GB1228335A - - Google Patents

Abstract

1,228,335. Gas igniter system; burner control system. FENWAL Inc. 15 Jan., 1970 [24 Jan., 1969; 31 Dec., 1969], No. 1963/70. Headings F4F and F4T. [Also in Division H3] In an alternating current . powered transformerless gas igniter system, gas is provided to an electrically earthed burner 11 from a supply main 13 through a valve 15 which is mechanically coupled to and controls a switch SW1, which is closed when the valve 15 is opened, allowing rectified current to flow through a diode D1 and resistors R1 and R2 to charge a timing capacitor C4 to a voltage which causes a neon lamp N1 connected between the timing capacitor C4 and the gate of a silicon controlled rectifier Q1 to conduct so triggering the SCR Q1 allowing an energy storage capacitor C3, which is charged by current flowing through the diode D1 and the resistor R1, to discharge through a circuit including the SCR Q1 and the primary winding W1 of a spark coil 23, as a result of which a current is induced in the secondary winding W2 of the spark coil 23 and causes a spark between an electrode 21 and the burner 11, both of which are connected in circuit with the secondary winding W2, so igniting the gas at the burner 11. A large isolating resistance R6 is connected between the side of capacitor C4 which is not earthed and the side of the secondary winding W2 of the spark coil 23 opposite to the electrode 21, in order to substantially isolate the burner 11 from the power supply, so reducing the risk of electric shock. A capacitor C2 is connected between the burner 11 and the secondary winding W2 to act as a discriminator allowing igniting pulses to pass while presenting an open circuit to the D.C. charging current flowing to the timing capacitor C4. The gate of the SCR Q1 is connected to the neon lamp N1 via a resistor R4 and to the power supply lead L2 via a resistor R5. The charging of the capacitors C3 and C4 and the firing of SCR Q1 will repeat periodically as long as the spark gap has a high impedance; but when the gas has ignited at the burner 11, the impedance will be low enough to shunt the capacitor C4 and prevent its being charged to the voltage necessary to fire the neon lamp N1. In another embodiment (Fig. 2, not shown) adapted for use with A.C. voltages which are of opposite polarity with respect to the ground, an intermediate voltage substantially equal to ground potential is provided by means of a pair of dropping resistors connected in series across the power supply leads. Alternative embodiments (Figs. 3 and 4, not shown) have the discriminating function of capacitor C2 performed by neon lamp (N2) and a second spark gap respectively.