Pressure responsive switch and vehicular air bag system using the same

A vehicular air bag system, comprising:

• an inflatable air bag arranged initially in a non-inflated state;
• a vessel containing compressed gas at a pressure of an initial predefined value;
• means for detecting a sudden deceleration of a vehicle in which the air bag system is mounted, and in response, releasing compressed gas from said vessel to inflate said air bag;
• and
• a pressure responsive switch for sensing a reduction of pressure in the vessel instantaneously or over time, the pressure responsive switch comprising:
• (1) a switch housing mounted in the vessel, wherein the interior of the switch housing defines a volume of an initial pressure that is the same as the initial pressure of the interior volume of the vessel;
• (2) a diaphragm attached to the switch in said vessel and forming a separator between the interior volumes of said switch housing and said vessel;
• (3) an electrical switch in the switch housing for establishing a closed electrical circuit path when the movable and stationary portions of .said switch are in a first relative position and an open electrical circuit path when the movable and stationary portions of said switch are in a second relative position;
• and
• (4) an air motion sensor displaced axially from the diaphragm in the housing for sensing the movement of gas into or out of the switch housing and breaking a breakable element of an electrical circuit;
• said diaphragm being so constructed and arranged as to rupture or shear in response to the force of a predetermined differential in pressure between the switch housing and vessel.

A pressure responsive switch for sensing a change of pressure in a closed vessel instantaneously or over time, the pressure of the closed vessel having an initial predefined value, and the vessel having an end cap, comprising:

• a switch housing mounted to the end cap of the vessel, said switch housing having a volume of an initial pressure that is the same as the initial pressure of the interior volume of the vessel;
• a diaphragm attached to said switch housing, said diaphragm forming a boundary between the interior volumes of said switch housing and said vessel;
• a pair of electrodes, each electrode having one end extending from said switch housing to be connected to a circuit for warning of a reduction of pressure in the vessel and the other end extending into said switch housing;
• a contact assembly arranged in said switch housing, said contact assembly comprising
• (1) a contact base;
• (2) a spring retainer fixed to said contact base;
• (3) a resistor arranged in the contact base, the resistor having two leads and forming an element of said warning circuit;
• and
• (4) a pair of helical springs maintained in compression between the other ends of said electrodes and lead or leads of said resistor, respectively, the ends of the helical springs being bent to closely spiral inward thereof for electrical contact with the electrodes and the leads so as to form part of the warning circuit;
• fill ports for supplying compressed gas into the vessel and switch housing, said fill ports being positioned side by side on the outer surface of said end cap, wherein the outer surface of the end cap is formed with a hemispherical recess intersecting the fill ports;
• and
• a trap surrounding said diaphragm to retain said diaphragm and elements of the switch contact assembly upon functioning of the switch;
• said diaphragm being so constructed and arranged as to rupture or shear in response to the force of a predetermined differential in pressure between the switch housing and vessel.

A pressure responsive switch for sensing a reduction of pressure in a closed vessel instantaneously or over time, the pressure of the closed vessel having an initial predefined value, comprising:

• a switch housing having stationary and movable portions, the stationary portion being mounted in the vessel, wherein the interior of the switch housing defines a volume having an initial pressure that is the same as the initial pressure of the interior volume of the vessel;
• a diaphragm attached to the movable portion of said switch and to a mounting element in said vessel and forming a separator between the interior volumes of said switch housing and said vessel;
• an electrical switch in the switch housing for establishing a closed electrical circuit path when the movable and stationary portions of said switch are in a first relative position and an open electrical circuit path when the movable and stationary portions of said switch are in a second relative position;
• and
• spring means in the housing for applying a force tending to urge said movable and stationary portions of said switch to said second relative position;
• said diaphragm being so constructed and arranged as to rupture or shear in response to the force of a predetermined differential in pressure between the switch housing and vessel, and then, together with the movable portion of said switch, separate entirely from the mounting element of said vessel under the force of said spring means.