Abstract:
In an airbag comprising at least one aperture ( 14 ) which is provided in an airbag shell ( 12 ) and to which a closure element ( 16 ) is attached a tether ( 34 ) via which the closure element ( 16 ) can be maintained in a closed position acts on the closure element ( 16 ). The invention moreover relates to a method of operating a vehicle occupant protection system.

Description:
RELATED APPLICATIONS 
       [0001]    This application corresponds to PCT/EP2015/000078, filed Jan. 19, 2015, which claims the benefit of German Application No. 10 2014 001 084.8, filed Jan. 30, 2014, the subject matter of which are incorporated herein by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to an airbag having at least one aperture provided in an airbag shell to which a closure element is attached, Moreover, the invention relates to a method of operating a vehicle occupant protection system. 
         [0003]    Such airbag is described, for example, in DE 10 2007 058 656 A1, where a closure element including discharge orifices is attached to the aperture in the airbag shell so that it forms an extension of the airbag wall adapted to be outwardly and inwardly everted. The closure element is connected to a tether and by the latter can be pulled into the interior of the airbag so as to close the discharge orifices. For opening the discharge orifices the closure element is forced outwardly by the gas pressure. 
         [0004]    EP 1 418 093 B1, too, illustrates an airbag having a closure element to be everted out of the airbag, the closure element in this case being a narrow hose having an end-side discharge orifice. As a standard, the hose and is drawn into the interior of the airbag shell and is connected to a release device via a tether. Prior to actuating the release device the closure element is forced against the inner wall of the airbag shell by the internal pressure within the airbag and the discharge orifice is dosed After actuating the release device the closure element is everted out of the airbag shell due to the internal pressure of the airbag and the gas may flow off through the discharge orifice. It is a drawback, inter alia, that only a small amount of gas may pass the long narrow hose, which impedes rapid ventilation. 
         [0005]    The present invention suggests improvements to the afore-described concept of ventilating an airbag. 
       SUMMARY OF THE INVENTION 
       [0006]    It is an object of the invention, on the one hand, to provide a controllable closure element by which rapid ventilation of the airbag is possible, if requested. 
         [0007]    In accordance with the invention, this is achieved by an airbag having at least one aperture provided in an airbag shell in which a closure element is attached to the aperture, wherein a tether by which the closure element can be maintained in the closed position acts on the closure element. As long as the closure element is provided in the closed position, substantially no gas can escape from the airbag through the aperture. Gas will escape only when the closure element adopts an opened position. The amount of gas flow can be influenced in this way by the cross-sectional area of the aperture in the airbag shell. 
         [0008]    In a preferred embodiment, the deployment of the airbag causes a tension onto the tether to be built up for maintaining the closure element inside the airbag in the closed position or pulling it to the interior of the airbag into the dosed position and causing the closure element to dose the aperture at least largely by a sealing fold. 
         [0009]    The aperture in the airbag shell therefore may be chosen to be relatively large as it is possible to keep it sufficiently tightly dosed by the inwardly pulled closure element maintained tensioned by the tether even in the fully inflated airbag upon immersion of a vehicle occupant. 
         [0010]    In a preferred embodiment, the tether is fixed to a release device which releases the tether depending on the situation, thus causing the closure element to reach an opened position. 
         [0011]    An optimum application of force onto the closure element can be achieved, for example, by the fact that on the inside of the airbag shell at least two defections for the tether are provided between the release device and the closure element, especially when the release device is arranged in the vicinity of the inflator. In this way, in all states of deployment of the airbag tensile forces can be transmitted to the closure element. Likewise it can be ensured in this way that the tether loosens upon actuation of the release device so that the tension on the closure element is dropped. 
         [0012]    The release device preferably is an actively controlled device coupled to a control unit which causes loosening of the tether as a function of parameters relating to the occupant and/or the vehicle. The parameters may relate, for example, to a current position of the vehicle occupant, to the fact whether a child safety seat is placed on the seat in front of the airbag, to the weight of the vehicle occupant, to the position of the seat, to the size of the vehicle occupant, to the time from release of the airbag system or else to the accident severity. 
         [0013]    The moment of releasing the tether and thus of moving the closure element into the opened position and the point in time from which gas escapes from the airbag are exactly determined by the time of activation of the release device and are freely selectable. 
