Patent Publication Number: US-2004045647-A1

Title: Method of folding a gas bag for a vehicle occupant restraint system and folded gas bag

Description:
TECHNICAL FIELD  
       [0001] The invention relates to a method of folding a gas bag for a vehicle occupant restraint system, as well as to a folded gas bag for a vehicle occupant restraint system.  
       BACKGROUND OF THE INVENTION  
       [0002] Numerous methods are known of translating a gas bag for vehicle occupant restraint system from an unfolded condition into a compact folded condition, in which the gas bag can be accommodated in a housing. In one known method fold tongues are used which are placed on the gas bag and form folding edges along which the gas bag can be folded together. Another known method uses pushers with which the gas bag is pushed together. The drawback of all these methods is the expense in being implemented.  
       [0003] The object of the invention consists in providing a method of folding a gas bag which can be implemented cost-effectively.  
       BRIEF SUMMARY OF THE INVENTION  
       [0004] According to the invention, a method of folding a gas bag comprises the following steps: firstly, the gas bag is unfolded between a base and an opposing surface, with a spacing being provided between the base and the opposing surface, this spacing corresponding to the height of a housing into which the gas bag is to be inserted after folding. Then, a folding funnel is provided which comprises one end having a large cross-section and one end having a small cross-section, the large cross-section being larger than or equal to a cross-section of the gas bag when unfolded between the base and the opposing surface, and the small cross-section corresponding to a cross-section of the housing. Finally, beginning with its large cross-section, the folding funnel is placed over the unfolded gas bag and moved relative thereto such that the gas bag is pushed together on the base by the folding funnel to the small cross-section. This folding method is thus based on pushing the gas bag together from the outside to the inside. Contrary to the pushers as known from prior art which are shifted in the same direction in which the gas bag is pushed together, the component, i.e. the folding funnel of the method according to the invention is slipped, so-to-speak, past the gas bag; the direction of movement of the folding funnel is roughly perpendicular to the direction in which the wall of the gas bag is pushed together. Due to the special cross-sectional shape of the folding funnel the wall of the gas bag is thereby pushed together from outside to the inside. The special advantage of this method lies in the fact that the gas bag is folded by a linear motion of one component only, namely the folding funnel. Such a motion is very easy to automate. Another advantage of the method according to the invention lies in the fact that practically any contour of the folded gas bag pack can be achieved by the corresponding shape of the small cross-section of the folding funnel at no extra expense whatsoever. When, for example, the housing for accommodating the gas bag has an oval cross-section, the folding funnel is configured with an oval small cross-section. In this way the gas bag is pushed together into a pack likewise having an oval cross-section.  
       [0005] A gas bag according to the invention that can be folded by the method according to the invention comprises a wall with a multitude of chaotically oriented single folds and an upper, substantially flat outer side and a lower, substantially flat outer side, with more single folds being provided in one of the outer sides than in the respective other outer side. This arrangement of single folds results from the relative movement between the folding funnel and the wall of the gas bag; corresponding to the direction of movement of the folding funnel the wall is shifted more strongly to the front outer side of the gas bag, as seen in the direction of movement of the folding funnel, so that the wall in this location becomes pleated.  
       [0006] Advantageous aspects of the invention will be apparent from the sub-claims. 
