US1544310A - Combustion regulation - Google Patents

Description

June 30, 1925.

G. H. GIBSON COMBUSTION REGULATION Filed Sept. 9, 1921 2 Sheets-Sheet 1 1N VETOR V 650/70: It 67550 0. A TTORNEY June 30, 1925. 1,544,310

' G. H. GIBSON COMBUSTION REGULATI 0N Filed Sept. 9, 1921 2 Sheets-Sheet 2 W 2 MM A TTORNEY Patented June so, 1925.

UNITED STATES GEORGE H. GIBSON, F MONTCLAIR, NEW JERSEY.

COMBUSTION REGULATION.

Application filed September a, 1921-. serial 1%. 499,403.

vTo all whom it may concern:

I Be it' known that I, C-nonen H. GIBSON, a citizen of the United States, and a. resident of Montclair, New Jersey, in the 6 county of Essex and State of New Jersey,

have invented certain new and useful Improvements in Combustion Regulation, of

' which the following is a specification.-

V The general object of the present invenl0 tion is to provide an improved method of and apparatus for regulating combustionin furnaces in automatic response to the heat reqviliirements of the furnaces.

y present invention in its entirety is 16 especially designed and'adapteil for use in regulating combustion in boiler furnaces heated by the combustion of solid-fuel, but some features of my invention are useful in other furnaces and some features are useful 20 in furnaces heated b the combustion of liquid orv gaseous fuel which solid fuel is burned.

. One s ecific object of my invention is to provi e an improved control of the sup- 5 ply of fuel to' the furnace in automatic response to the fuel requirements of the fur--' nace. Another specific object of the invention is to provide for the automatic regulation of the rate of combustion in boiler furnaces not only in response to the volume and pressure'of the steam generated by the boilers of the regulated furnaces, but also .in response to the, rate at which feed water is supplied to the boilers.

-, In general my invention comprises provisions for automatically supplying to the furnaces fuel, and primary and secondary air for the combustion of the fue 1,in proportionto the, heat requirements of the 40 furnaces, .but the proportions between heat requirements and fuel and air supplies which 1am enabled to maintain in accordance with the present invention are not necessarily linear proportions, as I have 4 found it desirable in some cases to vary the supply of fuel. to a furnace, and to vary the distribution of the total air supplied for combustion of the fuel into primary and secondary portions on changes in the heat requirements, at rates or proportions rela tive to the'heat requirements which rates or proportions vary as the heat requirements vary.

The various features of novelty which as well as those in.

of a battery of boiler furnaces and regulatmg apparatus therefor;

Fig. 2 is an elevation partly in section of one of the automatic regulators employed in carrying out the invention;

' Fig. 3 is a side elevation with parts broken ap aratus shown in Fig. 2;

ig. 4 is a sectional elevation of a por tion of one of the automatic damper control mechanisms;

Fig.6 is a section on the line 5-5 of .away'and in section of a portion of the Fig. 4; and

Fig. 6 is a view illustrating a modification of a portion of the apparatus shown in in the drawings A, A and A represent boiler furnaces each of which receives air through a corresponding branch 'pipe B from the discharge conduit B of a forced draft. fan (not shown).; The stack outlets C of the different furnaces connect to a common stack connection C, and the steam pipes D from the different boilers discharge ,into a common steam main or header D.

Each. of the boilers receives feed water through a correspondin branch p1pe G from a boiler feed pipe The supply of water to each boiler is controlled by a boiler feed regulator H which may beof any'usual or suitable type. Secondary air is supplied to each furnace above its fuel bed through an adjustable in'let B, the pressure in the combustion chamber in the furnace being regulated as hereinafter explained so as to draw into each furnace through the inlet 13 the proper amount of secondary air. Fuel is supplied to each boiler furnace by a corresponding automatic Stoker E driven by .an individual motor F ata rate dependent,

pressure conditionsin the latter are regulated by a damper I in the air inlet conneclators. K automatically operate to maintain.

