Abstract:
A method for producing a valve device is provided. The airbag has at least one substantially air-permeable textile, fabric layer and with a film. The textile layer and the film are arranged in a deep-drawing tool with at least area-wise reciprocal overlapping. The film is deep-drawn in deep-drawing regions by the deep-drawing tool to form a plurality of depressions of the film. The textile layer is connected to the film in regions of the film differing from the deep-drawing regions by the deep-drawing tool.

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
       [0001]    Exemplary embodiments of the present invention relate to a method and device for producing a valve device for an airbag. 
         [0002]    German Patent Document No. DE 10 2007 052 246 A1 discloses an airbag for a motor car, having a supporting structure that can be moved from a storage position into a restraining position. The airbag further comprises a shell, by means of which a restraining volume of the airbag formed by the supporting structure is surrounded in its restraining position. 
         [0003]    Depending upon the construction type, it is necessary for the restraining volume to fill particularly rapidly with, in particular, ambient air upon movement of the supporting structure into the restraining position in order to thus be able to receive and restrain occupants of the motor car particularly efficiently. 
         [0004]    Exemplary embodiments of the present invention provide a method for producing a valve device for an airbag that facilitates the production of a cost-effective valve device, wherein the valve device facilitates advantageous filling of a restraining volume of the airbag with air. 
         [0005]    A method according to the invention for producing a valve device for an airbag, having at least one substantially air-permeable textile layer, in particular a fabric layer, and having a film, comprises at least one step, in which the textile layer and the film are arranged reciprocally overlapping at least in areas in a deep-drawing tool. 
         [0006]    Subsequently, in at least one further step the film is deep-drawn in deep-drawing regions by means of the deep-drawing tool, whereby a plurality of depressions of the film are formed. In addition the method according to the invention comprises at least one further step, in which the textile layer is connected to the film, in regions of the film differing from the deep-draw regions, by means of the deep-drawing tool. Due to the fact that the film is deep-drawn by means of the deep-drawing tool and also connected to the textile layer by means of the same deep-drawing tool, the method according to the invention can be carried out particularly favorably with regard to time and costs. This facilitates low production costs and thus low overall costs of the valve device and thus of the whole airbag. 
         [0007]    The film and the textile layer are advantageously connected to each other at least substantially simultaneously with the deep-drawing of the film, whereby this keeps the production time and hence the production costs of the valve device particularly low. 
         [0008]    In addition the valve device produced through the method according to the invention facilitates a particularly rapid flow of a medium, in particular air, through the valve device in a flow direction so that, for example, a restraining volume formed by a supporting structure of the airbag (which is also described as a framework structure) can fill particularly rapidly with the medium, in particular ambient air. In addition the valve device can at least substantially prevent a flow of the medium in a second flow direction contrary to the first flow direction so that the medium remains in the restraining volume at least substantially or can only flow as desired very slowly out of the restraining volume if a relatively high inner pressure builds up in the restraining volume, for example in case of an accident, due to the impact of an occupant against the supporting structure or the airbag. Such a high inner pressure would cause the medium, in particular the air, to flow out of the restraining volume in the second flow direction. 
         [0009]    The valve device thus facilitates, for example, a particularly rapid movement, in particular unfolding, of the supporting structure from a storage position, in which the supporting structure is accommodated in a housing of the airbag, into a restraining position so that the supporting structure and possibly a shell surrounding the restraining volume in the restraining position can receive and restrain the occupant particularly efficiently. The valve device produced through the method according to the invention also guarantees a particularly good service life of the airbag so that it can thus protect occupant(s) particularly well from serious injuries. 
         [0010]    It should be noted that the airbag can also comprise at least one air sack, which is to be filled with a medium, in particular air, and in which likewise the valve device produced through the method according to the invention can be used in order to facilitate a particularly rapid filling of the air sack with the medium so that the air sack can receive and restrain the occupant(s) particularly well. 
         [0011]    The film of the valve device serves to at least substantially permit the flow of the medium through the valve device and thus the textile layer and corresponding regions of the film in the first flow direction and to at least substantially prevent the flow of the air in the second flow direction contrary to the first flow direction or correspondingly to allow a smaller air mass per time unit to flow through the valve device in the second flow direction than in contrast a higher air mass per time unit in the first flow direction through the valve device. 
         [0012]    It is thereby facilitated, for example, that by deep-drawing, the depressions are formed as tubular valves that facilitate a flow of the film through these in the first flow direction. If the described high inner pressure in the restraining volume causes a flow of the air in the second flow direction, the tubular valves thus close (e.g., by coming come together), at least substantially, and prevent air from flowing out of the restraining volume at least substantially and slow down this flow correspondingly in the second flow direction. It is thereby understood that the film is at least substantially air-impermeable in other regions in which the depressions are not formed. 
         [0013]    The textile layer of the valve device provides impact protection for the depressions formed, for example, as tubular valves so that they do not undesirably turn inside out when the air flows or tries to flow in the second flow direction, whereby this is at least substantially prevented by the closing tubular valves. By means of the valve device to be produced cost-effectively by means of the method according to the invention, a particularly advantageous valve functionality is thereby produced for the airbag. 
