Abstract:
An airbag assembly including one or more elongate tether elements that extend through vent openings along travel paths from anchoring locations such that the tether elements extend in sliding relation through the vent openings. The gas emission capacity of the vent openings may be adjustable based on internal cushion pressure.

Description:
TECHNICAL FIELD 
     This invention relates to an air bag assembly and more particularly to an airbag assembly including an inflatable airbag cushion in communication with a gas emitting inflator. One or more tether elements extend through vent openings and across the cushion such that the tether elements extend in sliding relation across the vent openings. The vent openings may be adjusted based on internal cushion pressure. 
     BACKGROUND OF THE INVENTION 
     It is well known to provide an airbag assembly including an inflatable airbag 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 positions opposing the knees and/or torso of a side passenger. Additional air bag assemblies may be located within the seats and/or door panels for protection of the occupants during a side-impact event. 
     One particular type of airbag assembly is an inflation driven bolster disposed in opposing relation to an occupant&#39;s lower extremities. Such systems typically incorporate an inflatable cushion disposed in an instrument panel behind an outer occupant contact surface in the form of a plate which is covered by a layer of foam with a aesthetic polymeric skin or fabric. Upon activation, the cushion inflates and pushes the plate into contact with the occupant&#39;s knees thereby providing early stage dissipation of kinetic energy. By way of example only, and not limitation, one such system is illustrated and described in U.S. Pat. No. 5,931,493 to Sutherland the contents of which are hereby incorporated by reference in their entirety. 
     As will be appreciated, when an airbag cushion in a knee bolster or other airbag assembly is activated, the pressure is generally proportional to the quantity of inflator gas expelled into the airbag and inversely proportional to the volume occupied by the gas. As the occupant comes into contact with the expanded airbag or outer contact surface, the inflator gas is forced out of the air bag thereby dissipating the kinetic energy of the occupant achieving a so called “ride down” effect. In order to facilitate the discharge of inflator gas from the airbag it is common to incorporate vents in the form of normally open fixed diameter apertures across the walls of the airbag. 
     In order to provide additional control over the inflation characteristics of the airbag cushion it is known to use tethering elements in the form of straps or webs extending between surfaces of the airbag and anchoring points on structural members. It has also been proposed to use elongate tethers in attached relation to vent closing members to facilitate adjustable venting. Such systems are illustrated and described in U.S. Pat. No. 6,932,385 to Hawthorn et al. the contents of which are hereby incorporated by reference as if fully set forth herein. 
     SUMMARY OF THE INVENTION 
     The present invention provides advantages and alternatives over the prior art by providing an airbag assembly including one or more elongate tether elements that extend through vent openings along travel paths from anchoring locations such that the tether elements extend in sliding relation through the vent openings. The gas emission capacity of the vent openings may be adjustable based on internal cushion pressure. 
     The air bag assembly reduces the number of tether attachments that must be formed during construction thereby simplifying assembly and reducing the number of fabric perforation seams. At the same time, tethering performance is substantially retained. 
     According to one exemplary embodiment, the airbag assembly may be a knee bolster assembly, wherein one or more elongate tethers extend from a support structure through vent openings and across an interior portion of an inflatable cushion in operative connecting relation with a plate or other occupant contact structure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present invention will now be described by way of example only, with reference to the accompanying drawings which constitute a part of the specification herein and in which: 
         FIG. 1  is a sectional view illustrating an airbag assembly in the form of an inflation driven knee bolster prior to activation; 
         FIG. 1A  is a view similar to  FIG. 1  illustrating the assembly during activation; 
         FIGS. 2 ,  2 A and  2 B illustrate various prior tethering systems that have been used in knee bolster airbag assemblies; 
         FIG. 3  is a view similar to  FIG. 2  illustrating an exemplary tethering system incorporating elongate tethers extending in sliding relation through vent openings in airbag cushion walls; 
         FIG. 4  is a view similar to  FIG. 3  illustrating another exemplary tethering system incorporating elongate tethers extending in sliding relation through vent openings in airbag cushion walls; and 
         FIG. 5  is a view similar to  FIG. 3  illustrating still another exemplary tethering system incorporating elongate tethers extending in sliding relation through vent openings in airbag cushion walls. 
