Patent GB-691104-A (GB)
Title: Improvements in or relating to automatic control systems for oil burners
IPC: F23N5/20
Filed: 1949-09-22
Abstract: 691,104. Burner control systems. FIANDER L. P. Oct. 18, 1950 [Sept, 22,. 1949], No. 24335/49. Class 75(i) An automatic control system for an oil burner comprises a set of mercury switches including an ignition switch TT, a timing-motor switch CT, a fuel supply switch MT and a relay switch RT which switches are actuated by a cam 10 driven by a timing motor 7 so that in one cycle all the switches are tilted upwardly from an intermediate position to an upper position, the ignition switch TT and the fuel supply switch MT are then released for return to a lowest position and then after a predetermined time the relay switch RT and the timing motor switch CT are released for return to the lowest position, the ignition switch TT being arranged to energize a fuel igniter and the timing motor switch CT to energize the timing motor 7 when both are in the intermediate position, the fuel supply switch MT being arranged to energize a fuel supply arrangement when in the upper position and the relay switch RT being arranged to complete the circuit to a relay 13 when near the upper position, the relay 13 being arranged to hold the fuel supply switch MT in the upper position after release by the cam provided, a device such as a flamestat 16 responsive to correct operation of the burner has responded before such release has taken place. The mercury switches are mounted on three platforms 1, 2, 3 separately hinged about a pin projecting from a panel 5. Platform 1 supports the timing- motor switch CT and the relay switch RT. the middle platform supports on its underside the ignition switch TT and platform 3 supports on its underside the fuel supply switch MT. The timing motor 7 is mounted on the back of the panel 5 and drives through reduction gear a shaft 8 which carries the cam 10. In operation the cam 10 which is of hook form engages first a cross-piece 6 secured to the middle platform 2 and extending under all three platforms so that rotation of the cam raises all three platforms together until the end of the cam slips off the cross-piece 6 and engages the end of platform 1. The middle platform 2 then drops to rest against a rubber ring 9 on the shaft 8 and the third platform 3 also drops unless retained in the unper position by a rod 14 which is pushed through a hole in the panel 5 by the relay 13 mounted on the back of the panel. Further rotation of the cam releases the platform 1 which then drops alongside the middle platform 2. The control system is actuated by a thermostat switch 15 responsive to the temperature of a body heated by the burner. When the thermostat switch is open the platforms 1. 2, 3 are in the intermediate position with the cam 10 engaged with the cross-piece 6, the contacts TT1, TT2, TT3, of the ignition switch, the contacts CT1, CT2 of the timing- motor switch, and the contacts MT2, MT4 of the fuel supply switch being closed. On a demand for heat the thermostat 15 closes its contacts to energize an ignition trans-- former 17 and the timing motor 7 through a fuse FF, the cold position contacts F1, F3 of a switch actuated by the flamestat 16 and the ignition switch TT and the tim-- ing motor switch CT. The cam 10 then raises the three platforms to close the con-- tacts RT1, RT2 of the relay switch and to close the contacts MTI, MT3, MT4 of the fuel supply switch so that a motor M supplying air and fuel to the burner isenergized. After 45 seconds and provided ignition of the fuel has been effected the flamestat 16 closes the hot position contacts F1, F2 and opens the cold position contacts F1, F3 of its switch whereby the relay 13 is energized and the rod 14 is pushed under the platform 3. The relay 13 also closes a pair of contacts to complete a circuit from the contact MT1 of the fuel control switch through the closed contacts RT1, RT2 of the relay switch to one side of the relay, this circuit maintaining the relay energized at the start period should the flamestat momentarily open the contacts F1, F2 due for instance to a bubble of air in the fuel feed. When the cam clears the cross-piece 6 the contacts TT1, TT2, TT3 of the ignition switch are opened and the ignition is de-energized and after a further five seconds the cam clears the platform 1 whereby the contacts of the relay switch RT and the contacts CT1, CT2 of the timing-motor switch are opened. The control remains in this condition until the demand for heat has been satisfied. When the thermostat 15 again opens the relay 13 is de-energized, the rod 14 is retracted and platform 3 falls to make contacts MT2, MT4 of the fuel supply switch. The timing-motor 7 is again energized through the contacts MT2, MT4 and through a second pair of contacts CT3, CT4 in the timing-motor switch. The cam then lifts all three platforms to the intermediate position, the timing-motor being deenergized finally by the mercury in the timing-motor switch moving from the contacts CT3, CT4 to the contacts CT1, CT2. If ignition fails the flamestat does not close the contacts F1, F2 so that the relay is not energized and platform 3 drops with the middle platform 2 leaving platform 1 in the upper position. The timing motor is de-energized in this position of the control but can be energized by manually closing a switch 11 which connects the closed contacts CT1, CT2 of the timing-motor switch directly to the supply. The cam again rotates and when platform 1 drops the motor is energized through the contacts MT2, MT4 and the second pair of contacts CT3, CT4 in the timing-motor switch as described for normal operation. Platform 3 in rising from the lowest to the intermediate position engages the dolly of the manual switch 11 and opens the contacts thereof. Ignition failure is indicated by a lamp W energized through contacts MT2, MT4 of the fuel supply switch and contacts LT1, LT2 on a third mercury switch LT mounted on platform 1 so as to have its contacts closed when the platform is in the intermediate and upper positions.