Liquid-fueled device to combine the functions of a low pressure switch (LPS), squib, and gas generator

A combination low pressure switch/initiator/gas generator device for an inflator of a hybrid inflatable air bag safety restraint system that includes a storage chamber containing stored inert inflation gas under high pressure comprising,

• an ignition train and pressure differential switch positioned in said storage chamber,
• said ignition train and differential switch comprising first and second diaphragms each of which is electrically conducting,
• electrically non-conductive spacer means having a first side and a second side, attaching means attaching said first diaphragm and said second diaphragm in opposed and sealing relation to said first and second sides, respectively, of said spacer means thereby forming a hermetically sealed chamber with said first diaphragm and said second diaphragm being movable toward and away from each other from a spaced relationship as the pressure in said inflator storage chamber increases and decreases relatively to the pressure in said hermetically sealed chamber,
• pyrotechnic means contained in said hermetically sealed chamber, said pyrotechnic means comprising a liquid fuel, a high pressure oxidizing environment, and squib means having a housing to effect ignition in said oxidizing environment of said fuel,
• a pressure monitoring resistor having first and second ends with said ends positioned so as to make and break electrical contact with said first and second diaphragms as said first and second diaphragms are moved toward and away from each other from a predetermined spaced relationship, and
• electrical circuit means to which said pressure monitoring resistor is connected when said ends of said pressure monitoring resistor are in electrical contact with said first and second diaphragms, said electrical circuit means being connected to said squib means for effecting initiation thereof but normally having a flow of electrical current therein which is too low to cause initiation thereof, but having a capability of having produced therein a flow of electrical current at a level high enough to cause immediate initiation of said squib means.

A liquid-fueled device to combine the functions of a low pressure switch, squib and gas generator for a compressed gas air bag inflator comprising,

• a hermetically sealed chamber containing a liquid fuel normally stored under a high pressure oxidizing environment,
• a brittle ceramic body in which said hermetically sealed chamber is housed,
• a first diaphragm partly bounding said hermetically sealed chamber,
• a pressure monitoring resistor situated adjacent said first diaphragm,
• a squib contained in said hermetically sealed chamber, and
• first and second externally located monitoring terminals electrically connected such that a predetermined excess of external pressure results in displacement of said first diaphragm causing electrical interconnection of the monitoring terminals via said pressure monitoring resistor, and
• electrical circuit means to which said pressure monitoring resistor and said squib are connected, said electrical circuit means normally having a flow of electrical current therein which is too low to ignite said squib in said hermetically sealed chamber, but having a capability of having produced therein a flow of electrical current at a predetermined level high enough to cause initiation of said squib,
• whereby upon combustion of the flammable mixture in said hermetically sealed chamber the high pressures generated immediately causes brittle fracture of said ceramic body with subsequent venting of the combustion products to the compressed gas air bag inflator.