US2240972A - Stoker - Google Patents

Description

May 6, 1941. H. E. wlNKLr-:R ETAL Y 2,240,972

ystroma VFiled March 17,' 1938 C ATTORNEYS.

Patented May 6, 1,941

sroxea Herman E. Winkler and Carl J. Winkler, Lebanon, Ind., assignors to U. S. Machine Corporation, Lebanon, Ind., a corporation of Indiana Application March 17, 1938. Serial No. 196,321 3 Claims. (Cl. 116-45) In a common form of small stoker, coal is fed horizontally by means of a feed screw through a pipe communicating with the bottom of a burnerl arises from the fact that most coals have the' property of becoming more or less plastic and adhesive in character as combustion temperature is approached, with the result that masses of coke are formed. These masses may be so dense that the air-supply can not penetrate them to an extent suilicient to consume them as rapidly as they form, and the mass grows vertically, as more fuel is fed into theburner, to form. a fcoke tree" which frequentlyrises to a considerable height. These coke trees, both while erect and after they have fallen, tend to produce uneven and meillcient combustion and to prevent the fire from reacting promptly to the heating demand on the Stoker. It is the object of our invention to maintain the upper surface of the fuel bed within the burner free from'any pronounced depressions, to

avoid segregation of large and small coal particles, and to prevent the formation of coke trees of any considerable height. Further objects of our invention are to facilitate quick response of stok-er-fed fires to heating demands, to improve the combustion rate, and to obtain greater eiliciency from the fire. i

In carrying out our invention, we mount inthe burner a. rotatable element which acts on the coal within the burner and which, conveniently, is driven fromgthe main feed screw. This rotatable element, in'A its preferred form, is adapted to prevent segregation and the accumulation of coal near the rear of the burner and also to prevent lthe formation-.of coke tree's. For the former purpose, it maybe provided withV a helical flight adapted to move` forwardly of the burner coal adjacent the rear wall thereof; and for the latter purpose, the rotatableel-ement may be .provided with a laterally projecting finger which, in its rotation, will traverse the zone occupied by coal in the plastic state and break up any incipient coke formation which mightfotherwise rise to a considerable height.

The accompanying drawing illustrates our invention: Fig. 1 is a fragmental side elevation of a furnace with an associated stoker; Fig. 21s a vertical section through the burner of our improved stoker; and Fig. 3 is a view similar toFig. 2 but illustrating a somewhat modified form of construction.

In the arrangement illustrated in Fig. 1 the Stoker is shown in association with a. furnace -1 having a fire-pot 8 including a bottom wall 9. The stoker includes -a coal bin I0 which, at its bottom, communicates with a feed pipe II. A feed-screw I2 located within the pipe II and extending rearwardly into the bottom of the bin I operates, when rotated, to feed coal from the bin I0 through the pipel I. l

At its innerl end, the feed pipe l communicates with an elbow-shaped passage I3 'in a burnerbase Il. A burner-head I5 is supported on the base Il with its interior communicating with the upper end of the passage I3 and with its top extending into a central opening in the bottom wall 9 of the fire-pot. The burner-wall is provided with tuyre sections I6 forming discharge openings for an annular passage I1 surrounding the burner, such passage being supplied with air from ablower I8. l

The structure. as so far described, is fairly common. The feed screw Il, blower lfand feed-screw drive mechanism are driven, as by an electric motor (not shown) which, in most instances, is under automatic control so that the supply of air and fuel to the furnace is proportioned in accordance with the heating requirements. Because of the action of the feed-screw,

-both in feeding coal into the passage I 3 .and in causing a measure of recirculation of coal, the- 'ner coal particles tend to accumulate along the outer orv rear wall of the passage I3 and to rise in the burner to a greater height than the coarser particles at the front of the burner, and uneven combustion therefore results.

To prevent this unevenness of fuel-distribution, both in respect to depth and particle size, we mount in the burner-base I4 a rotatable element 25 which extends into the coal-containing space within the passage I3 and within the burner. Desirably, but not necessarily, the element 2B is mounted in the rear wall of the passage I3 and projects forwardly toward the center of the burner. As shown in Fig. 2, the rotatable element 2l is mounted in an inclined position, extending forwardly 'and upwardly into the 'IIL-arid in alinement with the feed screw I2 a.

short' shaft 26, the front end of which is coupled to the rear end of the feed screw I2 as by a sleeve coupling 21. The rotatable eleme'nt 25 or 25 and the shaft 26 are provided with mating gears so that the rotatable element may be driven by the feed screw. In the arrangement illustrated in Fig. 42 bevel gears 28 are employed for thisA purpose; whereas in the arrangement illustrated in Fig. 3, where the feed screw and rotatable element are parallel, the gears 23' are simple spur gears.

To prevent the segregation of coal sizes in the passage I3 and at the rear of such passage, and thus to prevent the surface of the fuel bed from being higher `at the -rear of the burner than at the front,` the rotatable element 25 or 25' may be provided with a helical flight 30 which, if `the feed screw and rotatable element rtate in opposite directions, is of the same hand as thffe'ed;

screw I2. As the feed-screw I2 tends to force the coal toward the rear of the passage I3 the flight 30, rotating in the opposite direction, tends to move at least a part of such coal forwardly and to counteract the tendency toward segregation of coal sizes and to avoid any effect of the feed screw I2 in packing coal against the rear wall of the burner.

With fthe structure such as is illustrated either in Fig. 2 or in Fig, 3 it is possible to maintain the upper surface of the fuel bed within the.bl1rvrll ,A center of the burner, and means for rotating said.

I5 at a substantially constant elevation throughout its periphery and to obtain uniform distribution of coal sizes, thus creating better combustion at all points. I

To prevent the formation of large coke-masses which would grow', into coke trees, the rotating element 25 is shown in Fig. 2 `as provided at its 45 inner end with a laterally extending finger 3|. This finger is so disposed as to traverse that zone in .the burnerl where coalV in the more or less plastic state is located, andV may be a continuation of the helical flight 3|), if the rotatable ele- 50 ment 25 embodies such a helical Hight. The

the lowermost ofA the'tuy'rs.

As coal is fed to the burner and as the rotatable element 25 rotates, the finger 3| will serve to disturb the more or less plastic coal and thereby to create fissures in the resultant coke formation. Because of such fissures, the coke mass does not grow to any great height above the burner, but instead breaks up into relatively small pieces which spread loosely and evenly over the top of the fuel bed in the burner and over the bottom 9 of the fire-pot, as is ideal for efficient combustion.

We claim as our invention:

1. In a stoker having a generally horizontal necting said two screws, said auxiliary screw projecting forwar-lly toward the center of the burner and'being-of such a hand aswtoproduce .Within V the burner continuous movement of fuel from thewieinityof.-the l'ai' burner-wall toward the Center ofthe burneiffw" ,f j

2. In a stoker having a generally horizontal feed pipe communicating with the bottom of an upwardly opening burner having tuyres in its side walls, mechanism for feeding fuel through said feed-pipe into said burner, a screw rotatably mounted in the rear wall of the burner belga. said tuyres on an axis generallyprpcndicular to such rear burnerwiallfsaisrw projecting frQrnthareaaamrnerf-vall forwardly toward the screw to move fuel continuously toward the center of the burner from the vicinity of the rear wall thereof.

3. The invention set forth in claim 2 with the addition that said screw is provided near the center of the burner with a laterally projecting fuel-agitating finger which, in its rotation, passes through a zone extending above and below the lowermost of said tuyres.

HERMAN E. WINKLER. CARL J. WIN'KLER.

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