Patent Publication Number: US-11034321-B2

Title: Air bag module

Description:
RELATED APPLICATIONS 
     This application corresponds to PCT/EP2017/076687, filed Oct. 19, 2017, which claims the benefit of German Application No. 10 2016 120 176.6, filed Oct. 24, 2016, the subject matter of which are incorporated herein by reference in their entirety. 
     BACKGROUND OF THE INVENTION 
     The invention relates to an elongate airbag module of a vehicle occupant restraint system. 
     Side airbag modules are fastened to the roof rail of a vehicle according to a known procedure via fixing tabs projecting from the airbag which are provided along the airbag module, by fastening clips being inserted through openings in the fixing tabs and being latched in openings provided in the roof rail. In order to increase the assembling rate, it is aimed at pre-assembling the fastening clips to the airbag module. 
     For this purpose, in DE 10 2013 217 064 A1, for example, it was suggested to wrap the fastening clip into the fixing tab of the airbag prior to assembling the airbag module to the vehicle so that the fastening clip is inserted through a total of three openings in the fixing tab and the head of the fastening clip is wrapped in the fixing tab. In this way, the fastening clip can be pre-fixed to the airbag module without using any further fixing elements. For mounting the airbag module, furthermore merely the engaging portions have to be inserted into the opening in the vehicle body. 
     However, it is a drawback that the fixing tab has to be significantly longer than before so as to provide sufficient material for wrapping the fastening clip. This renders the fabrication more expensive and increases the waste when cutting the airbag parts. 
     SUMMARY OF THE INVENTION 
     It is the object of the invention to render manufacture more cost-efficient for an airbag module having a flexible fixing tab into which a fastening clip can be wrapped. 
     For an afore-mentioned airbag module this is achieved by the features of the claims. In the elongate airbag module of a vehicle occupant restraint system a folded airbag received in an envelope is provided, wherein the envelope has a weakened zone through which the airbag can deploy out of the envelope upon activation of the airbag module. The envelope includes at least one elongate flexible fixing tab having at least one opening by means of which the airbag module can be fastened to a vehicle via a fastening clip which in portions extends through the opening. Portions of the fastening clip are wrapped in the fixing tab. Since the fixing tab is not arranged on the airbag but is arranged on the envelope, the shape of the pre-cut part of the airbag, which is definitely more complicated than that of the envelope, may remain unchanged. Despite the additional fixing tab, it is more easily possible to determine suitable nesting, i.e. a suitable arrangement of the pre-cut parts on a fabric panel out of which the pre-cut parts are cut. 
     Preferably, the fixing tab is folded including the fastening clip inserted in the opening of the fixing tab so that the fastening clip is located at least in portions between fold layers of the fixing tab and thus is safely held by the fixing tab. The fastening clip may be wrapped into the fixing tab about 180°, about 360° or even about more than 360°. 
     The wrapping direction in which the fastening clip is wrapped into the fixing tab preferably is parallel to the longitudinal direction of the fixing tab. 
     The fastening clip typically comprises an engaging portion which engages in an opening at the vehicle body and usually is latched thereto, e.g. via appropriate locking projections. Moreover, it comprises a head which is coupled to the engaging portion and which is widened vis-à-vis the same. Those opening(s) in the fixing tab which serve for fastening to the vehicle basically have a smaller diameter than the head so that the fixing tab is locked through the head. 
     In the unfolded state, the fixing tab preferably extends toward a free end of the fixing tab substantially in parallel to a longitudinal direction of the airbag module. 
     Due to this design, the fixing tab may be placed along an edge of a pre-cut part, thus facilitating the nesting and minimizing any waste. Therefore, it is easily possible to cut out even a long fixing tab in one piece together with the respective pre-cut part. Consequently, the design according to the invention helps to facilitate manufacture of the airbag module while maintaining the advantages of simple and material-saving fixation of the fastening clips to the finished airbag module, and costs can be saved. 
     Preferably, all fixing tabs of the airbag module are designed as elongate fixing tabs aligned in parallel to the longitudinal direction of the airbag module at the envelope. However, it is, also imaginable to design one or more of the fixing tabs in a different shape and/or at the airbag. 
     Advantageously, the fixing tab includes plural openings and the fastening clip is wrapped in the fixing tab such that the engaging portion protrudes through plural superimposed openings so that the fastening clip is captively secured to the fixing tab. 
