US2788847A

US2788847A - Automatic electric ignition for oil burners

Info

Publication number: US2788847A
Application number: US439516A
Authority: US
Inventors: Frederick H Huntley
Original assignee: Motor Wheel Corp
Current assignee: Motor Wheel Corp
Priority date: 1954-06-28
Filing date: 1954-06-28
Publication date: 1957-04-16
Anticipated expiration: 1974-04-16

Description

April 16, 1957 F. H. HUNTLEY 2,788,847

AUTOMATIC ELECTRIC IGNITION FOR OIL BURNERS Filed June 28, 1954 3 Sheets-Sheet 2 I INVENTOR. FEEDER/CK H HUNTLEY 'ATTOEN 5.

April 16, 1957 F. H. HUNTLEY 2,738,847

AUTOMATIC ELECTRIC IGNITION FOR OIL BURNERS Filed June 28, 1954 3 Sheets-Sheet '3 g 30 LINE" I03 I a l mmvrox. FEEDER/CK HUNTLEV ATTOENEVS,

AUTOMATEQ ELECTRHJ IGNITION FOR H EURNERS Frederick H. li'untley, Lansing, Mich, assignor to Motor Wheel Corporation, Lansing, Mich, a corporation of Michigan Application June 28, 1954, Serial No. 439,516

Claims. (Cl. 158-28) This invention relates to automatic electric ignition for oil burners.

in older types of thermostatically controlled vaporizing oil burners, a constantly burning pilot flame is maintained in the burner to ignite the oil when the oil flow is increased in response to the demands of the room thermostat.

ln newer types of oil burners, the pilot flame has been replaced with an electric ignition device such as a resistance element which vaporizes and ignites the oil. When theroom thermostat calls for heat, electric heat motors start the flow of oil to the burner and at the same time energize the electric ignition device. With such a system, it is necessary that the oil flow be stopped it, for some reason, ignition of the oil fails to occur, because if the how of oil were allowed to continue, the burner would become flooded, thus creating a hazardous condition if and when the hooded burner were ignited.

It is, therefore, a primary object of this invention to provide an automatic, thermostatically controlled, electric ignition control system for vaporizing type oil burners which is reliable in operation and which will prevent pooling or flooding of the burner in case of failure to ignite.

It is a further object to provide automatic means for allowing a limited amount of oil to flow to the burner, to interrupt the flow of oil until ignition has been assured, and thereafter to reestablish the flow of oil to the burner.

It is also an object of this invention to provide a thermostatically controlled automatic electric ignition control system for vaporizing type oil burners which will always fail safe.

In the drawings:

Fig. l is a wiring diagram showing one form of control system of this invention, the switches and other elements being shown in the position they occupy when the burner is cool and shortly after the room thermostat has closed.

Fig. 2 is a view similar to Fig. 1 and showing the various elements in the position they occupy after the lapse of a short time interval from the position shown in Fig. 1.

Fig. 3 is a view similar to Fig. l and showing the various elements of the system in the positions they occupy shortly after ignition has occurred in the burner.

Figs. 4, S and 6 are wiring diagrams showing second, third and fourth modifications of the control system of this invention.

Fig. 7 is a wiring diagram showing still another form of control system of this invention wherein the thermostat employs an anticipator heating coil.

Fig. 8 shows a modified form of the switch illustrated in Fig. 7 for controlling the anticipator circuit.

Referring first to Figs. 1, 2 and 3, the arrangement shown therein includes a burner pot 19 which is supplied with oil from a constant level oil control 12. The flow of oil from control 12 to burner pot 10 is regulated by a rod 14 which extends upwardly from an oil metering stem 16 in control 12. Stem 16 is normally biased upite States Patent 0 2,788,847 Patented Apr. 16, 1-957 wardly to the open position by a spring 16a. Its upward movement is resisted by a pair of thermostatic

bimetallic elements

18 and 20 which normally hold stem 16 in the closed position. The flexing of

elements

18 and 20 is controlled by a pair of

electric heaters

22 and 24. The arrangement is such that when both elements 18 and 29 flex upwardly by reason of the heat from

heaters

22 and 24, metering stem 16 is permitted to rise and oil is admitted to the burner. It will be observed that rod 14 contacts the underside of element 18 and that element 20 is provided with an opening 26 therein through which rod 14 extends, the rod being provided with an abutment 28 contacting the underside of element 20. Thus, although the upward flexing of both elements 13 and 20 is required to establish flow of oil to the burner, the flow of oil to the burner is cut off when either element 18 or 2% flexes downwardly in response to cooling.

