GB1207649A - Control and monitoring means for oil or gas burners - Google Patents

Abstract

1,207,649. Burner control. LANDIS & GYR A.G. 1 Aug., 1969 [7 Aug., 1968], No. 38746/69. Heading F4T. A control and monitoring system for oil or gas burners comprises an electrically heated bi-metal strip 1 which controls first and second sets of contacts 3, 2, and an electromagnetic control 17 which is controlled by a photoresistor 15, a lever 9 being provided between a fuel supply control contact spring 4 and an armature 10 of the electromagnetic control 17, the lever 9 when the armature 10 is attracted, preventing the contact spring 4 firstly making contact with a starting supply contact spring 5 and secondly separating it from a control contact spring 7, or, after the bimetal strip 1 has tripped the second set of contacts 2 and the armature 10 is attracted, it separates contact spring 4 from contact spring 7 and holds the former in engagement with spring 5 while the bimetal strip 1 returns to its rest position. In operation, the switch 12, Fig. 2, is closed by a thermostat, supplying power to the blower 13, ignition coil 14 and heater coil 1. The bi-metal strip 1 bends, moving contact springs 4 and 6 together against contact 5 which energizes the valve 19 to supply fuel for starting the burner. On ignition, the photo-resistor resistance drops so that the electromagnetic control 17 receives sufficient current through the diode 16 to attract the armature 10, which traps lever 9 by means of hook means or roughened contact surfaces, and thus breaks the contact between 4 and 7, cutting off the current to the heater 1 allowing the bi-metal strip to cool and return to its original position together with the linked contacts 6 and 8, the latter of which cuts in the main fuel supply valve 20. If the flame goes out, the resistance of the photo-resistor 15 increases, reducing the current through the electromagnetic coil 17 causing armature 10 and lever 9 to be released, and contact 4 moves out of contact with contacts 5, 8, cutting off the fuel supply via valves 19, 20, and into contact with contact 7, re-commencing the ignition procedure. If no flame is produced, heater 1 is energized via contacts 4, 7 for longer than the normal period, so that contacts 3 are triggered cutting off power to the control circuit and causing the warning light 21 to come on. The contacts 3 lock in this position and have to be re-set manually. A control element 18 (a capacitor or a transistor amplifier) in parallel with the photo-resistor 15 provides a current surge through the coil 17 when switch 12 is closed, thus attracting armature 10. If the resistance of the photo-resistor is too low, due to ageing, high ambient temperature or stray light, the armature 10 remains attracted and prevents movement of the lever 9 and hence the contact 4, and current is supplied to the heater 1 until contacts 3 are switched.