US2976920A - Oil burner with air directing means - Google Patents

Description

March 28, 1961 w. SANBORN OIL BURNER WITH AIR DIRECTING MEANS 2 Sheets-Sheet 1 Filed Sept. 4, 1957 w QM o 1w. m ww v .M ml.

X M M March 28, 1961 w. SANBORN 6,

OIL BURNER WITH AIR DIRECTING MEANS Filed Sept. 4, 1957 2 Sheets-Shee t 2 IO iii-9'7 Mornegs 2,976,920 Patented Mar. 28 1961 01L BURNER WITH AIR DIRECTING MEANS William L. Sanborn, Milwaukee, Wis., assignor to Bell & Gossett Company, a corporation of Illinois Filed Sept. 4, 1957, Ser. No. 681,930

4 Claims. (Cl. 158-76) This application is a continuation-in-part of my copending application Serial No. 588,075, filed May 29, 1956.

This invention relates to oil burners and particularly to liquid atomization oil burners of the kind used in small domestic heating plants.

It has long been known that in large capacity oil burners of the high pressure or gun-type, the use of high oil pressures, usually in excess of 100 lbs. per square inch, enables fuel to be fed at a high rate usually in excess of two gallons per hour, and that fuel in such instances is atomized by what is termed liquid atomization. Large capacity burners of the aforesaid kindhave met with wide commercial success, but Whereeiforts have been to utilize similar structures in similar oil burner installations where low or medium oil pressures are employed, there has been very little success in obtaining acceptable operating characteristics in small burner installations where fuel consumption is to be from about one-half gallon to about one and one-half gallons per hour. In such small capacity burners the oil pressures employed are from about forty pounds to about seventy pounds per square inch, and burners of such low capacity, of course, represent a high proportion of the oil burners that are sold and used. The major faults that have been experienced with such small oil burners have been their noisiness and inefficiency, and in my aforesaid co-pending application I have disclosed an oil supply and air control means whereby the efliciency of such burner has been greatly increased and the noise 2 spect to prior oil burners, it is the primary object of the present invention to enable such objectionable characteristics to be overcome in a simple and effective manner, and to accomplish this in such a way as to attain unusual efiiciency of operation coupled with almost complete absence of noise. A more specific object of the present invention is to enable low capacity oil burners to operate at greatly increased flame temperatures, with low stack temperatures, low smoke or soot production, and with a high CO reading, and related objects are to accomplish this in such a way that natural draft is not needed and in such a way that efliciency is maintained even where there is appreciable back pressure in the combustion space, to eliminate the necessity for the usual firebox, and through the attainment of high flame temperatures, to enable the area of heat transfer surfaces of such heaters to be substantially reduced.

Other and further objects of the present invention will be apparent from the following description and claims, and are illustrated in the accompanying drawings, which by way of illustration, show a preferred embodiment of the present invention and the principles thereof, and what I now consider to be the best mode in which I have contemplated applying these principles. Other embodiments of the invention embodying the same or equivalent principles may be used and structural changes may be made as desired by those skilled in the art without departing from has been reduced. The present invention constitutes an improvement upon my prior disclosure under which there is marked simplification of the structure and improvement in operation as compared with the structure shown in my aforesaid co-pending application.

To more specifically set forth the deficiencies of prior low capacity oil burners of the aforesaid type, it may be pointed out that in almost all present day oil burners that have a fuel capacity of one gallon per hour, or less, the inefliciency is such that they rarely have a flame temperature as high as 2000 F., and they operate at a C0 reading that is rarely over 7, and with stack temperatures of from 500 F. Such burners all require fireboxes to maintain adequate flame propagation, and even with such fireboxes, diliicultly is experienced in maintaining a stable fire. Such small capacity burners also have required an appreciable natural draft, usually of a high order, and this has contributed to the inefficiency of the burners. These low capacity burners also produce a high soot content in the flue gases so as to be dangerous and objec tionable in this respect. I

The foregoing performance factors of present day small capacity oil burners have, of course, influenced and increased the size and cost of heaters or boilers, and have resulted in undue costs ininstallation, operation and upkeep of such oil burners and the related equipment.

Having in mind that the oil burner structure disclosed in my aforesaid copending application overcomes the basic objectionable characteristic above set forth in rethe invention.

In the drawings:

Fig. 1 is a horizontal plan view taken through the airtube and nozzle structure of an oil burner embodying the features of the invention.