     
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
     [0007]FIG. 1 is a diagrammatic view of a first folding machine, by means of which the gas bag according to a first embodiment of the invention can be pushed together;  
     [0008]FIG. 2 is a diagrammatic view of a second folding machine, by means of which the gas bag according to a second embodiment of the invention can be pushed together;  
     [0009]FIG. 3 is a diagrammatic view of a third folding machine, by means of which the gas bag according to a third embodiment of the invention can be pushed together;  
     [0010]FIG. 4 is a plan view of a base as may be used in the folding machine as shown in FIG. 3;  
     [0011]FIG. 5 is a cross-section view through a fourth folding machine, by means of which the gas bag according to a fourth embodiment of the invention can be pushed together; and  
     [0012]FIG. 6 is a diagrammatic view of a fifth folding machine, by means of which the gas bag according to a fifth embodiment of the invention can be pushed together. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
     [0013] Referring now to FIG. 1 there is illustrated a folding machine, by means of which a gas bag  10  can be pushed together by a method according to a first embodiment. The folding machine comprises a folding funnel  12  which in this case has the shape of a bottleneck and continually narrows from a large cross-section at a first end  14  of the folding funnel  12  to a second end  16  having a small cross-section. The folding funnel may be made of sheet metal or plastics and comprises a closed wall. The shape of the cross-section at the end  14  can be practically any; the folding funnel  12  in the simplest case having a circular cross-section at the first end  14 . The shape of the cross-section at the second end  16  corresponds to the cross-sectional shape of a housing (not shown) into which the pushed-together gas bag is to be later inserted. The folding funnel  12  may, for example, have an oval cross-section at the second end  16 . The folding funnel  12  is applied such that, starting from the location as shown in FIG. 1, it can be moved in the direction of the arrow P, i.e. downwards.  
     [0014] The folding machine comprises, in addition, a base  18  which in this case consists of several annular segments  20  and a middle section  22 . The middle section  22  is fixedly secured in place whilst the segments  20  can be likewise moved in the direction of the arrow P, i.e. downwards. Provided on the middle section  22  is a clamping device (not shown) by means of which the gas bag  10  can be fixed. The clamping device may be formed by hooks which engage the inflation port of the gas bag and tighten the wall of the gas bag at the middle section  22 . Provided furthermore at the middle section  22  is an inflating device (not shown) by means of which a slight overpressure can be built up in the interior of the gas bag  10 .  
     [0015] The folding machine finally comprises a plunger  24 , the end face of which forms an opposing surface  26  lying opposite the middle section  22  at a predefined spacing therefrom. This spacing corresponds to the height of the housing in which the folded gas bag is later to be accommodated. The cross-sectional shape of the plunger  24  corresponds to the cross-sectional shape of the second end  16  of the folding funnel  12 , so that it serves as a guide therefor.  
     [0016] The gas bag  10  is pushed together as follows: firstly, the gas bag  10  is secured to the middle section  22 , it then being unfolded by means of the inflating device into a shape which due to the opposing surface  26  lying opposite the middle section  22  is greatly oblate as compared to the freely deployed condition. The folding funnel  12  is then moved downwards in the direction of the arrow P, the inner surface area of the folding funnel engaging the gas bag and compacting it from outside to inside, i.e. in radial direction relative to the longitudinal centerline of the plunger  24 . In the process, the segments  20  are drawn out downwards corresponding to the constriction of the cross-section of the folding funnel  12 , so that they do not obstruct the downward shifting of the folding funnel  12 , and the inflating device makes possible a controlled deflation of the gas bag. The gas bag  10  is fully pushed together to the shape  10 ′ as shown by the broken line in FIG. 1 when the end  16  of the folding funnel is located in the region between the middle section  22  and the opposing surface  26  of the plunger (indicated as  16 ′ by the broken line in FIG. 1).  
     [0017] Referring now to FIG. 2 there is illustrated a second folding machine by means of which a gas bag can be pushed together by a folding method according to a second embodiment. It is to be noted that like components are identified by like reference numerals as known from the first embodiment and reference is made to the above explanations.  
     [0018] Unlike the first embodiment, the base  18  in the second embodiment is configured as a rigid plate on which the gas bag  10  is unfolded, the folding funnel  12  now being composed of a plurality of rings  28  each attached to the other but movable relative to the other. Each ring  28  comprises at its upper end an inwardly bent rim and at its lower end an outwardly bent rim. The inwardly bent rim at the upper end of each ring  28  is located above the outwardly bent rim of the ring located thereabove. To compact the gas bag the folding funnel  12  is lowered downwards so that each ring comes into contact with the base  18  one after the other. In this arrangement, for each new ring coming into contact with the base  18  the wall of the gas bag  10  is urged somewhat furthermore inwards until the gas bag finally attains a cross-sectional shape conforming to the cross-sectional shape of the plunger  24 .  