     
    
    
     While the invention has been illustrated and generally described above and will hereinafter be described in connection with certain potentially preferred embodiments, procedures and practices, it is to be understood that in no event is the invention to be limited to such illustrated and described embodiments procedures and practices. On the contrary, it is intended that the present invention shall extend to all alternatives and modifications as may embrace the principles of this invention within the true spirit and scope thereof. In particular, it is to be understood that while illustrations and descriptions are provided relative to an exemplary knee bolster system, the invention is in no way limited to such a system. Rather, it is contemplated that the invention may extend to any airbag system utilizing tethers including driver side, passenger side and side curtain airbags. 
     DETAILED DESCRIPTION 
     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  FIGS. 1 and 1A  an interior portion of a transportation vehicle such as an automobile, train, airplane or the like is illustrated. As shown, an airbag system  10  incorporating an inflatable cushion  12  such as a sewn bag of textile material or the like is disposed in opposing relation to a vehicle occupant  14  such as a passenger or operator. 
     In the illustrated embodiment, the cushion  12  is held within a chamber  16  such as an open ended housing or the like at the interior of an instrument panel  18 . The cushion  12  is in fluid communication with a gas emitting inflator  20 . In the illustrated embodiment a displaceable occupant impact panel  22  is supported in overlying relation to the cushion  12  for projection outwardly towards the occupant  14  upon inflation of the cushion  12  as shown in  FIG. 1A . In the event that the cushion  12  is to directly impact the occupant  14 , the impact panel  22  may be replaced by a door or other displaceable structure. 
     Under normal conditions the cushion  12  is held in folded relation within the instrument panel  18 . Upon the occurrence of a collision or other activating event, gas is emitted from the inflator  20  and into the cushion  12 . Gas pressure causes the cushion  12  to push the impact panel  22  outwardly while simultaneously acting as a cushion behind the impact panel. Various tethering arrangements such as those illustrated in  FIGS. 3-5  which will be discussed further hereinafter may be used to maintain an operative controlled connection between the impact panel  22  and the support structure of the instrument panel  18 . 
     As indicated previously, while the airbag cushion  12  is illustrated for descriptive purposes in a bolster system in opposed relation to the knees of a vehicle occupant, it is to be understood that the present invention is in no way intended to be limited to such a configuration. On the contrary, it is contemplated that the present invention may have equal applicability to airbag deployment in opposing relation to the upper torso of an operator from the steering column (not shown) or in opposing relation to the upper torso of a passenger as well as in relation to airbags deployed from other regions within the vehicle interior including, by way of example only, side-impact air bags and inflatable curtain structures. Accordingly, it is contemplated that the cushion  12  may have any suitable shape and may be deployed at any position relative to the occupant  14  as may be desired. 
     As indicated previously, the final deployed position of the impact panel  22  and shape of the cushion  12  may be at least partially controlled by one or more tether elements extending between anchor positions and the cushion  12 . By way of example only, various prior tether constructions which have been used are illustrated in  FIGS. 2 ,  2 A and  2 B. Such tether constructions may have been used either independently or in some combination with one another. 
     As illustrated in  FIG. 2 , in a first prior tether construction, an elongate strap  26  extends from an anchor position  28  to a seamed connection  30  at the exterior of the cushion  12 . In this construction an interior tether member  32  in the form of a strap or web is attached across an interior portion of the cushion  12 . The seamed connection  30  operatively connects the strap  26  to one end of the interior tether member  32 . Tether element  34  is seamed through the exterior of the cushion  12  to interior tether member  32  and is connected to an interior surface of the impact panel  22 . Tether element  35  is seamed through the exterior of the cushion  12  and is connected to an interior surface of the impact panel  22 . 
     A second prior tether construction is illustrated in  FIG. 2A , wherein elements corresponding to those previously described are designated by like reference numerals with a prime. In this construction an elongate strap  26 ′ extends from an anchor position  28 ′ to a seamed connection  30 ′ at the exterior of the cushion  12 ′. In this construction a first interior tether member  32 ′ in the form of a strap or web is attached across an interior portion of the cushion  12 ′. The seamed connection  30 ′ operatively connects the strap  26 ′ to the first interior tether member  32 ′ through the exterior of the cushion  12 ′. A second interior tether member  33 ′ in the form of a strap or web is also attached across an interior portion of the cushion  12 ′. Tether element  34 ′,  35 ′ such as straps or the like are seamed through the exterior of the cushion  12 ′ to interior tether members  33 ′,  32 ′ respectively and are connected to an interior surface of the impact panel  22 ′. 