         [0014]    The release means comprises e.g. a pyrotechnical trigger unit which may be formed especially by an explosive stud. Preferably, the release means is arranged in the area of the inflator which supplies filling gas to the airbag, wherein a control unit activating the inflator may also be used to activate the release device. 
         [0015]    From the closed position the closure element may preferably move to the opened position (or vice versa) substantially perpendicularly to the area of the airbag shell surrounding the aperture. 
         [0016]    The closure element in the outwardly everted opened position, especially when the airbag is inflated, preferably has a tapered hollow shape, especially a cone shape, cap shape or funnel shape, so that the closure element puts as little resistance as possible to the gas escaping from the interior of the airbag through the aperture. 
         [0017]    It is preferred that the closure element includes at least one, preferably two, lateral discharge orifices so that rapid flow of a large amount of gas can be reached and the airbag can be ventilated within short time. 
         [0018]    In a possible embodiment the closure element is located in its closed position inside the airbag shell in an initial deployment phase of the airbag. 
         [0019]    When the release device is actuated, the closure element may be everted out of the airbag into the opened position doe to the internal airbag pressure, when the tether is detached from its attachment, wherein especially the discharge orifice opens. 
         [0020]    This arrangement allows filling the airbag including the closure element very quickly in the closed position and possibly admitting escape of gas through the aperture specifically at the time of immersion of the vehicle occupant into the airbag or upon hitting an obstacle so as to enable soft absorption. 
         [0021]    When sensors detect a situation in which the airbag is to be softer from the beginning, for example the presence of a child safety seat or a vehicle occupant seated in an unfavorable position, the release device may be activated directly by igniting the inflator already at the beginning of inflating the airbag so that from the beginning gas may escape and the airbag is filling more slowly and/or not with the usual hardness. 
         [0022]    In another embodiment in an initial deployment phase of the airbag the closure element is provided in its opened position at least partly outside the airbag shell and the discharge orifice is open right from the beginning, in this case, due to the tension on the tether increasing during inflation, the closure element is gradually drawn into the interior of the airbag shell until it contacts preferably the inner side of the airbag shell in a folded state. 
         [0023]    It is possible to adjust the length of the tether and the geometry of the airbag so that the aperture is not closed before the airbag is completely deployed. When the airbag impacts an obstacle during deployment for example an unfavorably seated vehicle occupant or a child safety seat, the aperture remains opened and part of the gas escapes. If the airbag deploys as scheduled, however, without impinging on an obstacle, the closure element is pulled into the dosed position by the tether and the aperture is closed. The airbag deploys up to its maximum volume and reaches its maximum internal pressure so that a vehicle occupant can be optimally absorbed. 
         [0024]    In order to prevent the aperture from inadvertently opening again due to the pressure increase within the airbag when an occupant immerses, a locking structure may be provided on the tether which prevents a return movement of the closure element from a predetermined state of deployment of the airbag. 
         [0025]    It is another object of the invention to provide an airbag that can be compactly packed and to maintain the discharge orifice as tightly closed as possible in the closed state. 
         [0026]    According to the invention, this is achieved with an airbag having at least one aperture provided in an airbag shell to which a closure element having at least one discharge orifice is attached, wherein a peripheral edge of the closure element is fastened peripherally about the edge of the aperture so that the edge of the aperture forms a circumferential diaphragm protruding radially inwardly from the peripheral edge of the closure element. 
         [0027]    The airbag may be formed as afore described, for example, and may also be used as afore described. 
         [0028]    The peripheral edge of the closure element is fastened preferably circumferentially without interruption and at a radial distance from the edge of the aperture. In this way the edge of the aperture forms a diaphragm between the closure element and the interior of the airbag up to the peripheral seam by which the closure element is fastened to the airbag shell. This diaphragm supports the fabric layers of the closure element and laterally seals the closure element in the closed state in which the closure element is located inside the airbag. 
         [0029]    The diaphragm preferably remains at least largely movable relative to the closure element so that the closure element cannot excessively distort the edge of the closure element even in the case of high gas pressure. Therefore the entire cross-section of the aperture is always available for gas escaping from the airbag into the closure element. 
