Abstract:
A tethering restraint system is provided which restrains an inflatable air bag cushion during an extended period of inflation rather than limiting such restraint to the final stages of inflation. Maintaining tethering restraint during the inflation cycle increases the time over which energy is transferred between the air bag cushion and an occupant to be protected thereby reducing the instantaneous force transferred between the occupant and the air bag cushion as contact takes place.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates to an air bag module assembly, and more particularly to an air bag module including an inflatable air bag cushion deployable to an inflatable condition while being maintained under contouring restrained conditions during inflation. The restraint of the air bag cushion during deployment prolongs the period of energy transfer between the air bag cushion and an occupant to be protected thereby reducing the severity of the energy transfer.  
         BACKGROUND OF THE INVENTION  
         [0002]    It is well known to provide an air bag assembly including an inflatable air bag cushion for protecting the occupant of a transportation vehicle. In an automotive vehicle such air bag assemblies are typically located within the hub of the steering wheel and in a recess in the vehicle instrument panel for protection of the vehicle occupants seated in an opposing relation to such assemblies. Additional air bag assemblies may be located within the seats and/or door panels for protection of the occupants during a side impact event. Air bag assemblies typically include an inflatable cushion and a gas emitting inflator mounted in fluid communication with the inflatable cushion. In a driver side air bag module the air bag cushion typically includes a mouth disposed in substantially surrounding relation to the inflator with a perimeter portion of the mouth being held at a fixed position relative to the inflator. In a passenger side assembly the inflator is typically held within a trough-like housing with the air bag cushion being held within the housing such that inflation gas passes from the inflator into the cushion upon activation of the inflator.  
           [0003]    In the past, it has been advocated to adjust the inflated profile of air bag cushions by the use of tethering elements which are set to effective operative lengths so as to contour the profile of the air bag cushion at full expansion. The tethering elements may be of either a fixed length in operative relation to the air bag cushion or may be adjustable so as to accommodate persons of different sizes and/or collision events of different severity levels. By way of example only, representative systems for use in effecting a controlled deployment depth of an air bag cushion by the selective adjustment of tethering elements are disclosed in U.S. Pat. No. 6,422,597 to Pinsenschaum et al. and United States Patent Application 2002/0036400 A1 in the name of Winters et al. which are both incorporated by reference as if fully set forth herein. While such systems are believed to be useful in providing air bag cushions with discrete contoured profiles, such systems provide for controlled cushion restriction substantially only upon full extension of the tethering elements. That is, the tethering elements are extended to their full operative length before exerting a substantial restraining influence on the air bag cushion.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention provides advantages and alternatives over the prior art by providing tethering restraint systems which restrain the air bag cushion during an extended period of inflation rather than limiting such restraint to the final stages of inflation. Such arrangements are believed to increase the period of time over which energy is transferred between the air bag cushion and an occupant to be protected thereby reducing the instantaneous force transferred between the occupant and the air bag cushion when contact does take place. Moreover, due to the fact that the air bag cushion is controllably restrained during the filling cycle, the cushion may be targeted more directly to a desired location such as towards the chest of an occupant during the initial stages of impact. Such initial contact at the chest area may be beneficial in some instances.  
           [0005]    According to one aspect of the invention it is contemplated that elongate tethering elements may be fed away from a spool or other payout devices which apply a drag force to the tethering elements such that the operative length of the tethering elements is increased only upon the application of a sufficient pulling force by the inflating air bag cushion to overcome the applied drag force on the tethering elements. Thus, as the air bag cushion applies the required pulling force, a tensioning restraint is established along the tethers throughout the expansion cycle.  
           [0006]    According to another aspect of the invention an air bag module assembly is provided for use at the interior of a steering wheel assembly incorporating a fixed emblem substantially at the center of the steering wheel. Upon inflation, the air bag cushion emerges in a substantially toroidal configuration around the emblem. A tubular tether member is operatively connected to surface of the air bag cushion and is adapted to pass around the emblem as the cushion inflates. In an unstretched configuration the inner diameter of the tubular tether is slightly less than the outer diameter of the emblem such that a frictional restraining force is applied to the tubular tether as it is carried in stretched relation over the emblem thereby providing a restraining force substantially during the full inflation cycle of the air bag cushion. If desired, a hoop element may be disposed in at least partial surrounding radial relation to the tubular tether at a position below the emblem.  
