US1167343A - Furnace regulation. - Google Patents

Description

. u. H. Gllsow.' FURNACE REGULATION. 'APPLICATION FILED ocT.3.1914.

191719343', Patented Jan.4,1916.

4 SHEETS-.SHEET l.

A'rroRNEY G. H. GIBSON.

FURNACE REGULATION. APPLICATION FILED OCT. 3, I9I4.

Ll., Y Patented Jan. 4, 1916.

4 SHEETS-SHEEI' 2.

WITNESSES G. H. GIBSON;

FURNACE REGULATION.

' APPLICATION FILED 0CT.3| 1914. LIQB, v Patented Jan. 4, 1916.

4 SHEETS-SH-EET 3.

WITNESSES i" I .f ATTORNEY G. H. GIBSON. FuRNAcE REGULATION.

n0. R mm. o 14 T 4..... m n.w V hm m .am m... .w a P m m T. c o w N 0 U A c u DI DI A 4 @u W0 n@ HA. man,

WITNESSES ,AFEE PANT FFIQE.

i GEORGE H. GIBSON, OF MONTGLAIR. NEW JERSEY.

FUENACE REGULATION.

Lievens.

Application led October, i914. i Serial No. 864,734;

To all lwhom it may concer/n.:

Be it known that I, GEORGE H. Grissom-.a citizen of the United States of America, residing in Montclair, in the county of Essex and State of New Jersey, have invented certain new and useful Improvements in Furnace Regulation, of which the following is -a true and exact description, reference being had to the accompanying drawings, which formv a part thereof.

. The general object. of my present inven- `tion isto provide efficient and satisfactory Afed at a rate varying with and depending on service conditions.

Amay be fed to the furnacev at a rate varying For instance, they with the rate at which steam is withdrawn from the boiler, or'varying inversely withI the pressure of the steam generated by the.

, boiler.

My invention also comprises noveli'means for insuring a proper ,load distribution among the diiierentboilers of a steam generating plant comprising a plurality of separate boilers delivering steam -into the same distribution system.

-The various features of novelty characterizing my invention are pointed out with particularity in the claims annexed to and forming a part of this-specification. For a better understanding of the invention, however, and of the advantages possessed by it, reference should be had to the accompanying drawings and descriptive matter, in which I have illustrated and described sev` eral forms in which my invention may be embodied. i

Of the drawings: Figure 1 isa diagrammatic representation of a steamgenerating plant comprising a,plurality of boiler furnaces all delivering steam to a common distribution system, and having provisions for `automatically maintaining a predetermined ratio between the amount of fuel and the amount of the air to support the combustion Specification of Letters Patent.

Patented dan., 4L, i916.

of the fuel, fed' to each boiler furnace, andv i also Y having provisions for varying the amounts of fuel and-air fed toeach of the diiferentboilers of theI battery in proportion to the rate at :which steam is withdrawn from the plant as a whole; Fig. 2 is a largescale sectional elevation of one detail of the apparatus employed in Fig. l;

Fig. 3 is a large scale sectional elevation of 65 anotherdetail of 'the apparatus employed in Fig. 1; Fig. 4 is a diagrammatic representation of a steam generating plant embodying a modified form of my invention;

Fig. 5 is a diagrammatic representation of 70 a plant similar in numerous respects to, but different in other respects from, the plant shown in Fig. 4; Fig. 6 is a somewhat ,diagrammatic representation illustrating a special construction which may or may not i be utilizedin such plants asfshown in Figs. 1 and hand. Fig. 7 is a diagrammatic representation of a 'portion of a boiler plant, comprising electro-magnetic means for maintaining the volume of draft proportional to the Stoker feed.

