US2662542A - Hydraulic control device for highpressure liquid-fuel-supply pumps of pressure-atomizing oil burners - Google Patents

Description

Dec. 15, 1953 J, LOGAN ET AL 2,662,542

HYDRAULIC CONTROL DEVICE FOR HIGH-PRESSURE LIQUID-FUEL-SUPPLY PUMPS OF PRESSURE-ATOMIZING OIL BURNERS Filed Dec. 22, 1951 INVENTORJ- Jossrn Aloamv Aw 1 2 0 1 2 65000517. Foe/45o Jzcolvos \SZEco/ww BY .7,

ATTORNEYS Patented Dec. 15, 1953 when HYDR ULHC CONTROL DEVICE FOR HIGH- -FUEL-SUPPLY PUMPS PRE S SURE LIQUID OF PRESSURE-AT OMIZING OIL BURNERS Joseph A. Logan, Hadley, son, Agawam, Mass, Barker Manufacturing field, Mass, a corporati and George D. Robinassignors to Gilbert & Company, West Springon of Massachusetts Application December 22, 1951, Serial No. 262,954

6 Claims.

This invention relates to an improved hyd'raulically-operable control device for connection to the high-pressure liquid-fuel-supply pump of a pressure-atomizing type of oil burner for modifying the oil pressure conditions at the start and at the end of each cycle of burner operation.

The invention has for its object the provision of a control device of comparatively simple and inexpensive construction that can be sold to dealers or distributors of oil burners and attached, without requiring special skill, to oil burners, regardless of make or construction, so long as they utilize a high-pressure fuel-supply pum and that will materially improve the operation of the burner and enable higher eniciency of combustion to be obtained.

More particularly, the invention is adapted to be applied to an oil burner of the pressure-atomizing type, which is adapted for house-heating service, and which operates intermittently under automatic control and started and stopped many times during each day of the heating season. These burners customarily have positively-acting fue1-supply pumps, which have a pumping rate far in excess of that at which the fuel is consumed, the major part of the pumped 'fuel being by-passed. These pumps, if started simultaneously with the air-supply fan, build up the required high-atomizing pressure, say for eX- ample 100 p. s. i., very rapidly, almost instantaneously, and long before the fan, which is nonpositive in action, can get the air moving past the fuel nozzle at the rate necessary to secure good combustion. Consequently, the fuel-air mixture will be over rich during the starting interval of operation of the burner, resulting in initially smoky operation, unless the burner is adjusted to admit excess air, and in such case the efficiency of combustion, during normal running intervals of operation, will be decreased. The device of this invention is adapted to delay the building up of the rated fuel pressure for a short time, say for example, a few seconds, and long enough to enable the fan to reach full speed and get the air for combustion moving past the fuel nozzle at the proper rate for good and cilicient combustion. It is also important to modify the oil pressure at the end of each cycle of burner operation with the object of cutting off the oil flow to the burner nozzle as soon as possible after the power to the burner motor is cut off, and the control device of this invention enables the combustion conditions atthe end of each Lburner cycle to be materially improved by causing a quicker closure of the cut-off valve in the oil supply system of the burner than would otherwise be possible.

The invention will be disclosed with reference to an illustrative example of it in the accompanying drawings, in which,

Fig. 1 is a full-size sectional-elevational view of a control device embodyingthe invention, the parts being shown in the positions which they occupy when the fuel-supply pump is stopped; this view also shows, diagrammatically and on a small scale, a fuel-supply system for an oil burner of the class described;

Fig. 2 is a similar view of the control device only, the parts thereof being shown in the positions, which they occupy at the end of the time delay interval on starting the pump;

Fig. 3 is a graph showing how the building up of oil pressure in the conduit supplyin the atomizing nozzle of the burner is delayed at the start of each cycle of operation of the burner; and

