. Thus, energy applied to the bumper system in excess of the energy dissipation capability of the bumper beam and polymeric foam is transferred through the mounting bracket into the vehicle frame. As a result, significant and expensive damage may occur to a vehicle&#39;s frame, even in relatively low speed bumper impacts.  
         [0004]     Therefore, a need exists for a vehicle bumper system that includes an energy absorbing mounting bracket that significantly contributes to the overall energy dissipation capability of the vehicle bumper system.  
       BRIEF SUMMARY  
       [0005]     The embodiments described herein are directed to an energy absorbing mounting bracket having angulated walls, the mounting bracket being adapted for attaching a bumper to a vehicle frame. The angulated walls are disposed at selected cross-sectional elevations to avoid parallelograming under impact and provide maximum energy absorption. The mounting bracket includes a first surface and a second surface. The first surface of mounting bracket is adapted to be secured to the vehicle frame. The second surface of the mounting bracket is adapted to be secured to the bumper. The walls of the mounting bracket absorb an impact to the bumper. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0006]     The features and inventive aspects of the embodiments described herein will become more apparent upon reading the following detailed description, claims, and drawings, of which the following is a brief description:  
         [0007]      FIG. 1  is a perspective view of a vehicle bumper system according to an embodiment of the present invention;  
         [0008]      FIG. 2  is top view of the vehicle bumper system of  FIG. 1 ;  
         [0009]      FIG. 3  is another perspective view of the vehicle bumper system of  FIG. 1 ;  
         [0010]      FIG. 4  is a side view of the vehicle bumper system of  FIG. 1 , showing a bumper mounting bracket prior to attachment to a rail in a vehicle frame;  
         [0011]      FIG. 5  is a perspective view of a vehicle bumper system mounting bracket according to an embodiment of the invention, showing a bumper-facing end of the mounting bracket;  
         [0012]      FIG. 6  is a perspective view of the mounting bracket of  FIG. 5 , showing a rail-facing end of the mounting bracket;  
         [0013]      FIG. 7  is a perspective view of a portion of the mounting bracket of  FIGS. 5 and 6  remaining after being cut by a first imaginary horizontal cutting plane, showing a W-shaped portion of the mounting bracket;  
         [0014]      FIG. 8  is a perspective view of a portion of the mounting bracket of  FIGS. 5 and 6  remaining after being cut by a second imaginary horizontal plane, showing a U-shaped portion of the mounting bracket;  
         [0015]      FIG. 9  is an end view of the rail used in the vehicle bumper system of  FIG. 1 , showing the mounting bracket of  FIGS. 5-8  superimposed over the rail;  
         [0016]      FIG. 10  is another perspective view of the mounting bracket illustrated in  FIGS. 5-8 ; and  
         [0017]      FIG. 11  is a perspective view of the mounting bracket of  FIGS. 5-8  under load, showing the accordion-like collapse of the mounting bracket.  
     
    
     DETAILED DESCRIPTION  
       [0018]     Referring now to the drawings, illustrative embodiments are shown in detail. Although the drawings represent the embodiments, the drawings are not necessarily to scale and certain features may be exaggerated to better illustrate and explain an innovative aspect of an embodiment. Further, the embodiments described herein are not intended to be exhaustive or otherwise limit or restrict the invention to the precise form and configuration shown in the drawings and disclosed in the following detailed description.  
         [0019]     Referring to  FIGS. 1-4 , a vehicle bumper system  20  is shown that includes a transverse bumper  22 , a vehicle frame  24 , and a pair of mounting brackets  26  (only one mounting bracket is shown in  FIG. 1 ) for removably securing bumper  22  to the frame  24 . In the illustrated embodiment, the frame  24  includes a pair of longitudinally extending rails  28  (only one rail is shown in  FIG. 1 ), each having a generally U-shaped cross-section defined by a generally horizontal bottom wall  30  and two generally vertical side walls  32  and  34 . The longitudinal ends of each of the three rail walls  30 ,  32  and  34  have mounting flanges  38 ,  40  and  42 , respectively, for cooperative engagement with corresponding mounting surfaces of mounting bracket  26 . The vehicle bumper system  20  may be used as the front or rear bumper of a vehicle. It is understood that mounting brackets  26  may also be secured to the frame  24  having a generally “I” shaped, square shaped, or any complex shaped cross-section.  
         [0020]     As used in the description of the present embodiment, terms such as “horizontal” and “vertical” refer to the disclosed environment of a U-shaped rail that is oriented as shown, with the “open” side of the rail routing upwardly. For ease of description, those terms have also been used in the claims to discuss the interrelationship between the respective elements. Those terms are not intended to be limiting in an absolute sense, i.e., with respect to the plane of the Earth&#39;s surface. It should be understood that the embodiments could also be used where the rail and bracket were both oriented in a different angular position, as long as the three adjacent walls of the rail were similarly oriented relative to the bracket.  