' K of the same furnace.

tion B and a' damper IA in the stack outlet connection C. Each of the dampers I and adjusted by an-indivi IA is automaticall ual control mechamsm comprising a damper actuating motor J and-a regulator K;

In the embodiment of 'my invention il-' lustrated in the drawings, the various regua predetermined relation between the amount of fluid flowing through the air in-' let B or the stack connection C towhich the regulator pertains, and the strength of an electric control current. The latter is a joint function of the rate of steam outflow through the main D, the pressure of the steam in the main 1), and therate at which feed water passes to the boilers throu h the supply pipe G. Each regulator K acts to maintain a supply 'of fuel to the fuel bed of the corresponding furnace which will make the pressure drop .or loss of drafthead through'the fuel bed a function of the electric control current for the regulators The means shown forv maintaining the electric control current at the proper strength comprises a master controller KA responsive to steam floyv through the conduit D, a master controller KB responsive to the rate of waterflow through the boiler feed line G, and a master controller L responsive to the pressuref the steam in the conduit D j The master controller KA as shown in Figs. 2 and 3 consistsessentially of an electro-magnetic flow. balance comprising a tilting differential pressure gauge to the upper end of one leg I of which, the static pressure in the main D is transmitted by a com duit K and to the upper end of the other leg K of which, the total pressure in the conduit D is transmitted by a pipe K. The difl'erential pressure thus impressed on the tilting pressure gauge tends to displace the sealing liquid in the gauge and thereby exerts a tilting force on the gauge which is a function of the rate of flow through the conduit D. This tilting force is opposed by the resultant of an electro-magnetic interaction between coils K and an' electromagnetic intaraction between a coil P and a permanent magnet-P. The electriccurrent flowing through the coils I and P is automatically adjusted as required to nor- -mally maintain the balancein its neutral position by a current regulator including a resistance Q and mechanism for utilizing more or less of the potential impressed upon the resistance Q? in forcing current through the coils K and P, as I shall now explain.

As shown the arms K and K of the gauge are adjustably clampedto arms K of a gauge frame K having a knife-edge The frame K carries one of the coils between the other two coils K which are stationary; The movable and" stationary p{ivot K resting on suitable bearingtblocks a coils K corres 0nd in essence to the floating and movab e coils of.a Kelvin balance. The coil P is also carried by the .frame member K and thevarious coils may be so con-' nected that the electro-magnetic' pull between coil P andthe stationary permanent I ma et P opposes or assists the pull of the coi s K.

Associated with, and regulated by the magnetic flow balance of the master controller KA is an electrical current adjusting device Q- comprising in the form shown a supporting shaft Q on which" is loosely j ournalled a member Q having ratchet teeth on its periphery. Also journalled on the shaft Q is a ratchet oscillating lever P The latter is oscillated by a constantly running electric motor 0 through connections including "a gear wheel 1? 'in mesh with a pinion carried by the motor shaft and carrying a crank pin connected by a link P? to the lever P The latter is provided with two pawls P and P The to engage the ratchet teeth on the periphery 'of the member Q and turnthe latter pawl P tends with the lever P as the latter swings in the 1 clockwise direction as seen in Fig. 3, while on the return stroke of the lever P", the pawl P tends to move the member Q, in a 001mter clockwise direction. A pawl controller K carried by the lower end of the'flow balance frame member K prevents the s'imultaneous engagement of both pawls P- and .P with'the ratchet teeth of the mem-' ber Q and regulates the amount and direc- I tion of movement imparted to the-member Qtby the oscillatory movements of the leverin the form of an are shaped strip of sheet metal fitting over a portion of the periphery As shown the pawl controller K is of the member Q and serving when the tilt- 3 ing pressure gauge is in its neutral position as shown in Fig. 2 to hold both and P out of engagement with the ratchet teeth on the me her Q in all positions of the ,lever P ion the tilting pressure gauge is swung from its neutral position. in