Fig. 2 is a front view of the swirler and nozzle unit.

Fig. 3 is a rear view of the nozzle and swirler unit.

Fig. 4 is an enlarged transverse cross-sectional view of the air-swirler and nozzle assembly. 1

Fig. 5 is a cross-sectional showing further details of the internal construction of the nozzle.

Fig. 6 is an enlarged view similar to Fig. 4 and showing further details of air and oil flow.

Fig. 7 is a fragmentary front view of the structure shown in Fig. 6; and I Fig. 8 is a schematic view illustrating symmetrical relationships of the components of the air and fuel supply.

The invention is herein illustrated as embodied in a nozzle-air swirler unit 10 that forms a part of an oil burner 11, and the oil burner has an air tube 12 at the forward end thereof which projects through and beyond a wall 13 of the combustion space 14 of a heater. The nozzle-air swirler unit 10 embodies many of the structural and operational characteristics that are disclosed in my aforesaid copending application, and reference is hereby made to such application and the disclosure is hereby incorporated herein insofar as it is not inconsistent with the present disclosure. 7

The nozzle-air swirler unit 10 as herein shown comprises a nozzle 15 upon which a swirler 16 is mounted, and the nozzle 15 is secured on the forward end of an-oil supply pipe 17 and is connected at its rear end to a pipe 18 by means of a union-type coupling 19, while the forward or nozzle end of the pipe 17 is supported and centered in the forward end of the air tube 12 by the swirler 16 which is positioned within a forward positioning cap 20 that is fixed in the forward end of the air tube.

The oil supply pipe 17 also serves as a carrier for electrical ignition means comprising a spark plug 22 secured by a clamp 23 to the pipe 17 and having an elecsure atomized and discharged forwardly through an axial discharge orifice D of the nozzle to form a hollow conical spray S of oil in the combustion space, and air isfed forwardly through the air tube 12 at a predetermined rate so that such air is intermixed with the oil spray to form a combustible mixture that may burn forwardly of the nozzle 15 as a flame F.

The present invention is concerned with the production of a stable, high temperature, eflicient flame F and, as will be described in greater detail hereinafter, the

present inventionenables this flame F to be maintained in a substantially constant size and location so that efficient and substantially noiseless combustion is attained.

The structural features and relationships that enable such efiicient and noiseless combustion to be attained will be described in detail hereinafter, but as a preliminary to such specific description it may be stated that it is my present theory that these results are produced by coordinating the air supply and fuel supply so that, with respect to the axis of the nozzle, the air supply and the oil supply are individually symmetrical, and are symmetrical to each other, and by supplying flame propagation air at the nozzle tip so that flame propagation starts close to the tip. It is my present theory that the presence of flame propagation air at the tip assures continuity and uniformity of combustion at this point, thus to eliminate pulsation of the flame F toward and away from the nozzle, while the symmetry of the air and fuel supplies about and with respect to the nozzle axis, and with respect to each other, assures uniformity or symmetry of combustion in a circumferential sense and eliminates any tendency toward lateral pulsation of the flame F. As a result of such control of the fuel and air, the combustion of the fuel is completed while the fuel is within a relatively short distance of the air tube 32 and the flame F maintains a substantially constant position and a substantially constant form and size.

Thus, as shown in Fig. l, the flame F has the form of a parabolic conoid that is symmetrically positioned on the axis of the fuel nozzle 15 with the small end of the flame disposed at substantially onequarter inch from the nozzle tip. In a burner of the present construction operating at about one. gallon per hour the flame F has a length of about 4 inches and a maximum diameter of about 4 inches, and the flame burns without pulsation or noise.

Under the present invention the nozzle 15, the swirler 16 and the spark plug 22 are assembled as a unit that may be readily mounted or removed from the air tube 12. Thus, the assembly may be moved forwardly into the air tube 12 with the outer edge portions f the swirler 16 in engagement with the tube 12 and finally with the end cap 21 and the outer forward portions of the swirler 16 engage an inturned annular flange 26F of the air cap to limit and determine the forward position of the nozzle 15 and the swirler 16. The coupling 19 which is in the nature of a union is then attached to the pipe 18 so that the nozzle-swirler unit fit is located in a fixed position where it is coaxial with respect to the air tube 12.

