US3840323A

US3840323A - Continuously adjustable controls for oil burners

Info

Publication number: US3840323A
Application number: US00359728A
Authority: US
Inventors: O Eckerle; R Jung
Original assignee: Individual
Current assignee: Individual
Priority date: 1972-10-04
Filing date: 1973-05-14
Publication date: 1974-10-08
Anticipated expiration: 1991-10-08
Also published as: DE2248674A1; GB1432261A; FR2202581A5

Abstract

Continuously adjustable oil burner controls which include an electromagnetic metering valve in the fuel oil return line, the metering valve determining the supply of fuel oil to the atomizer nozzle of the burner as a function of the coil current which determines the throttling effect of the metering valve and thus the pressure in the fuel oil supply line. The latter also controls the air intake of a combustion air blower.

Description

United States Patent 1 [11] 3,840,323

Eckerle et al. Oct. 8, 1974 [54] CONTINUOUSLY ADJUSTABLE CONTROLS 3,547,093 12/1970 Sherman 431/89 X FOR 01 BURNERS 3,592,574 7/1971 Ettlingen 431/90 3,684,238 8/1972 Michellone 251/141 X [75] Inventors: Otto Eckerle, Benzstr. 6; Robert Hugo Jung, both of Malsch, Germany Primary Examiner-Edward G. Favors 73 Assignee: said Eckerle, by said Jung Almmey Agen" 661g [22] Filed: May 14, 1973 [21] App]. No.: 359,728 [57] ABSTRACT Continuously adjustable oil burner controls which in-' [30] Forelgn Apphcatmn Pnomy Data clude an electromagnetic metering valve in the fuel oil Oct. 4, 1972 Germany 2248674 return line the metering valve determining the Supply of fuel oil to the atomizer nozzle of the burner as a 2:51 hits. (51. "his 131mg function of the Coil current which determines the d 5 2 throttling effect of the metering valve and thus the 1 0 pressure in the fuel oil supply line. The latter also con- 5 References Cited trols the air intake of a combustion air blower.

UNITED STATES PATENTS 12 Claims, 3 Drawing Figures 2,979,124 4/1961 Kirk 431/90 CONTINUOUSLY ADJUSTABLE CONTROLS FOR OIL BURNERS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to oil burner controls, and in particular to automatically adjustable oil burner controls which are capable of varying the fuel and air supply to the burner so as to adjust its heat output within a wide range, while maintaining an optimal combustion ratio of fuel and air.

2. Description of the Prior Art Attempts have been made in the past to provide oil burner controls which incorporate means for adjusting the fuel and air supply to the burner, in order to vary its heat output. One such prior art solution suggests a system where an electric motor drives a control cam which engages a push rod controlling a spring-biased throttle valve whose setting determines the oil supply pressure and combustion rate. The cam position thus determines, via the intermediate push rod, the opening of the throttle valve, the latter setting the atomizing pressure and consequently the heat output. Although this solution is a comparatively reliable one, it is complex and therefore very expensive.

Another prior art solution suggests the arrangement of a pressure control valve in the return line of a plunger shutoff valve, whereby the atomizing pressure is adjusted. This solution is relatively simple; however, it cannot be used in conjunction with automatic burner controls which use a thermastat, or a switching timer, or similar pre-settable controls.

SUMMARY OF THE INVENTION It is a primary objective of the present invention to suggest a simple, inexpensive system of continuously adjustable oil burner controls which is free of the above-mentioned shortcomings.

The present invention proposes to attain the above objective by suggesting an oil burner control system which uses an electromagnetically controlled metering valve, whereby an electromagnet determines the opening of the metering valve as a function of the electric current being applied to it, the latter being conveniently adjustable by means ofa potentiometer, for ex- Among the advantages offered by the present invention are its reliability of operation over a wide range of adjustment settings and its simplicity of design and correspondingly low production costs.

