US1576754A - Furnace control - Google Patents

Description

March 16,1926; 1,576,754

* E. MCLEAN FURNACE CONTROL Original Filed Dec. 10. 1921 4 Sheets-Sheet 1' B LER Pm ssuns m INVENTOR.

ATTORNEYS E. M LEAN FURNACE CONTROL March 16 1926.

Original Filed Dec.

10, 1921 4 Sheets-Sheet 2 INVENTOR.

MA TTORNEYS Z W Z 4/ 44 W Z Y .z y If 2 y a Z W j f 2 W 6 & WZZ$ z W Z W March 16 1926.

E. M LEAN FURNACE CONTROL 4 Sheets-Sheet 5 Original Filed Dec. 10. 1921 WITNESS:

March 16 1926.

E. M LEAN FURNACE CONTROL l0. 19%1 4 Sheets-Sheet 4 ,1 76.

'IIIIIIIIIIIIII/IIIIIIIIZ Original Filed Dec.

% A TTORNEYS Patented Mar. 16, 1926.

UNITED STATES PATENT ounce.-

EMBURY MOI-EAR, F BROOKLYN, NEW YORK, ASSIGNOR TO THE ENGINEER COI- PANY, OF NEW YORK, N; Y., A CORPORATION OF NEW YORK.

FURNACE CONTROL.

Application filed December 10, 1921, Serial No. 521,318. Renewed April 22, 1925.

provements in furnace control, and more particularly to that type of furnace fired with fluid fuel. 1 g

The object of the invention is'to provide means whereby asupplyof air necessary for combustion w1ll be efiiciently and properly controlled atall times so as to bear the proper relation to the supply of oil or fluid fuel fed to the furnace during a given period.

The invention consists in the improvements to be more fully described hereinafter,

and the novelty of which will be particular- -ly pointed out and distinctly claimed.

have fully and clearly illustrated a preferred embodiment of my invention in the accompanying drawings to be taken-as a part of this specification, and wherein- Figure 1 is a view in side elevation, partly in section, of a furnace having one embodiment of my invention applied thereto.

, Fig. 2 is a similar .view showing another embodiment of the same. invention.

Fig. 3 is a section on the line 33 of Fig. 1 and Fig. 2. I I so Fig. 4 is a view in front elevation, partly iIn section, of a controlling means shown in Fig. 5 is a section on the line 55 of Fig. 4. v

$0 Fig. 6 is a view in rear elevation, partly in section, of a controlling means shown in Fig. 2. I

Fig. 7 is a section onthe line 7-7 of Fig; 6

-- 4 Fig. 8 isaplan view of the lower ortion of the controller shown in Figs. 6 an 7.

Fig. 9is'a top lanview of the top member of the control er shown in Figs. 6, 7 and Fig. 10 is .a' longitudinal central section through the controller shown in Figs. 6, 7, 8 and 9, l

Fig. 11 is a longitudinal section through a control device for regulating the supply of 4 boiler furnace fired by fluid fuel, and having means for controlling the draft or supply of air for combustion.

In thedrawings, the furnace is shown as consisting of a side wall 1, front wall 2, rear wall 3, and an intermediate or bridge wall 4,

a steam drum of a steam boiler being indicated generally at 5. Between the front wall 7 2 and the bridge wall 4 is located the combustion chamber 6, located over a substan tially horizontal partition 7 extendin from the front wall to the said bridge wa and from one side wall to the other, so as to pro- 7 vide an. air inlet chamber 8 beneath said partition. An area or portion of said partition may be open-work or checker-work structure so as to provide a plurality of'openings from which airmay flow from the chamber 8 to the furnace chamber 6, said area being substantially co-e'igtensive with the size of the flame when the burner is working with a large vollime of oil. By reference to Fig.

