US3588299A - Fuel-oil burner control system - Google Patents

Abstract

A CONTROL DEVICE FOR BURNER INSTALLATIONS INCLUDING A BURNER WHICH COMPRISES AN ELECTRICAL IGNITION APPARATUS AND A SINGLEPHASE ELECTRIC MOTOR FOR DRIVING A FUEL FEED APPARATUS. THE MOTOR INCLUDES A MAIN WINDING AND AN AUXILIARY STARTER WINDING, OPERATIVELY CONNECTED IN PARALLEL TO EACH OTHER. A MAIN CONTACT IS PROVIDED FOR ENERGIZING AND DEENERGIZING THE CONTROL DEVICE. A FIRST HEATING WINDING OF A SAFETY RELAY IS ARRANGED FOR OPERATIVELY CONTROLLING THE MAIN CONTACT. AN APPARATUS IS ADAPTED TO DETECT THE PRESENCE OF A FLAME AT THE BURNER. A FLAME DETECTOR RELAY IS ALSO PROVIDED, WHICH IS RESPONSIVE TO THE FLAME DETECTING APPARATUS. AN AUXILIARY CONTACT IS RESPONSIVE TO THE FLAME DETECTOR RELAY AND IS CONNECTED OPERATIVELY TO THE AUXILIARY STARTER WINDING. THE LATTER IS DISPOSED SUCH, AS TO BE ENERGIZED THROUGH THE AUXILIARY CONTACT WHEN STARTING THE INSTALLATION AND ALSO THROUGH A FIRST HEATING WINDING OF A SAFETY RELAY. THE SAFETY RELAY COMPRISES A SECOND HEATING WINDING DISPOSED IN A CIRCUIT BRANCH CONTAINING THE MAIN WINDING OF THE MOTOR. ALSO THE FLAME DETECFOR RELAY CONTROLS OPERATIVELY THE ELECTRICAL IGNITION APPARATUS.

Description

United States Patent {72] Inventor ,loseph Callet Grenoble, France [2] 1 Appl. No. 814,346 [22] Filed Apr. 8, I969 [45] Patented June 28, i971 [73] Assignee Appareillage Thermoi'lerr, Etalilissements J.

M. Dar-d Grenoble, France [32] Priority Apr. 24, 1968, Aug. 9, 1968, Jan. 17, R969 [33] France [31 1 149,272, 162,433 and 69,00?

[54] FUEL-OIL BURNER CONTROL SYSTEM 6 Claims, 5 Drawing Figs.

[52] [1.8. Cl 431/78, 431/24 [5 l 1 int. Cl F23n 5/20 [50] Field otSearch... 431/69, 78, 24

[56] References Cited UNITED STATES PATENTS 3,273,626 9/1966 Brown 43 1/69)( ABSTRACT: A control device for burner installations including a burner which comprises an electrical ignition apparatus and a single-phase electric motor for driving a fuel feed apparatus. The motor includes a main winding and an auxiliary starter winding, operatively connect-ed in parallel to each other. A main contact is provided for energizing and deenergizing the control device. A first heating winding of a safety relay is arranged for operatively controlling the main contact. An apparatus is adapted to detect the: presence of a flame at the burner. A flame detector relay is also provided, which is responsive to the flame detecting apparatus. An auxiliary contact is responsive to the flame detector relay and is connected operatively to the auxiliary starter winding. The latter is disposed such, as to be energized through the auxiliary contact when starting the installation and also through a first heating winding of a safety relay. The safety relay comprises a second heating winding disposed in a circuit branch containing the main winding of the motor. Also the flame detector relay controls operatively the electrical ignition apparatus.

FlUlElL-Olll. BURNER CONTROL SYSTEM The present invention relates to an apparatus for controlling fuel oil burners in general and to a system for controlling the automatic operation of an installation comprising a burner operating on fuel oil or any other liquid or gaseous fuel, in particular.

