Patent GB-1450053-A (GB)
Title: Control systems for gaseous fuel fired appliances
IPC: F23N5/06
Filed: 1972-11-17
Abstract: 1450053 Burners; igniters T I DOMESTIC APPLIANCES Ltd 16 Nov 1973 [17 Nov 1972] 53239/72 Headings F4T and F4F [Also in Division F2] A control system for a gaseous fuel-fired appliance comprising a fuel valve 57, having a first member 59, and a second member 61 a movable member 85 connected to 59 by a link 63, means 65 for varying the ratio of movement, an arrangement 70 for moving both members 59, 61, between an OFF and an ON position wherein further movement of 59 to regulate the flow of fuel is effected by member 85, and further means for adjusting the crosssection of a fuel passage 69 to control the rate of fuel flow. A single rotary knob 5 actuates valves 9, 54, 48, sets the bellows 85 of a thermostat 84, actuates the microswitch 77 of an electromagnet 76, and pivots the hammer 90 of a piezo-electric crystal 89, through cams 13, 56, 49, 86, 79, 92. The appliance comprises a gas burner 4, having a thermo-couple 25, a pilot burner 26 and an ignition device (97), Fig. 11 (not shown). Gas shut-off valve 9 is moved against a spring 10, to allow gas to flow through elbow 8 into casing 6 by cam 13 which actuates a push rod 14 and levers 14-17, which latter form a locking mechanism for holding the valve off its seat, the rod 14 having an extension 22 which co-operates with a spring-urged armature 23 of an electromagnet 24 whose coil is energized from thermo-couple 25. A diaphragm 28 is loaded in an upward direction against a spring 37 by a spring 33 acting through a pivoted lever 34, and carries two valves 39, 40, on a rod 31. Gas flow from the interior of casing 6 to the burner 4 is controlled by modulating valve 57 which comprises disc closure 59, a tubular part 60 in which the second tubular part 61 is slidably mounted, part 60 being connected to lever 63 pivoted about an adjustable pivot 65, and part 61 being connected to a rod 70 secured to the armature 71 of an electromagnet in a housing 72. A second thermostat and bellows 82 operates a release lever 83 associated with the locking mechanism for holding valve 9. In operation, knob 5 is rotated, cam 13 opens valve 9 and moves armature 23 towards electromagnet 24, so that gas flows into the lower part of casing 6. Cam 56 opens valve 54 and gas passes through passageway 53 to the upper face of diaphragm 28, which flexes downwardly to open valve 39 and close valve 40. Pilot valve 48 is opened by cam 49 and gas passes via passages 45 and 51 to pilot 26. As knob 5 is rotated spring 91 is tensioned until hammer 90 strikes the piezoelectric crystal to ignite the pilot. As thermocouple 25 is heated, electromagnet 24 is energized to hold armature 23 against spring 27. Spring 21 pivots lever 15 so as to allow levers 15, 16 to lock valve 9 in the open position. Further rotation of knob 5 allows cam 79 to close microswitch 77, energization of electromagnet 76 and opening of the main gas valve 57 so that gas passes to the main burner 4 to be ignited by the pilot. Still further rotation of knob 5 sets phial and bellows 84, 85, to a particular temperature through cam 86, and as that temperature is approached bellows 85 acting through lever 63 closes valve 58 so as to modulate the gas flow according to the water temperature. If the temperature continues to rise pivotal movement of lever 63 compresses spring 64, member 85a actuates lever 78 so as to operate microswitch 77, which de-energizes electromagnet 76, so that the slot 69 of valve 58 is closed by member 60 and gas ceases to flow to burner 4. If now the water temperature drops, the sequence is followed in reverse, but if the temperature continues to rise phial and bellows unit 81, 82, unlocks levers 15, 16, to close valve 9, and cutoff the supply to burner 4 and pilot 26. A lockout device preventing re-ignition whilst electromagnet 24 is energized is provided.