US2312559A - Oil burner - Google Patents

Description

March 2, 1943. I w. F. 'KLOCKAU OIL BURNER Filed Aug. 2, .1939

2 Sheets-Shut 1 I I I 211151- MZ/zbm zfficzau' March 2, 1943. w. F. KLOCKAU on, BURNER Filed Aug. 2, 1939 WW da n Patented Mar. 2, 1943 UNITED STATES PATENT OFFICE OIL BURNER William F. Klockau, Moline, Ill.

Application August 2, 1939', Serial No. 287,873

12 Claims.

The present invention relates to oil burners, and has particular reference to the provision of improved means for thermally insulating the burner nozzle from heat radiated from the flame and the combustion chamber.

For a considerable time, manufacturers of boilers and furnaces have been endeavoring to develop successful heating units of relatively small size, i. e., in the neighborhood of 80,000 B, t. u. output, in which oil is used for fuel. The principal difficulty encountered in the development of these small heating units is that of obtaining a burner which can successfully burn oil at a rate low enough to overcome high stack losses. Heretofore, there have been very few burners, if any, capable of giving satisfactory performance when using nozzles of such small capacity as approximately one gallon per hour, and even these burners usually produce too much heat for many of the smaller heating units to absorb eificiently.

There is a considerable demand for small heating units of the approximate size above mentioned, owing to the large number of small four and five room homes being built at the present time. For example, an oil burner that can successfully burn oil at a rate as low as gallon per hour would fill an immediate need. It is well known, of course, that vaporizing burners and low pressure burners are now available in relatively small sizes. However, the vaporizing burners are unsatisfactory inasmuch as they require a light grade, high priced fuel and are difiicult to operate automatically. The low pressure burners are too noisy in their operation, and are relatively expensive to manufacture. Contrasted to these, the high pressure burner is the most desirable or the only practical type of burner now known as having definite potentialities for this market. This type of burner is low in cost, quiet in operation, requires little service, and uses the heaviest grades of domestic fuel oil.

The principal difficulty experienced with pressure type oil burners using nozzles of very small capacity has been the clogging of the nozzles, owing to the extremely fine passages necessary to keep the fuel delivery rate low enough at atomizing pressures. For example, the slots in a typical one-gallon per hour nozzle are approximately .008 inch wide. Screens and filters that will screen out particles much smaller than .008 inch in diameter have been used in conjunction with these one-gallon per hour nozzles, but such nozzles are still subject to clogging, and must be cleanedat frequent intervals. Under all but the most extremely favorable conditions, these intervals are so short that such nozzles have generally been deemed impractical, at least for ordinary operating conditions.

From the fact that the use of filters of smaller screening size than the size of the nozzle slots and orifice does not avoid this frequent clogging of the slots, it follows that this clogging is not due to sediment or particles suspended in the oil. I have determined by conclusive experiments that this frequent clogging of extremely small capacity nozzles is due to high temperatures, particularly the action of radiant heat from the combustion space impinging on the nozzle. Fuel oil is a compound of hydrocarbons of a complex nature, whose molecules are distilled off by heat. Some molecules pass off at relatively low temperatures, and as the temperature rises more and more pass off. Finally, a temperature is reached (in the neighborhood of 680 F.) where no more evaporation takes place, but a sticky tar-like substance remains. A very small deposit of this substance will interfere with the proper spraying action of the nozzle, or will clog it up entirely.

Moreover, it is not necessary for the nozzle to attain a temperature of 680 F. to cause it to clog. If only 40% or 50% of the oil remaining in the nozzle is distilled off, the remaining oil is of a consistency that will be very difficult to expel when the burner again resumes operation. Gradually, a mass of material accumulates in the nozzle until clogging occurs. It must be borne in mind that only a very minute quantity of oil remains in the nozzle passages after a burner stops operating, and that distillation takes place very rapidly. Furthermore, at temperatures as low as 200 F. the liquid oil will be driven off, while solids and semi-fluid residues will remain in the nozzle passages. A small quantity of this material is deposited after each burner operation, until finally the nozzle clogs.