the direction in which it moves when the steam flow through the conduit D decreases relative to the electric current flow through the coils .K and P, the shield K will hold the pawl I out of engagement withthe ratchet teeth on the member Q throughout the complete stroke of the lever I, but the pawl 'P will then be permitted to engage the the conductor P o ra-tively engages and adjusts the member 2 will de nd upon the extent of displacement of t e shield K from its neutral position owing to the shape of the correspondingly stepped or inclined side edge K of the shield member. Similarly when the shield member is displaced to the right from its neutral position as shown in Figr2, the pawl P wil be held out of engagement with the teeth of the member Q and the pawl P willefi'ect the adjustments of the member Q in a' counter clockwise direction as seen in Fig.- 3 in steps the magnitude of which depends u n the extent to which the shield K is (i position.

The member Q. includes a resistance element Q woundin a flattened helix about a ring shaped su port Q3. The terminals of 3 are connected to inner and outer centrally disposed contact or slip rings Q and Qf. S and S represent stationary brushes engagingthe slip rings Q, and Q respectively. S is a stationary brush engaging the resistance conductor Q The brushes S and S- are'connected by branch conductors 3 and 4 respectively to main current supply conductors 1 and 2, respectively, between which a suitable potential difference is maintained. The coils K and P of the' master co'ntroller KA are connected in a control circuit including the portion of the resistance Q between the end of the latter connected to the slip ring Q and thereby to the main supply conductor 2, and the point at which the resistance is engaged by' the brush S, the latter, a conductor 5 and aconductor 6. The conductor 6 is connected to a similar 'conductor 6' from the master controller KB. The common continuation 110i the control conductor 6 and 6 is connected to the main supply conductor 1 through branch conductors 13, 14 and 15in each of which isplaced I ipe-connections K and K of the controler KB transmitting the static and total ressures in the boiler feed line G to the diferential pressure gauge of the balance KB.

The connections 3' and 4 between the mas ter controller KB and the supply conductors 1 and- 2, correspond to the connections 3 and 4 forthe controller KA.-

The master controller L comprises in the construction illustrated a hollow head to isplaced from its neutral I transmitted by a pipe L and two flexible hollow curved arms L each of which is in effect a Bourdon tube. The-movable ends of the two flexible tubes L are connected by a part L which serves as a movable contact member sliding over three resistances L. The three resistances L are connected by conductors 13, 14 and 15 respectively to the conductors 13, 14 and 15 respectively at points between the corresponding balances i K and KC and the rheostats R; The movable contact member L is connected to the conductor 11. In consequence of the described arrangement, the portion of the resistance L between the contact I? and the conductor 13 forms a shunt about the balances K and KC of the furnace A, so that when the steam pressure in the pipe D increases above normal and the contact member L is correspondingly depressed, the resistance of the shunt including the conductor 13 about the balances K and KC of the furnace A is reduced and the electric current flowing through the balance K and KC of the furnace A is correspondingly reduced. On a decrease in the pressure of the steam, the shunt resistance is increased and the effect of this is' to increase the current flow through the balances K and KO. The

resistances L* connected to the'conductors 14 and 15 respectively, form similar and balances as the ressure of the steam in the main D decrease and increases.

Ea h of the regulators K com rises an may be K however, the current regulator-Q, of the master controller KA .is replaced by a regu-- lator for the corresponding damper actuatin motor J. The motor J as shown is a flui pressure motor comprising a piston J,