     [0019] Referring now to FIG. 3 there is illustrated a folding funnel for a third folding machine which similar to the embodiment as shown in FIG. 1 is shaped bottlenecked. In this case, however, the folding funnel has no sheet-like wall, it instead being formed by a plurality of juxtaposed rods  30  each connected to the other at the first end  14  and second end  16  of the folding funnel  12 .  
     [0020] Referring now to FIG. 4 there is illustrated the base  18  as used together with the folding funnel  12  as shown in FIG. 3. In this case, however, the base  18  consists of a plate in which several slots  32  are provided. The slots  32  are arranged and configured such that the rods  30  of the folding funnel  12  are able to enter into them.  
     [0021] To pack the gas bag it is first unfolded on the base  18 , here too, use being made of an opposing plunger. Then, beginning with its first end  14  having the large cross-section the folding funnel  12  is placed over the base  18  and moved such that the rods  30  enter the slots  32  in forcing the gas bag inwards to the middle. The width of the slots  32  is dimensioned such that the wall of the gas bag cannot gain access to the slots  32  where it could become jammed with the rods  30 . Apart from this, the spacing of the rods  30  from each other is dimensioned such that the gas bag is unable to yield outwards from the folding funnel.  
     [0022] Referring now to FIG. 5 there is illustrated in a diagrammatic section view a fourth folding machine, noting that this section is made radially relative to the longitudinal centerline of the plunger used and roughly in the region of the first end  14  of the folding funnel.  
     [0023] In this case, the base  18  comprises a middle section  22 , from which four supporting webs  34  extend radially outwards. The base  18  comprises furthermore a coil spring  36  resting on the supporting webs  34 .  
     [0024] The folding funnel  12 , in this case, consists of four wall segments  38  arranged spaced away from each other such that a slot for passage of the supporting webs  34  is formed between them. Each of the wall segments  38  is oriented such that together they again form a bottleneck-shaped folding funnel.  
     [0025] The gas bag to be folded is applied to the middle section  22  and unfolded. The coil spring  36  resting on the supporting webs  34  serves as a lower support for the gas bag. Axially slipping the folding funnel over the base  18  causes the inner sides of the wall segments  38  to urge the wall of the gas bag inwards, the coil spring also being urged radially inwards so that it does not obstruct the folding funnel. The spacing of the coils of the coil spring and the slot between the wall segments  38  of the folding funnel  12  are dimensioned such that the gas bag cannot become jammed there.  
     [0026] Referring now to FIG. 6 there is illustrated a fifth folding machine, it using the same folding funnel  12  as the folding machine shown in FIG. 1. On this folding machine, however, the base  18  is formed by the surface of a liquid  40 , for example, water. In this embodiment the gas bag is secured to the opposing surface  26  of the plunger  24 , so that it unfolds between the surface  18  of the liquid  40  and the opposing surface  26 . In this embodiment the folding funnel  12  simply dives into the liquid  40  when moved, whereas the gas bag  10 , since it is filled with air, is prevented by its buoyancy from diving into the liquid  40 ; it instead being compressed radially from outside to the inside on the surface of the liquid  40  by the wall of the folding funnel  12 . In this embodiment, before being unfolded, the gas bag is inserted into a packing envelope  42  extending within the folding funnel and between the surface  18  of the liquid  40  and the gas bag  10 . Once the gas bag has been fully pushed together, the packing envelope can be closed off so that the gas bag is fixedly held in its folded condition.  
     [0027] Should the packing density become excessive, resulting in lack of buoyancy, an opposing plunger  24 ′ of the same size as the plunger  24  may be present in the liquid, ending at the surface of the liquid. Where necessary, in this variant the plunger  24  may be lowered later than the folding funnel  12 .