Abstract:
An air bag system and method of making the same are provided including a reinforced cover for a vehicle seat having an air bag module hidden therein. The reinforced cover includes cover material that is stretchable and a backing reinforcement material that is stiffer than the cover material. The reinforcement material is attached to the cover material to provide a repeatable deployment path for the air bag as it inflates so that the air bag breaks through the seat cover at a preferred location thereon, e.g. bolster seam. The reinforced cover will not expand as the bag inflates as its stiffness or rigidity as provided by the reinforcement material will cause the bag to seek out the area of greater weakness in the cover at the bolster seam which the reinforcement material does not block. As the reinforcement cover provides the repeatable deployment path for the air bag to the bolster seam, there is no need for complicated and expensive modifications to the air bag module for proper and timely deployment thereof simplifying the installation of the present air bag system.

Description:
This invention relates to an air bag system having an air bag module mounted within an upholstery material, such as a side-impact air bag mounted within a vehicle seat. 
     BACKGROUND OF THE INVENTION 
     Some side-impact air bag modules are currently secured to an internal frame of a vehicle seat and are concealed within the seat by the seat cover. Upon being deployed, the air bag is supposed to expand through a frangible seam in the seat cover at a predetermined location to protect the occupant&#39;s head and torso at the event of a side impact sufficient to cause deployment. The timing of air bag deployment in the event of crash conditions is critical in terms of providing the maximum safety benefit thereby, and delays in deployment even on the order of fractions of a second can impair the safety functioning of the air bag. Where the air bag is contained within a seat, it therefore must not experience delays in the time from firing of the air bag to the time the air bag breaks through the intended seam of rupture. However, seat covers are usually of a stretchable material, and in some instances, it has been found that rather than having a proper and timely break through the seam, the air bag will start to inflate the stretchable seat cover prior to emerging from the seam thus delaying the desired time of rupture and bag inflation exterior of the seat. Accordingly, a more predictable path of deployment for an air bag that deploys from within a seat and through an intended seam of rupture is needed to obtain maximum safety benefits with the bag. 
     Sometimes a new special frangible seam is provided in the seat cover adjacent a bolster seam in the upholstery seat cover material through which the air bag is to be deployed. It is usually preferred that the air bag module be mounted in the seat so that its location is invisible to the seat occupant; and, to this end, the air bag is preferably deployed through a conventional bolster seam joining together adjacent, vertical edges of adjacent panels of the seat cover. If a new deployment seam is used, it is often located near the bolster seam to allow the air bag to deploy at an angle which is not possible with the use of the existing bolster seam. The use of a special seam for air bag deployment detracts from the appearance of the seat and adds additional cost and time to manufacture the seat having an air bag module hidden therein. 
     To ensure that the air bag properly deploys in a predictable or repeatable path to protect the seat passenger, a chute of fabric material has been wrapped about the air bag module and is fastened to the back of the air bag module by a zipper or threaded fastener. The fastening of the chute behind the air bag is difficult; and, in some instances, so difficult that it has caused the seat manufacturer to use a separate hard plastic panel at the back of the seat rather than the usual upholstery cover fabric at the back of the seat. The hard plastic back panel adds weight and cost to the seat. 
     Another suggested approach to guide the air bag to deploy through a frangible upholstery seam involves the use of a rigid plastic sheet attached to the foam seat pad and having a slit in the plastic sheet through which the rigid expanding air bag will proceed. The use of the chute or the hard plastic sheet on the foam pad may result in sink marks in the seat deployment seam when the fabric is pulled tight and stitched together. This is especially true where the chute is connected or integral with the seat upholstery material stitched together to form the seam. The appearance of the seam and seat cover are very important and any such air bag sinks or location marks in the fabric are undesirable. 
     Thus, it will be seen that these chute systems are costly in terms of manufacturing due to the added complexity of the chute and the labor to properly install the chute and air bag module, particularly where the chute fastening is difficult and where it has led to the use of a more costly, hard plastic back seat panel, as above described. Moreover, if a special new seam is required to deploy the air bag at a particular angle, this results in a variety of seat covers each being specific to certain vehicle or vehicle location. Thus, there is a need to eliminate the chute, and/or the special deployment seam in the seat cover, upholstery material. 
