Patent Publication Number: US-2006011495-A1

Title: Pyrotechnic safety device and method of use

Description:
FIELD OF THE INVENTION  
      The present invention relates generally to an apparatus for use with the transport of a pyrotechnic device, and more specifically to an apparatus and method for safely transporting an air bag inflator used in vehicle air bag safety systems.  
     BACKGROUND AND SUMMARY  
      This invention generally relates to the field of transportation of pyrotechnic systems such as for example and without limitation a vehicle airbag system having a pyrotechnic device such as an initiator in combination with an inflator. Several references disclose the operation of conventional airbag systems, including, for example, U.S. Pat. Nos. 5,454,593; 5,683,102; and 6,669,226, the disclosures of which are incorporated herein by reference. One or more conventions, rules, guidelines or regulations, including without limitation regulations of the United States Department of Transportation and a United Nations document entitled “The Recommendations on the Transport of Dangerous Goods Manual of Tests and Criteria,” which is incorporated herein by reference, require that pyrotechnic devices be somewhat heat and flame resistant during transport or travel. For example and without limitation test  6   a  of The Recommendations on the “Transport of Dangerous Goods Manual of Tests and Criteria” describes a bonfire test that such a pyrotechnic system or device must undergo and pass.  
      An illustrative inflator may contain pressurized gas, which is released or discharged into the airbag when the igniter ruptures the inflator under normal conditions. The igniter may also rupture the inflator causing discharge of the pressurized gas under abnormal conditions such as caused by a fire, flame, or excessive heat as described in the bonfire test of test  6   a  noted above. An abnormal condition may also melt the passageway by which the discharging gas normally is vented into the airbag. If such an abnormal or high heat condition occurs during transport of the pyrotechnic system or the pyrotechnic device, then the energy or force of the discharging gas may cause the pyrotechnic device to shoot off like a missile or other projectile. What is needed is a pyrotechnic safety device that dissipates the energy of the discharging gas.  
      The pyrotechnic safety device disclosed herein comprises one or more of the features identified in the various claims appended to this application and combinations of such features as well as one or more of the following features or combinations thereof. A pyrotechnic safety device generally comprises a pyrotechnic device, a conduit or hose, and airbag, and an airbag input channel. The pyrotechnic device is equipped coupled to the conduit or hose. The hose is generally flexible and heat and fire resistant. The hose illustratively may have a rubber or silicon rubber outer layer surface and a fiberglass inner layer or surface. The hose remains coupled to the pyrotechnic device during an abnormal event such as fire or high heat. If the abnormal event causes autoignition of the pyrotechnic device and a resultant discharge or release of pressurized gas, then the hose will dissipate the energy of the discharged gas. The hose may receive therein an input passageway having one end in fluid communication with the pyrotechnic device and another end in fluid communication with an airbag. A method of preventing projectile movement of a pyrotechnic device comprising the steps of coupling together the pyrotechnic device and a heat and flame resistant conduit, configuring the conduit to remain coupled with the pyrotechnic device when the pyrotechnic device is subjected to a heat source sufficient to cause autoignition of the pyrotechnic device, and allowing the conduit to dissipate the energy produced by a gas generated by the pyrotechnic device as a consequence of autoignition is also disclosed.  
      These and other features of the present invention will become more apparent from the following description of the illustrative embodiments. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  is a diagramatic view of an illustrative pyrotechnic safety device.  
       FIG. 2  is a sectional view through an illustrative conduit depicted in  FIG. 1  taken generally along the line  2 - 2 .  
       FIG. 3  is a sectional view through an illustrative conduit and input passage way depicted in  FIG. 1  taken generally along the line  3 - 3 . 
    