` In the embodiment of my invention illustrated diagrammaticallyin Fig. 1, there are three steam generating boilers A, which may be. duplicates of one another, and which de-w 85 liver steam through pipes B to the commori steam main or header B. Fuel is fed to each boiler by an individual .mechanical stoker C; the various stokers being driven through the common shaft D and suitable 9o which, as shown, receives air from the 95 blower or rotary pump E.r The flow of air through each branch pipe E2 is controlled as shown by a slide damper E3. Each slide damper E3 is actuated by a fluid pressure motor F, which comprises, as shown, a cyl- 10o inder, a piston F. working therein, and a spri'iigF2 tending to move the piston in the direction to sold the damper F3 wide open. Associated with each Apressure motor F are means. for automatically maintaining a pressure; against its piston F in a direction opposing theaction'of the spring F2 suchthat the flow of air through the correspondin'gpipe E2 will be proportional to the speed of the/Stoker motor D, and hence to the rate 1w at which fuel is supplied tothe correspond- Iing furnace. The means shown for accom- (see Fig. 2),

plishing this purpose comprise mechanism by which a force, which is a function of the rate of flow through each air conduit E2, is opposed to a force which is a similal` function of the speed of the stoker engine, in a balancing mechanism or comparator, which on a change in the ratio between these two forces varies the pressure acting against the piston F of the corresponding motor F and thereby opens or closes the connected damper E3 as required to restore the ratio between two forces to a predetermined value. The particular form of means illustrated in F ig, 1 for accomplishing this result, comprises a fluid pressure balancing device or comparator I, consisting of a lever pivoted on a fulcrum block 4, which is. advantageously adjustable, as b means of the threaded rod 5 passing through the fulcrum block.

The lever is connected at one end to a flexible diaphragm forming one wall of a pressure chamber z". The pressure chamber is connected to the outlet of the rotary lpump M, shown as driven by the Stoker engine D. At the opposite side ofthe fulcrum block z'JI from the chamber z" a similar pressure chamf ber 2 has its diaphragm wall connected to the lever z', so that the pressure exerted against the lever by the diaphragm of the chamber 2 lopposes the thrust on the lever of the diaphragm of the chamber C As shown, the chamber 2 is connected by a pipe G to a Pitot tube g located in the corresponding air conduit E2. A static pressure pipe H is connected to the conduit E2 adjacent the Pitot tube g and extends from there to a pressure chamber 3 which has a flexible diaphragm connected to the lever so as to directly oppose the latter in its action on the lever The cylinder of each damper actuatingy pressure motor F is connected through a corresponding branch pipe f to a compressed air reservoir J, or other source of pressure fluid. Each branch pipe f is formed with a restricted orifice f (see Fig. 3), and between the orifice f and the motor F is formed with a vent or leakage orifice f2 controlled, as shown, by the normally closed ball valve f3. The ball valve f3 is arranged to be lifted ofi'l its seat by a linger G carried by the lever whenever f the effect of the pressures within the cham- 'bers a" and 3 on the lever exceeds the eect of the pressure in the chamber 2. The difference between the pressures transmitted to the chambers 2 and 3 will be a function of the rate of air liow through the corresponding conduit E2, and this pressure differential will in practice be approximately proportional to the square of the rate of air flow through the conduit. Similarly, the pressure maintained in the closed discharge pipc of the pump M will be a function ol' thil rate at which the stoker motor D operates. and in practico may be made approximately proportional to the square of the speed of rotation of the Stoker motor. When the ratio of air flow to stoker speed increases above the predetermined value, the finger z'6 permits the valve f3 to close the port f2, and when this ratio diminishes,` the valve f3 is lifted off its seat, permitting leakage out of the pipe f througlrthe port f2. The pressure in the motor F and the piping f at the outlet side of the restricted port f tends to rise to an equality with the pressure in reservoir J when the valve f3 is seated-` and when the latter is off its seat tends to fall to an equality with atmospheric pressure. As the pressure in motor F falls the damper E3 opens .permitting a greater air liow through the pipe E2. This increase of air flow tends to shift the lever z' to permit the valve f2 to seat and thereby increase the pressure in motor F and close the damper E3. It will be understood, of course, that the pressure in the reservoir or supply source J should be at least as great as the maximum pressure needed in the motor adjustment.

