US2407743A - Air draft timing and volume control - Google Patents

Description

sept, 17, '1946.

AIR DRAFT TIMING AND VOLUME CONTROL y Filed April so,v 1942 2 Shets-Sheet l c. M. HELYAR 2,407,743

sept. 17, 1946.` c. M, HELYAR 2,407,743

AIR DRAFT TIMING AND VOLUME CONTROL Filed April 30, 1942 2 Sheets-Sheet 2' Patented Sept. 17, 1946 AIR DRAFT TIMING AND VOLUME CONTROL charles M. Heiyar, saint vital, Manit'oba, canada Application April 30, 1942,)Serial No. 441,248

12 Claims.

My invention relates to an air draft timing and volume control assembly particularly but not exclusively for automatic stokers, designed to be located within the air duct leading to the retort thereof, an object of this invention being to provide a device of the character described, by the use of which, at the commencement of each cycle of stoker operation, the fuel bed will be given an opportunity to kindle without the intervention of a forceddraft, until there is sufiicient incandescence and burning strength in the fuel bed to Warrant the introduction of a gradually increasing volume of air.

f l furtheruobject of my invention is to provide an assembly of the character herewithin described, by ther use ofwhich, at the conclusion of raicycle of stoker operation, the fuel bed may continue to drawa natural draft through the st'oker air duct for a predetermined period of ti1 ne, suchk draft being however, gradually obstr-uctedand eventually closed off. V

j A Vfurther object of my invention is to provide an assembly of the character herewithin described which is of eminently simplified construction, can readilyV be installed by service men following simplified-instructions, can readilyV be adjusted to the conditions of any stoker, Will give long service andlcannot readily become out of order.

With the above more important objects in view and such other minor objects as may appear as the specification proceeds, my invention consists essentiallyV in the arrangement and construction of; parts all asV hereinafter more particularly described, reference being had to the accompanying drawings, in which:

Figure 1 is a side elevation of my air draft timing*V and Volume control assembly, in situ with both dampers closed. i

AFigure 2 is similar to Figure 1 but showing both dampers fully open.

, Figure 3 is an end elevation of my assembly. i Figure 4 is a -perspective detail illustratingthe structure' employed to adjust my control damper. Figure 5 is a detail illustrating my airdischarge elbow and associated valve; 1 v

v:Figure 6- is a perspective detail illustrating the structure -employed -tov adjust my -measuring damper.

V means being provided to regulate the volume of In the drawings like characters of reference I indicate corresponding parts in the different figures. 1- I; I

V,according to conventional practice in the construction and operation of automatic stokers, the fan is synchronised to start up simultaneously with the motor operating the coal feed screw, no

air fed to the dormant fire bed. l

As a result, the Violent kindling action of a full head of air under forced draft, can, and sometimes does have the elfect of extinguishing the fire completely, blowing the remaining incandescent particles up the chimney. When this extreme is not reached, a considerable quantity of fiy-ash is blown about inside the fire box to settle on the castings and effectively insulate the same against the transmission of heat..

Dealing with the effect upon a fire bed, of the shutting off of the fan at the conclusion of a cycle of stoker operation, I would explain that two conventional expedients are followed in construction and installation. The Afirst is to provide a heavily weighted damper within the air duet leading to the retort, so that immediately after the fan stops, the damper will drop, being sufficiently heavy to resist being lifted by natural chimney draft. The vother is to provide no damper in the duct, which permits of the continuance of a natural draft after the stopping of the fan.

The first expedient results in the fire being suddenly banked at a moment when valuable volatiles are being liberated, these volatiles thus, being deprived of 'the necessary oxygen required to ignite the same. With the second expedient, a fire can burn itself out before the next cycle of stoker operation commences. i

My assembly is therefore designed to 'obstruct the passage of air from the fan for a short period immediately following the commencement of a cycle of stokeroperation so as to give the fuel bedan opportunity to kindle while in its initial attenuated state, thereafter permitting the passage of a nursing'draft as the heat of the fuel bed increases and the fire grows stronger, and from there gradually increasing as more coal is fed In conventional stoker practice, it should be understood that a fixed damper `is, provided in the forced air duet, the damper being adjusted to each particular job. As an arbitrary example, it may be .said that such damper is adjusted to cut off four fifths of the area of the duet.

