Patent GB-826406-A (GB)
Title: Improved electric ignition and safety device for burners
IPC: F23N5/20
Filed: 1956-01-18
Abstract: 826,406. Controlling burners. HEIMERL, O. Jan. 18, 1956 [Feb. 3, 1955], No. 1726/56. Classes 75(1) and 75(3) [Also in Groups XIII and XXXVII] in an electric ignition and safety device for burners of the kind including means sensitive to the heat of the burner and adapted to open and close a fuel valve, a lever 57 actuated by the heat sensitive means moves a contact carrier 64 between a counter contact 69 and a stop, for instance a second counter contact 68 and the contact carrier 64 is movable relative to the lever 57 against a restraining force. The contact carrier 64 is in the form of a stud slidable in an eye 63 on the end of the lever 57 but its movement in the eye is restrained by a spring wire 66 secured to the lever 57 and passing through an aperture 67 in the eye to press on the stud 64. The counter contacts 68, 69 are mounted on resilient plates 70, 71 having bent-over ends provided with slots 87, 88 into which the ends of angle plates 72, 74 extend to. define the limits of the movements of the resilient plates. The movement of the upper resilient plate 70 can be adjusted by elastically deforming the angle plate 72 by means of a screw 89 screwed into a further angle plate 73. The heat responsive means for actuating the lever 57 comprises a ceramic rod 49 displaceably mounted in a metal sleeve 48 and bearing at one end against a stop 51 in the sleeve. A filament 5 for igniting the burner is situated in front of the end face of the ceramic rod and a heating wire 52 connected in series with the filament 5 is coiled around the ceramic rod and serves to heat the rod and the metal sleeve 48. The lever 57 is pivoted on a knife edge bearing 56 supported on two arms 55 and a spring 61 urges the lever in clockwise direction so that an adjustable ball 60 on the pivoted end of the lever is held in abutment with the end of the ceramic rod 49. In operation when a main switch is closed the ignition filament 5 and the heating wire 52 are energized through stud 64 and upper contact 68. The ceramic rod 49 and metal sleeve 48 are thus heated and due to their different thermal expanions the lever 57 is moved clockwise. The stud 64 is therefore carried downwardly and eventually also contacts the lower contact 69 to energize an electromagnetic fuel valve. The burner is ignited by the filament 5 and heats the metal sleeve 48 and ceramic rod 49. Further downward movement of the stud 64 breaks the filament and heating wire circuit at the upper contact 68 and when the lower contact 69 is arrested by the angle plate 74 the eye 63 of the lever 57 moves over the stud against the frictional resistance of the spring wire 66. When the burner is extinguished the lever 57 rotates anticlockwise to open the electromagnetic valve circuit at contact 69 and to close the filament and heating wire circuit at contact 68; but since the stud 64 was displaced in the eye 63 at the end of the burner starting up process the electromagnetic fuel valve closes at a higher temperature than that at which it opened and the filament and heating wire circuit is energized again at a higher temperature than that at which it was de-energized. In a modified construction the ignition filament and heating wire circuit are not controlled by the stud 64, the upper contact 68 being replaced by a fixed stop. In a further modification the heating wire is coiled around the metal sleeve 48 and serves also as the ignition filament. In a still further modification the ignition filament and heating wire are replaced by a spark igniter and the electromagnetic fuel valve is energized initially through a push button switch.