US2480019A

US2480019A - Rotary air atomizing burner

Info

Publication number: US2480019A
Application number: US745760A
Authority: US
Inventors: Herman O Grimmeisen
Original assignee: Gilbert and Barker Manufacturing Co Inc
Current assignee: Gilbarco Inc
Priority date: 1947-05-03
Filing date: 1947-05-03
Publication date: 1949-08-23
Anticipated expiration: 1966-08-23

Description

Aug. 23, 1949- H. o. GRIMMEIEN 2,480,019

ROTARY AIR ATOMIZING BURNER Filed May 3, 1947 5 Sheets-Sheet 1 INVENTOR HVR/VAN dv 6km/umn BY Y CLIM Y ATTO NEYs Aug 23, 1.949. H. o.. GRIMMEISEN 2,480,019

ROTARY AIR ATOMIZING BURNER Filed May s, 1947 5 sheets-sheet 2 ATTO NEYS Aug. 23, 1949. H. o. GRIMMElsEN 2,480,019

ROTARY AIR ATOMIZING BURNER Filed May C5. 1947 5 Sheets-Sheet 3 mvsmon Y HEP/MN d' Www/az E ATITO P/// r v Iliff/A .NQ

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Aug. 23, 1949, H. o. GRlMMElsEN -2,480,019

ROTARY AIR ATOMIZING BURNER Filed May 5, 1947 v 5 sheets-sheet 4 y INVENTOR Hmmm' Q @Mnz/w# BY f afl y ATTORN YS Aug 23 1949 H. o. GRIMMEISEN 2,480,019

ROTARY AIR ATOMIZING BURNER Filed May s, 1947 5 sheets-sheet 5 INVENTOR GMM/maur Panarea Aug. 23, 1949 Herman 0. Grimmeisen, assignor to Gilbert & Company, West Sprin tion of Massachusettsr Application May 3. 1947, Serial No. 745,760

West Springfield, Mass., Barker Manufacturing geld, Mass., a corpora- 4 Claims. (Cl. 158-77) 'I'his invention relates to improvements in oil burners of the so-called air-atomizing type.

The invention has for its general object the provision of a burner which will burn fuel oil eiliciently and, safely, with a clean nre at starting and stopping, over a wide range of rates. from the very low rates required for the heating plants of small homes and for hot water heaters, to the high rates required for heating large buildings and for industrial purposes.

The invention has for a particular object the provision of an improved nozzle in which oil and air are efliciently mixed and from which the oilair mixture is emitted in a spray to be mixed .with more air and burned.

The invention has for another object the provision in a nozzle of the type described, of an arrangement for expelling residual oil from the nozzle passages after the oil feed has been cut off, the arrangement including revolving the nozzle to throw oil from the oil feed passages of the nozzle into the air passage from which it is swept out of the nozzle by a high velocity air stream and including also a bellmouth outlet aring outwardly from the nozzle orifice and adapted to remove oil therefrom by centrifugal force due to the nozzles rotation.

The invention has for another object the provision in an oil burner of an improved construction and arrangement of parts adapted for economical manufacture and for convenient servicing in the field.

The invention will be disclosed with reference to the accompanying drawings, in which,

Fig. 1 is a sectional elevational view of Aa burner embodying the invention;

Fig. 2 is a fragmentary cross sectional view taken on the line 2-2 of Fig. 1 and showing the constant level reservoir and oil control valves;

Fig. 3 is a front elevational view of the burner;

Fig. 4 is a cross sectional view taken on the line 4 4 of Fig. 1;

Fig. 5 is a fragmentary sectional elevational view, drawn to a larger scale and showing the oil and air supply conduits for the atomizing nozzle;`

Fig. 6 is an enlarged sectional elevational view of the air-atomizing nozzle;

Fig. 7 is a fragmentary exterior elevational view showing the air control shutter and having parts broken away to show the mounting of the pump and fan housing on the burner casing;

Figs. 8 and 9 are cross sectional views respectively taken on the lines 8-8 and 9-9 of Fig. l

and respectively showing the air control shutter and air pump;

Fig. 10 is a rear elevational view of the burner;

Fig. 11 is a wiring diagram illustrative of the burner control system; and

Fig. 12 is a sectional view of a timing motor used in the control system of the burner.

