US2398008A

US2398008A - Burner control mechanism

Info

Publication number: US2398008A
Application number: US480673A
Authority: US
Inventors: Siegfried G Isserstedt
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1943-03-26
Filing date: 1943-03-26
Publication date: 1946-04-09
Anticipated expiration: 1963-04-09

Description

April '9, 1946: s. G. ISSERSTEDT 2,393,008

BURNER CONTROL MECHANISM Filed .March 26, 1945 attorney I Patented 9,

. zseaoos PATENT? orrlCB I mm 'con'rnor'. measures! 7 Weir-midi, Toronto, Ontario, Canada,

a n-lgnor macaroni-Honeywell UNI-ran Regulator to. GompanLmnnegpolilJflnn-Jesrpontionof Delaware Application m es. 194:. Serial No. am;

DCla-imI- -(Cl.158--28') The present invention is concerned with burner control mechanism and more particular y 'w mechanism oi the type designed to detect the Proper operation of the burner ignition means ignition means employing a single temperature responsive element to detect both the pr p r operation of the ignition means and also the eslo tive to stop operation of the timer first if ignition has not been successfully established and finally if combustion is not established.

A still further object of the invention is to provide a burner control mechanism of the type set forth in the previous object in which the temperature responsive element is a. thermocouple hot junction subjected to the heat produced by the ignition means and also to that 5 I produced by the burner flame.

A still further object of the invention is to provide such a burner control'me'chanism in which the thermocouple controls the energize-tion of one 1 winding of a relay, this winding being capable of holding the relay incapableof moving it to its energized position. A further object of the invention is to provide a burner control mechanism in which provision is made for determining whether ignition has been successfully established and in recycling if I it has not, with means for rendering a safety controller efiective to 'stopoperation oi the mechanism after a plurality of such unsuccessful attempts have been made.

Other objects of the invention will be apparent from a consideration oi! the appended specification, claims and drawing of which the single figure is a schematic illustration of my burner control mechanism embodied in a burner control,

Referring specifically to the drawing, an oil 7 burneris designated by the reference numeral It. This oil burner is of a conventional design comprising an'oil burner motor llhaving motor terminals I2 and IS. The motor H operates in the conventional manner to operate a blower to force an atomized mixture ofiuel and air-through a burner nozzle ll. Associated'with the oil burary winding of this ignition transformer is connected through .conductors l1 and il to a pair of ignition electrodes II and II. These ignition electrodes II and II are eitective'when the-ignition transformerll atomized fuel mixture issulng irom'nozle II.

The operation of the burner is controlled by a main control switch which isfillustratively shown in the form of a room thermostat 25. This thermostat comprises a bi-metallic element 20 to which is secured a pair of yieldable contact blades 21 and 20, adapted sequentially to engage a pair of fixed contacts}! and 3|, respectively. Contact blade 21 and contact 20 are less widely spaced from each other than are contact blade 28 and contact II. Thus upon contact blades 21 and 28. being moved to the leit as occurs upon a reduction in the temperature to which bi-metallic element 26 is exposed. contact blade 21 engages with contact 19 before contact blade 28 engages with relays ll and I. The relay I l comprises a relay winding 42 and switch blades 43, I4, and I5 actuated thereby. The switch blades 43, M, and 45 are adapted to engage fixed contacts 46,11, and u. The switch blades 43 to ll and the contacts 48 to A8 are biased apart by any suitable means (not shown). 'Upon energization oi relay winding 42, the switch blades 43 to 45 are movedinto engagement with contacts 46 to II.