By placing a small thermocouple tightly against the nozzle tip, I have made accurate temperature measurements of the nozzle during burner operations and immediately following cessation of burner operation. These tests show that the nozzle begins to heat up very rapidly after the burner is started, notwithstanding the fact that cold air is being passed over the burner at a relatively high velocity, and cold oil is being passed through it. The temperature rise is due to the absorption of radiant heat from the flame and adjacent refractory and metallic parts. Numerous tests were made on various types of boilers and furnaces, as well as with different designs of combustion chambers and combustion chamber material, during which the rate of temperature rise, and the maximum temperature reached, varied under different conditions. The lowest maximum temperature recorded while the burner was in operation was 260 F., while the highest was 490 F. Maximum temperature was attained in from ten to fifteen minutes of operation from a cold start, depending upon conditions. Immediately after stopping the burner, the temperature usually rises about ten degrees F. and then slowly drops. After thirty minutes or so it comes down to about 150 F.

The foregoing observations and experiments have demonstrated to me the importance of shielding the nozzle tip from the radiant heat of j the flame while the burner is in operation, and also of shielding the nozzle tip from the radiant heat of the combustion chamber after the burner has stopped. To the attainment of these ends, I V

have devised different forms of improved heat shields for the burner nozzle, which I shall now describe in connection with the accompanying drawings. In these drawings:

Figure 1 is an axial sectional View through a conventional design of burner of the type described above, illustrating one embodiment of my improved heat shield;

Figure 2 is a perspective view of this heat shield;

Figure 3 is a fragmentary view similar to Figure 1, showing another embodiment of my improved heat shield;

Figures 4 and 5 are front elevational and sectional views, respectively, on a larger scale, of the nozzle shield illustrated in Figure 3;

Figure 6 is an axial sectional view through a conventional burner, illustrating my invention embodied in the form of a combination nozzle shield and electrode bracket;

Figure '7 is a transverse sectional view taken approximately on the plane of the line 'i-'l of Figure 6, and

Figure 8 is a fragmentary sectional view similar to Figure 6 but showing the use of a difierent form of nozzle shield, similar to that illustrated in Figure 3.

One of the refractory enclosing Walls of the combustion chamber is indicated at 52. Enter ing the combustion chamber through this wall is the abovedescribed type of burner assembly comprising a draft tube id for the air supply, and an oil pipe I6 for the fuel supply. The inner end of the draft tube [4 is usually provided with an air deflector ring which is fastened to or formed integral with the draft tube. This deflector ring serves to constrict the air stream to a high velocity taperin jet converging toward a point beyond the nozzle head. As hereinafter described in connection with Figure 3, this deflector ring may be provided with inclined vanes for imparting a helical or spiral .twist to the air stream. Secured to the innerend of the oil pipe I5 is the nozzle body IT. The nozzle tip l8 at the inner end of this body is provided with a relatively small central orifice I9. The slots or passageways which determine the capacity of the burner are usually located in the body of the nozzle, anterior to this discharge orifice E3. The draft tube I4 is usually connected to receive air under pressure from a displacement blower, turbo blower, fan or the like. The oil pipe i6 is usually connected to receive fuel oil under pressure from V a gear pump, pressure chamber, or other source Ignition is usually effected of pressure feed. electrically in these burners by a spark drawn between two electrodes 22 disposed slightly beyond and above the nozzle tip l8. These electrodes are mounted in sleeves 23 of porcelain or other suitable insulating material which are clamped in the arms of a supporting spider 24. The spider clamps about the oil pipe l6, and comprises three equidistantly spaced arms 2 ia2-'ia and 242) which extend radially outwardly into proximity to the inner surface of the draft tube l4, thereby centering the oil pipe within the draft tube. The two spider arms 24a-24a are of split clamping construction adapted to clamp over the insulating sleeves 23 of the electrodes.