         [0030]    When using equal closure elements, the gas escape can be easily adapted by varying the area of the discharge orifice. 
         [0031]    It is also possible, of course, to provide a separate annular fabric piece around the edge of the aperture as a diaphragm, wherein the aperture then is defined by the fabric piece. 
         [0032]    The cross-sectional area of the aperture preferably takes approximately a diamond shape as it has turned out that in this way a fiat folding of the airbag can be achieved. 
         [0033]    The peripheral edge of the closure element preferably is not located in a plane but is shaped so that is takes approximately the same shape as the aperture in the airbag shell, when the closure element is fastened to the airbag shell This shape reduces and, respectively, prevents constrictions at the diaphragm. 
         [0034]    It is another object of the invention to design the closure element such that it adopts a stable shape in the opened position and at the same time can be easily housed in the airbag in a space-saving folded manner. 
         [0035]    In accordance with the invention, this is achieved with an airbag having at least one aperture provided in an airbag shell to which a closure element having at least one discharge orifice is attached, wherein the closure element includes at least two overlying cut portions interconnected along a peripheral edge, and wherein at least one of the cut portions includes one or more stitched-down folds or quillings and/or is composed of plural cut portions having at least one curved seam so that the cut portion cannot be flatly spread. 
         [0036]    It is possible to form both cut portions in this way. However, it has turned out that sufficient stability is reached already when the second cut portion is formed of a one-piece fabric portion adapted to be flatly spread. 
         [0037]    The shape of the one cut portion which is not fiat but pre-shaped to be arched provides a reduced opening time of the discharge orifice, i.e. a reduction of the time required by the closure element to be everted out of the airbag shell from the dosed position into its opened position and causes stabilization of the shape of the closure element in the opened position. 
         [0038]    In this case, too, the airbag may of course exhibit the further features already discussed in the foregoing and can be used just as the already described airbags. 
         [0039]    An especially suited shape for the closure element is resulting when each of the cut portions has a subarea extending from the peripheral edge into the surface of the cut portion, wherein, when the discharge orifice is closed, the two subareas complement each other into one surface corresponding in its shape to the cross-sectional area of the aperture in the airbag shell. 
         [0040]    It is favorable to select a shape that permits folding the closure element in total so that a closed flat surface is resulting from subareas of the two cut portions, the shape of the surface corresponding to the aperture in the airbag shell but being somewhat larger so that it can be sewn onto the airbag shell above the aperture. In this way tensile forces acting on the edge of the aperture which might deform the aperture are prevented. This ensures that in all deployment stages of the airbag the flow of gas from the interior of the airbag shell into the closure element is constant. Darts or quillings possibly located in this subarea should be configured so that they fit into the flat surface. This applies mutatis mutandis to the use of curved seams which should be configured so that in the subarea a surface adapted to be flatly spread is formed. 
         [0041]    The closure element may be formed, for example, of two overlying cut portions each being approximately club-shaped or bell-shaped. A tether is attached to an elongate end of each of the cut portions, while the respective cut portion is fastened on the airbag shell at the peripheral edge opposite to the elongate end. The cut portions are interconnected at the elongate end as well as at a respective portion in the area of the peripheral edge, preferably by stitching, wherein the out portions are not connected over a major part of the side edges located between the elongate end and the peripheral edge so that two lateral discharge orifices are formed in the closure element. The cut portions are connected preferably at a point where the side edges meet the peripheral edge of the respective cut portion so that the peripheral edge forms a closed ring. 
         [0042]    It is substantially sufficient when the two cut portions are connected at three points, i.e. at the elongate end as well as at the two outermost areas of their peripheral edge. In this way, substantially the entire side edges between the peripheral edge and the elongate edge may serve as discharge orifice, thus permitting high gas flow. Moreover, the number of the seams and the length of the seams are minimized in total. 
         [0043]    It is possible to use two separate cut portions. The two cut portions may also be integrally interconnected at the elongate ends thereof, however. 
         [0044]    For fastening the tether preferably a loop on which the tether acts is provided at the closure element For this, for example, the two cut portions may be sewn up to form a fabric loop through which a cord is pulled. This is obvious mainly when the two out portions are integrally formed. 
