Abstract:
A cassette comprising a frame member having at least two sides interconnected by a cross member, and a reinforcement material partially encapsulated by and suspended by the at least two sides of said frame member such that the reinforcement material is positioned at a predetermined location when placed in a mold tool.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention relates in general to molding of a trim component, and in particular, to an apparatus and method for consistently and accurately positioning a reinforcement material, such as a scrim material, within a layer of material of an interior trim panel.  
         [0003]     2. Description of the Related Art  
         [0004]     Inflatable restraint systems that protect passengers are located in trim panels, such as instrument panels, in front or to the side of passengers in a vehicle. Typically, the inflatable restraint system includes an air bag that is enclosed within a storage receptacle, which is typically mounted behind an interior trim piece, such as a steering wheel cover in the case of the driver&#39;s side air bag, or a section of the instrument panel, in the case of the passenger&#39;s side air bag. In some vehicles, side impact air bags are also provided in some or all of the vehicle doors.  
         [0005]     One or more air bag deployment doors normally overlie the air bag receptacle and are forced open when the air bag is inflated to allow deployment of the air bag through the opening created by the door panel movement. However, automotive interior trim substrates and covering materials, such as plastics, are relatively tough and difficult to sever. Thus, a predetermined severing pattern may be necessary for proper opening of the airbag door in the trim panel.  
         [0006]     One mechanism for insuring proper opening of the trim cover in an “invisible seam” installation in which the deployment airbag door pattern is totally invisible to a person seated in the vehicle is by performing a secondary operation, such as laser cutting or scoring, to pre-weaken the trim cover. However, laser scoring of the trim cover from the inside, if not done accurately, can over time become at least faintly visible causing “witness lines” from the exterior of the trim piece. Thus, fabrication of the automotive interior trim pieces, particularly for invisible seam applications, is thus a difficult manufacturing challenge.  
         [0007]     To achieve a high level of capability required to manufacture safety critical items, such as integrated invisible airbag doors in instrument panels or the like, it is necessary to demonstrate repeatability of all steps of the process. In addition, to achieve the opening of an airbag door at a range of temperatures without fragmentation, it is desirable to reinforce the airbag door area with a mesh, fabric, scrim, or other type of reinforcement material, which may also provide a hinge or tether when the door opens with the force of the airbag deployment. Typically, the trim component, such as an instrument panel, is comprised of carrier layer or substrate, an optional layer of foam material, and a cover material visible to the occupant.  
         [0008]     In order to demonstrate the repeatability of the process steps, it must be shown that the reinforcement material can be encapsulated consistently in the desired position from one manufactured trim component to the next manufactured trim component during the molding process. In the manufacture of an instrument panel, for example, an inaccuracy of the placement of the reinforcement material may result in the reinforcement material not to be positioned immediately adjacent to the desired pre-weakening of the substrate or trim covering material. In addition, the reinforcement material may migrate within the substrate toward an exterior surface during the molding process, thereby increasing the probability of “read-through” of the reinforcement material.  
         [0009]     One current method of positioning the reinforcement material is to utilize pins within the instrument panel substrate molding tool that will accept punched holes in the reinforcement material. One problem with this method is that all of the surface shapes required by the instrument panel stylist are difficult to accommodate. In addition, this method only positions the reinforcement material accurately in one plane, and only at the positions of the punched holes, thereby allowing the injected material to distort the reinforcement material at other locations.  
         [0010]     Thus, there is a need to provide a method for positioning a reinforcement material, such as a scrim material or the like, consistently in three dimensions within a trim component, such as an instrument panel, during an injection molding process. There is also a need to position the reinforcement material within the substrate material in such a way that secondary operations, such as laser scoring, can be eliminated by the use of alternative methods to promote tearing of the foam and/or covering materials.  
       SUMMARY OF THE INVENTION  
       [0011]     The inventor of the present invention has recognized these and other problems associated with manufacturing a trim component having a reinforcement material and has developed a method and apparatus for alleviating such problems. Specifically, the inventor of the present invention has developed a cassette comprising a frame member and a reinforcement material held in place by the frame member such that the reinforcement material is positioned at a predetermined location within a mold tool.  