Referring to these drawings; lthe burner frame includes a horizontally-disposed tubular housing l (Fig.l 1), suitably supported. as by the pedestal 2 and floor plate 3. The housing I affords a passage 4 for the supply of secondary or low pressure air. The rear (right hand) end of the housing I vis made larger in diameter than the front and outlet end in order to receive a fan 5 located with its axis of rotation coincident with the axis of the air passage 4. suitably secured to the rear end of housing I, as by the multiple thread lock indicated at 6, is a housing 'l which has in its front face a hollow cylindrical recess 8 cooperating with the enlarged opening 9 in the rear end of housing I to form the housing for fan 5. The

hollow end housing I4. These housings I2'andl I4 (Fig. l) afford within them oil-receiving chambers I5 and I6, respectively, separated by a suitable oil filter I1, which is clamped between the two housings. The burner frame further includes a bracket I8, which extends upwardly from the top of housing I and rearwardly thereof to support an electric motor I9, which as shown in Figs. 3 and 10 is secured to the bracket by-cap" screws 20.

Rotatably mounted and coaxially located within the housing I (Fig. 1) is a shaft 2I, suitably supported, as by ball bearings 22 and 23. The

bearing 22 is mounted in pump housing 1. The bearing 23 is mounted in a tubular housing 24, integrally connected by inclined blades 25 to an annular rim 26, which is slidably engaged with a cylindrical wall portion of passage 4. A pin 25 in housing I engages in a slot 26' in rim 26 to prevent the latter from turning. The blades 2'5 form a turbulator serving to whirl the air forced through passage 4 by fan 5. The fan 5 is iixed to shaft 2|, as by the set screw 2l. Keyed to shaft 2| (Fig. 5) is a driving pulley 28, which is held in axial position between a shoulder on the shaft and the inner race of bearing 22. The shaft 2l extends into the chamber Ill and has fixed thereto the rotor 29 of the air pump. This rotor and the inner race of bearing 22, both fixed to shaft 2I, engage opposite faces of the bearing-supporting wall of housing 1 and thus hold the shaft against any substantial axial displacement therein. The drive pulley 28 is connected by a belt 30 to a pulley 3I fixed on the outer end of the shaft 32 of motor I9. a The shaft 2|' serves to revolve the atomizing nozzley of the burner and contains within it the 3 supply passages for air and oil. Referring Fig. 6, the front end of` shaft 2| is turned down and threaded, as at 33, to receive a cap 34, which forms vthe outer part of the nozzle and which engages a shoulder 35 on the shaft. This cap has a cylindrical inner Wall 38 and a frustoconical inner wall 31 which connects wall 86 to the outlet oriiice 38 of the nozzle. This orifice has an outwardly flaring wall 38 forming a small spinning cup. The front end of shaft 2i forms the inner part of the nozzle. This shaft is turned down to provide a cylindrical part 39, a frusta-conical part 48, the outer surface of which closely nts the wall 31 of the nozzle cap, and two frusto-conical portions 4| and 42, each of different slope and of a slope different from that of wall 31. Between these frusto-conical portions 4| and 42 and the frusta-conical wall 31 is formed an annular venturi 43. A plurality of radial openings 44 connect the throat of the venturi to a central oil feed passage 45, which is formed in shaft 2| and leads from those openings rearwardly to a larger bore 46 in the shaft (the rod 48 and packing 5|) is considered absent for the moment). This bore 48 extends to the rear end of the shaft as shown in Fig. 5. At the intersection of bores 45 and 48 is a square shoulder 41. A rod 48, having an axial passage 49 therethrough is pressed into bore 48 with its inner end pressing against an annular rubber gasket 58. The rod may be xed to shaft 2| in any suitable way as by a set screw 48' (Fig. 5). The other end of rod 48 extends beyond shaft 2| and through a sleeve bearing 5| in housing I2 into the oli chamber I5. Oil may thus ow through passage 49, the hole in gasket 50, passage 45, and to and through the radial jets 44 into the throat of the annular venturi passage 43. The rod 48 has two longitudinal slots 52 at diametrically opposite locations in its external periphery. These slots are formed like keyways in a shaft and, when the rod 48 is in place in the bore 46, of shaft 2|, these slots form passages for conducting air from the air pump to the atomizing nozzle. These slots 52 extend from the bearing 5I nearly to the front end of rod 48, terminating as shown in Fig. 6, just short of such end and communicating one with each of two inclined holes 53, formed` in the threaded end of shaft 2| at diametrically opposite locations and opening into an annular chamber 54. This chamber communicates `with the annular venturi 43 by means of a. plurality of slots 55 formed in the frusta-conical part 48. These slots are inclined to the axis of revolution of part 40 so that air from chamber 54 will enter the annular venturi with a helical motion. The whirling air, as it advances in the annular venturi, increases in velocity until it reaches the throat of the venturi where it is met by oil ejected from radial passages 44 by the rotating inner part of the nozzle. The oil and air mix in the venturi forming an emulsion, which'is allowed to expand as it advances, iinally leaving the nozzle orice in a finely atomized conical spray of air and oil. This spray meets and mixes with the whirling stream of secondary air which is forced by fan 5 through passage 4 and which is turned into the spray by the cone 58 (Fig. l) on the outlet end of the air tube I.

