Abstract:
A method for producing an airbag package for an airbag module, which airbag package at least comprises an airbag and a protection covering surrounding the airbag is provided. The method using a first tool that comprises a recess for receiving the airbag package. The method comprising the steps of: covering the recess with an evenly outspread first protection covering part of the protection covering, folding the airbag, and inserting the folded airbag into the recess under interposition of the first protection covering part.

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATIONS 
     This application is a Continuation of International Patent Application PCT/EP2008/061427, filed on Aug. 29, 2008, which was published in German on Mar. 19, 2009 as WO 2009/033962 A1. The foregoing International Application is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND 
     The invention relates to a method for producing an airbag package for an airbag module comprising at least an airbag and a protection covering surrounding the airbag. 
     SUMMARY 
     The problem underlying the invention is to improve a method of the afore-mentioned kind. 
     According to an exemplary embodiment of the invention the method comprises the steps of: covering the recess of the first tool with an evenly outspread first protection covering part as an element of the protection covering, folding the airbag in front of the covered recess, and inserting the folded airbag into the recess, so that the first protection covering part is arranged between the airbag and a wall of the recess limiting the recess. 
     Due to the method according to this exemplary embodiment of the invention, a pre-forming of the elements of the protection covering (first protection covering part) is abdicable. Exemplary, the protection covering or its protection covering parts are formed expandable. Exemplary, the first protection covering part or the protection covering is formed flexible and elastic (resilient) and is exemplary formed by a film. The expansibility of the first protection covering part (or the protection covering) lies exemplary in the range of 300% and above. An expansibility of 600% and above is advantageous as well. Therefore, the protection covering takes its final form only after the evacuation. Thereby, the protection covering shrinks or expands until it takes the shape of the folded airbag, i.e., the protection covering can fill hollow spaces of the folded airbag that are communicating with the exterior space or are residing at the surface of the folded airbag, so that nearly no air remains in the airbag package. Elastic or resilient thereby means in particular, that the protection covering tends to take an unexpanded initial state. 
     Exemplary, the airbag gathered above the recess is pressed into said recess of the first tool by means of a second tool. Hereto, the first protection covering part is preferably fixed to the first tool, so that it covers the recess. This effects that the first protection covering part is arranged into the recess under expansion of the first protection covering part upon pressing of the airbag package into the recess and thereby exemplary adapts to a wall limiting the recess. Further, the first protection covering part is pretensioned against the airbag. 
     It is also possible not to fix the first protection covering part to the first tool so that the first protection covering part slips in said recess upon insertion of the airbag into the recess. 
     For closing the protection covering, a second protection covering part of the protection covering is provided that exemplary comprises the same properties like the first protection covering part and that is arranged at a surface of the second tool facing the recess for closing the protection covering, so that the second protection covering part upon movement of the second tool towards the first tool is pressed against the folded airbag. Thereby, a contact area of said surface of the second tool is pressed against a contact area of the first tool limiting the recess under interposition of a circumferential outer boundary area of the second protection covering part and a circumferential outer boundary area of the first protection covering part, so that both boundary areas are pressed against each other and the airbag is enclosed between both of the two protection covering parts. 
     Afterwards the boundary areas of the two protection covering parts are connected to each other, particularly by means of welding or gluing. Hereto, the contact areas may be formed partially heatable. 
     Exemplary, an area for generating an indentation of the airbag package protrudes from a bottom of the recess of the first tool. I.e., upon insertion of the airbag into the recess of the first tool (under interposition of the first protection covering part) the first protection covering part is pressed against said protruding area, so that an indentation corresponding to the shape of said area is formed in the first protection covering part and in the airbag arranged behind it. The height of said area with respect to the bottom of the recess of the first tool thereby determines the depth of the indentation of the airbag package. In order to adapt the indentation with respect to its depth in the airbag package to the respective desired circumstances, the height of the protruding area with respect to the bottom of the recess is preferably variably adjustable. This may take place for example by a continuous or staged movement of the protruding area with respect to the bottom, wherein this movement essentially runs perpendicular to the ground surface of the bottom. I.e., in this embodiment of the invention, the protruding area is retractable into the recess in different manners or is formed extendable out of the recess. 
     In order to allow for a better adaptability of the dimensions of the recess with respect to airbag packages of different size that are to be produced, the cross section of the recess can be exemplary reduced by the insertion of a limiting element. Preferably, this insertion takes place prior to a welding of the protection covering of the airbag package in order to allow for an adaptation of the size of the airbag package to be produced to the reduced size of the forming recess. Due to the employment of a limiting element, it is possible that the recess is significantly larger than the desired size of the airbag package. The actual size of said airbag package is then determined (at least in two dimensions) by means of the limiting element. 
     Furthermore, prior to folding the airbag, a diffuser for vortexing a gas stream can be arranged in an interior space of the airbag through an inlet opening of the airbag. The diffuser comprises a convex shape that corresponds to the later indentation of the airbag package, i.e., the diffuser surrounds said indentation. 
