US2465675A - Safety control for oil burners - Google Patents

Description

March 29, 1949. w. H. DE LANCEY SAFETY CONTROL FOR OIL BURNERS 3 Sheets-Sheet 1 Filed Jan. 20, 1945 ATTORNEYS March 29, 1949. w H, DE LANCEY 2,465,675

SAFETY CONTROL FOR OIL BURNERS 5 Sheets-Sheet 2 Filed Jan. 20. 1945 m MM m March 29, 1949. w H, DE LANCEY 2,465,675

SAFETY CONTROL FOR OIL BURNERS lllllllrl nnnf'rlnnnn INVENTOR Mifm/K f/wcfy BY y. ya E e ATTORN EYS Patented Mar. 29, 1949 SAFETY CONTROL FOR OIL BURNERS Warren H. De Lancey, Springeld, Mass., assignor to Gilbert & Barker Manufacturing Company,

West Springfield, Mass.,

Massachusetts a corporation o! Application January 20, 1945, Serial No. 573,697

4 Claims. (Cl. 15S- 28) This invention relates to improvements in the safety control mechanism of oil burners for stopping the burner on failure of combustion.

Safety control mechanism oi this class is old and well known in the art. It generally, comprises a time switch, effective to open the circuit to the burner motor in a predetermined time (say 30 seconds) after closing of such circuit by the room thermostat, or other control, provided that combustion does not occur, and a flame-responsive element or name detector, which functions, on occurrence of combustion within the predetermined time, to prevent the opening of the time switch. The flame detector and the time switch mechanism may take various forms and operate in various ways but the general functions accomplished are as stated.

It has been customary heretofore to mount the ame detector, which is generally a thermostat, outside of and separately from the air tube of the burner. It has thus been necessary to cut two holes in the wall of the rebox, one to accommodate the inner end of the air tube of the burner and the other to accommodate the burner thermostat or other flame detector. The name-responsive element should be sighted at the burner name and yet it should be protected against all conditions which are likely to adversely aect its operation and prevent it from functioning in the intended manner.

This invention has for one object to mount the flame detector in the air tube of the burner, locating it so that it is sighted at the ame and yet so that it is suiciently shielded from the air ow through the tube so as not to be unduly inluenced by the presence or absence of a low of relatively cool air through said tube.

Another object of the invention is to locate the burner thermostat in and symmetrically of the air tube of the burner near the outlet end of the tube so that the thermostat does not project into the air stream as an obstruction and cannot therefore interfere with the desired uniformity of ilow of air to the fuel nozzle and cannot therefore disturb the resulting i'lre.

The invention has for another object the provision of a complete safety control mechanism, including a name-responsive element, a safety thermostat or time switch, and a heating element for the safety thermostat, all located in the air tube of the burner and shielded from the air iow through such tube.

Another object of the invention is to locate the 4iiame-responsive element, together with the safety thermostat, and its heating member if desired, in a recess in the inner end of the member. which supports the oil nozzle, so that said element is completely shielded from the air ow through the tube and yet located back of the oil nozzle in confronting relation with the flame from the burner.

Another object of the invention is to utilize snap disc thermostats, one for the ilamerespon i sive element and one for the time switch thermostat, and to mount these snap disc thermostats in opposed relation so that changes in ambient temperature balance out, leaving said element to react solely to the presence o flame at the burner, whereby the flame-responsive element may be mounted in the air tube of the burner and yet function satisfactorily.

The invention will be disclosed with reference to the accompanying drawings, in which- Fig. l is a sectional elevational view of an oil burner embodying one form of the invention;

Fig. 2 is a fragmentary sectional elevational view drawn to a larger scale and iilustrating the burner thermostat and safety switch;

Fig. 3 is an end elevational view of the burner;

Fig. 4 is a cross sectional view taken on the line -e of Fig. 1;

Fig. 5 is a sectional plan view taken on the line 5--5 of Fig. 4;

Fig. 6 is a fragmentary sectional view taken on the line @-5 of Fig. 3;

Figs. 7, 8 and 9 are sectional views taken on the v lines 1 1; 8 3; and S, respectively of Fig. 2.

