US2008562A - System and method of regulation - Google Patents

Description

July 16, 1935. A. M. ROSSMAN SYSTEM AND METHOD OF REGULATION 4 Sheets-Sheet 1 Original Filed Jan. 29, 1930 July 16, 1935. A. M. ROSSMAN ,0 8, 62

SYSTEM AND METHOD OF REGULATION Original Filed Jan. 29, 1930 4 Sheets-Sheet 2 Z Par/f jnz/wz'f'ow 971672 lffpossm 6272 :9 My;

A. M. ROSSMAN 2,U8,562

SYSTEM AND METHOD OF REGULATION gully 16, 1935.

Original Filed Jan. 29, 1930 4 Sheets-Sheet 5 Fig.2 Par) 17 saw/AER? July 116, 19350 A. M ROSSMAN SYSTEM AND METHOD OF REGULATION Original Filed Jan. 29, 1950 4 Sheets-Sheet 4 m w mm faverzf'ow vi [Zen Mffassmmz Patented July 16, 1935 I UNITED STATES PATENT- OFFICE Allen M. Rossman, Wilmette, 11L,

Bossman- Engineering Company, a.

of Illinois 7 asslgnor to corporation Application January 29, 1930', SerialNo."424,38'0

Renewed September 19,1934 r t reclaims (01.23'6-14) My invention relates to a system and method; of regulation. a

While the particular embodiment which I shall herein describe comprises an automatic system of combustion control for boilers or the like; the

invention is not to be restricted to such use.

The present invention is an improvement upon the system and method disclosed in my co-pending application, Serial No. 411,336, filed December are}: 1929-; r

In controlling combustion the primedesiderat to I mtain a value of" combustion which is proportioned to the steam or other load to be carried; The next desideratum is to" do this carryin the load is substantially directly 1proportiorial to the load.- The" fuel -such as powdered coal this iristance'maythen be. fed at a ratewhich Will secure substantially complete and ellici ei-it' union with the oxygen of the'air.

'The eiiiciency of combustion may be checked either automatically or manually, by a C02 meter or, afte calibration of theinstallation, by a steam flou -air flow meter. A'ste'am flow-air fiowiun'eter is more convenient and prompt. in

operationthan a C02 meter and I show the sameas" a suitable element for checkingthe efficiency of combustion and mmring. adjustment of the con trols accordingly,- but it is to be understood that any suitable means which will determine the eiiiciericy of combustion may be employed 'instead.

The air flow in the present instance is main may beascertained and by suitable responsive mechanisms maintained as desired? Theiurn-ace and boiler'may be calibratedvto determine the various absolute values of air now coal feed to steam' flow and a general or mean-relation established which will be substanuauy correct for various loads within the, run e oftlie unit. 'Ifhe' regulating system is then rec; red to provide" regulation only for devia time from the'i said'm'ean relation. 2 V p In" the preferred embodiment of the present invention aswell as thesyst'em of the above recited application, I employ variable speed drives for controlling directly the rates of fuel feed and air feed. The air feed is divided between forced draft v fans and induced draft fans, each fan driven" by a; variable speed drive; These variable speed drives are under rheost'at control and hence regulation and control are greatly simplified.

Assuming that combustion is proceeding at a fixedrate and thesteam demand is increased,- such increased demand will be reflected in a reduction of boiler pressure.- I employ the-steam pressure gauge as a master gauge to control in common the speed of the forceddraft fans, the induced draft fans and the coal feeders.

The controller of my invention proportions the 7 rate of correctionto the amount of deviation in a noveland efl'icient manner which, at the same time, takes care of the conflicting requirements of the furnace pressure gauge and the efhciency meter gauge.

While the steam pressure gauge is the master controller, the furnace pressure gauge and the efficiency gauge preempt-control of the proper elements to maintain furnace pressure and cilicienoy, cutting out at the same time the master control- -I-his is desirable because the master controller effects changes according to the aforesaid mean or general relation and the special controls are required to cut in when deviations from the mean are required. for the sake of proper efficiency or proper coordination of the induced and forced draft fans. Hence, the special con- 7 trolscut and assume control and are caused to act more speedily than the action of the roaster controller.

My invention performs another desirable function in a novel manner. When the number of boilers operate to supply a common load the division of work performed or load carried must be properly controlled.

the preferred embodiment the speed of the coalfeed motor, hence, the rate of e combustion, for each furnace; is varied in proportion to the variations of potential impressed upon the armatures' o-i the motors, which are D, C.,' separately excited motors-".

Now, bysuitable voltage regulation of the impress-ed voltage of any particular set of coal feed motors a suitable rate of combustion is established. Such voltage may be established by ccmparison with the voltage impressed upon the coal feed-motors of one" boiler which is selected as the master boiler.

If the bcilersare to be equally loaded a substantially ratio of suchvoltages is maintained. Where aboiler is to be operated at reduced load In my prior system of regulation periodic con-- trol over the speed of the induced draft, forced draft and coal feed, or any of them, was given to the steam pressure gauge, the fire-box pressure gauge and the efficiency meter, in succession, by

a series of rotary distribution switches. Theseswitches gave each controlling gauge, or meter, definite period or time of control.

. According to the present invention the steam pressure gauge is the master controller and it is periodically given control of the coal feed, induced draft andf-orced draft to raise or lower the same. The periods of control are proportioned to the degree of deviation from normal.

My invention provides means for automatically maintaining a predetermined division of load between boilers. In proportioning the load of the various boilers one of the boilers may be considered as the master boiler and the others regulated with respect to it. Since the generation of steam in a particular boiler depends, primarily, upon the rate at which fuel is burned thereunder, the proper proportioning of the rate of fuel burning under the respective bo-ilerswill result in the proper proportioning of'load between or among them.

In the preferred form of the invention I'regulate the'speed of the coal feed motors by varying the potential impressed upon the'motor armatures; by means of a suitable balanced relay the voltages upon the coal feed motors of the respective boilers may be compared and a certain voltage. relation between the coal feed circuits of .the respective boilers maintained.

The air supply mechanism which includes forced draft and induced draft fans is then automatically regulated to correspond to the rate of coal feed to maintain the proper combustion efliciency and the induced draft fan and forced draft fan are adjusted with respect to each other to maintain the proper furnace pressure.

It will be observed in the preferred embodiment of the invention that the master controller involves the master pressure gauge which is preferably a steam pressure gauge connectedto the delivery main of the boilers. Any suitable device responsive to the load of the boilers may be con sidered the equivalent of the steam pressure gauge The field of thisinvention is not limited to fur-' naces for heating boilers. Any furnace heated by combustion may be controlled by this system; In some cases; such as, in metalheating furnaces,

the master control device may be responsive to such elements as temperature in the furnace, temperature of the heated product, etc. of these applications it may be desirable to install a master controller on each furnace but the principles, of operation will be the same. As one of the largest applications of automatic combustion control, however, is in connection with boiler furnaces, a description of this type of control system is made the basis of this disclosure.

The mastercontroller also includes an intermittent contact device'which serves to regulate the air and fuel supply of any number of boilers which are under automatic control. This intermittent contact device has off periods and on periods, alternately, the fon periods effecting a In some 1 regulation of the fuel supply and air supply. Due to the fact that the response of the fuel supply mechanism is not immediately felt inthefirebox it is desirable to make a regulating adjustment and then wait for the same to take effect before carrying the regulating adjustment further. It is for this reason that an intermittent regulating adjustment is performed.