the stem J of which is connected-to the op-- crating arm of the corresponding damper I or IA. Fluid under ressure is admitted to and exhausted from t e opposite ends of the cylinders in which the piston J operates t rough pipe connections U and U to a valve chest U. The valvechest U is provided with an inlet U for a suitable motive fluid, as water under pressure, with an exhaust outlet U and with spaced apart portsto which the pipes U and U are connected- Working in the valve chestU is a cylin drical valve member X provided with spaced apart ports X which are interposed between the inner wall of the valve chest and a valve f tion of the corresponding pawls P a clockwise direction to thereby permit pressure fluid to flowthrough the valve chest U member W of the rotary D valve type. The ports X open at their outer ends into pockets or recesses U and U in the inner wall of the valve chest U into which the pipes U and U open. The valve member W is se-. cured to the shaft T 'to which is also secured a segmental ratchet T. Associated with the ratchet T of each balance K is oscillatingmechanism for operating it, comprising an oscillating lever P its actuat-- -The intended operation of each regulator- K is to adjust the corresponding dam r I or IA as required to maintain a pr eterflowing throizfih the coils K" and Ed the balance, and p e volume of primary air flowing through the'pi e B, or-the volume of mined ratio between the electric current the products of com ustion flowingthrough the stack connection C, as the-case. may be.

When the current flow through the branch conductor 13, for example, ncreases, the shields K ofthe two balances K pertaining to the furnace'A are shifted to the left as.

seen in Fig. '5 and *thei'member T of each balanceis thereby-adjusted through the acand the .pi'peU into the right hand ends ofthe corresponding icylinder- J as shown in Fig; 4, while at the same time ermitting the left hand end of the cylin er to exhaust through the ipes U and exhaust outlets U This shi s the piston J to the left as seen in Fig; 4, and opens the corresponding damper'l or-IA- and thereb increases the How through the cori'espon ing conduit B or C. The adjustment of the member Tin the counter clockwise] direction correspond-- ingly adjusts the damper in the closing direction. VVith either adjustment of the damper, the corresponding movement of the valve member X producedthrough the arms Jtand X and the linkJ tends to prevent over-travel and hunting of the damper.

The stoker regulators KC may eachbe identical in construction and general mode @operation' with the master controller KA. e pressure transmitting connections K and K of each regulator KC- are connected to. thev furnace chamber above: andbelow the fuel bed in the latter'and hence thedifi'erential pressure gaugev element of each balance KG is responsive to. the drop in draft headthrough the fuel bed. The

coils of each regulator KC corresponding to, the coils K and. P of the balance KA are connected in series with the corresponding circuit conductor 13, 14 and 15, and are not connected to resistances Q of the" regulator. In the balance KC, the resistance Q forms a part of the control mechanism for the electric motor F by. which the corresponding-stoker E is driven. For example, the re.=sistan ce of each regulator KC may have its terminals connected to the supply conductor 1 and 2 and one terminal of the motor F may be connected to the suppl .conductor 2, while the other terminal o the member is connected to the conductor leading from the brush-of the controller KC ,corres ondin to the brush S of thecontroller t e connections, in any event, bein suchthat as the electric current flows tfirough the-control circuit conductor 13 increases and decreases, the 'rate at 'which 'the stoker member F runs tends to increase and decrease. Y

With the electro-magnetic flow balance shown in Figs. 3 and 4,,it is ossible to maintain many difl'erentkinds 0 ratios between the pressuredifielential to which the flow balance. is (subjected on the onehand, and'the balancing electric current on the other hand. For exam Is, by disconnecting the coil P and setting t e difierent pressure gauge legs K" and K vertical, the pressure differential will vary 'in linear proportion .1 with the square of the strength ,of the bal- -ance current and hence, in the case of thebalance KA for example, the electric current flowing through the control conductor 6 will be proportional in; stren h to the. 10 volume of steam flow throughvt e conduit D, sincev the pressure'difierential in that 3 case is proportional to the square off the rate of steam flow. When the coil P is con nected in circuit with" the coils K" as shown in Figs. 2 and 3, the magnetic pull between the coil P and the permanent magnet P is (proportional to the strength of the electric current and in this case with vertically disposed pressure gauge legs K and K the flow balance will tend to maintain an equality between 'the pressure diflferential impressed on the gauge of the balance, and an 'electro-mag'netic force which increases more. rapidly than doesthe electric current flow ing throughthe coils, but less rapidly than the square of the electric current' y The effect ofsecuring the difl'erent differential pressure gauge legs K and K to their supporting frame arm K in difl'erent angular adjustments is to vary the change in tilting moment; produced 1) a given. amount of displacement of t e sealingliquid in the gau e. B such adjustments of the gauge legs an K? it is possible to 3 so calibrate the flow balance that the presl sure difi'erential im ressed u on the gauge will vary more rapidly than oes the square of the electric current by which it is balanced, or will vary less rapidly than the electric balancing current, or will vary according to some intermediate relation between the pressure difierential and the electric balancing current. Much the sort of gauge adjustment obtained by changes in the mclination of the axes of t e gauge legs K and K may be secured without changing the inclination of the legs by replacing one or both of the legs K and K by others which vary in horizontal cross section along their lengths, but the adjustment by change in inclination is simpler and more flexible.

