Abstract:
An airbelt inflator ( 10 ) is provided for supplying and directing gas from the combustion of pyrotechnic materials into an inflatable safety belt or airbag. The airbelt inflator ( 10 ) includes a substantially cylindrical body ( 12 ). One or more ledges ( 26, 42 ) are defined by the junctions of inner walls ( 34, 36 , and  38 ) wherein each ledge ( 26, 42 ) functions to retain an inner inflator component. In another aspect of the invention, an enhancer disc ( 56 ) features a metallic density greater than an associated filter ( 48 ) whereby tailoring of the density of the metallic disc ( 56 ) facilitates a quick and easy method of modifying the gas flow exiting the inflator ( 10 ).

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]    The present application claims the benefit of U.S. Provisional Application No. 60/358,790 filed on Feb. 22, 2002. 
     
    
     
       FIELD OF THE INVENTION  
         [0002]    The present invention relates to vehicle occupant protection systems, and specifically to a gas generator or inflator that provides an adjustable gas output rate, and an enhanced thrust for airbelts or side impact airbags, for example, while minimizing the size of the inflator.  
         BACKGROUND  
         [0003]    Ongoing improvements in vehicle occupant protection systems include the advent of sub systems such as a side impact airbag and an airbelt system. To facilitate such systems, a gas generator featuring an adjustable gas output rate, an enhanced thrust and a minimal size is desired. Although many of the state-of-the-art gas generators are useful in these contexts, improving the thrust, ready tailoring of the gas output, and minimizing the size of the inflator presents certain advantages over known inflators.  
         SUMMARY OF THE INVENTION  
         [0004]    In a preferred embodiment, the above referenced concerns are resolved by an airbelt inflator ( 10 ) provided for supplying and directing gas from the combustion of pyrotechnic materials into an inflatable safety belt or airbag. The airbelt inflator ( 10 ) comprises a substantially cylindrical inflator body ( 12 ) having a first end ( 14 ) and a second end ( 16 ). An initiator assembly ( 18 ) is positioned in the inflator body ( 12 ) adjacent the first end ( 14 ), and rests upon an interior ledge ( 26 ). A filter assembly ( 48 ) is positioned in the inflator body ( 12 ) proximate the second end ( 16 ), and rests upon a second interior ledge ( 42 ), being separated from the initiator assembly ( 18 ) by a cavity containing gas generant tablets ( 32 ). An output enhancer ( 56 ) is placed in intimate association and in coaxial alignment with the filter assembly ( 48 ) and a gas output disk ( 52 ), the gas output disk itself being adjacent a nozzle adaptor ( 50 ) positioned at the second end ( 16 ). Crimping the second end ( 16 ) of the inflator body ( 12 ) secures the nozzle adaptor ( 50 ), gas output disk ( 52 ), the output enhancer ( 56 ), and the filter assembly ( 48 ). Assembly of the airbelt inflator ( 10 ) begins by inserting the pre-assembled initiator assembly ( 18 ) into the inflator body ( 12 ) until it rests upon the ledge ( 26 ), then crimping the end ( 14 ) of the inflator body ( 12 ) to hold the initiator ( 18 ) in place. Once the initiator ( 18 ) is secured, the inflator body ( 12 ) can be inverted, and the main propellant tablets ( 32 ), filter assembly ( 48 ), output enhancer ( 56 ), and the nozzle adaptor ( 50 ) can be loaded into the inflator ( 10 ). Output enhancers having different densities may be incorporated into the inflator body to reduce or increase the relative rate of gas output. Finally, the second end ( 16 ) of the inflator body ( 12 ) is crimped to secure the components, completing assembly. 
       
    
    
