Abstract:
An apparatus ( 10 ) for helping to protect an occupant of a vehicle ( 12 ) comprises a vehicle occupant protection device ( 14 ) that is inflatable between a part ( 16 ) of the vehicle and a vehicle occupant. The apparatus ( 10 ) also comprises an inflation fluid source ( 24 ) that is actuatable to direct into the vehicle occupant protection device ( 14 ) both gas for initially inflating the vehicle occupant protection device and materials ( 82, 124 ) for forming a low-density closed cell foam material in the vehicle occupant protection device. The closed cell foam material assists in maintaining the vehicle occupant protection device ( 14 ) in an inflated condition.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a vehicle safety apparatus and, in particular, to an inflator for an inflatable vehicle occupant protection device, such as an inflatable curtain. 
     BACKGROUND OF THE INVENTION 
     It is known to inflate a vehicle occupant protection device to help protect a vehicle occupant. The vehicle occupant protection device is inflated by inflation fluid from an inflator. One particular type of vehicle occupant protection device is an inflatable curtain that is inflatable into a position between the vehicle occupant and the side structure of the vehicle to help protect the vehicle occupant in the event of a side impact to the vehicle and/or a vehicle rollover. It may be desirable for the inflatable curtain to remain inflated for an extended period of time. 
     SUMMARY OF THE INVENTION 
     The present invention is an apparatus for helping to protect an occupant of a vehicle. The apparatus comprises a vehicle occupant protection device that is inflatable between a part of the vehicle and a vehicle occupant. The safety apparatus also comprises an inflation fluid source that is actuatable to direct into the vehicle occupant protection device both gas for initially inflating the vehicle occupant protection device and materials for forming a low-density closed cell foam material in the vehicle occupant protection device. The closed cell foam material assists in maintaining the vehicle occupant protection device in an inflated condition. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other features of the present invention will become apparent to one skilled in the art to which the present invention relates upon consideration of the following description of the invention with reference to the accompanying drawings, in which: 
     FIG. 1 is a schematic view of a vehicle safety apparatus in a deflated condition according to the present invention; 
     FIG. 2 is a schematic view of the vehicle safety apparatus of FIG. 1 in an inflated condition; and 
     FIG. 3 is a sectional view of an inflator assembly that forms a part of the vehicle safety apparatus of FIG.  1 . 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     As representative of the present invention, a vehicle safety apparatus  10  helps to protect an occupant of a vehicle  12 . As shown in FIGS. 1 and 2, the safety apparatus  10  includes a vehicle occupant protection device in the form of an inflatable curtain  14  that is mounted adjacent to a side structure  16  and a roof  18  of the vehicle  12 . The side structure  16  of the vehicle  12  includes side windows  20 . An inflation fluid source comprises an inflator assembly  24  that is connected in fluid communication with the inflatable curtain  14  through a fill tube  22 . 
     The fill tube  22  has a first end portion  30  for receiving fluid from the inflator assembly  24 . The fill tube  22  has a second end portion  32  disposed in the inflatable curtain  14 . The fill tube  22  has a plurality of openings (not shown) that provide fluid communication between the fill tube and the inflatable curtain  14 . It will be recognized by those skilled in the art, however, that the vehicle safety apparatus  10  may have alternative configurations. For example, the fill tube  22  may be omitted and the inflator assembly  24  may be connected directly to the inflatable curtain  14 . 
     The inflator assembly  24  may have a variety of configurations. As representative of the present invention, the inflator assembly  24  is illustrated in FIG.  3 . The inflator assembly  24  includes a housing  40 , a first vessel  42 , and a second vessel  44 . 
     The housing  40  includes a body  50  having first and second end surfaces  52  and  54 , respectively. An inner surface  56  of the housing  40  defines a central chamber  58  in the housing. The body  50  is centered on an axis  60  and has a first end  62  and an opposite second end  64 . The first and second ends  62  and  64  are spaced apart along the axis  60 . 