- eration.-

The properrelation to be maintained be-,

tween the pressure differential and the strength of the balancing current in the damper controlling regulators vand master controllers will depend on conditions of opus, for example, in some cases it is desirable to have the rate of combustion in linear proportion to the rate of steam generation so long as the steam ressure is constant and feed water is being introduced into the boilers at the same rate at which steam is generated. This result may be ob-' tained by dispensing with the coils P, or disconnecting the latter, in the regulators K and master controller. KA, and by an ad-- justment of the corresponding gauge. legs balances.

and with boiler feed water supplie K and K so that they W111 be vertical in the neutral positions of the various flow If with constant steam ressure at the same rate at which the steam 1s generated it is desired to have the rate of combustion increased more rapidl than 'does the rate of steam generation, t 's result may be accomplished by inclining the le of the master controller KA tical as shown in Fi 2 so that when the sealing liquid is disp aced from the leg K into the leg K the change in turning moment on the gauge frame exerted by the [displaced liquid will be greater than the change in the volume'of displaced liquid.

In theoperation of some furnaces it is desirable to increase the ratio of primary to seconda .air as the rate of combustion increases.v ith apparatus as shown in Fig. 1 iii which the ratio of primary to secondary air is obtained b maintaining a determined ratio between t e volume of primary air and the volume of products of combustion,

the ratio of primary tosecondary air may be caused to increase with the load by a relative adjustment of gau the corresponding dampers I and IA of a furnace so that as the load increases the volume of primary air passing from the furnace to the conduit B will increase at a more -K and K om the ver-" legs K and K. v of the regulators K respectlvely, controlling ance in the regulator KC does not require the coil P and should have the legs K and K'*="6f its pressure gauge vertically disposed in order to "so operate the-Stoker motor as to maintain a fuel bed of approximately constant 'thiclmess. With a furnace equipped products of combustion leavingthe. fur

with an under feed Stoker however the pressure drop through the fuel bed does not increase with the square of the volume of. flow through the fuel bed, as would be the case if the flow resistance of the fuel bed \were constant with, different volumes of, flow. Insuch'a furnace the effect of increase of draft is in general to so loosen or open up the fuel bed that in some cases the pressure drop through the fuel bed increases butv littl more rapidly than does the volume of aft. For this case the coil P may advantageously be used in the regulator KC and the gauge legs K and K may be inclined o positely to the direction of inclination ofthis sort the coil P is not olil desirably employed but may be used to fhrnish the ent re electro mag'netic balancing force, the coils K belilig then dispensed with or disconnected. uch the same results obtainable. with the coil P and permanent magnet-P can be obtained by replacing the permanent magnet by an electro magnetlhavin an oversaturated core.

n addition to the variations in the characteristics of the controllers and regulators,

resulting from the use or non-use of the various coils and the changes in the inclmation of the gauge tube I mentioned above, it is possible to modifyt e relativeefiect of one; controller or regulator upon the othersown in Fig. 2. Indeed in a case" in the system by the use of adjustable resistance shunts R about the electro-mag--" netic nce coils-of the flow balance element of'the controller or regulator. Similarly the rheostats- R in the conductors 13,