One of the important characteristics of the present structure is the provision of a relationship between the elements which causes those forward surfaces of the nozzle 15 where carbon deposits would usually be formed to be kept clean and free from oil so that carbon formation on these nozzle surfaces is prevented. In attaining this result the specific form of the nozzle 15 is quite important as well as the relationship of the nozzle to the air directing means of the swirler l6, and as a preliminary to the description of functioning in this regard, the specific form of the nozzle will be described. Thus, the nozzle 15 is in many of its characteristics of conventional construction as shown in Fig. 6 of the drawings, and the specific structural characteristics and relationtionship that are important in attaining the objectives of this invention will be described in detail. As shown in Fig. 6.of the drawings, the nozzle 15 comprises an outer forward tip 1ST in the forward end of which the axial discharge passage 15!) is formed. The rear end of the tip 1ST takes the form of a nipple 15N to which a union fitting 17U on the forward end of the supply pipe 17 maybe connected, and just forwardly of the nipple 15N, a nut portion 15H is provided.

Within the tip 151", an inner core 150 is provided and is held in place by a set screw 158 that is threaded axially into the rear end of the nipple ISN. The core 15C and the set screw 153 have aligned axial passages 15? formed therein so that oil fed forwardly through the pipe 17 enters these passages and is discharged radially from the core 15C through bores 15A into a pressure space 15B that surrounds the core 15C within the forward portion of the tip EST. The forward portion of the core 15C is formed as a plug that closes the forward end of the passage or bore 15A and has a rounded forward face 115C that has an annular area of engagement with a rearwardly facing internal surface 115T, and the oil from the pressure chamber, in order to reach the discharge orifice 15D, passes this annular area of engagement of the surfaces 115C and 115T through passages that are formed as slots 1158 in the surface 115C of the core. The oil that thus passes through these slots 115$ enters a space formed between the forward surface of the core 15C and the rear or inner end of the discharge passage 151) so that the streams of oil that are formed as the oil moves through the slots 1158 may be discharged through the passage 15D.

It is important to note that the slots 1158 are symmetrically related to each other and to the axis of the nozzle, and are so positioned that the oil passing through these slots is given a swirling motion about and with respect to the axis of the nozzle, and this relationship is known in the art and is shown in Fig. 5 of the drawings. The manner in which the streams of oil pass into the discharge orifice 15D and are discharged as a spray S will be discussed in some detail hereinafter.

On the forward face of the nozzle tip 1ST a novel and extremely important form or shape is employed which functions as will hereinafter be described in cooperation with the swirler '15 to assure that oil does not flow rearwardlyalong the nozzle surface. Thus, as shown particularly in Figs. 4 and 6 of the drawings, the forward face of .the nozzle tip 151 is formed with a forwardly converging conical surface 315C that extends to a point where it is of relatively small diameter, and at this point the conical surface 315() merges with or meets a cylindrical surface .4156 that extends forwardly in a concen tric relation with respect to the nozzle axis to meet a forward nozzle face 15F that is circular in form and through which the discharge orifice 15D opens.

The fuel oil that is being fed under pressure through the nozzle 15 has a swirling motion imparted thereto by reason of the angular positioning of the slots 1-153, and it is formed into four distinct and relatively fine streams of oil that leave the respective slots 1158 and move with a spiral or swirling motion through the outlet or dis charge opening 151). As this fuel leaves the discharge opening 15D it forms into a hollow conical spray S that may be described in general as constituting a thin layer of finely divided oil particles shaped in the form of a cone that is centered on the axis of the nozzle 15 and has its apex located approximately at the forward end of the orifice 15D. The internal angle of the cone that constitutes the spray S varies according to known practices in accordance with the specific internal design of the nozzle 15, and the nozzle herein shown is one that produces what is called a spray as indicated in Fig. 6, but under the present invention ditferent spray angles may be used as, for example, a 60 or 75 spray angle, as is common in the art.

1 As above pointed out, the spray S is made up in a general sense as a thin layer of oil that defines a cone,

but I haveobserved, and in accordance with the present invention, have made advantageous use of the fact that within or as a part of this thin layer there are well defined concentrations of fuel that take the form of streams SS.

as indicated on an exaggerated scale in Fig. 8. These streams SS correspond in number and in circumferentiallocation with the number and location of the slots 1158, and between the streams SS, the spray is defined by the thin layer S as indicated in Fig. 8. As will become apparent from the following description, the supply of air to the combustion space is controlled by the swirler 16 and the design of the swirler is correlated with the form of the spray, as above described, so that the proportioning of the air and fuel is maintained uniform throughout the entire circumference of the spray, and through this control, the present invention eliminates the usual tendency of the flame to burn unevenly in a lateral sense. This'results in the attainment of what may be termed lateral stability of the flame, as will be described hereinafter.

