US2768676A

US2768676A - Burner primary control

Info

Publication number: US2768676A
Application number: US334174A
Authority: US
Inventors: Justin A Deubel
Original assignee: General Controls Co
Current assignee: General Controls Co
Priority date: 1953-01-30
Filing date: 1953-01-30
Publication date: 1956-10-30
Anticipated expiration: 1973-10-30

Description

Oct. 30, 1956 J. A. DEUBx-:n 2,768,675

BURNER PRIMARY CONTROL Filed Jan. 30, 1953 nl@ @f JNVENTOR. Q .JUSTIN A. DEUEIEL L o BY 5x5 Jl-/ffjufsm ATTEIRNEYE United States Patent O 8 Claims. (Cl. 158-28) This invention concerns a control circuit and components for the operation of a fuel burner system.

More particularly it concerns a novel circuit arrangement that provides optimum control of the burner system i utilizing a minimum number of components and is especially adaptable to the control of a vaporizing or pot-type burner.

Safety regulations andrequirements for etlicient operation have necessitated a corresponding increase in the complexity and multiplicity of parts in conventional burner control systems. It is an object of this invention to provide a control system that contains all the safety features and provides cyclic operation to ensure timed sequential actuation of the control components without adding numerous components.

- One of the objects of this invention is to provide sequential operation in a control system wherein the ignition means is deenergized immediately upon energization of the fuel supply means to prevent the ignition from being energized while the fuel is burning. This feature is desirable to lengthen the eiective life of the ignition means.

Another object of the invention is to provide sequential operation in a control system Awherein the blower supplying combustion air is maintained in operation at all times except during the ignition period. `This feature is desirable to provide purge-or evacuation periods prior to and after fuel burning operation, and to prevent blower interference during the ignition of the fuel.

riA further object of the invention is to provide sequential operation under the guidance of a timer to ensure positive and definitive functioning of the components during a timed period.

These and further objects will be explained in the following description and more particularly pointed out in the appended claims.

In the drawing, Figure l'shows a circuit diagram illustrating the electrical relationship between the control components; and Figure 2 shows a simple graph illustrating t the control sequence of operation of the major burner components.

i Referring now to Figure 1, a source of electrical supply (not shown), such as the conventional 110 volt domestic power source, has connected thereto a hot line 10 and a ground line 12. A transformer 14 and more particularly its primary 16 is connected across the lines 10 and 12. A normally closed limit switch 18 is interposed in series with the `primary 16 and is operative to open the circuit upon the attainment of an undesirable high temperature in the burner or as a result of some other unsafe condition.

In parallel circuit with primary 16 and across the lines 10 and 12 is connected a blower motor 20 for supplying combustion air to the fuel burner. A relay switch A2, shown in normally closed position, controls the operation of motor 20. i

Also, in parallel circuit with primary 16 and with motor 20 is an ignition means 22 controlled by anormally open relay switch A1. The ignition means 22 may consist of an electric hot wire type of ignitor which obtains incandescence after electrical energization thereof and maintains incandenscence for a period after electrical deenergization thereof, sufficient to ignite the fuel.

The previously described elements are located in the high voltage circuit (110 volt) of the control system. The following elements to be described are located in the low voltage secondary circuit. The use of a low voltage secondary is well known in the art and permits the use of more economical components without sacrificing safety and operating characteristics. The secondary 24 of transformer 14 is connected by wire 26 to a conventional type room thermostat 28. The thermostat 28 operates to close a circuit between wire 26 and thermostat contact 30 upon a temperature drop below a set value. Contact 30 is subsequently described as the low tire contact because it completes a circuit to a fuel supply valve to provide a low metered flow of fuel to the burner to maintain a low tire condition `during the ordinary operating cycle. A high tire thermostat contact 32 is provided which upon failure of the thermostat 28 to be satisfied on low fire will be engaged by the thermostat arm 29 to perform a high tire function. The high lire function will be later described in connection with its co-operating circuit.

A wire 34 connects contact 30 with a relay coil A. Relay coil A is connected by wire 36 to a bimetallic timer switch T1 and by wire 38 to a relay switch B1; The switches T1 and B1 are shown in their normally closed contact position. Note, that the position of all the switches as shown in the drawing represent the system in the standby position prior to a call for heat from the thermostat 28. The other side of switch T1 is connected by wire 4t) to a wire 48 which is connected to one side of transformer secondary 24. The other side of switch B1 is connected by wire 42 to a normally open relay switch A3 and'by wire 44 to a normally open relay switch B2. Switch A3 is connected by wire 46 to the wire 48 and transformer secondary 24. Switch B2 is connected by wire 50 to the wire 48 and secondary 24 and by Wire 52 to a timer heater T. The timer heater T is connected by wire 54 with contact 30.

