US2572675A - Gas burner with modulated flame orifice - Google Patents

Description

Oct. 23, 1951 Filed April 7, 1947 GAS BURNER WITH MODULATED FLAME ORIFICE 2 SHEETSSHEET l 46 54 25 45 17 54 11 19 "n n l -u INVENTOR. H61 944/4 F .fi'wzmsav BY AM new A Pvnvon Patented Oct. 23, 1951 GAS BURNER WITH MQDULATED FLAME ORIFICE Paul F. Swenson, Cleveland Heights, and Milton F. Pravda, Redford, Ohio, assignors to The Cleveland Research Corporation, Cleveland,

Application April 7 1947, Serial No."739,738

'7 Claims. 1

This invention relates to gas "burners and more specifically to gas burners of the so called "modulating type in which the gas discharge is increased and decreased'gradually in response to the heat requirements of a room or space being heated, as distinguished from a burner of the on and off type in which the gas discharge is intermittently turned on and off in response to the heat requirements.

Attempts have been made heretofore to provide amodulating gas burner but, so far as these applicants are aware, none of the attempts have proven practical or satisfactory. One disadvantage in the modulating burner heretofore provided has been that when the burner had numerous discharge openings for the gas and air mixture and the gas supply to the burner was throttled down to a condition corresponding with a low heat requirement, the flame could not be sustained at all of the discharge openings. resulted in the issuance of unburned gas'from certain of the openings and the unburned gas passing up the flue was not only uneconomical u cr at d a d n er u cond t on Mo eover, the burn n of t m x u r o ly a po t on of the burner openings also created a condition in which a complete extinguishment of the flame could easily be produced by the occurrence of a down-draft.

To eliminate the undesirable condition just described attempts have been made to construct a modulating gas burner with fewer burner openings and to make the burner openings of larger size. Another disadvantage was then encountered in that when the gas discharge in the burner was throttled down to a condition-corresponding with a low heat requirement, hackfires in the burner were a frequent occurrence. The backfires caused the gas to burn at the dis charge orifice instead of at the burner openings and this also created an unsatisfactory and hazardous condition.

The present invention provides an improved modulating gas burner of a simple andinexpensive construction capable of functioning :in a safe and economical manner and in which the above and other disadvantages areovercome.

Another object of this invention is to provide a modulating gas burner in which the gas stream and the gas and air mixture stream are varied simultaneously .so that an efiicient and depend:- able "functioning will be obtained throughout substantially the entire range of burner operation.

A further object of the inventionis to. provide a modulating gas burner in which the :size .of the 2 as delivery orifice and the size of the gas and air mixture discharge opening are varied simultaneously by gradually increasing or decreasing the same. V

Still another object is to provide a gas burner of the character mentioned, in which the gas delivery orifice, the gas and air mixture discharge opening and the combustion air passage are varied simultaneously bygradually increasing or decreasing the same.

Yet another object is to provide a gas burner of this character, in which gas pressure responsive means is employed for varying the gas stream, the mixture stream and the supply of combustion air.

A further object is to provide a gas burner of this character, in which temperature responsive means is employed for controlling the variation being produced in the gas stream, the mixture stream and the combustion air stream, by the gas pressure responsive means.

As "another of itsob'jects this invention provides an improved gas burner of the character mentioned, in which'the volume of the gas stream and the volume of the gas and air mixture stream can be simultaneously varied gradually and throughout substantially the entire range of burner operation in response to heat requirements but in which a desired discharge velocity is maintained for these streams such that a safe andefiicient functioning of the burner will be obtained at all times.

The invention can be further briefly summarized asconsisting in certain novel combinations and arrangements of parts, hereinafter described andparticularly set out in the appended claims.

In-the accompanying sheets of drawings,

Fig. l is an elevational View, mainly in vertical section, showing a modulating gas burner embodying the present invention, the view also including control devices associated with the :burner and :which are likewise shown in sections :Eig. 2.is. a partial vertical sectional .view taken through the upper portion of the pilot burner and showing this portion on .a larger scale.

Fig. .3 is .a partial vertical sectional view-taken through the lower portionof the pilot burner and showing this portion on a larger scale, and

jfilighe is an elevational View, mainly in vertical section, showing another modulatin as burner embodying the present invention.

.-.As one practical embodiment of the invention Fig. 1 shows a modulating gas burner III which comprises, general, a hollow casing H and a pair.ofxgcoaxialouternnd inner burner tubes 12 3 and I3. In this instance the burner I is shown in an upright position in which the casing N forms the base of the unit and the burner tubes I2 and I3 extend substantially vertically above the casing. It will be understood of course that a modulating gas burner embodying the same characteristics and features as the burner II] can be designed for operation in a horizontal position or in any other desired position or location.

