US2265294A - Control system - Google Patents

Description

Dec. 9, 1941. F. E. LANGE 2,265,294

CoNTRoLgsYsTEM Filed Feb. le, 1959 Patented Dec. 9, 1941 CONTROL SYSTEM Frederick E. Lange, Minneapolis, Minn., assignor Minneapolis-Honeywell Regulator Company,

Minneapolis, Minn., a corporation of Delaware Application February 16, 1939, Serial No. 256,737

16 Claims.

This invention relates to a simplied control system for fuel burners and incorporates a plurality of thermo-couples which provide certain novel functions withsafety shut-down features in the event of ignition failure.

In fluid fuel burner control systems employing pilot burners, it is customary to provide some means for interrupting the flow of fuel to the main burner if the pilot burner is extinguished. In certain cases, this means for interrupting the fuel ow'has taken the form of an electrically operated control device which is energized by a thermo-couple exposed to the pilot burner llame. Such an arrangement has the advantage that it i s independent of any external power supply and permits the safe manual operation of the burner before electrical wiring has been installed in the house or during periods of power failure. It has been proposed to further extend this idea by using a thermopile instead of a thermo-couple so as to increase the current available and to then place various condition responsive switches in the connections between the thermopile and the control'device so as to provide a complete electrically operated control system independent of an external power supply and employing only one electrically operated control device. Such an arrangement, however, has the disadvantage that it is impossible to provide a thermopile small enough to be used with a conventional pilot burner which is still capable of generating a current adequate for such purposes. The condition responsive switches accordingly must have an extremely low contact resistance which cannot be maintained as they become worn out with'use. Furthermore, certain features desirable in a control system such as heat anticipation cannot be used in such an arrangement.

It is an object of the present invention to provide an electrically operated control system wherein only one electrically operated control device is employed and wherein two thermo-couples are employed for actuating this control device, a first of which is responsive to pilot'iiame conditions and the second of which is controlled in accordance with other controlling conditions.

It is a further object of the present invention to provide such a system wherein the second thermo-couple is heated by an external heater, the energization of which is controlled by a condition responsive switch.

A still further object of the present invention is to provide an arrangement wherein there are two thermocouples controlling the energization of a device biased -to one position wherein one thermo-couple is able to hold the device against the biasing means and wherein the second thermocouple under one set of conditions aids the rst thermo-couple to move the device against its bias and under other conditions opposes the first thermo-couple to release the device to its biased position.

A further object is to provide such an arrangement as set forth in the last object in which the second thermocouple is a thermo-couple having one junction capable of giving up and absorbing heat more readily than the other junction.

A still further obj ect is to provide a system such as is set forth in the last object in which both junctions of the second thermo-couple are heated by a heater, the energization of which is controlled by a condition responsive switch.

A further object is to provide a control system, as set forth in th'e above objects, which has means for manual operation in the event of failure of the source of power.

Other objects will be apparent in the following specification and claims when interpreted with reference to the accompanying drawing.

The single figure of the drawing is a diagrammatic view of my invention as used in combination with a gaseous fuel burner.

The drawing shows a main burner Ill which is located in a boiler, a warm air furnace, or some other conventional heating device (not shown). The burner I0 is supplied with gaseous fuel through a pipe Il. A mixing means indicated at I2 provides for mixing gaseous fuel and air to insure a mixture having proper combustion characteristics.

The fuel supply for the burner I0 is controlled by a valve generally indicated by the reference character I3. The valve comprises a lower portion I4 and an upper portion I5. The lower portion is provided with an inlet port I6, an outlet port Il, and a partition I8 which provides a port I9 upon which the valve disc 2B is adapted to seat. Secured between the upper and lower portions I4 and I5 is a flexible diaphragm 2l. Secured to the diaphragm 2I by means of the through bolt 22 is the valve disc 20 and the upper and lower plates 23 and 24, respectively, which support the center of the diaphragm 2| and the valve disc 20. A lock nut 25 is adapted to secure these members together. The through bolt 22 has an aperture 26 which allows gas to iiow from the lower chamber 21 to the upper chamber 28 formed by the diaphragm 2I.

