US2193829A - Liquid fuel burner - Google Patents

Description

March 19, 1940. .1.'1-1. MclLvAlNE Er AL LIQUID FUEL BURNER 5 sheetsfsheet 1l Filed April 17, 1936 March 19 1940- J. H. MclLvAlNE Er AL 2,193,829

LIQUID FUEL BURNER Filed April 17, 193e 5 sheets-sheet s Ej l y y@ MuqQ/m @$75.

March 19, 1940. J. H. MclLvAINE ET AL LIQUID FUEL BURNER Filed April 17, 1936 5 Sheets-Sheet 4 Qms.

Mulch 19 19,40, J. HjMclLvAlNE mm. 2,193,329

LIQUID FUEL BURNER www.

Patented Mar. 19, 1940 PATENT OFFICE I LIQUID FUEL BURNER 1 John H. Mcllvaine and Peter I. Hollman, Chi-y cago, Ill., assignors to Mcllvaine Burner Corporation, Chicago, Ill. Application April 17,

7 Claims.

'Ihis inventionrelates to liquid fuel or hydrocarbon burners, usually referred to as oil burners, suitable for industrial or domestic heating, and is particularly concerned with an improved firepot or combustion head.

One of the principal objects of our invention is to provide a combustion head of built-up sectional construction whereby to allow each part to expand and contract freely relative to associlO ated parts without danger of cracking, even though ordinary cast iron is used instead' of special heat resisting metals. This type of construction, wherein the parts are assembled one 'over another loosely on a bottom or base piece l 4that forms a support for the rest, also has the advantage of easy assembling and disassembling and easy replacement of parts, because there are no bolts or screws which are always hard to loosen after they have been subject to heat of Bothe furnace for any length of time. Also a feature permitted by this construction is the use of refractory or other heat resisting material in the part or parts subjected to the most intense heat.

2.?, Another of the principal objects of our invention is to provide an limproved method and means of vaporizing the oil in a groove in the combustion head and introducing the air to the groove in such a way that the air and vapors y :To are churned together and thoroughly mixed be.

fore combustion takes place.

Our invention also embraces other important objects, amcng the more prominent ones of which might be enumerated the following:

:2.3 (a) The provision of ample clearance around the burner tray inside the enclosing ring, which space is in direct communication with the air conduit so that air will circulate around and under the tray for cooling purposes and prevent zu overheating of the tray and ring as well as the overilowpan therebeneath;

(b) The provision at opposite ends of the groove in the burner tray of pockets shielded by baiiies from the direct play of the incoming air if) to protect the flame against blowing out on low settings of the burner, the baffles also causing the incoming air to have a spinning action in Ithesejioclrets to insure good mixing and com plete combustion;

.in (c) The provision of a spiral surface'cn the burner tray extending from the aforesaid groove and having thereon a series of steps onto which o il from the groove may run when the burner is turned up from low to high, and thus confine mythe oil and prevent the air from washing itv a corporation of Illinois 1936, Serial No. 74,952

farther forward on the spiral surface in a surge, and ff (d) The provision of a top for the combustio-n head having an oblong opening in the center thereof for the purpose of spreading or flattening out the flame issuing from the combustion head, so as to make better heat transfer with the side walls of the furnace.

'Ihe invention is illustrated in the accompanying drawings, in which- Figure 1 is a side view of an oil burner embodying our invention, shown installed in a domestic heater orfurnace;

Fig. 2 is a plan view of Fig. 1 with intermediate portions of the air conduit and oil return pipe broken away;

Fig. 3 is a central longitudinal section in a vertical plane through the combustion head or lirepot showing the same on a larger scale;

Fig. 3a is a fragmentary sectional detail showing a modified construction of the burner tray.