The embodiment of heat shield illustrated in Figures 1 and 2 is of a readily attachable and detachable design adapted for widespread use on various constructions of burners now on the --market, without necessitating any change in the burner construction. 'In this embodiment, the shield, designated 21 in its entirety, is in the form of a semi-spherical or dome-shapedmember 23 having an arm 29 extending rearwardly from the edge of the member 28, which armis formed with a U-shaped clamp 39 at its inner end. An aperture 3| located centrally in the semi-spherical cap portion 28 is adapted to align with the jet orifice IS in the nozzle tip. The entire unit can be readily formed as va sheet metal stamping, or can be cast,.as desired. I prefer to construct it as a stainless steel stamping, and to give a high polish to the outer surface of the spherical cap portion 28 for reflecting a maximum amount of the radiant heatimpinging nozzle tip it so as to leave an air space 33 be- V tween the shield and tip. .A relatively rapid flow of air passes through this space 33 .and out through the aperture 3| in the shield, this flow of air resulting from the forced draftthrough the draft tube I 4, and also from the aspirating action of the fuel nozzle, the airflow exerting a cooling influence on the nozzle tip and also on the inner surface of the heatshield. It will'be seen from the foregoing thatmy improvedshield will thermally insulate the nozzle tip from ra-' diant heat emanating from thefiameduring burner operation, and will also act as a thermal barrier against the radiant heat of the combustion chamber afterrthe burnerhas ceased operating. During the running period, the ,high speed air flow impelled through the passageway 33 by the forced draft and by the ,aspirating action of the nozzleexerts .a substantial cooling effect on the nozzle tip, shield 28, arm 29,.clamp 30, etc., and duringthe non-running periodari air flow is also impelled through this passageway 33 byreason of the natural draft through the combustion chamber. This air flow prevents convection heat from reaching'the. nozzl'ejtip. If desired, the supporting arm portion 29.01? the shield may be made somewhat longer, so that the spring-clamp portion 33. can be engaged over. the ,oil pipe 16 instead of overQthenozz'le head. a

In Figures 3, 4 and 5, I have illustrated a modified construction of heatlshield in lwhich Qa relatively large aggregate area of opening is effective in the outer portion of the shield for the circulation of a considerable amount of air therethrough, but through which increased area of opening radiant heat cannot pass from the flame into the sleeve 42. Spider arms 45 extend inwardly from this skirt portion 44 to a central mounting boss 46 which slips over the oil pipe or from the combustion chamber back to the nozzle tip. The construction is analogous to a Venetian blind or overlapping vane effect for permitting a large volume of air to flow through the shield, but without aflording any straight line paths which would enable radiant heat to reach the nozzle tip. In the preferred construction of such embodiment, the shield comprises a short cylindrical member 33, preferably composed of tubing, and a plurality of vanes 31 mounted in staggered or offset relation across the front end of this cylindrical section. The latter end is formed with a series of notches 3B occurring around the entire tube and inclined in the relation of saw teeth. The vanes 3'! are individual stampings of segmental form, having their narrow ends cylindrically notched or rounded out, as indicated at 39, so as to form the central aperture 3| of the shield when the vanes are all assembled over the end of the cylindrical section. This assembly of the vanes is preferably effected by welding the rounded outer edges of the vanes to the outer faces of the notches 3B. The vanes are preferably of sufficient width so that the edges of adjacent vanes will overlap the requisite amount to prevent radiant heat from the flame or from the combustion space reaching the nozzle tip [8, this overlapping relation being indicated in dotted lines in Figure 4. The arm 29' and U-shaped spring clamp 35' extend from the front portion of the shield in substantially the same relation described of the arm 29 and clamp 30 in Figure 1, being either formed integral with the cylindrical section 36, or in the form of a separate stamping which is welded or riveted to said cylindrical section. This embodiment of heat shield is assembled over the nozzle in the same relation described above, and performs the similar function of preventing radiant heat from the flame or from the combustion space from reaching the nozzle tip. The relatively large aggregate area of the openings between the staggered vanes enables a large volume of air to be circulated through the shield. It will be noted that the inclined disposal of the vanes 31 results in a helical or spiral twist being imparted to the air flowing through the shield. In many instances, the air deflector ring I5 is provided with inclined deflecting vanes 15 for imparting a helical motion to the main body of air discharged through said deflector ring. These inclined vanes I5 may be employed in connection with either of the embodiments illustrated in Figure l or 3, and when employed in connection with the embodiment of Figure 3 the vanes 15 and 3! are preferably arranged to have the same direction of inclination, so that the helical motion imparted to the air will be in the same direction for both the deflector ring and the heat shield.

