Patent GB-775501-A (GB)
Abstract: 775,501. Safety control systems for burners. ROBERTSHAW-FULTON CONTROLS CO. Dec. 2, 1954 [Jan. 26, 1954], No. 34959/54. Classes 75(1) 'and 75(3) A control system for a main fuel burner 10 comprises a pilot burner 22 for lighting the main burner, a thermally responsive element 58 heated by the pilot burner, a main valve 16 and a thermally responsive valve 14 both controlling the supply of fuel to the main burner, the thermally responsive valve 14 being moved to open position on the heating of the thermally responsive element 58 to a predetermined temperature, and means for providing fuel to the pilot burner at a high rate whilst the main valve 16 is open but the thermally responsive valve 14 is still closed, at an intermediate rate sufficient to maintain the thermally responsive element 58 above the predetermined temperature when both valves 14, 16 are open and at a low rate sufficient to ignite the main burner but insufficient to maintain the thermally responsive element 58 above the predetermined temperature when the main valve 16 is closed but the thermally responsive valve 14 is open, and means for cutting off the supply of fuel to the pilot burner when both valves 14, 16 are closed. Three fuel supply lines to the pilot burner 22 are provided the first consisting of conduit 68, main valve 16, conduit 66 conduit 98, a thermally responsive valve 102, conduit 100 needle valve 118 and conduit 24, the second consisting of conduit 68, main valve 16, needle valve 74, conduit 70 and conduit 24, and the third consisting of needle valve 96, conduit .78, thermally responsive valve 80, conduit 76 and conduit 24. The three thermally responsive valves 14, 80, 102 have stems operated simultaneously by a pivoted lever 50 actuated by an expansible element 56 communicating through capillary tubing 60 with the thermally responsive fluidcontaining bulb 58 heated by the pilot burner. Expansion of the expansion element 56 causes the valves 14, 80 to open and the valve 102 to close. When the main valve 16 is opened fuel passes to the pilot burner through its first and second supply lines and is ignited by an electrically heated catalytic igniter 20. The needle valve 118 in the first supply line is set to provide a high burning rate. When the bulb 58 reaches the predetermined temperature the lever 50 is tilted to open valve 14 to supply fuel to the main burner 10, to open valve 80 to supply fuel to the pilot burner through its third supply line and to close valve 102 to cut off the supply of fuel to the pilot burner through its first supply line. The pilot burner is then supplied through its second and third supply lines and the needle valve 96 in the third supply line is set to provide an intermediate burning rate which is sufficient to maintain the temperature of the bulb 58. This condition is the normal operating one. If the main valve 16 is now closed the fuel to the main burner and to the first and second pilot supply lines is cut off at the main valve but the pilot burner continues to be supplied through its third supply line since the thermally actuated valve 80 in the third supply line remains open until the bulb 58 cools below the predetermined temperature. The rate of burning at the pilot burner in this condition however is not sufficient to prevent cooling of the bulb 58 but serves to ignite the main burner should the main valve 16 be opened before the bulb 58 has cooled sufficiently to close the valve 14 to the main burner. The main valve 16 is manually operated but may be remotely controlled.