Patent GB-598538-A (GB)
Title: Burner control apparatus
IPC: F23N5/08
Filed: 1944-07-05
Abstract: 598,538. Electrically controlled burners. TRIGGS, W. W. (Combustion Control Corporation.). July 5, 1944, No. 12831. [Class 75 (i)] [Also in Groups XXXV, XXXVII and XL] In an electrically controlled burner for a domestic heating plant the closure of a thermostat by the ambient temperature completes a circuit from a tapping I in the secondary winding of a mains-energized transformer 3 to an electromagnet A through a safety switch D1, priming, switches Cl, C2, a heating winding D around a bimetallic strip 22 normally holding the spring contacts 25, 26 of the switch D1 closed, and a heating winding C around a bimetallic strip 21 normally holding the spring contacts 27, 28, 29 of the switches C1, C2 closed. The electromagnet A closes switches Al, A2, the switch A1 completing the mains circuit to the burner motor M and burner ignition device i and the switch A2 shunting the switch C1. If ignition is effected the light from the burner flame lowers the impedance of a photo-cell P connected to the secondary winding of the transformer 3 and raises the potential of the starting electrode g of an electronic tube T, preferably of the cold cathode type, thereby energizing an electro - magnet B which opens a switch B2 in the ignition circuit and closes a switch B1 to shunt the heater D. The heater C continues in operation and opens first the switch C1 and later the switch C2. The burner normally continues in operation until the thermostat S opens contacts 11, 12 to de-energize magnet A and stop the motor M. If ignition fails to occur the photocell P fails to render the tube T conductive and the heater D operates to open switch D<1> which de-energizes magnet A and opens the motor and ignition circuits. If flame failure occurs after ignition the photocell ceases to be conductive and the magnet B is de-energized.. The switches B, A1 then open and the motor M stops. After a scavenging period, in which the heater C cools, the switches Cl, C2 close and the magnet A is again energized. Normal operation may then begin if proper combustion is possible. The switch D1 is opened by its bimetallic element 22 bending upwardly to pass over the top of the spring contact 25 and is held in this position when the circuit of the heater D is broken to prevent re-engagement of the spring contacts 25, 26 until disengaged by the manual operation of a push-button 30. In the case of failure of the power supply, oil, or any of the electric elements the burner is also shut down or prevented from starting. The closure of the switch Cl after the switch C2 when the circuit of the heater C is broken ensures a scavenging period if the thermostat circuit is only broken for a short period. The photo-cell may be connected either to the end III of the secondary winding of the transformer 3 or through the secondary winding of a transformer 40 to.a tapping II, the primary circuit of the transformer 40 opening if the water level in the boiler falls below a probe L. If a thermostat having an independently heated resistor is employed the resistor circuit is provided with a normally open switch controlled by the magnet A.