US2581636A - Oil burner safety control system - Google Patents

Description

OIL BURNER SAFETY CONTROL SYSTEM Filed April 9, 1948 COMBUSTION CHAMBER CHIMNEY LIMIT 1,65 [0/ CONTROL TRANSFER SWITCH SAFETY TIMER.

145 7i gi RELAY Mn Q TH ERMOSTAT OR Pl LOT Patented Jan. 8, 1952 OIL BURNER SAFETY CONTROL SYSTEM Lewis L. Cunningham, Sherman Oaks, Calif., and Albert L. Judson, Portland, Oreg., assignors to Iron Fireman Manufacturing Company, Portland, Oreg.

Application April 9, 1948, Serial No. 20,008

4 Claims.

This invention relates generally to electrically operated and controlled oil burners and more particularly to the control of the driving motor and the ignition mechanism of such a burner.

An electrically operated oil fired heating system generally requires the use of a temperature or pressure responsive limit control, a condition responsive control, and a combustion temperature responsive primary control including relay and safety functions. Limit controls such as pressure controls and furnace switches are well known as are also condition responsive controls such as pressure regulators and thermostats. Instruments of these types are used with the primary control of this invention but are not part of the invention.

It is an object of this invention to provide a primary control having a direct, reliable and greatly simplified circuit scheme which can be readily understood by a service man.

The methods and mechanisms for accomplishing these and other objects are explained in the following description referring to the single figure of the attached drawing which shows diagrammatically the circuits and mechanism of this invention.

Referring to the single figure of the drawing there is shown a combustion chamber connected by a smoke pipe to a chimney. For purposes of description it is assumed that the combustion chamber is surrounded by a chamber through which is circulated a heating medium such as air or water which is transported in the usual way to a space to be heated. The thermostat instrument is assumed to be in the space or medium whose temperature is to be controlled and the limit control is assumed to be so situated as to be responsive to the temperature of the heating medium surrounding the combustion chamber.

As shown in the figure, tension spring 62 acting through lever 46, adjustable fulcrum 6|, and lever 58, biases temperature insensitive stem 4| toward the smokepipe where it bottoms on the inner end of temperature sensitive tube 40. As the temperature in the smokepipe increases stem 4| recedes in the smokepipe and the left end of lever 46 is moved downward by spring 62. As temperature in the smokepipe decreases, tube 40 contracts forcing stem 4I downward and the left end of lever 46 upward against the bias of spring 62. The relative movements of stem 4| and lever 46 is adjustable by right or left movement of fulcrum 6| and is indicated by pointer 54 on scale 55. Held in lever 46 are friction blocks 52 which frictionally engage stem 48 and cause stem 48 to travel with lever 46 within the range of movem t 9- termined by the adjustable top in the cooling direction and by the limit of throw of resilient switch arm I60, to which lever I68 is secured. in the heating direction. Resilient switch arm I60 is biased towards the open position of contacts I31, I12 and towards the closed positions of contact pairs I66 and I61 by the action of permanent magnet I55 on armature I64 secured to arm I60. Arm I60 is stiff enough for the lever action of blade I68, when forced by stem 48, to cause armature I64 to overcome the biasing action of magnet I55 and come to rest against adjustable stop I65.

The safety timing switch has two bimetal blades I49 and H2 substantially parallel and similarly affected by ambient temperature. Additionally blade 2 is affected by its associated electric resistance heater 5 when the circuit in which the heater is connected is energized. Resilient blade I48 carries insulating rigid bar I16 to which it is riveted with silvered rivets. Bar I16 is secured with a hollow rivet to conducting resilient leaf spring I80. Leaf spring I is secured with silvered rivets to stiff conducting bridge I18. A depending tongue on bimetal blade I49 inserts through slots in bar I16, leaf I80 and bridge I18 and bears laterally on bridge I18 to compensate for the effect of ambient temperature on blade I I2 and therefore to maintain the proper relation of the right hand end of bridge I18 with the lower end of blade II2 with which it is normally engaged. When electric current passes through resistance heater II5 for a predetermined time bimetal blade II2 warps to the right sufliciently to slide off the end of bridge I18 the right end of which is biased upwardly by both support I48 and leaf I80. When this occurs the circuit from blade I48 to blade H2 is interrupted both at the junction of bridge I18 and blade I I2 and by the separation of the rivet heads at the left end of bridge I18 from the rivet heads at the lower end of blade I48. To reset the switch it is necessary to allow blade I I2 to cool and then manually to press the right end of bridge I18 downward until blade II2 can spring back into place over the right end of bridge I18.

