US2299727A - Furnace and associated parts - Google Patents

Description

06:27, 1942. w, s, BLAUVELT E 2,299,727 FURNACE- AND kssocn'rnn mi'rs Filed Feb. 1, 1940 3 Sheets-Sheet 1 Zilx //v1 /v TOPS Warren Sifilauvelt Nolan A. Curry A T TOR/V5 Y Oct. 27, 1942. w, s, BLAUVELT AL 2,299,727

FURNACE AND ASSOCIATED PARTS Filed Feb. 1, 1940 a Sheets-Sheet 2 -//vv/v 7-023 Warren 5. Blauvelt No)anA.Cur1y I W%wa %MW Oct. 27, 1 94 2. w, s, uv -r ETAL 2,299,72T

FURNACE AND ASSOCIATED PARTS Filed Feb. 1. 1940 3 Sheets-Sheet 3 l /NV.'N7"0/?-Slt Warren S. B auve Nolan A.Curry y Waf m A 7' TOR/V5) Patented Oct. 27, 1942 FURNACE. AND ASSOCIATED PARTS Warren S. Blauvelt and Nolan A.,Curry, Troy, N. Y., assignors to BlauveltAssociates, Ina, Troy, N. Y., a corporation of New York Application February 1, .1940, Serial No. 316,808

18 Claims.

One of the objects of our invention is the provision of a mechanically operated and automatically controlled solid fuel burning appliance and the method of operating the same which So correlates the delivery of fuel to the fuel bed of the furnace, the removal of ashesfrom said fuel bed and the control of the air supplied to the furnace and of the draft therefrom that will, when burning any selected suitable kind and size of fuel, maintain, during periods when heat is demanded, a substantially uniform predetermined rate of combustion, and will'also maintain during periods when heat'is not demanded (hereinafter referred toas idling) a substantially uniform reduced rate of consumption, merely sufficient to'maintain the temperature in the combustion portion of the fuel bed above the ignition temperature of the fuel used.

A further object of our invention lies in providing, in a furnace of the foregoing character, a system of automatic controls which will maintain substantially constant combustion conditions in' the combustion po'rtion of the fuel bed at the selected rate of combustion thustending to produce substantial uniformity in the composition of the mixture of gases leaving the furnace.

A further object of our invention is to eliminate the possibility of the formation in the fuel bed, by the fusing together of ash particles set free from the fuel during its combustion, of

clinkers too large to readily pass through the openings in, or at the periphery of, the grate.

A still further object of our invention is the limitation to a negligible minimum of the quantity of fly ash particles carried from the fuel bed to the gas passages of the appliance and their deposit therein, during, and for a period after, agitation of the fuel bed for the removal of ashes therefrom.

It is believed that our invention will best be determines the rate at which fuel is burned and heat generated thereby; control of the stoking operation, which includes the conveying of fuel from the fuel storage bin to the fuel magazine of the furnace; the separation of the ash refuse set.

from the unburned fuel therein; and the conveying of such ashrefuse from the ashpit of the barely sufficient draftto maintain the desired" temperature of the fuel bed when idling. Natural draft varies with the outside temperature, and may be notably affected by the direction and velocity of the wind. To substantially, avoid such uncontrolled variation in draft we employ. a motor' driven induced draft fanor exhausterto withdraw flue gas from-the furnace and deliver it to the chimney, said fan being operated at substantiallyconstant speed so as to produce a substantially uniform pressure differential when running. This fan operates only when heat is demanded,,its operation being controlled by the draft control motor which also controls the position of the main air inlet valve which is opened when heat is demanded and closed when the furnace is idling. An idling air inlet valve is also provided which is large enough to admit sufficient air to maintain the desired temperature of the fuel bed during idling periods when combustion is maintained by natural draft. This idling air inlet valve is closed only during the stoking cycle as will be explained later.

To maintain a substantially uniform rate of combustion of a selected kind andsize of fuel with a, substantially uniform draft, that is, with a uniform pressure differential between the spacesimmediately above the fuel bed and immediately below the grate, the depth of fuel in each part of the burning portion of the fuel bed should be kept substantially constant and the total. cross sectional area of the voids between the piecesof fuel, through which air and other gases pass, should also be kept substantially. constant. To meet these conditions, ashes Set free by combustion of the fuel must be removed from the fuel bed at such frequent intervals that ashes, are

never permitted to accumulate on the grate below the burning fuel in such quantity as; to appreciably reduce the depth of burning fuel, and that ashes are never permitted to accumulate in the voids between the pieces of fuel in such quantities as to materially increase the resistance to the flow of airgand other gases through free by the combustion of fuel in the fuel bed the fuel bed. In accordance with our invention the total depth of the burning portion of the fuel bed from its top surface to the supporting grate in each part of said burning portion of the fuel bed is kept substantially constant; the elevation of the upper surface thereof is fixed by the elevation of the lower edge of the fuel magazine and the natural angle of repose of the fuel as it feeds downwardly and outwardly from the magazine by gravity; and the elevation of the bottom of said burning portion of the fuel bed is fixed by the upper surface of the grate, and the fre-" quency of the removal of ashes from the fuel bed is so related to the rate of combustion that the relatively constant conditions in the burning portions of the fuel bed as above. described are.

maintained.

