Gas monitoring system with leak detection and flow cutoff

Claim 1

A gas monitoring system for detecting combustible gas in low concentration and shutting off the source of gas when a leak thereof is detected comprising the combination of gas valve means connected to control the flow of gas from said gas source to a consuming device, said gas valve means including a solenoid having an energized position for opening said valve means to allow gas flow and a deenergized position in which said valve means is urged toward a closed position to prevent gas flow; valve means comprising a valve body; a valve plunger slidable in said body, said valve plunger being movable by said solenoid to an open position when said solenoid is energized, said valve plunger carrying a valve member; means defining a gas flow path; a valve seat in said gas flow path; and spring means urging said valve plunger toward said closed position in which said valve member contacts said valve seat and closes said flow path; a solid state switch for energizing and deenergized said solenoid; a gas sensor for detecting the presence of leaked gas; an integrated alarm circuit responsive to signals from said sensor to operate when said gas sensor senses leaked gas, said alarm circuit including a visual integrated alarm circuit, an audible integrated alarm circuit including an audio oscillator, integrated circuit driver circuits driving said audio oscillator, actuating said visual integrated alarm circuit, and causing said solid state switch to deenergize said solenoid when leaked gas is sensed, and an integrated circuit voltage comparator for driving said driver circuits; circuit means for connecting the output of said sensor to the input of said integrated circuit voltage comparator; a direct current power supply for said sensor and said integrated alarm circuit; a switch for turning said power supply on and off; and manual override means for mechanically urging said valve means away from said closed position to allow gas flow without energization of said solenoid said override means comprising a plug having an axis and an eccentric member thereon eccentric to said axis; and means for rotatably supporting said plug adjacent said valve plunger, said plug being rotatable between a first position in which said eccentric member allows said plunger to move to said closed position and a second position in which said eccentric member moves said plunger away from said closed position against the force of said spring means, thereby separating said valve member from said seat and opening said path to gas flow.