The combustible mixture of air and oil is ignited in any suitable way, as by an electric spark produced between a pair of electrodes 51 (Figs. 1, 3 and 4). These electrodes are mounted one in each of two insulating tubes 58, which are suitably fixed as by set screws 5,9 (Fig. 4), in holes formed in the blades 25 of the air turbulator. The rear end of each electrode (Fig.` l) is upturned at right angles, as at 68, to engage a spring contact Si. These contacts 6I' are fixed, one to each, of the high tension terminal conductors 52 of an ignition transformer contained within the casing 63. The base plate 64 of this casing is secured, as by screws 65, to posts 88 and to a boss 81 on housing I. The conductors 62 extend from the transformer through depending insulators 68, the lower ends of which extend through the housing I into passage 4, bearing the terminals 5I on their lower ends. The arrangement enables axial separation, and electrical disconnection, of the electrodes from the high tension terminals of the transformer when the parts within the housing I are withdrawn for servicing, as hereinafter explained in detail.

The air pump may be of any suitable kind. One suitable form of pump is shown in Fig. 9. The rotor, which is located eccentrically of chamber I8, is radially slotted to slidably receive a plurality (six as shown) of blades 1li. The ends of the blades lie ush with the end faces of the rotor. These end faces have cylindrical recesses 'II therein to receive, one in each, annular rings 12 upon which the ends of the blades rest and by which the outer edges of the blades are held engaged with the internal periphery of chamber III. The inner ends of all the blades and the inner end face of rotor 29 engage the inner end wail of chamber Ill while the outer ends of all the blades and the outer end face of the rotor engage the outer end wall of the chamber. The outer end wall of the chamber III is formed in part by a circular disk 13 set into a circular recess in the housing I2. The latter has a recess 14 in communication at one end with the outlet port 15 of the air pump and at its other end with the grooves 49 in rod 48. The inlet port 18 of the air pump communicates with one end of a passage 11 in housing i2 and into the other end of' this passage is set a suitable air filter 18. Thus,

the air pump, when revolved, will draw in air through the lter 18, passage 11 and port 15 and force it out through port 15, into recess 14, slots 52 and passages 53 into the annular air chamber 54 of the atomizing nozzle.

Oil is supplied to the chambers I6 and I5 and thus to the nozzle feed passage 49 by gravity Iiow from a constant level reservoir 19 (Fig. 2) formed in a casing 88, secured as by screws 8|, to a pad k82 on thecasing of motor I9. The outlet 83 of this reservoir is connected by a pipe 84 to the inlet 85 (Fig. 1) of chamber I6. A valve 88 (Fig. 2) controls the outlet 83. This valve is fixed to the lower end of the plunger 81 of a solenoid contained in a casing 88. This casing is screw threaded into an annular casing 89, which is supported by legs 98 xedto the bottom wall of the reservoir. The casing 88 has a serrated head 9| xed to its upper end for convenience in turning the casing. when the cover 92 of the casing 88 is removed. The upward movement of the plunger 81, caused by energization of the solenoid is limited by the abutment of a collar 81' on the plunger with the bottom wall of the casing 88 of thus the rate at which oil will be fed under the constant head to the atomizing nozzle of the burner. A spring 93, fixed at one end to a side wall of reservoir 60, has on its other end a n to engage between successive serrations In the head 9| and hold the latter in any of the various positions of adjustment to which it may be moved. The valve 86 is held by gravity in closed position. when the solenoid is not energized.