The relatively constant condition of the burning portion of the fuel bed maintained by such method makes possible an exceptionally uniform composition of the flue gases escaping from the furnacewith practicallyno unburned combustible.

and only a' small percentage of free oxygen.

Furthermore the frequent removal of'free ashes. from the fuel bed so limits the quantity of ashparticles coming in contact with each other in any placein the fuel bed'that when fused together the clinker so formed is so'smalll as. to

readilypassthrough the openingsin, or at the.

periphery of, the grate.

The methods employed'and a meansprovided by'our invention for securing the correlation, se-

quence and relative timing'of the variousoperations in the stoking" cycle so as to obtain the results described above will be more clearly understood by'reference to the attached drawings in which-=- Fig. 1 is'a diagrammatic View illustrating: the controls embodying our invention;

Fig. 2 is'a diagrammatic viewillustrating a succeeding position of the shaft and associated-parts and electrical connections of the draft control:

motor;

Fig. 3 is a view similar to Fig.2 illustratinga' further succeeding position of the shaft of the draft controlmotor and'the parts and electrical connections associated therewith;

Fig. 4 is a diagrammatic view illustrating a.

solid fuel furnaceand a'solid fuel magazineleading to the combustion portion of the fuel bed, an

associated follower rod normally resting onthe surface of the fuel bed and illustrating the rela-' tion of the same to the control system for the furnace; i r Fig. 5 is a front view of a cam, secured to the shaft of a pilot motor, which controls the position of the idling air inlet valve and the fuel inlet valvefor the furnace;

Fig. 6 illustrates diagrammatically a second c'am device, secured to the shaft of' a pilot' motor, for controlling the operation of the stoker motor;

Fig. '7 is a front view, somewhat diagrammatic in character, illustrating a conveyor for deliver-- ing solid fuel to the furnace' andan ash conveyor which removes ash from the" furnace and carries air inlet valve 34 and the operation or stoppage Any suitable device which utilizes a deviation from the selected standard temperature or pressure to be maintained, may be used to control the operation of the draft control motor, the connections therewith being so arranged that ordinarily, that is, except as hereinafter explained, any drop below the selected temperature or pressure will cause the draft control motor to place the draft producing elements in a draft on po sition and keep them in such position until the demand for more heat or pressure has been satisfied and will then cause the draft control motor to place the draft producing elements in an idling position until temperature or pressure drops below the selected standard.

To illustrate and describe our invention any one of the usual types of three points, thermostat actuated, switch IO and the electrical connections therefrom to the draft control motor ll may be used. The draft control motor ll so controls the supply of air for combustion to the furnace that the variation of temperature or.

pressure at the point of. control is kept within. While we have illustrated. thev three-point switch. ltljas, a thermostatitwill, of.

desired limits.

course, be understood that a pressure-operated device, or an equastat may'likewise be used. The

draft control motor I l causes a shaft 32, to which it is suitably connected, to rotate at a predetermined rate, preferably between 1 and 4 revolutions per minute. Secured to the shaft, 32 is a cam IS, the periphery of which is generally-circular in form, preferably through an arc of. approximately 330" and is concentric with the center of the shaft 32, the remaining portion of its periphery being occupied by an inwardly extending and preferably 'curved notch I4.

Two conducting spring arms l5 and I6, equipped with suitable contact elements; near their lower ends, (Fig. 1) are mounted onsuitable conducting supports I! and [8, respectively, and

' 3 devices embodying our invention is derived from line conductors 25! and 252 connected through a suitable transformer 253 to conductors 25 and 25a. A fixed contact member 2| is connected through a conductor 23 and conductor to the 7 conductor with the parts in the positions illustrated in Fig. 1, and with the boss l9 resting in the notch M of'the cam l3, thecontact 2| is spaced from the contact element of the conducting spring arm l5. Similarly, a fixed contact member 22 is connected through a conductor 24 to a conductor leading from the fixed contact member 29 of the thermostat I0 to one side of the motor H, the opposite side of which is connected by a conductor 204 to the conductor 2511.

In the position illustrated in Fig. 1, the boss 20 mounted on the arm it rests against the circular portion of the cam I3 and is forced outwardly against the contact 22; The arms I5 and I6 are connected to a jumper connection 26 which is connected to a conductor 21. connected to the arm 28 of the thermostat which cooperates with the fixed contacts 29 and 29a.

In accordance with our invention, the draft control motor I I controls the position of the main substandard temperature causes the thermostat arm 28 to make contact with fixed contact 29a,

and conversely establishing and maintaining an idling conditionwhen a temperature above standard causes the thermostat arm 28 to make contact with fixed contact 29. The operation of the draft control motor II is also interlocked with the operation of the pilot motor 45 which in turn controls the starting and stoppingof the stoker motor 88; the methods of this interlocking and purposes thereof are fully described later.