14 -and 15 permit of a-modification of the efiec't of the master controller L on the different control circuits. A 1 7 When, as will .somet' es 'be necemary or desirable, one or more of the boilers in the battery is temporarily cut out of service, thel switch M in thecircuit. with each of the corre ending control conductors 13, 14 and 15 an shunt conductors 13, 14 or 15v for the furnace-or furnaces cut out of operation should be opened so that the master controllers KA, KB and L may continue to conduitin operation.

exercise the-pro r control upon the regu lators K and K of the furnaces remaining N, N and N? represent electrical instruments connected in series with the'conductors 6 which may be used to indicate, record and integrate the steam flow.through the When the flow balance of the master controller KA is of such character that the electric current -flowing through the conductor 6 is in linear pro rtion to thef rate of steam flow-throughJt e conduit D, the instruments N, N and N may be ordi-' nary arnmeters having indicating, recording and integratin provisions, respectively.

.The. apparatus ownin' Fig.- 1 embodies. a substantial improvement'over somewhat "similar apparatus heretofore devised by me in which the rate of-combustion is made proportional solely to the volume, or to the volume'and pressure of the steam generated,

in that provisions are made in the present case for supplementing the regulatlon 1n 5 response to steam generation,-by a regulay 2 4 tion. responsive to the rate at which feed water is introduced into the boiler. The im rtance of this will, be recognized when it is. realized that in a high pressure boiler plant a very considerable portion of the total amount of-heat required to convert cold boiler feed water into steam is utilized in; raising the temperature of the Thus in converting a pound of boiler. feed water at F. into steamat 250 pounds pressure,.'about one half as many heat units are requiredto raise thetemperature of thewater as water to the temperature of the steam, as are to evaporate the water after it is so heated. Even with lower pressure and higher feed water temperaturethe regulation of the rate. oficombustion solely in response to the volume and pressure of the steam. generated is less accurate than may often bedesirable at periods in which the-demandJfor-steam is relatively low but in whichthe supply of feed water maybe quite rapid as' quently mag be the case with fluctuating steam deman s. p

- In. Fig. 6 .I have illustrated a modified form of'ontrol for the stoker motor F of the boiler furnace .A' whereby the speed of the stoker is made a function of the strength of the electric: current flowing throu h the corresponding control conductor 13. or--this purpose I may advantageolasilfy emplo abalance KC, but the pressurec ferential to which the rssure gau of the. balance is'subjectedm this case, s the. difference betweelp the pressure'oftheatmosphere and the suction or: inlet pressure of a fan'W driven bytheis'toker motor and:

varying in speed with the latter. As shown the pipe K of the balance KC shown in Fig. 6 has its outer-end. open"to th e atmoshere and the pressure transmittlng pipe and Serial No. 41808 lin of the fan W. The suction of the fan W may be adjusted as disclosed in myprior K runs from the balance to the inlet W Patent-No. 1,360,285 by means of a radial slot W in the side of the fan housing and tersection of the slots W andlW may be adjusted toward and away fromthe fan.

me but not claimed herein as they are dis closed and claimed in my prior a vplications, Serial No.121547, filed Septem r 22,

1916; Serial No. 247858, filed August 1,

\a rotatable dampenW formed with a slot -W intersecting the slot W so that the in- 1918,; Serial No.3757 28 filedApril 22,1920,

filedthe 19th of October, 1920. i

While in accordance with" the provisions of the statutes 1 have illustrated and described the best forms of mypresent inventothose skille'd'in the art that-changes may be made in the form of m invention without departing tion as set orthin the ap nded claims, and that certain features-o my invention may sometimes be usedjto advan' without' a corresponding use of other eatures.