Mounted upon the upper portion I5 of the valve I3 by means of the bolts 3| is a bonnet fclent value to pull the armature 51 toward the magnetic core 58. In the modification shown, the armature 51 is sloped so that the amature 51xnay be drawn into abutting engagement with the legs of the magnet core 58 and thus form a closed flux path. Therefore it is seen that it is necessary for the electromotive forces of the two thermo-couples 6| and 66 to be in the same direction and thus cooperate to pull the armature 51 into engagement with the magnet core 58.

As previously explained. when the heater 80 is rst energized, the junction 10 becomes the hot junction because the normally cold junction 1| is placed within the heat insulating block 12. However, after the heater 80 has .been energized for a predetermined, preferably short, period of time, the normally cold junction 1| will gradually approach the temperature of the normally hot junction 10. When the temperature ofthe normally cold junction 1| reaches the temperature of the normally hot junction 10, the thermocouple Will then cease to act as a generator of electromotive force and will merely serve as a conductor between the conductors 65 and 69 in the'circuitu of the thermo-couple 6|. Therefore it is seen that the thermo-couple 66 initially assists the thermo-couple 6| in pulling in the armature 51 but shortly thereafter ceases to generate any electromotive force. However, the thermo-couple 6| may be so chosen that the electromotive force generated will be great enough to hold the armature 51 in engagement with.the legs of the magnet core 58 once the armature has been moved to that position.

Therefore it is seen that this arrangement of thermo-couples provides a system whereby two thermo-couples cooperate to pull in an armature and one thermo-couple generates suiicient electromotive force to maintain the armature in that position once it has been brought to that position by the cooperation of the two thermo-couples and that .the second thermo-couple loses its characteristics as an electromotive force generator shortly thereafter.

It will be noted that when the contact |04 is closed and the heater 80 is energized, the second heater |06 which is located adjacent the bimetal is also energized. By energizing the second heater |06 adjacent the thermal responsive element 10| when that thermal responsive element is in position calling for heat, there will be a tendency to supply artificial heat as well as ambient heat to the bimetal. In other words, when the contact |04 is made and is calling for heat, the heater |06 adjacent the bimetal is energized and therefore will heat the bimetal |0| and thus tend to separate the blade |02 and the contact |04 lbefore such separation would occur solely by reason of a rise in ambient temperature. Therefore it will be seen that the result will be to shorten the time of the burner on" period and thus tend to compensate for the lag in the heating system in connection with the delivery of heat to the vicinity of thermostat |00.

When the thermostatic blade |02 moves away from the contact |04,the electrical circuit which supplies energy to the heater 80 will be opened. Prior to the opening of the contact |04, the heater 80 had been energized and had heated the Junctions of the thermo-couple 66 up to substantially the same value. However, when the .heater 80 is deenergized, there will be a tendency for the normally hot junction 10 and the nor- However, in cooling, theV normally cold junction 1| will cool oil at a substantially slower rate than the normally hot Junction and will serve now as a hot Junction rather than as a cold junction as it did when heating up in response to the heat generated by the heater 80. electromotive force now generated by the thermo-couple 66 will be in a direction opposite to the electromotive force which is generated by the thermo-couple 6|. When the reverse electromotive force generated by the insulated junction 1| reaches a value which is substantially equal and opposite to the electromotive force generated by the thermo-couple 6|, the total electromotive force applied to the field winding of the electromagnet will be negligible. Therefore the apper valve 55 will move toward the left Iby the action of the spring 54 to a position to close the bleed port 50.