           [0007]    Other aspects of the invention will be apparent through a reading of the following description and/or through practice of the present invention. Accordingly, while the invention will hereinafter be described in connection with certain exemplary illustrated embodiments, constructions and procedures, it is to be understood that in no event is the invention to be limited to such illustrated and described embodiments, constructions and procedures. On the contrary, it is intended that the present invention shall extend to all alternatives and modifications as may embrace the broad principles of this invention within the true spirit and scope thereof.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]    The present invention will now be described by a way of example only, with reference to the accompanying drawings which constitutes a part of the specification herein and in which:  
         [0009]    [0009]FIG. 1 is a view of the interior of an automotive vehicle incorporating driver side and passenger side air bag modules;  
         [0010]    [0010]FIG. 2 is a cut-away view of an air bag module assembly incorporating an arrangement of extendible tethers extending between an inflatable cushion and a rotatable spool incorporating a torsion bar assembly;  
         [0011]    [0011]FIG. 3 is a perspective view of an exemplary tether arrangement extending away from a rotatable spool in mounted relation over an inflator;  
         [0012]    [0012]FIG. 4 is a cut-away side view of an air bag module for use at a steering wheel incorporating a fixed decorative emblem;  
         [0013]    [0013]FIG. 5 is a view illustrating the module of FIG. 4 with the air bag cushion in a partially inflated state;  
         [0014]    [0014]FIG. 6 is a view similar to FIG. 5 in which the air bag cushion is fully inflated;  
         [0015]    [0015]FIG. 7 is a cut-away side view of an air bag module for use at a steering wheel incorporating a fixed decorative emblem and an extendible tubular tether disposed at the interior of a radial hoop element;  
         [0016]    [0016]FIG. 8 is a view illustrating the module of FIG. 7 with the air bag cushion in a partially inflated state; and  
         [0017]    [0017]FIG. 9 is a view similar to FIG. 7 in which the air bag cushion is fully inflated; 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0018]    Reference will now be made to the drawings wherein to the extent possible like reference numerals are utilized to designate like components throughout the various views. In FIG. 1 there is illustrated the interior of a vehicle  10  for transporting an operator  12  and a passenger  14 . As illustrated, the vehicle  10  may include a passenger side air bag module assembly  16  mounted within the dash panel in substantially opposing relation to the vehicle passenger  14 . The vehicle  10  will also preferably include a driver side air bag module assembly  20  mounted within the steering wheel  18  for protection of the vehicle operator  12 . Activation of the air bag assemblies  16 ,  20  typically takes place upon the occurrence and measurement of predetermined vehicle conditions such as deceleration at a rate exceeding a predetermined value.  
         [0019]    Referring to FIGS. 2 and 3, an exemplary construction of an air bag module assembly for use in either a driver side or passenger side orientation is illustrated. As shown, the air bag module assembly in FIG. 2 includes an inflatable air bag cushion  30  held in fluid communication with a gas emitting inflator  32  supported at a base structure  34 . While the exemplary cushion  30  illustrated in FIG. 2 is of a construction as is normally used in a driver side application, it is to be understood that the actual geometry of the cushion itself is in no way critical to the present invention. Accordingly, it is to be understood that the invention will have equal applicability in a passenger side module assembly as well as in driver side modules incorporating cushions of other configurations.  
         [0020]    As illustrated, an arrangement of elongate tethering elements  38  extend in operative connective relation between a surface of the air bag cushion  30  and a payout device  40  which releases the tethering elements  38  from a first operative length to a second increased operative length upon the introduction of an adequate pulling force applied to the tethering elements  38 . In practice, this pulling force is introduced by the expansion of the air bag cushion  30  which causes the operatively connected tethering elements  28  to be placed into tension so as to be pulled away from the payout device  40 .  
         [0021]    According to the illustrated embodiment, the payout device  40  may be in the form of a rotating spool  42  around which the tethering elements  38  are wound. As will be appreciated, while a number of tethering elements  38  are illustrated in wound relation to the spool  42 , the device may likewise be operative with either a greater or lesser number of tethering elements  28  as may be desired. In the exemplary device illustrated, the spool  42  is preferably rotatable only upon the introduction of a tensioning force exceeding a predetermined value and will operate in a manner so as to maintain tension within the tethering elements  38  as the air bag cushion  30  is inflated. That is, the payout device  40  applies a drag force opposing tether extension such that during extension tension is maintained within the tether.  
