US2410881A - Heating apparatus - Google Patents

Description

R E T N u H H R HEATING APPARATUS Filed July 29, `1942 2 Sheets-Sheet 1 ATTORNEY N., B2, E946.

. R. H. HUNTER HEATING APPARATUS Filed :July 29, 1942 2 Sheets-Shee 2 FeG-6 mvENoR MTRNEY Patented Nov. 12, 1946 UNITED STATES PATENT OFFICE HEATING APPARATUS Robert H. Hunter, Cleveland, Ohio Application July 29, 1942, Serial No. 452,712

'Z Claims. (Cl. 158-28) l' l I This invention relates to an improved combustion-operated, forced air heating apparatus and mechanism useful also for heating and/'or ventilating generally closed spaces which mechanism and apparatus will effectively utilize ordinary motor fuel (gasoline) notwithstanding impurities (e. g. tetraethyl lead) likely to be contained therein. T'he above indicates the general object of the invention.

Additional objects include the provision of: a new or improved heat exchange head for heaters of the type illustrated herewith; a new or improved burner; a new or improved injector gun device for a heater adapted to utilize atomized and/or vaporized liquid fuel such as mentioned above; an improved igniting means for intimately mixed fuel and air; improvements inl respect to making and assembling parts of a heat exchange head; a new or improved method of igniting and burning liquid fuels such as ordinary motor gasoline in a heater; a new or improved method and apparatus for controlling a forced air and combustion-operated unit heater employing liquid fuel; and certain improvements in air forcing units for heaters of the type shown.

Other objects and novel features of the invention will be'pointed out in the following description of the illustrative forms thereof shown in the accompanying drawings, wherein:

Fig. 1 is an end view of a heater cabinet in one form: Fig. 2 i's a vertical cross sectional view of the blower and heater assembly taken along a line 2--2 Fig. l; Fig. 3 is a cross sectional view taken as indicated by the line 3--3 on Fig. 2 showing mainly the heater and burner and, schematically, one manner of storing and supplying fuel; Fig. 4 is a longitudinal, relatively enlarged, sectional detail'view illustrating one manner of making heat pick-up ngers as will be explained later; Fig. 5 is a relatively enlarged longitudinal fragmentary sectional view showing the fuel injector and ignition means more in detail and showing a modied manner of making heat pickup fingers in the burner; Fig. 6 is an electrical diagram showing the preferred control arrangement for the blower and burner; and Fig.v

l is a side elevation, partly broken away, showing a mociied blower unit arrangement.

The specific forms of apparatus shown are adapted for heating and/or Ventilating generally closed spaces, for example; tents, cabs, cockpits, automobile and trailer bodies. A sheet metal cabinet i, Fig. l, houses the heater and blower unit 2 and a supply of fuel such as a gas tank 3.

An air. inlet is shown as comprising a grilled or otherwise generally guarded opening 4 leadlng into the interior of the cabinet. The cabinet has a removable wall section for access thereto, shown in the form of a detachable cover 6.

Air entering the grilled opening 4, Figs. l and 2, is drawn through a cleaner or filter 8 which may be arranged as an inlet device of the unit 2 and supported thereby. As shown in Fig. 2 the air cleaner comprises a cylindrical tube I I formed of several layers of wire mesh such as commonly used on automobile carburetors for air cleaning purposes. A supporting canister or frame part I2 of the air cleaner is attached to the blower housing in such manner that air must pass through the cleaner material while enabling the .tube II of air cleaning material to be replaced readily when necessary as by releasing an attaching bolt or screw I3 operatively engaging a fixed part I3' of the cleaner assembly.

The blower casing member I5 is also generally cylindrical and, opposite the entrance opening I6, a separate dome-shaped wall member I'I of the blower casing is telescopingly joined to the member I5 partially closing the same. A suitable number of air outlet openings I8 are formed in the dome-shaped portion of the member I1, the number and size of openings being proportioned to the relatively low pressure air movement capacity of the blower so that air accumulates in a plenum 20 at appreciable pressure. Thereby the air is ejected from all the outlet openings I8 and ows uniformly over the heat exchange surfaces of the heater, designated generally 2|, and without substantial turbulence.