The relay ll comprises two windings I0 and I and a, pair of switch blades 2 and 58. The switch blades 52 and 53 are adapted to cooperate with fixed contacts 54 and 55.. An armature it is associated with relay winding BI and an-armature burner nozzle it in such a position that the hot ner is an ignitiomtransi'ormer II. The secondas junction is aiiected by the heat or the burner is energized'to ignite theflame as wellas by the heat of the spark existing between electrodes 18 and, 28 when the ignition means is operating properly. Thearmature 51 is of a material having a high permeability and the winding II as well as the

conductors

88 and 88 are of extreme y low resistance so as to utilize as fully as possible the electromotive force generated by thermocouple 8!. Because of this, the winding 8! and armature 8'! are capable of holding

switch blades

82 and 88 in engagement with contacts 54 and 88 after' they have beenmoved into such engagement by the previous uperation of coil 88 and armature 88. It is to be understood, however, that coil II and armature 81 are incapable of moving the

switch blades

82 and 88 into engagement with contacts 84 and 85 but are merely capable of holding them insuch engagement after they have been moved. While the winding 8i and the armature 81-have been shown as a solenoid winding and core in 'orderto simplify the illustration, it is to be understood in a double helix bi-metallic element of the type disclosed in Parsons Patent 2,121,259, dated June 21,

1938. Such an element consists of a bi-metallic element wound in a form of a helix about a helical axis. Such an element, because of the large amount of bi-metal and its particular disposition, operates when heated to move in a straight line and to exert a substantial force in so moving.

Furthermore, because of the length of the element, its resistance is appreciable so that it is capable of being heated by the passage of current therethrough. ,As a result, no external heater is necessary. The element 84 is connected toa pair of

switchblades

85 and 88 and a pair of switch actuating arms 88 and 18. The

switch blades

85 and 88 cooperate with

contacts

81 and 88, respectively. Switch blade 85 is biased into engagement with contact 81 while switch blade 88 is biased out of engagement with contact 88. Upon the element 84 65 is moved out of engagement with contact 81 and later switch blade 88 is moved into engagement with contact 88. Switch actuating arms 88 and 18 are designed to cooperate with snap switches 12 and 13. Snap switches 12 and 13 each comprise a switch blade adapted to move with a snap actuation out of engagement with one contact and into engagement with another contact or a fixed stop. ,The snap switch 12 comprises a switch arm 14 normally in engagement with a contact 15 and adapted to move into engagement with a contact 18. Associated with the arm is snap action mechanism (not shown) and a button 18. Upon the button 18 being pushed inwardly, the arm 14 is moved with a snap action out of engagement with contact 15 and into engagement with contact 18. The snap switch 13 comprises a switch blade "which is normally in engagement with contact 8| and a switch actuating button 82 which upon being pressed inwardly causes the switch blade 88 to be moved being heated so that the right I hand end thereof moves to the left, switch blade with a snap action out of engagement contact 8i and into'engagement with a stop 83.

Thetwo snap switches 18 and 13 may take any conventional form, one desirable form being that in the patent to Albert E. Baal: No.

2,318,734 dated my I1, 1943.

The

switch blades

88 and 88 and the switch actuating arms 88 and 18 are so spaced with respect -to the associated contacts and the switch actusiting buttons 18 and 82, that upon the element 84 being heated, snap blade 85 is first-moved out of engagement with contact 8!, switch actuating arm 88 is next moved into engagement with switch actuating button 18 to move switch blade 14 .out of engagement with contact 15 and into engagement with contact 18, switch actuating arm 1|! isnext moved "into engagementgwith ly switch blade 88 contact 68.

The numerals I, 2, 3, and 4, enclosed 'in circles V have-been applied to the 'drawingto indicate the order in which the various switch switch actuating arms are'actuated.