3, it will be seen that the checker-work is of flaring form, the tapering sides of which are provided by imperforatedportions 10 of said partition at the forward corner of the furnace, the outwardly inclined edges 11 of said imperforate portions defining the forward boundaries of the flaring checker-work portion. In the present embodiment. the said flaring edges 11 extend from a point ad jacent the center of the front wall to 8. int substantially midway the length of the Side 05 walls of the furnace, so that the checkerwork extends from said boundaries rearwardsto the bridge wall lengthwise 01' the furnace, and the entire width "of the furnace at points in rear of the points at which said 1 boundaries merge with said side walls; It will be seen that the area of the 'open work portion of the partition 7 conforms substantially to the maximum form of the flame in the furnace chamber. r

The furnace is-also provided with a 'suit-. able draft-controlling means, in this instance, consisting of-a'suitable outlet stack 12 through which the products of combustion find exit, the area of the passage throu h the stack being controlled by a suitable damper v13 pivoted, as at 14, on the stack, in any suitable manner.

The furnace is provided with any suitable nozzle or burner 15 for feeding fluid fuel to the furnace, and in which the fuel is atomized by steam or air under pressure fed to the burner simultaneously with the fluid fuel. The burner or nozzle is preferably located in the front portion of the furnace chamber above the partition 7 and central of the transverse width of the" furnace chamber, and'over the forward portion of the open-work area of said partifrom a suitable source is fed to the burner er through the pi es 17 and 19 is controlled by a regulator, s own generall at 21, in Figs. 1, 2 and 3, and specifica ly, in Fig.

11, operating valves in the fluid fuel and steam pipes, the valve in thelatter being located between the hand-valves20; This re%1lator may be of any suitable type capa 1c ofadjustment so as to automatically regulate theamou'ntof oil fed to the burner tofore describe steam within the chamber22: I

of the spring 36 may be regulated by ad-' in accordance with the steam pressure of the boiler, and also the quantity of steam fed to theburner to atomizethe oil.

Referring particularly to Fig.11, I have shown a wel -known type of regulator for this purpose; the same consisting lindrical chamber 22 having iaphragm heads 23, 24 sealin the chamber, the latter being connecte by a pipe 25 with a source of steam at boiler pressurei Over the diaphragm 23 is a plate 26" supporting a frame 27 connected at'its uper end, in any suitable manner to a'va ve body or casing 28 located in the steam ipe between the valves 20, as stated, said ody having a valve I seat 29 with which "cooperates a valve 30 co'nnected' to a stem 31 guided by a stufling-box 32, and a sleeve 33, thev latter being threaded in the said frame 27, as at 34. The valve stem 31 is connected to a plate 35 resting1 on'the diaphragm 23, hereis an expansion spring .36; thefe'ndsof which respectively abut the said plate35 and an abutment'37 resting against the'lower end of said sleeve '33, the function of'saidspring being to urge the valve, 30 -toward open position in opposition to the ressure of he pressure justing said screw sleeve 33 and consequent of a cy- Surrounding the stem 31 ly the position of said plate 37 so that the latter maybe adjusted relative to the plate 35 to compress or relieve the compression of the spring 36..

A construction similarzto the above is provided for regulating the, uantity of fluid fuel, and includes a valve ody or casing 38 in the pipe 17 having a seat 39 having a passage controlled by a valve 40, the latter beingconnected to a stem 41 uided through a stufling box 42 correspon ing to the stuffing-box 32, heretofore described, and supported by 'a frame 43,'which is in turn supported by a plate v44 similar to the plate 26, heretofore described; I The stem 41 is guided through an adjustable screw sleeve 45 threaded through a portion of the frame, as at 46, and carrying an abutment plate 47 against which abuts one end of a coil spring 48 coiledabout the said stem 41, and the other end of which spring is connected to the plate 49 on the outer face of the diaphragm 24. This spring 48 normally urges the valve 40 towards open position in opposition to the steam pressure within the chamber 22 tending to close the valve. By adjustment of the elements 33 and 46, heretofore described, the relative area of the opening in the steam supply pipe 9 and the oil supply pipe 17 may be regulated in accordance with a given steam pressure in order to determine theamounts or quantities of oil and steam fed to the boiler.

