US2231212A

US2231212A - Burner control apparatus

Info

Publication number: US2231212A
Application number: US62479A
Authority: US
Inventors: Ernest M Miller
Original assignee: Honeywell Inc
Current assignee: Honeywell Inc
Priority date: 1936-02-05
Filing date: 1936-02-05
Publication date: 1941-02-11
Anticipated expiration: 1958-02-11

Description

Feb. 11, 1941. E. M. MILLER BURNER CONTROL APPARATUS 3 Sheets-Sheet 1 Filed Feb. 5, 1936 Evvzeaf MMZ Feb. 11, 1941. E, MILLER 2,231,212

BURN ER CONTROL APPARATUS Filed Feb. 5, 1936 3 Sheets-Sheet 2 Feb. 11, 1941.

E. M. MILLER BURNER CONTROL APPARATUS Filed Feb. 5, 1936 3 Sheets-Sheet 3 Patented Feb. 11, 1941 UNITED STATES PATENT OFFICE Application February 5, 1936, Serial No. 62,479

24 Claims.

The present invention relates to simplified control systems for controlling the operation of a fuel burner.

One of the objects of the present invention is 5 the provision of a burner control system in which the safety mechanism thereof is mechanically actuated by a timer, combustion responsive means being associated with the safety mechanism and timer in such a manner that the safe- 10 ty mechanism cannot be operated by the timer to shut down the system if combustion is successfully established.

Another object of the invention is the provision of novel systems of control for fuel burn- IJ ers, in which the cycle of operations are primarily controlled through a timing means. Preferably, the timing means takes the form of a thermo-electric timer and the arrangement is such that the length of the time of the trial ignition period is measured by the cooling of the timer instead of by the heating of a thermal safety switch.

Another object of the invention is the provision of an inexpensive and simplified fuel burner control system which performs all of the usual functions such as only starting after the temperature of combustion has dropped a predetermined amount, shutting down if combustion has not been established, and re-cycling after a delay either upon power failure or flame failure.

Other objects of the invention reside in the various combinations and sub-combinations to L5 be described in detail hereinafter and will be found in such description, the drawings and the claims.

For a more complete understanding of the invention, reference may be had to the following description and accompanying drawings, in

which:

Fig. 1 is a front view of the combined combustion responsive and safety switch mechanism of the present invention,

Fig. 2 is a sectional view of the apparatus shown in Fig. l and is taken about on the line 2-2 of Fig. 1,

Fig. 3 is a showing of a detail of the safety switch mechanism and is taken about on the to line 3-3 of Fig. 1,

Fig. 4 is a schematic wiring diagram of one of the systems of the present invention which utilizes the apparatus shown in Figs. 1, 2 and 3,

.Fig. 5 is a diagrammatic showing of another 55 of the systems of the present inventiom Fig. 6 is a further diagrammatic showing of one of the systems of the present invention, and r Fig. '7 is a diagrammatic showing of a further modification of the present invention.

Referring first to Figs. 1, 2 and 3, the com- 5 bined combustion responsive and safety switch mechanism of the present invention is mounted upon an insulated panel III which is secured to and spaced from a base plate ll. Secured to the base plate H in any suitable manner and 10 extending perpendicularly therefrom is a tubular member I 2. One end of a bimetallic helically coiled actuating element I3 is secured to the outer end of tubular member I! as indicated at 14. The other end of this bimetallic element 13 is secured to a torsion rod l5, as indicated at IS. The torsion rod l5 extends through the axis of the helically coiled bimetallic element i3, through the tubular member 12, base plate H, panel III and terminates in front of panel 10. This torsion rod is provided with a first reduced portion IT and a second reduced portion l8. Mounted upon the reduced portion i1 and abutting the shoulder formed by the junction of the reduced portion 11 with the torsion rod I5, is a cup I9 which receives a friction washer 20. Also mounted upon this reduced portion 11 is an actuator 2| of insulating material which abuts the friction washer 20. A second friction washer 22 then abuts the actuating member 21 and this friction washer is housed in a cup 23. A third cup 24 abuts the cup 23 and receives one end of a coiled spring 25, the other end of this coiled spring being received by a similar cup 26. This last named cup is held in place on the reduced portion 11 of the torsion rod IS in any suitable manner, as by a cotter pin 21. From the foregoing description, it will be evident that the actuator 2| is frictionally coupled to the torsion rod 15.

The actuator 2| is provided with an extension 30 which has a notch 3| therein that receives the upper end of a flexible switch arm 32, the other end 01' which is secured to a bracket 33 that is in turn fastened to the insulating panel II as by the screw 34. This switch arm 32 is disposed between a pair of contact members in the form of

brackets

35 and 36 which are also secured to the insulating panel [0.

Also mounted upon the insulating panel 10 60 is a bracket 31 to which is secured a bimetallic element 33 that extends upwardly and terminates a short distance below the reduced portion ll of the torsion rod 15. Mounted upon this reduced portion ll of the torsion rod ii is a mercury switch holder 33 which is loosely journaled thereon. This holder 38 is prevented from sliding off the reduced portion l3 by means of a cotter pin 40. The mercury switch holder 39 is utilized to mount a mercury switch 4| of any desired form, the particular construction of the mercury switch varying according to the type of system in which the apparatus is used, as will become apparent hereinafter. Secured to the mercury switch holder 33 is a bracket 42 having a downwardly extending portion which is provided with a notch 43 into which the upper end of the bimetallic element 38 extends; The bimetallic element 33 moves to the right upon cooling and the amount of movement which this bimetallic element 38 can make in this righthand direction is limited by a stop member 44.

