US2325444A

US2325444A - Air register

Info

Publication number: US2325444A
Application number: US441452A
Authority: US
Inventors: Robert C Vroom; David P Graham
Original assignee: Peabody Engineering Corp
Current assignee: Peabody Engineering Corp
Priority date: 1942-05-02
Filing date: 1942-05-02
Publication date: 1943-07-27
Anticipated expiration: 1960-07-27

Description

July 27, 1943.

R. c. vRooM ET AL 2,325,444

AIR REGISTER 5 Sheets-Sheet 2 AIR REGISTER Filed May 2, 1942 R. C. VROOM ET AL July 27, 1943.

July 27, 1943. R. c. vRooM ET AL 2,325,444

AIR REGISTER Filed May 2, 1942 3 Sheets-Sheet 5 Patented July 27, 1943 UNITED STATES PATENT OFFICE AIR REGISTER Application May 2, 1942, Serial No. 441,452

10 Claims.

This invention relates to air registers or the like and more particularly to an air register for use in a burner of the general type disclosed in Vroom Patent No. 2,210,476, dated August 6, 1940.

In a burner of this type, an air register is provided which may take the formnof a casing having peripheral doors through which air for combustion is admitted. The doors control the di?- rection and velocity of the air and cause the same to form a rotating mass of air within the air register having a degree of turbulence and a velocity of rotation best adapted to promote the mixture of air and fuel for combustion.

It is an object of the present invention to provide a new and improved means for controlling the velocity of air supplied to a burner of the y above type.

Another object of the invention is to provide, in a burner of the above type, improved means for controlling the velocity of air at the burner throat.

Another object is to provide a register of the type above specified in which air for combustion is admitted at different radial and axial zones for purposes of stabilization and control.

Various other objects and advantages Will be apparent as the nature of the invention is more fully disclosed.

Although the novel features which are believed to be characteristic of this invention are pointed out more particularly in the claims appended hereto, the invention itself may be better understood by referring to the following description, taken in connection `with the accompanying drawings forming a part thereof in which a specic embodiment of the invention has been set forth for purposes of illustration.

In the drawings,

Fig. 1 is a longitudinal sectional view of a burner embodying the present invention; and

Figs. 2 and 3 are longitudinal sectional views illustrating two other embodiments of the invention.

In the following description and in the claims certain specic terms have been used for con-` venience in referring to various details of the invention. These terms, however, are to be given as broad an interpretation as the state of the art will permit.

Referring to the drawings more in detail, the invention is shown in Fig. l. as applied to a burner for a furnace having a front wall l of the usual refractory material and an opening BI in which is positioned a ring of refractory blocks i2 having flared inner surfaces i3` forming the burner throat. A plate I4 is positioned over the front wall I0, and to this plate there is secured, as by bolts I5, an annular flanged member I6 having an annular opening I1 registering with the burner throat. Suitable vanes I8 are disposed about the sloping annulus of member I6 for controlling the direction of air flow at the burner throat.

The burner is shown as comprising an air register having a front plate I9 secured, as by bolts 20, to a plate 2| which is spaced from the plate I4 to form a plenum chamber 23 in which air is supplied under pressure to the register. A back plate 24 is secured to the front plate I9 by suitable means, such as stay bolts 25. The back plate 24 bears against the surface of member I6 for effecting an air seal. In certain embodiments, such as, for example, an air register for use at atmospherlc pressure, the register may be supported by securing the back plate 24 to the plate I4 in which event the plate 2l may be omitted.

The register front plate I9 is provided with a hub 2l, and an atomizer barrel 2B having an atomizer tip 29, and a diffuser 30 is mounted in the hub 2l and secured in position by a set screw 3l. The tip 29 and diffuser 30 are arranged to direct a stream of nely divided fuel into the burner throat. The atomizer barrel 28 may also carry a coupling member 32 containing the fuel connections, not shown.

The atomizer barrel may be of the type disclosed more in detail in the Peabody Patent No. 1,528,424, dated May 10, 1927, and may coniprise, for example, means for supplying fuel under pressure to the atomizer tip and for discharging the same in a nely divided spray. The operating capacity may be varied by varying the supply pressure or by returning a portion of the fuel from the atonnzer tip to the fuel pump and controlling the pressure in the return line, `as more fully described in the said patent. Other luel supply means may be used for burning various types of gaseous, liquid or pulverized fuel as shown, for example, in Warner Patents Nos. 1,790,395, dated January 27, 1931, and 1,865,983, dated July 5, 1932.