     The body  50  includes a first wall portion  70  located at the first end  62  of the housing. The first wall portion  70  defines a first chamber portion  72  that is centered on the axis  60  and extends from the first end  62  of the body  50  to the central chamber  58 . The first vessel  42  is connected to the first wall portion  70  and is also centered on the axis  60 . The first chamber portion  72  is in fluid communication with a chamber of the first vessel  42 . The first vessel  42  is secured to the first wall portion  70  of the housing  40  by a weld, but could alternatively be secured by other known techniques, such as brazing or screw threads. The first vessel  42  includes an axially extending, cylindrical side wall  74  and a domed end wall  76 . 
     The first vessel  42  and the first chamber portion  72  define a first fluid storage chamber  80 . The first fluid storage chamber  80  contains a quantity of a first inflation fluid  82  that comprises a combination of a pressurized volume of a gas and a foaming agent material. A rupturable burst disk  84  is secured to the body  50  and blocks flow of the first inflation fluid  82  out of the first fluid storage chamber  80 . 
     The body  50  includes a portion  100  (shown on the right side of FIG.  3 ). The portion  100  includes an inlet passage  102  that is centered on a lateral axis  104  of the housing  40 , which extends perpendicular to the axis  60 . The inlet passage  102  extends from the first end surface  52  of the body  50  to the central chamber  58 . The second vessel  44  is connected to the portion  100  and is centered on the lateral axis  104 . The inlet passage  102  provides fluid communication between the second vessel  44  and the central chamber  58 . The second vessel  44  is secured to the portion  100  of the body  50  by screw threads, but could alternatively be secured by other known techniques, such as welding or brazing. The second vessel  44  has an axially extending, cylindrical side wall  110  and a domed end wall  112 . 
     The second vessel  44  has a central opening  114  in fluid communication with the inlet passage  102 . A rupturable portion  116  of the second vessel  44 , such as a burst disk or foil membrane, is secured to an inner end portion  120  of the second vessel  44 . The rupturable portion  116  closes the second vessel  44 , forming a second fluid storage chamber  122  defined by the side wall  110 , the end wall  112  and the rupturable portion  116 . The second fluid storage chamber  122  contains a quantity of a second inflation fluid  124  that comprises a combination of a pressurized volume of a gas and a foam reactant material. The rupturable portion  116  blocks flow of the second inflation fluid  124  out of the second fluid storage chamber  122  through the central opening  114  of the second vessel  44 . 
     The inlet passage  102  includes a threaded portion  130  that receives a threaded end portion  132  of the second vessel  44 . The threaded end portion  132  of the second vessel  44  is screwed into the threaded portion  130  of the inlet passage  102 . The threaded end portion  132  retains a spring  134  and a needle  136  in the inlet passage  102  when the second vessel  44  is screwed into the threaded portion  130 . 
     The needle  136  is hollow and includes an inflation fluid passage  140 , which extends through the entire length of the needle  136 . The needle  136  has a sharpened end portion  142  disposed in the central opening  114  of the second vessel  44 , adjacent to the rupturable portion  116  of the second vessel. The needle  136  has an inner end portion  144  exposed to the fluid pressure in the central chamber  58  of the housing  40 . The spring  134  biases the needle  136 , against the fluid pressure in the central chamber  58 , into a position such that the sharpened end portion  142  of the needle is spaced apart from the rupturable portion  116  of the second vessel  44 . 
     The body  50  also includes an outlet portion  150 . The outlet portion  150  is located along the lateral axis  104  and is spaced opposite the portion  100 . The outlet portion  150  includes an outlet passage  152  that extends from the second end surface  54  of the body  50  to the central chamber  58 . The first end portion  30  of the fill tube  22  is connected to the outlet portion  150  by known means such as screw threads or a weld. The outlet passage  152  provides fluid communication between the central chamber  58  and the fill tube  22 . 
     An electrically actuatable initiator  154  of a known construction is mounted on the second end  64  of the body  50  and projects into the central chamber  58 . The initiator  154  is actuatable to actuate the inflator assembly  24 . The vehicle  12  includes a sensor  160  (FIGS. 1 and 2) for sensing a collision or a rollover involving the vehicle and for actuating the inflator assembly  24  in response to the sensing of the collision or rollover. The sensor  160  may include a sensor and vehicle electric circuitry for actuating the inflator assembly  24  in response to sensing a vehicle acceleration or deceleration indicative of a vehicle collision having a severity greater than a predetermined threshold value. The sensor  160  provides an electric signal over lead wires  162  to the initiator, when the inflator assembly  24  is to be actuated. 
