US2652106A - Electrical control means for liquid fuel burning apparatus - Google Patents

Description

Patented Sept. l5, 1953 ELECTRICAL CONTROL MEANS FOR LIQUID FUEL BURNING APPARATUS Allen E. Cleveland, Detroit, Mich., assignor to Perfection Stove Company, Cleveland, Ohio, a

corporation of Ohio Application September 8, 1948, Serial No. 48,312

9 Claims. l

This invention relates to the class of electrical control systems for combustion devices and has particular, though not exclusive, utility as a means for automatically effecting a series of operations in response to certain conditions occurring in the functioning of a combustion device.

For the purpose of the present disclosure and explanation, the invention is shown and described herein in connection with an engine heating apparatus incorporating a liquid fuel combustion device that forms the subject matter of the copending application of Marc Resell, Serial No. 674,012, iiled June 3, 1946, now Patent No. 2,509,399, dated May 30, 1950, the present invention embracing improvements in the circuits of an electrical control system for such a heating apparatus--a somewhat similar control system constituting the subject matter of my copending application Serial No. 719,374, filed December 31, 1946, now Patent No. 2,500,663, dated March 14, 1950. The present, as well as my earlier invention just referred to, has special application to combustion devices wherein an electrical igniting element is employed to initiate combustion, and some means is desirably ineluded or required to deenergize said igniting element upon the attainment of proper combustion within the device.

lIhe primary object of my invention is the i),

provision of an electrical control system for heating apparatus incorporating a liquid fuel combustion device, and by means of which system a complete cycle of operation is automatically accomplished which includes a starting or igniting phase, a so-called operating phase, and a shut-down phase, and wherein there is a safety feature that effectively protects the heating apparatus and the various parts of the system from damage in case of failure of combustion during said operating phase, as well as during starting phase.

Other objects and advantages will appear as this description proceeds, in the course of which reference is made to the accompanying drawing wherein the figure is a diagrammatic representation of my improved electrical control system in operative association with a heating apparatus of the liquid fuel combustion type equipped with a fuel pump and a combustion air fan, said apparatus being shown in central vertical section.

The heating apparatus is designated, generally, by the reference letter H. It includes a heat exchanger h in the form of an annular 2 liquid circulating element having a central ue and the usual inlet and outlet connections h2 and h3, respectively. Said exchanger occupies a combustion chamber provided by the upper portion of a casing h4. Situated in the lower portion of said casing is a combustion device 11,5, shown as a burner bowl that is arranged to discharge its products upwardly into the combustion chamber and through the heat exchanger h. Interior parts of the apparatus are so shaped an-d related and so joined to the casing as to set off within the latter a combustion air space h6 to which air is supplied by an air impeller or blower F, hereinafter called the combustion fan, and which is driven by an electric motor f.

The combustion device is equipped with an electrical igniter hl, the terminals of which are designated ha and hf.

Liquid fuel is Supplied to the combustion device by a pump P, desirably of the kind known to the trade as an autopulse pump and which is actuated by electromagnetic means, such as a solenoid, the winding of which is indicated diagrammatically in dotted lines at p3. The outlet of the pump has communication with the combustion device through a pipe p', and receives fuel from a suitable source (not shown) through a pipe p2 that has connection with the inlet of the pump.

A so-called control head or unit C surmounts the heater casing h4 and it is shown as comprising an inverted cup-like shell c', having substantially the same cross sectional size and shape, or diameter, as the casing h4 and it is slightly enlarged at its open end and is telescoped over the top of the casing to which it is secured by a Suitable number of screws c3. An outlet for the products of combustion is provided by an elbow c4 which has the end 0f its vertical branch extended into the ue of the heat exchanger h', while its horizontal branch is projected through an opening in the peripheral wall of the shell c', the elbow and shell being welded together about said opening so as to make a rigid structure of two parts. The outer end of the horizontal branch of the elbow is equipped with a clamp ci5 by which a flexible conduit or other type of iiue may be fastened to the element for carrying oil the products.