A wire 56 connects contact 30 with a second relay coil B. The other side ofrelay coil B is connected by wire 58 to a normally open relay switch A4. Relay switch A4 is an optional component and its specific purpose will be later described. A wire 60 connects switch A4 with a normally open bimetallic timer switch T2 which is connected to wire 48 by a wire 62.

A wire 64 connects contact 30 with a fuel valve actuator 66 which may take the form of an actuating coil of a solenoid valve. A wire 68 conects the other side of valve 66 with switch A4, and wire 70 connects valve 66 with a normally open relay switch B3. Switch B3 is also connected by wire 72 to wire 48 and by wire 74 to a bimetal heater 76. The heater '76 is connected bypwire '78 to the high re thermostat contact 32. p

The relay coils A and B are composite units with their switches A1, A2, A3, A4, and B1, B2, B3, respectively, to form conventional relays which may be mounted on the primary control in a manner well known in the art. The switches A1, A3, A4, B2, and B3 are shown in the open contact position and switches A2, and B1 are shown inthe closed contact position which are their positions at the point or standby position of the operating cycle of Figure 2.

The timer heater T and bimetallic switches T1 and T2 form a timer unit whereby the switch T1 is in the closed contact position and switch T2 is in the open contact position, as shown, when the heater T is cle-energized. Upon energization of heater T, the heat is transmitted to the bimetals of the respective switches T1 and T2 and they this amount of metered fuel will be sufficient to satisfy the thermostat demand. However, under extreme temperature demand conditions the thermostat will not be satisfied by the limited flow of fuel and the room or enclosure temperature will drop even though the heating system is operating and the thermostat arm 29 remains in engagement with contact 30. Under these latter conditions the thermostat arm 29 will engage the high fire con- Vtact 32. This action completes a circuit for energizing the bimetal heater 76 which acts upon the metering valve 77, heretofore mentioned, to increase the ow of fuel to the burner. This latter position constitutes the high lire position of the control system. Both the low and high fire positions can be made adjustable to permit various degrees of fuel flow operation. The thermostat 28 can be adjusted to vary the temperatures at which the low and high fire positions are obtained.

Operation The operation of the fuel burner system as applied particularly to a pot-type oil burner will now be described. With particular reference to Figure 2, which indicates by the heavy dark areas the energization of various functional components, the control system is assumed to be at the position 80, which represents any position prior to starting. The time lengths between the positions von the graph are merely indicative of the relationship which may exist under one particular setting and may be correspondingly adjusted for different time intervals according to particular requirements.` However, the relationship between the components and their positions of energizationfor deenergization is critical and important I for any position or unit of time.

The moment of starting is indicated at start and is effected by the closing of thermostat 28 and arm 29 with contact 30 upon a demand for heat. This completes a circuit for the energization of relay coil A through the vclosed timer switch T1 and they energization of. timer "heaterT through switches T1 and B1. The energization of relay coil A effects the closing of switches A1, A3,

` A4 and the opening of switch A2. The closing of switch A1 energizes the ignitor 20, which may be a hot wire type of ignitor that reaches incandescence after a short time period of heating occasioned by the passage of electrical'current therethrough.y The opening of switch A2 deenergizes the blower motor 18 which has been effecting a purging or evacuation of unburned fuel remaining from the previous operating cycle. The closing of switch A3 completes a holding circuit, in conjunction with closed relay switch B1, around the time switch T1, to maintain energization of relay coil A and timer heater T. The

closing of switch A4 does not immediately effect the completion of a circuit but acts to prepare a circuit for subsequent completion by another switch.