The relay switch comprises three stationary contacts I34, I45, and I40 and three moving contacts 84, 96, and 90, carried respectively on resilient switch blades 83, 95, and 88, formed to bias the moving contacts towards their respective stationary contacts. The relay operator comprises frame I84, coil I85, armature I86 hinged to frame I84 and toggle compression spring I94 biasing armature I86 to the open position of the switch contacts as shown. Operating lever I26 linked to e armature I86 by adjustable stop screw I3I and arcuate spring I98 allows the switch contacts to close when coil I85 is energized and opens the switch contacts 'due to the action of spring I94 overcoming the bias of blades 83, 95, and 89 when coil I65 is ole-energized.

In actual use with an oil fired heating system, the primary control is usually mounted with heat responsive tube 49 extending into a smoke pipe connecting a combustion chamber with a chimney. The primary control is supported on tube 36 which extends into a close fitting flanged collar attached to the smoke pipe. The electric service will usually be single phase, 110 volt, 60 cycle having two service wires one of which will be at earth potential. The service will be supplied through a fused switch and then the grounded line will be brought in to terminal I62 of the primary control while the hot line will be connected through a suitable limit control and then connected to terminal IIII of the primary control. The oil burner driving motor will be connected between terminals I03 and I02 of the primary control and the oil burner ignition transformer will have its primary (110 volt) winding ccnwill :be in operrcircult position, no current will be drawn from the low voltage winding of transformer 14, the relay coil I85 will be Lin-energized, toggle spring I94 will have forced armature I86 upward takingwith it tail I21 of relay lever I26 which will be forced downward and by pressure on contact-carrying and closing springs 63, 89, 95 will have opened the three pairs of relay contacts 84-I34, 9Il-I4Il and 96-445. The smoke pipe is cool or cooling and heat responsive tube 40 has been contracting, forcing head 43 of heat insensitive tube II against lever 59 which in turn presses button 6! against lever 46 overcoming force of spring 62 and through friction of block 52 raising stem 43 thus allowing magnet I55 by its attraction of armature I 64 to rotate switch blade I 69- clockwise, opening contacts ISL-I12 and closing contacts I66 and I 61 againsttheir respective mating stationary contacts.

7 The only closed circuit through the primary control is from terminal IIiI, through I42, hinge I 62, blade I 66, contact I66, conductor I41, sup port I49, rivet head contacts between I46 and I18, contacts I19, vI.I"9,bimetal H2, bolt II 6, resistance I-I5, conductor 1, conductor 296, primary winding of transformer 14, and conductor I99 to terminal I62. Only the small magnetizing current of transformer 14 will be flowing through this circuit.

It particularly should be noted that contact blade I'III-isfrictionally hinged to blade I68 and that the motion'of} blade I1I is limited between an upward-stop and contact I31. This novel arrangementcomb'ined with the magnetically biased action of the right end of blade i66 assures the essential relativeaction of the contacts at the two ends of blade I60, which is that as blade I60 rotates clockwise contact I12 will leave contact I31 before contacts I66 and I61 make their respective stationary contacts and that as blade I 69 rotates "counterclockwise contact I12 will -make contact i 31 before contact I66 and .161

I44, I45, 96, 95, 9E, and I64.

