GB1509534A - Control systems for gas-fired appliances - Google Patents

Abstract

1509534 Burner controls VALOR NEWHOME Ltd 5 May 1975 [4 May 1974] 19713/74 Heading F4T A control system for an oven burner 18 of the type having a pilot burner 24 with a spark igniter 28 comprises three switches 38, 40 and 42 in series in the power supply line to a spark generator 30 for the igniter. The first switch 38, normally open, is closed when a tap 10 for gas supply to the pilot and main burners is opened. The second switch 40 is incorporated with a valve 26 in the pilot gas supply line in a timer mechanism 22 and is also closed when the valve 26 is opened. The third switch 42 is incorporated in the actuating mechanism of a valve 46 (normally closed) controlling the gas supply to the main burner such that when the pilot flame is detected by a thermal device 60 and bellows 48 expand, the switch, which is normally closed, is opened to cut off the power supply to the spark generator. Should the flame fail, the thermal device acts to close valve 46 and close switch 42 so that ignition can be reinitiated. The power supply to the spark generator is provided with stepping down and stepping up transformers so that the voltage through the switching circuit acting across the switches is reduced. A switch 36 is included in the circuit for manual actuation of the generator. Other methods of reducing the voltage or current through the circuit are disclosed. These include tapping off from the transformer with a high resistance in the tapping line. In one embodiment the switch 42 is placed outside the housing 44 and is actuated by a magnet positioned on the end of the lever 50. A spark generator is shown in Fig. 6. The switches are connected across leads 118 and 120 and when closed allow capacitor 126 to charge up and eventually discharge across a neon lamp 128 and trigger a thyristor 114 so that a capacitor 106 can discharge through a transformer 112 and produce a spark at the spark gap. Switching circuits are shown in Figs. 7 and 8 which are designed to initiate a timed burst of sparks when the gas tap 10 is opened so as to ignite any gas that may be leaking into the appliance and hence prevent explosion. The three switches 39, 40 and 42 are shown in Fig. 6 with switch 38 as a two position switch. The switch 38 can connect a capacitor 132 across the terminals of the generator to produce initial sparks. In Fig. 8 the switch 38 has a passing contact 38b which allows the capacitor 138 to charge up and cause the generator to spark.