US2584235A - Automatic control means for stokers - Google Patents

Description

Feb. 5, 1952 J. s. SKELLY AUTOMATIC CONTROL MEANS FOR STOKERS 4 Shecs-Sheet 1 Filed April 50, 1948 i w F INVENTOR John S Skelly flafin ai ATTORNEY Feb. 5, 1952 J. s. SKELLY 2,584,235

AUTOMATIC CONTROL MEANS FOR STOKERS Filed April so, 1948 4 Sheets-Sheet 2 INVENTOR John S. Skelly Feb. 5, 1952 J. s. SKELLY AUTOMATIC CONTROL MEANS FOR STOKERS 4 Sheets-Sheet 5 Filed April 50, 1948 Stoker Drive Motor Speed Adjuster INVENTOR John S Skelly BY ATTOR Y Patented Feb. 5, 1952 UNITED STATES orF AUTOMATIC CONTROL S FOR .STOKERS corporation of Delaware Application Apri130, 8, Serial No. 24,13

'6 Claims.

My invention relates to the control of stokers which feed and burn coal or other fuel in furnaces utilized by steam generating boilers and/or other heating systems.

Broadly stated the object of my invention is to provide means for automatically controlling the operating rate of such stokers including underfeed stokers equipped with an open-top retort having a screw-type fuel feeder and a reciprocating fuel pusher bar organized in the general manner disclosed by my U. 3. Patent 2,049,688 of August 4, 1936, for Fuel Burning Device.

A more specific object is to provide improved means responsive to stoker-supplied heat demand for effecting an automatic control of stokers such as are referred to above when same are equipped with variable-speed-drive mech nisms organized as disclosed by my U. S. Patent 2,070,756 of February 15,1937, entitled Variable Speed Drive for Mechanical stokers.

Another object is to overcome certain deficiencies in prior systems of automatic stoker control such as that disclosed by my 'U. 5. Patent 2,199,012 of April 30, 1940, entitled Automatic Control Means for stokers.

A further object is to effect the foregoing automatic control of stoker operating rate in such' an improved way as to avoid wastage of fuel, minimize smoke and increase fuel burning efficiency.

A still further object is to accomplish the desired control through the medium of apparatus which is low in cost, simple and compact in construction and reliable and trouble-free in operation.

Other objects and advantages of my invention will become apparent from the following description of illustrative embodiments thereof when read in conjunction with the accompanying drawings wherein:

Figure 1 is a view in longitudinal vertical sec tion of a stoker equipped with my improved automatic control and serving to fire a boiler which generates steam for heating and/or other purposes;

Figure 2 is a front elevational view (enlarged and looking from the 'left in Figure 1) of the stokers operating and speed adjusting mechanism, some parts being shown in section on line 22 of Figure 3 to illustrate construction details;

Figure 3 is a side view, taken'on line 3-3 of Figure 2, of the stoker driving mechanism showing my improvedspeed-selecting facilities applied thereto;

Figure 4 is a diagram showing the electrical connections between the control instrument (pressure-responsive here) and the speed-augusting motor (on the stoKer) governed thereby pursuant to this invention;

Figure 5 is a front view of an instrument case in which the main control, step-timer and selector devices utilized by my invention may conveniently be housed;

Figures 6 and '1 are front and side views which correspond to Figs. 2 and 3 and which disc ose another organization for the stokers speed-selector actuating parts; and

Figure 8 is a diagrammatic showing of how the rearranged parts appear when viewed from line 8-8 of Fig. 6.

The drawings hereof show my automatic control improvements applied to an underr'eed stoker whose organization is broadly similar to that disclosed and claimed by my earlier Patent 2,049,668 (of 1936) above identified. This showing is merely illustrative and is not to be considered as restrictive; as the description proceeds it will become evident that my automate control improvements also are useful with adjustable-speed stokers of other designs.

The illustrative stoke) to be benefited In the stoker construction illustrated, a wind 'box 9 organized as in my earlier Patent 2,049,668

of 1936 supports the stokers open-top retort it within the combustion chamber of a furnace 3. Coal or other fuel (not shown) is supplied to the retort from hopper il outside the furnace by way of conveyor tube I2 extending through the furnace front wall i3. Fuel conveyor screw i i within the tubeis rotated by motor l5 (or other power means) through reduction gearing IS, the screw speed (relatively slow as several R. P.1M.) being selected by lever ll to provide the desired rate of fuel supply. Entry of conveyor tube I2 into the retorts end wall i8 is somewhat above the retort bottom as shown.

Extending lengthwise of the retort I!) just above bottomwall is the stokers fuel feeder bar 22 which passes through front end wall is below conveyor tube 12. As here shown, this feeder bar 22 rests on end bearing plates 23 and has the non-packi ng cross section taught by my U. S. Patent 2,433,713 of December 30, 1947, for Stoker Pusher Ba-r; reciprocating motion is imparted thereto by wobble cam 24 through driving bar 25 (which carries roller 2 and connecting plates 26; the bar-driving wobble cam 24 is-mounted in front of stoker hopper ll outside the furnace where it is rotated with conauxiliary pushers 36 closer to the center of the main body of retort fuel) feeder bar 22, when reciprocated as aforesaid, progressively, advances fuel delivered into the retort by conveyor l4 away from the retorts front end wall and into the main body of retort fuel (not here shown) toward inclining rear wall 3|. Such advancement displaces other fuel in that body upwardly toward the burning fuel bed at the retorts opentop and outwardly upon grate bars 32-33 at the retorts top sides.