For controlling the velocity of air to the burner, the register is provided with stationary annular walls 34 and 35 which are secured to the back plate 24 by stay bolts 31, and with three sets of peripherally spaced air doors which are curved to form the peripheral wall of the air register chamber. The three sets of air doors comprise the main air doors 39, auxiliary air doors 40, and tertiary air doors 4I. The main air doors 39 form a peripheral wall between-the .interior annular walls 34 and 35 of the register,

the auxiliary air doors 40 form a peripheral Wall between the front plate I9 and interior wall 34, and the tertiary air doors 4l form a peripheral wall between interior wall 35 and back plate 2d of the register.

The main air doors 39 and the tertiary air doors 4l are Pivotally mounted on the bolts 3l and are adapted to be swung angularly about said bolts so as to adjust the air inlet openings between said doors. The doors 35 and il are actuated by a rotatable shaft i3 which is journaled in front plate i9 and back plate 2li and is provided with an operating handle le at the front of the register. The shaft 33 carries a lug l5 having a slot 4S engaged by a pin il on a ring l5 which is rotatably mounted on the outer periphery of annular wall 35 of the register. The ring llt also carries a plurality of spaced pins engaging in slots formed in lugs 5i and 52 carried by each of the main air doors 35 and. each of the tertiary air doors di, respectively. The arrangement is such that rotation of the shaft i3 by handle dll causes rotation oi the ring it which, through pins 5G and lugs 5l and 52, swings the doors 39 and li angularly about the bolts 3l so as to adjust the air inlet openings between said doors. In some instances individual adjustment of each door or separate controls for doors 39 and for doors il may be desired. The auxiliary air doors it are shown as simultaneously actuated by means of shafts 5d each of which is secured individually to each of said doors and is journaled in the interior wall 55 of the register. Each shaft 54 extends through the front plate l@ and carries a lug 55 having a slot engaged by a pin 56. The pins 56 cooperating with the various lugs 55 are carried upon a ring 5? which is rotatably mounted upon the front plate i9. Suitable means may be provided -or operating the ring 5l, such, for example, as a pinion 58 carried on a shaft 59 and engaging a rack 60 on said ring. The shaft 59 may be operated by suitable means such as a handle 5l. Actuation of the ring 5l causes pivotal movement of the lugs 55 and swings the auxiliary air doors il@ about the rods 5d so as to adjust the openings between said doors. As in the case of air doors 39 and lll mentioned above, it may sometimes be desirable to provide individual adjusting means to permit individual adjustment of each of the auxiliary air doors 4t.

An auxiliary burner throat 53 is supported within the air register by a pair of rods till which extend through openings 65 in the front plate I9 and are provided with suitable handles 65 by means of which the auxiliary throat 63 may be moved axially within the register. The auxiliary throat 63 is of V-shaped cross section, having an inwardly sloping annular wall 6l and an outwardly sloping annular wall 58. The outwardly sloping annular wall 6B is adapted to register with the iiared surface i3 of the burner throat, thus reducing the eiective area of the burner throat when the auxiliary throat 63 occupies the position shown in full lines in Fig. 1, and at such time the inwardly sloping annularA Wall El of auxiliary throat E3 ts Within the inwardly sloping annulus of the stationary wall 35 and forms a continuation thereof. Suitable vanes l@ are disposed about the sloping surface 6l of the auxiliary throat 63 for controlling the direction of air flow.

Operation In the normal operation of the burner, the auxiliary throat 63 is retracted within the air register to the dotted line position shown in Fig. l, and the actuating rods 64 may be provided with limiting stops ll which are engageable with the front plate I9 to insure the proper positioning of the auxiliary throat 63 at the restricted central annulus of the stationary wall 3ft to control the flow of air from the auxiliary doors L1B. However, when the auxiliary throat 63 is moved axially through the air chamber into registery with the nared surface I3 of the burner throat, not only does the inwardly sloping annular Wall 5l of the auxiliary throat reduce the eiective throat area of the burner, but, furthermore, the outwardly sloping annular wall 5B of said auxiliary throat 53 in registering with the iared surface i3 of the burner throat bears against the flanged member l5 and blocks the now of air from the tertiary doors il to the burner.