Installations of this type are designed for automatically starting the operation of the burner when a temperature decrease is detected by a thermostat and/or other temperature-responsive means, and automatically stopping the operation of this burner when the desired or predetermined temperature has been restored, or in case a failure or other incident has occurred in the installation.

To this end, these installations control as a rule, on the one hand, the starting of the electric motor driving the fuel feed means, as a rule a fuel pump, and on the other hand, the starting of an electric apparatus for igniting the flame of the burner.

The present invention is concerned more particularly with devices of this general type which are designed for controlling the operation of a single'phase motor supplied with current from a single-phase mains. Up to now the main inconvenience of motors of this type was that they developed a useful torque only when they were actually operating.

Now recent technical improvements in the field permit of constructing single-phase two-winding motors (i.e., with a main winding and an auxiliary starter winding), which have very reduced dimensions, without impairing the starting torque.

Motors of this type have already been used in certain oil burner installations. However, hitherto known installations of this character comprise a magnetic cutout element or a mechanical cutout device which, after the motor has been started, operate somewhat in the fashion of centrifugal couplings, so as to deenergize the auxiliary winding of the motor.

It is obvious that the use of these cutout systems increases considerably the final cost of the installation. Besides, these various cutout systems are objectionable in that they are relatively fragile and their operation is attended by frequent failures after a certain service period.

It is therefore an essential object of the present invention to provide a device designed for controlling an oil burner installation comprising a motor of the type set forth hereinabove, but without utilizing the above-mentioned cutout system. This device is also adapted to efficiently meet the various safety requirements usually demanded in these installations, whether in the case of breakup or deterioration of one of the various component elements of the burner control device, or in case of deterioration of the component elements of the motor proper.

This control device is characterized in that the auxiliary starter winding of the motor, which is connected in parallel to the main winding, is energized when the installation is switched on by a contact of a relay responsive to an apparatus capable ofdetecting the presence ofa flame at the burner, and also through a heating winding incorporated in a safety relay controlling a contact adapted to deenergize the complete circuitry of this device, the safety relay having a second heating winding inserted in the circuit branch comprising the main winding of the motor.

Therefore, in addition to this safety relay, the present device comprises a single control relay responsive to the burner flame detector apparatus.

However, according to a modified form of embodiment, this single control relay may be replaced by purely static elements, in order to avoid the inconveniences inherent in the use of electromagnetic relays.

In this modified form of embodiment the contact or contacts controlling the energization of the auxiliary motor starter winding and of the electrical ignition device are replaced by at least one alternistor adapted to be energized by an oscillating circuit capable of delivering current pulses and comprising a capacitor and a gate-trigger diode. However, this circuit is dependent in turn on a capacitor connected in parallel to a burner flame detector device of which the resistance varies when the flame is produced at the burner.

With these and other objects in view which will become ap' parent in the following detailed description, the present invention will be clearly understood in connection with the accompanying drawings, in which:

FIG. l is a wiring diagram of a first embodiment ofa control device according to the present invention;

FIG. 2 is a fragmentary view ofa modified circuit comprising an alternate embodiment of the arrangement shown in FIG. ll;

FIGS. 3 and 4 are two other modifications of the wiring diagram of FIG. l; and

FIG. 5 is a wiring diagram of still another embodiment of the control device of the present invention.

Referring now to the drawings, and more particularly to FIG. I, a control device in accordance with the present invention is adapted to start a single-phase electric motor M driving the fuel pump of an oil burner as well as a fan or turbine supplying combustion air thereto. This device is also designed for controlling, when starting the motor, the operation of an electrical apparatus TA adapted to ignite the flame of the oil burner.