A crank arm 3| (Fig. 4) provided with a crank pin 31! issecured to a shaft 32, actuated by the draft control motor II, preferably through a speed reducing mechanism, and pin 3 is connected by a flexible element, such as a cable 33, to the main air inlet valve 34 shown pivotally mounted above a draft opening 35 (Fig. 4), the cable passing over suitable idlers 36 and 31 so that when the draft control motor is in the position illustratedin Fig. 4 and indicating a demand for heat, the main air inlet valve is open. A crank arm 38, whch may be secured to the end of the shaft 32 opposite to that to which the crank arm 3| is secured, controls switches which, in turn, control the operation of the draft fan motor 44 and prevent the operation of thepilot motor 45 except when the draft fan motor 44 is shut off and the main air inlet valve 34 is closed. A crank pin 38! mounted on the end of the crank arm 38 is connected by a chain 39 or other flexible connection to the upper end of an inclined arm 40 pivoted at 4|, on which are mounted two mercury switches 42 and 43 provided with respective contacts. The contacts in the switch 42 are closed when the arm is inits raised position and corresponding to a position where the main air inlet valve is open thereby closing the circuit to the fan motor 44 when the main air inlet valve is open. At the same time the contacts of the mercury switch 43 are open. The circuit to the fan motor 44 is thus closed through the switch 42 so long as the demand for heat continues and provided another control device, hereinafter described, does not operate to cause motor H to open switch 42. The startingcircuit for the pilot motor 45 includes contacts disposed'at the raised end of the mercury switch 43 so that such circuit is open when the parts occupy the positions indicated in Fig. 1 thereby precluding the possibility of operating the stoker motor when the main air inlet valve 34 is open and the draft fan motor 44 is running.

In accordance with our invention means are provided for conveying a substantially uniform" predetermined quantity of fuel from thestorage bin to the fuel magazine of the furnace whenever the top surface of the fuel therein subsides below the selected elevation. In the embodiment of our invention illustrated, a follower rod 46 (Fig. 4) passes through an opening 41 in the top cover 48 of the fuel magazine, the lower end of the follower rod normally resting on thetop surface of the fuel 49 in the magazine 50. The upper end of the follower rod is connected by a cable 5| to a crank pin 52 on a crank arm 53mounted on a arm 53 when said crank arm 53 is in the position shown in Fig. 4i. The upper end of an inclined bar 58, .pivotally mounted as at 59 on a bracket 59a secured to the fuel magazine 50, is so ari ranged as to assume the position illustrated when the end thereof, which is located in the path of movement of a cross bar 51 mounted above follower rod 46, is not depressed thereby.

shaft 54 actuated by the pilot motor 45', the cable r 5! passing over suitable idlers 55 and 56. As combustion of the fuel in the furnace proceeds, the surface of the fuel 49 subsides and the follower rod 48, being free to move vertically, descends, sufficient slack being provided in the horizontal portion of the cable to permit the follower rod to trated,

When the follower rod descends the inclined bar 58 is tilted counter-clockwise as viewed in Fig. 4 thereby opening the circuit between a first pair of contacts indicated at 81R in a switch 6|, mounted on said bar, which contacts are included in circuit with the conductors 202 and 283 in the starting circuit of the draft control motor 1!. This movement of bar 58 also causes a circuit to be closed between a second pair of contacts indicated at GIL in switch 6!, which contacts are respectively connected to conductors 2fl5and 208 which in turn are connected to the, conductors 38 and 21, respectively. A closure of the circuit through said second pair of contacts GIL and conductors 205 and 206 serves to effect an actuation of the draft control motor ll to place the arm 38, operated thereby, in the position in which the switch 42 will be open, or,

in other words, the motor II will be actuated to place the draft control elements in the idling position, and will then hold them in that position as long as said closure of the circuit is maintained through the contacts BIL of switch El.

We have illustrated in Fig. 7 a preferred device for stoking the furnace which comprises means for delivering fuel to the furnace and means for shaking the ashes from the fuel bed and removing the same from the furnace room, which stoking device is controlled by the follower rod, above described, which operates in response to subsidence of fuel in the fuel-magazine or fuel bed of the furnace.

The furnace is provided with a hopper 82 the mouth 83 of which may be inclined as illusthe hopper communicating with the magazine 50. The fuel conveyor, indicatedgenorally at 84, passes over a driving sheave 85 on a shaft 88, both the fuel conveyor 84 and the ash conveyor indicated generally at 81 being driven by a common motor 88 through suitable reduction gearing 89. The fuel conveyor preferably comprises spaced blades or vanes 90 (Fig,

8) suitably secured by supporting brackets 9| to an endless chain 92 which passes over an idling s sheave 93 located adjacent the mouth of the hopper 82 and is so arranged that the fuel conveyed thereby is delivered to the hopper as the conveyor element approaches the idler 93. In

the form of our invention shown, the upper flight of the fuel conveyor is substantially horizontal,

" the other two flights thereof extending downwardly beneath the fuel chute l4l leading from the fuel storage bin as illustrated in Fig. '7.

The ash. conveyor 8'! is preferably in the form of a straight link chain 95 which passes over a driving sheave (not illustrated) on the shaft 86 and over a sheave 95 mounted near the bottom and outside of the furnace as illustrated in Fig. 7. The upper flight 95! of the chain 35 passes through the bottom of the ash pit of the furnace and thence upwardly through an inclined tube 91 from the upper end of which ash is delivered to a chute 9H1 leading to a suitable re ceptacle (not illustrated). The lower flight 952 of the chain passes downwardly from the sheave on the shaft 86 and beneath the floor 98 of the descend independently of its connection to the ashpit of the furnace. The details of the ash conveyor are more fully illustrated in app ication Ser. No. 275,612 which was filedby Warren S.

Blauvelt in the Patent Office on or about May 25, 1939, and issued June 3, 1942, as Patent No. 2,244,442.