A thermal safety switch is designated by the reference numeral 88. This comprises a pair of

switch blades

88 and 81 which are biased apart but are held in engagement by a bi-metallic element 88. Associated with the bi-metallic element 88 is an electric heater 88. The bi-metallic element 88 is so arranged that upon being heated by the heater 88, it warps to the left so as to tend to move out of engagement with switch blade 81. If the heating continues until bi-metallic element 88 moves out of engagement with switchblade 81, switch blade 81 moves away from switch blade 88 and it is necessary manually to reclose the switch blades. v

' Operation The various elements are shown in-the position that they assume when which the thermostat 25 is responsive is at or above the desired value so that there is no demand for burner operation. Now let it be assumed that this temperature drops so as to cause the sequential engagement of contact blades 21 and 28 with contacts 28 and 38. No energizing circuit is established until both contact blades 21 and 28 have engaged with contacts 28 and 80. When this happens, an energizing circuit is established to relay winding 42 as follows: from the right-hand terminal, of secondary 33 through conductor 82, contact 28, contact blades 21 and 28, contact 38, conductors 83 and 84, contact 81, switch blade 85, conductor 88, heater 88, conductor 88,

switch blades

81 and 88, conductor 81, relay winding 42, and conductor 88-to the other terminal of secondary 33; The establishment of this energizing circuit to relay coil 42 causes switch

blades

43, 44, and 45 to be moved into engagement with

contacts

48, 41, and 48.

The engagement of switch blade 44 .with contact 41 establishes a holding circuit for relay winding 42 as follows: from the right hand terminal of relay winding 33 through conductor 82. contact 28, contact arm 21,"bi-metallic element 26, conductor 99, switch blade 44, contact 41, conductor 84, contact 81, switch blade 85, conductor 85, heater '88, conductor 88,

switch blades

81 and 88, conductor 81, relay winding 42 and conductor 88 to the otherterminal of secondary 33. It is noted that the new circuit is independent of contact blade 28'and contact 80. Thus,

blades and the temperature to,

as the temperature rises, the apparatus is not placed out of operation until the temperature has risen suiiiciently to cause separation'of contact blade 21 from contact 29. This insures against chattering of the relay due to any rapid fluctuation in temperature or vibration of the thermostat.

The movement of switch blade 45 into engagement with contact 46 causes. the following energizing circuit to be established to relay winding 50: from line wire 31 through conductor IOI, contact 46, switch blade 46, conductors I02, I03, and I04, switch blade 14, contact 15, conductor I05, relay winding 50, and conductors I06, I01, I06, and I 09 back to the other line wire 36. The energization of relay winding 50 causes switch blades 52 and 53 to be moved into engagement with contacts 54 and 55. The engagement of switch blade 52 with contact 54 establishes a new holding circuit to relay coil 42 as follows: from the right hand terminal of secondary 33 through conductor 92, contact 29, contact blade 21, bi-metallic element 26, conductor 99, switch blade 44, contact 41, conductor III, switch blade 43, contact 46, conductor 2, switch blade 52, contact 54, conductors I I3 and 95, heater 69, conductor 96,

switch blades

61 and 66, conductor 91, relay winding 42, and conductor 96 to the other terminal of secondary 33. It will be noted that the new circuit is independent of switch blade 65 and contact 61 of timing switch 63. The original energizing circuits included this switch 65 and con-. tact 61 so that it was necessary for timer 63 to be in its cold position before the system could be placed into operation. It is desirable, however, after this first check has been made to cause energization of the relay 40 to be independent of the time switch so that it will not be deenergized when the time switch begins to move the various switches associated with it upon being heated.

The movement of switch blade 45 into engagement with contact 46 also establishes the following energizing circuit to the primary of the ignition transformer I6: from line wire 31 through conductor IOI, contact 46, switch blade 45, conductors I02 and 5, contact 6|, switch blade 60; conductor 6, ignition transformer I6, and conductors H1 and I09 to the other line wire 36. The establishment of this energizing circuit results in a spark being produced across the electrodes I9 and 20 if the ignition means is functioning properly. If this spark is established, the spark begins to heat up the hot junction of. ther-- mocouple 6 I.

