Air bag gas inflator

A gas generator for an air bag, comprising:

• an outer shell vessel having a pressurized gas accommodating chamber for storing a gas therein, a first opening and a second opening for discharging the gas from said gas accommodating chamber, said first opening being sealed by a rupturable partition wall such that the gas is released into the air bag when said rupturable partition wall is ruptured;
• ignition means disposed within said outer shell vessel and adapted to rupture said partition wall upon receiving a first operation signal;
• gas generating means for generating gas to increase a pressure of the gas inside said gas accommodation chamber when said ignition means operates;
• and
• a gas discharge chamber for selectively prohibiting the gas from being discharged from said second opening, said gas discharge chamber including,
• a discharge port in communication with an atmosphere,
• a gas sealing plate for sealing said second opening, said gas sealing plate ruptures and releases the gas when said ignition means operates and the pressure of the gas inside the gas accommodation chamber increases,
• a pyrotechnic that activates upon receiving a second operation signal, and
• a piston member that moves, upon activation of said pyrotechnic, from a first position that permits the gas to discharge from said second opening, and a second position that closes said second opening to prohibit the gas from being discharged from said second opening.