It therefore follows, that When a thick -and possibly denseflfueI bed has been `built up,- that such fuel bed will resist the penetration of a forced draft. It is therefore necessary to increase the volume of air so as to overcomeiob-i structions, -but this` cannot be done with a fixed damper and consequently valuable products of combustion liberated, cannot dissipate their full thermal efficiency owing to lack of oxygen.

With my assembly, when a fixed, dense and hot fuel bed has been created, I am able to overcome the resistance to the passage of air by permitting an increase in the volume of air which will pass through the duct, a vo1ume which is only limited by the capacity of the fan and thus the fuel bed-of anautomatic stoker to which my assembly *has I'been fitted, will never be overnourished or unclernourished with air to impair its thermal efficiency.

In view of the foregoing brief rsum comparing my assembly with conventional Apractice, -a rsum which could be considerably tamplified, I will proceed to describe the construction of my assembly.

.At any convenient point upon the length of a stoker duct I, I locate an intermedially journalled volume regulating damper 2 capable of sealing one side of the duct from theother completely. ,It is generally found convenien't l.w-hen inserting ga damper Vin a Vduct to frame Vthe same a'sby means -of the'frame 3, which, however, yI do Anot 'claim to be part vof my invention. A small A-stop 4 may -also 1be provided to prevent rotation of the damper 2 in a counterclockwise direction beyondthe limits imposed bythe stop.

4'One-of the trunnions 5 of ythe damper '2 projectssubstantially*beyond the side "wall 35 of the duct, a qu-adrant plate l'l being secured to *the end thereof for rotation therewith and vwith `the plate. A s`1eeve'8 ``is also f-reely `mounted upon the trunnions between the Quadrant plate'l and the wallv', a radial. Quadrant lock 19 of Lthefcongurati'on clearly fillustrated 'in the Vaccompany'ing- Figure zlfbeing secured -for rotation with the sleeve 8; lThis'Quadrant lock, itwill be seenfterminates at--the=lower 'end' thereof in a reverse-'angulated portion 1!!! lprovided with the set-screw ll Which is -capableofficlamping onto the larcuateedge'o'f the -pl'a-te 'I atanydesiredpoint -so that the sleeve and Lthe'trunnions, and-consequently the -damper too, moves as a unit.

iSecure'd a-t its inner -end to theb sleeve 8 Vis a bi-metallic heat -`motor 'IE-formed of spiral bimetal tape and `'substantially like la spiral-type thermostat. SIPheouter end '5,3 of Jthe --motor 172 is -anchored -atfa convenient point upon fthe perimeterof a-fairly bymassive heat retaining 'ring [4 which surrounds "the motor, thisring being preferably imade of cast iron or-some other isubs'tance capable of l`retaining Vheat fairly efficiently. This'ring is clamped tojthe wall. i

hnfloffsetlportion l' of'V the ring :Id/is provided withlthe passage Plt, .Which passage -opens :onto the i internal ,circumference of the ring ,at :one .end thereof, right angling at uthe other .end thereof as I have indicated by :the chain-line ,ring AElin Figure lgand by the parallel chain lines :ll' in Figure 5, and opening upon the posterior surface IB of the offset portion and in alignment with an air discharge `port IQ which includes an aperture (not shown) in the wall 6 and .an upwar'dly directed elbow Vprovided `with the 'vertically movablevalve'z. V V''Also within the duct l but spaced vfrom the damper 2 'and upon the retort side thereofis an Vair fievv responsive vane 2! normally Vbiassed to the .position'illustrated in vFigure 1, andalso preferab-ly mounted Within a frame 22 similar Vto the frame 3, a stop 23 being provided similar =to the stop 4.

