US2603282A - Horizontally discharging pot-type - Google Patents

Description

y 1952 G. M. SCHUEDER ETAL 2,603,232

HORIZONTALLY DISCHARGING POT-TYPE BURNER Filed April 9, 1947 2 SHEETS-SHEET 1 a; 6 WW?- ear c z/ E- E. flaws; P 21%??? July 15, 1952 e. M. SCHUEDER ETAL 2,603,282

HORIZONTAL-LY DISCHARGING POT-TYPE BURNER Filed April 9, 1947 2 SHEETSSHEET 2 5) w iwdizu FTTa/WYEXS,

Patented July 15, 1952 UNITED STATES PATENT OFFICE 2,603,282 HORIZONTALLY DISCHARGING POT-TYPE BURNER George -M. Schueder, Dearborn, and Harrison P.

Zimmer, Rockwood, Mich., as's'ignors to Evans, Products Company, Detroit, Mich, a corporation of Delaware Application April 9,

p 2 Claims.

The present invention relates to heating-apparatus'and is more particularly directed to improved constructions of vaporizing or so -called pot type burners for use in such apparatus. Illustrative uses of the improved burners of the present invention are in connection with floor supported cabinet types of 'unit space heaters, fioor furnaces, and the like. Certain of the improvements of the present invention are generically useful in burners of the vaporizing type, including the conventional vertically discharging types. Other features of the invention are partic- 1947, Serial No. 741L454 ularly related to vaporizing burners of the type which discharge the products of combustion in a direction other than vertical, suchtas in a horizontal direction. By way of illustration, the improvements of the invention are disclosed herein as embodying a horizontally discharging vaporizing type burner which is well adapted for use in unit type space heaters of the typewhich are disclosed and claimed in the copending application, Schueder, Serial No. 35,917, .filed June 29, 1948, andin the copending application of the present applicant Schueder, Krokus and Tracht, Serial No. 36,738, filed July 2, 1948, both said applications being assigned to the assignee oi the I present invention.

Principal objects of the presentinvention are to provide improved burners of the vaporizing type, which are simple in construction, economical of manufacture and assembly, and which are reliable and efiicient in operation; to provide such constructions wherein the shape of the burner body is such as to substantially reduce the overall height of the burner and wherein, more particularly, the burner body is generally elbowshaped, defining a generally horizontal burner or vaporizing floor and a burner outlet from which heated gases are discharged in a generally horizontal direction; to provide"such'construc tions embodying anjimproved arrangement of primary and secondary air openings, which 00- operate in an improved manner in causing the vaporized fuel to properly travel through the elbow-shaped passage and in insuring the formation of a combustible mixture of suchfvaporized fuel and air; to provide such constructions wherein the, arrangement of the primary openings permits the location of the burner outlet at a desirably low level with respect to the burner floor; to provide such constructions embodying improved means for insulating the burner floor,

so as 'to promote a desired-rate of vaporization of the fuel; to provide such constructions embodyingan improved casing or shroud for the burner body and further embodying an improved arrangement of air openings in the casing, associated with the primary and secondary air openings of the burner body; to provide such constructions embodying an elbow=shaped--burner body having a generally horizontally discharging outlet at one end, a vaporizing fio0r=at :-the other end,-and a pilot ring positioned adjacent the burner floor; to provide an improved :construction of burner or vaporizingfioor which improves the vaporizing action of the burner; and to generally improve and simplify the construction and arrangement of burners -of the vaporizing type. v

With the above as well as other and inore qdetailed Objects in View, which appear in the; f ollowing description andin the appended claims, a preferred but illustrative embodiment of 'the invention is shown in theaccompanying drawings throughout the several views of which corresponding reference characters are used to designate corresponding parts-and-in which V v Figure 1 is a perspective viewof the improved burner "of the present invention, embodied" cabinet type space heater of the type specific 11y disclosed and claimed in the aforesaid impending application Serial No. 35,917; 1

