Abstract:
An airbag assembly for a seatbelt restraint such that the deflated airbag lays flat when it is stacked and secured to a webbing of the seatbelt. The airbag is assembled from a plurality of material strips. The strips are edge joint welded together so that the joints lay flat between the individual strips comprising the airbag.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
       [0001]    The present patent application claims the benefit of and is a divisional of U.S. patent application Ser. No. 14/183,724, filed Feb. 19, 2014, which is incorporated herein by reference. 
     
    
     BACKGROUND OF INVENTION 
       [0002]    The present invention relates generally to a method of assembling an automotive airbag and more particularly to a method of assembling an automotive airbag such that it packs flat. 
         [0003]    Automotive vehicles use airbag systems to protect a vehicle occupant during collisions. The airbag is a bag that rapidly inflates during a collision to provide cushioning for the vehicle occupant. A housing from which the airbag deploys may be located throughout a vehicle passenger compartment, including being incorporated into a webbing of a seatbelt restraint. 
         [0004]    The seatbelt webbing in automotive vehicles typically slides over a D-ring when extended and retracted. However, incorporating the airbag into the webbing increases the thickness of the webbing and the tendency of the webbing to bubble up or pucker. The increased thickness and tendency to bubble up or pucker makes the airbag incorporating webbing both less aesthetically pleasing to the vehicle occupant and more difficult to pass over the D-ring and thus more difficult to for the vehicle occupant to don and doff the seatbelt. The difficulty in passing over the D-ring may necessitate designing the seatbelt system so the airbag component does not pass over the D-ring, which then may require the addition of a second retractor for the lap portion of the seatbelt assembly. This makes packing the system with a vehicle more difficult and costly. Additionally, in applications where a D-Ring is not required, such as a sedan, a thin flexible airbag pack is still desired to allow for the webbing with integrated airbag to be stowed on a conventional sized retractor. 
       SUMMARY OF INVENTION 
       [0005]    An embodiment contemplates a method of assembling and packing an airbag. Stacking a plurality of material strips having first and second edges. Welding pairs of first edges together and pairs of second edges together, the pairs of second edges being staggered from the pairs of first edges, to form an accordion stack in which the strips in the stack lay flat. Forming a tube having first and second openings by edge joint welding together top and bottom strips of the stack. Closing the first and second openings by edge joint welding to form an inflatable bag. Securing the bag to a seatbelt webbing. 
         [0006]    Another embodiment contemplates a safety restraint airbag assembly comprising an inflatable bag comprising a plurality of material strips edge joint welded together such that, at weld joints between the strips, the strips lay flat in a stack. The bag is secured to a seatbelt webbing. 
         [0007]    Another embodiment contemplates a method of assembling and packing an airbag. Welding a plurality of material strips into an inflatable bag such that, at weld joints between the plurality of strips, a first strip lays flat on top of a second strip. Stacking the strips in a stack. Securing the bag to a seatbelt webbing. 
         [0008]    An advantage of an embodiment is that the airbag packs flat, which is advantageous when used in the seatbelt restraint, and may also be useful for other vehicle airbag applications. This reduces cost and complexity of needing a second seatbelt retractor, or taking up more packaging space then is desirable by allowing for a conventional sized seatbelt retractor. The seatbelt is also easier for the vehicle occupant to don and doff. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0009]      FIG. 1  is a schematic elevation view of an airbag in a seatbelt restraint. 
           [0010]      FIG. 2  is a schematic elevation view of an airbag assembly. 
           [0011]      FIG. 3  is a schematic perspective view of an airbag assembly. 
           [0012]      FIG. 4  is a schematic perspective view of a packed airbag. 