The wiring diagram shows a circuit connected across the two phases 1 and 2 of the supply mains. However, the energization of this circuit is controlled by a contact Aq responsive to a thermostat and/or other temperature detecting means of the corresponding installation. This circuit comprises four branches 3, 4i, 5 and 6 connected in parallel. The first and second branches 3 and 4 comprise respectively the main winding E, and the auxiliary or starting winding E of the motor M. The third branch comprises the electrical ignition apparatus TA.

Finally, the fourth branch 6 of the circuit comprises an ap paratus DF for detecting the presence of a flame at the oil burner of the installation, as well as the winding RA of the single control relay of the control device ofthe present invention. In the example illustrated in FIG. 1 the winding of this relay is connected in series with the flame detector DF. The latter may consist of a photoresistant cell having a protection device VDR connected across its terminals.

According to an essential feature characterizing the present invention the windings E, and E of motor M are connected in series respectively with a pair of heating windings RS1 and RS2 both incorporated in a safety relay RS controlling a movable relay contact RSC. This movable contact RSC is normally engaging the terminal m in order to close the complete circuit of the device.

However, when the safety relay RS is released, this movable contact RSC is switched from fixed contact m to contact n, with the dual effect of opening the general circuit of the device and closing an ancillary circuit 7 comprising a signal or telltale device L.

The safety relay RS advantageously comprises a bimetaltype relay adapted to actuate the aforesaid movable contact RSC as a consequence of the heat developing in its heating windings RS1 and/or RS2.

According to an essential feature characterizing the device of the present invention, the auxiliary starter winding E is energized through a contact RA, inserted in the corresponding branch 4 of the circuit and responsive to a single control relay RA. This relay RA also controls another contact RA in serted in the circuit branch 5 together with the electrical ignition device TA.

Since the winding RA of this relay, in the embodiment illustrated in FIG. 1, is connected in series with the flame detector DF, both contacts RA, and RA, are normally closed, and during its operation the relay RA keeps these contacts open.

The above-described device operates as follows. When the contact Aq is closed for starting the operation of the burner installation, both contacts RA, and RA, of ignition relay RA remain closed, since no flame is produced so far at the burner; therefore, the flame detector DF remains inoperative and provides a relatively high resistance.

The auxiliary starter winding E, of the motor is thus energized and the motor M can start.

However, the ignition starting apparatus is also energized and will thus ignite the liquid fuel atomized in the burner.

If a flame is produced at the outlet of the burner, the resistance of the flame detector DF decreases, thus causing the operation of the control relay RA and therefore opening its two contacts RA, and RA,.

Then the installation is in its normal operating conditions, since only the main winding E, of the motor is energized.

ln this case, the safety relay RS cannot be operated since its heating winding RS, receives only normal operating current not sufficient to heat it by Joule effect. Besides, this current is definitely lower than that adapted to circulate in the corresponding branch of the circuit in case the motor rotor were jammed.

If no flame appears at the burner, the flame detector DF remains inoperative and the contacts RA, and RA of relay RA remain closed. Therefore, winding RS of safety relay RS still receives the very high current circulating through the auxiliary winding E, of motor M. This will cause a rapid heating of this winding and therefore the release of the safety relay RS which will open the complete circuit of the device while closing, on the contrary, the ancillary circuit 7 comprising the signal device L.

As already explained in the foregoing, the presence of two separate heating windings in the safety relay RS and their se' ries connection with the two motor windings constitutes one of the essential features of the present device. Besides, this advantageous feature provides the safety characteristics necessary for the proper operation of the installation.

In this respect, it may be noted that in case ope of the two heating windings RS, or RS, were destroyed, the motor M could not be started.

On the other hand, if winding RS, were destroyed for any reason during the normal operation of the motor, the latter would'be stopped immediately.

Moreover, if the other heating winding RS, were destroyed, the motor could notbe restarted in case the contact Aq were reclosed after the burner has been extinguished.

FIG. 2 illustrates in fragmentary view a modified form of embodiment of the circuitry of the device of the present invention. In this alternate arrangement the winding RA of the ignition relay is connected in parallel with the flame detector DF in the corresponding branch 6a of the circuit. Under these conditions, a capacitor C is also inserted in this branch.

