US2108770A - Preignition oil burner system - Google Patents

Description

Feb. 15, 1938. J KRIECHBAUM 2,108,770

PREIGNITION OIL BURNER SYSTEM 2 Sheets-Sheet l Filed May 21, 1934 BURNER fr MOTOR STACK SWITCH gwumtot JO HN P. KRI ECH BAU M Patented Feb. 15, 1938 UNITED STATES PATENT OFFICE A John P. or to Kriechbaum, Minneapolis, Minneapo -Honeywell Regulator Company, Minneapolis, Minn, a corporation of Delaware Application May 21, 1934, Serial No. 726,764

3 Claims.

The present invention relates to improved control systems for fuel burners, such as the wellknown oil burner, by which the ignition means is rendered operative for a timed period prior to the of the invention.

supplying of fuel to the burners.

One of the objects of the present invention is the provision of a fuel burner control system in which the ignition means is rendered operative prior to the supplying of fuel, the system being so arranged as to provide all of the usual safety features such as a safety shut-down upon a failure of combustion to be properly established and a recycling upon a momentary power failure or flame failure only after the interposition of a timed delay whereby the unburned vapors may have time to dissipate.

Other objects of the invention include the specific arrangements to be hereinafter shown and described and covered by the appended claims.

For a better understanding of the invention,

reference may be had to the following detailed description andaccompanying drawings, in which:

Fig. 1 is a schematic showing of one form of the invention, and

Fig. 2 is a schematic showing of another form 1, the system includes an fuel supply controlling means herein shown in the form of a burner motor and indicated at H]. The fuel supplied by the burner motor I0 is adapted to be ignited by ignition means ll. Operation of burner motor l0 and ignition means H is normally controlled by a main control switch herein shown as comprising a room thermostat generally indicated at l2.

Referring first to Fig. electrically operable The room thermostat l2 includes a bimetallic element I3, having one of its'ends secured as to a post I4. The other end of bimetallic element 13 carries a pair of contact blades l5 and I6 which, upon a fall in the room temperature, are adapted to engage sequentially relatively stationary contacts l1 and I8 in the order named. Upon a rise in room temperature, contact blade l6 first disengages contact l3 and upon a further rise in such temperature of say 2 F., the contact blade 15 disengages contact ll. This room thermostat may well take the form shown in Frederick S. Denison Patent No. 1,818,697 issued August 11, 1931. The room thermostat l2 controls a first or ignition relay generally indicated -at 20 and a thermal time switch generally indicated at 2|.

The relay 20 comprises a relay coil 22 which,

of any suitable type indicated at.

when energized, is adapted to attract an armature 23 that in turn moves switch arms 24, 25 and 26 respectively into engagement with contacts 21, 28 and 29. Upon deenergization of the relay coil 22, the armature 23 and switch arms 25, 25 and 26 fall by gravity to the position shown in Fig. 1 of the drawings.

The thermal time switch 2| comprises a bimetallic element 30, having one of its ends secured as indicated at 3|, its free end being adapted to engage a stationary contact 32 when the bimetallic element is heated to a predetermined extent. An electrical heating coil shown at 33 is closely associated with the bimetallic element 30 and is adapted to heat the same to cause such movement of its free end into engagement with the cooperating contact 32.

The room thermostat l2 andthermaltime switch 2| cooperate in the control of a second or burner motor relay generally indicated at 35. This relay 35 includes a relay coil 36 which, upon energization, is adapted to attract an armature 31. When armature 31 is attracted it moves switch arms 38, 39, 40 and H into respective engagement with contacts 42, 43, 44 and 45. Upon deenergization of relay coil 36, the armature 31 and the associated switch arms 38, 39, 40 and ll move by gravity to the position shown in Fig. 1 of the drawings.

The operation of the complete system is further controlled by a stack switch mechanism generally indicated at 50. This stack switch mechanism is diagrammatically shown as comprising a switch arm 5| that engages a cold contact 52 during the absence of combustion and engages a hot contact 53 upon bustion. This stack switch mechanism is of the usual slip friction type which responds to reversals in stack temperature rather than to definite stack temperatures and the arrangement further is such that switch arm 5| engages hot contact 53 prior to disengaging cold contact 52 upon the establishment of combustion and first disengages hot contact 53 and then engages cold contact 52 after a delayed interval upon the cessation of combustion. Such stack switch mechanisms are now well-known in the art and no further description thereof is thought to be necessary at this time. For the details of construction of such a stack switch mechanism, reference may be had, if desired, to Daniel G. Taylor Patent No. 1,941,502 which issued January 2nd, 1934.

