This invention relates to improvements in automatic gun type oil burners.
The invention involves a centrifugal device, driven with the shaft of the oil pump and controlling the opening and closing of a valve, which r suddenly opens and closes a by-pass around the pump, whenever the speed of the latter respectively falls below or rises above a predetermined value. With the by-pass open, the pump is completely unloaded. Because the by-pass is open, when the burner mechanism is started, the motor, fan and pump attain full speed in less time than would otherwise be possible. No oil can issue from the burner nozzle until the by-pass closes. The by-pass automatically closes when the motor, fan and pump attain a predetermined speed, which preferably is as nearly as feasible to top speed, so that no oil will be emitted from the nozzle of the burner until an adequate supply of air is available to insure proper combustion. When the motor is deenergized, the bypass will automatically open before the speed of the fan slackens enough to materially decrease the supply of air, thereby stopping the flow of oil from the nozzle before the supply of air becomes inadequate for proper combustion.
An important effect, which is desired and which is obtained by the invention, is to secure a sudden opening of the by-pass for the purpose of causing the cut-off valve, which controls flow of the pumped oil to the atomizing nozzle of the burner, to close quickly on deenergization of the burner motor and to remain closed, at least until the motor, fan and pump have come completely to rest. The purpose is to stop the dribbling flow of oil from the nozzle that frequently follows the initial closing of the cut-off valve. The pump continues to rotate for a time after the initial closing of the cut-off valve and, by so doing, builds up pressure enough to open this valve. As the cut-off valve opens, the pressure is relieved and the valve closes again, only to open again by the pressure rise which ensues following the closing of the valve. This cut-off valve may close and open two or three times before the pump slows down enough to lower the pressure sufficiently to stop the action. And on each opening, a spurt of oil is ejected into the pipe leading to the nozzle, causing emission of oil in a dribbling flow incapable of proper atomization. The same action is theoretically possible during the starting interval of the burner, just after the opening of the cut-off valve. Practically, however, the action is not so liable to occur because there is not sufficient time. The starting interval of the burner is much shorter than the stopping interval. However, the invention also provides for a sudden closing of the by-pass and an equally quick opening of the cut-off valve. The described vacillating closure of the burner cut-off valve and the resulting spurts of oil which cause the dribbling flow from the atomizing nozzle, occurs principally because of the prevalent use in gun type burners of an oversize pump, one whose pumping rate is much in excess of the rate of oil consumption of the burner.
The problem of stopping oil flow from the atomizing nozzle during the starting and stopping intervals of operation of the burner mechanism, in order to avoid faulty combustion due to the then over-rich mixture of air and oil, is an old one. Several ways have" been proposed in the prior art for the purpose. One example is shown in my prior Patent No. 1,985,934, of 1935.
The improvement will be disclosed in an illustrative example in the accompanying drawings, in whichFig. 1 is a side elevational view of one form of oil burner embodying the invention; Fig. 2 is a similar view, but partly in section, of another form of burner in which the invention may be embodied; Fig. 3 is a fragmentary end elevational view, partly in section and drawn to a larger scale, showing the by-pass valve and its actuating mechanism, the by-pass valve being shown in open position; Fig. 4 is a view similar to Fig. 3 but showing the by-pass valve in closed position; and Fig. 5 is a fragmentary sectional plan view showing the by-pass between the outlet and inlet of the pump and the by-pass valve.
Referring to Fig. 1, the burner there shown is well known in the art. It includes a tubular air conduit I, leading from the outlet of a fan housing 2, which contains a suitable fan (not shown) for supplying the air for combustion. Within the tube, near its outlet end, is a pressure-atomizing nozzle 3 to which oil is supplied by a pump 4 and from which a substantially conical spray of finely atomized oil issues to mix with the air supplied by the fan. The fuel mixture is ignited by a spark from suitable electrodes, one of which is shown at 5. The fan and pump are driven by an electric motor (not shown) but usually attached to that wall of casing 2 lying opposite the wall to which pump 4 is attached. The inlet and outlet of the pump are shown at 6 and 7, respectively. The outlet 7 is connected by a pipe 8 to a valve casing 9 which contains a nozzle cut-off valve and a pressure-regulating and by-pass valve. When the pumped oil reaches a predetermined minimum pressure, say 85 pounds per square inch, the cut-off valve will open and allow oil to flow by way of a pipe 10 to the nozzle 3.