Besides, both contacts RA, and RA, controlled by relay RA are then normally open and the relay RA is adapted to close these contacts during the starting period and to open them during the normal operation of the installation.

With this modified arrangement the operation is exactly the same as in the preceding form of embodiment.

ln the arrangements illustrated in FIGS. 1 and 2, a bipolar cutout of the electrical ignition apparatus TA can be obtained by providing in the circuit branch another contact RA, actuated by a control relay RA.

If desired, the two contacts RA, and RA, may be replaced by a single contact RA, controlling concomitantly an arm 4a of the circuit which comprises the auxiliary starter winding E and another branch 5a comprising the ignition apparatus TA (see FIG. 3).

H6. 4 illustrates another embodiment of the device which differs from the one shown in FIG. I by the fact that the circuit further comprises an electromagnetic valve EV adapted to control the injection of fuel into the burner. This valve EV is inserted in an additional branch 8 of the circuit which is connected in parallel with respect to the other branches. ln this branch 8 a front contact RA, is inserted and adapted to be closed by means of the control relay RA when the latter causes the opening ofcontacts RA, and RA,.

However, a contact CS, is mounted in parallel in relation to contact RA,. This contact CS is a front contact adapted to be closed under the control of a heating winding CS inserted in the circuit branch 4, i.e., the branch comprising the auxiliary starter winding E, of the motor.

The same heating winding CS may also control the opening of a front contact CS, connected in parallel with the winding RS, of safety relay RS.

Therefore, this arrangement permits of utilizing an electromagnetic valve EV and also the following program sequence:

l. Energization of ignition transformer TA and starting of motor M by means ofits auxiliary winding E,,

2. After a few seconds, energization' of electromagnetic valve EV so as to inject fuel through the burner,

3. Ignition of the fuel in the burner and normal operation of the installation.

In fact, the device according to this embodiment of the present invention operates as follows:

When contact Aq is closed and the ignition transformer TA as well as the auxiliary winding E, of the motor are energized, the burner is not ignited immediately since the valve EV, which is to supply fuel thereto, is still inoperative. Thus, during a few seconds a preignition takes place, considering the operation of transformer TA as well as the forced scavenging of the burner which is caused by the immediate operation of the motor.

These few seconds permit the heating of winding CS inserted in the circuit branch 4 to a degree sufficient for concomitantly controlling the opening of contact CS, and the closing of contact C5,. This last movement causes the energization of valve EV so that fuel is fed to the burner to permit its ignition.

Immediately as a flame is produced at the burner the resistance of flame detector DF decreases, thus permitting the energization ofthe winding of control relay RA controlling the opening of contacts RA, and RA, and therefore deenergizing the ignition transformer TA and the auxiliary or starter winding E, of the motor.

However, the relay RA has simultaneously controlled the closing of contact RA, provided in circuit branch 8. Under these conditions the valve EV remains energized through this contact.

After a certain time period, the winding CS inserted in circuit branch 4 has cooled down due to the opening of contact RA,. Thus, contacts CS, and CS, resume their initial positions.

But as already explained in the foregoing the valve EV remains energized through contact RA,. Thus, the device is normally operative and remains in this state throughout the subsequent steps.

If, by accident, during the normal operation of the installation, the flame were extinguished at the burner, this would be attended by the increment in the resistance of flame detector DF, causing the winding of control relay RA to be deenergized, thus releasing this relay. Therefore, its contact RA, is open immediately, thus stopping the operation of valve EV. But simultaneously the ignition transformer TA is reenergized by the closing of contact RA,, and the auxiliary winding E, of the motor is also reenergized by the closing of contact RA,. The heating element CS inserted in branch 4 can thus be heated so that the conditions obtaining during the initial starting of the burner are restored.