Fig. 4 is a graph showing how the oil pressure in the supply conduit for the atomizing nozzle is quickly cut off following the cutting on of power to the motor, which drives the oil supply Referring to these drawings; the control device includes a chamber, such as a cylinder l, formed within a casing, such as a tubular barrel 2, having heads 3 and 4, suitably fixed, one in each of the ends of the barrel. As shown, head 3 has a drive fit in one end of barrel 2 and head 4 has an eXteriorly-threaded annular portion 5, which is screwed into the interiorly-threaded end of the barrel 2. A gasket 6 seals the joint between the head 4 and the barrel. The control device also includes a movable wall in the chamber I, such as a piston'l. A spring 8, acting between one face of the piston and the head l, and partially telescoped within the annular portion 5, tends to move the piston into engagement with head 3 and hold it-in the position shown in Fig. 1. As shown, piston i has a circumferential groove, containing an O-ring which may for example be of synthetic rubber and which prevents leakage of liquid past the piston. Inlet and outlet ports it and H, respectively, are provided for cylinder I and, as shown, these ports are respectively formed in the heads 3 and 4. The piston 7 has a passage 22 therethrough and at least a portion of this passage is of very small diameter, in the present example .024". The piston is adapted to be moved by the pressure of oil which enters inlet It, away from head 3 and to the right until it abuts the end face of the annular portion 5 as a stop. The passage 12 is so located as to communicate at such time with the space 13 within the annular portion 5. This space 13 communicates with one end of an axial passage M in head 4. The other end of passage I4 opens into the inner end of a coaxial passage IS, the outer end of which is closed by a plug 16, screw outer end of the passage l5, and sealed by a gasket H. The intersection of the passages 14 and i5 affords a seat for a ball valve l8. which is held to its seat by a spring l9 acting between the ball and the closure plug IS. A radial passage in head 4 connects the passage l5 with the outlet port II.

The control device described is especially adapted for use in connection with the high-- pressure positively-acting, fuel-supply pumps commonly used in oil burners of the mechanical or pressure-atomizing type such as are adapted for house heating service and are started and stopped many times each day under automatic thermostat control. One purpose is to delay the emission of oil from the atomizing nozzle until the motor, which drives the pump and also a non-positively-acting, air-supply fan, has acquired high speed, and preferably full speed, in order to secure the proper rate of air flow to result in good combustion. Another purpose is to secure a quick cutting off of oil flow to the nozzle after the pump motor is deenergized.

Fig. 1 shows diagrammatically and on a small scale, the fuel-supply means for a pressure atomizing oil burner of the class described. A pump 25, adapted for connection to a fuel-supply by suction pipe 23, forces oil through a conduit 21 to a casing 28, containing a bypass valve 29, and from such casing through a conduit 30 to a casing 3!, containing a cut-off valve 32. The pump, in the present example, is designed to pump oil at the rate of 18 gallons per hour. The outlet of casing 3|, which is controlled by valve 32, is connected by a conduit 33 to the mechanical or pressure-atomizing nozzle 34 of the oil burner. The nozzle, in the present example, is rated to deliver oil at the rate of 2 gallons per hour when supplied with oil at 100 p. s. i. The outlet of casing 28, which is con trolled by valve 29, is connected by a bypass conduit 35 to the suction side of pump 25, as to pipe 26. The pump has a screw plug 35, which may be loosened in order to rid the system of air, whenever necessary, as for example, when initially installing the burner or whenever the pump. after having stopped because of exhaustion of the oil supply, is subsequently started.

The cut-off valve 32 is held closed by a Sprin 31 until the pressure of pumped oil reaches a predetermined minimum value, say for example about 90 p. s. i. The bY-pass valve 29 is held closed by a spring 38 until the pressure of the pumped oil reaches a predetermined maximum value, say for example, 100 p. s. i., which is the normal operating pressure. The inlet of the control device is adapted to be connected to the pressure side of the oil pump between its outlet and the by-pass and cut-off valves and, as indicated by the dot-dash line 39, to conduit 21. The outlet H is adapted for connection to the suction side of the oil pump, and, as indicated by the dot-dash line 40 to pipe. 26.

In an oil-supply system of the type described. the pump 25 must be vented initially and each time after the fuel-supply has become exhausted.

threaded into the K in order to rid the system of air. The only outlets for the pump are usually closed by valves, such as 29 and 32 which open at relatively high pressures, greater than any that the pump can produce when pumping air alone. For example, in the present case, the greatest pressure which pump 25 can produce, when pumping air is 20 p. s. i. Hence, the valve 32 will not open and allow air to escape from nozzle 34. Therefore, the plug 36 on the pump is provided and this plug, when loosened, will afford an outlet for the pump air to escape. As soon as oil appears, the plug 38 is screwed in tightly and the system will then operate in the normal manner.

