Abstract:
A gas bag has several walls of layers of fabric, which delimit the interior of said gas bag, adjacent walls being connected in one piece with each other by interweaving, and an outer periphery along which said walls are connected to each other by interweaving, and several chambers which are separated from each other by the provision of an elongated, interwoven region. The interwoven region provided for separating chambers has opposite ends and terminates at least at one of said ends at a distance from said interwoven outer periphery, in order to delimit at least one overflow channel in the region of said outer periphery of said gas bag. The interwoven region runs out in at least one of a rounding and a drop shape at the end terminating at a distance from the outer periphery.

Description:
TECHNICAL FIELD 
     The invention relates to a gas bag for a vehicle occupant restraint system. More specifically the invention relates to a window bag covering the side windows of a front and a rear occupant. 
     BACKGROUND OF THE INVENTION 
     Such a gas bag is known from DE 297 09 389 in the form of a so-called side gas bag. A side gas bag extends similar to a curtain in the case of restraint between the occupant and the side windows of the vehicle and in particular reduces the risk of head injuries in the case of a side impact. Along the outer periphery of the gas bag the fabric layers are connected to each other by interweaving. The inner edge of the interwoven periphery is wave-shaped with successive concave shaped sections. 
     The walls of the gas bag are stressed most intensively during the inflation process in the region of the interwoven portions in the form of the peaks of adjacent concave shaped sections and at the end or ends of elongated interwoven regions separating adjacent chambers which stress can lead to the tearing of the fabric material. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention provides a gas bag in which the stress on the warp and weft threads is reduced during inflation in fact at the end of the interwoven region. The gas bag according to the present invention has several walls of layers of fabric, which delimit the interior of said gas bag, adjacent walls being connected in one piece with each other by interweaving, an outer periphery along which said walls are connected to each other by interweaving, and several chambers which are separated from each other by the provision of an elongated, interwoven region. The interwoven region provided for separating chambers has opposite ends and terminates at least at one of said ends at a distance from said interwoven outer periphery, in order to delimit at least one overflow channel in the region of said outer periphery of said gas bag. The interwoven region, usually having the form of a line, runs out in at least one of a rounding (line defining a curve) and a drop shape at the end terminating at a distance from the outer periphery. 
     Through the measure according to the invention, the force peaks are reduced at the free end of the interwoven regions. The forces are introduced into the fabric so as to be distributed onto warp and weft threads over a larger area so that stress peaks are reduced. 
     The interwoven regions are preferably undulating lines which define the outer periphery of the gas bag and/or also define separations between gas bag chambers. 
     It is possible according to the invention that the entire line or else only the edge of the interwoven region adjoining the interior of the gas bag runs in an undulating shape which shape is defined by successive concave and convex portions of the edge. 
     The preferred embodiment of the gas bag makes provision that it is constructed as a side gas bag similar to a curtain. The interwoven region runs along the outer periphery. The interwoven regions separating adjoining chambers run obliquely to the warp and weft threads. For this, they can run in a straight line or else also in an undulating shape, as was already previously indicated. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a side view of a gas bag according to the invention in the fully inflated state, which, in the case of restraint, is arranged as a so-called ABC side gas bag laterally between the head of the front occupant and the head of the rear occupant and the side windows, 
     FIG. 2 shows a side view of the gas bag shown in FIG. 1 with the gas lance inserted, so that a gas bag restraint system according to the invention is produced, 
     FIGS. 3,  4  and  5  each show cross-sectional views through the gas bag and the gas lance according to FIG. 2 in the region of the outer periphery, each figure illustrating a different embodiment with respect to a temperature protection, and 
     FIG. 6 shows an enlarged longitudinal sectional view of the restraint system according to FIG. 2 in the region of the introduction opening in the gas bag for the gas lance. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     In FIG. 1 a gas bag is shown which consists of two opposite walls of one layer of fabric each, only one wall  3  of which is visible. The other wall, which lies behind the wall  3 , is constructed in an identical manner. The gas bag  1  is adapted in the region of its upper outer periphery  5  to the shape of the roof frame of the vehicle, behind the paneling of which it is accommodated. In the region of the outer periphery, the two walls are connected in one piece with each other by interweaving. The interwoven region is designated by  7  and extends completely around the outer periphery of the gas bag up to an introduction opening  9  at the end of the gas bag on the rear side of the vehicle. The interwoven, linear region  7  is approximately 1 to 2 cm wide. The interwoven region  7  runs in an undulating form in the region of the lower outer periphery, the latter running approximately horizontally and being subjected to particularly high stresses owing to the dynamic inflation of the gas bag. With respect to the interior of the gas bag concave and convex portions  7  and  7 , respectively, immediately adjoin each other in harmony without steps. Thereby, the warp and weft threads which are illustrated by way of example with the aid of one thread  11  and  13 , respectively, are subjected to lower stresses than in a case in which the interwoven region were to run for example parallel to a warp thread  11 . In the latter case, namely the warp thread  11  could not receive any tension and the entire tension would have to be received by the weft threads  13 . Through the undulating interwoven region  7 , in addition a high degree of gas-tightness results, because the warp and weft threads  11  and  13 , respectively, can scarcely be displaced with respect to each other. 