         [0022]    By way of example only, and not limitation, the payout device  40  may be in the form of a web retraction unit including a torsion bar  44  such as is used in a seat belt retractor or the like disposed at the interior of the spool  42 . One such assembly is illustrated and described in U.S. Pat. No. 6,237,869 to Ahn the contents of which are incorporated herein by reference in their entirety. In operation, as the spool  42  is rotated the torsion bar  44  twists thereby imparting a retracting tension force to the tethering elements  38 . Thus, tension may be maintained along the tethering elements  38  substantially over the full inflation cycle of the air bag cushion  30 .  
         [0023]    It is to be understood that the tension inducing payout device  40  may be of any suitable construction which applies a drag force opposing tether extension. By way of example only, and not limitation, it is contemplated that the torsion bar  44  may be replaced by a torsion spring or an arrangement of deformable elements if desired. It is also contemplated that the tension within the tethering elements may be maintained by introducing a friction element such as a spring loaded slot opening or the like along the length of the tethering elements  38  which requires a predetermined pulling force to permit sliding passage of the tethering elements  38 . Of course, any of these elements may be used either alone or in combination with one another as may be desired to provide the desired level of opposing force.  
         [0024]    As will be appreciated, the actual arrangement of the tethering elements  38  may be selected so as to define a desired depth profile in the air bag cushion  30 . In particular, it is believed that the restrained elongation of the operative length of the tethering elements  38  may be used to promote the early radial expansion of the air bag cushion  30  with substantial depth being developed only at the latter stages of deployment. Such a deployment pattern may be beneficial in some instances.  
         [0025]    It is contemplated that the present invention may be susceptible to a wide array of variations and alternative designs. By way of example only, and not limitation, one alternative embodiment is illustrated in FIGS.  4 - 6  wherein elements corresponding to those previously described are designated by like reference numerals increased by  100 . In FIG. 4 a cut-away view of a driver side air bag assembly  120  is shown with a centrally disposed fixed emblem  150  disposed in overlying relation thereto. As shown, in this arrangement the air bag cushion  130  is packed within a housing  152  in surrounding relation to the inflator  132 . Upon the expulsion of inflation gas by the inflator  132  the air bag cushion  130  is caused to break out of the housing  152  causing upper portions  154  of the housing  152  to fold back away from the emblem  150 . The air bag cushion  130  thereafter expands substantially in the form of a torus or doughnut shape around the emblem  150  which remains at a fixed position. Due to the toroidal shape of the inflated air bag cushion, the emblem  150  can be substantially covered against impact by an imposing occupant.  
         [0026]    According to the illustrated embodiment, the air bag assembly  120  includes a tubular tether element  138  having a proximal end  160  (FIG. 6) secured at a first position  162  below the emblem  150 . The tubular tethering element  138  further includes a distal end  164  operatively connected around its perimeter to a surface of the air bag cushion  30  such that the tethering element  138  defines a tube adapted to slide over the emblem  150  as the air bag cushion  130  expands towards the occupant to be protected.  
         [0027]    As best illustrated through simultaneous reference to FIGS. 5 and 6, the normal internal diameter of the tubular tethering element  138  is preferably slightly smaller than the outer diameter of the emblem  150 . In such an arrangement the tubular tethering element  138  is forced to undergo localized stretching as it passes around the emblem  150 . The need to engage in such localized stretching imparts a restraining force to the outward projection of the air bag cushion  130  due to the friction between the tubular tethering element and the emblem  150 . As will be appreciated, this restraining force may be adjusted by the selection of the materials forming the tubular tethering element  138  as well as by controlling the internal diameter of the tubular tethering element  138  relative to the emblem  150 . That is, if a high degree of restraint is desired the tubular tethering element  138  may be formed of a material having low elasticity and with an internal diameter substantially less than that of the emblem  150 . Conversely, if little restraint is desired the tubular tethering element  138  may be formed of a highly elastic material and/or may have an internal diameter which is only slightly less than the outer diameter of the emblem  150 .  