Disposed between the stop member 44 and the bimetallic element 38 is an electrical heating element 45.

The safety switch includes a stationary contact in the form of a bracket 43 which is secured to the insulating panel I. Cooperating with this bracket is a switch arm 41 that is secured to a similar bracket 43, which is in turn mounted upon the insulating panel l3. The switch arm 41 is flexible and the arrangement is such that it tends to move from engagement with the bracket or contact 43. However, the switch arm 41 is normally held in engagement with contact 43 by means of the extended end 43 of a bracket 33 which is pivotally mounted upon a stud shaft 5| that is carried by the insulating panel II. This bracket 53. is normally biased to the position shown in Fig. 1 of the drawings by means of a coiled spring 32. Secured to the bracket 33 is an upwardly extending strip of insulating material 53 by means of which the bracket 53 can be mechanically rotated in a clock-wise direction so as to move the end 43 thereof upwardly and cause it to register with an opening 34 formed in the switch arm 41. When this occurs, the switch arm 41 can then move to the right and disengage the contact 43 and will then remain in such position until the apparatus is reset manually.

For the purpose of automatically moving bracket 53 in a clock-wise direction, a lever 33 is provided which is formed with an elongated slot 3| by means of which the lever 33 is mounted upon a stud shaft 32. 'lhe stud shaft 33 is in turn secured to the panel l3. The left-hand end of lever 33 is provided with a reduced extension 63 which extends beyond the bimetallic element 33. The bimetallic element 38 is also provided with a reduced portion 34 and this is the portion which extends into the notch 43 of the bracket 43. By this arrangement, the lower edge of lever 33 normally rests upon the bimetallic element 38. The lever 33 is further provided with an extension 35 which lies in the path of movement of a pin 33 carried by an arm 31 of the actuator 2 I.

In order to manually reset the safety switch after the same has opened, a bracket 33 is mounted upon panel III and receives a manually operable pin 33 to which a collar 13 is secured. A coiled spring 1| has one of its ends engaging the collar 13 and its other end engaging the bracket 38 and tends tomove the pin 33 in a right-hand direction. The pin 33 is provided with a manually operating handle or button 12.

With the parts in the position shown in Figs. 1, 2 and 3, the temperature to which element |3 responds has dropped at least a predetermined amount and the bimetallic element 38 is cold and has moved to the right as far as the stop member 44 will permit. Under these conditions, the pin 33' is considerably spaced from the extension 35 of lever 33 and the switch arm 32 is engaging the contact 35, which is the cold contact of the apparatus. Now, if the electric heating element 45 should be energized, the bimetallic element 33 will move to the left. Such movement will gradually rotate mercury switch 4| in a clock-wise direction and will also cause the bimetallic element 33 to move past the main portion of lever 33, whereupon the lever 33 moves downwardly so that extension 33 now engages the bimetallic element 33. Now, if the heating element 45 should be deenergized and if the temperature at the bimetallic element |3 should rise, bimetallic element 38 will start moving towards the right and the actuator 2| will be rotated in counter-clockwise direction. Such rotation of the actuator first allows stitch arm 32 to disengage cold contact 35 and thereafter the extension 33 of the actuator 3| moves switch arm 32 into engagement with the contact 33, which is the hot contact. Also, this counterclockwise rotation of the actuator 2| causes the pin 33 to move upwardly and engage the extension 33 of lever 33. Lever 33 is thereby raised so that the bimetallic element 33 is free to move back to the position shown in Fig. 1 so that the parts are in exactly the same position shown in Fig. 1 except. that switch arm 32 is engaging the hot contact 33.

If, on the other hand, the heating element 43 is deenergized but the temperature of bimetallic element l3 does not rise, then the lever 33 will not be lifted upwardly by the pin 33. The bimetallic element 33 in moving to the right will then engage the shoulder formed by the junction of extension 33 with the lever 33 and will move the lever 33 to the right. Such motion of the lever 33 is permitted by the elongated slot 3| and the extreme right-hand end of lever 33 thereupon moves the piece of insulating material 33 to the right wherefor to rotate bracket 33 in clock-wise direction. The extension 43 of the bracket 33. is thereby brought into registry with the opening 34 in switch arm 41 whereupon switch arm 41 moves to the right and separates from the contact 43. In this manner, the safety switch is opened. This occurs before mercury switch 4| returns to the position shown in Fig. 1. If it is now desired to reclose the safety switch, it is necessary to lift up the lever 33 so that the lower edge thereof may again rest on the upper edge of the bimetallic element 33. Also, it is necessary to push inwardly upon the button 12 and cause the pin 33 to engage the lower end of switch arm 41 so as to move this switch arm into engagement with contact 43. This having been done, the spring 33 will rotate bracket 33 in counter-clockwise direction so as to move the extension 43 below'the opening 34 in the switch arm 41. This again locks the safety switch in the position shown in Fig. 1.

Referring now to Fig. 4, the mercury switch that operates switch arms' 11 and 13. These switch arms respectively cooperate with

contacts

19 and 88 and the arrangement is such that switch arm 11 first engages contact 19 on temperature fall and, if the temperature continues falling, then the switch arm 18 engages the contact 88.