Thefluid fuel fed' from the burner or nozzle 15 to the furnace chamber, this being' under ressure, is in a form which results in a: ame which iseither substantial- 'ly cone-shape or fan-shape, according to the vt .pe of .burner used.j .It is desirable that t eyair entering the'f'urnace chamber be admitted over an area: conforming as nearg as possible to the form or area of the ame, in order 'that'the best results be obtained as regards com lete combustion.

I- will now descri e improved means whereby the draft of the furnace or the air supplied thereto for combustion is varied or controlled by the oil fed to the furnace. This means includes a regulator, shown in the present instance as being'of the same general'construction as shown and described in my prior Patent No. 1,071,771, dated September 2, 1913. One adaptation of this regulator forthe present furnace is shown in Figs. '4 and 5, wherein 5O designates a rectangular frame set in an opening in one of the said walls of the furnace and providing an opening between the furnace chamber and the external atmosphere. In

this rectangular frame is arranged a swing- 1 ing' rectangular plate 51 fulcrumed at a point adjacent its lower end, as at 52 to the side members ofv the-said frame, said fulcrum being located preferably at, or closely lll) so that said plate will remain stationary on its pivot at any point to which it may be moved. In order to assure the axis being through the center of gravity of the plate, a weight 53 issupported on the lower portion of said plate, said weight being adjustably supported and held by upper and lower nuts 54:, 55 on threaded rods 56, secured to the lower portion of the plate 51. The movement of the plate on its fulcrum is opposed by up er and lower tension springs 57, 58, the former being connected at its :-lower end to a projection 59 on the lower end of the swinging plate, and at its opposite end, to an adjustable anchorage consisting of .an'eye 60 on a threaded shank 61 1 extending slidably through a bracket 62 se- The movements of this vide a cured rigidly to the side of the frame 50, said threaded shank being adjustably held by means of upper and lower nuts 63, whereby the tension of the spring 57 may be adjusted.

movement of the plate, and also to balance the action of the draft pressure in the furnace, in a manner to be presently described. pressure regulator are employed to control t e positionof the stack damper 13 so as to control the rate of outflow of furnace gases through the stack. 1

-In order to accom lishthis result, I projiilot valve 68 aving an inlet 69 connected y a pipe 70with a source of fluid 'under pressure, and a combined inlet and outlet 71 connected by a pipe 72 to the lower end of anoperating'cylinder 73 containing a piston .74 connected to a piston rod 75,

which in turn is connected by a flexible connection 76 with a lever arm 77. for operating the damper, said flexiblefoonnection being passed over an intermediate'guide pulley 78. The pilot valve is provided with ,a piston valve 79 connected loosely to. a'bracket arm 80 on the lower portion of the swinging plate 51. The pipe is connected by a pipe 81 to the up or endof the cylinder 73, above described: Thepipe 70 contains hand- valves 82, 83 on opposite sides of the connection with said .pipe. 81,.and the pipe 72 contains a hand-valve 84. The

" pilot valve casing is provided with an escape opening 85 at its lower end.

The operation of .said pilot valve is to control the flow of fluid pressure to'and from the-lower end of the cylinder 73 in order to operate the piston 74 to control the damper 13. On the lever 77 is a weight 86 normally tending to hold the damper in open position. The construction of this pilot valve is specifically shown in Fig. .4, but I do not deem it necessary to describe the same with greater detail, as it is of well-known construction, and specifically does not form a part of my present invention.

On the frame 50 is a bracket arm 87, upon the lower end of which is supported a pressure chamber 88 formed by a rigid side wall 89,;and an opposing diaphragm wall 90 against which engages a plunger head 91 on a plunger stem 92, having one end in engagement with one member 93 of a bellcrank lever fulcrumedas at 94 on a bracket 95, and the other member 96 of which lever is pivotally connected at 97 to the lower end of the threaded shank 65. The diaphragm chamber isconnected by a pipe 98 with the pipe 17 leading to the burner 15, so that the pressure of oil in the pipe 17 is com-- municated to the diaphragm chamberand acts against the diaphragm 90 and the plunger head 91. The pressure of oil against the plunger-head'91' is opposed by an expansion Spring 99, one end of which'is located in the spring head 100 engaging the opposite side of the bell-crank lever 93 from that which en ages the plungerrod 92, and the other en of which spring isseated in a spring seat 101 which abuts an adjusting screw 102 threaded through a fixed abutment 103 supported by the rods 104 at- ;tachedto the diaphragm chamber structure.

