US2261540A - Stoker - Google Patents

Description

V. F. CODER Nov. 4, 1941.

S TOKER Filed April 4, 1958 2 Sheets-Sheet l Vane 'E Codlm- BKM @Maf Gttomeg V. F.- CODER Nov. 4, 1941.

S TOKER Filed April 4, 1938 2 Sheets-Sheet 2 Figa I Patented Nov. 4, 1941 STOKER Vance Frank Coder, Seattle, Wash., assignor to Northlake Fuel Co., Seattle, Wash., a corporation of Washingtonv Application April 4, 1938, Serial No. 199,805

6 Claims.

My invention relates to stokers for solid fuel, and the principal object of my invention is to provide a stoker construction which is adapted, without alteration, to the burning of any and all grades and kinds of coal, from the highest grade low-ash coal to the coals of high ash content and low grade or coking coals. It is also suitable for burning briquets, sawdust and other solid fuels, supplied in theform of granules or lumps.V

It is a further object to provide a simplified construction of such a stoker, which is neither an underfeed nor an overfeed stoker in the sense of providing a structure on which the fuel burns, but which in eilect is merely a means to accomplish the feed of fuel to be burned and combustion air to a combustion chamber. 'I'he combustion does not occur upon any hearth or grate which is incorporated as a part of the stoker, but rather is accomplished within the normal combustion chamber of the furnace into which the fuel is discharged from the stoker.

It is a further object to provide such a stoker which requires but' a minimum of attention, either to itself or to the fire which it supplies, which is rugged and substantially indestructible under the conditions of use, which is subject to independent control of the rate of feed of the fuel and of the rate of supply of air, and which is adapted to control by manual or automatic means at will.

The above are the general objects of my invention, and more specific objects will appear hereafter, as this specification progresses, or may be ascertained from a study of the drawings alone or in conjunction with the speciflcation and claims.

- In the accompanying drawings I have shown my invention embodied in a form which at present is preferred by me, it being understood that various changes may be made in the form, 'arrangement and character of individual parts, and

` in their relationship to each other, within the principles of my invention as herein disclosed.

Figure 1 is a general longitudinal vertical section through such a stoker and a portion of the combustion chamber with which it is associated in use.

Figure 2 is a general plan view of the same, with parts broken away and shown in section for better illustration.

Figure 3 is a transverse section substantially on the line 3-3 of Figure l.

Figure 4 is a bottom perspective view of the discharge end of the trough which forms part of (Cl. 11o-109) it, and showing a coke breaker operatively associated therewith.

A tunnel l, which may be of sheet metal, in part at least, of appropriate length and preferably rectangular in cross section, is disposed horizontally with its inner end 'entering a combustion chamber F. Preferably its inner end is formed as a cast metal mouth" l0, the cast metal being better able to withstand the heat within the combustion chamber, and the two-part tunnel construction facilitating installation. At its outer end it is provided with an appropriate opening Il, above which is disposed a hopper 5 to deliver the fuel, preferably by gravity, through the top of the tunnel and into its interior. While gravity feed into the tunnel is preferred, as being simple and direct, if the circumstances require a more positive feed may be employed, or in any event means may be provided, if necessary, to obviate bridging of fuel (as sawdust) at the hopper throat, but such auxiliary features are known, and in themselves form no part of my invention. For a purpose which will appear hereafter the inner end of the tunnel, from its inner end to a point intermediate the mouth I0 and the hopper 5, is raised or domed above the general level of the top of the outer end of the tunnel, to form the chamber I2, and there is thereby formed an upright wall i3.

Within the tunnel is disposed a trough 2, preferably of cast metal, which divides the tunnel into a lower aii` conduit A and an upper fuel conduit B. The trough has upstanding flanges 2f, is of a width to substantially separate the two conduits from each other, and extends from a point outwardly of the'hopper 5 and its throat Il into the inner end of the tunnel within the combustion chamber F. At this point it may be provided with a renewable end piece or ange 20, for this end is subjected to the most intense heat of the ilre. The trough 2 is suitably supported for lengthwise reciprocation, as for instance upon the ball bearing rollers 2|, mounted upon the walls of the tunnel I.