In the event the pilot llamev issuing from the pilot. burner 4| is extinguished, a dangerous condition would result if the valve 20 were open to admit gas to the main burner I0. When the flame is extinguished, the thermo-couple 6| will be generating no electromotive force to energize the field winding 59. However, if thetemperature in the space falls, the thermostat |00 will close the contact |04 and thus energize the heater 8,0, and by energizing the heater will establish an electromotive force in the field winding 59 by the action of the thermo-couple 66. The thermo-couple 66 is adapted, on heating, to generate suicient electromotive force to actuate the apper valve 55. However, shortly after sufficient electromotive force has been generated to actuate the flapper valve, the normally cold junction 1| of the thermo-couple 66 will have heated up to substantially the same temperature as the normally hot junction 10 thus'causing the electromotive force to drop to a negligible value, therefore allowing the armature 51 to move away from the magnet core 58 and thus close the bleed port 50. It is seen that the apper valve will have actually been away from the port 50 for only a very short period of time. During this time an insuicient amount of gas will be allowed to escape through the bleed port 50 to allow the valve 20 to move awayA from its seatV I9 and, therefore, the valve 20 cannot open when the pilot flame is extinguished.

In the event of failure of power supply in the line conductors and 9|, it may be desired to actuate the valve I3 between open and closed positions. Therefore the valve opening push rod 44 is provided to move the apper valve 55 away from the bleed port 50 to open the valve 20, and the push rod 45 is provided to push the apper valve 55 into engagement with the bleed port 50 to close the valve 20. When the flapper valve 55 is pushed away from the bleed port 50 by the push rod 44, the armature 51 will engage the magnet core 58 and the pilot burner in cooperation with the thermo-couple 6| will generate enough electromotive force across the eld winding 59 to maintain the apper valve 55 away from the bleed port 50 until such time as it is` desired to close the valve which is accomplished by pushing the i'lapper vvalve 55 into engagement with the bleed port 50 by pressing the push rod 45.

It will be noted that the existence of a pilot llame is necessary to accomplish the manual operation of the valve 20 because it is essential that there be a flow of electric current through the iield winding 59 to maintain the fiapper valve 55 Therefore it is seen that the'v in a position away from the bleed port 50. Therefore, if the pilot ame issuing from. the pilot burner 4| is extinguished there will be no kelectromotive force'generated in the junction 63 of the thermo-couple 6|, and the fiapper valve 55 will be moved by the spring I to a position closing the bleed port y50. y

It isseen that I have provided a control system which is simple and economical of structure and Y fool-proofy in operation, that is applicable in controlling a condition and isresponsiveto a second condition which mayk modify control. Many forms and applications of thisinvention will octure into a position adjacent said electromagnet and the second Junction of said second thermocouple being adapted to oppose saidiirst thermoy couple sufficiently to allow said armature' to drop out of engagement with saidv electromagnet.

- 3. Inafiuid f-uel burner control system, a fluid fuel `burner,-ignition means adjacent said fuel e yburner radapted to thermally ignitey fuel issuing from said burner, fuelsupply means adapted to deliver fuel to said burner, control kmeans to prof vide a,burner on condition and a burner off cur to those skilledin the art, therefore it should f be clearly understood that I am not to be limited in my invention to the preferred form vshown and described but by ythe claims.

I claim as my invention: f y 1. In a control system, yan armature, an elec-r tromagnet cooperating with said armature, a first thermo-couple responsive to a thermal condition scope of the appendedr adjacent said electromagnet, a second thermocouple, an electric heater adapted to affect said second thermo-couple, an electric switch, a source of electric power controlled by said switch for supplying yelectric current rto said f heater, said second thermo-couple having a first junction capable ofr quickly absorbing and giving up heat and a second junction capable of only slowly absorbing and giving up heat, the first junction of y said second thermo-couple being adapted to cooperate with said first thermo-couple to pull said armature into a position adjacent said electromagnet and the second junction of said second thermo-couple being adapted to oppose said rst thermo-couple suiciently to allow said armature to drop out of engagement'with said electromagnet.