Fig. l0 is a sectional plan, view showing the mounting of one of the ignition electrodes; and

Fig. 11 is a wiring diagram of a burner control system for the invention.

Referring to these drawings, the invention will be disclosed, by way of illustrative example, in connection with an oil burner of the so-called gun type. Such a burner has a pressure-atomizing nozzle l (Fig. 1) for producing a spray of nely atomized oi! and a tube 2 through which air for combustion is supplied to the oil spray. The forward and open end of tube 2 is adapted to be inserted in an opening in the wall of the rebox of the furnace. The mixture of air and oil is ignited by an electric spark occurring between the electrodes 3 and combustion occurs beyond the end of tube 2 and in said firebox. The invention is not, however, limited to pressure atomization of the oil and is equally suitable f or any burner,

wherein an oil-spray-producing means of any type is surrounded by a tube through which air is supplied and wherein the open end of the tube is inserted in the wall of a rebox so that such open end confrontsthe flame resulting from com- --bustion of the oil and air mixture'.

sighted directly at the flame in the firebox, when` combustion occurs. And the burner thermostat must be shielded sufficiently from the air supply flowing through tube 2 so as not to adversely eect its functioning in the intended manner.

To secure these results, the burner thermostat` or ame detector is mounted back of the spray nozzle I and in coaxial relation therewith and the air flow through the tube is directed away from the thermostat by a member 4, suitably supported in tube 2 in substantially coaxial relation therewith. The oil supply conduit 5 passes through member 4 (Fig. 2) and the nozzle I is threaded into the enlarged outer end 6 thereof. The member 4, as shown in Fig. 1, is approximately cylindrical and its outer end, which lies nearest nozzle I, is provided with a cylindrical recess 'I (,Figs. 2 and 8) having in its inner end Wall an arcuate groove 8. The outer end of recess 'I is counterbored to receive an annular snap disk thermostat 9 which is held in place by a snap ring I or any other suitable means. This snap disk 9 is the burner thermostat or flame detector. This thermostat thus has an annular area which directly faces the flame produced by the burner. At the same time the thermostat, being located in the outer end of recess 'I is effectively shielded from the air flow through the tube 2.

In the form at present preferred, the safety thermostat switch and its heating element are also located in the recess 'I. Mounted on conduit 5 in coaxial relation therewith and seated against the inner end of recess 'I is an annular disk II of suitable insulating material, such as Bakelite for example, suitably held in place as by the screws II (Fig. 7). This disk has three terminal buttons I2, I3 and I4, suitably fixed thereto, with extensions of the buttons I3 and I4 passing through the disk and into the arcuate groove 8. An electric heater, comprising a resistance wire I5 of suitable material is connected to and supported by the buttons I2 and I3. The disk II further has a circumferentially grooved hub I6 (Fig. 2) on which is mounted an annular snap disk thermostat I 1. A snap ring I8 in the groove in the hub holds disk I1 in place axially while a flattened portion I9 (Fig. 9) on the hub I6fls engaged with a corresponding portion in the hole of the disk to prevent the latter from turning. The disk I 'I carries two contacts 20 and 2I for engagement with contacts I2 and I3 on disk II. The burner thermostat 9 has fixed coaxially thereto, a metal sleeve 22 to which is also suitably fixed an annular member 23 of suitable insulating material. As shown, the member 23 and the disk 9 are each held in place against a shoulder on the sleeve 22 by spinning one end of the sleeve against the member or disk as the case may be. The purpose of member 23 is to apply pressure against the outer rim of thermostat I1 and hold its contacts 20 and 2I engaged with the contacts I2 and I3, respectively, if combustion occurs. The two thermostats 9 and I1 are normally bowed in opposite directions,l as shown, whereby changes in -ambient temperature balance out as they tend to move the disks equally but in opposite directions. The safety thermostat I1. when heated by the electric element I5.

tends'to move to the left as viewed in Figs. 1 and 2. If combustion does not occur, disk I'I will snap to the left and, through member 23, press against the central part of disk 9 and cause the latter to snap to the left. Thus, the hitherto engaged pairs of contacts 20, I2 and 2|, I3, will be disengaged and the burner circuit, later to be described, will be opened. The burner thermostat 9, when subjected to the high heat of the flame produced by the'burner, tends to move toward the right with the result that enough pressure is applied against thermostat I1 to hold it in its illustrated and switch-closing position even though thermostat I1 is fully heated by the heater I5.