The burner I0 is also shown in this instance as being installed in a domestic furnace or the like F which is here represented by the side wall portion I4 and the refractory slab l5. It should be understood, however, that the burner I0 is applicable to all kinds of heating service and can be used for any desired purpose.

The outer burner tube I2 is supported by the casing I and has its outwardly flared lower end |2a connected therewith as by means of the screws I6. The lower end of this outer burner tube is spaced from the casing so as to provide therebetween an annular air inlet opening I1. The burner tube can be maintained in this relation to the casing II by suitable spacers I8 through which the screws I6 extend. The upper end of the burner tube I2 extends into an opening |a of the refractory slab I5 and carries a deflector plate I9. The deflector plate extends transversely of th open upper end of the burner tube I2 and is mounted thereon as by a plurality of circumferentially spaced axial arms 2|. A second refractory slab 22 is supported by the deflector plate I9 and held thereby in spaced relation above the refractory slab I5, The slab 22 has a central opening 22a therein and can be maintained in position on the deflector plate I9 by means of a stem I9a. provided on the latter and which engages in this central opening.

The casing II has a gas supply connection 24 connected therewith in the form of a pipe which extends to a suitable source of gas under pressure. The casing also has a gas delivery nozzle 25 mounted on the upper side thereof and located substantially on the common axis of the burner tubes I2 and I3. The nozzle 25 is supplied with gas from the connection 24 through the casing I I, as will be explained in detail hereinafter, and has an outwardly converging orifice or passage 26 for discharging a stream of gas axially of the burner tubes.

The inner burner tube I3, which is at times referred to as a mixing tube, extends longitudinally in the outer burner tube I2 and is spaced therefrom so as to provide therebetween an annular passage 21 for secondary combustion air. The tube I3 has approximately the shape of a Venturi tube and is disposed with its outwardly flared lower end 3a located immediately above the nozzle 25 so that the discharge of a velocity stream of gas from the nozzle will induce a flow of primary combustion air into such lower end for mixing with the gas. The upper end of the tube I3 has an outwardly flared portion |3b which is disposed in adjacently spaced relation to the deflector plate |9 so as to provide therebetween an annular space or discharge opening 29 for the gas and air mixture and from which the gas and air mixture issues as a velocity stream and burns as a sustained flame. The flame produced by this velocity mixture stream travels away from the discharge opening 29 in laterally spreading relation adjacent the underside of the refractory slab 22.

The volum of the gas stream being delivered by the nozzle 25 is varied in accordance with the heat requirements of the room or space being heated by the burner I0. This variation of the gas stream is accomplished by gradually varying the effective size of the orifice opening 26 by means of a movable valve element 3| which cooperates with the nozzle 25 in forming a metering valve for the gas. The valve element 3| is preferably in the form of the needle valve element here shown and which has an outwardly converging portion 3|a which is movable in and cooperates with the tapered nozzle 25 for varying the effective size, of the orifice opening 26.

The volume of the gas and air mixture stream is varied simultaneously with, and in corresponding relation to, the variation in the volume of the gas stream being delivered from the nozzle 25. For this purpose the mixing tube I3 is movable axially of the burner unit so as to vary the spacing of its flared upper end I3b' relative to the deflector plate I9. The mixing tube I3 is adapted to be shifted by the movement which is imparted to the valve element 3| for varying the gas stream and, to this end, the valve element has an upwardly extending stem extension 311) on which the mixing tube I3 is mounted as by means of the spider 32.

With the construction and arrangement just described it will be seen that when the valve element 3| is moved upwardly, that is, in a direction outwardly of the nozzle 25 to decrease the volume of the stream of gas being delivered from the nozzle, the mixing tube I3 will also be moved upwardly causing its flared end |3b to approach the deflector plate I9 and thereby decrease the size of the gas and air mixture discharge opening 29. Conversely, when the valve element 3| is moved in the opposite direction, that is, inwardly of the nozzle 25 to increase the size of the orifice opening 23 and the volume of the gas stream being discharged therefrom, the flared upper end |3 b of the mixing tube I3 will be shifted away from the deflector plate I9 thereby increasing the size of the mixture discharge opening 29. During these axial movements of the mixing tube I3 its flared upper end will be guided by the group of axially extending arms 2|.

For the eificient functioning of the modulating burner II] it is desirable to control the supply of combustion air simultaneously with the control of the gas stream and the gas and air mixture stream. In the'gas burner illustrated in Fig. 1 this is accomplished by the damper 34 which is connected with the lower end of the mixing tube I3 for movement therewith and controls the flow of combustion air into the burner through the air inlet opening IT. The damper 34 is here shown as comprising a dished sheet metal disc having a central opening 34a surrounding the nozzle 25 and guided thereon. The damper can be connected with the mixing tube I3 as by means of a plurality of spaced rods 35 so as to leave an opening or passage 36 between the damper and the lower end of the mixing tube for the above mentioned flow of primary'combustion air into such lower end of the mixing tube.