Air for supporting fuel combustion passes upwardly from Wind box 9 and through small passages 34 between fire bars 32-33. Such air may be maintained under pressure in the wind box by a forced draft fan 36 (see Figure 2) driven by motor i5 as taught by my earlier Patent 2,049,668 of 1936. In proper cases a small portion of this wind box air may be admitted over the bed of burning fuel through overfire passage 31 here shown as including an adjusting damper 33.

All fire bars in the side rows 32-33 may be stationary, or certain bars in each row may be arranged to reciprocate toward and from the retort I0 as taught by my U. S. Patent 2,136,807 of November 15, 1938, for Side Retort Stoker and as further disclosed by my Patent 2, 142,701 of January 3, 1939 for Underfeed Stoker. A dumping grate (not shown) also may be provided at the outer edge of each of these fire bar rows.

Stoker installation represented Underfeed stokers organized as here disclosed in accordance with my earlier Patent 2,049,668 of 1936 (application therefor filed in 1932) have enjoyed high commercial success in such uses as firing the boilers of heating and power systems for schools, churches, apartment houses, garages and the like as well as in other applications including laundries, factories and other industrial establishments; this form of stoker uniquely combining the advantages of the screw feed stoker and of the sliding bottom, pressure and plunger type of stoker without being subject to the disadvantages inherent in those other stoker types;

In the illustrative application of Figure l the described stoker is shown as being mounted underneath a boiler 40 arranged to generate steam supplied through outlet 4| to one or more utilizers typified by radiator 42 employed to heat a room or other enclosure 43. The steam pressure in supply line 4| is indicated by a conventional gauge 4 3, while the temperature of room 43 (heated by radiator 42) is responded to by a thermostat 45.

The purpose of my invention is to provide improved means responsive to changes in the reading of pressure gauge 44 or to the indication by thermostat 45 (or to some other measure of the demand for Stoker-supplied heat) for automatically adjusting the stokers speed-setting lever i! in a way which maintains the boiler-steam pressure or the heated-room temperature (or other selected measure of the heat output by the controlled stoker) substantially constant.

The stokers drive and speed change mechanism The here represented variable-speed stoker drive is broadly similar to that disclosed and claimed by my earlier Patent 2,070,756 of 1937 previously identified. Stoker drive motor l5, stationarily mounted as shown, is of a conventional type suitable for energization from an elec- ,tricaipower circuit of commercial voltage and frequency (such as 110 or 220 volts, 25 or 60 cycles) and represented at A-BC in Figure l.

When so energized (as upon the closure of switch 4?) the motor rotates at a substantially constant speed (of the order of 1700 to 1800 R. P. M.) sufficiently fast to operate forced-draft fan 36 (see Figure 2) efficiently.

A pulley 48 on the other end (right in Figure 2) of the motor shaft drives belt is running over an intermediate pulley 50 mounted on a jack shaft 5| that is journaled in a bearing support 52 (see Figures 23) which is slidable along a track 53 that is pivoted at 56. Gravity anda spring 56 urge the free end of the track downwardly thereby keeping belt 69 under proper tightness regardless of the position of slide sup port 52 along track 53. In this Way pulley 50 rotates jack shaft 5| at a substantially constant speed fixedly related to that of motor I5.

Driving into reduction gearing 16 for the purpose of rotating feed screw l4 and wobble cam 24 (at the relatively slow speed earlier indicated) is a third pulley 58 over which there rides a second belt 59 having the flat cross section shown. This second belt is driven from a composite pulley that is carried by the jack shaft 5% (see Figure 2) and that includes left and right members 565 and 6013 having opposed frusto-conical faces against which the edges of belt 59 bear. Member 60A is fixed to motor-driven pulley 56 on the jack shaftfwhile member 6033 also receives turning movement from that shaft 5i but is slideable lengthwise thereof, it being urged toward 60A by spring 5| (again see Figure 2).

Upon separation of members 60A and 66B, produced by a pulling of fiat belt 59 closer to the center of pulley 60, the effective diameter of that composite pulley is reduced with the result that the gear box input wheel 58 is driven at a lower rate of speed; likewise, upon closer approach of members 60A and 6613 one to the other, as accompanies a riding (aided by spring 6%) of belt 59 farther from the pulley center, the eifective diameter of pulley 60 is increased with the result that the gear box input wheel 58 then is driven at a higher rate of speed. To facilitate the separation of members 60A and 603 when the belt 59 is placed under added tension, the latter may satisfactorily be provided with bevelled edges giving it the wedge shape represented.

.Belt 59 being of constant total length, the aforesaid effective diameter of composite pulley 60 is determined by the position of jack shaft support 52 along slide 53. Serving to establish that position is the earlier mentioned speed change lever l1 keyed as shown in Figure 2 to the left end of an adjuster shaft 62 whose right end carries an arm 63 as shown in Figures 23. A link 64 connects the lower end of arm 63 with the slidable jack shaft support 52. With this arrangement movement of lever ll away from hopper II (to the left in Figures 1 and 3) increases the effective diameter of composite pulley 60 and hence raises the speed of gear box drive;

wheel 58; while movement of lever l1 toward hopper H (to the right in Figures 1 and 3) decreases the effective diameter of pulley B9 and correspondingly lowers the speed of gear box drive pulley 68.

Conventional reduction gearing within box it steps down the speed of input pulley 53 (of the order of several hundred of R. P. M. and adjustable as aforesaid) to a relatively low value (of the order of only several R. P. M.) suitable for rotating the stokers feed screw i i and wobble cam 25. Theseso driven feeder parts accordingly operate; (a) at their minimum speed when lever ll is in the position closest in hopper II; (b) at a progressively increasing speed as lever ll is moved back (to the left in Figures 1 and 3) away from hopper l l; and (c) at their maximum speed when lever l1 occupies the position most remote from the hopper.

