GB1469048A - Circuit arrangements for controlling automatic ignition devices - Google Patents

Abstract

1469048 Ignition control L G Z LANDIS & GYR ZUG AG 3 April 1975 [11 April 1974] 13756/75 Heading F4T [Also in Division G3] A circuit for controlling an automatic igniter 12, Fig. 1, for liquid or gaseous fuels comprises means for ensuring the preservation of a safety time in the event of a temporary interruption in a supply voltage, a flame monitoring relay FR, an operating relay AR, a timer TZ based on the change in a physical parameter, contacts tz s actuated by the timer, a switch tz 2 controlling supply of fuel and dependent on the condition of the timer arranged in the actuating circuit of the operating relay, and an operating switch contact ar 3 which is closed when the operating relay is energized, connected in parallel with the timer. The timer TZ comprises a thermal switch with two heating windings TZ 1 , TZ 11 and switch contacts tz 1 , tz 2 , tz s . The flame monitoring relay FR comprises switch contacts fr 1 , fr 2 , fr 3 , fr 4 , fr 5 , and a flame monitor 7 and the operating relay AR comprises switch contacts ar 1 , ar 2 , ar 3 . In operation, a bimetal closes switch tz s and a thermostat 3 is closed so that current flows to neutral line 2 via components 1, 3, tz s , 4, 5, fr 1 , TZ 1 , Fig. 1. Winding TZ 1 is heated to control the pre-scavenge or safety time, a blower 6 is operated and igniter 12 is energized through closed switch fr 1 and line 11. After expiry of the safety time timer TZ actuates change-over switch tz 1 so that there is an additional current flow from line 5 to line 16 through switches fr 1 , tz 1 and thence to line 2 via switch tz 2 , diode 20, two windings 22, 23, switch fr 3 and winding TZ 11 or resistor 25. AR is actuated to operate its switches to thus hold the relay and actuate valve MV 1 to supply fuel, which is ignited. FR is actuated to operate its switches, and the ignition is switched-off, whilst contact 13 holds relay AR, switch fr 2 cuts out winding TZ 1 and switch fr 3 cuts out winding TZ 11 . Relay AR is now held by winding 23 and resistor 25. The bimetal of TZ cools and switch tz 1 switches back to apply voltage to valve MV 11 so that the greater burner output required is attained. If no flame were to be produced windings TZ 1 , T 11 arranged on the same bimetal would have actuated switch tz s after expiry of the safety time, and the system would be de-energized. The arrangement of switches tz 1 , tz 2 may be simplified, Fig. 1a (not shown). In a modification, switch tz 2 is replaced by an electronic switch (te 1 ), Fig. 2 (not shown). In a further modification, electronic switch (te 2 ), Fig. 3 (not shown), is dependent on the condition of timer TZ, and is connected in parallel with a circuit which includes switch ar 3 , winding TZ 11 , and a further diode (33), the two circuits being connected by a fuse (35). In another modification, Fig. 4 (not shown), switch (te 1 ) is connected to the circuit including switch ar 3 by a rest switch (fr 3 ).