When the valve element 3| and the mixing tube I3 are moved in an upward direction to decrease the volumes of the gas stream and the mixture stream as explained above, the damper 34 approaches the flared lower end |2a of the outer burner tube to decrease the effective size of the air inlet opening IT. This causes the volume of both primary and secondary combustion air to be decreased. Conversely, when the valve element 3| and the mixing tube I3 are moved downcontrol compartment 44 through the restricted outlet 52 is prevented and the gas pressure on opposite sides of the diaphragm 38 has equalized through the restricted passage 49, the spring 69 willshift the valve element 3| upwardly and hold this valve element in its closed position. When gas is bled or permitted to escape from control compartment 44 through the restricted passage 52, the pressure in the control compartment drops and is overbalanced by the gas pressure in the supply compartment 45 causing down ward movement of the diaphragm 38 and a corresponding downward or opening movement of; the valve element 3|. Increase or decrease in the flow of gas out of the control compartment 44 through the restricted passage 52 results in a corresponding downward opening or upwardclosing movement of the valve element 3|. It will accordingly be seen that by controlling the pressure of the gas in the control compartment 44, the gas pressure actuation of the valve ele ment -3| can be controlled in a positive and sen-l sitive manner for modulating the gas flame.

The escape or bleeding of gas from the control compartment 44 for the above explained purpose can be controlled by the use of any appropriate control device or devices. In the modulating gas burner illustrated in Fig. 1 the escape of gas from the control compartment 44 is controlled by the pilot burner unit 55 and also by the two additional control devices H and 12. The pilot burner unit 55 and the control devices II and 12 are disposed in a series relationship or cirj cuit, that is to say, the gas bled from the control compartment 44 first flows to the pilot burner unit, then to the control device H and then to the control device 12.

The control device 1| may be a temperature responsive limit control device which is associated with the heating furnace F being served by the burner unit I and hence is disposed in local relation to the burner unit. The control device 12 may be a room thermostat which is located relatively remote from the burner H) such as in a room or other space to which heat is supplied by the burner. The control gas circuit in which the pilot burner unit 55 and the control devices 1| and 12 are located includes the bleed conduit 54 which connects the pilot burner unit with the restricted outlet 52 of the control compartment 44, a conduit 13 which connects the control device "H with the pilot burner unit and a conduit 74 which connects the control device 12 with the control device H. This control circuit also includes a return conduit l Which connects the control device 12 with the gas escape conduit 43.

The pilot burner unit 55 is itself of novel construction and cooperates with the main burner in anovel manner. This pilot burner unit is provided with a burner tube 11 which is mounted on the main burner tube I2 as by means of the bracket 18 and includes a head 19 which is mounted on the upper end of the burner tube 11. The pilot burner unit also includes an auxiliary burner tube 80 which projects from the upper end of the burner tube 11 and extends through the head 19. The pilot burner unit 55 is disposed in the secondary combustion air passage 21 of the main burner and is located therein so that the upper end of the auxiliary. burner tube 80 will occupy a position near the discharge opening 29 of-"the main burner.

The auxiliary burner tube 89 is open at its upper end and may also have side openings 8| therein adjacent its upper end. A gas and air mixture is discharged continuously from the end and side openings of the auxiliary burner tube for maintaining a pilot flame Pl adjacent the discharge opening 29 of the main burner. The burner tube 11 is provided with one or more air inlet openings 82 and with a gas delivery nozzle 83. The lower end of the auxiliary burner tube. an has openings 84 therein by which it is connected with the interior of the burner tube 11 to receive a gas and air mixture from the latter. The discharge of gas from the nozzle 83 induces a flow of air into the burner tube 71 through the openings 82 for mixing with such gas. A supply of gas is fed continuously to the pilot burner unit '55 through a conduit 85 which connects the gas delivery nozzle 83 with the inlet compartment 40 of the casing through a manually adjustable control valve 85. The conduit 85 is connected with the passage of the nozzle 83 through the groove 81 and the inclined passages 88 formed in the plug portion 83a of the nozzle.

The head 19 which is carried by the pilot burner tube 11 also has a discharge opening 89 for discharging gas and air mixture from the tube 11 and which opening surrounds the auxiliary burner tube 8|]. The head 19 also has a recess 90 therein connecting the discharge opening 89 with a flame space 9| which is defined in part by a bracket portion 190. of the head and in part by a bimetal temperature responsive arm 92 which overlies the flame space. The gas and air mixture which issues from the discharge open ing 89 and the recess 90 burns as a sustained pilot flame P2 which plays against the underside of the temperature responsive arm 92. The sides of the flame space 9| are open and permit the flame P2 to spread-laterally and rise on opposite sides of the temperature responsive arm 92 as shown in Fig. 2.

