Patent GB-786472-A (GB)
Abstract: 786,472. Controlling gas burners. ROBERTSHAW-FULTON CONTROLS CO. Jan. 27, 1956 [June 7, 1955], No. 2759/56. Class 75(1) [Also in Group XXXV] A control system for gas range having a surface burner 16 and means, such as a spider 10, for supporting a cooking vessel 12 comprises means 14 responsive to a temperature in the region of the burner, ignition means for igniting the burner, means for controlling the fuel supply at a predetermined rate to the burner until the temperature sensed by the means 14 rises to a first predetermined value, second means for controlling the fuel supply at a second predetermined rate when the temperature sensed by the means 14 exceeds the first predetermined value, means for stopping the fuel supply when the temperature rises to a second predetermined value and means for reversing the action of the fuel stopping means when the temperature falls below the second predetermined value, whereby the temperature in the region of the burner may be maintained at the second predetermined value. The flow of gas to the burner 16 is controlled by an adjusting and shut-off cock 68 and by two electromagnetic valves 90, 98 co-operating with openings 86, 88 in a partition wall 80 dividing a housing 72 into a gas inlet chamber 82 and a gas outlet chamber 84. The opening 88 is smaller than the opening 86 and may be varied by a rod 93 screwed into a tapped bore 94 in the partition and having a passage 95 which may be wholly or partially aligned with the opening 88. The electromagnetic valves are biased by springs to their closed positions and are opened by solenoids 112, 114 separately energized by movable contacts 138, 140 engaging fixed contacts 134, 136 in a casing 128. The movable contact 138 is carried on the free end of an arm 142 secured to a flexure plate 144 and the movable contact 140 is carried on the free end of an arm 148 secured to a second flexure plate 150, the flexure plates biasing the movable contacts into engagement with the fixed contacts. The switch arm 142 overlies the thrust button 122 of an expansible power element 120 connected by capillary tube 18 to the temperature responsive means 14 which consists of a bulb 15 disposed within a container 17 and biased toward the cooking vessel 12 by a coiled part 19 of the capillary tube 18. The expansible power element is supported on a stud threaded through the casing 128 and having a dial for rotating the stud to adjust the axial position of the power element. The other switch arm 148 has a screw extending downwardly and engageable with an insulating blocK 154 carried on the switch arm 142. At starting both electromagnetic valves are open and the burner 16 is ignited by a pilot burner 20. When the temperature rises to a first value the power element 120 opens the switch contacts 134, 138 to close the large electromagnetic valve 90 so that the burner then burns at a reduced rate determined by the small electromagnetic valve 98. When the temperature reaches a higher value the power element opens the other contacts 136, 140 to close the small electromagnetic valve so that the burner is extinguished. When the temperature drops sufficiently the small electromagnetic valve again opens and the burner is again ignited by the pilot burner. The supply of gas to the pilot burner 20 and to the shut-off cock 68 for the main burner 16 is controlled by an electromagnetic valve 40 biased to closed position and held in open position by the current generated by a thermocouple 54 heated by the pilot burner. The electromagnetic valve 40 is opened initially by a reset stem 56. A valve member 58 slidably mounted on the reset stem and urged by a spring 57 against a stop thereon stops the flow of fuel to the main burner when the reset stem is actuated at starting.