An air current, generated by any suitable means, is dischargedfwithin the outer end of the lair conduit A to pass through this air conduit,

beneath the trough 2, as indicated by the arrows in Figure l, and to discharge beneath the inner end of the trough, and through coal which has fallen off this inner end of the trough into the combustion chamber cavity ahead of it. 'I'he air source, as shown, is a blower 3 with its discharge pipe 30 directed into the conduit A, the

the Stoker, removed from the'tunnel which houses 55 blower being driven by a motor M. The motor and blower may be conveniently supported on the top of the tunnel I and beneath the overhang of the hopper 5. A plate or plates I3 at the blower intake are adjustable to control the amount of.

air supplied.

To eect advance of fuel through the conduit B from the hopper 5 to the combustion chamber F the entire trough 2 is reciprocated, and this may be accomplished by any .suitable means. As herein shown, a worm pinion 4 is driven through pulleys 4| and 42- and a belt Il from the motor M, and in turn drives a worm gear Il, carrying an eccentrically disposed'. roller l5 I -upon the abutment 22 to advance the trough and fuel-resting thereupon towards its' inner end, and then upon the abutment 23 to retract the trough. By the thrust upon such illxed abutment the trough is always moved to the same forward position shown in broken lines in Figure 1. A The extent of recipocation of the trough rearwardfrom this forward position is dependent upon the spacing between the abutments 22 and 23, and this spacing can be varied while the stoker is in operation, because of the troughs slow motion, by turning screw 2l. In the position shown the abutment 23 is set for maximum stroke of the trough, and its travel may be decreased by increasing the spacing of the abutments. It may be pointed out here that the supply of air is preferably controlled independently of the control of the fuel feed by means of the plate or plates 33 previously described. Also, the reciprocation of the inner end of the trough maintains a hollow space clear of ashes, clinker, and the like, for the emission of air through the fresh coal deposited in this cavity over such trough end from the tuyre slot between flange 20 and the tunnel bottom ywhich slopes up toward it as shown in Figure l. Because of the considerable thickness of flange 20 lengthwise of the trough 2 the single tuyre slot is of substantially constant width in all reciprocated positions of the trough. While the several controls are indicated as manually operable, the air supply control, the fuel feed control, and the control of the motor M may be arranged to be accomplished by suitable automatic means, but this in the advance of the trough in the direction of its inner end. Fuel resting upon it has a tendency to move inward with it during its inward movement. A stop plate I6, depending from the roof of the tunnel to the bottom of the' trough partitionsthe fuel space from the portion of the tunnel beyond the hopper 5. As the fuel moves forward with the feed movement of the trough, a space is progressively opened behind the fuel on the trough and ahead of plate I6, allowing fresh fuel to drop through the hopper throat II into such space. This fuel is pressed against trough, and since it cannot be displaced upwardly against the fuel above pressing downwardly through the throat, and it cannot move outwardly of the hopper because of the stop plate, the entire bed of fuel on trough 2 retains its advanced position. the trough sliding rearward beneath it. This opposition to retrograde movement of the fuel is further assisted by the upright edge Il, being engaged by'fuel which has passed just beyond it. As the trough is thus retracted from beneath the fuel at its inner end, this fuel falls progressively over the trough end into the hollow left by retreat of flange l2li, and is there burned.

The chamber' I2, however, has another pur pose, in that the fuel is heated as it approaches the discharge end of the tunnel, and gases and smoke arise from it. These gases rise through the fuel into the comparatively unrestricted chamber I2, and since their entrance into the combustion chamber F is substantially unrestricted from this chamber I2, they pass into the combustion chamber and are consumed, rather than passing backwardly through the fuel and out through the hopper.

'I'he trough nts closely within the upper por tion of the tunnel throughout the greater portion of its length, in order to prevent escape of air between the side flanges of the trough and the side walls of the tunnel and thence into the fuel conduit. However, I prefer that these surfaces be spaced somewhat from each other in the vicinity of the discharge end of the tunnel, so that air from the air conduit A may pass.

about this heated end of the trough to cool the latter somewhat. To this end the outer walls of the trough are relieved somewhat, as indicated at 26, and this-materially assists in maintaining the inner end of the trough and the mouth of the tunnel cool, and lengthens their effective life. Likewise the end piece 20 is grooved, as indicated at 21, to permit its mass to be more readily cooled by the air which escapes beneath it into the combustion chamber, and to improve the tuyre effect on the air discharge opening beneath it.