The wiring system includes a pair of line conductors 30 which are adapted for connection with a volt source. The conductors 30 are connected with the primary of a voltage reducing transformer 32. A room thermostat 34 has a movable contact 36 connected with one end of the secondary of transformer 32 by a condoctor 38. A conductor 40 connects the fixed contact 42 of the thermostat 34 with one end of each of

heaters

22 and 24. The opposite ends of

heaters

22 and 24 are connected together by

conductors

44 and 46 through a normally closed switch 48 which is controlled by a heat responsive switch arm 50 to open in response to heat from either or both

heaters

22 and 24. Conductor 46 connects with the other side ofthe transformer secondary. Switch 45 is, of course, mounted in heat influence relation with both

heaters

22 and 24 so that it will open or remain open in response to the heat from either heater.

The system includes a second temperature sensitive switch 52 which is connected in parallel with switch 48 by conductors S4 and 56. The contacts of switch 52 are controlled by a heat responsive switch arm 58. Switch 52 is normally open and is mounted adjacent the burner pot 10 so as to be sensitive to the heat of the burner to close.

An igniter 60 is employed for initially vaporizing and igniting the oil admitted to the burner. Igniter 60 may be of either the high voltage or low voltage type. In the arrangement shown, igniter 60 is of the high voltage type and is therefore connected across conductors 30. One side of igniter 69 is connected with one of the conductors 30 by a conductor 62. The other side of igniter 69 is connected with the other conductor 30 through a conductor 64, a mechanical switch 66, a conductor 68, a temperature sensitive switch 70 and conductor 72. Switch 66 has a stationary contact 74 and a movable switch arm 76 which is biased to make with contact 74. Switch arm 76 is provided with an extension 78 which underlies the free end of bimetallic element 20. When the element 20 is not in a heated condition, it engages extension 78 to hold switch arm 76 out of contact with contact 74.

Temperature sensitive switch 70 is also positioned in heat influence relation with the burner pot 10. This switch includes a heat responsive switch arm 8-9 which is normally in closed position and which is adapted to open the switch in response to heat from the burner. Thus, switch 7% is in the nature of a safety switch which prevents any attempt to ignite 'oil in a hot but -er. It also lengthens the life of the igniter and economizes on electricity by cutting out the igniter circuit when the fire is burning. Switches 52 and 71 are preferably calibrated so that switch 52 closes substantially at the same time that switch 70 opens and switch 7! closes at substantially the same time switch 52 opens. Switch 52 is furthermore calibrated to close within a few minutes after ignition occurs in the burner mostat 34 stops calling for heat.

' closed temperature sensitive switch 48.

is as follows: When the temperature in the room in which thermostat 34 is located drops to a value below the setting of thermostat 34, the'thermostat closes'and thereby closes the circuit through

heaters

22 and 24. The circuit through heater 22 is closed directly by thermostat 34 while the circuit through heater 24 is closed through the normally moments after

heaters

22 and 24 have been energized, the bimetallic elements 18 and20 flex upwardly thus permitting rod 14 and metering stem 16 to rise and admit oil to At this timeiswitches 48 and 74 are closed,

the burner.

and switch 52 is .open, as shown in Fig. 1. When bimetallic element 29 flexes upwardly, switch arm 76 closes with contact 74 and thereby closes the circuit through igniter 60. The igniter becomes heated and starts to vaporize the oil admitted to the burner.