The embodiment illustrated in Figures 6 and 7 is in the form of a combination nozzle shield and electrode supporting bracket. It comprises a relatively long sleeve 42 provided with an end cap or end head 43, this unit enveloping the entire nozzle body I! and also the outer portion of the oil pipe It. A flaring skirt portion 44 at the opposite end of the sleeve 42 deflects an added amount of air from the draft tube l4 I6 and is rigidly secured thereto by the set screw 41. It will be noted that the entire forward portion of the sleeve 42 and the end cap 43 are spaced entirely out of contact with the nozzle I1 and nozzle supply pipe I6, and that the spider structure 45 is the only supporting means capable of conducting heat from the heat shield to the nozzle. This supporting structure is spaced so far to the rear of the nozzle head that the heat must travel a considerable distance along the shield to reach the spider structure, and this travel is in opposition to the cooling flow of air traveling in contact with the heat shield. The result is that very little heat reaches the spider structure. As best shown in Figure '7, electrode supporting arms 5l5i project outwardly from the sleeve 42, and are formed with bifurcated outer ends for effecting clamped engagement over the insulating sleeves 23 of the electrodes. Screws 5252 pass through the bifurcated ends of these arms for clamping the latter over the electrode sleeves. A third arm 54 also extends from the heat shielding sleeve 42 for engaging with the inner surface of the draft pipe I4, whereby to center the sleeve 42 and burner nozzle Within said draft pipe. The electrode supporting arms 5l-5I and the third arm 54 function as heat dissipating surfaces for dissipating heat from the rear portion of the heat shield.

The heat shielding end head 43 may be formed integrally with the sleeve 42, or may be in the form of a separate sheet metal stamping, as illustrated. I preferably make it of stainless steel, and apply a high polish to the outer surface thereof, as previously described in connection with Figures 1 and 2.v The inner edge of said end cap is formed with an inwardly crimped bead 56 adapted to snap into an annular groove 51 formed in the outer .end of the sleeve 42. At one point around the sleeve there is formed a longitudinally deeper recess 58 for receiving the bit end of a screwdriver, by the rotation of which the cap 43 can be forced off the end of the sleeve 42. The aperture 6| in the removable head member 43 is preferably so proportioned that the entire conical discharge 32 from the nozzle orifice l9 just clears the edge of this aperture 6|, as previously described in connection'vvith Figure I. Said end cap is spaced axially from the nozzle tip I8 so as to leave an air passageway 63 between the end cap or shield and the nozzle tip. The operation of this embodiment will be readily understood from the description of the preceding embodiments. A greater degree of thermal shielding is obtained by employing the sleeve 42 to envelop the entire nozzle and adjacent portion of the oil supply pipe.

The embodiment illustrated in Figure 8 employs the same construction and arrangement of thermally insulating sleeve 42, but in lieu of the end head 43 of Figure 6 it employs an end head or shield portion 65 which is substantially the same as that illustrated in Figures 3, 4 and 5. That is to say, it comprises a tubular portion 66, and a plurality of vanes 61 mounted in staggered or offset relation across the front end of this tubular section, in substantially the same relation as the tubular member 35 and vanes 31. The other edge of this tubular section is formed with an inwardly crimped bead H which is adapted to snap into the annular groove 51 formed in theouterhend of the sleeve.

In either of the two embodiments illustrated in .Figures 6 and 8, the air deflector ring l5 maybe provided with inclined deflecting vanes l5, and

when employed in connectionwith the embodiment of Figure 8 the vanes l5 and 61 are preferably arranged to have the same direction of inclination. If desired, anyone of the embodiments illustrated in Figures 1, 3, 6 and 8 may be arranged so that the heat shield has direct mounting attachment or support on this air deflecting ring I5.

While I have illustrated and described What I regard to be the preferred embodiments of my invention, nevertheless it will be understood that such are merely exemplary and that numerous modifications and rearrangements may be made therein without departing from the essence of the invention. In this regard, While my invention has its greatest field of utility in high pressure burners, nevertheless it also has advantageous utility in all nozzle types of burners.