         [0045]    The term “tether” is not restricted to flat ribbons but comprises all flexible elongate bodies that transmit tension. 
         [0046]    It is also possible to sew each cord or fabric loop to the elongate end of either both cut portions or one cut portion so that a loop is resulting. 
         [0047]    The advantage of the use of an additional loop as compared to the fixed stitching of the tether directly on the closure element resides in the fact that better force distribution may be brought about when the tether may align itself vis-à-vis the closure element. 
         [0048]    Furthermore, the invention also achieves the object to offer improved vehicle occupant protection. 
         [0049]    This is achieved by a method according to the invention for operating a vehicle occupant protection system, with said vehicle occupant protection system including an airbag as afore described. The control unit coupled to the release device may prompt the release of the tether already at the beginning of the deployment operation, when a sensor system connected to the control unit recognizes predetermined parameters relating to the occupant and/or the vehicle. In this context, especially parameters from which an obstacle in the deployment path of the airbag can be concluded are relevant. 
         [0050]    This object is also achieved by a method of operating a vehicle occupant protection system that may be equipped with an afore-described airbag, wherein in an initial deployment state of the airbag the closure element is in its opened position and with increasing deployment of the airbag the closure element is pulled into the interior of the airbag shell into the closed position. Via fixation of the tether sufficient tension is exerted on the closure element from a predetermined deployment state of the airbag so as to maintain the closure element in the closed state. The release device may loosen the tether depending on predetermined parameters relating to occupants and/or the vehicle so that the closure element is moved by the internal pressure of the airbag into the opened position again. In this case, basically gas flows off through the aperture, when the airbag hits an obstacle even without the release device being triggered. If the airbag deploys as scheduled, however, the gas discharge is stopped in the course of deployment. If, however, the airbag shall have a hardness lower than the maximum hardness upon impact of an occupant for example because sensors have detected a particular position or a particular weight of the vehicle occupant, the release device is activated at the appropriate point in time and the tether is loosened so that gas is discharged again. 
         [0051]    All described features of the individual embodiments can be exchanged for each other or combined with each other at the discretion of those skilled in the art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS Hereinafter the invention shall be described in detail by way of plural embodiments with reference to the enclosed drawings, in which: 
         [0052]      FIG. 1  shows an airbag according to the invention in accordance with a first embodiment in a schematic top view, with the closure element being in the closed position; 
           [0053]      FIG. 2  shows the airbag of  FIG. 1  in a schematic sectional view along the line II-II in  FIG. 1 ; 
           [0054]      FIG. 3  shows the airbag of  FIG. 1  in a schematic top view, with the closure element being in an opened position; 
           [0055]      FIG. 4  shows the airbag of  FIG. 3  in a schematic sectional view along the line IV-IV in  FIG. 3 ; 
           [0056]      FIG. 5  shows the closure element of the airbag of  FIG. 3  in a schematic perspective view; 
           [0057]      FIG. 6  shows an airbag according to the invention in accordance with a second embodiment in a schematic top view, with the closure element being in the opened position; 
           [0058]      FIG. 7  shows a schematic sectional view of the airbag of  FIG. 6  along the line VII-VII in  FIG. 6 ; 
           [0059]      FIG. 8  shows a schematic top view of the airbag of  FIG. 6  during closure of the discharge orifice and detent of the locking element; 
           [0060]      FIG. 9  shows a schematic perspective representation of the detent of the locking element of the airbag of  FIG. 8 ; 
           [0061]      FIG. 10  shows a schematic sectional view of the airbag in  FIG. 8  along the line X-X in  FIG. 8 ; 
           [0062]      FIG. 11  shows a schematic view of the airbag of  FIG. 6  with the discharge orifice being closed and the tether being blocked; 
           [0063]      FIG. 12  shows a schematic sectional view of the airbag of  FIG. 11  along the line XII-XII in  FIG. 11 ; 
           [0064]      FIG. 13  shows an airbag according to the invention in accordance with a third embodiment in a schematic sectional view with the discharge orifice being opened upon impacting a vehicle occupant; 
