Abstract:
The invention relates to a gas bag having at least one chamber. The gas bag comprises at least two fabric layers arranged opposite one another and delimiting the at least one chamber which can be filled with gas. The fabric layers each form a surface area and consist of threads which comprise warp and weft threads. The gas bag further comprises at least one spacer which is joined to the fabric layers and, in an inflated state of the gas bag, limits a distance between the fabric layers. The spacer is made up of some of the threads which, related to the inflated state of the gas bag, depart from the surface area formed by their associated fabric layer and extend towards the opposite fabric layer to be joined to threads of the opposite fabric layer.

Description:
TECHNICAL FIELD 
     The invention relates to a gas bag. 
     BACKGROUND OF THE INVENTION 
     A gas bag known from U.S. Pat. No. 5,464,250 has a zigzag-shaped section of fabric, sewn at the edge sections with the fabric layers, which section acts as a spacer. The effect of this spacer is to prevent the gas bag from bulging excessively, i.e. from becoming too thick between its edges. Other types of spacers are so-called tethers, the ends of which are sewn to the fabric layers and limit the spacing locally. The fitting of spacers is a very expensive and elaborate procedure and hinders inversion of the gas bag after sewing. The arrangement of the spacers is therefore very complicated, and for manufacturing reasons the spacers cannot be arranged at any site whatever. On the other hand, the inflated gas bags would become unnecessarily thick without spacers, which presents problems. Optimum restraint calls to some extent for no extreme thickness of the gas bag, so that an unnecessarily large amount of gas would be needed to completely fill the gas bag. Moreover, as the thickness becomes greater, the risk of the occupants being struck by the deploying gas bag also increases. 
     For this reason, side gas bags (known as “window bags”) are produced that have numerous, parallel, narrow chambers. Here, the fabric layers are interwoven in one piece on the outside contour of the gas bag and between the chambers. The numerous chambers, in some cases elongated and having a low cross-section, can increase the time to inflate the gas bag. Furthermore, these require precise delivery of the gas to the chambers themselves, e.g. by means of a gas lance which extends along the roof frame. 
     BRIEF SUMMARY OF THE INVENTION 
     The invention relates to a gas bag which has at least one chamber and which is distinguished by spacers that can be manufactured with extreme ease and at low costs, at the same time the spacers having less influence on the flow within the gas bag than those previously known. Furthermore, the gas bag proposed is distinguished by the possibility of having spacers at any sites and in any number without making the manufacture of the gas bag significantly more expensive or more difficult. This is accomplished with a gas bag which comprises at least two fabric layers arranged opposite one another and delimiting the at least one chamber which can be filled with gas. The fabric layers each form or define a surface area and consist of threads which comprise warp and weft threads. The gas bag further comprises at least one spacer which is joined to the fabric layers and, in an inflated state of the gas bag, limits a distance between the fabric layers. The spacer is made up of some of the threads which, related to the inflated state of the gas bag, depart from the surface area formed by their associated fabric layer and extend towards their opposite fabric layer to be joined to threads of the opposite fabric layer. The term “thread” used throughout the description stands for warp and/or weft threads of the gas bag fabric. In the proposed gas bag, the spacers are formed by several warp and/or weft threads which depart, so to speak, from the composite fabric and extend towards the opposite fabric layer. The spacer is, therefore, not a separate part that must be attached to the fabric layers, but an integral part of the fabric layers. The technique of partial interweaving of fabric layers permits the spacers to be positioned anywhere. Moreover, in the region where they function as spacers, the warp and/or weft threads hinder the flow of gas within the gas bag only slightly because they do not necessarily have to be designed as a sheet-like fabric in the region of the spacer. The gas can therefore flow between the individual threads and cause rapid deployment of the gas bag. Due to the inexpensive and variable technique of interweaving in one piece, the invention makes it possible for the first time to manufacture at low cost large-area gas bags that almost resemble mattresses. 
     The warp and/or weft threads that function as spacers can, after departing from the surface formed by the associated fabric layer (usually the outside wall of the gas bag) and after formation of the spacer, go into the opposite fabric layer and thus become an integral part of this fabric layer. Furthermore, after the spacers have been formed, they can go back into their associated fabric layer and integrate with it. However, they must then be joined to warp and/or weft threads of the opposite fabric layers in the region of the spacer. This can be accomplished, for instance, by also separating warp and/or weft threads from the composite arrangement of the opposite fabric layer and joining them between the two external walls of the gas bag to the warp and/or weft threads separated from the composite fabric of the opposite fabric layer. 
     In this way, spacers can be made that form an H shape, an X shape, or a Y shape when viewed in cross-section. 
