US2195650A - Oil burner control - Google Patents

Description

April 2, 1940. l v. H. HARDY 2,195,650

OIL BURNER CONTROL Filed April 14, 1938 2 Sheets-Sheet 2 *LINE l 25 26 TRANSFORMEP RELAY WARP SWITCHES 56 5a 57716K SWITCH Snoentor l Pm-sied Apr. 2, 1940 UNITED STATES PATENT OFFICE OIL BURNER CONTROL Vaughn H. Hardy, Rochester, N. Y., assignor to General Motors Corporation, Detroit, Mich., a

corporation of Delaware Application April 14, 1938, Serial No. 202,025

8 Claims.

i 5 With the advent of the domestic use of fluid fuel burners such as oil or gas fire furnaces, it has become necessary to provide suitable controls for said burners or furnaces which will require ,very little, if any, attention, maintain the heat l at a predetermined set level, and embody certain safety features which will keep the device sufIiciently safe for home use.

It is therefore an object of my invention to r provide such a system for burner control. il It is a further object to provide a control syste n embodying the necessary safety features to deenergize the whole system under certain circumstances, namely, when lthe burner does not initially start or where therey is a ame or cur- `2|) rent failure after the burner isoperating normally. n

It is a still further object of my invention to providesuch a control system as will be comv.paratively simple in constructionand easily ap- "25 plied to .an existing heating plant.A K y With these and` other objects in view, the. em-

bodiments of my invention will be best understood by'reference to the following specification .and` claims and the illustrations in the accomn panying drawings, in which:

yl'igure 1 is a circuit diagram of a control sys` tem of my invention.

Figure 2 is also a circuit diagram of a, modiiiedform of my invention;

. a Figure 3 is a circuit diagram of a further modication. l Referring now more specifically to Figure 1, there is provided an incomingline 2, 4 to which the supply such as llOvolts is` provided. There is form of Vstack switch 8, whichfhas a bimetal portionV I0 extending into and sensitive to the heat in the furnace chamber; .a room thermostat I2;

`and a transformer relay I4' having a primary l 5 I6 and a secondary I8, ythe magnetic `field of.

which operates afplurality of switches-20 and l22.v

There is also provided-an ignition transformer 24, thefmain warp switch`26 which Iincludes a heating coil 28 and aswitch 30,' and a vsecond .kggwarp switch or electrically heated time element, 32 including aheating coil 34 anda plurality of switches 36 and 38 operated thereby.` Thereis in the secondary circuit of the transformerrelay I4 a resistance coil 40, the purpose'of whichwill also shown the burnerv motor 6;`the conventional f to one of the switches zo perated by the trans' systemis' deenergiced`,a n v l areI closedfbut the''-:llresting*element` 34A is-heated` lfor thewhole-period-that'the-motor Gis in oper;y 'u

The main warp switch 30 is connected directly to the line 4 and the opposite side is connected to its own heating element 28, the opposite side of the heating element being connected by line 42 to the primary I6 of the transformer relay I4. v5. The opposite side of the primary I6 is connected by a line 44 back to the incoming line 2. Line 4 is also connected directly to switchiil,` the opposite side of which is connected ,by line 46 to the burner motor 6 which is also connected 10 f to the line 2 by a further line 48. Also connected to line 46 is a branch 50 which is connected both to the heating element 34 and one switch 36 of the group operated by the warp switch designated at 32. The opposite side of the heating coil 34 is connected back through line 52 to incoming line 2 and the opposite side of the switch 36 is directly connected to the primary of the ignition transformer 24 which is then directly connected to line v2. The secondary of the ignition transformer of course is connected to a pair of spaced contacts which provide sparks for ignition purposes. This concludes the high voltage side of the system and the secondary or low voltage side will nextbe described.A n 25 One terminal ofthe transformer relay secondary AI8 is connected through line 54 to one side of theroomtliermostat I2 which has its oppositesidel connected toa switch 56 controlled by the stack switch and normally closed when cold.

y Also inbranchcircuitto onefterminal of the resistance also connected to switchil is 'a' line opposite end of the resistance 40. A line 62 connects the opposite terminal of the resistance 40 former relay which'is then extended up to the 40 same terminal of the secondary I 8 Vas that t which line 60 is attached. s I, v The warp switch 30 is normallyclosedunder all conditions andy isyonly' opened; when some ab- 45 normal safety condition requires V,itvto do so., The room thermostat'v is ofl fcourseopened whenk the f temperature of .the roorriis's atbovea certain predetermined level and Vclosed.` as the temperature falls belowthatjleveh@ The stackvswit'ch 8g-isu closedI whencold andmopefnsJ-uponan application switches `is andati .I v

'der normal conditions.

former and the magnetic iieldofv thesame will increase appreciably which causes a'closing ofthe two switches 28 and 22. The' closing of switch 22 i closes an obvious 4circuit to the vburner motor 8` and at the f same time a parallel circuit through the-heating coil 34, the ignition transformer 24 V and switch 38.