The gear box here illustrated is further provided with a clutch '86 by means of which the drive connection from motor E5 to the stokers fuel feeder members l4 and 2d may at proper times be broken (as upon actuation of a suitable hand lever not represented). Such declutching completely stops the stolrers fuel feed thereby allowing forced draft fan 36 to continue in operation, as is sometimes useful when it is desired to burn v all the fuel in retort l9 and on grate bars 32-413 before adding new fuel thereto. c The complete stoker of Figures l--2-3 sti further includes for fan 36 an air intake fitting 6'! (see Figure 2) provided with conventional damper means (not here represented) controlled by a lever 68 and otherwise organized as disclosed by my earlier Patent 2,199,012 of 1940 as previously identified. Upward movement of this lever opens the inlet and thereby allows constant-speed fan 36 to supply (by way of air duct 69) more air to the stokers burning fuel bed; downward movement of this lever cuts down the area of inlet opening and correspondingly reduces the supply of air to the fuel bed.

' Through suitable linkage means including shaft H (see Figure 2) and associated elements l2--'i3'4, the position of damper lever 68 is made to follow the position of fuel-feed speed selector lever H in such a way that each increase in fuel feed rate is accompanied by a corresponding increase in fan-air output, and vice versa; all as taught by my earlier Patent 2199,012 just mentioned. In this way the represented stoker simultaneously adjusts both its fuel-feed rate and its air-supply rate in a way assuring rnost effective fuel combustion throughout the entire range of stoker operating speed.

Means for actuating speed selector lever 17 For imparting the required speed-adjusting movements to lever ll my new control system utilizes a reversing motor '56 which through reduction gearing ll drives a pinion it that meshes with a large gear wheel '19 mounted on idler shaft 80 and carrying aroller 8i engaged by the forked opening '(see Figure 4) in "a lever 82 attached at its lower end to the same sp eed-adj-uster shaft 6 2 as isupportsthe' stokers speed selector lever ll earlier described.

Control motor 76, shown as1mounted on top of the stokers main-drive gear box H3, may satisfactorily be of fractional horse power capacity suitable for energization from the alternating current voltage (110 or 220 volts, 25 or 60 cycles) appearing between .two of the conductors ABC of the main power circuit which suppliesv stoker driving motor id as indicated in Figure 4. There current for operating control motor "1% is fed through conductors A and B. Connection (as later described) of conductor A with motor terminal I produces forward rotation, while connection of A (again as later described) with terminal D causes motor '16 to rotate in the reverse direction.

The normally high speed (such as of theyorderof 1706-1800 R. P. M.) of. the control motor it is by gearing H (which may include a worm or other equivalent drive) stepped down to the point where pinion it is driven at the reiativeiy slow speed of onl two or three R. P. M. In consequence gear wheel 19 meshed with that pinion is during motor operation moved at an even slower rotational speed, so that forked lever 82 engaged by gear-carried roller 8! (see Figure l) requires a substantial time to move from the extreme left position of Figure 4 (corresponding to the minimum stoker-speed setting of selector shaft 62) to the extreme right position of Figure 4 (corresponding to the maximum speed setting of shaft 62).

In order to prevent motor 76 from moving forked lever 82 too far ineither the speed-raising (right in Figure 4) or the speed-lowering (left in Figure 4) direction, use is made'of normallyclosed limit switches 8d and 85 respectively inserted in the increase and in the decrease I supply leads to motor 16, as per the diagram of Figure 4. These limit switches are conventional and lend themselves to mounting in a number of well known ways; one of these is indicated in Figures 2 and 3 where the box representations tie-85 designate the two so numbered switches of Figure land where the actuating means therefor take the form of a pin 88 protruding as shown from the bolt which secures roller ill to the gear wheel 19. Still other arrangements may of course be employed to cause these limitswitches 8 l85 to selectively open when forked lever 82 approaches the extremes in its range of adjustment positioning.

motor 7 6 In the illustrative organization shown by Figure 4 energization of reversing speed-adjuster motor 76 is automatically controlled by means of a novelly-organized system made up of: (1) a pressure-responsive device '81 including a bellows 88 connected at 39; (see Figure 1) with the steam oiftake line it from boiler 43 and functioning to urge floating contact 90 against static-nary contact 'H when the boiler pressure rises above a predetermined value and to engage floating contact 90 with stationary contact L when the boiler pressure drops below that value; (2) a step-timer device 92 including contacts 93-434 which are repeatedly closed and opened under the cyclic action of .a cam 95 continuously rotated (at some relatively slow speed such as about 1 R. P. M.) by a minimum; automatic; maximum) marked for purposes later to be made evident; and (4) the interconnecting conductors represented by Figure 4.

All three of the devices 81, 92 and 98 may satisfactorily be housed in an instrument casing indicated at Inn in each of Figures 1 and 5.

This casing can be made relatively compact, one practical design therefor having height, width and depth dimensions approximating eight, seven and four inches respectively.

In this illustrative instrument organization the pressure-responsive device 81 is totally housed inside the casing I00, pressure connection thereto being established through top tubing 89. Calibration of this device 81 is adjusted by turning a top screw I92 which adjusts the tension on a spring I93 that opposes (see Figure 4) the tendency of bellows 88 to close contacts Bil-H upon rising pressure of the boiler steam (see Figure 1). For each setting of screw I02 there exists a pressure at which floating contact 99 is disengaged from both contacts H and L. As thepressure in bellows 88 falls below that predetermined value spring I93 brings contacts 90 and L together; and as the bellows pressure rises above that predetermined value the added bellows expansion brings contacts 90 and H together.