     In order that the protection covering can tear open upon inflation of the airbag, a tear line is exemplary formed by means of a second tool on the second protection covering part. For this, the second tool can stamp the tear line into the protection covering (second protection covering part) mechanically or by heating the second protection covering part. 
     In order to compact the airbag package, the protection covering is evacuated prior to closing the protection covering, wherein the protection covering tightly adapts to the folded airbag under expansion. Evacuation thereby means, that a pressure is provided inside the protection covering that is considerably smaller than the air pressure of the atmosphere surrounding the airbag package. 
     Furthermore, the problem according to an exemplary embodiment of the invention is solved by means of a folding device for producing an airbag package for an airbag module comprising at least an airbag and a protection covering surrounding the airbag. The folding device thereby comprises a first tool having a recess for receiving the folded airbag under interposition of a first protection covering part of the protection covering, as well as a second tool that is formed for pressing a folded airbag against the first protection covering part, in order to insert the airbag and the first protection covering part butting against the airbag into the recess. 
     Exemplary, the first tool of the folding device comprises a fixation means for fixing the first protection covering part, so that the first protection covering part fixed to the first tool by means of the fixation means dimensionally covers the recess of the first tool. Exemplary, the second tool is designed for pressing the folded airbag in such a manner against the first protection covering part fixed to the first tool, so that this first protection covering part is arranged in the recess under expansion, i.e., enlargement of its surface and at the same time reduction of its thickness. For forming the already explained indentation of the airbag package, the recess of the first tool comprises a bottom having an area protruding therefrom. The recess itself as well as said area of the bottom are exemplary formed cylindrically and are oriented coaxially with respect to each other. 
     The protruding area can be formed movable with respect to the bottom, in order to vary its height essentially perpendicular with respect to the bottom. In this way, the folding device can be adapted especially easily for different indentations (that means for differently shaped airbag packages). 
     In order to also adapt the recess to different airbag package shapes or sizes, the folding device exemplary comprises a limiting element that can be particularly inserted into the recess essentially perpendicular with respect to the bottom. Thus, the cross section of the recess is reduced, so that the airbag package to be formed comprises a small cross section as well. 
     Furthermore, the problem according to an exemplary embodiment of the invention is solved by means of an airbag package that comprises a folded airbag and an evacuated protection covering surrounding the airbag, which protection covering is formed by expandable protection covering parts in the form of flexible films, so that the protection covering tightly butts against the airbag after evacuation. Exemplary, said expandable protection covering parts (or the protection covering) comprise an expansibility of at least 300%. Thereby, the expansibility states the elongation of the protection covering parts or the protection covering in percent under load until the breakdown (tearing). Thereby, the protection covering parts are exemplary resilient, i.e., formed elastically and thus have the property to go back to their initial (unexpanded) state. Hereby, the protection covering enclosing the airbag is at least in sections (with a force corresponding to the elasticity) pretensioned against the airbag and thus contracts about said airbag. Hereby, an evacuation of the protection covering is eventually abdicable. 
     For housing a gas generator or for fastening the airbag package to a module mount, the airbag package comprises exemplary an indentation (bulge) whose shape is predetermined by a cap shaped diffuser that is formed convex and arranged at the gas generator. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further particulars and advantages of the invention are clarified by means of the following description of embodiments with reference to the Figures. 
         FIG. 1  shows a schematic cross section of a folding device for producing an airbag package having two tools for enclosing an airbag between two protection covering parts. 
         FIG. 2  shows a schematic cross section of the device shown in  FIG. 1  having an airbag arranged between the two protection covering parts. 
         FIG. 3  shows a schematic cross section of the device shown in  FIGS. 1 and 2 , wherein the airbag is pressed into a recess of a first tool by means of a second tool, so that both protection covering parts surround the airbag. 
         FIG. 4  shows a schematic cross section of the device shown in  FIGS. 1 to 3  after connecting both protection covering parts. 
         FIG. 5  shows a schematic cross section of a further embodiment of a folding device. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows in conjunction with  FIGS. 2 to 3  a folding device for producing an airbag package  1  for an airbag module comprising at least an airbag  2  and a protection covering  3  surrounding the airbag  2 , wherein the protection covering  3  consists of two protection covering parts  31 ,  32  that consist of a highly elastic (resilient) film whose expansibility is preferentially 300%. 
     The folding device comprises at least a first and a second tool  4 ,  5  of which the first tool  4  serves for pressing a folded airbag  2  into a recess  41  of the second tool  5 . 
     The first tool  4  comprises a body having a planar surface  40  comprising a recess  41 , which surface  40  is formed as a basis for the first protection covering part  31  that is to be spread there upon, wherein the first protection covering part  31  is arranged sheet-like in its state in which it is arranged with respect to the first tool  4  as intended and covers the recess of the first tool  4 . For fastening the sheet-like spreaded first protection covering part  31  above the recess  41 , fixation means  45  in the form of pins protruding from said surface  40  are provided at said surface  40  of the first tool  4 , which pins can engage through openings which are formed in the first protection covering part  31 . Since the first protection covering part  31  is formed expandable, the first protection covering part  31  can be attached to said surface  40  also under tension, i.e. firm, by means of the fixation means  45 . 