The energization of timer heater T starts a timing period for the system by means of the bimetallic switches T1 and T2 which are subsequently moved to their opposite positions in response to heat. The movement of switches T1 and T2 to their hot positions opens switch `T1 and closes switch T2 which correponds to the posi- A tion 82 of Figure 2,

Thus, the time period between start and position 82. is determined by the length of time required for heater T to effect the switching action of bimetallic switches T1 and T2. This latter period may be adjustable by varying the resistance of heater T to give different time periods according to individual requirements. The closure of switch T2 completes a dual circuit; the circuit through previously closed switch A4 to the relay coil B, and the circuit to the fuel valve actuator 66. Operation of the fuel valve actuator 66 permits the flow of oil or other fuel to the burner where it is ignited by action of the ignitor 20 (previously energized). Note, that de-energization of the ignitor 20 .is effected at this point (82) because the energized relay coil B opens switch B1 which breaks the circuit to the relay coil A (switch T1 opened by action of timer heater T) and thereby opens the switches A1, A3, and A4. Even with switch A1 in the open position, the ignitor 20 is sufficiently hot enough to provide fuel ignition for a period after de-energization thereof.

The energization of relay coil B closes switches B2 and B3 resulting in the completion of two holding circuits; switch B2 maintains the timer heater T energized after switch A3 opens, and switch B3 maintains the fuel valve actuator 66 energized after switch A4 opens. The de-energization of relay coil A closes switch A2 which completes the circuit for the blower motor 18 and combustion air is supplied to the burner to aid the fuel burning process. The de-energization `of relay coil A also opens switches A3 and A4 which places the system under the control of relay B.

The operation ofthe burner is now complete and will continue until the thermostat 28 is satisfied or an unsafe condition results in safety shut-down, The latter condition may be provided for by the use of a -dump bucket type safety control (not shown but well known in the art) which operates to shut down the system upon a failure of combustion or over-supply of fuel. The limit control 18 is also provided to shut down the system in the event of over-heating, etc. These controls are ancillary and form no part of the present invention.

In the event that insufcient heat is being supplied during the running period of the cycle (between positions 82 and stop) the thermostat 28 and its arm 29 move into engagement with the high fire contact 32. This action completes a circuit for the bimetal heater 76 which after a short heating period affects metering valve 77 in the fuel supply line to increase the volume and flow of fuel to the main fuel valve (operated by 66) and the burner. For example, the thermostat 28 may be adjusted so that a drop of 21/2 degrees below the demand setting (indicating a failure of the low fire Vsystem to satisfy the heat demand) results in engagement of thermostat arm 29 with contact 3 2 as well as with contact 30. Upon completion or satisfaction of the heat demand, either in the low fire or high fire positions, the thermostat arm 29 breaks with contact 30 and of course contact 32 if it was previously engaged thereto. This action de-energizes the entire transformer secondary circuit and therefore relay coil B. The de-energization of relay coil B places the secondary circuit back in its standby or stop position with one exception. The system cannot immediately re-start in the event of a 4short off period because the timer heater T has just v beende-energized.V This means that for a timed period of cooling, the timer switches T1 and T2 remain in their hot position, i.l e. switch T1 is open and switch T2 is closed. With switch T1 in the open position and relay switches A3 and B2 already in their open positions the starting relay coil Acannot be energized. 'Thus a forced time period is 'created after each operating cycle which prevents'immediate recycling of the system and allows a purge period to be effected by the blower 18 during the cooling time of timer heater T.

Certainxsafety features of the invention will now be pointed out. In the event the electric power supplied to the system fails f or ny reason during the operating cycle, and the power fail s of short duration, i. e., for a time period less than vthe cooling time of heater T, the following safetyfeature results. The Vcessation of power de-energizes the system and the relay coils A and B return v the timer heater T to cool in order to re-cycle.

their switches Yto the positions shown in the drawing. However, the thermostatarm 29 remains in engagement with` contact 30 and the timer switches T1 and T2 are in their hot positions in contradistinction to their positions shown in the drawing, so that with re-occurrence of power ,the system would supply fuel to the burner without ignition, if `it were not for relay switch A4. Relay switch A4 prevents the re-energization of relay coil B upon the occurrence of power failure of short duration. This condition may be further explained by assuming a circuit without -switch A4. With the above conditions prevailing and the re-occurrence of power, the closed hot timer switch T2 would allow the energization of Vrelay coil B and actuator 66 with the subsequent delivery of oil or fuel to the burner. The relay coil A remains de-energized because the open, hot timer switch T1 prevents energization thereof. Thus the ignitor 22 remains de-energized and having been in the cold position for some time is ineffective to ignite the delivered fuel. This condition would be, of course, quite dangerous and switch A4 is added to prevent the system from cycling in this manner, in that it requires the system to re-cycle from the beginning after the timer heater T has cooled sufficiently to return its switches to their cold posi-tions.