Inasmuch as it is the difference betweenA the pressures in the chambers 2 and 3, and not simply the static pressure in the pipe E3, to which the lever' is subjected, variations in the resistance to flow through the combustion chamber due to varying thicknesses and varying degrees of perviousness of the fuel bed and other varying conditions of operation will not prevent the maintenance of the proper gaseous flow through the combustion chamber. While, if the boiler furnaces A are similar in type and capacity, the gaseous flow through each combustion chamber should ordinarily be the same as through each of the others at all times, this does not mean that the different dampers E3 should 'all be open to the same extent at any one time. On the contrary, with a comparatively open fuel bed in one furnace and a less pervious fuel bed in another, the damper E3 for thefirst lchamber would be less widely open than the damper E3 for the other furnace. It' will bel understood, ofcourse, that in the arrangement described, the blower E and the piping connecting it to the different furnace chambers should, be of such capacitythat the flow through each conduit E2 will increase and 1decrease as the /corresponding damper E3 is `penedfand closed throughout the entire range of damper adjustment.

It will be 'apparent that the apparatus already described operates to maintain a predetermined ratio between the air and fuel supplied to each furnace, 'and that this ratio does not depend 'upon Whether the speed of the motor D, and consequently the fuel rate of feed, is manually or automatically controlled. It is quite desirable in some cases, however, to automatically proportion the feed of the fuel and of the air supporting combustion tothe rate at which l steam is Withdrawn from the boilers, and means for accomplishing this result are GII shown in Fig. 1. This means comprises a throttle valve D3- in the branch pipe D2" through which steam is supplied from the steam main B to the stoker motor D for operating the latter, fluid pressure motor FA for operating the valve D3, and a balancing mechanism IA subjected to the opposing action of a force proportional to the square of the rate of steam flow through the conduit B, and of the delivery pressure of the pump M, and means actuated by the balancing mechanism IA for varying the pressure ofthe motive fluid supplied to the motor FA as required to maintain a predetermined ratio between said force and pressure.

The balancing device -IA is generally similar to the balancing device I heretofore described, except that the fluid pressure chamber 3 acting` on the lever il is dispensed with, and the fluid pressure chamber 2 is subjected to a fluidpressure which is proportional to the difference between the velocity and static heads, or pressures, in the pipe B, but which may be different from,

y and in practice is substantially smaller than either of these pressures. As shown, the

pipe GA leads from the Pitot tube gato the chamber n. of a fluid pressure analyzer or dierential pressure device N. The static' pressure pipe HA leads from pipe B to thechamber n2 of the device N. The chambers n and n? are separated by a flexible diaphragm n, and opposed Wall portions of theJ two chambers, at and n2, are formed by two flexible diaphragms n.3. The two diaphragms n3 are similar to. one another in size, but are smaller` than the central diafn? separated from the chamber nf'by the phragm n. All three of the diaphragms n, n3, which are coaxial, are connected by a central stem, which is provided at its upper end with an extension-adapted to unseat the ball valve n? normally closing a leak` age port from a chambern. rIhe latter is connected by suitable, piping to a chamber corresponding smallA diaphragm n3. The

' chambers 'm" fand 'nF are also connected to the pressure chamber 2 and this chamber and the connecting piping receive pressure fluid from the. source J through Vthe restricted port fb. It will be apparent, therefore, that the pressure maintained in the chamber nl will be proportional to the excess of the pressure in the chamber n over that in the chamber n2 of the device N, for the balancing pressure in the 4chamber fn.7 will be increasedor diminished bythe clos- .ing and opening of the valve ne as the diaphragms n and n3 move in one direction or the other from their neutral' positions. The pressure motor FA receives pressure fluid through the branch pipes fa and restricted port fa', and the pressure.' in the piping fa at the outlet side of the restricted port fa.'

is controlled by the ybalancing device IA acting on the ball valve f0.3 normally clos .i3 of the balancing device IA might be con* nected directly to the pipes GA and HA, respectively.