Switch 43 is positioned in relation to

heaters

22 and 24 so that after a short time interval, for example, four to six minutes, switch arm 50 is raised sufliciently in temperature by the heat from

heaters

22 and 24 to flex and thereby open the switch. This time interval is of sufficient duration to initiate combustion in the burner under normal conditions. Upon the opening of switch 48 the circuit through heater 24 is broken and bimetallic element 20 therefore cools and flexes downwardly to shut off the flow of oil to the burner and at the same time open the circuit through igniter 60 (Fig. 2). If upon opening of switch '48 ignition has been initiated in the burner, the tem- "perature of the burner will gradually rise to a point where the heat of the burner is suflicient to open switch 70 and close switch 52. Thus, the circuit through the igniter 64} is maintained open and the circuit'through heater 24 is closed through switch 52. Upon closing of switch 52, element 20 is again heated and flexes upwardly to reestablish flow of oil to the burner (Fig. 3). Switches 48 and 2 are calibrated with reference to each other such that there will be enough oil in the burner upon the opening of switch 48' to insure closing of switch 52 before all the oil is consumed. Thus, as long as thermostat 34 calls for heat and ignition of the oil in the burner has taken place, the flow of oil to the burner is continued.

When thermostat 34 stops calling for heat, it opens the circuit through both

heaters

22 and 24. Bimetal elements 18 and 25 flex downwardly and stop the flow of oil to the burner. Within about six to ten minutes after switch 48 starts to cool, it closes and switch 52 opens in about twenty to thirty minutes after thermostat 34 stops calling for heat because of the remaining oil in the burner pot. Thus, after opening of thermostat 34, switch 48 closes before switch 52 opens. If the thermostat should thereafter close again, the circuit through heater 24. will be closed either through switch 48 or through switch 52.

If upon the opening of switch 48 ignition has not taken place in the burner 10, then switch 52 will not close and switch 48 will be maintained in the open condition by the heat from heater 22. Therefore the flow of oil to the burner will not be reestablished since the circuit through heater 24 is open both at

switches

48 and 52. At the same time the circuit through the igniter 60 will be opened at switch 66. Thus, pooling of oil in the burner will be prevented in case of ignition failure. It will be observed that if the electric system fails for any reason whatever such as failure of power, burn-out of

heaters

22 and 24, or burn-out of igniter 60, the flow of oil will be positively shut off. In other words, the system fails safe in every case.

c In Fig. 4 there is shown an arrangement which is generally the same as that shown in Figs. 1 through 3 with Within a few trols the opening and closing of switch 66,.the circuit through the igniter 69 will be energized continuously when the thermostat 34 calls for heat until it is broken by the opening of switch 7%. With this arrangement if failure of ignition should be due to a temporary drop in the line voltage, ignition will occur subsequently when the line voltage rises to its normal value and normal operation of the system will be resumed as described above;

The arrangement shown in Fig. 5 is generally the same as that shown in Fig. 4 with the exception that the switch 66 has been omitted. In this form of automatic electric ignition system the igniter will be energized continuously until combustion occurs in the burner, at which time the heat of the burner will open switch 70 and thereby open 7 the circuit through the igniter 60.

In Fig. 6 there is shown a system which is generally the same as that shown in Fig. 5 with the exception, however,

that switch 79 has been omitted and the igniter 60 is of V the low voltage type, being connected with the high voltage line 38 through a step-down transformer 84. With this arrangement the igniter 6% is energized continuously'as long as the line 30 is connected with a source of current.

This arrangement has been made possible through the development of low voltage igniters which are adapted to be energized continuously withoutcburning out and which consume relatively little power.