The operation of the system as a whole is completely dominated by a thermal safety switch generally indicated at 55. This thermal safety the establishment of comswitch includes a switch 56 that is operated by a thermal element (not shown), the arrangement being such that upon heating of the element to a predetermined degree, the switch 56 opens and is latched in open position, thereby requiring man- 'ual resetting before the system can again be placed in operation. An electrical heating element 51 serves to actuate the thermal element for the switch 56. Such manually resettable thermal safety switches are well-known in the art and the thermal safety switch 55 can, for instance, take the form shown in Frederick S. Denison Patent No. 1,958,081 which issued May 11th, 1934.

Line voltage electrical power is furnished by line wires 60 and 6|. Low voltage electrical power is furnished by a step-down transformer generally indicated at 62 which includes a low voltage secondary 63 and a high voltage primary 64. Primary 64 of transformer 62 is connected to line wires 66 and 6| by means of wires 65 and 66. The remaining circuit connections will be described in connection with the operation of the system of Fig. 1. 9

Operation of the system of Fig. 1 With the parts in the position shown, the room temperature is at or above the desired value so that the relays 28 and 35 are both deenergized. As a result, burner motor Ill and ignition means II are both inoperative. Furthermore, the system has been inoperative for a reasonable length of time inasmuch as the contact arm of the stack switch mechanism 58 is engaged with cold contact 52 and is disengaged from hot contact 53.

The room temperature will soon begin to decrease since no heat is being furnished thereto and such decrease in room temperature will first bring contact blade I5 into engagement with contact I1 and thereafter bring contact blade I6 into engagement with contact I8 to energize the electrical heating element 33 of time switch 2| and the relay coil 22 of relay 28, in series, as follows: secondary 63 of transformer 62, wire 10, safety switch 56, wire 1|, contact |1, contact blades I5 and I6, contact I8, wire 12, wire 13,

time switch heating element 33, wire 14, wire 15,

. 22 which is independentof contact blade I6 and contact I8 of the room thermostat I2. This holding circuit is as follows: secondary 63, wire 10, safety switch 56, wire 1|, contact I1, contact blade I5, bimetallic element I3, wire 18, contact 21, switch arm 24, wire 19, wire 88, wire 13, time switch heating element 33, wire 14, wire 15, switch arm 5|, cold contact 52, wire 16, relay coil 22 and wire 11 to the other side of secondary 63. Engagement of switch arm 26.with contact 29 energizes ignition means II as follows: line 60, wire 8|, wire 82, contact 29, switch arm 26, wire 83, ignition means II and wire 84 to line 6|. Engagement of switch arm 25 with contact 28 conditions an energizing circuit for relay coil 36 for completion as will hereinafter become apparent.

Ignition means I I is therefore in operation and at the same time the heating element 33 of time switch 2| is generating heat which is transswitch heating element 51, in series, is estab- 1 lished as follows: secondary 63, wire 10, safety switch 56, wire 1| contact I1, contact blade I5, bimetallic element I3, wire 18, contact 21, switch arm 24, wire 19, wire 85, switch arm 25, contact 28, wire 86, safety switch heating element 51, wire 81, wire 88, contact 32 and bimetallic element 39 of time switch 2|, wire 89, wire 99, relay coil 36, wire 9| and wire 11 to the other side of secondary 63. Energizati'on of relay coil 36 moves switch arms 38, 39, 49 and 4| into engagement with their respective contacts 42, 43, 44 and 45. Engagement of switch arm 38 with contact 42 establishes a second holding circuit for relay coil 22 which is independent of time switch heating element 33 as well as being independent of contact blade I6 and contact I8 of room thermostat I2, this second holding circuit being as follows; secondary 63, wire 10, safety switch 56, wire 1|, contact I1, contact blade I5, bimetallic element I3, wire 18, wire 92, contact 42, switch arm 38, wire 93, wire 15, switch arm 5|, cold contact 52, wire 16, re-

