Abstract:
A structural reinforcing member is provided to improve localized stiffness in frames, rails, body cavities or other such areas found in automotive, marine or aviation applications. The reinforcing member includes a frame having a first and second arm extending laterally therefrom. The frame is configured to be securely positioned in the area of interest. A thermally expandable material is disposed on the arms such that a gap is formed between the thermally expandable material of the first arm and the adjacent second arm prior to expansion. A bake process allows the expandable material to expand around the immediate area, thereby providing localized stiffness and support.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates generally to thermally expansible structural reinforcing members used to provide localized stiffness to frames, cavities, panels or other structural members, and more particularly to a reinforcing member including a base and a series of laterally extending arms each having a portion of thermally expansible reinforcing material secured thereto.  
         BACKGROUND  
         [0002]    The design of automobiles, aircraft, watercraft and other common vehicles incorporate body structures having hollow cavities and open frame sections. The hollow cavities are commonly formed when it is desired to have an inner and outer wall defining a preferred structural or aesthetic characteristic. It is common for such structures to experience linear and rotational forces generated from environmental inputs associated with a given common vehicle. Such forces may encourage unwanted noise or premature fatigue failure in the structure.  
           [0003]    It is frequently desirable to reinforce these areas for purposes of improving the structural integrity of the body. Increased stiffness in localized critical areas generally result in reduced vibration, noise, and/or fatigue propagation. Additionally, an increased stiffness in these areas generally has proven to improve energy management during crash or impact situations.  
           [0004]    It is known to reinforce such areas by introducing self-sustaining reinforcing products into the cavity. The reinforcing products may include a support or carrier structure used to hold the material in the desired location. While this known technique has generally proven to provide increased stiffness, it adds access weight to the structural member.  
           [0005]    Another known technique incorporates the use of a thermally expandable reinforcing material. The reinforcing material is positioned in a cavity and is heated during thermal convection activation process. The material is configured to expand and contact the surrounding cavity walls during a bake process. Often, however, the expandable material is disposed or arranged on a carrier or frame such that effective thermal exposure is difficult. Failure to fully penetrate the expandable material with heat results in inconsistent material density after expansion. It is therefore desirable to provide a frame and expandable material configuration such that the thermal activation process enables full heat penetration throughout the structure, thereby yielding a more consistent reinforcing structure.  
         SUMMARY OF THE INVENTION  
         [0006]    It is a general object of the present invention to provide a reinforcing support having a rigid frame including a first and second laterally displaced shelf members, the shelf members carrying thermally expandable material thereon.  
           [0007]    In one form, the present invention provides a reinforced structural member having a frame including a first mounting portion and first and second shelf members laterally extending therefrom. A thermally expandable reinforcing material is carried by each shelf member. The arms are preferably configured such that a gap is realized between the reinforcing material of a first shelf member and an adjacent shelf member prior to expansion.  
           [0008]    The configuration of the frame increases the heat transfer to the core of the material where it is needed most. The gaps provided allow the shelf members of the frame to absorb and transfer heat more efficiently to the reinforcing material. Additionally, the shelved frame provides support for the reinforcing material to reduce the potential of material sag due to gravity during the expanding and curing process.  
           [0009]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood however that the detailed description and specific examples, while indicating preferred embodiments of the invention, are intended for purposes of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0011]    [0011]FIG. 1 is a perspective view of a portion of an exemplary motor vehicle shown partially cut-away, the motor vehicle incorporating a multi-tiered reinforcing structure constructed according to a first preferred embodiment of the present invention.  
         [0012]    [0012]FIG. 2 is a cross-sectional view taken along the line  2 - 2  of FIG. 1.  
         [0013]    [0013]FIG. 3 is an enlarged perspective view of the multi-tiered reinforcing structure of the first preferred embodiment of the present invention removed from the exemplary motor vehicle for purposes of illustration.  
         [0014]    [0014]FIG. 4 is a perspective view of a portion of the exemplary motor vehicle of FIG. 1, shown again partially cut-away and now illustrated to include a multi-tiered reinforcing structure constructed in accordance with the teachings of a second preferred embodiment of the present invention.  
         [0015]    [0015]FIG. 5 is an enlarged perspective view of the multi-tiered reinforcing structure of the second preferred embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    With initial reference to the perspective view of FIG. 1, a multi-tiered reinforcing structure constructed according to the teachings of a first preferred embodiment of the present invention is illustrated and generally identified at reference numeral  10 . The reinforcing structure  10  is shown operatively incorporated into a portion of a motor vehicle  12 . As particularly shown, the reinforcing structure  10  is fixedly attached to intermediate wall  26  between inner and outer panels  14  and  16  of a bed wall  18  of a pick-up truck  12 . It should be readily appreciated by those skilled in the art that vehicle type and the location of the reinforcing structure as shown in FIG. 1 are merely exemplary. The reinforcing structure  10  provides localized stiffness to panels  14 ,  16 ,  18  and  26  of the vehicle  12 .  
         [0017]    With continued reference to FIG. 1, and additional reference to FIGS. 2 and 3, the reinforcing structure  10  of the present invention will be further described. The reinforcing structure is shown to generally include a frame  20  defined by multiple tiers for supporting portions of expandable material  28 . In the exemplary embodiment illustrated, the frame  20  defines a two tiered configuration. However, it will be clearly understood that the subject invention may include three or more tiers.  