     SUMMARY OF THE INVENTION 
     In accordance with the present invention, an air bag system and method of making the same are provided including a reinforced cover for a vehicle seat having an air bag module hidden therein. The reinforced cover includes cover material that is stretchable and a backing reinforcement material that is stiffer than the cover material. The reinforcement material is attached to the cover material to provide a repeatable deployment path for the air bag as it inflates so that the air bag breaks through the seat cover at a preferred location thereon, e.g. bolster seam. The reinforced cover will not expand as the bag inflates as its stiffness or rigidity as provided by the reinforcement material will cause the bag to seek out the area of greater weakness in the cover at the bolster seam which the reinforcement material does not block. As the reinforcement cover provides the repeatable deployment path for the air bag to the bolster seam, there is no need for complicated and expensive modifications to the air bag module for proper and timely deployment thereof simplifying the installation of the present air bag system. 
     Accordingly, a new and improved air bag system is achieved by using a reinforcement, such as a fabric sheet, associated with the upholstery cover material in a manner to direct the expanding air bag to deploy through an adjacent, frangible seam. In the illustrated and preferred embodiment of the invention, an outboard end of the air bag is positioned adjacent a bolster seam in the seat cover and a girdle of reinforcing fabric is attached to seat upholstery material reinforcing the same to reduce or minimize elongation of the seat cover as the air bag expands within the seat. This concentrates the expanding force to break the adjacent bolster seam and to deploy the air bag therethrough. The preferred reinforcing fabric is sewn to the seat cover material and may be a low elongation material such as a fabric sheet of silicone-coated nylon fabric. 
     In the preferred embodiment of the invention, an opening or cavity is formed in the seat foam pad to receive the air bag module with the outboard end of the folded, air bag essentially flush with the seat foam pad about the air bag module. The outboard end of the folded air bag may be positioned against a portion of bolster seam through which it is to deploy without the use of a chute or use of a hard plastic piece. Thus, the labor and cost of the chute system is eliminated with the present invention. 
     In another aspect of the invention, a method of making a side-impact air bag installation is provided including providing a seat frame, providing a seat pad material on the seat frame, positioning an air bag module in the seat pad material adjacent the seat upholstery, providing a seat cover upholstery material with a reinforcing fabric thereon at selected portions to cause the inflating air bag to be directed to expand at a predetermined location for air bag deployment, and stitching together adjacent panels of the reinforced upholstery material to form a bolster seam at the predetermined location and through which bolster seam. the air bag deploys. In the preferred method, there is an encircling of the air bag module by the reinforcing fabric. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front elevational view of a vehicle passenger seat with a deployed side-impact air bag; 
     FIG. 2 is a side elevational view of the deployed side-impact air bag of FIG. 1; 
     FIG. 3 is an enlarged fragmentary sectional view of a conventional passenger seat having a air bag therein for being deployed through a bolster seam thereof; 
     FIG. 4 is a view similar to FIG. 3 showing deployment of the air bag expanding the seat cover prior to breaking through the bolster seam; 
     FIG. 5 is a fragmentary sectional view of an air bag system constructed in accordance with the invention showing an air bag module and reinforced upholstery material; 
     FIG. 5A is an enlarged, fragmentary view of the bolster seam showing the reinforcement fabric ply behind the seat cover; 
     FIG. 6 is a fragmentary view of the air bag of FIG. 5 deployed through the frangible bolster seam; 
     FIG. 7 is an interior view of the back panels of a reinforced upholstery seat cover used in accordance with the invention; 
     FIG. 8 is an interior view of the side panels of a reinforced upholstery seat cover used with the panels shown in FIGS. 7 and 9 to cover a seat; and 
     FIG. 9 is an interior view of the reinforced panels of the front portion of the seat cover. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in the drawings for purposes of illustration, the invention is embodied in a side-impact air bag module or assembly  10  mounted within a vehicle seat  12  for expansion into an expanded state, as shown in FIGS. 1 and 2 to protect the head and torso of a seated passenger from side impacts. The distance or space between an adjacent vehicle side  14  and trim  15  and a facing vehicle side  16  of the seat, door and window is quite short. Also, the packaging constraints are tight within the seat itself for the air bag module alone, without the addition of a chute within the seat to direct the air bag. 
     In some prior art installations and as previously described, a fabric chute pouch surrounds the air bag module  10  and the pouch has a deployment chute end located adjacent a seam  20  which can be either a new special seam for some vehicles or a bolster seam joining together adjacent panels  22  and  24  of a seat cover upholstery material  25 . The air bag module and chute pouch are attached to a rigid vehicle structure such as a rigid rail  26  of a seat frame  28 . The module and pouch are surrounded by foam material  30  of a cushion portion of a seat back  32  of the seat. The pouch has its chute opening aligned with the frangible seat cover seam  20 . As explained hereinbefore, the chute is fastened to the back of the air bag module by means of a zipper or threaded fasteners. At the time of a suitable impact, gas generator  33  is actuated to generate gas, which is discharged into the air bag in a forwardly direction towards folds  10   a  in the folded deployment portion of the air bag which expands to move through the now-open end of the pouch and to the upholstery seam and to break open the upholstery seam. 