A flared diiuser extension 13 is supported within the air register by a pair of rods 'lll which extend through openings l5 in the front plate l@ and are provided with suitable handles it by means of which said extension i3 may be moved axially within the register. In the normal operation of the burner, the diiuser extension lt is retracted against the front plate I9 of the register as shown in dotted lines, in which position said extension has no effect upon the passage of the air through the register. However, when the burner is operated at reduced capacities, at which time the auxiliary throat t3 is moved into registry with the iiared surface i3 of the burner throat to reduce the effective throat area and to block oi the ow of air from the tertiary air doors All, the diiuser extension l may be moved inwardly to its limiting position in contact with the diiiuser Sii, as shown in full lines to further reduce the eiective area of the burner throat. Of course, either the auxiliary throat 63 or the diffuser extension may be used separately if desired.

When the burner is to be operated at maximum capacities, the auxiliary throat E3 and the diffuser extension 'i3 are retracted within the air chamber, as shown in dotted lines. Under such -conditions the main air doors 3%, the auxiliary air doors il@ and the tertiary air doors il! may all be adjusted, by proper manipulation of the operating handles 454i and tl, as previously described, to permit the desired iiow of air to the burner throat. At such times it will be noted that the tertiary air doors lll admit air directly at the burner throat under the directional guidance of the stationary vanes it on plate l5, while the air entering through the main doors 3@ is directed to the burner throat by the sloping annulus of stationary wall 35, and the flow of air from the auxiliary doors ll is controlled by the restricted annulus of stationary wall 3d and the retracted throat S3. When it is desired to operate the burner at extremely low capacities, however, the auxiliary throat 53 and the diuser extension Z3 are moved axially within the air chamber to the positions shown in full lines in Fig. l.. Under such conditions, as previously described, the auxiliary throat S5 reduces the edective area of Ithe burner throat and furthermore blocks the ow of air from the tertiary air doors 6l; hence even though said tertiary doors All may be opened simultaneously with the main air doors 3Q by actuation of handle (it, no air will now to the burner throat from the tertiary doors. Further- Fig. Z

Fig. 2 shows a modiication of the invention which employs only two sets oi peripherally spaced air doors, and in which one of said sets of doors comprises telescoping sections which are adjustable axially of the air chamber to regulate the flow or air therethrough as disclosed in Vroom Patent No. 2,210,476, above mentioned. The gen y eral construction of this air register, however, is similar to that previously described, and similar reference numerals have therefore been applied to the same elements, including the framework encompassing the plenum chamber 23 and the atomizer barrel 28 and associatedY parts. For controlling the supply of air to the burner, the register of Fig. 2 is provided with a plurality of peripherally spaced main air doors 8U which are curved to form the peripheral wall of the air register chamber. Each door Bil comprises a section iii provided with ears 82 which rotate on a pinV lis, and a section 85 having an ear `86 which is slidably held on the pin 83. The pins 83 are secured in the back plate 24 and extend through a slidable flanged plate 84. Each section -85 may be provided with a slot 8l engaged by a pin 88 carried by a section 8|. The sections 85 are similar in shape to the sections 8| and are adapted to slide thereover in a direction axially of the register. A spring 89 may be carried on the pin t3 to normally hold the sections 85 in their forward position. Itis to be understood, of course, that the pins 88 may be positioned in the sections 35 and the slots 8l may be formed, in the sections l if desired, or other securing means may be used.

Angular adjustment of the main air doors Sii about the pins 83 is controlled by a rotatable shaft 90 which is journalled in front plate I9 and back plate Ztl and is provided with an operating handle 9| at the front of the register. The shaft 90 carries a lug 92 having a slot dit engaged by a pin Sil on a ring 95 which is rotatably mounted on the outer periphery of the main air doors d. The ring 95 also carries a plurality of spaced pins @l engaging in slots formed in lugs 98 carried by each of the air doors ilu. Rotation of the shaft Sil by handle el causes rotation of the vring t5 which, through pins Sl and lugs gli, swings the doors Bil about the pins et so as to adjust the openings between said doors. It will be noted that this angular adjustment of the doors till by means of handle Si in Fig. 2 is similar to the adjusting operation performed by handle @d in Fig. l..

