911,297. Controlling burners. DOWTY FUEL SYSTEMS Ltd. Dec. 7, 1959 [Dec. 11, 1958], No. 40019/58. Class 75 (1). [Also in Group XXIX] A liquid fuel supply system for burner nozzles has three stages of operation controlled by selector valves. In the first or pre-heating stage the fuel is preheated and circulated around the installation without being fed to the burners; in the second or normal running stage the fuel is preheated and fed to the burners; and in the third or close-down stage the fuel is punped from the burners. The selector valves are operated by a single control member which is held in one extreme position against the action of a spring by a solenoid to determine the normal running stage. On de-energization of the solenoid the control member is urged by the spring to its other extreme position to define the preheating stage, and the close-down stage is determined by a position of the control member between the extreme positions. The movement of the control member from one extreme position to the other is slowed down by a mechanism so that the close-down stage in which fuel is pumped from the burners occupies a predetermined time. The fuel pump is driven by an electric motor which is de-energized with the solenoid holding the valve control member in the normal running position but the motor keeps on running due to its inertia throughout the close-down stage. Alternatively a time delay mechanism may be provided on the motor circuit breaker to keep the motor energized for a period after the solenoid has been de-energized. ' ' Fig. 2 shows the fuel supply system with the selector valves 15, 16, 17 set to determine the normal running position. The pump 14 draws fuel through a filter 18 and a pipe 13 from a reservoir and delivers it through a preheater 19 and the valve 17 to the inlet of a spill burner 1. The return fuel passes through a spill line 3 to the inlet of the filter 18 and is controlled by a spill valve 5. Some fuel also passes from the pump and heater through a pressurizing valve 22 to the inlet of the filter 18. In the preheating stage, Fig. 1 (not shown), the valves 16, 17 are closed and fuel is drawn by the pump through the valve 15 and discharged through the heater 19 and the pressurized valve 22 to the inlet of the filter 18. In the close-down stage, Fig. 3 (not shown), the valve 16 connects the spill line 3 with the valve 15, and valve 17 connects the supply line 2 with the valve 15 and the latter connects the pipes from the valves 16, 17 to the inlet of the pump and closes the connection between the filter and the pump. Fuel is therefore drawn from the supply line 2 and the spill line 3 of the burner and discharged through the heater 19 and the pressurized valve 22 to the reservoir. The three selector valves 15, 16, 17 are formed in one unit shown in Figs. 7, 9 and are operated by a spindle 48 actuated by a solenoid. The unit also includes the filter 18, the pressurized valve 22 and the spill control valve 5. The selector valve 15 comprises a cylindrical member 29 secured to the spindle 48 and rotatably mounted in a bore 28. Two ports 41, 42 in the cylinder 29 are adapted to register with a bore 33 extending from the filter 18 in the two end positions of ninety degree rotation of the cylinder and a third port 43 registers with a bore 31 leading to the pump in all positions of the cylinder. In the middle position of the cylinder the bore 33 from the filter is closed. A valve plate 44, Fig. 9, providing the selector valves 16, 17 is loosely mounted by means of pins 45 in the outer end of the cylinder 29 and is coupled to the spindle 48 to rotate with the cylinder 29. The plate 44 has a pair of through ports 69 (only one is shown) which in the normal running stage connect a pair of ports 67, 68 in a flat closure member 66 for the bore 28 of the valves to sleeves 57, 58 urged by springs against the plate 44. The plate also has a pair of grooves 71 (only one is shown) which in the middle position of rotation of the spindle connect the ports 67, 68 to the interior of the cylinder valve 29. In the preheating stage a flat part of the plate 44 is located between the sleeves 57, 58 and the ports 67, 68 to close communication therebetween. The filter 18 is mounted in a large bore 35, Fig. 7, in the valve unit and comprises an end plate 30 which is held on a shoulder 36 by a spring 40a. If the pressure drop through the filter increases unduly in consequence of the filter clogging, the filter and plate 30 lift from the shoulder 36 and the fuel by-passes the filter. The spill valve 5, Fig. 8 (not shown), is also mounted in the valve unit and comprises a rotary valve member 6 in a cylinder having a port leading to the bore containing the filter. The inclined end of the plunger controls the effective area of the port. The pressurizing valve 22 is also mounted in the valve unit and comprises a sleeve slidable in a bore in a body member and having a pair of ports in its side wall. A spring urges the sleeve into the bore so that the ports are closed and oil pressure within the sleeve urges the sleeve outwardly to uncover the ports. The mechanism for delaying the rotation of the spindle 48 of the selector valves through the middle close-down stage is shown in Fig. 4 and comprises a lever 83 clamped to the end of the spindle 48 and coupled by a link 85 to the solenoid 87; a spring 88 returns the lever 83 in an anti-clockwise direction when the solenoid is de-energized. A second lever 92 is loosely mounted on the end of the spindle 48 and is coupled by a link 94 to a timing mechanism 95. The link 94 can be pushed inwardly by a projection 96 on the first lever 83, without great resistance, to wind the timing mechanism 95 but a return spring 101 acting on another lever 99 adapted to keep contact with the second lever 92 can only pull the link 94 away from the timing mechanism at a slow rate. On release of the solenoid the first lever 83 rotates away from the link 94 until its projection 96 engages a detent 97 on the third lever 99. The link 94 slowly withdraws from the timing mechanism and the third lever 99 eventually moves the detent 97 to release the projection 96 on the lever 83 which then moves to its full extent. The burner is controlled by the circuit shown in Fig. 10 which includes a cam motor 110 driving five cams A ... E operating contacts Al ... E1, a motor 106 driving the fuel pump and a fan supplying combustion air, two oil heaters 111, 112, a burner ignition transformer 116, a motor 118 for actuating the spill control valve in response to a thermostat 117 on a boiler to be heated, the solenoid 87 for the selector valves and a relay R having contacts Bl, R2, R3. In operation when a main switch is closed the heaters 111, 112 are energized and when the fuel reaches a predetermined temperature a thermostat 114 closes. The relay R is then energized and closes contacts R1 and R3 and connects contact R2 to contact R22. The cam motor 110 is then energized through contacts A1, A3. If the cam motor had been stopped with cam E closing contact El, E2 then the cam motor would be energised at starting through these contacts and contacts R2, R21. The cam E would then close contacts El, E3 momentarily to energize the relay R. Cam D then energizes the solenoid 107 of circuitbreaker 105 to start the fuel and air motor 106. The fuel therefore circulates but does not reach the burner. Cam C then energizes the ignition transformer. Cam B then energizes solenoid 87 to move the selector valves to the normal running position in which fuel is sprayed from the burners. Cam C then de-energizes the ignition transformer. Cam A then de-energizes the cam motor 110 and energizes a relay 119 which closes a contact in the supply circuit to the motor 118 for the spill valve. Known safety devices which protect against flame failure and excessive temperature or pressure in the boiler may be provided.