l'astened to the side of the shell c opposite that through which the horizontal branch of the elbow c4 projects, is a bracket c" that supports a switch c8 of a type known as a Micro switch, although switches of other suitable types may be substituted. The Micro switch includes a leaf 3 spring conducting element C that is suitably fastened at its upper end to a part of the switch casing C11, and its opposite end swings between and alternately engages contacts C14 and C15. The conducting element C10, by reason of its normal shape and inherent resiliency is biased toward and (if not otherwise influenced) held in engagement with the Contact C15; and it is adapted to be swung into engagement with the Contact C14 by movement of a plunger C10 that is guided within a bore of the casing C11 and has a head that engages the Conducting element near the fixed end of the latter, wherefore a very slight movement of the plunger is required for swinging the conducting element from the Contact C15 to the Contact C14.

The outer end of the plunger C10 is engaged by a lever C18 that is pivoted on a pin C19, supported by and between the sides of the bracket C1. A relatively short distance above the pivotal axis of the lever C10; compared to the distance between said axis and the point of Contact between the lever and the thrust pin C10, said lever is provided with an opening within which is guided the head of an adjusting screw C20, said headv and opening being shapedI to prevent turning of the former within` the latter. A nut C21 is threaded on the screw C and bears against the lever C10. Fastened tothev head of the adjusting screw C20, as by having its encl brazed within an axial bore of the head, is one end of a thermostatic tension element C24, This element, in the present embodiment, consists of a wire of heatv resistant thermosensitive metal, and its end opposite the screw C20 is projected through a hole in the bottom of theV horizontal branch of the elbow C4 a short distance outwardlyy beyond the plane of the wall through which said elbow projects and is turned back and welded to said wall immediately below said branch. The member c and elbow c4 have apertures that are in alignment with the hole in the bottom` of the branch c4 through which the fixed end of the element C24 passes and the connection between the opposite end of said element and the screw C20 for the accommodation of said element. When relatively cool, as when subjected to atmospheric or ambient temperature, the ther,- mostatic tension element is suiiciently' taut to hold the lever C18 in a position which, through the-intervention of the plunger C10, will maintain the conducting element C10 of the Micro switch C11-in engagement with the contact C14,v as illustrated in the drawing. When subjected to the temperature ofthe hot products of combustion that rise fromv the combustion device h5 through the heat exchanger h and escape through the elbow C4, said element will expand and relax its tension, allowing the conducting element C10 of the Micro switch to swing into engagement with theY Contact C15. Obviously (all other factors being constant), the time element involved in this operation may be Varied by changing the tension of the element C24, and this s accomplished by adjusting the nut C21 along the screw C20. to-the upper end of the bracket c7 and is held thereto, and to the member C', by screws C28;

By reason ofthe fact that the functioning of the. control head is dependent entirely upon the linear expansion and contractionr of the thermo- Static tension element, and in viewl of the relatively small crosssectional area of said element, which causes it to absorb and give up heat at a very rapid rate, the control head is quick and To protect these parts, a cap C27'is applied lOV accurate in operation. In other words, it responds quickly when subjected to the exact temperature value at which it .is set to shift the conducting element of the switch c8 from one contact to the other.

I shall now proceed to describe the other electrical devices and circuits represented diagrammatically in the drawing, and which, with the beforementioned parts incorporated in the control head, constitute the electrical control system of my invention by which is automatically accomplished a series of operations in orderly sequence, inaugurated by the lighting of the combustion device.

Briefly, the control system embraces a comparatively low resistance main circuit, shown in the drawing in relatively heavy lines. This main circuit includes a source B of electric current, represented as a battery; an overload cutout thermo-switch O (which may be any of the well known varieties); the conducting element C10 of the switch C8 that is incorporated in the control head C, and the Contact C14 thereof; contacts 2| and 20 of a voltage relay V2; a high current relay A, illustrated diagrammatically as a solenoid; the resistance heating coil t of a time-temperature cutout switch T (which involves, also, a thermosensitive element t2, shown as a bimetal strip, andY which is in circuit closing position when cold,I as indicated in the drawing), and the electrical igniter h1 ofv the combustion device h5. The conductors which-y with the foregoing electrical devices, make up the main circuit, will be presently introduced by reference characters.

