Fluid control system

A fluid control system for use with combustion apparatus comprising:

• a valve assembly having primary and secondary valves in series between an inlet and an outlet of said assembly;
• a main burner in said combustion apparatus connected to said valve assembly outlet;
• a pilot burner for said combustion apparatus positioned adjacent said main burner, said valve assembly having fluid flow conduits including first and second passages connected to said pilot burner;
• means to sense a flame at the pilot burner and to generate a first control signal in the presence of a flame and a second control signal in the absence of a flame;
• a third valve movable between first and second positions, when in said first position directing fluid through said first passage to said pilot burner;
• and when in said second position directing fluid through said second passage to said burner and preventing fluid from flowing through said first passage;
• a first actuator for selectively operating said primary valve including means to open said valve to permit the passage of fluid from a first chamber to a second chamber of said assembly;
• said first fluid flow passage being in communication with said first chamber and said second fluid flow passage being in communication with said second chamber, with said pilot burner flame sensing means providing a selected one of said first and second control signals to said actuator to respectively open and close said primary valve, the closure of said primary valve in the absence of a flame at said pilot burner discontinuing flow of fluid to said second chamber and to said second flow passage;
• said primary valve means including means to lock said third valve in said first position when said primary valve is in said closed position to direct fluid in said first chamber, to said pilot burner, through said first passage, the opening of said primary valve means in response to a sensed pilot burner flame releasing said locking means to place said third valve in its second position to close said first fluid flow passage and to open said second fluid flow passage to thereby communicate said pilot burner with said second chamber, the subsequent closure of said primary valve discontinuing flow of fluid into said second chamber and into said second fluid flow passage to said pilot burner;
• and
• a second actuator for selectively operating said secondary valve including means to open said valve in response to a demand for heating in a space served by said combustion apparatus to permit passage of fluid from said second chamber of said valve assembly to said main burner, said pilot burner sensing means providing said second control signal to said second actuator to maintain said secondary valve closed in the absence of a flame at said pilot burner.