The delivery of gas through'the nozzle 83 of the pilot burner unit 55 is controlled by an axially movable needle valve element 93 having a stem extension 93a on which the auxiliary burner tube 80 is mounted. The discharge opening 89 is controlled by a valve element 94 which is here shown in the form of a collar carried by the axially movable auxiliary burner tube 80. Downward or opening movement is imparted to the valve element 93 through the auxiliary burner tube 80 by the temperature responsive arm 92 which has one end thereof anchored on the bracket portion 19a of the head 19 by means of the screw 95. The arm 92 extends laterally in overlying relation to the space 9| and the free end of this arm is in the form of a fork 96 which straddles the auxiliary burner tube 80 immediately above a transverse pin 91 carried by the latter.

In this position the temperature responsive arm 92 will be contacted by the pilot flame P2 formed by the burning of the gas and air mixture issuing from the opening 89 and will act to automatically maintain the flame P2 at a desired predetermined size or temperature value. Whenever the arm 92 cools it will be deflected downwardly causing the auxiliary burner tube 80 and the valve element 93 to be shifted in a downward direction by'the pressure of the forked end 96 on the pin 91; This downward movement increases the opening of the gas delivery nozzle 83 thereby increasing the supply of gas for the pilot flame P2. Conversely, whenever the temperature of the arm 92' increases above a predetermined value this arm will be deflected upwardly thereby releasing the pin 91 and permitting the valve element 93 and the auxiliary burner tube 80 to be-lifted by a 9. compression. spring, 99 which. is. embodiedin' the pilot. burner and located beneath thecontrol gas valve I00. This upward movement of the valve element 93 decreases the size of the opening of the delivery nozzle: 83 and thereby reduces. the supply of the gas for thepilot flamePr.

In this manner the temperature responsive arm 92 automatically controls and varies the supply of. gas for the. pilotv flame: P2 and maintains: this gas supply at such. a: volume that an adequate but not excessive heating of the arm 92 will.- take place. The pilot. flame PI which burnsv from the upper end of the auxiliary burner tube 80 will burn continuously at. approximately the same fiamesize but the pilot flametPZx will be gradually varied or modulated, as explained: above,. in: accordance with the temperature condition in.- fiuencing the temperature responsive arm 92. As shown in Figs. 1 and 2 the arm. 92 can be protected from the heat of the main burner flame by means of a guard I I which is disposed over this arm and is held in place by the screw 95.

The lower portion ofthe pilot burner unit. 55 contains the above mentioned control valve member I00 which constitutes one of the series controls for controlling thebleeding of gas from the control compartment 44 of the casing II. This valve member controls-the flow of gas from the conduit 54 into the conduit 13 leading to the control device II. During such time that the pilot burner 55 is ignited, a relatively h-ot condition exists for the temperature responsive arm 92 andthis' arm will then be deflected upwardly, as explained above; and this will permit the spring. 99 to lift the valve member I00 to its open position in which gas can" be bled from the control compartment 44' and will" be permitted to flow into the conduit I3 to the temperature responsive. limit. control device 1 If. During the time thatthe pilot burner 55'is extinguished, the arm 92 will be relatively cool and willv be deflected downwardly to a position in which. the control valve member I00 will beheld closed by the lower end ofthe valve element 93' and even though the. t'emperatureresponsive'devices H and I2 should call for'operation of th main burner, theisi'gnal will not: be: transmitted to the control compartment 44: and the valve element 3| of the main burner will remain closed.

The temperature responsive limlt'. control device TI may be any. suitable form? of device of this type and, in this instance, comprises a body I02 adapted to be mounted on the furnace structure l4 and having a valve passage I03 and a valve chamber I04 thereirrconnect-ing conduitltt with the conduit. A.- valve member I05 movable-in the valve chamber I04 controls the passage I '23 andis adapted to be moved toward aclosed position in opposition. to a compression spring I06 by the bimetal' element I01 acting through the stem I08; A flexible member or bellows I09 forms a seal for the passage through which. the stem I08 extends and. prevents the escape of gas from the valve chamber I04 around this stem. The actuation of t-he'valve member I05 by the bimetal element I01 can be adjusted or calibrated by means of the thumb screw IIO which: varies the compression of. the spring I06.

The temperature responsive device 12 is a room thermostat or thelike comprising a suitablev casing II2 containing a body H3 having a valve chamber I I4 therein with. which the return conduit is'connected. A-valve passage H5 is controlled by a movable valve member H6 and connects the supply conduit 14 with the valve chamher '4. The valve member I I Iiv is moved toward its closed. position by' a; temperature responsive member II! which is here showninthe form of an expansibletemperature responsive bellows device. The bellowsdevice- I I1 acts throughalever II8 which is rockable on the pivot. H and imparts movement to a valve actuating stem I=20 in a direction to close the valve member H6v in opposition to the compression Spring I 2 I... The action of theb'ellows I I! can be adjusted orcalibrated by means of the adjusting screw- I22. which carries a graduated dial I23", the latter being movable relative to a fixedpointer I24.