In the illustrative step timer shown at 92 (Figure 4), clock motor 96 is during the represented automatic positioning of selector switch 98 continuously energized over a circuit extending from supply conductor A through switch segment 99, conductors IDS-I06, the winding of timer motor 96 and conductor I01 back to supply conductor B. Under this condition motor 96 rotates timer cam 95 at some slow and uniform speed such as one R. P. M.; the two cam lobes represented then serving to move timer contact 9 up and down once each 30 seconds in regularly repeated cycles. Each upward movement engages contact 94 with companion contact 93 while each downward movement breaks that engagement.

For adjusting the ratio of on (engaged) to off (disengaged) periods in these recurring timer contact cycles, provision is made for moving the upper contact 93 either closer to or further away from the lower contact 9d. As here shown this provision takes the form of a second cam 91 settable in different rotational positions by a timer adjusting dial I08 protruding through the front of instrument casing I as indicated in Figure 5. When dial I98 is turned counterclock wise to the extreme left, each thirty second cycle of timer operation will include a five second on period during which contacts 93-99 are engaged, and a twenty-five second off period during which contacts 93-94 are disengaged.

Turning dial 108 clockwise increases the length of the timer on periods and decreases the length of the timer off periods. If set to the extreme clockwise direction (marked Increase in Figure the timer contacts 93-94 will be engaged for twenty-five seconds and disengaged for five seconds during each thirty second cycle. In this way there is provided a simple and effective adjustment in the relative lengths of timer on and ofi periods throughout a relatively wide range.

The four-position selector switch represented at 98 in Figure 4 is arranged for setting by means of a knob H0 extending through the front of instrument casing I00 as shown in Figure 5. With the knob in the vertical or "automatic position representedswitch segment 99 connects conductor A with conductor I05; turning knob IIB clockwise to the maximum position causes segment 99 to transfer the connection of conductor A to a conductor I I2; shifting of the knob How the automatic control system of Figure 4 operates In considering operation of the complete control system of Figure 4 assume that step timer 52 is adjusted so that each recurring thirty-second cycle of closing and opening by contacts 93-94 includes a fifteen second on period (contacts engaged) and a 15-second oii period (contacts disengaged); that pressurestat 87 is set to hold contact 99 between contacts H and L when the pressure in boiler is (see Figure 1) has a selected value of 60 pounds per square inch (as indicated by gauge 94); and that selector switch 98 is in the automatic position with segment 99 vertical as indicated.

In order to maintain the steam pressure in boiler at this value of 60 pounds per square inch the stoker of Figure 1 will need to operate at some intermediate value of fuel-feed rate such as istypified by the represented position of manual speed selector lever ll (Figures-1-2-3) and by the corresponding intermediate position of forked lever 82 which is fixed to the same speed-adjuster shaft 62 as is the first lever I'i. Underthese conditions contact of pressurestat 8i floats between contacts H and L and keeps both of terminals D and I of speed-adjuster motor "at disconnected (at pressurestat 8'!) from supply conductor A.

Upon a drop in the steam pressure in boiler 59 (as may result when the demand for supplied steam increases) pressurestat contact 99 engages contact L thereby completing for feed adjuster motor '59 a forward energizing circuit which extends from supply conductor A through selector switch 98, conductor [05, step-timer contacts 93-94 (when recurrently closed), conductor I I3, contacts sir-L of pressurestat Bl, conductor lit, limit switch 84, terminal I of motor 19, and the motors forward driving winding back to supply conductor 13'.

Thus energized motor 19 rotates forwardly causing pinion 8 to drive gear wheel 19 in a direction (clockwise as viewed in Figure 4) to increase the rate at which stoker feed screw 14 and wobble cam 24 (see Figure l) are driven by motor l5 and further to open the air damper 67 for forced draft fan 39. This increasing adjustment in the rate of stoker fuel feed and air supply (accomplished through gear wheel 19 and forked lever 82) proceeds in step fashion; the adjuster motor '55 running only when step-timer contacts 93-94 are closed (fifteen out of each thirty seconds for the assumed setting of step timer 92) and stopping during the intervening off periods (also assumed to be fifteen seconds each) when the step timer contactsareopened.

In consequence of the increased supply of fuel and air by the stoker to furnace sthe steam pressure in boiler ill again builds up. Upon close ap proach thereof to 60 pounds per square inch, pres surestat contact 50- separates from contact L and thereby disconnects adjuster motor 86 from supply conductor A. Further corrective action by motor 16 is now discontinued.

In the event that the steam pressure'in boiler 46 rises above the assumed predetermined value of 60 pounds per square inch (as may result when the demand for boil-er supplied steam suddenly drops) pressurestat 81 engages contact Eli? with contact If and thereby completes for adjuster motor '55 a reverse circuit which extends from supply conductor A through-selector switch conductor H35; contacts 93'$4 of steptimertii, conductor H3, contacts Elli-H of pressurestat 8?, conductor H5, limit switch 85, terminal D of motor l8, and the motors reverse driving winding back to supply conductor B.

Thus energized motor I6 rotates reversely causing pinion E8 to drive gear whee]. E9 in a direction (counterclockwise as viewed in Figure 4) to decrease the rate at which stoker feed screw l4 and wobble cam 25 (see Figure l) are driven by motor I and toeifect a closing adjustment in the air damper Ell for forced draft fanBE. This "dc-creasing adjustment in the rate of stoker fuel and air feed proceeds in the same step fashion (due to timer 92) as was explained for the increasing adjustment by motor lfi.

In consequence of the. decreased supply oi fuel and air by the stoker to furnace 3 the steam pressure in boiler ie again falls. Upon close approach thereof to the. assumed 60 pounds per square inch desired value, pressurestat contact separates from contact 1-! and thereby disconnects adjuster motor 76 (terminalD) from supply conductor A. Further corrective action by motor E5 is thereupon discontinued.

