Abstract:
An instrument panel of an automotive vehicle includes a rigid retainer preformed with an air bag opening and a recessed ledge extending about the opening. A separately formed door is installed on the opening and hinged to the retainer along one edge. The remaining three edges overlie the ledge to prevent inward movement of the door. The retainer and door are placed in a cavity of a mold tool in spaced relation to an outer skin and foam constituents are reacted therebetween to develop a foam layer. A foam seal is provided at the interface of the ledge and door to prevent the escape of foam past the ledge.

Description:
This is a U.S. Pat. No. 6,123,356 division of application Ser. No. 09/128,513, filed on Aug. 3, 1998. 
    
    
     This invention relates generally to instrument panels for automotive vehicles of the type having a retainer panel formed with an airbag deployment opening and a separately formed deployment door installed in the opening and covered by a continuous foam and skin layer and, more particularly, to the means of controlling foam leakage past the door during manufacture of the instrument panel. 
     BACKGROUND OF THE INVENTION 
     In manufacturing instrument panels of the above type, the separately formed door is typically hinged along one edge to the retainer and a gap exists along the remaining edges to provide clearance for installation and opening. The overlying foam layer is foamed in place in the space provided between the outer skin layer and an upper surface of the door and retainer members. 
     According to known practice, the gap between the door and retainer is masked off with adhesive tape after the door has been installed in the opening. The tape is applied to the outer surfaces of the door and retainer members across the gap and serves to block the foam material from leaking past the door. Application of such tape, although effective, adds an extra step in the manufacturing process and further presents a barrier to the direct adhesion of the foam material to the door and retainer members in the region of the masked areas. 
     air bag closure assembly according to a method and construction of the invention overcomes and greatly minimizes the foregoing objections. 
     SUMMARY OF THE INVENTION 
     An instrument panel closure assembly for an air bag system of a vehicle according to the invention comprises a rigid retainer member having a top surface and a preformed air bag deployment opening surrounded at least in part by a retainer ledge recessed below the top surface. At least one separately formed door member is accommodated in the deployment opening of the retainer member and supported by the recessed retainer ledge against movement inwardly of the retainer ledge. A continuous outer flexible polymeric skin layer is spaced in overlying relation to the retainer and door members, between which an intermediate layer of foam material is foamed in place. A foam blockage seal is provided at the interface between the door member and the recessed ledge of the retainer member and is operative to block the passage of foam layer material past the door member and ledge during the formation of the foam layer. 
     The foam blockage seal may be formed as an integral part of the ledge and/or door or may be formed separately and applied to the ledge before installation of the door. The recessed seal eliminates the need for surface-applied masking tape and in doing so promotes complete, uniform direct adhesion of the foam layer to the underlying door and retainer members. 
    
    
     These and other features and advantages of the invention will become readily apparent when considered in connection with the following detailed description and drawings. 
     THE DRAWINGS 
     Presently preferred embodiments of the invention are disclosed in the following description and in the accompanying drawings, wherein: 
     FIG. 1 is a fragmentary perspective view of an interior instrument panel trim component constructed according to the invention; 
     FIG. 2 is a fragmentary plan view of such trim component showing the outer skin and foam layer broken away to expose the underlying door and retainer members; 
     FIG. 3 is an enlarged cross-sectional view taken along lines  3 — 3  of FIG. 1; 
     FIG. 4 is an enlarged cross-sectional view illustrating a preferred method of fabricating the trim component according to the invention; and 
     FIGS. 5-8 are each enlarged fragmentary cross-sectional views illustrating alternative sealing arrangements of the invention. 
    
    
     DETAILED DESCRIPTION 
     Referred now to FIGS. 1-3, an interior instrument panel trim component assembly  10  is illustrated concealing an air bag assembly  14  of known type. 
     The assembly  10  includes a retainer member  16  constructed as a rigid plastic or metal panel having a top surface  18  and a preformed deployment opening  20  normally closed by a separately formed door member  22 . While in the illustrative embodiment the assembly  10  has a single door member  22 , it will be appreciated that the invention is applicable and contemplates multiple door arrangements, such as that disclosed in U.S. Pat. No. 5,451,075, which is commonly owned by the assignee of the present invention and its disclosure incorporated herein by reference. 
