Abstract:
A vehicle air bag ( 10 ) comprises an outer bag ( 50 ) having an inflation fluid volume ( 59 ). The outer bag ( 50 ) has a retainer portion ( 54 ) defining a central opening ( 56 ). The retainer portion ( 54 ) has a plurality of fastener openings ( 58 ) spaced apart around the central opening ( 56 ). An inner bag ( 60 ) is located in the inflation fluid volume ( 59 ) of the outer bag ( 50 ). The inner bag ( 60 ) has a retainer portion ( 110 ) defining an inflation fluid opening ( 114 ) for receiving inflation fluid. The retainer portion ( 110 ) has a plurality of fastener openings ( 79, 89, 99, 109 ) spaced apart around the inflation fluid opening ( 114 ). The inner bag ( 60 ) has at least one vent opening ( 130-136 ) movable from a closed condition to an open condition, in response to increase in fluid pressure in the inner bag, to enable flow of inflation fluid from the inner bag into the inflation fluid volume ( 59 ) of the outer bag ( 50 ). The air bag ( 10 ) further comprises a plurality of fasteners ( 32-38 ) extending through the fastener openings ( 58 ) in the retainer portion ( 54 ) and through the fastener openings ( 79, 89, 99, 109 ) in the retainer portion ( 110 ) to secure the inner bag to the outer bag without sewing. The retainer portion ( 54 ) is free of stitching openings.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to an inflatable air bag having an inner bag that defines an inflation fluid volume inside an outer bag. 
     2. Description Of The Prior Art 
     U.S. Pat. No. 5,249,824 discloses an air bag including an expansible inner bag that is located in an internal fluid cavity of an outer bag. The inner and outer bags are sewn to each other at the mouth portion of the air bag, surrounding the inflation fluid opening. The inner bag has a plurality of vent openings for directing inflation fluid from the inner bag into the internal cavity of the outer bag in a direction away from the occupant impact area. 
     SUMMARY OF THE INVENTION 
     The present invention is a vehicle air bag comprising an outer bag having an inflation fluid volume and being inflatable to a predetermined configuration when inflation fluid is directed into the outer bag. The outer bag has a retainer portion defining a central opening. The retainer portion of the outer bag has a plurality of fastener openings spaced apart around the central opening of the retainer portion. 
     An inner bag is located in the inflation fluid volume of the outer bag and is inflatable to a predetermined configuration within the inflation fluid volume when inflation fluid is directed into the inner bag. The inner bag has a retainer portion defining an inflation fluid opening for receiving inflation fluid. The retainer portion of the inner bag has a plurality of fastener openings spaced apart around the inflation fluid opening of the retainer portion of the inner bag. The inner bag has at least one vent opening movable from a closed condition to an open condition, in response to increase in fluid pressure in the inner bag, to enable flow of inflation fluid from the inner bag into the inflation fluid volume of the outer bag. 
     The air bag assembly further comprises a plurality of fasteners extending through the fastener openings in the retainer portion of the outer bag and through the fastener openings in the retainer portion of the inner bag to secure the inner bag to the outer bag without sewing. The retainer portion of the outer bag is free of stitching openings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other features of the present invention will become apparent to one skilled in the art to which the present invention relates upon consideration of the following description-of the invention with reference to the accompanying drawings, in which: 
     FIG. 1 is a schematic illustration, partly in section, of an air bag module including an air bag constructed in accordance with the present invention; 
     FIG. 2 is a schematic bottom plan view of portions of the air bag module of FIG. 1; 
     FIG. 3 is a schematic side view of portions of the air bag module of FIG. 1, showing the air bag in an inflated condition; 
     FIG. 4 is a bottom plan view of a retainer that forms part of the air bag module of FIG. 1; and 
     FIG. 5 is a plan view of an inner bag that forms part of the air bag of FIG.  1 . 
    
    
     DESCRIPTION OF THE INVENTION 
     The present invention relates to an inflatable vehicle occupant protection device, such as an air bag. In particular, the present invention relates to an air bag having an inner bag that defines an inflation fluid volume inside an outer bag. As representative of the present invention, FIGS. 1-5 illustrate an air bag  10 . Other inflatable vehicle occupant protection devices that can be used in accordance with the invention include, for example, inflatable seat belts, inflatable knee bolsters, inflatable head liners, inflatable side curtains, and knee bolsters operated by inflatable air bags. 
     The air bag  10  (FIG. 1) forms a part of a driver side air bag module  12 . The module  12  includes an inflator  14  of a cylindrical configuration having a plurality of inflation fluid outlets  16  disposed in a circular array around an axis  20  of the module. The module  12  also includes a mounting plate  22  for securing the module to the steering wheel (not shown) of the vehicle. 