A centrifugal blower element 22 coaxially of the blower casing member l5 and adjacent the inlet I6 is (as shown) a conventionally bladed centrifugal impeller lin radial alignment with which, and extending substantially tangentially of the casing member I5, is a relatively high pressure air outlet duct 23 for purposes to be described later. Only a relatively small portion of the output of the blower leaves by way of the duct 23, the remaining larger portion being forced as a relative low pressure diiused column from the openings i8 generally parallel to the axis of the casing member l5. A suitable electric motor 25 for the blower is contained by and appropriately supported in said casing section I5 by means not shown.

The heater unit 2| has a easing 2s in the form` of a generally rectangular hollow sheet metal box, a portion 2l of which, in the particular arrangement shown, telescopes and is fastened to the dome-shaped discharge member Il of the blower unit. Opposite the portion 21 the casing has a Warmed-air-discharge opening 28 which may, for example, be guarded by wire mesh or other grillwork 29. The peripheral walls of the heater casing 28 are substantially closed as will be apparent from comparison of Figs. 2 and 3, so that all the air blown into the heater casing must leave by way of the outlet opening 28.

The entire blower-heater unit may be supported in the cabinet as by a pair of angle rails 3U fixed at their ends-to vertical side or end walls of the cabinet and passing beneath the heater casing 26, being appropriately secured to said casing. The blower casing I5 may be specially supported from said rails 30 by means of a cross piece 3i .connecting the rails and extending beneath and in supporting relationship to the blower casing. The rails 30 may also support the main elements of the control system on a suitable panel (not shown), which panel is exposed at one face of the cabinet.

Referring particularly to Fig. 3 a burner fuelinjector and ignition device or gun 32 is located exteriorly of and at one side of the heater casing 26 and connected as by a brazed joint 32a, shown as a cupped flange in Fig. 3 only, with a burner and exhaust tube 33 of U-shape within the heater casing -and supported by engagement with the heater casing walls at openings therethrough as will be apparent from the drawings. The main burner portion of the tube 33 is indicated at 34, elbow thereof at 35, and an exhaust and burnerdischarge portion at 36. The U-shape of tube enables utilization of substantially all the heat of combustion and has other advantages as will be made apparent later herein. fAt the elbow portion of the tube is a supporting pin 31 which is slidably engaged with a complementary opening in the adjacent wall of the casing 26, the supporting arrangement thus allowing the tube 33 to expand and contract freely horizontally with reference to the walls of the casing 2B as necessitated by the fact that the tube is heated rapidly upon starting up the heater.

Air is forced by the blower mechanism of Fig. 2 across the tubes; and to facilitate heat exchange the tube 33 has spaced parallel sheet metal radiating plates 38 thereon in tight peripheral engagement with the tube portions which pass through the plates at openings thereof. The plates may be spaced apart by tubularly flanged portions 39 defining the plate openings, which portions 39 are preferably brazed or welded to the tubes to facilitate heat conductivity from the tube 33 to the plates. Certain of the plates 38 (left hand group, Fig. 3) may be secured only to one of the tube portions, 34 or 35, so that the tube portions 34 and 36 are free to move toward and away from each other, under the inuence of heat, without distorting the plates, in which event those particular plates may be in staggered relationship as maintained by short marginal flanges 40. The radiator plate assembly is generally the same shape as the interieor of the casing 28, i. e., rectangular as shown in Fig. 2; but the shape of the individual plates may vary considerably from each other.