         [0014]    The deep-drawing tool comprises, for example, cylindrical depressions whereby these depressions constitute negative counter contours in order to form the depressions as positive contours corresponding to the counter contours. The depressions of the deep-drawing tool respectively comprise at least one passage opening, in particular a borehole, whereby these are respectively arranged on a respective end face, in particular on a respective bottom, of the depressions of the deep-drawing tool. By means of these respective passage openings the depressions of the deep-drawing tool can be impacted with a pneumatic underpressure and thus at least substantially emptied so that the film for forming the depressions of the film can be sucked into the depressions of the deep-drawing tool and the film can thus be deep-drawn. 
         [0015]    In order to deep-draw the film and to produce the valve device, the deep-drawing tool is advantageously initially covered with the film, on which the air-permeable textile layer is then laid for example as a supporting fabric. 
         [0016]    The film and textile layer are thereby laid, for example, on a lower part of the tool. Subsequently the deep-drawing tool is closed by an upper part of the deep-drawing tool under high pressure, followed by the emptying of the depressions of the deep-drawing tool, so that the film is deep-drawn in a cup shape. 
         [0017]    During and advantageously at least substantially simultaneously during the deep-drawing of the film, the connection of the film to the textile layer also takes place in regions of the film that are not or were not deep-drawn, thus between the at least substantially cylindrical depressions of the film that have already been formed, are formed during the connection or are formed following the connection. The film and the textile layer are connected, for example, by means of a bonding agent, mechanical pressure, and/or by heat, wherein, for example, the film is fused with the textile layer. 
         [0018]    Further advantages, features and details of the invention ensue from the following description of preferred embodiments and by reference to the drawing. The features and feature combinations mentioned above in the description and the features and feature combinations mentioned below in the description of the figures and/or shown solely in the figures can be used not only in the respectively indicated combination but also in other combinations or alone without going outside of the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
         [0019]    In the drawing: 
           [0020]      FIG. 1  shows, in a cut-out, a schematic perspective view of a deep-drawing tool for carrying out a method for producing a valve device for an airbag, wherein a supporting fabric is connected to a film and the film is deep-drawn to form tubular valves; 
           [0021]      FIG. 2  shows, in a cut-out, two schematic sectional views of a sub-region of the deep-drawing tool according to  FIG. 1 ; and 
           [0022]      FIG. 3  shows, in a cut-out, a schematic sectional view of the deep-drawing tool according to  FIGS. 1 and 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0023]      FIGS. 1 to 3  show a deep-drawing tool  10 , by means of which a valve device  12  can be produced for an airbag of a motor car. In order to produce the valve device  12 , initially a film  14  of the valve device  12  is placed on a lower part  16  of the deep-drawing tool  10 . An air-permeable supporting fabric  18  of the valve device  12  is placed on the film  14  (which is initially air-impermeable), so that the film  14  and the supporting fabric  18  reciprocally overlap each other at least in areas. Subsequently the deep-drawing tool  10  is closed in that an upper part  20  of the deep-drawing tool  10  is applied under high pressure to the lower part  16 , as indicated by a force arrow F in  FIG. 1 . 
         [0024]    The deep-drawing tool  10  comprises depressions  22  that respectively have the shape of a straight circular cylinder and are formed in the lower part  16 . The depressions  22  of the deep-drawing tool  10  comprise respective air chambers  24  that are connected via passage openings  26  in respective bottoms  28  of the depressions  22  and corresponding lines  30 , indicated schematically in  FIG. 1 , with a vacuum pump  32 . The vacuum pump  32  can suck away air in the air chambers  24  via the lines  30  and the passage openings  26  and thus at least substantially empty the air chambers  24  and hence the depressions  22  so that the film  14  is deep-drawn into the depressions  22  thus in a cup form. 
         [0025]    Within the scope of this deep-drawing, a connection of the film  14  to the supporting fabric  18  also takes place in regions of the film  14  which have not or are not deep-drawn, thus between depressions  34  of the film  14  to be formed or which have been formed though the deep-drawing. 
         [0026]    Through the at least substantial emptying of the air chambers  24  the film  14  is sucked in corresponding deep-drawing regions into the depressions  22  of the deep-drawing tool  10 , so that the depressions  34  of the film  14  formed in that the film lay in deep-drawing regions against the depressions  22  of the deep-drawing tool  10 , in such a way that the depressions  34  of the film represent positive contours that correspond to the depressions  22  of the deep-drawing tool  10  as corresponding negative contours. The connection between the film  14  and the supporting fabric  18  takes place for example by means of bonding agent, mechanical pressure, and/or heat. 