For controlling the axial position of the sections 85 of the air doors 8i), it is necessary to move the flanged plate Bil axially within the air chamber. This may be accomplished by means of a rod 99 which is secured to the plate di and extends outwardly through a hub ill@ on the front plate i9 and is provided with an actuating handle lill. It will be observed that, by forcing the rod 99 towardthe right or left as viewed in Fig. 2, the axial position of the sections 85 of the air doors may be adjusted as desired.

The air register of Fig. 2 is also provided with a set of auxiliary air doors |513 which are generally similar in construction and operation to the auxiliary air doors Ml of Fig. 1. The auxiliary air doors |03 are actuated by means of pins iill each of which is secured individually to one of said doors and is journaled in the vertical flange of a cylindrical member lil which tele scopes within the annular flange |05 of the movable plate ed. Each pin it extends through the front plate lil of the register and carries a lug lil@ having a slotengaged by a pin lili. The pins lill cooperating with the various lugs itu are carried upon a ring |63 which is rotatably mounted upon the front plate l2. In the embodiment illustrated, the ring tilt is operated by a pinion Mld carried on a shaft i lil and engag ing a rack H2 on said ring. The shaft il@ may be operated by a handle H3. Rotation of the ring l causes pivotal movement of the lugs it@ and swings the auxiliary air doors it about the pins |06 so as to adjust the openings between said doors. It will be noted that this operation of the auxiliary air doors |83 is similar to the operation of the auxiliary air doors 4H in Fig. l. In the embodiment illustrated, the cylindrical member |05 is provided with an inwardly sloping annular throat lill whereby the air admitted through the auxiliary doors |03 is directed through the air chamber to the burner throat.

An auxiliary burner throat IIB is supported Within the air register of Fig. 2 by a pair of elongated rods which extend through openings ll in the front plate I9 and are provided with suitable handles H9 by means of which the auxiliary throat I6 may be moved axially within the register. The auxiliary throat H6 has an inwardly sloping wall I9 carrying vanes |20 for controlling the direction of air ilow, and an outwardly sloping annular wall l2| which is adapted to register with the flared surface i3 of the burner throat for reducing the eiective throat area. when the auxiliary throat H8 is in the operative position illustrated in full lines. A diffuser extension |23 is supported within the air register by a pair oi rods l2@ which extend through openings |29 in the front plate lil and are provided with suitable handles |26 by means of which said extension |23 may be moved axially within the register.

Operation of Fig. 2

In the normal operation of the burner at maximum capacities, the auxiliary throat lit and the diffuser extension E23 are retracted within the air chamber, vand under such conditions the inwardly sloping wall lili of auxiliary throat il@ registers with a sloping annulus l lf3 of the cylindrical member |835, to control the air flow from the auxiliary doors |63. The atomizer being set by suitable means for the required load, the air doors til and |03 are adjusted by means of the handles 9i and H3 to cause the air to enter the register with the desired direction and velocity to set up a whirling motion within the register adapted to produce an ecient mixture of air and fuel at the burner throat. When the load is reduced by suitable adjustment of the atomizer, the air flow through the register may also be reduced by sliding the plate 8d axially of the register. When operating the register at low capacities, the auxiliary throat l lt and the diffuser extension |23 are moved axially within the air chamber to the positions shown in full lines. Under-such conditions, as previously described, the

auxiliary throat H6 reduces the effective area oi the burner throat, which eiective throat area may be further reduced by the diffuser extension |23,

Fig. 3

- The cylinder is tapered inwardly adjacent' its forward (fireroom) end to provide a throat |3| and the forward edge is provided with a ange E32 by means of which the cylinder is secured to the front plate i9 as by bolts |33.

rotation of which handle causes pivotal movement of the lugs |36 and swings the main air doors |34 about the shafts |35 so as to adjust the openings between said doors.

At the rear (furnace end) of the air register of Fig. 3 a cylindrical collar |44, of a diameter larger than the cylinder |30, is mounted concentrically about thepylinder |30 and is secured to the plate i4 by means of the bolts I5 which also secure the annular flanged plate |6. Since the cylindrical collar |44 is spaced from the cylinder |30, and since the rear end of cylinder |30 is spaced from the plate I6 which registers with the burner throat I3, an annular peripheral air passage 45 is formed between cylinder |30 and collar |44 permitting the flow of air from the plenum chamber 23 through the air passage |45 directly to the burner throat. Suitable Vanes |46 are disposed about the inner wall of collar |44 for controlling the direction of air flow through the passage |45.

