Patent GB-714007-A (GB)
Title: Improvements in or relating to control apparatus for fuel burning appliances
Inventor: WEBER VICTOR
IPC: F23N5/10
Filed: 1952-06-06
Abstract: 714,007. Controlling the supply of fuel to burners. ROBERTSHAW-FULTON CONTROLS CO. June 6, 1952, No. 14403/52. Classes 75 (1) and 75 (3) In a safety control apparatus for a fuel burner appliance comprising a safety control device controlling the flow of fuel from a main fuel control means to a main burner, electromagnetic means energized by means responsive to a burner flame for holding the safety control device in open position against bias, resetting means adapted by the opening of the main control means to be moved to cause the safety control device to open and a timing device adapted to cause the resetting means to return to its inoperative position after a period sufficient to allow ignition of fuel to produce the said flame and to allow energization of the electromagnetic means, the resetting operation is effected by rotation of a lever which is held in operative position, permitting fuel to flow to a pilot burner, by a thermal timer biased into latching engagement with the lever and responsive to the flame of the pilot burner to become disengaged from the lever so that the lever returns under bias to its inoperative position and the fuel to the pilot burner is cut off. The fuel to a cooking range including an oven burner 10 is controlled by a main shut-off valve 20 and by a safety control device 22. The safety control device 22 comprises a casing 26 having a fuel inlet chamber communicating with a fuel outlet chamber through a passage 34, the inlet end of the passage 34 forming a seat for a valve 38 controlling the fuel to the oven burner 10. The valve is urged by a spring 40 to closed position and the stem of the valve carries an armature 48 attracted by a horse shoe electromagnet 52 energized by a thermo-couple 146 heated by a burner 74, the attraction of the magnet being sufficient to hold the valve in open position but insufficient to move it from closed to open position. The valve is opened by a reset stem 44 which extends through a cap 60 on the casing and through the fuel passage 34 to abut the valve. A spring 68 urges the reset stem outwardly from the valve, the outward movement being limited by a collar on the stem abutting the end cap. The safety control device also includes a valve controlling the fuel to the thermo-couple heating burner 74 and to an auxiliary pilot burner 72 heating a bimetal timing element 126 mounted on one leg of a bell crank 130 the other leg of which is urged by a spring 128 into abutment with a set screw 132, the valve comprising a ball 80 urged by a spring to seat on the end of a fuel passage and having a stem 86 disposed parallel to the reset stem 44 and projecting through the wall of the casing. Both valves 38, 80 are opened by a pivoted lever device 92 which engages the projecting ends of the valve stem 86 and the reset stem, the lever device comprising a lever 94 and a latching element 98 both pivoted to a bracket on the cooking range and connected together resiliently by a pin 100 having spaced cross pins between one of which and the lever a coil spring 104 is disposed. The latching element has a lug engaged with the end of a stud 118 threaded into the end of a rod 110 extending to the main shut off valve 20 and adapted to be rotated through an arc, when the shut off valve is opened, by a cam plate 106 on the shaft of the shut off valve engaging an arm 108 on the end of the rod. When the cam plate 106 clears the arm the rod is returned by a torsion spring 114. The stud 118 is prevented from rotating with the rod by an arm 120 on the stud engaging in a slot in the supporting bracket and accordingly moves longitudinally, upward longitudinal movement causing the lever device 92 to pivot clockwise and open both fuel valves. The lever device is held in this position by the bimetal element 126 engaging the end of the latching element 98. Fuel is now supplied to the auxiliary pilot burner 72 and to the thermocouple heating burner 74, the auxiliary burner being ignited by a flash tube 148 from a constantly burning pilot burner 12 and the thermo-couple heating burner being ignited by a flash tube 150 from the auxiliary burner. Although the valve 38 to the oven burner 10 is open fuel is not supplied thereto as a spring- urged disc 42 slidably mounted on the reset stem closes the outlet end of the fuel passage 34 when the reset stem is moved inwardly. The auxiliary pilot burner 72 heats the bimetal element causing it to warp and disengage the latching element 98 whereupon the lever device returns in an anti-clockwise manner under the action of the spring 68 of the reset stem 44. The fuel to the auxiliary pilot burner and to the thermo-couple heating burner is thus cut off but as the electro-magnet 52 is now energized the valve 38 to the oven burner remains open and the slidable disc 42 is carried from the outlet end of the fuel passage 34 by abutments 66 on the reset stem. The oven burner is then ignited by an ignition pilot burner 17 located beside and ignited by the thermocouple heating burner. This ignition pilot burner 17 is supplied directly from the shutoff valve 20 and heats the thermo-couple when the thermo - couple heating burner is extinguished. In order to retard the anticlockwise return of the lever device 92 to avoid setting up vibration which might cause the armature to separate from the electro-magnet resulting in closure of the valve 38 to the oven burner a gear sector 136 is secured to the lever 94 and meshes with a gear train terminating in a fly-wheel. The main shut-off valve may include the usual adjustable thermostatic control device for throttling the supply in response to oven temperatures. Specification 624,742 is referred to.