Whenever the room temperature is relatively low a contraction of thebellows' I I1 permits the valve member I |6 to=be opened'by'the' spring I2I and this permits the bleeding of gasirom the control compartment 44 of the casing. I I', provided that the control valve member I00 of the pilot burner unit 55 and the valve member I05 of the limit control device II, are open. The escape of gas from the control compartment 44 causes the above explained: opening movement of the needl'e valve element 3 I of the main burner I0 which increases the volume of the gas stream being delivered from the nozzle 25. If" the pilot burner unit is extinguished the control valve member I00 will be held closed, as explained above, or if the operating temperature of the furnace F is excessive the valvemember I05 of the control device H will remain closed and; in either event;

,the opening of the valvemember I I 6 of the room thermostat will not cause bleeding ofgas from the control compartment 44 andat' this time the pressures in the control compartment 44 and the supply compartment 45 will beequalizedand the spring 69 will hold" the needle valve element 3I closed. When the pilot burner-55 is lighted and the temperature of the furnace F'i's not excessive, the control valve members I00 and I05 will be open and a modulating control-of the main burner will then be carried out by" the room thermo' statIZ;

Since the return conduit 15' connects with the conduit 43' leading to the mixing tube 21 it will be seen that the small flow of control gas which is bled from the control chamber 44' and which has passed in series relation through the valve chamber of the pilot burner unit 55, the valve chamber of the control device II and the valve chamber of the thermostat 12, will be returned" to the main burner and will be mixed" with the air stream and burned as a part of the main burner flame.

In connection with the construction and operation of the burner I0 it will be observed that if a down-draft occurs it will travel downwardly relatively freely in the. annular passage 21 because the latter is in open communication with the main combustion chamber with which the burner is being used. This movement of the down-draft will be arrested by the damper II' which acts as a barrier thereby causing the velocity fiow of the down-draft to be converted into a pressure at this point which moves upwardly into the lower end of the mixing. tube I3. Although some ofthe down-draft stream may attempt to enter the upper end of the mixingtube I 3- it will be met and equalized by the upward pressure. surge from the lower end. and will thus be prevented. from blowingv outthe. gas. flame.v

Fig. 4 of the drawings. shows another modulating gas burner I30 which is generally similar to theburner I0 above described: but-which is of a moresimplified. construction. Theburner I30 11 comprises coaxial outer and inner burner tubes I31 and I32 having an annular secondary combustion air passage I33 therebetween and a hollow control casing I34 through which the gas is supplied to a gas delivery nozzle I35. The outer burner tube I3I is mounted on the casing I34 by the spaced studs I35 so as to provide therebetween an inlet opening or passage I31 for combustion air.

The upper end of the outer burner tube extends into an opening of a refractory slab I38 which may form a portion of the'wall of the combustion chamber with which the burner is being used. A second refractory slab I39 is supported from the upper end of the outer burner tube in spaced relation to the slab I38. The slab I39 can be mounted on the outer burner tube I 3I by means of the bridge member I45 having spaced axial arms I40a which are connected with the upper end of the outer burner tube.

The inner burner tube I32 may be in the form of Venturi tube as here shown and is mounted in the outer tube I3I by means of a group of radially extending arms MI which extend through the inner tube and have their outer ends connected to the outer tube. The inner tube is disposed in axial alignment with the nozzle I35 and has its lower end in adjacently spaced relation to this nozzle so that a velocity stream of gas being discharged through the orifice I42 of the nozzle will be directed upwardly through the inner tube and will induce a flow of primary combustion air into the lower end of this tube from the air inlet opening I31. The upper end of the inner tube is disposed so that it lies in substantially the same horizontal plane as the upper end of the outer tube I3I. A deflector plate I43, located adjacent the upper end of the inner tube and extending transversely thereof, defines with such upper end of the inner tube a discharge opening or space I45 for discharging a velocity stream of the gas and air mixture being produced in the tube I32. The annular space between the upper ends of the outer and inner tubes I 3I and I32 forms a discharge opening I46 for secondary combustion air.

The orifice opening I42 of the gas delivery nozzle I35 is controlled by needle valve element I41 having a tapered portion I48 axially movable in this orifice opening. This needle valve element also has an extension stem portion I45 which extends through, and is guided in a sleeve I50 carried by the inner ends of the arms MI. The deflector plate I43 is mounted on the upper end of the stem extension I49 so that control I movements imparted to the needle valve element will also shift the deflector plate for varying the size of the gas discharge opening I45 and the size of the secondary air discharge opening I48.

