Abstract:
A headliner comprising a substrate having a weakened area, the weakened area defined by at least one slit that completely penetrates through the substrate; and a decorative cover adhered to the substrate. A method of manufacturing a headliner with a weakened area, comprising the steps of forming a substrate, weakening the substrate by forming at least one slit that completely penetrates through the substrate, and concealing the substrate with a decorative covering.

Description:
TECHNICAL FIELD  
       [0001]     The present invention generally relates to a weakened vehicle interior trim piece, and in particular to a weakened headliner for ease in airbag deployment and to a method of making the same.  
       BACKGROUND OF THE INVENTION  
       [0002]     Airbag safety systems are widely used in automotive vehicles and generally comprise an inflatable cushion, folded in an airbag receptacle. The airbag receptacle is typically mounted behind an airbag deployment door on an interior trim piece, such as an instrument panel, steering wheel column, headliner, or the like. Vehicles today typically include driver side airbags, front passenger airbags, side impact airbags, headliner airbags, knee airbags, and rear passenger airbags; consequently, airbag receptacles are mounted to several interior trim pieces.  
         [0003]     The airbag must be able to rapidly deploy when the vehicle is in a collision. Therefore, the airbag must be able to force open the airbag deployment door when the airbag is inflated during deployment. To ease opening of the airbag deployment door, the trim piece in front of the airbag receptacle is weakened. Weakening of the trim piece is carried out by creating scored lines, or otherwise removing material, from the back surface of the trim piece. The scored lines form the perimeter of the deployment door.  
         [0004]     A critical component of the weakening process is the amount of the trim piece material removed, or in other words, the amount of material remaining after being weakened. Enough material must be removed to weaken the trim piece and allow for airbag deployment, however, care must be taken to prevent removal of too much material. Removal of too much material from the trim piece may negatively effect the dimensional, or structural integrity of the trim piece and the aesthetic appearance of the trim piece.  
         [0005]     In the case of headliners, maintaining structural integrity and aesthetic appearance of the part provides many challenges. Headliners are one of the largest trim pieces in the vehicle, thus the sheer size of the headliner presents difficulties in maintaining its structural integrity, even without the addition of areas of weakness. However, headliners conceal or hide, among other components, airbags, including side airbags that deploy from the roof rail. Consequently, it is necessary to weaken the headliner in several locations. In addition to the areas of weakness, headliners require apertures for overhead compartment bins, lighting, and entertainment devices, to name a few. The passengers&#39; attention is drawn to the headliner whenever a component is utilized. The end result is that maintaining the structural integrity and aesthetic appearance of the headliner is very crucial and complicated.  
         [0006]      FIGS. 4 and 5  illustrate a conventional headliner  100  comprising a substrate  110  and a decorative cover  120 . The substrate  110  is weakened by partially scoring the substrate  110  with a groove  130 . In efforts to maintain the structural integrity of the headliner while providing weakened areas for airbag deployment, the scored lines only partially penetrate the substrate  110  of the headliner  100 .  
       SUMMARY OF THE INVENTION  
       [0007]     The inventors of the present invention have recognized these and other problems associated with maintaining structural stability of a headliner while providing a weakened area for airbag deployment. To this end, the inventors have unexpectedly developed a headliner comprising a substrate having a weakened area, the weakened area defined by at least one slit that completely penetrates through the substrate; and a decorative cover adhered to the substrate. A method of manufacturing a headliner with a weakened area, comprising the steps of forming a substrate, weakening the substrate by forming at least one slit that completely penetrates through the substrate, and concealing the substrate with a decorative covering. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  is a perspective view of the interior of a vehicle, including a headliner, in accordance with an exemplary embodiment of the invention.  
         [0009]      FIG. 2  is an exploded view of a back surface of the headliner according to an exemplary embodiment of the present invention.  
         [0010]      FIG. 3  is a cross-sectional view of the headliner taken along line  3 - 3  of  FIG. 2 .  
         [0011]      FIG. 4  is a partial view of a back surface of a substrate, with an airbag deployment door created by partially scoring the substrate, of a conventional headliner.  
         [0012]      FIG. 5  is a cross-sectional view of the back surface of the substrate taken along line  5 - 5  of  FIG. 4 . 
     
    
     DETAILED DESCRIPTION  
       [0013]     Referring to  FIG. 1 , a multilayer headliner  10  within a vehicle  11  is generally shown. The headliner  10  includes a substrate  12  having a front surface  14 , or a Class “A” surface, that faces the interior of the vehicle, and a back surface  16 , or a Class “B” surface, that faces away from the interior of the vehicle  11 . A coverstock or decorative covering  18  may be adhered to the front surface  14  of the substrate  12  to conceal the substrate  12  for aesthetic purposes. The decorative covering  18  may be adhered to the substrate  12  through conventional means and may be comprised of cloth, leather, vinyl, or any other type of decorative covering. In the illustrated embodiment, the substrate  12  and decorative cover  18  form the multilayer headliner  10 . However, the multilayer headliner  10  may include other layers of material, such as a foam layer disposed between the substrate  12  and the decorative cover  18 .  
         [0014]     The substrate  12  may be made from a thermoset material, such as, for example, foam or crushed urethane material, also known as polyurethane. The thermoset material may be a composite material and therefore, include reinforcements, such as, strands of fiber glass. Alternatively, the substrate  12  may be made from crushed and reinforced cardboard material, commonly sold as F10™, or the like.  