BRIEF DESCRIPTION OF THE DRAWINGS Further special features and advantages of the inven tion will become apparent from the description following below, when taken together with the accompanying drawings which illustrate, by way of example, several embodiments of the invention, represented in the various figures as follows:

FIG. 1 shows a first embodiment of the invention in which a portion of the fuel pump and the metering valve are shown in cross section, the through-flow atomizer nozzle and the remainder of the oil burner system being shown schematically;

FIG. 2 shows a second embodiment of the invention, similarly represented as a partial cross section in combination with a schematic representation of the oil burner system, the latter including a bypass-type atomizer nozzle; and

FIG. 3 shows in an enlarged elevational cross section the metering valve of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the first embodiment of the invention, illustrated in FIG. 1, an electric motor 6 drives a fuel pump 4 and a combustion air blower 8. A suction'line 3 connects the fuel oil pump 4 to a fuel oil reservoir 2 from which the latter'pumps fuel oil through the channels 39 and 37, and via a bore in the pole core 34, into the return line 40, from where the fuel oil returns to the reservoir via line 1. The blower wheel 8 simultaneously takes in air through an intake As which is determined by the movement of an air clappet 11 against the intake opening of the housing 12 of the combustion air blower. The

combustion air passes through

air conduits

13 and 16 into the combustion chamber (not shown in the drawing).

As long as the electromagnetic coil 28 is not energized, a back pressure valve, consisting of a ball 23, a spring 22 and a set screw 21, prevents the recirculating fuel oil from passing through channel 24, via the I threaded bore 20, into the atomizer line 18 of the atomample. The potentiometer in turn may be part of a ther- I biased against the valve seat in response to the magnet coil current, so that the gap between the valve seat and the armature forms a variable throttling passage which determines the fuel oil supply pressure. This throttling passage is either arranged in the fuel oil return line which is branched to the fuel oil supply line, between the oil pump and the atomizer nozzle, or it is arranged in the return line between the atomizer nozzle and the oil reservoir, in the case of a bypass-type atomizer nozzle.

izer nozzle 17.

A readjustment of a potentiometer 36 admits an electric current to coil 28 so as to pull the armature 33 inside the electromagnet toward the valve seat on the upper side of pole core 34, thereby reducing the throttling gap between the armature and the valve seat. The force with which the armature 33 is urged against the valve seat of pole core 34 is a function of the current that flows through coil 28 and this force determines the oil pressure which is required in the center bore of pole core 34, in order tokeep the metering valve open. The pressure buildup due to the throttling pressure of the armature 33 against the valve seat of pole core 34 causes the ball 23 of the back pressure valve to open against the biasing spring 22 so that some of the fuel oil flows through channels 20 and 18 to the atomizer nozzle 17, the fuel oil pressure at the nozzle being determined by the armature position of the metering valve.

The air clappet 11 which determines the air intake gap As with the housing 12 of the combustion air blower is part of a hydraulic control cylinder 9 in which the plunger is stationary while the cylinder itself is axially movable in response to the pressure in the fuel oil supply channel 39, thereby opening the air clappet 11 against a biasing spring 10. The hydraulic cylinder 9 communicates with the supply channel 39 via a control line l9, 15, 14. An increase in the oil supply pressure caused by the adjustment of control member 35 causes the hydraulic cylinder 9 and the air clappet 11 to move against spring 10 so as to increase the air intake gap As, reducing the throttling effect of air clappet 11 on the blower intake accordingly, so as to admit more air to the latter. Through appropriate coordination of the characteristics of the biasing spring 10, of the cylinder 9, and of the size of the air clappet 11 with the atomizing characteristics of nozzle 17, it is thus possible to obtain automatically an optimal combustion mixture of fuel oil and air within a wide range of supply pressures as adjusted through control lever 35.

