Abstract:
A system and method for venting an airbag is provided. The system includes a set of vent doors, thereby reducing the overall package spaced that would otherwise be required to allow the doors to swing open. The vent doors are connected by a single tether or by multiple tethers to the primary surface of the airbag cushion.

Description:
TECHNICAL FIELD 
       [0001]    The disclosed invention relates generally to an airbag system for a vehicle. More particularly, the disclosed invention relates to a tether venting system for an airbag module that reduces package space by incorporating a plurality of hinged vents. 
       BACKGROUND OF THE INVENTION 
       [0002]    Automotive vehicles incorporate a variety of restraint systems to provide for the safety of occupants. These systems are generally included to reduce the likelihood of injury to the occupants in a crash event, Common safety systems include front airbags, side airbags, and seatbelts. The airbags are deployed within a vehicle and expand within the passenger compartment in a crash event to serve as a cushion between the occupant and interior vehicle components such as the steering wheel, the instrument panel and the windshield. 
         [0003]    One of the more difficult challenges for manufacturers of airbags is in the design of a system that properly responds to the out-of-position (“OOP”) occupant, and particularly to the occupant positioned close to the airbag. As a result, the same amount of airbag-expanding gas is released by the inflator without accounting for the position of the vehicle occupant, this in spite of the fact that the out-of-position occupant may not require the same level of deployment energy as compared to the in-position occupant. 
         [0004]    In response to this challenge some manufacturers have turned to the use of a tethered vent system in which a vent door is provided and is opened during initial pressurization of the airbag. The vent door is typically situated in the airbag housing and is attached to the housing by a living hinge. The vent door is open only temporarily and closes at a later stage in the airbag deployment event by a tether attached at one end to the vent door and at the other end to the primary surface of the airbag cushion. As the airbag cushion deploys vehicle-rearward, it pulls the tether and the tether pulls the vent door closed. 
         [0005]    While this arrangement has proven largely effective, it suffers from size limitations, particularly when the airbag is positioned in the steering wheel. Specifically, there is a limited amount of package space between the driver&#39;s-side airbag and the steering wheel. 
         [0006]    It would be desirable to have an airbag venting system that is effective in gas ventilation but which occupies less package space than used in known arrangements. 
       SUMMARY OF THE INVENTION 
       [0007]    The disclosed invention provides an airbag module for use in an automotive vehicle which includes an airbag housing and an airbag attached to the airbag housing. The airbag housing has a vent area. A pair of vent doors is attached to the airbag housing, although more than two vent doors may be used. Each of the pair of doors is attached to the airbag housing by a hinge such as is known in the art. The doors are provided adjacent one another such that their free ends are generally located side-by-side. The doors may be of equal widths or may be of different widths. A tether arrangement is provided between the vent doors and the airbag. 
         [0008]    The tether arrangement may include a first tether portion connected to one of the vent doors, a second tether portion connected to the other vent door, and a common tether connecting the first tether portion and the second tether portion to the airbag. As an alternative, the tether arrangement may include an airbag connecting end and a vent door connecting end. One of the vent doors has a tether-passing hole. The airbag connecting end is connected to the airbag. The vent door connecting end is passed through the tether-passing hole of one door and is connected to the other door. In an additional embodiment, the tether arrangement includes one tether connecting one of the doors to the airbag and another tether connecting the other of the doors to the airbag. 
         [0009]    Other features of the invention will become apparent when viewed in light of the detailed description of the preferred embodiment when taken in conjunction with the attached drawings and the appended claims. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    For a more complete understanding of this invention, reference should now be made to the embodiment illustrated in greater detail in the accompanying drawings and described below by way of examples of the invention wherein: 
           [0011]      FIG. 1  illustrates a sectional view of a portion of an airbag module including a vent arrangement according to the first embodiment of the invention; 
           [0012]      FIG. 2  illustrates a sectional view of a portion of an airbag module including a vent arrangement according to the second embodiment of the invention; and 
           [0013]      FIG. 3  illustrates a sectional view of a portion of an airbag module including a vent arrangement according to the third embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0014]    In the following figures, the same reference numerals will be used to refer to the same components. In the following description, various operating parameters and components are described for one constructed embodiment. These specific parameters and components are included as examples and are not meant to be limiting. 