lay coil 22 and wire 11 to the other side of secondary 63. Engagement of switch arms 39 and 40 with contacts 43 and 44 establishes a holding circuit for relay coil 36 and safety switch heating element 51, in series, which is independent of contact 32 and bimetallic element 36 of time switch 2| this holding circuit for relay coil 36 being as follows: secondary 63, wire 10, contact 56, wire 1|, contact I1, contact blade I5, bimetallic element I3, wire 18, contact 21, switch arm 34, wire 19, wire 85, switch arm 25, contact 28, wire '86, safety switch heating element 51, wire 81, wire 94, contact 44, switch arm 40, wire I8I, wire 95, switch arm 39, contact 43, wire 96, wire 96, relay coil 36, wire 9| and wire 11 to the other side of secondary 63. Engagement of switch arm 4| with contact 45 establishes an energizing circuit for burner motor I 8 as follows: line 60, wire 8|, wire 91, contact 45,

. switch arm 4|, wire 98, burner motor I 8 and wire the safety switch heating element 51 is heating its associated thermal element (not shown) so as to institute a trial ignition period.- In the event combustion is not established, the thermal safety switch 55 will open in the usual manner well-known in the art so as to interrupt all of the low voltage circuits from transformer secondary 63 whereupon the system is rendered inoperative until manual intervention.

' Assuming that combustion is properly established within the timed period allowed by safety switch 55, the switch arm 5| of stack switch 50 will move into engagement with hot contact 53 thereof to establish a maintaining circuit for relay coil 36 which is as follows: secondary 63, wire 18, safety switch 56, wire 1|-, contact I1, contact blade I5, bimetallic element I3, wire 18, wire 92, contact 42, switch arm 38, wire 93, wire 15, switch arm 5|, hot contact 53, wire I90, wire 95, switch arm 39, contact 43, wire 96, wire 90, relay coil 36, wire 9| and wire 11 to the other side of secondary 63. It will be noted that this maintaining circuit is independent of time switch 2| as well as all of the switches controlled by relay coil 22. It will also be noted that this circuit is independent of the safety switch heating element 51 and short circuits the former circuits therefor. As the temperature of combustion continues to rise, switch arm 5I will disengage cold contact 52 whereby to interrupt all of the circuits for relay coil 22. The system is now operating normally and upon restoration of the room temperature so as to move contact blade It from engagement with contact I8 and then separate contact blade I5 from contact I1, the system will be shut down and after a timed delay, the parts will return to the position shown in Fig. 1 of the drawings. a

In the event there should be a failure of flame during normal operation of the system, switch arm 5I will move from engagement with hot contact 53 of stack switch 50 whereupon the maintaining circuit for relay coil 36 will be interrupted and the burner motor III will become deenergized by movement of switch arm 4| from engagement with contact 35. As heretofore pointed out, upon fall in stack temperature, contact arm 5I disengages hot contact 53 a timed period before it reengages cold contact 52. It will therefore be impossible for the system to again establish ignition and fuel feeding until there has been a predetermined standby period as measured by changes in the temperature of combustion. At the endof this standby period, switch arm 5I will engage cold contact 52 whereupon the cycle of operations above described, including the pre-ignition and trial ignition periods, will be repeated, whereupon the system will either be shut down until manual intervention because of a failure to establish combustion properly or will again be placed in normal operation.

In the event of a momentary failure of power while the system is in normal operation, relay coils 22 and 35 will both be deenergized. If the power returns prior to the time switch arm 5I moves from engagement with contact 53 as the result of discontinuance of combustion, it will be impossible for either relay coils 22 or 35 or time switch heating element 33 to be energized since the initial energizing circuit for relay coil 22 goes through the cold contact 52' and the initial energizing circuit for relay coil 35 must go through the time switch 2I. The temperature of combustion will therefore continue to fall and after a time period switch arm 5i will engage cold contact 52 at which time the system will recycle in the same manner as upon a failure of flame, if the power supply has returned in the meantime. Otherwise, the system will remain inoperative until the supplyhf power is returned whereupon the controls will recycle in a new attempt to establish combustion.