The control device provides by the passage l2 through its piston a by-pass between the inlet and outlet of the pump that is continuously open during normal operation. This bypass has to be closed before air can be eliminated from the fuel-supply system of the burner. The check valve I8 automatically closes this by-pass to enable elimination of air to be effected, when required, and yet enables the by-pass to be open during normal operation of the burner to accomplish its purpose. The spring i9 is designed so that the check valve l8 will open at 25 p. s. 1. Thus, this valve l8 cannot open, when the pump is pumping air alone. The same result might be effected by manual closure of a hand valve, such as 4!, in the pipe 40, whereby the valve It might be eliminated but it is desirable and preferred because it takes care of the condition automatically without requiring any attention on the part of the operator.

The spring 8 is designed to have sufficient force to return the piston from the Fig. 2 to the Fig. 1 position, when the oil pump stops. This spring must have sufficient force to overcome the friction of the O-ring 9 sliding on the wall of cylinder i and also to force oil from the left hand to the right hand side of the piston through the restricted portion of the passage 12 in the piston, and the spring 8 must yield before the check valve 18 opens. In the present example, this spring 0, when fully stressed, exerts a force of 23 p. s. i. on the piston.

Normally, the parts of the control device will occupy the positions shown in Fig. 1, when the burner is not in operation. When the pump is started, it will very quickly build up a pressure of 25 p. s. i., and open check valve 18 and thus open the by-pass around the pump. The piston I will then move slowly to the right under pressure of the pumped liquid. Some oil may pass through the passage l2 in the piston but, initially, the rate of flow therethrough is only verty small compared to that at which oil is forced out of the pump and into the cylinder I. After the piston has engaged its stop, more and more oil will flow through the passage [2 until at the full operating pressure a rate of about 4.5 gallons per hours is established. The passage I2 is not an important factor in delaying the building up of the atomizing pressure. The major factor is the expansible chamber afforded by the cylinder and piston 1. This cylinder has a relatively large volume which has to be filled before the pump can build up the high pressure necessary to open the cut-off and by- pass valves 32 and 29, respectively, and it is the displacement of the piston in the cylinder that is relied on to produce the desired time delay. The signiflcant factors in producing the time delay are the cross sectional area of. cylinder I and the length of stroke of its piston.

The pressure will slowly rise from 25 p. s. i. as the piston moves to the right but not until the piston is arrested by its stop, does the sharp increase occur that is necessary to open the cut-off valve a2 and shortly after the by-pass valve The result is indicated in 3 by the graph M, which shows pressure in the supply conduit plotted. against time in seconds after the starting of the pump. The cut-off valve 32 remains closed for 2.4 seconds after the pump 25 is started and no pressure exists in the supply conduit at until this valve does open. When cut-oil valve 32 opens, at around 90 p. s. i., there is a very rapid rise in pressure to the full atomizing pressure of 100 p. s. i., when the by-pass valve 29 opens to maintain the pressure of oil supplied to conduit 33 constant. It will thus be seen that the corn trol device enables a delay in the opening of the cut-off valve 32 and thus the supply of oil to the atomizing nozzle This delay is adequate to enable the burner fan to reach full speed and move air past the nozzle at a sufiicient rate to effect eihcient and smokeless combustion.