the thermostat closes the secondary circuit of transformer 14 through the relay coil I65. Relay armature I86 is attracted downward taking with it tail I21 of lever I26 which lifts and allows spring members 69, 95 and 69 to close relay contacts 84I34, 96-466, and 9llI49. The burner motor is energized through circuit IOI, I43, I39, I46, 99, 89, 65, and I93. The ignition transformer is energized through circuits I6I, I42, I62, I61, Since current is flowing through the transformer secondary an equivalent load current will traverse the primary winding and this relatively large increase over the small charging current previously flowing will greatly augment the heating effect of resistance II5 on bimetal H2. Screw I 99 previously has been adjusted so that with the transformer load current through resistance II5 bimetal II2 will absorb enough heat to'flex to the right and slip point I I 3 off the end of tongue I19 in approximately ninety seconds (or any other chosen value of time) if the current continues to flow.

Assuming that fuel is available and the burner is working properly the products of combustion will flow from the combustion chamber to the chimney through the smoke pipe and surrounding heat sensitive element 69. As the temperature of the products of combustion rises element 46 elongates and element II retracts allowing spring 62 to pull stem 46 downward through fric tional engagement with bracket 41 of lever 46.- Strap I68 moves downward under the influence of blade 46 and takes with it switch blade I11 and contact I12 which closes on contact I31 and thus closes a circuit between blade I60, I69, I11, I12, I31, I32, I94, 84, 63, and 269, and lay-passes the transformer primary current around the cir-' cuit of heater II5 so that bimetal IE2 starts to cool. Further downward motion of blade I1I by strap I68 is stopped and taken up in the nic tional hinge betweeen I1I and I68, but as strap I69 is further depressed by blade 49, due to a further rise in temperature of the stack gases, blade I69 is strained over hinge support I62 and armature I64 is suddenly lifted away from mag net I55 and contacts I66 and I61 are freed from contact with their respective mating contacts.- After this only two circuits are complete through the control, one to the burner motor through relay contacts I46, 99 and the other through the transformer primary of transformer 14 through transfer switch contacts I12, I31 and relay contacts I64, 64. Ignition is no longer necessary and this circuit is interrupted by the raising of contact I61. After this with everything running normally which means, essentially, that the stack gas temperature is stationary or trending upward the burner will continue to operate as long as the pull of the relay coil on armature I66 is greater than the armature opening thrust of spring I94. Spring I94 will open the relay if the line voltage (and therefore the relay coil voltage) becomes less than suflicient to safely operate the burner motor or if the thermostat is satisfied and opens the low voltage circuit to the relay'coil.

Should the thermostat not be satisfied but the relay opens due to low voltage all circuits through the control will be interrupted and even though the proper voltage is again immediately available the burner will not start until the stack tempera-- ture has dropped sufficiently first to open contacts- I12, I31 and then close contacts I66 and I6! against their respective mating contacts, thus ree turning the control to its original starting COIldie tion,

Again assume that the burner has been started as before but that due to lack of fuel, or other fuel or air difliculty, or due to a fault in the ignition system, the fire is not ignited and the stack gases do not rise in temperature. Friction stem 48 does not move down and transfer switch blade I60 does not move. Transformer primary current continues to traverse heater I I5 and the temperature of bi-metal II2 increases until after about ninety seconds point II3 moves to the right enough to slip off the end of tongue I19 of bridge I18. Biasing spring leaf I48 tips insulator I16 upward and to the right and due to gravitational unbalance as well as the biasing action of leaf spring I80, bridge I falls away at its left end and breaks the circuit contact between the rivets holding I48 to I16 and the rivets holding I18 to I80. Bridge member I18 remains supported from insulator I16 by the loose rivet at its right end and the T-shaped ear near its left end extending through the central slot in insulator I and with its T head resting on the top of insulator I16 at each side of the slot. With the transformer primary circuit thus broken at both ends of bridge I10 the relay drops open and the burner motor stops. Nor can a circuit through the control be reestablished until bi-metal II2 cools and moves to the left sufficiently for point I I 3 to be in position to latch with tongue I19 of bridge I 18. This relatching of I I3 and I19 can only be done manually and is accomplished by means of manually turnable knurled knob 205 to which is secured crank 206 journalled in switch cover I2I and biased in a counterclockwise direction by spring 201. Crank 206 is limited in its rotation by forward stop 208 and backward stop 209 molded on the inside of cover I2I. When cover I2I is in position over switch base 12, crank arm 206 extends into the space above insulator I16 and be tween bi-metal elements II2 and I49. Due to biasing spring 201, arm 206 normally rests against back stop 209. But when knob 205 is rotated to the right, arm 206 contacts the top of insulator I16 and further movement crowds tongue I19 past point I I3 which then springs back into position and latches bridge I18 in its heater circuit closing position.