         [0015]     Referring to  FIGS. 2 and 3 , the substrate  12  includes a weakened area indicated generally at  20 . The weakened area  20  reduces the strength of the substrate  12 , including the yield strength of the substrate  12 , in the general locality of the weakened area  20 . The weakened area  20  comprises one or more slits  22  cut entirely through the substrate  12 . The slits  22  completely penetrate the substrate  12 , as shown in  FIG. 3 . The substrate  12  may be unexpectedly and completely pierced by slits  22  because of the material properties of the thermoset material.  
         [0016]     The weakened area  20 , defined by the pattern of dashed lines, forms an area of deployment for an airbag (not shown). In the exemplary embodiment, the slits  20  form a pattern of dashed lines at one or more desired locations, such as, around a portion or all of the perimeter of the substrate  12 . However, it can be appreciated that the slits  22  can form any configuration of dashed lines on the substrate  12 , so long as the substrate  12  is sufficiently weakened to allow proper deployment of the airbag. It has been found unexpectedly that weakening the substrate  12  by completely penetrating the substrate with slits  22  sufficiently weakens the substrate  12  for deployment of the airbag. However, quite unexpectedly, the structural integrity of the substrate  12  is not compromised by completely penetrating the substrate  12  with slits  22 . Once the decorative cover  18  is adhered to the substrate  12 , the slits  22  are not visible to passengers in the vehicle, thus, completely penetrating the substrate  12  with slits  22  does not effect the aesthetic appearance of the substrate  12 .  
         [0017]     The substrate  12  may be manufactured using several different processes depending upon the material composition of the substrate  12 . For example, the substrate  12  may be manufactured by an extrusion process, an injection molding process, a low compression molding process, a melt compression molding (MCM) process, or the like. For illustrative purposes, the substrate  12  is manufactured using a conventional injection molding process. After one cycle of the injection molding process, the substrate  12  undergoes a secondary trimming process. The secondary trimming process may include, for example, water jet trimming, laser beam trimming, die cut trimming, or the like.  
         [0018]     In one method of manufacturing the substrate  12 , the secondary trimming process includes undergoing trimming of the substrate  12  in a water jet trimming machine (not shown). The water jet trimming machine includes, among other components, a robotic arm having a water jet head (not shown) and a computer (not shown). The computer may be programmed to move the robotic arm in any configuration and to supply the water jet head with pressurized water at selective intervals. During the water jet trimming process, the water jet head is programmed to remove any excess flash around the perimeter of the substrate  12 . During this secondary process, the slits  22  in the substrate  12  may also be cut, thereby eliminating a separate process needed to form the weakened area  20 .  
         [0019]     Once the substrate  12  has finished the secondary trimming process, the decorative cover  18  may be adhered to the front surface  14  of the substrate  12 , thus forming the headliner  10 . The decorative covering  18  conceals the slits  22  in the substrate  12 . Therefore, the slits  22  are not visible to occupants of the vehicle  11  and do not effect the aesthetic appearance of the headliner  10 .  
         [0020]     In an alternate method of manufacturing the substrate  12 , the slits  22  may be molded into the substrate  12  during the injection molding process. In other words, the slits  22  are in-molded into the substrate  12 . After the substrate  12  and slits  22  are manufactured, the substrate  12  may further undergo the secondary trimming process to remove any flash or excess material. After the secondary trimming process, the decorative cover  18  may be adhered to the front surface  14  of the substrate  12 , thus forming the multilayer headliner  10 . As before, the decorative covering  18  conceals the slits  22  in the substrate  12 . Therefore, the slits  22  are not visible to occupants of the vehicle  11  and do not effect the aesthetic appearance of the headliner  10 . It can be appreciated that the slits  22  in the substrate  12  can be formed using other means known to those skilled in the art. For example, the slits  22  can be formed using a laser, or the like.  
         [0021]     During airbag deployment, the airbag deploys in the vicinity of the weakened area  20 . The weakened area  20 , defined by the pattern of dashed lines, acts an airbag deployment door. The slits  22  may also perform the function of a hinge, a pivot, an axis, or the like between the substrate  12  and the weakened area  20  of the substrate  12 . When the airbag deploys, the weakened area  20  of the substrate  12  gives way to the airbag, due to the forces exerted by the airbag against the substrate  12 . The substrate  12 , along with the decorative cover  18 , breaks apart at the weakened area  20 , forming an aperture or door for the deployed airbag. The pieces of the substrate  12  that broke apart remain adhered to the decorative cover  18 , thereby protecting the passengers from any broken pieces of the substrate  12 .  
         [0022]     It can be appreciated that the substrate  12  may be made from any material and by any manufacturing process, so long as the substrate  12  and the decorative covering  18  form the multilayer headliner  10  with the decorative covering  18  being adhered to the substrate  12  during a separate manufacturing process.  
         [0023]     It can be appreciated that while the exemplary embodiment of the invention is directed towards weakening the substrate  12  for purposes of airbag deployment, the substrate  12  may be weakened for any number of reasons. For instance, the headliner may be weakened in specific locations for the addition of aftermarket products, such as, supplementary lighting in the interior of the vehicle. In other instances, the substrate  12  may be weakened in areas instead of requiring apertures. For example, the substrate  12  may be weakened around the location of the assist grips (not shown) so that during assembly, the assist grip may pierce through the decorative covering  18  and the weakened substrate  12  to attach to the sheet metal of the vehicle.  
         [0024]     The embodiments disclosed herein have been discussed for the purpose of familiarizing the reader with novel aspects of the invention. Although preferred embodiments of the invention have been shown and described, many changes, modifications and substitutions may be made by one having ordinary skill in the art without necessarily departing from the spirit and scope of the invention as described in the following claims.