2. In a control system, an armature, an electromagnet cooperating with said armature, a first thermo-couple responsive to a thermal condition and controlling the energization of said electromagnet, said first thermocouple being capable of energizing said electromagnet in a value sufficient to hold said armature in a position adjacent said electromagnet when the condition exists but incapable of performing the same function when the condition is non-existent and incapable of independently pulling said armature into a position adjacent said electromagnet, a second thermo-couple, a firlt electric heater adapted -to affect said second thermo-couple, a thermostatic switch, a source of electric power controlled by said switch for supplying electric current to said heater, a second-electric heater adjacent said thermostatic switch and adapted to affect the same simultaneously said first heater is energized in a manner to substantially diminish the time that .said first heater will be energized, said second thermo-couple having a first junction capable of quickly absorbing and giving up heat and a second junction capable of only slowly absorbing and giving up heat, the first junction of said second thermo-couple being adapted to cooperate with said first thermo-couple to pull said armacondition, a first thermo-couple electrically connected to said control means and thermally responsive to the ignition means, a second thermocouplehaving afhot junction and a heat insulated cold junction electrically connected to` said first thermo-couple and said control means, the hot junction of said second thermo-couple being adapted to cooperate with said first thermocouple to place the control means in burner on condition and the `cold junction ofr said second thermo-couple being adapted to oppose said first thermo-couple vto place the control means in burner o "condition, a source of electric power,

an electric heater adjacent said second thermocouple 'and adapted to supplyvheat thereto, and

a thermostat controlling the electric circuit toy said heater. f

f y 4. In a fluid fuel burner control system, a fluid `rfuel burner, ignition means adjacent said fuel burner adapted to thermally ignite fuel issuing from said burner, fuel supply means adapted to e deliverfuel to said burner, control means to providea burner on condition and a burner off condition, a first thermo-couple electrically connected to said control means and thermally responsive to the ignition means, a second thermocouple having a hot junction and a heat insulated i cold junction, electrically connected to said first thermo-couple and said control means, the hot junction of saidv secondv thermo-couple being adapted to cooperate with said first thermocouple to place the control means in burner on condition and the cold junction of said second thermo-couple being adapted to oppose said first thermo-couple to place the control means in burner off condition, a source of electric power, an electric heater adjacent said second thermocouple and adapted to supply heat thereto, a thermostat controlling the electric circuit to said heater, and manual means to actuate said control means in the event of failure of the source of electric power.

5. In a fluid fuel burner control system, a uid fuel burner, a pilot burner adjacent said fuel burner, a valve controlling the supply of fuel to said fuel burner, valve actuating means adapted to open and close said valve, a first thermo-couple electrically connected to said valve actuating means and responsive to the existence of a pilot flame, said first thermo-couple being adapted to generate an electromotive force only when the pilot flame is burning and in a value only suflicient to maintain said valve actuating means in burner on position after said valve actuating means have been moved to that position and unassisted said first thermo-couple generates insuicient electromotive force to move said valve actuating means to burner on position, a second thermo-couple having a hot junction and a heat insulated cold junction electrically connected to said valve actuating means and said first thermo-couple, the hot junction of said second thermo-couple being adapted to cooperate cold junction of said second thermo-couple being adapted to oppose said first thermo-couple to allow said valve actuating means to move to burner olf position, a source of electric power, a rst electric heater, a thermostat being adapted to energize said rst heater when the temperature being controlled reaches a predetermined low value, a second heater adjacent said thermostat being adapted to supply heat to said thermostat when the circuit to said first heater is ener- -gized thus tending to open said circuit and shorten the burner 'on periods, and manual means to open and close said fuel supply valve in the event of failure of the source of electric power.