Flame. projected from the burner-igniter device 32 impinges upon serially arranged and staggered sets of heat-pickup pins or ngers 42, Figs. 2, 3 and 4, projecting inwardly from the interior surfaces of the tube 33. designed to form a maze which causes the heating media (flame and heated air and gas) to follow tortuous paths through the burner and exhaust portions of the tube 33. There may be as many sets of ngers 42 used as will obtain maximum heat exchange efficiency, the number being increased as the size and/or length of the tube 33 is or are increased. The fingers or pins may be made in VallOuS Ways.

One manner of making the heat-pickup fingers is to cut them in comb-teeth formation at one margin of a piece of flat strip stock of heat and corrosion resisting (e. g., stainless steel) alloy; then roll or form the piece into a cylindrical ring 43 and then bend the fingers alternately at different angles from the base or uncut part of the piece. The described procedure results in directing some of the fingers, for example half of them, at a greater angle of relative convergence than others, as brought out particularly in Fig. 4. It may be noted that two, intermeshed, sets of comb-like blanks may be cut simultaneously to minimize scrap.

The manner in which the heat-pickup finger supporting rings 43 described above are disposed in the tube depends somewhat upon the manner of aiiixing the rings to the tube. It would be preferable to have the ngers of all the rings converge in the direction of movement of ame and hot gas through the tube, but that is not essential at least in regard to those farther from the region of most intense heat (e. g.. those in the discharge or exhaust portion 36 of the tube 33 wherein the fingers, as shown, converge toward oncoming flame or hot gas). The tube is preferably seamless, heat and corrosion resistant alloy (e. g., stainless steel) tube stock and bent into U-shape in such manner as not appreciably to stretch the outer region of the bend. As noted at 44 the tube is purposely wrinkled, accordion fashion, at the inner side of the bend to minimize such stretch.

The rings 43, if made, as preferred, from strip stock, although they could be made from tubing, are of somewhat less length than the inner circumference of the tube 33, so that the ends of each piece of strip are definitely spaced to enable the rings to slide into the tube without much forcing and be spring-stressed into contact with the tube at all regions of contact.

If the rings 43 are spot welded into place the necessary inner electrode may be used to insert the rings into proper position, as by abutment with the farther inwardly bent fingers 42 there- `of, prior to applying welding current thereby.

With the two sets of ngers (indicated sets being those in tube portions 34 and 36 respectively) extending in relatively reversed direction, as with the fingers of each set converging toward the elbow, the same method can be followed in assembling the rings of both sets. Further, in case or spot welding the rings in place, a staggered arrangement of spot welds 45, i. e., alternately positioned in zig-zag fashion along and around each ring, has been found to be most satisfactory from the standpoint of heat conductivity through the welds to the tube wall.

Instead of spot welding, the rings 43 can be secured by other means, for instance by known brazing methods.

Referring to Fig. 5, showing a short section of burner tube 34 containing a modified heat-pickup finger arrangement, a pair of relatively narrow, crossed, curved sheet metal strips 46, welded or otherwise joined at their intersecting or overlapping positions, are illustrated as in contact with the tube, being joined thereto as by welding or brazing, at flange portions 41 of the strips, which flanges are transversely curved to fit the tube. Another pair of curved, crossed strips, similarly joined together and secured to the tube, are illustrated at 48. The latter pair are relatively rotated 45 with reference to the first pair about the axis of the tube and also offset from the first pair along the tube a short distance. Other pairs of crossed strips, not shown, may be provided to complete the heat-pickup finger assemblies in the tube portions 34 and 36 as will be apparent. The modified arrangement of heat-pickup elements can be produced at somewhat less cost and usually results in securing more uniform contact between the base portions of the fingers, flanges 41, and the tube. The individual strips 46 and 48 of each pair, being curved uniformly, tend to hold the flange portions 41 in contact with the tube before and after the securing operation such as brazing or welding is effected. The arrangement just described minimizes the effects of cor-'- rosion and erosion since even if the individual strips 46 and 48 are burned in two the flame and hot gases are still forc'ed to follow tortuous paths through the tube 33.

