Abstract:
An aluminum layered heat shield assembly ( 30 ) includes a pair of spaced metallic facing sheets ( 32 ) fabricated from an aluminum composition. In the interstitial space between the facing sheets ( 32 ), a perforated steel core ( 34 ) is formed in the general shape of a zigzag baffle with segments that adjoin and maintain a generally consistent spacing. The perforated steel core ( 34 ) is fabricated with non-perforated flanges ( 42 ) which project outwardly from between the aluminum facing sheets ( 32 ) to establish extensions for attachment to a supporting structure.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     The present application claims priority to U.S. provisional application entitled AL-RE HEAT SHIELD WITH FABRICATED IN-PLACE ATTACHMENT FLANGES having Ser. No. 60/737,973 and filed on Nov. 18, 2005. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The subject invention relates to a heat shield, and in particular a heat shield made from a layered sheet material including aluminum facings and a perforated steel core which maintains an air-space separation between the aluminum facings.  
         [0004]     2. Related Art  
         [0005]     Modern internal combustion engines are typically designed to have high working temperatures to provide high thermodynamic and fuel consumption efficiencies. These high working temperatures, however, are a source of great practical difficulty for features in proximity to a heat source. Accordingly, careful heat management is necessary to ensure that the components of an engine which are ill-suited for operation in high temperature environments are properly protected from high heat sources. Proper heat protection will ensure reliable system and component operations over the life of the engine.  
         [0006]     Heat shields are used as a technique for managing heat in a vehicular engine. According to the prior art, a heat shield is affixed to the components to be shielded by brackets or clips. These mounting techniques require features added to the heat shield and/or the component to be shielded to hold the heat shield in position. Because the exact configuration of the heat shield can vary from model to model and application to application, it can be difficult and expensive to provide mounting features in some applications. In addition, when mounting features are secured to the heat shield with rivets or other fasteners, stress concentrations can be induced leading to premature cracking or other failure modes.  
         [0007]     Accordingly, alternative techniques for mounting heat shields, other than clips, brackets or other added features, would be beneficial.  
       SUMMARY OF THE INVENTION  
       [0008]     A layered heat shield assembly is provided of the type used in vehicular applications to create a thermal barrier between a heat source and a temperature sensitive component. The assembly comprises first and second metallic facing sheets having generally aligned peripheral edges. A metallic core is disposed between and directly connects the first and second facing sheets. The core establishes a generally consistent spacing between the first and second sheets. The core includes a plurality of integral flanges projecting in cantilever fashion outwardly from the peripheral edges of the first and second sheets. The integral flanges establish extended fixation points for supporting the assembly relative to a heat source.  
         [0009]     According to another aspect of the invention, a method is provided for making a layered heat shield assembly of the type used in vehicular applications to create a thermal barrier between a heat source and a temperature sensitive component. The method comprises the steps of forming a first metallic facing sheet having peripheral edges and also forming a second metallic facing sheet having peripheral edges that are substantially equivalent in size and shape to the first facing sheet. The method further includes forming a metallic core from sheet material and then perforating the core in a plurality of spaced-apart locations. At least one leg is bent out of the sheet material obliquely away from each perforation. The method includes affixing each leg to respective inside surfaces of the first and second facing sheets so that the core establishes a generally consistent spacing between the first and second facing sheets and holds the first and second facing sheets in an overlapping, generally aligned condition. The improvement comprises forming a plurality of flanges integrally from the core and directing the flanges outwardly from the generally aligned peripheral edges of the first and second facing sheets so that the integral flanges establish extended fixation points for supporting the assembly relative to a heat source.  
         [0010]     The integral flanges which extend directly from the core can be directly attached to a supporting article to affix the subject heat shield assembly in an operative position without the need for added brackets, clips or other features to accomplish fixation.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     These and other features and advantages of the present invention will become more readily appreciated when considered in connection with the following detailed description and appended drawings, wherein:  
         [0012]      FIG. 1  is a cross-sectional view of a typical prior art heat shield of the type including a pair of spaced apart aluminum facing materials having an interstitial perforated steel core forming a baffle-like gap filling function;  
         [0013]      FIG. 2  is a simplified view showing a prior art heat shield affixed to a feature requiring protection from a heat source using prior art bracket and clip devices;  
         [0014]      FIG. 3  is a cross-sectional view as in  FIG. 1  but showing a heat shield according to the subject invention including flange-like extensions formed by the core material to provide fixation points; and  
         [0015]      FIG. 4  is a view similar to  FIG. 3  but showing a heat shield according to the subject invention which is supported relative to a heat source through the flanges. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0016]     Referring to the Figures, wherein like numerals indicate like or corresponding parts throughout the several views, a prior art style heat shield is generally shown at  10  in  FIG. 1 . The assembly  10  includes a pair of sheet-like aluminum facings held in a spaced, generally parallel orientation by a core material  14 . The core  14  is fabricated of a perforated steel or stainless steel material in an off-set, zigzag pattern by which the point of attachment between the core  10  and one aluminum facing is off-set from its point of attachment to the other aluminum facing. Accordingly, heat conducted through the core material  14  between the aluminum facings  12  is forced to traverse a distance greater than the normal spacing between the aluminum facings  12 . In addition, the core  14  is perforated thereby enhancing cooling through ventilation and natural convection. The prior art heat shield assembly  10  has a perimeter defined by boundary edges  16  which may be formed by a simple cutting or stamping operation wherein all three material layers  12 ,  14  are simultaneously formed and sheared.  