     The warp and/or weft threads forming the spacer are missing present in the region of the spacer in the fabric layer associated with it. Consequently, the fabric layer is less gas-tight at this point. This can be used to deliberately provide the external wall of the gas bag with a specific gas permeability. If the gas permeability becomes too great, however, the fabric layer providing the warp and/or weft threads can also be coated, at least in the region where the spacer is provided. In the case of side gas bags, for instance, that should be filled completely for as long as possible, the fabric layers are coated with film, preferably on the outside. Numerous spacers can thus be provided because, due to the coating with film, it is no longer disadvantageous in terms of gas permeability for the external wall to have just a few threads in the region of the spacers. The fabric itself thus forms essentially a supporting structure only and the gas-tightness as such is provided by the film. 
     When the gas bag is a large-area side gas bag and has several chambers formed by interweaving into one piece the opposite fabric layers, the spacers described above are provided additionally within the chambers. Although the chambers themselves have a small cross-section, the thickness of the gas bag can be reduced once again by the spacers and be brought down to the dimension that is adequate for the purposes of restraint. The spacers can be of elongated and, for example, linear shape, i.e. form an elongated, gas-permeable wall. The spacers can, however, also be point-shaped or ring-shaped, rather like a bed mattress where knobs visible on the outer side form the end of spacers. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows an inflated head/side gas bag according to the invention in a first embodiment. 
     FIG. 2 shows a perspective view of a section through a single chamber of the gas bag shown in FIG. 1 in the inflated state. 
     FIG. 3 shows a cross-sectional view through two other embodiments of the gas bag according to the invention, in its non-inflated state. 
     FIG. 4 shows the region of the gas bag shown in FIG. 3 in the inflated state. 
     FIG. 5 shows a cross-sectional view through a gas bag in the inflated state according to a fourth and fifth embodiment. 
     FIG. 6 shows a head/side gas bag in the inflated state according to a sixth embodiment. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     In FIG. 1, a head/side gas bag  3  is shown which extends in the inflated state in the vehicle from the A-pillar  5  across the B-pillar  7  through to the C-pillar  9  and completely covers the side windows  11 ,  13 . In the inflated state, the side gas bag  3  has a large surface area and is shaped like a mattress, with nearly uniform thickness. It consists of two fabric layers  15 ,  17  that can be identified better in FIG.  2 . The fabric layers  15 ,  17  form the outer walls of the gas bag. Both fabric layers  15 ,  17  consist of warp and weft threads  21  and  19 , respectively; in FIG. 2, several warp threads  21  and one weft thread  19  are shown. The two fabric layers  15 ,  17  are interwoven into one piece in the region of the outside contour  23 . 
     The gas bag consists of a plurality of chambers  25  to  33  which are connected to one another in terms of flow at the lower edge of the gas bag. A so-called gas lance  35  extends from the C-pillar  9 , starting at a gas generator  37 , into the interior of the gas bag and runs along the roof frame up to the A-pillar  5 . Between the chambers  25  to  33 , the fabric layers  15 ,  17  are also interwoven into one piece in the regions  37  that represent the partitions. The region  39  is interwoven over a large area; it also represents a partition and is arranged in a region that is at a considerable distance from the head of the occupant. The partitions  37  to  39  are gas-tight and therefore do not allow gas to flow from one chamber to the next. 
     The gas bag is coated on the outside of both fabric layers  15 ,  17  by a film  41 ; in FIG. 2, a small section of the film  41  is shown just by way of example. In fact, the film  41  covers the entire outside of both fabric layers  15 ,  17 . The film  41  ensures that the gas bag  3  is gas-tight. 
     From FIG. 2 it is possible to see how it is accomplished that in the region of each chamber  27  to  33  the gas bag has only a small thickness and bulges outward only slightly. In each chamber there is arranged one or a plurality of spacers  43  that hold the fabric layers  15 ,  17  so as to keep a specific distance to each other. The spacers  43  are formed by threads of the fabric layers  15 ,  17  that depart from the composite fabric over a predetermined length and finally go back into the composite fabric of the original (i.e. their corresponding) fabric layer or of the opposite fabric layer. The spacers  43  are therefore integrated so as to form one piece with the fabric layers  15 ,  17 . 
