Patent GB-929298-A (GB)
Title: Improvements relating to control systems for pressure-jet oil burners operating on heavy oil
IPC: F23N5/20
Filed: 1958-09-03
Abstract: 929,298. Photo-electric control of oil burners. A. J. LANGHAM. Nov. 27, 1959 [Sept. 3, 1958], No. 28361/58. Class 40 (3). [Also in Group XI] A control system for a pressure jet burner operating a preheated heavy oil comprises a first timing device capable on actuation of cutting off the oil supply to the burner nozzle assembly after a selected interval following the failure of the flame, a second timing device capable, after being actuated, of cutting off the oil supply to the nozzle assembly after an interval corresponding to a predetermined warming-up period, a flame detector responding rapidly to the absence of combustion at the burner and capable of actuating the first timing device, when connected thereto, in response to flame failure, means sensitive directly or indirectly to nozzle assembly temperature for establishing normal running conditions when, during starting up, such temperature achieves a selected value, such means including a changeover device which during the starting-up period brings into action said second timing device, and which upon the establishment of normal running conditions, disconnects the second timing device and connects the first timing device to the flame detector. On closure of a switch 21, the circuit of a relay 14 is completed to terminals L, N over released contact 8c and released contact 13 of a first thermal switch 12. Initially a temperature-sensitive switch 5 in the oil return line and the pressure switch 4 in the oil feed line will be closed so that relay 6 is operated and at contacts 6a energizes the stop valve 3 to hold it open. At operated contacts 14a a motor 2 connected to the mains L, N operates a fan to blow air through the burner and oil from a heater circuit through the open valve 3. When the oil reaches the predetermined temperature, the switch 5 opens and releases relay 6 so that the stop valve 3 closes and when the pressure of the oil fed to the burners reaches a predetermined value the switch 4 opens. Later during normal feed of oil the temperature switch 5 closes. When there is no flame at the burner, the photo-cell 7 in conjunction with an amplifier 9 does not operate relay 8 so that at released contacts, the ignition device 1 is energized. Also at contacts 6c a relay 16 is operated and the coil 18 of the thermal relay 17 energized. At this time the coil 11 of the thermal switch 12 is short-circuited by contacts 6b of relay 6. If, after a predetermined time, the burner is not ready for operation, i.e. relay 6 released, contact 19 of the switch 17 moves to its lower position and breaks the circuit of relay 14 which at contacts 14a disconnects the motor 2. If the relay 6 is released by normal operation the short-circuit is removed from the coil 11 of the switch 12 and if the oil at the burner nozzle is ignited, the photo-cell 7 operates relay 8 which at contact 8a opens the circuit of the ignition device 1, at opened contact 8c breaks the circuit of the coil 11 and at contact 8b holds relay 14 energized. If the oil is not ignited within a predetermined period after the release of relay 6 the thermal relay 12 operates contact member 13 to its lower position to light warning lamp 15 and to release relay 14 so that motor 2 is disconnected. If the flame should fail during normal running, the relay 8 releases to bring into operation the ignition device 1, and if the flame is restored before thermal switch 12 operates, relay 8 is again energized and normal operation is resumed.