Since the valve EV is reenergized within a few seconds if the flame did not appear at that time on the burner, the currents flowing through the heating elements RS, and RS, of the safety relay (contact CS, being opened in the meantime) would be such that within a predetermined time period the contact RSC of this safety relay would move to position n, thus stopping the installation while energizing the signal means L The essential feature characterizing this circuit liesin the fact that the main control relay RA provided in FIG. 1 and its contacts RA, and RA are replaced by a pair of alternistors Al and Al adapted to be energized through a resistor R, and a socalled relaxation" oscillating circuit. This last-named circuit adapted to deliver current pulses comprises the following elemerits: a pair of resistors R, and R a capacitor C and a gate trigger diode DlD,.

However, this circuit is subordinate to a capacitor C, connected in parallel to an apparatus DF constituting the flame detector of the burner. This apparatus, of which the resistance decreases when this flame appears, may advantageously consist of a photoresistant cell.

Besides, a pair of matching resistors R, and R ai'e provided.

This device operates as follows:

When contact Aq is closed for operating the installation the main winding E, of the motor M is energized immediately, but this is not sufficient for starting the motor.

Besides, capacitor C, is charged since the resistance of the flame detector DF is then relatively high, considering the absence of flame at the burner. Thus, this capacitor is charged at a voltage permitting the oscillation of the relaxation circuit.

Under these conditions, this circuit will deliver current pulses to permit the energization of alternistors Al, and A1 so that they become conductive and the auxiliary winding E, of the motor is energized while the electrical ignition apparatus TA itself is energized. As the fuel, for instance fuel oil, is thus injected, the spark produced by this ignition should normally ignite the fuel flowing through the burner.

Immediately as the flame is obtained the flame detector DF is energized so that its resistance decreases. Thus, capacitor C, is discharged through the relaxation circuit. During this discharge time this circuit continues to energize both alternistors Al, and Al Under these conditions, the electrical ignition apparatus TA will continue to be energized and produce sparks, even after the flame has appeared at the burner.

it is thus clear that a post-ignition operation is obtained which promotes the stability of the flame produced at the burner. In fact if this flame were extinguished accidentally the sparks produced due to the continued operation of the ignition apparatus would certainly reignite the fuel issuing from the burner.

But after a few seconds, the discharge of capacitor C, is ended and therefore no more pulses are delivered by the relax ation circuit, so that the two alternistors are no more energized.

Consequently, the energization of the electrical ignition apparatus TA and of the auxiliary winding E, of motor M is discontinued.

Nevertheless, the motor M continues to rotate due to the energization ofits main winding [5,.

Thus, the burner operates normally and is no more tributary of the thermostat or other temperature-sensitive device of the installation, and of the heating element RS, of the safety relay which could possibly become operative in case of overvoltage across the main winding E, of motor M.

The normal return of this device to inoperative conditions is controlled when the contact Aq of the thermostat or other temperature-responsive device is opened. Then, all the control circuits are deenergized.

However, with the present device all the safety measures necessary or required by existing regulations for the operation ofa burner installation are obtained:

1. During the starting period:

A. In case of absence of flame at the burner In this case the flame detector DF is not energized while the motor was actually started.

Under these conditions, the resistance of detector DF remains high so that capacitor C remains charged, thus maintaining the relaxation circuit and therefore the auxiliary winding E of the motor in their energized condition. Consequently, current continues to flow through the resistance of safety relay winding RS Now the characteristics of this current are such that after a certain time period corresponding to the safety time period of the installation, the movable contact RSC of this safety relay is moved from contact m to contact n.

Thus, all the control circuits are open, the motor is stopped and the electrical ignition apparatus TA is deenergized.

Since the movable contact RSC engages contact n the signal or alarm device L is operated by direct energization. Nevertheless, the installation remains in its safety condition as long as the safety relay is not reset manually.