The engagement of blade 45 with contact 46 also establishes the following energizing circuit to bi-metallic element 64: from line wire 31 through conductor contact 46, switch blade 45, conductors I02, I03, and H9, bi-metallic element 64, and conductors I20, I01, I06, and I06 back to the other line wire 36. The establishment of this energizing circuit to bimetallic element 64 causes the latter to begin to heat so as to move switchblades 65, 66, and switch actuating arms 69 and '10 towards the left. As previously explained, the first element to be moved is switch blade 65 which moves out of engagement with contact 61 and thus interrupts the original energizing and holding circuits to relay winding 42. Since, however, a new holding. circuit has been established as described above, relay coil 42 remains energized 'despite the separation of switch blade 65 from contact 61. After a predetermined .period of time suflicient for the thermocouple 6| to be heated by the ignition spark if the ignition ing it to be deenergized. The deenergization of relay coil 42 will in turn result in the bi-metallic element 64 of timer 63 and-the ignition transformer I6 being deenergized. Since relay coil 42 cannot be reenergized until the timer 63 has moved back to its cold position so as to reengage switch blades 65 with contact 61, it is necessary for the system 0t recycle completely.

If, however, the ignition means operates properly, relay 4| will remain in its energized position holding switch blade 53 in engagement with contact 55. Under these conditions, the engagement of switch blade 14 with contact 16 will cause the following energizing circuit to be established to burner motor II: from line wire 31 through conductor |0I, contact 40, switch blade 45, conductors I02, I03, and I04, switch blade 14, contact 16, conductor I23, contact 56, switch blade 63, conductor I24, motor terminals I2 and I3, and conductors I25, I06, and I09 back to the other line winding 36. The establishment of this circuit results in the establishment of all the conditions necessary to combustion taking place. Under normal conditions, since-the proper operation of the ignition means has already been checked, the atomized fuel mixture issuing from nozzle will be ignited by the spark between electrodes I9 and 20.

At the end of a predetermined period of time after switch actuating arm 69 has actuated switch blade 14, switch actuating arm 10 is effective to actuate switch blade 60. Upon switch actuating I arm 10 being moved to the left into engagement with button 62, as previously explained, switch blade is moved with a. snap action out of engagement with contact 6|. When this happens, the circuit previously traced to the ignition transformer I6 is interrupted. The period of time between the actuation of

switch blades

14 and 60 is normally sufficient to permit combustion to be properly established. Thus, in spite of the ignition being deenergized, the thermocouple 6| remains heated because of the presence of the burngized position and thermal element 64 continues to heat. I

After a further predetermined period of time,

switch blade 66 of timer 63 is moved into engagement with contact 66, establishing the following new circuit to relay coil 42: from the right hand terminal of secondary 33 through a conductor 92, contact 29, contact blade 21, bimetallic element 26, conductor 99, switch blade 44, conductor 41, conductor III, switch blade 43, contact 46, conductor I I2, switch blade 52, contact 54, conductors H3, and I26, switch blade 66, contact 66, conductor I29,

contact blades

81 and 66, conductor 61, relay coil 42, and conductor 96 to the other terminal of secondary 33. It will be noted that the new circuit does not include the safety switch heater 69. Theestablishment of this circuit shorts out the safety switch heater so as to terminate its heating eifect. The timing of time switch 63 is sumcient that this entire means is functioning satisfactorily, switch actu-.

sec' uence takes place before the bi-metallic element '88 has become heated suiiiciently to move from out of engagement with switch blade 81. Hence, the system continue in operation until thermostat 25 is satisfied.

Whenever the temperature of the medium to which bi-metallic element 28 is responsive has risen sufliciently to cause separation of contact blade 21 from contact 29, all of the circuits traced to relay coil 42 will be interrupted so as to terminate energization of the burner motor II, the timer 83, and relay 4|.

The system cannot be again placed into operation until the temperature has dropped sufliciently to cause reengagement of contact blades 21 and 28 with contacts 28 and 80 and until the timer 88 has been allowed to cool suiliciently to reengage switch blade 85 with contact 81 which occurs only after switch blade 68 and switch actuating armatures 68 and 18 have again assumed the position shown'in the drawing. Thus, it is assured that adequate time will be provided for the thermocouple 6| to cool off before the apparatus is again placed in operation.