Some room thermostats are provided with what is commonly referred to as an anticipator heating coil. The

operation and construction of a thermostat of this type is described in the Jones et al. Patent No. 2,586,826. The purpose of incorporating an anticipator heating coil in a room thermostat is to prevent a cold 70 in the space being heated, as discussed in the aforementioned patent. It has been found that when a thermostat having an anticipator heating coil is employed in the automatic electric ignition system of this invention, in mild weather there is a possibility of the thermostat being opened solely in response to the heat of the anticipator heating coil rather than from a rise in temperature of the space in which the thermostat is located resulting from the heat produced by the burner. Under these conditions, the thermostat may cycle on and ofi several times before the room' temperature has dropped low enough to overcome the heating effect of the anticipator coil and allow the thermostat to remain closed until ignition occurs. In order to avoid this difi'iculty, the arrangement shown in Fig. 7 may be employed. This arrangement is generally the same as that shown in Fig. 1 with the exception, however, that the switch 86, which corresponds to the switch 52, Fig. 1, is provided with a second contact 88 which is connected by a conductor 90 with one end of an'anticipator heating coil 92 in thermostat94 having a stationary contact 96 and a movable switch arm 98. Switch 86 is designed such that switch arm 1G0 normally closes with contact 88 when the burner is cold but flexes to close with contact 102 when'the burner is hot. The switch is calibrated however so that switch arm will snap to the cold position closing with contact 88before the fire in the burner goes out completely. Thus, whenever thermostat 94 calls for heat and switch arm is in the position closing with contact 88, the anticipator heating coil 92 is bypassed and the circuit through

heaters

22 and 24 is closed through conductor 90 and since the current will follow the path of least resistance,

there will be little or no anticipating heat generated at the thermostat. When the burner becomes hot and causes arm of switch 86 to flex .to the position closing with contact 102 and thermostat 94 calls for heat, the circuit through

heaters

22 and 24 will be closed through the anticipating coil 92 and conductor 103. Thus, by bypassing the anticipator in the circuit when the burner is cold, it will be seen that once the thermostat closes it will stay closed until heat is received from the burner itself.

It will be observed that in the arrangement shown in Fig. 7, switch 86 controls not only the circuit through the anticipator heating coil 92 but also the circuit through switch 43. if desired, switch 36 may be replaced with two separate switches 104 and 106, shown in Fig. 8. Switch 104 is normally closed when the burner is cold and switch 166 is open when the burner is cold. Thus, when the thermostat calls for heat and closes, the circuit through the

heaters

22 and 24 is closed through switch 106 and anticipator heating coil 92 is bypassed. When the thermostat calls for heat and the burner is hot, the circuit through

heaters

22 and 24 is closed through switch 196 and anticipator heating coil 92. Thus, with the arrangement shown in Figs. 7 and 8, in mild weather when the burner is liable to cool off considerably between successive periods of burning, the anticipator heating coil 92 is bypassed and the thermostat 94 responds substantially solely to the heat produced by the burner itself. This eliminates the possibility of the anticipator heating coil 92 causing the thermostat to cycle on and off one or more times before ignition of the oil occurs.

I claim:

1. In combination with a vaporizing pot type oil burner having a valve regulating the feed of oil to the burner and ignition means for igniting the oil admitted to the burner, an automatic control system comprising a source of current, a room thermostatic switch connected with said source of current, a pair of electrically energized heat motors in circuit With said source of current, means including said thermostatic switch for closing the circuit of said heat motors and said source of current, said heat motors being operatively connected with said valve, said valve being biased to open in response to energization of both of said heat motors and arranged to close in response to deenergization of either of said heat motors, a pair of heat responsive switches responsive to change in temperature to open and close, one of said switches being disposed in proximity to the burner and being normally open and responsive to the heat of the burner to close, the other switch being disposed in proximity to said heat motors and being normally closed and responsive to the heat of either of said heat motors to open, said last mentioned switch being responsive to deenergization of both or" said heat motors to close, the circuit of one of said heat motors and said source of current being closed upon the closing of said thermostatic switch and the circuit of said other heat motor including said heat responsive switches in parallel and being closed upon the closing of said thermostatic switch and either one of said heat responsive switches whereby oil is admitted to the burner only when the temperature of the burner is above a predetermined value or during the interval of time which elapses between the closing of said thermostatic switch and the opening of said switch responsive to the heat of said heat motors and whereby upon closing of the thermostatic switch and the failure of ignition in the burner, said switch responsive to the heat of said heat motors will open and upon opening of said thermostatic switch said switch responsive to the heat of said heat motors will close.

