US2537295A - Component checking circuit for burner control apparatus - Google Patents

Description

Jan. 9, 1951 W. H. GILLE COMPONENT CHECKING CIRCUIT FOR BURNER CONTROL APPARATUS. Filed Aug. 9. 1948 INVENTOR. WILL/5 G/LLE' Patented Jan. 9, 1951 COMPONENT CHECKING CIRCUIT FOR BURNER CONTROL APPARATUS Willis H. Gille, St.'l aul, Minn., assignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application August 9, 1948, Serial N 0. 43,247

The present invention is concerned with a fuel burner control apparatus and more particularly with that type of apparatus which will be rendered inoperative in the event that the flame fails in the burner or there is a false indication of flame by the flame detection apparatus.

In present day fuel burner controls, especially those utilizing electronic types of flame detection devices, it has been found that certain faults may occur which will result in the flame detection relay remaining energized even though the burner is no longer operative. To protect against this situation it is necessary to cause the control apparatus to be rendered inoperative in the event that there is a flame failure or a false indication of flame and this may be accomplished by energizing a safety cutoff device whenever either of these undersirable conditionsexist.

It is therefore an object of the present invention to provide an improved burner contol apparatus which will be rendered operative in the event of flame failure or upon a false indication of flame by the flame detection device.

Another object of the present invention is to provide an improved burner control apparatus which has a pair of transformer secondary windings for energizing a main control relay and which is maintained energized by one of the secondary windings through a circuit that includes a safety cutofi device until a flame detection relay is cperated when the cutoff device becomes shunted and when the flame detection relay opcrates falsely the safety cutolf device is connected in an energizing circuit with the other secondary winding.

These and other objects of the present invention will be understood from a consideration of the specification, claims and the single figure of the drawing attached hereto.

The figure is a diagrammatic illustration of the control.

Referring to the single figure, the numeral l represents a fuel burner of any desired type. For indicating when it is desired to render the burner l0 operative, a thermostatic device II is provided which when actuated is efiective to cause energization of the controls located in the housing l2 which in turn will cause energization of the burner Ill as long as there is indication-for the need for operation of the burner by the thermostatic device H.

-The thermostatic device ll may be seen to consist of a temperature sensing bimetal which is operative to move a pair of switch blades i7 and I8 into and out of engagement with a 5 Claims. (Cl. 15828) pair of associated switch contacts i9 and 26, respectively. These. switch blades are adjusted so that they engage sequentially with blade l8 engaging contact 20 before blade 11 engages contact i9. The reasons for this will be explained in the operation portion of the specification. This thermostatic device may be located at any desired place wherein it is desired to maintain a certain temperature by means of the heat supplied by the burner l0.

Located within the housin I2 are the controls of the subject invention and supplying power to these controls is a transformer 22 which has a primary winding 23 which is connected to any suitable source of power and a pair of secondary windings 24 and 25. A burner control relay is indicated by the numeral 21 and may be seen to consist of a relay winding 28 which is operative to move switch blades 29, 30 and 3| from their deenergized position, where they are biased by means not shown, into engagement with their associated switch contacts 32, 33 and 34 respectively.

The numeral 35 represents the flame detection relay portion of the subject apparatus and may be of the type disclosed in the copending application of John M. Wilson, Serial No. 465,476, filed November 13, 1942 for Control Device, now Patent No. 2,448,503, granted August 31, 1948. Associated with this flame detection relay is a photocell 36 which is used to detect the presence of flame emitting from the burner l0 and which is effective to cause the controls located within the boxed-in portion 31 to energize a relay winding 38. This relay winding 38, upon becoming energized, causes a switch blade '39 to be moved from engagement with a switch contact 4!, where it is biased by means not shown, into engagement with an associated switch contact 40. The numerals 42 and 43 indicate input power lines to the circuits which effect operation of the relay winding 38.