Fig. 4 is a horizontal section taken on the line 4-4 of Fig. 3;

Figs. 5 and 6 are fragmentary sectional details taken on the lines 5 5 and 6-6 of Fig. 3;

Fig. 7 is a plan view of the overflow pan which forms the supporting base part of the combustionv head, this view including a' plan view of the end of the air conduitand oil return pipe;

Figs. 8, 9, and 10 are perspective views of the combustion head tray, ring and top, respectively;

Fig. 11 is a view similar to Fig. 3, showing a modif-led or alternative construction for the combustion head;

Fig. 12 isa plan view of Fig. 11;

Fig. 13 is a View similar to Figs. 3 and 11, showing still another modification;

Fig. 14 is a horizontal section of Fig. 13 taken approximately.` on the line Ill- I4 thereof;

Fig. 15 is a cross-section on the line l5-l5 of Fig. 13, and

Fig. 16 is a diagrammatic view in perspective illustrating the mode of operation of the construction shown in Figs. 13 to 15.

Similar reference numerals are applied to. corresponding parts throughout the views.

In our copending application Serial No. 26,112, filed June 12, 1935, we disclosed an oil burner of the type illustrated in Figs. 1 and 2, with a combustion head or repot ofthe type herein disclosed in Figs. 13 to 16. However, it Will be, noted that in Figs. 1 and 2 we show the combustion head herein disclosed in Figs. 3 to 10, that being the preferred form and an improvement upon the form of Figs. 13 to 16. The combustion head or repot shown in Figs. 11 and 12 represents a further step from that of Figs. 3 to 10.

In describing our invention, the liquid fuel will be referred to as oil, and we shall first trace the oil circuit by reference to Figs. 1 and 2. The oil is stored in a basement storage tank at a certain elevation above the oil burner or in an underground storage tank outside. Where an underground tank is used, an automatic transfer pump is provided to pump the oil into the basement tank. The oil flows by gravity feed through the pipe to a illter I8 which removes any dirt and foreign matter therefrom. Next the oil enters the bottom of a float valve I9, the purpose of which is to maintain a constant level of fuel so as to insure an even pressure and an even llame free from pulsations or surges. Pipe 213 conducts the oil from the float valve by gravity to a solenoid valve 2| which permits an unrestricted flow of oil therethrough so long as the current for the electric motor 22 is not interrupted, the solenoid valve being kept open by the energization of its coil by the current for operating the motor. If

A the current is interrupted, a main valve in the solenoid valve 2| is closed, and the oil is bypassed through a secondary valve therein that is adjusted to reduce the flow to about one-third of the maximum capacity of the burner, whereby to maintain a reduced flame using natural draft and sufficient to keep the house warm until normal operation will be resumed. The oil passes from the solenoid valve 2| into a control valve 23 which is preferably of the type disclosed in the copending application of Peter I. Hellman, Serial No. 751,865, led November 7, 1934. The valve 23 is adjusted to regulate the oil feed according to the heat demand. From this valve the oil ilows by gravity through the connection 24 to the pipe 25 which extends lengthwise inside the air conduit 26, and has a downwardly bent end 2'! to discharge the oil into the groove 28 in the burner tray 29 forming a part of the combustion head indicated generally by the numeral 3Q. The oil so discharged is vaporized and mixed with air and burned in the combustion head in the novel manner hereinafter fully set forth.

It is clear, then, that the present burner has simple gravity feed regulated in accordance with heat demand by the valve 23 and controlled by the solenoid valve 2| to change from a normal oil feed to a restricted feed to provide a low1 carryover llame When the current for the motor is interrupted, as, for example, by `reason of a temporary shut-down of electric service for the home.