         [0012]     The inventor has also developed a method for positioning a reinforcement material comprising the steps of providing a cassette including a frame member, and securing a reinforcement material to the frame member such that the reinforcement material is positioned at a predetermined location within a mold tool. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     In the drawings:  
         [0014]      FIG. 1  shows a top view of a cassette for positioning a reinforcement material according to an embodiment of the invention.  
         [0015]      FIG. 2  shows a cross sectional view of an embodiment of the cassette taken along line  2 - 2  of  FIG. 1 .  
         [0016]      FIG. 3  shows an enlarged view of an alternate embodiment of the frame member illustrating the reinforcement material being encapsulated by the frame member of the cassette.  
         [0017]      FIG. 4  shows another enlarged view of another alternate embodiment of the frame member illustrating the reinforcement material being encapsulated by the frame member of the cassette.  
         [0018]      FIG. 5  shows a top view of a cassette for positioning a reinforcement material according to an alternate embodiment of the invention.  
         [0019]      FIG. 6  shows a cross sectional view of the cassette taken along line  6 - 6  of  FIG. 5 .  
         [0020]      FIG. 7  shows a top view of a cassette for positioning a reinforcement material according to yet another embodiment of the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0021]     Referring now to  FIGS. 1-4 , a cassette  10  is shown according to one embodiment of the invention. The cassette  10  is to be used in conjunction with a trim panel incorporating an inflatable restraint system. The cassette  10  includes a frame member, shown generally at  12 , that defines an outer periphery of the cassette  10 . The frame member  12  includes at least two opposing sides and is made by any conventional means, such as injection molding a semi-rigid material, such as a plastic material or the like. In the illustrated embodiment of  FIG. 1 , the frame member  12  forms a three-sided “picture frame” structure with a fourth side including an extension area  24  and a hinge line, indicated at  26 . The hinge line  26  is the approximate line along which an airbag door would bend open.  
         [0022]     The frame member  12  may include one or more feed bars  16  extending inwardly from the frame member  12  to a substantially centrally located feed point  20  to define one or more openings  18  therebetween. The feed point  20  can be at any desired location on the cassette  10 . Preferably, the feed bars  16  have a thickness less than a thickness of the frame member  12  to allow injected material that forms the trim panel to fill the openings  18 . As seen from the top view of  FIG. 1 , the cassette  10  includes four (4) feed bars  16  that define four (4) openings  18  that define an “X-shape” configuration (when viewed from the top) in which the feed bars  16  extend inwardly from each of the four corners of the frame member  12  and converge at the substantially centrally located feed point  20 . It will be appreciated that other configuration are within the contemplation of the invention. For example, the feed bars  16  and the feed point  20  may define a star-shaped configuration or the like. Thus, the frame member  12 , the feed bars  16  and the feed point  20  of the cassette  10  form a “spoke and hub” geometric configuration.  
         [0023]     The main purpose of the feed bars  16  is to provide a means for locating and positioning one or more spacer lugs  28  at an appropriate location between the frame member  12  and the feed point  20 . However, the invention is not limited by the number of feed bars  16  and openings  18 , and that the invention can be practiced with any sufficient number of feed bars  16  and openings  18  the feed bars  16  In fact, the invention can be practiced without the use of the feed bars  16  and the feed point  20  by simply providing a pair of opposing frame members  12  having the one or more spacer lugs  28  located thereon.  
         [0024]     One aspect of the invention is that a reinforcement material  22 , such as a scrim or the like, is encapsulated by the frame member  12  for positioning the reinforcement material  22  at a predetermined location within a mold tool used to form a trim component during an injection molding operation, casting operation, or the like. Although not necessary to practice the invention, the reinforcement material  22  may also be encapsulated by the feed bars  16  and/or the spacer lugs  28 . The reinforcement material  22  can be encapsulated by the frame member  12  and/or the spacer lugs  28  by over-molding material during the manufacture of the cassette  10 .  