The system of Fig. 4 further includes a relay,-

generally indicated at 8|, that includes a relay coil 82 and an associated armature 83. The armature 83 operates switch

arms

84 and 85. Switch arm 84 engages a contact 86 when the relay coil 82 is deenergized and'is moved into engagement with a contact 81 upon energization of the relay coil 82. The switch arm 85 moves into engagement with a contact 88 whenever the relay coil 82 is energized. This relay 8|, the thermostat 15 and the other associated devices all cooperate in the control of a motor 89, which, for instance, may be the usual oil burner motor, and an igniter 98, which may be of any suitable electrical or electrically operated type.

High voltage power is supplied to the system by means of line wires 9| and 92. Low voltage power is supplied by means of a step-down transformer 93, having a high voltage primary that is connected to the line wires 9| and 92, and a low voltage secondary 94.

Operation of the system of Fig. 4

The parts are shown in the position they assume after the apparatus has been shut down by reason of opening of the thermostat 15, suiiicient time having passed since the shut-down so that the combustion responsive mechanism is in its cold position. As the temperature to which thermost-at 15 responds falls, switch arms 11 and 18 move towards

contacts

19 and 88. Switch arm 11 first engages contact 19 but this completes no circuit. Upon further fall in temperature, switch arm 18 engages contact 88 whereupon the electrical heating'element 45 is energized by a circuit as follows: Secondary 94, wire 95, contact 46, switch arm 41, wire 96, contact 19, switch arm 11, switch arm 18, contact 88, wire 91, heating element 45, wire 98, contact 35, switch arm 32, wire 99, switch arm 84, contact 86, wire I88 and wire I8I to the other side of secondary 94. Energization of heating element 45 causes bimetallic element 38 to be heated and move towards the left. Mercury switch 4| i therefore slowly rotated in clock-wise direction and, after a time period, mercury switch 4I' will be tilted to the opposite position so as to close the circuit therethrough. At this time, the bimetallic element 38' has moved beyond the main portion of lever 68 so that lever 68 has moved downwardly until its extension 63 engages the bimetallic element 38.

Closure of mercury switch 4| energizes relay coil 82 as follows: secondary 94, wire 95, contact 46, switch arm 41, wire 96, contact 19, switch arm 11, bimetallic element 16, wire I82, wire I83, mercury switch 4|, wire I84, wire I85, relay coil 82, wire I86 and wire IN, to the other side of secondary 94. It will be noted that this circuit is independent of the switch arm 18 and contact 88 so that even though these parts are not firmly in engagement the circuit for relay coil 82 will nevertheless be a steady one. Energization of relay coil 82 attracts armature 83 and moves switch arm 84 from engagement with contact 86 and into engagement with contact 81. Switch arm 85 is also moved into engagement with contact 88. Separation of switch arm 84 from contact 88 interrupts the circuit for electrical heater 45.

Engagement of switch arm 85 with contact 88 establishes an energizing circuit for the burner motor 89 and igniter 98 as follows: line wire 9|,

wire I81, contact 88, switch arm 85, wire I88, and

wires I89 and III) to the motor 89 and igniter 98, respectively, wires III, H2 and wire I13 to the line wire 92. Energization of the burner motor 89 and igniter 98 should result in the establishment of combustion. However, if combustion is not'established, the pin 66 will not raise lever '68 so that as soon as bimetallic element 38 has had enough time to cool the safety switch will be opened as described above and the system will be shut down until manual intervention. This opening of the safety switch takes place before mercury switch 4| is returned to open circuit position.

Assuming, on the other hand, that combustion does take place, switch arm 32 will disengage contact 3'5 and move into engagement with the hot contact 36. Also, the pin 66 will raise lever 68 so as to prevent opening of the safety switch. Engagement of switch arm 32 with the hot contact 36 establishes a holding circuit for relay coil 82 as follows: Secondary 94, wire 85, contact 46, switch arm 41, wire 96, contact 19, switch arm 11, bimetallic element 16, wire I82, wire II4, contact 81, switch arm 84, wire 99, switch arm 32, hot contact 36, wire II5, wire I85, relay coil 82, wire I88 and wire I8I to the other side of secondary 94. The relay coil 82 is therefore maintained energized after the mercury switch 4| is returned to the position shown in Fig. 4 as a result of further cooling of the bimetallic element 38. The system is now in normal operation.

If there should be even a momentary power failure during this normal operation, the relay coil 82 will be deenergized so that switch arm 84 will separate from contact 81. This interrupts the holding circuit described above so that it is impossible for relay coil 82 to be again energized even though the power failure is of such short duration that switch arm 32 is still engaging the hot contact 38. It will be obvious then that the system must completely re-cycle and go through the operation set out above in an attempt to reestablish combustion when power is resumed.

On the other hand, if the flame should go out for any reason during normal operation, switch arm 32 will separate from contact 38. This will interrupt the holding circuit for relay coil 82, whereupon switch arm 85 will separate from contact 88 to interrupt the burner motor and igniter circuit. The relay coil 82 cannot now again be energized until the temperature of combustion drops sufficiently to move switch arm 32 into engagement with the cold contact 35 until after the mercury-switch 4| is again closed by the action of the thermal timer.

