US2266185A - Fluid fuel burner control system - Google Patents

Description

Dec. 16, 1941. F. B. FILLO FLUID FUEL BURNER CONTROL SYSTEM Filed Aug. 12, 1958 M l M vo m. H mn Nl m Wfl/I+ w :lL/ f 8 Ro Z /02 sfu/rw@ f L m 9W TMILI. o? l/YI..

O m 4 l A 6 A 0 u.. 6 6 9 2 6 5N o 4 S 7 to f 4 l MMII. 6 Am wl I u l./. 4: s 6 `/l O M @Ms l 4 Snnmtor Francis B. Fillo- Patented Dee. 1s, 1941 2.266.185 FLUID FUEL BUaNna coN'raoL SYSTEM Francis B. Fillo, Webster Groves, Mo., assignor to Minneapolis-Honeywell Regulator `Company, Minneapolis, Minn., a corporation of Delaware y Application August 12, 1938, Serial No. 224,542

8Claims.

The presentinvention relates to a uid fuel burnerv control system and more particularly to one in-which certain switching operations take place upon the,v initiation of combustion.

It is the usual practice with fluid fuel burner control systems, particularly oil burning systems, to perform certain switching operations upon combustion taking place. One need for such switching operations arises from the fact that it is the usual practiceto employ some cut-out mechanism, usually a safety switch, which is effective unless rendered inoperative vto terminate operation of the fuel feeding means after a predetermined period of time. The switching operations incidental to combustion have as one of their objects to render inoperative this cut-out mechanism after combustion takes place within the predetermined period of time. It is usually also the practice to render ineifective the ignition means after the burner is ignited, particularly 2.0.

a burner control system according to the previous objects in which the electromagnetic switch is in the form of a balanced relay having opposed coils and a pair of thermo-couples each connected to one of said coils, the hot junctions of said thermocouples having different capacities for absorbing oil burner control circuit although it is to be where electric ignition is employed. The logical time for doing this is when combustion is first definitely established.

In order to have these operations performed relatively quickly upon a temperature risc and also in order to have certain safety operations performed quickly after combustion is interrulited, it is necessary to have a switch which does not operate at a predetermined temperature but rather operates as a result of predetermined temperature changes. In the past, it has been the usual practice to employ what is known as a "slip friction switch. This switch consists essentially of a temperature responsive element connected to one or more switches by a connection which is capable of slipping after the switching function has been accomplished. It may be readily seen that such devices are subject to the possibility of unstable operation in that they depend upon two members slipping relative to one another but still having sufficient friction between them that they initially. move together.

An object of the present invention is to provide a burner control system in which the switchingfunction incidental to the initiation of combustion is accomplished by means of an electromagunderstood that the invention is not limited to the oil burning art.

Referring to the figure, an oil burner is indicated by the reference nulmeral Il. This oil burner comprises a yburner nozzle Il through which a mixture of fuel and air is forced by the control of the system. l This thermostat consists of a bimetallic element I1 to which issecured a contact arm I8. This contact arm I8 carries a pair of blades I9 and 20, which blades are adapted to engage fixed contacts 2| and 22. The blade 201s adapted to engage contact 22 first upon movement of the -arm Il to the left and thereafter blade IS is adapted to engage contact 2l.

. 'I'he thermostat i6 controls the energization of a relay 25. This relay comprises a relay coil 2i and a pair of switch blades 21 and 28 adapted to be moved in engagement with contacts 29 and Il.

tion is accomplished by means of an electromag- I netic switch energized by thermo-couple means having at least two junctions of different capability for absorbing and giving up heat.

A further object o f the invention listo provide awayifrom the upper blade unless otherwisere-l Ihe switch blades 21 and 2l are normally out of engagement with contacts 2! and 3l but are moved into engagement therewith by energization of relay coil 2i.

A thermal safety switch 35 also controls the energization of relay 25. This thermal safety switch may beof any suitable form, one preferable form being that shown in the patent to Frederick S. Denison No. 1,958,081, issued May 8, 1934. The switch is shown in schematic form as comprising switch blades and 31, the .lower v one of whichis pivotally mounted so as to drop strained. Located so as to extend under the right-hand end of switch blade 3l is a bimetallic element 38. A heating element 39 is located adswitch blade 3b by the bimetallic element 32.