Branching from said main circuit is an auxiliary one including a switch S that is in series with a thermostat R, as will hereinafter more fully appear. The thermostat R is subjected to the temperature that is to be, controlled. Said auxiliary circuit also includes a Voltage relay V. This voltage relay acts, when energized, to close two circuits. The rst of said circuits includes the previously mentioned voltage relay V2 (which,

.. as will presently appear, controls the main circuit), and the second of said circuits includes a voltage relay V4, the latter, upon being ener.- gized, closing a circuit through the thermosensitive element t2 of the beforementioned timetemperature cutout switch T, as well' as through the winding p2 of the pump actuating electromagnetic means previously referred to.

The two circuits last referred to eifect a cycle of operation of the combustion device which includes a starting phase and a so-called normal operating phase. I shall'rst describe the circuit responsible for the starting phase, and therefore termed the starting circuit. Preliminary to this, however, I shall complete the main and auxiliary circuits by introducing the conductors thereof.

One terminal of the battery B isr grounded through a conductor l, while the other terminal thereof is connected, through a conductor 2, to a resistance heater o that forms a part of the overload cutout switch O and is in a position to heat the thermosensitive element o2 (shown as a bimetal strip) thereof; Said element o2 is normally in circuit closing position, as when cold; as

indicated-in-the drawing. When said element o2 is heated and warps tocircuit opening position, it is held in such position, as by a latch o3, until manually released. A conductor 3 leads from the other side of the said overload cutout switch to a junction represented at 4. From this junction a conductor leads to one side of the switch S, while the other side of said switch is connected, through a conductor 6, to the thermosensitive element of the thermostatic switch R. A contact r', into engagement with which the thermosensitive element of the switch swings when subjected to a sufficiently low temperature, has connection, through a conductor l, with the coil of the relay V which is grounded through a conductor B.

It is evident from what has so far been said that when the switch S is closed, and it is assumed that the overload switch O` and the thermostatic switch R are closed, that current will ow from the battery through the switch O, conductors 3 and 5, switch S, conductor 6, thermostatic switch R, conductor l, the coil of the relay V and conductor 8 to the ground. Upon energization of the relay V', a switch element Iii, that is swung from normal to circuit closing position by the armature of the relay, bridges contacts Il and I2, resulting in the closing of the two circuits previously referred to, one as the starting circuit, and which will presently be described. A part of the current supplied by the battery passes the junction 4 and continues through a conductor I3, past a junction I4, and via a conductor I5 to the conducting element 010 of the switch C8 that is incorporated in the control head C.