As will now be apparent, fuel placed in the hopper i feeds by gravity downwardly until it comes to rest upon the trough 2, and by the reciprocation of the latter is advanced step by step until it reaches the inner end of the trough and falls over this inner end into the hollow left in combustion chamber F by retraction of flange 2l. The combustion chamber may be the normal combustion chamber of a furnace, and suitable structure is provided. which may be the usual furnace grates G serving simply as trusswork, to support a combustion chamber floor formed by plate P. 'Ihis iioor is preferably imperforate in order that air may enter the combustion chamber only from the air conduit A and through the tuyre opening between flange 2li and the thickened inner end of the tunnel bottom. The plate P protects the floor supporting structure from burning out, although it is not cooled by air passing upward through it.

The coal, then, falls upon the plate P, or upon a bed of ashes or coals resting upon the plate P. coal thus falling over being indicated at C. By the time it reaches this point (which is beyond the end of the tunnel I and trough 2) it has been heated substantially tothe point of ignition, and the air, passing out of the inner end of the air conduit A through the tuyre opening,

stop plate I6, upon return movement of the 7,6 blows immediately through the fresh coal and arsenicoA heated by contact with the stoker surfaces, ef-

fects prompt combustion of the coal, with the result that the fire burns with any degree of brightness desired, and controlled by the rate o! feed of the fuel and the rate of supply of air. A forge effect is thus obtained, and regardless of the character of the coal, it is burned promptly and substantially wholly.

It will be seen that as the trough end 20 moves forward or in the inward direction to the broken line position shown in Figure 1, such end flange 20 and the coal supported on the discharge end of the trough 2 will push burning coal and ash ahead of it down to the level of the flange edge, or to the bottomof breaker blade 6 to be described hereafter. A hollow in the coal and ashes, occupied by the end of trough 2, will thus be formed into which fresh coal drops during its backward or outward movement, and this hollow constitutes the principal combustion zone. On the next forward stroke this deposited coal, which by that time-has largely burned, will in turn be pushed across plate P ahead of flange 20, to be piled up beyond the unvarying limiting forward position of travel of flange 20 shown in broken lines in Figure l. This operation repeats, the flange on each forward stroke clearing a hollow in the space through which it travels and piling the ashes up beyond it, and on each backward stroke progressively opening the hollow thus formed to receive a charge of fresh' fuel dropping over the end of the trough during such movement.v All coals will eventually form a clinker, but this clinker, being acted upon by the fresh coal pressed transversely against it by flange 20, and exerting a wedging action on the bottom of the pile 'formed beyond the zone of movement of such member, aided by the upward draft of the entering air, is pushed upwardly and to one side, as indicated at Y.4 When this ash pile becomes so high 'that an appreciable amount falls down on the fresh coal when trough 2 recedes, or interferes with the feed of fresh coal, it can be cleaned out from time to time from above. Actual tests have demonstrated that such a stoker will burn any and all grades of coal completely down to the absolute ash content.

With coking coals it may be desirable to provide means to break the clinker in the immediate vicinity of the inner end of the tunnel, to eliminate appreciable obstruction to the` supply of air to the combustion chamber, and to this end I provide a coke or clinker breaker, consisting of a flat blade 6 and a shank 60, supported upon and movable with the trough 2, the blade 6 projecting into the bed of coals in advance of the inner end of the trough, and by th`e reciprocation of the trough poking and breaking up the clinker within its range of movement. This breaker may be removably secured in place, so that it may be removed when the grade of coal used does not require its use, and to this end a two-fingered lug 28, upon the under side of the trough 2, is formed with a longitudinal keyhole opening 29, the inner end of the shank 60 being noncircular, as indicated at 6I, and having a locking and driving lateral extension 62 engaged between the separated lfingers of the lug 28, as seen in Figure 4. By these or equivalent means the shank of the breaker may be inserted through the air discharge opening and engaged with the lug 28, and when turned into its flat operative position, ii cannet be disengaged from the ing What I claim as my invention is:v

1.' A stoker for solid fuel comprising a 'tunnel adapted to open at its inner end within a combustion chamber, reciprocable fuel delivery mechanism extending lengthwise of'said tunnel and dividing it into anupper fuel conduit and a lower air conduit, a flange imperforate relative to and depending from the inner end of said reciprocable mechanism downwardly toward the bottom of said tunnel to define a single tuyre slot constituting the sole Outlet for lthe lower air conduit, for discharge ofvair from said air conduit only forward of the inner end of said mechanism, and means to reciprocate said mechanism lengthwise of said tunnel, thereby to spill fuel, all in unburned condition, from said fuel delivery mechanism over and beyond its inner end down into the path of air being discharged through the single tuyre slot beneath said flange.