Another safety feature is obtained by the use of timer `heater T,the switches operated by it and switch A4. In

the event that the` thermostat 28 has just completed an operating cycle and someone turns it to a higher setting while timer heater T has insufficient time to cool, the resulting dangerous condition would be obviated because switch A4 in the open position would prevent immediate fuel delivery and the system would have to wait for This condition is equivalent to a short power failure.

Fuel delivery by actuator 66 is also prevented in the event of failure of the following components, timer heater `T, relay coil A, and transformer 14. Thistis a further :safety feature. p

Other possible safety features are evident and the in- `vention is intended to be limited only by the scope of theappended claims.

What is claimed is:

l. In a fuel burner control system, a pair of terminals connectible `to a source of electrical power; means for burning fuelV including fuel supply means and an electrically operated blower motor for controlling combustion air; a first normally closed switch controlling said motor; a first series circuit coupled to said terminals comprising serially said rst switch and said motor; said .fuel supply means including an electrically operated con- `trol valve actuator; a heat retentive electrical ignitor for effecting ignition of said fuel-after deenergization of said ignitor; a second normally open switch controlling said ignitor; a second series circuit coupled to said terminals comprising serially said second switch and said ignitor; a timer comprising an electrically operated actuator and timing switches operatively associated therewith for providing timedl operation `of said blower, ignitor and actuator; a temperature responsive element having switchlling means operatively associated therewith for initiating operation of the control system; a relay coil for operating "said first and second switches and having a thirdnormally l open. switch operatively associated therewith; a third series circuit coupled to said terminals comprising serially i saidswitching means, said coil and a first normally closed 'one' o'fsaid timing switches; a normally closed control ,said switching means, said timer actuator, and said nor'- mally open switch; said relay coil and timer actuator being controlled by said temperature responsive element in response to a demand for heat to close said second switch energizing said ignitor and to open said first switchpdeenergizing said motor after a period of purging of the system; means automatically effective to operate said normally open control switch and said normally closed control switch upon operation of said second one of said timing switches; said second one of said timing switches upon closing after a predetermined time period effecting operation of said valve actuator and simultaneously deenergizing said relay coil to deenergize said ignitor and reenergize said blower.

2. ln a fuel burner control system, a pair of terminals connectible to a source of electrical power; means for burning fuel including fuel supply means and an electrically operated fuel valve actuator controlling ow of fuel; a timer including an electrically operated actuator and timing switches operatively associated therewith for energizing said valve actuator; a heat retentive electrical ignitor capable of ignition for a period after electrical deenergization thereof for effecting ignition of said fuel; a first normally open switch controlling said ignitor; a lirst series circuit coupled to said terminals comprising serially said switch and said ignitor; a relay coil for operating said switch and having a second switch operatively associated therewith; a temperature responsive element having switching means operatively associated therewith for energizing said relay coil and said timer actuator in response to a demand for heat; a second series circuit -coupled to said terminals comprising serially said switching means, said relay coil, and a first normally closed one of said timing switches; a third series circuit coupled to said terminals comprising serially said switching means, said valve actuator, a second normally open one of said timing switches, and said second switch; a normally closed control switch; a fourth series circuit coupled to said terminals comprising serially said switching means, said timer actuator, said normally closed control switch, and said rst one of said timing switches; said relay coil closing said rst switch to energize said ignitor; a normally open control switch, a fifth series circuit coupled to said terminals comprising serially said switching means, said timer actuator, and said normally open control switch; means automatically effective to operate said normally open control switch and said normally closed control switch upon operation of said second one of said timing switches; said timer actuator operating said second one of said timing switches to energize said valve actuator after a timed period to supply fuel to the burner and to energize said automatic means to simultaneously deenergize said relay coil to deenergize said ignitor.

3. In a fuel burner control system, a pair of terminals connectible to a source of electrical power; means for burning fuel including fuel supply means and an electrical blower motor for controlling combustion air; a first normally closed switch; a rst series circuit coupled to said terminals comprising serially said iirst switch and said motor; said fuel supply means including a control valve actuator; a heat retentive electrical ignitor capable of ignition for a'period after electrical deenergization thereof for effecting ignition of said fuel; a second normally open switch controlling said ignitor; a second series circuit coupled to said terminals comprising serially said second switch and said ignitor; a relay coil for operating said first and second switches and having a third switch operatively associated therewith, a temperature responsive element including switching means for energizing said relay coil in response to a demand for heat; timing means including an electrical timing actuator and timing switches operatively associated therewith controlled by said temperature responsive element providing timed operation of said blower, ignitor and valve actuator; a