I have provided, in conjunction with the intermittent contact device, means for varying the length of the on periods in accordance with the of fuel supply, under the control of twoseparate controls, namely, first the master controller, which regulates the fueland air supply simultaneously, according to a predetermined ratio,

and next, under the control of the efijciency meter or the like, which adjusts independently of the master controller and to the exclusion of the same, they air supply means.

As between forced and induced draft a relative adjustment is made in addition to the main adjustment of the two fans made. by the master controller by means responsive to the furnace pressure which, acting upon the induced. draft fan, adjusts its speed relative to the speed of the forced draft fan to maintain the proper pressurein thefire box at all times. This latter adjustment is independent of the master con troller and acts to the exclusion of the latter.

Now,.in order to acquaint those skilled in the art with the manner of constructing and operating a device according to my invention, I shall same type shown in Figure 2, part 1, for. boiler number 2 and indicates the same, partly, for boiler number 3, and Figure 2, part 3, shows the master controller.

To assemble the complete diagram of Figure 2, part 2 is joined to the right of'part 1 and part 3 is joined to the bottom of parts 1 and 2;

7 Referring first to Figure 1, I have shown herein diagrammatically the main operating and control parts for a power generating boiler l, which may be of any suitable type. This boiler l is provided with a steam pressure gauge 2 of a' type suitable to. operate the electrical controls hereafter to be described. The fire box 3 is shown in this case as fired with powdered coal through two sets of nozzles, 4 and 5 respectively, having individual means for supplying powdered coal thereto. While the invention is herein shown as embodied in a steam generating plant employing powdered fuel it is to be understood that 9 gauge 3-3.. iit hen the ratioof induced to not this is merely by way of illustration and of limitation.

The furnace 3' is fed with coal and air by duplicate apparatus for each,' mainly for thesake of reliability. Thenozzles 4 and 5 receive their mixture of powdered coal and air through a passageway 6- fr'om the coal-pulverizer 1, this mixture being moved by the exhauster 8 driven a by a suitable driving mot'orB.

Fuel from a suitable source of supply is detrical drive #5. The exhauster motor 9 may be driven at substantially constant speed although this may be a variable speed motor or drive if desired.

Primary air for carrying the pulverized fuel is supplied to the pulverizer I through the'duot [6, this duct leading from the forced draft supply duct ll leading from the air heater l8. A controlling damper {9, operated by a pilot motor 26 controls the air supply through the duct IS. the primary air supply.

The nozzles 4 are fed with fuel and primary air by apparatus shown at the left of Figure 1, which is a duplicate of that shown at the right of Figure I and having primed reference numerals applied thereto to designate like parts.

The main air supply to the furnace 3 is furnished by a pair of forced draft fans 22 and 22', driven by variable speed drive mechanisms 23, 23'. These fans 22 and 22"deliver air through the conduits 24, 24' to the air heater I8, I8,

pass through the economizer 2'5. 7

After the air'passes out'of the air heater [8 into the conduits IT, IT, the major volume of the same is delivered to the furnace 3 through the secondary air supply ducts 26, 26'; The main volume of air is supplied through the ducts 25, 2.6, the air supplied through the ducts l6, It being insuflicient to support complete com- 29,'2i, leading to the induced draft 3d,

which are driven at any desired within limit by the variable speed driving devices 32, 32 which may be of a charactersim to the devices '23-, 23 for driving fore-ed l pheric, generally inthe neighborhood of.1 of an. inch of Water. The pres a prevailing in the furnace indicated upon he furnace ppv draft is. proper the above stated pressure, slightly less than atmospheric, is maintained within the furnace In other words,'the damper l9 regulates "aft fans.- The pressure of air in the furnace preferably maintained at a pressure slightly below atrnosa developed in the mass must be likewise varied;

assuming a constant condition of efliciency and the like in. the boiler and the furnace. Such variation in developedheat' ineansvariation of the chemical union of fuel and oxygen of the 'air.. In order to maintain eilicient combustion it is necessary that the ratio of fuel to air be maintained at a proper value. Variation of the heat developed, therefore, must be accomplished by simultaneous variation of air supply and fuel supplyin order to maintain the efficiency of combustion which is desired. This problem of varying simultaneously the airand' fuel is, in the present instance, complicated by the necessity for maintaining the proper ratio of forced to induced draft, or vice versa.

The efiiciency of combustion is determined by' a carbon dioxide meter, generally termed a C02 meter; this is indicated at 3 as connected to the conduit 2?, through which the products of combastion flow to the stack.

obtain. the best possible combustion e'fr fici'encyjfrom the boiler it is necessary to mix with the fuel as nearly as possible the correct amount ofair to provide two parts of oxygen for each part of carbon in the fuel. If too much air is furnished too much heat is wasted up the stack. If too little air is furnished,'insufiicient oxygen is supplied and not all the fuel'is' burned. in excess of the amount" necessary must be supplied to insurethat, so far as possible, each par of carbon omes in'contact with the required t' carts o This is checked by measurii the percen f CO; in the flue gases, this percentage being in the neighborhood of. 12% to 14% under the best practicable conditions.

Instead of employing the 06: meter 3 as means respo sive to \efiiciency of combustion, I may employ a meter i which is responsive to the ratio between steam flow and air flow. Such steam flow to air flow meters or responsive dewhich is heated by the exhaust gases after they vices are known and the construction of the same forms-no part of the present invention. Suffice it to say that the flow of air'through the furnace maybe determined by measuring the drop in presst of the gases passing through a portion of furnaceor connections and the flow of steam delivered may be measured by means of a Pit'ot' tube or the like, and the two measurements com pared in meter 3! which then responds to the ratio of steam how to air flow whichfor a giv 1 fuel, should remain substantially col stunt, since a predetermined amount of air is required to develop a predetermined amount of steam at con tant pressure. 7

th the boiler incontinuous operation and connected to the steam main ii, for delivery of steam to a' turbine or the like, the load may be assumed to be properly carried, so long as the steam pressure gauge 2 indicates that an. adequate pressure is maintained. That is to say, so long as. the: steam pressure gauge indicates that a constant pressure is maintained, the rate of combustion is proper for'the load carried by the boiler. v

Anydeviation of the ratio of combustion to load will be evidenced by rise or fall of pressure, which will atonce affect the gauge 2. Therefore, with agiven speed of the induced draft fans v.1. I and the forced draft fans for passing a presired pressure, the boiler may be assumed to be in proper operation, carrying the load.

While the deviation from normal pressure by the master steam pressure gauge is-a satisfactory load responsive device, a steam flow meter which is responsive to steam flow may be employed instead, or any other element which is re= sponsive substantiallyto B. t. u. delivered by the boiler. The master pressure gauge is a simple load responsive device which fulfills the requirements of the present regulating system.

If the boiler pressure or the measurement of steam fiow should drop, indicating that the rate of heat development is not as great as required, fuel and air feed should be simultaneously increased in proportion to substantially a predetermined ratio of air and fuel. This is then to be carried out by the automatic mechanism diagrammatically shown in Fig. 2.

If the resultant ratio of air to fuel is not exactly right to secure the desired percentage of carbon dioxide in the fuel gases as measured by the meter 34, a correction of the ratio of air to fuel feed must be made. Also, in increasing the rate of combustion, the induced draitand forced draft must be simultaneously increased in such a manner as to maintain the furnace pressure at a proper value as determined by the furnace pressure gauge 33.

Now it can be seen that the automatic control system is called upon to vary atleast three things, namely, forced draft, induced draft and coal feed, while maintaining a predetermined ratio between total air flow and fuel supply and between forced and induced draft, total air flow in this case being controlled by the two factors, namely, the forced draft fan 22 and the induced draft fan 36.