When the pumped oil reaches another and higher predetermined pressure, say from 90 to 125 pounds per square inch, the pressure-regulating valve opens and allows oil to by-pass into a pipe II, which may lead either to the inlet side of pump 4 or to the supply tank. Usually the pump is oversize-having a pumping rate much in excess of the rate of flow from the nozzle-and the major portion of the pumped oil is by-passed and the minor portion flows to the nozzle. The pressure of the oil fed to the nozzle is maintained constant at the predetermined maximum pressure by the pressure-regulating and by-pass valve 9.
The unit 9, comprising the cut-off valve and the pressure-regulating and by-pass valve may be of any of the many suitable types available on the market, as will be well understood by those skilled in the art. An example of one suitable type will be found in Fig. 4 of Patent No. 2,100,997, granted November 30, 1937.
It will be understood that the burner will include the usual thermostatic control for the burner motor and the usual safety devices together with an ignition transformer and connections from it to the ignition electrodes. These elements have been omitted because they are so well known in the art and because they are unnecessary to an understanding of the present invention.
The improvement of this invention provides a pump by-pass (Fig. 5),' comprising two passages 12 and an opening 12' which interconnects them.
This by-pass connects the outlet 7 to the inlet 6. A valve 13 controls the by-pass. This valve 13 is opened and closed with a snap action by means of the toggle mechanism shown in Figs. 3 and 4, under the control of centrifugal devices, such as the weights 14, which are mounted on and rotated by the shaft 15 which drives pump 4. When the burner is at rest, the by-pass is open as shown in Fig. 3. When the burner is operating with its motor revolving at full speed, the by-pass is closed as shown in Fig. 4. When the motor of the burner is energized, shaft 15 will be rotated with it and the weights 14 will be thrown outwardly by centrifugal force. When a predetermined speed is reached, the weights will have moved outwardly to the position shown in Fig. 4. In moving outwardly, the toggle mechanism is shifted to the Fig. 4 position to cause valve 13 to suddenly close. This occurs as nearly as feasible to the normal speed of the burner motor. On deenergization of the motor, after its speed has slackened somewhat, the weights 14 will move inwardly and cause the toggle mechanism to suddenly open the by-pass valve.
This occurs before the pressure of the oil has dropped to a point low enough to allow the cutoff valve to close and preferably before pressure has dropped low enough to allow the pressureregulating valve to close. The result is a sudden unloading of the oil pump, causing almost instant collapse of oil pressure and a sudden closing of the cut-off valve, and usually also the pressure-regulating valve, in such a way as to preclude the heretofore-described vacillating action of the cut-off valve with the rapid succession of openings and closings and the resulting spurts of oil which cause dribbling from the nozzle.
Referring now to the details of the exemplary mechanism, the by-pass 12 may be formed, as shown, in the upper portion of the casing of pump 4. The by-pass valve 13 has a stem 16 which is slidably mounted in the inwardly-extending hub of a cover 17, suitably fixed to the casing of pump 4. Leakage between the stem and cover is prevented in any suitable way, as by the bellows 18, which at its inner end is fixed to stem 16 and at its outer end is fixed between the cover 17 and the pump casing. Fixed on the outwardly-projecting portion of the valve stem 16, in axially1~ spaced relation, are two collars or abutments 19 and 20. Slidable on the stem between these abutments is a member 21, having on opposite sides V-shaped grooves to receive, one in each, the knife edges of the fixed heads 22 of toggle links 23. Each link has on its outer end a slidable head 24 to fit in a V-shaped recess in a stationary arm 25. These arms are joined by an integral part 26 which is suitably secured to the cover T1. The outer and V-shaped portion of each arm 25 is centrally slotted to permit passage of the outer ends of the toggle links 23. A spring 27 encompasses each toggle link and tends to spread the heads 22 and 24 apart and hold them engaged with their respective members 21 and 25. The springs of the toggle links serve to hold the by-pass valve both in its open and closed position. Thus, in Fig. 3, the springs 27, acting against heads 24 and the fulcrums on arm 25 with which such heads are engaged, force the heads 22 inwardly to press slide 21 against collar 19 and thus force the stem 16 axially inward to hold valve 13 in open position and against the stop 28 on the pump casing. Similarly, with the parts positioned as in Fig. 4, the same springs force slide 21 against collar 20 and press stem 16 axially outward to hold valve 13 in its closed position.