2. The combination called for in claim 1 wherein said ignition means is connect d with said source of current and including a switch in series circuit with said ignition means and an operative connection between one of sai heat motors and said last mentioned switch for closing 6 said last mentioned switch in response to energization of said last mentioned heat motor.

3. The combination called for in claim 2 including a second switch in series with said ignition means, said second switch being responsive to the heat of the burner for opening the circuit of the ignition means.

4. In combination with a vaporizing pot type oil burner having a valve for regulating the feed of oil to the burner and ignition means for igniting the oil admitted to the burner, an automatic control system comprising a source of current, a room thermostatic switch in circuit with said source of current, said thermostatic switch including a thermostatic bimetal element, a pair of electrically energized heat motors connected with said source of current through said room thermostatic switch and operatively connected with said valve, said Valve being biased to open in response to energization of both of said heat motors and to close in response to deenergization of either of said heat motors, a pair of heat responsive switches, one of said switches being normally open and in heat exchange relation with the burner and the other being normally closed and in heat exchange relation with said heat motors, said one switch being responsive to the heat of the burner to close and the other switch being responsive to the heat of either of said heat motors to open and to deenergization of both of said heat motors to close, one of said heat motors being energized directly by the closing of said thermostatic switch and the other being in parallel circuit with said heat responsive switches and being energized upon the closing of said thermostatic switch and either of said heat responsive switches, an anticipator heating coil in heat exchange relation with said thermostatic switch and in series circuit with the heat motor energized directly by the closing of said thermostatic switch and switch means responsive to the absence of heat at the burner for shunting said anticipator heating coil to prevent energization thereof when the room thermostat closes.

5. In combination with a vaporizing pot type oil burner having a valve for regulating the feed of oil to the burner and ignition means for igniting the oil admitted to the burner, an automatic control system comprising a source of current, a room thermostatic switch in circuit with said source of current, said thermostatic switch including a thermostatic bimetal element, a pair of electrically energized heat motors connected with said source of current through said room thermostat and operatively connected with said valve, said valve being biased to open in response to energization of both of said heat motors and to close in response to deenergization of either of said heat motors, a pair of heat responsive switch mechanisms, one of said switch mechanisms being normally open and in heat exchange relation with the burner and the other being normally closed and in heat exchange relation with said heat motors, said one switch mechanism being responsive to the heat of the burner to close and the other switch mechanism being in parallel circuit with said heat motors and responsive to the heat of either of said heat motors to open and todeenergization of both of said heat motors to close, one of said heat motors being energized directly by the closing of said thermostatic switch and the other being energized upon the closing of said thermostatic switch and either of said heat responsive switch mechanisms, said thermostatic switch including an anticipator heating coil in heat exchange relation therewith and in series circuit with said thermostatic switch and said other heat motor and means forming a shunt circuit around said anticipator heating coil, and further switch mechanism operatively associated with said switch mechanism in heat exchange relation with the burner, said further switch mechanism being arranged to open said shunt circuit when the burner is at an elevated temperature and to close said shunt circuit and thereby shunt out the anticipator heating coil when the burner is relatively cool.

6.- The combination called for in claim 1 wherein said heat motors are connected in parallel with each other and in series with said room thermostatic switch.

7. The combination called for in claim 1 wherein said switch responsive to the heat of said heat motors is calibrated to close in response to deenergization of said heat motors in a shorter period of time than the time required for the opening of said other heat responsive switch in response to stopping of fiow of oil to the burner.

8. The combination set forth in claim 1 wherein said valve includes a movable member normally biased to open said valve, and said heat motors when deenergized acting to move said movable member to closed position.

9. The combination set forth in claim 4 wherein said last mentioned switch means is in circuit with said switch responsive to the heat of said heat motors.

10. The combination called for in claim 5 wherein said one switch mechanism in heat exchange relation to the burnertcomprises a normally open switch responsive to the heat of the burner to close the circuit through said one heat motor and said further switch mechanism comprises a normally closedswitch responsive to the heat of the burner to open said shunt circuit. I

References Cited in the file of this patent UNITED STATES PATENTS De Lancey Nov. 19, 1935