           [0065]      FIG. 14  shows the airbag of  FIG. 13  with the discharge orifice being opened upon impacting a child safety seat; 
           [0066]      FIG. 15  shows the airbag of  FIG. 13  in the fully inflated state with the discharge orifice being closed before immersion of the vehicle occupant; 
           [0067]      FIG. 16  shows the airbag of  FIG. 15  upon immersion of the occupant with the discharge orifice being opened; 
           [0068]      FIG. 17  shows a schematic top view onto a section of an airbag according to the invention from the outside of the airbag shell with a closure element being in the closed position; 
           [0069]      FIG. 18  shows a schematic view of a closure element for the airbag of  FIG. 17 ; 
           [0070]      FIG. 19  shows a possible configuration of a cut of the closure element of  FIG. 17  in which two cut portions are integrally connected; 
           [0071]      FIGS. 20 and 21  show a possible configuration of the cut portions of a closure element of the airbag of  FIG. 17  in which the two cut portions are in the form of separate parts; 
           [0072]      FIG. 22  shows another configuration of the cut of a closure element of an airbag of  FIG. 17  in which one of the cut portions is composed of three parts being connected by respective curved seams; 
           [0073]      FIG. 23  shows another configuration of a cut of a closure element of the airbag of  FIG. 17  in which one of the cut portions is composed of three parts being connected by respective curved seams, wherein the two cut portions constitute separate parts; 
           [0074]      FIG. 24  shows another configuration of a cut of a closure element of the airbag of  FIG. 17  in which one of the cut portions is composed of two parts connected by curved seams; 
           [0075]      FIG. 25  shows a schematic representation of the fastening of the tether to the closure element in which the tether is sewed up with both cut portions; 
           [0076]      FIG. 26  shows the detail XXVI of  FIG. 25 ; and 
           [0077]      FIG. 27  shows a schematic representation of the fastening of the tether to the closure element in which the tether is fastened separately to each of the cut portions. 
       
    
    
     DESCRIPTION 
       [0078]    For reasons of clarity, in the Figures the same reference numerals are used for all embodiments, unless any parts are definitely different from a previous embodiment, in such case the respective part is provided with a respective numeral increased by 100. 
         [0079]      FIGS. 1 to 5  illustrate an airbag  10  according to a first embodiment. 
         [0080]    The Figures illustrate of the airbag  10  only a cutout of an airbag shell  12  which substantially encloses the interior of the airbag  10 . 
         [0081]    In the airbag shell  12  an aperture  14  is formed which is covered by a separate closure element  16  sewn up with the airbag shell  12 . The entire aperture  14  in the airbag shell  12  is covered by the closure element  16  as is evident from  FIG. 1 . 
         [0082]    Instead of sewing, in the entire application also a different suitable type of fastening may be used, for example welding, gluing or weaving in one piece. The term “sewing” or “seams” is used throughout here for reasons of clarity only. 
         [0083]    The closure element is illustrated in detail in  FIG. 5 . In this case it is formed of two cut portions  18   a,    18   b  each including a surface area delimited by a peripheral edge  20  and by two side edges  21  as well as an elongate end  22  opposite to the peripheral edge  20 . In a top view, the cut portions  18   a,    18   b  are approximately bell-shaped or club-shaped. 
         [0084]    The peripheral edge  20  of each of the cut portions  18   a,    18   b  is sewn up with the airbag shell  12  by means of a peripheral seam  24 . 
         [0085]    At the elongate ends  22  the two cut portions  18   a,    18   b  are connected by means of a seam  26 . In this example, the two cut portions  18   a,    18   b  are moreover sewn together at the two most external edge areas  28  (cf. FIG.  5 ) so that the closure element  18  in total has a circumferential peripheral edge. Apart from said connections, the cut portions  18   a,    18   b  are not fixed to each other so that the closure element  16  is completely open above the aperture  14  in the airbag shall  12 . Likewise, the sides  21  between the edge area  28  and the elongate end  22  are open so that two large lateral drop-shaped discharge orifices  32  are formed. 
         [0086]    The closure element  16  may take a closed position as shown in  FIGS. 1 and 2  in which it is folded into the interior of the airbag shell  12  and the discharge orifices  32  and thus the entire aperture  14  are closed in a substantially gaslight manner by the folded closure element  16 . 