     In the event of an impact to the vehicle  18  of a magnitude greater than the predetermined threshold value or a vehicle rollover, the sensor  160  provides an electrical signal over the lead wires  162  to the initiator  154 . The initiator  154  is actuated in a known manner to rupture the burst disk  84 . The first inflation fluid  82  is released from the first fluid storage chamber  80  and flows into the central chamber  58 . 
     The first inflation fluid  82  flows through the central chamber  58 , through the outlet passage  152  and into the fill tube  22 . The fill tube  22  directs the first inflation fluid  82  into the inflatable curtain  14 . The inflatable curtain  14  is initially inflated by the first inflation fluid  82 . The inflatable curtain  14  is inflated away from the vehicle roof  18  and into a position between a part of the vehicle  12  and an occupant of the vehicle. In the illustrated embodiment, the inflatable curtain  14  is inflated into a position between the side structure  16  of the vehicle  12  and the vehicle occupant. 
     As the first inflation fluid  82  flows into the central chamber  58 , the fluid pressure in the central chamber  58  increases. The increasing fluid pressure in the central chamber  58  acts on the inner end portion  144  of the needle  136  and overcomes the biasing of the spring  134 , causing the needle to move towards the rupturable portion  116  of the second vessel  44 . The sharpened end portion  142  of the needle  136  moves into engagement with and ruptures the rupturable portion  116  of the second vessel  44 . The second inflation fluid  124  flows from the second fluid storage chamber  122  to the central chamber  58  through the inflation fluid passage  140  in the needle  136 . The second inflation fluid  124  is combined with the first inflation fluid  82  in the central chamber  58 . The mixture of first and second inflation fluids  82  and  124  flows through the outlet passage  152  and the fill tube  22  and into the inflatable curtain  14 . 
     When the first and second inflation fluids  82  and  124  are mixed together, the foaming agent of the first inflation fluid  82  reacts with the foam reactant of the second inflation fluid  124  to generate a low-density closed cell foam material. The closed cell foam material may be any suitable foam material, such as a polyurethane foam material or a polyester foam material. For example, if a polyurethane foam material is desired, the foaming agent of the first inflation fluid  82  would preferably be a polyether polyol, such as polyether glycol. The foaming agent could also include flame retardant and/or flame resistant ingredients. The foam reactant of the second inflation fluid  124  would preferably be an organic isocyanate, such as an aromatic isocyanate. An example of such an aromatic isocyanate is tolulene isocyanate. 
     The gas of the first and second inflation fluids  82  and  124  is an inert gas such as argon, nitrogen or carbon dioxide. The gas of the first and second inflation fluids  82  and  124  acts as a blowing agent that carries the foaming agent and foam reactant from the inflator assembly  24  into the inflatable curtain  14 . The gas of the first and second inflation fluids  82  and  124  also fills the closed cells of the foam material generated by the reaction of the foaming agent and foam reactant. 
     As the foam material is generated in the inflatable curtain  14 , the volume of the foam material increases. The combined first and second inflation fluids  82  and  124  continue to generate the foam material after the inflator assembly  24  stops propelling the inflation fluids into the inflatable curtain  14 . The volume of the foam material continues to increase as the gas pressure in the inflatable curtain  14  drops. This helps to maintain the inflatable curtain  14  in an inflated condition throughout the duration of a vehicle collision and/or vehicle rollover. Also, as the foam material is produced by the reacting first and second inflation fluids  82  and  124 , heat is generated, which may help to maintain the gas pressure in the inflatable curtain  14 , and thus may help to maintain the curtain in an inflated condition. The inflatable curtain  14  is maintained in the inflated condition for at least four seconds. 
     From the above description of the invention, those skilled in the art will perceive improvements, changes and modifications in the invention. Such improvements, changes and modifications within the skill of the art are intended to be covered by the appended claims.