The air for mixture with the vaporized oil and to support combustion is supplied by a centrifugal fan in the housing 3| driven by the motor 22. The housing 3| has a tangential discharge neck 32 communicating at its flanged downturned end 33 with the flanged end 3d of the air conduit 26 to deliver air to the combustion head 30. The amount of air delivered to the combustion head is regulated by the turning of a shutter plate 35 relative to an apertured side wall 36 on the housing 3|. The air shutter 35-36 conforms generally to what is shown in McIlvaine Patent 1,797,293, there being closure plates 3l adjusted relative to openings in the shutter plate 35 so that only the proper amount of air will be allowed to enter at each one of a series of positions, the shutter plate being turned one step at a time and adjustments of the appropriate closure plates thereon being made at each step so as to secure the correct amount of air in proportion to oil. A link 38 provides an operating connection between the shutter plate 35 and the rotatable crank arm 3B of the regulator 58, that is, where automatic control is desired; in some installations a remote control unit is provided having connection with the shutter plate 35 for direct manual adjustment thereof. In the automatic control, the room thermostat located conveniently upstairs causes the regulator d'3 to operate so as to regulate the size of the flame and constantly balance the heat loss of the building. and thus maintain an even temperature. Another link 4| provides an operating connection between the shutter plate 35 and a lever 42 acljustably connected with a quadrant 43 fixed to the rotatable stem of the control valve so that the control valve will be opened wider and wider'at each step in the progressive opening of the shutter plate, wherebyr to secure correct proportioning of oil and air for each name, from the low flame, which serves as a pilot, through the various intermediate sized llames to the high flame.

In the event the flame in the combustion head 3B is accidentally extinguished, oil overflows the tray 29 into the overilow pan M, and runs out through an opening 45 in the 'bottom of this pan and is conducted through a return pipe 46 to a trap The latter is on one side of the housing 18 in which a trip bucket is enclosed, and oil is discharged from the trap into the bucket. rIhe bucket, as disclosed in our cope-riding application Serial No. 26,112, is connected with trip mechanism inside the housing 49 cooperating with the float valve |9 to close the needle valve thereof and shut off communication between the supply pipe |1 and the float chamber so that no further oil will be delivered.

Combustion head-Figs. 3 to 10 The combustion head 35 is made of four separate parts:

(l) The overflow pan 44 cast integral with the end of the air tube or conduit 2li;

(2) The tray 29 which is placed in the pan M;

(3) The ring 5G which rests on the pan 44 and surrounds the tray 29, and

(4) The top 5| which rests on the ring 5D.

There are several reasons for this built-up sectional construction. Firstly, it allows each part to expand and contract freely relative to other parts, whereas a pot cast in one piece would very likely crack due to stresses set up therein by uneven heating. We are therefore enabled to use ordinary cast iron instead of special heat resisting metals, and a saving in cost is realized. Secondly, the sectional construction reduces each part to a simple and inexpensive casting that can be made easily without complicated cores or molds. Thirdly, the sectional construction permits our making parts of refractory or other heat resisting material which are subjected to the most intense heat. Thus, the top 5| which will be the hottest part of the head when the burner is running on all except the low flame, is made of ceramic material. We have, it will be noticed, made it in two halves to prevent cracking, the halves being iltted together by a lap-joint 52. As will presently appear, we also contemplate making the ring 50 of refractory material, and in that case, as will soon appear (see Figs. l1 and 12), the ring 5G and top 5| are combined and the part is made in two sections to prevent cracking. Fourthly, the sectional construction enables replacement of any part in case it gets cracked or burns out, and such replacement poses, as will presently appear.

cooling p rposes in the placing of the ringin the recess 65, fits means very little' expense as compared to the necessity 4for replacing the entire combustion head. Then too, since the parts are loosely assembled one over another, it takes very little time' to yassemble or disassemble the head, there being no bolts or screws to loosen, which in-` variably become difficult to loosen after they have been subjected to the heat of the furnace for any length of time. In this connection it should also be noted that the most expensive part of the assembly-the combined overflow pan v 44 and air conduit ZS--is safeguarded against likelihood of cracking due to heating, by the fact that the thick tray 29 shields the overflow pan from the heat. It is that fact which warranted casting the overflow pan integral with the air conduit. n