For controlling the supply of air to the burner throat through the auxiliary passage |45, a movable barile plate |41 may be provided having a circular opening |48 which ts over the cylinder |30, and having holes |49 through which guide rods 25 extend, permitting the bale plate |41 to be moved axially within the air chamber. Axial movement of the baille plate |41 Within the air chamber is effected by means of a rod |50 which is secured to said plate and extends outwardly through a hub |5| on the front plate i9, the rod |50 being provided with 'an actuating handle |52. By actuating the rod |50, the baille plate |41 may be moved either to the right or the left in Fig. 3, thus varying the size of the entrance to the auxiliary air passage |45, or completely blocking said entrance when desired.

An auxiliary burner throat |54 is supported As in the embodiment within the cylinder |33 by a pair of elongated rods 655 which extend through hubs |56 on the front plate i9 and are provided with suitable handles i5?! by means of winch the auxiliary throat |54 may be moved axiaily Within the register. The auxiliary throat 54 is of V-shaped cross section having an inwardly sloping annular wall |53 which closely fits the inner wall of cylinder |30, and an outwardly sloping annular wall E53 which is adapted to register with the flared surface i3 of the burner throat, thus reducing the effective area of the burner throat when the auxiliary throat |54 occupies the position shown in full lines. Furthermore, when the annular wall |53 of auxiliary throat lbl registers with the flared surface I3 of the burner throat, it also abuts against the flanged plate l0 and blocks the auxiliary air passage |45, thusshutting oil' the flow of air through air passage |45 to the burner throat. It therefore permits closure with damper lili omitted.

When the burner of Fig. 3 is to be operated at maximum capacities, the auxiliary throat 634 is retracted within the cylinder |30, as shown in dotted lines, and when in such retracted position the auxiliary throat |54 cooperates with the flared surface |3| of cylinder |30 to control the flow of air from the main air doors |34 to the burner throat I3. Under such conditions air flows through the auxiliary air passage |45 directly to the burner throat 3. When operating the burner in this manner, the main air doors |34 may be adjusted angularly` to control the admission of air as in the embodiments previously described, and the baille plate |41 may be moved axially within the air chamber to' control the flow of air through the auxiliary passage |45..

The auxiliary throat |54 forms an adjustable constriction which may be adjusted axially within the cylinder |30 to regulate the zone at which the air admitted behind the fuel admission means is directed toward the axis. When it is desired to operate the burnel` at low capacities, the auxiliary throat |54 is moved axially within the cylinder |30 to the position shown in full lines, thus reducing the effective area of the burner throat and at the same time blocking the ilow of airv through the auxiliary passage |45.

Although several specic embodiments of the invention have been shown for purposes of illustration, it is to be understood that various changes and modiiications may be made therein as will be readily apparent to a person skilled in the art.

What is claimed is:

1. A burner comprising a throat, and means including a fuel atomizer barrel, an atomizer tip and diuser for. introducing fuel for combustion, an air register for supplying air to said burner having air inlet passages, and having a discharge opening supplying air for combustion to said throat, and an adjustable diffuser extension positioned to cooperate with said burner throat to reduce the effective throat area so as to control the air velocity therethrough.

2. A burner comprising a throat, and means including a fuel atomizer barrel, an atomiz'er tip and diifuser for introducing fuel for combustion, an air register having adiustable air inlet openings and having a discharge opening supplying air for combustion to said throat, an auxiliary throat movable axially in said chamber and adapted to cooperate with said burner throat to reduce its e'ective throat area. and. an adjustable di'user extension cooperating with said diffuser adjacent said burner throat to further reduce the effective area thereof so as to control the air velocity therethrough.

3. A burner comprising a throat, and means including a fuel atomizer barrel, an atomizer tip and diffuser for introducing fuel for combustion, an air register for supplying air to said burner comprising front and back walls and a peripheral Wall having a plurality of axially spaced peripheral inlet passages, one of said inlet passages being disposed adjacent said burner throat to admit air directly thereto, means for regulating the flow of air through said inlet passages, an auxiliary throat movable axially in said chamber and adapted to cooperate with said burner throat to reduce its effective throat area, means on said auxiliary throat for blocking the flow of air through the inlet passage adjacent said burner throat, and an adjustable diifuser extension cooperating with said diffuser adjacent said burner throat to further reduce the eiective area thereof so as to control the air velocity therethrough.