l/Vith the arrangement described for controlling the valve D3- it will be apparent that the motor "D will be supplied with steam as required to maintain its speed proportional to the velocity How through the steam main B." It will also be observed that the supply of fuel and o-f the air supporting the combustion of the fuel to the combustion chamber of each of the different boilers in proportion to the rate at which steam is withdrawnV from the battery of boilers as a whole. rllhis tends to equalize the amount of work done by the differentfboilers In the modified form of apparatus illustrated in Fig. 4,-the escape of the gaseous products of combustion 'from the combus -tion chamber A2 of th`e boiler is controlled by a damper EA3 located in the .chimney lor breeching A of the boiler, and opened and closed, as the pressure of the steam generated by the boiler diminishes and increases, by the fluid pressure motor FC, which, as shown, comprises a flexible diaphragm acted against on the one side by the steam pressure and on the other side by a spring FC. As shown in Fig. l, the stoker motor DA driving the mechanical stoker C, feeding solid fuel to the boiler A, is governed by means of the steam supply throttle valve DA3 operated by the pressure motor FD, and the latter is controlled by a pressure balancing device IB, generally similar to the devices I and IA heretofore described. As shown, the device IB comprises opposed pressure chambers-1 and i connected'by the `pipes GB and HB to the combustion chamber A2 and the smoke outlet A', respectively; and also comprises afiuid 'pressure chamber im connected to the-dis` charge from the blower MA operated by the stoker motor DA. kThe diaphragm of the pressure chamber-z12 yacts on the lever of' the balancing device IB: to oppose the v,action ofdther diaphragm .of the pressure chamber ilo, and to assist the action of the diaphragm of the pressure chamber 11.

ries a` finger 13, terminating in a valve '14 controlling the leakage port )cd2 from the The lever of the balancing device IB carpiping fd through which pressure fluid passes from a suitable source to the pressure motor FD. The leakage port feliz is located between the pressure mtor FD and the restricted port fai in the pip fd.

It will be apparent that with the apparatus shown in Fig. 4 the passage of air into the combustion chamber A2 is indirectly controlled by the damper EA3 in thesmoke outlet A in response to the steam pressure generated by the boiler, and thereby tends to ,maintain a predetermined steam pressure. The supply of fuel to the combustion chamber, however, is proportional to the gaseous rate o-f flow -through the combustion chamber into the smoke outlet, which is a function of the difference between the pressures transmitted by the pipes GB and HB, and is not directly dependent on the setting of the damper EAS, or the perviousness of the fuel bed.

In some cases it may be desirable to automatically maintain a constant rate of air flow into the combustion chamber of a boiler, as where the manual or automatic mode of firing employed insures a uniform rate of .fuel introduction into the combustion chamber. One arrangement for this purpose is'illustrated in Fig. 5, wherein the balancing device IC employed comprises chambers 12'10 and 11. The chamber 1 is connected by pipe G to the Pitot tube g in the draft inlet A3 of the furnace. The chamber 11 is connected by the static pressure pipe H to the inlet' A3. The blower MA of Fig/2 is omitted, however, and the pressure chamber 12 of Fig. 4 is replaced by the scale pan @'15, on which are placed weights 1G which ydetermine the gaseous rate of flow through the combustion chamber and may be varied to vary this rate of flow. |The finger 11 of the balancing device IC acts against the leakage valve fc3 regulating the pressure in the pressure motor `FIC governing the throttle valve P in the steam supply pipe P of the steam engine driving the draft blower EB.

Vith the apparatus shown in Fig. 5, a given rate of fuel feed to the combustion chamber A? may be maintained by a proper f setting of the supply valve DA3 in the steam supply pipe for the 4stoker engine DA, and with any given rate of fuel feed, the proper rate of air flow through the combustion chamber may obviously be had by..

placing the pan 15.

The blower fans M and MA are convenproper weights @'16 on the scale tionally illustrated in Figs. land 4, as

operated at a speed directly proportional to the speed of the Stoker engine. In practice, however, with the common type of stokers, such as are illustrated in Figs. 4,'

5v and 6, the rate at which fuel is fed into the combustion chamber depends upon two factors; namely, the speed of travel of the chain grate C', and the height of the gage or feed'gate C2. The effect of an adjustment of the gate C2 in apparatus such as is shown in Figs. 1 and 4, can be compensated for by a correspoiiding adjustment of the lever fulcrums of the balancing devices I of Fig. 1, or of the balancing device IB of Fig. 4. The effect of this adjustment of the feed gate may well be automatically compensated for,'however, by the means for the purpose shown in Fig. 6. rllhis means comprises a gearing connecting thestoker motor DB to the fan MB and provisions for automatically adjusting this gearing as the gate C2 vis adjusted. As shown, a friction disk D10, rotated by the Stoker engine, drives the blower MB by means of a friction roller M11 and connected to the blower MB by a shaft M10 which is arranged to slide through the blower to permit the parent that the speed of the blower MB will be proportional to the product of two factors, one of which is the speed of the stoker engine DB and the other of which is proportional to the elevation of the feed gate C2.