The system of control shown in Figure 2 is of relatively greater simplicity as compared with' devices of the prior art for accomplishing the same object. 7 r

-Prior systems ofautomatic combustion control are complicate because prior systems of draft control are complicate. Consider, for example, a system which employs two-speed squirrel-cage motors for driving the fans, a change'in lo'ad which calls for a change in motor speeds, also calls for the operation of damper controls both before and after the switching operation and,

when dropping from the higher to the lower speed, the proper timing of the switching to prevent undue mechanical stresses from being thrown upon the equipment. All of these operations must be controlled by the automatic combustion control system.

The simple variable speed drive which I have recently developed and which is the subject matter of my 7 copending application, Serial No. 275,641, filed May 7, 1928, whereby the speed of the fans may be varied smoothly and continuously throughout their working range, permits the correspondingly simple scheme of automatic with alternating current through suitable slip rings. 1

A direct, current machine, 49 has a stationary field 42 .and a. rotatable armature 43,.the shaft of which is connected to the outer rotatable member 38 of the squirrel-cage motor 31.

A D. C. generator 44 has a stationary field 45 and an aramture 45, the armature 46 being connected in series with the armature 43 of the machine 40. a

tor v4i of the motor generator set 48 are fed inparallel from the A. C. means 49.

While Ihave shown three phase current supply, and this is preferable, it is to be understood that I am not to be limited to three phase current, as single phase or other type of alternating current supply may be employed.

The field of the D. C, motor 40 is separately excited from the D. C. constantpotential supply mains An adjusting rheostat 52 is inserted in the separately excited field circuit for the motor 563 for the purposes of adjustment.

This rheostat is suitably adjusted for operation within a certain range andthen is not disturbed during variations of speed of the drive, except as the range is changed or for operation of the drive at speeds below that forwhich the rheostat 53 provides control.

The separately excited field 45 of the generator 44 is supplied with a potential which isvaried to control the speed of the drive. A potentiometer type of rheostat 53 is connected across the constant potential mains 5E! and the terminals of the field winding 45 are connected to the brushes 54, 55, these brushes being adjusted as shown in the present instance by the pilot motor 55 and a suitable worm drive 51..

The squirrel-cage motor 31 provides the base 7 speed and the direct current motor 49, which is of much smaller rating, furnishes the increase or decrease in speed from the base speed.

The part 38, which is normally the stator of the induction motor is mounted on bearings so that it may be rotated aboutv the same axis as the rotor 39. I r

The stator may be driven-in either direction by means of the small D. C. motor '49, which draws 7 power through the motor generator set 48. The speed of the D. C. motor 4!! and its direction of drive are varied by varying the voltage of the generator 44 from maximum positive to maximum negative.

The speed of the fan 36 is increased above the base speed by causing the direct current motor 49 to drive the stator of the A. C. motor 31 in thesame direction as the rotor. The speed of the fan then is the sum of the rotor and stator speeds.

The speed of the fan 35 is decreased below the base speed by causing the stator 38 to rotate in the opposite direction to that of the rotor 39. It then drivesthe D. C. motor 4!] as a generator, which forces power back through the" series connection between the armatures 43 and 46 and through the A. C. motor 4'! back on to the A. C. mains 49. The fan speed then is the difference between the rotor and stator speeds. When the fan speed has reached the lower limit of speed by armature voltage control-of the D. C. motor 40, the speed range may be extended still lower by draft fan 30. H. P. rating to the two motors on the forceddrait fan is, in the ratio of A. C. motors, 85.5 per'cent ccesses a field controlat the rheostat 52 of the'D. C. motor 49, if desired.

The H. P. ratings of the two motors '31 and 40 'on "the induced draft fan 31! are, in the ratio of A. C. motors, seventy-nine per cent (79%) and l D. C. motors, twenty-one per cent (21'%)- in one example of my invention;

Thedrive for the forced draft fan 22 may be identical with that shown at 32'for the induced In this particular 'infiance the control bus 64. This bus 64 is supplied with variable potential by the motor generator set 65 comprising a squirrel-cage or other alternating :cur- .zrent motor 66 operated from the AFC. supply -ma'ins 49 and a separately excited direct current r motor 167, having its field 68 variably excited through the control of the motor adjusted rheostat 69 and having its armature '10 connected to I the bus 54 for the delivery of current at variable potential thereto.

The variable .speed- :coal feed drive is of the so-called Ward-Leonard type.: "The field rheostat 69 for controlling the potential impressed upon the coal feed motors IZisoperated through suitable gearing 12 by a rheostat actuating motor 73. The motors 62, 56 and1'3 are similar in having their fields 14 separately excited from the constant potential bus 59 and having their armatures supplied with current from the branch 15 of the bus 50. l

As will be pointed out later, the master controller, under the direction of the master pressure gauge or other load responsive device, closes the armature circuits for the armatures 1.6 of said rheostat operating motors, in unison, -to drive them forward or backward, as the case may be, in unison, and the armature circuits of these rheostat operating motors are preferably so adjusted with respect to each other that they move at rates which will maintain at all times substantially a predetermined mean ratio of air to fuel and of forced draft .to induced draft. The relative rates of adjustment are regulated by individual rheostats ll, 18 and 19 for the motors '13, 56. and

The bus 5!] and the branch :bus 15 are supplied with direct current through a motor generator set as, comprising the A. C. motor .82 and ashunt wound exciter generator 83. A disconnecting switch 84 and fuse 85 are indicated in the branch 1'5 and a rheostat 8! for providing a common adjustment forthe motors 13, 55 and 62 is included in the branch 15. The field circuit of the exciter generator 83 has a field rheostat 86 to adjust the voltage impressed upon both branches .ili and 1-5.

The master controller 88, which includes the master steam pressure gauge 2 and the timing controller 39, increases the speed of the coal feeders, the forced draft fans and the induced draft fans when the rate of steam demand is in excess of the rate of firing. When the steam pressure gauge 2 is employed a drop in steam pressure indicates that increase in firing is required and 1ikewise an increase in steam "pressure indicates that a reduction in firing is required. The timing controller has a rheostat 90 subject to steam pressure acting upon the gauge 92, or through any other suitable load responsive device, for varying the on periods of control of the timing controller 89 with respect to the off periods of control. In-t'he present construction thedevice 92 is a steam pressure responsive element connected "to the movable contactor 93 of the rheostat 90 for increasing the resistance in the armature circuit of the driving motor 94 in proportion to the deviation from normal of the steam pressure. Obviously, if any other form of load responsive device were employed instead of the steam pressure gauge 2, the device 92 would be responsive also to deviations of load from the predetermined value.

The driving motor 94 has a separately excited held 85 and has the armature circuit connected in series with the rotary contactor brushes 9% bearing upon the rotating disc Q? having the conducting segment .98 for bridging the brushes 9B. The off-normal rheostat 9G is connected in shunt of the brushes 96 and in series with the armature 9 of the motor 94, the field of the =-mot0r 94 being separately excited from the constant potential battery bus 108.

The motor 94 rotatescontinuously, driving the controller shaft Hi2 through suitable gearings 1-03. When the conductingsegment 93 bridges the brushes 96, these brushes being adjustable to vary the angular space, or part of each rotation during which the brushes 98 are bridged, the i motor 94 rotates at maximum speed." As soon as the conducting segment 98 opens circuit between the brushes 95, the off-normal rheostat 90 controls the speed of the motor.

If the contactorS-i includes more resistance, the motor 91 rotates ata slower speed during that part of the angular motion when the brushes so are dis connected. Now it can be seen that the shaft I102 will have a constant speed during a predetermined part of each rotation and a controllable or variable speed during the remainder of the -angula-r part of the rotation, the variations in speed being made to correspond to the deviations of the position of the load responsivedevice from normal.

