Patent GB-285974-A (GB)
Title: Improvements in safety mechanism for fuel burning devices
IPC: F23N5/24
Filed: 1926-11-23
Abstract: 285,974. Marks, E. C. R., (Williams Oil- O-Matic Heating Corporation). Nov. 23, 1926. Electrically controlling fuel and air supplies.- In an oil fuel burning apparatus of the type in which the fuel and air projecting means are driven by an electric motor controlled by a room thermostat arranged in a secondary circuit, a normally closed shunt from the secondary circuit maintains a safety switch closed under normal working conditions. In abnormal conditions the shunt circuit is broken and the safety switch then operates to effect the interruption of the motor circuit. The burner apparatus shown in Fig. 1 comprises an electric motor 10 operating a rotary atomizer to supply a mixture of fuel and air to a nozzle 22 discharging into a combustion chamber 23. The motor also drives a fan 24 supplying air to the combustion chamber through a housing 25 and a pump 14 supplying fuel to the atomizing chamber through a strainer 18. A diaphragm member 28 in a casing 32 is moved upwardly by the pressure in the atomizing chamber 11 when the motor starts and raises a lever 38 against the resistance of a dashpot 31, thereby opening the fuel valve 30 of the atomizing chamber and a gas valve 33 of a pilot light adjacent the burner nozzle. The pilot light is ignited by sparks from a coil 44 which is energized by the lever 38 engaging with a knife switch 45 during its movement. At the completion of the movement of the lever its pivoted end 42 snaps over the stem 36 of the gas valve and allows the valve to close. Fig. 2 shows the electrical circuit for the motor 10, main-switch R and transformer X. The main switch R comprises a pivoted armature 52 adapted to make or brake at the contact 56 the main circuit to the motor 10 when one of two opposed electromagnets 54, 55 is energized from the secondary circuit of the transformers X on the movable arm of the thermostat T making contact with the " ON " or " OFF " contact points. A spring switch 57 operated by the armature 52 causes the secondary circuit to be completed only momentarily to effect the movement of the armature. In the " common " supply lead to the thermostat is arranged a safety switch 61 which is normally maintained in engagement with a contact 123 to close the secondary circuit by an electromagnet 58. The electromagnet 58 is energized by a circuit 80 arranged as a shunt to the secondary circuit through the thermostat. In the normal operation of the burner the circuit is completed while the burner is alight by a mercury switch 65 operated by the expansion of air in a chamber 63 subjected to the heat of the flame and while the burner is out by the engagement of the lever 38 with the knife switch 45. During normal ignition the dash pot 31 delays the break of the circuit at the knife switch 45 until the mercury switch 65 is closed by the heat of the flame. Should however the ignition of the burner fail either initially or subsequently the circuit through the electromagnet 58 will be broken and a spring 60 will move the switch 61 from engagement with the contact 123 into engagement with the contact 124, thereby completing a circuit through the electromagnet 55 and stopping the motor 10 until the switch 61 has been reset by hand. In a modified form of apparatus the breaking of the circuit through the electromagnet 58 releases a weighted lever operating the armature 52. Specification 283,261 [Class 75 (iii), Lamps &c., Details of], is referred to.