     Chutes are undesirable as they increase the complexity of the air bag module driving up costs therefor. Other systems use plastic doors or panels which similarly raise costs for the system. Further, hard portions of the module adjacent the outer cover or skin of the seat are not desirable such as plastic doors as they can produce discomfort and create sink marks, as previously discussed. 
     A further problem which can even occur where chutes are used are inherent to the use of seat cover upholstery material that is stretchable and gives to allow for different sizes of passengers to seat comfortably thereon. Referring to FIGS. 3 and 4, the stretchable seat cover can delay the time at which the deployed air bag breaks therethrough, as instead of rupturing the seam  20 , the expanding bag pushes the cover  25  outward so that, as illustrated, it separates from the foam  30  and as the bag continues to inflate it spreads in directions away from the seam  20  as opposed to causing its rupture at the desired time. Manifestly, this delay in proper operation of the bag is to be avoided as the timing of air bag deployment from the time the generator  33  fires to the time the bag is inflated between the vehicle side  14  and trim  15  and seat side  16  is critical to its effectiveness. 
     In accordance with the present invention, the expandable upholstery cover material  25  is reinforced to direct the expansion of the folded air bag to break the frangible bolster seam  20  in the reinforced upholstery material to deploy through this seam as the folded air bag portion moves from the undeployed position of FIG. 5 to the deployed position of FIGS. 1,  2  and  6 . In this regard, the inflation of bag folds  10   a  causes the bag to rupture the seam  20  at the appropriate time after air bag firing without undue delays caused by stretching of the seat cover material  25  prior to seam rupture due to its reinforcement with a low elongation fabric material. Herein, this reinforcement of the upholstery cover material is achieved by a reinforcing material  40  in the form of a fabric ply  41  which is secured to an inner side or face  25   a  of the upholstery cover material, as discussed. Preferably, the reinforcing material  40  is a material having a significantly lower elongation than the upholstery fabric material that is often a readily elongated material. As will be explained in conjunction with FIGS. 7 and 8, the preferred reinforcement comprises an encircling girdle of fabric surrounding the air bag module on the left and right sides of the seat as well as the front and back sides of the seat Preferably, the outboard end  10   b  of the folds  10   a  in the air bag is located essentially flush with the bolster seam  20  allowing the entire module  10  to be placed closer to the seat external cover  25  thus providing space savings in the seat  12 , as best seen in FIG.  5 A. 
     Continuing with reference to FIG. 5A, the reinforcing ply  41  is secured by stitches  42  to join its panels  41   a  and  41   b  (FIGS. 5 and 8) to the respective seat cover panels  22  and  24  on opposite sides of the bolster seam  20 . The bolster seam  20  joins together the adjacent edges of the reinforced seat cover panels with the outboard end  10   b  of the folded air bag essentially flush with the foam  30  adjacent the bolster seam  20 , as depicted in FIG.  5 . Herein an opening or pocket  50  is formed in the foam material to receive the air bag module  10  and to mount the outboard end  10   b  of the folded, air bag adjacent to the frangible bolster seam  20 . Because there is no chute or hard plastic doors necessary with the present system, the foam can keep areas around the seam  20  free from sink marks and make the location of the air bag module deployment end invisible to the seat passenger. As will be explained hereinafter, the present invention provides easier assembly than the prior art chute systems. Also, compared to prior art chute systems, particularly those using a hard plastic back seat cover panel, the present invention is lighter in weight and lower in overall cost. The present invention provides flexibility in that the same reinforced seat material may be used in non-air bag applications as well as air bag applications. 