6. In a uid fuel burner control system, a fluid fuel burner, a pilot burner adjacent said fuel burner, a valve controlling the supply of fuel to said fuel burner, valve actuating means adapted to open and close said valve, electromagnetic means cooperable with said valve actuating means, a iirst thermo-couple electrically connected to said electromagnetic means and responsive to the existence of a pilot flame, said rst thermo-couple being adapted to generate an electromotive force only when the pilot flame is burning and in a value only sufiicient to maintain said valve actuating means in "burner on" position after said valve actuating means have been moved to that position and unassisted said rst Athermo-couple being capable of generating insufiicient electromotive force to move said valve actuating means to burner on position, a secondthermo-couple having a hot junction and a heat insulated cold junction electrically connected to said electromagnet and said first thermo-couple, the hot junction of said second thermo-couple being adapted to cooperate with said first thermo-couple to move said valve actuating means to burner on position and the cold junction of said second thermo-couple being adapted. to oppose said first thermo-couple to allow said valve actuating means to move to burner on' position, a source of electric power, a rst electric heater, a thermostat being adapted to energize said first heater when the temperature being controlled reaches a predetermined low value, a second heater adjacent said thermostat being adapted to supply heat to said thermostat when the circuit to said first heater is energized thus tending to open said circuit and shorten the burner on periods, and manual means to open and close said fuel supply valve in the event of failure of the source of electric power.

'7. In a fluid fuel burner control system, a iiuid fuel burner, a pilot burner adjacent said fuel,

burner, a valve controlling the supply of f uel to said fuel burner, a pressure motor adapted to open and close said valve, a bleed port controlling the action of said pressure motor, a apper valve cooperating with said bleed port, an electromagnet adapted to cooperate with said apper valve, a first thermo-couple electrically connected to said electromagnet and responsive to the existence of a pilot flame, said rst thermocouple being adapted to generate an electromotive force only when the pilot iiame is burning and in a value only suflicient to maintain said iiapper valve away from said bleed port after said `dapper valve has been moved to that position and said rst thermo-couple independently generating insuiilcient electromotive force to move said ila'pper valve' out of engagement-with said bleed port, a second thermo-couple having a hot junction and a heat insulated cold junction electrically connected to said electromagnet and said first thermo-couple, the hot junction of said second thermo-couple being adapted to cooperate with said first thermo-couple to moveV said napper valve away from said bleed port and the cold junction of said second thermo-couple being adaptedto oppose said nrst thermo-couple to allow said dapper valve to close said bleed port, a first electric heating element in heat transfer relationship to said second thermo-couple, a source of electric power, a thermostat being adapted to energize said first heater when the temperature being controlled reaches a predetermined low value, a second electric heater adjacent said thermostat which supplies heat to said thermostat when the circuit to said first heater is energized thus tending to open said circuit and shorten the burner on periods, and manual means to open and close said fuel supply valve in the event of failure of the source of electric power.

8. In a control system, an armature, an elec'- tromagnet cooperating with said armature, a first thermo-couple responsive to a thermal condition and controlling the energization o1 said electromagnet, said first thermocouple being capable of energizing said electromagnet sufliciently to hold said armature in a position adjacent said electromagnet when the condition exists but incapable of performing the same function when the condition is nonexistent and incapable of independently pulling said armature into a position adjacent said electromagnet, a second thermocouple, means for effecting a temperature differential between the junctions of said second thermocouple to produce an electromotive force of such direction and intensity that said second thermocouple will assist said first thermocouple in pulling said armature into engagement with said electromagnet, and further means to provide a reversall in direction of the electromotive force generated'by said second thermocouple whereby said second thermocouple will oppose said rst thermocouple to allow said armature to drop out of engagement with said electromagnet.

9.A In la control system, an armature, an electromagnet cooperating with said armature, aflrst thermocouple responsive to a thermal condition and controlling the energization of said electromagnet, said rst thermocouple .being capable of energizing said electromagnet sulciently to hold said armature in a position adjacent said electromagnet when the condition exists but incapable of performing the same function when the condition Vis nonexistent and incapable of independently pulling said armature into a position adjacent said electromagnet, a second thermocouple, means for effecting a. temperature differential between the junctions of said second thermocouple to produce an electromotive force. of such direction and intensity that said second thermocouple will assist said first thermocouple in -pulling said armature into engagement with said electromagnet, further means to provide a reversal in direction of the electromotive force generated by said second thermocouple whereby said second thermocouple will oppose said rst thermocouple to allow said armature to drop out of engagement with said electromagnet, and condition responsive means for controlling said temperature differential effecting means.