B. In case of nonopcration of theflame detector:

The same sequence of steps take place in this case, thus providing the necessary safety condition.

2. During the normal burner operation:

A. in case ofcurrent failure:

The various circuits and elements of the device are restored immediately to the conditions corresponding to the nonoperation of the burner.

When the voltage is restored the conditions obtaining are somewhat those described hereinbelow in the case ofa normal burner ignition sequence.

B. in case the flame is extinguished:

The flame detector DF is deenergized, so that capacitor C, is charged and energizes the relaxation circuit. This circuit causes the energization of alternistors Al, and Al and therefore the energization of auxiliary winding E of motor M, as well as ofthe electrical ignition apparatus TA.

Now two cases may arise:

a. If the flame is restored by the operation of the electrical apparatus TA, the conditions thus restored are those prevailing during the normal starting period of the installation,

b. If no flame appears at the burner, the protection conditions obtaining during the starting period are restored.

If desired, a single alternistor may be used instead of two (Al,, A1,), but in this case the general circuit arrangement will be such that this single alternistor will control the energization both of the ignition transformer TA and of the auxiliary winding E of the motor.

Similarly, without departing from the basic principle of the control circuit, it is possible to have each alternistor controlled by a separate relaxation circuit.

While I have disclosed several embodiments of the present invention, it is to be understood that these embodiments are given by example only and not in a limiting sense.

lclaim:

ll..Control device for burner installations including a burner comprising an electrical ignition apparatus and a single-phase electric motor for driving a fuel feed apparatus;

said motor including a main winding and an auxiliary starter winding operatively connected in parallel to each other,

a main contact for energizing and deenergizing said control device;

a first heating winding of a safety relay operatively controlling said main contact;

an apparatus adapted to detect the: presence of a flame at the burner;

a flame detector relay responsive to said flame detecting apparatus;

an auxiliary contact responsive to said flame detector relay and connected operatively to said auxiliary starter winding;

the latter disposed so as to be energized through said auxiliary contact when starting the installation and also through said first heating winding of said safety relay;

said safety relay comprising a second heating winding disposed in a circuit branch containing said main winding of said motor; and

said flame detector relay operatively controlling said electrical ignition apparatus.

2. The control device, as set forth in claim 1, further comprising:

7 8 a third heating winding in series with said first heating windresponsive in turn to a second capacitor connected in ing and said auxiliary starter winding; parallel to said flame detecting apparatus; and an electromagnetic valve operative to caise fuel to be insaid flame detector apparatus includinga resistance varying jected into said burner, said valve being connected in whcnaflame is produced at said burner. parallel in a specific circuit branch in said control device 5 4. The control device, as set forth in claim 3, and further and the latter comprising in parallel a first contact operacomprising: tively connected to said flame detector and ada ted t b a second alternistor connected in series to said ignition apclosed by said flame detector relay responsive to said paratus and operatively energized by said oscillating curflame detector and a second front contact operatively connected to and da ted t b l d b id hi d h m. l said first alternistor controlling the energization of said auxing winding; andiliary starter winding of said motor and said second ala third front contact disposed across the terminal of said temismr Controlling energilatio" of Said electrical first heating winding of said safety relay operatively conpp nected to d i hi heating winding the lane! com 5. The control device, as set forth in claim 1, further comtrolling said third front contact so as to open the latter prising: 4 upon heating f i third heating winding an ignition contact in series with said electrical Ignition ap 3. The device, as set forth in claim 1, wherein: Params; and I said auxiliary contact controlling the encrgization of said flame detector relay operatively Connected Sald auxiliary starter winding of said motor comprises a first contact- 6. The control device, as set forth in claim 1, wherein:

said auxiliary contact is further connected in series with said electrical ignition apparatus.

alternistor; said flame detector relay comprises an oscillating circuit energizing said first alternistor and capable of delivering current pulses and comprising a first capacitor and a gate-trigger diode, said oscillating circuit being

Images