Turning now to Fig. 2 of the drawings, a slightly modified system is shown by which the same general results are accomplished as are accomplished by the system of Fig. l. The system of Fig. 2 includes a burner motor H5 and an ignition means III shown in the form of a hot wire igniter. The flow of current to hot wire igniter III is controlled by a constant current transformer H2, having a low voltage secondary and a line voltage primary, the secondary being adapted constantly to supply approximately 80 amperes. The constant current transformer H2 also supplies power to a current transformer H3 having a primary H4 and a secondary H5 which delivers a. constant current supply of ap proximately ampere.

The flow, of power to the constant current transformer I I2 is controlled by a relay generally indicated at I I5 which comprises a relay coil I I1 that controls an armature H8. Upon energization of relay coil I I1, armature H8 moves switch arms H9, I20 and I2I into engagement with respective contacts I22, I23 and I24. The flow of current to the burner motor H0 is controlled by a similar-relay generally indicated at I25. This relay I25 includes a relay coil I26 which, upon energization, attracts an armature I21 and moves switch arms I28, I29 and I30 into engagement with contacts I3I, I32 and I33 respectively. Armature I21, when attracted by energization of relay coil I26, further moves the switch arm I29 I from engagement with a contact I33.

Energization of relay coil III is primarily controlled by a room thermostat, generally indicated at I35, which includes a bimetallic element I35 and a pair of contact blades I31 and I38. Upon temperature fall, contact blade I31 first engages a contact I39 and upon a further temperature fall of about 2 F., contact blade I38 engages a similar contact I43. Relay I25 is controlled both by the room thermostat I35 and by a time switch generally indicated at IM. Time switch MI includes a bimetallic element I412 which is secured at one end, the. free end thereof being adapted to engage a contact I 33 when the bimetallic element I42 has been heated to a predetermined extent. The time switch MI is provided with an electrical heating element I33.

The system further includes a stack switch generally indicated at I35 which functions in the same manner as the stack switch 53 of Fig. 1. This stack switch I45 includes a switch arm I45 and cooperating cold and hot contacts M1 static element (not shown) and an electrical heat- I ing element I52. The thermal safety switch I53 of Fig. 2 takes the same general form as the thermal safety switch 55 of Fig. 1.

High voltage power is supplied to the system of Fig. 2 by line wires I53 and I53. Low voltage power is supplied thereto by means of a step down transformer I55 having a high voltage primary I55 and a low voltage secondary I51. The high voltage primary I56 is connected to line wires I53 and I53 by means of wires I58 and I59. The rema ning circuit connections will be described in detail under the heading operation.

Operation of the system of Fig. 2

With the parts in the position shown, the room temperature is at orabove the desired value so that both relays H6 and I25 are deenergized and the igniter III and burner motor III] are inoperative. Furthermore, the burner motor I III has been inoperative for a timed period inasmuch as switch arm I35 of stack switch I45 is in engagement with the cold contact I31 thereof. As a result, the room temperature will soon begin to fall and bring contact blade I31 into engagement with contact I39 and thereafter will bring contact blade I38 into engagement with contact I I!) whereupon an energizing circuit for relay coil III is established as follows: secondary I51,

engagement with contact wire I60, safety switch I5I, wire I6I, contact I39, contact blades I31 and I38, contact I40, wire I62,

'wire I63, wire I64, switch arm I 46, cold contact I41, wire I65, relay coil H1 and wire I66 to the other side of secondary I51. Energization of re- -lay coil II1 moves switch arms II9, I20 and I2I tact blade I31, bimetallic element I36, wire I61,

contact I22, switch arm II9, wire I68, wire I69, wire I63, wire I64, switch arm I46, contact I41, wire I65, relay coil H1 and wire I66 to the other side of secondary I51. Engagement of switch arm I20 with contact I23 conditions an energizing circuit for relay coil I26 for completion by the time switch I4I as will hereinafter become apparent.