Upon sufficient warping of the bimetallic element 33, however, switch blade 3i! will drop vaway from switch blade 36 and the switch'cannot bereclosed automatically. v

A second relay is generally indicated by the reference numeral d5. This relay comprises a pull in coil it and a bucking coil 377. The relay also comprises a plurality of Switch blades llt, G9, and E@ which are adapted to cooperate with fixed contacts 5l, 52, 53, and 5G. Switch blades l and 5@ are biased into engagement with contacts 52 and 5G, and switch blade 68 is biased out of engagement with contact 5l. Upon the relay being energized, switchblades 38 and 52 are moved into engagement with contacts 5l and 53, switch blade 5@ being InovedoutY of engagement with contact 5G and switch blade lll out of engagement with contact 52. Switch blade E@ is so designed with respect to contacts 53 and till that it engages Contact 53 before it disengages contact 5G. This is indicated in the drawing by the legend Overlapping contacts.

A relay t@ controls the energization of relay This relay comprises a U-shaped armature 6l pivoted adjacent its midpoint at 62 and 'carrying a switch blade S3. The. armature is adapted to cooperate with two coils til and 135, the energization of which exert opposing forces upon the armature 6l. The switch blade t3 is adapted to cooperate with two xed contacts t6 and tl. Upon relay coil bil being more highly energized than relay coil E5, the left-hand portion of armature til is drawn downwardly and switch blade 63 .is moved into engagement with contact 6l. On the other hand, when relay coil t5 is the more highly energized of the two, the switch blade t3 is moved into engagement with contact 6B.

The reference numeral l@ is used to generallyl refer to a thermo-couple means comprising two ,thermo-couples ll and l2.

The thermo-couple means i extends into a pipe 76 which constitutes a stack pipe of the furnace in which the oil burner lll is located. It is to be understood that upon operation of the oil burner, the stack temperature rises very quickly and upon the oil burner stopping, the stack temperature cools down very rapidly. The stack temperature is thus a very good indication of the combustion conditions and it is quite common to` place combustion responsive switches in the stack. The hot junction. of therm-couple 'H `is indicated by the Nreference numeral 13 and the hot junction of the thermo-couple 12 by the reference numeral 14. The thermo-couple 72, particularly adjacent .the hot junction thereof, is entirely Y surrounded with insulating material which is shown in section in the drawing and indicated by the numeral 15. The purpose of this insulating materialisto insure that the hot junction 14 of thermo-couple "l2 will not be heated immediately and-when the temperature within the stack is falling will not cool rapidly as the hot junction 13 of thermo-coup e 1I.

Power is supplied for operation of the control portion of the system by a step-down transformer generally indicated by the reference numeral 80. This transformer comprises a line voltage primary l and a low voltage secondary 82. The line voltage primary 6l is connected to line wires 83 and Bil leading to a suitable source of power (not shown).

Operation The various elements of this system are shown in the position which they occupy when the temperature to which thermostat i6 is subjected is above the desired value. Let it be assumed now that this temperature starts dropping. The eiiect of this would be to cause contact yarm lil to move to the left bringing rst blade 2@ into engagement with contact 22 and then blade l@ into engagement with contact 2l. Upon engagement of both blades l@ and 2li with contacts 2l and 22, the following circuit to relay coil 2li is established: from the upper terminal of secondary 82 through conductors 35 and 86,' Switch blades 3l and 36, conductor Sl, contact 22, thermostat switch blades 22 and i9, contact 2l, conductor 82, contact 5B, switch blade 5t, conductors t9 and 9d, heating, element 39, conductor 9i, relay coil 26, and conductor 92 to the other terminal of secondary 82. The establishment of this circuit results in the energization of relay coil 2t and the moving of switch blades 2l and 22 into engagement with contacts 29 and 3U, respectively. The movement of switch blade 2l into engagement with contact 29 establishes a holdingcircuit to the relay coil 26 as follows: from the upper terminal of secondary 22 through conductors 25 and 2S, switch blades 3l and 36, conductor 2l, contact 22, blade 2li, arin l2, bimetallic element lill, conductor Qll, contact 29, switch blade 2l, conductors 95 and 92, heating element 39, conductor Sl, relay coil 2B, and conductor 92 to the other terminal of secondary 82. It will be noted that this holding Acircuit is independent of the engagement of contacts i9 and 2l. Thus the temperature must lrise sulciently to cause disengagement of not only contacts H9 and 2l but also of 2@ and 22 before the relay is again deenergized. The result of this is that there is a differential between the energization and deenergization of the thermostat, this differential preventing any chattering of the relay as the thermostat first makes or iirst breaks the contacts.

It will be noted that both the holding and energizing circuits through relay coil 26 include the heating element 39 and also include the switch blades 36 and 3l. Thus if these circuits remain unchanged for a length of time, the relay will be deenergized by reason of the safety switch 35 opening.