     The module includes a retainer  30  for securing the inflator  14  and the air bag  10  to the mounting plate  22 . The retainer  30  includes a plurality of fasteners in the form of threaded studs. In the illustrated embodiment, four studs  32 ,  34 ,  36  and  38  (FIG. 4) are provided, in an array centered on the axis  20 . The retainer  30  has a generally rectangular configuration including a circular central opening  40  that receives the inflator  14 . 
     The air bag  10  (FIG. 2) includes an outer bag  50  and an inner bag  60  that are associated with each other, in a manner described below, to form the completed air bag  10 . The outer bag  50  is of a known, pillow-shaped configuration and comprises an outer panel  52  (sometimes called a “front panel”) that is engageable by the vehicle occupant when the air bag  10  is inflated. 
     The outer bag  50  has a retainer portion  54  defining a central opening or inflation fluid opening  56  of the outer bag. The retainer portion  54  of the outer bag  50  has a plurality of fastener openings  58  spaced apart around the inflation fluid opening  56 . The outer bag  50  has an inflation fluid volume  59 . 
     The inner bag  60  comprises an inner panel  62 . The inner panel  62  is a single sheet of flexible fabric material having a cross-shaped or cruciform configuration, as shown in FIG.  5 . The inner panel  62  could, alternatively, be made from more than one piece of material sewn or otherwise joined together to form the inner panel. 
     The cruciform configuration of the inner panel  62  includes a central portion  64  and four arm portions  70 ,  80 ,  90  and  100 . The first arm portion  70  is defined by an end edge  72  and two opposite side edges  74  and  76 . The first arm portion  70  has an outer end portion  78  that includes the end edge  72  and a pair of fastener openings  79  adjacent the end edge. 
     The second arm portion  80  is defined by an end edge  82  and two opposite side edges  84  and  86 . The second arm portion  80  has an outer end portion  88  that includes the end edge  82  and a pair of fastener openings  89  adjacent the end edge. A curved edge portion  81  extends between and interconnects the side edge  76  of the first arm portion  70  and the side edge  84  of the second arm portion  80 . 
     The third arm portion  90  is defined by an end edge  92  and two opposite side edges  94  and  96 . The third arm portion  90  has an outer end portion  98  that includes the end edge  92  and a pair of fastener openings  99  adjacent the end edge. A curved edge portion  91  extends between and interconnects the side edge  86  of the second arm portion  80  and the side edge  94  of the third arm portion  90 . 
     The fourth arm portion  100  is defined by an end edge  102  and two opposite side edges  104  and  106 . The fourth arm portion  100  has an outer end portion  108  that includes the end edge  102  and a pair of fastener openings  109  adjacent the end edge. A curved edge portion  101  extends between and interconnects the side edge  96  of the third arm portion  90  and the side edge  104  of the fourth arm portion  100 . A curved edge portion  103  extends between and interconnects the side edge  106  of the fourth arm portion  100  and the side edge  74  of the first arm portion  70 . 
     The inner bag  60  has a retainer portion  110  that comprises the four outer end portions  78 ,  88 ,  98  and  108  of the arm portions  70 ,  80 ,  90  and  100 , respectively. Thus, the retainer portion  110  of the inner bag  60  includes the fastener openings  79 ,  89 ,  99  and  109  of the inner bag. 
     The inner panel  62  is assembled to the retainer  30  by placing the retainer in a position overlying the central portion  64  of the inner panel. Next, the four arm portions  70 ,  80 ,  90  and  100  of the inner panel  62  are folded over to at least partially overlie the retainer  30  and the central portion  64  of the inner panel, as shown in FIG.  2 . 
     Specifically, the outer end portion  78  of the first arm portion  70  is folded over so that the fasteners  32  and  38  of the retainer  30  extend through the fastener openings  79  in the first arm portion. The outer end portion  98  of the opposite third arm portion  90  is folded over so that the remaining two fasteners  34  and  36  of the retainer  30  extend through the fastener openings  99  in the third arm portion. 
     The outer end portion  88  of the second arm portion  80  is folded over so that the fasteners  32  and  34  of the retainer  30  extend through the fastener openings  89  in the second arm portion. The outer end portion  108  of the fourth arm portion  100  is folded over so that the fasteners  36  and  38  of the retainer  30  extend through the fastener openings  109  in the fourth arm portion. 