         [0018]    In the first preferred embodiment, the frame  20  is preferably made of a rigid, heat conductive material such as metal, and includes a first or upper element  30  and a second or lower element  32 . The first and second elements  30  and  32  are stepped in shape and welded or otherwise suitably secured to one another. More particularly, the first element  30  includes first and second vertically oriented flange portions  34  and  42  interconnected by a horizontally oriented arm or shelf member  38 . Flange  42  includes an aperture or passageway  24  which allows expandable material  28  to expand therethrough. In a similar manner, the second element  32  includes first and second vertically oriented flange portions  40  and  36  interconnected by a horizontally oriented arm or shelf member  44 .  
         [0019]    The second flange portions  42  and  36  are welded together and cooperate to define a base or first mounting portion for the frame  20 . As particularly shown in the cross-sectional view of FIG. 2, the reinforcing member is fixedly attached to panel  26  by flange  36 , and disposed within a cavity  46  defined between the inner and outer panels  14  and  16 . The expandable material  28  of first element  30  is configured to expand to contact wall  26 . Similarly, the expandable material  28  of second element  32  is configured to expand through passageway  24  to contact panel  26 . Those skilled in the art will recognize that flange  36  may alternatively be attached to panels  14 ,  16  or  18  without departing from the scope of this invention.  
         [0020]    Portions of the expandable material  28  are disposed on the first and second arms  38  and  44 . The expandable material  28  may be heat staked, pinned or otherwise attached to the arms  38  and  44 . The expandable material  28  is a material that expands from heat such that is generated in automobile assembly plants during heat cycles. One suitable composition for use as the expandable material  28  is commercially available under the name SikaReinforcer from Sika Corporation of Madison Heights, Mich. However it will be recognized by those skilled in the art that other thermally expandable materials, including but limited to epoxy adhesives, may be employed without departing from the scope of the present invention. The portions of expandable material  28  are shown throughout the drawings in an unexpanded state (i.e., prior to the application of heat).  
         [0021]    Significantly, the tiered configuration of the frame  20  allows the portions of the expandable material  28  to be placed apart from one another thereby facilitating expansion through enhanced thermal exposure. The expandable material  28  is preferably a dry, initially non-tacky material that develops adhesion upon expansion such that it adheres to the surrounding structural members when heat activated.  
         [0022]    With reference now to FIGS. 4 and 5, a reinforcing structure  10 ′ constructed in accordance with the second preferred embodiment of the present invention is illustrated. The use and construction of the reinforcing structure  10 ′ has many common aspects as compared to the reinforcing structure  10  of the first preferred embodiment. Like reference numbers have been used in the drawings to identify substantially identical components between the embodiments. The description of the reinforcing structure  10 ′ of the second preferred embodiment will focus on the differences between the embodiments.  
         [0023]    An upper element  30  of the frame  20 ′ of the reinforcing structure  10 ′ includes first and second vertical flanges  34  and  42 . The first and second vertical flanges  34  and  42  are interconnected by a horizontal arm or shelf  38 .  
         [0024]    A lower element  32 ′ of the frame  20 ′ of the reinforcing structure  10 ′ includes first and second vertical flanges  40 ′ and  36 . The vertical flanges  40 ′ and  36  are interconnected by a horizontal arm or shelf  44 . In addition, the lower element  32 ′ includes a horizontal portion  50  extending from an upper end of the first vertical flange  40 ′. The horizontal portion  50  is welded or otherwise securely attached to the arm  38  of the upper element  30 . The reinforcing structure  10 ′ is welded or suitably attached to panel  26  at flange  36  as described for the preferred embodiment.  
         [0025]    Prior to installation in a vehicle, the reinforcing structures  10  and  10 ′ of the present invention significantly provide an arrangement that can be preloaded with the reinforcing material  28 . This type of arrangement facilitates assembly and helps to maintain desired spatial relationships.  
         [0026]    As discussed above, the portions of the expandable material  28  are vertically offset a predetermined distance to enhance thermal exposure during heat activation. Explaining further, in the first preferred embodiment the first arm  38  and the second arm  44  are displaced at predetermined distance. The thermally expandable material  28  disposed on the first arm  38  occupies a predetermined height prior to expansion such that a gap  22  remains between the expandable material on the first arm  44  and the second arm  38  of the frame  20 . The heat transfer characteristics of the frame and the spatial relationship therebetween allows for increased heat transfer properties during the activation process. Such a configuration promotes heat penetration to the core of the thermal expandable material  28 . The tiered frame  20  furthermore provides intermediate support for the expandable material  28 , which reduces the tendency of the material to slump from gravity during the expansion process.  
         [0027]    Upon heating, the material  28  on the first arm  44  expands to substantially fill the surrounding area of cavity  46  and is forced laterally. Similarly, the material  28  substantially fills a space thereabove. Expansion of the thermally expandable material  28  is identical in the second preferred embodiment.  
         [0028]    While the invention has been described in the specification that illustrated drawings with reference to particular preferred embodiments, it will be understood by those skilled in the art that various changes may be made and equivalence may be substituted for elements thereof without parting from the scope of the invention as defined in the claims. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments illustrated by the drawings and described in the specification as the best mode presently contemplated for carrying out this invention, but that the invention will include any embodiments falling within the description of the appended claims. For example, while the embodiments described herein are illustrated in connection with a side wall of a pick-up truck, the reinforcing structures  10  and  10 ′ according to this invention may be employed in other structural cavities as well (e.g., other areas in motor vehicles, boats, airplanes, or the like).