The safety control described may be automatically or manually reset after having stopped the burner motor on a failure of combustion. These thermostat disks may be made so as to automatically move back from their abnormal to their normal position when the temperature falls sufliciently or they be so made as to remain in their abnormal positions until manually moved back in any suitable way. Thermostat 9 may be constructed in either of these ways although it is generally desired to compel a manual resetting. This may be done by any suitable means. For example, a push rod 24 (Fig. 1), mounted as will later be described in detail, for movement longitudinally of tube 2, has one end accessible from outside the rear end of the tube and the other end pivoted to one end of a lever 25. The latter (Fig. 2) is pivoted intermediate its ends to member 4 and its inner end is adapted to engage and push member 23 ,inwardly,when

rod 24 is pushed inwardly, thereby pulling in.

wardly on disk 9 to snap it back from its left hand position int'o its normal and illustrated position and at the same 'time to snap back thermostat I'I and close the 'safety switch.

In Fig. 11, there is shown, by way of illustrative example, one form of burner control system with which the safety control mechanism of this invention may be used. The electric motor, which causes air and oil to be supplied to nozzle I and tube 2, respectively, is shown at 26 and the ignition transformer which supplies high tension electricity to the electrodes 31s shown at 21. This motor and transformerare connected in parallel in an electric circuit-say a volt circuit-comprising the wires 28; 29 and 30 and a switch 3l, interposed between the wires 29 and 30. magnet 32, which also actuates a 'second switch 33. When the magnet 32 is energized both switches will be closed and when it is deenergized both switches will open. The two switches and electromagnet form the so-called relay commonly referred to in oil burner controls. The magnet 32 is included in a low voltage starting circuit from the secondary of a transformer 34. the primary of which is connected to the supply wires 23 and 29. This starting' circuit is usually closed by a room thermostat switch 35, 4although any other suitable means may be provided-for the purpose. The starting circuit may be traced as follows, from one terminalpfthesecondary of transformer 34 by a wire 36 to one terminal of the room thermostat 35. from the other terminal of the latter by a wire 3,1 to button I2 ofthe safety control mechanism. through contact 20, disk I1 and'contact 2| to button I3, through heater I5 to button I4, thence by a wlr'eg33, to one terminal of magnet 32, and from the other terminal of magnet 32 by'a wire 39 to the other Switch 3I is operated by an electroterminal of the secondary of transformer 34. When thermostat switch closed, magnet 32 is energized and both switches 3| and 33 close. Closure of switch 3| starts motor 26 and energizes transformer 21 to supply the ignition spark across the electrodes 3. Failure of combustion. as heretofore described, causes contacts 20 and 2| to separate from buttons |2 and I3, respectively, and thus open the low voltage starting circuit described, whereupon the relay drops out, opening switch 3| and stopping the burner. Normally, the safetythermostat would be sumciently heated by heater |5 to open the safety switch I1 in about 30 seconds. If combustion occurs within this time, the safety switch cannot open for the reason above described. Closure of switch 33 simply closes a second circuit of lower voltage suiiicient to hold the relay closed once it is pulled in, but insufficient to initially pull the relay in. In place of the wire 39, which connects one terminal of magnet 32 to an end terminal of the secondary of transformer 34, wires and 4| with the interposed switch 33 are provided to connect the same terminal of magnet 32 to a terminal of said secondary which lies intermediate those already described. It will be clear that both the starting and the holding circuits can be opened by the safety control mechanisms on failure of combustion. The invention is not limited to use in the one form of control circuit herein described. The one form of circuit described is merely one illustrative vexample of many control circuits with which the invention may readily be used.