Operation if combustion is not initially established It will be noted from the preceding description that when the switch blade 14 dlsengages from contact 15 to deenergize relay coil 50 and later when switch blade 88 disengages from contact 8| to deenergize the ignition, the relay 4| moves to its deenergized position unless the mechanism is properly operating. In the first case, the proper operation involves the proper operation of the ignition means. In the second case, it involves the establishment of combustion. In either case, the movement of relay 4| to deenergized position causes deenergization of relay 48 and timer 83 and stops all operation of the system until switch blade 65 of timer 83 reengages contact 61. If at this time, both the thermostat contact blades 21 and "are in engagement with contacts 29 and 30, theiicycle is started over again. While the heater 88 is deenergized during the time that relay 4!) is deenergized, while the timer is cooling it will be obvious that when the system recycles, heater 89 will still retain a certain amount of heat. Thus, if the system again fails to operate properly, bi-metallic element 88 wil1 be at a higher temperature than at the beginning of the first attempt to start operation of the system. Depending upon the relative timing of timer 63 and safety switch 85, the bi-metallic element 88 may be made to disengage the safety switch blade 81 and shut down the system after two or more attempts to start. It will thus be seen if combustion is not successfully established at first, one or more further attempts will be made to establish combustion. If these attempts are likewise unsuccessful, the-cumulative heating of bi-metallic element 88 by heater 89 will cause the safety switch to open to shut down the system until the safety switch is manually reclosed.

Operation in case of combustion failure timer 63. It is not possible for the system to again be placed into operation until timer 83 cools down to a point where the various switch 7 blades again resume their cold positions, as in the drawing. This timing period is 'sufllcient for the thermocouple to cool and for any unburned gases in the furnace to pass out throu h the stack. If, at this time, both thermostat blades 21 and '28 are in engagement with their associated contacts 29 and 30, the operation first described will be repeated. If this attempt is unsuccessful, the cycle will be repeated. In other words, a series of attempts will be made to restart the system and if these attempts are un-' successful, the safety switch will be opened so as to shut down the system awaiting manual intervention.

vConclusion It will be seen that I have provided a burner control mechanism employing a single element to detect both the proper operation of an actuating means and also the establishment of combustion. It will further be seen that this burner control mechanism provides for safe operation in the event of any possible type of abnormal operation.

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

I claim as my invention:

1. In control apparatus for a fuel burner con trol motor and ignition means; a safety controller for interrupting operation of said apparatus at the end of'a timed period; a timer, means including said timer for establishing circuit connections adapted to lead to said motor means,

then interrupting circuit connections adapted to control energization of said ignition means, and finally rendering said safety controller inoperative, means adapted to respond to a condition indicative both of the proper operation of the ignition means and of the presence of combustion, and means including said last named means adapted to continue operation of said timer after the circuit connections for said ignition means have been interrupted only if said condition responsive means indicates the maintenance of said condition due to the establishment of combustion.

2. In control apparatus for a fuel burner con} trol motor and ignition means, a safety controller for interrupting operation of said apparatus at the end of a timed period, a timer, means including said timer for establishing circuit connections adapted to lead to said motor means, then interrupting circuit connections adapted to control energization of said ignition means, and

finally rendering said safety controller inopera-' tive, a temperature responsive element adapted to be located so as to be subjected to the heat produced both by the ignition means and by combustion, and means including said temperature responsive element adapted to continue operation of said timer after the circuit connections for said ignition means have been interrupted only if said temperature responsive element continues to be heated as the result of the establishment of combustion. 4

3. In control apparatus for a fuel burner control motor and ignition means, a safety controller for interrupting operation of said. apparatus at the end of a timed period, a timer, meansninclud-. ing said timer for first establishingpircuii; conascaoos said timer only if the ignition means is functionlng properly and later after the ignition means has been deenergized to continue operation of said timer only if combustion has been established.