           [0013]      FIG. 5  is a schematic perspective view of an airbag assembly. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]      FIG. 1  schematically illustrates a seatbelt airbag system  10  for an automotive vehicle  12 . The seatbelt airbag system  10  is merely exemplary, and may take other forms, which may be a three point system or a four point belt system. The seatbelt airbag system  10  includes a seatbelt restraint  14 . The seatbelt restraint  14  may be a type known to one skilled in the art. For example, illustrated is a three-point seatbelt restraint comprising a seatbelt webbing  16 , a buckle  18 , a D-ring  20 , and a retractor  22 . The webbing  16  is secured to vehicle structure or a vehicle seat  26  at a first end, passes over the D-ring  20  and is guided towards the retractor  22 , which receives a second end of the webbing  16 . The retractor  22  provides tension in the webbing  16  by taking up and spooling an excess of the webbing  16 . The webbing  16  passes through the tongue slot  17  which attaches to the buckle  18  and holds the seatbelt restraint  14  across a vehicle occupant  24  seated in the automotive vehicle seat  26 . An airbag  28  is secured to the webbing  16 . For example, the airbag  28  may be secured in a sleeve  88  on the airbag  28 . 
         [0015]      FIG. 2  schematically illustrates an airbag assembly. A method of assembling the airbag  28  for packing flat in the seatbelt airbag system  10  will also be discussed relative to  FIG. 2 . A plurality of intermediate strips  30  is vertically stacked between a top strip  32  and a bottom strip  34 . The intermediate strips  30  each have a first and second edge. The intermediate strips  30 , the top strip  32 , and the bottom strip  34  are fabricated from airbag material known to one skilled in the art. For example, the material may be a woven nylon fabric. A volume of the airbag  28  is a function of, in part, a quantity of intermediate strips  30  between the top strip  32  and the bottom strip  34 . The greater the quantity of the intermediate strips  30 , the greater the volume of the airbag  28 . The width of each strip  30  is generally determined by the width of the webbing  16 , which may also affect the volume of the airbag  28 . The intermediate strips  30  may all be the same size or vary in size. 
         [0016]    The intermediate strips  30  are welded together in accordance with a weld pattern. In the weld pattern, a first edge  38  of a first strip  36  is edge joint welded to a first edge  42  of a second strip  44 . A second edge  40  of the first strip  36  is edge joint welded to a second edge  46  of a third strip  48 . The second strip  44  and the third strip  48  are on opposite sides of the first strip  36 . Neither the first edge  38  nor the second edge  40  of the first strip  36  are welded to both the second strip  44  and the third strip  48 . The weld pattern results in the edge joint welds of the intermediate strips  30  being staggered between the first and second edges. The airbag  28  may be assembled by sequentially stacking and edge joint welding adjacent strips. Alternatively, the airbag  28  may be assembled by stacking all the strips and then, after stacking, edge joint welding the strips. In either case, the result is an accordion (bellows) shape. 
         [0017]    Assembly of the airbag  28  uses edge joint welds. As understood by one skilled in the art, an edge joint weld involves laying a first substrate flat on a second parallel, or nearly parallel, substrate and welding a contact area between the first and second substrates along an edge. The edge joint weld allows the two substrates to be retained parallel and flat against each other. As used for the airbag  28 , the edge joint weld permits an upper strip to lay flat on top of a lower strip, including at a joint between the upper and lower strips. By using the edge joint weld, the intermediate strips  30  stack flat between the top strip  32  and the bottom strip  34 . In the weld pattern, the use of the edge joint weld allows the first strip  36 , the second strip  44 , and the third strip  48  to stack flat. 
         [0018]    The top strip  32  has a first edge  50  and a second edge  52 . The bottom strip  34  has a first edge  54  and a second edge  56 . The top most intermediate strip  30  is a top transition strip  58 . The top transition strip  58  has a first edge  60  and a second edge  62 . The first edge  60  of the top transition strip  58  is edge joint welded to the first edge  50  of the top strip  32 . The second edge  62  is edge joint welded in accordance with the weld pattern. The bottom most intermediate strip  30  is a bottom transition strip  64 . The bottom transition strip  64  has a first edge  66  and a second edge  68 . The first edge  66  of the bottom transition strip  64  is edge joint welded to the first edge  54  of the bottom strip  34 . The second edge  68  is edge joint welded in accordance with the weld pattern. The second edge  52  of the top strip  32  is welded to the second edge  56  of the bottom strip  34 . 
