GB819099A - Improvements in flame detector or flame failure protection systems - Google Patents

Abstract

819,099. Controlling burners. COLNE SWITCHGEAR (K. & W.) Ltd. June 19, 1957 [June 20, 1956], No. 19027/56. Classes 75(1) and 75(3) A flame detector comprises a pair of electrodes E, E<SP>1</SP> arranged in the flame and connected to the secondary winding of a transformer A, the primary winding of which controls a relay F adapted to control a device for indicating the presence or absence of the flame. On closing the switch I and the press button switch J the primary of the transformer is energized and a solenoid gas valve G is opened to supply gas to a burner K which is ignited by known means. A spark discharge takes place between the electrodes in the flame and the primary current of the transformer operates the relay F to close contacts FC shunting the press button switch J which can now be released. In the event of flame failure sparking between the electrodes ceases and in consequence the primary current of the transformer falls causing the contacts FC of the relay to open. A resistance D in the secondary circuit of the transformer minimises the generation of electro-magnetic waves. In a simplified circuit, Fig. 1, not shown, the rectifier C in the primary circuit is dispensed with and the relay contacts may be used to operate a signalling system instead of a fuel valve. In a modified circuit, Fig. 4, not shown, the transformer has a tapped primary and at starting the supply voltage is connected by a push button switch to a portion only of the primary winding and in consequence the secondary voltage causes sparking between the electrodes E, E' in the absence of a flame, the sparking being used to ignite the burner. The closing of the relay contacts, as a result of the sparking, energizes a gas valve and also connects the whole of the primary winding to the supply through a choke so that, when the push button starting switch is released, the secondary voltage is reduced to a value sufficient to maintain sparking only in the presence of a flame. In an alternative arrangement, Fig. 5, not shown, an auto-transformer is connected in series with the primary of the transformer to boost the primary voltage at starting when the electrodes are used for ignition.