It should be noted that unheated bi-metal strip I49 has a narrow tongue at its lower end which extends through slots in insulator I16 and bridge I18. When insulator I16 is pushed downward by crank 206 against the bias of conducting spring leaf support I48, all members supported by leaf I48 are moved to the left and the right edge of the slot in insulator I16 contacts the tongue of bi-metal I49. Bi-metal I49 as well as bi-metal I I2 are influenced by the same ambient temperature and with bi-metal I49 biased against the right edge of the slot in insulator I16 it is seen that all of the parts supported from leaf I48 are constrained by bi-metal I49 to take a lateral position responsive to the ambient temperature of bi-metal I49. Since bi-metal H2 is subject to the same ambient temperature it is seen that the degree of overlap of point H3 and tongue I19 is not affected by ambient temperature and there fore the timing of the release of tongue I19 by point 3 is affected only by the heat received from resistor II5 by bi-metal II2. We believe this to be a new and effectively compensated safety timing switch for a primary control.

Now assume that the burner has started normally as above described, the smoke pipe temperature has come up to operating normal and the transfer switch has cut off the burner ignition system. Then assume that something happens to the fire such as running out of oil, partial clogging of the oil nozzle, water in the oil, etc., so that the flame is interrupted and if the burner were to continue to operate a dangerous condition might develop. Any of these conditions would be indicated by a temporary or a continued reduction in the temperature of the products of combustion which would be felt immediately by temperature responsive element 40 and transfer switch contacts I12, I31 would separate thus dropping out the relay and shutting down the burner, after which there would have to be a sufiicient time delay for the stack gases to cool sufficiently for transfer switch contacts I66, I61 to close against their respective mating contacts before the burner would again be startable. In restarting if the flame trouble had been corrected the burner would start normally and continue to operate but if the diftlculty persisted and the flame did not come up normally within the safety time (say ninety seconds), heater I I5 would influence bi-metal II2 to shut the burner down as previously described.

Having thus fully disclosed the circuit of our invention and forms of mechanisms which can be used therewith, and having described the operation thereof, we have defined the invention by the appended claims.

We claim:

1. In a control system for an oil burner, a first circuit including a first pair of relay switch contacts and a burner motor, a second circuit including a, first pairof transfer switch contacts, a second pair of relay switch contacts and ignition means for said burner, a third circuit including a second pair of transfer switch contacts, a normally closed safety timing switch, an electrically energized actuator for said timing switch 1 and the primary coil of a transformer, a fourth circuit including a third pair of transfer switch contacts and a third pair of relay switch contacts, a fifth circuit including the secondary coil of said transformer, a relay operating coil and condition responsive means for closing said fifth circuit to energize said relay coil, means for closing said relay contacts when said relay coil is energized and opening said relay contacts when said relay coil is de-energized, said first, second, and third circuits being connected in parallel across a source of electric power, said fourth circuit being connected in parallel across the transfer switch contacts and the safety switch of said third circuit, and oil burner combustion temperature responsive means for sequentially closing said third pair of transfer switch contacts and opening said first and second pairs of transfer switch contacts when said combustion temperature is trending upward and for sequentially opening said third pair of transfer switch contacts and closing said first and second pairs of transfer switch contacts when said combustion temperature is trending downward.