         [0087]    In the opened position as illustrated in  FIGS. 3 to 5  the closure element is everted out of the airbag shell  12 , on the other hand, so that a perpendicularly outwardly projecting bulge is resulting which is substantially perpendicular to the airbag shell  12  in the surrounding of the aperture  14 . The closure element  16  in its opened position resembles an outwardly tapered hollow which is cone-shaped, funnel-shaped or cap-shaped, for example. 
         [0088]    In order to maintain the closure element  16  in the closed position or bring the same into the closed position a tether  34  which at least initially is tightly fixed in the airbag  10  is attached to the elongate ends  22  of the cut portions  18   a,    18   b  of the closure element  16 . 
         [0089]    When tension is exerted on the tether  34 , the closure element  16  remains within the shell  12  even with an increasing internal pressure of the airbag or is drawn into the shell, if it is in the opened position. The tension exerted on the tether  34  moreover effectuates that the gas pressure does not evert the closure element  16  outwardly but urges the same against the airbag shell  12  from inside and hence closes or keeps the discharge orifice  32  closed. 
         [0090]    In the embodiment shown here the tether  34  is connected to a release device  36  which is provided e.g. on the inflator  38  supplying filling gas to the airbag  10  (schematically shown in  FIGS. 13 to 16 ). 
         [0091]    The release device  36  is configured such that it can release the tether  34  initially connected thereto so that there is no more tension acting on the tether  34 . 
         [0092]    In this example the release device  36  is a pyrotechnical device, for example including an explosive stud, wherein ignition and thus release of the tether is carried out by a control unit  40  (cf.  FIG. 13 ) which in predetermined situations sends a trigger signal to the release device  36 . 
         [0093]    In a first possible method the closure element  16  is housed in its closed position in the folded airbag  10 . The tether  34  is arranged and dimensioned as to its length so that at the beginning of deployment of the airbag  10  sufficient tension acts on the tether  34  so as to maintain the closure element  16  in the closed position inside the airbag shell  12 . 
         [0094]    During normal deployment of the airbag  10  the closure element  16  throughout remains in the closed position and the discharge orifices  32  remain closed so that through the latter substantially no gas escapes from the airbag  10 ,. 
         [0095]    A sensor system (not shown) detects situational parameters, parameters relating to occupants and/or to the vehicle such as, e.g., a seating position, size and weight of the vehicle occupant, a current position of the occupant, the time elapsed since the inflator has been activated or an accident severity. Based on one or more of said parameters the control unit  40  may decide to release the tether  34 , whereupon the internal pressure prevailing inside the airbag  10  averts the closure element  18  out of the airbag shell  12  through the aperture  14  and moves it to its opened position so that gas may escape through the discharge orifices  32 . 
         [0096]    In case that, for example, an unfavorable current position of the vehicle occupant is detected or it is detected that a child safety seat is mounted on the vehicle seat, in this example the release device  36  releases the tether  34  directly at the beginning of deployment of the airbag  10  so that part of the filling gas permanently escapes from the airbag  10 , 
         [0097]      FIGS. 6 to 12  illustrate a second embodiment. 
         [0098]    It is provided in this case that the closure element  16  in the folded airbag  10  is in its opened position so that already at the beginning of deployment it is provided in its opened position and the discharge orifices  32  are released. 
         [0099]    With a progressive deployment of the airbag  10 , the airbag due to its expansion exerts tension on the tether  34  and thus pulls the closure element  16  through the aperture  14  into the closed position thereof in which the discharge orifice  32  is closed, in the completely deployed state the discharge orifice  32  is completely closed in this case. 
         [0100]    When the airbag  10  impacts an obstacle upon initial deployment, however, the closure element  16  remains in its opened position and the discharge orifices  32  remain opened (cf. also embodiment according to  FIGS. 13 to 16 ). 
         [0101]    In order to prevent the discharge orifice  32  from inadvertently opening by the pressure increase inside the airbag  10  upon absorbing the vehicle occupant, a locking structure  42  which retains the closure element  16  in the closed position is provided in this case. 
         [0102]    The locking structure  42  is formed of a tab  44  arranged on the inside of the airbag shell  12  and a pertinent stop element  46  at the tether  34 . The stop element  46  is simply formed by a stitched-down loop of the tether  34  in this case. 