To adapt the system for maintaining the boiler steam pressure constant at some value other than the 60 pounds per square inch above assumed, it is only necessary to reset the pressurestat 8'? for contact disengagement at the other pressure se lected. As already indicated, the necessary re setting is readily accomplished by simply turning the calibrating screw N22; to increase the tension on spring Hi3 when it is desired to maintain a higher pressure and to decrease the spring tension when it is desired to maintain a lower pressure. p i

Heat requirement measurements other than boiler steam pressure may also be used as the.

control factor in my improved automatic system. For example, the pressurestat tlof Figure 4 may be directly replaced in the circuits disclosed by the thermostat 35 of Figure 1. In effecting such replacement the thermostat contacts L, 3!? and II will be connected with conductors I Hi, H3 and i 55 in the same manner as-are the pressurestat contacts 'L, as and H of Figure 4. 010-. eration of the thermostat-controlled system will then be the same as that above described for the; pressurestat-controlled system of Figure 4;'subject to the single difference that the temperature of room 33 (Figure 1) will then be main- 1 i an? speed.

lie

system of Figure 4 to hold the temperature of that water constant as some desired value.

In either arrangement step timer 92 functions to eliminate hunting or overrunning in the fuelfeed adjustment made through motor '46 in the stoker driving mechanism of Figures l-23. Such hunting is prevented by adjusting the length of the timer on (closed contact) steps to suit the fuel burning characteristics of the stoker. As has been seen each on portion of the timer cycle is during corrective action accompanied by a running of adjuster motor 76 and each intervening off (open contact) interval produces a waiting period between motor operations.

Hence with the thirty second cycle timer illustrated at 92 the earlier assumed fifteen second on and fifteen second off periods were chosen merely to facilitate description. In certain fuel burning systems such equal on and off periods may proye most suitable; in other systems a shorter on and a longer off period may prove most satisfactory; and in still other systems a longer on and a shorter off period may resuit in the best operation. As earlier indicated the optimum adjustment for each installation is readily efiected through timer-adjuster dial I98.

The step-timer 92 obviously may be connected into the control system in manners other than the illustrative one shown by Figure 4. For eX- ample, the timer contacts 9394 may if desired (but not here shown) be reconnected to that they serve recurrently to interrupt only one of speed adjuster motor ltis forward and reverse energizing circuits M l and H5 (instead of both as Figure 4 illustratively shows).

Moreover, by proper reorganization (not here illustrated) of the system it is possible to make energization of timer motor 96 dependent upon engagement of the contacts (-4-1 or 90-L) in master control device ill. With such an arrangement the timer cam 95 will be rotated only when the stokers speed-adjuster motor 96 is energized (at one or the other of its terminals D and I); this permits inactivity on the part of timer device $32 at all times except when motor 16 actually is being called upon to adjust the stoker Non-automatic control of the stokers fuel-feed speed Under certain conditions it may be desirable shaft or under manual control independently of the automatic facilities just described. Provision for doing this is made in my new system. In the organization shown by Figures 1 to 5 such provision includes the selector switch 98 plus a releasable clutch mounting for pinion 18 which drives into gear wheel 79 (see Figure 4) from motor '56.

Referring to, Figure 2, pinion 18 is there shown as being loosely mounted on the shaft I H of the control motor assemblage lii'll and-receives turning movement therefrom through a collar H3 fixed to the shaft. Abutting ends of tained constant instead of the steam pressure in to this collar and gear "it are each provided with V boiler ill. Furthermore, temperature-responsive contacts such as H--%L" can also be incorporated into an aquastat (not shown) submerged in water heated by the stokerefired furnace 8 and functioningthroughmynew control notches H9 which look into each other as long as a hand screw me on shaft H'ls threaded end holds gear '58 against collar I I8. Under these conditions pinion i8 is rigidly fixed to and rotates with the shaft 1 ll of speed adjuster motor ll gearing 11. The effect then is the same as were pinion 18 to be keyed to shaft I I1.

Should, however, it be desired to utilize manual lever I1 for setting the stokers fuel-feed speed, it is only necessary to turn hand screw I20 along threaded shaft end II'I away from gear 18 for a short distance as limited by cotter key I2I. The V notches I I9 now are effective to disengage gear 18 from collar II 8 and allow it to rotate freely on shaft I I1.

Pinion 18 is in this way freed to turn loosely on shaft II1. Under this condition forked lever 82 (see Figure 4) can under the turning action (through shaft 62) of hand lever I1 rotate gear wheel 19 (through roller 9|) to any speedad justing position which it may be desired to establish by lever I1. Once the position is so selected, it may be there held by retightening hand screw I28 against pinion 18, thereby again looking it to control gearing shaft II1. Access to hand screw I22 may conveniently be provided for by equipping the casing of the stoker drive mechanismwith an access door as shown at I22 in Figure 3. e

Incident to the foregoing manual setting of the stoker feed drive, the selector switch 98 of Figures 4 and 5 is preferably set to the off position wherein supply conductor A is disconnected from all three of system conductors H35, 7

III and H2.

Under certain conditions this selector switch 98 is further useful in selectivelv running the speed-adjuster motor 16 (with pinion 18 locked to shaft III) to the extreme position for forked lever 82 in either the maximum or the minimum speed-adjusting direction.