In a preferredarrangement of the furnace, the shaft upon which the sheave 96 is secured has also secured thereto a crank arm 952 which is arranged to rotate and reciprocate the grate 953, upon which the fuel bed rests, through the medium of links 864 and 965 and bell crank 966. Hence, while the stoking device is operated, supplying fuel to the magazine, the grate is moved, thereby agitating the fuel bed and permitting the ashes which have been separated fromthe burning fuel to fall from the grate to the ash pit, and the ash conveying element of the stoking device removes said ashes therefrom to the ash receptacle.

Further, in accordance with our invention, the

follower rod 46 and associated devices which are,

operated thereby not only control the draft control motor I! but also control the pilot motor 45 which, in turn, controls the circuit to the stoker motor.

In the illustrated embodiment of our invention, the inclined arm 58 carries switch 8!, above described, and a second switch 65. When the follower rod, with the projection 51 thereof engaging the free end of the pivoted bar 58, descends a predetermined distance, the inclination of the two mercury switches 60 and 6| is reversed from that illustrated and, therefore, the mercury in both switches 60 and 6| will flow to the opposite ends thereof. Switch 60 has electrical contacts in one end only and is connected in circuit with mercury switch 43 and the pilot motor 45. The switch 60 is closed only when the follower rod 46 is in its lowered position, indicating a need for additional fuel in the magazine, and, when the movable. end of the pivoted arm 40 is in its lowered position, switch 43 also is closed and when both of these switches are closed a ircuit to pilot motor 45 is established.

In effect, therefore, the pilot motor 45 is primarily controlled by the follower rod 46 and can start only when the follower rod is down, indicating a need for a charge of fuel. Of course, when the rod 46 drops sufiiciently to closed switch 55, switch 6! will be actuated to close the circuit through the contacts BIL and through conductors 205 and 206 thereby effecting an actuation of motor H to idling position or, in other words, motor II is actuated to raise crank arm 3! thereby closing the air inlet Valve 34, and depressing crank arm 38 thereby opening the circuit through switch 42 to draft fan motor 44 and closing the circuit through switch 43 to pilot motor 45.

With the foregoing arrangement, it will be seen that if the fan motor is in operation when the follower rod 45 drops and closes the switch 60, the pilot motor 45 cannot operate to close the switch to the stoker motor because switch 43 is open. However, when switch 68 is closed, the contacts (ML of switch 8! also close the circuit through conductors 205 and 205 and thereby effect an operation of motor H to stop the fan motor, and motor I! in this operation, also closes the switch 43 and the pilot motor 45 can then operate to place the stoker motor in operation. Switch 42, controlling the fan motor and switch 43 may be so arranged that switch 42 opens substantially when switch 43 closes.

In the foregoing, we have described the cirthe draft control motor This circuit serves initially to, connect motor 45 across the line when the. fuel in the fuel magazine has subsided to a predetermined elevation. In addition we provide a second circuit for the pilot motor 45 which functions to continue the operation of motor '45" after such operation has been started by the" closure of the circuit through switches 6B and 43, if said circuit should subsequently be opened, until the shaft 54 driven by said motor 45 shall have been caused to rotate approximately one" complete revolution. This second or shunt cir-' cuit comprises a conductor 209 which is connected between the line'conductor 25 and the resilient conducting arm 2H1 of a switch indicated generally at 268. Arm 2|EI is provided with a contact adaptedto engagea contact mounted on a second but relatively fixed conducting arm 2 I! of switch 208. Arm 2 is also provided with'a boss 2|2 which is held in engagement with the periphery of a cam 2E3 mounted upon and ro-' tatable with shaft 54 which is rotated by pilot motor 45, preferably through a suitable speed reducing mechanism. Cam 2|3 is provided with a recess 2|4 in which boss 2|2 lies when cam 2! 3 is in the position shown, which is its position during periods when motor 45 is not operating.

Vlith this arrangement, an energization of motor 45 through the closure of switches 43 and 6!] will produce rotation of cam 2|3 thereby forcing boss 2|2 out of the recess 2! 4 in the cam surface and maintaining the contacts on the arms 2!!) and 2! I in engagement with each other during substantially a 360 degree movement of rotation of shaft 54. The engagement of the contacts on arms 2H! and 2H closes a circuit from line conductor 25 through conductor 203, arms 2H] and 2| l and a conductor 2l5 which is connected from arm 2H to one side of motor 45, the other side of the motor being connected directly to the other line conductor 25a. Hence, the second or shunt circuit will maintain an operation of motor 45, after it has been initially energized, to effect approximately one complete revolution of the cam 2l3 and shaft 54.

The shaft 54 which is actuated by the pilot motor 45 has mounted thereon a crank arm 53 provided with the crank pin 52, as hereinbefore described. To this crank pin is connected the' cable 5| which, at the other end thereof, is con-' nected to the follower rod 46. A second cable 5|! is connected to crank pin 52 and to a lever 2|! which is pivotally supported at one end. thereof as indicated at 2|8. Upon lever 2!! is mounted a switch 200 which is so arranged that when the crank arm 53 lies in its raised position the switch is closed and, when the crank arm is lowered, the inclination of switch 200 will be reversed and the switch will be opened. The contacts of switch 20!) are respectively connected.

surfaces 153.

elements may be fixed thereto.