     The opening  20  of the retainer  16  is generally rectangular and framed on three sides thereof by an integral ledge  24  recessed below the top surface  18  of the retainer  16 . As illustrated best in FIG. 3, the ledge  24  has a generally L-shaped cross section including a downwardly depending side wall  30  and a transverse support wall  32  having an upper surface  34  generally parallel to but spaced from the top surface  18  of the retainer member  16 . 
     The ledge  24  underlies corresponding side  25  and rear  26  edge regions of the door  22  (with respect to their relative positions in relation to the front and rear of the vehicle) supporting the door  22  against movement inwardly of the retainer and a top surface  28  of the door  22  aligned preferably flush with the top surface  18  of the retainer  16 . Alternatively, the top surface  28  of the door  22  may be raised above the top surface  18  of the retainer  16 , or the top surface  28  of the door  22  may be subflush with the top surface  18  of the retainer  16 . 
     A forward edge  36  of the door  22  is secured to an adjacent forward edge  38  of the retainer  16  by a separate hinge  40  having a generally S-shaped strap configuration with one leg  42  overlying the forward edge  36  of the door and the other leg  44  extending beneath the forward edge  38  of the retainer and secured to each by a plurality of spaced rivets  45 , or the like. 
     The retainer and door members  16 ,  22  are covered by a cushioning foam layer  46  and an outer flexible, decorative shell or skin layer  48 . The skin layer  48  is preferably formed of a thermoplastic polymer, such as polyvinyl chloride, thermoplastic urethane, or thermoplastic olefin, according to known manufacturing techniques but could also be a thermoset polymer such as thermoset urethane. The skin  48  has a weakened invisible seam  50  formed therein corresponding in location and shape to the unhinged marginal edges  26  of the door member  22  according to known techniques. The foam layer  46  is fabricated by known foam-in-place techniques and foam reactant materials, such as urethane foam, in the space  52  between the skin layer  48  and the top surfaces  18 ,  28  of the retainer and door members  16 ,  22 . 
     FIG. 4 schematically illustrates the general technique for molding the foam layer  46 . As shown, the preformed skin layer  48  is positioned topside down in a cavity  54  of a mold tool  56  shaped in accordance with the desired shape of the instrument panel  12 . The assembled retainer and door members  16 ,  22  are inserted into the mold and supported in spaced relation to the outer skin  48  to provide the foam space  52 . Suitable foam reactants are then introduced into the space  52  where they react, expand and cure to fill the space  52  and generate the foam layer. 
     According to the invention, a seal  60  is provided between the ledge  24  of the retainer member  16  and the confronting edges  26  of the door  22  to prevent the foam  46  from escaping or leaking past the door  22  and ledge  24 . The seal is formed between the door member  22  and the ledge  24  upon installing the door  22  in the opening  20 . The invention contemplates various seal arrangements between the ledge  24  and door  22 , the first of which is illustrated in FIGS. 3 and 4, with additional embodiments shown in FIGS. 5-8. 
     Turning now specifically to FIGS. 3 and 4, the support wall  32  of the ledge  24  is shown formed with at least one and preferably a pair of raised inner  62  and outer  63  ribs that project above the upper surface  34  of the support wall  32 . The ribs  62 ,  63  are spaced inwardly of the side wall  30  and spaced laterally with respect to one another to define open channels  64 ,  66  underlying the door  22  adjacent the side wall  30  and between the ribs  62 ,  63  respectively. The ribs  62 ,  63  run continuously along the ledge  24  and preferably are in contact or close proximity with the underside of the door member  22  along the unhinged sides of the door  22 , such that the ribs  62 ,  63  together with the hinge  40  seal the space  52  against foam leakage beyond the ledge  24 . The expanding foam  46  enters a peripheral clearance gap  68  between the side wall  30  of the ledge  24  and the edge of the door  22  and from there pass into the first channel  64  beneath the door  22 . The channel  64  serves as a reservoir for the foam  46  and in some cases may completely contain the excess foam. The invention contemplates that small gaps or spaces may exist between the top of the ribs  62 ,  63  and the confronting surface of the door  22  due to imperfections, pressure buildup, or designed clearance, allowing some of the foam material  46  to pass from the outer channel  64  into the adjacent inner channel  66 . In this way, the ribs  62 ,  63  cooperate with the door  22  to define a tortuous, constricted flow path (i.e. a labyrinth seal) for the foam as it passes between the door  22  and ledge  24 , causing the foam to accumulate and be retained in one or both channels  64 ,  66 . As foam flows through thin cross-sections as at gap  68  and small gaps between ribs  62 ,  63  and door  22 , its viscosity tends to increase and limit foam leakage at the door/retainer interface defined at gap  68 . 