The screw 102 IS adjustable to vary the force of the spring 99, and may be held in adjusted position by a jam-nut 104. 3

When the pressure of oil is at the minimum 'for firing the furnace,- the tension of the springs '57, 58, is adjusted so that the excess tension on the lowerspring over the upper spring added to the draft pressure on the inside of the plate is just suflicient ressure on the to balance the atmospheric 7 outside of the plate; where y theplate is heldin neutral position, as shown in'Fig; 5,

. and the pilot valve GS iB mainta-in'ed in position to cut off flow of fluid under pressure to the bottom of the cylinder 7 3, The lower adjusting nut 67 is then set against the bottom. of the bracket 66, and the upper ggju stingnut 67- is movedQtoward the eye i to 've play to the threaded shank 65 throng the said bracket. The feed of fluid fuel to thefburner is then increased to the maximum pressure desired, andthis pressure exerted on the diaphragm 90p'ushes the plunger head 91. andjpl-unger rod 92. outward toward the right of Fig, 4 against the force of the spring 99 moving the bell-crank in a direction to increase the tension on the lower spring 58. The adjusting screw 61 similar parts, to which reference may is then turned until the bracket and the plate 51 are pulled outward enough to cause the damper 13 to open sufficiently to give the desired amount of draft in the furnace chamber 6 for a maximumsupply of oil. The action of the spring 99 opposing the diaphragm will now hold the bell-.

crank controlling the tension on the lower spring 58, in such position that eve pressure of oil to the burner intermediate between the minimum and maximum of the regulator will automatically holdthe flue damper 13 in a position to give a draft in the furnace chamber 6 that will give the desired air supply for the fuel being fed to the furnace at that time. The spring 99 should be of such proportions that for the range of variation of pressure of oil to the burner it will give the desired travel to the threaded shank to give the desired variations in tension of the lower spring 58 to control the draft to the desired amount for minimum pressure of oil supplied to the burner, and 'for maximum pressure of oil supplied to the burner. In the form of the invention shown in Figs. 2 and 6 to 10 inclusive, the operation of the regulator is controlled by the rate of flow of oil passing to the burner as distinguishedfrom control by pressure of oil fed to the burner, as heretofore described. In this form of the invention, I employ a plate regulator, such as heretofore described, and in view of the similarity of the structure I do not repeat the description as to features which are in common, but have applied similar reference numerals to e made by the description previously g ven. Upon a suitable bracket 105 is supported a regulator of my invention for controlling the operation'of the swinging plate in accordance with variations in the rate of flow of oil or other fluid fuel fed to the burner. This regulator is shown specifically in Figs. 6 to 10 inclusive, whereini106 designates a lower half or member of a diaphragm chamber, the upper half of which is shown at 107, said members being connected by headed bolts 108 and nuts thereon, and said members clamping between them a flexible diaphragm 109 shutting of! communication between said members; except as hereinafter described. Integral with the. lower member is an inlet connection 110 having a port 111 leading to'an opening 112 through the flange of the member 106 leading into a, passage 113 in the wall of the upper member 107,

said passage 113 communicating with the s ace in said ulpperimember above the said aphragm. T ed to that. ortion of the pi e 17 of Fig. 2 (corresponding to the pi e 1 heretofore described) leading from t e pump 16. Connected' to the lower member 106 is an outlet e connection 110 is connect-.