The swirler 16 embodies certain of the physical characteristics of the swirler shown in my prior Patent No. 2,485,244, as well as certain of the physical characteristics of the swirler of my aforesaid copending application, but as will become apparent hereinafter, the swirler '16, as compared with the structure of such patent, includes additional cooperating structural elements and accomplishes additional functions that enable the desired efficiency and operating characteristics to be attained in small oil burners.

' Thus the swirler 16 constitutes a singleblade unit having a plurality of segmental blades B formed integrally with and as outward generally radial extensions of a coneshaped inner air directing member C. The swirler 16 is formed from sheet metal as by stamping and forming operations in which the several blades B are defined by cutting a series of radial slits 30 which at their inner ends have circumferentially extending slits 31 formed at a uniform distance from the center of the cone C and extended in the same circumferential direction from the related radial slits 30. After the slits 30 and 31 have been formed, metal of each segment is bent forwardly to give the desired fan-like shape to the several blades B. The several blades B are of identical form and are uniformly spaced. As will be evident in Fig. 7 of the drawings, this fan-like formation enables the blades B to impart changes of direction to the forwardly moving air that must pass from the air tube 12 through the swirler 16. Thus air will be directed inwardly in a radial direction through the opened slit 31 to provide an inwardly directed air component 32 at each of the several blades B, and also air will be directed with a swirling component gem each of the several blades B as indicated at 33 in The inwardly directed stretms or compontnts 32 of air are directed somewhat forwardly along the forward surface of the air directing cone C as will be evident in Fig. 6 of the drawings.

At their outer forward corners, the several blades B are interconnected by an annular connecting band 34 that is made of sheet metal and is welded or brazed to the corners of the several blades B as indicated at 34W in Fig. 6.

The swirler 16, as above pointed out, is supported in a fixed and centered relationship on the nozzle 15, and this is accomplished by a supporting spider that is made from sheet metal and has an annular mounting rim 35R of angular cross-section which fits with a snug press fit on the annular surface of the tip 1ST just forwardly of the nut portion 15H, and the mounting rim 35R has a plurality of connecting arms 35A that are relatively narrow, as will be evident in Fig. 3 of the drawings, and which extend outwardly and then forwardly for welded connection as at 35W with the outer rear surface of the air-directing cone C. The narrow arms 35A provide for adequate area through which forwardly,

moving air may move to strike the outer rear face. of the air-directing cone C so that such air may be directed inwardly and forwardly along the conical surface 315C of the nozzle tip 1ST for subsequent discharge through the central discharge opening 37 of the air-directing cone C. The discharge opening 37 is, of course, concentric with the axis of the nozzle and is spaced outwardly from the cylindrical surface 415C of the nozzle tip. As shown herein, the opening 37 is disposed in a plane that is relatively close to the rear end of the cylindrical surface 415C, but this relationship may be varied to a considerable extent within the purview of this invention.

The conical forward surface 315C of the nozzle tip and the rear face of the air-directing cone C are arranged so as to converge slightly toward each other as they approach the axis of the nozzle, and this relationship is important in that it imparts an increased velocity to the air that is moving therethrough toward the discharge opening 37.

The inwardly moving cone of air that passes between the cone C and the surface 315C has been indicated diagrammatically at 38 in Figs. 6, 7 and 8, and when this air reaches the discharge opening 37 its direction of movement is altered in a large measure by the cylindrical surface 415C of the nozzle tip so that this air is discharged in a forward direction as a sleeve 39 of air that moves longitudinally along the cylindrical surface 415C. The forwardly moving sleeve 39 of air thus moves forwardly past the annular corner where the cylindrical surface 415C meets the face 15D so that the sleeve of air strikes the spray S in a uniform and symmetrical manner relatively close to the point where the spray S emerges from the nozzle. The forwardly moving sleeve of air that has been identified at 39, and which thus strikes the spray S, is important in further breaking up or atomizing of the oil of the spray and in mixing with the spray to assure a combustible mixture closely adjacent to the nozzle tip, and it is also of particular importance in that it actsin a novel manner to assure thatoil from the forward tip face 15F cannot move in a rearward direction along the forward faces 415C and 315C of the nozzle. Thus, it may be noted that the face 15F of the nozzle tip operates in a wet condition in that oil that is not discharged as a part of the spray S gathers in small amounts on the forward face 15F. This wet tip-face condition has long been known and recognized in the oil burner art, and it has been known that it is this oil on the. wet tip-face of the nozzle that hts been responsible for carbon deposits or varnishing on the nozzle surface. I have found that where rapidly moving air is discharged as a sleeve past and perpendicular to the outer annular corner of the nozzle tip face 15F, any oil that has moved outwardly or radially to the annular edge of this face is picked up by advancing sleeve of air and is thus transported forwardly into the spray so that it is burned in the normal manner. When this arrangement is employed, it has been found that no carbon deposits are formed on any of the for ward surfaces of the nozzle.