`This vane will :preferably be mounted to swing about a line .above its central horizontal axis,

so that the foregoing parts may ybe caused to rotate as a unit,

Upon the 'sleeve =2-6 isa trip rod 28 of the configuration best illustrated in the accompanying Figure "6, capable of intercepting the lever 29 Lbest :illustrated in Figures 1, 2 and 6, provided with the right angled portion 29', which lever is 'journalled in the bearing 33, being angulated adjacent the bearings and therefore projecting through the wall 16 `'into the interior of the duct where it angles Ebackwardly as 'II have indicated at Sl in Figures land `l`2,1ina1l5y 2beinganlgulated as fat 32, transversely lof the duct Vand as best illustrated fin Figure 5 extending lfreely through a transverse drilling in the headf-33of the 'valve 2G so that rotation of Ithe lever in a clockwise direction with respect'to the accompanying Figures A-1 and 2, will liftthe-valve.

Secured to thewall 46 below the A-ring 114 *isian electric-coil :in fthroughfiwhichcurrent is designed to pass upon the commencement of -a cycle -'of stoker operation to heat the ring *Hi andthe heat motor 1,!2, and finally, those parts of ?the-*foregoing structure whichflare positioned upon the outer Vsideof the duct l, lare enclosed Withinthe housing the end wall '36 of this -housingfbeing providedv with'the air Aescapeaperture131 'for the -purpose-presently tolbe described.

Proceeding now todescribe theoperation of my assembly, I Would explain =that irmnediately upon Ithe commencement of a 'cycle of stoker operation, the -co'il 434 `=commences to heat up `and radiatei-tsiheat 1against the ring M. fHoweverfa certainvilength of time will elapselbefore *the-ring has absorbedsufiicient heat-to transmit -an'yfto theibi-'me'tallicfheat motor or coil [2 'and'during that time, the *fuel bed in the fstoker retort is kinding :naturally *rather than vbeing Lblown apart vand struggling against =a Violent draft of air. a

'Eventually, the coil -or ib-i-metal tape 'of' the motor 12 commences 'to `lengtlfien and unwind opening Lthe damper 2 v'very s'lowly and gradually permitting air therepast. f 'k 'Thesair lflowing therepast will graduaHyacquire sufiicientflvolume'to 'liftfi the lya'ne 2 I, and-at this point, I would specically-explain, as willjbe clearly noted from Figures -1 and 2,-that the vane lZI does not entirely seal the duct -asdoesthe damper 2l When closed, the upper and 'lowerhorizorit'alwedges 53% and `39 of the -vane 12l providing the'nfarrow itr'ansverse Vspaceslltil V and 'M Kat'top and'bottom through 'lwhichfiaksmall 1volume of air may @pass without raisingfth'efdamper,

=At alcertainrstage,V after the fuel "bed has ibecomef replenished-with coal `andthe same' ist-giving off its products o f combustion freely, thecontrol damper '2 will 'have-f'rotated almost as far as I havelshown in the Laccompanyingi'Figure '21, thus permitting the passage of a certain volume-ofb airto' `liftthe vane 2l almost as far as `-I -have shown it jin fthe same figure. f VThe accumulated heat fwithin'fth'e ringl |f4hand the-continued radiationof heat from-the coil '34, will-eventual-l-ylmove the same, thereby contracting it and causing the i damper plate 2 to rotate slowly in the opposite and closing direction. In this way, it will be seen that I have provided an accurate means for governing and controlling the maximum volume of air to be permitted into the retort. Air discharged through the port l 9 may escape through the aperture 31 in the end Wall 36 of my casing 35.

As I have previously indicated, a considerable volume of air at Substantial pressure is required to penetrate through a dense, thick fuel bed--a greater volume, that is, than Would ever practicably be permitted With a fixed damper, the position of Which is a compromise to provide at least reasonable efficiency under a variety of fire bed conditions.