         [0015]    Referring to  FIG. 1 , there is shown a sectional view of an occupant protection device, generally illustrated as  10 . The device  10  includes an inflatable protection component embodied in the structure of an airbag  12 . The inflatable protection component may be an airbag as shown or may be another inflatable safety device. Regardless of the configuration, the airbag  12  is composed of a variety of woven or non-woven materials, including nylon or a polymerized material. 
         [0016]    The airbag  12  includes a pair of opposed, spaced apart side panels  14  and  14 ′ and an outer panel  16 . The airbag  12  also includes a bottom panel  18  and a top panel (not shown). Together the side panels  14  and  14 ′, the outer panel  16 , the bottom panel  18  and the top panel define the airbag  12 . The airbag  12  is open at open end  20 . 
         [0017]    The open end  20  is attached to an airbag base assembly  22 . The airbag base assembly  22  includes a base plate  24  that is fixedly attached to the vehicle at an appropriate location. An inflator  26  is mounted on the base plate  24 . The inflator  26  includes a housing  28  having a series of gas passages  30  formed therein in a known manner. It is to be understood that the configuration of the airbag base assembly  22  as shown is for illustrative purposes and is not intended as being limiting. Other configurations of the airbag base assembly  22  could be adapted for use with the tether and vent door arrangement disclosed herein. 
         [0018]    As is known in the art, the non-deployed airbag  12  is in a deflated and folded state and is packed within the airbag module  10 . However, in certain events in which the vehicle is impacted, the inflator  26  is engaged. When the inflator  26  is activated, inflating gas outflows from the inflator  26  through the series of gas passages  30 . The inflating gas enters the airbag  12 . The figures illustrate the airbag in its initial inflation stages. 
         [0019]    A vent aperture  32  is formed in the base plate  24 . The vent aperture  32  is provided to allow the exhaust of a certain amount of inflating gas out of the airbag  12  during the initial stage of inflation. By exhausting gas very early in the inflation of the airbag  12  allowance is made for the out-of-position vehicle occupant by reducing the initial force of the airbag  12 . 
         [0020]    However, this early stage exhaustion of gas must be halted after a very short period of time. A pair of opposed vent doors  34  and  36  are provided for this purpose. The vent doors  34  and  36  are attached to the base plate  24  adjacent the vent aperture  32 . The vent doors  34  and  36  are movable between the open positions illustrated to allow for the early exhaustion of inflating gas during initial inflation of the airbag  12 . The out-passing inflating gas forces the vent doors  34  and  36  to the illustrated open positions. 
         [0021]    A tether assembly  38  is provided to effect closure of the vent doors  34  and  36  at a predetermined stage of inflation of the airbag  12 . The tether assembly  38  includes a first tether portion  40  attached to the vent door  34  and a second tether portion  42  attached to the vent door  36 . The first tether portion  40  and the second tether portion  42  connect to an airbag tether portion  44  at a connection point  46 . The airbag tether portion  44  is connected to a point  48  on the outer panel  16  of the airbag  12 . 
         [0022]    In operation, when an impact event occurs sufficient to activate the inflator  26 , inflating gas is introduced into the interior of the airbag  12 . The inflating gas pushes open the vent doors  34  and  36  and a portion of the gas escapes. Concurrently the airbag  12  is inflating. When a predetermined volume of gas occupies the airbag  12  the outer panel  16  of the airbag  12  is pushed away from the inflator  26 . The tether assembly  38  is pulled upon by the movement of the outer panel  16  away from the inflator  26 . As the tether assembly  38  is generally extended the first tether portion  40  pulls upon the vent door  34  and the second tether portion  42  simultaneously pulls upon the vent door  36 . The vent doors  34  and  36  continue to move toward their closed positions illustrated in broken lines in  FIG. 1  until the tether assembly  28  is pulled taught and the full closure of the vent doors  34  and  36  is achieved. Closure of the vent doors  34  and  36  stops the outflow of inflating gas. 