2.2 .7 7 that the follower rod 48 is held in a raised pothereby preventing any operation of the fan mo- 3 tor while the stoker motor is in operation.

Upon the shaft 54 driven by pilot motor 45, are also mounted two cam elements 62 and I5. Cam B2 is designed to effect an opening and closing of the fuel gate 68 in the chute 82 leading to the fuel magazine and cam is designed to control the circuit to the stoker motor 88. An arm 63 controlled by cam 62 is connected bycable 65 passing over pulleys B6 and 61 to the fuel gate 68.

The arm 63, pivoted at one end as indicated at 64 in Fig. 5 so that it can move radially in a vertical plane, is provided with a suitable weight 631 which suffices to keep the outer end. of the arm 63, which may be provided with a roller 632,1

riding upon and supported by the surface of the cam 62. Except as explained below,'cam 62 is stationary as shown in Fig. 5 supporting the pivoted arm 63 in its elevated position, in which position thereof the fuel gate 68 closes the open ing through which fuel is supplied to the magazine. However, when motor 45 starts and in its operation causes shaft 54 to revolve in a counter clockwise direction, cam 62 will permit arm 63 to plete revolution. Furthermore, if both cam ele- I ments are adjustable relative to shaft 54, the

interval during which arm 11 is lowered may be varied witth respect to the interval during which the cam is actuated. A switch 18 is mounted upon arm 11 and is connected by means of conductors 8H and M2 in circuit with the stoker motor 88 which operates the fuel supplying and ash removing devices. When arm 11 is lowered and the lip 19 thereof lies within the notch 16, the switch 18 is closed and, of course, when the lip engages the surfaces 'I5l of the cam elements, the switch is open.

In connection with the cams 62 and 15, above described, it should be noted that, due to the provision of switch 208 which maintains the operation of the pilot motor45 after it has once started, each cycle of operation of said motor comprises one complete revolution of the shaft 54. Hence, generally speaking, cams 62 and 15 may be so constructed and arranged upon the shaft 54 that an operation of the devices controlled thereby may be eifected simultaneously or in substantially any desired sequence and the time interval during which the cams operate the various devices may be adjusted relative to the interval during which the pilot motor 45 isoperated or, in other words, they may be fixed to operate their associated devices during any debe lowered under the force exerted by the weight.

63! and fuel gate 68 will thereby be raised.

In the embodiment of our invention herein illustrated, the furnace is provided with a second air inlet opening 14 which is designed to be closed during the period when fuel is supplied to" 1 the magazine but which is otherwise open. A closure element 13 for the opening 14 is connected by means of a cable 10 to the cable 65,

cable 70 passing over pulleys II and 12 and the cables being fastened together as illustrated at some point intermediate pulley 61 and fuel gate 68. Hence, whenarm 63 is elevated by cam62 the closure element 13 is elevated to permit air to enter through the opening 14 but, when arm 63 is lowered, element 13 is also lowered and effects?- a closure of the air inlet opening 14.

The cam 15, which is also mounted on shaft 54, is preferably formed of two similar cam elements. These elements comprise generally circular surface portions 'l5l and 152, the surface 151 having: 2

a larger radius than the surface'l52 and these surfaces being connected by intermediate, sloping Both of said cam elements may be adjustably fastened on shaft 54 or one of said face which may be varied in length up to sub-- stantially the length of the cam surface 152. A lever arm 11 having a depending lip 19 of sulficientwidth to engage both of the cam elements of cam 15 is pivotally supported at one end as indicated at 191 with the lip thereof in engagement with the surface of cam 15. Hence, when cam 15 is rotated, arm 'l'l will be lowered when it leaves the surface 15! and enters the notch" and will again be raised when it engages the intermediate surface 153 and passes to the surface 151. By varying the extent of the notch 16, therefore, the time interval during which arm 11 is lowered may be varied with respect to the time However, by

interval during whichthe cam makes one com- (5 sired part of the cycle of operation of said pilot motor.

We prefer so to arrange our control system that an operation of the draft fan motor cannot occur until after a short interval has elapsed following the terminationof an operation of the stoker mechanism. This time interval is preferably sumcient to permit at least the largerash particles to settle upon the fuel bed, after a shaking operation of the grate, before draft is supplied to the furnace.

The ability to vary the period of operation of the stoker motor 88, thereby varying both the quantity of fuel delivered to the magazine in each cycle of operation, and the quantity of ashes setfree in the fuel bed by the burning of a like quantity of fuel during the elapsed period from the preceding stoking operation, makes it possible to avoid such an accumulation of ashes in the fuel bed as would appreciably affect com-bustion conditions therein. Lengthening the period, of course, increases the charge in each cycle .and shortening the period decreases the charge. In practice it is found that about 6 oz. of free ash may be permitted to accumulate in a fuel bed having a grate with an area of 1 sq. ft. Hence, to maintain uni-form combustion conditions when using high ash fuel the quantity of fuel delivered in each charge is preferably less than would be the case if a low ash fuel were being supplied. In addition to having means for adjusting the proportion of time of stoking to the time required for the complete cycle, we may also provide an adjustable fuel supplying device (not illustrated) by which the quantity of fuel delivered to the fuel conveyor per linear foot of movement thereof may be varied. 1

