Cooktop gas safety valve hold open circuit with ceramic heater

Abstract

A cooking gas safety apparatus is shown and described. The apparatus includes a cooking gas safety valve assembly that supplies cooking gas to one or more burners. The cooking gas safety assembly includes at least one coil that is energizable to hold the valve assembly in an open position when subjected to a current that exceeds a threshold value and a hold open circuit. The hold open circuit comprises the coil and a hot surface igniter that is in electrical communication with the coil. The valve assembly is actuated by manually opening the valve and energizing the igniter such that it receives a threshold current that corresponds to an autoignition temperature of the gas. At the threshold current, an electromagnet in the cooking gas safety valve assembly holds the valve open so that it remains open without user intervention. In the event of an igniter failure, the current flow to the coil ceases, causing the valve to shut and cease gas flow to the burner. In certain examples, hold open circuit allows the igniter to operate off of alternating current while the coil receives a time-varying, direct current.

What is claimed is: 
     
         1 . A cooking gas safety apparatus comprising:
 a valve assembly comprising a valve and at least one coil, the valve comprising a fluid inlet and a fluid outlet and being manually operable to place the fluid inlet in fluid communication with the fluid outlet, wherein the at least one coil is energizable to hold the valve in the open position only when subjected to a current that exceeds a threshold current value; and   a hot surface igniter electrically connectable to the at least one coil to define a hold-open circuit, such that when subjected to a potential difference of 120V AC rms, the hot surface igniter reaches a surface temperature of at least 1400° F. in no more than eight seconds after the at least one coil is subjected to the threshold current.   
     
     
         2 . The cooking gas safety apparatus of  claim 1 , wherein when subjected to a potential difference of 120V AC rms, the hot surface igniter reaches a surface temperature of at least 1800° F. in no more than four seconds after the at least one coil is subjected to the threshold current. 
     
     
         3 . The cooking gas safety apparatus of  claim 1 , wherein the at least one coil is at least one alternating current coil. 
     
     
         4 . The cooking gas safety apparatus of  claim 1 , wherein the at least one coil is at least one direct current coil. 
     
     
         5 . The cooking gas safety apparatus of  claim 4 , further comprising a diode electrically connectable to the at least one coil and a source of alternating current to supply the at least one direct current coil with a time-varying direct current. 
     
     
         6 . The cooking gas safety apparatus of  claim 4 , further comprising at least one capacitor, wherein the at least one capacitor is connectable in parallel with the hot surface igniter and the at least one direct current coil. 
     
     
         7 . The cooking gas safety apparatus of  claim 1 , wherein the at least one coil is not electrically connected to a thermocouple. 
     
     
         8 . The cooking gas safety apparatus of  claim 1 , wherein the hot surface igniter is a silicon nitride igniter having a room temperature resistance of from about 20 ohms to about 60 ohms. 
     
     
         9 . The cooking gas safety apparatus of  claim 1 , wherein the ceramic igniter has a ceramic body with a length defining a length axis, a width defining a width axis, and a thickness defining a thickness axis, the ceramic igniter comprising:
 first and second ceramic tiles having respective outer surfaces;   a conductive ink pattern disposed between the first and second ceramic tiles, wherein the igniter has a thickness along the thickness axis of from about 0.047 to about 0.060 inches and when subjected to a potential difference of 120 V AC rms, at least one of the respective igniter outer surfaces reaches a temperature of at least 1400° F. in no more than 8 seconds.   
     
     
         10 . The cooking gas safety apparatus of  claim 9 , wherein the conductive ink pattern has a positive temperature coefficient of resistivity. 
     
     
         11 . A cooking gas safety apparatus comprising:
 a valve assembly comprising a valve and at least one coil, the valve comprising a fluid inlet and a fluid outlet and being manually operable to place the fluid inlet in fluid communication with the fluid outlet, wherein the at least one coil is energizable to hold the valve in the open position only when subjected to a current that exceeds a threshold current value; and   and   a hot surface igniter electrically connectable to the at least one coil to define a hold-open circuit, such that when subjected to a potential difference of 120V AC rms, a surface of the hot surface igniter reaches an autoignition temperature of at least one of butane, butane 1400, propane, natural gas, and mixtures thereof no more than eight seconds after the at least one coil is subjected to the threshold current.   
     
     
         12 . The cooking gas safety apparatus of  claim 11 , wherein the surface of the hot surface igniter reaches the autoignition temperature of the at least one of butane, butane 1400, propane, natural gas, and mixtures thereof, no more than four seconds after the at least one coil is subjected to the threshold current. 
     
     
         13 . The cooking gas safety apparatus of  claim 11 , wherein the at least one coil is at least one alternating current coil. 
     
     
         14 . The cooking gas safety apparatus of  claim 11 , wherein the at least one coil is at least one direct current coil. 
     
     
         15 . The cooking gas safety apparatus of  claim 14 , further comprising a diode electrically connectable to the at least one coil and a source of alternating current to supply the at least one direct current coil with a time-varying direct current. 
     
     
         16 . The cooking gas safety apparatus of  claim 14 , further comprising at least one capacitor, wherein the at least one capacitor is connectable in parallel with the hot surface igniter and the at least one direct current coil. 
     
     
         17 . The cooking gas safety apparatus of  claim 1 , wherein the at least one coil is not electrically connected to a thermocouple. 
     
     
         18 . The cooking gas safety apparatus of  claim 1 , wherein the hot surface igniter is a silicon nitride igniter having a room temperature resistance of from about 20 ohms to about 60 ohms. 
     
     
         19 . The cooking gas safety apparatus of  claim 1 , wherein the ceramic igniter has a ceramic body with a length defining a length axis, a width defining a width axis, and a thickness defining a thickness axis, the ceramic igniter comprising:
 first and second ceramic tiles having respective outer surfaces;   a conductive ink pattern disposed between the first and second ceramic tiles, wherein the igniter has a thickness along the thickness axis of from about 0.047 to about 0.060 inches and when subjected to a potential difference of 120 V AC rms, at least one of the respective igniter outer surfaces reaches a temperature of at least 1400° F. in no more than 8 seconds.   
     
     
         20 . The cooking gas safety apparatus of  claim 9 , wherein the conductive ink pattern has a positive temperature coefficient of resistivity.