A safety cutoff device 45 is provided for rendering the apparatus inoperative whenever this cutoff device has been energized for a predetermined length of time.' To accomplish this type of cutout, a safety heater 46 is provided and is located so as to apply heat to a bimetal 41. The bimetal 41 is, when not energized by the heater 46, adapted to hold switch contacts 48 and 49 in the engagedposition so that an electrical circuit will be completed through the contacts. If the heater 46 has been energized for a predetermined length of time the bimetal 41 will be heated and will warp toward the right from under the contacts 48 and 49 and the contacts will separate. A reset actuator 59 is provided for putting the safety cutoff device back in operation after the bimetal has been Warped from under the contacts 4B and 49. This actuator is of the type that prevents the contacts 48 and 49 from reengagin until such time as the actuator is released and the contacts 48 and 49 rest upon thebimetal 41. A current limiting resistor is indicated at 52 and is effective to prevent short circuiting of the secondary winding 25 whenever the burner control relay 2! becomes energized.

Operation The apparatus as shown in the'drawing is in the deenergized position and when in this position the thermostatic device II isnot calling for operation of the burner I so that the burner control relay is deenergized and the flame detection relay is also deenergized. In the event that the space wherein the thermostatic device II is located begins to cool, the change in temperature of the bimetal I5 will cause the switch blades I1 and I8 to be moved into engagement with their associated contacts I9 and 26 respectively. The switch blade I9 will actually engage the switch contact 29 before the blade I! engages contacts I9 as it is desired to prevent the closing of the thermostatic device from "causng any'chattering of the burner control relay when it becomes energized for, as will be seen from the circuit to be traced hereinafter, as soon as the blade I! engages contact I9 and the burnercontrol relay becomes energized, a holding circuit for .maintaining the relay energized is established that is .separate'from this blade I! and contact I9, this holding circuit being effective to prevent deenergizationof the reayuntilthe temperature has risen enough to cause separation of blade I8 from contact 26. When the blades I1 and I8 are engaging their contacts I9 and 26, an energizing circuit for the burner control relay 2'! may be traced from the upper terminaL of the .secondary 24 through conductor 55, relay winding 28, conductor 56, switch contact 26, switch blade I8, switch blade I'Lswitch contact I9, conductor 51, switch contact 4I, switch blade 39, conductor 58, resistor 52,=conductor 59, secondary 25, conductor 66, heater '46, switch contacts 49 and 48 and conductor 6| back to the lower terminal of the secondary "24. As soon as the burner control relay 2"! becomes energized, the switch blades 29, 36 and 3| will move into engagement with their associated switch contacts .32, 33 and 34 respectively. When the switch blades 29 and 36 engage with'contacts 32 and 33 respectively, a new ma ntaining circuit is estabished for the burner control relay. This maintaining circuit may be traced from the upper terminal of the secondary 24 through conductor 55, relay winding 28, conductor 56, switch contact 26, switch blade I8, bimetal I5, conductor 62, switch contact .33, switch blades 36 and 29, switch contact 32, conductor 63, heater 46, switch contacts 49 and .48, and conductor 61 to the lower terminal of the secondary 24. It will be noted that, with switch blade 29 engaging contact 32, a shunt has been placed around the transformer secondary and this shunt circuit may be traced :from the upper terminal of the transformer 25 through conductor -66, conductor 63, switch contact 32, switch blade 29, conductor 64, resistor 52 and conductor 59 back to the lower terminal of the secondary 25.

When the switch blade 3i engages switch c0ntact 34 an energizing circuit is completed to the burner I6 and this energizing circuit may be traced from the input power line 66 through conductor 61, switch contact 34, switch blade 3I, conductor 66, burner I6, and conductor 69 back to the other input power line ID. with the burner I6 energized, there should be a flame emitting from the burner and this flame will be detected by the photocell 36 which in turn will cause en- :ergization of the relay winding 38. With the relay winding 38 energized, the switch blade 39 will move into engagement with switch contact 46 and this will form a new maintaining circuit for the burner control relay 2! which will be independent of the heater 46 of the safety cutout device 45. This second maintainng circuit may be traced from the upper terminal of the transformer 24 through conductor 55, relay winding 28, conductor 56, switch contact 26, switch blade I8, bimetal I5, conductor 62, switch contact 33, switch blade 39, conductor 64, conductor 58, Switchblade 39, switch contact 46, conductor II, switch contact 49 and 48, and conductor 6| to the lower terminal of the secondary 24. This :last traced circuit will be seen to effectively shunt out the heater for the safety cutout device 45 and this shunt circuit may be traced from the upper \terminal of the heater 46 through conductor ll, switch contact 46, switch blade 39, conductors 58 and 64, switch blade 29, switch contact 32 and conductor 63 to the other terminal of the heater :46.