     The recess  41  is blindhole-shaped, namely preferentially cylinder-shaped having a bottom  43  that extends parallel to said surface  40  of the first tool  4 . A cylinder-shaped area  44  protrudes from the bottom  43  along the cylinder axis of the cylinder-shaped recess  41 , which area  44  serves for forming an indentation  35  in the airbag package  1 . Thus, the indentation  41  forms a negative shape for the airbag package  1  that is to be produced. 
     For forming the airbag package  1 , the airbag  2  is initially arranged onto the first protection covering part  31  fixed to the first tool  4  and is folded up or folded to a package, so that the package is arranged above the recess  41 . The airbag  2  comprises an interior space  22  which can be filled with gas through an inlet opening  23 . For vortexing the gases that are to be discharged into the airbag  2  a cap-shaped diffuser  21  is arranged in the interior space  22  of the airbag  2 , which diffuser  21  comprises a convex bulge towards the interior space  22 . The diffuser  21  comprises a circumferential boundary area  24  which serves for fastening a boundary area  25  of the inlet opening  23  limiting the inlet opening  23 , for example by clamping the boundary area  25  of the inlet opening  23  by means of the boundary area  24  of the diffuser  21  to a mount. 
     After arranging the airbag  2  above the recess  41 , the folded up airbag  2  is pressed into the recess  41  by means of the second tool  5 , wherein the first protection covering  31  is expanded due to the fixation to the first tool  4  and is pressed into the recess  41  by means of the airbag  2 . Additionally, an indentation  35  is pressed into the first protection covering part  31  and the folded up airbag  2  residing behind it, since the first protection covering part  31  including airbag  2  is pressed against the protruding area  44  of the bottom  43 . The indentation  35  corresponds to the convex bulge of the diffuser  21 . 
     For covering the airbag  2  with a second protection covering part  32 , the latter is fixed to a surface  51  of the second tool  5  that faces the first tool  4  so that it extends two-dimensionally along said surface  51 . For retaining the second protection covering part  32 , low-pressure nozzles  53  may be provided at the second tool  5 , which nozzles  53  absorb the second protection covering part  32  in order to retain it. 
     In case the second tool  5  is now brought to butt against the surface  40  of the first tool  4  with its surface  51  under interposition of the protection covering parts  31 ,  32 , in order to arrange the airbag  2  in the recess  41  of the first tool  4 , a contact area  52  of the second tool  5  presses a circumferential outer boundary area  34  of the second protection covering part  32  against a circumferential outer boundary area  33  of the first protection covering part  31  that is supported on a contact area  42  of the first tool  4  limiting the recess  41 . Hereby, the airbag  2  is enclosed between the two protection covering parts  31 ,  32 . 
     In order to finally form the protection covering  3 , the inner area surrounded by the protection covering parts  31 ,  32  is initially evacuated, so that the highly elastic, expandable protection covering (film)  3  contracts about the airbag  2 . In this way, the protection covering  3  tightly adapts to the airbag  2  and compacts the airbag package  1 . Afterwards, the boundary areas  33 ,  34  of the protection covering parts  31 ,  32  abutting against each other are welded to one another. For this, at least one of the both contact areas  33 ,  34  is formed heatable. Furthermore, a tear line  36  can be stamped into the second protection covering part  32  of the protection covering  3  by means of the second tool  5 . 
     The protection covering  3  formed in this manner surrounds with its first protection covering part  31  the folded airbag  2  (including diffuser  21 ) in a pot-like manner; the cover surface of the protection covering defined by the first protection covering part  31 , which—related to a state in which it is arranged in a motor vehicle as intended—faces a person to be protected, is formed by the second protection covering part  32  connected to the first protection covering part  31 . 
       FIG. 5  shows with reference to  FIGS. 1 to 4  and the explanations related thereto a further embodiment of a folding device in a cross-sectional view, wherein the forming process of the airbag package  1  is in the state shown in  FIG. 3 . 
     As a difference to the folding device shown in  FIGS. 1 to 4 , the folding device of  FIG. 5  comprises an additional hollow cylindrical shaped body  46  as a limiting element. The latter is brought into the recess  41  in order to limit its cross section. Thereby, the cross section of the recess  41  is taken to be the distance that extends in the depiction of  FIGS. 1 to 5  from the left edge of the recess  41  to the right edge of the recess  41 . 
     By means of the shaped body  46 , the space available to the airbag package  1  that is to be formed is limited. Therefore, airbag packages  1  can be formed in the folding device which are smaller than the recess  41  or comprise a different shape than the latter. 
     The shaped body  46  must therefore not necessarily be formed hollow cylindrically. It may also comprise an irregular hollow body shaped form, in order to effect a special shape of the airbag package  1 . 
     The priority application, German Patent Application Number 10 2007 043 936.0, filed on Sep. 12, 2007, including the specification, drawings, claims and abstract is incorporated herein by reference in its entirety.