         [0019]    The intermediate strips  30 , top strip  32 , and bottom strip  34  have a first face  70 . The first face  70  alternates between facing upward and downward in the intermediate strips  30 . The first face  70 ′ of the top strip  32  faces opposite the orientation of the first face  70  of the top transition strip  58  and the first face  70 ″ of the bottom strip  34  faces opposite the orientation of the first face  70  of the bottom transition strip  64 . This puts the first face  70  outside the volume of the airbag  28  when the airbag  28  inflates. The first face  70  may be coated. For example, the first face  70  may be coated with a silicone coating to retain an inflation gas longer when the airbag  28  is inflated. 
         [0020]    Fabrication of the intermediate strips  30 , top strip  32 , and bottom strip  34  allows for measurement tolerances. The material strips may be cut from a double layer of material. This results in paired upper and lower strips. An upper strip matches the size of its corresponding lower strip. When the pairs of upper and lower strips are located, an equal number of strips from the center of the intermediate strips  30 , the summed tolerance of the upper strips will be offset by the summed opposite tolerance of the lower strips. 
         [0021]    In a direction perpendicular to a weld of the weld pattern, the top strip  32  and bottom strip  34  have a greater dimension than the intermediate strips  30 . This allows the second edge  52  of the top strip  32  to reach the second edge  56  of the bottom strip  34  for welding. Further, first and second edges of the intermediate strips  30 , top strip  32 , and bottom strip  34  are on non-intersecting lines. The edge joint weld may be made by any suitable welding technique known to one skilled in the art. For example, the welds may be ultrasonic. 
         [0022]      FIG. 3  schematically illustrates the airbag  28  with all first and second edges welded. The weld pattern assembles the intermediate strips  30  into a Z-shaped accordion stack  80 . The airbag  28  has a first end  82  and a second end  84 . The first end  82  and the second end  84  are welded closed so that the volume of the airbag  28  may be inflated. 
         [0023]      FIG. 4  schematically illustrates a packed and uninflated airbag  28 . Connected to the airbag  28  is an inflation input  86 . The inflation input  86  is used to deploy the airbag. The uninflated airbag  28  is secured in the sleeve  88  (illustrated partially cutaway for clarity) of the seatbelt webbing  16 . 
         [0024]      FIG. 5  schematically illustrates an airbag  128 . As  FIG. 5  is a variation of the airbag illustrated in  FIG. 2  and  FIG. 3 , like reference numerals designate corresponding parts in the drawings (but with 100 series element numbers) and detailed description thereof will be omitted. 
         [0025]    A top strip  132  extends beyond a top weld  190  and a bottom strip  134  extends beyond a bottom weld  192 . Beyond welds  190  and  192 , the top and bottom strips  132  and  134 , respectively, are joined by a rip stitch  194 . The rip stitch  194  allows the top and bottom strips  132  and  134 , respectively, to unstitch when airbag  128  inflates. 
         [0026]    The top and bottom strips  132  and  134 , respectively, contain the airbag  28  without needing the sleeve  88  illustrated in  FIG. 4 . The top and bottom strips  132  and  134 , respectively, may be fabricated from a tactilely pleasing material that still allows for gas retention when airbag  128  is inflated. Alternatively, outward faces of the top strip  132  and bottom strip  134 , respectively, may have a tactilely pleasing coating or layer. 
         [0027]    The top and bottom strips  132  and  134 , respectively, are sewn at a joint  196  to a seatbelt webbing  116  by a stitch  198 . Alternatively, the top and bottom strips  132  and  134 , respectively, may be seatbelt webbing. 
         [0028]    While certain embodiments of the present invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.