The apparatus is now in the operating condi tion with the burner I6 energized and both the relays 21 and 35 energized and while so energized the safety cutout device 45 will be effectively deenergized. The apparatus will remain in this position until such time as the heat from the burner I6 has been felt by the bimetal I5 and the temperature of the bimetal begins to rise. With the rising temperature of the b metal, the switch blades ll and I8 will be moved out of engagement with their associated contacts I9 and 26 so that the energizing circuit for the burner control relay 2! Will be broken and this relay will become deenergized. When the relay becomes deenergized the switch blade 3 I, in moving out of engagement with its associated contact 34, will break the energizing circuit to the burner I6 and the burner will no longer be 0perative to supply flame for heating purposes. With burner I6 no longer operative the photocell 36 will not indicate the presence of a flame and the flame detector circuits, located in the box 31, will result in the deenergizaton of the relay winding 38 so that the switch b ade 39 will move out of engagement with switch contact 46 and into engagement with switch contact 4|. With both the flame detection relay 35 and the burner control relay 2'! deenergized, the apparatus Will be in the condition in which it is shown on the drawing and will be ready for another operating'cycle.

Operation upon flame failure Assume now that the apparatus is in its oper ating condition with the thermostatic device II calling for operation of the burner I6 and both the burner control relay 2! and the flame detection relay 35 being in the normal operating or energized position. In the event that the flame from the burner I9 should become extinguished for some reason or other, the photocell 36 will no longer indicate flame and this will result i the adeenergization of the relay winding 38.

When the winding 38 becomes'deenergized;'the 'switch blade 39 moves out of engagement With switch contact 40 and into engagement with switch contact 4|. With the opening of the electrical circuit between the switch blade 39 and switch contact 40, the shunt about the heater 46 is removed and a circuit'may be traced through this heater from theupper terminal of the secondary 24 through conductor 55, relay winding 28, conductor 56, switch contact 211; switch blade [8, bimetal l5, conductor 62, switch contact 33, switch blade 36, switch blade 29, switch contact 32, conductor 63, heater 45, conductors 49 and 48, and conductor 6| to the lower terminal of the secondary 24. If this circuit through the heater 45 is maintained for a predetermined length of time, the heat from the heater will cause the bimetal 41 to warp toward the right so that there will be a separation of the switch contacts 48 and 4&7. When switch contacts 48 and 49 separate, the maintaining circuit for the burner conv trol relay 2'! will be broken and it will be impossible for the relay to remain in the energized position.

When the relay becomes deenergized the switch blade 3! moves out of engagement with its associated switch contact 34 to open the energizing circuit to the burner motor Ill. The burner H'I will remain deenergized until an electrical circuit is completed through switch contacts 48 and 49 in the energizing circuit of the burner control relay 21. It will be noted that with the separation of switch contacts 48 and 149 the energizing circuit for the heater 4$, traced above, is open so that the heater will become deenergized and will no longer supply heat to the bimetal 4'!. With the cooling of the bimetal 41, the bimetal will move toward the left. Upon depressing the actuator 53, to raise the contacts to permit the bimetal to move under the contacts, and the subsequent release of the actuator 59, there will be a reestablishing of an electrical circuit through the contacts 48 and 49, as they reengage.

With contacts 48 and 49 engaging again, an energizing circuit for the control relay willbe completed and this circuit will correspondto the circuit originally traced during the discussion above on the starting of the apparatus. In the event that the reenergization of the burner control relay 2'! does not result in the burner I9 producing a flame, the apparatus will become shut- .down in the same manner as explained above because of the fact that the heater 45 will have an energizing current flowing therethrough and .thebimetal will warp toward the right and'cause .the opening of the contacts 48 and 49.

From this it will be seen that the apparatus will be rendered inoperative either when there is a flame failureduring normal operation or when there is a failure of combustion when the apparatus is brought into operation.

