Patent Publication Number: US-2005127652-A1

Title: Method for folding a gas bag, a device for folding a gas bag and a folded gas bag

Description:
The invention relates to a method for folding a gas bag. The invention also relates to a device for folding a gas bag. Finally, the invention relates to a folded gas bag.  
     BACKGROUND OF THE INVENTION  
      Such a gas bag is part of a vehicle occupant restraint system by which a vehicle occupant is to be protected from injuries. In an emergency, the gas bag must be transferred as quickly as possible from a folded, space-saving state into an unfolded state. Inter alia, the manner in which the gas bag has been folded plays a part here, because both the unfolding speed and also the unfolding direction of a gas bag can be influenced by how the wall has been folded.  
      In the prior art, a plurality of methods is known in order to fold a gas bag in a space-saving manner. Most methods consist of a plurality of individual, precisely defined folding steps. In addition, methods are known in which the gas bag is substantially pushed together, so that no precisely folded gas bag is obtained, but rather a folded gas bag with a wall running at least partially in a chaotic manner.  
      The object of the invention consists in providing a method for folding a gas bag which is distinguished by a small effort. The object of the invention further consists in providing a device for folding the gas bag. The object of the invention finally consists in providing a gas bag which folded by simple means.  
     BRIEF DESCRIPTION OF THE INVENTION  
      To solve this problem in accordance with the invention, a method is provided for folding a gas bag, which contains the following steps: Firstly the gas bag is spread out flat on a base. Then a ring-shaped outer region of the gas bag, which surrounds a central regions, is bent through approximately 90 degrees, so that the outer region surrounds the central region in an apron shape. Finally, the outer region is pushed together towards the base. In this way, with little effort, a gas bag is obtained which is folded in a space-saving manner. It is particularly advantageous here that the wall is situated largely in a ring which surrounds the central region of the gas bag. This method is suitable in particular for so-called doughnut gas bags, i.e. for gas bags which consist substantially of a tube-shaped bead.  
      To solve the above-mentioned problem, a device is also provided for folding a gas bag, which is characterized in that it has a base which has a fixed central section and a moveable folding element, and also a ring-shaped outer stamp, the external diameter of which corresponds approximately to the external diameter of the central section and which can be moved from an initial position into a folding position pressed against the base. This device is distinguished in that the gas bag can be brought with very little effort into a cup-shaped form, from which it can be pushed together with little effort.  
      The above-mentioned problem is solved, finally, by a folded gas bag which is characterized in that it has a central region, spread out flat, and a ring region surrounding the latter, in which the wall of the gas bag is pushed together in a chaotic manner.  
      Advantageous developments of the invention will be apparent from the sub-claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The invention is described below with the aid of preferred embodiments which are illustrated in the enclosed drawings. In these:  
       FIG. 1  shows a diagrammatic section through a device according to a first embodiment of the invention for folding a gas bag in a state before the start of the process;  
       FIG. 2  shows diagrammatically a top view along the arrows II of  FIG. 1 ;  
       FIG. 3  shows a view corresponding to that of  FIG. 1 , the device being in an intermediate stage of the process;  
       FIG. 4  shows a view corresponding to that of  FIG. 3 , the device being in a state after completion of the process;  
       FIG. 5  shows a diagrammatic section through a device according to a second embodiment of the invention for folding a gas bag in a state at the start of the process;  
       FIG. 6  shows a diagrammatic section through the device of  FIG. 5 , after a first process step has been carried out;  
       FIG. 7  shows a diagrammatic section through the device of  FIG. 5 , after a second process step has been carried out;  
       FIG. 8  shows a diagrammatic section through the device of  FIG. 5  after the gas bag has been folded in finished form; and  
       FIG. 9  shows a section along the plane IX-IX of  FIG. 8 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
      In  FIGS. 1 and 2  a first embodiment is shown of a device for folding a gas bag. The device has a base  10  which consists of a fixed central section  12  and a foldable outer section  14 , which forms a folding element. The foldable outer section extends in a ring shape around the central section  12  and consists of a plurality of individual segments which are constructed here as fingers  16  having a constant width. The fingers  16  can be folded from an initial position, which is shown in  FIGS. 1 and 2  and in which they are situated in the same plane as the central section  12 , through approximately 90 degrees upwards with respect to  FIG. 1 . This is explained in further detail below. To move the fingers  16 , any desired mechanism (not illustrated) can be used.  
      At a distance from the central section  12 , a folding unit  18  is arranged, which consists of a guide  20 , an outer stamp  22  and a central stamp  24 . The guide  20  is fixed relative to the central section  12 ; in addition, it is arranged concentrically thereto. The ring-shaped outer stamp  22  is movable towards the base, starting from the initial position shown in  FIG. 1 , in which it is situated at a distance from the central section  12  of the base  10 . For this, any desired thrust system can be used. The external diameter of the outer stamp  22  corresponds approximately to the external diameter of the central section  12  of the base  10 . Within the ring-shaped outer stamp  22 , the central stamp  24  is arranged, which can likewise be moved, starting from the initial position shown into a position displaced forward towards the base  10 . For this, also, a suitable thrust mechanism (not illustrated) is provided.  