Oil is supplied to reservoir 19 by means of a suitable pump 94 (Fig. 10) mounted on the end bell of motor I9 and driven by the latter. `The inlet of this pump is adapted to be connected by a pipe, such as is shown in part at 95, to a low-level, oil-supply reservoir (not shown). The outlet of pump 94 is connected by a pipe 96 to the reservoir 19 (see also Fig. 2). The latter contains a float 91, suitably guided as indicated and carrying a valve 98 to control a second outlet 99 from the reservoir. Outlet 99 is connected by a pipe |00 to the suction pipe 95 (Fig. 10) of the oil pump. The pump will supply oil to reservoir 19 at a rate at least equal to, and usually slightly in excess of, the maximum rate at which oil may be used by the burner, as controlled by the adjustment 9| of valve 86. When the Vpump 94 is in operation, the i'loat 91 will rise and open valve 98 to by-,pass part of the pumped oil through pipe back to the suction side of the pump. In this way. oil is maintained at a constant level in the reservoir and a xed head of o il is maintained for the gravity ow of oil to the atomizing nozzle.

Oil fed into the chamber l is prevented from flowing into the lair pump by means of a seal ring I0| (Fig. 5), mounted on and rotating with rod i8 and pressed into sealing engagement with the flanged end face of sleeve bearing 5| by means of a coil spring |02. This spring actsagainst a washer |03 held in place by a snap washer |08, engaged in -a circumferential groove in rod 46 near its outer end.

The rate at which secondary air is supplied through the air passage to the atomizing nozzle is controlled by an air shutter comprising an arcuate band |05 (Figs. '1 and 8) mounted in a circumferential groove in the exterior peripheral portion of housing 1. lSuch portion has air inlet ports |06 (Fig. 8) in addition to the hole |01 through which belt 30 extends into the fan housing. The shutter is held in place by two screws |08, each passing through a slot |09 (Fig. 7) in band |05 and threaded into the housing 1. When the screws |08 are loosened, the band |05 .may be moved by a handle I|0 to increase or decrease the effective area of the ports |06. This is done by a slot |08' in the band moving nearer to or farther from a position of registration with the right hand port |06 shown in Fig. 8 and by the left hand end of the band overlapping the other port |06 to a lesser or greater extent as the case may be.

The bearing 23 for the rotatable, nozzle-carrying shaft 2| is protected from the heat reflected back in the passage 4 from the ame produced by the burner by a shield |II (Figs. 1 and 5). This shield comprises a tubular extension of the bearing housing 29, which extension closely encompasses shaft 2| and extends a substantial distance toward the nozzle. 'I'he bearing is also cooled by air picked up by the cup-like outer end I2 of the bearing housing. A stream of air is forced through the bearing, leaving by the small annular passage II3 between the shield and shaft 2|. When the burner stops and the flow of cooling air ceases the shield ||I will keep the heat reflected back into passage 4 from reaching the bearing.

. 6 The controls for the burner may be contained in a box `I I4, .secured to a pad on the motor Il. as indicated in Figs. 1 and 3.

A control system for the burner is shown dlagrammatically in Fig. 11. This system is arranged to start the burner motor I9 by a room thermostat switch ||5 on a demand for heat from the burner but the flow of delayed until the motor I9 has acquired full speed so thatthe atomizing nozzle, the air pump, and the air fan 5 are all rotating at full speed before oil reaches the nozzle. After the demand for heat is satisfied, the room thermostat switch ||5 opens and the ilow of oil to the nozzle is stopped but the motor I9 is continued in operation for a. time after the oil ow has ceased. The arrangement avoids smoky operation during the intervals in which the motor I9 with the nozzle, air pump and air fan 5 are accelerating or decelerating.