For actuating the toggle mechanism described, the weights 14 are pivotally mounted at 29 in diametrically-opposed relation in a collar-like enlargement 30 on shaft 15. The inner ends of these weights are thin and are mouAted side by side in abutting relation in a diametrical groove 30' in such collar and shaft. These inner ends rO engage one end of a rod 31, slidably mounted in an axial hole in shaft 15. Slidable on this shaft is a grooved clutch collar 32. A pin 33 passes diametrically through this collar, through a diametrical groove 34 in the shaft and diametri,5 cally through the rod 31. A spring 35, coiled around the shaft, acts between an abutment 36 on the shaft and the clutch collar 32 to force the latter to the left and hold rod 31 engaged with the weights 14. The centrifugal device is adjustable by varying the tension of spring 35 which may be done by adjusting the axial position of abutment 36 on shaft 15. The abutment 36 is threaded on the shaft for such purpose and may be held in various positions of axial adjustment 05 by a lock nut 37. Inward movement of the clutch collar under the force of spring 35 is limited by the abutment of weights 14 with shaft S5, as shown in Fig. 3. Outward movement of the clutch collar, under the force of weights 14, is limited by the abutment of the outer end of rod 31 with the inner end of a stop screw 38, threaded into the outer end of the axial hole in shaft 15 and held in place by a lock nut 39. The clutch collar 32 receives the rounded lower ends 40 of a shifter fork 41 which straddles the collar and which is rigidly connected by a stem 42 to the slide piece 21.
With the parts positioned as in Fig. 3, if the burner motor is energized, its fan, the pump 4 and shaft 15 will be driven. With the by-pass in the pump open, the motor will build up speed more rapidly than would otherwise be possible because the pump is completely unloaded. A smaller motor or one with lower starting torque can be used than if the pump were not unloaded at the start. As the motor acquires sufficient speed, the weights 14 are swung outwardly by centrifugal force and, pressing aagainst rod 31 shift the same to the right, against the force of spring 35, moving the clutch collar 32 in the same direction. The first movement of clutch collar 32 to the right will engage the rounded ends 40 of fork 41 and cause the toggle slide or actuator 21 to move to the right. This slide moves freely on stem 16 until it abuts the collar 20. At the time when the slide 21 engages collar 20, the toggle links 23 have been moved to midposition. Hence, a slight movement of the collar 20 to the right by the slide 21 will carry the links 23 across centers, after which the toggle springs 27 will expand and drive the slide 21 and stem 16 rapidly to the right, moving valve 13 to the closed position shown in Fig. 4, and closing the by-pass. The collar 32 is wide enough to allow the fork 41 to be moved rapidly ahead by the toggle springs. The closing of the valve 13 is thus effected with a snap action and practically instantaneously. The closing of the by-pass is preferably timed to occur as nearly as feasible to the top speed of the burner motor for the purpose of delaying the supply of oil to the burner nozzle until the fan has acquired nearly full speed and has created a flow of air at the proper rate to the nozzle so that proper combustion will result.
When the burner motor is deenergized, the weights 14 will begin to move inwardly as soon as the motor speed slackens somewhat. As the weights swing inwardly toward shaft 15, the spring 35 will move the clutch collar 32 to the left from the position shown in Fig. 4. The first movement of collar 32 will shift the slide 21 to the left and move the toggle links 23. As these links are moved to midposition, slide 21 will engage collar 19. When this occurs, the links will be moved across centers and the expanding springs 27 will then move the collar 19 and stem 16 almost instantaneously into the position shown in Fig. 3. The groove in the clutch collar 32 is wide enough to enable the shifting fork 41 to be moved ahead by the toggle springs.
The by-pass is thus suddenly opened, completely unloading the pump. The almost instantaneous opening of the by-pass in the pump results in an almost instantaneous collapse of oil pressure so that the burner cut-off valve will close with a snap action, preventing the oscillating action which is caused by a more gradual lowering of the pressure and which results in the dribbling flow of oil from the nozzle. Since the pump is unloaded, the resistance to motion of the connected pump, motor rotor and fan is materially lessened and these members will continue in motion by their momentum, and especially by the momentum of the heavy rotor of the burner motor, whereby the fan will continue in motion for a longer interval than it otherwise would. This results in prolonging the air flow and completely scavenging the air tube of the burner.