The shaft 102 bears another rotating disc l-M bearing a conducting segment 495 cooperating. with a pair of brushes 106, controlling the circuit "UH of the master steam pressure gauge 2, which is a load responsive device.

The battery circuit from the battery bus M0 extends through the brushes I06, wire 108 to the contacting needle m5 of the gauge 2. A

pair-of stationary contacts all-El and H2 are adapted to be engaged by the needle H38 when it is of! of its mean or normal position, selectively. -The contact H0 is connected through the relay winding 11-4 to the return wire i 53. The contact H2 is connected through the relay winding back to the return wire H3. Energization of the winding H4 closes a circuit through the relay con tactor switch M6 to apply a potential (in this case positive battery) to the increase wire H8. The energization ofwinding ll5 closes a circuit through the relay contactor switch Hi to "place a potential (in this case'positive battery) upon the decrease wire 1 A hand-control switch I22, having a movable contact 123 for engaging the stationary contacts 124 and .125, selectively, is provided for energizing the control wires by hand. A transfer switch 128 selectively puts the increase and decrease motor 55 is governed for increase by the increasecontrol wires I 21 and I 28in circuit with either the automatic control '2 or the manual control I222. The increase and decrease control wires I21 and'i28 are connected to increase andrdecrease control wires I29 and I30 which are extended to the controlledmechanism of each of the boilers in the system. Theconductors I29 and I39 are thus increase and decrease control bus wires extending to each boiler control station.

'lhese'master control wires governing increase and decrease, I 29 and I30, are connected through load division relays I32, I33 and i34 to each of the three boiler controls, so that an increase or decrease of firing, as found to be necessary by the master pressuregauge 2, can be simultaneously effected upon the combustion control switch I42 comprises a pair of selectable contacts I43 and i4 4 and a selector contact I45, by which suitable battery potential from the battery bus ififirnay be impressed upon either of the local control wires I49 and I58.

The local firing control wires M9 and I59 are connected directly to the windings of the increase and decrease control relays I53 and I54 for the coal feeder rheostat adjusting motor 13.

'Thereby, whenever potential is put upon either of the local firingcontrol wires I49I50 the rate of coal feed is changed. The relay I53 closes a set of contacts 55 extending from the constant potential leads 15 to the armature 16 of the coal feed rheostat adjusting motor 13. The switch i55, controlled by the relay I54 applies potential from the bus 15 through the armature 19 of the coal feed rheostatadjusting motor 13 *in reverse direction for shifting the rheostat 69 to a position which will decrease the rate of coal feed. The series rheostat 11, which is adjustable,

is inserted in the circuit of the armature 16 so as to control the rate at which said motor 13 operates ,as compared with other motors in the group controlling combustion of the particular boiler. r

The operation of the rheostat, adjusting motor 56 for adjusting the speed of the induced draft fan 391s normally under the control of the local firing control wires I 49 and 50 and these are vnormally connected to the master controller, but any deviation from efficiency, asindicated by the ehiciency meter 3I, or any deviation from proper furnace pressure, as indicated by furnace pressure gauge 33, is arranged to interrupt the control of the induced draft fan 35 and of the'forced draft fan 22, respectively, by the master controller or the hand controlled switch I42 or by the motor differential relay I35 and, governed exclusively by the efiiciency meter 3I and the furnace pressure gauge 33, respectively. is accomplished as follows. The armature circuit of the induced draft rheostat controlling controlling relay I51 and for decrease by the decrease controlling relay l58 which have corresponding forward and reverse connection con- This tactors I59 and I60 controlled'thereby. The windings of these relays I51 and I 58 have branch connections I63 and. I64 cut'through the normally closed'relay contacts of the cut-in relays I69 ;and I10, which relays are under the control of relay I58 is cut through the contacts I61 of the cut-in relay I10 and of the contacts I68 of the cut-in relay I69. Hence, when either relay I69 or I10 is energized the branches I63 and I64 which lead tothe local firing control Wires I49 and I50 are disconnected.

The cut-in relay I69 has normally open-con I tacts I14 for closing the branch connection I16 of the decrease relay winding I58 to battery and likewise the cut-in relay I10 has contacts I13 forclosing the branch connection I15 from the Winding of the increase relay I51 to battery to cause the same tooperate respectively.

The efliciency meter selector contact I62 is arranged to close a circuit from positive battery wire I11 to either contact I19 leading to the increase cut-in relay I10 or contact I leading to decrease cut-in relay I89, and thereby energizing increase relay I51 through closing of contacts I13, or energization of decrease relay I58 through closing of contacts I14.

A manually operable transfer switch I18 takes control away from the automatic action of the efiiciency meter and transfers the same to the hand switch I82. Then, by either pulling out the button I83 or pushing the same in, the increase relay I51 or the decrease relay I58, respectively, may be energized.

'The forced draft fan rheostat control mechanism has the same relation with respect to the local firing control wires I49 and I55 and the furnace pressure gauge 33, which exists between therlooal firing control wires and the efiiciency meter 3| for the induced draft fancontrolling rheostat mechanism. That is to say, normally the branch circuits I81 and I88 for the increase and decrease relays I and I86, respectively, are connected through the contacts of the cut-in relays I89 andI99 to the local firing control wires I49 and 150. However, the furnace pressure gauge 33, through its selecting contact I84 and cooperating with the contacts I93 and I94,

.is able to energize the cut-in relay windings of the relays I89 and I90 and interrupt thebranches normally connected to the local firing control lcrease relays I85 or I86.

.A selector switch I92 is operable by hand to cut out the automatic control of the furnace pressure gauge 33 and transfer control to the' manual switch I91, thisswitch having a selector contact and a button I98 so arranged that by pulling out on the. button I98 the cut-in relay I90 may be energized to cause energization of the increase relay I85. When the button I98 is de- .pressed the decrease relay I86 is energized accordingly.

No'wyfrom the above it can be seen thus far that the speeds of the driving motors of the coal [ing through the .master control wires and through branches leading to each of the local firing control wires, is able to increase or decrease the rate of firing of all of the boilers at-the same time. The rate of operation of the respective rheostat adjusting motors is normally so arranged that a substantially fixed relation between fuel and air will be maintained throughout the range of regulation.

I term herein regulation raising and lowering of the rate of firing. I term herein change in the relation between fuel and air, or between induced draftand forced draft, adjustment of the relation. 7

adjustments is immediate since the speed of the corresponding fan is immediately felt by either the efficiency meter or the furnace pressure gauge, whereas response of change in rate of feeding coal is not so prompt, due to the fact that the coal must first be passed through the grinder and some time is required before either an increase or decrease in rate of feeding coal will be felt in the fire box.

By means of the system thus far described, regulation and adjustment of the firing of each boilor may be accomplished.

Now it frequently occurs that it is desirable to fire one of the boilers at a reduced rate as compared with another. If the total load is increased it will be apparent that either the two boilers may be fired at a proportionately increased rate or the additional required load might be carried by the-boiler operating at reduced load.

I consider that the most effective, but the most difficult way to handle the situation is that so long as the changes in rate of load are relatively minor as compared with the total capacity, such changes in demand should be met by a proportionate change in the rate of firing of both or all of the boilers operating together.

