GB1419653A - Fuel flow control apparatus for a burner - Google Patents

Abstract

1419653 Burner controllers WALTER KIDDE & CO Inc 15 Jan 1973 [26 Jan 1972] 1991/73 Heading F4T A burner controller has a fuel valve 23; flame responsive means 12 for providing a flame rectified direct current in response to a flame at the burner, said means including electrodes 13, 17 for conducting said current and defining a gap filled by the flame rectifying said current, an energy source including capacitor means C1, C2 so arranged that following fuel ignition the only energy received by the capacitor means is that energy provided by said flame rectified current; electrical sampling means CSCR for detecting the energy level provided by said direct current and stored in said capacitor means, the sampling means drawing power only from said capacitor means and providing a periodic output signal indicative of flame at the burner; and control means SCR1, 31 responsive to said sampling means for closing the valve 23 in response to the absence of a minimum energy level sampled by said sampling means. To start up, a switch 47 is closed and a capacitor C5 delays operation of a relay 42 so that contacts 43, 44 remain initially engaged whereby capacitor C1 is initially charged via diode D4 from a line A.C. supply at input 18, 19. A diode D1 biases the gate of a complementary silicon controlled rectifier CSCR so that CSCR is non-conductive and conductive during negative and positive half-cycles respectively on line 20, CSCR being triggered on at positive-going zero crossings on line 20; a capacitor C2, charged from C1 via resistor R2, is thereby periodically discharged to trigger SCR1 and discharge capacitor C4 thereby energizing ignition spark transformer T1 and relay, 31. After the delay provided by C5, relay 42 is energized to charge contact 43 from contact 44 to 45 whereby solenoid valve 23 opens and charging of C1 from the A.C. supply is discontinued. If ignition occurs C1 is charged from flame rod 17 whereby C2 continues to be charged via R2 and discharged via CSCR to continue energization of relay 31 and thereby of valve 23. If ignition does not occur or if the flame goes out, the charge on C1 continues to be effective for a short period to charge C2 whereby ignition sparks continue to be produced for that period. If ignition is not established, or re-established, in said period the charge on C1 becomes too low for the resulting charge on C2 to cause triggering of SCR1 whereby valve 23 is closed but relay 42 remains energized thereby requiring interruption of the A.C. supply, e.g. by switch 47, to re-start.