Turning now to Fig. 5, a similar system has been shown but which is completely high voltage and wherein a simple single circuit type of controlling thermostat is used. Similar parts have been marked with reference characters corresponding to those used in Fig. 4. The thermostat 15 of Fig. 5 comprises a bimetallic element I 28 which operates a single switch arm I2I that cooperates with a single contact I22 to close a circuit on temperature fall.

Operation of the system of Fig. 5

As in the case of Fig. 4, the parts are shown in the position which they assume when the apparatus has been idle for a reasonable length of time. If the temperature to which the thermostat 15 responds should now lower, switch arm l2I will move into engagement with contact I22 whereupon heating element 45 is energized as follows: line wire 9|, wire I23, bimetallic element I20, switch arm I2I, contact I22, wire I24, switch arm 41, contact 45, wire I25, wire I26, electrical heating element 45, wire I21, cold contact 35, switch arm 32, wire I28, switch arm 84, contact 86 and wire I29 to line wire 32. The bimetallic element 38 therefore is heated and rotates mercury switch 4| in clock-wise direction.

After a time period, the mercury switch M will have been moved to closedposition whereupon relay coil 82 is energized as follows: line wire 3|, wire I23, bimetallic element I20, switch arm I2I,

contact I22, wire I24, switch arm 41, contact 46,

wire I25, wire I30, wire I3I, mercury switch 4|, wire I32, wire I33, relay coil 82 and wire I34 to line wire 32. Energization of relay coil 62 moves switch arm 85 into engagement with contact 33 to establish energizing circuits for the burner motor 63 and the igniter as formerly traced in connection with Fig. 4. Also, switch arm 34 is separated from contact 86 so that heating element 45 is deenergized and the bimetallic element be-' gins to cool. If combustion is not established, then again, as in the case in Fig. 4, the safety switch is opened and the apparatus is shut down until manual intervention.

If combustion is successfully established, however, operation of the safety switch by the bimetallic element 38 is prevented, as previously explained, and the switch arm 32 engages the hot contact whereupon a holding circuit for the relay coil 82 is established as follows: line wire 3 I wire I23, bimetallic element I20, switch arm I2I,

contact I22, wire I24, switch arm 41, contact 45, wire I25, wire I30, wire I35, contact 31, switch arm 84, wire I23, switch arm 32, hot contact 36, wire I36, wire I33, relay coil 32 and wire I34 to line wire 92. The apparatus is now operating normally and from the description given in connection with Fig. 4 it is thought to be apparent how this apparatus will re-cycle either on a flame failure or on a power failure, even though the power failure be of momentary duration.

Turning now to Fig. 6, a considerably different type of system is shown in which the relay 8| has been entirely eliminated. In this instance,

the mercury switch H is of the double-circuit type. It is provided with an electrode I40 in its left-hand end, an electrode I H in its right-hand end, and a common electrode I42 which cooperates both with the electrode I40 and the electrode MI. The mercury switch H is provided with suflicient mercury so that when the mercury switch is substantially horizontal all three electrodes, I40, MI and I42 are bridged thereby. This mercury switch 4|, therefore, comprises a double circuit switch in which the one switch is closed prior to the opening of the other switch. The roomthermostat 15 is exactly the same as utilized in Fig. 5.

. Operation of the system of Fig. 6

The parts are again shown in the position they assume after the apparatus has been shut down sufficiently long for the temperature of combustion to have fallen enough so that switch arm 32 engages the cold contact 35. If the temperature to which the thermostat 15 responds should now fall, switch arm I2I moves into engagement with contact I22 whereupon electric heater 45 is'energized as follows: line wire I45, wire I 46, bimetallic element I20, switch arm I2I, contact I 22, switch arm 41, contact 46, wire I41, electrode I42, elecline wire I5I.

trode I43, wire I43, switch arm 32, cold contact 35, wire I43, electric heater 45 and wire I to Bimetallic element 33, therefore moves to the left and rotates mercury switch H in clock-wise direction. When the mercury switch has thus been moved sufficiently far, all the electrodes I40, I and I42 will be bridged. As soon as electrodes HI and I42 are bridged, motor 33 is energized as follows: line wire I45, wire I46, bimetallic element I23, switch arm I2 I, contact I22, wire I52, switch arm 41, contact 46, wire I41, electrode I42, electrodr I4I wire I53, wire I54, wire I55, motor 33, wire I56, and wire I53 to line wire I5I. The igniter 30 is also energized, being connected in parallel with motor 33 by means of a wire I53 which is connected to the junction of wires I54 and I55 and by a wire I which is connected to the junction of wires I56 and I53.

Continued heating of the bimetallic element 33 causes the switch H to be rotated sufiiciently far to break the circuit between electrodes I43 and I42 whereupon the heating element 45 is deenergized. The mercury switch, after passing the horizontal position, moves over a. considerable distance by reason of the lost motion between the bimetallic element 33 and the notch 43 in the bracket 42. Now, if combustion is not established, the reverse cooling movement of the bimetallic element 33 will open the safety switch before mercury switch -4I is returned to its counterclockwise direction far enough to reenergize the electrical heating element 45.