Figure 2 is a top plan view of the barrier or Figure 1;

Figure 3 is a view, generally in vertical central section, taken along the line 33 or Figuie 1'; Figure 4 is a view in front elevation, taken al'ff'g the line 4-4 of Figure 3; I

Figure 5 is a fragmentary sectional viewt'aken on the line 5--5 of Figure 3';

Figure 6 is a fragmentary sectional view ta "eh along the line '66 of Figure 3 v Figure 6A is a view, generally like rigur '6, but showing a modification of the invention; and,

Figure 7 is a fragmentary view, based on Figure '3, of a modification of the invention.

It will be appreciated from a complete understanding of the present invention that, generic sense, the improvementsthereof may "be embodied in vaporizing burners of various dif- 1 fer'en't specific constructions, adapted for any of a'variety of different specific applications, cabinet type space heaters and floor fur ac shaving been mentioned heretofore as illustrative 'bi such Certain features of the invention e peculiarly related to the non-vertically (and preferably horizontally) discharging types :oi burners and other features have amore generic application. I,

Referring now to the drawings, the-illustrated improved burner, designated as a whole 851m, comprises generally a protectiveshroud or casing l2, and an elbow-shaped burner'body M whi'cli is disposed Within the casing I2, aliid isprote'cte'd thereby from undesirable air cur-rehts wh-ich might adversely afi-t the introduction Ofair to the burner body through the hereinafter described primary and secondary air openings.

Generally stated, the burner body 14 is elbowshaped, having a closed lower end l6 which constitutes a generally horizontally disposed vaporizing floor, and a generally vertically disposed 4. mental advantage that the under side of the lower pass of the drum constitutes a primary heat transfer surface, and the present horizontally discharging burner ID has the important outlet, defined by relatively closely spaced burner and secondary rings [8 and 2D.

The term elbow shaped is used herein in a generic sense as comprehending any configuration which causes gases issuing (in this vcase, rising) from the vaporizing floor It to follow a path having a substantial bend therein so that the gases emerge from the burner outlet in a non-vertical direction. 4

Fuel is supplied to the burner floor I6, through an inlet opening 22,.' which communicates,

'- through a usual float controlled and regulatable supply valve 24, with a source of supply of fuel (not-shown) To accommodate low fire or pilot operating conditions, means are provided to protect the pilot flame, and this means may conveniently comprise a pilot ring 26, which is posi- 'tioned at a slight angle to facilitate bending of the gases as mentioned hereinafter and is located a. relatively short distance above the burner floor. In the region between the burner fioor I6 and the secondary ring 20, the burner body! 'is provided with a plurality of rows of primary air openings 28, 30, 32, 34, 36, and 38,-the number and distribution of which constitute an important phase of the present invention and are described in more detail below. In the region between the burner ring 18 and the secondary ring 20, the body [4 is provided with a plurality of rows of secondary air openings 41', 43 and 45, the number and distribution of which are also discussed in more detail below. Air for combustion purposes enters the body through the primary and secondary openings, and is admitted to the interior of the casing, through an en- 'larged opening 40 in the rear wall of the shroud and through two series of openings 42 in the side walls of the shroud.

Before considering the above identified generally described elements in more detail, it is .noted that the burner i is removably associated with a generally L-shaped expansion drum 44, composed of two generally complemental sections 46 and 4B. Thenotched out portion of the drum 44, which receives the burner I0, is closed by a horizontal partition 50, and a vertical partition 52. The interior of the drum 44 is divided into two generally. parallel vertically spaced retrovertly arranged gas passages, by a baffle 54, which extends throughout the full width of the drum 44, and further extends from the partition 52, to a point within a relatively short distance of the left-hand end of thedrum 44. As is discussed in more detail below, depending upon the setting of the control valve 24, combustion takes place either within the body ,of the burner I0, or within the lower pass of 'the drum 44, immediately adjacent the burner outlet. Heated gases, resulting from the combustion process, pass through the lower pass of the drum, around the end of the baffle 54, into the upper pass of the drum, and are discharged to the stack, through the stack connection 56. The portion of the drum 44 immediately above the burner l0 constitutes a draft regulator chamber, .into which air for draft regulating purposes is admitted through the connection 58.