     One of the openings in the fixing tab may be in the form of slit and a part of a head of the fastening clip, especially an edge portion of the head, may be inserted through said slit. This opening is provided in addition to the openings through which the engaging portion of the fastening clip extends, and the engaging portion does not extend through said slit-shaped opening. The length of the fixing tab may be reduced in this way to save material. 
     The head is preferably designed to be out-of-round and the fixing tab is folded around an edge portion of the head. By insertion in portions into the slit-shaped opening, thus also the entire fastening clip is prevented from being rotated vis-à-vis the airbag module. 
     The head may be a spring, for example, especially a spring extending curved in cross-section, including edges inclined toward the engaging portion so as to reduce a bias acting on the latching connection to the vehicle body. In general, any type of fastening clip may be used within the scope of this invention, even fastening clips consisting of plural portions movable relative to each other which are pre-fixed in a pre-assembled position, where necessary, and adopt their final position not before they are inserted in the opening of the vehicle body. In this case, in its pre-assembled position the fastening clip is wrapped into the fixing tab and is fixed by the latter to the airbag module. 
     The fastening clip is preferably fastened to the airbag module only by being wrapped and inserted into the fixing tab. Further fixations for the fastening clip are usually not provided. 
     In order to lock the airbag together with the envelope tightly to the vehicle, at the airbag a fixing portion may be provided which includes an opening arranged so that in the mounted state it is aligned with the opening in the fixing tab of the envelope. The engaging portion of the fastening clip then extends also through the opening in the fixing portion of the airbag. The fixing clip is retained at the airbag module preferably solely by being wrapped into the fixing tab of the envelope, however. 
     The fastening clip is advantageously wrapped in the fixing tab which is folded several times so as to fix the fastening clip to the airbag module. 
     A favorable cutting form for the envelope, for which no additional material is required and no additional waste will occur, is resulting when the fixing tab is formed by an area cut out of the surface area of the envelope and thus is not attached to an outer edge of the pre-cut part of the envelope. 
     Preferably, the fixing tab includes a first portion which merges into the remainder of the envelope or of the airbag (depending on the part at which of said components the fixing tab is formed) and a second portion at which a free end of the fixing tab is located and which is connected to the remainder of the envelope or to the airbag via the first portion only. 
     When flatly spread, the fixing tab preferably takes an elongate and especially substantially rectangular shape. 
     When the fixing tab takes a rectangular shape, the only connection to the remaining element bearing the fixing tab exists, for example, through a portion of a longitudinal side of the rectangle. 
     This configuration is especially favorable when the fixing tab is cut out of the surface area of the envelope, as only a spiral cut following the two short sides and one of the longitudinal sides of the rectangle completely and the second longitudinal side approximately in half to three quarters has to be made for producing the fixing tab. 
     In all of said cases, there is retained a first portion which merges into the remainder of the pre-cut part of the envelope or of the airbag, as well as a second portion at which a free end of the fixing tab is located, with the second portion being connected to the remainder of the pre-cut part through the first portion only. The transition from the envelope or the airbag to the first portion and the transition from the first portion to the second portion never form a straight line but especially form a right angle. 
     If the fastening openings are intended to have a larger distance from the upper edge of the airbag, for example, the first portion may be lengthened in the direction perpendicular to the second portion, where necessary, so that the fixing tab adopts an angular shape. 
     The fixing tab may hang freely over at least half of its longitudinal extension, with the fastening clip being wrapped in the fixing tab preferably about 360°. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Hereinafter, the invention shall be described in detail by way of an example embodiment with reference to the enclosed drawings, wherein: 
         FIG. 1  shows a schematic sectional view of an airbag module according to the invention in the area of a fixing tab, along the line I-I in  FIG. 5 , wherein the fastening clip is wrapped in the fixing tab about 360°; 
         FIG. 2  shows a schematic sectional view of an airbag module according to the invention in the area of a fixing tab, wherein the fastening clip is wrapped in the fixing tab about 180°; 
         FIG. 3  shows a schematic side view of an airbag module according to the invention illustrating a first step of wrapping the fastening clip into the fixing tab; 
         FIG. 4  shows the airbag module from  FIG. 3  according to a second step of wrapping the fastening clip into the fixing tab; 
         FIG. 5  shows the airbag module from  FIG. 3  according to a third step of wrapping the fastening clip into the fixing tab, in the final mounting position; 
         FIG. 6  shows a schematic top view onto a cutout of an envelope of an airbag module according to the invention in the area of a fixing tab. 