         [0103]    In the direction of tension toward the closed state the stop element  46  slides through the tab  44  without any significantly higher force having to be exerted. However, any return movement will be inhibited as the projecting loop of the stop element  46  gets caught at the tab  44  (cf.  FIG. 9 ). 
         [0104]    In this embodiment no release device  36  is provided. It would be possible, however, to fasten the tether  34  also in this case to such release device  36  which in particular situations releases the tether  34  so that the closure element  16  may return to the opened position again. In this event, the locking structure then may be omitted or may be designed so that it is suspended upon triggering of the release device. 
         [0105]    Such combination is shown in  FIGS. 13 to 16 . 
         [0106]      FIG. 13  illustrates the case where a vehicle occupant  48  is in an unfavorable position when the airbag  10  is deploying. 
         [0107]    The closure element  16  in this case is provided in its opened position at the beginning of deployment of the airbag  10  so that the discharge orifices  32  are released and open. When the airbag  10  impacts the vehicle occupant  48 , no sufficient tension has been built up yet via the tether  34  to move the closure element  16 . The closure element  16  therefore remains in its opened position. The gas can escape from the airbag through the discharge orifices  32  and the airbag  10  remains relatively soft. 
         [0108]    The tether  34  is deflected at two locations between the fastening points on the release device  36  and the closure element  16  at the upper and lower ends of the airbag  10  in the Figure by deflections  50 . 
         [0109]      FIG. 14  illustrates the case in which a child safety seat  52  is mounted on the vehicle seat. Analogously to the afore-described situation, during its entire period of deployment the airbag  10  remains in a state in which the closure element  16  is in the opened position and gas may escape via the discharge orifices  32 . 
         [0110]    In both cases the release device  36  does not respond. The tether remains connected to the release device  36  throughout the entire deployment period of the airbag  10 . 
         [0111]      FIG. 15  illustrates the case in which a vehicle occupant  48  is absorbed by a completely filled airbag  10 . The airbag  10  deploys, as provided, into its full size without hitting an obstacle. From a particular deployment state tension starts acting on the tether  34  so that the closure element  16  is pulled into the closed position and the discharge orifices  32  are closed. 
         [0112]      FIG. 16  shows the case in which, upon complete deployment and inflation of the airbag  10 , the hardness of the airbag  10  is to be reduced, for example in the case of a small, light-weight vehicle occupant  48  seated closely to the airbag. After the airbag  10  has adopted its completely deployed state, the release device  36  is activated and the tether  34  is loosened. By the internal pressure of the airbag, but at the latest when the vehicle occupant  48  immerses into the airbag  10 , the closure element  16  is everted out of the airbag shell  12  through the aperture  14  into its opened position and the discharge orifices  32  are opened so that the gas can escape. 
         [0113]      FIGS. 17 to 27  illustrate different variants of the closure element  16 . 
         [0114]      FIG. 17  shows the edge of the aperture  14 , although it is covered in the top view by the overlying closure element  16 . 
         [0115]    In the embodiments shown here the aperture  14  in the airbag shell  12  is diamond-shaped having rounded corners. 
         [0116]    The peripheral edge  20  of the closure element  16  takes substantially the same shape but is somewhat larger. 
         [0117]    The peripheral seam  24  connecting the peripheral edge  20  of the closure element  16  to the airbag shell  12  is configured to have a radial distance b from the inner edge of the aperture  14 . In this way, between the peripheral seam  24  and the edge of the aperture  14  a diaphragm  54  is formed which is substantially movable relative to the closure element  16  and projects inwardly from the peripheral seam  24 . One or more sacrificial seams  55  may be provided in addition to the peripheral seam  24 . 
         [0118]    The diaphragm  54  which always extends approximately along an extension of the airbag shell  12  inter alia has the function of providing a sealing in the closed state of the closure element  16 . 
         [0119]    Moreover, by the diaphragm  54  a direct application of force on the edge of the aperture  14  is avoided, which is why the aperture  14  retains a substantially constant cross-section and thus there is always a reproducible gas escape from the interior of the airbag into the closure element  16 . 
         [0120]    The diamond shape of the aperture  14  and the peripheral seam  24  enables the fabric layers of the airbag  10  to be packed flatly. 