The pan M has a hollow boss 53 cast integral therewith and a set screw t is threaded therein to clamp the pan onto the supporting post 55 at the proper elevation from. thefloor. We have, however, dispensed with the set screw and used a threaded post with an adjusting nut `below and a lock nut above the hollow boss. The post forms one of three supports for the burner, there being two supporting feet 56 provided on opposite sides of the housing -48 on which the housing is vertically adjustable, as indicated (see Fig. l). The air conduit 26 communicates with the combustion vhead 30 at a point appreciably above the bottom of `the overflow pan M, so that la shoulder is defined at 51 (Fig. 3). An upwardly projecting bead 58 on the bottom of the pan 44 describes a three-quarter circle extending clockwise from one lend ofthe shoulder 5l, as shown in Fig. '7, and

then on a tangent to the circle to the other end'l cavity. The tray 29 is shaped to conform to the cavity 59, as best appears in Figs. 4' and 8, and has three feet Eil-62 serving to support the same 1 Yin elevated relation to the bottom of the cavity,

so that anyoil overflowing the tray will have easy access across the bottom of the pan 44 to the drain opening 45. This space also permits air circulation under the tray for cooling pur Sockets 5| and E2' are suitably formed on the bottom of the pan v M within the cavity 59 to receive the feet 6l and 62, respectively, and thus accurately locate the tray 29 with `respectto the air conduit 25. The tray also has a flat surface S3 on the front thereof which comes into abutment with the shoulder 5'! on the pan 4d to further locate the tray. The pan 44 has an outer rim 64 which is spaced from the ybead 58 so as toA provide a marginal recess 65 in which the lower edge of the ring 50 is arranged to fit. The ring is, of course, shaped to conform to the profile of the tray 29 and surrounds the tray with ample clearance left thercbetween. This annular space, as will presently appear, also plays an important part Vin the circulation of-air around and under the tray, for Since the tray 29 has contact with the pan i4 only at the three points where the feet (iii-$2 rest thereon, there will obviously be very little heat conducted to the pan from the tray.v The ring 5U has three feet E6 on the bottom thereof to hold the ring out of contact with the pan M so much as possible, and thus reduce heat transfer from the ring to lthe pan to a minimum. The ring 50 has a collar portion 61 which,

, ally turned toward horizontal axes.

ing of the air at a, b and c, it must be rememover the neck 68 formed on the end of the air conduit 26 and defined by the outwardly projecting bead G6 cast integral with the conduit. The interftting of the collar and neck portions insures accin'ate location of the ring 50 with respect to the air conduit 25 and tray 28. Proper registration of these parts is important, because the ring has a downwardly curved transverse hood 10 thereon adjacent the collar 6l, which it is important to have properly disposed in transverse relation in front of the discharge end of the air conduit 25 and inr proper transverse relation over the groove 28 in the tray 29. A recess 'H is provided in the top of the ring 50 to accommodate the split combustion head top 5l. This recess is circular except for a right-angle jog, indicated at l2, into which a projection '13 provided on one half of the top 5I is arranged to fit. In that way, we secure the desired registration of the oblong or oval shaped opening I4 in the top, With the tray 29. That is to say, it is desired to have this oblong flame opening with the major axis at right angles to the air conduit 26, and that is insured by means of the locating projection T3 on the top 5l fitting into the locating recess 12.