The above expansion drum has the fundaadvantage of a low overall height, which permits such under surface of the drum to be located comparatively near the bottom of the enclosing cabinet 60. Reference is made to the aforesaid copending application, Serial No. 35,917 for further description of the drum, cabinet, and arrangements whereby heat is extracted from the heating transfer surfaces of the drum and de livered to the surrounding surface.

Referring now to the details of the construction of the burner 10, the substantially elbowshaped body I4 is illustrated as being conveniently formed of three interconnected substantially cylindrical sheet metal sections 62, 64, and 66,

each of which is truncated to provide the elbow shape. The individual sections are securedtogether in end to end relation in any suitable manner, as by a weld extending continuously around the joint therebetween, all as is described in more detail in the aforementioned copending application of Schueder, Krokus and Tracht, Serial No. 36,738, filed July 2-, 1948.

The lower endof section 6*6'is closed'by the previously identified vaporizing or burner'iioor I6, which is circular, and which, in accordance with an important feature of the present invention, is slightly domed as indicated at Ilia. As shown in Figure 3, the fuel inlet 22 is positioned at the'side, and at a point very close to the level of the periphery of the floor [6, whereas, in Figure 7, the inlet 22a is substantially opposite to the burner outlet l8-20. V

The burner floor It andthe adjacent wall portions of section 66 thus define an annular reservoir or storage space for liquid fuel, into which such fuel is introduced through the inlet 22, and from occupied portions of which such fuel may gradually rise, by a natural physical action which would appear to be related to capillary action, towards the higher or domed central portions [6a of the burner floor. The shape of the floor l6 (including the height of the domed center above the annular rim, and also the configuration of the floor betweenthe center and the periphery), is of critical importance, limiting values being given below when properly proportioned, this generic arrangement of the fuel-receiving and vaporizing portions of the burner achieves several important advantages, some of which may briefly be outlined as follows.

As will be understood, the liquid fuels customarily used in heating apparatus of the present type fall within the general class of nonhomogeneous hydrocarbons, the several constituents whereof have a wide range of boiling points, and which also contain a certain percentage of relatively unstable and carbonizable constituents. In vaporizing such fuels for admixture with an air stream andultimate combustion, it is very desirable that the fuel be passed'gradually through areasof progressively increasing temperatures, so that the lighter constituents can vaporize before they reach areas of high temperature. Abrupt subjection of such constituents to high temperature regions results in objectionable deposits on the burner floor, and this difiiculty is markedly minimized by the just-mentioned gradual transition. i

It will be noticed that the oil flows during the course of the progressive vaporizing action, in

the same direction as does the air which is being admixed therewith, the oil being derived from the annular reservoir, and the air from the circumferentially distributed-holes. This unityof direction is important from the standpoint ofefflcient utilization of the available vaporizing area.

, Heat for vaporizing purposes is derived, in heating apparatus of thety to which .the present structures relate, primarily by radiation from the flame, andeonsequently it has become conventional to so arrange the burner body that throughout the full range from high fire to .low firesettings, the burner floor can see the flame, whicharrangementgis also employed in the structure now being described, The present arrangement is further such that the portion of the burner floor which sees the flame is the central or raised portion Ilia thereof. Accordingly, in the present. structure, as distinguished from prior structures wherein the center of the burner floor is do ressed, oil for vaporizing purposes, is stored in the. materially cooler annular reservoir portioniand reaches the relatively hotter central ptnftion .only after a radual ascent along the slightly upwardly sloping floorportion between the rim and the center.

