Patent GB-668778-A (GB)
Title: Improvements in control devices for fluid fuel burners
Inventor: CAPARONE MICHAEL JOHN
IPC: F23N5/10
Filed: 1950-02-02
Abstract: 668,778. Valves. ROBERTSHAW-FULTON CONTROLS CO. Feb. 2, 1950, No. 2753/50. Class 135 [Also in Group XI] In a flame-failure control device for a burner apparatus a reciprocable stem is manually moved against resilient bias from an "off" position to a "pilot" position to effect 1. the opening of a valve biased to closed position controlling the flow of fuel to the main burner, 2. the resetting of electro-magnetic means energised by a flame at the burner apparatus for holding the main valve in open position, 3. the interruption of the flow of fuel to the main burner, 4. the opening of a valve controlling the flow of fuel to a pilot burner, and as long as the main valve is held open by the electro-magnetic means the return move-' ment of the stem is limited to an intermediate "on" position in which the flow of fuel to the main burner is no longer interrupted, and means are provided responsive to the movement of the stem for giving a visible indication of the "off", "pilot" and "on" positions of the device. The control device comprises a casing 10 having a partition 16 separating a chamber 12 having a fuel inlet 18 connected by a pipe 118 (Fig. 3) to a main fuel cock 120, from a chamber 14 having a fuel outlet 20 connected to the main burner 122. The chambers 12, 14 communicate through a passage 22, the ends of which constitute valve seats 24, 68 for a valve member 26 controlling the fuel flow to the main burner and for a valve member 66 which interrupts the flow of fuel to the main burner at manual operation of a reciprocable reset stem 62. The valve member 26 is urged into its closed position by a spring 28 and its stem 38 is secured to the armature 40 of a horse-shoe electro-magnet 42 secured to a terminal member 44 on an end cap 32 screwed into the casing 10. The magnet is energized by a thermocouple 138 - (Fig. 3) heated by an ignition burner 132 disposed between a pilot burner 126 and the main burner 122, the ignition burner being supplied by a pipe 134 connected to a main fuel cock outlet 136 which is open when thermostatic control means responsive to the oven temperature has shut off the supply of fuel to the main burner. The magnet is incapable of opening the valve 26 but can hold it in open position. The valve 26 has a second stem 48 extending through the passage 22 between the inlet and outlet chambers 12, 14 and provided with an enlarged head 50 abutting an extension stem 54 slidable in a bore 62a in the reset stem 62 and provided with a collar 56 forming an abutment for a sleeve 58 threaded in to the reset stem 62 and slidable on the head 50 and on the extension stem. A coiled override spring 64 is disposed between the collar 56 and a shoulder in the bore of the reset stem. To prevent the sleeve 58 from sliding off the end of the stem 48 it is slotted to receive a horse-shoe retaining spring 60 which engages with the head 50 of the stem. The extension 54 and stem 48 may be made integral, in which case the retaining spring is not required. The valve member 66 for interrupting the flow of fuel to the main burner is slidably mounted on the reset stem, a shoulder 67 thereon defining the limit of movement of the valve member under the action of its bias spring 70. A cup shaped member 72 threaded to the reset stem slidably engages the wall of the inlet chamber 12 and operates a spring-urged ball 84 projecting slightly into the chamber 12 and constituting a valve member controlling the fuel flow to the pilot burner 126. The reset stem terminates in an operating button 76 extending through a neck 98 in the casing and formed with stepped surfaces 77, 112, 114 which co-operate in turn with a pivoted spring urged lever 104 to position suitable indicia, on the end of the lever, opposite a window 96 in the casing. A diaphragm 78 extends from the reset stem to the casing 10 to seal the chamber 12. On pushing the button 76 inwardly the reset stem slides on the valve stem 48, the ball valve 84 for the pilot burner is opened by the cup member 72 and the valve 66 closes before the sleeve 58 pushes the valve member 26 off its seat and the armature 40 contracts the magnet 42. The pilot burner 126 is ignited by flash back through a tube 130 from a constantlyburning burner 124 and the ignition burner 132 is ignited by the pilot burner and heats the thermocouple. On releasing the button 76 the reset stem is moved backwardly by the override spring 64, until arrested by the engagement of the sleeve 58 with the collar 56, but as the magnet holds the valve 26 in open position the collar 56 is to the left of its original position thus defining an intermediate position of the reset stem. In this position the valve 66 is again open so that fuel passes to the main burner and the pilot burner ball valve 84 is again closed. The main burner is then ignited by the ignition burner. In the modified construction shown in Figs. 6 and 7 a passage 144 leading from the pilot burner control valve 84 to the pilot burner supply pipe is partly or fully closed by a member 146 threaded into the casing and protected by a cap 148. In this embodiment the reset stem also controls the flow of fuel to the ignition burner 132. A ball 152 biased by a flexible diaphragm 156 to project into the inlet chamber 12 is moved upwardly by the cup member 72, when the button 76 is pressed inwardly, to lift a spring-urged ball 166 off its seat in a housing 160 screwed into a chamber 158 in the wall of the control device. Fuel then flows from an inlet 176 past the non-circular valve stem 164 extending between the ball 166 and the diaphragm to an annular recess 172 in the housing 160 and then to the pipe leading to the ignition burner. The valve actuating ball 152 is so positioned in the chamber 12 that the ignition burner valve opens before the pilot burner valve and remains open in the most inward position of the reset stem and also in the intermediate position of the stem when the pilot burner valve 84 is again closed.