The inwardly directed air indicated at 32 as flowing inwardly from the respective blades 16 and along the forward surface of the cone C is of course consolidated with the sleeve 39 of air adjacent the apex of the spray S, and this is accomplished in such a way that symmetry of air supply is maintained and further break up and early combustion of the fuel is assured.

With the swirler 16 related to the nozzle 15 as above described, the desired flame propagation air is supplied relatively close to the nozzle 15, and by using a structure that provides such flame propagation air in relatively large volume, it is found that the fuel starts to burn almost immediately after it is discharged from the nozzle 15, thus to locate the flame F, quite close to the end of the nozzle. The air that emerges from the swirler, as at 33, has a swirling motion and engages the sprayed fuel so as to provide additional air for combustion while at the same time acting to confine the flame Within the envelope afiorded by the advancing swirling body of air.

An important characteristic of the present invention is that the air is supplied to the fuel in a symmetrical relationship with respect to the fuel spray, and in this respect the specific composition or form of the spray, as hereinabove described, is important. Thus, I have found that Where four slots 115$ are used in a nozzle, the flame characteristics are vastly improved by utilizing a swirler construction in which the number of blades is equal to the number of slots employed in the nozzle multiplied by a Whole number. In the present instance, where four slots 1153 are used in the nozzle, the desired combustion characteristics are attained by using eight blades B in the swirler. The swirler, however, may, under the present invention, be formed for use with a four-slot nozzle so as to have an even greater number of blades, such as twelve blades each, or sixteen blades. This same general theory may be applied to other nozzles having different numbers of slots 1158. Through this arrangement and relationship, the air supply is symmetrical in a circumferential sense to the streams SS of the spray as Well as to the intermediate web-like portions of the spray, and in Fig. 8 of the drawings this symmetrical relationship has been schematically illustrated.

In considering the symmetry of the air supply and the oil supply with respect to each other and with respect to the nozzle axis, it is important to note that, in attaining the desired swirling movements and inward movements of the air, the blades B of the swirler act initially to divide the main air stream into a plurality of separate air streams which have been schematically indicated by arrows in Fig. 8, and further that the nozzle 15 produces a spray that includes a conical web-like portion with a number of discernible streams SS therein corresponding to the number of nozzle slots 1158. Thus, in carrying out the basic concept of the present invention, each stream SS (along with the related thin web portions of the spray) is acted upon in a like manner by one of several like groups of related air streams, with the result that each portion of the spray is subjected to like forces and is supplied with like amounts of air.

To consider the foregoing analysis more specifically as applied to the illustrated embodiment, each blade B may be considered as producing or causing a circumferentially directed air stream 33 that passes through the related slot 30 and an inwardly directed air stream 32 that passes through the related slot 31, such inward air streams 32 being substantially directed slightly forwardly by the outer surface of the cone C.

InFig. 8 of the several streams of air that are produced by the eight blades B are shown in relation to the spray S and its four streams SS that are produced by a four-- slot fuel nozzle. Thus with this particular relationship of the number of blades B, and nozzle slots 115$, and with the slots and the blades in a symmetrical or equidistantly spaced relation about the nozzle axis, each of the four similar segments of the fuel spray is acted upon in a similar manner by the same number and type of air streams. This result follows regardless of the rotativc or angular positioning of the swirler with respect to the slots 1258 of the nozzle, and the four similar segments of the fuel spray are thus subjected to like controlling conditions and to like combustion conditions so that lateral unbalance and lateral pulsation of the flame F are prevented.

