Patent GB-1136606-A (GB)
Title: Improvements in and relating to safety control systems for burners
IPC: F23N5/20
Filed: 1965-12-28
Abstract: 1,136,606. Controlling burners. JUNKERS & CO. G.m.b.H. 28 Dec., 1965 [28 Dec., 1964], No. 54935/65. Heading F4T. . In a flame safety control circuit for a gas or liquid fuel burner, 161, including an electrode 136 for detecting the flame of an ignition burner 157 and a spark electrode 64 for igniting the ignition burner, a preignition or purge period is determined by the charging of a capacitor 56 through a resistor 53. The circuit includes a starter relay 79 operating contacts 81 ... 86 and a monitor relay 42 operating change-over contacts 43, 44; 46, 47. The relay contacts are shown in the start position. When a mains switch 16 is closed current flows through a thermostat switch 17, a manual reset lock-out switch 37, the contact 43 of the monitor relay 42, a protective resistor 49, a rectifier 51, the charging resistor 53, the contact 46 of the monitor relay 42, the primary winding 57 of a high-frequency ignition transformer 58 to the capacitor 56. When the capacitor voltage reaches a predetermined value a gas-filled diode 70 breaks down and discharges the capacitor through a diode 94 and through the starter relay 79 which is thus energized and closes its contacts 81 ... 85 and opens its contact 86. Any fuelair mixture in the burner installation is dispersed by a blower M during the purge period between actuation of the mains switch 16 or the thermostat switch 17 and the energization of the starter relay 79. The closed contact 82 provides a holding current from the rectifier 51 to the starter relay 79. The closed contact 85 energizes a solenoid valve 107 which opens to supply fuel to the ignition burner 157. The closed contact 81 connects a smaller resistance 54 in parallel with the charging resistance 53 so that the charging of the capacitor 56 through the primary winding of the ignition transformer is faster. The closed contact 84 allows the capacitor to discharge through the gas-filled diode 70 direct to the neutral mains line 12. The strong discharge pulses through the ignition transformer 58 cause sparking at the electrode 64 to ignite the ignition burner 157. The closed contact 85 also energizes a protective transformer 118 and if a flame exists at the ignition burner 157 to form a conduction path the secondary winding of the protective transformer applies a voltage to the grid of a cold cathode valve 124 which causes the valve to conduct and energize the monitor relay 42. The changeover contact 40 de-energizes the starter relay 79 and by closing its contact 44 it keeps the solenoid valve 107 of the ignition burner energized and energizes a further solenoid valve 113 to supply fuel to the main burner 161 and keeps energized the protective transformer 118. The other change-over contact 45 discharges the capacitor 56 so that the correct purge period is obtained at the next starting up.  If the ignition burner 157 fails to ignite the monitor relay 42 does not operate and the starter relay remains energized. The closed contact 84 energizes a load resistor 100 which subjects the manual re-set lock-out switch 37 to a load which causes it after a predetermined time to interrupt the current.  If the ignition burner flame fails during operation the monitor relay is de-energized to cut off the supply to both solenoid valves 107, 113. The starting up sequence is then carried out and if the ignition burner fails to ignite the lock-out switch 37 operates.  If a chort-circuit occurs between the flame electrode 136 and the ignition burner 157 the voltage across a gas-filled diode 146 is sufficient to cause the diode to conduct with consequent operation of the lock-out switch 37. The circuit includes a switch 21 controlling the mains supply and actuated by a fuel or air shortage, and a radio interference suppressor comprising chokes 31 and capacitors 32.