         [0021]     The bumper  22  is made of a structural material, such as steel, polyamide resin, or the like and may be configured in accordance with various bumper designs known in the art. In the illustrated embodiment, for example, bumper  22  is a curvilinear design having two relatively flat portions  44  adapted for engagement with the mounting bracket  26 .  
         [0022]     Referring to  FIGS. 5-11 , an embodiment of mounting bracket  26  is shown. In the illustrated embodiment, mounting bracket  26  includes a first end  46  (see  FIGS. 2 and 5 ) having mounting surfaces  48  and  50  adapted for connection to bumper  22  and a second end  52  (see  FIGS. 2 and 6 ) having mounting surfaces  54 ,  56  and  58  adapted for connection to rail mounting flanges  38 ,  40  and  42 , respectively. To facilitate easy connection and removal of mounting bracket  26  from bumper  22  and rail  28 , mounting surfaces  48 ,  50 ,  54 ,  56  and  58  each include at least one hole  59 A that co-aligns with a corresponding hole  59 B on mounting flanges  38 ,  40  and  42  (see  FIG. 1 ) and a hole  59 C on bumper  22  (see  FIG. 3 ). Holes  59 A,  59 B and  59 C are sized to receive a removable fastener (not shown), such as a nut and bolt arrangement, which is used to secure mounting bracket  26  to each of bumper  22  and rail  28 . Those skilled in the art will appreciate that, for ease of economy of assembly, the bracket could be welded to one of the rail  28  and bumper  22 , and bolted to the other.  
         [0023]     Mounting bracket  26  is made from a material that provides the necessary structure to attach and support bumper  22  on rail  28 , yet is deformable to absorb impact energy applied to bumper  22 . In a particular implementation of one embodiment, mounting bracket  26  is made from draw quality steel (e.g., 2 mm in thickness) and is formed in a conventional stamping operation as a single, continuous, piece of metal, without joints. Alternatively, and without limitation, mounting bracket  26  may be made from a polymeric material, such as plastic, or deformable composite materials.  
         [0024]     As shown in  FIGS. 5 and 6 , mounting bracket  26  includes first and second pairs of generally longitudinally extending walls  60  and  62 , respectively, which are connected at their respective ends to the first and second end mounting surfaces  48 ,  50 ,  54 ,  56  and  58 . The second pair of longitudinally extending walls  62  is located transversely between the first pair of longitudinally extending walls  60  so that the first and second pairs of longitudinally extending walls  60  and  62  define a generally W-shaped configuration at a selected imaginary horizontal cutting plane (see  FIG. 7 ). The first pair of generally longitudinally extending walls  60  converge toward the first end  46  of mounting bracket  26 , and the second pair of longitudinally extending walls  62  converge toward the second end  52 . a portion of the mounting bracket  26  defines a generally W-shaped configuration an the imaginary cutting plane and a portion defines a generally U-shaped configuration.  
         [0025]     With reference to  FIG. 5 , the first and second pair of longitudinally extending walls  60  and  62  are also generally upwardly converging. In an embodiment, the first pair of longitudinally extending walls  60  extend upwardly to an optional longitudinally extending wall  63  that separates walls  60 . In contrast, the second pair of longitudinally extending walls  62  intersect and connect with each other at a common upper end  64 .  
         [0026]     As shown in  FIG. 5 , mounting surfaces  48  and  50  at first end  46  of mounting bracket  26  extend generally continuously between the upper and lower ends of both the first and second pairs of longitudinally extending walls  60  and  62 , and join together the first ends of one wall from each of the first and second pairs of longitudinally extending walls  60  and  62 . Similarly, mounting surfaces  48  and  50  also join together the first ends of the other wall from each of the first and second pairs of longitudinally extending walls  60  and  62 , to thereby form a portion of the generally W-shaped configuration.  
         [0027]     As shown in  FIG. 6 , mounting surfaces  56  and  58  at second end  52  of mounting bracket  26  extend generally continuously between the upper and lower ends of the first pair of longitudinally extending walls  60 . Similarly, mounting surface  54  extends generally continuously between the upper and lower ends of the second pair of longitudinally extending walls  62 . Mounting surface  54  also extends between the second pair of longitudinally extending walls  62 , to thereby form another portion of the generally W-shaped configuration.  
         [0028]     In an embodiment, the first pair of longitudinally extending walls  60  extends upwardly beyond the upper ends of the second pair of longitudinally extending walls  62 . When so configured, the first pair of longitudinally extending walls  60  and mounting surfaces  48  and  50  at the first end  46  of mounting bracket  26  define a generally U-shaped configuration at imaginary horizontal cutting planes through the portions of mounting bracket  26  above the common upper end  64  of the second pair of longitudinally extending walls  62  (see  FIG. 8 ).  