Referring now to the details of the exemplary apparatus, theburner includes a hollow frame comprising end members 40 and 4| (Fig. 1), and a pair of abutting intermediate members 42 and 44 which are interposed between the end members. All these members are held together by a series of screws 43 (Figs. 4 and 5). This frame is supported by a post 45 from a pedestal 46, as indicated in Figs. l and 3. The tube 2 is iixed in an opening in the member 4| in axial alignment with a tubular extension 41 of the member 40. A gasket 48 is interposed between the inner end of extension 41 and the inner face of member 4| to make a tight joint between it and tube 2. The outer end of tubular extension 41 is closed by the ignition transformer 21 which is iixed toa plate 49, connected by a hinge pin 50 to member 40 and normally held in closed position by two screws 5| which pass through plate 49 and thread into member 40. The high tension terminals of transformer 26 are springpressed buttons 52 mounted in insulators 53 xed to the transformer. These button terminals lie inside the air tube near its outer and closed end. The outer end of extension 41 is of larger diameter and receives a two armed spider 54, which spans the extension and has each outer end received between a pair of ribs 55 (Fig. 4) on the extension, thereby preventing the spider from turning. The spider (Figs. 1, 3 and 4) has a central hollow tubular portion 56 which is closed at its outer end and has fixed in its inner end the outer end of the described oil conduit 5. A exible copper tube 51, connected to the portion 56, extends out of the air tube through a recess 58 in member 40 and is connected to the oil pump-a union 51' being interposed in the connection. The ignition electrodes consist of wires 3, each bent as best shown in Fig. l0 and inserted in a longitudinal hole in an insulator 60 with a right angularly bent portion 3b lying in a radial groove in the insulator. A nut 58 threaded on the outer end of each wire 3 holds said bent portion in the groove and holds the wire against longitudinal movement in the insulator. These insulators lie in recesses 6I in the sides of member 4 and are held together by a metal strap 62 which is fixed as by screws 63 to member 4. This member 4 is supported near the inner end of tube 2 by three radial pins 64, the inner ends o f which are screw threaded into member 4 and the outer ends of which b ear against the inner peripheral wall of tube 2. The inner ends of the nuts 59 (Fig. 1) are engaged by the spring pressed transformer terminals 52, whereby the member 4 is thrust inwardly in tube 2 until the outer ends of the spider arms 54 abut the shoulder 64 on extension 41.

The wires 31 and 38 are connected to the portions of their respective buttons I2 and I4 that project into the arcuate groove 8 and these wires extend along the groove to a hole 65 (Fig. 2) through which they pass to a recess 66 (Figs. 1 and 2 in the bottom part of member 4. The wires pass through the tube 2 and include a separable connection comprising a plug 61 and socket 61' (Fig. 1), the former being suitably attached to the member 4. These wires pass radially out of the rear end of the air tube 2 (Figs. 1 and 5) into a compartment 68 (Figs. 4 and 5) which is formed in the hollow frame member. Fixed in this compartment is a panel 10, bearing the relay 32 and the transformer 34. This compartment is normally closed by a cover 1I (Figs 1 and 5) having on one side spaced hinge lugs 12 (Fig. 5) bearing on ribs 13 on one wall of the compartment 69 and having on the other side ya spring 14 which snaps into a recess in the other wall of the compartment to hold the cover closed.

The electric motor 26 (Fig. 3) is suitably secured to the frame member 40,as by a series of screws 15. The wires 28 and 30 extend from the compartment 69 through a groove 16 into the interior of the motor casing. This motor (Fig. 1) has xed to the inner end of its shaft 11 a fan 18. Within the motor casing are an oil pump, also driven from shaft 4, an oil pressureregulating valve, a burner cut-ofi' valve for oil, and a strainer. These elements may, for exam.- ple, be arranged in the motor casing as disclosed in the copending application of Virgil E. Duemler, Serial No. 529,048, filed April 1, 1944, now Patent No. 2,447,744 granted August 24, 1948 and owned by the assignee of the present application, or in any other suitable way.