The operation of the device embodying our in? the draft off position and that the bi-metallic arm 28 of thermostat [0, due to a drop in tern"- perature, engages the contact 29a, a circuit will be completed to motor ll provided switch 200 and contacts BIR of switch '61 are in their closed positions to complete the circuit through conductors 282 and 233. The switch 200isactuated by crank arm 53secured to. shaft 54 actuated by motor 45 and is so arranged that the circuit therethrou'gh is broken when the stoker motor 88 is in operation. Switch BI is mounted on the lever 58 which is tilted by the fuel-follower rod 46 and, in the position illustrated in Fig. 4, the contacts GIR at the lower end of the mercury switch BI complete a circuit through switch 200,

and the thermostat Ii) to the motor II. This circuit through contacts MB of switch BI is normally closed but when the fuel in the magazine has subsided sufficiently to allow the follower rod to reverse the inclination of the lever 58, theforegoing circuit is broken at the contacts SIR of switch 51 and an operation of draft control motor I I to draft on position is prevented.

However, ordinarily when arm 28 of the thermostat engages the contact 29a the circuit to motor I I. is completed as follows: from the leg 25 of the main line conductors through conductors and 252, through contacts SIR of switch 6!, conductor 2I9 and switch 200, conductor 203 to contact 2911 and thence through arm 28, con-.

ductor 2T, jumper connection 26 and spring arm 16, engaging contact 22, and through, conductor 24 to one side of the motor II, the other side of themotor being. connected through conductor 204 to the other leg 25a of the main line conduc- When motor II commences to rotate, the

Hence one side of the motor and, therefore, continuous operation of the motor is insured until the crank arm 3| and shaft32 have revolved through 1 80" at. which position thereof the cam-engaging boss 20 on arm I'6 drops into the recess I4 of cam I3 and thereby breaks the circuit be'tween arm IG and contact22.

When sufiicient heat has been developed by the furnace, the bi-metallic arm 28 of th ermostat I0 engages contact 29 to effect an operation of motor II to its idling position. Since in the last described position of cam I3, inwhich position thereof the motorll and crank arms 3| and -38 are in the draft on position, a circuit from leg 25 of the main lines had been created through conductors 20] and 23, contact 2|, arm

I5,,J'umper 26 and conductor 2'I-to the bi-metallic arm 28, engagement of arm 28 with con tact 29 will complete a new circuit to the motor including the foregoing described partial circuit and conductor 30 which connects contact 29 with one side of the motor. After the crank arms and shaft 32 have revolved through a second arc of 180, the bossv I9 again drops into the notch I4 thereby breaking the circuit between contact 2| and arm I5 and reconnecting the motor I! in the circuit including contact 29a; in other words, the circuit is again closed for operating the motor II when the arm of the thermostat engages contact29a. V s v The above described circuits embody devices which control the normal operation of the furnace through a cycle wherein the furnace is operated under forced draft and under idling conditions and this cycle of operation is carried out under heat and no;heat demands, respectively, to;

which the thermostat I0 is responsive. The opconductors 2 05 and 206 i closed which serveslas a direct connection betweenthe bi-metallic arm 28 and contact 29 and, therefore, Whenthis circuit is closed through the actuation of switchfil, the motor I I is actuated to move the crank arms 3| and 38 to idling position. With the foregoing arrangement, draft will be cut off and a stoking operation may occur. V

While we have described a draft control motor II which is driven in the same direction and associatedmeans which permit combustion under draft to take place after the shaft, actuated by .said motor, has made one half revolution, and

which stop such combustion and permit a stoking operation to take plac after the shaft, operated by said motor, has made another half revolution, it will, of course, be understood that the same result may be accomplished by a reversible or other two positional motor, and that the motor and associated parts are intended to illustrate one embodiment of our invention.

7 Since switch 60 will be closed when the last described circuit is made through contact BIL of switch 61 which, of course, has no utility in the event motor II is, at this time, in the idling position, the circuit to the motor 45 which controls the stoking cycle is closed through switch 60. In series with switch 60 is asecond switch 43 which is closed only when arm 49 uponwhich it is mounted, has an inclination the reverse of that shown. Hence, switch 43 will be closed when themotor II is in idling position and, therefore,

motor 45 cannot effect a stoking operation unless the draft is cut off to the furnace. Assuming that switch 43 is closed and that th fuel-follower rod 46 effects a closure of switchBO, the circuit to motor 45 will be completed and a continued operation of motor 45 to effect a rotation of the shaft 54, actuated thereby, through 360 is linsured by the provision of the automatic switch indicated generally at 208 which shunts the switches 43 andBfl following an initial 'energization of motor 45 through a closure of these switches. A rotation of shaft 54 through 360, of

course, serves through themedium of associated devices, he reinbefore described, to close and open the idling airinlet port I4, to open and close, the fuel gate 68 in the chute to the fuel magazine,

to raise and release the follower rod 46, to close and open the switch 78 which controls the stoker motor 88 and open and close switch 200. By raising and releasingthe rod 46, the depth of fuel inth magazine may be gauged and if an insufficient amount of fuel has been supplied to the magazine, the rod will again close switch 60 and effect another operation of motor 45 through a stoking cycle.