4. In control apparatus for a fuel burner control motor and ignition means; a safety controller for interrupting operation of said apparatus at the end of a timed period, a timer, means including said timer for first establishing circuit connections adapted to lead to said ignition means, then after a first timed period establishing circuit connections adapted to lead to said motor means, then interrupting said circuit connections for said ignition mean's aftera further timed period and finally rendering s'aid safety controller inoperative, a temperature responsive element adapted to be located so as to be subjected to the heat produced both by the ignition means and by combustion. and means including said temperature responsive element adapted to interrupt operation of said timer before said circuit connections for said motor are establishedif said temperature responsive element is not heated by said ignition means and later to interrupt operation of said timer after said ignition circuit conhas not been established.

5. In a fuel burner, control system, a burner, ignition means therefor, a thermocouple having its hot junction located so as to be heated either by the heat produced by the ignition means or by that produced by the flame of the burner,

tion of said ignition means after the end of a second timed period independently of said winding to cause termination of the operation of said burner and said timer if said winding does not remain energized because of the thermocouple being heated by the fiame of the burner.

6. In control apparatus for a fuel burner motor and ignition means; a temperature responsive element adjacent said ignition means and exposed to the heat thereof; a time switch including an electrically energized timer and first and main in energized position independently of said first circuit means upon said temperature responsive element being heated by said ignition means; further circuit means adapted to cause energization of said burner motor upon closure of both said second and third switches; said timer being operative a period of time after closure of said main switch to open said first switch and terminate energization of said relay by said first circuit means and to close said second switch to cause energization of said burner motor by said I further circuit means if said relay remains ,in energized position following the opening of said first switch.

7. In control apparatus for a fuel burner motor and ignition means; a thermocouple having its hot junction adjacent said ignition means and exposed to the heat thereof; a time switch inf cluding an electrically energized timer and first nections have been interrupted if combustion? second switches; a relay comprising a third switch closed when said relay is energized; a main control switch; a first circuit means adapted upon closure of said main switch to cause energization of said timer, said relay and the ignition means; second circuit means including said temperature responsive element for causing said relay to reand second switches; a relay comprising a plurality of windings and a third switch, said third switch being closed when either one of said windings is energized; a main control switch; a first circuit means adapted upon closure of said main switch to cause energization of said timer, a first of said relay windings, and the ignition means: connections between the other of said relay windings and said thermocouple for causing said relay to remain in energized position independently of said first circuit means upon the hot junction of said thermocouple being heated by saidignition means; further circuit means adapted to cause energization of said burner motor upon closure of both said second and third switches; said timer being operative a period of time after closure of said main switch to open said first switch and terminate energization of said. one relay winding by said first circuit means and to close said second switch to cause energization of said burner motor by said further circuit means if said relay remains in energized position following the opening.

burner operation first to initiate operation of said ignition means, then to terminate operation of said ignition means and said timer after a first timed period if said temperature responsive element has not been heated by said ignition means, and finally to terminate operation of said ignition means at the end of a second timed period independently of said temperature responsive element to cause termination of the operation of said burner and said timer if said temperature responsive element is not maintained hot by the flame of the burner.

9. In control apparatus for a burner fuel control motor and ignition means; a time switch including an electrically energized timer and switch means operated thereby, said timer moving in one direction when energized and in an opposite direction when deenergized; a first relay adapted to control the energization of said timer, saidfuel control motor, and said ignition means; circuit connections controlled by said time switch and ignition means is functioning properly or combustion is established; and means controlled by said time switch and operative to cause deenergizetion or said ignition means a predetermined period or time aiter energization oi said timer so that said second relay becomes deenergized if combustion has not then been established.

ISSERSTEDT.