If, on the other hand, combustion is properly established, opening of the safety switch is prevented, as explained above, and the switch arm 32 moves into engagement with contact 36. This establishes a holding circuit for the motor 33 and igniter 30 as follows: line wire I45, wire I46, bimetallic element I23, switch arm I2I, contact I22, wire I52, switch arm 41, contact 46, wire I41, electrode I42, electrode I43, wire I43, switch arm 32, contact 33, wire I54, wire I55, motor 03, wire I55, and wire I53 to line wire "I, it being remembered that the igniter 33 is connected in parallel with motor 33. This holding circuit will be made effective upon cooling of the bimetallic element 33 prior to interruption of the initial energizing circuit traced above. The apparatus is now operating normally.

In the system of Fig. 6, if there should be a momentary power failure, it would be possible for the motor and igniter to again be energized without having the apparatus go through its normal cycle but the mechanism would re-cycie in the event of a failure of flame since a flame failure will cause switch arm 32 to separate from hot contact 33 thereby to interrupt the motor and igniter holding circuit. They cannot again be energized without the apparatus going through its normal cycle. This failure to re-cycle on a momentary power failure is eliminated, however. in the system of Fig. '7.

Referring now to Fig. 7, the apparatus itself is identical to that of Fig. 6, except that a small relay of simple and inexpensive construction has been included. Also, the circuit arrangement is different. This relay comprises a coil I60 and a cooperating plunger I5I which, when the coil I50 is deenergized, engages a switch arm I62 and moves the same from engagement with a switch arm I63. Theseswitch arms are normally biased in such a manner that the switch arm I62 tends to engage the switch arm I63.

i for motor 89 and relay coil I88 is established as Operation of the system of Fig. 7

Upon a call for heat by the system of Fig. 7, the electrical heater 45 is energized as follows: line wire I85, wire I66, bimetallic element I28, switch arm IZI, contact I22, wire I51, switch arm 41, contact 46, wire I68, electrodes I42 and I48 of mercury switch 4 I, wire I59, switch arm 32, cold contact 35, wire' I18, electrical heater 45, wire III, wire I12, igniter 98, wire In and line wire I14. In this system it will be noted the igniter is energized the same time as electrical heater 45 and thereby provides a pro-ignition period. Bimetallic element 38 is thereupon heated and mercury switch 4] is rotated in a clock-wise direction. When the same is substantially horizontal, all three electrodes will be simultaneously bridged by the mercury therein whereupon motor 88 and relay coil I68, in series, will be energized as follows: line wire I65, wire I66, bimetallic element I28, switch arm IZI, contact I22, wire I51, switch arm 41, contact 46, wire I58, electrodes I42 and I of mercury switch 4|, wire I15, wire I15, relay coil IGII, wire I I1, motor 89 and wire I" to line wire I74. Energization of relay coil I58 raises plunger IBI so that contact I82 moves into engagement with contact I83.

If the fuel delivered by the operation of motor 89 is not ignited as it should be so that combustion is not established, the system will go to the safety position, as previously explained in connection with the other systems. If combustion is established, however, switch arm 32 disengages cold contact 35 and engages hot contact 35. Disengagement of switch arm 32 and cold contact 35 deenergizes heater 45 and igniter 98. Bimetallic element 38 then begins to cool. Then as soon as mercury switch 4 I returns sufficiently far to again bridge all three electrodes a maintaining circuit follows: line wire I65, wire I88, bimetallic element I28, switch arm I 2|, contact I22, wire I51, switch arm 41, contact 45, wire I68, electrodes I42 and I 48 of mercury switch 4|, wire I69, switch arm 32, hot contact 35, vin're I19, switch arm I63, switch arm I62, wire I88, wire I15, relay coil I88, wire I", motor 89 and wire I18 to line wire I14.

If there should now be a momentary power failure, relay coil I88 will be deenergized whereupon plunger IGI will move downwardly and cause switch arm '62 to separate from switch arm I63. Even though the power now returns while the switch arm 32 is still engaging the hot contact 36, relay coil I88 and motor cannot be energized again until the cold contacts close so as to permit reenergization of the heater 45.

It should be particularly noted that the system of Fig. 7 can utilize a very simple relay since only a single set of contacts need to be controlled thereby.

I claim:

1. In a fuel burner control system, in combination, a burner, an electrically operable fuel controller, a circuit therefor, a normally closed safety switch associated with said circuit in a manner to interrupt the same whenever the safety switch opens, a thermo-electric timing means including an element movable in a first direction upon heating and in a second direction upon cooling, said element being associated with the safety switch in a manner to mechanically open the same upon movement in said second direction, a main control to energize said timing means whereby the same moves in said first direction,

means operated by the timing means to complete said fuel controller circuit when the timing means element has been moved sufficiently far in said first direction and to deenergize the timing means, whereby said timing means cools and moves in said second direction, and means responsive to the establishment of combustion to prevent opening of said safety switch by the timing means element.

7 2. In a fuel burner control system, in combination, a burner, an electrically operable fuel controller, a circuit therefor, a normally closed safety switch associated with said circuit in a manner to interrupt the same whenever the safety switch opens, a thermo-electric timing means including an element movable in a first direction upon heating and in a second direction upon cooling, said element being associated with the safety switch in a manner to mechanically open the same upon movement in said second direction, a main control to energize said timing means whereby the same moves in said first direction, means operated by the timing means to complete said fuel controller circuit when the timing means element has been moved sufficiently far in said first direction and to deenergize the timing means, whereby said timing means cools and moves in said second direction, and means responsive to the establishment of combustion to mechanically prevent opening of said safety switch by the timing means element while permitting unrestricted movement of said timing means, and a switch closed upon the establishment of combustion which maintains energization of said fuel controller,

3. A control system for a fuel burner, comprising, in combination, an electrically operable fuel controller, an electrical timer in control of energization of the fuel controller, a combustion responsive switch which is closed in the absence of combustion, a main control switch, an energizing circuit for the timer controlled by said two switches in series, a normally closed safety switch to terminate operation of the fuel controller if opened, mechanical connections between the safety switch and timer by which the timer may open the normally closed safety I switch, and mechanical means operated upon the establishment of combustion to prevent opening of said safety switch by the timer while permitting unrestricted movement of the timer.