The direction of the taper I48 of the needle valve'element is such that when the latter is moved in a downward direction, that is to say in a direction inwardly of the nozzle I35, the volume of the gas stream being discharged from the nozzle andthesize of the orifice opening I42 will be decreased and, conversely upward or outward movement of the tapered portion I48 will increase the size of the orifice opening and the volume of the gas'stream being delivered therefrom. The corresponding movements imparted to the deflector plate I43 will be such that when the volume of the gas stream being discharged from the nozzle orifice I42 is decreased the size of the mixture'discharge opening I45 and the secondary air discharge opening I46 will likewise be decreased. On the otherhand whenthe movement of needle valve element increases the size of the orifice I42 the corresponding movement imparted to the deflector plate I43 will increase the size of the mixture and secondary combustion air discharge openings I and I46.

The hollow casing I34 is formed by connecte top and bottom casing sections I34a and I342) which have a flexible diaphragm I53 mounted therebetween. This diaphragm divides the in.- terior of the casing I34 into a gas supply compartment I5I and a control compartment I52. A' restricted passage I53 formed in the wallyof the casing connects the supply and control compartments I5I and I52 and permits a pressure equalization therebetween. The size of the restricted passage I 53 can be varied by the adjusting screw I54. The' supply compartment'I5I is connected with a source of gas under pressure by means of the-pipe I55. I

The needle valve element I i'I which controls the orifice I42 of the gas deliver nozzle I35, is connected with the diaphragm I55 for actuation thereby. This valve element is connected with the diaphragm by means of a tubular stem I5'I whose lower end extends through the diaphragm and, is in open communication with the supply compartment I5I. The upper portion of the tubular stem I57 has openings I58 therein through which the gas from the supply compartment I5-I is delivered to the interior of the nozzle I35. The tubular stem portion I5! is axially movable in an opening I 59 provided in the base portion I35a of the nozzle I35. The escape of gas through the opening I59 is prevented by a flexible sealing dia-v phragm I65 having its central portion connected with the central portion of the main flexible diaphragm I and whose edge portion ISIla is seal.- ingly pressed against the top casing section I34a by the compression spring I M This compression spring is preferably a tapered low rate spring which also acts on the main diaphragm I so as to cooperate with the gas pressure in causing the desired actuation of the needle valve element I47 and the deflector plate I43. A small breather passage I62 is also formed in the base portion [35a of the nozzle I35 and connects the sealing space or chamber I63 surrounding the hollow stem I57 with the interior of the nozzle I35.

The control compartment 152 of the casing "I34 has an outlet or bleed conduit I35 connected therewith so that the pressure of the gas in the control compartment can be varied so as to produce a desired pressure differential between the control compartment I52 and the supply compartment I 5i for'actuating the diaphragm I50 and. the needle valve element I41 connected therewith. The escape or bleeding of gas from the control compartment I52 through the conduit I55 can be controlled by suitable control devices, such as the above described limit control device II which would be located in local relation to the burner I35 and the room thermostat 72" would be located at a point relatively remote from the burner. When either of these control devices permits the escape of gas from the control compartment I52, the resulting pressure differential on oppositesides of the diaphragm I53 will cause upward movement thereof to thereby lift the needle v'alve element I41 and increase the orifice opening I42 to correspondingly increase thevolume of the gas stream being delivered by the nozzle I35. .Wheheither' of the control'devices II and 72 acts to decrease or terminate the escape of gasfrom the control compartment I52 the resultingequalization of pressure between the 13 control and supply compartments and the ac tion of compression spring I6.I cause a down ward movement of the diaphragm. I50. and a corresponding downward or closing movement of the valve element I4'I..

In the operation of. the burner I30 as just described it will be observed that the movements imparted. to the. needle valve element IE1 and. to the deflector plate I43 will be such as to cause gradual increase or decrease in the size of. the gas delivery orifice I42 and in the size of the mix.- ture discharge opening I45 and also in the secondary combustion air discharge opening I46. This gradual variation in the. size of theseopenr ings produces a desired modulation of the gas flame. formed by the combustion. of the gas and air mixture .being discharged through the opening I45; The gas which isbled from. the control compartment I52 can be returned to the burner and discharged into the lower end. of the mixing. tube I32 by the return conduit. I66.

A pilot burner IG'Imay be provided adjacent the main burner I30 and, in this instance, is of a simple construction comprising merely a gas and air mixing tube I68. extending axially along thev outside of the outer burner tube I3I and mounted thereon by means. of the brackets I69. The? pilot burner I6! also includes a gas delivery nozzle I10 which discharges av stream of. gas upwardly through tube I68 but is spaced from the lower end. thereof to permit. an induced flow or air to enter this tube for mixing with the gas stream.. The. nozzle I10 is connected with the supply compartment II of the casing I34; and the flow of gas through this. nozzle can. be regu lated by means of the adjustable valve. key MI; The upper end, of the pilot: burner I61 extends through the refractory slab I33 and is located opposite the discharge. opening I45 so that a pilot flame burnin continuously from the upper end of the tube I68 will be in adjacent relation to the discharge opening forigniting, the mixturestream issuing therefrom.