Operation upon false indication of flame Assume now that the apparatus has been operating properlyand the thermostatic device it no longer indicates a need for operation of the burner ill. When the bimetal I5 moves the switch blade [8 out of engagement with switch contact 29, the energizing circuit for the burner control relay 2l' will be broken and the relay will become deenergized so that the burner It will have its operating circuit interrupted. If for any reason the flame detection relay 35 remains energized, so that the winding 38 is maintaining switch blade 39 in engagement with switch con- '6 'tact 40 so-as to give a falseindication of flame, it is desired that the apparatus be-renderedv inoperative to prevent a further operation of the control apparatus until the fault causing false operation of the relay 35 has been removed.

To accomplish shutdown of theapparatus under these conditions it is desired to complete an electrical energizing circuit through the heater '46 and this circuit may be traced from the upper terminal of the secondary section 25 through conductor 6G, heater 4S, conductor ll, switch contact 40, switch blade 39, conductor 58, resistor .52, and conductor 59 back to the lower terminal of the secondary 25. Upon continued energization of this heater 46; the bimetal 4'! will be warped toward the right and the switch contacts 48 and 49 will open circuit in the manner explained above. The open circuiting of the switch contacts 48 and 49 will prevent the completion of an energizing circuit through the burner control relay 2? in the event that the thermostatic device I I should call for subsequent operation of the burner Hi. It will be noted that the energizing circuit for the heater 4% was traced independently of the contacts as and 4S and this will mean that the heater 4t will be continually applying heat to the bimetal 47 to maintain it in its warped position. Subsequent depressing of the actuator iii] will not result in the fclosing of the contacts 48 and as for the bimetal 41 will not be in a position to permit the contacts to close when the actuator Si! is released. From this it will be seen that the contacts 48 and '49 will remain separated until the fault is cleared from the flame detection relay circuit so that the switch blade 39 will move into engagement with contact ll.

When the fault is removed from the flame detection relay, so that the switch blade moves out of engagement with switch contact 40, the energizing circuit for the heater 46 will be broken. The bimetal 41 will then cool and move back toward the left so that it will be possible to re engage the contacts 48 and 49 upon the subsequent depressing and release of the actuator '50.

From the foregoing it will be seen that I have provided a burner control apparatus which is effective to maintain an associated burner inoperative in the event there is a false indication of flame or there is a flame failure. It may further be seen that this has been accomplished by employing a pair of secondary windings with a safety cutout device and a heater therefor connected between the windings in such a manner that the relays of the control apparatus will connect the heater in an energizing circuit with one of the secondaries upon a flame failure and with the other or" the secondaries upon a false indi cation of flame. While I have disclosed one particular embodiment of my invention, it will be obvious to those skilled in the art that the control may be accomplished in many ways within the scope of the invention and I therefore intend to be limited solely by the scope of the appended claims.

x p I claim as my invention:

' l. A burner control apparatus comprising in combination; a source of power comprising two transformer secondary windings; a first relay :adapted when energized to cause energization of the burner; a resistor; a safety cutout device comprising an actuator and switch "contacts operable when said actuator is energized a predetermined length of time to render said first relay inoperative; condition responsive means for indicating the need for operation of the burner; means including said condition responsive means for connecting said first relay in an energizing circuit which includes said two secondary windings, said resistor, said cutout device actuator and said condition responsive means; means including a switch contact of said first relay when energized for connecting said first relay in a maintaining circuit which includes one of said secondary windings, said condition responsive means and said cutout device actuator; a second relay adapted to be energized upon proper operation of the burner; means including switch contacts controlled by said second relay when energized for deenergizing said actuator and for connecting said first relay in a second maintaining circuit, said second maintaining circuit including said one of said secondary windings, said condition responsive means and switch contacts of said second relay; and means connecting said actuator of said cutout device in an energizing circuit upon said second relay remaining in energized position when said first relay becomes deenergized, said means including the other of said secondary windings, switch contacts of said second relay and said resistor.