During the starting phase of the operation, which is at present under consideration, the thermostatic tension element C24 of the control head is cold, so to speak, and, therefore sufficiently taut to act, through the lever C18 and plunger C16, to hold the conducting element c1 of the switch c8 against the contact C14. Consequently current will continue on through a conductor it, past a junction I'I, to the coil of the relay V2, and thence through a conductor I8 to the previously mentioned Contact I I of the relay V. As will be remembered, this relay V has previously been energized to swing the switch element IEB into engagement with the contacts II and I2, Wherefore the current owing through the circuit last W described, involving the conductor I8 and the Contact Il, taking the course of least resistance will be grounded through a conductor I9. Energization of the relay V2 causes the switch element 20 thereof to engage a contact 2| that is included in the circuit that branches off from the junction Il of the previously described circuit involving the conductor I6. The greater part of the current reaching junction il continues through the contact 2 l, switch element 2l), and conductor 33 through the coil of the first described relay A, the current continuing on through conductor 34, the resistance heater t and conductor 35 to the terminal h8 of the igniter hl, the other terminal h9 of the igniter being grounded through a conductor 36. It may be explained that a relatively heavy current is required to operate the relay A and cause it to move a switch element into engagement with a contact 4I that joins the previously mentioned conductor 34. When the relay A is energized it closes a circuit including the contact 4I, whereupon current will iiow through a conductor i2 to its junction 43 with a conductor 2l. This conductor is represented as including a resistance 3l, which as designated on the drawing, is symbolic of a distributed resistance in the circuit whereof said conductor is a part. Accordingly, a relatively small amount of the current passing relay A will reach the conductor 21 through the path just described-that is to say, by way of the contact 4I, element 40 and conductor 42 to junction 43. From junction 43 a part of the current will go in one direction through the conductor 21 to a contact 28, and thence through the thermosensitive element t2 and a conductor 29 to the coil p3 of the electromagnetic operating means of the pump P and thence to the ground through a conductor 3i). The remainder of the current reaching junction 43, will momentarily pass in the other direction through the conductor 21, past junction 26, through the coil of the relay V3, conductor 25, contact I2, circuit closing element I0 and conductor i9 lto the ground. This will result in the relay V3 operating to close the circuit between the contact 45 and element 46, thereby to eiect a flow of the current supplied to the pump operating means through a path described as follows: from junction I4, through a conductor 50, to element 46 and thence through contact 45, conductor 2l, thermostatic element t2 and conductor 29 to the coil p3 of the pump and on to the ground through the conductor 36. A part of the current flowing from junction I4 will flow past junction 25 through the coil of the relay V3 and, through a path already described, to the ground, thereby to maintain the relay V3 energized and, as a consequence, the circuit closing element 45, in engagement with the contact 45. Thus, it will be seen that, when this point in the operation of the system is reached the relay V3 will serve to lock in the pump circuit, and this condition will continue so long as the system is in operation. It will be understood that the impedance, as symbolized by the resistance 3l, of the circuit represented by conductor 50, the conducting element 46 and contact 45 of relay V3, conductors 2l and 42, and the conducting element 4i) and contact 4I of relay A (which circuit is closed when the relay A is energized), is of sufficient magnitude as compared to the impedance of relay coil A to prevent that current necessary for the continued energization of relay A from being diverted through said circuit and short circuiting said coil.

Remembering that We are still concerned With the starting phase of the operation, with the conducting element C10 of the control head switch cs in engagement with the contact C14, due to the fact that the thermostatic tension element C24 is cold, so to speak, the igniter h7 is supplied with current through the ignition circuit already described. Now, with the pump operating to supply fuel to the combustion device h5, and with the igniter hr1 energized, the latter will vaporize and ignite the fuel and start the combustion device in operation, provided that conditions are normal.

At this point it may be explained that there is an advatnage in supplying a limited amount of air to the combustion device h5 during the starting phase. Such amount, however, should be much less than that required during the normal operating phase. Consequently, I desire to provide a circuit for supplying a limited amount of current to this`A combustion fan motor y" at the time the igniter hl is energized. Therefore, I include a circuit represented in part by a conductor 5I that leads from conductor 33 to one terminal of a resistance element 52, the other terminal of which is connected, through a conductor 53, to one of the binding posts `of the combustion fan motor f', the other binding pest of which is grounded through a conductor 54. The conductor 53 also electrically connects the combustion fan motor f with the contact C15 of the control head switch e8. Intermediate the point at which the resistance element 52 has connection with the conductor 53 and the combustion fan motor, a signal circuit branches from the .conductor 53 which is represented by a conductor 55, an incandescent lamp 56, and a conductor 51 that leads to the ground.

Accordingly, during the starting phase, a limited amount of current flows through the conductor l, past the resistance element 52, and by way of conductor 53, through the combustion fan motor, and on to the ground, causing the fan motor to turn relatively slowly and supply a draft of air to the combustion device which will aid in initiating combustion. At the same time, this condition wil be indicated by a Weak glow of the lamp 56.