It will be observed that with the foregoing arrangement of circuits, draft will be out off to the furnace under all circumstances when the fuel-follower rod moves to a position indicating that a stoking operation should occur to supply fresh fuel tolthe furnace and that before the stoking operation occurs an actuation of the motor II to draft-off position, will take place. When, however, a stoking operation commences, the draft cannot be turned on and automatic control of the furnac by the thermostat is temporarily suspended during the stoking operation. In this connection it will be noted that when the motor45 is energized to effect a stoking operation, switch 260 is opened and, therefore, th circuit to motor II is opened and an actuation thereof cannot occur to open the drafts and closethe circuit tothe draft fan motor 44.

It will also be noted that in the cycl of operation of motor I I, shaft 32 is rotated first through 180 and then through another 180". When the shaft rotates through the first 180, for example, it sereves to open air inlet valve 34, close switch 42 and open switch 43.,thereby supplying draft to the furnace and preventing an operation ofthe pilot motor 45. When the shaft rotates through the second 180, it functions through associated means to close the main inlet valve 34, to open switch 42, cutting out the fan motor 44 and closing switch 43 in the circuit to pilot motor 45.

It will be understood that the term fuel bed as employed in the appended claims is used in its usual sense and, as applied to the embodiment of our invention herein illustrated, is intended to designate the bed of fuel which is above the grate and within the fuel magazine.

While we have described our invention in its preferred embodiment, it is to be understood that th words which we have used arewo-rds of description rather than of limitation and that changes within the purview of the appended claims may be made withoutdeparting from the true scope and spirit of our invention in its broader aspects.

What we claim is:

1. In a control system for a furnace comprising a grate adapted to support a bed of fuel, electrically operated means for producing a draft through said bed of fueLmeans for supplying fuel to the bed of fuel, means for controlling the draftproducing means, means for preventing an operation of said fuel-supplying means while said draft-producing means is in operation, means for preventing an operation of said draft-producing means while said fuel-supplying means is in operation, and means operable in response to subsidence of the fuel in said furnace for operating said two last mentioned means.

2. In a control system for a furnace comprising a grate adapted to support a fuel bed, an electrically operated means for producing a draft through said fuel bed, means for supplying fuel I to said fuel bed, a thermostat for controlling the operation of said draft-producing means, a switch for controlling the operation of said fuel-supplying means and a switch in the circuit of said electrically operated draft-producing means, and means including a common means operable in response to the subsidence of fuel in the fuel bed of said furnace for effecting an operation of both of said switches.

3. In a control system for a furnace comprising a grate adapted to support a fuel bed, an electrically operated means for producing a draft through said fuel bed, means for removing ashes from said fuel bed, a thermostat for controlling the operation of said draft-producing means, a:

switch for controlling the operation of-said ashremoving means and a switch in the circuit of said electrically operated draft-producing means, and means including a common means operable bed of said furnace for effecting an operation of both of said switches whereby to opena first thereof and to close the second and to open the second and close the first.

4. In a control system for a furnace comprising a grate adapted to support a fuel bed, means for producing a draft through said fuel bed, means for removing ashes from said fuel bed, means for controlling the operation of said draft-producing means, means for controlling both the operation of said draft-producing means and the operation of said ash-removing means, said control means being operable in response to subsidence of fuel in the fuel bed of said furnace to terminate an operation of said draft-producing means if in operation and to effect an operation of said ashi removing means, and means for delaying an operation of said draft-producing means for a time interval after the operation of said ash-removing means has terminated.

5. In acontrol system for a furnace comprising i a grate adapted to support a bed of fuel, electrifor opening and closing said main air inlet valve;

said control means being so correlated and arranged that said main air inlet valve will be open when said draft-producing means is in operation and will be closed when said draft-producing means is inoperative, an idling air inlet port in said furnace and a valve therein adapted to admit air to support combustion of fuel in the fuel bed, means for removing ashes from said fuel bed, means for controlling the operation of said ashremoving means, and control means for opening and closing said idling air inlet valve; said last mentioned control means and said means for controlling the operation of the ash-removing means being so constructed and arranged that said idling air inlet valve will be closed during and for a brief time interval after an operation of said ash-removing means.

6. In a control system for a furnace comprising a grate adapted to support a bed of fuel, electrically operated means for controlling the draft through said bed of fuel, means for removing ashes from said bed of fuel, a thermostat, a switch connected in circuit with said draft-controlling in response to the subsidenceof fuel in the fuel means, a first electrical means electrically connected with and controlled by said thermostat and operatively associated with said switch for opening and closing said switch, an electrical circuit including a second electrical means for controlling the operation of said ash-removing means, and a switch in said circuit operatively associated with said first electrical means whereby to be opened and closed thereby; said switches being so constructed, correlated and arranged that an operation of said first electrical means will open one thereof and closethe other.

7. In acontrol system for a furnace comprising a grate adapted to support a bed of fuel, electrically operated means for controlling the draft through said bed of fuel, means for removing ashes from said bed of fuel, a thermostat, a first switch connected in circuit with said draft-controlling means, a first electrical means electrically connected with and controlled by said thermostat and operatively associated with said switch for opening and closing said switch, an

electrical circuit including a second electrical from, movable means associated with said pasremoving means for a time interval, a second switch in said circuit operatively'associated with said first electrical means wherebyto'be opened and closed thereby; said firsta'ndsec'on'd switches being so constructed, correlated and'arr'anged that an operation of said'fir'st electrical means will open one switch and close the other, and means operable in response to subsidence of fuel in said furnace for closing the electrical circuit to said second switch and for effecting an operation of said draft controlling means to--prevent the'passage of a draft through said bed of fuel.