connection 114 (Fig. 8) opening) into the lower chamber of the device slow the diaphragm 109,- said connection being connected to a pipe 17 leading from said reguinternal bore 119 of the valve, which inturn communicates with a passage 120 leading into the member 106 beneath the diaphragm 109. In order to provide for a tight fit, the valve 117 is preferably tapered and fitted to a correspondingly tapered bore in the casing 116, and is urged to its seat by a spring 121 surrounding a stem 122 on said valve and at one end abutting a packing gland123 threaded. into the casing 116, and at its other end abutting the upper end of the said valve 117. The valve is provided with a head 124 adapted to be en aged by a wrench or other suitable means, y which it may be rotated. Connected to the diaphra m 109, in a suitable manner, 'as at 125, is one end 126 of a rod 127 extending upwards through a stufling-box 128 in the upper wall of the member 107, the upper end. of said rod 127 being fitted with an eye :piece 127 and connected by a link 129 to one threaded member 130 of a turn-buckle 131, the other threaded member 132 of which is connected to one end of a tension spring 133, the opposite end of which is connected to a bracket arm 134 rigidly fixed to the swinging plate adjacent the axis thereof. Around the rod 127 and between the stuffing box 128 and, the shoulder of the eye piece 127 is placed acompression 5 ring 128. The means for connecting the ro 127 to the diaphragm109 consists of a dished plate 135 having a flange 136 secured by a fluid tight joint to the lower face of the diaphragm 109, by means of screws 137, extending through said flange and packing washers 138 between the said flange and the diaphragm, and threaded into a washer or ring 139 on the upper side of the diaphragm. The dished portion of the plate 135 extends u wards through a central to ening in the diaphragm and has a centra opening 140 through which the rod 127 extendspthe rod having beneath said plate an enlargement or head 1410f greater diameter than the opening. in the said plate, so that the rod and plate are connected. The. underside of the plate is closed against leakage by a plate 142'held in place by the screws 137 When there is a minimum rate of flow of oil to the barrier the nut 131 is adjusted to increase the tension on the'spring 133 pulling the plate outward, which moves the V damper towardsitsopen position. As soon as the damper is moved suflicientl to give" ave? the desired draft in the furnace c mber 6 to give the requisite quantityof air for proper combustion of, the volume or oil then fed to the furnace-,1 thenut 131 is left in that position. The flowfof'oil' to the burner is then increased to the maximum rate of flowrequired, with the restriction valve 117'wide open, "This valve is then gradually closed until the restriction is sufcient to cause a difference in pressure between the upper and lowermember, so that the dia hragm .is pushedfldownwa'rd, and acting't rough the rod 127 the tension of the spring 133 is increased, pulling the plate outward and moving the damper 13 toward open position. The restriction valve 117 is then moved towards its closed position until app'roximatel the'shape and area of thethe draft. in the furnace chamber 6 is sufficient to give-the desired amount ofair fo'r themaximum rate of flow of oil fed to the furnace. For any intermediate rate of flow between the minimum and the maxi-3 ward movement ofthe rod 127.

The fluid] fuel fed from the burner or nozzle to the furnacechamber 6 bein under pressure is in the form which resu ts in a .flame which iseither substantially coneshaped or fan-shaped, according to the t of burner employed. It is desirable 'thatt e air entering the'furnace chamber 6 be admitted over an area conformm as nearly as possible to the form or area 0 the flame, in order that the best results be obtained as regards complete combustlon. My invention rovides an efficient means for regulat-.

ing t e area of air distribution, and for this provide means for controlling the ur I realfl f the o en-work portion of the partition 7 throng which theair flows fromthe space 8 to the chamber 6, so that send area will conform substantially to the area of the flame, and will supply a iluantity of an desirable for combustion. or this purpose I divide the chamber 8 into a pluralityofairchambers, each preferabl hav ng anmdeaving outlets up- 7 ndent alr supply and sv ards into the furhace chamber 6 through that rtion of the open-work partition 7 imme iately over-the partlcular chamber beneath said partition. In the present embodiment, I referably divide chamber 8 :z'into three suc air supply chambers, and do 7 exten wall, asshown at 7 The inner ends of sald partitions 7 are connected by outwardl directed end partitionsv 7 with the si e walls of the furnace, respectively. The par-v titions and 7 extend from the floor of the furnace to the underside ofthe partition 7, so as to form three separate independent chambers, It will be seen that by the arrangement of partitions 7" and 7", the space beneath the partition 7 is divided into a central flaring chamber '2' and two wing com partments 7 said central chamber being;