The time delay of the opening of the oil valve on starting and the time delay of the stopping of the motor I9 after closing of the oil valve on stopping are effected by the use of a timing shaft I I6, which is driven by an electric motor and operates a switch 1, controlling certain circuits to be later described. This timing motor may be of any suitable type. One such type is shown in Fig. 12. It is a self-starting, single-phase, synchronous motor of the shaded pole type of the kind disclosed in U. S. patent to Haydon No. 1,996,375, dated April 2, 1935, to which reference may be had for a more complete disclosure, if necessary or desired. Briefly, the motor includes a eld winding |I8 adapted for connection to a volt, alternating-current, supply circuit and mounted on a magnetizable core H9, the ends of which carry magnetizable disks |20 and 62|, bearing the pole pieces of the motor. The rotor |22 is fixed to the outer end of a shaft |23 which is rotatably mounted in bearings within the tubular core |I9 and which carries on its inner end a driving pinion |26. The rotor shaft and pinion are also bodily movable in an axial direction to move the pinion into and out of mesh with one terminal gear |25 of a train of gears |26. The other terminal gear of the train is shown at |21, fixed to the timing shaft ||6. A spring |28 acting between the outer end of core II9 and rotor |22 tends to hold the rotor, with its shaft |23 and pinion |24, in the extreme right hand position shown, in which the pinion |24 is disengaged from gear |25 and abuts the inner end of core II9. When the fleld winding ||8 is energized. core I I9 and disks |20 and |2I are magnetlzed and the magnetic pull from disc |20 and core I9 draws rotor |22 to the left, compressing spring |28 and moving pinion |24 into mesh with gear |25. The rotor will also be rotated which will through the gear train described. rotate the timing shaft I |6 clockwise, as viewed in Figs. 1l and 12. The shaft ||6 may, for example, turn at the rate of 1` revolution per minute. It turns clockwise until a stop |29 (Fig. 11) on the shaft ||6 is arrested by abutment withv the right hand side of a stationary stop |30. The shaft then remains stationary as long as the winding Ill is energized. When this winding is deenergized. a spiral spring |3I, which was wound up by the clockwise rotation of the shaft, will turn the shaft ||6 counterclockwise back to its initial position illustrated, in which the stop |29 engages the left hand side of the stop |38. When the motor winding ||8 is deenergized, the axial magnetic pull on the rotor |22 ceases and spring |28 will pull shaft |23 to the right, drawing pinion |24 out oil to the burner is coil |38 of a relay, an electric heating coil |39,

a thermostat switch |40 adapted` to be heated by coil |39 and Wires |4|, |42, |43, |44 and |45, which connect these elements in series. When the switch I| closes on a demand for heat from the burner,r the relay coil |38 -is energized and this causes the closing of a switch |46.

The switch |46 controls a circuit to the winding ||8 of the timing motor and a starting circuit for the burner motor I9. The circuit to the winding I I8 may be traced as follows: from supply wire |36 by wire |41, switch |46, wires |48 and |49 to winding ||8 and thence by wire |50 to supply wire |31. The starting circuit for the burner motor I9 may be traced as follows: from supply Wire |36, by wire |41, switch |46, wires |46, I5| and |52, engaged switch contacts |53 and |54, wire |55 to motor |9 and thence by wires |56 and |50 back to supply wire |31.

One effect of the closing of this relay switch is to remove the burner motor I9 from control by room thermostat switch I |5 and place it under the control of relay |58 and the switch |I1 driven by timing shaft II6. The motor I9 is now in a running circuit which may be traced as follows: from supply wire |36, `by wire |65, engaged contacts |59 and |54, wire |55 to motor I9 and thence as before by wires |56 and |50 back to supply wire |31, The opening of relay switch will not cause motor I9 to stop immediately but only after the timing shaft ||6 has been moved back far enough to allow switch |I1 to open and this may take, say 30 seconds.

The contacts |51 and |60, which are aso engaged on energization of relay coil |58, control the solenoid |66, which when energized, opens the valve 86 and allows cil to flow to the atomizing nozzle of the burner. The circuit for solenoid |66 may be traced as follows: from supply wire |36 by wire |41, switch I46,wires |48 and |5I, engaged opening. The stack thermostat switch is indicated at |69 and its terminals are connected by wires |10 and |'I I to the' terminals of the electric heating coil |39. Closure of switch |69, on occurrence of combustion at the burner, shunts out the heating coil |39 and stops the heating of the bimetallic element of switch |40. This switch, ii.' heated for say 90 seconds would open and stop the burner. However, if combustion occurs within the interval of 90 seconds, the switch |69 will be closed and the heating eiIect on switch |40 will be stopped before switch |40 can open. The arrangement described is the usual combustion safety control. It functions here a little difierently than in the ordinary burner control system in that opening of switch |69 on failure of combustion does not immediately deenergize the burner motor I9, The iiow of oil to the burner is immediately cut off by the closing of valve 86 on the deenergization of solenoid |66 and the timing motor is deenergized but the motor I9 continues to run until the timing shaft has been turned backward far enough to allow switch |I1 to open. Thus, the burner motor and the air pump, air fan and atomizing nozzle will be rotated for a substantial time inter-val, say 30 seconds after the oil ow has been cut oil'.