         [0025]     In the illustrated embodiment, the reinforcement material  22  extends across the openings  18  between the frame member  12  and the feed bars  16 . In addition, the reinforcement material  22  also extends across the hinge line  26  and into the extension area  24  of the cassette  10 . The hinge line  26  acts as a tether or hinge during deployment of an airbag door (not shown) when the cassette  10  is used during manufacture of an instrument panel. The reinforcement material  22  and the extension area  24  may include one or more holes  30  for aligning the cassette  10  when the cassette  10  is loaded into a molding tool  50 ,  52 . A pair of arms  32  extending from the frame member  12  may also be provided to position the reinforcement material  22  in the extension area  24 . The reinforcement material  22  associated with the extension area  24  can be cut or trimmed in a separate cutting operation.  
         [0026]     The reinforcement material  22  can be made of any design or materials known in the art including, but not limited to, metal (e.g. steel straps, steel mesh screen), plastics (e.g. thermoplastics, thermoset plastics, elastomers, plastic mesh screen,) and fibers (e.g. nylon straps, PVC coated nylon scrim, hemp, cotton, woven or non-woven). For example, the reinforcement material  22  can be constructed from strips of tough, strong, flexible, resilient, scrim material formed of resinous plastic fibers, such as that sold under the trademark “NYLON”. In another example, the reinforcement material  22  can be made of fabric material. The reinforcement material  22  can be woven with an open weave to form a mesh-like structure.  
         [0027]     As seen in  FIG. 2 , the frame member  12  and the spacer lugs  28  position the reinforcement material  22  within a mold tool  50 ,  52  such that the reinforcement material  22  will be positioned consistently at approximately a mid-plane of a layer  46  of material. The layer  46  of material may be used, for example, as a carrier or substrate of an interior trim panel (not shown), such as an instrument panel. The interior trim panel may be of a multi-layer or single layer construction. The cassette  10  can be entirely or partially embedded in any layer or layers of the interior trim panel. The use of the spacer lugs  28  of the cassette  10  ideally positions the reinforcement material  22  at approximately the mid-plane of the layer  46 , unlike conventional methods that position the reinforcement material  22  at either the upper or lower surface of the layer  46 . As a result of this mid-plane positioning the reinforcement material  22  within the layer  46 , the reinforcement material  22  is positioned at an optimal location with the layer  46  to prevent fragmentation of the instrument panel upon deployment of the airbag. In addition, the cassette  10  of the invention also consistently positions the reinforcement material  22  proximate to an airbag deployment door opening to further prevent fragmentation of the instrument panel upon deployment of the airbag.  
         [0028]     However, the invention is not limited by the location at which the reinforcement material  22  is positioned within the layer  46  of the interior trim panel, depending on the type of trim panel. For example, in a simple trim panel comprised of a single layer of material with a textured or grained surface that is visible to the occupant, the reinforcement material  22  can be positioned at a predetermined distance directly within the single layer of material of the interior trim panel. In addition, it will be appreciated that the invention is not limited by the type of molding operation for forming the trim panel, and that the invention can be practiced with any conventional manufacturing process, such as injection molding, casting, or the like.  
         [0029]     Referring now to  FIGS. 3 and 4 , another aspect of the cassette  10  of the invention is that the combination of the frame member  12  and the layer  46  of material may be designed to form a shear plane  48  at the interface between the frame member  12  and the layer  46  of material. The purpose of the shear plane  48  is to assist in severing the layer  46  upon deployment of the airbag, thereby eliminating or reducing the need for supplemental pre-weakening of the layer  46  of material. One way of forming the shear plane  48  is by using non-compatible molding materials for the frame member  12  and the layer  46  of material. Another way of forming the shear plane  48  is by using compatible molding materials, but forming an incomplete bond between the molding materials. By selectively determining the relative bond strength between the frame member  12  and the layer  46  of material, the shear plane  48  will cause the layer  46  of material to tear at the interface between the frame member  12  and the layer  46  of material when a shear force is applied to the layer  46  of material, such as a shear force generated during the deployment of the airbag. As a result, the shear plane  48  will assist in severing the layer  46  of material at the interface between the layer  46  of material and the frame member  12 .  