4. A control system for a fuel burner, comprising, in combination, an electrical fuel controller, a theme-electric timer which moves in a first direction when heated and moves in a second direction upon cooling, a main switch to energize said timer, means operated by said timer when the same has moved to a predetermined position in said first direction to energize said fuel controller and deenergize said timer, a normally closed safety switch that shuts down the system whenever opened and arranged to be opened by said timer when the same reaches a predetermined position upon movement in said second direction as a result of deenergization of the timer, and means responsive to the establishment of combustion to prevent such opening of the safety switch by the timer.

5. A control system for a fuel burner, comprising, in combination, an electrical fuel controller, a theme-electric timer which moves in a first direction when heated and moves in a second direction upon cooling, a main switch to energize said timer, means operated by said timer when the same has moved to a predetermined position in said first direction to energize said fuel controller and deenerglze said timer, a no:-

till

mally closed safety switch arranged to be or a by said timer when the same reaches a pre-ae mined position upon movement in sa direction as a result of deenergizati timer, means responsive to the establishn e s of combustion to prevent such opening of the safety switch by the timer, hot and cold switches which are respectively closed and Opened upon the establishment of combustion, said cold switch also controlling the circuit to said timer, and a maintaining circuit for said fuel controller controlled by said hot switch.

6. In a control system for a fuel burner, in combination, an electrical fuel controller, an electrical timer which moves in a first direction when energized and which moves in a second direction when deenergized, a timer switch moved to closed position when said timer moves sufficiently far in said first direction, means responsive to the presence and absence of combustion including a cold switch and a hot switch, an electro-magnetic coil, a fuel controller switch and a second switch which are closed and a third switch which is opened by said coil when energized, a main switch, means to energize thetimer upon closure of the main switch including said cold switch and said third switch, a circuit for the electro-magnetic coil controlled by said timer switch, a fuel controller circuit controlled by said fuel controller switch, a second circuit for said electro magnetic coil controlled by said third switch and hot switch in series, a safety switch to deenergize said fuel controller when opened and associated with said timer to be opened thereby when the timer returns to a predetermined position while moving in said second direction as a result of deenergization, and means operated by said combustion responsive means to prevent opening of said safety switch by the timer if combustion is established.

'2. A timing by cooling fuel control system of the class described, comprising, in combination, an electro-magnetic coil, first second switches moved to closed position a third switch moved to open position by said coil when energized, a thermo-electric timer, a fourth switch that is closed upon the establishment of combustion, a main switch, a timer energizing circuit controlled by said main switch and third switch in series, a timer switch moved to closed position by said timer when heated to a predetermined degree, an energizing circuit for said coil controlled by the timer switch, an electrical fuel controller, a fuel controller circuit controlled by said first switch, a second circuit for said coil controlled by said fourth switch and second switch in series, a safety switch to terminate operation of the fuel controller if opened, mechanical connections between said safety switch and timer by which the timer opens the safety switch upon cooling, and means operated upon the establishment of combustion to prevent termination of operation of the fuel controller if combustion is successfully established.

8. A control system for a burner, comprising, in combination, an electrical timer which moves in a first direction when energized and moves in a second direction when deenergized, a first switch that is opened and a second switch that is closed by the timer upon movement of said timer in the first direction, a main control switch, a circuit for the timer controlled by the main control switch and first switch, an electrical fuel controller, a circuit therefor controlled by said second switch, a separate combustion responsive closed upon the successful estab- :ombu on, and a second circuit for the iuel con cller which is independent of Silt, second time bustier: respon 9. a control combination, an electrical timer which moves in first direction when energized and moves in second direction when deenergized, a if"; switch that is opened and second switch that is closed upon movement of said timer in the first direction, a main control switch, a circuit for the timer controlled by the main control switch and first sndtch, an electrical fuel controller, a circuit therefor controlled by said second switch, a separate combustion responsive switch that is closed upon the successful establishment of combustion. a second circuit for the fuel controller which is independent of said second timer switch controlled by said combustion responsive switch, a normally closed safety switch associated with said timer to be opened thereby when the same moves to a predetermined position while moving in said second direction, and means controlled by the successful establishment of combustion to prevent opening of the safety switch by said timer.

10. A timing by cooling control s'stem for a fuel burner, comprising, in combination, a thermo-electric timer, a first timer switch which is opened and a second timer switch which is closed by said tuner when heated, a main switch, a first combustion responsive switch that is closed in the absence of combustion, a timer circuit controlled by -said first timer switch, main switch and first combustion responsive switch in series, an electrical fuel controller, a circuit therefor controlled by said second timer switch, a second combustion responsive switch which closes upon the establishment of combustion, a second fuel controller circuit controlled by said second combustion responsive switch, a normally closed safety switch to deenergize the fuel controller which is opened by the timer when cooling, and means operated upon the successful establishment of combustion to prevent opening of the safety switch by the timer.