Referring to the burner-igniter and injector gun 32, shown best in Fig. 5, a main body member 50 thereof is generally cylindrical and formed with heat radiating fins I which may be malntained in a stream of air, for example, by location adjacent the inlet of a tube which supplies the blower (or adjacent the outlet of a special by-pass tube, not shown, connected with the low pressure side of the blower), so as to keep the temperature of the gun body well below 150 F. at all times. Flame ori-ignition failures frequently result from heating of the body much above that temperature because of "vapor lock and because impurities, (e. g., lead deposits) tend to clog the outlet passages in event of excessive heating. The body 50 has an opening at 52 (shown threaded to receive the discharge end of an injector fitting 53, to be described later), and a conical enlarged chamber coaxially of the discharge orifice of the fitting 53. Lying within the conical chamber, and forming therewith a generally conical distribution space or manifold 56 for mixed fuel and air, is a generally conical igniter housing member 54 having a relatively thin flange 55 seated in a counterbore of the body 50v and held there as by brazing. The flange 55 generally closes the conical distribution space 56 between the members 50 and 54 in a direct-i toward the burner chamber, but the flange has a number of holes 51 therethrough so proportioned relative to the conical space 54 as to build up some static pressure in said conical space during operation of the burner. There may, for example, be eight holes 51 equally angularly spaced 'around the flange 55, said holes constituting jets for discharging a combustible mixture of fuel and air and projecting the mixture a considerable distance into the burner tube portion 34.

For igniting the mixture at the start of operation of the burner, the housing member 54 has, inter alia, an axial bore 58 leading thereinto from the small end of the conical chamber 56, the bore being somewhat enlarged, as by flaring, adjacent the injector outlet orifice 53a and in line therewith whereby the bore 58 is certain to receive a definite portion of the mixture which is forcibly delivered from said orifice. A lateral discharge J'et bore 59 is formed near the outer end of the bore 58, at an effectively enlarged portion of the bore, see Fig. 5, and said lateral bore 59 communicates with and discharges flame into the burner chamber, tube 34. Theaxis of the lateral-ignition-flame discharging bore is directed obliquely to and against the more or less continuous hollow column of unignited gaseous fuel and air mixture projected from the series of jets 51.

Ignition of the mixture which is received into the center bore 58 is accomplished by an incandescent igniting element in a lateral bore 60 of the housing member 54 forming Aa definitely enlarged ignition chamber between the effective ends of the passage constituted by the bores 58 and 59. A more or less conventional (glow type) ignition plug 6I is secured in a wall of the body 5U, the inner open end of the plug being received.

fairly snugly, but with sufficient clearance to render binding unlikely, into a counterbore of the bore 60. Current is supplied to the plug only at the start of burner operation as will be clear from the description of Fig. 6 (control circuits, etc.) later herein.

The relatively greater total outlet area of the jet openings 51, as compared to the average cross sectional area of the ignition duct 58--59, taken with the fact that the duct 59 is directly in line with the injector discharge orifice 53a whereas the distribution space 56 is out of alignment therewith causes the unburned gaseous mixture discharged from the jet openings 51 to issue into the burner chamber at a much slower rate than the ignition pencil of flame issues from the igniter jet 59. Nevertheless the pencil of flame is always certain to'contact and ignite the oncoming mixture from the main jet openings forthe outer end portion of the igniting flame is deflected back from the wall of the burner tube toward the center thereof in case the ignition flame is fairly long.

The velocity at which the fuel and air mixture is projected from the distributing chamber 56 is, such that no flame ever comes into'contact with'l the main jet openings 51 and the wall surfaces of the conical distribution chamber are kept clean of deposits, which might otherwise normally tend to form thereon by the continuous outward ow of unburned fuel and air thereover. The rate of flow increases at the relatively restricted jet openings 51, keeping their wall surfaces clean. The flame jet outlet passage 59 may be cleaned out from time to time by means of a wire which may easily be passed throughl the glow plug seat opening whenever the plug is inspected or cleaned.