Such maximum-direction running results when knob IIO of the switch is rotated clockwise to its maximum osition to connect (through segment 99) supply conductor A with system conductor II2. This by-passes both the step-timer 92 and pressurestat 81 by connecting A directly to motor conductor I I I, thereby energizing motor terminal I and causing gear wheel 19 to be advanced in the speed-increasing direction (clockwise as viewed in Figure 4) until forked lever 82 contacts and opens limit switch 84 in the motor circuit. Motor 16 then stops with forked lever 82 in the maximum fuel-feed position.

To run motor 16 to the opposite or minimum range of travel for speed adjusting lever 82, it is only necessary to turn knob III! of selector switch 98 counterclockwise to the minimum position wherein segment 99 connects supply conductor A with system conductor III. Devices 92 and 81 are again bv-passed and the resultant connection of A with conductor II5 applies energizing voltage to terminal D of motor 15. This causes the motor to rotate gear wheel 19 in the fuel-speed decreasing direction (counterclockwise in Figure 4) until forked lever 82 contacts and opens selector switch 85 to interrupt the supply circuit and stop the motor with lever 82 in the position of minimum fuel-feed adjustment.

As earlier indicated a setting of selector switch 98 in the off position disconnects supply conductor A from all other system conductors and thereby renders speed adjuster motor 15 totally inactive.

The modified speed-adjusting mechanism of Figs. 6-7-8 Figures 6-7-8 disclose an alternative organization for the parts through which gear wheel 19 (driven by control motor 16) transmits speed adjusting movements to the shaft 62 of the stokers speed selector mechanism earlier described. In this alternative organization: (a) the two arms I1 and 82 of Figures 2-3 are replaced by a single arm shown at I1 in Figures 6-7-8; (b) the pinion 18 for driving gear wheel 19 is fixedly mounted on the shaft II1 of the control motor assemblage 16-11; (0) gear wheel 19 has supported from its left face (as viewed in Figure 6) a disc I24 upon which is mounted the roller 8I' that engages one side of arm I1 as shown; (d) enough of the casing wall I21 is cut away opposite gear wheel 19 to permit the engagement named; and (e) movement of arm I? in the speed raising direction can at proper times be limited to a selected position by placing a stop pin I26 ahead of the arm (on same side as roller 8I') in one of the holes provided in a bracket I28 that is secured to the stoker casing I29 as shown.

Except for the changes above listed, the speedchange mechanism represented in Figures 6-7- 8 duplicates that already described by reference to Figures 2-3. In it lever I1 is continuously urged against (to the left in Figure '7 and to the right in Figure 8) roller 8I' due to the tendency of composite pulley B0 to ride belt 59 as far towards the outer edges of beveled members GOA-60B as the positions of link 64, arm I53 and speed-change shaft 62 will permit. The named tendency results from the continuous urging by pulley spring 6| (see Figure 6) of member 6013 towards member 60A; this, in turn, urges belt 59 away from the center of pulley 60; and, in consequence, the shaft support 62 for that pulley continuously urges link 64 to the right in Figure 7. Arm 63 converts that urge into a torque on shaft 62 which is counterclockwise as viewed in Figure 7 and clockwise as viewed in Figure 8 and which continuously urges lever I1 towards roller 8I as earlier stated.

This modified mechanism of Figures 6-7-8 employs the same reversing motor 16 as does the mechanism of Figures 1-2-3 and it contem plates that this motor 16 be automatically con trolled through the novel apparatus shown in Figure 4, as earlier described in detail. In 9.0-- tual use the parts of Figure 8 therefore form part of the complete automatic control system of Figure 4; lever I1 of Figure 8 then replacing the forked arm 82 of Figure 4 and limit switches'9e and 85 then being actuated (at proper times) directly from the gear wheel 19 through the actuator 86' carried thereby as indicated in each of Figures 6-7-8.

Operation of the complete automatic control system so disclosed by Figures 4, 6-7-8 therefore proceeds in the same way as was earlier explained for the equipment of Figures 1 through 5. In examining this operation first assume that stop pin I26 is removed from bracket I28 thereby allowing lever I1' freely to follow roller 8i through all speed adjusting rotations of gear wheel 19. Under this condition the modified linkage mechanism of Figures 6-7-8 functions in precisely the same manner as does the mechanism of Figures 2-3-4, except that lever I1" takes the placeof forked arm 82.

Thus, rotation ofgear wheel 19. in the speed decreasing direction (counterclockwise in Figure 8 and clockwise in Figure 7) pushes lever I1 to the right in Figure 7 (and to the left in Figure 8) thereby causing link 64 to push composite pulley 50, further away (to left in Figure 7) from the fixedly mounted pulley 58 over which the belt 59 rides. This pulls belt closer to the composite pulleys center and thereby appropriately reduces the stoker driving speed; such reduction being accompanied by a corresponding adjustment of air damper 53 (through linkage ll-44) in the draft reducing direction.

Similarly, rotation of gear wheel 7% in the,

speed increasing direction (clockwise in Figure 8 and counterclockwise in Figure 7) allows lever H to follow roller 8 l to the left in'Figure '7 (and to the right in Figure 8) and thereby permits composite pulley 50 (urged by spring iii) to ride belt 59 closer to the pulleys outer edges with a resultant increase in stoker driving speed. moving, as stated, lever ll effects a corresponding adjustment of air damper $3 in the draft increasing direction.

This modified apparatus of Figures 6--7--8 offers special advantages, The first of these is that of permitting ready establishment of an upper driving speed limit at some selected value that is less than the highest attainable stoker speed which rotation of gear wheel '59 into its extreme speed increasing position (wherein limit switch' 84 opens) determines. Such establishment of a reduced upper limit is accomplished by inserting stop pin I26 into the opening along the length of bracket I28 which corresponds to the particular reduced upper limit desired.