The frame member 4|) is recessed to form a scroll chamber 19 (Fig. 4), a plenum chamber 80, which encompasses the air tube extension 41 and a connecting passage 8| to deliverv air from the fan tangentially into the plenum chamber. The plates 42 and 44, which are respectively of metal and of sound deadening material (the latter serving also as a gasket), serve to close the scroll chamber except for a central air inlet `82 (Fig. 1) from the space within the upper portion of the frame member 4|. Louvres 83 in the latter serve to admit air to said space and thus to the fan. These plates 42 and 44 also form an inner wall for the passage 8| but not for the plenum chamber 80. The inner end of the walls of such chamber (Fig. 1) abut corresponding walls 84 on member 4I and provide for an-axially inward extension of the plenum chamber. Air from the fan will thus be delivered into the plenum chamber and whirl around the air tube extension 41. The inner portion of the outer 4periphery of extension 6l.

this sleeve (Fig. 6) are two axially-spaced radi-` in a whirling stream which is advanced through` tube 2 to the oil spray issuing from nozzle I.

To regulate the volume of air supplied to tube 2, a sleeve valve 86 (Figs. 1 and 4) is mounted for axial sliding movement on the outer part of ally-outwardly extending lugs 8l which receive between them the lower part of a. piece 88, which as shown in Fig. 4 is shaped'roughly like the gure 3. A pin 89 (Fig. 4) passes freely through this piece 88 and has its ends fixed one in each lug 9i. The upper part of piece 83 has a screwthreaded hole extending axially therethrough. A screw 90 (Fig. 6) is engaged in such hole. At each end of this screw, is a plain cylindrical portion 9| of smaller diameter than the screw. These portions 9| are rotatably mounted one in each of the two frame members di and 4I. The outer end 9| of the screw is slotted (Fig. 3) to receive a screw driver and extends through an opening in the hinged and transformer-supporting plate 69. By turning screw 90, the nut piece thereof. 'I'he weight of the longer and horizon- I tal arm of the bell crank is enough to normally hold it in the illustrated position in which it rests on one of the ribs 55. A slide 93 (Figs. 1

and 3) is slidably mounted in a groove 94 in` member, 40 and has an outturned end 95 by` which it may be pushed upwardly. The upper end of slide 93 (Fig. 1) is movable into the interior of extension 41 between the transformer plate 49 and the bottom wall of the groove and can engage the horizontal arm of bellcrank 92` and move it to thrust rod 24 forwardly and reset the burner thermostat, when necessary. The slide is held in place by a smallstud 9B which passes through a vertical slot in the slide.

l The mounting of the electrodes is believed to be important. Each electrode consists simply of a wire, having a straight portion 3a to pass through the longitudinal hole in the insulator together with a right-angularly bent portion 3b at one end of the straight portion. The portion Fixed to` radially projecting parts of each clamp are drawn together to contract the clamp around its insulator so that the holding force is distributed around the periphery of the insulator instead of being concentrated at one location or localized as heretofore. The same screws, that serve to tighten the insulator clamps, also serve to bind the strap to the support 4 and hold the insulators and electrodes in position.

In the operation of the invention, when the room thermostat 35 closes on a demand for heat. a circuit is established through the relay 32 and through the safety switch I1, 20, 2i and the elec- 3b lits into one half ofva diametrical groove in l one end face of the insulator and prevents the electrode from turning in the insulator and acts threaded into the nozzle support, such as 4. and

which press against the insulator either directly or through the intermediary of a bushing. The difilculty is to clamp the porcelain insulators firmly in position without cracking them. The presentarrangemenr provides in the strap 62, two separate clamps, one to encompass each insulator, and 'by means of the screw 83 the This mounting of an tric heater I5. The relay 32 closes switches 3| and 33, causing motor 26 to start and supply air and oil to tube 2 and nozzle I, respectively, and causing an ignition spark to be produced at electrodes 3 to ignite the oil and air mixture issuing from tube 2. If combustion occurs, the burner thermostat 9 will be heated and through sleeve 22 and member 23 exert enough pressure on the thermostat Il and safety switch to prevent thelatter from opening. A failure of combustion. either initially or at any time during operation of the motor 26, will enable thermostat 9 to cool and then snap to the left and allow the safety switch to open under the heat supplied 'by heater I5.