     When the four arm portions  70 ,  80 ,  90  and  100  of the inner panel  62  are thus connected with the retainer  30 , the inner panel forms the inner bag  60  of the air bag  10 . The inner bag  60  defines an inflation fluid volume  112 . The outer end portions  78 ,  88 ,  98  and  108  of the arm portions  70 ,  80 ,  90  and  100  of the inner panel  62  define an inflation fluid opening  114  of the inner bag  60 . The inflation fluid opening  114  is in fluid communication with the inflation fluid volume  112  of the inner bag  60 . 
     The inner bag  60  as thus configured has a generally rectangular configuration (in this case, square) including four corners  120 ,  122 ,  124  and  126 . The inner bag  60  also has four fluid vents or vent openings  130 ,  132 ,  134  and  136 . Each one of the vent openings  130 - 136  is located at a respective one of the corners  120 - 126  of the inner bag  60 . 
     The first vent opening  130  is located at the corner  120  between the first and second arm portions  70  and  80 . The second vent opening  132  is located at the corner  122  between the second and third arm portions  80  and  90 . The third vent opening  134  is located at the corner  124  between the third and fourth arm portions  90  and  100 . The fourth vent opening  136  is located at the corner  126  between the fourth and first arm portions  100  and  70 . When the air bag  10  is deflated, the inner bag  60  is folded flat, and the vent openings  130 - 136  are substantially closed. 
     The subassembly of the inner bag  60  and the retainer  30  is assembled with the outer bag  50  as shown in FIGS. 1-3. The fasteners  32 - 38  of the retainer  30  extend through the fastener openings  58  in the retainer portion  54  of the outer bag  50 . The inner bag  60  is located in the inflation fluid volume  59  of the outer bag  50 . 
     The assembly of the outer bag  50 , the inner bag  60 , and the retainer  30  is then joined with the inflator  14  to form the module  12 . When the assembled air bag  10  is secured in the module  12  (FIG.  1 ), the inflator outlets  16  are disposed within the inflation fluid volume  112  of the inner bag  60 . Nuts  121  screwed onto the fasteners  32 - 38  secure the parts of the module  12  together. 
     The fasteners  32 - 38  and the nuts  121  clamp the retainer portion  110  of the inner bag  60  to the retainer portion  54  of the outer bag  50 . The outer bag  50  is not sewn to the inner bag  60 , thus eliminating a sewing step in manufacture of the air bag  10 . There are no stitching openings in the retainer portion  54  of the outer bag  50 , thus eliminating an area of possible fluid leakage from the air bag  10 . 
     The inflator  14  is connected with vehicle electric circuitry  130  (FIG. 1) including a power source  132 , which is preferably a vehicle battery and/or a capacitor, and a normally open switch  134 . The switch  134  is part of a sensor  136  that senses a vehicle condition indicating the occurrence of a collision. The collision-indicating condition may comprise, for example, sudden vehicle deceleration that is caused by a collision. If the collision-indicating condition is at or above a predetermined threshold level, this indicates the occurrence of a crash having a level of severity for which it is desirable to inflate the air bag  10  or other vehicle occupant protection device to help protect an occupant of the vehicle. 
     When the sensor  136  senses a collision-indicating condition at or above the predetermined threshold level, the switch  134  closes and the inflator  14  is actuated electrically. The inflator outlets  16  direct inflation fluid into the inflation fluid volume  112  of the inner bag  60 . 
     As inflation fluid fills the inner bag  60 , the inner bag inflates to a condition as shown schematically in FIG.  3 . The central portion  64  of the inner bag  60  moves away from the retainer portion  110  of the inner bag. As the inner bag  60  inflates, the vent openings  130 - 136  move from the closed condition to an open condition. Inflation fluid flows out of the inner bag  60  through the vent openings  130 - 136  in the inner bag. The inflation fluid flows outwardly away from the axis  20 , into the inflation fluid volume  59  of the outer bag  50 . 
     The inflation fluid that flows into the outer bag  50  through the vent openings  130 - 136  of the inner bag  60  is the only inflation fluid that flows into the outer bag. The outer bag  50  is inflated only with inflation fluid flowing from the inner bag  60  through the vent openings  130 - 136 . The size and shape of the vent openings  130 - 136  in the inner bag  60  are controlled by the configuration of the arm portions  70 ,  80 ,  90  and  100  of the inner bag. The size and shape of the vent openings  130 - 136  can help to control the inflation of the outer bag  50 . 
     From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications in the invention. For example, the invention is also applicable to a passenger side air bag, which has a more rectangular configuration than the driver side air bag shown in the drawings. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.