         [0017]     As shown in  FIG. 2 , the heat shield assembly  10  can be deployed in an application where a component  18  (or components) to be protected is maintained in close proximity to a heat source  20 . The heat shield  10  thus forms a barrier between the heat source  20  and the components  18  to be protected primarily from radiant heat energy but also from convective heat energy. Supplemental attachment features such as bracket  22  and clip  24  are required for mounting the heat shield assembly  10  to the component to be protected  18 . These brackets  22  and clips  24  add expense and complexity to the assembly operation, and can contribute to premature failure of the assembly  10 . For example, bracket  22  requires an added fixation bolt  23  set into a drilled and tapped hole. And clip  24  requires the formation of a special mating feature  25  which adds weight and complexity to the system. Furthermore, the rivets  26  can diminish the overall heat shielding efficiency of the assembly  10  by providing a thermal conductive path directly between the facings  12 . The rivets  26  can also lead to premature failure by creating stress concentrations.  
         [0018]     In contrast,  FIGS. 3 and 4  illustrate an improved heat shield assembly generally shown at  30 . The heat shield assembly  30  is constructed similarly to the prior art device in that a pair of aluminum facings  32  are held in a consistently spaced, generally parallel orientation by an interstitial core material  34  having the characteristic zigzag baffle pattern described above. The edges  36  of the aluminum facing  32  establish the general boundary of the effective area for shielding components from a heat source.  
         [0019]     As best shown in  FIG. 3 , the core  34  includes a plurality of perforations  50  which are formed in a stamping or other suitable operation. The tooling used to form the perforations  50  create alternating up and down legs  52  from the upset material. The legs  52 , in turn, are attached such as by welding to the inside surfaces of the first and second facing sheets  32 , creating an integral assembly. The rigid nature of the core  34  results in a stiff corrugation-like construction where first and second facing sheets  32  are held parallel and spaced from one another and air is enabled to circulate convectively through the interstitial space via the network of perforations  52 . An equivalent construction of the core  34  comprises a plurality of discrete segments formed in the depicted zigzag baffle pattern with leg segments adjoining the respective inside faces of the first and second facing sheets  32  for maintaining a generally consistent spacing.  
         [0020]     Referring to  FIG. 4 , the heat shield assembly  30  is shown in an exemplary operative position affixed near components  38  to be protected. A heat source  40  is depicted in close proximity. Instead of the prior art add-on bracket and clip features, which have certain disadvantages, the subject heat shield assembly  30  is provided with integral flanges  42  extending from the core  34  and beyond the edges  36  of the aluminum facing materials  32 . Noticeably absent from the component  38  to be protected are additional fixation bolts and special mating features to anchor clips and brackets. The flanges  42  are preferably made from non-perforated material, whereas the remainder of the core  34 , i.e., residing between the aluminum facings  32 , is perforated to promote air circulation and better heat transfer.  
         [0021]     The flanges  42  are ideally suited for fixation directly to the components to be protected  38 , such a by welding as shown at  44 . Alternatively, high temperature adhesive or mechanical clipping or interlocking of the flanges  42  may be used instead of welding, as well as fasteners.  
         [0022]     The flanges  42  provide substantial enhanced versatility to the heat shield assembly  30 , while reducing cost and improving service life through the elimination of high failure rate, high stress components. The novel flange construction  42  enables the heat shield assembly  30  to be affixed directly to certain heat sources, for example an exhaust pipe, rather than to the component  38  to be protected as illustrated in  FIG. 4 . Of course, many other application mounting locations are possible. By proper selection of materials, the flanges  42  can be modified to allow for welding directly to stainless steel surfaces.  
         [0023]     While prior art heat shield assemblies to not allow for welding unless added features are provided to the outside of the base material construction, the subject heat shield assembly  30  overcomes this disadvantage. By fabricating the core  34  with non-perforated strips (which may include stainless steel core materials), flanges  42  are formed beyond the terminal edges  36  of the aluminum facings  34 , and allow for convenient welding points  44 .  
         [0024]     Obviously, many modifications and variations of the present invention are possible in light of the above teachings. It is, therefore, to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described.