Ihe tray 29 has a front wall 15 on which the surface 63, previously mentioned, is provided. A notch 16 at the middle of this front wall serves to receive and locate the downwardly bent end 2l' of the oil pipe 25, whereby to have the oil dis'- charged into the groove 28 at about the middle. Now, obviously, with the air entering the combustion head from the conduit 25 between the top of the front wall l5 and the hood lil, it follows that the incoming air will be deflected downwardly toward the groove 28, and, since the wall 'l5 forms a shelter or baille with respect to the air current, a whirling motion of some of the air on substantially horizontal axes will bev set up. in a clockwise direction, as indicated by Vthe arrows a in Fig. 3. These may be termed eddy currents. The groove 28 is somewhat wider than the discharge end of the air conduit, as indicated in Fig. 4, and there are moreover two obstructions or baliles Tl and 18 on the front wall on opposite sides of the oil pipe locating notch 76, so that the two ends of the groove 28 Yare shielded from the direct play of the air curably below the bottom of the hood 10, it follows that some air flows nearly straight through and into the combustion head 'from the air conduit 26 over the groove 2S, as indicated by the large gently Vcurved arrow d in Fig. 3. This air flowing nearly straight through carries with it the eddy currents a, b and c, as represented in Fig. 4, wherein it will be noticed how the clockwise and counterclockwise currents b and c gradually reduce in radius as they get farther and farther down stream. What actually happens is that these eddy currents b and c whirling on Vertical axes come in contact with the eddy currents a whirling on horizontal axes and the horizontally flowing air current d, and as a result are gradu- This churnsof bered, occurs in the groove 28 into-which oil is being delivered from the oil pipe 2li. The tray 29. which upon starting the burner has been pre-heated by a gas torch or in some other suitable way, and which thereafter remains heated by the flame of the burning combustible mixture of oil vapors and air, is hot enough at the groove 23 to vaporize the raw oil upon contact thereof with the groove. The oil vapors in the groove are picked up by the whirling air currents a, b, and c in what we choose to term pre-mixing. Then these rich mixtures coming in contact with the main air current d form a leaner mixture that will burn with a clean hot flame. The flame is visible through the opening T4, on low, as two distinct tongues issuing from the vicinity of the pockets 'I9 and 30 onto the spirally formed bottom 8l of the tray 29. This indicates how great an eect these pockets have upon the operation of the combustion head; without these pockets there would be danger of the llame being blown out, but since these pockets are protected by the baiiles 'I'l and 18, respectively, the llames originating therein will not be extinguished. The baffles 'l1 and 18 are closer together than the walls 82 and 82 defining the sides of the spiral bottom 8l, thereby leaving the side portions of the spiral surface somewhat protected from the direct play of the air flowing up the middle of this surface. The two tongues referred to as being visible on low are seen as made up of numerous small whirling flames, indicating how the eddy currents b and c originating in the pockets 19 and 8G are carried forward with the main air current d over the spiral bottom 8i of the tray. Of course, when the burner is turned up to a medium or a high flame, there are no longer two distinct tongues of flame as just described, but one large flame forms from these two flames, which, as it builds up, gradually reaches farther and farther over the spiral bottom 8| of the tray and finally issues from the combustion head through the opening E4 with a spinning motion, as indicated f by the arrows e in Figs. 3 and 4. The ring 5D and top 5I together serve to conne the air delivered to the combustion head and cause it to mix into the flame to support combustion, and, of course, if it were not for the ring 5U and top 5l, the tray 2Q would not perform its various functions properly. The flame on high is best described as an inverted cone, having a counterclockwise spinning motion. This direction of spinning motion results from the way the air is delivered into the combustion head at one side of the ring 5D, between the vertical walls 82 and 82' of the tray. The side wall 82 is substantially semi-circular surrounding the spiral surface 3l. The latter has a gradual rise from the groove 28 through approximately 180 and then, as indicated at 33, has an abrupt rise to deflect the flame upwardly and out through the opening M. The spinning motion given the flame accounts for its spreading out in the form of inverted cone after it leaves the combustion head. The flame does not describe a true inverted cone, but rather an inverted cone of oval shape, due to the oblong shape of the opening lll. This tends to flatten out the flame and give it greater width so as to make for better heat transfer to the side walls of the furnace.