         [0023]    An alternate arrangement for the tether connection is illustrated in  FIG. 2  in which a sectional view of an occupant protection device, generally illustrated as  50 , is shown. The device  50  includes an airbag  52  which, as in the case of the airbag  12  described above and shown in  FIG. 1 , may be another inflatable protection device. The device shown is intended as being illustrative rather than limiting. 
         [0024]    The airbag  52  includes side panels  54  and  54 ′ and an outer panel  56 . The airbag  52  further includes a bottom panel  58  and a top panel (not shown). An open end  60  is formed by the pair of side panels  54  and  54 ′, the outer panel  56 , the bottom panel  58  and the top panel. 
         [0025]    The device  50  includes an airbag base assembly  62  to which the open end  60  of the airbag  52  is attached. The airbag base assembly  62  has a base plate  64  upon which an inflator  66  is mounted. The inflator  66  includes a housing  68  having a series of gas passages  70 . 
         [0026]    The airbag  52  is illustrated in  FIG. 2  its partially inflated state as would be the case during initial inflation following a vehicle impact event in which some inflating gas has flowed out of the inflator  66  and into the airbag  52 . At this stage a quantity of the inflating gas is exiting the airbag  52  by way of a vent aperture  72  formed in the base plate  64  by a pair of open opposed vent doors  74  and  76 . The vent door  74  is hingedly attached to a position adjacent the vent aperture  72 . The vent door  76  is hingedly attached to a position adjacent the vent aperture  72 . The vent doors  74  and  76  are movable between the illustrated open positions in which inflating gas is allowed to pass and a closed position (illustrated by broken lines) in  FIG. 2 . 
         [0027]    After a quantity of gas has been allowed to flow out of the expanding airbag  52  the vent doors  74  and  76  are moved to their closed positions. A tether arrangement is provided for closure of the vent doors  74  and  76 . Provision for the tether arrangement is made in part by a tether-passing aperture  78  that is formed through the vent door  74 . (The tether passing aperture could be formed as well through the vent door  76  instead of the vent door  74 . The arrangement shown is for illustrative purposes.) 
         [0028]    A tether  80  is provided and includes a door attachment end  82  and an airbag attachment end  84 . The airbag attachment end  84  is attached to a point on the inside of the airbag  12 . The door attachment end  82  of the tether  80  is attached to the vent door  76 . The tether  80  passes through the tether-passing aperture  78 . A movement-halting bead  86  is attached to a portion of the tether  80  at a point between the tether-passing aperture  78  and the airbag attachment end  84 . The movement-halting bead  86  is provided to minimize the amount of tether  80  that can pass through the tether-passing aperture  78 . By controlling the amount of tether  80  that is allowed beyond the point of the tether-passing aperture  78  tangling of the tether  80  is prevented. 
         [0029]    In operation, when an impact event occurs sufficient to activate the inflator  66 , inflating gas is introduced into the airbag  52 . Some of the inflating gas pushes the vent doors  74  and  76  to the open positions illustrated in  FIG. 2 . The vent doors  74  and  76  are permitted to swing open freely. Only a certain length of the tether  80  will be permitted to pass through the tether-passing aperture  78  as limited by the movement halting bead  86 . The airbag  52  continues to inflate and when a predetermined volume of gas occupies the airbag  52  the outer panel  56  of the airbag  52  is pushed away from the area of the inflator  66 . The tether  80  is pulled by movement of the outer panel  56  and as it is pulled the a portion of the tether  80  passes through the tether-passing aperture  78  while the door attachment end  82  of the tether  80  pulls upon the vent door  76 . Both the vent door  74  and the vent door  76  are moved to their closed positions as the tether  80  is pulled taught between the airbag attachment end  84  and the door attachment end  82 . Venting of the airbag  52  is halted upon closure of the vent door  74  and the vent door  76 . 