It will be understood that to stop the dribble flow caused by oscillation of the cut-off valve, a snap action opening of the by-pass valve is required and that this may occur at any time before the oil pressure falls to the point at which the cut-off valve is set to open. However, to secure the other advantage of preventing emission of oil from the nozzle at times, when the flow of air is inadequate to support good combustion, the by-pass valve 13 should be set to open not much below the top speed of the motor.
The burner, shown in Fig. 2, is one which is intended to practice the inventions disclosed in my copending applications Serial Nos. 557,119 and 569,452, filed October 4, 1944, and December 23, 1944, respectively, and both owned by the assignee of the present application. In each of said prior applications, the air for combustion is admitted through a multitude of small perforations 43 in a tube 44 the interior of which provides a combustion chamber. Projecting through the closed rear end of this tube are the pressure atomizing nozzle 45 and ignition electrodes, one of which is shown at 46. The outer end of tube 44 is open. The annular space 47 between tubes I and 44, to which air is supplied by the fan in casing 2, is closed at its outer end as indicated.
The rest of the burner may be constructed as already described in connection with Fig. 1. In a burner of the Fig. 2 type, it is more than ordinarily important to prevent dribbling from the ;o nozzle or improper combustion from any other cause because the resulting carbonization might cause stoppage of some of the perforations 43 and partial stoppage of air flow which would quickly put this burner out of action because it is the 5 radial jets of air which keep the flame away from the wall of tube 44 and maintain it cool.
The by-pass, its control valve and the actuating mechanism therefor have for simplicity and clearness of illustration been shown as exposed outside the pump. Of course, these parts would in practice be suitably encased. It is frequently the case that the burner cut-off valve and the pressure regulating valve are built into the same casing, which houses the pump, and the by-pass, its valve and the actuating mechanism for such valve may also be incorporated into the same casing.
Reference to my above-named prior patent will show the importance of having the air and oil in proper proportion for good combustion during the intervals of starting and stopping the burner, whereby to avoid the smoke and resulting soot deposits which would otherwise occur. The use of excess air as a compromise to reduce the troubles from poor combustion during such intervals lowers the efficiency of the burner. With the present invention the difficulties from incomplete combustion during the starting and stopping intervals are avoided and troubles resulting from 00 dribbling feed of oil are stopped. Therefore, the air supply to the burner may be adjusted more closely to the ideal proportions, theoretically necessary, and much improved efficiency of combustion secured.
35 I claim: 1. The combination in an oil burner, having a nozzle, a pump to supply oil to the nozzle, and a cut-off valve for preventing flow of oil to the nozzle whenever the pressure of the pumped oil is less than a predetermined value; of a by-pass from the outlet to the inlet of said pump, a valve to control said by-pass and normally closed during operation of the burner while the pump is moving at full speed, means for opening said valve with a snap action, a centrifugal device rotatable with said pump and operable when the speed of said pump falls below a predetermined value and before the pressure of the pumped oil falls to said predetermined value to initiate the action of said means and cause the sudden opening of the by-pass valve.
2. The combination in an oil burner, having a nozzle, a pump to supply oil to the nozzle, and a cut-off valve for preventing flow of oil to the nozzle whenever the pressure of the pumped oil is less than a predetermined pressure; of a bypass from the outlet to the inlet of said pump, a valve to control said by-pass, a centrifugal device rotatable with the pump and operable to cause the opening and closing of said by-pass valve accordingly as the speed of the pump is respectively below or above that speed necessary to maintain said predetermined pressure.
3. The combinatioh in an oil burner, having a pressure atomizing nozzle, a motor driven pump to supply oil to the nozzle, an automatic pressure regulating valve for maintaining a constant atomizing pressure of the oil supply to the nozzle, and means to supply air to the atomized oil for ignition and burning; of a by-pass from the outlet to the inlet of said pump, a normally open valve for said by-pass, an actuating device, including a part driven with the pump, automatically responsive to pump speed, and having an operative connection with said latter valve constructed and arranged to close said valve in burner starting operations when the pump acquires its high speed range and to again open said valve for suddenly unloading the pump, when the latter slows down below its high speed range in burner stopping operations, whereby in the slow speed range of the pump operation both the pump and the aforesaid automatic pressure regulating valve will be unloaded.
JOSEPH A. LOGAN.