Abstract:
Systems, methods, and apparatus for use in an airbag inflation system are disclosed. An explosively formable projectile piece is positioned adjacent to an opening and, upon deployment of an initiator, is forced through the opening, thereby changing the shape of the projectile piece. The projectile piece is projected towards a rupturable wall. Once the projectile piece has ruptured the wall, the airbag inflation gas can pass through the opening in the wall and inflate the airbag.

Description:
TECHNICAL FIELD 
   The present invention relates generally to the field of automotive protection systems. More specifically, the present invention relates to systems for inflation of airbags. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Understanding that drawings depict only typical embodiments of the invention and are not therefore to be considered to be limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which: 
       FIG. 1  is a cross-sectional view of one embodiment of an airbag inflation system. 
       FIG. 2A  is a cross-sectional view of an airbag inflation system at a point in time immediately following deployment. 
       FIG. 2B  is a cross-sectional view of the airbag inflation system of  FIG. 2A  showing the explosively formable projectile piece being projected towards a rupturable wall. 
       FIG. 2C  is a cross-sectional view of the airbag inflation system of  FIG. 2B  showing the projectile piece immediately after it ruptures the rupturable wall. 
       FIG. 3  is a cross-sectional view of another embodiment of an airbag inflation system having a slotted opening. 
       FIG. 4  is a cross-sectional view taken along line  4 — 4  in  FIG. 3  showing the slotted opening. 
       FIG. 5  is an end view showing an explosively formable projectile piece following projection through a slotted opening. 
       FIG. 6  is a cross-sectional view of still another embodiment of an airbag inflation system. 
       FIGS. 7A–7E  are cross-sectional views of several embodiments of explosively formable projectile pieces. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   Described below are embodiments of an inflator projectile system used to puncture or otherwise open a burst disk or other rupturable wall of an airbag inflation system. The system uses an initiator, which is stored in a housing. The initiator, once deployed, forces an explosively formable projectile piece through an opening in the housing. As the projectile piece is forced through the opening, its shape is changed. The projectile piece is then typically shot through a rupturable wall, such as a burst disk, which had formerly obstructed a second opening. Once the rupturable wall has been ruptured, fluid communication may take place through the second opening in order to, for instance, allow for inflation of an airbag. 
   With reference now to the embodiment depicted in  FIG. 1 , an airbag  10  connected with an airbag inflation system  100  is shown. The airbag inflation system  100  includes a main housing  105 , an initiator housing  110 , a first opening  107 , a second opening  112 , and an initiator  120 . Initiator  120  in the depicted embodiment comprises a squib. It should be understood that, although the embodiment depicted in  FIG. 1  comprises two housings, a single housing may be used. Alternatively, any number of housings greater than two may be used, each of which is connected with at least one other housing. Likewise, the first and second openings may be in the same housing or, alternatively, they may be in different housings connected with one another. 
   First opening  107  is obstructed with a rupturable wall  125 . Rupturable wall  125  in  FIG. 1  comprises a burst disk. Once burst disk  125  has been ruptured, fluid communication may take place through the first opening  107  and into the airbag  10 . 
   An explosively formable projectile piece  130  is positioned adjacent to a second opening  112 . Explosively formable projectile piece  130  may be formed to a wide variety of shapes and sizes, including the disk-shaped embodiment shown in  FIG. 1 . Projectile piece  130  may also be concave-shaped, or shaped somewhat like a contact lens, as also shown in  FIG. 1 . Of course, whereas the embodiment shown in  FIG. 1  shows the concave side of piece  130  facing away from the initiator  120 , the concave side may instead face initiator  120  if desired. 
   It may also be preferable in some embodiments to provide an explosively formable projectile piece that is thicker or otherwise has more mass towards its center than along its perimeter. In such embodiments, there may be a gradual increase in thickness from the perimeter to the center or there may be a pointed tip, rounded dome, or other bulge at or near the center of the projectile piece. Embodiments of explosively formable projectile pieces including such features will be discussed later with reference to  FIGS. 7A–7E . Configurations having increased mass or thickness at the center may facilitate desirable shaping and flight patterns. It is intended that the term “disk shaped” be construed to encompass the “contact lens” or concave projectile piece embodiment and also some embodiments having increased thickness or otherwise increased mass towards their center. 
   Piece  130  may also be comprised of a variety of different materials, such as armco iron, tantalum, brass, low carbon steel, high strength low-alloy steel, copper, stainless steel, aluminum, nickel-based superalloys, or precipitation hardening stainless steel. In addition to the materials listed, any metallic material with the ductility to deform into a desirable projectile shape and the strength to withstand an explosive blast without fragmenting would be suitable for use as an explosively formable projectile piece. 