For the purpose of proportioning the load on boileris assumed to be a master boiler and the load of the others is adjusted relative to it, then for variations in load the entire group is fired more or less, to meet the variations in demand. 'Where the" change in load is of a major-character, then the boilerwhich has beenfired at a lower rate is adjusted to be fired at a higher rate and then put back on automatic regulation to float up and downwith the master boiler and theother boilers in the group. a

Each individual control system for each boiler has a rheostat Bl governing the potential upon the branch main 75 from which the armature circuits for the rheostat adjusting motors are derived. Thus, by increasing the resistance in the corresponding rheostat 8? the impressed potential upon the armature circuit of the rheostat adjusting motor for the particular boiler is reduced. As a result they respond to a less extent per unit of time. Thereby it can be seen that under impulses from the master controller for rege ulating all of the boilers in unison, less change in increase or decrease will be made in the rheostat adjusting motors of a boiler where less rein proportion to the voltage on said bus 64.

sistance has been included in the corresponding rheostat 81.

Sincethe rate of firing is that of the rate of coal feeding and the rate of coal feeding in my system is dependent upon the potentials impressed 11 upon the armature circuits of the coal feeder motors, it is possible to maintain any desired ratio .of firing by maintaining a corresponding ratio of coal feeding and that can be done by maintaining a corresponding ratio of voltage upon the coal feeder motor armature circuits.

The voltage upon the coal feeder motor armature circuit is that of the variable potential motor generator set, of each boiler. Hence, by manually operating the local firing control switch M2, the selectorswitch i33 being shifted accordingly, the firing rate may be changed by impressing a potential upon one of the local firing control wires, M9 or lEt, thereby to cause the rheo stat adjusting motors Z3, 56 and 52 to regulate the firing rate of the particular boiler. For example, assume that it is desired to run the. boiler 'No. 1 at half: of the load which is carried by boiler No. 2. 'The first thing to do is to shift the selector switch I38, then operate the manual control switch M2 to close the contact to the decrease wire through contact Hi l.v This energizes the decrease relays E54, lbs, and 86. When the regulating adjustment has. proceeded to a point where the voltage on the coal feed motor bus '64 has been brought down to that corresponding to half speed for the coal feeder motors, the switch I42 is opened. Then the rheostat 8'! is adjusted to decrease the potential upon the motors 13, 56

and 62 so that they will respond less rapidly to regulating impulses. Where the rate of coal feeding' has been reduced to half speed the rate of response of the motors i3, 56 and 52 will also be reduced to half the normal speed of response.

In order, thereafter, to maintain automatically the relation of the firing rate of one boiler with respect toanotherboiler, I have provided the voltage dlifferential relays l35, I35 and I31, for the three boilers here indicated.

The relay i35 comprises a pair of coils, 20D and 202, the coil 20c being connected to the coal feeder bus 64 of boiler No. 1 so as to be energized In series with the coil 2m) 1 provide an adjusting rheostat 203, for regulating the current flow through the winding Elli for the purpose of maintaining a balanced relation between the voltage of the bus 64 and that of the load balancebus, 26 5, to which the coal feeder potential bus 205 of boiler No. 2, or 2% of boiler No. 3 may be connected. Assume that boiler No. 2 is connected to the load balance bus 264 as indicated by the plug switch 29?. and the potential upon said coal feeder potential bus'2ll5 is full potential corresponding to normal firing rate, the rheostat 233, connected in series with the windings Hit-2% is so adjusted that the predetermined lower voltage on the bus 64, acting through the voltage differential relay I35, will just. balance the normal voltage applied to the winding 262 through the series resistance 203. i

The coils 20D and 2&32 operate upon a balanced member having a movable contact 208. and adapted to engage contact 259 or 2 i 9 to increase or decrease the rate of firing of the-boiler corresponding to the relay i35. These contacts 209 and 2!!) control the circuits of cut-in relays 2I3 and 214 for interrupting the control exercised by the master control wires 5 29 and I30 and for substituting the control of the voltage differential may I35. Thus the control wire 129. is'c'ut through the normally closed contacts 2 I 5 and 2 I 8 'leading to the one set of contacts of the selector firing control wires M9 and I50, respectively, un-

'der the control of the voltage differential relay I35. The load division relay I33 for boiler No. 2 operates in the same manner for the controls of the second boiler under the control of its voltage differential relay I35. 7 V

The load balance bus has branches leading to the windings 222 of the relay I35, 222 of the relay I36 and 223 of the relay I31. The opposite windings 2539, 224 and 225 may be connected to the load balance bus 294 through the plug switch 201, in order to permit the potential of individual coal feeder potential bus to supply the potential to the load balance bus, as the master boiler, for determining the relation between the rates of firing of the various boilers. Thus, for example, boiler No. 2 may be selected as the master boiler and the potential of its coal firing potential bus may be taken as the reference potential on the balancing coils of the respective voltage differential relays. Then, if through any difference in rate of response of, for example, the rheostat adjusting motor, the potential and hence the rate of ,feeding of one of the coalfeeders tends to vary from the predetermined ratio with respect to the master boiler, the voltage differential relay becomes unbalanced and through its load division relay cuts into the local firing control wires of the particular boiler and adjusts the rate of firing accordingly. As soonas this regulating adjustment has been made the voltage differential relay comes to balance and the operation proceeds in the proper relation. I p r If, due to variations in the total load, a lower rate of firing of the boiler is required, then the master controller, through the action of the master pressure gauge 2, or other load responsive device, imposes upon the master control wires I29 and I30 for all of the boilers, impulses for energizing the decrease relays, for example, for operating the rheostat adjustment motors to decrease the voltage of the motor generator set 65, the speed of the induced draft fan 30 and the speed of the forced draft fan 22 for each of the boilers. I 7

If, in so doing, any unbalance as between fuel and air is occasioned for any particular boiler, this is automatically adjusted by. the efficiency meter of the particular boiler, which seizes the control of the local firing control wires to make the necessary adjustment. Likewise, if any un-' balance between induceddraft and forced draft in anyparticular boiler occurs, the furnace pressure gauge of that boiler assumes control of the local firing controlwires of that boiler and makes a corrective adjustment. These corrective adjustments are made to the exclusion of the master controller. In the same manner, if any unbalance in the rate of firing between boilers occurs, the voltage differential relays detect the differ ence and through the load division relays cut into the control for the local firing control wires to the exclusion of the master control and make a regulating adjustment of fuel and air for that particular boiler.

The number of boilers which may thus be controlled is, within limits, anything desired.

'ciency responsive means.

7 The use of adjustable speed motors for driving the fans and fuel feeders as herein described is i not an essential part of this invention. :Instead of operating rheostats to regulate the elements of combustion, the regulating pilot motors could,

-within the scope'of this invention, operate dampbased on allowing the corrective controller to operate to the exclusion of 'the master controller, it could easily be arranged to give the precedence to the master controller. 7

It is not necessary for an embodiment of my invention to have both induced and forced draft fans, as I intend to cover broadlyfuel and air.

Hand controls may be substituted for automatic controls by selector switches and hand operatedswitches, as indicated on the drawings, at each point where an automatic device responsive to some action of the boiler or furnace is provided. j

I do not intend tobe limited to the details as shown and described, except as the same are specifically recited in the appended claims;

I claim:.