     Turning now in greater detail to the reinforcing material  40 , it is preferably a fabric sheet material that does not interfere with the use or the appearance of the seat cover, yet is strong enough to add resistant to elongation of the seat cover, which is usually a readily stretchable and elongatable material. A preferred reinforcing material  40  is a ply  41  of silicone-coated nylon fabric, e.g.  420  denure. Herein, the fabric ply  41  is in the form of a girdle comprised of ply portions  41   a - 41   i  attached to respectively associated seat cover panel portions, as best seen in FIGS. 7-9. FIGS. 7-9 illustrate the interior sides or surfaces of the seat panels  22  and  24  as well as the interior surfaces of the remaining front and seat back panels shown in FIGS. 7 and 9. The reinforcement side panels  41   a  and  41   b  have, as shown in FIG. 8, vertical side edges or ends  51  attached by stitches  42  to vertical ends of the cover panels  22  and  24 , respectively. The reinforcing plies  41   a  and  41   b  have upper ends  52 , which are not stitched horizontally to the seat cover panels  22  and  24 , which are located substantially below uncovered upper seat panel portions  22   c  and  24   c . Lower ends  53  of the respective reinforcing plies  41   a ,  41   b  are located above lower panel portions  24   d  and  24   e , respectfully, on the seat cover panels  22 ,  24 . Thus, the reinforcing plies  41   a  and  41   b  are coextensive in width between vertical sides of the seat, side panels  22 ,  24 , but are much shorter in height leaving the upper and lower portions  22   c ,  24   c  and  22   d ,  24   d , respectively, uncovered and exposed. 
     The reinforcing plies  41   a  and  41   b  are thus attached to the side panels  22  and  24  of the seat cover along vertical lines of stitches  42  adjacent bolster seam  20  between the cover panels  22  and  24 . As described above, the reinforcing plies are preferably not stitched along their upper and lower horizontal ends to the associated seat cover panels. This assists in allowing the seat panels  22  and  24  to perform from a passenger seating and comfort standpoint substantially as though the reinforcing panels are not present. When the air bag is expanding, the reinforcing plies  41   a  and  41   b , along with the other reinforcing plies of the girdle, resist elongation or stretching of the seat cover panels to assure proper deployment of the outboard end  10   a  through the closely adjacent bolster seam  20 . The seat will have left and right side cover portions, as shown in FIG. 8, with one being for the inboard side of the seat and the other being for the outboard side of the seat. Only the outboard one of the side seat cover portions of FIG. 8 will have the air bag module located adjacent its bolster seam  20 . 
     Preferably, the back portion  56  of the seat cover has reinforcing ply portions  41   c ,  41   d , and  41   e  that are substantially coextensive in width to their respectively attached, back panels  56   a ,  56   b  and  56   c . Herein, the vertical, inner stitches  42  (FIG. 7) attach the respective inner vertical edges of the respective ply portions along bolster seams  18   a ,  18   b ,  18   c  and  18   d  at the vertical inner edges of the respective seat back panels  41   c ,  41   d  and  41   e . The bolster seams have stitches  46  (FIG. 5A) joining together the respective back panels  56   a ,  56   b  and  56   c . Upper edges  52  of these respective reinforcing plies are not stitched to their associated seat cover panels; and likewise, lower edges  53  of the respective reinforcing plies are not stitched to their associated seat cover panels. This leaves lower portions  56   d ,  56   e  and  56   f  of the respective back panels  56   c ,  56   d , and  56   e  without being reinforced by a reinforcing ply thereon. Thus, the girdle portion of the reinforcing material  40  covers only a central, selected portion of the back of the seat cover and this is where the expansion forces of the expanding gas will be trying to elongate the wide expanse of seat cover. Because the upper and lower edges  52 ,  53  of the reinforcing material sheets on the back panel are not stitched to seat cover material, the back panel  56  should be able to stretch and perform much in the same manner that it would if the reinforcing plies were not attached thereto. The back seat cover also has an upper panel  56   g  that is secured along its lower edge by stitches to a bolster seam and thereby to the tops of the respective back seat panels  56   a ,  56   b  and  56   c . The upper panel  56   g  is not reinforced with a reinforcing backing ply and is free to elongate and stretch as the air bag is deployed. The back cover is joined by stitches to opposite side covers, such as shown in FIG. 8, and to the front cover, as shown in FIG. 9, to enclose the seat pad, air bag module, and seat frame therein. 