Under this condition (represented in each of Figures 6-7-8), automatic stoker adjustments within the speed range below that selected by pin I26 continue to proceed as before. However, once lever i1 is by roller 8! allowed to move into contact with pin 12% then further advancement of the lever is prevented even though gear wheel '59 may be further rotated by control motor '15 in the speed'increasing direction. This means that the automatic control facilities are rendered ineffective within the range above the intermediate speed value selected by pin 126.

A second advantage afforded by the modified apparatus of Figures 67-8 isthat of permitting a setting of the speed adjuster lever ll} under full manual control and with complete independence of the automatic facilities diagrammed in Figures 4 and 8. To accomplish Summary From the foregoing it will be seen that I have provided improved means for automatically controlling the operating rate of stokers including undcrfeed' stokers organized as taught by my Patent 2.9%,668 of 1936 and equipped with varispeed drive mechanisms as taught by my Patent 2,070,756 of 1937; that I have effected the foregoing automatic control of stoker operating rate in such an improvedway as to avoid wastage of fuel, minimize smoke and increase fuel burning efficiency; that I have accomplished the desired control through the medium of equipment which is low in cost, simple and compact in construction and reliable and trouble-free in operation; and that I have organized the automatic control apparatus in a way permitting the sicker operating speed to be adjusted manually, when and if desired.

My inventive improvements are therefore extensive in their application and hence are not to be restricted to the specific form here disclosed by way of illustration.

What I claim is:

1. In combination, a furnace, a stoker therefor including fuel-feed elements, continuously operthis it is only necessary to turn selector switch 53 of Figure 4 to the maximum position.

Such turning connects (through segment 99) supply conductor A with system conductor H2. This by-passes both the step timer 52 and pressures-tat 8i by connecting A directly to the motor conductor li i thereby energizing terminal I of .motor 16 and causing gear wheel E9 to be advanced in the speed increasing direction (clockwise as viewed in Figure 8) until actuator 86 contacts and opens limit switch in the forward motor circuit. Motor it then stops with the roller 3! in the maximum full speed position (to the right in Figure 8 and to the left in Figure 7).

Roller Si is now completely out of the normal-range path of lever ii and that lever is accordingly free for manual setting to any position in the stoker speed range which may be desired. Each such selected position can now readily be retained by inserting stop pin 126 in the appropriate place along the length of bracket 23. It will thus be seen that the modified organization of Figures 6-'?--3 permits manual setting of the stoker feed speed to be effected motor assemblage shaft ill.

able mechanism for driving said elements, a member in said mechanism movable to adjust the speed at which said fuel-feed elements are driven, a gear wheel rotatively mounted to impart speed-adjusting movement to said member,

" an electric motor for slowly rotating said gear Wheel through a meshing pinion mounted on a motor-driven shaft, an instrument responsive to the demand for furnace-supplied heat, first contacts engaged by said instrument when said supplied heat falls below said demand, second contacts engaged by said instrument when said supplied heat rises above said demand, a forward energizing circuit for said motor completed during each engagement of said first contacts and then effective to cause the motor to move said stoker-adjusting member in the fuel-feed increasing direction, a reverse energizing circuit for said motor completed during each engagement of said second contacts and then effective to cause the motor tomove said stoker-adjusting member in the fuel-feed decreasing direction, a

selector switch forat times rendering said forward and reverse motor circuits both unresponsive to said automatic instrument control, and means mounting said gear-driving pinion on said motor-driven shaftv in a way permitting selective release of the. shaft-to-pinion driving connection when during the aforesaid times it may be desired to free said gear wheel for a manual rotative shifting to any selected point in said stoker-adiusting inembers range of feed-speed varying movement.

, 2. In combination, av furnace, a stoker for supplying said furnace with fuel to be burned therewithin and with air to support said burning, continuously operable stoker driving mechanism including a lever effective to adjust therate at which the stoker feeds both said fuel and said air into the furnace, a gear wheel rotatively mounted to impart speed-adjustingmovement to said lever, a pinion meshing with said gear wheel and carried by a shaft, an electric motor for driving said shaft in order slowly to rotate said gear wheel through said pinion, an instrument responsive to the demand for furnace-supplied heat and effective to engage a first set of contacts when said supplied heat is less than said demand and to engage a second set of contacts when said supplied heat is greater than said demand, a forward energizing circuit for said motor completed during each engagement of said first contacts and then effective to cause the motor to move said stoker-adjusting lever in the fuel-feed-increasing direction, a reverse energizing circuit for said motor completed during each engagement of said second contacts and then effective to cause the motor to move said lever in the fuel-feed-decreasing direction, a selector switch for at times rendering said forward and reverse motor circuits both unresponsive to said automatic instrument control, and means mounting said gear-driving pinion on said motor-driven shaft in a way permitting selective release of the shaft-to-pinion driving connection when during the aforesaid times it may be desired to free said gear wheel for a manual rotative shifting to any selected point in said stoker-adjusting levers range of feed-rate varying movement.

3. In combination, a furnace, a stoker for supplying said furnace with fuel to be burned therewithin and with air to support said burning, continuously operable stoker driving mechanism including a lever effective to adjust the rate at which the stoker feeds said fuel and air into the furnace, said lever being settable anywhere between an extreme low speed position and an extreme high speed position, means urging said lever in the direction of its said high speed position, a gear wheel rotatively mounted and carrying at a point displaced from its axis a -roller organized to restrain said lever from travel beyond the roller towards said extreme high speed position, an electric motor for imparting rotation to said gear wheel, a motor-control instrument responsive to the demand for furnace-supplied heat, a forward energizing circuit for said motor activated by said instrument when said supplied heat is less than said demand and then effective to produce forward rotation of said gear wheel causing said roller to allow advancement of said lever in the feed-speed-increasing direction, a reverse energizing circuit for said motor activated by said instrument when said supplied heat is greaterthan said demand and then effective to producereverse rotation of said gear wheel causing said roller to move said lever in the feed-speed-decreasing direction, and means supplemental to said motor-driven gear wheel and roller for restricting said lever in its said speed-raising movement to a selected intermediate position in the aforesaid lever travel range notwithstanding that said gear wheel may advance said roller in the speed-raising direction to beyond said selected intermediate position.