2. A burner control apparatus comprising in combination; a source of power comprising two transformer secondary windings; a first relay adapted when energized to cause energization of the burner; a resistor; a safety cutout device com-:- prising a heater and switch contacts operable when said heater is energized a predetermined length of time to render said first relay inoperative; condition responsive means for indicating the need for operation of the burner; means including said condition responsive means for connecting said first relay in an energizing circuit which includes said two secondary windings, said resistor, said cutout device heater and said condition responsive means; means including a switch contact of said first relay when in a contacting position for connecting said first relay in a maintaining circuit which includes one of said secondary windings, said condition responsive means and said cutout device heater; a second relay adapted to be energized upon proper operation of the burner; means including contacts actuated by said first and second relays when in a contacting position for connecting a short circuiting shunt around said heater of said cutout device so that said first relay is maintained in an energizing circuit independently of said heater of said cutout device; and means connecting said heater of said cutout device in an energizing circuit upon said first relay becoming deenergized and said second relay remaining in energized position falsely indicating proper burner operation, said means including the other of said secondary windings, switch contacts of said second relay and said resistor.

3. A burner control apparatus comprising in combination; a source of power comprising two transformer secondary windings; a first relay having a plurality of switch contacts and adapted when energized to cause energization of the burner; a resistor; a safety cutout device comprising an actuator and switch contacts operable when said actuator is energized a predetermined length of time to render said first relay inoperative; condition responsive means for indicating the need for operation of the burner; means including said condition responsive means for connecting said first relay in an energizing circuit which includes said two secondary windings, said resistor, said cutout device actuator and said condition responsive means; means including switch contacts of said first relay when in a contacting position for connecting a shunt across one of said secondary windings so that said relay is maintained energized by the other of said secondary windings in a maintaining circuit, said maintaining circuit including said cutout device actuator; a second relay having a plurality of switch contacts adapted to be energized upon proper operation of the burner; means including contacts controlled by said second relay when in a contacting position for connecting said first relay in a second maintaining circuit and for deenergizing said actuator, said second maintaining circuit including said other of said secondary windings, said condition responsive means and switch contacts of said second relay; and means connecting said actuator of said cutout device in an energizing circuit upon said second relay remaining in energized position when said first relay becomes 'deenergized, said means including said one of said secondary windings, switch contacts of said second relay and said resistor.

4. A burner control apparatus comprising in combination; a source of power comprising first and second transformer secondary windings; a first relay adapted when energized to cause energization of the burner; resistor; a safety cutout device comprising an actuator and switch contacts operable when said actuator is energized a predetermined length of time to render said first relay inoperative; condition responsive means for indicating the need for operation of the burner; means including said condition responsive means for connecting said first relay in an energizing circuit which includes said first and second transformer windings, said resistor, said cutout device actuator and said condition responsive means; means including switch contacts of said first relay when in a contacting position for connecting a shunt across said first transformer winding so that said relay is maintained energized in a first maintaining circuit by said second transformer winding, said maintaining circuit including said cutout device actuator; a, second relay adapted to be energized upon proper operation of the burner; means including switch contacts controlled by said first and second relays when in a contacting position for connecting a short circuiting shunt around said actuator of said cutout device so that said first relay is maintained in an energizing circuit independently of said actuator; and means connecting said actuator in an energizing circuit upon said first relay becoming deenergized and said second relay remaining in energized position falsely indicating proper operation of the burner, said means including said first transformer winding, switch contacts of said second relay and said resistor.

5. Apparatus for controlling a fuel burner, comprising in combination: a source of power comprising two secondary windings; first relay means having switch means for initiating burner operation; an energizing circuit for said first relay comprising said two secondary windings, a resistor, a safety cutout device having a, heater and a pair of switch contacts, and a circuit adapted to be completed by means indicative of the need for burner operation, said switch contacts being connected in controlling relation to said apparatus such that said apparatus is rendered inoperative upon operation of said safety cutout device; a first holding circuit for said relay 9 closed by the energization thereof, said holding circuit by-passing said resistor and one of said secondary winding; a second relay means having switch means which are actuated upon a flame appearing at the controlled burner; means including said second relay switch means for establishing a second holding circuit for said first relay which is independent of said heater, said resistor and said one of said secondary windings and for deenergizing said heater; and means including said second relay switch means when in energized position, with said first relay deenergized, for connecting said heater in a closed circuit with said resistor and said one secondary winding.

' WILLIS H. GILLE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 10 Number Name Date 2,102,618 Francis Dec. 21, 1937 2,254,984 Tate Sept. 2, 1941

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