         [0029]     A common problem exhibited during a vehicle collision is that the impact forces generated on bumper  22  are not always centered on the bumper  22 , and further are not always parallel with a longitudinal centerline of the vehicle. When imbalanced and off-centered impact forces occur, there is a risk that the W-shaped portion of mounting brackets  26  may distort in a parallelogram-like fashion (so-called “matchboxing”), instead of crushing like an accordion. A parallelogram-like collapse is undesirable, since it typically absorbs much less energy than an accordion-like collapse. The reason is because in a parallelogram-like collapse, the mounting bracket material bends only at opposing ends of the longitudinally extending walls  60  and  62  (i.e., only bends at a front end near the bumper and at a rear end adjacent the vehicle frame). Contrastingly, in an accordion-like collapse, longitudinally extending walls  60  and  62  bend and crumple along multiple locations, including locations between their ends, with each of the bending locations absorbing energy from an impact.  
         [0030]     To reduce the parallelogram or “matchbox” effect, the horizontal cross-section of mounting bracket  26  transitions from the generally W-shaped configuration in the lower portion of mounting bracket  26  ( FIG. 7 ), to the generally U-shaped configuration in the upper portion of mounting bracket  26  ( FIG. 8 ). This transition is characterized by the convergence of longitudinally extending walls  60  and  62  as they extend from their lower end to their upper end. Convergence of longitudinally extending walls  60  and  62  reduces the individual lateral shifting of walls  60  and  62  that results when walls  60  and  62  are subjected to shearing/torsional forces, and inhibits each walls&#39; failure in a parallelogram-like collapse. Walls  60  and  62  define a portion of a bracket channel. In an embodiment, the walls  60  and  62  are angulated. Angulated means more than or less than ninety degrees.  
         [0031]     In addition to reducing the tendency of longitudinally extending walls  60  and  62  to “matchbox”, the transition from a generally W-shaped profile to the generally U-shaped profile permits mounting bracket  26  to uniformly load the generally horizontal bottom wall  30  and the two generally vertical side walls  32  and  34  of rail  24 . As shown in  FIG. 9 , the convergence of the first pair of longitudinally extending walls  60  allows imaginary longitudinal projections of walls  60  to intersect upper and lower portions of the generally vertical side walls  32  and  34  of rail  28 . Similarly, the convergence of the second pair of longitudinally extending walls  62  allows imaginary longitudinal projections of walls  62  to intersect bottom wall  30  of rail  28 .  
         [0032]     The portions of first and second pairs of longitudinally extending walls  60 ,  62  that imaginarily project onto rail  28  may be defined by a longitudinally extending bead  70  in walls  60  and  62 . Notably, each bead  70  may be positioned to intersect rail  28  proximate a structurally significant portion of rail  28 , such as the transition between bottom wall  30  and side walls  32  and  34 , or the transition between side walls  32 ,  34  and upper longitudinally extending flanges  43  of rail  28 . Thus, the lower portion of mounting bracket  26  may be adapted to load the lower, closed portion of rail  28  and the upper portion of mounting bracket  28  may be adapted to straddle the upper, open portion of rail  28 , while uniformly loading side walls  32  and  34 .  
         [0033]     As will be appreciated, mounting bracket  26  significantly enhances the energy management efficiency of bumper system  20 , since mounting bracket  26  is designed to collapse before the rail-buckling load is reached. Thus, in relatively low energy bumper impacts that exceed the energy dissipation capability of bumper  22  alone, mounting bracket will collapse and absorb the excess energy before any damage occurs in rail  28 . It is also understood that in one embodiment, the use of straight or curved angulated walls form a bracket channel in the mounting bracket  26  that provides uniform loading of the rail  28 .  
         [0034]     Among other features of the embodiments described herein, the W-shaped portion of mounting bracket  26  provides the surfaces necessary to secure mounting bracket  26  to bumper  22  and rail  28  and, importantly, the wall material needed to collapse in an accordion-like fashion to absorb energy as bracket  26  is crushed during an impact. To inhibit parallelogram-like deformation of the W-shaped portion, the W-shaped portion of bracket  26  transitions into a U-shaped configuration as the first and second pairs of longitudinally extending walls  60  and  62  upwardly converge. Further, the convergence of the first and second pairs of longitudinally extending walls  60  and  62  allow imaginary longitudinal projections of walls  60  and  62  to intersect structurally significant portions of the generally vertical side walls  32  and  34  and bottom wall  30  of rail  28 , to uniformly load the walls of rail  28 .  
         [0035]     The embodiments herein have been particularly shown and described, which are merely illustrative of the best mode for carrying out the invention. It should be understood by those skilled in the art that various alternatives to the embodiments described herein may be employed in practicing the invention without departing from the spirit and scope of the invention as defined in the following claims. It is intended that the following claims define the scope of the invention and that the method and apparatus within the scope of these claims and their equivalents be covered thereby. This description of the invention should be understood to include all novel and non-obvious combinations of elements described herein, and claims may be presented in this or a later application to any novel and non-obvious combination of these elements. Moreover, the foregoing embodiments are illustrative, and no single feature or element is essential to all possible combinations that may be claimed in this or a later application.