Pressure sensor system

A pneumatically operated pressure sensitive electrical switch for detecting a hazardous rate of change of pressure in a pressure sensitive penumatic system comprising;

• (a) a housing having walls that enclose a pressure chamber,
• (b) a flexible diaphragm mounted in said housing, said diaphragm forming one of said walls of said pressure chamber, said diaphragm serving to separate the pressure chamber from said pressure sensitive penumatic system in use, said diaphragm being free to move independently to and fro between a first position and a second position in response to said hazardous rate of change in the pressure system,
• (c) one of said walls of said pressure chamber being a permeable wall which is sufficiently permeable to permit air to pass therethrough at a rate which will serve to permit equalization of the pressure on opposite sides of the diaphragm at a rate that would prevent the detection of a change in the pressure in said pressure sensitive system which occurs at a rate that is less than said hazardous rate, said permeable wall being sufficiently impermeable to prevent the passage of air therethrough at a rate which will serve to prevent equalization of the pressure on opposite sides of the diaphragm at a rate which would prevent the movement of the diaphragm from said first position to said second position when said hazardous rate of change occurs in the pressure in said pressure sensitive system,
• (d) switch means carried by said housing and communicating with said diaphragm to open and close in response to movement of said diaphragm to and fro between said first and second positions.

In an inflation chamber of a tire which is inflated to a predetermined inflation pressure the improvement of an alarm system for generating an alarm signal when air leaks from the inflation chamber at a rate which could be hazardous comprising;

• (a) a housing mounted in said inflation chamber, said housing having a wall that forms a pressure chamber therein,
• (b) a flexible diaphragm mounted in said housing, said diaphragm forming one of said walls of said pressure chamber, said diaphragm serving to separate the pressure chamber from said inflation chamber such that said diaphragm is free to move independently to and fro between a first position and a second position in response to said hazardous rate of change in the pressure in the inflation chamber,
• (c) one of said walls of said pressure chamber being a permeable wall which is sufficiently permeable to permit air to pass therethrough at a rate which will serve to permit equalization of the pressure in the pressure chamber and the inflation chamber on opposite sides of the diaphragm at a rate that will prevent the detection of a change in the pressure in said inflation chamber which occurs at a rate that is less than said hazardous rate, said permeable wall being sufficiently impermeable to prevent the passage of air therethrough at a rate which will serve to prevent equalization of the pressure in the pressure chamber and the inflation chamber on opposite sides of the diaphragm at a rate which would prevent the movement of the diaphragm from said first position to said second position when said hazardous rate of change occurs in the pressure in said pressure sensitive system,
• (d) alarm means communicating with said diaphragm and operable to generate an alarm signal in response to movement of said diaphragm from said first position to said second position.