     In order to illustrate this, FIG. 2 shows by way of example several weft threads  119  from the upper fabric layer. These weft threads  119  are still integrated in the fabric layer  17  in the region of the arrow relating to the reference numeral  17 . The fabric layer  17  defines a surface or, in other words, an outside wall of the gas bag. The weft threads  119  then depart from the composite fabric and hence the surface defined by its associated fabric layer  17  and extend at an angle toward the opposite fabric layer  15  into which they then go in the region  51 . On the other hand, whilst weft threads  219  from the lower fabric layer  15  are still present in the composite fabric in the region of the reference symbol  15 , they depart from the fabric layer  15  in the region of the spacer  43  and extend at an angle toward the opposite fabric layer  17  into which they then finally go. Viewed in cross-section, the weft threads  119 ,  219  form an “X”. The weft threads  119 ,  219  do indeed contact each other here, but they are not joined together between the fabric layers  15 ,  17 . Because only individual weft threads  119 ,  219  depart from the fabric layers  17  and  15 , respectively, no partition is created but a spacer  43  which runs linearly and parallel to the partitions  37  over almost the entire height of the gas bag  3 . 
     Instead of or in addition to the weft threads  19 , warp threads  21  can also run out of the fabric layers  15 ,  17  and extend toward the opposite fabric layer in order to form a spacer. 
     FIG. 3 shows two different embodiments of the spacer. In the embodiment on the left, the spacer  43 ′ is formed by warp threads  119 ′ departing from the fabric layer  17  (in the direction of the arrow, i.e. described from left to right) and run toward the fabric layer  15 . Equally, warp threads  219 ′ depart from the fabric layer  15  and run toward the fabric layer  17 . The warp threads  119 ′ and  219 ′ encounter each other and are joined together in a portion  61  in that weft threads  121  from the upper fabric layer  17  and weft threads  221  from the lower fabric layer  15  extend into the portion  61  and are joined to, i.e. woven with, the warp threads  119 ,  219 . Beyond the portion  61 , the warp threads  119 ′,  219 ′, as well as the weft threads  121 ,  221 , return to their associated fabric layers  17  and  15 , respectively. 
     In the embodiment on the right in FIG. 3, the spacer  43 ″ is formed by the warp threads  119 ′,  219 ′ running toward the opposite fabric layer  15  and  17  respectively, being joined together in the portion  61  and then not running back to the fabric layer associated with it but to the opposite fabric layer and going into this fabric layer. For reasons of clarity, the weft threads  121 ,  221  are not shown in the embodiment on the right even though they exist in order to create the portion  61 . 
     In FIG. 3, the portrayed section of the gas bag is shown in the non-inflated state, but slightly pulled apart. In FIG. 4, however, the gas bag is shown in the region of the spacer  43 ′ in the inflated state. It can be seen that in the inflated state the spacer  43 ′ assumes an H-shape with vertical legs each of which runs at an angle to the outside towards the end of its free ends, and with a connecting leg which is formed through the portion  61 . Between the attachment points  71 , the gas bag bulges slightly outwards. All in all, this results in a kind of mattress shape. 
     In the embodiment shown in FIG. 5, the spacers  43 ′″ and  43 ″″ have a Y-shape when viewed in cross-section. This is formed by the warp threads  119 ′ that separate from the fabric layer  17  joining in a portion  61 ′ (middle piece of the Y) with the separating warp threads  219 ′. In the V-shaped upper region of the Y, the threads run separately from each other. Finally, the warp threads  119 ′ go into the fabric layer  15  and the warp threads  219 ′ go into the fabric layer  17 . The portion  61 ′ is immediately adjacent to the fabric layer  15 , but for the purpose of better illustration the lower end of the portion  61 ′ is shown somewhat pulled apart. 
     In the embodiment on the right in FIG. 5, the spacer  43 ″″ is formed by the warp threads  119 ′ first running toward fabric layer  15  where they are joined in a portion  61 ″ with the warp threads  219 ′ from the fabric layer  15 . The warp threads  119 ′ then run back again into the fabric layer  17 . In both embodiments in FIG. 5, that on the left and that on the right, there are weft threads that contribute to defining the portions  61 ′,  61 ″ and  61 ′″. In the embodiment shown on the right in FIG. 5, it must furthermore also be ensured that the length of the warp threads  119 ′ is the same as the length of the warp threads  219  in the region where they have been separated from the composite fabric; otherwise the fabric layers would become displaced by a large amount relative to each other. 
     When the embodiments shown in FIG. 5 are used, it must also be ensured that the quantity of spacers  43 ′″ or  43 ″″ is always an even number because in the region of the spacers there is a curvature of one fabric layer toward the outside whereas the other fabric layer has no curvature. Consequently, the wall with the curvature is also shortened in the longitudinal direction. This shortening is balanced out only with an even number of spacers. 
     FIG. 6 is intended to show that the spacers do not have to be just elongated and run linearly as in FIG. 1, but can also be of point or circular shape for instance, e.g. when the embodiments shown in FIG. 5 are designed such that the warp and weft threads separate from the composite fabric in the region of a circle.