With combustion under way, the products will rise into the combustion chamber and pass out through the flue of the heat exchanger h' and on through the passage provided by the elbow c4. The heat imparted under these conditions to the thermostatic tension element C24 will cause said element to expand and lengthen suiiciently to relax the pressure of the lever C18 on the plunger 016-, thereby to permit the conducting element C of the switch o8 to shift from contact 014 to contact, C15, thus interrupting the flow o1 current through the circuit represented in part by the conductor le and including the coil of the relay A. Deenergization of this relay causes withdrawal of the circuit closing element 4G from the contact 4| which opens the ignition circuit. Opening of the aforesaid circuit also deprives voltage relay V2 of c-urent, resulting in thev Withdrawal of element 2U. from contact 2l of said voltage relay. Although deenergization of the relay A causes withdrawal of the circuit closing element ll from the Contact 4I, this has no effect upon the supply of current to the pump, due to the fact that the pump circuit is locked in by the relay V3, as previously described.

Therefore,` the pump will continue to supply fuel to the combustion device, and to meet the demands of normal operation, the motor of the combustion. fan F wil be operated at full speed by current now supplied from conductor l5,

through conducting element c1 of the switch c5',

contact. C and conductor 53. rIhe fact that the fan is now operating at full speed will be indicated by abrilliant glow of the lamp 5S, to which a greater amount of' current is. now supplied from the fan circuit.

Thenal or shut-down phase ofV operation of the control system may be effected manually by opening the switch S, or it may result from the opening of the thermostatic switch R caused by a rise, to a given value, of the temperature to which said thermostatic switch is subjected. Upon the opening of the auxliary circuit at either of these points, the relay V is deenergized'- This resultsin the. circuitV closing element L'li withdrawing from the contacts Il and I2'. The breaking of ther circuit including the last mentioned corrtact causes deenergization of the relay V3. This results in the opening of the pump circuit. by the withdrawal of the switch element e5 from the contact 45. Consequently, the combustion device n.5 will be deprived of fuel, excepting for that which remainsin the device at the time` the pump circuit is interrupted. In order that this remaining` fuel may be consumed without creating a smoky condition and the formation of an undue amount of carbon, it is necessary to keep the combustion fan running until said fuel is consumed. This is automatically brought about by the fact that the thermostatic tension element c24k remains heated so long as combustion prevails, and, therefore, in sufficiently relaxed condition to leave the conducting element C10 of the switch o8 in engagement With the contact 015. It is through this contact that current is supplied to the motor f of the fan for normal operation of the latter. When the fire dies out and the heat subsides and the thermostatic tension element C24 cools and contracts and thus recovers its former tension, it will function, through the intervention of the lever 018 and plunger C16, to shift the conducting element c1 from contact C15 to contact C14, thus conditioning the system for a subsequent operation.

During the foregoing description of the cycle of operation of the heating apparatus and its control system, it has been assumed that all conditions are normal. There are times, however, when abnormal conditions occur, as will hereinafter be explained, when the system functions to safeguard the apparatus and associated parts from injury under these abnormal conditions. Such abnormal conditions may consist of failure of the fuel to ignite; the lack of fuel, or a short circuit anywhere in the system.

In the event the fuel in the combustion device fails to ignite, prolonged flow of current through the ignition circuit will build up sufficient temperature in the resistance element t of the timetemperature cutout switch T to cause the thermosensitive element t2 thereof to withdraw from the contact 28., thus interrupting the pump circuit at this point and preventing ooding of the combustion device with fuel. If this condition prevails for any appreciable length of time, as for exam-ple, four or five minutes, suicient heat 'will build up in the resistance element o of the cutout O to cause the thermosensitive element o2 thereof to withdraw from the contact wherewith it normally engages. The element o2 will be held out of engagement with said contact by the latch o3, even after said element cools and until an opportunity is afforded to correct the conditions responsible for the present failure. After correction of such conditions the latch o3 may be released to allow the circuit to close at the cutout O, thereby to place the system in condition for a repetition of the starting phase, it being understood. that, upon cooling due to decnergization of the resistance element t', the thermosensitive element t2 resumed normal condition and closed the pump. circuity at the contact 23.