The: term materially cooler is relative, only, in comparison with the 'higher temperature of the central domed or convex portion, it being important that the temperature of theannular area bebelow values at which carbonization or cracking or coking can occur. However,:the-temperature of the annular area is high enough to give a large heat input to the oil inthisthin or shallow, relatively wide, annular or ,ring form, thereby preparing the oil for completion of the vaporizing action. For a given quantity of .1011 in-the burner, a much larger surface area of oil is thus exposed to the preparatory heating action than would bathe case with a single oil receiving 4 depression at one side :of the burner. :It will further be understood that the rate at which oil flows from .a reservoir toward .a xvaporizing area under theinfluence of the previously mentionedcapillary or wetting action is, generallyastated, a function of, among others, the length of the boundary line of the reservoir from which the spreading takesplace. vIn the present structure, the 'peripherallength of the portion of the annular reservoir which is occupied by oil is, in .generaLa function of ,the rate at which-oil is introduced through the inlet; The Iboundaryof an annular "reservoir .ofz'course, relatively long per unit area of the reservoir-and consequently the annular shape'of the present oil reservoir provides,jthroughout the range of settings ofjt-he float valve, a desirably long boundaryiline from which the oil may flow-towards the hotter vaporizing floor areas. Thus, flow ocours-fromall directions toward the raised central portion. .n'j Coming now'to the questionof criticalvalues for the shape of the burner floor it it hasbeen found that if the rate of riseofthe areaacross which the oil film advances is too steep, that the rate of advance-is'unduly's-low and-thatthecentral portionactually becomes inactive. Conrersely, if the rate of-rise is too low, oil acoumulates to an undesirable pool-like depth over too great a portion of the floorarea; i. e.,the ring-like pool is too wide. Constructionswhlch introduce both of these difliculties are illustrated in various prior patents, for example, the Behrendt PatentNo.-2,302,287.-

lnaccordancewith the present invention,-it has been found that the domed-center should be 6 maintained at a height such that the average slope of the vaporizing floor does not exceedten per cent. (10%); that is, in a burner having-a fioor diameter of ,8'f, the center shouldnot rise more than approximately :above the rim. Preferably, the rise in such a burner is approximately It has further been foundthatthe slopeshould be approximately linear, starting nearthe periphery. Within these limitsya floor which represents a segment of a-spherical surfaceiis satisfactory, and such a surfacemayyary readily-.be-formed from sheet-metal by simple diev formingflOperations. i i 1 The present arrangement is also a marlredrim provement in connection with the generally-thousom p oling problems.- As willbe understood, pooling, asthe term is generally understood in the industry, takes place principally whenchanging relatively rapidly irom low to high fire settings, The problem is thus more, acute in-automatically controlled heaters whichinresponseto thermostatic or other apparatus, abruptly change float valve settings from full heat to: pilot .heat conditions. No automatic control apparatus for the float valve is illustrated herein, but itwill-be understood that such automatic control apparatus may be provided if desired- Even underfixed valve settings, as in manually regulatedsp'ace heaters, or during the oncycle, of an automatic heater, there appears to-be a lack of true equilibrium between the rate of oil delivery and the rate of oil vaporization or the rate at which heat is supplied to the vaporizing floor..:'I-'hus,, in either manual or automatic heaters, there :may be a varying amount of unvaporizing oil distributed about the vaporizing floor, peach ,changein such amount representingat least a partial'trarisition or pooling condition. With" the present structure, wherein theunvaporized fuelv is stored in a relatively cooler portion of, the burner body (the annular space), such transitions have little if any adverse eifects, since the additionalexcess oil still passes gradually; and from a desirably longjboundaryjline, from relatively low temperature regions to relatively high temperature regions. ,t