8. In a control system for a furnace comprising a grate adapted to support a bedof fuel, electrically operated means for producing a draft through said bed of fuel, electrically operated means for regulating thequantity of material on said fuel bed, thermostatically controlled means for controlling the operation of said draft-producing means, means for controlling the operation of said material-regulating means, a pair of switches connected in circuit with said last'mentioned means, one ofsaid switches being associated'with and operable by said thermostatically controlled means to effect a closure of said switch when an operation of said'draft-producing means is stopped, and means operable in response to subsidence of fuel in the fuel bed of said furnace for closing the other of said pair of switches and 1 bed for the flow therethrcugh of airto said fuel bed and-the flow of products of combustion therefrom, movable means associated with said passage forming means and operable to passair and substantially to prevent the free passage of air to said fuel bed, a' first control'means for said second mentioned means, means for supplying 'fuel to said bed of fuel, and a second control means operable in response to subsidence of fuel in the fuel bed of said furnace for controlling an operation of both said second mentioned means and said fuel-supplying means; saidfirst and second control means being so constructed, correlated and arranged as to prevent the supply of air to said fuel bed When'said fuel-supplying means is in operation.

10. In a control system for a furnace compris- "ing'a grate adapted to support a fuel-bed, means for removing ashes from said fuel bed, 'means forming a passage above and below said fuel bed for the flow therethrou'gh of air to said fuel bed and the flow of products of combustion therean operation of both said third mentioned'me ans and said ash-removing means; said first and second control means being so constructed; correlated and arranged as to prevent the supply'of air to said fuel bed when said ash-removing means is in operation.

11. In a control system for a furnace of the character described comprising a grate adapted "to-support a fuel bed; means for producing a means for maintaining an operation of said ash- -draft through said fuel bed, means for supplying fuel to the bed of fuel, a first means for controlling the operation of said draft-producing means, and-a second means operable in response to subsidence of fuel in the fuel bed of said furnace for controlling-both the operation of said fuel-supplying and said draft-producing 'means; said first and second control means being so constructed, correlated and arranged as to prevent the operation of said draft-producing means when said fuel-supplying means is in operation.

12. In a control system for a furnace of the character describedcomprising a'grate adapted to support a fuelbed, means for removing ashes from said fuel bed, means for producing a draft through said fuel'bed, -a first means for controlling the operation of said draft-producing means, and a second means operable in response to the subsidence of 'fuel in said fuel bed for controlling both the operation of said ash-removing an'd said'draft-producing means; said first and second control means being so constructed, correlated and arranged as to prevent the operation of said draft-producing means when said ash-removing'means is in operation.

13. In a control system for a furnace of the character described comprising a grate adapted to support a bed of fuel, means for supplying fuel to the bed of fuel, a first electrical operating means therefor, means for producing a draft through said bed of fuel, a second electrical operating means therefor, a thermostat for controlling said second electrical operating means, electrical circuits including said clectrical operating means and electrical means for controlling the circuits thereto; said last mentioned means being operable to open the circuit to said second electrical operating means when closing a circuit to said first electrical operating means.

14. In a control system for a furnace comprising a grate adapted to support a fuel bed, means forming a passage above and below said fuel bed for the flow therethrough of air to said fuel bed and the flow of productsof combustion therefrom, movable means associated with said passage-forming means and operable to pass air and substantially to prevent the free passage of air to said fuel bed, control means for controlling the operation of said second mentioned means, means for supplying fuel to said bed of fuel, control means for controlling the operation of said fuel-supplying means and means for preventing an operation of said second mentioned means to pass air tosaid fuel bed while and each time said fuel-supplying means is in operation.

15. In a control system for a furnace comprising a grate adapted to support a fuel bed, means forming a passage above and below said fuel bed for the fiow therethrough of air to said fuel bed and the flow of products of combustion therefrom, movable means associated with said passage-forming means and operable to pass air and substantially to prevent the free passage of air to said fuel bed, control means forcontrolling-the operation of said second mentioned ing a grate adapted to support a fuel bed, means bed, means for controlling the operation of said ash-removing means and means for preventing an operation of said draft-producing means While andeach time said ash-removing means is in operation.

17. In a control system for a furnace comprising a grate adapted to support a fuel bed, means for producing a draft through said bed of fuel, means for controlling said draft-producing means, means for removing ashes from said fuel bed, means for controlling the operation of said ashremoving means and means for preventing an operation of said draft-producing means when said ash-removing means is in operation, and for a time interval after an operation of said ash-removing means has terminated.

' 18. In a control system for a furnace comprising a grate adapted to support a fuel bed, an electrically operated fuel-supplying means including a tubular chute arranged to pass fuel to the fuel bed, means for controlling the admission of air to said furnace for combustion purposes, a valve arranged in said chute substantially to prevent, when closed, the flow of gas through said chute, electrical means for controlling the operation of said fuel-supplying means and for effecting an opening and closing of said valve in said chute, and means for actuating said air-control means substantially to prevent the admission of air to the furnace for combustion purposes when said valve in said chute lies in other than substantially closed position.

,WARREN S. BLAUVELT.

NOLAN A. CURRY.

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