Under-these conditions .the burner motor will of course start to discharge a combustible mixture into the chamber andthe ignition will bepresent to/ignite this mixture. The heating ele-- ment 34 however will tend to cause the switch 38 to operi after a predetermined interval which cuts off the ignition andthe burner. thereafter continues to function normally. The closure of switch 28 closes a shunt circuit around the warp switch 38. This however acts to complete the secondary when 38 opens due to the heat of the warp switch which willl be actuated at the samefore continueto operate until a sufficient amount of heat has been provided and when the roomj thermostat opens the whole system -will return to its normal deenergized condition.

If,` for example, for some reason the flame does notignite when ther motor startstthe switch 58 will remain closed and the secondary of the transformer relay will continue to absorb a comparatively large a'mount of current which will of course necessitate a comparatively heavy current flowthrough the primary I8 and the heating coil 28 which will, after a predetermined time, cause the safety switch 38 to open and the whole system will then be deenergized. vThe safety switch 38, as in most conventional switches of this type, requires a manual resetting after it is once opened. Likewise, if the burner has been operating normally and for some reason the flame is extinguished momentarily, the stack temperature will begin to descend and switch v58 will close which will, as before, require a heavy current flow through the secondaryand thereforethe primary-of the transformer I4 and the heating coil 28 of Warp switch 28 will lagain cause safety switch 38 to open; If, during normal operation, the current isvcaused to cease for a short period of time, the switches 28 and 22 will open. At such time, however, the stack switch 58, as well as switch 38, is open, and if the current returns to* throw oil or the combustible mixture intothe furnace. Under these conditions', the switchl I8 is provided to be operated jointly with the ignithebbuner without ignition such as might occur, for instance', if such switch 38were not provided and the stack switch 58 returned to its cold closed-position prior to closing of the ignition switch 38 by cooling of the heating coil 34.

The system shown in Figure 2 is a modification of that shown in Figure ,1. In this instance the transformer relay I4 is connected to the main warp switch 28 in exactly the same way and it operates its rtwo switches 28 and 22 in the same manner asbefore. The' warp switch 82 is however, altered as shown a't`32- and a heating coil 84 operates fa' switch 88 which controls the ignition transformer 24. The resistance '48 still shunts the switch 58 operated by the stack switch 8. The. main difference is that the warp switch 32 has in this instance only one contact, namely f that for operating the ignition transformer and does not control the circuit through the stack tion switch 38 to positively prevent starting of' switch which'is in shunt with the control resistlance 48. The normal operation ofthis vcircuit is substantially the same as shown in Figure -1 vfor upon closure of vthe room thermostat I2 the secondary I8 of the transformer relay is energized which draws' current from the primary and causes the closure '-ofthe two switches 28 and 22, the firstv completing the circuit through the shunt resistance 48 and the second completing Y, thev circuit for the second warp switch, the ignition and motor.

As before, when the stack switch opens the current through the secondary I8 is cut down due to the series relation of the resistance 48, butthere is suflicient magnetic force to maintain the switches- 28 and 22 closed. When a suilicient ,amount of heat has been provided the room thermostat opens to deenergize the whole sys-v tem.v As far as the safety features are concerned,

that shown in Figure 1, with the exception that since there is no switch in series with the stack switch and operated jointly with the ignition switch,'as provided in Figure 1 by switch 38, it

' this system operates substantially the'same as is necessary t'oso construct the warp switch'32 for the ignition switch 88 that in the event of a momentary current failure such ignition switch will be closed by cooling of the heating coil 84 before the stack switchv 58 closes on cooling of the stack to prevent starting of the burner motor without ignition. v

The system disclosed in Figure 3 has a slightly different variation in that in this case the second warp switch 32 of Figure 1 or 32'v of Figure 2 is eliminated entirely and the warp switch 28 in this instance is provided with an extra switch 88 which controls the ignition transformer 24. The circuit is otherwise the same as that shown in Figure 2. It should -be pointed out however that in this construction it is necessary to design the two switches 38 and 88 in such a manner lthat they will operate at different times; in other words, a certain amount of'heat is necessary to operate ignitionswitch 88 to open position but at this time safety switch 38` will still remain closed and it will require a substantial increase in the amount of heat supplied before the switch 38 will open so that under normal running conditions of the burner the ignition switch 88 will be opened soon after starting the burner and the safety switch 38 remain closed. This canbe done of course by merely designing the bimetal switch 'armeno burner circuit, a transformer, a warp switch and,

actuating element so that this result can be obtained. I

The operation in this case is exactly the same whereby the closure of room thermostat I2 will, through the closed stack switch 50, complete the secondary circuit of the transformer relay I4 which will then cause the two switches and 22 to close and the motor 8 and ignition transformer 24 will be energized through the closed switches 3l and 58. After a predetermined time, switch 6B will open cutting off the ignition, but as before mentioned safety switch is so designed as to remain closed fora longer period and before this time has elapsed switch 56 should open due to actuation of the stack switch However the amount of current drawn by the secondary after 56 opens because ofthe resistance 40 is enough to maintain a suilicient amount of heat by`coil 28 in the primary to keep the switch 58 open as long as the burner operates. In this case of course if the burner does not ignite, safety switch 30 will eventually open deenergizing the whole system, or if the ame is extinguished for any reason switch 56 will close after a short interval due to the cooling down of the stack and this will again cause switch 30 to open. If the current fails, contacts 20 and 22 lwill `open and the secondary cannot again be energized until the switch 56 is closed by cooling of the stack which will allow a purging time for the furnace. y