Therefore, it is to 4'be understood that When a fuel bedis Well filled with coal, giving up its volatiles freely, my control damper 2 is in such position that it is permitting a greater volume of air to pass and force its way through the bed than Would be the case with a fixed damper, the air discharge port I 9 and associated valve being provided to check the damper 2 against ipermitting the admission of an even greater, and excessive Volume of air, as the motor |2 gets hotter and increases in length.

At the conclusion of a cycle of stoker operation, at Which time the fan comes to rest, it Will be recognized that -my control damper 2 is open to the maximum extent, and the same will only close at a very slow rate of speed, as the heat motor and the heavy cast ring 14 surrounding it, give up their heat so that a brisk natural Vdraft may continue to be indrawn into a fire bed, the oxygen therein being utilized to ignite the volatiles as they continue to be liberated but at a decreasing rate.

Referring to the adjusting means associated With my damper and vane and including the Quadrant plates 'I and 25 et seq. respectively, it will readily be understood by reference to the accompanying Figures 1 and 4 for instance, that rotation of the quadrant lock 9 in a clockwise direction following the loosening of the screw ll, around the quadrant plate, Will increase the tension of the motor L2. Conversely, rotation of the arm 9 in the opposite direction, will slacken the motor, and in this connection, I desire to explain that I generally prefer that my motor be so adjusted that the damper 2 is caused to bear against the stop 4 with a certain amount of pressure When in closed position, so that it will not commence to rotate immediately the bi-metal tape of the motor commences to deform responsive to the adjacent heat source.

As to my flow responsive vane 2l and air discharge lvalve l9, it will readily be recognized that rotation of the quadrant lock 21 on the quadrant plate 25, together With the sleeve 26 and the trip rod 28, will control the point at Which the-'valve 20 opens responsive to the action of the rod 29, and so, With these adjustments on each of my plate and vane, I am able to provide accurately.

for every installation.

In conclusion, although the title of this specification directs my invention to its use for automatic stokers, I desire to explain that the same Would also be practicable and useful in certain other industrial arts such for example as in the drying of a mass of material varying in density. I therefore do not Wish this specification to be interpreted as limiting my rights under thispatent to the use of my invention on automatic stokers but only as limited by the appended claims.

Since various modifications can be made in my invention as hereinabove described and many apparently widely different embodiments of same made Within the scope of vthe claims Without departing from such spirit and scope, it is intended that all matter contained in the accompanying specification shall be interpreted as illustrative only and not in a'limiting sense and I desire only such limitations placed thereon as are specifically expressed in .the accompanying claims.

What I claim as my invention is:

1. An air draft timing and volume control for automatic stokers, comprising in combination With the air duct thereof a rotatable volume regulating damper and a rotatable flow responsive vane normally biassed to one position and mov-I able from such position by an amount dependent on the flow therepast, said vane being positioned in spaced relationship with respect to said volume' regulating damper, within said air duct and upon the downstream side of said regula-tlng damper, the area of said vane being less than the right angled .tr-ansverse area of said duet, a heat motor connected to said regulating damper and governing the movement thereof so as to permit an increased flow therepast as the temperature of said motor increases, a coil for heating said motor upon the commencement of a cycle of stoker operation, means for cooling said motor upon dthe opening of said vane to a predetermined extent, a trunm'on rotatable With at least said damper or said vane, a pl-ate secured for' rotation .to and With said trunnion, a loose sleeve on said trunnion, and means projecting from said sleeve, said means being secured for unitary movement to and With said sleeve for looking said plate -and said sleeve in a plurality of selected positions so that said plate and sleeve may rotate as a unit.

2. An air draft timing and volume control comprising in combination with an air duct, a volume regulating damper, a flow responsive vane normally biassed to one position and being inovableA from such position by an amount dependent on the flow therepast, said vane being positioned in spaced relation With respect to said volume regulating damper, within said air duct, a heat motor connected to said regulating damper and governing vthe movement thereof so as to permit an increased flow therepast as the temperature of said motor increases, means for periodically heating said motor, and automatically operable means for cooling said motor upon the movement of said vane from its normal position a predetermined extent.