flame when t e burner is being operatedat: a relatively low pressure, and the air through the open work portion of the partition 7 from the wing compartment 7 being available for an increased areaof the flame when the burner is operated at relatively high pressures. It will thus be seen that am able to control the area of air sup: plied throu h the artition -7 in order. to conform su' stantia y to the area of the flame when the burner is o erated at different pressures, As stated, preferably pro vide separate means for controlling the supply of air to each of the chambers 7 and- 9, such means preferably consisting of dampers 8*, the same being pivoted, respectively, in the passage between the inner ends of the walls 7, and openings 7 in the said partitions 7. In the resent embodiment, I desire it understood, however, that my invention, as re ards the method of air distribution toconorm to the area of the flame, is not limited to any articular means suitable bearings, carrying operating levers 8, for swinging the dampers. Any suitable manual operating means may be used for this purpose. The central damper is mounted on a shaft 8 connected by a universal joint 8 with one or both of the said shafts 8",. so as to move all three of said dampers in'unison. 'Th6 connection between the central dam erfand the outer dampers is so adl sted closed, the mantral damper W111 be partlally open, so as to admit air to the central chamber 6, but as-the outer dampers are moved toward open position, the inner damper. will bemov'ed to increase the area of the opening controlled thereby to the central at when the .outer. dampers are chamber 6. Air is admitted to the front portion of the furnace beneath the partition and in front of the walls 7, through an air duct 9 in the front wall of the furnace. The general construction is the same as that shown and described in my copending application, Serial No. 391,779, filed June 25, 1920, but in the present instance the automatic control of the air dampers shown in said prior application is omitted, and said dam rs are set by hand as stated herein, to give suflicient opening to admit sufficient air, the amount of which is controlled by the automatic regulator which controls the draft in the furnace.

While I have shown an eflicient means for suppl ing air to the combustion chamber distributed in accordance with the shape of the flame, I desire it understood my present invention is not limited-to such means but that any suitable means may be employed for supplying air to the combustion cham- So far, as I am aware, I am the first to utilize a characteristic of the flow of fluid fuel to the furnace, and illustrated either as ressure'or rate of flow for varying the action of a means controlled by the furnace gas pressure, which in turn controls the supply of air to the furnace.

What I claim and desire to secure by Letters Patent of the United States is 1. In a fluid fuel fired furnace in combination, means for feeding fluid fuel to the furnace means for varying a characteristic of the flow'of fluid fuel fed to the furnace, means for controlling the supply of air to the furnace for combustion, means controlled by furnace gas pressure for operating said means for controlling the supply of air, and means capable of actin in accordance with a characteristic of t e flow of the 'fluid fuel to the furnace for varying the action of said means controlled by furnace gas pressure.

2. In a fluid fuel fired furnace in combination, means for feeding fluid fuel to the furnace means for varying the rate of flow of fluid fuel fed to the furnace, means for controlling the supply of air to the furnace for combustion, means controlled byfurnace gas pressure for o crating said means for controlling the supp yof air, and means capable of acting 'in accordance with variations in the rate of flow of fluid fuel fed to the furnace'for varying the action of said means; controlled by'furnace gas pressure.

3 In a fluid fuel fired furnace in combinatlon, means for feeding" fluid fuel to the furnace, means for varying a characteristic of the flow of fluid fuel fed to the furnace, means for controlling the supply of air to "the furnace for combustion, means controlled by furnace gas pressure for operating said means for controlling the su ply of air, a regulating spring for controlling the action of said means controlled by furnace gas pressure, and means capable of' acting in accordance with variations in a characteristic of the fluid fuel fed to the furnace for varying the action of said spring.