   Projectile piece  130  may also be formed using a wide variety of formation processes, such as stamping or impact forming processes. Moreover, it could be built into the squib or other initiator or could be installed at the time the initiator is installed into the inflator system. One embodiment of an explosively formable projectile piece used in testing the invention was a disk ⅜ inch in diameter, about 0.035 inches thick, and had a mass of approximately 500 mg. Obviously, this is but one example of a limitless number of shapes, sizes, and masses that may be suitable for use as an explosively formable projectile piece. 
   The embodiment shown in  FIG. 1  also has a shaping ring  135 . The shaping ring  135  may be a separate piece which is attached to one or both of the housings or, alternatively, it may be integrally formed with a housing. As best seen in  FIG. 1  and  FIG. 2A , shaping ring  135  defines the diameter of the second opening  112 , which is smaller than the diameter of the projectile piece  130  before it is projected. In this manner, as the projectile piece is forced through the second opening by the initiator, the shape of the projectile piece is changed. 
   With reference now to  FIGS. 2A–2C , the deployment of the initiator and associated firing of the explosively formable projectile piece through the rupturable wall will now be discussed further. In  FIG. 2A , airbag inflation system  100  is shown immediately after deployment of the initiator  120 . As can be seen in  FIG. 2A , explosively formable projectile piece  130  is being forced through opening  112 . More specifically, explosively formable projectile piece  130  is being forced through shaping ring  135 . As projectile piece  130  is forced through shaping ring  135 , its shape is changed from the disk shape shown in  FIG. 1  to more of an elongated dome shape, as shown in  FIGS. 2A–2C . 
   Once projectile piece  130  has exited the opening defined by shaping ring  135 , it is then projected towards rupturable wall  125 , as depicted in  FIG. 2B . Explosively formable projectile piece  130  then penetrates rupturable wall  125 , as shown in  FIG. 2C , thereby permitting fluid communication to take place through opening  107  in order to allow airbag  10  to inflate. 
   It may be preferable under certain circumstances to create an opening in the rupturable wall with a greater area to allow for more rapid expansion of the airbag. Under such circumstances, an alternative embodiment such as the embodiment depicted in  FIG. 3  may be used.  FIG. 3  is similar to the embodiments previously discussed, with one exception. Opening  212  in airbag inflation system  200  is a slotted opening. In other words, opening  212 , which is defined by shaping ring  235 , is formed with a series of slots, as best seen in  FIG. 4  at  237 . Although the embodiment shown in  FIGS. 3–4  includes a shaping ring  235  having six slots  237 , any number of slots may be used as desired. Even a single slot may be used, although a shaping ring with a single slot may not facilitate the creation of an opening in a rupturable wall that is as large as a shaping ring with multiple slots. 
   After an explosively formable projectile piece is projected through a slotted opening, such as shaping ring  235  with slots  237 , it will have one or more projections at its perimeter corresponding with the number of slots in the shaping ring.  FIG. 5  is an end view depicting an explosively formable projectile piece  230  following projection through a slotted opening. As can be seen from  FIG. 5 , projectile piece  230  has six projections  232  corresponding with the six slots  237  in shaping ring  235 . A domed tip  233  at the center of projectile piece  230  is also shown in  FIG. 5 . As formerly disk-shaped projectile piece  230  is forced through a slotted opening, each of the slots  237  in the slotted opening forms a projection  232  at the perimeter of the projectile piece. Projections  232  facilitate the creation of tears or petals in burst disk  235 , such that a larger opening is created in the burst disk than would otherwise have been created by a projectile piece having a circular perimeter without projections extending therefrom. 
   Another embodiment of an airbag inflation system is depicted in  FIG. 6  at  300 . This embodiment is similar to the airbag inflation system  200  shown in  FIG. 3 , with one exception. Airbag inflation system  300  includes a slotted opening defined by a shaping ring  335  that is attached to housing  305 , rather than integral with the housing as in airbag inflation system  200  of  FIG. 3 . 
     FIGS. 7A–7E  depict various explosively formable projectile piece embodiments. Each of the embodiments depicted in these figures are disk shaped. In addition, each of the embodiments depicted in  FIGS. 7A ,  7 C, and  7 E are examples of explosively formable projectile pieces having more mass towards their center than along their perimeter. 
   The embodiment shown in  FIG. 7A  includes a pointed or cone-shaped central portion  137 . The embodiment of  FIG. 7C  has a rounded or dome-shaped central portion  137 . The embodiment of  FIG. 7E  also has a dome-shaped central portion  137 , but the central portion of the embodiment of  FIG. 7E  has a more gradual increase in thickness from its perimeter to its center. 
   It should be understood that the principles of certain embodiments of the invention allow for firing a formed metal projectile typically much larger than a “jet” from a shape charge. Moreover, certain embodiments of the invention allow for mechanical forming of the projectile without the use of high explosives, which results in a process that is typically much safer and more controlled for use in automotive inflation systems. 
   It will be obvious to those having skill in the art that many changes may be made to the details of the above-described embodiments without departing from the underlying principles of the invention. The scope of the present invention should, therefore, be determined only by the following claims.