GB992632A - Improvements in or relating to control devices for burners - Google Patents

Abstract

992,632. Controlling burners. PERL CONTROLS Ltd. Feb. 8, 1962 [Feb. 22, 1961], No. 6502/61. Heading F4T. [Also in Divisions G1 and G3] In a burner control system, energization of a solenoid 18 opens the fuel supply to a pilot burner and energization of solenoids 16 and 19, respectively opens the fuel supply to a main burner and holds open the fuel supply to the pilot burner, the arrangement being such that the main fuel supply cannot be opened until the pilot supply has been opened and until a signal has been received from a flame-sensitive device upon occurrence of a flame at the pilot burner. Valve arrangement (Fig. 2). The main fuel supply is controlled by a diaphragm valve 3 which has a pressure chamber 4 fed from the main fuel supply line 6 through a permanently open bleed passage 8 and through ducts 10 and 11 controlled by a valve 1a connected to a valve 1 which controls the fuel supply to the pilot burner through a line 12. A valve 2 operated by solenoid 16 controls release of pressure from the chamber 4 through a duct 5 and a flow restrictor 9 to the fuel outlet 7 from the main valve, the restrictor allowing sufficient flow to permit the diaphragm valve 3 to open when valve 2 is open and valve 1a closed, but preventing opening of the diaphragm valve when both valves la and 2 are open. Control circuit and operation.-When burner ignition is required, power is supplied through a transformer 13 to valves V 1 and V 2 and an ignition filament 29 in series with the cathode heaters 28. Conduction of current through the valve V 2 energizes solenoid 18 to supply fuel to the pilot burner and biases the valve V 1 below cut-off. After ignition of the pilot burner, the flame at the latter causes a flame rectifier 22 to become conductive, thus applying a negative bias to the grid of valve V 2 sufficient to cut off the latter. Valve V 1 is thus rendered conductive, causing energization of the holding solenoid 19 and the main fuel valve solenoid 16. If the fuel supply fails during operation, the negative bias is removed from valve V 2 and valve V 1 will cut off so that the main fuel valve closes and the pilot valve remains open to be relighted automatically on re-establishment of the fuel supply. The presence of a false flame signal due to a circuit fault will prevent burner ignition by rendering valve V 2 non-conductive. In modifications the filament 29 may be replaced by a spark or hot wire ignition device arranged to be activated through a transformer by a relay whenever the valve V 2 is energized, and the anode circuits of the valve may be fed with D.C. In a further modification, Fig. 3 (not shown), the flame rectifier is replaced by a photo-electric cell which, through a third thermionic valve and a rectifier circuit, cuts off the valve V 2 when irradiated with light from the pilot flame.