It will now be noticed that the tray 29 has a series of steps 84-88 formed on the spiral bottom 8l resembling a spiral staircase. The rst step Bcl which is parallel with the groove 28 and with the rst -step 85 of the spiral steps, represents an appreciable rise from the level of the groove 28, but the spiral steps 85-88 which radiate from the center 89 of the tray have small risers. This formation is to prevent surging of oil when the burner is suddenly turned from low to high. Under those conditions, the tray 29 is not heated to a high enough temperature because of the low flame and therefore does not have suicient residual heat to vaporize the suddenly increased inow of oil. If it were not for these steps 84-88, a deep pool of oil would form in the groove 28 and flood a large portion of the spiral bottom 8l, and the air current impinging upon the edge of this pool would wash some oil up onto the hotter part of the tray and cause vaporization there, with the result that the combustion head would burn with an uneven flame until the tray would reach a higher temperature, due to the radiant heat of the larger llame, and the level of the oil would subside to the edge of the groove 28, or some other point of stability. Then too, if the oil were allowed to run too far forward on the surface 8|, the products of combustion passing over the surface of the oil would contaminate the vapors rising therefrom and the iiame would become hazy. With the present construction, when the burner is set for a low llame, the oil is vaporized in the groove 28 just as soon as it comes in contact with the hot surface thereof, and then when the burner is turned up for a higher flame the oil spreads over the bottom of the groove, which confines the oil as much as possible close to the air intake so as to produce an intimate mixture of air and vapor, but when the oil enters faster than it is vaporized, upon sudden turn-up from low to high, oil will fill the groove and finally run out over the surface SD to the step 84. The step 84 having an appreciable riser, confines the oil again as close as possible to the air intake to continue producing an intimate mixture of air and vapors and avoid the condition previously referred to of having products of combustion passing over the surface of the oil and contaminating the vapors. The name will ordinarily build up fast enough to stem the tide so that the oil will not pass the step 84 at its highest level, but, if the oil should rise above the step 84, it is confined by the step 85, and so on with regard to steps 86, 81 and 8B. In any event, it is apparent that whichever step is confining the oil pool, there is a sharply defined boundary for the pool; the oil cannot surge forward and result in an uneven flame and the hazy condition previously described. As the tray heats up, the level of the oil subsides until finally the oil is vaporized mostly in the groove 28.

In case the flame is accidentally extinguished and oil continues to flow into the groove 28, it will fill the tray and then run over the edge into the overflow pan 44 and nd its way to the trip bucket previously mentioned, so as to shut off the oil supply.

In passing, attention is called in Fig. 4 to the dotted arrows A and B, showing how incoming cool air from the conduit 26 enters the annular clearance space between the tray 29 and ring 50 and circulates around and under the tray to prevent overheating of the tray and ring, especially when the burner is operating on high. The air A flows along the right side of the tray and, inasmuch as it is traveling at a high velocity when it whirls around the inside of the ring 5 0 it has sumcient centrifugal force to cause greased f, it to see'kto travel in on a larger diameter, so

that .it is deiiected downwardly by the inclined upperportion 94 of the inside wallof the ring Y50, and once it gets under the tray it moves over toward the other side of the tray, and comes up, as indicated at C, and joins the incoming air B and rises with the flame issuing from the openy ing lll. The fact that the trayand 'ring are :cooled in this fashion prevents their burning out. The' side wall of the ring 50 is relieved at Q5 next to the conduit 25 to provide a wider inlet into the clearance space for the air A, and it will lthe front of the tray 29 isformed to provide an opening at 91, as shown in Fig. 4, serving as an entrance to the clearance space for the'air B, open to the' conduit 26. We may, as illus- 'trated in Fig. 3a, provide vertical passages '55a in the iront wall 'l5 of the tray 29 to provide for additional circulation of air from the conduit 26 beneath the tray, as indicated by the arrows in this figure.

` v Combustion headf-Figs-11 and 12 The combustion head 30 is similar 'to the head 3@ so far as the tray 29 and combination air conduit 26 and overflow pan 44 are concerned.

.- In this head, however, the ring Eli and topr5I are combined into a single ring 92 of refractory ma- -terial made in two sections, as indicated by the joint line 93, whereby to prevent cracking. The skirt portion 4iof this ring is formed on the inside with inwardly sloping side walls 9d like the walls 94 on the inside of the ring 5U, whereby to better confine the air flowing over the tray 29 and cause it to mix more intimately with the fiame. There is also a hood portion 'l0' depending from the top portion 5| which serves the same purpose as the hood 10 on the ring ii. yThe two halves of the ring 92 are located properly so that the opening 'M' will be disposed with its major axis at right angles to the conduit 26 when the collar portion lil formed integral with the top portion 5l' of the ring 92 is set over the neck 68 on the conduit 26. The operation of this head should obviously be the same as the one previously described.