10. In -a control system, an armature, an-elecmagnet. said rst thermocouple being capable ofV energizing said electromagnet sufilciently to hold said amature in a position adjacent said electromagnet when the condition exists but incapable of performing the same function when the condition is nonexistent and incapable of independently pulling said armature into a position adjacent said electromagnet, a second thermocouple, means for eiecting a temperature diierential between .and means associated with said condition responsive means for modifying the controlling operation thereof.

11. In combination with a plural position electrically actuated device, a ilrst thermo-electric current generating means responsive to a condition to produce an electromotive force sufficient to maintain said device in one position but insufficient to move it from one to another position, a second thermo-electric current generating means responsive to a controlled condition to produce a selectively reversible electromotive force, and connecting means between said generating means and said device whereby said two generators cooperate to produce an electromotive force to move said device to one position wherein it maintained by said first generating means and said second generating means will oppose said rst generating meansto produce a counterelectromotive force to cause said device to move to another position.

12. In combination, an armature, an electromagnet cooperating with said armature, a rst thermocouple, a second thermocouple, means associated with said second thermocouple to create a temperature diierential between the junctions thereof to cause said second thermocouple to generate an electromotive force in a direction and of such intensity that said second thermocouple will assist said iirst thermocouple to pull said armature into engagement with said electromagnet, and further means to change the direction of the electromotive force generated by said second thermocouple to cause said force to effectively oppose the electromotive force generated by said rst thermocouple to allow said armature to drop out oi' engagement with said electromagnet.

13. In combination, an armature, an electromagnet cooperating with said armature, a iirst thermocouple, a second thermocouple, means associated with said second thermocouple to create a temperature differential between the junctions amature into engagement with said electromagnet, further means to change the direction of the electromotive force generated by said second thermocouple to cause said force to eiiecf tively oppose the electromotive force generated by said first thermocouple to allow said armature to drop out of engagement with said electromagnet, and condition responsive means for controlling the operation of said last means.

14. In combination, an armature, an electromagnet cooperating with said armature, a nrst thermocouple, a second thermocouple, means associated with said second thermocouple to create a temperature diiierential between the junctions thereof to cause said second thermocouple to generate an electromotive force in a direction and of such intensity that said second thermocouple will assist said first thermocouple to pullv said armature into engagement with said electromagnet, further means to change the direction of the electromotive force generated by said second thermocouple to cause said force to eiiectively oppose the electromotive force generated by said ilrst thermocouple to allow said armature to drop out of engagement with said electromagnet, condition responsive means for controlling the operation of said last means, and means associated with said condition responsive means for modifying the controlling operation` thereof.

15. In combination, an electrically actuated device movable between rst and second positions, a member controlled by said device, a nrst thermocouple responsive to a condition that is substantially constant when present, said first thermocouple being operable to produce a substantially constant electromotive force in one direction,` a second thermocouple responsive to a controlled condition, said second thermocouple being operable to produce a reversible electromotive force substantially equal in either direction to the electromotive force produced by said first thermocouple, and connecting means between said thermocouples and said device whereby said two thermocouples cooperate in producing an electromotive force suiilcient to move said device to said rst position and oppose each other in producing electromotive force'to move said device to said second position.

16. In combination with a two position electrically actuated device, a iirst electromotive force generator responsive to a condition to produce a substantially constant electromotive force in one direction sumcient to maintain said device in one position but insufcient to move it from one to the other position, a second electromotive force generator responsive to a controlled condithereot to cause said second thermocouple to '35:

generate an electromotive force in a direction and of such intensity thatsaid second thermocouple will assist said rst thermocouple to pull said tion to produce a selectively reversible electromotive force, and connecting means between said generators and said device whereby said two generators cooperate to produce an electromotive force to move said device to one position wherein it is maintained by said iirst generator and said second generatorwill oppose said iirst generator to produce a counter-electromotive force to cause said device to move to its other position.

FREDERICK E. LANGE.

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