Abstract:
An improved air bag deployment system that protects welds or other bonds that are made between the underside of an instrument panel substrate and the outer flange of an air bag deployment chute. A deflector element is located in the gap between the chute flange and the substrate to prevent the deploying air bag from expanding into the gap and potentially damaging the bond.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    This invention relates to the field of air bag deployment systems for an automotive vehicle and more particularly to the area of an air bag deployment chute that is bonded to the underside of an instrument panel substrate. 
         [0002]      FIG. 1  illustrates a prior art configuration of an air bag deployment system  100  in which an air bag deployment chute  150 , having a flange  152 , is bonded to the underside of an instrument panel substrate  120 . Chute  150  is a one piece molded structure that contains several apertures  155  into which hooks  280  extending from an air bag container is attached. Although not shown, the air bag container is permanently attached to the vehicle structure. Hooks, such as  280 , together with the air bag container perform the task of restraining the instrument panel  100  and the air bag deployment chute  150  from movement during air bag deployment. In such a manner, most all energy from the deploying air bag is directed outward to cause the pre-weakened seams  102  that form the deployment door  110  to fracture and allow release of the air bag from its container. 
         [0003]    Instrument panel base substrate  120  contains a pre-weakened seam  102  that, depending on the outer layers, may extend through the base and in some cases partially through the upper layers to provide a desired invisible seam. In this illustration, air bag chute  150 , foam layer  130  and outer layer of a class “A” skin  140  are all formed of TPO (Thermoplastic Olefin) materials to facilitate recycling. As such, only the base substrate  120  needs to be scored or otherwise formed to be undercut in the tear seam path that defines the deployment door. The layers  130  and  140  are typically bonded together with adhesives or the like. However, the bonding of the flange  152  of deployment chute  150  to the underside of the substrate  120  is typically performed via ultrasonic welding. In such bonding, ribs  154 ,  156 ,  158 ,  160 , etc. are integrally formed in the upper surface portion of flange  152 . When welded to the underside of substrate  120 , a small gap  166  often remains between the flange  152  and substrate  120  due to the volume of the melted ribs. 
         [0004]    Air bag  170  is shown in  FIG. 1  as beginning its deployment. Arrows are used to represent the side forces developed against the air bag side wall  172  due to the expanding gas that is generated to inflate the air bag against internal wall  151  of the deployment chute  150 . In the configuration of  FIG. 1 , the air bag  170  fabric is shown as diverting around the upper corner  153  of internal wall  150  and into the gap  166 . When this occurs, excessive pressure can be generated on the weld  154  that may cause fracturing of the weld bond between flange  152  and substrate  120 , before the door seam  102  fractures and allows the air bag to fully deploy. It is also believed that the side wall  151  of chute  150  may be slightly expanded during this early stage of deployment that, in turn, may cause corner  153  to be lowered and gap  166  to be enlarged and therefore allow the air bag  170  fabric to further migrate towards the weld  154 . 
       SUMMARY OF THE INVENTION 
       [0005]    The described embodiments are directed to an improved apparatus and method for protecting the welds or other bonds that are made between the underside of an instrument panel substrate and the outer flange of an air bag deployment chute. Diversion barriers are placed in the gap between the chute flange and the substrate to prevent the deploying air bag from expanding into the gap and potentially breaking the bond. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0006]      FIG. 1  is a cross-sectional view of a portion of an air bag deployment system of the prior art. 
           [0007]      FIG. 2  is a cross-sectional view of a portion of an air bag deployment system employing a disclosed embodiment. 
           [0008]      FIG. 2A  is a perspective view of one version of the embodiment shown in  FIG. 2  with a barrier of varying heights. 
           [0009]      FIG. 2B  is a a perspective view of another version of the embodiment shown in  FIG. 2  with a barrier of a continuous height. 
           [0010]      FIG. 3  is a cross-sectional view of a portion of an air bag deployment system employing another disclosed embodiment. 
           [0011]      FIG. 3A  is a perspective view of one version of the embodiment shown in  FIG. 3  with a barrier of varying heights. 