In the 4apparatus illustrated in Figs. 1 to 6, inclusive, fluid pressure balancing devices (I and IA, form the means through which the forces to be equilibrated act against one another, and through which one of said forces may be adjusted when necessary to preserve or restore the balance. In its broader aspects, however, my present invention is not dependent upon the form or general character ofl the" equilibrating mechanism, and in Fig. 7 I have illustrated an embodiment of my invention in which electrical balancing and controlling mechanism is employed. As shown in Fig. 7, the speed of the Stoker motor DC is independently controlled through the valve DC, and is connected to and drives a magneto S at a proportional speed, so that the electric current generated by the magneto will be proportional in strength to the speed of the stoker motor. The terminals of the magneto S are connected by conductors 20 and 21 to the terminals of44 one coil X of an electro-magnetic balancing device X.

l'Ihe latter controls the draft regulating damper Z in a manner hereinafter described.

. The balancing device X comprises, as shown Lief/,aas

valready referred to are means for maintaining an electric current ilow through the coil X2 proportional in intensityV to the volume of draft through the furnace. This means as shown comprises a differential pressure device NA having two spaced apart chambers N10 and N11, adjacent wall portions of which are formed by similar iexible diaphrag'ms N12 and N15. is connected by a pipe G to a Pitot tube g `projecting into the draft inlet passage A3r of the furnace, and the static pressurein this passage adjacent the point at which the Pitot tube, is located, is transmitted to the chamber N11 through the pipe H. Thel diaphragms N12 and N13 are connected to the opposite sides of a lever N14v which has a stationary fulcrum support N15 at one end, and at the other end is connected by means of a link N16 to a lever R10. The lever R10 is pivoted on an adjustable fulcrum R11 and carries at one end an adjustable counterweight R12 and at the other end carries the floating coil R' of an electro-dynamometer R, of the Kelvin balance type. j Coperating with the, floating coil R of the electrodynamometer are upper and lower stationary coils R5 and R6. The electric current passing in series through the coils R', R5 and R6 is supplied by a suitable source, conventionally illustrated as a batteryS, and

the intensity of this current is regulated as required vto maintain the ,lever R10 in its neutral positi/onby means of a rheostat T, which is adjusted by a motor U. The rheosta't T, as conventionally illustrated, comprises a contact arm T sweeping over a series of contact studs' T2, connected 1n series by the usual resistance sections. The arm T is carried by a shaft T4, which also carries' a gear T5 in mesh with the worm U4 carried by the shaft of the motor U. The motor U is reversible, and runs in one direction when a suitable source ofelectric current is connected .to its terminals U arid U3, and in the opposite direction when current is supplied to the terminalsU and U2.

The.circuit connections are as follows: A

conductor l leads from one side of the battery S to the flexible terminal R5 of the floating coil R. The other flexible terminal R4 of the coil R is-connected by the conductor 2 to onev terminal of the stationary coil The'second terminal of the stationary coll R5- is connected by the conductor 3 to one terminal of the stationary coil R5. A conductor 4 connects the second terminal of the coil R6 to one terminal of the ammeter V, and the other terminal of the latter is connected by the conductor 5 and brush T6 to the movable contact arm T of the rheosjtat T. f

The contact stud T2 at one end of the row The chamber N1.

of studs T2 is connected by the conductor 6 to one terminal of the balance coil X2. The other terminal of the balance coil X2 is connected by the conductor 7 to the opposite side of the battery S from that to which the conductor l is connected. The conductor 1 is connected by a conductor 8 to one of a pair of contacts 20, and to one of a pair of contacts 30. The second of the pair of contacts 20 is connected to the motor terminal U2 by a conductor9, and the second of the contacts 30 is connected by a conductor 10 to the motor terminal U5. The motor terminal U is connected to the conductor 7. In the n eutral position of the floating coil R of the balance R, the two contacts 20 are out of engagement with one another, and this is true also of the two contacts 30.` When the floating coil R moves upward, as it does on an increase in the volume of draft through the passage A3, the contacts 20 are closed, thus energizing the winding of the motor of which U and U3 are the terminals, whereupon the motor U is operated in the direction to ipove the contact arm T clockwise, and thus decrease the number of resistance sections in circuit. This, by increasing the strength of the current iowing through the coils R, R5 and R, tends to restore the floating coil to its neutral position. On a decrease in the volume of draft, the decrease in the differential of the pressures in the chambers N10 and N11 results in a closure of the contacts 30, and this causes the motor U to rotate the arm T in the counter-clockwise direction, increasing the number of resistance sections in circuit, and correspondingly reducing the current flow through the dynamometer coils R', R5 and R6.