     It is preferred that the ribs  62 ,  63  be formed integrally with the formation of the ledge  24 , and as such they may be molded, stamped or cast as unitary projections rising above the top surface  28  of the ledge  24  to meet the underside marginal regions  26  of the door  22 . 
     FIG. 5 illustrates an alternative embodiment of the foam blockage seal, in which like reference numerals are used to identify like parts, but are offset by one hundred. The construction of the foam seal  160  is the same as that of the first embodiment of FIGS. 3 and 4, except that an additional resilient strip or gasket  70  is provided in the channel  166  to block the passage of the foam material  146  beyond the gasket  70 . The gasket  70  is formed of a resilient, compressible material such as rubber, elastomeric plastic, and synthetic foam. However, it should be understood that any natural or synthetic gasket material will suffice, depending upon a particular application. 
     In the preferred embodiment, the foam strip or gasket  70  extends continuously along the ledge  24  around all three unhinged sides of the door member  22 , and further is adhered at least to the ledge and preferably to the door  22  as well by means of an adhesive carried on the facing top and bottom surfaces  72 ,  74  of the gasket  70 . 
     The foam gasket  70  is strong enough to hold the door  22  and ledge  24  sealed, yet is separable upon deployment of the air bag  14  to allow the door member  22  to swing outwardly of the retainer member  16  during such deployment. According to a preferred construction, the adherence strength of the foam strip  70  exceeds its tear strength, such that the foam layer  70  is caused to tear in half upon deployment of the air bag  14  with one half of the foam strip  70  remaining adhered to the ledge  24  and the other separated half remaining adhered to and carried outwardly with the door member  22 . 
     FIG. 6 illustrates another embodiment of the invention, wherein like features are referenced by like numerals, but offset by two hundred. The foam seal  260  of the FIG. 6 embodiment is identical to that described above with respect to FIG. 5 except that the FIG. 6 embodiment lacks the rib formations  62 ,  63  and has only the foam strip  270  adhered to the door  22  and ledge  24  members. 
     FIG. 7 illustrates a still further embodiment of the invention with like features referenced by like numerals offset by three hundred. The ledge  324  is molded with a rib  362  as described previously. The door  22  is molded with a corresponding channel or recess  78  aligned to nest with the rib  362  of the retainer member. As shown in FIG. 7, the interleaving rib  362  and channel  78  may be located inwardly from the edge of the door  322  and side wall  330  of the ledge  324  to provide a reservoir  80  for the foam material  346  functioning as a labyrinth seal like that of the channel  64  described previously with respect to the first embodiment of FIGS. 1-4. 
     FIG. 8 shows yet another embodiment of the foam blockage seal  460  wherein the support wall  432  of the ledge  424  is formed with a mounting channel  82   10  in which a resilient foam or rubber gasket  470  is installed to provide a seal between the ledge  424  and door  422 . The gasket  470  in this embodiment has enlarged end regions or heads  84 ,  86  that reside above and below the channel  82  when the gasket  470  is installed therein. In this way, the gasket  470  can be installed with a snap-fit connection into the channel  82  for ease of assembly. 
     If desired, the rib and seal configurations of the prior embodiments can be formed on the door rather than the ledge to serve the same function. 
     Furthermore, while it is preferred that the ribs, seals and gaps therebetween be formed continuously around the sides and rear of a door, the invention also encompasses an arrangement wherein such seal structure is provided over at least part of such sides and rear. 
     The disclosed embodiments are representative of a presently preferred forms of the invention, but are intended to be illustrative rather than definitive thereof. The invention is defined in the claims.