           [0012]      FIG. 3B  is a top view of another version of the embodiment shown in  FIG. 3  with a barrier of a continuous height. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0013]    The embodiment shown in  FIG. 2  illustrates an improvement to an air bag deployment system. In the  FIG. 2  embodiment, a portion of an air bag deployment system  200  is shown in which a base substrate  220  supports a foam layer  230  and an outer skin  240 . An air bag deployment chute  250  with an inner side wall  251  and flange  252  is shown with deformable ribs  254 ,  256 ,  258  and  260  on flange  252  that are preferably ultrasonically welded to the lower surface of substrate  220 . A pre-weakened tear seam  202  is slightly off-set from the opening of air bag deployment chute  250 , and the deployment door  210  is defined by the tear seam path and hinge (not shown). Although only a small portion of the air bag deployment system is shown, it should be understood that flange  252  extends and weld ribs are provided around the entire door  210  outward from tear seam  202 . 
         [0014]    Air bag deployment chute  250  contains a gusset  257  to stiffen side wall  251  and flange  252  during air bag deployment. Deflector rib  253  is formed into the corner between the side wall  251  and flange  252  so as to protrude into a non-bonded area forming an air gap  266  between the flange  252  and lower surface of substrate  220 . Although only shown in cross-section, deflector rib  253  extends along the corner edge of air bag deployment chute  250  so as to protect all flange welds adjacent the chute opening. Deflector rib  253  is sufficiently high to block the entry of the air bag  270  fabric into gap  266  and prevent damage to weld  254  during air bag deployment. 
         [0015]    Air bag  270  is depicted in  FIG. 2  at the moment during deployment activation prior to sufficient force build up that fractures tear seam  202 . As can be seen, deflector rib  253  prevents the air bag  270  fabric from entering gap  266  and from causing damage to weld  254 . 
         [0016]      FIGS. 2A and 2B  illustrate alternate versions of the embodiment shown in  FIG. 2 . In  FIG. 2A , the deflector rib  253  is formed to have portions of varying heights  253   i  and  253   ii  that are spaced apart, but provide a sufficient barrier to air bag fabric entering the gap  266 . In  FIG. 2B , the deflector rib  253  is formed to have a substantially continuous height to block the air bag fabric from entering gap  266 . 
         [0017]    The embodiment shown in  FIG. 3  illustrates another improvement to an air bag deployment system. In the  FIG. 3  embodiment, a portion of an air bag deployment system  300  is shown in which a base substrate  320  supports a foam layer  330  and an outer skin  340 . An air bag deployment chute  350  with an inner side wall  351  and flange  352  extending from the corner  353  at the chute opening. Flange  352  contains deformable ribs  354 ,  356 ,  358  and  360  that are preferably ultrasonically welded to the lower surface of substrate  320 . A pre-weakened tear seam  302  is slightly off-set from corner  353  at the opening of air bag deployment chute  350 , and the deployment door  310  is defined by the tear seam path and hinge (not shown). 
         [0018]    Air bag deployment chute  350  contains a gusset  357  to provide stiffening to side wall  351  and flange  352 . Deflector rib  359  is formed onto flange  352  between weld rib  354  and tear seam  302  so as to protrude into gap  366  that results between the flange  352  and lower surface of substrate  320 . Deflector rib  359  is sufficiently high to block the entry of the air bag  370  fabric into gap  366  to a point where it could damage weld  354  during air bag deployment. Alternatively, the deflector rib could be formed on the lower surface of base substrate  320  to protrude into gap  366  with equivalent results. 
         [0019]    Air bag  370  is depicted in  FIG. 3  at the moment during deployment activation prior to sufficient force build up that fractures tear seam  302 . As can be seen, deflector rib  353  prevents the forces from the air bag fabric from damaging the weld  354 , while applying forces against tear seam  302  and deployment door  310 . 
         [0020]      FIGS. 3A and 3B  illustrate alternate versions of the embodiment shown in  FIG. 3 . In  FIG. 3A , the deflector rib  359  is formed to have portions of varying heights  359   i  and  359   ii  that are spaced apart, but provide a sufficient barrier to prevent air bag fabric from damaging weld  354 . In  FIG. 2B , the deflector rib  359  is formed to have a substantially continuous height to prevent the air bag fabric from damaging weld  354 . 
         [0021]    As can be seen by the drawings and accompanying explanation, the described embodiments are unique improvements over conventional air bag deployment systems. And while the embodiments shown here are preferred, they shall not be considered to be a restriction on the scope of the claims set forth below.