    
     DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENT  
      For the purposes of promoting an understanding of the principles of the invention, reference will now be made to an illustrative embodiment depicted in the drawings. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended.  
      Referring now to  FIG. 1 , there is shown an illustrative pyrotechnic safety device or system  20  comprising generally a pyrotechnic safety device or conduit  10 , a pyrotechnic device  22 , an airbag  18 , and an airbag input passageway  16 .  
      The pyrotechnic device  22  generally includes in combination an igniter or initiator and an airbag inflator. The pyrotechnic device  22  generally is in fluid communication with the air bag  18 . For example, the airbag input passageway  16  is coupled to the output of the inflator of the pyrotechnic device  22 . The passageway  16  illustratively may comprise a tube and/or a tube within a sleeve, which, like the airbag  18  may be fashioned out of any material suitable for containing hot expanding gases such as for example and without limitation nylon 12, nylon 6,6 or polyester fiber.  
      As best seen in  FIG. 2 , the pyrotechnic safety device or conduit  10  generally comprises a heat and flame resistant outer surface or layer  12 . For example and without limitation, the outer layer may be fashioned out of a rubber material, such as for example and without limitation a silicon rubber, or of a ceramic or composite material that is heat and flame resistant. It will be appreciated however that any heat and flame resistant material capable of passing the bonfire test may be used. Illustratively, the conduit  10  has an elongated cylindrical cross section, although conduits with other cross sections fall within the scope of the invention. For example and without limitation, the conduit  10  may be an elongated tube or a hose  10 . Illustratively, the conduit or hose  10  is flexible or semi-flexible and may comprise an inner layer  14 . The inner layer  14  may be for example and without limitation fiberglass or other suitable material. The inner layer may, for example and without limitation, be homogeneous, or may instead be braided, interwoven, or the like. In addition to providing some structure to the conduit  10 , it may also provide further heat and flame resistance. The outer layer  12  may or may not be bonded to the inner layer  14 .  
      Referring to  FIG. 3 , it can be seen that the hose or conduit  10  is sized to receive therein the airbag passageway  16 , which is in fluid communication with the airbag  18  and the inflator or pyrotechnic device  22 . Illustratively, hose clamp  15  is fitted around the conduit or hose  10  and the passageway  16  received within the hose  10  in order to couple together the hose  10 , the passageway  16  and the pyrotechnic device  22 . It will be appreciated that the passageway  16  need not extend all the way through the hose  10 , but instead could be coupled to the hose separate and apart from the pyrotechnic device  22 , such that one end of the hose  10  is in fluid communication with the pyrotechnic device  22  and the other end of the hose is in fluid communication with the passageway  16 .  
      The assembled pyrotechnic safety system  20  has the airbag input passageway or tube  16  received within the conduit or hose  10 , which hose  10  is coupled with the pyrotechnic device  22 , and the airbag input passageway is coupled in fluid communication at one end with the pyrotechnic device  22  and in fluid communication at the other end with the airbag  18 . When the pyrotechnic safety device or system  20  is subjected to abnormal heat or flame such that autoignition of the pyrotechnic device  22  causing the discharge of pressurized gas from the inflator, then all or a portion of the input passageway may melt or disintegrate. So too, portions of the conduit or hose  10  may melt; however, the structural integrity of the hose  10  will substantially be retained and the hose  10  will remain coupled to the pyrotechnic device  22 . For example the outer layer  12  and/or the inner layer  14  may retain its structural integrity. The retention of this structural integrity will allow the discharged gas to be received within the hose  10  and/or within the portions of the input channel received within the hose or conduit  10 . The hose  10  and/or the portions of the input channel received within the hose or conduit  10  will illustratively flap about as the discharged gas is received therein and exhausted at the end that is no longer connected to the airbag  18 . Because the hose flaps about, there is insufficient directed thrust to cause the pyrotechnic device to become a projectile or to fly off in a projectile motion. Of course, if the abnormal event is sufficient to causes autoignition but insufficient to melt the input passageway  16  such that the airbag  18  is still in fluid communication with through the passageway  16  with the pyrotechnic device  22 , then the discharged gas will inflate the airbag  18  and the pyrotechnic device  22  will not become a projectile.  
      Illustratively, the hose or conduit  10  may be any suitable length. Tests have proven that a hose or conduit  10  about 12 inches in length are suitable to dissipate the energy of the gas discharged due to an abnormal autoignition event. Conduits or hoses in excess of 12 inches are also suitable to dissipate the energy generated by autoignition. In addition, conduits or hoses of less than 12 inches in length, for example and without limitation, hoses about four inches in length or greater fall within the scope of the invention.  
      A method of preventing projectile movement of a pyrotechnic device comprises the steps of coupling together a pyrotechnic device  22  and a heat and flame resistant conduit  10 . The conduit is configured  10  to remain coupled with the pyrotechnic device  22  when the pyrotechnic device is subjected to a heat source sufficient to cause autoignition of the pyrotechnic device  22 , and the conduit is allowed to dissipate the energy produced by a gas generated by the pyrotechnic device as a consequence of autoignition.  
      While the invention has been illustrated and described in detail in the foregoing drawings and description, the same is to be considered as illustrative and not restrictive in character, it being understood that only illustrative embodiments thereof have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.