In operation, on a demand for heat from the burner, the roomthermostat switch II5 closes and this causes closure of the relay switch |46, which in turn closes a circuit to the winding I8 of the timing motor and a starting circuit for the burner motor I9. The latter starts the air pump, air fan and atomizing nozzle and these elements are in rotation at full speed before oil is supplied to the nozzle. The timing shaft |I6 starts to turn coincidentally with the burner motor and `after it has been turning for about 20 seconds,

switch I|1 closes and causes energization of relay coil |58, which in turn causes the closing of a circuit to solenoid |66, whereby the oil valve 86 is opened. Oil now ows to the atomizing nozzle and mixes with the air as described in detail hereafter and the combustible mixture is ignited and burns, causing heat to be supplied to the rooms needing heat. 'I'he energization of relay |58 also opens the startngcircuit for the burner motor I9 by separation of the contacts |53 and |54 and establishes a running circuit by the closure of contacts |54 and |59, which running circuit is under the control of relay |58 and thus of switch II1. When the demand for heat is satisfied, the room thermostat switch I I5 opens,

and this causes switch |46 to open, deenergizing the solenoid |66 and causing the oil valve 86 to close and stop flow of oil to the .burner and also deenergizing the timing motor and allowing the timing shaft |I6 to turn backwardly, After this shaft has turned backwardly for say 30 seconds, switch ||1 will open to cause deenergizatlon of relay coil |58 and the separation of contacts |51 and |60, |54 and. |59, which deenergizes the burner motor, and the engagement of contacts |54 and |53 to reestablish a starting circuit for the burner motor under control of relay switch |46. It will thus be seen that full air iiow and f ull rotation of the atomizing nozzle are established for a substantial time interval before oil is allowed to flow to the atomizing nozzle. The switch II1 closes 20 seconds after the timing motor and burner motor are simultaneously energized and in a second or two after its energization the burner motor will be operating at full speed. Likewise on stopping, the air flow and rotation of the nozzle will be continued at full speed for say 30 seconds after oil flow has ceased. These provisions avoid smoky combustion, during the interval while the burner motor is accelerating, by delaying the admission of oil until the motor I9, fan, air pump and atomizing nozzle have acquired full speed and, during the interval when the motor is decelerating, by cutting off the flow of oil to the nozzle well .before the circuit to the burner motor is opened.

In the operation of the atomizing nozzle, on a demand for heat, the motor I9 is immediately started to drive the air pump, fan and nozzle. In

a very brief time, say about one second. these elements will be rotating at full speed and, soon thereafter, the pump will have established flow of air through the nozzle and ow of air through passage 4 outside of the nozzle at the desired rates. The air fed into chamber 54 by the air pump is forced through the slots 55 and caused to whirl as it enters the annular venturi passage 43. As the whirling air streams advance in this venturi, their velocity increases until they reach the throat of the venturi.v Subsequently, the velocity is reduced somewhat as the air streams advance to the end of the venturi and issue from the nozzle orifice 38. After the described air ow has been established within the nozzle and the whirling air flow has been established through passage 4 outside of the nozzle, the solenoid valve 86 is opened and oil allowed ,to flow from the constant level reservoir. Oil advances, under gravity head, through the central oil passage 49, 45 and, when oil reaches the end of passage 45, it is thrown outwardly through radial passages 44 by centrifugal force aided also by the suction effect created by the rush of air at high velocity. through the throat of the venturi across the outer ends of passages 44. The jets of oil, issuing into the whirling air stream moving at maximum velocity through the throat of the venturi, mix with the air and form an emulsion. This emulsion advances through the venturi and the mixing of air and oil continues as the mixtures progresses and expands. The emulsion leaves the venturi and enters the outlet orifice 38, expanding in a conical spray. This spray is met by the whirling air stream outside the nozzie, which stream is directed into the spray by cone 56 and caused to mix therewith. The combustible mixture is ignited by a spark produced between the electrodes 51 and combustion occurs and continues until the demand for heat is satised. The solenoid valve 86 closes on the opening of thermostat switch II5 and the oil ow is immediately cut off. However, air continues to flow through the nozzleand outside the nozzle for a time to avoid smoky combustion. The oil remaining in the passages 44 will be thrown outwardly into the venturi by centrifugal force and such oil will be carried forward through the venturi by the rushing air stream and discharged through orice 38. Any oil remaining on the outwardly flaring wall 38 will be thrown outwardly by centrifugal force and discharged by the knife edge terminus of the wall. The effect is to clean the surface 36 free of oil film and leave nothing there to carbonize from the heat reflected back on the nozzle from the hot walls of the combustion cham-ber after combustion has stopped.