         [0030]    An additional arrangement for the tether connection provided herein is illustrated in  FIG. 3 . With reference to that figure, an occupant protection device, generally illustrated as  100 , is shown. The occupant protection device  100  includes an airbag  102 . As set forth above with respect to both  FIG. 1  and  FIG. 2 , the airbag  102  may be another inflatable occupant protection device. 
         [0031]    The airbag  102  includes side panels  104  and  104 ′ and an outer panel  106 . The airbag  102  further includes a bottom panel  108  and a top panel that is not shown. An open end  110  is defined by the pair of side panels  104  and  104 ′, the outer panel  106 , the bottom panel  108  and the top panel. 
         [0032]    The occupant protection device  100  includes an airbag base assembly  112 . The open end  110  of the airbag  102  is attached to the airbag base assembly  112 . The airbag base assembly  112  includes a base plate  114 . An inflator  116  is mounted to the base plate  114 . As set forth with respect to inflator discussed above with respect to the embodiments of the invention shown in  FIG. 1  and  FIG. 2 , the inflator  116  includes a housing  118  having a series of gas passages  120 . A vent aperture  122  is formed in the base plate  114 . 
         [0033]    The airbag  102  shown in  FIG. 3  is illustrated in its partially inflated state shortly after initial inflation by the inflator  116 . Some of the inflating gas is escaping through the vent aperture  122 . A pair of vent doors is provided to control the escape of the inflating gas. The pair of vent doors includes a first vent door  124  and a second vent door  126 . As illustrated, the width of the first vent door  124  is less than the width of the second vent door  126 . However, the width of the first vent door  124  could be greater than the width of the second vent door  126 . The configuration shown is for illustrative purposes only. The first vent door  124  and the second vent door  126  are hingedly attached to the area adjacent the vent aperture  122 . The first vent door  124  and the second vent door  126  are both movable between the illustrated open positions and closed positions shown in broken lines in  FIG. 3 . A first vent door tether  128  is connected at one end to the first vent door  124  and at the other end to the airbag  102 . A second vent door tether  130  is connected at one end to the second vent door  126  and at the other end to the airbag  102 . 
         [0034]    A quantity of inflating gas is allowed to escape through the vent aperture  122  as discussed above upon initial inflation. However, after the quantity of gas has been allowed to flow out of the expanding airbag  102  the passage of gas is halted by movement of the vent doors  124  and  126  to their closed positions illustrated by the broken lines, Closure of the vent doors  124  and  126  is achieved by movement of the outer panel  106  of the airbag  102  in a direction essentially away from the inflator  116 . As the first door vent tether  128  is pulled taught the first vent door  124  is moved from the illustrated open position to the closed position shown in broken lines. Similarly, as the second door vent tether  130  is pulled taught the second vent door  126  is moved from the illustrated open position to the closed position shown in broken lines. Passage of inflating gas is halted by closure of the first vent door  124  and the second vent door  126 . 
         [0035]    The arrangement of the occupant protection device  100  illustrated in  FIG. 3  and explained in conjunction therewith also provides a variation of the size of the vent aperture  122  over time. Specifically, the first vent door tether  128  and the second vent door tether  130  may be of different lengths, providing for the closure of one or the other of the vent doors  124  and  126  before the other of the vent doors  124  and  126  upon inflation of the airbag  102 . 
         [0036]    The foregoing discussion discloses and describes an exemplary embodiment of the present invention. One skilled in the art will readily recognize from such discussion, and from the accompanying drawings and claims that various changes, modifications and variations can be made therein without departing from the true spirit and fair scope of the invention as defined by the following claims.