Engagement of switch arm I2I with contact I24 energizes the constant current transformer II2 as follows: line wire I53, wire I10, wire I1I, contact I24, switch arm I2I, wire I12, constant current transformer I I2 and wire I13 to line wire I54. Energization of constant current trans, former I I2 energizes the hot wire igniter I I I and the current transformer H3, in series, as follows: constant current transformer II2, wire I14, hot wire igniter III, wire I15, primary II4 of transformer H3 and wire I16 back to the constant current transformer II2. Energization of transformer I I3 results in energization of heating element I44 of time switch MI by a circuit which is as follows: secondary II5 of transformer II3, wire I11, wire I18, wire I19, switch arm I29 and contact I34 of relay I25, wire I80, heating element I 44 and wire I8I to the other side of secthe hot wire igniter will be supplied with a proper amount of current to cause the same to become incandescent. By having this same constant current transformer control the flow of current to the current transformer II3 which in turn energizes the time switch heating element I 44, the timing period of this time switch will also be quite constant. After a timed period during which the hot wire igniter III is heated sufficiently to become incandescent, the heat generated by time switch heating element I44 will become sufficient to cause bimetallic element I 42 to move its free end into engagement with contact I43. When this occurs, the heating element I52 of thermal safety switch I 50 and the relay coil I26, in series, are energized as follows: secondary I51, wire I60, safety switch I5I, wire I6I, contact I39, contact blade I31, bimetallic element I85, wire I61, contact I22, switch arm II9, wire I68, wire I82, switch arm I20, contact I23, wire I83, safety switch heating element I52, wire I84, wire I85, contact I43, bimetallic element I42, wire I86, wire I81, relay coil I26, wire I88 and wire I66 to the other side of secondary I51. Energizatien of relay coil I26 moves switch arm I 29 from engagement with contact I34 and into I32 and also moves switch arms I28 and I30 into engagement with contacts I 3| and I33 respectively. The arrangement is such that switch arm I29 engages contact I32 prior to disengaging contact I 34, such overlapping in and out contacts on relays being well-knownin the art. Disengagement of switch arm I29 from contact I34 deenergizes the circuit for time switch heating element I44 whereas engagement of switch arm I29 with contact I32 establishes a holding circuit for relay coil I26 which is independent of contact I43 and bimetallic element I42 of thermal time switch I4 I. This holding circuit is as follows: secondary I51, wire I60, safety switch I5I, wire I6I, contact I39, contact blade I31, bimetallic element I36, wire I61, contact I22, switch arm II9, wire I68, wire I82, switch arm I20, contact I23, wire I83, safety switch heating element I52, wire I84, Wire I18, wire I19, arm I29, contact I32, wire I89, wire I81, relay coil I26, Wire I88 and wire I66 to the other side of secondary I51. Engagement of switch arm I30 with contact I33- energizes burner motor IIO as follows: line wire I53, wire I10, wire I90, contact I33, switch arm I30, wire I9I, burner motor H0 and wire I92 to line wire I54. Energization of burner motor IIO causes the feeding of fuel which should be ignited by the hot wire igniter III. In the event ignition of this fuel is not successful, then, after a timed period,- safety switch I 5| will open as is wellknown in the art and render the system inoperative until manual intervention.

Assuming that combustion is successfully established however, switch arm I46 of stack switch I45 will move into engagement with hot contact I48 to establish a maintaining circuit for relay coil I26 as follows: secondary I51, wire I60, safety switch I5I, wire I6I, contact I39, contact blade I31, bimetallic element I36, wire I 61, wire I93,

contact I3I, switch arm I28, wire I94, wire I64,

switch arm I46, hot contact I48, wire I95, wire I19, switch arm I29, contact I32, wire I89, wire I81, relay coil I26, wire I88 and wire I66 to the other side of secondary I51. It will be noted that this maintaining circuit for relay coil I26 shunts the initial energizing and holding circuits therefor and the heating element I52 of safety switch I50 whereby the safety switch I50 is operatively deenergized. Upon further increase in the temperature of combustion, switch arm I 46 of stack switch I45 will disengage cold contact I41, whereupon all circuits for relay coil H1 and all but the maintaining circuit for relay coil I26 are interrupted. The system is now operating normally and will continue to so operate until the room thermostat becomes satisfied so as to disengage both contact blades I38 and I31 from their respective contacts I 40 and I39 unless there should be a flame failure or a failure of electrical power.

In the event of a flame failure or in the event of a failure of electrical power, the system will recycle after a standby period measured by the time required for switch arm I46 to engage cold contact I41 after disengagement of hot contact I48 in the same manner as heretofore explained in connection with the system of Fig. 1.