A burnable mixture of liquid, for instance `mo tor fuel and air, is generated in the fitting 53,

referred to above, by the Venturi injector princlple, air under 'I to 13 water-inches, for example, being forced through a fitting 65, connected with the duct 23, to a bore 66 leading to the discharge orifice 53a of the fitting 53. Communicating with the fbore 66 between its ends is a` fuel gland assembly 61. l The gland body 68 receives liquid fuel, as from a tank or float chamber, through a tube 69 and fitting 69a thereof which conveys the liquid fuel from the tank to a space 10 around anl adjustable conically pointed needle valve pin 1| projecting from the gland and having for instance a screw driver slot 1| a for enabling adjustment. 'I'he body 68 has a conical fuel-discharge end or tip portion 13 in which the needle valve is formed, and the tip 13 extends into the 70 bore 66 a short distance so that the outlet of the tip is exposed to air projected through the bore 66 for atomlzing ,fuel fed through the gland assembly 61. l

The fuel fed to the assembly 61 is preferably under the same pressure as that applied through 7 the fitting 85, as by connecting a small lateral branch portion 23a (Fig. 2) of the high pressure line 23 to the supply container or tank 3 for said fuel. The fuel could, of course, be fed merely by gravity from a constant head float chamber or by some independent pressure source.

As more or less schematically shown in Fig. 2, the fuel tank 3 has a pressure release valve 5, which may be a 'ball check seated by gravity, the tank being otherwise generally sealed. The ball weight is such as to allow air to be vented from the tank whenever the blower motor approaches full speed, the object being to prevent a too rich or unsuitable fuel and air mixture from being generated by reason of excessive pressure. The suction produced by the Venturi effect through air movement alone is adequate to maintain the proper balance of air and fuel for eiiicient combustion at the higher operating speeds of the blower.

It should be mentioned that the particular positions in which the air line connection and oil line connection fittings 85 and 68 respectively are shown is for illustrative purposes only. Ordinarily both fittings mentioned are disposed in such positions as to render the making of feed line connections and of adjustment, as by the needle valve 1I, as convenient as possible. The needle valve housing fitting, for example, would not be in the dependent position shown.

The operation of the burner apparatus as a whole will be apparent from the above. The igniting device is not subject to explosions, blowbacks or ignition failures, even though low quality motor gas is used as fuel, mainly because only a small portion of the combustible mixture is exposed to the incandescent element; the distribv uting and ignition device as a whole is kept comparatively cool, and the portion of the mixture which is exposed to the igniting surface is traveling rapidly, being impelled 'by constant pressure, whereas the surrounding mixture travels slowly, so as to tend to force an igniting pencil of flame from the bore 59 in proper relationship to the unignited mixture and be certain to cause lighting of some portion of the enveloping column thereof.

The main burner flame, when formed, is caused to play over the heat-pickup fingers, traveling in a tortuous path, quickly raising the temperature of the first set of fingers to glowing heat and causing the second set (in exhaust tube portion) also to be heated nearly to the glow point. Disspation of heat through the walls of the tube 33 to the radiating plates 38 takes place rapidly, and the extraction of heat from the plates by air passed through the casing 26 has been found to be highly efficient. The tube 33 for example does not get appreciably hotter on one -side than on the other, in the direction-of air travel, and the waste products of combustion from the exhaust tube are comparatively cool.

Referring to the control diagram, Fig. 6, current from one side of a power inlet 80 is carried by the line 8| to a contact arm 82 (shown in off position) of a ring type rheostat and contactor 83 and also, as by a branch line Bla, to a terminal 84 of a thermal relay 85 (Spencer Klixon thermal relay ER-l, for example). Current from the other side of the power inlet passes, via a. line 88, to the primary of an ignition transformer 81 and thence, via line 88, to a contact element 89 which is engageable by the arm 82 of the rheostat at a first operating or on position of the arm 82. The secondary 88 of the transformer is 8 connected to the igniter glow plug Il and with a pilot or tell-tale lamp 82 suitably positioned on or observable from the exterior of the cabinet I toshow when the plug is energized and disengaged. The transformer secondary, plug and lamp are suitably grounded as indicated conventionally.