     A third prior tether construction is illustrated in  FIG. 2B , wherein elements corresponding to those previously described are designated by like reference numerals with a double prime. In this construction a pair of elongate straps  26 ″ extends from anchor positions  28 ″ to seamed connections  30 ″ at the exterior of the cushion  12 ″. In this construction a first interior tether member  32 ″ in the form of a strap or web is attached across an interior portion of the cushion  12 ″ by seam connections  38 ″. The seamed connections  30 ″ are remote from the seam connections  38 ″. A second interior tether member  40 ″ in the form of a strap or web is attached across an interior portion of the cushion  12 ″. Tether element  34 ″,  35 ″ such as straps or the like are seamed through the exterior of the cushion  12 ″ and are connected to an interior surface of the impact panel  22 ″. 
     As will be appreciated, in each of the prior tethering arrangements illustrated and described in relation to  FIGS. 2 ,  2 A and  2 B, the travel path of the tethers is interrupted at the cushion walls. The establishment of an operative connection between the internal and external tethering elements thus requires the formation of attachment seams. The introduction of such seams may require substantial skill and may increase manufacturing complexity. 
     It has been found that airbag tethering systems incorporating elongate tethering elements extending from anchor positions in sliding relation through openings in the cushion wall to the cushion interior may be used to substantially reduce complexity while maintaining the tethering function. By way of example only, and not limitation,  FIG. 3  illustrates a contemplated tethering system wherein elements corresponding to those previously described are designated by like reference numerals increased by  100 . In this arrangement a first elongate strap  126  extends from a first anchor position  128  at the instrument panel  118  along a travel path to a second anchor position  128 ′ at the inner surface of the impact panel  122 . Along the travel path, the first elongate strap  126  extends through vent openings  140 ,  140 ′ in the cushion wall such that the first elongate strap slides or floats within the vent openings  140 ,  140 ′. In the exemplary construction a second elongate strap  142  may be attached to the first elongate strap  126  by stitching or the like and extends through a vent opening  140 ″ for attachment to anchor position  128 ″. Of course, the actual arrangement and number of tether elements may be adjusted depending upon the final desired configuration. 
     As illustrated, vent cover panels  146 ,  146 ′,  146 ″ of fabric, polymeric film or other pliable material are preferably disposed in attached opposing relation at least partially across the vent openings  140 ,  140 ′,  140 ″. As shown, the vent cover panels  146 ,  146 ′,  146 ″ are preferably attached to the walls of the cushion  112  by seams outboard of the vent openings. The attachment of the cover panels to the cushion walls may be by sewn seams, adhesive seams or the like as may be desired. The vent cover panels  146 ,  146 ′,  146 ″ preferably include openings  150 ,  150 ′,  150 ″ that are positioned out of alignment with the corresponding vent openings  140 ,  140 ′,  140 ″. The openings  150 ,  150 ′,  150 ″ may be at an interior portion of the cover panels or at a boundary edge such as by using a discontinuous seam attachment around the perimeter of the vent cover panels. As shown, the openings  150 ,  150 ′,  150 ″ are preferably sized so as to have a larger effective cross section than the elongate straps. Thus, the straps may normally slide freely through the openings in the vent cover panels. 
     In the illustrated construction wherein tethering straps extend through the vent openings  140 ,  140 ′,  140 ″ and misaligned openings  150 ,  150 ′,  150 ″, the introduction of inflation pressure may be used to substantially close the vent openings and lock down the tethering straps. Specifically, as pressure is built within the cushion  112 , the portion of the vent cover panels overlying the vent openings is pushed into the vent openings in a plug-forming relation. As the vent openings  140 ,  140 ′,  140 ″ are closed, the tethering straps running through those opening are locked in place thus forming a secure tethering relation. 
       FIG. 4  illustrates a contemplated tethering system wherein elements corresponding to those previously described are designated by like reference numerals increased by  200 . In this arrangement a first elongate strap  226  extends from a first anchor position  228  along a travel path to a second anchor position  228 ′. Along the travel path, the first elongate strap  226  extends through vent openings  240 ,  240 ′ such that the first elongate strap slides or floats within the vent openings  240 ,  240 ′. In the exemplary construction a second elongate strap  242  extends from an anchor position  228 ″ at the impact panel  222  through a vent opening  240 ″ for attachment to a wall of the cushion  212 . Of course, the actual arrangement and number of tether elements may be adjusted depending upon the final desired configuration. 