         [0027]    Subsequently the deep-drawing tool  10  is opened so that the upper part  20  is removed from the lower part  16 . Passage openings of the depressions  34  of the film  14  are then formed so that a medium, in particular air, can flow in a first flow direction not only through the air-permeable supporting fabric  18  but also through the film  14  via the depressions  34 . In this way the depressions  34  are formed as tubular valves that facilitate the through-flow of the air through the valve device  12  in the first flow direction. The tubular valves prevent flowing of the air in a second flow direction contrary to the first flow direction at least substantially so that the tubular valves close at least substantially by coming together, for example, in the direction of the supporting fabric  18 . The supporting fabric  18  hereby serves as an impact protection so that the depressions  34  and the tubular valves do not turn inside out and extend in an extension direction contrary to an extension direction shown in  FIG. 3 , whereby they would then facilitate a flow of the air in the second flow direction and would at least substantially prevent a flow of the air in the first flow direction, whereby this would constitute an undesirable valve functionality contrary to the previously described valve functionalities. 
         [0028]    The passage openings of the depressions  34  are formed, for example, in such a way that a respective bottom  36  of the depressions  34  is cut away after the valve device  12  has been removed from the deep-drawing tool  10 . 
         [0029]    It can also be provided that the bottoms  36  are removed from the remaining film  14  while the film  14  and the valve device  12  are still in the deep-drawing tool  10 . In this connection the lower part  14  is formed, for example, in two parts and comprises an upper part  40  and a lower part  42  so that a clearance  38  is created that facilitates a relative movement between the upper part  40  and the lower part  42 . A corresponding section to separate the bottoms  36  then takes place within a gap that results when the two parts  40  and  42  are opened. Depending upon the position of the clearance  38 , which thus constitutes a tool division of the deep-drawing tool  10 , the extension, in particular the length, of the resulting tubular valves can be defined. 
         [0030]    The tool division need not necessarily take place at least substantially in a planar manner, as shown in illustration A of  FIG. 3 . The provision of an inclined separating line according to illustration B in  FIG. 3  is also possible. Through such inclined separating lines it can be ensured, for example, that the bottoms  36  of the depressions  34  are cut off in an inclined manner, whereby this may be advantageous for the valve function of the valve device  12 . It is also possible to cut off or separate the bottoms  36  of the depressions  34  at least substantially in a curved manner, whereby this is shown by reference to illustration C in  FIG. 3 . 
         [0031]    The separation of the bottoms  36  of the initially still closed depressions  34  can take place through different cutting methods. The use of at least one mechanical knife, of a laser, in particular a laser beam and/or a water jet is/are possible for example. The separation of the bottoms  36  with the valve device  12  arranged at least still on the lower part  16 , in particular the deep-drawing tool  10 , is characterised in that the depressions  34  are thereby still in a defined and fixed position. This defined position can advantageously also be supported by introducing overpressure  44  via corresponding lines  46  and passage openings  48  in the upper part  20  into the depressions  34  so that the depressions  34  are pressed against inner walls of the depressions  22  of the lower part  16  so that these lie against the inner walls and are thereby stabilized. 
         [0032]    It is also possible to form the passage openings of the depressions  34  in such a way that the bottoms  36  are penetrated, in particular pierced after deep-drawing by means of a hot needle, so that a hole, is formed in the middle of the bottoms  34 . By expanding the depressions  34  formed through the film  14 , which are impacted, for example, with the overpressure  44 , this hole expands, in particular advantageously so far that the diameter of the respective hole corresponds to the respective total diameters of the at least substantially cylindrical depressions  34  and the film  14  is formed in a tubular manner in the corresponding regions in order to form the tubular valves from the depressions  34 . 
         [0033]      FIG. 2  shows in illustrations D and E possible embodiments of edge regions  50  of the depressions  22  formed in the lower part  16 . According to illustration D it is possible to form the edge region  50  in a curved manner with a radius without edges. 
         [0034]    According to illustration E it is also possible to form the edge regions  50  with corners, wherein a first length region  52  is provided at an angle to a length region  54  connecting thereto. A further length region  56  is connected thereto, which is formed at a respective angle both to the first length region  52  and to the second length region  54 . The edge region  50  thus comprises two edges or corners. 
         [0035]    The deep-drawing tool  10  facilitates a production of the valve device  12  that is particularly favorable in terms of time and costs due to a small number of steps and an at least substantial parallelization of method steps. This also keeps the costs for the corresponding airbag, in which the valve device  12  is used, very low. 
         [0036]    The valve device  12  further has a low packing volume and a low weight, which benefits a low packing volume and a low weight of the whole airbag. If the airbag or the corresponding supporting structure is in a storage position, from which the airbag or the supporting structure is moved into a restraining position for receiving and restraining an occupant, the supporting structure has only a very low construction space requirement. 
         [0037]    In addition the valve device  12  has a very high functional integration, which keeps the number of parts, the construction space requirement, the weight and the costs of the valve device  12  and hence of the whole air bag at a very low level. 
         [0038]    The foregoing disclosure has been set forth merely to illustrate the invention and is not intended to be limiting. Since modifications of the disclosed embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed to include everything within the scope of the appended claims and equivalents thereof.