11. A control system for a fuel burner, comprising, in combination, an electric timer which moves in a first direction when energized and in a second direction when deenergized, an electrical igniter, a main switch, means to energize the igniter and timer controlled by the main switch, an electrical fuel controller, switching means operated by the to energize the fuel controller and thereafter deenergize the timer and igniter all while said timer is moving in said first direction, combustion responsive cold and hot switches, said cold switch being in circuit with said time? and igniter, and a circuit to maintain energize, tion of said fuel controller controlled by said hot switch.

12. A control system for a fuel burner, comprising, in combination, an electrical timer which moves in a first direction when energized and moves in a second direction when deencrgized, first and second timer operated switches which are respectively opened and closed by said timerwhile moving in said first direction, a main switcl 1. a timer energizing circuit controlled by the main switch and first timer switch, an electro-magnetic coil, 2. control switch closed thereby when energized, an electrical fuel controller, circuit connections to energize said coil and fuel controller controlled by said main switch and second timer switch, a combustion responsive switch that closes upon the establishment of combustion, and a circuit to maintain energization of said coil and fuel controller controlled by said main switch, control switch and combustion responsive switch.

13. A control system for a fuel burner, comprising, in combination, an electrical timer which moves in a first direction when energized and moves in a second direction when deenergized, first and second timer operated switches which are respectively opened and closed by said timer while moving in said first direction, a main switch, a timer energizing circuit controlled by the main switch and first timer switch, an electro-magnetic coil, a control switch closed thereby when energized, an electrical fuel controller, circuit connec tions to energize said coil and fuel controller controlled by said main switch and second timer switch, a combustion responsive switch that closes upon the establishment of combustion, a circuit to maintain energization of said coil and fuel controller controlled by said main switch,

. control switch and combustion responsive switch,

a normally closed safety switch associated with said timer and arranged to be opened by the timer when the same reaches a predetermined position while moving in said second direction, and means operated upon the successful establishment of combustion to prevent opening of said safety switch by said timer.

14. In a fuel burner control device, a burner star-ting means, a retractable power means having a source of energy and operable upon movement in one direction to actuate said burner starting means and to discontinue its further supply of energy, safety means for controlling burner operation, means having an active position for transmitting the retractive movement of said power means to said safety means and being movable to an inactive position, said power means retracting to safety means operating position upon discontinuance of said supply, combustion responsive means, and means controlled by said responsive means upon establishment of combustion to move said transmitting means to said inactive position.

15. In a fuel burner-control device, a main burner switch, a thermally actuated retractable power means movable in one direction upon heating and retractable in another direction upon cooling, an electrically energized heater for said power means, a switch controlling the circuit of said heater, said power means being arranged to close said burner switch and to open said heater switch upon movement in said one direction, a safety switch controlling the burner circuit, means having an active position for transmitting the retractive movement of said power means to said safety switch and being movable to an inactive position, said power means retracting to safety means operating position upon opening of said heater switch, combustion responsive means, and means controlled by said responsive means upon establishment of combustion to move said transmitting means to said inactive position.

16. In a fuel burner control device, a safety means having a burner operating position and being operable on movement to another position to'stop operation of the burner, a heat actuated timing means movable in one direction upon heating and in another direction upon cooling, a burner starting means operated upon movement of said timing meansin said one direction, means controlled by movement of said timing means in said one direction to discontinue the heating of said timing means, a shiftable operating member having an active position and an inactive position and bein operable on movement when in said active position to move said safety means to said other safety means position, said shiftable member being movable with said timing means upon timing means cooling movement, and means operable to shift said shiftable member to said inactive position upon establishment of combustion so that said safety means will remain in said operating position upon movement of said timing means in said other direction.

17. In a fuel burner control device, a safety switch, a thermally actuated power means, a longitudinally movable thrust member for transmitting movement from said power means to said switch, means to heat said power means, means supporting said thrust member for lateral movement out of motion transmitting position, and means operable upon establishment of combustion to move said thrust member laterally.

18. In a fuel burner control system, in combination, a burner, an electrically operable fuel controller, a circuit therefor, a normally closed safety switch biased to open position associated with said circuit in a manner to interrupt the same whenever the safety switch is opened, a latch device for retaining the switch closed and requiring manual resetting whenever said switch is opened, timing means operable by heat and only after heated to a predetermined extent operating to mechanicall release said latch and permit the opening of said safety switch, the timing means being incapable of relatching said switch in closed position, a main control the closin of which renders applicable the application of heat to said timing means, said main control also permitting the completion of said fuel controller circuit, and means responsive to the establishment of combustion associated with said timing means to mechanically prevent releasing said latch and opening of said safety switch by the timing means if combustion is established prior to the timing means being heated to the predetermined extent.

19. In a fuel burner control system, in combination, a normally closed biased open safety switch wired in the system in a manner to interrupt the supplying of fuel whenever said switch is opened, means for retaining said switch closed, a normally cold thermal element for rendering said retaining means inoperative to permit opening of the safety switch after the thermal element has been heated to a predetermined extent, said thermal element being incapable of reclosing said switch, an electric heater for heating said thermal element to said predetermined extent, an electric fuel controller, a main control switch in control of the flow of power to the fuel controller and electric heater, and means responsive to the establishment of combustion including a structural member to mechanically prevent the thermal element rendering said retaining means inoperative thereby preventing opening of the safety switch, while permitting unrestricted movement of said thermal element in response to changes in the temperature to which it responds.