.In case the supply of fuel to the combustion device stops from any cause during a normal operating phase, the fire will go out and the :ierinostatic tension element c24J will cool and contract wd, through its operative connections with the control switch es, shift the conducting element C10 of the latter out of engagement with the con-tact C15 and into engagement with the contact cli, thus conditioning the system for a starting phase of operation. Naturally, if the cau-sel of the trou-ble is not removed, the heating apparatus will fail. to function and conditions of the system will remain unchanged until suicient heat builds up in the` resistance element o to cause the cutout` to open the circuit in the mannel1 already described. Likewise, if a short circuit occurs in the system, the cutout O will function in the manner stated to shut down the system.

I-n. case the thermostatic tension element 024 breaks during a normal operating phase, the heating apparatus and system will continue to operate in a normal way until the auxiliary circuit is opened, either at switch S, or at the thermostat R; but, under these conditions, while the blower will continue to run with the advantageous effect of thoroughly purging the combustion apparatus of gases before it can be reignited, the system will not operate automatically to reestablish the ignition and pump circuits until the broken thermostatic tension element is replaced.

Having thus described my invention, what l claim is:

1. In an electric control system for a liquid fuel combustion device, means governing the supply of fuel to said device, an electric actuator for said means, an electrical igniter for the combustion device, an air im`^eller for supplying combustion air to the device, an electric motor for driving said impeller, a source of direct electric current, a circuit closing instrument, an electric control-unit switch having two circuit closing positions represented, respectively, by a iirst contact member and a second contact member and characterized by a conducting element movable alternately into engagement with one and the other of said members, a rst circuit closing relay involving two circuit closers, a second circuit closing relay, a third circuit closing relay, and a fourth circuit closing relay, each relay comprising an energizing coil and a circuit closer; a main circuit including said source, said conducting element of the control unit switch and the first contact member thereof, the circuit closer of the second relay, the coil of the third relay, and the igniter; an auxiliary circuit, branching from the main circuit between said source and the controlunit switch and including said circuit closing instrument and the coil of the rst relay, and energizable by said source of current; a branch circuit also energizable by said source of current and leading from the main circuit between the first contact of control-unit switch and the circuit closer of the second relay and including the coil of the second relay and one circuit closer of the first relay; a second branch circuit energizable by said source of current and including the second circuit closer of the first relay, the coil of the fourth relay, and the actuator of the fuel supply means; a shunt between the main circuit, at a point intermediate the coil of the third relay and the igniter, and the second branch circuit, at a point intermediate the coil oi the fourth relay and the fuel supply means, and including the circuit closer of the third relay, and through which shunt said second branch circuit is first energized; a second shunt between the second branch circuit, at a point intermediate the coil oi the fourth relay and the last named point, and the main circuit at a point in the latter between its junction with the auxiliary circuit and the control-unit switch and including the circuit closer of the fourth relay, and through which second shunt the second branch circuit is supplied with current after the first mentioned shunt is opened; a circuit leading from the second contact member of the control-unit switch and including the electric motor of the air impeller, and a thermostat subjected to the heat of the combustion device and having operative connection with the conducting element of the controlunit switch for causing said element to move out of engagement with the rst contact member of said switch and into engagement with the second it? contact member thereof when said thermostat is heated.

2. An electric control system comprising the combination and arrangement of parts dened by claim l, and, in addition thereto, a circuit leading from the last mentioned circuit at a point between the second contact member of the control-unit switch and said motor to a point in the main circuit intermediate the circuit closer of the second relay and the coil of the third relay, and a resistance element included in the last mentioned circuit whereby the motor is caused -to operate at relatively low speed while the igniter is energized.

3. An electric control system comprising the combination and arrangement of parts defined by claim l, and, in addition thereto, a thermostatic switch in the second branch circuit serving, when cold, to maintain said circuit closed, and an electrical resistance heate;x in the main circuit in heating relation to said thermostatic switch to actuate said thermostatic switch after the igniter has been energized for a given period of time.