     The girdle of reinforcing material  40  is also, preferably, applied to the front portion  58  of the seat cover, which is shown in FIG. 9, as having three reinforcing ply portions  41   g ,  41   h  and  41   i  secured to the front seat cover. The interior side of front seat cover which is shown in FIG. 9 has the girdle attached to three seat cover panels  58   a ,  58   b  and  58   c .The right hand panel  58   c  will be on the left and joined to the side panel  22 , which is shown in FIG.  8 . The reinforcing plies  41   g ,  41   h  and  41   i  each have their respective edges stitched by stitches  42  to a corresponding vertical edge on the underlying front cover panel  58   a ,  58   b  and  58   c .The illustrated front seat cover also has upper and lower central panel portions  58   d  and  58   e  which are not covered by a reinforcing ply, in this instance. The central front cover panel portion  58   b  has its upper edge stitches at area  60  to the lower edge of the upper cover panel portion  58   d  and its lower edge stitched to the upper edge of the lower cover panel portion  58   e  at area  62 . Bolster seams  64  are shown in FIG. 8 joining the respective back panels together. 
     As with the back cover described in connection with FIG. 7, the upper and lower, horizontal edges of the reinforcing plies are not stitched to the associated panel of the front seat cover. The reinforcing cover material covers only a central portion of the front seat cover leaving the seat cover without reinforcement plies above the ply upper edges  52  and below the ply lower edges  53 . 
     Thus, the front, back and two side seat cover portions all have a central band of reinforcing plies  41   a - 41   h  that cumulatively comprise an encircling band or girdle about the gas generator module  10  and the folded air bag  10   a . Manifestly, the reinforcing plies need not totally surround or encircle the air bag module as described herein for this illustrated embodiment of the invention. Different seats and different seat covers from that illustrated herein may allow the elimination of or the addition of additional reinforcing material. Seat covers are made of various woven fabrics and often are made of leather with each seat cover material having different elongation characteristics. Also, various seats have different pad, frame constructions, and various shapes and numbers of cover panels sewn at different locations. Thus, the present invention is not limited to any particular seat or seat cover construction, such as that illustrated and described herein, but is adapted to be used with various seats and seat covers. While the reinforcing material is shown as being sewn by stitches to the superimposed seat cover panel, the reinforcing material can be positioned in the seat in various other manners and fall within the purview of the invention as defined by the claims, as set forth hereinafter. 
     The reinforcing material  40  is a significant advantage as rather than expanding the stretchable seat cover material  25 , the low stretch nature of the material  40  causes the inflating, unfolding air bag to seek out the path of least resistence which, in this instance, is to and through the adjacent bolster seam  20 . This is because the reinforced seat cover  25  of the present invention provides greater resistance to bag travel and expansion such as between it and the padding material  30  therein than does the stitched seam  20 . In this manner, the present invention provides a repeatable deployment path for the air bag without requiring expensive modifications via chutes and the like to the module  10  herein. Further, the invention herein provides advantages in assembly of the seat having the air bag module hidden therein and no longer do accommodations need to be made for accessing the rear of the module for attaching a chute thereto such as by providing a plastic panel on the seat, as discussed earlier. 
     The present invention eliminates some problems with current manufacturing processes involving the packaging of the air bag module in a seat by reducing labor and/or complexity of installation associated with the use of a chute. Also, the method of the present invention eliminates problems with appearance when using a chute and pulling the fabric taut around the module leaving sink marks in the seat cover seam. Moreover, the present invention eliminates the sometimes difficult labor problem encountered with fastening the chute behind the air bag module; and eliminates the need, in some instances, for a hard plastic back panel to close out the seat. 
     From the foregoing, there is described the method of the invention which comprises providing a seat pad  30  on a seat frame  28 , positioning an air bag module  10  in the seat pad adjacent a cover portion of the seat cover material  25 , providing reinforcing material  40  on the seat cover material at selected portions of the seat cover material to reinforce the seat cover to reduce elongation caused by the inflating air bag  10   a  and to direct the air bag to expand through a frangible seam, and stitching together adjacent panels  22  and  24  of the reinforced, upholstery material to form a bolster seam  20  at a predetermined location adjacent to and through which the expanding air bag deploys. In the preferred method, the foam pad has an opening or cavity  50  therein and the air bag module is positioned in the cavity  50  with an outboard end of the air bag  10   a  adjacent the bolster seam  20  and, preferably, substantially flush with the outboard side of the foam pad  30  around module  10 . Herein, the reinforcing panels are stitched to the seat cover panels and the same seat cover panels may be used whether or not an air bag module is used with the seat. As compared to use of a hard plastic back panel for the seat, the method of the invention provides reduced weight and lower cost. No special new deployment seam is used or needed as with some prior art chute systems. 
     While there have been illustrated and described particular embodiments of the present invention, it will be appreciated that numerous changes and modifications will occur to those skilled in the art, and it is intended in the appended claims to cover all those changes and modifications which fall within the true spirit and scope of the present invention.