For the control device to be thoroughly satisfactory, it must do more than merely delay the supply of oil to the atomizing nozzle ti l. It must also modify the oil pressure at the end of the cycle of burner operation. This is the function of the by-pass passage I2 in the piston. There needs to be available at the insta t, when the power to pump 25 is out 01?, a bypass that will cause a quick drop in pressure. Without such a by-pass, the pressure will diminish only as the speed of the pump diminishes and this would require considerable time because the pump is oversize. At the same time, this by-pass must be restricted because it is always open during normal intervals of operation of the burner and causes a great deal of oil to be lay-passed. In the present example, oil is by-passed at the rate of 4.5 gallons per hour. Thus, 25% of the pumped oil is by-passed through the passage i2. If the diameter of the restricted portion of this passage were doubled, its area would be quadrupled and the device and burner would be inoperative because all the pumped oil would be by-passed through passage i2 and the pump could never build up pressure enough to open the cutoii valve 32. The area of this passage is therefore critical. The effect of the by-pass around the piston is shown in the graph 43 of Fig. 4, which shows oil pressure in the nozzle-supply-conduit plotted against time in seconds after the power to the pump motor has been cut-off. There is a gradual drop in pressure until the cut-off valve 32 closes, which occurs in .7 second, followed by a rapid decrease in pressure to zero. With a slight increase in diameter of the restricted portion of passage I 2 to .028", the time necessary to cause closure of the cut-ofi valve will be reduced to .3 second and the time delay will be increased to 3 seconds but the amount of oil by-passed through passage it will be increased to 3 gallons per hour, which is considered too much to be safe to rely on in commercial practice. The practical limit on the size of the restricted portion of passage iii that which would by pass no more than a third of the rated capacity of the pump.

The invention thus provides a control device, which is readily installed in an oil burner to control pressure conditions in the oil supply to the atomizing nozzle, so as to be effective, on starting of the pump, to delay the building up of at pressure long enough for the fan to establish the full rate of air flow to secure good combustion and so as to be efiective, on stopping of the pump, to quickly cut-off the supply of oil to the nozzle and avoid the pufi of smoke that would otherwise occur due to the rapidly diminishing rate of air flow.

What is claimed is:

l. A hydraulically-operable ccntrol device for the high-pressure fuel-supply pump of a sure-atomizing oil burner, comprising, a tuhular barrel affording within it a cylinder, heads closing opposite ends of the cylinder and provided one with an inlet and the other with an outlet therethrough, the head provided with the outlet passage having an exteriorly threaded annular part screw threaded into one end of said barrel and the entrance to the outlet passage opening into the space within the annular portion, a piston slidable in said cylinder, a spring acting between the piston and the last-named head and in part telescoped within said annular part for movin the piston against the other head and adapted to yield under pressure of oil pumped into said inlet to allow the piston to move toward and into engagement with the end face of said annular portion, said piston having a passage of restricted area therethrough for interconnecting the inlet end of the cylinder to the space within said annular portion and thus to the outlet when the piston engages said end face.

2. The combination as claimed in claim 1, in which a spring closed check valve is mounted in the outlet passage and opens at a pressure slightly greater than that exerted by the first-named spring on the piston when the latter is engaged with said end face as a stop.

3. A hydraulically-operable control device, adapted to be connected in by-pass relation with a fuel-supply pump having a predetermined maximum pumping rate and adapted to supply oil at a predetermined maximum pressure to a pressure-atomizing oil burner, comprising, a cas ing affording a chamber having a single inlet near one end and a single outlet near the other end and being otherwise closed, said inlet and outlet being respectively adapted for connection to the pressure and suction sides of a pump, a wall partitioning said chamber and interposed between said inlet and said outlet and having two opposite sides one confronting the inlet end and the other confronting the outlet end of said chamber, said wall being mounted for movement between two extreme positions one near said inlet end and the other near said outlet end, a continuously-open conduit afiording a by-pass for said wall interconnecting the spaces in said chamber on opposite sides of said wall at all positions of the latter, throughout its range of movement, said conduit having a portion of restricted cross sectional area as compared to the cross-sectional area of said inlet and outlet, and a spring tending to move said wall from its secend-named extreme position to its first-named extreme position, said spring being yieldable at a pressure much lower than said predetermined maximum pressure and said wall adapted to be moved from the second-named to the first-named extreme position by pressure of liquid supplied to said inlet.

4,. The combination, as claimed in claim 3, in which said maximum pressure is several times said second-named pressure.

5. The combination, as claimed in claim 3, having a valve controlling said outlet and a spring for holding said valve closed and yielding at a pressure about equal to said second-named predetermined pressure.

6. The combination, as claimed in claim 3, in which the restricted portion of the by-pass conduit has a cross sectional area such as to pass oil under said maximum pressure at a rate no greater than one third of said maximum rate.

JOSEPH A. LOGAN. GEORGE D. ROBINSON.

8 References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Nightingale et a1. Aug. 30, 1932 Murphy Mar. 3, 1936 Murphy Sept. 30, 1941 Logan Feb. 15, 1949

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