A branch 88a of the line 88 leads to a heatins element of the thermal relay 85, which heating element is placed in circuit with the power line 8l, through a line 83 connected with the line 88 and contact 89, as soon as the arm 82 touches the latter contact (first "on position above mentioned) Thus at the first position of the contact ann 82 the incandescent element of the glow plug is energized, the pilot light 82 is flashed on and the `thermal element of the thermal relay starts to become heated. The' latter operation after a short period, say thirty seconds, closes a thermosensitive switch (not shown) connecting the contact 84 of the thermal relay to a line 84 leading from the relay to one end of the resistance element 96 of the rheostat 83. The opposite end of the resistance element is connected to the blower motor 25 which, in turn, is connected to the power line 86 by a second branch thereof 85h.

The connections described above result in starting the blower motor during the time the rheostat arm 82 occupies its first position, thus supplying the necessary relatively low pressure at the burner air supply line 23 to cause vaporization and injection of a combustible mixture into the body 50 of the ignition and burner injector gun 32. Ignition of the mixture and initial operation of the main burner thus takes place also during the first position of the rheostat arm but the blpwer is then operating at its lowest speed because current is supplied to the motor through the entire resistance element of the rheostat. Ignition is more effectively accomplished at the minimum supply rate of injection air flow because too rapid air flow does not allow sufiicient ignition contact period between the ignition name and oncoming fuel and air. As soon as flame starts to be generated in the main burner the operator moves the rheostat arm 82 into contact with the resistance 98 thus rendering the connection 8la-84 unnecessary in order to supply the blower motor with current. When the arm 82 moves free of the contact 89 the circuits are broken which contain, respectively, the heater element of the thermal relay and the ignition transformer. The thermal relay recycles in a short period, say thirty seconds, to break the connection between the lines 8Ia and 8l which temporarily supply the blower motor with current during the ignition and starting period described above.

Fig. 'I illustrates an upright blower and heater assembly wherein separate air forcing mechanisms are provided on a single blower-operating motor Il for supplying, respectively, low pressure air to the heater and high pressure air for fuel vaporization, etc. The air warmed by the heat exchange head is discharged upwardly in the position of the unit illustrated. The mechanism would, of course, be in a suitable cabinet and provided with a fuel supply and controls generally in accordance with the preceding description and showing hereof.

In Fig. 7 the air cleaner is omitted from the illustration but may be used, for example. across the main inlet (not shown) to the heater cabinet. Air is admitted to the blower casing l5 between its ends as through a series of openings 18. The opcasing 15 centrally thereof, and one end of the motor drive shaft operates a multi-stage centrifugally acting blower two stage high pressure air blower of conventional 'form in an end casing section or portion 11 of the unit for supplying relatively high pressure air as through the duct 23 for vaporizing and/or feeding fuel as already described. The upper end of the casing 15 contains an axial-flow type fan 18 connected to the upper end of the motor shaft. A set of xed radially arranged, spaced apart plates or vanes 19, with their principal planes' vertically disposed, and being distributed uniformly around the motor shaft axis in vertical alignment with the fan blades, straightens the air currents delivered by the radial fan for projecting said currents in lineal paths through the heater head casing 26 past the burner tubes 33 which can be substantially as previously described except for being in the same horizontal plane. The arrangement according to Fig. 7 in event of using a rapidly r0- tating radial fan 'I8 may, if it is desired or necessary to reduce noise of operation, require that the plates or vanes 19 be streamlined or (e. g.) rounded and blunted on their lower edges as by an upwardly turned liange extending along the lower edge of each vane. The vane strips can be folded into a more elcient stream line section if desired.

l1. In combination with an injector gun having air and fuel inlet means arranged for atomlzing fuel, said gun having a discharge orifice, means forming a distribution chamber in general alignment with the injector discharge orice for receiving mixed fuel and air therefrom, said means having a discharge Jet, an igniiton duct having an inlet in direct alignment with said injector discharge orice and an outlet directed laterally of the axis of said jet, and means for igniting mixed fuel and air between the eifective ends of said duct.