         [0030]     As seen in  FIG. 3 , the relative bonding strength between the frame member  12  and the layer  46  of material can be selectively determined by a variety of factors. One factor for selectively determining the relative bonding strength between the frame member  12  and the layer  46  of material is by using a mechanical interlock, shown generally at  60 . In the illustrated embodiment, the mechanical interlock  60  comprises an inwardly extending concave portion  62  and an outwardly extending convex portion  64 . As a result of the mechanical interlock  60 , the relative bonding strength between the layer  46  of material and the frame member  12  can be increased as compared to a frame member  12  that does not include the mechanical interlock  60 , even though compatible or non-compatible materials are used for the frame member  12  and the layer  46  of material.  
         [0031]     As mentioned above, another factor for selectively determining the bonding strength between the frame member  12  and the layer  46  of material is the type of materials used for the layer  46  of material and the frame member  12 . For example, the use of non-compatible materials for the frame member  12  and the layer  46  of material will tend to weaken the relative bond strength between the frame member  12  and the layer  46  of material. On the other hand, the use of compatible materials for the frame member  12  and the layer  46  of material will tend to strengthen the relative bond strength between the frame member  12  and the layer  46  of material. However, this increase in the relative bonding strength by using compatible bonding materials can be selectively adjusted by forming an incomplete bond between the materials for the frame member  12  and the layer  46  of material during the manufacturing process for the layer  46  of material.  
         [0032]     As described above, the shear plane  48  defines a location at which the layer  46  of material will tear or separate during deployment of the airbag. As seen in  FIG. 4 , the frame member  12  may also include a knife edge  54  to further assist in severing any other layers of material above the layer  46  of material upon deployment of the airbag. In addition, the knife edge  54  may be fully embedded within the layer  46  of material to assist in severing the layer  46  of material. Preferably, the knife edge  54  is located on an outer surface of the frame member  12  and substantially on a peripheral upper edge of the frame member  12 . The knife edge  54  is substantially aligned with the shear plane  48  such that the knife edge  54  further assists in the separation or tearing of material located above the frame member  12 . This aspect of the invention may be particularly useful in multi-layer applications. For example, when the layer  46  of material is used in an instrument panel with other layers of material, such as a foam layer, a covering layer, or the like, the knife edge  54  assists in severing or separating any such layers of material upon deployment of the airbag, thereby minimizing or eliminating the need to perform a secondary pre-weakening operation. As a result, the cost of manufacturing the instrument panel is significantly reduced.  
         [0033]     It will be appreciated that the shear plane  48  may be used in conjunction with alternative methods of promoting tearing of the layers of materials of the instrument panel. Because the shear plane  48  is located proximate to the reinforcement material  22 , the cassette  10  of the invention consistently positions the reinforcement material  22  proximate to the tear seam pattern for the deployment of the airbag, thereby minimizing the fragmentation of the instrument panel upon deployment of the airbag.  
         [0034]     As mentioned above, the cassette  10  of the invention is not limited by a particular geometric configuration. For example, a cassette  10 ′ of the invention may comprise a “rib and backbone” geometric configuration, as shown in  FIGS. 5 and 6 . The cassette  10 ′ includes a backbone or spine  34  and one or more ribs  36  extending laterally from the spine  34  to define openings  38  therebetween. Unlike the cassette  10 , the cassette  10 ′ does not include a frame member  12 , but rather the reinforcement material  22  of the cassette  10 ′ is encapsulated within the spine  34  and the ribs  36  by overmolding material. As a result, the cassette  10 ′ is particularly useful in situations in which a folding of the airbag during deployment is desirable in order to minimize damage to the windscreen (not shown) or other parts of the vehicle. Specifically, the laterally extending ribs  36  provide a flexible support structure for the reinforcement material  22  that promotes folding of the cassette  10 ′ without complete separation of the cassette  10 ′.  