      In a first step for folding a gas bag  30 , the latter is spread out flat on the base  10 . Assuming that the gas bag is circular in the spread out state, it is arranged centrally on the base  10 . In a central region  32 , the gas bag has an emblem  36  which is later a part of a gas bag module in which the folded gas bag  30  is arranged. The ring-shaped outer region  34  of the gas bag lies on the fingers  16  of the base  10 . Owing to the inherent rigidity of the gas bag, it is not harmful that the fingers  16  have an increasing distance from each other with an increasing distance from the center of the base  10 ; the fingers  16  are arranged so that they only touch each other at their radially inner end.  
      In a second step for folding the gas bag, firstly the central stamp  24  is moved forward in the direction of the arrow P of  FIG. 3  so that the central region  32  of the gas bag  30  is clamped against the central section  12  of the base  10 . In so doing, the central stamp  24  engages with a recess  26 , provided on its front end side, on the emblem  36 . The central region  32  of the gas bag is therefore fixed securely. Then the fingers  16  are folded upwards through 90 degrees (see arrows Q in  FIG. 3 ), so that together with the central section  12  of the base  10  they form an almost closed cup. On folding up of the fingers  16 , the ring-shaped outer region  34  of the gas bag  30  is likewise folded or bent upwards so that it is arranged in the space between the central stamp  24  and the fingers  16 . This state is shown in  FIG. 3 .  
      As a next step, the outer stamp  22  is pushed forward from its initial position downwards towards the central section  12  of the base into a folding position (see arrow R in  FIG. 4 ). Here, the outer region  34  of the gas bag is pushed together towards the base  10  in a ring-shaped space between the central stamp  24  and the fingers  16 , which form an almost closed, cylindrical wall. In this way, the desired space-saving folded state of the gas bag  30  is obtained.  
      After the folding of the gas bag, the latter can be further processed in a manner known per se, for example inserted into a gas bag module or enclosed in a casing.  
      A particular advantage of the method for folding the gas bag consists in that an optimum utilization of the available packing space is achieved, in particular because only with the last stage of folding, carried out by the forward movement of the outer stamp  22 , is the desired high tamping of the gas bag package is achieved. The previous steps, on the other hand, can be carried out with little expenditure of force. A particular advantage of the device for folding the gas bag consists in that it is constructed so as to be mechanically simple. In addition, the gas bag is transferred with little effort from its flat, spread-out state into the state shown in  FIG. 3 , in which it an be pushed together in an annular space. In particular, no complicated grippers are necessary in order to bring the gas bag into the annular space, and the gas bag also does not have to be inflated, so that it would subsequently have to be relieved of air again on folding. The folded gas bag is distinguished in that its wall is reliably folded in an annular space and can not be pushed together in a central region. This is particularly advantageous in doughnut gas bags.  
      In FIGS.  5  to  9  a second embodiment of a device for folding a gas bag is shown. The same reference numbers are used for the components known from the first embodiment, and in this respect reference is to be made to the above descriptions.  
      The most essential difference between the first and the second embodiment consists in that in the second embodiment the base  10  is constructed as a whole so as to be fixed; the fixed central section  12  is surrounded by a ring-shaped, likewise fixed, outer section  13 . Between the central section  12  and the outer section  13 , a gap is situated, under which a folding element  15  is arranged in the form of a turnover sleeve. The turnover sleeve is movable upwards in a translatory manner through the gap, i.e. towards the outer stamp  22 .  
      Also in the second embodiment, the gas bag is firstly spread out flat on the base  10 . Then the gas bag can be filled slightly with air, so that the side parts  34  bulge slightly (see  FIG. 5 ). This facilitates the further processing. Then the central stamp  24  is moved downward in the direction of the arrow P (see  FIG. 6 ), so that it engages with its recess  26  on the emblem  36  and thereby fixes the gas bag on the base  10 .  
      Then the turnover sleeve  15  is moved upwards in the direction of the arrow T (see  FIG. 7 ), so that the gas bag is drawn upwards and is brought into an apron-shaped form around the central stamp  24 . The turnover sleeve  15  is moved so far until it overlaps with the outer stamp  22 . Finally, the outer stamp  22  can be moved towards the base  10  again in the direction of the arrow P (see  FIG. 8 ), so that the gas bag  30  is pushed together in the annular space between the inner stamp  24  and the turnover sleeve  15 . In so doing, the air contained in the gas bag escapes out of the inflation opening.  
      The second embodiment is distinguished by a small structural effort; all the moving parts can be moved simply in a translatory manner, for example by hydraulic cylinders.