In the modulating gas burners I0 and; I30 as described. above it should be noted that the gas: is

discharged from the nozzle as a velocity stream which induces a flow of primary combustion. air into the mixing tube and. the resulting gas. and air mixture is. discharged from the burner opening. as a velocity mixture stream. When the vol ume of gas being discharged from the nozzle is varied, the. size of the mixture discharge. opening and the amount of combustion air are varied simultaneously and in. corresponding relation. This provides for a gas and air mixture in proper proportions for a substantially complete combustion and a substantiallyconstant flue gas analysis throughout the full range of burner operation, and also insures a velocity discharge of the mixture from the burner opening which at all times prevents the occurrence of a backfire. Even though the volumes of the gas stream and mixture stream are varied the discharge velocity" for these streams is maintained and the burners have what can be referred to as a substantially one hundred percent turn down ratio. Because of these characteristics the main burner flamecan be gradually increased or decreased in accordance with heat requirements and the burning of the gas will; take place safely and efficiently throughupp ends of theburner tubesm-and I32 d r prevents down-drafts from. entering thesetubes. and hence, the gas flame is not likely to be blown out. The inner tube I32 is particularly well shielded by the deflector M3 and any portion of: the down-draft stream which enters the outer tubeI3I canpass freely therethroughwithout materially affecting the gas stream or the flame.

Although the improved gas burner has been disclosed. herein to a detailed extent, it should be understood that the invention is not intended to be correspondingly limited in scope but includes all changes and modifications coming within the scope of the appended claims.

Having thus described our invention, we claim: 1. In a gas burner, a housing comprising a casing and a main burner tube connected therewith, a mixing tube member located in said main burner tube and extending substantially coaxially thereof, a deflector member, said mixing tube member having an air inlet at one end thereof and a discharge opening at its other end for discharging a gas and air mixture, said deflector member being located adj acent to and extending transversely of said other end of said mixing tube member and cooperating therewith in defining said discharge opening, one of said members being movable relative to the other axially of said main burner tube for varying said discharge opening, a gas delivery nozzle adapted to discharge a velocity stream of gas in said mixing tube member axially thereof for mixing with 'air from said air inlet, means for supplying gas under pressure to said nozzle, a. movable valve element controlling the delivery of gas from said nozzle, means connecting said one memberwith said valve element. for movement coniointly with the latter, gas pressure responsive diaphragm means in said casing. and. operable to ca se such conjoint movement of said one member and valve element, and pressure regulating valve means, in said casing for controlling the pressure of the gas acting. on said pressure responsive means;

2. A gas burner of the character described comprising a burner tube having an air inlet, a

mixing tube member having one end located to receive airfrom said inlet, said mixing tube. member being disposed in said burner tube and spaced from the wall of the latter to provide therebetween a passage for secondary air from said: air inlet, a gas delivery nozzle adapted to discharge gas axially in said mixing tube memher. for mixing with air from said inlet, a deflector member spaced from the other end of said mixi-ngtube member to provide therebetween a discharge opening for a gas and air mixture, one of said-members being shi ftable for varying saidv discharge opening, a movable valve element'- cooperating; with said nozzle for controlling the delivery of gas through the latter, a damper controlling. the flow of airthroughsaid inlet",- said one member and damper being adapted for'movemerit proportionately with said: valveelement, a

hcllowcasing having supply con trol: comps-rt m'cnts therein and. a restricted passage: connect ing; said. compartments. with each other; a dia: phragm in said casing between said compart-' ments and: operably connected with said valve element for: causing. actuation of the valve: ele merit, said. one member and-said damper in re: sponseto a: pressure'differential between sal'di compartments, means for supplyinggas: under pressure to: saidinozzle; and having communication with said supply compartment; and; means for discharging gas from said control chamber at a'controlled rate for creating said pressure differential. i

3. A gas burner of the character described comprising, a casing, a burner tube having one end thereof connected with said casing, a mixing tube in said burner tube and spaced "from the wall of the latter to provide an air passage .therebetween, a deflector mounted on the other end of said burner tube and extending transversely of one end of said mixing tube and spaced therefrom so as to provide therebetween a discharge opening for a gas and air mixture, said mixing tube having an air inlet at its other end and being shiftable relative to said deflector for varying the size of said discharge opening, a gas delivery nozzle adapted to discharge a velocity stream of gasaxially of said mixing tube and toward said discharge opening, arnovable valve .element cooperating with said nozzle for controlling the delivery of gas therefrom and having operative connection with said mixing tube for simultaneously shifting the latter, and gas pressure responsive diaphragm means in said casing and connected with said valve element for causing the simultaneous actuation of said valve element and mixing tube.