         [0028]    By way of example only, and not limitation, it is contemplated that the tethering element  138  may be formed from a textile material of relatively limited stretching character and with air permeability characteristics substantially matching those of the air bag cushion. Such materials may include woven Nylon and polyester. In the event that additional stretch is desired, it is contemplated that a knit construction and/or fibers of elastic character may be incorporated within the tethering element  138 .  
         [0029]    As illustrated, it is contemplated that a bridging surface element  166  of construction such as a half toroid or the like may be disposed at a position immediately below the emblem  150 . The bridging surface element  166  preferably has a relatively smooth rounded profile of gradually increasing diameter so as to provide a relatively uniform transition surface to effect the stretched passage of the tethering element around the bridging surface element  166  and thereafter over the emblem in a substantially uniform manner. Such a bridging surface may aid in the substantially uniform progressive passage of the tethering element  138  around the emblem  150 .  
         [0030]    In operation, the air bag cushion  130  will normally tend to expand preferentially in a radial dimension until forces are built up which are sufficient to carry the tubular tethering element  138  around the bridging surface element  166  and the fixed emblem  150 . Thus, a relatively broad inflation profile is developed at an early stage of deployment which may be beneficial in some instances.  
         [0031]    Another exemplary embodiment is illustrated in FIGS.  7 - 9  wherein elements corresponding to those previously described in relation to FIGS.  4 - 6  are designated by like reference numerals with a prime. In FIG. 7 a cut-away view of a driver side air bag assembly  120 ′ is shown with a centrally disposed fixed emblem  150 ′ disposed in overlying relation thereto. As shown, in this arrangement the air bag cushion  130 ′ is packed within a housing  152 ′ in surrounding relation to the inflator  132 ′. Upon the expulsion of inflation gas by the inflator  132 ′ the air bag cushion  130 ′ is caused to break out of the housing  152 ′ causing upper portions  154 ′ of the housing  152 ′ to fold back away from the emblem  150 ′. The air bag cushion  130 ′ thereafter expands substantially in the form of a torus or doughnut shape around the emblem  150 ′ which remains at a fixed position. Due to the toroidal shape of the inflated air bag cushion, the emblem  150 ′ can be substantially covered against impact by an imposing occupant.  
         [0032]    According to the illustrated embodiment, the air bag assembly  120 ′ includes a tubular tether element  138 ′ having a proximal end  160 ′ (FIG. 9) secured at a first position  162 ′ below the emblem  150 ′. The tubular tethering element  138 ′ further includes a distal end  164 ′ operatively connected around its perimeter to a surface of the air bag cushion  130 ′ such that the tethering element  138 ′ defines a tube adapted to slide over the emblem  150 ′ as the air bag cushion  130 ′ expands towards the occupant to be protected. The tethering element  138 ′ may be at least partially surrounded by a hoop element  170 ′ such as a ring, flexible cord or the like which provides constraining radial containment to the tethering element in the vicinity of the transition zone between the tethering element  138 ′ and the emblem  150 ′. Such constraining radial containment at this position may aid in the uniform progressive passage of the tethering element over the emblem  150 ′.  
         [0033]    As best illustrated through simultaneous reference to FIGS. 8 and 9, during extension the tethering element  138 ′ passes through the interior of the hoop element  170  and thereafter passes around the overlying emblem  150 ′. It is believed that the presence of the hoop element may aid in stabilizing the tethering element during extension thereby providing a more uniform extension characteristics. As with the previously described embodiments, the normal internal diameter of the tubular tethering element  138 ′ is preferably slightly smaller than the outer diameter of the emblem  150 ′. In such an arrangement the tubular tethering element  138 ′ is forced to undergo localized stretching as it passes around the emblem  150 ′. The need to engage in such localized stretching imparts a restraining force to the outward projection of the air bag cushion  130 ′ due to the friction between the tubular tethering element and the emblem  150 ′. Of course, as with the previously described embodiments, this restraining force may be adjusted by the selection of the materials forming the tubular tethering element  138 ′ as well as by controlling the internal diameter of the tubular tethering element  138  relative to the emblem  150 .  
         [0034]    It is to be appreciated that while the present invention has been illustrated and described in relation to various exemplary embodiments, constructions and practices, that such embodiments, constructions and practices are intended to be illustrative only in that the present invention is in no event to be limited thereto. Accordingly, it is contemplated and intended that the present invention shall extend to all such modifications and variations as may be incorporated within the broad principles of the invention within the full spirit and scope thereof.