I claim:

.1. In a burner of the class described including a nozzle adapted to discharge liquid fuel under pressure into a combustion chamber, the combination of a thermally insulating shieldsurrounding said nozzle and operative to insulate said nozzle from the radiant heat of the flame during operation of the burner and from the radiant heat of the combustion chamber following cessation of operation of the burner, said shield having a substantially central aperture therein aligned with the nozzle orificeforthe'discharge of fuel into the combustion chamber, and having secondary apertures for the passage of air through said shield, said secondary apertures being angularly inclined in such relation as to prevent said radiant heat of the flame andof the combustion chamber passing through said latter apertures and impinging on said nozzle.

2. In a burner of the class described including a'nozzle having an orifice .adapted'todischarge liquid fuel under pressure into a combustion chamber, the combination of a thermally insulating shield surrounding said nozzle and operative to insulate saidnozzle from the radiant heat of the flame during operation. of the burner and from the radiant heat of the combustion chamber following cessation of operation of the burner, said shield comprising a cylindrical body portion having its front end notched in sawtooth profile, vane segments seated in said notches in overlapping relation to provide apertures through which air can pass but through which radiant heat cannot reach said nozzle, and an oil transmitting aperture in said shield aligned with the nozzle orifice for the discharge of fuel into the combustion chamber.

.3. .In a liquidfuelburner comprising an air duct adapted to discharge air into a combustion chamber and a nozzle Within said air duct adapted to discharge liquid fuel under pressure into saidcombustion chamber, the. combination of a heat shield surrounding said nozzle for shielding the latter from the radiant heat of thefiame during operation of the burner and from the radiant heat of the combustion chamber following cessation of operation oi the burner, said heat shield comprising a relatively long tubular casting surrounding said nozzlein spaced relation thereto to define an air passageway therearound, asheet metal end head mounted on the front end of said tubularcasting in position .to substantially: enclose; and. shieldsaid; nozzle; from the radiant heat emanatingfrom either of said sources, said-end head having=an=aperture therein through which the liquid'f-uel 'dischargefrom saidnozzle occurs, aspider-at' the rear end of said tubular casting for maintaining said nozzle and tubular casting in:radially-spaced relation, said end'head and the-forward-portion of said tubular'casting being spaced entirely out of 'heat conducting contact with said nozzle-to minimize the conduction of heat'to thelatter, said tubular casting having an annular groove around its outer-end, and said end head -having an annular bead formed around the inner end thereof for releasably engaging in-said groove. V

4. In a liquid fuel burner comprising an air duct adapted to'discharge air into a combustion chamber and a nozzle within said air duct adaptedto discharge liquid fuel under pressure into said combustion chamber, the combination of a heat shield surrounding said nozzle for shielding the latter from the radiant heat of thefiame during operation of the burner and from the radiant heat of the combustion chamber following cessation of operation of the burner, said heat shield comprising a relatively long sleeve front 'endof said sleeve member inposition to substantially enclose and shieldsaid nozz1e=from the radiant heat emanating from either ;of said sources, said end head-member having an aperture therein through which the liquid fuel discharge 'from said nozzle occurs, a spider at the rear end of said sleeve for maintaining said nozzle'and sleeve in-radiallyspaced relation, said end head member and the forward portion of said sleeve being spaced outofyheatconducting contact with said nozzle to minimize the conduction of heat to thelatter and means for'relea sably coupling said head ;member ;to said sleeve member, comprising an annulargroove formed around the outer end of said sleevemember, and an'annular bead formed around the ;inner end of said head member forreleasably engaging-in saidgroove.