     
    
    
     DESCRIPTION 
       FIGS. 1 through 5  illustrate views of an airbag module  10  which in this case is an elongate side airbag module, as it is mounted for example on a roof rail of a passenger car in order to offer protection in the case of side impact. 
     The airbag module  10  comprises an airbag  12  (cf.  FIGS. 4 and 5 ), in this case a side airbag which is only indicated in the Figures, as well as an envelope  14  surrounding the airbag  12  in the folded state. The envelope  14  includes, as is known, a weakened zone (not shown) which opens upon activation of the airbag module so that the airbag  12  can deploy unhindered. 
     In order to fasten the airbag module  10  to the vehicle, plural fixing tabs  16  are provided, only one of which is shown here, which are fixed to the vehicle body via a respective fastening clip  18 . 
     The fixing tabs  16  are formed at the envelope  14 . 
     The fastening clip  18  always is a separate part which has an engaging portion  20  as well as a head  22  connected thereto, the engaging portion  20  being inserted in an opening in the vehicle body and engaging behind the vehicle body by means of latching projections formed at the engaging portion  20 , and in this way fixes the airbag module  10  to the vehicle. 
     The head  22  is widened vis-à-vis the engaging portion so that the fixing tab  16  is held between the vehicle body and the head of the fastening clip  18 . The fastening clip  18  may be formed in various ways known from the state of the art, the exact shape and function of the latching on the vehicle is not decisive to the present invention. 
     The head  22  of the fastening clip  18  in this example is out-of-round and, in a top view, is H-shaped. Especially, the head  22  forms a spring extending in curved shape in cross-section and including edges inclined toward the engaging portion  20 . 
     The fixing tab  16  extends in parallel to the longitudinal direction L of the airbag module  10  so that its longitudinal extension is parallel to the longitudinal direction L of the airbag module  10  and therefore is also denoted with “L” in this case. 
     In this example, the fixing tab  16  takes an elongate substantially rectangular shape, as is especially clearly visible in  FIGS. 3, 6 and 7 . In the fixing tab  16  plural openings  24   a ,  24   b ,  26  are provided. 
     The two openings  24   a ,  24   b  are circular in this case having a diameter which is larger than the diameter of the engaging portion  20  but smaller than that of the head  22 , and they are located on a straight line in parallel to the longitudinal extension L. 
     In addition to the two openings  24   a ,  24   b , a slit-shaped opening  26  is further provided which is equally located on the straight line connecting the openings  24   a ,  24   b  and between the two openings  24   a ,  24   b . The slit-shaped opening  26  is longer than the diameter of the head  22  so that an edge portion  27  of the head  22  may be pushed therethrough, as shall be explained in the following. 
     The fixing tab  16  in this example is integrally connected to the remainder of the envelope  14 . The transition  28  to the remainder of the envelope  14  is formed in a first portion  30  of the fixing tab  16 . The first portion  30  merges into a second portion  32  which ends in a free end  34 . An imaginary line from the surface area of the envelope  14  to the first portion  30  forms an angle with an imaginary line from the first portion  30  to the second portion  32 , especially a 90° angle. 
     When the approximately rectangular outer circumference of the fixing tab  16  is described by two parallel longitudinal sides a 1 , a 2  as well as two narrow sides b 1 , b 2  which are perpendicular to the latter (cf. e.g.  FIG. 3  for the purpose of clarification), the transition  28  to the envelope  14  is provided at one end of the longitudinal side a 2 , whereas the remainder of the longitudinal side a 2  is suspended freely vis-à-vis the envelope  14 . The narrow side b 2  adjacent to the transition  28  is equally free just as the longitudinal side a 1  as well as the narrow side b 1  which forms the free end  34 . The transition  28  in this example accounts for about half the length of the longitudinal side a 2 , but it might as well comprise a smaller part, up to about 25%. 
     The second portion  32  is connected to the envelope  14  only via the first portion  30  and in this example is completely freely suspended. 
     The (imaginary) division between the first and second portions  30 ,  32  of the fixing tab  16  is emphasized by a dot-dash separating line in  FIGS. 6 and 7  which is perpendicular to the transition  28  at the end of the transition  28  on the longitudinal side a 2  and extends vertically. 
       FIG. 6  illustrates a possible arrangement of the fixing tab  16  relative to the envelope  14 . 
     In this case, the fixing tab  16  is cut out of the surface area of the envelope. 
