GB1332153A - Safety device for gas-burning appliances - Google Patents

Abstract

1332153 Controlling gas burners A G SUTHERLAND Ltd 29 Oct 1970 [28 Jan 1970 17 Feb 1970] 4032/70 and 7447/70 Heading F4T [Also in Division H2] A safety device for a gas burning appliance comprises a magnetic flame-failure device having an electromagnet 1 powdered by the current from a thermocouple 2 which is heated by a main or pilot burner, the electromagnet maintaining a gas valve, (not shown) coupled to the armature 3, in an open position unless the main or pilot burner is extinguished, a switch controlled means being operative to apply an electrical signal to the electromagnet 1 so that the electromagnet can no longer retain the valve in its open position. In Fig. 1 the switch controlled means comprises the secondary 4 of a mains transformer 5, a rectifier diode 6, a current limiting resistor 7 and a thermally operated switch 8. The switch 8, which may be positioned in a part of the burner subject to overheating, closes above a specified temperature and a D.C. voltage of equal value but opposite polarity to that generated by the thermocouple is applied across the electromagnet causing the valve to close. In Fig. 5 a full wave rectifier 32 is connected across a secondary 24 of a mains transformer, closure of a thermally operated switch 28 resulting in current from the rectifier being fed via resistor 35 to the electromagnet, closing the valve. A cell 29 is connected across the rectifier and is continually charged so that if switch 28 closes during a mains failure, cell 29 supplies the current. Alternatively the full wave rectifier is omitted, the cell supplying the current at all times. In other embodiments the electrical signal is provided by the discharge of a capacitor or by an A.C. signal superimposed on the D.C. or the thermocouple. To permit the gas supply to be cut off in response to variables other than the absence of flame or over-heating a circuit comprising a transformer secondary 33, electrical switches 31 and a solenoid operated valve 30 in series with the main gas valve is provided, closure of both switches 31 serving to cut off the gas supply.