The electromagnetic metering valve thus constitutes an essential element of the oil burner system. The coil 28 of the metering valve is surrounded in a known manner by an iron circuit which consists of a yoke bracket 30 and a yoke plate 27. At the inside of coil 28 is arranged a guide sleeve 32 of magnetically nonpermeable material which serves as a guide for the axially movable armature 33 and which forms a hermetic seal in cooperation with a gasket 26, positioned against the pump housing 25 on which the metering valve is mounted. The guide sleeve 32 thus hermetically encloses the stationary pole core 34 and the movable armature 33 which constitute the throttling elements of the metering valve.

The electromagnetic metering valve is preferably designed for operation with d-c current, and it may be connected in a parallel circuit with the electric motor 6, the d-c circuit being supplied by a rectifying bridge circuit 38, for example.

In FIG. 2 is shown a second embodiment of the invention in whichv the atomizer nozzle 43 is of the bypass-type (with a return line to the fuel oil reservoir). This embodiment requires in addition to the metering valve a plunger shutoff valve 55 which assures a constant supply pressure in the fuel oil supply line 45 leading to nozzle 43, the metering valve being arranged in the return portion of the flow circuit. This embodiment has the advantage of a still wider range of adjustments which is possible through the use of the bypass-type atomizer nozzle 43.

Before combustion startup, and at the beginning of the operation of pump 4, the plunger shutoff valve 55 keeps both the connection 48 to the nozzle line 45 and the connection 54 to the return line 1 closed, the shutoff valve position as shown in FIG. 2 indicating a positive closing overlap a for connection 48 and a somewhat larger positive closing overlap b for connection 54. As soon as the pressure against the plunger of the shutoff valve 55 reaches the predetermined operating value set by a biasing spring, the positive closing overlap a is eliminated so that pressurized fuel oil flows through the

channels

48, 47, 46, 45 into the atomizer nozzle 43. If the supply pressure from pump 4 increases still further, the positive closing overlap b likewise disappears, thereby opening an overflow connection to the fuel oil reservoir 2 via connection 54 and return line 1.

As long as the electromagnetic metering valve is not supplied with an electric current, a major portion of the fuel oil fed to the atomizer nozzle 43 returns to the reservoir via the

bypass line system

44, 49, 50, 51, because only a minimal flow resistance is present in this line portion. Thus, the amount of fuel oil being atomized by passing through the atomizer nozzle 43 itself is minimal and corresponds to the lower end of the adjustment range of the nozzle. The air intake gap As of the combustion air blower is accordingly narrow, the position of the air clappet 11 being determined by the pressure in the return line 44 which is connected to the cylinder 9 of the air clappet 11 via a control line 42. The response characteristics of the biasing spring 10, of the air clappet 11, and of the atomizer nozzle 43 are again coordinated so as to obtain an optimal mixing ratio of fuel oil and combustion air. The adjustment of the flow rate through the atomizer nozzle 43 is again obtained by means of a control lever 35 which adjusts a potentiometer 36 controlling the electric current flowing through coil 28 of the electromagnetic metering valve. The latter is of the same type as described previously. However, in this case the metering valve is arranged in the bypass-

line portion

44, 49, 50, 52, 53, 1 through which the fuel oil returns to the reservoir 2. A movement of the armature of the metering valve thus increases the resistance in the bypass-line, thereby causing the quantity of oil being atomized in the atomizer nozzle 43 to be similarly increased. The higher pressure in the bypass line 44 simultaneously causes the air clappet control cylinder 9 to move against the spring 10 so as to admit more combustion air through the intake gap As. With appropriately coordinated response characteristics as previously described, the oil burner system of the invention permits a continuous adjustment of the rate of combustion within a wide range and under optimal combustion conditions.