1. In a system of the class described, afurnace, a fuel feeding device for said furnace, a controller therefor, air supply means for said furnace, controller therefor, means responsive to the demand upon the furnace for governing both controllers simultaneously and means responsive to the efficiency of combustion for exercisinga governing action upon said second controller, and means for continuously excluding the governing action of said demand responsive means during, the governing action of the efii- 2. In a system of the class described, the combination of afurnace, a fuel feeding device for said furnace, a controller therefor,- air supply means for said furnace, comprising a forced draft producin means and an induced draft producsaid control -means simultaneously and means responsive to efficiency of combustion for'governing one of said draft controllers to the continuous exclusion of the governing action of said demand responsive means. I 3

3. In combination, a furnace, a fuel feeding device for said furnace, a controller therefor, air

supply means for the furnace comprising a forced draft producing means and an induced draft producing means, individual controllers for both draft producing means, means responsive to the demand upon the furnacefor'governing all of said controllers simultaneously and means responsive to furnace pressure for governing one of said'draft controllers to thecontinuous ex-' F means.

vidual controllers for death draft means, means responsive to the demand upon the. furnace for governing :all of said controllers simultaneously, means responsive to the emcienoy of combustion for governing one of vsaid controllers and means responsive to firezhcx sure for governing the other of :said mmtrollers, in each case to the iexclusirm of mm cming action of said demand responsive 55.. In :a system of the class described, a pmrality of furnaces, a plurality :of imiivinhnlly operable fuel feeders for said fend trol means for reach of said fuel feeders, adynsh ment varying means for said feed mama means for controlling the adjnslment varying means of all of the furnaces responsive to the demand upon said furnaces, means responsiverbo: the rates of operation of said fuel feeders, and a differential element governed by the rates of operation of said fuel feeders for oun-- tnolling one of said adjustment means.

6,. In a system of the classa. pinof fumaccs, a. plurality of individually or erable fuel feeders for said furnaces, vval-inculcspeed driving means for each of said fuel fccd-.

ers, speed control means for each of said Mable speed driving means, adjustment varying means for said speed control means, means'for controlling the adjustment varying means of all of the furnaces responsive tothe load dcmaadsupm said fumaces, means responsive to the mm of operation of said fuel feeders, and a differential element governed by said last named means for controlling one of said adjustment varying '7. In a system of the class describedthe combination of a furnace having fuel feed means, air supply means, means responsive at all times: to the efficiency of combustion, a dcvice responsivc to the heat demand to be supplied by said furnace, regulating means periodically under the control of said device for regulating the action of both the fuel feed means and the air supply means in common, and adjusting means, governed by said efficiency responsive means for adjusting the action of said air supply means and said fuel feed means relative to each other, said adjusting means being capable of acting at any time to the exclusion of said regulating means.

8. In combination, a furnace, a. boiler, a steam load responsive means, a. fuel feeding device, a variable speed drive therefor, means for supplying current flow of variable potential to said drive i V to vary the speed thereof, an adjustable rheostat for said current supply means, a timing controller, means governed by said. load responsive 1 means and acting through said timing controller for adjusting said rheostat, air supply means for said furnace, a variable speed drive therefor, a. rheostat for governing said latter drive and means for automatically controlling the second rheosta-t individually to the exclusion of the control of said load responsive means.

therefor, a furnace for the boiler, afu el feeder for the furnace, a rheost-at for controlling the sole icontml lof said :eficiency meter so long as said meter (abnormal efficiency.

10. mocmbination, a. :boiler, a steam pressure gauge therefor, a mirnace for the boiler, a fuel feeder for the a rheostat for controlling the weed iof thefueL-feeder, a motor for adjustiursnid rheoamtmir-supply means, a rheostat for ma h speed of said air, supply means,

a motor for adjusting said secondgrheostat, a pair of firing cmtrol wires for governing the operation of said motors under the control of said We, atfurnaoepnessure gauge and a relay for the second motor under the sole control of-aa'id furnace pressure gauge so long as said indicates an abnormal furnace pressure.

11. The method of regulating the output of a comprises firing the boiler at a selectcdwta, periodically making adjustments of them-lug mtc atladefinite rate of adjustment and varying the length of the periods in proporclcviation of the boiler output from a 7 if. valua r 1% Khemcthod of regulating the output of a battery tit-boilers which comprises, firing each of 'theboiiers at a selected rate, periodically increasing ordecreasing the firing rate of all of the boilers in proportion to the load demand upon the boilers, and adjusting the ratio of fuelto air of boiler, independently of "said periodic adjustment. f I V 13. The method of regulating the output of a battery of boilers which comprises firing each of the boilers at a selected rate, periodically increasing or decreasing, the firing rate of all of the boilers-in proportion-to. the load demand upon the boilers and adjusting the rate of fixing one boiler with respect to the rate offlring an-' other boiler independently of said periodic common regulation of therfiring rate of all of the 14. 'I'he;method' of regulating the output of a battery-of boilers which comprises firing each of the boilers at a selected rate, periodically increasing or: decreasing the ,firing rate of all the boilers in proportiomto-the'load demand upon the boilers, adjusting the ratio of fuel to air of each boilerindependently of said periodic adjustment and adjusting the rate of firing one boiler withresp t to the rate of firing another boiler, independently of said periodic common regulation of the-firing rate of all the boilers.

15. In aboiler control system, the combination of a furnace havingfuel supply means, a fan for supplying-air to, said: furnace, a'variable speed drive for the fan, said drive comprising" a constantspeed type A. C. motorfor supplying power to the fan, a D. G. machine connected in diiferen tial relation to the fan and said A. C. motor for supplying a suitable increment or decrement of power, tosccure the desired speed of the fan, a rheostat for definitely controlling the speed of the D. C. machine, and automatic controlling means for adjusting said rheostat to govern the 9. In combination, a boiler, a pressure gauge speed of the 16, In a control system, a'series of furnaces, fuel supply means forthe furnaces, lair supply means for the furnaces, rheostats for controlling said; supply means, motors for operating said rheostats; means for closing the circuits of said motors in common, and a rheostat in series with the motors of one furnace for controlling the rate of responsesofth e said motors of one furnace with respect tothe rateiof response of the motors of another-furnace, j

17. In combination, a battery of boilers,- aload ognosmoe feed and an. adjusting smotor for :the Lcontroller, an :air :supply means, :a zcontroller star :the ;air supplyzmeans,,anadjustingzmotortfor:saidisecond controller, rheostats :for controlling ithe rates 10f response of said adjusting :motors rand ameans underthecontrol 'of the gauge for energizingisaid adjusting vmotors :simultaneously.

:25, :In :combination a iboi-ler, rah-steam :pressure gauge therefor, a furnace :for .the boiler, J a ifuel feed.:for theefurn-ace, a controller .for =the fuel 7 feed, and-ralradjusting imotor for "the .;controller,

an air supply means, :a .controller ?for i the air supplyimeans; an: adjustingimotoriforsaid' second controller, rheostats :for controlling ?the i rates :of response of said adjusting :motors and mean-s underithe :controlsof: the gauge f or energizing-said adjusting .:motors simultaneously, :an refli'ciency meterzfor the furnace andimeans under :the control of the efficiencymeter:for individually controllin'githesecond'adjusting motor.

26. aIn i. combination, ;a :rboiler, assteam :pressure gauge :therefor, :a furnace ifor ithe :boiler, 1 a duel feed for :they furnace, a icontroller I 'for the fuel feedianiadjustingimotoriorithe controller an air supply means, a -:controller :for the air supply means, :an adjusting smotor :fOI said second A con-' trol-ler, llhQQStfitS ;for controlling the: rates of response 101 said adjusting :motors, Ifiring I control wires, :relays'under :the :control of said firing control wires "for closing ;the acircuits 1of said-adjusting:motors:simultaneouslyiforiforward orrreverse motion; said .firinga control wires'sbeing a under the controlofsaidgauge.

.27, In combination, aipiurality of rboilers, zfurnaces forw said rboilersrfiring means for each furnace; variable. speed: motors-fortdriving said. firing means, rheostatsifor controlling the: speedv of. said motors, :power supply :mains "for @the motors of each boiler, :means :for varying :the potential of said mains ;to:adjust the relative z-rspeedsefsaid motors, adjusting motors :for -.-said Lrheostats, means foryaryingthe rate of operation =rof the adjusting motors relative toaea-ch other, :relays for closing the circuits 10f: said adjusting :motors :to said :mains for .forward or reverse zoperation, firing control avires'for said relaysiand :aimaster controller comprising; amuresponsivetdevicetfor energizing the :firing control iwires selectively When :the output :of the boilers :deviates from $3 predetermined value.