2. In a control system for an oil burner, a first circuit including a first pair of relay switch contacts and a burner motor, a second circuit including a first pair of transfer switch contacts, a normally closed safety timing switch, an electrically energized actuator for said timing switch and the primary coil of a transformer, a third circuit including a second pair of transfer switch contacts and a second pair of relay switch contacts, a fourth circuit including the secondary coil of said transformer, a relay operating coil and condition responsive means for closing said fourth circuit to energize said relay coil; means forclosing said relay contacts when said relay coil is energized and opening said relay contacts when said relay coil is'de-energized; said first and second circuits being connected in parallel across a source of electric power; said third circuit being connected in parallel across the transfer switch contacts and the safety switch of said second circuit, and oil burner combustion temperature responsive means for sequentially closing said second pair of transfer switch contacts and opening said first pair of transfer switch contacts when said combustion temperature is trending upward and for sequentially opening said second pair of transfer switch contacts and closing said first pair of transfer switch contacts when said combustion temperature is trendingclownward.

3. An electric control system for liquid fuel burners comprising a high voltage supply, a step down transformer having a primary winding and a secondary winding, a first combustion responsive switch which is closed on lack of combustion and opened when combustion occurs, a second combustion responsive switch which is opened on lack of combustion and closed when combustion occurs, means for connecting said primary winding to said high voltage supply including said second combustion responsive switch. and a first normally open switch, means for connecting said primary winding to. said high voltage supply including said first combustion responsive switch a delay switch and an electrically energized operator for said delay switch, an ignition means, a third combustion responsive switch which is closed on lack of combustion and opened when combustion occurs, means for connecting said ignition means to said high voltage supply including said third combustion responsive switch and a second normally open switch, a burner motor, means for connecting said burner motor to said high voltage supply including a third normally open switch, a relay having an operat ing coil, means for connecting said relay coil to said secondary winding including a condition responsive switch and thereby loading said primary winding of said transformer with the equivalent load of said relay coil on said secondary, winding, and means operatively associated with said relay coil for closing said first, second and third normally open switches when said relay coil is energized, whereby when said primary winding is encombustion within the delay time for which said delay switch is pre-set.

4. In a control system for an oil burner: a first circuit including a burner motor and a first normally open switch; a second circuit including a first pair of transfer switch contacts, a normally closed safety timing switch, an electrically energized actuator for said timing switch and an elec 4 tric load; a third circuit including a second pair of transfer switch contacts and a second normally open switch; and means for sequentially closing said second pair of transfer switch contacts and opening said first pair of transfer switch contacts on a rise of combustion temperature, and for sequentially opening said second pair of transfer switch contacts and closing said first pair of transfer switch contacts on a decrease in com bustion temperature; said first and second circuits being connected in parallel across a source of electric power; said third circuit being connected in parallel with that part of said second circuit which includes said transfer switch con.- tacts, said safety timing switch and said actuator; and said electric load including means operable for closing and opening said first and second nor mally open switches in response to -a condition.

LEWIS L. CUNNINGHAM. ALBERT L. JUDSON.

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

UNITED STATES PATENTS Number Name Date 1,366,731 Hoeschen Jan. 25, 1 921 1,376,462 Robertshaw May 3, 1921 1,834,288 McCabe Dec. 1, 1931 1,941,540 Denison et a1 Jan. 2, 1934 1,948,938 Lawton Feb. 27, 1934 1,991,185 Williams Feb. 12, 1935 2,021,407 Erickson Nov. 19, 1935 2,022,188 Denison Nov. 26, 1935 2,117,021 Cotea May 10, 1938 2,195,649 Hallenbeck Apr. 2, 1940

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