With the nozzle and the swirler formed and related as thus described, the flame F maintains a steady form and position so that the fire is substantially free from objectionable noise and is highly efficient in all respects. In

actual use it has been found that in a small capacity heater the fuel feed rate, and the air supply rate, may be adjustably varied or modulated over a substantial range while maintaining the eflicient and noiseless opera tion of the burner. In such operation, the inward flow of air over the conical surface of the nozzle tip serves to keep the nozzle cool, and as this cone of advancing air passes forwardly through the annular opening 37 and is formed into a sleeve of air along the cylindrical surface 415C, it passes the annular outer corner of the tip face 15F and picks up any excess oil at the edge of the face 15F so as to carry the same into the flame F. The longitudinal stability of the flame F avoids contact of the flame with the nozzle and eliminates baking or clogging of the nozzle.

The flame propagation air that flows through the annular opening 37 so as to cool and clean the nozzle is of course intermixed with the fuel at substantially the apex of the fuel spray so the combustion starts and is uniformly maintained at but a short distance from the nozzle, and as a result the burning of the fuel is completed within a relatively short travel of the fuel and while the fuel is well within the controlling range of the swirling envelope of combustion air that advances between the blades of the swirler.

With a small capacity burner of the construction described, operating at a fuel consumption rate of one gallon per hour of No. l or No. 2 oil, it has been found that flame temperatures of as high as 2700 F., stack temperatures of as low as 250 F., may be readily and consistently attained with CO readings of 12 and 13% and with CO readings of zero. Such performance has been attained without natural draft and even in the presence of appreciable back pressure, and in every instance the fire has been free from noise and the flame stable in a longitudinal as well as a lateral sense.

The low nozzle temperature that is attained by the present invention is of particular value inthat it avoids production of a clogged or varnished nozzle so that the nozzle operates in a cool and clean condition despite its proximity to the unusually hot flame that is produced. Hence one of the most frequent causes of burner failure has been overcome. This results in part from the longitudinal flame stability which prevents contact of the flame with the nozzle, in part from the continuous and symmetrical supply of flame propagation air at the nozzle tip so that positive pressure at this point prevents rearward flow of heated gases past the nozzle, and from the continuous flow of cooling air over the nozzle and the swirler blades which are located in the airstream and act as cooling fins for the nozzle.

Thus, the present invention enables a medium pressure,

liquid atomization burner to operate with extremely high efliciency and in a trouble-free manner, and since the high oil pressures, that have heretofore been considered necessary for efficiency, have been eliminated, the characteristic oil burner roar has been substantially eliminated.

From the foregoing description it will be apparent that the present invention enables small capacity, medium pressure, oil burners to operate without objectionable noise and at uniform and extremely high levels of chiciency; and further, that the stability and efliciency thus attained simplifies and reduces the cost of production, installation, operation and upkeep of small capacity oil fired heaters.

Thus while I have illustrated and described the invention in a particular embodiment, it will be recognized that changes and variations may be made within the spirit and scope of the invention.

1 claim:

.1. In an oil supply and air control unit for use in a liquid atomization type oil burner having an air tube through which low pressure air is directed in a forward direction toward an open forward end of the tube, an oil supply pipe adapted to be mounted in the tube through which oil may be forced at a predetermined pressure, a liquid atomization nozzle connected to said pipe at the forward end of an air tube for receiving oil under pressure from the pipe, said nozzle including an outer nozzle tip having an axial discharge orifice for spraying oil forwardly from said nozzle and having an outer forward face formed as a concentric, truncated conical surface from the smaller forward end of which a small cylindrical projection extends and terminates in a flat tip face normal to and through which said discharge orifice opens, a cone-shape air directing member disposed forwardly of said conical face and extended radially outwardly beyond said nozzle to direct air inwardly along said conical face for discharge as a forwardly moving sleeve along said cylindrical projection and past the edge of said tip face at right angles to said tip face to carry any oil present at the edge of the tip face directly forwardly into the oil spray, a mounting spider supporting said air directing member on said nozzle, an annular series of radially disposed air directing blades formed as outward extensions of said cone-like air directing member and arranged in uniformly spaced relation in a circumferential sense for directing air with a swirling action direction against the divergingly sprayed oil.