The engagement of switch blade 28 with contact 30 results in the following energizing circuit to oil burner motor l2: from line wire 84 through conductor S6, contact 30, switch blade 28, conductors 97 and 98, burner motor I2, and conductorsmg and E02 to the other line wire 83. At the same time, a circuit is also established to the ignition means M 'as follows: from line wire 8d through conductor 96, contact 30, switch blade 28,' conductor 91, switch blade $9.' contact 52, conductor lill, ignition means I4, and conductors H32 and H00 to the other line wire 83.'

The establishment of the last two traced cirmally insulated, the hot junction 18 will be the only one which heats to any appreciable extent initially. The result is that the current owing through coil 84 Awill far exceed that flowing through coil 85. "The effect of this will be that the armature 8| is rotated in a counter-clockwise direction moving switch blade 88 into'engagement with contact 61.

The movement of'switch blade 88 into engagement with contact 81 results in the establishment of the following energizing circuit to relay coil 46 of relay 4,5: from the upper terminal of secondary 82, through conductors 85, |08, and |04, contact 81, switch blade 88, conductor |05, relay coil 48, and conductors |08.and 82 to the other secondary 82. energizing circuit to relay coil 46 results in switch blades 48 and 58 moving out of engagement with contacts 52 and 54 and switch blades 48 and 58 moving into engagement'with contacts 5| and 58. The moving of switch blade '48 out of engagement with contact 52 results in the deenergization of the ignition. This will be obvious inasmuch as the only circuit traced to the ignition means was through contact 52. The deenergization of the ignition is desirable at the present stage since it is assured" that the oil burner has been properly lighted for at least.

several seconds and there is no need of further operation of the ignition with the resultant current consumption and deterioration of the parts.

'I'he moving of .switch blade 48 into engagement with contact 5| establishes a holding circuit to relay coil 46 which is independent of relay 80. This holding circuit is as follows: from the upper terminal of secondary 82 through conductors 85, |88, and |88, switch blade 48, contact 5|, conductor |08, relay coil 46,- andconductors |88 and 82 to the other terminal of secondary 82.

The moving of switch blade 50 out of engagement withcontact 54 andinto engagement with contact 58 establishes a circuit to relay coil 28 which is independent of the heating element 88 and also breaks the previouslyV established cir- .cuits through the heating element. As previously indicated, the switch blade 50 is so designed The establishment of this with respect to contacts 58 and 54 that it engages contact 58 before it disengages contact 54.

` Thus the old circuit is not br'oken until the new circuit is/established, which is as follows: from the upper terminal of secondary 82 through conductors 85 and 88, switch blades 81 and 86, conductor 81, contact 22, blade 20, arm I8, bimetallic element l1, conductor 84, contact 28,switch blade 21, conductors 85 and 88, switch blade 50, con- The operation which has just been described is that which takes place under normal circumstances. If for some reason or other combustion does not take place, the stack 'temperature will not rise and consequently the heating element will: not be deenergized by the action of relay 45. 'Ihe result will be that the safety switch 85 will open causing deenergization of the entire system. The system cannot then be restarted without the safety switch 85 being manually reset.

After theburner hasv been in operation for a while, the temperatures of the hot junctions 18 and 14 will becomesubstantially equalized due to the heat penetrating through the insulation 15. Under theseI circumstances, the switch blade 68 will assume a position intermediate contacts 88 and 61. If for any reason combustion should be interrupted while the thermostat is still calling for heat, provision is made for attempting to restart the burner. Under these circumstances the stack temperature will cool down Very quickly. Since the hot junction 18 is exposed, this junction will cool down. On the other hand, the hot junction 14 will remain quiet hot since the insulation 15 prevents the heat from being dissipated therefrom. Under these circumstances, the relay coil 85 will be the more highly energized of the two causing switch blade 88 to move into engagement with contact 88. 'I'he effect of this will be to establish an energizing circuit to bucking coil 41 as follows: from the upper terminal of secondary 82, through conductors 85, |88, and |88, switch blade 48, contact 5|, conductors |08 and |05, switch blade 88, contact 88, conductor bucking coil 41, and conductors |82, |85, and 82 to the other term al of secondary 82. The establishment of this circuitto the bucking coil 41, in view of the fact that the coils' 48 and 41 have 'an opposite eect, results in the deenergization oi the relay causing the various switch blades to assume the position shown in the drawing. The separation of switch blade 48-from contact 5| insures the deenergization 'of the relay even though switch blade 88 a moment later.disen gages from contact 88, since the only circuit established to coil 48 is through switch blade 48 and contact 5|. The moving of the switch blade 58 out of engagement 'with contact 58 and into engagement with contact 54 reestablishes the circuit to the heating element 88 and breaks the previously established circuit to relay coil 28 which is independent of the heating element 88. The moving of switch blade 48 back into engagement with contact 52 results in the reestablishment of the ignition. If the condition which caused the extinguishment of the burner was merely a temporary one, the oil burner will now be reignited and the apparatus will go through the same cycle previously traced. If, however, -combustion does not 'take place, the continued heating of heating element 88 will cause an opening of the thermal safety switch 85 causing deenergization of the system.