20. In a fuel burner controlsystem, in combination, an electrically operable fuel controller, a normally cold thermal element adapted to move back and forth in response to tempera ture changes, an electrical heater for changing the temperature of said thermal element, a main controller to place the system in operation, means including circuit connections interconnecting the fuel controller, electrical heater and main controller to cause energization of the fuel controller and electrical heater each time the system is placed in operation by the main controller, a safety switch to stop operation of the fuel controller and which remains continuously closed during normal cycling of the system 'in response to changes in demands for heat by the controller, said safety switch being biased to open position, latching means to hold said safety switch in its closed position, means mechanically interconnecting said safety switch and thermal element in such manner that the safety switch will be unlatched by the thermal element each time the system is placed in operation by the main controller but only after said thermal element has moved a predetermined amount as a result of heating thereof by the electrical heater, said thermal element being incapable of relatching said switch in its closed position, a mechanical member associated with said safety switch and thermal element to prevent such unlatching of the safety switch, a thermal device responsive to combustion conditions operating said mechanical member to prevent unlatching of the safety switch if combustion is established before said thermal element has moved said predetermined amount, and a slip friction connecting means connecting said thermal device and mechanical member to cause immediate movement of the latter upon initial combustion temperature rise.

21. In a fuel burner control system, in combination, an electrically operable fuel controller, a normally cold thermal element adapted to move back and forth in response to temperature changes, an electrical heater for changing the temperature of said thermal element, a main controller to place the system in operation, means including circuit connections interconnecting the fuel controller, electrical heater and main controller to cause energization of the fuel controller and electrical heater each time the system is placed in operation by the main controller, a safety switch to stop operation of the fuel controller that remains continuously closed during normal cycling of the system in response to changes in demands for heat by the controller, salid safety switch being biased to open position, latching means to hold said safety switch in its closed position, means mechanically interconnecting said safety switch and thermal element in such manner that the safety switch will be unlatched by the thermal element after a time period each time the system is placed in operation by the main controller, said thermal element being incapable of relatching said switch in closed position, a mechanical member associated with said safety switch and thermal element to prevent such unlatching of the safety switch by the thermal element while permitting unrestricted movement of said thermal element, a thermal device responsive to combustion conditions operating said mechanical member to prevent unlatching of said safety device if combustion is established before the elapse of said time period, and a slip friction device interposed between said thermal device and mechanical member to cause immediate movement of the latter to such position upon initial combustion temperature rise.

22. In an electrically operated fuel burner con- 7 trol system adapted to be energized for operation and fully deenergized when the burner is not operating, in combination, a burner, an electrically operable fuel controller, a circuit therefor} a relay in control of said circuit, a normally closed safety switch associated with said circuit in a manner to interrupt the same whenever the safety switch is opened, the safety switch requiring manual reclosing when open, actuating means forsaid switch including at least one movable element and normally deenergized electrically influenced timing means, said actuating means being operable to mechanically open said safety switch after a time period in the absence of means for preventing the opening of said safety switch, movement of the timing means being incapable of closing the switch after it has been opened by the actuating means, a main control the closing of which places said timing means in operation by energizing the same, electrical connections by which at least initial energization of said relay is dependent upon flow of current to said electrically influenced timing means, and means responsive to the establishment of combustion associated with said safety switch and actuating means and comprising an element movable into engagement with the movable element of said actuating means to mechanically prevent opening of said safety switch by the timing means if combustion is established within said time period.

23. In an electrically operated fuel burner control system adapted to be energized for operation and fully de-energized when the burner is not operating, in combination, a burner, an electrically operable fuel controller, a normally closed safety switch associated with said" fuel controller in a manner to interrupt the supp y 'of fuel whenever the safety switch is opened,

the safety switch requiring manual reclosing when open, actuating means for said switch including at least one movable element and normally deenergized electrically influenced timing means operable independently of said fuel controller, said actuating means being operable to mechanically open said safety switch after a time period in the absence of means for preventing the opening of said safety switch, movement of the timing means being incapable of closing the switch after it has been opened by the actuating means, a main control the closing of which places said timing means in operation by energizing the same, a fuel controller circuit the completion of which is dependent upon flow of cuI- rent to said electrically influenced timing means, and means responsive to the establishment of combustion associated with said safety switch and actuating means and comprising an element I movable into engagement with the movable element of said actuating means 'to mechanically prevent opening of said safety switch by the timing means if combustion is established within ment and normally deenergized electrically influenced timing means, said actuating means being operable to mechanically open said safety switch after a time period in the absence of means for preventing the opening of said safety switch, the timing means being unable to recluse said switch, a main control the closing of which places said timing means in operation by energizing the same irrespective of operation of said fuel controller, a fuel controller circuit the completion of which is dependent upon flow of current to said electrically influenced timing means, thermal means responsive to the establishment of combustion associated with said safety switch and actuating means and comprising an element movable into engagement with the movable element of said actuating means to mechanically prevent opening of said safety switch by the timing means if combustion is established within said time period, and slip connecting means associated with said thermal means to enable the same to quickly prevent the opening of the safety switch upon initial temperature rise when combustion is established.

ERNEST M. MILLER.