2. Heating apparatus comprising air forcing means, a burner, a fuel-atomizing injector device operatively connected with the air forcing means. an atomized fuel distributing chamber communieating with said device and arranged to discharge the mixed fuel and air as a hollow column into the burner, an ignition chamber associated with the distributing chamber but generally discommunicated therefrom and including a duct having an inlet for atomized fuel in alignment with the iniector device and an outlet directed transversely of said hollow column, and igniting means for the mixed fuel and air between the effective ends of the duct.

3. In a heating apparatus of the class described, a burner, a fuel-atomizing injector device, including means to supply air, a fuel distributing chamber arranged to receive the atomized fuel from said devic and provided with an annular series of jet outlets to the burner, ignition means associated .with the distributing chamber and including a duct having an inlet for erating motor is contained and supported in the l atomized fuel open adjacent and in alignment with the injector device whereby directly to-receive atomized fuel therefrom and an outlet directed transversely oi' at least one of said jet outlets, and igniting means for fuel between the effective ends of the duct.

4. In a heater of the class described in com.. bination, a burner tube, an injector for mixing liquid fuel and air and having a discharge oriiice, means forming a hollow generally frustoconical chamber having its small end aligned with said orice and its large end arranged to discharge mixed fuel and air into the burner tubev as a generally hollow column, said means including a generally conical member forming an inner wall for the hollow chamber and having an ignition chamber therein open at the small end of said hollow chamber for receiving mixed fuel and air and open laterally ofthe longitudinal axis of the hollow chamber for directing an igniting pencil of flame against said generally hollow column of mixed fuel and air, and means inside the ignition chamber for igniting mixed fuel and air received thereby.

5. 'I'he arrangement according to claim 4 wherein the igniting means is a glow plug which is supported by the outer wall of the hollow frusto-conical chamber and having a glow element exposed only in the ignition chamber.

6. In combination, means including a tube arranged to project a mixture of fuel and air in a predetermined direction, means forming an annular distribution chamber arranged to receive said mixture from the tube, said chamber having outlet jet forming means opposite the tube, said distribution chamber forming means comprising an outer tubular part and an inner part surrounded by the outer part and having a passage for mixed fuel and air extending therethrough open only at its two ends to provide an inlet opening positioned to intercept a portion of the mixture projected from the tube and an outlet opening, said latter opening being so directed as to discharge the portion received by the passage in intercepting relationship to a portion of the mixture delivered by the jet forming means. and an igniter in exposed relationship to the interior of said passage between said ends for igniting said portion of the mixture.

7. In combination, means including a tube arranged to project a mixture of fuel and air in a predetermined direction, inner and outer burner head members, one surrounding the other to provide an annular distribution chamber of gradually expanding diameter arranged to receive said mixture from the tube, said chamber having relatively restricted outlet jet forming means opposite the tube, radiating fins on said outer membertending to cool the same, said inner member having a passage for mixed fuel and air extending therethrough and open only at its two ends to provide an inlet opening positioned to intercept a portion of the mixture projected from the tube and an outlet opening, said latter opening being so directed as to discharge the portion received by the passage in intercepting relationship to a portion of the mixture delivered by the jet forming means, and an igniter in exposed relationship to a portion of said passage between said ends for igniting the portion of the mixture conveyed by said passage.

ROBERT H. HUNTER.

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