4. ln an electric control system for a liquid fuel combustion device, means governing the supply of fuel to said device, an electric actuator for said means, an electrical igniter for the combustion device, a source of direct electric current, a circuit closing instrument, an electric controlunit switch including a contact member and a conducting element movable into and out of engageznent with said member, a first circuit closing relay involving two circuit closers, a second circuit closing relay, a third circuit closing relay, and a fourth circuit closing relay, each relay comprising an energizing coil and a circuit closer; a main circuit including said source, said conducting element of the control-unit switch and the contact member thereof, the circuit closer of the second relay, the coil of the third relay, and the igniter; an auxiliary circuit, branching from the main circuit between the source and the control-unit switch and including said circuit closing instrument and the coil of the iirst relay, and energizable by said source of current; a branch circuit also energizable by said source of current and leading from the main circuit between the control-unit switch and the circuit closer of the second relay and including the coil of the second relay and one circuit closer of the first relay, a second branch circuit energizable by said source of current and including the second circuit closer of the rst relay, the coil of the fourth relay, and the actuator of the fuel supply means; a shunt between the main circuit, at a point intermediate the coil of the third relay and the igniter, and the second branch circuit, at a point intermediate the coil of the fourth relay and the fuel supply means, and including the circuit closer of the third relay, and through which shunt said second branch circuit is first energized; a second shunt between the second branch circuit, at a point intermediate the coil of the fourth relay and the last mentioned point, and the main circuit at a point in the latter between its junction with the auxiliary circuit and the control-unit switch and including the circuit closer of the fourth relay, and through which second shunt the second branch circuit derives current after the iirst mentioned shunt is opened.; and a thermostat subjected to the heat of the combustion device and having operative connection with the conducting element of the control-unit switch for causing said element to withdraw from the contact member of said switch when said thermostat is heated.

V5. In an electric control system fora liquid `Jfuel combustion device, means governing the zsupply of fuel to said device, .an electric vactuator for said means, an electrical igniter for the combus- .tion device, a source of direct electrical energy, .a control-unit switch, a .thermostat subjected to the .heat of the combustion device and 'having operative connection with said switch, three relays, each comprising an lenergizing coil vand a circuit closer, a main circuit including said source, said switch, the circuit closer of the rst relay, the coil Iof the second relay, and vsaid igniter; a branch circuit energizable by said source of energy and leading from the main circuit in advance of the circuit closer of the first relay and including the coil of said first relay; Va second branch circuit energizable by said source of energy and leading from the main-circuit intermediate said source and the control-unit switch and including the circuit closer of the third relay and the aforesaid actuator, a further circuit energizable by said source of energy and leading from the second branch circuit between the circuit closer .of the third relay and said actuator and including the coil. lof sai-d third relay, and a shunt between the main circuit, at a point intermediate the coil of the second relay and the igniter, and the second branch circuit at a point intermediate the circuit closer of the third relay and said actuator, said shunt including the circuit-closer of said second relay, the thermostat, when heated, causing the control-unit switch to open.

6. In an electric control system for use with a liquid fuel combustiondevice, electrical means for supplying fuel `to said device, an electrical igniter for the device, a control-unit switch, a thermostat subjected to the heat of the combustion device, operative connections between said thermostat and said switch, the switch being closed when the thermostat is cool and open when the thermostat is heated, a source of direct electrical energy, a main circuit including said source and separating into a first branch and a second branch, a relay comprising a ycoil and a circuit closer., the first branch including said switch, the coil of said relay, and the igniter, the second branch including the fuel supply means, a shunt .between the first and second branches from a point in the first branch intermediate the igniter and the coil of said relay to a point in the second branch on the source side of the fuel supply means, .and including the circuit closer of said relay, the relay coil in the first .branch serving, when energized, to hold said circuit closer of .the relay .in circuit closing position, a second vcircuit closer in the second branch between the shunt and the main circuit and having an associated electrical means for actu-ating it, said latter electrical means being in a leg from the second branch that is in parallel circuit relation with said fuel supply means and that leads from a point in said second branch between the second circuit closer and the .shunt and serving to maintain the second branch closed after the aforesaid switch is opened by the thermostat in response to heat generated by the combustion device.