The electromagnetic metering valve of the invention is illustrated in more detail, and at an enlarged scale, in FIG. 3 of the drawing. As can be seen from this illustration, the throttling elements of the valve are of the flatseat type, although they could likewise be of any other suitable type. The flat-seat valve has the following advantages:

a. No precision-machined parts are needed, and the requirement of small effective areas for the armature and for the pole core is met;

b. In the fully energized condition of the electromagnet the armature 33 is almost closed against the pole core 34 so as to provide an excellent flow path for the magnetic field, the advantage of this arrangement being that the magnetic energy is used optimally and that the operating temperature of the coil 28 is therefore kept low;

c. The valve seat is not very sensitive against the accumulation of deposits, the latter being continuously removed by the fuel oil flow, under the action of the armature against the valve seat;

d. The highest pumping pressure acting against the electromagnetic metering valve when the latter is closed, is only reached very shortly before the valve is completely closed, the required valve closing force determined by the hydrostatic load on the armature being therefore only required in a position of the armature which is magnetically desirable, i.e. when the armature is as little as 0.5 to 1 mm from the pole core, in which position the force flow of the magnetic field is accordingly greater, thereby conveniently providing the required higher holding force against the metering valve.

In order to reduce the pressure-affected area of the valve, the seat of pole core 34 is provided with a circular relief groove 60 which communicates with two lateral return flow grooves 61. This arrangement eliminates the pressure against the seat area outside the circular relief groove 60.

It was found, however, that the fuel oil which passes through the central bore 59 of pole core 34 may lead to a pressurization of the upper end face of armature 33, as a result of being deflected from the inner wall of the guide sleeve 32, after moving radially outwardly along the lower end face of armature 33. Such a pressurization of the upper end face of armature 33 pushes the latter against the pole core 34 in an undesirable manner, because the circular relief groove 60 on the upper face of pole core 34 encloses a smaller pressure area than that presented by the upper end face of armature 33. A small hydraulic pressure buildup on the armature is therefore sufficient to produce a higher pressure inside bore 59. Such an autonomous readjustment of the electromagnetic metering valve is not desirable. In order to avoid this phenomenon, the armature 33 is provided with a peripheral skirt 58, preferably of a magnetically non-permeable material, the skirt 58 deflecting the oil stream downwardly so as to prevent any pressure buildup in the space 62 above the armature.

A short-circuiting ring 63 in the lower end face of armature 33 eliminates any humming tendency of the latter.

It should be understood, of course, that the foregoing disclosure describes only preferred embodiments of the invention and that it is intended to cover all changes and modifications of these examples of the invention which fall within the scope of the appended claims.

What is claimed is:

1. In an oil burner system adapted for the continuous combustion of fuel oil with air, a control device for adjusting the combustion rate of the burner comprising in combination:

a fuel oil pump connected to an oil reservoir, said pump being driven by a motor at a substantially constant speed, thereby supplying a substantially even flow of oil to the system;

a combustion air blower being similarly driven at a substantially constant speed, thereby supplying a flow of combustion air to the system;

a burner head including an atomizer nozzle by means of which the fuel oil and combustion air are mixed and combusted;

a fuel oil supply line leading from said pump to the atomizer nozzle, including a bypass junction in said line;

a fuel oil return line leading from said bypass junction to the fuel oil reservoir;

an electromagnetic metering valve in said return line for adjustably throttling the oil flow therein so as to determine an adjustable fuel oil supply pressure and flow rate in the oil supply line;

means for adjustably pre-setting the throttling action of the metering valve independently of other adjustments in the system by adjusting its electric current;

an air supply line leading from the outlet side of said blower to the atomizer nozzle; and means for adjustably throttling the air flow at the intake side of said blower so as to adjust the rate of 5 air flow in response to said adjustable fuel oil supply pressure in such a way that the rate of air flowing through the blower is increased as the oil supply pressure increases. 2. An oil burner control device as defined in claim 1, 10 wherein:

the electromagnetic metering valve includes a field coil and an axially movable armature inside the coil, the magnetic field of the coil biasing the armature toward a flow throttling position with a force that increases with increasing coil current; the metering valve further including a stationary pole core which cooperates with the movable armature to create the throttling action of the valve; and

the valve adjustment controlling means includes means for adjusting said coil current.