From the foregoing, it will be seen that the sys temsof the present invention provide for a predetermined preignition period which is timed by a thermal timer in an oil burning system having all of the usual safety features including delayed recycling upon a flame failure or momentary power failure and a recycling upon a power failure of longer duration together with the safety shut down in the event of a failure to establish combustion during any trial ignition period whether it be an initial trial ignition period or one resulting from a recycling of the system. Furthermore, it will be noted that the delayed recycling upon a flame failure or momentary power failure is obtained entirely by the action of the stack switch mechanism and independently of the thermal time switch that measures the preigniton period. Furthermore, it will be noted that the thermal timers by which the pre-igintion period is measured are rendered inoperative as soon as the pre-ignition period has expired whereby the thermal timers are only energized during the actual measuring of the pre-ignition period. Also, in one embodiment of the invention, each relay coil is arranged in series with one of the heating elements for the thermal safety switch or for the thermal timer whereby the particular relay cannot be energized unless its series-connected electrical heating coil is operative. Furthermore, in another one of the modifications, the timing of the thermal time switch that measures the pre-ignition period is rendered quite accurate by the use of a constant current transformer which also supplies the ignition means with electrical current.

It will be apparent that many detailed changes can be made by those skilled in the art without departing from the spirit of the inventionand I therefore intend to be limited only by the scope of the appended claims.

I claim:

1. In combination, a fuel control device, a first relay in control thereof, an igniter, a second relay in control of said igniter, a thermal timer including a thermal actuating element and an associated electrical heater, a timer switch closed by the'timer thermal actuating element when heated to a predetermined degree by its associated heater, hot and cold combustion responsive switches arranged to close the cold switch a delayed interval after opening of'said hot switch upon combustion failure, said hot switch bein closed before openingof said cold switch upon establishment of combustion, a main switch, circuit connections for energizing the actuator of said igniter relay and the heater of said thermaltimer controlled by said main switch and cold switch, circuit connections for energizing the actuator of said fuel control device relay controlled by said timer switch and said main switch, and a maintaining circuit for the actuator of said fuel control device relay controlled by said main switch and said hot switch, whereby opening of said hot switch as a result of a failure of flame during normal operation deenergizes said fuel control device relay and tlia subsequent reclosing of said cold switch causes the system to repeat its normal cycle of operations.

2. In a fuel burning system, in combination, a

first relay including an operator and a load switch controlled thereby, combustion responsive switching means having cold and hot positions, a main switch, a circuit for the operator of the first relay controlled by the main switch and the combustion responsive switching means when in its cold position, a constant current transformer, a circuit for the constant current transformer controlled by the load switch of said first relay, a hot wire igniter, a thermal timer including a thermal actuating element and an associated electrical heater, means including circuit connections associating the igniter and timer heater with the constant current transformer for energization thereby, a timer switch moved to circuit closed position by said timer actuating element when the same has been heated to a predetermined extent by its associated heater, a second relay including an actuator and a load switch, a thermal safety switch including a controlling thermal element and an associated electrical heating element and arranged to render the system inoperative if the thermal element thereof is heated to a predetermined extent by its heating element, an energizing circuit for the actuator of said second relay and the safety switch heating element, in series, controlled by said timer switch,

a fuel controller, a circuit therefor controlled by I the load switch of the second relay, and connections controlled by the combustion responsive switching means when in its hot position for maintaining energization only of the actuator of the second relay if combustion is successfully established before the thermal element of the safety switch has been heated to said predetermined extent.

3. In combination, ignition means, a thermal timer, a constant current transformer to supply current to the thermal timer and ignition means, a main control switch, cold and hot combustion responsive switches overlappingly controlled upon temperature rise' only, circuit connection controlled by said main control switch and cold switch to energize said thermal timer and ignition means from the constant current transformer, a timer switch operated by the thermal timer, a solenoid, a circuit for the solenoid controlled by the thermal timer, a fuel control device controlled by the solenoid, a maintaining circuit for the solenoid controlled by the hot switch, and means to deenergize the timer prior to the deenergizing of said ignition means, opening of said hot switch during normal operation deenergizing the solenoid and subsequent closing of the cold switch initiating a new cycle of operation of the system.

JOHN P. KRIECHBAUM.

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