7. In a direct current electric control system for use with a liquid fuel combustion device, a source of -direct electric current, an electrical actuator for effecting the delivery of fuel to said device, an electrical igniter for the combustion device, an air impeller for supplying combustion air to said device, an electric motor for operating said impeller, an electric control-unit switch having two circuit closing positions represented, respec- 12 tively, by a first contact member and a second contact member and characterized by a conducting element movable alternately into Yengagement lwith one and the other of said members, a thermo'stat lsubjected to the heat of the 'combustion device, operative "connections between said thermostat 1and Vsaid conducting element, the latter being in engagement with therst contact memiber when the Vtl'iermostat 'is cold and in engagement with the second contact member when the thermostat is heated, fan 'electric circuit energizable by said source of current and including the 'first contact ymember of said switch and the igniter, a second electric circuit energizable by said source of current and including the other contact member Kof said switch land said electric motor, a Arelatively high Vresistance circuit leading from a junction 'with the Afirst 4mentioned circuit intermediate said rst contact merriber and the igniter to a junction with the second circuit intermediate said iot'her cont-act member and the :electric fmotor, 'said 4high resistance circuit being energizable by said ysource oi current, and :an- -other electric circuit in Aparallel circuit relation 'with said control-unit switch and -energizable by :said 'source land including the :aforesaid electrical actuator.

8. An electrical control system comprising the `combination and arrangement lof parts donned by claim 7, and, in addition thereto, -a iur-ther electric Vcircuit energizable by said lsource of current and branching 'from the -second circuit intermediate Vsai-d junction and the mot-cr, .and yan :electrical indicator yin said vfurther circuit for 'indicating the vstrength 'of the current flowing therethrough.

9. In an electric :control system for use with a liquid fuel combustion device, electrical lmeans for supplying fuel to 4said device, an electrical igniter for the device., an :air `impeller vfor supplying ycombustion air to the device, an electric motor for driving lsa-idiirnpeller,:a control-unit switch having two circuit closing positions represented, respectively, by a i'lrst contact member and a second contact member 4and characterized by -a conducting element movable alternately into Aengagement with one and the other of said 4contact members, a lthermostat subjected to .the heat of the combustion device, operative connections betweensaid thermostat and the conducting element of said control-unit switch, ,said'conducting element engaging the iirst contact member when the thermostat is cool and `.the second contact member when the thermostat is heated, a source of electrical energy, a first circuit closer, a second circuit closer, a nrst felcctni'cal means and a second electrical means which serve, when individually energized, to hold the respective .circuit closers in circuit closing position, :a main circuit including said source andseparating into a first branch and `a second branch, the rst branch including said conducting element, the first contact member of said .control-unit switch., `the :first electrical means and the igniter, the ,second branch leading from the main circuit .in advance of the controlunit switch and including the secondcircuitcloser and the fuel supply means, a `shunt including said rst circuit closer and extending from the first ybranch at A'a point :intermediate 'the iirst electrical means and the igniter to the second branch intermediate the second circuit `closer and the fuel supply means, said second electrical means having electrical connection with the second fbranch at apoint in the latter .intermediate the second circuit closer and the junction of said shunt with the second branch, whereby said second electrical means is irst energized by current supplied thereto through said shunt and through the intervening part of the second branch, and, upon the shifting of the conducting element of the control-unit switch from the rst contact member to the second contact member in response to the action cf the thermostat when heated, is thereafter maintained energized by current supplied from the main circuit through the second circuit closer, and a further circuit energizable by current from said source and including the second contact member of the control-unit switch and the electric motor of the impeller.

ALLEN E. CLEVELAND.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date Booth Dec. 4, 1928 DeLancey Nov. 19, 1935 Pagano June 15, 1937 Kriechbaum Feb. 15, 1938 Bergey Aug. 8, 1939 Brace Oct. 3, 1939 Mason Sept. 9, 1941 Taylor Sept. 15, 1942 Fox Sept. 25, 1945 Hall May 7, 1946 Cleveland Mar. 14, 1950 Collins et a1 June 27, 1950

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