     BRIEF DESCRIPTION OF DRAWINGS  
       [0005]    [0005]FIG. 1 is a cross-sectioned view of a gas generator in accordance with the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0006]    Referring to FIG. 1, there is shown an airbelt inflator  10  according to a preferred constructed embodiment of the present invention. Inflator  10  is preferably designed for supplying and directing gas from the combustion of pyrotechnic materials into an inflatable vehicle safety airbelt, but is not thereby limited in use. Exemplary, but not limiting airbelts are described in U.S. Pat. Nos. 6,439,601; 6,170,863; 6,145,873, and 6,142,512, the teachings of which are herein incorporated by reference.  
         [0007]    Inflator  10  includes a substantially cylindrical inflator body or housing  12 , preferably metallic, having a first end  14  and a second end  16 . It is contemplated that ceramic, polymeric, and other suitable materials may be useful in manufacturing the various components of inflator  10 . An initiator assembly  18  having a first outer diameter is positioned in inflator body  12  within first end  14 , and preferably held in place by crimping first end  14  in a conventional manner. Initiator assembly  18  includes an initiator body  20  with an attached igniter  22 . The igniter  22  or squib has a set of electrical contacts  24  preferably accessible from first end  14 . Igniter  22  is preferably a conventional igniter such as that taught in U.S. Pat. Nos. 5,934,705 or 5,727,813, herein incorporated by reference, and is preferably connected to an automobile electrical system by which it may be activated in a conventional manner. In the preferred embodiment, body  20  rests upon a first interior ledge  26  of inflator body  12  and is held by a crimp at first end  14 , although it should be appreciated that some other suitable affixing method such as threads or snap-fitting might be used without departing from the scope of the present invention. An elastomeric O-ring  28  is preferably positioned in an annulus  30  encircling initiator body  20  and creating a fluid-tight seal with inflator body  12 .  
         [0008]    In accordance with the present application, a first inner wall  34  is formed proximate the first end  14 , and defines a first diameter about equal to the outer diameter of the initiator assembly. A second inner wall  36  is formed proximate the second end  16  and defines a second diameter. As shown in FIG. 1, the first and second diameters are essentially equal, although the present invention is not thereby limited. A third inner wall  38  is formed intermediate of the first and second inner walls  34  and  36 , and forms a third diameter thereby containing a bed of propellant tablets  32 . A first ledge  26  is formed at a point  40  where the first inner wall  34  and the third inner wall  38  meet. If desired, a second ledge  42  is formed at a point  44  where the second inner wall  36  and the third inner wall  38  meet. Each ledge represents an integral structural obstruction within the housing  12  that facilitates discrete placement or orientation of inflator components without the need for welding.  
         [0009]    The plurality of tablets of a main propellant charge  32 , are positioned within the interior of inflator body  12 , and are ignitable by igniter  22  in a conventional manner. The charge or gas generant composition may be any suitable propellant known in the art, and is preferably a non-azide propellant. Exemplary, but not limiting, compositions are described in U.S. Pat. Nos. 5,872,329, 5,756,929, and 5,386,775, herein incorporated by reference. A second charge consisting of an autoignition material  46  is preferably positioned within inflator body  12  adjacent the main charge  32 , and is ignitable in a conventional manner. A filter  48  is positioned within inflator body  12  adjacent the propellant charges  32  and  46 . In a preferred embodiment, filter  48  is a well-known conventional metallic mesh filter, however, some other suitable type of filter might be used. The second ledge  42  preferably abuts filter  48 , and assists in maintaining the various components of inflator  10  in their desired positions.  
         [0010]    Turning to second end  16 , a preferably metallic nozzle adaptor  50 , is fixed therein and directs the flow of combustion gases out of inflator body  12  and into an inflatable airbelt or airbag (not shown). Nozzle adaptor  50  is also preferably held in place by crimping the second end  16  of inflator body  12 , however, it might also be affixed with threads, adhesives, welds or some other suitable attachment method. A perforated gas output disk  52  is positioned adjacent nozzle adaptor  50 , and preferably has a second elastomeric O-ring  54  around its circumference, creating a fluid-tight seal at second end  16 .  
         [0011]    In yet another aspect of the invention, an enhancer disc  56  is oriented intermediate of filter  48  and at end  16 , and is juxtaposed against the filter  48  in coaxial alignment therewith. The metallic density of the enhancer disc  56  is tailored to accommodate the desired gas flow rate depending on design criteria. As such, the present inflator may be tailored to modify the gas flow rate from the inflator by altering the metallic density of the enhancer disc  56 . Stated another way, the metallic density of disc  56  generally exceeds that of filter  48 , wherein the metallic density of disc  56  may be modified to be slightly greater to much greater relative to the metallic density of filter  48 . Known suppliers such as Wayne Wire Cloth of Hillman, Mich. or Expan Metal of Saginaw, Mich. may supply filter  48  and the enhancer disc  56 . A burst shim  58  seals the enhancer disc  56  thereby facilitating a pressure increase within the inflator  10  for combustion of propellant  32 .  
         [0012]    Assembly of inflator  10  preferably begins by inserting the pre-assembled initiator assembly  18  into inflator body  12  until it rests upon ledge  26 , then crimping the edges of the first end  14  toward the interior of inflator body  12  to secure initiator assembly  18  therein. Once initiator assembly  18  has been inserted, inflator body  12  is inverted, and the main propellant tablets  32  are loaded. Next, the autoignition material  46  is added, followed by the filter  48 . The filter  48  is preferably biased against the second ledge  42  whereby the outer diameter  49  of the filter  48  is essentially equal to the second diameter defined by the inner wall  36 . Assembly of inflator  10  is completed by serially loading the enhancer disk  56 , burst shim  58 , gas output disk  52 , and finally nozzle adaptor  50 . Nozzle adaptor  50  is preferably secured by crimping the edges of second end  16  about the adapter  50 . The various components herein described as positioned in inflator body  12  are all preferably substantially discoidal.  
         [0013]    In the event of an impact, sudden vehicle deceleration, or other desired condition, an electrical signal is sent to igniter  22  from an onboard electronic controller (not shown) in a conventional manner. Igniter  22  subsequently ignites the gas generant tablets  32  located within inflator body  12 . If desired, a booster material (not shown) can be included in inflator  10  to facilitate ignition of the main charge  32 . Ignition of tablets  32  results in the very rapid creation of combustion gases in inflator body  12 , and a consequent very rapid rise in the internal gas pressure in inflator body  12 . When the internal gas pressure has risen to a sufficient level, it ruptures burst shim  58 . The combustion gas passes through filter  48 , thereby removing slag, then through enhancer disk  56 , gas output disk  52 , and finally into an associated airbelt or airbag via nozzle adaptor  50 .  
         [0014]    Airbelt inflator  10  represents a relatively simple design, is light in weight, and uses relatively few components. The manufacturing of inflator  10  is thus relatively easy and inexpensive. In addition, inflator  10  is capable of meeting any required gas output without compromising its structural integrity. Inflator  10  is preferably positioned in a vehicle B-pillar, and operable to direct inflation gas into an inflatable safety restraint belt when activated by a conventional vehicle sensing system known in vehicle occupant protection systems. However, inflator  10  might also be positioned in a vehicle C-pillar, or even elsewhere in the vehicle. Furthermore, inflator  10  is not limited in application to vehicle airbelts, and could be applicable to conventional vehicle airbags as well. It should be understood that the present description is for illustrative purposes only and should not be construed to limit the breadth of the present invention in any way. Thus, those skilled in the art will appreciate that various modifications might be made to the presently disclosed embodiments without departing from the spirit and scope of the present invention, as indicated in the appended claims.