4. A-gas burner comprising a casing having an inlet for gas under pressure and a gas deliv ery nozzle connected with said inlet to be sup- .plied therefrom, a. burner tube having an air inlet end connected withsaid casing and pro- .vided with an air inlet opening, a deflector carried by said burner tube, a movable valve needle cooperating with said nozzle for controlling the delivery of gas therefrom, a mixing tube in said burner tube and disposed so that gas is discharged thereinto by said nozzle for mixing with air from said air inlet, said mixing tube having one end thereof spaced from said deflector to provide a discharge opening therebetween for a gas and air mixture, means connecting said mixing tube with said valve needle for movement by the latter relative tothe deflector for varying said discharge opening, and gas pressure responsive diaphragm 'fneans in said casing and adapted to cause simultaneous actuation of said valve needle and mixing tube. r

5. Ages burner comprising a casing having an inlet for gas under pressure and a gas delivery nozzle connected with said inlet to be supplied therefrom, a burner tube having an air inlet end connected with said casing and provided with an air inlet opening, a deflector carried by said burner tube, a movable valve needle cooperating with said nozzle for controlling the delivery of gas therefrom, a mixing tube in said burner tube and disposed so that gas is discharged thereinto by said nozzle for mixing with air from said air inlet, said mixing tube having one end thereof spaced from said deflector to provide a discharge opening therebetween for a gas and air mixture, means connecting said mixing tube with said valve needle for movement by the latter relative to'the deflector for varying said discharge opening, a movable air control member controlling the flow of air through said air inlet, means connecting said air control member with said valve needle, and gas pressure responsive diaphragm means in said casing and operable to cause actuation of said valve needle, mixing tube and air control member simultaneously.

6'. A gas burner comprising a burner tube having an air inlet opening and a discharge opening,

16 a mixing tube in said burner tube and spaced from the wall thereof to provide a passage therebetween for secondary air, said mixing tube having a discharge opening lying in substantially the same plane as the discharge opening of said burner tube, a gas delivery nozzle adapted to discharge gas into said mixing tube for mixing with air from said air inlet opening, a movable valve needle cooperating with said nozzle for controlling the discharge of gas therefrom, a control member disposed adjacent to and extending transversely of the discharge openings of said burner tube and mixing tube, means connecting said control member with said valve needle for movement thereby relative to said burner tube and said mixing tube for varying said discharge openings, and means for supplying gas under pressure to said nozzle including gas pressure responsive diaphragm means for causing actuation of said valve needle and control member simultaneously.

7. A modulating gas burner comprising a bottom casing having a transverse top wall, an upright burner tube supported by said casing and extending upwardly from said top wall, a mixing tube member extending upwardly within said burner tube in substantially coaxial relation thereto and being spaced from said burner tube to define therebetween an upright annular passage for secondary combustion air, said burner tube being open at its upper end and having an air inlet opening at its lower end adapted to supply said secondary combustion air to said annular passage, said mixing tube member having a substantially Venturi shaped passage and being open at its upper and lower ends and having its lower end disposed above said air inlet opening so as to receive primary combustion air there from, a deflector member extending transversely of and spaced from the upper end of said mixing tube member and' cooperating therewith in defining an annular discharge opening for a gas and air mixture, said bottom casing having gas supply and control compartments therein and a restricted passage connecting said compartments with each other, a diaphragm in said bottom casing between said compartments and being movable in response to a pressure differential therebetween, a gas delivery nozzle carried by said top wall and disposed so as to discharge a velocity stream of gas from said supply compartment upwardly into the lower end of said mixing tube member for inducing a flow of said primary combustion air thereinto from said air inlet, a valve element axially movable in said nozzle for controlling the discharge of gas therefrom and hav-.- ing its lower end connected with said diaphragm for actuation thereby, one of said members being movable in the direction of the axis of said burner tube and relative to the other of said members for varying the size of said annular discharge opening, means connecting said one member with said valve element to vary said discharge opening proportionately with the opening and closing of the valve element, and means for discharging gas from said control compartment at a controlled rate for creating said pres sure differential.

PAUL F. SWENSON. MILTON F. PRAVDA.

(References on following page) I 7 REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date Merrill Oct.-8, 1889 Elliott May 27, 1902 Mavrogordato Nov. 21, 1911 Killam Mar. 31, 1914 Anderson Ma'y29, 1923 Morgan Jan-15, 1924 Ronstrom Nov. 11, 1924 McMullen Aug. 25, 1931 Hegwein et a1 July 31, 1935 Number Name Date Leahy Dec. 29, 1936 Engels Apr. 5, 1938 Kronmiller May 23, 1939 Long Nov. 25, 1941 Jones Aug. 31, 1943 Higley Nov. 7, 1944 Hopkins June 5, 1945 Higley May 6, 1947 FOREIGN PATENTS Country Date Great Britain Feb. 4, 1921 France Nov. 19, 1925

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