JPS5563315A - Combustion safety device - Google Patents

Abstract

PURPOSE:To provide an uncostly combustion safety device capable of positive stop of fuel supply at the time of imperfect combustion or go-out of flames. CONSTITUTION:At the time of imperfect combustion, the DC electro-motive force of flame rod 15 drops, so that the absolute value of gate potential of field effect transistor 17 becomes smaller than the cut-off voltage, resulting in a reduced potential of drain 20 of field effect transistor 17. However, emitter 24 of transistor 22 is maintained at a constant potential by resistors 25, 26, so that when the potential of drain 20 becomes lower than the level substantially equal to the emitter potential, transistor 22 is turned off to disenergize solenoid valve coil 29. Thus, if the emitter potential of transistor 21 is properly set, fuel supply can be shut off by solenoid valve coil 29 at the time of imperfect combustion. At the time of go-out of flames, the potential of gate 18 becomes positive, so that field effect transistor 17 is perfectly turned ON, that is, the potential of drain 20 becomes substantially zero.