5. In a liquid fuelburner comprising'an air duct adapted to discharge air'into a combustion chamber and a nozzle within said air ductjadapted to discharge liquid -fuelunderpressureinto said combustion chambenthe-combination of a heat shield surroundingsaid nozzle for shielding the latter from'the radiantheat of thefiame during operation of the burnerandfrom the radiant heat'of the combustion chamber following cessation of operation of the burner," said heat shield comprising a -relatively long sleeve surrounding said nozzle inspaced; relation thereto to define an air passageway' therearound, an end head-mounted on the front-end of'said sleeve inposition to substantially enclose and :shield said'nozzle from the radiant heat emanating from either of saidsou'rces, said end head ,hav-f chamber, and a nozzle member comprising a nozzle supply pipe and a nozzle head adapted to discharge liquid fuel under pressure into said combustion chamber, the combination of a heat shield surrounding said nozzle member for shielding the latter from the radiant heat of the flame during operation of the burner, and from the radiant heat of the combustion chamber upon cessation of operation of the burner, said heat shield comprising a relatively long sleeve surrounding said nozzle member in spaced relation thereto to define an air passage therearound, and an end head mounted on the front end of said sleeve in position to substantially enclose and shield said nozzle member from the radiant heat emanating from either of said sources, a spider at the rear end of said sleeve for maintaining said nozzle member and sleeve in radially spaced relation, said end head and the forward portion of said sleeve being spaced out of heat conducting contact with said nozzle member to minimize the conduction of heat to the latter, said sleeve having an annular groove around its outer end, an annular bead formed around the inner end of said end head releasably engaging in said groove, said end head having its front portion notched in saw-tooth profile, and vane segments seated in said notches in overlapping relation to provide apertures through which air can pass but through which radiant heat cannot reach said nozzle member.

7. In a liquid fuel burner comprising an air duct adapted to discharge air into a combustion chamber, and a nozzle member comprising a nozzle supply pipe and a nozzle head adapted to discharge liquid fuel under pressure into said combustion chamber, the combination of a heat shield surrounding said nozzle member for shielding the latter from the radiant heat of the flame during operation of the burner, and from the radiant heat of the combustion chamber upon cessation of operation of the burner, said heat shield comprising a relatively long sleeve surrounding said nozzle member in spaced relation thereto to define an air passage therearound, and an end head mounted on the front end of said sleeve in position to substantially enclose and shield said nozzle member from the radiant heat emanating from either of said sources, a spider at the rear end of said sleeve for maintaining said nozzle member and sleeve in radially spaced relation, said end head and the forward portion of said sleeve being spaced out of heat conducting contact with said nozzle member to minimize the conduction of heat to the latter, said end head having its front portion notched in saw-tooth profile, and Vane segments seated in said notches in overlapping relation to provide apertures through which air can pass but through which radiant heat cannot reach said nozzle member.

8. In a liquid fuel burner comprising an air duct adapted to discharge air into a combustion chamber, and a nozzle member comprising a nozzle supply pipe and a nozzle head adapted to discharge liquid fuel under pressure into said combustion chamber, the combination of a heat shield surrounding said nozzle member for shielding the latter from the radiant heat of the flame during operation of the burner, and from the radiant heat of the combustion chamber immediately after stopping the operation of the burner, said heat shield comprising a supporting casting attached to said nozzle supply pipe at a point to the rear of said nozzle head, and a sheet metal end head mounted on said supporting casting in position to substantially enclose and shield said nozzle member from the radiant heat emanating from either of said sources, said supporting casting having an annular seating surface,

said sheet metal end head having a cooperating annular seating surface for releasably engaging the seating surface on said casting, said heat shield being supported entirely out of contact with said nozzle supply pipe and nozzle head except at said point of attachment of said supporting casting on said nozzle supply pipe, whereby to minimize the conduction of heat from said heat shield to said nozzle head, the front of said end head being of substantially semi-spherical formation and having an aperture through which the liquid fuel discharge from said nozzle occurs, said aperture having a diameter less than half the diameter of said nozzle head whereby said end head shields the major frontal area of said nozzle head from radiant heat. f

9. In a liquid fuel burner comprising a draf tube adapted to discharge air into a combustion chamber, and a nozzle member comprising a nozzle supply pipe and a nozzle head having an orifice adapted to discharge liquid fuel under pressure longitudinally of said draft tube into said combustion chamber, the combination of a diately following cessation of operation of the burner, the outer surfaces of said heat shield being cooled by the outer stream of air flowing through said draft tube, said heat shield comprising a supporting casting surrounding said nozzle member, and a sheet metal end head mounted on said supporting casting in position to substantially enclose and shield said nozzle member from the radiant heat emanting from either of said sources, said end head being supported in spaced relation to said nozzle member to permit air flow therebetween, means for detachably connecting said end head to said supporting casting the front of said end head having a relatively small aperture through which the liquid fuel discharge from said nozzle occurs, said aperture having a diameter less than half the diameter of said nozzle head whereby said end head shields the major frontal area of said nozzle head from said radiant heat.

