Bilevel flame signal sensing circuit
AssigneeHoneywell Inc.
InventorJohn E. Bohan, Jr.
Life of this patent
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Abstract
A fuel burner control system that has a fail safe mode of operation utilizes a flame sensing means that controls two separate signal processing circuits that have two different threshold levels of operation. Each of the signal processing circuits controls a separate switch means and these switch means are interrelated to ensure that a pilot valve and main valve are opened in sequence and that a pilot flame is properly burning before the main valve is opened. If the flame sensing means for the device senses any abnormality, the interrelationship of the output circuits prevents the main valve from opening.
Claims11
A fuel burner control system having a fail safe sensing circuit to insure that a pilot valve has been opened and a pilot flame is established at a pilot burner before a main fuel valve is opened, including:
- flame sensing means responsive to a flame at said pilot burner with said sensing means having output circuit means;
- first threshold signal processing circuit means for operation of first threshold switch means;
- said switch means including normally nonconductive circuit means;
- second threshold signal processing circuit means for operation of second threshold switch means;
- said second threshold switch means including normally conductive circuit means and normally nonconductive circuit means;
- said first and said second threshold signal processing circuit means each being connected to said flame sensing output circuit means;
- said second threshold conductive switch means connected to initially energize said first threshold switch means and said pilot valve through said normally conductive circuit means;
- said first threshold circuit means being in an energized state upon said first threshold signal processing circuit means sensing a first flame signal by causing said first threshold normally nonconductive circuit means to become conductive;
- and said second threshold signal processing circuit means subsequently sensing a second, larger flame signal and opening normally conductive circuit means and closing normally nonconductive circuit means to energize said main fuel valve in a safe manner through the normally nonconductive circuit means of said first threshold conductive switch means.
A fuel burner control system having a fail safe sensing circuit to insure that a pilot valve has been opened and a pilot flame is established at a pilot burner before a main fuel valve is opened, including:
- flame sensing means responsive to a flame at said burner with said sensing means having output circuit means;
- first signal processing circuit means for operation of first switch means;
- said switch means including normally nonconductive circuit means;
- second signal processing circuit means for operation of second switch means;
- said second switch means including normally conductive circuit means and normally nonconductive circuit means;
- said first and said second signal processing circuit means each being connected to said flame sensing output circuit means;
- said second conductive switch means connected to initially energize said first switch means and said pilot valve through said normally conductive circuit means;
- said first circuit means being in an energized state upon said first signal processing circuit means sensing a first flame signal by causing said first normally nonconductive circuit means to become conductive;
- and said second signal processing circuit means subsequently sensing a second, larger flame signal and opening normally conductive circuit means and closing normally nonconductive circuit means to energize said main fuel valve in a safe manner through the normally nonconductive circuit means of said first conductive switch means.
Dependencies are inferred from the claim text.