28. In combination, a plurality :of aboilersgiurnaces for-said boilers, firing means :for each .furnace, variable-speed motors for .driving gsai'd firingu means, -rheostats:for controlling the speed. of said motors, 3 power supply mains ;:for the motors of reach boiler, (means {for varying :the zcpotential ofssaidmainsto-adjust the,rekitivesspeeds;:of.:said mo tors; adjusting mo tors. f or-saidrrhe ostats 11s for varying the rate of operation. of lithe! adjusting l motors re'lative ato 'teachiot'ner, relays ifOl ielosing the cireui oft-said: adj usting: motors? tOF-Sfildl mains for .riorward :or ,reverse separation, :firing control Wires for saidmelaysfiand afmasterzcontrollencomprising" a load responsive device ffor :energizing the firirrgacontrol avires selectively when :the 1 out putrof' therboilersrdeviatesifromr a predetermined value, a differential irelay :for. comparing 1 the firing rate of 'one .boiler with :the firing rate :of another it) oiler "and means controlled by said-differential relay, upon deviation of the firing rates from a predetermined ratiog'for removing control of 5 the Hiring control wires of one 'boiler 1 from the master controller assuming control of the same.

29. In: oombination w plurality of furnaces; firingrmeanszfon eachifurnac'era variablezsiaeed Amotorsion eachrfiringmeans, arsourcenfwariablesp tentialforxea-ch motori to.controlitha'speedlthereof :governing means If or reach source ifor varying the potential ith'ereof, a r-difierential :relay :controlled'zbyr said sources .of variable potential zsaid governing means :being controlled byz'said dilferential relay :to'vary the relative rates :of .firingio'f saidfurnaces.

30. rIn: combination, 1 a; plurality 10f afurn'aces, fi firing means '11" or each i urnace, saxvariablerspeed: motQZif or each firingsmeans, a;sourceofavariablezpotential:;for: each motorwto controlzthesspeeditlrere of, governing :means :for 1 each source 'foruvarying the potential thereof, a differential relay 'eontrolled aby said sources 1 of avariable ipotential said governingzmeans being controlledaby saidrdlfierelement forwariations ofs'totalrload.

;Inrcombination, aabattery aof lboilers, *aiload responsive ziclevice for said :batteryrof i,b01181 S, f11'I nacesifors saidiboilers, =eachifurnacezlravingsa fuel feedx'device, atvariable speedzmotorttherfonm source rof wv-ariable potential 'fOI vcontrollin-g :the speed lofesaid variable speed .m0tor governing means :ifor said source, ran ;air supply device, a variable speed :motor therefor, :rgoverningsmeans forlesaid :lastsnamed .motor, :a pair of adjusting means for said pair of governing means and means rior :controlling ithe relative rrates of actionoof said adjusting meansiforseaehiboiler, a common itiming .controller :for ithe battery s'of boilers .ifor periodically placing ithe adjusting ineans z'of all the boilers iin common =under the control :off saiddevice.

532. :Inrarfurnace. control system, means for reg-- ulating the air :suppiy, means including a normally inoperative pilot motor I or :adjusting the regulating tmean's, means .responsive i to predetermined conditions :for controlling tlie adjusting means, additional means controlling the 'a'djusting .means responsive to the demand on the furmace, ;and :means ifor rendering one K of tsaid two controlling means ineffective: during the entire periodiof regulation: of i theair supplya'means by "the other-scontrolling means.

iIl'l a furnace control system,"means for regulating? the: airasupply, means ineludinga normally inoperative pilotvmotor J for adjustingi the regulating means, i means responsive to predetermined conditions ifor icontrolling the adjusting imeans, additionalimeans: controllingtheadjusting means responsive to a the demand: on I the furnace, means for i rendering i one of said i two controlling means ineffective during thaentire per-io'd o'f regulation of Ithezair: supplymeans by 1 the: other controlling means, fuel feed means, and' means for eontrolling the fuel feed uneans responsive to the demandonstheffurnace.

:34. In combination, a furnace fuel feeding'dev-ice,:a ifurnace air f feeding device, separate controllers lfor said devices, means including a normally inoperative I pilot 5 motor for adjusting each of 'sai'd controllers, means responsive to-the-demand: upon thafurnace for governing"both adjusting means simultaneously means *responsi-veto the eiii cienoy of combustion 'for exercising governin-g action upon'one of said' adjusting means, and means'elfectiveat all *times for preventing the simultaneousgoverning action of said-(amendjusting means by both-of 'saidresponsive means.

35. 'Incombinatioma furnace-fuelfeeding device, a furnace air feeding device, separate controllers for said devices, means including a normally inoperative pilot motor for adjusting each of said controllers, means responsive to the demand upon the furnace for governing both. adjusting means simultaneously, means responsive to the efficiency of combustion for exercising governing action upon one of said adjusting means, and means effective at all times for preventing the simultaneous governing action of said last named adjusting means by both of said responsive means, said last named adjusting means being always under the control of one of said responsive means regardless of the condition of the other responsive means.

36. In combination with a battery of furnaces supplying a common load and having variable air supply means and fuel supply means, means including a normally inoperative pilot motor for adjusting each of said means, controlling means common to all of the furnaces for controlling the air and fuel supply adjusting means at the respective furnaces responsive to variations in the load, additional controlling means individual to the respective furnaces for controlling the air supply adjusting means responsive topredetermined conditions, and means individual to each furnace and at all times under the control of one of said controlling means for excluding regulation of the air supply by the other controlling means during the entire period of action of said one controlling means/ 37. In combination with a battery of furnaces, means for regulating the fuel supply to the respective furnaces, means associated with each furnace for comparing its rate of fuel supply with that of another furnace, and means controlled by said last named means for controlling the fuel regulating means of its associated furnace to maintain a predetermined ratio of fuel feed between its furnace and that of the other furnace.

38. In combination with a battery of furnaces carrying .a common load, variable fuel supply means and air supply means for each furnace, means for automatically maintaining a'predetermined fuel to air ratio in each furnace, means for varying the fuel and air supply to the respective furnacesresponsive to variations in the common load, and means for comparing the loads carried by the respective furnaces and for automatically maintaining a predetermined load distribution between the furnaces.

39. In combination with a plurality of furnaces carrying a common load, variable fuel supply means and air supply means for each furnace, means for automatically maintaining a predetermined fuel to air ratio in each furnace, means for varying the fuel and air supply to the respective furnaces responsive to variations in load, and means for comparing the load carried by one of the furnaces with that carried by each of the other furnaces and for maintaining a predetermined ratio between the loads on each of said other furnaces and the load on said one furnace.

40. In combination with a plurality of furnaces carrying a common load, variable fuel upply means and air supply means for each furnace, means for automatically maintaininga predetermined fuel to airratio in each furnace, means for a varying the fuel and air supply to the respective f ratio-between the loads on eachof said other furnaces and the load on said one furnace, .and'

for feeding thereto the elements of combustion,

regulating means for said feeding means, each of said regulating means including a pilot motor normally inoperative, a common means responsive to the demand for effecting a'simultaneous operation of said motors at substantially constant predetermined speeds, and means for adjustably fixing the relative rates at which the regulating means adjust the feeding means, said last named means including adjustable rheostats in the pilot motor circuits for establishing the'relative predetermined pilot motor speeds.