' Combustion head-Figs. 13 to 16 .The combustion head 30a, here illustrated, resembles the ones previously described principally from the fact that the conduit 26 and overflow pan 44 are combined into a single casting. The tray 29 differs from the trays of heads 30 and 30', although it is designed to serve generally the same purposes, namely, to vaporize the oil, assist in the mixing of the vapor with the air, and also assist in causing the flame to spin as it issues from the head. The ring 92' more closely resembles the vring 92 of head 30' than any part of head 30, but is herein shown as a one-piece casting. In this head there is no sharply defined groove or trough like the groove 28 of the heads 30 and 30'; the oil is simply delivered into the lower end 28 of the spiral bottom 8l', whichA taken with the wall l5' defines a fuel receiving trough, as best appears at 28' in Fig. 13, and vaporzation occurs at that point in front of the 'end wall 15 over which the air from the conduit and over which air is delivered from thev con- .duit 26', as-indicated by thelong arrowsf in Fig. 16. In this case, the fingers result in the creation, of partial vacuums on the leewardside,

and oil `vapors are drawn up thereby, .asindicated at g in Fig. 16, formingfour separate columns of vapor each nanked on both sides Aby the air streams. This gives the vapors and fair an opportunity to mix thoroughly for kgood combustion. Then too, when the burner is 'operating on low', this construction results in .a considerable amount of flame staying on the leeward side of the fingers so that the trough 28 is heated to a higher temperature, which, ofcourse, im-

-proves vaporization and minimizes danger of the burner going out. Then too, the vapor rising from the trough is drawn back into the ame .instead ci being permitted to escapeunderneath the incoming air. Furthermore, the fingers taken together' with the `Wall 15 provide protection for the name when the burner is running on low, so that there is less danger of the flame being extinguished even when a very small flame is maintained for economy. The fact that the vapors are actually drawn up into the zone where they have a good opportunity to come in contact with the incoming air, avoids the condition of ahazyflarne, previously referred to; the vapors cannot escape underneath'theair current and fail to ignite, but are drawn directly into the air current and mixed with theair and burned. In'

this combustion head We have also provided steps 11W-S3. These serve as in the other headsto prevent surging ,of oil when the burner is suddenly rturned from low to high. The ring 92'.: f `confines the iiame and also confines the incoming air so that it will mix properly with the flame. The sloping sides of the opening 14a which in this case is circular, but may be oblong,

cause the name to flare out into an invertedv cone as it issues from the head. yThe tray has a spiral formation lBI starting from the trough 28 asr the lowest point and terminating at 83' as the highest point, this level being substantially at the same elevation as the top of the wall l5', from which the fingers 'i1' and 18 rise, a

,bestappears in Fig. 15. Y

It is believed the foregoing description con- 'veys a good understanding ofthe objects and and adaptations.

,A bottom plate, a burner traykon which liquidfuel is vaporized in the presence of air and burned, said tray being supported in spaced relation to said bottom plate, an enclosing ring in spaced relation annularly with respect to said tray and supported on said bottom plate, means on top of said ring providing a top wall having a flame outlet opening above said tray, means for delivering liquidfuel to said tray, and meansfor supplying air under presure in such a way as to cause some oi' the air to circulate annularly between the tray and ring, said ring being formed on the inside to provide inwardly inclined upper side walls above the tray adapted to direct some of the air flowing between the tray and the ring downwardly to circulate between the tray and bottom plate.

2. A burner tray for a generally circular oil burning iirepot comprising a generally circular claims have been drawn witha View to covering 50 vthe circular portion having a spiral top surface formation extending substantially spirally from a relatively low starting level adjacent and at one elevation above the bottom of the trough through about 180 to a higher take-off level, said spiral formation being stepped intermediate the ends thereof at one or more predetermined elevations above the starting level.