In further accordance with the present in vention, :means are provided; to insulate the burner ;,floor it, which meansserves not only to preventv an undesirable loss of the just-mentioned radiated vaporizing heat, but also to protect adjacent portions of the associated'heater' from such heat. More particularly, in accordance with the present invention, a heatinsulating shield IE is secured tothe undersideo'fx-the floor it, as by an attaching screwn'lll. Shield 78 base generally planar body portion, and oppositely disposed flanges it, which abutthe under side of the "floor I 5, and maintain thebody in spaced relation to the floor i6,'thus ailording a substantially dead airinsulating area, particu larl-yinthe hot spot center. If desired, the ends of this -:dead air space may be closed, butthis has not been i'ound'to be necessary; The shield t lies intermediate the floor Hi, and the lower wall-Moi the casing l2 'anda further heat insulating-spaceis thus defined between elementsw'lfl 9111:176 I The outer end of the body section 152 :is flanged as indicated at-tll, which fiange'is suitably cured, asby spot welding or otherwise, to the body of a peripherally flanged mounting panel Panel 82 is provided with fittings B l and 86,- which serve toremovably secure the burner iilras a whole, to the previously iden-tifiedsup- 7 porting partition 52. Partition 52 is provided with an opening 90 leading from the burner'into the drum 44, and which openingis surrounded by a recessed seat 92 which receives the burner I0.

The previously identified burner ring I0,- which may be conventionally formed of cast iron or the like, is provided with a central outlet 94, and the peripheral portion of the ring I8 is directly received'by the seat 92. Such peripheral portion of ring I8 is removably secured to the panel 82, as by screws 96, and agasket or other sealing element 90 is interposed between elements I8 and 82. It is here noted that Figure 4 is drawn with the cabinet partition 52 omitted.

The previously identified secondary ring is removably secured within the body of the burner section 62, by means of a plurality of bendable clips I00, and is provided with a central aperture I02, which cooperates with aperture 94 in defining the burner outlet. To promote the low level discharge of the burner, apertures 94-402 are preferably placed at' a point not higher than the horizontal axis of the section 02, and, as shown, such openingsandsection 62 are coaxial.

The present general organization, including the number and distribution of the primary and secondary air openings makes it possible to use the illustrated large burner outlet which as stated above, is preferably concentric with the final burner section 62, and such a large outlet, arranged as aforesaid, provides several important advantages. For example, the large outlet makes it possible for a substantial portion of the previously described burner floor to see the luminous flame, even at high fire settings, and thus the burner floor receives ample radiant or vaporizing heat. This arrangement further makes it possible to make use of the desirable pilot ring without objectionably reducing the area of the burner floor which sees the flame. Viewed otherwise, the present concentric arrangement is much simpler to fabricate and manufacture, the importance of which feature will be appreciated by production men in the highly competitive field to which the present invention relates.

As a specific example, the illustrated structure has a choke ratio, 1. e., the ratio between the cross-sectional area of the burner body and the area of the burner outlet, of approximately 2.65 to 1. Markedly improved operating results have been found available in structures in which this ratio is up to three-to-one.

The previously identified pilot. ring 26, is removably secured adjacent the upper end of the lowermost section 55, by a plurality of bendable clips I04, and is provided, as shown, with a sub stantially central opening I06, which is substantially concentric with the slightly ellipsoidal outer periphery of ring 26. As shown, ring 26 is disposed at a slight angle, which action promotes the "bending of the gases as they rise from the burner floor I6. In the preferred practice of the invention, the angularity of ring 26 is such that it extends substantially normal to, or makes a maximum angle with, the gas path. Stated otherwise, the ring 26 lies substantially normal to the imaginary arcuate line which extends from the center of the floor I6, through the center of the section 64, and also through the center of the burner outlet. Further, and as illustrated, it is prefered that the pilot ring 26 lies between successive rows of primary air openings, so that all of the openings in a particular row lie on one side or the other of the pilot ring and so that none of such rows are intersected by the pilot ring.

