Dual stage inflator

A dual stage inflator capable of producing at least a first output level and a second output level, comprising:

• (a) a pressure vessel, said pressure vessel comprising at least one exhaust nozzle adapted to permit passage of gases within said pressure vessel out of said pressure vessel;
• (b) a first chamber within said pressure vessel, comprising:
• (i) a first gas-generant cup comprising at least one sidewall;
• and
• (ii) a lid positioned across an open top of the first gas-generant cup;
• (iii) a first gas-generant charge disposed in the first gas-generant cup and present in an amount sufficient to generate the first output level;
• and
• (iv) a first initiator assembly adjacent said first gas-generant charge and capable of initiating said first charge;
• and
• (c) a second chamber within said pressure vessel and separated from said first chamber by a one-way seal, said second chamber comprising:
• (i) a cylinder having a bottom and a top and extending into the first chamber, the cylinder bottom sealed against the pressure vessel and the cylinder top sealed by the one-way gas seal;
• (ii) a second gas-generant charge disposed in the cylinder and present in an amount sufficient to generate enough output to combine with the first output level to form the second output level;
• and
• (iii) a second initiator assembly adjacent the second gas-generant charge and capable of initiating said second charge independent of the first charge.

A dual stage inflator capable of producing a gas output modulated between at least a first output level and a second output level, said dual stage inflator comprising:

• (a) a pressure vessel, having a discoidal shape, and comprising at least one exhaust nozzle adapted to permit passage of gases within said pressure vessel out of said pressure vessel;
• (b) a first non-pressurizable chamber within said pressure vessel, said first non-pressurizable chamber comprising:
• (i) a first gas-generant charge present in an amount sufficient to generate the first output level;
• and
• (ii) a first initiator assembly adjacent said first gas-generant charge and capable of initiating said first charge;
• and
• (c) a second non-pressurizable chamber within said pressure vessel, said second non-pressurizable chamber, comprising:
• (i) a second gas-generant charge present in an amount sufficient to combine with the first gas-generant charge to generate the second output level;
• and
• (ii) a second initiator assembly adjacent said second gas-generant charge and capable of initiating said second charge independent of said first charge;
• wherein
• said second chamber is separated from said first chamber by a one-way seal comprising a second chamber lid, said second chamber lid configured and adapted to inhibit passage of gas from said first chamber to said second chamber prior to initiation of said second gas generant charge, and, upon combustion of said second gas-generant charge, to at least partially open, thereby forming an opening defined by said second chamber lid and said second chamber to permit passage of gas from said second chamber to said first chamber upon initiation of said second gas-generant charge.

A method for producing a total gas output level modulated between a first gas output level and a second gas output level from a dual stage inflator having a single pressure vessel comprising at least two non-pressurizable independently initiatable chambers, the dual stage inflator comprising a first mode of operation in which the first chamber only is initiated to produce a minimum gas output level, a second mode of operation in which the second chamber only is initiated to produce a maximum gas output level, a third mode of operation in which the first and second chambers are initiated simultaneously to produce the maximum gas output level, and a fourth mode of operation in which the first chamber is initiated followed by initiation of the second chamber after a delay to produce an intermediate gas output level, comprising:

• (a) determining the total output level;
• and
• (b) selecting an appropriate mode of operation;
• wherein
• initiation of either one of the second or third modes of operation produces a maximum mass of gas pressure and a maximum mass flow rate and the initiation of the first chamber followed by the second chamber after a delay produces an intermediate mass of gas and an intermediate mass flow rate, and the ratio of the maximum mass of gas to the intermediate mass of gas is less than the ratio of the maximum mass flow rate to the intermediate mass flow rate.