Inasmuch as the difference between the pressures in the chambers N1o and N11 will through these coils is in linear proportion to the volume of draft or rate of air flow through the passage A2, hence a simple am- 'meter V will furnish direct and proportional readings of the volume of draft.

The lever X of the balancing device X is adapted to engage and close a normally separated pair of contacts X20 on a movement of the lever resulting from an increase in the ratio of the current passing through the coil X1 to the current passing through the coil X2, and on a diminution in this ratio, to engage and close a pair of normally separated contacts X30. When the contacts X2o are closed,l a circuit is thereby established which includes a source of current, as the battery SA, and Athe winding of a motor UA, which causes the latter to rotate in the moves the nut U11 to the right. This shifts the lever U12 so as to lower the damper Z,

and permit a greater' How of air into the 'combustion chamber A2 of the, furnace,

whereby the pull of the coil X2 will be increased sufficiently to return the lever X4 to its normal position. Conversely, when the ratio of the speed of the stoker motor to the volume of draft decreases, the lever X4 is shifted to close the contacts X30 and thus close the second circuit of the motor UA, whereupon the latter is rotated in the opposite direction, and the damper Z moved-toward its closed position. It will be understood, of course, that the current generated by the magneto S may or may not be the equal in strength to the current flowing through the coil X2 of the balance X, when the balance lever X4 is held in its neutral position. The ratio between these two currents necessary to maintain the balance'X in its neutral'position may be adjusted, as for instance by shunting the coil X2 by a variable resistance X7, as shown.

While the electric and fluid pressure controlling devices illustrated are full equivalents of one another in many respects, each possesses lcertain advantages over the other for use in certain conditions. For instance, with an electrical balancing device of the Kelvin dynamometer type, the electric current passing in series through the stationary and floating coils may be made to vary in linear proportion to the velocity of air flow, I, `or steam flow, so that an ordinary ammeter will directly indicate the rate of iiow of the air or steam. With the fluid pressure apparatus shown, however, the pressures balanced are proportional, not to the rates of flow, but to the squares of the rates'of flow,

. so that simple pressure gages will not give f trical apparatus, and can be used -under con# direct proportional indications of the rate of flow. The fluid pressure balancing devices are-simpler, however, than the elecditions unsuitable for vthe use of the electrical. apparatus.

In the appended claims hereto I have .used the term volume of draft as a means for defining draft` quantitatively; (i. e. cubic feet or pounds of gaseous fluid) flowing .through the combustion chamber; .instead of defining the draft by the pressure differential between stack andatmospheric pressures, or in some analogous manner.

In all of the forms of apparatus illustrated, except that shown in Fig. 4, provisions are made .for automatically main- 60.

taining a standard orpredetermined volume of draft notwithstanding variations in fuel bed resistance or variations in other draft affecting conditions. In the form of apparatus shown in Fig. 5, the standard or predetermined volume of draft is a constant for rate of fuel -feed and `the volume of draft,

notwithstanding Vvariations in one or the other of these quantities in response to'other conditions. 0n a variation in the'draft from the predetermined `standard the draft regulating mechanism tends to produce a compensating adjustment in the draft controlling device which is progressive in the sense that the device continuously undergoes adjustment until the draft returns to the standard.

While in accordance with the provisions of the statutes, I have illustrated and described the best forms of my invention now known to me, it will be apparent to those skilled in the art that changes may be made in the forms of apparatus disclosed without departing from the spirit `of my invention, and that under some conditions certain features of my invention may be used without a corresponding use of other features.

Having now described, my invention, what I claim as new anddesire to secure by Let -ters Patent, is:

1. In a furnace a draft regulating device and in combination therewith means re sponsive to the volume of draft controlling said device and tending on a departure in the volume of draft from a predetermined standard to eect a progressive" compensating adjustment of said device continuing until the draft returns to said standard.