3. An air draft timing and volume control comprising in combination With an air duct, a volume regulating damper, a flow responsive vane normally biassed to one position -and being movable from such position by an amount dependent on the. flow therepast, said vane being positioned in spaced relation with respect to said volume regulating damper, Within said -air duct, said vanebeing located upon the downstream 'side of said regulating damper, a heat'motor connected to said regulating damperfand governing the 'movement thereof so .as to 'permit 'an 'increased flow therepast as 'the .temperature 'of said motor increases, means for periodically 'heating Lsaid motor, an air discharge :port in said air duct Aconstructed land arranged to 'direct its discharging air onto 'said motor, .together With 'an 'associated normally closed valve, and `means designed so vas to `open said valve and permit air from within said duet to impinge upon and cool Vsaid motor When said vane is moved from its normal position apredetermined extent.

4. An air draft timing and volume 'control comprising in combination With an air duet, a volume regulatin'g damper, 'a flow responsive vane normally biassed to one position .and being movable from "said position by an .amount dependent 'on .the flow therepast, said vane being positioned in spaced relation with respect to said volume regulating damper, within said duct, said vane being positioned upon the down-stream side of said regulating damper, 'a heat motor connected to said regul'ating damper and governing the movement thereof so as to permit an increased flow therepast a's the temperature of said motor increases, means for periodically heating said motor and an air discharge port 'in said air duct constructed and arranged to direct its discharging air onto said motor together 4with an associated valve normally closing said 'ducts, said valve being opera'bl'e to open position by the movement of said vane fromv its normal position a predetermined extent xt'hereby permitting the air from within said duct to impinge upon said motor to cool the same.

5. An air draft timing and volume control comprising in combination withra'n 'air duct, a volume regu'lating damper, a flow responsive vane normally biassed .to one position and being movable from said position by an amount dependent upon the flow 'therepast, said vane being positioned in spaced relation with respect to said volume regulating damper, within said duct, said vane being positioned upon the downstream side 'of said regulating damper, a heat motor connected to Vsaid regulating damper and governing the movement thereof so as to permit an increased 'flow therepast las-'the temperature of said motor in'creases, means for periodically heating said motor, *an air discharge port in the form of an elbow in one Wall of sai-d duet constructed and arranged .to direct its discharging lair onto said motor, a valve normally closing said port within lsaid duct, *a lever connected to said valve, said lever being rotated by .the movement of said vane when the latter is moved from its normal position a predetermined extent to open said valve, thereby permitting the escape of air 'from within'said duct through said port to impinge upon said motor and cool the same.

6. An air 'draft timing and volume control 'comprising in combination `Vwith lan air duet, a volume regulating damper, a flow responsive Vvane normally biassed 'to ,one position land being movable from said position by an amount dependent on the flow therepast, said vane being positioned in spaced relation with respect to said volume regulating damper, within said Vduct, said vane being positioned upon the downstream side of said reg'- ulating damper, a heat' motor connected to said regulating damper and governing the movement of same so .as to permit an increased fiow therepast as the temperature of said motor increases,

8 a heat radiating ring around Asaid motor, means for periodically heating said ring 'and thereby said motor, and means for cooling said motor upon the movement of 'said'vane from its normal position 'a predetermined extent.

7. An air 'draft timing'and volume vcontrol 'comprising in combination with an air duct, 'a'volu'me regulating damper, a flow responsive vane normally biassed to one position and being movable from said position by an amount dependent upon the flow therepast, said vane being positioned in spaced relation With respect to said'volume resulating damper, Within said duot, said vane being located upon the 'downstream side of *said regulating damper, `a heat motor connected to said regulating damper and governing the movement thereof so as to permit an increased flow ltherepast as the temperature of said motor increases, a heat radiating ring around said motor, means for periodically heating said ring and thereby said motor, and an Vair discharge port in said air duct constructed and arranged to direct itsV discharging lair onto 'said motor together With an associated valve normally 'closing said ducts, said valves being operable to open position by the movement of said vane from its normal position a predetermined extent, thereby permitting air from within said duct to impinge upon said motor to cool the same.