The continued movement of air at high velocity through the venturi, after the oil ow has been cut off, has the effect of wiping the lwalls of the venturi free of oil lm. The nozzle is thus cleaned of oil back to the passage 45. In particular, the narrow passage of the venturi, the small -10 orifice 38 and its cup like discharge mouth 38' are cleaned of oil to avoid carbonization and the resulting clogging of the nozzle passages from soot and the depositing of soot on the Wall of cup 38'. The continued flow of air after cessation of oil flow, tends to cool the nozzle at a time tity manufacture of theburner at low unit cost.

All parts of the burn'er are also easily accessible for convenient servicing and are easily replaced, when required. By removing the belt 3Q from pulley 3l, disconnecting oil pipe 84 at the union which connects it to the outlet 83 of the float chamber, and by turning the housing 1 a third of a revolution to unlock it from the main housing I, the unit, comprising the housings 1, I2 and I6, the atomizing nozzle, electrodes 51, turbulator 25 and fan 5 may be withdrawn from the interior of housing I, while maintained assembled in working relation. The act of withdrawing these parts, automatically disconnects the electrodes 51 from the high voltage terminals 6I of the transformer. The air lter 18 can readily be removed for servicing. 'I'he oil lter I? can readily be removed for cleaning by dis-connecting the housing i4 from housing I2. Should access to the air pump be required, it can be had by disconnecting the housing I2 from housing 1. Ther aforesaid unit may be replaced in housing I byv first inserting the` nozzle 34, shaft ZI, electrodes 51, and the turbulator 25, part way into the housing until the leading end of projecting part of rim 26, having the slot 26', is about opposite the pin 25'. A substantial space will then be left between the adjacent ends of housings I and 1.

The operator inserts his ngers through this space and turns the turbulator until the slot 26' and pin 25' are aligned and then he pushes forwardly on the turbulator enough to engage the pin in the front end of the slot. The operator then withdraws his fingers from the interior of housing I and thrusts housing 1 inwardly to close the aforesaid space after which he turns the housing 1 to engage the multiple threads and lock the housing 1 to housing I. The belt 30 is replaced on pulley 3I and/the burner is ready to operate. For regulating the flow of combustionsupporting air through the `passage y4 after the parts are again assembled in working relation, the air shutter |05 is accessible from outside the burner and may be moved by handle IIIJ after screws |08 have been loosened.' The rate of oil ilow may be regulated by adjustment of solenoid casing 8-8, effected by turning member SI after the cover 92 of the constant-level, oil-supply reservoir has been removed.

75 orifices. And sootless operation during the peri- 11 ods of acceleration and deceleration of motor, air pump, and fan is insured by the arrangement described for preventing the admission of oil on starting up the'burner until full air ow has been established at the atomizing nozzle and by stopping the oil flow before the motor which drives the air pump and fan, is cut off, whereby air flow at the nozzle is continued after oil dow has ceased to scavenge the combustion chamber.