2. In a furnace, the combination of means responsive tothe rate at which fuel is fed into the furnace, means responsive to the volume of furnace draft and means jointly controlled thereby for regulating the ratio of fuel feed to the volume ofdraft.

3. The combination with a steam generating boiler, of a mechanical stoker therefor, means automatically responsive to the rate at which said stoker operates, means automatically responsive to the volume of boiler -draft and a device jointly controlled by both of said means for regulating the draft.'l

4. In a steam generating plant, the combination of means responsive to the rate at which steam is withdrawn from the plant, and coperating means including la fuel feeding device, a draft regulating device, and a device responsive to the volume of draft for regulating the fuel feed and volume of draft in accordance with the rate at which steam is withdrawn from the plant. l

bustion in the different furnaces according to variations in said rate of steam generation.

6. In a boiler plant comprising a plurality of boiler furnaces, the combination of means responsive to the joint rate of steam generation of the furnaces and means including a device responsive to the volume of draft of each boiler furnace for correspondingly varying the rate of combustion in each of said furnaces in response to variations in said joint rate of steam generation.

7. In a boiler plant comprising a plurality of boiler furnaces, the combination of means responsive to the joint rate of steam generation, means, one for and responsive to the volume of draft of each boiler furnace, and draft regulating devices, one for each boiler furnace, and each jointly controlled by the corresponding draft responsive means and the first mentioned means.

8. In a furnace, the combination of a mechanical stolrer comprising a variable speed fuel feeding device and an adjustable feed gate, a draft regulating device and controlling means therefor responsive botli to the speed of said feeding device and the setting of said gate.

9. In a furnace, the combination of a mechanical Stoker, means for maintaining a fluid pressure which is a function of the rate at Which fuel is fed, means for maintaining a differential pressure'which is a function of the volume of furnace draft, a fluid pressure device in which the first mentioned pressure is balanced against said differential pressure -and draft regulating means controlled by said device.

10. rIhe combination With a steam generating boiler, of means responsive to the amount of steam being Withdrawn from the boiler, means responsive to the rate at which combustion occurs, and means controlled jointly by the two first mentioned means for adjusting the combustion rate.

11. The combination With a steam generating boiler of means automatically respon sive to the volume of boiler draft, means automatically responsive to another varying condition of operation in the boiler and a draft regulatingmotor jointly controlled by both of said means whereby a predetermined relation between the volume of said draft and said other condition of operation is maintained as the latter varies.

12. In a furnace, the combination of a draft regulating motor and controlling means therefor, comprising a balancing mechanism, means for subjecting said mech-` anism to opposing forces one of which is a function of the volume of draft, and means actuated by said balancing mechanism controlling said motor whereby the draft is varied as required to maintain said balancing mechanism in its neutral condition.

13. In a furnace, the combination of a. draft regulating motor, a device responsive to the volume of draft and controlling means for said motor actuated by said device for progressively operating said motor as required to maintain a redetermined volume of draft notwithstanding variations in the resistance to the draft occurring in the furnace.

14e. In a furnace the combination of fuel feeding mechanism, air supplying means and means for automatically proportioning the supply of air to the iate at which fuel is fed comprising means for generating a force Which is a function of the rate at which fuel is fed, means for generating a force which is a function of the rate at which air is supplied and balancing means acted upon by said forces.

15. In a furnace burning solid fuel, mechanism for effecting an efficient combustion comprising in combination means for supplying fuel to the combustion chamber of the furnace at a regulated rate, means for adjusting the volume of furnace draft, and means responsive to the volume of draft and automatically controlling the adjustment of one of the previously mentioned means, whereby variations in the ratio of fuel feed to the volume of draft may be compensated for.

16. In a furnace, a draft regulating device and in combinatioi. therewith means for creating a pressure differential which is a function of the volume of draft, and means` for utilizing said pressure differential on the occurrence of a variation therein from a predetermined standard toefect a progressive compensating adjustment of said device continuing until said pressure dif,

ferential returns to said predetermined standard.

GEORGE II. GIBSON. Witnesses:

WM. B. CAMPBELL, ROBERT G. CLIFTON.

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