`8. An air draft timing and Volume control comprising in lcombination with an air duct, a volume regulating damper, a fioW responsive vane normally biassed to one position, 'and being movable from such position by an amount dependent on .the flow .therepast, said vane being positioned in spaced relation With respect to said volume regulating damper, Within said duet, said vane being located upon the downstream side of said regulating damper, a heat motor connected to said regulating damper and governing the movement V thereof so as to permit an increased flow therepast `as the temperature of said motor increase's, a heat radiating ring around said motor, means for periodically heating said ring and thereby said motor, an air discharge port in the form of an elbow in one wall of said duct constructed and `arranged to direct its discharging air onto said motor and cool the same.

9. An air draft 'timing and volume control comprising in combination With an air duct, a volume regulating damper, a flow responsive vane normally biassed 'to one position and being movable from such position by an amount dependent upon the flow therepast, said vane being positioned in spacedrelation with respect to said volume regulating damper, Within said duet, said vane being positioned upon the downstream side of said regulating damper, said vane being supported on projecting trunnions, a plate secured for rotation to one of said trunnions, -a sleeve on the trunnion to which said plate is connected, said sleeve being interposed between said vane and said plate, a radial lock Vs'ecuring saidl plate 'to 'said sleeve, a trip rod also secured to said sleeve, a heat motor connected to said regulating damper .and governing the movement thereof so as to permit an increased flow therepast as the vtemperature of said motor increases, means for periodically heating said motor, an air discharge port in .the form of an elbow in one wall of said duct constructed and arranged .to direct its discharged air onto said motor, a valve normally closing said port within said duct, a leverl connected to said valve, said lever being engaged'by said trip rod upon the rotation thereof, together with said lock, plate and vane, a predetermjifned extent to open said valve and permitting :the passage of air from within t said duct through said elbow to impinge on said motor and cool the same.

10. An air draft timing and volumeV control comprising in combination With an air duct, a volume' regulating damper positioned therewithf' in, a heat motor connected .to said damper upon '1 the external side of said ,duct and governing the i' movement of said damper so as to permit an inf] creased flow .therepastiasrthe temperature of said .f motor increases, an air discharge port in .the wall of said duct constructed and arranged to direct its discharging air ont'o said motor, a valve normally closing said port, means for periodically; heating said motor, afnd automatically operablefff" means for opening said valve to permit air to es-@rcape through said portjand impinge on said motor to cool same and thereby move said damper -to-jx wards or into the closed position following .th

opening of said damper a predetermined maxi-fff mum extent.

11. An air draft timing and volume contro comprising in combination with an air duct,

volume regulating damper positioned within saidf'f' air duet, a heat motor connected to said damper upon .the external side of said duct and governing .the movement of said damper so as to permit an increased flow therepast as the temperature of said motor increases, a heat radiating ring around said motor, an air discharge port in the wall of said duct constructed and arranged to direct itsy discharging air onto said motor, a valve normally closing said port, means for periodically heating said ring and thereby said motor, and automatically operable means for opening said valve to permit air to escape through said port and impinge on said motor .to cool the same and thereby move said damper towards or into the closed position following the opening of said damper a predetermined extent.

12. An air draft timing and volume control comprising in combination with an air duct, a volume regulating damper, a fiow responsive vane normally biassed .to one position and being movable from such position by an amount dependent on the fiow .therepast, said vane being positioned in spaced relation with respect .to said volume regulating damper, within said air duct, said vane being positioned upon the downstream side of said regulating damper, a heat motor connected to said regulating damper and governing the movement thereof so as .to permit an increased flow therepast as the temperature of said motor increases, means for periodically heating said motor, means for cooling said motor upon the movement of said vane from its normal position a predetermined extent, the area of said vane`

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