公开(公告)号：US3619724A

公开(公告)日：1971-11-09

申请号：US3619724D

申请日：1970-06-11

Applicant: COMBUSTION ENG

Inventor： BROWN THOMAS W ,  DELIN MICHAEL A ,  SCOVILLE ROBERT D

IPC: F23N5/24 ,  H02H3/247 ,  H02H3/24

CPC classification number: F23N5/245 ,  F23N2031/04 ,  H02H3/247 ,  Y10T307/766 ,  Y10T307/773

Abstract: A fuel burner safety control circuit for burner safety shutoff valves functioning in different operational modes depending upon the occurrence of an interruption in power to the circuit or an unsafe operating condition in the overall system so as to be capable of distinguishing between a momentary power interruption where the burner should not be shut down and an emergency condition where the burner should be shut down substantially immediately. The safety control circuit has a deenergize-to-trip burner safety shutoff valve with an integral time delay to maintain burner safety shutoff valve energization during momentary power interruption, and a bypass arrangement permitting the time delay to be bypassed during emergency trip conditions to provide substantially immediate burner safety shutoff valve deenergization for closing down the burner system. This capability of distinguishing between momentary power interruptions and emergency trip conditions is accomplished by using a circuit having parallel time delay relays to activate switches set in series in a time delay circuit. The time delay relays function in opposite energization senses (i.e., energize to trip and deenergize to trip) in activating the switch with which it is associated, one switch being normally closed and the other closed on application of power to the safety control circuit. On a power interruption, both relays would assume a deenergized state maintaining the switches closed for a set period of time to continue the integrity of the time delay circuit to prevent trip of the deenergize-to-trip burner safety shutoff valve. This is accomplished by the deenergize-to-trip relay holding in the powered closed switch for a discrete period of time and the energize-to-trip relay (being deenergized) having no effect on the normally closed switch. In an emergency unsafe operating condition the deenergize-to-trip relay would again be deenergized to maintain the powered closed switch closed, but the energize-to-trip relay would assume an energized state substantially immediately opening the normally closed switch to trip the deenergize-to-trip burner safety shut off valve for closing down the burner system.