3. An oil burner control device as defined in claim 2,

wherein:

the movable armature has agenerally fiat throttling surface facing the pole core;

the pole core has a cooperating flat throttling seat facing the throttling surface of the armature, the seat area being bounded by a relief groove whose diameter is considerably smaller than the diameter of the armature; and

the path of the fuel oil return line through the metering valve includes a central entry bore through the pole core to its throttling seat and one or more radially spaced exit channels in the pole core which communicate with the relief groove.

4. An oil burner control device as defined in claim 3,

wherein:

the metering valve armature includes a peripheral skirt which surrounds its throttling surface and extends toward the pole core so as to deflect the oil flow toward the latter and into the exit channels.

5. An oil burner control device as defined in claim 1',

further including:

a pressure check valve in the fuel oil supply line and means for biasing the check valve toward its closed position against the fuel oil flow, the valve biasing means being so calibrated that the check valve remains closed, when less than a predetermined supply pressure is established in the supply line upstream of the check valve.

6. An oil burner control device as defined in claim 5,

wherein:

the check valve is a ball-type back pressure valve arranged between the supply line bypass point and the atomizer nozzle; and

the valve biasing means is a compression spring.

7. An oil burner control device as defined in claim 5,

wherein:

the check valve is a plunger valve which includes a moving plunger; and

the valve-biasing means is a spring which engages one end of the plunger, urging the latter into its closed position against the supply pressure in the fuel oil supply line which impinges on the plunger from the opposite end. 8. An oil burner control device as defined in claim 7, wherein:

the burner head includes a bypass-type atomizer nozzle to which the supply line feeds fuel oil, the bypass junction of the supply line being part of said atomizer nozzle;

the plunger valve is arranged in the oil supply line between the fuel oil pump and said bypass point, and further includes a pressure relief line between it and the fuel oil reservoir;

the fuel oil supply line and the valve plunger define a first closing overlap in the closed valve position and the pressure relief line and the valve plunger define a second, larger closing overlap in the same closed valve position; and

the valve biasing means is so calibrated that the valve plunger displacement is less than said first closing overlap as long as the oil supply pressure determined by the metering valve is below a predetermined value, and is more than said second closing overlap when the supply pressure exceeds a predetermined value.

9. An oil burner control device as defined in claim 1,

wherein:

the combustion air blower includes a blower housing and an air intake opening defined by said housing; and

the air flow throttling means is a clappet valve at the air intake opening, the clappet valve including a means for biasing it toward its closed position, and a hydraulic cylinder means for progressively opening it against the biasing means, as the pressure in the fuel oil supply line increases. 10. An oil burner control device as defined in claim 9, wherein:

the hydraulic cylinder means includes a control line connecting it to the fuel oil supply line. 11. An oil burner control device as defined in claim 9, wherein:

the hydraulic cylinder means includes a control line connecting it to the fuel oil return line upstream of the throttling means in the latter. 12. An oil burner control device as defined in claim 1, wherein:

the fuel oil pump is a positive displacement pump producing a constant oil flow rate independent of the counter-pressure to be overcome in the supply line; and the combustion air blower is rotatably coupled with the fuel oil pump.

Claims

1. In an oil burner system adapted for the continuous combustion of fuel oil with air, a control device for adjusting the combustion rate of the burner comprising in combination: a fuel oil pump connected to an oil reservoir, said pump being driven by a motor at a substantially constant speed, thereby supplying a substantially even flow of oil to the system; a combustion air blower being similarly driven at a substantially constant speed, thereby supplying a flow of combustion air to the system; a burner head including an atomizer nozzle by means of which the fuel oil and combustion air are mixed and combusted; a fuel oil supply line leading from said pump to the atomizer nozzle, including a bypass junction in said line; a fuel oil return line leading from said bypass junction to the fuel oil reservoir; an electromagnetic metering valve in said return line for adjustably throttling the oil flow therein so as to determine an adjustable fuel oil supply pressure and flow rate in the oil supply line; means for adjustably pre-setting the throttling action of the metering valve independently of other adjustments in the system by adjusting its electric current; an air supply line leading from the outlet side of said blower to the atomizer nozzle; and means for adjustably throttling the air flow at the intake side of said blower so as to adjust the rate of air flow in response to said adjustable fuel oil supply pressure in such a way that the rate of air flowing through the blower is increased as the oil supply pressure increases.