I claim:

' l. In a system for controlling huid fuel burners, a burner circuit, an electrically heated safety switch controlling said burner circuit, a heating element for said switch in series therewith, a transformer having its primary in series therewith, a secondary circuit for vthe transformer and means in the secondary circuit and actuated by temperature changes of the burner to vary the lflow of current therethrough which causes a variation of current flow in the primaryand said heating element to control the actuation of the safety switch thereby.

2. In a control system for fluid fuel burners,

a burner circuit, an electrically heated safety;

switch controlling said burner circuit, a heating element for said switch in series therewith, normally maintained energized atall times, a transformer primary winding in series therewith and with a source of power, a secondary transformer winding in inductive relationship to the first',

a resistance in series with the secondary circuit,

a shunt circuit around the resistance and means actuated by temperature changes of the burner to apply or remove the shunt thereby varying the current in the secondary which reflects back into the primary and affects the operationy of the safety switch by said heating element.

3. In a control system for fluid fuel burners,

a motor for discharging combustible mixture into the burner, a switch for controlling motor operation, a transformer having windings located in juxtaposition to the switch so that the magnetic field will operate the same, an electrically heated safety switch in series'with one of the windings, a heating element for said safety switch in series therewith, a resistance in serieswith the other winding and means actuated by temperature changes in the burner to shunt the resistance whereby the ow of current may be varied in that winding which reect's a change in Aflow in the other winding and in the operation of the safety switch by said heating element.

4. In a control system for fluid fuel burners, a j

a heating element for said switch in series with the transformer primary and normally having the transformer no-load current flowing therethrough at all times, said switch controlling the burner circuit, a transformer secondary, a thermostat and a stack operated switch in series with the secondary to cause a high current to flow, -and a resistance in shunt to the stack switch and limiting the secondary current when the stack switch opens.

5. In a control system for fluid fuel burners, a source of current, a transformer relay having a primary and secondary winding, the primary winding being connected to'the source, an electrically heated warp switch and a heating element for said switch connected in series with the primary and normally in circuit at all times, a burner circuit controlled by said warp switch, a thermostat, a resistance, both in series with the secondary winding, a shunt circuit around the resistance, switching means'in the shunt circuit and means responsive to temperature changes of the burner connected to and operating the switching means whereby burner temperatures.

winding being connected to the source, an electrically heated Warp switch and a heating element for said switch connected in series with the primary and normally in circuit at all times, a thermostat, a resistance, both in series with Athe secondary winding, a shunt circuit around the resistance, switching means in the shunt circuit, means responsive to temperature changes of the burner connected to and operating the switching means whereby burner temperatures will alter the secondarycurrent and reflect through the transformer to vary the primary current and operate the warp switch, a motor for discharging fuel into the burner and switching means for the motor operated by the transformer relay whereby as the current is reduced when the resistance is included in the secondary the flux of the transformer will maintain the motor switch closed but will be unable to close it.

7. In a system for controlling fluid fuel burners, a burner motor circuit, an ignition circuit,

an electrically heated safety switch controlling said circuits, a heating element for said switch in series therewith, a transformer having its primary in series with said switch and heating element, a secondary circuit for the transformer,

means in the secondary circuit actuated by temperature changes of the burner to vary the ow of current in the secondary circuit to cause a variation of current flow in the primary and thereby control the actuation of said safety switch by said heating element, a burner motor switch in said motor circuit, means including a thermostat in the secondary circuit to control said motor switch,v an ignition switch in said ignition circuit, athermal time element for operating said ignition switch, and a switch in the l secondary in series withv said thermostat and operated by said thermal time element to prevent closure of the burner motor circuit unless lthe ignition circuit is also closed.

8. In'a system for controlling fluid fuel burnondary windings, a burner motor circuit, an ig- 1| nition circuit, an electrically heated safety switch `said relay switch, a thermal time element concontrolling said circuits, a heating element for said safety switch in series therewith and in series with the primary winding, a thermostat and a resistance in series with the secondary winding,

a shunt circuit around the resistance, a switch in said shunt circuit, means responsive to burner temperature connected toand operating said switch, a relay switch in said burner circuit,

mA means including said thermostat for controlling trolied by said relay switch, a normally closed ignition switch'in said ignition circuit operated by said thermal time element, and a switch in the secondary in series with said thermostat and secondary winding, said switch being also operated by said thermal timeelement to thereby prevent closure of said relay switch unless the ignitionl circuit 'is closed by said ignition switch.

' VAUGHN H. HARDY.

Images