10. In a liquid fuel burner comprising a draft tube adapted to discharge air into a combustion chamber, and a nozzle member comprising a nozzle supply pipe and a nozzle head having an orifice adapted to discharge liquid fuel under pressure longitudinally of said draft tube into said combustion chamber, said nozzle head being of relatively small size and comprising an outer portion inclined inwardly toward said nozzle orifice the combination of a heat shield surrounding said nozzle head for shielding the latter from the radiant heat of the flame during operation of the burner, and from the radiant heat of the combustion chamber immediately following cessation of operation of the burner, said heat shield comprising a heat reflecting shell enveloping said nozzle head in spaced relation thereto to define a passage for a cooling flow of air therebetween, and mounting means associated with the rear portion of said reflecting shell for: supporting-t the. latter. in: such relation l as to. conduct .a minimum amount of heat from saidreflecting-shellito saidlnozzle member, said! reflecting shell extending acrossthe frontsurface of .said nozzle head and/having a relatively restricted. aperture therein through which the.- liquidlfuel .is ,discharged ,from said nozzle 7 head andQthrough which said coolingflow, of air isdischarged, the outer-portion of saidlrefiecting shell jextending inwardly at. almore acute angle thancthetouter portion of said nozzleflhead so as to dispose the planeofvsaid aperture in close proximity to..the .plane of .the. nozzlerorifice, and the, diameter of said aperturepbeing much .less than the. diameter .ofmsaid .nozzle head, whereby said passages. for. conducting cooling air dimin-.

ishes in effective area adjacent .to said apertureto accelerate the flow-chair. through said, aperture, and; whereby; said i. reflectingshellshields.-

the major frontal .area of .said nozzlerheadrfr'om the radiant heat .'.of ,the flame.v and f the. come bustion chamber.

11. In a liquidifuel burnercomprising. an air duct vadapted 'to dischargeQair. into a combustion chamber, and a, nozzle member comprising a nozzle supply pipe and'a. nozzlehead engaging over the end of 'saidsupplypipe and having an orifice discharging liquid 'fuel under pressure into said combustion chamber, ,thecombination ofa heat shield surroundingsaid nozzlev member for shielding the latter from the radiant heat'of. the flame during operation of "the burner and from.

the radiant heat of the combustion chamberimmediately after stopping the operationof the burner, said (heat shield comprising a mounting member and'an end'headrcarried thereby, said mounting member being mounted on said nozzle.

supply pipe at a point substantially in rear ofsaid nozzle head, means for detachably securing said end head to said mounting member,.said ,end

headsubstantially enclosing and shielding, said. nozzlemember from the radiant heat emanating: from either. of said sources and beingsupported.

in spacedvrelation to saidnozzleshead to permit a coolingfiow of air therebetween, the entireheat shield beingsupported out of contact with saidnozzlev supply pipe and .nozzle head except at saidpoint of mounting-0f said mounting member on said nozz1e.,supply pipe in rearof said nozzle head said end head having an aperture'in.

its vfront end through whichthe liquid fuel discharge from the nozzle orifice occursand through which said cooling flow of .air canralso discharge, said aperture beingof relatively small size where-- by theentire conical discharge from the nozzle orifice just clears the..edge of theaperture. and.

' nozzlefrom. the radiant heat of the flame dur- 2E ing operation of the burner and from theradiant heatofthe combustion chamber immediately afterstoppingthe operation of the burner, said shield comprising a castrmetal sleeve enveloping said'nozzle, and a removable sheet metal end cap mounted on said sleeve,.said sleeve; and said cap being spaced from said nozzle and being substantially out of heat conducting relation to said nozzle, said .end caplhaving an aperture therein adapted Etolalign with the orifice innsaid nozzle; the aperture in saidlcapbeing relatively small whereby the entire'conical discharge of liquid fuel'from the nozzle orifice-just clears said aperture and whereby the major portion of said nozzle is protected. from radiant heat.

WILLIAM F. KLOCKAU.

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