I claim: A

1. In an oil burner, a shaft having therethrough a central oil conduit and an air conduit, means for rotating said shaft, an atomizing nozzle fixed to one end of said shaft, said nozzle comprising a hollow outer member having a hollow cylindrical part intersecting at one end with a hollow conical part which terminates with a small discharge orifice, and an inner member having a cylindrical part closely fitting the other end of the hollow cylindrical part of the outer member and provided with air and oil passages therethrough respectively communicating at one end with the air and oil conduits in said shaft and closing the other end of the hollow cylindrical part of the outer member except for said air and oil passages, said inner member having a conical part located in spaced and coaxial relation with the first-named conical part, said conical parts forming between them an annular venturi leading to the discharge orifice, said venturi in longitudinalrsection converging from its entrance end to a throat and diverging from the throat to said orifice, said air and oil passages respectively communicating at their other ends with the entrance end and throat of said venturi, means for supplying oil to the oil conduit in said shaft, and means for supplying high pressure air to the air conduit in said shaft.

2. In an oil burner, a shaft having therethrough a central oil conduit and an air conduit, means for rotating said shaft, an atomizing nozzle fixed to one end of said shaft, said nozzle comprising a hollow outer member having a hollow cylindrical part intersecting at one end with a hollow conical part which terminates with a small discharge orifice, and an inner member having a cylindrical part closely fitting the-other end of the hollow cylindrical part of the outer member and provided with air and oil passages therethrough respectively communicating at one end with the air and oil conduits in said shaft and closing the other end of the hollow cylindrical part of the outer member except for said air and oil passages, said inner member having a conical part located in spaced and coaxial relation with the firstnamed conical part, said conical parts forming between them an annular venturi leading to the discharge orifice, said venturi in longitudinal section converging from its entrance end to a throat and diverging from the throat to said orice, said air and oil passages respectively communicating at their other ends with the entrance end and throat of said venturi, means for supplying oil to the oil conduit in said shaft, and means for supplying high pressure air to the air conduit in said shaft, said discharge orifice terminating with an outwardly-haring frusto-conical wall for slinging outwardly by centrifugal force any oil thereon` 3. In an oil burner, a shaft, a nozzle fixed to one end of said shaft and comprising inner and outer members forming between them an annular pas-l sage converging from one end of large diameter to another end of small diameter, the small end of said passage terminating with an outlet ori- 12 I fice formed in said outer member, said annular passage in longitudinal section converging from its large end to a narrow throat located intermediate its ends and then diverging toward its other and small end, the inner member having a central oil passage and a circular series of branch passages connecting one end of the central passage to the throat of the annular passage at a plurality of angularly spaced points, a highpressure air pump, means including a conduit in .said shaft for connecting the pump to the large end of said annular passage, means including a conduit in said shaft for feeding oil to the other end of said central oil passage, means for rotating said shaft and nozzle and for actuating the high pressure air pump, and means for starting and stopping the oil feed to the oil conduit in said shaft operable to stop such oil feed before the shaft-rotating means and air pump actuating means are stopped, whereby to purge the nozzle by the action of centrifugal force in throwing the oil out'of said branch passages into the throat of said annular passage and by the discharge of high pressure air through the annular passage and outlet orifice to sweep the oil therefrom.

4. In an oil burner, a shaft, a nozzle fixed to one end of said shaft and comprising inner and outer members forming between them an annular passage converging from one end of large diameter to another end of small diameter, the small end of said passage terminating with an outlet orifice formed in said outer member, said outer member having an outwardly-flaring frusto-conical wall forming a cup surrounding said orifice and receiving oil therefrom, said annular passage in longitudinal section converging from its large end to a narrow throat located intermediate its ends andthen diverging toward its other and small end, the inner member having a central oil l passage and a circular series of branch passages able to stop such oil feed before the rst-named means is stopped, whereby to purge the nozzle by the action of centrifugal force in throwing the oil out of said branch passages into the throat of said annular passage and by the discharge of high-pressure air through the annular passage and outlet orifice to sweep the oil therefrom, said cup by its rotation after the flow of oil is cut off slinging ofl' by centrifugal force anv oil deposited thereon during the purging of the nozzle passages.

HERMAN O. GRIMMEISEN. REFERENCESA CITED The following references are of record in the file of this patent:

UNI'IED STATES PATENTS K vNumber Name Date 1,443,317 French Jan. 23, 1923 1,656,486 Huntington Jan. 17, 1928 1,934.83? Zulver- Nov. 14, 1933 2.214.912 Valjean s Sept. 17, 1940 2.254.123 Soaper Aug. 26, 1941 .2,370,345 l.'rost Feb. 21, 1945