Patent GB-795187-A (GB)
Title: Safety device for fluid fuel burners
IPC: F23N5/12
Filed: 1954-06-01
Abstract: 795,187. Controlling gas burners. HEGWEIN, G. June 1, 1954 [June 9, 1953; Jan. 18,1954; Jan. 18.1954], No. 16156/54. Classes 75(1) and 75(3) A flame safety control system for a burner comprises spaced electrodes 22<SP>1</SP>, 24 in the flame of a pilot burner 15 and connected to a voltage source, for instance the secondary winding of a mains energized transformer 26, so that a current passes through the flame and through the primary winding of a transformer 57, the secondary winding of which is connected to means adapted to open or hold open a valve 4 controlling the supply of fuel to a main burner 3, there being no means such as electronic valve means for amplifying the electrical energy of the electrode circuit. To start the burner installation a push button 19 is pushed in to open the valve 4 and close a switch 56 connecting spark electrodes 22, 22<SP>1</SP> to the transformer 26. Gas is thus supplied to the pilot burner 15 which is ignited by the sparks and the pilot burner ignites the main burner 3. The ionized current through then energizes an electromagnet which the flame holds the valve, 4 open so that the push button can be released to open the switch 56 of the spark circuit. In a modified circuit only two electrodes are provided one of which is movable and at starting is disposed at a small distance from the fixed one so that an ignition spark can pass between them. After ignition the movable electrode is moved to a greater distance from the fixed one and an ionized current passes between them. The movable electrode is connected to the push button for opening the fuel valve or is actuated by an electrical device switched on by the push button. In the arrangement shown in Fig. 3 the gas supply to the pilot burner 15 is not controlled by the electromagnetic valve 4 but by a stop lock 1 only. The pilot burner is ignited by closing switch 56 to cause sparking between the electrodes 22, 22<SP>1</SP>. The ionized current passes between electrodes 24, 24<SP>1</SP>. The primary circuit of the transformer 57 includes a switch 60 which is controlled by means responsive to time, temperature or pressure and the secondary circuit of the transformer 57 includes further switches 60, a recifier 61 and a condenser 62 in the neighbourhood of the coil of the electromagnetic valve 4. In the arrangement shown in Fig. 4 the pilot burner has two concentric nozzles 15, 15<SP>1</SP> supplied with gas through valves 14, 10 and producing an inner flame 25 and an outer enveloping flame 25<SP>1</SP>. In operation button 19 is pushed in to close contacts 42 in the circuit of the mains transformer 26, to close contacts 23 to cause sparking between electrodes 22, 24 and to open valve 14 supplying the inner nozzle. An ionized current passes through the inner flame 25 between electrodes 24, 24<SP>1</SP> and energizes transformer 57 which energizes a coil 21 adapted to hold the valve 14 open and the contacts 42 closed when the button 19 is released. The transformer 57 is also connected to the electromagnetic valve 4 through contacts 40, closed when the button 19 is released, but the energization of the electromagnetic valve 4 is insufficient to open the valve. The valve 10 supplying the outer nozzle 15<SP>1</SP> is controlled by a thermostat 9 and when this valve opens the enveloping flame 25<SP>1</SP> reduces the resistance between the electrodes 24, 241 so that the ionized current increases and the energization of the electromagnetic valve 4 is sufficient to open the valve to supply the main burner. Several pairs of sparking and ionized current electrodes may be provided, each pair of ionized current electrodes requiring a higher voltage than the preceding pair and controlling a different switching means. The fuel supply at starting may be shut off at regular intervals by a device which is maintained in fuel flow position by a switching device actuated by the-ionized current