After the oil burner has started, under normal circumstances, the burner will continue to run until the thermostat |8 is satisfied, that is, until switch blade'20 has disengaged from contact 22. Since the circuits to both relays 48 and 28 are controlled by the thermostat i8, the opening of the thermostat will cause deenergization tact 58, conductor |88, relay coil 28, and cony, dnctor 82 to the other terminal of secondary 82.

of bothl relays and consequently of the oil burner.

It will be seen that with my improved fuel y accordance with the direction of temperature change.

While I have shown a specific embodiment of my invention, this is for purposes of illustration only and it is to be understood that the invention is limited only by the scope of the appended claims.

I claim as my invention:

l. A switching device responsive to the direction and extent of temperature changes comprising a relay having actuating coil means and a switch movable into and out of a circuit making position dependent upon the direction and extent of energization of said coil means and a pair of thermo-couples independently connected to said coil means, the hot junction of one of said thermo-couples being capable of quickly absorbing and giving up heat and the hot junction of the other of said thermo-couples being capable of only slowly absorbing and giving up heat whereby upon a temperature rise the first mentioned junction is the hotter of the two and upon a temperature fall the other junction is the hottest.

2. A switching device responsive to the direction and extent of temperature changes comprising a relay having actuating coil means and a switch movable into and out of a circuit making position dependent upon the direction and extent of energization of said coil means and a pair of thermo-couples independently connected to said coil means, the hot junction of one of said thermo-couples being exposed and the hot junction of the other being insulated whereby upon a temperature rise said iirst junction will be the first to heat up and upon a temperature fall said first junction will be the rst to cool off.

3. A switching device responsive to the direction and extent of temperature changes comprising a balanced relay having a pair of opposing coils and a switch positioned in accordance with the relative energization of said coils, a pair of thermo-couples each connected to one of said coils, thehot junction of one of said thermo-couples being capable of quickly absorbing and giving up heat and the hot junction of the other of said thermo-couples being capable of only` slowly absorbing and giving up heat, whereby upon a temperature rise one of said coils will be more highly energized and upon a temperature fall the other will be more highly energized.

' 4. A switching device responsive to the direction and extent of temperature changes comprising a balanced relay having a pair of opposing coils and a switch positioned in accordance With the relative energization of said coils, a pair of thermo-couples each connected to one of said coils, the hot junction of one of said thermocouples being exposed and the hot junction of the other of said thermo-couples being insulated whereby upon a temperature rise said first juncperature fall said rst .junction will be the rst to cool oi so that upon a temperature rise one of said coils will be more highly energized and upon a temperature fall the other will be more highly energized. v

5. A device responsive to the direction and extent of temperature changes comprising a pair of opposed electromagnetic coils, a balanced armature positioned in accordance with the relative energization of said coils, a pair of thermo-couples each connected to one of said coils, the hot junction of one of said thermo-couples being capable of quickly absorbing and giving up heat and the hot junction of the other of said thermocouples being capable of only slowly absorbing and giving up heat, whereby upon a temperature rise one of said coils will be more highly energized that the hot junction of the inner thermo-couple absorbs and gives up heat more slowly than the hot junction of the outer thermo-couple with the result that upon a temperature rise the coil to which said outer thermo-couple is connected will be more highly energized and upon a temperature fall the other coil will be morehighly energized.

7. A thermocouple device responsive to rate of temperature change, comprising a pair of thermocouples disposed with one surrounding the other, heat insulating material between the inner and outer thermocouples so that the hot junction of the inner thermocouple absorbs and gives up heat more slowly than the hot junction of the outer thermocouple, and electrical means connected to said thermocouples so as to respond to the difference between the electromotive forces of said thermocouples.

8. A thermocouple device responsive to rate of temperature change, comprising a pair of thermocouples mounted adjacent each other, the hot junction of one of said thermocouples being capable of quickly absorbing and giving up heat and the hot junction of the other of said thermocouples being capable of only slowly absorbing and giving up heat, and electrical means associated with said thermocouples so as to respond to the diierence between the electromotive forces thereof.

FRANCIS B. FILLO.

Images