4. In a fluid fuel fired furnace, in combi nation, means for feeding fluid fuel to the furnace, means for varying a'characteristic of the flow of fluid fuel fed to the furnace, means for controlling the supply of air to the furnace for combustion, a member exposed to internal furnace pressure and to atmospheric pressure, an adjustable resist ance opposing atmospheric pressure on said member, and means capable of acting in accordance with variations in a characteristic of the flow of the fluid fuel fed to the furnace for varying said resistance.

5. In a fluid fuel fired furnace in combination, means for feeding fluid fuel to the furnace, means for varying the rate of flow of fluid fuel fed to the furnace, means for controlling the supply of air to the furnace for combustion, a member exposed to internal furnace pressure and to atmospheric pressure, an adjustable resistance opposing atmospheric pressure on said member, and means capable of acting in accordance with variations in rate of flow of fluid fuel fed to the furnace for varying the action of said resistance.

6. In afluid fuel fired furnace in combination,,means for feeding fluid fuel to the furnace, means for varying the rate of flow of fluid fuel fed to the furnace, means for controlling the supply of air to the furnace for combustion, a member exposed to internal furnace pressure and to'atmospheric pressure, and adjustable resistance opposing atmos pheric pressure on said member, and means capable of acting in accordance with variations in rate of flow of fluid fuel fed to the furnace for increasing said resistance when the rate of flow of oil increases and decreasin said resistance when the rate of flow of oi decreases.

7. In a fluid fuel fired furnace in combination, means for feeding fluid fuel to the furnace, means for varying the rate of flow of fluid fuel fed to the furnace, means for controlling the supply of air to the furnace for combustion, a swinging plate exposed on one face to furnace gas pressure and on the other face to the atmosphere, an adjustable resistance opposing atmospheric pressure on said plate, and means capable of acting in accordance with variations of the rate of flow of fuel fed to the furnace for automatically adjusting said resistance in accordance with variations in the rate of flow of fluid;

fuel fed to the furnace.

8 a fluid fuel fired furnace in combination, means for-feeding fluid fuel .to the furnace, means for varying the rate of flow of fluid fuel fed to the furnace, means for controlling the supply of air to the furnace for combustion, means controlled by furnace gas pressure for operating said means for controlling the supply of air, a regulating spring for controlling the action of said means controlled by furnace gas pressure, and means capable of acting in accordance with variations in-the rate of flow of fluid fuel fed to the furnace for varying the action of said spring.

9. In a fluid fuel fired furnace in combination, means for feeding fluid fuel to the furnace, means for varying a characteristic of the flow of fluid. fuel fed to the furnace, means for controlling the supp-1y of air to the furnace for combustion, means controlled by furnace gas pressure for operatingv said means for controlling the supply of air, a regulating spring for controllin the action of said means controlled byurnace gas pressure, and means capable of acting in accordance with variations in a characteristic of the fluid fuel fed to the furnace for inof the flow of fluid fuel fed to the furnace,-

means for controlling the supply of air to the furnace for combustion, a member exposed to internal furnace pressure and to atmospheric pressure, a spring opposin the movement of said member under atmosp eric pressure, and means capable of acting in accordance with variations in a characteristic of the fluid fuel fed to the furnace for varying the resistance of said spring.

11. In a fluid fuel fired furnace in combination, means for feeding fluid fuel to the furnace, means for varying the rate of flow of fluid fuel fed to the furnace, means for controlling the supply of air to the furnace for combustion, a swinging plate exposed on one face to furnace gas pressure and on the other face to the atmosphere, a s ring resisting atmospheric pressure on the plate, and means capable of acting in accordance with variations in the rate of flow of fluid fuel fed to the furnace for varying the resistance of said spring.

12. In a furnace, means for controlling the supply of air to the furnace for combustion, means controlled by furnace gas pressure for operating said means for controlling the supply of air, and means for automatically varying the action of said means controlled by furnace gas pressure.

In testimony whereof, I have hereunto signed my name.

EMBURY MOLEAN.

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