4. In combination, a furnace, a stoker for supplying said furnace with fuel to be burned therewithin and with air to support said burning, continuously operable stoker driving mechanism including a lever efiective to adjust the rate at which the stoker feeds said fuel and air into the furnace, said lever being settable anywhere between an extreme low speed position and an extreme high speed position, means urging said lever in the direction of its said extreme high speed position, a gear wheel rotatively mounted and carrying at a, point displaced from its axis a roller organized to restrain said lever from travel beyond the roller towards said extreme high speed position, an electric motor for imparting rotation to said gear wheel, a motorcontrol instrument responsive to the demand for furnace-supplied heat, a forward energizing circuit for said motor activated by said instrument when said supplied heat is less than said demand and then effective to produce forward rotation of said gear wheel which causes said roller to allow advancement of said lever in the feedspeed-increasing direction, a reverse energizing circuit for said motor activated by said instru ment when said supplied heat is greater than said demand and then effective to produce reverse rotation of said gear wheel which causes said roller to move said lever in the feed-speeddecreasing direction, means including a selector switch for at times rendering said forward and reverse motor circuits both unresponsive to said automatic instrument control and for thereupon causing the motor to drive said gear wheel forwardly to a position wherein said roller frees said lever for full advancement into its said extreme high speed position, and means effective to hold said lever in any position within its complete range of travel that during the aforesaid times it may be desired to select by manual setting.

5. In combination, a furnace, a stoker for supplying said furnace with fuel to be burned therewithin, continuously operable stoker driving mechanism including a lever effective to adjust the rate at which the stoker feeds said fuel into the furnace, said lever being movable between an extreme low-speed position and an extreme high-speed position, a gear wheel rotatively mounted and carrying a roller at a point displaced from the gear wheel axis, means causing said lever to'move with said roller upon changes in the rotational position of said gear wheel, an electric motor for imparting rotation to said gear wheel, a motor-control instrument responsive to the demand for furnace-supplied heat, a forward energizing circuit for said motor activated by said instrument when said supplied heat is less than said demand and then elfective to produce forward rotation of said gear wheel causing said roller and said lever to move in the feed-speed-increasing direction, a reverse energizing circuit for said motor activated by said instrument when said supplied heat is greater than said demand and then effective to produce reverse rotation of said gear wheel causing said roller and said lever to move in the feed-speeddecreasing direction, and a selector switch for at times rendering said forward and reverse motor circuits both unresponsive to said automatic instrument control and for at other times enabling each circuit selectively to be supplied with energizing current under manual control directly through the switch in by pass relation to said instrument.

6. In combination, a furnace, a stoker for supplying said furnace with fuel to be burned therewithin, continuously operable stoker driving mechanism including a lever effective to adjust the rate at which said stoker feeds fuel into the furnace, said lever being movable between an extreme low-speed position and an extreme highspeed position, a gear wheel rotatively mounted and carrying a roller at a point displaced from the gear wheel axis, means causing said lever to move with said roller upon changes in the" rotational position of said gear wheel, an electric motor for imparting rotation to said gear wheel, a motor-control instrument responsive to the demand for furnace-supplied heat, a forward energizing circuit for said motor activated by said instrument when said supplied heat is less than said demand and then effective to produce forward rotation of said gear wheel causing said roller and said lever to move in the feed-speedincreasing direction, a reverse energizing circuit for said motor activated by said instrument when said supplied heat is greater than said demand and then effective to produce reverse rotation 01. said gear wheel causing said roller and said lever to move in the ieed-speed-decreasing directicn, a timing device for said forward and reverse motor circuits effective upon activation of each as aforesaid then recurrentiy to interrupt the activated circuit and thereby cause said steker-speed-adjusting motor to operate in recurring steps which are separated by intervening periods or" motor stoppage, a selector switch for at times rendering said forward and reverse motor circuits both unresponsive to the foregoing automatic instrument control and for at other times enabling each circuit selectively to be supplied with energizing current under manual control. directly through the switch in by pass relation to said instrument and said timing device, a first limit switch functioning to deactivate said forward motor circuit upon either instru ment or selector-switch initiated movement by said motor of said stoker-adjusting lever to its extreme limit of travel in the fuel-feed-increasing direction, and a second limit switch functioning to deactivate said reverse motor circuit upon either instrument or selector-switch initiated movement by said motor of said stoker-ad- ,iusting lever to its extreme limit of travel in the fuel-feed-decreasing direction.

JOHN S. SKELLY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,335,008 Miner Mar. 30, 1920 1,418,871 Harrington June 6, 1922 1,472,280 Ousdahl Oct. 30, 1923 1,520,922 Baker Dec. 30, 1924 1,698,989 Chadwick et a1. Jan. 15, 1929 2,012,934 Hardgrove Aug. 27, 1935 2,070,756 Skelly Feb. 16, 1937 2,196,802 Potter et al. Apr. 9, 1940 2,251,483 Denison et al. Aug. 5, 1941 FOREIGN PATENTS Number Country Date 332,440 Germany Feb. 5, 1921 OTHER REFERENCES Ser. No. 421,940, Kool, et al. (A. P. 0.), published May 25, 1943.

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