         [0121]      FIG. 18  solely illustrates the closure element  16  shown in  FIG. 17 . 
         [0122]    The elongate ends  22  of the two cut portions  18   a.    18   b  are sewn up together (of, also  FIG. 5 ). Furthermore, the two cut portions  18   a,    18   b  are fastened to each other at the outer areas  28  by means of a respective cross-seam  56  and a head seam  57 . In this example no further fixations and connections are provided. 
         [0123]    The peripheral edge  20  of each of the cut portions  18   a,    18   b  encloses, together with an imaginary line l (cf, also  FIGS. 18 to 21 ), a subarea  58 , wherein the two subareas  58  when being adjacent form a surface which corresponds as to its shape to the aperture  14  but is so large that it can completely cover the aperture  14 . This allows forming a closed surface above the aperture  14  by means of the two subareas  58 , when the closure element  16  is in its closed position (of.  FIG. 18 ). 
         [0124]      FIG. 19  illustrates a out for the closure element  16  in which the two cut portions  18   a,    13   b  are integrally connected at their elongate ends  22 , The peripheral edge of the cut portion  18   a  located on the outer right side in  FIG. 18  already exhibits Use contour of use peripheral seam  24  corresponding as to its shape to the edge of the aperture  14 . 
         [0125]    In this example the surface area of the cut portion  18   b  is larger than that of the out portion  18   a,  as in the former additional fabric  60 ′ is provided for two folds  60  in this example. The folds  60  are folded starting from the elongate end  22  of the cut portion  18   b  and are permanently fixed to the peripheral edge  20  by means of a cross-seam  82 . In this manner, a curved shape that cannot be completely flatly spread is imparted to the cut portion  18   b.  The folds  60  provide for pre-curvature and stabilization for the closure element  16  in the opened position. 
         [0126]    In the subarea  68  the folds  60  are formed so that the subarea  58  including the folds  60  can be flatly spread. 
         [0127]      FIGS. 20 and 21  show a similar embodiment in which merely the two cut portions  18   a,    19   b  are cut out separately from each other and are not integrally connected. 
         [0128]      FIG. 22  illustrates an embodiment in which the cut portion  118   b  is made of a total of three cut parts  164   a,    164   b  and  164   c.  instead of the folds  60 , in this case curved seams  162  are used to produce the curved three-dimensional shape of the cut portion  118   b  which cannot be flatly spread, in this example, all connecting seams are in the form of curved seams, but it would also be possible to design some of the seams to be straight depending on the desired shape. 
         [0129]    In this case the central out part  164   b  is connected integrally with the cut portion  118   a  formed as in  FIG. 19 . The residual cut parts  164   a  and  164   c  are sewn up laterally with the central part  164   b.    
         [0130]    A variant in which all three cut parts  264   a,    264   b,    284   c  are configured as separate parts is shown in  FIG. 23 . 
         [0131]      FIG. 24  illustrates a similar configuration in which the cut parts  364   a  and  364   c  are integrally formed, whereas the central cut part  364   b  is a separate part. Here also the portion  318   a  corresponding to the cut portion  18   a  is in the form of a separate cut pad. 
         [0132]      FIGS. 25 to 27  illustrate the fixation of a tether to the closure element  16 . The two cut portions  18   a,    18   b  may be fabricated in anyway, also as described concerning the cut portions  118   b,    218   b  and  318   b.    
         [0133]    In  FIG. 25  a loop  66  having a connected fabric portion  68  is fixed to the elongate ends  22  of the two superimposed cut portions  18   a,    18   b  in that the fabric portion  68  is sewn up simultaneously on both cut portions  18   a,    18   b  by a specific seam geometry  70  (see  FIG. 26 ). 
         [0134]    Afterwards the tether  34  is pulled through the loop  66 , when the closure element  16  is inserted in the airbag shell  12 . 
         [0135]      FIG. 27 , on the other hand, illustrates a variant in which a ribbon  72  (which may also be a string, a cord or anything else, of course) including two fabric portions  68  tightly fixed thereto is provided each of which is sewn up at the elongate ends  22  of a respective out portion  18   a,    18   b.  When the two cut portions  18   a,    18   b  are fixed to each other, the ribbon  72  automatically forms a loop through which afterwards the tether  34  is pulled.