GB589663A - Improvements in or relating to safety control apparatus for fuel burners - Google Patents

Abstract

589,663. Burners, controlling. MAY, P. (Robertshaw Thermostat Co.). Nov. 16, 1944, No. 22732. [Classes 75 (i) and 75 (ii)] [Also in Group XXIX] The manual or thermostatic operation of a valve 14 in the gas supply pipe 12 allows gas to pass to a pilot burner 18 and closes the secondary circuit of a mains-energized transformer 28 thereby operating a relay 30 to raise a hinged armature 32 to close at contacts 36, 38 the circuit through a resistor 54 to the pilot burner ignition coil 22 and at the contact 40 the circuit through the relay coil 66 and a resistor 56 to a ballast resistor 42 adjacent to the pilot burner. The increased resistance of the resistor 42 on being heated by the pilot burner reduces the current through the relay-coil 66 and the armature 32 drops thereby breaking the ignition coil circuit and making at a contact 34 a circuit to the resistor 42 through an electromagnetic valve 16 which opens to allow gas to pass to the main burner 10 for ignition by the pilot burner 18. This circuit includes the heating coil 72 of a bimetallic switch 48 which closes at contacts 50, 52 a shunt to the ignition coil 22 thereby ensuring a purge period if both burners are extinguished before current again passes to the ignition coil. A cut-out 58 in the circuit of the ballast resistor 42 opens after a predetermined time if the burner 18 fails to ignite. Specification 572,130 is referred to.