3. A burner tray for an oil burning repot comprising a generally circular body having approximately one quarter thereof of generally rectangular form, the rectangular portion having a trough provided therein, and the circular portion having a spiral top surface formation extending substantially spirally from a relatively low starting level adjacent the trough through about 180 to a higher take-off level, said spiral formation being stepped spirally in one quadrant near the trough at a plurality of elevations with respect to the bottom of said trough.

4. A burner tray for an oil burning firepot comprising a generally circular body having approximately one quarter thereof of generally rectangular form, the rectangular portion having an elongated substantially rectangular depression provided therein, the outer longer wall of which is higher than the inner longer Wall, and the circular portion having a plain substantially spiral top surface provided thereon extending circlewise from a relatively low starting level at the inner wall of said depression through about 180 to a higher take-off level, said spiral formation having a relatively high step thereon near and substantially parallel to the inner wall of said depression and being stepped to a lesser extent at one or more points more remote from and at predetermined elevations with respect to the bottom of said depression.

5. A burner tray for an oil burning iirepot comprising a generally circular body having approximately one quarter thereof of generally rectangular form, the rectangular portion having an elongated substantially rectangular depression provided therein, the outer longer wall of which is higher than the inner longer wall, and the circular portion having a plain substantially spiral top surface provided thereon extending circlewise from a relatively low starting level at the inner Wall of said depression through about 180 to a higher take-off level, said spiral formation having a high and then a lower step thereon substantially parallel to one another and to the inner wall of said depression, the high step being near said depression and the low tep farther away, and said spiral formation being stepped spirally to provide a plurality of low steps in one quadrant thereof starting with the second step.

6. In a liquid fuel burner, a burner tray of generally circular form having a projecting substantially right angle corner portion in one quadrant thereof, said corner portion being formed to provide an elongated trough therein, the tray being further formed to provide a spirally extending top surface on the circular portion starting from one side of the trough, a casing for enclosing said tray comprising a generally circular ring body having substantially vertical side walls and having a projecting right angle corner portion whose side walls are substantially tangent to the side walls of the rest of said body, the last.

named corner portion enclosing the corner portion of said tray and one of the side walls thereof having an elongated opening provided therein extending lengthwise of said trough and said side wall also having a downwardly curved elongated hood thereon projecting inwardly from above said opening over said trough and downwardly to a predetermined elevation above said trough, the upper edge of the side walls of said ring body having a recess provided therein, and a substantially centrally apertured top member removably supported in said recess.

7. In a liquid fuel burner, a burner tray of generally circular form having a projecting substantially right angle corner portion in one quadrant thereof, said corner portion being formed to provide an elongated trough therein, the tray being further formed to provide spirally extending top surface on the circular portion starting from one side of the trough, and a casing for enclosing said tray comprising a generally circular ring body having substantially vertical side walls and having a projecting right angle corner portion Whose side walls are substantially tangent to the side walls of the rest of said body, the last named corner portion enclosing the corner portion of said tray, a top wall extending inwardly from the top of the side walls and having a substantially central opening provided therein substantially .concentric with said tray, one of the side walls of the square-cornered portion of said ring body having an elongated opening provided therein and extending lengthwise of said trough, and a downwardly curved elongated hood under the top wall extending inwardly from above said opening over,

said trough and downwardly to a predetermined elevation above said trough.

JOHN H. MCILVAINE. PETER I. HOLLMAN.

CERTIFICATE OF CORRECTION.

' patent No. 2, 195,829. .March 19, 19m.

JOHN H. MCILVAINE, ET AL.

It is hereby certified that error appears in the printed specification Iof the above numbered patent requiring correction as follows: Page 5, second column, line 6h, claim l, for "presure in such a Way" read pressure into said ring in such a Way; page 6, first column, line 511 olaim5, for

"tep" read step; and that the said Lett-.ens-Patent` shouldbe readwith this correction therein that the same may conform to the vrecord of the oase in the Patent Office.

signed and sealed this 50th day of April, A. D. 19m.

Henry VanArsdale,

(Sea'l) Acting Commissioner of Patents.

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