2. The stoker defined in claim 1, a coke or clinker breaker projecting inwardly beyond the inner end of the fuel delivery mechanism and beneath the flange depending therefrom through lthe tuyre opening, and means carried by such mechanism supporting said breaker for reciprocation in conjunction with it.

3. A stoker for solid fuel comprising a tunnel adapted to open at its inner end within a combustion chamber, reciprocable fuel delivery mechanism extending lengthwise of said tunnel and dividing it into an upper fuel conduit and a lower air conduit, a flange of considerable thickness lengthwise of said reciprocable mechanism, imperforate relative to said mechanism, and depending from its inner end downwardly toward the bottom of said tunnel to define a single tuyre slot of substantially constant width in all reciprocated positions of said mechanism, constituting the sole outlet for the lower air conduit, for discharge of air from said air conduit only forward of the' inner end of said mechanism, and having in its lower edge spaced air discharge grooves extending generally lengthwise of said reciprocable mechanism to cool the flange, and means to reciprocate said mechanism lengthwise of said tunnel, thereby to spill fuel, all in unburned condition, from said fuel delivery mechanism over and beyond its inner end down into the path of air being discharged through the single tuyre slot beneath said flange.

4. A stoker for solid fuel comprising a. tunnel adapted to open at its inner end within a combustion chamber, reciprocable fuel deliveryA mechanism extending lengthwise of said tunnel and dividing it into an upper fuel conduit and a lower airconduit, a flange, imperforate relative to and depending from the inner end of said reciprocable mechanism downwardly toward the bottom of said tunnel, the tunnel bottom being inclined upwardly toward the lower flange edge, with said flange to define a single narrow tuyre slot constituting the sole outlet for the lower air conduit substantially the entire width of the tunnel, for discharge of air from said air conduit only forward of the inner end of said mechanism, and means to reciprocatev said mechanism lengthwise of said tunnel, thereby to spill fuel, all in unburned condition, from said fuel delivery mechanism over and beyond its inner end down into the path of air being discharged through thev single tuyre slot beneath said flange.

5. A stoker for solid fuel comprising a tunnel adapted to lopen at its inner end within a combustion chamber, a fuel delivery trough extending lengthwise of said tunnel and dividing it into an upper fuel conduit and a lower air conduit, means to reciprocate` said trough lengthwise of the tunnel, and a step in the roof of said tunnel adjacent to its combustion chamber end, defining'a substantially vertical wall extending downward from the inner section of the tunnel roof to join with the outer roof section, constituting an abutment for engagement by fuel on said trough to impede outward fuel movement in conjunction with said trough during its outward stroke, thereby to deposit fuel over the end of said trough, and defining with the inner section of the tunnel roof a gas trap chamber above the fuel on said trough and adjacent to and communicating with the combustion chamber. A

6. A stoker for solid fuel comprising a tunnel adapted to open at its inner end within a comtion thereof, and extending downwardly toward the bottom of said tunnel. which bottom slopes upward toward its inner end. to define a tuyere opening for the lower air conduit between such flange and the tunnel bottonameans to reciprocate the trough lengthwise of thev tunnel, first in an inward direction to clear a hollow in the combustion chamber by said flange moving forward with the trough, and thereafter in an outward direction, simultaneously to withdraw said flange out of the hollow cleared by it and to deposit fresh fuel over the end of the trough into such hollow upon retraction of the trough from beneath such fuel, and a step in the roof of saidtunnel adjacent to its combustion chamber end defining a substantially vertical wail extending downward from the inner section of the tunnel roof to join with the outer roof section, constituting .an abutment for engagement by the fuel on said trough to impede outward fuel movement in conjunction with said trough during its outward stroke, thereby to effect such deposit of fuel over the trough end, and defining with the inner section of the tunnel roof a gas trap chamber above the fuel on said trough and adjacent to and communicating with the combustion chamber. l

VANCE FRANK CODER.

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