42. A combustion control system comprising in combination with a battery of furnaces having a common demand, each furnace having a plurality of means for controlling the various conditions of combustion, regulating means for each of the controlling means comprising separate pilot motors normally inoperative, a common means responsive toothe demand for effecting a 'simulta neous operation of said motors at substantially constant predetermined speeds, and means for adjustably fixing the relative rates at which the pilot motors of each furnace adjust the controlling means, said last named means including a rheostat in common with all of the pilot motor circuits of each furnace for adjustably establishing the relative predetermined pilot motor speeds. 4 3. A combustion control system comprising in combination with a furnace having a plurality of means for controlling the various conditions of combustion, regulating means for each of the controlling means comprising separate pilot motors normally inoperativameans for effecting an operation of said motors at a substantially constant predetermined speed, and means for adjustably fixing the rate at which the pilot motors adjust the controlling means,said last named means including a rheostat in common with all of the pilot -motor circuits foradjustably establishing the predetermined pilot motor speeds and at least one rheostat individual to a pilot motor circuit for adjusting the relative predetermined speeds of the pilot motors.

i 44. A combustion control system comprising in combination with a furnace having a plurality of means for feeding thereto various elements of combustion, regulating means for each of the feeding means comprising separate pilot motors normally inoperative, means for effecting a simultaneous operation of said motors at a substantially constant predetermined speed, and means for adjustablyfixing the relative rates at which the various regulating means adjust their feeding means, said last means including adjustable rheostats in the various pilot "motor circuits.

; In combination with a furnace, variable means for feeding thereto one of the elements of combustion, said means-including a feeding motor and an adjusting motor, variable means for feeding another element of combustion and including a second feeding motor and a second adjusting motor, a common supply bus for said adjusting motors, separate variable rheostats in the respective adjus ing motor circuits for controlling the relative rates of response of the adjusting motors, means effective responsive to predetermined conditions for simultaneously connecting anddisconnecting the adjusting motorstothe bliSiBilId a variable rheostat in the bus cir'cuitfor Sim-til taneous'lycontrolling the rates of 'response of the adjusting: 1,,

46? In I combinationw'ith a furnace variable means for feeding tlier'eto one of the" elements of combustion,- said means fincludingaresume-me torand' an adjusting motor, variiabl?means for: feedinganother element of combustionand m eluding "a-notlrer feeding "motor and amother iad j justiiig= motor} separatevariable rheostats irrtlie? respective adjusting motorcircuits forcontrolling the relative rates of response of the adjusting motors, and-means for siinultaneously energizing and deenergizing both of said adjusting motors.

47. In a control system, a furnace, fuel supply means and air supply means for the furnace, de-- vices for controlling said supply means, pilot motors for controlling said devices, means for simultaneously closing and opening the circuits of said motors in common, and an adjustable rheostat in the pilot motor circuits for adjusting the rate of response of said motors.

48. In a combustion control system, an electric motor for varying one of the elements of combustion, a controller therefore, adjusting means for said controller including a normally inoperative pilot motor, separate control circuits for the pilot motor each controlled responsive to different predetermined conditions, and means responsive to the control of the pilot motor over one circuit for producing a gap in the other circuit.

49. In a combustion control system, motor driven means for supplying one. of the elements of combustion, means for varying thespeed of the motor driven means said speed varying means being actuated by a normally inoperative pilot motor, means controlled in accordance with variations in predetermined conditions for governing the speed varying means, means controlled in accordance with variations in other predetermined conditions for governing the speed varying means, and means for preventing the simultane ous control of the speed varying means by bothof the governing means.

50. In combination, a plurality of variable speed motors, separate rheostats for varying the speeds of the respective motors, separate normally inoperative pilot motors for controlling the respective rheostats, means for simultaneously energizing and de-energizing said pilot motors and variable resistors individual to certain of the pilot motors for adjustably fixing the relative extents of motion of the rheostats during the period of energization.

51. In combination, a plurality of variable speed motors, separate resistors for varying the speeds of the respective motors, separate normally inoperative pilot motors for controlling the respective resistors, means for effecting an operation of said pilot motors at substantially constant predetermined speeds, variable rheostats individual to certain of the pilot motors for adjustably fixing the relative predetermined constant speeds of the pilot motors, and a variable rheostat in common to the pilot motors for adjusting the predetermined speeds of all of the pilot motors.

in unison.

52. A control system for apparatus having a plurality of factors which tend to vary from predetermined values during operation of said ap ,paratus, means for maintaining said factors at said predetermined values comprising means for cruising an adjustmentof the values of the facto1's;- constant speed normally inoperative pilot'- mdtors v'tfiieliwlien operated tnd to operate said last" means? a oomrnonresistor forad justing the p'red'ete'rnriir'ied speeds of the pilot motors iir coriimongand individual resistors for the respeotlvel pilot motors for adjustably fixing V the" asta -'53'. Iri comib'inationa" furnace having means for feeding thereto the elements of com-'- b ustioma coinfiustion controlsystem comprising eaeh of' said feeding means, to the demandincluding a timing controller for periodically eifecting a simultaneous adjustment of said regulating means, means for adjustably setting the rate at which said last named means regulate said feeding means. to maintain approximately correct proportions of feed during said adjustment, and means responsive to predetermined conditions for effecting individual adjustments of said regulating means to correct the relative rates of feed.

54. In a control system for a furnace, fuel supply means and air supply means for the furnace, devices for controlling said supply means, pilot motors for adjusting said devices, means redetermined' speeds of 5' the pilot for simultaneously closing and simultaneously opening the circuits of said motors in common, and adjustable rheostats in certain of the pilot motor circuits for adjusting the relative extents of adjustment of said control devices.

'55. In a control system for a furnace, fuel supply means and air supply means for the furnace, devices for controlling said supply means, pilot motors for adjusting said devices, means including a timing controller for energizing and 'deenergizing said pilot motors, whereby each of the motors receives energy for a predetermined interval of time, and adjustable rheostats in certain of the pilot motor circuits for adjusting the relative extents of adjustment of said control devices during the interval of energization.

56. In combination with a furnace having means forfeeding thereto the elements of combustion, a combustion control system comprising a regulating means for each of said feeding means, a normally inoperative pilot motor for adjusting each of said regulating means, demand responsive means including a timing controller for energizing all of said pilot motors during a timed interval, and resistors individual to certain of the pilot motors for predetermining the numbers of revolutions of the respective pilot for setting the relative amounts of adjustment of said controllers during each of said equal time intervals.

58. In a control system, a pair of control devices, adjusting motors for said devices, means responsive to predetermined conditions for intermittently energizing said motors, both motors receiving equal periods of energization, and means for co-ordinating the amounts of adjustment of said devices during the periods of energ'mation,

IOI

said co-ordinating-means including an adjustable resistor in the circuit of at least one of the motors. I 59'. 'In combination with a furnace having supply means for feedin thereto the elements of combustion, regulators for said supply means, adjusting motors 'for said regulators, means responsive to the heat demand on the furnace for transmitting intermittent control impulses,. the;

length of each impulse being timed in accordance with predetermined conditions, means forefiecting'energizationof said motors during an interval of a length'determined by theulength of the impulse, and a resistor individual to the circuit of each of said motors for adjustably setting the extents of adjustment of the respective controllers during said-interval of energization.

for said supply means, adjusting means for said regulating means, -contrbl means for effecting adjustments of each of said regulating means during a timed interval and means individual to certain of said adjusting means for adjustably setting the relative amounts of adjustment during said timed interval. a

- ALLEN M. ROSSMAN.

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