     The side gas bag  1  which is shown has several chambers  15 ,  17 ,  19 ,  21 , which however are all in flow connection with each other. The chambers are separated from each other by further interwoven, linear regions which are designated by the reference numbers  23  to  27 . These interwoven regions run partially likewise in an undulating shape (see regions  23  and  25 ) with immediately adjoining concave and convex portions  23 ,  25 , and  23 ,  25 , respectively, or linearly and obliquely to the warp and the weft threads  11  and  13 , respectively (cf. region  27 ). The interwoven regions  23  to  27  do not extend up to the lower outer periphery which is defined by the lower part of the interwoven region  7 , but rather terminate at a distance therefrom, so that overflow channels  29  are produced. 
     The interwoven linear regions  23  to  27  each end in the form of a drop or a rounding, which are wider in their dimensions (maximum width W of a drop or maximum outer dimension Z of a rounding) than the linear regions  23  to  27  (having a width V immediately before the end of the regions  23  to  27 ), in order to avoid stress peaks in the region of the ends. Inside the drop-shaped end  31 ,  33  of the interwoven regions  23  and  25 , the opposite walls are interwoven completely with each other, which means that the interwoven drop-shaped end is filled over the entire area. The lower end of the interwoven region  27 , which terminates in a rounding, is not filled, however, but rather is only defined by a frame-shaped peripheral line  35 . 
     The terminations of the interwoven regions  23 ,  25  and  27  extend in the region of the upper outer periphery, these regions  23 ,  25  and  27  continuing into each other, parallel to the outer periphery but at a distance therefrom. These parallel regions are designated by  37  and  39 . Within the regions  37  and  39  there are interwoven regions  41  and  43  having a larger area, which each surround a slot  45  which extends through both walls and through which clamps for the fastening of a gas lance can be inserted in each case. 
     The distance between the upper outer periphery and the regions  37  and  39  running parallel to the outer periphery is adapted with respect to the outer periphery of the gas lance such that this does not have much play. 
     Previously, it was always stated that the interwoven regions as a whole run in an undulating shape. This can indeed be the case, as is also shown in FIG.  1 . However, it is important for reducing the stress of the warp and weft threads  11 ,  13  that the edge of the interwoven region adjoining the interior of the gas bag runs in an undulating shape. This edge is designated by  51  with respect to the interwoven region  7 . The outer edge  53  does not have to run in an undulating shape, because the interwoven region scarcely receives further forces along the outer edge, which is designated by  53 . 
     The interwoven regions  23 ,  25  and  27  not only have an edge which adjoins the interior of the gas bag. Here, in fact, both opposed edges  55 ,  57  adjoin the interior of the gas bag, more precisely adjoin another chamber in each case. Accordingly, the edges  55  and  57  also do not have to run parallel to each other, as is illustrated in FIG. 1, in order to achieve the effect according to the invention. 
     In FIG. 1, tensioning straps  61 ,  63  and  65  are also shown. These tensioning straps are connected with the roof frame or with one of the columns of the vehicle. The gas bag is tensioned in the inflated state between the tensioning straps  61 ,  63  and  65 . The tensioning strap  61  is connected with the walls  3  in the region of the rounding of the interwoven region  27 , so as not to apply any additional stress onto the warp and weft threads in inflated sections. 
     FIG. 2 shows a gas bag restraint system with the gas bag according to the invention and also with a gas lance  71  introduced into it and running parallel to the roof frame, which gas lance is inserted via the introduction opening and is in flow connection with a gas generator which is not shown. The gas lance  71  has outflow openings on its lower edge in the region of the chambers  15 ,  17 ,  19  and  21 . The gas lance is connected with the gas bag  1  by fastening clamps  73 ,  75 . The fastening clamps  75  extend through slots  45  in the gas bag walls which, however, lie in interwoven regions  41 ,  43  and thus can not lead to a tearing of the gas bag, starting from the slots  45 . 
     In order to avoid a thermal stressing of the fabric material in the region of the gas lance  71  at the start of the unfolding process, when the fabric material lies very close to the outflow openings, additional fabric layers are provided. These fabric layers are only provided in the regions of the outflow openings  72 . The fabric layers can be fastened to the gas lance  71  or to the walls of the gas bag. FIGS. 3 to  5  show embodiments in which the fabric layer  81  is placed in a U-shape in cross-section around the gas lance  71  (FIG.  3 ), is slipped as a tubular band, closed circumferentially, onto the gas lance  71  and has a perforation line  84  on the underside (FIG. 4) or is wound around the gas lance  71  (FIG.  5 ). In each case, the fabric layer  81  permits an outflow of gas downwards into the gas bag. 
     In the case of restraint, gas is introduced into the gas bag  1  via the gas lance  71 . The gas flows via the outflow opening into the chambers  15 ,  17 ,  19  and  21  and leads to a rapid unfolding of the gas bag downwards. Only when the gas bag is almost unfolded and offers its almost entire surface for protection, does a pressure equalization occur between the individual chambers via the overflow channels  29 . The gas bag is tensioned between its tensioning straps  61 ,  63  and  65  and is positioned in a stable manner in the vehicle, laterally of the heads of the front and rear occupants and in front of the side windows. In the case of restraint, the head of the rear occupant can be protected approximately in the region of the chamber  21  from an impact onto the side window. In the case of a side impact, the head of the front occupant is protected from contact with the side window in the region of the chamber  17 . With an impact from obliquely to the front, the chambers  15  and  19  can offer additional protection.