     As illustrated, vent cover panels  246 ,  246 ′,  246 ″ of fabric, polymeric film or other pliable material are preferably disposed in attached relation at least partially across the vent openings  240 ,  240 ′,  240 ″. As shown, the vent cover panels  246 ,  246 ′,  246 ″ are preferably attached to the walls of the cushion  212  by seams outboard of the vent openings. The attachment to the cushion walls may be by sewn seams, adhesive seams or the like as may be desired. The vent cover panels preferably include openings  250 ,  250 ′,  250 ″ that are positioned out of alignment with the corresponding vent openings  240 ,  240 ′,  240 ″. The openings  250 ,  250 ′,  250 ″ may be at an interior portion of the cover panels or at a boundary edge such as by using a discontinuous seam attachment around the perimeter of the vent cover panels. As shown, the openings  250 ,  250 ′,  250 ″ are preferably sized so as to have a larger effective cross section than the elongate straps. Thus, the straps may normally slide freely through the openings in the vent cover panels. 
     In the illustrated construction wherein tethering straps extend through the vent openings  240 ,  240 ′,  240 ″ and misaligned openings  250 ,  250 ′,  250 ″, the introduction of inflation pressure may be used to substantially close the vent openings and lock down the tethering straps. Specifically, as pressure is built within the cushion  212 , the portion of the vent cover panels overlying the vent openings is pushed into the vent openings in a plug-forming relation. As the vent openings  240 ,  240 ′,  240 ″ are closed, the tethering straps running through those opening are locked in place thus forming a secure tethering relation. 
       FIG. 5  illustrates another contemplated tethering system wherein elements corresponding to those previously described are designated by like reference numerals increased by  300 . In this arrangement a first elongate strap  326  extends from a first anchor position  328  at the instrument panel  318  along a travel path to a second anchor position  329 . Along the travel path, the first elongate strap  326  extends through vent openings  340 ,  341  such that the first elongate strap slides or floats within the vent openings  340 ,  341 . In the exemplary construction a second elongate strap  342  extends from an anchor position  343  at the instrument panel along a travel path extending across the cushion  312  to anchor position  345  at the impact panel  322 . Along the travel path, the second elongate strap  342  extends through vent openings  360 ,  361  such that the second elongate strap slides or floats within the vent openings  360 ,  361 . Of course, the actual arrangement and number of tether elements may be adjusted depending upon the final desired configuration. 
     As illustrated, vent cover panels  346 ,  346 ′,  347  and  347 ′ of fabric, polymeric film or other pliable material are preferably disposed in attached relation at least partially across corresponding vent openings. As shown, the vent cover panels  346 ,  346 ′,  347  and  347 ′ are preferably attached to the walls of the cushion  312  by seams outboard of the vent openings. The attachment to the cushion walls may be by sewn seams, adhesive seams or the like as may be desired. The vent cover panels preferably include openings  350 ,  350 ′,  351 ,  351 ′ that are positioned out of alignment with the corresponding vent openings. The openings  350 ,  350 ′,  351 ,  351 ′ may be at an interior portion of the cover panels or at a boundary edge such as by using a discontinuous seam attachment around the perimeter of the vent cover panels. The openings  350 ,  350 ′,  351 ,  351 ′ are preferably sized so as to have a larger effective cross section than the elongate straps. Thus, the straps may normally slide freely through the openings in the vent cover panels. 
     In the illustrated construction wherein tethering straps extend through the vent openings and misaligned openings in the cover panels, the introduction of inflation pressure may be used to substantially close the vent openings and lock down the tethering straps. Specifically, as pressure is built within the cushion  312 , the portion of the vent cover panels overlying the vent openings is pushed into the vent openings in a plug-forming relation. As the vent openings  350 ,  350 ′,  351 ,  351 ′ are closed, the tethering straps running through those opening are locked in place thus forming a secure tethering relation. 
     It is to be understood that while the present invention has been illustrated and described in relation to potentially preferred embodiments, constructions, and procedures, that such embodiments, constructions, and procedures are illustrative only and that the present invention is in no event to be limited thereto. Rather, it is contemplated that modifications and variations embodying the principles of the present invention will no doubt occur to those of skill in the art. In particular, it is to be understood that the present invention is in no way limited to any particular mechanism for the retention and release of tethering elements and that all description of such mechanisms is explanatory and exemplary only. It is therefore contemplated and intended that the present invention shall extend to all such modifications and variations as may incorporate the broad aspects of the present invention within the full spirit and scope thereof.