According to the invention, the burner thermostat is located in back of the oil nozzle and in coaxial relation therewith and as near as possible in confronting relation with the burner flame so as to react to the heat therefrom and function eliciently as a llame detector. The location of the Vburner thermostat is of prime importance. What is desired, is a quick response of large magnitude following the occurrence of combustion and also following cessation of combustion. Cooling of the burner thermostat by exposure of it to a flow of relatively cool air would in any event act to delay the response of the thermostat to occurrence of combustion and the magnitude of such response. And if the cooling effect were great enough, the burner thermostat might never reach a temperature high enough to operate at all. On cessation of combustion, if the burner thermostat had ben exposed to a ilow of cool air, there would be a quick rise of temperature due to the heat from the combustion chamber following cessation of air flow rather than the quick drop in temperature that is desired. Hence, it is important if a quick response of large magnitude is to be secured on occurrence and on cessation of combustion, to shield the burner thermostat from the air now through tube 2. It will be clear that the burner thermostat is completely shielded from the air flow through tube 2. So also'is the thermostat of the safety switch.

The location of the Iburner thermostat symmetrically' of the air tube and near the outlet end thereof is important all apart from the advantage of shielding the thermostat from the current of cool air. When the thermostat is located near the fuel nozzle and the outlet of the air tube. as it should be in order to have it function elciently as a flame detector. it is essential that the thermostat be kept from interfering with the air ow. If the thermostat should pro- 9 remains smooth and uniform and the nre undisturbed.

The invention thus provides means whereby a burner thermostat may be located in the air tube of an oil burner and yet function properly with a quick and adequate response both to the occurrence and cessation of combustion.

I claim:

1. In an oil burner, a tube having inlet and outlet ends, the outlet end adapted to be inserted into an opening in the wall of a ilrebox, an oil supply conduit supported in part in said tube, a spray nozzle in the tube on the outlet end of said conduit, electrically-operated means for forcing oil through said conduit and nozzle, means connected to the inlet end of said tube for forcing air therethrough to mix with the oil emitted from said nozzle, means for igniting the air and oil mixture, a member located adjacent but back of said nozzle and encompassing said conduit, said member supported in said tube and spaced from the peripheral wall thereof and having a recess in that end which lies nearest the nozzle; and a safety control unit mounted in said recess and including a normally closed safety switch in circuit with said electrically-operated means and a snap disk thermostat to operate it -both located in the inner end of said recess, an electric element in said recess for heating said disk and operable in a predetermined time after starting of said electrically-operated means if combustion doe's not occur to cause the disk to open said switch and stop said electrically-operated means, and a second snap disk thermostat mounted in the outer end of said recess in opposed relation to the rst-named disk and in position to be exposed to the flame in the iirebox, said second disk operable on occurrence of combustion to pre.

vent the first disk under the heat of said element from opening said switch.

2. In an oil burner, a tube having inlet and outlet ends, the outlet end adapted to be inserted into an opening in the wall of a rebox, an oil supply conduit supported in part in said tube, a spray nozzle in the tube on the outlet end of said conduit, electrically-operated means for forcing oil through said conduit and nozzle, means connected to the inlet end of said tube for forcing air therethrough to mix with the oil emitted from said nozzle, means for igniting the air and oil mixture, a member located adjacent but back of said nozzle and encompassing said conduit, said member supported in said tube and spaced from the peripheral wall thereof and having a recess in that end which lies nearest the nozzle; a safety control unit mounted in said recess and including a normally closed safety switch in circuit with said electrically-operated means and a snap disk thermostat to operate it both located in the inner end of said recess, an electric element in said recess for heating said disk and' operable in a predetermined time after starting of said electrically-operated means if combustion does not occur to cause the disk to open said switch and stop said electrically-operated means, a second snap disk thermostat'mounted in the outer end of said recess in opposed relation to the first-named disk and in position to be exposed to the flame in the iirebox, said second disk operable on occurrence of combustion to prevent the nrst disk under the heat of said element from opening said switch, and means manually operable from outside said tube for resetting said disks and closing said switch.