Having now describedmy invention, what tion now known to me,.it will be apparent from the spirit of my inven- I claim as new and desire to secure by Letters Patent,.is:

.1. The meth d nace which consists in'varying the. rate of combustion therein inautomatic. response of operating a. boiler furboth to" the. rate at which feed water is supplied tothe boiler and to'the rate at which steam is withdrawn from thefurnace.

2. The method 'ofoperating a boiler furnace'which consists in varying the rate of," combustion therein in automatic response.

to the ,rate' at which-feed water. is supplied to the boiler and to the rate at which steam I is withdrawn from the fumace,"and to the pressure'- of-.-the steam generated. 3.. The-method of regulatin in a furnace which consists n-separately supplying primary and secondary air for combustion and varyingthe ratio. of prig combustion mary to secondary .air in a'predetermmed relation to the rate of combustionasthe latter varies." Y

' 4. The method .of automaticall regulate .ing combustion in a plurality o furnaces supplying heat ."for one or moreuses which consists in building upa fcontrollin force I by adding together elements each-o which is proportional to the requirements-of one" of said uses, subdividing-the total controL' force into. proportional parts, one for .eac 'furnace," and controlling the. combusf tion .ineach furnace by the corresponding .part' of'said force.

.5. The: combination with a boiler mites .W

of means for regulating the rate of combustion therein including provisions, automaticall responsive to the rate at which feed water is supplied tothe boiler tending to. increase and decrease the rate of combus-- of means automatically responsive to the through the fuel bed increases.

rate ofsteam generation, the pressure of the steam generated and to. the rate at 'which feed water is supplied to the boiler for jointly regulating the-"rate of combustion. 7. The combination with a furnace having separate'primary and secondary air sup-. plies of means for increasing and decreasingthe' ratio of primary to secondary air supplied in automatic response to increases and decreases in the heat requirements of the furnace.

by the combustion of solid fuel on a fuel bed, of means automatically responsive both supplying fuel to the fuel bed at a rate increasing more rapidly than does said differencein pressure as the volume of draft 9. In combination with a plurality .of boiler furnaces, means individually responsive to separate heat requirements of all the furnaces for maintaining electric cur-.-

rents corresponding in intensity to the different requirements, means for combining said currents into a single control current, separate combustion controlling circuits for. the different furnaces,"and means fordi'vidinggsaid control current among said circuits. i 10'. In combination with a plurality of boiler furnaces, automatic means for supplying an electrical current which is proportional to the sumeof the heat require- .ments of all thefurnac'es, separateycombustion controlling circuits. for the different furnaces, means for dividing said current" among said c1rcu1ts,- and means for modifying the current in each of said circuits response to changes in the steam pressure.

11. The combination with a boiler furnace, ofmeans separately responsive to different heat requirements of the furnace for maintaining electric control currents corre-' spending in intensity to the different requirements, and means jointly controlled by said currents for regulating combustion in said furnace. i

12. In a flow responsive device consisting of a tilting frame carrying a U-tube manometer subject to apressure difference due to' the flow of the. fluid and also carrying electro-magnetic 'means for opposing. the tilting action of the manometer, the improvement which consists in provisions for varying the angle at which the limbs of the.

gmanometer are attached to the frame. 8. The combination with a furnace heated 13, The combination with a steam boiler having a furnace, of means for regulating the pressure of'gases in the furnace, means for feeding fuel to the furnace, and means responsive both to steam conditions and to fuel bed resistance, for controlling the 'feed' of fuel. p

a 14. The combination with a steam boiler having afurnace, of means for controlling the flow ofgases through the furnace, means for feeding fuel to the furnace, and means' responsive to steam conditions and fuel bed resistance, for controlling the feed of fuel.

15. The combination with a plurality of boiler furnaces, means individually responmm to separate heat requirements. of. all

the furnaces for maintaining electric currents corresponding in intensity to the different requirements, means "for combining said currents into a single control current,

GEORGE". H. GIBSON

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