2. An oil burner control device as defined in claim 1, wherein: the electromagnetic metering valve includes a field coil and an axially movable armature inside the coil, the magnetic field of the coil biasing the armature toward a flow throttling position with a force that increases with increasing coil current; the metering valve further including a stationary pole core which cooperates with the movable armature to create the throttling action of the valve; and the valve adjustment controlling means includes means for adjusting said coil current.

3. An oil burner control device as defined in claim 2, wherein: the movable armature has a generally flat throttling surface facing the pole core; the pole core has a cooperating flat throttling seat facing the throttling surface of the armature, the seat area being bounded by a relief groove whose diameter is considerably smaller than the diameter of the armature; and the path of the fuel oil return line through the metering valve includes a central entry bore through the pole core to its throttling seat and one or more radially spaced exit channels in the pole core which communicate with the relief groove.

4. An oil burner control device as defined in claim 3, wherein: the metering valve armature includes a peripheral skirt which surrounds its throttling surface and extends toward the pole core so as to deflect the oil flow toward the latter and into the exit channels.

5. An oil burner control device as defined in claim 1, further including: a pressure check valve in the fuel oil supply line and means for biasing the check valve toward its closed position against the fuel oil flow, the valve biasing means being so calibrated that the check valve remains closed, when less than a predetermined supply pressure is established in the supply line upstream of the check valve.

6. An oil burner control device as defined in claim 5, wherein: the check valve is a ball-type back pressure valve arranged between the supply line bypass point and the atomizer nozzle; and the valve biasing means is a compression spring.

7. An oil burner control device as defined in claim 5, wherein: the check valve is a plunger valve which includes a moving plunger; anD the valve biasing means is a spring which engages one end of the plunger, urging the latter into its closed position against the supply pressure in the fuel oil supply line which impinges on the plunger from the opposite end.

8. An oil burner control device as defined in claim 7, wherein: the burner head includes a bypass-type atomizer nozzle to which the supply line feeds fuel oil, the bypass junction of the supply line being part of said atomizer nozzle; the plunger valve is arranged in the oil supply line between the fuel oil pump and said bypass point, and further includes a pressure relief line between it and the fuel oil reservoir; the fuel oil supply line and the valve plunger define a first closing overlap in the closed valve position and the pressure relief line and the valve plunger define a second, larger closing overlap in the same closed valve position; and the valve biasing means is so calibrated that the valve plunger displacement is less than said first closing overlap as long as the oil supply pressure determined by the metering valve is below a predetermined value, and is more than said second closing overlap when the supply pressure exceeds a predetermined value.

9. An oil burner control device as defined in claim 1, wherein: the combustion air blower includes a blower housing and an air intake opening defined by said housing; and the air flow throttling means is a clappet valve at the air intake opening, the clappet valve including a means for biasing it toward its closed position, and a hydraulic cylinder means for progressively opening it against the biasing means, as the pressure in the fuel oil supply line increases.

10. An oil burner control device as defined in claim 9, wherein: the hydraulic cylinder means includes a control line connecting it to the fuel oil supply line.

11. An oil burner control device as defined in claim 9, wherein: the hydraulic cylinder means includes a control line connecting it to the fuel oil return line upstream of the throttling means in the latter.

12. An oil burner control device as defined in claim 1, wherein: the fuel oil pump is a positive displacement pump producing a constant oil flow rate independent of the counter-pressure to be overcome in the supply line; and the combustion air blower is rotatably coupled with the fuel oil pump.