The relation between the inclined pilot ring 26 and the oil inlet to the vaporizing floor is also important. In Figure 3, as previously mentioned, inlet 22 is at the side whereas in Figure '7, the inlet 22a is opposite the outlet I8-20. In both arrangements, the inlet lies beneath the relatively higher one-half of the pilot ring. Thus, under substantially all operating conditions, much of the vaporized fuel rises from a portion of the burner floor which is below the upper one-half of the pilot ring 26. This arrangement causes the fuel vapors to rise naturally along a line substantially normal to the ring 20, which produces a desirably turbulent flow of such gases through the opening in the ring, and is particularly preferable to known arrangements wherein the oil inlet is beneath the lowest por tion of the pilot ring. In such known structures the gases flow along the under side of the ring, which action, in addition to producing insufiicient turbulence, also requires that the gas stream shall bend through a substantial angle in passing through the opening in the pilot ring. Generically, therefore, it is proposed in the present structure to utilize an inclined bailie ring and to dispose the fuel inlet below at least the higher one-half of such ring.

The casing I2 is composed of a generally U- shaped sheet metal section IIO, which defines the side and rounded rear end wall of the casing, and generally flat top and bottom walls H2 and 16, members H0, H2, and 15 being secured together in any suitable manner, as by welding. The open left-hand end of the casing is received within the flanged body of the mounting panel 82, and may be removably secured or permanently secured therein in any desired manner. The walls of casing I2 are imperforate, with the exception that the rounded rear wall is provided with a relatively smaller upper opening I20 and the previously identified relatively larger lower opening 40, and with the further exception that the side walls are provided, in alignment with the space between the burner and secondary rings I8 and 20, with two series of vertically spaced secondary air inlet openings 4|. As will be appreciated, the opening I20 affords access to the usual closable lighter fitting I30. Opening 40 serves primarily to admit air for combustion purposes to the previously identified primary air openings of the burner, and the openings I! serve primarily to admit secondary air to the secondary air openings 4|. It will be appreciated that the casing I2 serves to protect the burner II against eddies, gusts, and the like which might have an adverse effect upon the flow of air through the primary and secondary air openings in the burner body.

Coming now to the number and distribution of air openings in the burner body, it is noted that these factors have been found to be of primary importance in overcoming difliculties which, so far as the present applicants are aware, have, prior to the advent of the present invention, prevented the design of successful horizontally discharging vaporizing burners.

In this specification, the term primary air refers to all air entering in advance of the initial discharge ring 20. This air includes the pilot air which, in this embodiment, enters in advance of the pilot bafile or ring 26. Generically, pilot air is considered as that air being composed of those air pencils which control the initial mixing annular space is of considerably smaller volume than the air entering through rows 4|, 43, and 45 and; is entrained in the; swirling air in this annular space. 3 I

In the modified embodiment shown in Figure 6A,,the openings M3 43, and 45' are formed in a cylindrical portion of the bodysection 62, the number. and sizes of the holes, as well as the tipped relation thereof being preferably as described in connection with holes 4!, 43, and 45. It will be noted in comparing the two forms of Figure 6 and Figure 6A, that while the non-ribbed formof Figure 6A is simpler to manufacture, the ribbedform of Figure; 6 simplifies a problem of causingconvergence of they air pencils immediately adjacent the annular surface of the body. In both forms, however, convergence occurs inside of the annular space between the rings l8 and 2|),which space constitutes an air mixin chamber. In the preferred and illustrated practice of the inventionthis premixing chamber is a space defined by apair of rings having approximately the same outside and inside diameter, thus giving a mixing or final air chamber of substantial radial depth in contrast with, for example, structures of the type shown in Hayter Patent No. 2,415,098.