     The envelope  14  can be manufactured e.g. of a substantially rectangular pre-cut part.  FIG. 6  shows a cutout from the pre-cut part of the envelope  14  in the area of one of the fixing tabs  16 . 
     The upper and lower edges  36 ,  38  of the envelope  14  are laid around the folded airbag  12  so that a centerline  40  of the envelope  14  coincides with an upper edge of the airbag module  10  (see  FIG. 3 ), wherein equally an upper edge  42  of the airbag  12  is arranged in the area of said centerline  40 . 
     The fixing tab  16  is cut out symmetrically to said centerline by a spiral cut and then can be folded upwards around the transition  28  perpendicularly to the plane of projection. Of course, it is possible to reinforce the fixing tab  16  by reinforcing layers which are stitched to the fixing tab  16 , if required. 
     In this example, the fixing tab  16  is arranged symmetrically to the centerline  40  with respect to its narrow sides b 1 , b 2 , with the openings  24   a ,  24   b ,  26  being displaced somewhat toward the free longitudinal side a 1 , however, to obtain more free space for the fastening to the vehicle body. It is also imaginable to displace the fixing tab  16  somewhat with respect to the centerline  40  to take the frame geometry of the vehicle into account. 
     The fastening clip  18  is pre-assembled on the airbag module  10 . The steps required for this are shown in  FIGS. 3 to 5 . 
     Initially, the engaging portion  20  of the fastening clip  18  is pushed through the opening  24   a  which is closest to the free end  34 , in this case into the image plane, so that the head  22  of the fastening clip  18  rests on the fixing tab  16 . 
     A part of the head  22 , in this case the edge portion  27  located on the right of the engaging portion  20 , is pushed through the slit-shaped opening  26  to the rear side (in the Figures) of the fixing tab  16  so that it is covered by the material of the fixing tab  16  in  FIG. 3  (indicated by broken lines). Due to the H shape of the head  22 , the fastening clip  18  is protected against rotation about its longitudinal axis defined by the engaging portion  20 . 
     In the next step, the fixing tab  16  is folded from the free end  34  once about 180° to the right along the longitudinal direction L. The result is shown in  FIG. 4 . Now the engaging portion  20  projects from the image plane, and the edge portion  27  of the head  22  is exposed on the left side. Since the fixing tab  16  was severed out of the surface area of the envelope, now an area of the folded airbag  12  previously covered by the fixing tab  16  is visible. 
     In the next and last wrapping step, the fixing tab  16  is further folded in the same folding direction (to the left in this case), with the engaging portion  20  being pushed through the second opening  24   b.    
     The result is shown in  FIG. 5  and in a section is shown in  FIG. 2 . As is evident, the head  22  of the fastening clip  18  is wrapped once about 360° into the fixing tab  16  and the engaging portion  20  extends two times through the fixing tab  16 , wherein the openings  24   a ,  24   b  now are superimposed. 
     The engaging portion  20  is pushed through the openings  24   a ,  24   b  so far that the latching projections of the engaging portion  20  engage behind the edge of the openings  24   a ,  24   b  and in this way prevent the fastening clip from slipping out of the openings  24   a ,  24   b.    
     The fastening clip  18  is wrapped about 360° into the fixing tab  16 , with the head  22  being located at least in portions between folding layers of the fixing tab  16  and being wrapped in the fixing tab  16  which is folded several times. From outside, merely the edge portion  27  of the head  22  is visible here. 
     After inserting the fastening clip  18  through the second opening  24   b , the fastening clip is also pushed through an opening  46  in a fixing portion  48  projecting from the airbag  12 , which opening is arranged so that the openings  24   b ,  46  are aligned. The engaging portion  20  also engages behind the edge of the opening  46  so that the fastening clip  18  is captively fixed to the envelope  14  and to the airbag  12  and is pre-assembled to the airbag module  10 . 
     The fixing portion  48  on the airbag  12  in this case is a short tab projecting perpendicularly from the upper edge  42  of the airbag  12  and only includes one single opening  46 . As the fastening clip  18  acts directly upon the airbag  12 , a safe load-bearing connection is provided between the airbag  12  and the vehicle body. 
     All fixing tabs  16  of the airbag module  10  are provided with fastening clips  18  in this way. The airbag module  10  now may be mounted on the vehicle. 
     It would also be possible, as shown in  FIG. 2 , to design the fixing tab  16  to have one single opening  24   b  only and to wrap the fastening clip  18  about 180° only.