3. In an oil burner, oi the type having a tube which has an open delivery end adapted for insertion in an opening in the wall of the flrebox and through which tube air for combustion iiows. an oil supply pipe terminating with a part which is supported in said tube in substantially coaxial relation therewith and which has an oil-atomizing nozzle on its delivery end, a pump for forcing oil through said pipe, and a motor for driving the fan and pump; a casing having a cylindrical peripheral wall, a back wall and an opening at the front; said casing being mounted on said part of the oil pipe in back of said nozzle, said part of the conduit passing through said back wall into the casing and out through the front of the casing with the peripheral wall of the conduit spaced from the peripheral Wall of the casing forming an annular recess, the front opening of said casing facing the delivery end of said tube in position to be exposed to the radiant heat from the flame in the rebox, an annular snap-disk thermostat located in said annular recess of the casing in encompassing relation with said part of the oil pipe, said thermostat being exposed through said front opening to said radiant heat and shielded by the peripheral wall and back wall of the casing from the air ow through said tube, and means controlled by said thermostat and operable on failure of combustion to stop said motor.

4. In an oil burner, of the type having a tube which has an open delivery end adapted for insertion in. an opening in the wall of a rebox and through which tube air for combustion iiows, an oil supply pipe terminating with a part which is supported in said tube in substantially coaxial relation therewith and which has an oil-atomizing nozzle on its delivery end, a pump for forcing oil through said pipe, and a motor for driving the fan and pump; a casing having a cylindrical peripheral wall, a back wall and an opening at the front; said casing being mounted on said part of the conduit passing through said back Wall into the casing and out through the front of the casing with the peripheral Wall of the conduit spaced from the peripheral Wall of the casing forming an annular recess, the front opening of said casing facing the delivery end of said tube in position to be exposed to the radiant heat from the flame in the rebox, an annular snap-disk thermostat located in said annular recess of the casing in encompassing relation with said part of the oil pipe, said thermostat be ing mounted near the front of said casing and exposed through said front opening to said radiant heat, a second annular snap disk thermostat mounted in said annular recess in encompassing relation with said part of the oil pipe and located rearwardly of the first thermostat, an electric heater in said recess for the second thermostat, a control circuit for the burner motor including a safety switch located in said recess and operable by the second thermostat after the latter has been heated for a predetermined time interval to open and stop the motor, the first thermostat being connected to the second thermostat and operable on occurrence of combustion within said interval to dominate the second thermostat and prevent it from opening said switch, said thermostats being reversely arranged to compensate for changes in ambient temperature, said thermostats being shielded by the peripheral wall and back wall of said casing from the air flow through said tube.

WARREN H. DE LANCEY.

(References on following page) mamen M 12 .1. mismas man Number Name Dafa The following references are of record in the 1640'728 .Seott Aug' so' 1931 me of this Paten? 1,835,087 Scott Dec. 8, 1931 1,904,549 Scognamillo et al. Apr. 18, 1933 UNITED STAT@ PATENTS 5 1,945,385 Schmidt Jan. 30, 1934 Number Name Date 2,048,495 Eaton July 21, 1936 343,232 swung et aL June 3, 1336 2,149,853 McCabe M91- 7: 1939 546 ept. 24. 2,162,098 McCabe June 13; 1939 01,242 Hochheim: ot.1o, 1905 2312312 Anders@ l- 20 194 Dec. Mar.

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