2. In a nozzle-swirler unit for use in a liquid atomization type oil burner having an air tube through which low pressure air is directed in a forward direction toward an open forward end of the tube, an oil supply pipe adapted to be mounted in the tube through which oil may be forced at a predetermined pressure, a liquid atomization nozzle connected to said pipe at the forward end of an air tube for receiving oil under pressure. from the pipe, said nozzle including an outer nozzle tip having an axial discharge orifice from which a spray of oil may be discharged in a forward direction and having an outer forward face formed as a truncated conical surface concentric with said orifice and from the smaller forward end of which a small cylindrical projection extends and terminates in a flat tip face normal to and through which said discharge orifice opens, a swirler stationarily mounted concentrically on said nozzle and having an annular series of radially disposed air directing blades arranged in uniformly spaced relation in a circumferential sense for directing air with a swirling action against the sprayed oil, and a cone-shape air directing member disposed forwardly of said conical face to direct air inwardly along said conical face for discharge as a forwardly moving sleeve along said cylindrical projection and past the edge of said tip face at right angles to said tip face to carry any oil present at the-edge of the tip face directly forwardly into the oil spray.

3. In an oil supply and air control unit for use in a liquid atomization type oil burner having an air tube through which low pressure air is directed in a forward direction toward an open forward end of the tube, an oil supply pipe adapted to be mounted in the tube through which oil may be forced at a predetermined pressure, a liquid atomization nozzle connected to said pipe at the forward end of an air tube for receiving oil under pressure from the pipe, said nozzle including a nozzle tip having an axial discharge orifice and an outer forward face formed as a concentric, truncated conical surface from the smaller forward end of which a small cylindrical projection extends and terminates in a fiat tip face normal to and through which said discharge orifice opens, means forming part of said nozzle and located within said tip for forming forwardly moving oil into a predetermined number of fine streams of equal size and pressure for discharge with a swirling action in a predetermined rotative direction and in uniformly diverging relation and in uniformly spaced relation to a circumferential sense, a swirler stationarily mounted on said nozzle and having an annular series of radially disposed air directing blades provided in a number that is a whole number multiple of said predetermined number of streams of oil arranged in uniformly spaced relation in a circumferential sense for directing air with a swirling action in said predetermined direction against the divergingly sprayed oil, and a cone-shape air directing member disposed forwardly of said conical face to direct air inwardly along said conical face of the nozzle for discharge as a forwardly moving sleeve along said cylindrical projection and past the edge of said tip face at right angles to said tip face to carry any oil present at the edge of the tip face directly forwardly into the oil spray.

4. In an oil supply and air control unit for use in a liquid atomization type oil burner having an air tube through which low pressure air is directed in a forward direction toward an open forward end of the tube, an oil supply pipe adapted to be mounted in the tube through which oil may be forced at a predetermined pressure, a liquid atomization nozzle connected to said pipe at the forwardend of an air tube for receiving oil under pressure from the pipe, said nozzle including a nozzle tip having an axial discharge orifice and an outer forward face formed as a concentric, truncated conical surface from the smaller forward end of which a small cylindrical projection extends and terminates in a flat tip face normal to and through which said discharge orifice opens, means forming part of said nozzle and located within said tip for forming forwardly moving oil into a predetermined number of fine streams of equal size and pressure for discharge with a swirling action in a predetermined rotative direction and in uniformly diverging relation and in uniformly spaced relation to a circumferential sense, a swirler stationarily mounted on said nozzle and having an annular series of radially disposed air directing blades provided in a number that is a whole number multiple of said predetermined number of streams of oil arranged in uniformly spaced relation in a circumferential sense for directing air with a swirling action in said predetermined direction against the divergingly sprayed oil, each of said blades also being formed to direct air inwardly toward the axis of the discharge orifice, and air directing means disposed forward- 1y of said conical face to direct air inwardly along said conical face of the nozzle for discharge as a forwardly moving sleeve along said cylindrical projection and past the edge of said tip face at right angles to said tip face to carry any oil present at the edge of the tip face directly forwardly into the oil spray.

References Cited in the file of this patent UNITED STATES PATENTS 1,536,046 Anthony May 5, 1925 2,120,387 Bargeboer June 14, 1938 2,156,405 Smoot May 2, 1939 2,221,519 Jones Nov. 12, 1940 2,267,451 Eweryd Dec. 23, 1941 2,485,244 Sanborn Oct. 18, 1949 2,501,414 Schoenwetter Mar. 21, 1950 2,551,276 McMahan May 1, 1951 2,603,279 Pohle July 15, 1952 2,634,806 Hirtz Apr. 14, 1953 2,765,028 Kienle Oct. 2, 1956 FOREIGN PATENTS 146,708 Sweden Aug. 31, 1954

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