         [0035]     As seen in  FIG. 6 , similar to the cassette  10 , the cassette  10 ′ can consistently position the reinforcement material  22  at any desirable predetermined location within the layer  46  of material, such as a carrier or substrate material, of an interior trim panel. In the illustration of  FIG. 6 , the reinforcement material  22  is located proximate to the mold  52  and farthest from the mold  50  such that the reinforcement material  22  is located toward an interior surface or “B” surface of the layer  46  of material when the interior trim panel is installed. By ensuring consistently positioning the reinforcement material  22  proximate to the layer of material  40  forming the “B” surface of the interior trim panel, “read-through” of the reinforcement material  22  through the opposite surface or “A” surface is minimized.  
         [0036]     As described above, the cassette  10 ,  10 ′ of the invention can consistently position the reinforcement material  22  at a predetermined location within the layer  46  of material forming an interior trim panel. In the case where the interior trim panel is an instrument panel, the cassette  10 ,  10 ′ can consistently position the reinforcement material  22  within the region defining the airbag door such that the reinforcement material  22  is consistently positioned proximate to the tear seam pattern that assists in the deployment of the airbag.  
         [0037]     It will be appreciated that the cassette  10 ,  10 ′ of the invention can also be utilized to consistently position the reinforcement material  22  in a region outside the airbag door opening, but proximate to the tear seam pattern to further assist in minimizing fragmentation of the interior trim panel upon deployment of the airbag. It is contemplated by the inventor of the present invention that positioning the reinforcement material  22  proximate to the tear seam pattern outside the airbag door opening can be accomplished in a variety of different ways.  
         [0038]     Referring now to  FIG. 7 , a cassette  100  according to an alternative embodiment of the invention. The cassette  100  comprises a “frame within a frame” construction and includes an inner cassette member, shown generally at  70 , and an outer cassette member, shown generally at  80 . In the illustrated embodiment, the inner cassette member  70  is substantially identical to the cassette  10  described above. However, it will be appreciated that the invention is not limited by the configuration of the inner cassette member  70 , and that the invention can be practiced with other configurations. For example, the inner cassette member  70  can comprise the cassette  10 ′ as described above.  
         [0039]     The outer cassette member  80  includes an inner frame member  82  and an outer frame member  84 . The reinforcement material  22  is secured between the inner and outer frame members  82 ,  84  by over-molding material when forming the frame members  82 ,  84 , similar to the manner in which the reinforcement material  22  is secured to the frame member  12  of the cassette  10 . The inner and outer frame members  82 ,  84  may include one or more spacer lugs  28  to position the reinforcement material  22  at a predetermined location within the layer  46  of the trim panel, similar to the cassette  10 .  
         [0040]     One aspect of the cassette  100  of the invention is that the reinforcement material  22  is positioned not only at a predetermined location within the layer  46  within the airbag door, but also outside of a tear seam  90  to prevent or eliminate fragmentation of the trim panel upon deployment of the airbag. It should be noted that the tear seam  90  can be located at the intersection of the frame member  12  of the inner cassette member  70  and the layer  46  of material, or at the intersection of the inner frame member  82  of the outer cassette member  80  and the layer  46  of material by the using the shear plane  48  as described above. Alternatively, the tear seam  90  can be located between the frame member  12  of the inner cassette member  70  and the inner frame member  82  of the outer cassette member  80  without the use of the shear plane  48 , as shown in  FIG. 7 .  
         [0041]     As described above, the reinforcement material  22  provides reinforcement and prevents fragmentation of the trim panel during the deployment of the airbag door by being located within and proximate to the area defining the opening for the deployment of the airbag door. In addition, the reinforcement material  22  can be located both within and outside the area defining the opening for the deployment of the airbag door to provide additional prevention of the fragmentation of the trim panel. Further, the shear plane  48  can be positioned to provide any desirable pre-weakening tear seam pattern. For example, the shear plane  48  can be in a star-shape pattern, or the like. However, it will be appreciated that the invention can be practiced with or without the shear plane  48  to assist in the deployment of the airbag door.  
         [0042]     While the invention has been specifically described in connection with certain specific embodiments thereof, it is to be understood that this is by way of illustration and not of limitation, and the scope of the appended claims should be construed as broadly as the prior art will permit.