Patent GB-639878-A (GB)
Title: Oil pressure atomizing burners for heating houses
IPC: F23D11/26
Filed: 1947-11-11
Abstract: 639,878. Liquid fuel burners. GILBERT & BARKER MANUFACTURING CO. Nov. 11, 1947, No. 30015. Convention date, March 8. [Class 75 (i)] [Also in Group XXIX] In a variable firing rate oil burner of the kind adapted to start and stop under the control of a room thermostat and comprising a motor driving an air fan and an oil pump, means are provided for changing the pressure of the oil supplied to the burner nozzle to provide a high or a low firing rate. The oil-pressure changing means shown in Fig. 8 comprises a gear pump 13 which draws oil through a pipe 12 and an oil filter 17 and delivers it into a chamber 21 in which is mounted a cut-off valve 23 which opens to allow oil to pass to the burner nozzle 10 and a bye pass valve 37 which opens to allow oil to pass to a two-way valve 44. The cut-off valve 23 is mounted on the lower end of a cylindrical member 24 which is attached to the lower closed end of a bellows 25 and which is slidable in a tubular member 26 secured to the base of the chamber 21. Radial holes 27 in the member 26 enable oil to flow to the valve 23. The bellows 25 has an upper flanged end which is held between a washer 32 and an annular shoulder 29 on the valve casing by a spring 30 disposed between the washer and the cover 31 of the casing. A second spring 33 acts between the lower closed end of the bellows and an adjustable screw 34 mounted in the cover 31. An oil pressure of ninety pounds per square inch causes the bellows to rise upwardly to open the valve 23 so that oil flows through an outlet passage 35 to the burner nozzle. The bellows also control the bye pass valve 37 which comprises a hole 37 in the wall of the slidable cylinder 24 adapted to be covered by the fixed cylinder 26. When the oil pressure reaches ninety-five pounds per square inch the nole 37 is lifted above the end of the cylinder 26 by the bellows and oil flows into the upper chamber 39 and thence to a chamber 41 connected to the twoway valve 44. In one position of the two-way valve oil passes to the suction pipe 12 of the gear pump, and in the other position it flows to a casing 49 containing a second bye pass valve 50, which is similar to the valve 23 and is adjusted to open when the oil pressure is two-hundred pounds per square inch ; its outlet is connected to the suction pipe 12. The casings for the pump, filter, cut-off valve 23 and first bye pass valve 37 are combined as shown in Fig. 6 into a single unit 16 mounted on the fan housing 2. The pump shaft 62 is connected to the motor shaft 67 by a flexible coupling 145 and by a speed responsive clutch coupling 143, 146. With this arrangement the air fan 66 acquires a considerable speed before the pump starts so that air is supplied before oil to the burner nozzle ; and on switching off air continues to flow for a time to scavenge combustion products after the oil pump has stopped. The air supply to the burner is controlled by a valve on the inlet side of the air fan 66 and by a valve in an annular passage between two concentric tubes 7, 8 (Fig. 3) enclosing the burner nozzle. The valve on the inlet side of the air fan 66 comprises an annular shutter 65 (Fig. 6) adjustable to vary an air inlet opening 69 in the end face of the fan housing 2. A screw 71 slidable in the fan housing 2 and in a rigid cross-beam 59 has a threaded engagement with the shutter so that the position of the shutter can be adjusted by rotating the screw. A spring 73 urges the screw towards the left and a depending arm 76 slidably mounted on the screw engages an adjustable abutment formed by two nuts on the screw to move the screw toward the right and open the shutter. A spring 77 holds the arm 76 against the nuts. The shutter and adjusting means are enclosed in a removable casing 80 which has air openings 83 and a slot 78 for the arm 76. The latter is actuated by an arm 79 which is secured to the actuating means of the two-way valve 44 so that the air control is synchronized with the firing rate control. By varying the lost motion between the arms 76, 79 the amount of movement of the shutter can be regulated. The driven element 146 of the speed responsive pump coupling is located in a sleeve 148 on the air shutter and is provided with blades which tend to extract air from the air fan 66 so that a lean fuel mixture is obtained at both starting and closing down as described in Specification 615,393. The air supply to the nozzle 10 is delivered through two concentric tubes 7, 8 (Fig. 3)'and a valve s arranged to close the annular space 90 between the tubes 7, 8 when the nozzle is being fired at the low rate. This valve is made from two stampings 92 of triangular cross-section fitted together to form an annular stream-lined ring 91 secured to two studs 94 sliding in bearings 95 and urged by springs 98 to hold the ring 91 in the closed position. The studs 94 are connected by a bell-crank lever 100 and a link 102 to an arm 85 adapted to actuate the two-way valve 44. The arrangement is such that the valve 91 is open when the burner operates at the high firing rate. The cross-sectional areas of the two concentric tubes 7, 8 may be so proportioned that the air will have the same velocity at both burner firing rates. The two-way valve 44, the shutter 65 and the air valve 91 are all operated by a lever 83 which is actuated by the plunger of a solenoid housed in a casing 87. The nozzle end of the oil feed pipe 36 and ignition electrodes 11 disposed at the nozzle are mounted on a support 106 provided with radial legs engaging the inner wall of the tube 8. This support.106 is interconnected with a support 96 for the air valve 91 by two tie rods 111. The support 96 is provided with radial legs 103 engaging the inner wall of an air passage 4 leading to the concentric tubes 7, 8 and is secured to rods detachably held at their ends to a removable end cover 6 for the passage 4. The nozzle 10, electrodes 11, air valve 91 and the oil pipe 36 thus form a unit which can be readily removed from the air passage. Fig. 11 shows the electrical circuit of the burner. The motor 68 and an ignition transformer 132 supplying the ignition electrodes 11 are connected in parallel and are controlled by a switch 124 which is closed by a relay coil 115 when a room thermostat 113 connects a low voltage from a transformer 114 to the relay coil. The solenoid 135 which actuates the two-way valve 44, the shutter 65 and the air valve 91 is arranged in a circuit including the switch 124 and a second thermostat 136 responsive to any temperature, such as an outdoor temperature, by which it is desired to select the firing rate of the burner. Alternatively a manual push button switch may replace the thermostat 136. In either case the energization of the solenoid 135 changes the firing rate from low to high. The change in oil pressure to the burner nozzle may be effected by changing the pressure of the spring 33 of the cut-off valve 23 by means comprising a solenoid 154 (Fig. 9). The upper seat 149 of the spring 33 is carried by a plunger 150 slidable in the cap 151 of the valve casing and a pivoted lever 152 connected to the armature of the solenoid engages the upper end of the plunger. Adjustable stops 156, 157 are provided for the lever 152. The solenoid 154 may be connected in parallel with the solenoid 135 which in this case would operate only the air valve 91 and the shutter 65. Another arrangement for changing the fuel pressure to the nozzle is shown in Fig. 10. The oil pump 158 discharges to three valves, a cut-off valve 160 which opens when the pressure reaches 90 pounds per square inch, a bye pass valve 161 set to open at twohundred pounds per square inch and a second bye pass valve 162 set to open at ninety-five pounds per square inch. A valve 165, which may be controlled by the outdoor thermostat, can cut off the supply of oil to the second bye pass valve 162 with the result that the nozzle 10 is supplied at the high firing rate. Safety controls (not described) operating to 'stop the burner in the event of combustion failure are fitted and are of the re-cycling type so that if the safety controls operate as a result of a change from high to low firing the burner will not be shut down permanently.