In connection with the secondary air, not only the quantity or right amount is important but its directional characteristics are of prime importance in achieving complete mixing close to the burner discharge to thus get a short or bushy flame for higher overall efliciency of the whole heater. 4 r

- Although only asingle specificembodiment of the invention has been described indetail, it will be appreciated that various modifications in the form, number, and arrangementof the parts may be made withoutdeparting from the spirit and scope of the invention, I

What is claimed is:

1. In a burneror the vaporizing surface type, the combination of an elbow-shaped burner positioned so that one leg thereof is vertical and the other leg is horizontal and above the vertical leg, the end of the burner in the horizontal leg having aburner discharge opening therein transverse to the axis of the horizontal leg, the center of said opening .beingsubstantially at the axis ofsaid horizontal leg, said vertical leg havinga bottom providing a centrally located vaporizing surface anda fuelreceiving and pool holding portion surrounding the surface, a dished baffle ring mounted in said burner adjacent the top of the vertical leg thereof and on an angle to the vertical so that the portion of the baffle on the inside of the elbow is lower than the portion of the baffle "on, the outside of the elbow, the concave portion of said baffle facing the bottom of .the vertical leg, said burner having a fuel inletopening in the side thereof adjacent said pool holding portion and located at least as far as the axis of theburner from the inside of the elbow whereby it is substantially beneath the higher half of thebaifle, said burner having primary airlinlet openings, spaced around the periphery and along the length thereof, the total area of the primary, airv inlet openings on the outer side of the elbow being substantially greater than the total area of theopenings on the inside of the elbow whereby more airmay be admitted from the outside of the elbow bend to assist in bending the vaporized fuel around the elbow. i r

2. In a burner of the vaporizing surface type,

the combination of a shroud having an imporforate bottom, an elbow-shaped burner encased in said shroud and positioned so that one leg thereof is vertical and the other leg is horizontal and above the vertical leg, the end of the burner in the horizontal leg having an opening therein transverse to the axis of the horizontal leg and providing a discharge opening forthe burner, the center of said discharge opening being sub stantially at the axis of said horizontal leg, said burner having secondary air inlets located around its periphery adjacent said discharge opening whereby a name may be located at said discharge opening, said vertical leg having an imperforate dome-shaped floor at the bottom thereof, said floor comprising an outer annular fuel receiving and pool holding portion and a central vaporizing surface portion elevated above said outer annular portion and the level of a normal fuel pool held in said outer portion, a dished annular pilot bafile mounted in the burner am acent the top of the vertical leg and on an angle to the vertical so that the portion of the baifle on the inside of the elbow is lower than the portion of the baffle on the outside of the elbow, the concave portion of said baffle facing said floor, the central opening'of said annular pilot baffle and said central vaporizing surface being located so that at least a portion of said central surface can see a flame at said discharge opening, said pilot bafile being located so that it prevents a substantial portion of said annular fuel pool holding portion from radiation from a flame at said discharge opening, said burner being located in said shroud so that the imperforate floor thereof is spaced slightly above the imperforate bottom of said shroud, means between the imperforate-floor andbottom providing an insulative barrier between them, the sides of said shroud having inlet openings for air, said burner having primary air inlet openings spaced around the periphery and along the length thereof, the total area of the primary air inlet openings on the outer side of the elbow being substantially greater than the total area of the openings on the inside of the elbow whereby more air may be admitted from the outside of the burner to assist in bending the vaporized fuel around the elbow, said burner having a fuel inlet opening in the side thereof adjacent said pool holding portion and located at least as far as the axis of the burner from the inside of the elbow whereby it is substantially beneath the higher half of the baffle.

GEORGE M1. SCHUEDER. HARRISON P. ZIMMER.

REFERENCES CITED.

The following references are of record in the file of this patent:

v UNITED STATES PATENTS Number Name Date 2,091,658 Sturgis -1 Aug. 31, 1937 2,214,403 Chadwick et al. Sept. 10, 1940 2,293,697 Chadwick Aug. 25,1942 2,306,443 Howard Dec. 29, 1942 2,337,673 McCurtain Dec. 28, 1943 2,341,355 Bovee Feb. 8, 1944 2,342,272 Hayter Feb. 22, 1944 2,369,999 Behrendt et a1 Feb. 20, 1945 2,392,757 Miller Jan. 8, 1946 2,393,248 Hayter et al. Jan. 22, 1946 2,415,098 Hayter Feb. 4, 1947 Breese Sept. 30, 1947

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