third seriescircuit coupled to said terminals comprising serially said Vswitching means, said relay coil, and a first normally closed one of said timing switches; a normally closed control switch; a fourth series circuit coupled to said terminals comprising serially said switching means, said timing actuator, said normally closed control switch, and said first one of said timing switches; a fifth series circuit coupled to said terminals comprising serially said switching means, said valve actuator, a second one of said timing switches, and said third switch; a normally open control switch7 a sixth series circuit coupled to said terminals comprising serially said switching means, said timer actuator and said normally open control switch; means automatically effective to operate said normally open control switch and said normally closed control switch upon operation of said timing switches; said relay coil upon energization thereof closing said second switch to energize said ignitor and opening said rst switch to deenergize said blower motor, and said second of said timing switches effecting operation of said valve actuator after a time period sufficient to obtain ignition of said fuel.

4. In a fuel burner control system, a heat responsive element including first switching means operatively associated therewith; means for burning fuel including fuel supply means and an electrical blower for controlling combustion air; electrical fuel igniting means; a relay coil having second switching means operatively associated therewith for alternatively energizing said motor and deenergizing said igniting means; electrical timing means having an electrical actuator and a normally closed timing switch operatively associated therewith; a first energizing circuit for said coil comprising serially said first switching means, said coil and said normally closed timing switch; a normally closed control switch; a second energizing circuit for said actuator comprising serially said first switching means, said actuator, said normally closed control switch and said timing switch; a normally open control switch; and a third energizing circuit for said,-

actuator comprising serially said first switch means, said actuator, and said normally open control switch; and means automatically effective to operate said normally open control switch and said normally closed control vswitch upon operation of said timing switch.

5. An arrangement as set forth in claim 4 wherein said fuel supply means includes an electrically operated valve actuator; said relay coil having other switching means operatively associated therewith; said timing means having a normally open timing switch; and an energizing circuit for said control valve actuator comprising serially said first switching means, said other switching means and said normally open timing switch.

6. In a fuel burner control system, means for burning y fuel including fuel supply means and an electrical blower vmotor for controlling combustion, electrical fuel igniting means; a relay coil having first switching means operatively associated therewith and arranged to normally energize said motor and to normally deenergize said igniting means; heat responsive means having second switching means operatively associated therewith; electrical time delay means having an actuator and an associated timing switch for instituting a time delay; a normally closed control switch; first circuit means for energizing said actuator through said second switching means and said normally closed control switch and said timing switch to initiate said time delay; second circuit v ing means and said timing switch to effect deenergization of said motor andl energizationI of said igniting means during the interval of said time delay; a normally open control switch; third circuit means for energizing said actuator through said second switch-means, and said normally open control switch; and means automatically effective upon operation of said timing switch for operating said normally open control switch and said normally' closed control switch. l f

7. An arrangement as set forth in claim 6 wherein said fuel supply means includes an electrically operated control valve actuator; said relay coil having other switching means operatively associated therewith; said time delay means having an additional timing switch operatively associated therewith; and an energizing circuit for said valve actuator including serially said second switching means, said other switching means andvsaid additional timing switch. l

8. In a fuel burner control system, means for burning fuel including fuel supply means and an electrical blower motor for controlling combustion; Velectrical fuel igniting means; a relay coil having first switching means operatively associated therewith and arranged to'normally energize said motor and to normally deenergize said igniting means; heat responsive means having second switching means operatively associated therewith; electrical time delay means having an actuator and an associated timing switch for instituting a time delay; a normally closed control switch; first circuit means for energizing said actuator through said second switching means and said normally closed control switch, and said timing switch, to initiate said time delay; second circuit means for energizing said coil through said second switching means and said timing switch to effect deenergization of said motor and energization of said igniting means during the interval of said time delay; a normally open control switch; third circuit means for energizing said actuator through said second switching means, and said normally open control switch; means automatically effective upon operation of said timing switch for operating said normally open control switch and said normally closed control switch; said fuel supply means including an electrically operated control valve actuator; said relay coil having other switching means operatively associated therewith; said time delay means having an additional timing switch operatively associated therewith; an energizing circuit for said valve actuator including serially said second switching means, said other switching means, and said kadditional timing switch; said means automatically effective to operate said normally open and said normally closed control switches including a second relay coil with said control switches being operated by said second relay coil; and said second relay coil being connected in parallel with said valve actuator.

References Cited in the le of this patent UNITED STATES PATENTS