4. A burner comprising a throat, and means including a fuel atomizer barrel, an atomizer tip and diiiuser for introducing fuel for combustion, an air register for supplying air to said burner comprising front and back walls and a plurality of axially spaced sets of periphera1 air doors cooperating therewith, the doors of each set overlapping when closed to form the peripheral wall of an air register chamber and being adjustable angularly to control the air flow therethrough, one of said sets of doors being disposed adjacent said burner throat to admit air directly thereto, an auxiliary throat movable axially in said chamber and adapted to cooperate with said burner throat to reduce its effective throat area, means on said auxiliary throat for blocking the flow of air through the set of doors adjacent said burner throat, and an adjustable diii'user extension movable axially in said register and adapted to cooperate with said diifuser and said throat to further reduce the effective area oi.' said burner throat so as to control the air velocity therethrough.

5. A burner comprising a throat, and means including a fuel atomizer barrel, an atomizer tip and diffuser for introducing fuel for combustion, an air register for supplying air t said burner comprising front and back walls and a set of peripheral air doors cooperating therewith, said doors overlapping when closed to form the peripheral wall of an air register chamber and being adjustable angularly to control the air ow therethrough, an auxiliary air passage opening into said air register chamber adjacent said burner throat to admit air directly thereto and having an annular inlet opening directed forwardly around the outside of said register, and means including a transverse baffle plate movable axially of said register to variably close said annular inlet opening for controlling the flow of air through said auxiliary passage.

6. A burner comprising a throat, and means including a fuel atomizer barrel, an atomizer tip and diffuser for introducing fuel for combustion, an air register for supplying air to said burner comprising front and back walls and a set of peripheral air doors cooperating therewith, said doors overlapping when closed to form the peripheral wall of anv air register chamber and being adjustable angularly to control the air ow therethrough, an auxiliary air passage opening into said air register chamber adjacpnt said burner throat to admit air directly thereto, means for controlling the flow of air through said auxiliary passage, an auxiliary throat movable axially in said chamber and adapted to cooperate with said burner throat to reduce its effective throat area, and means on said auxiliary throat for blocking the iiow of air through said auxiliary air Passage.

7. In a burner having a throat and fuel supply means adapted to introduce fuel for combustion, an air register having adjustable air inlet openings and having a discharge opening for supplying air for combustion to said throat, and an auxiliary throat movable axially in said register and adapted to cooperate with said iirst mentioned throat to control its effective throat area so as to control the air velocity therethrough, air directing vanes carried by both of said throats, said auxiliary throat having means rendering the vanes on said rst throat ineffective when said auxiliary throat is in operative position.

8. In a burner having a throat and fuel supply means adapted to introduce fuel for combustion, an air register comprising a peripheral wall having a plurality of axially spaced peripheral inlet passages therein for admitting air to different portions of said register and having a discharge opening for supplying air for combustion to said throat, at least some of said inlet passages being disposed in front of the zone of fuel admission, and an annular throat restriction having means to direct the air toward the axis of the burner, and means to adjust said restriction axially to vary the location of the axial zone at which the air from said last-mentioned passages is directed by said restriction toward the axis of the burner.

9. In a burner having a throat and fuel supply means adaptedgto introduce fuel for combustion, an air register comprising a peripheral wall having a plurality of axially spaced peripheral inlet passages therein for admitting air to different portions of said register and having a discharge opening for supplying air for combustion to said throat, said inlet passages being disposed both in front and in back of the zone of fuel admission, and an annular throat restriction having means 50, to direct the air toward the axis of the burner,

and means to adjust said restriction axially to vary the location of the axial zone at which the air from said last-mentioned passages is directed by said restriction toward the axis of the burner, said restriction being arranged to close the back inlet passages when adjusted to its rearmost position.

10. In a burner having a throat and fuel supply means adapted to introduce fuel for combustion, an air register having adjustable air inlet openings and having a discharge opening for supplying air for combustion to said throat, an auxiliary air passage opening into said air register chamber adjacent said burner throat to admit air directly thereto, means for controlling the flow of air through said auxiliary passage, an auxiliary throat movable axially in said chamber and adapted to cooperate with said burner throat to reduce its effective throat area, and means on said auxiliary throat for blocking the ow of air through said auxiliary air passage.

DAVID P. GRAHAM. ROBERT C. VROOM.