US443110A - Automatic stoker - Google Patents

Description

(No Model.) 4 Sheets-Sheet l.

N. W. PRATT. AUTOMATIC STOKE-R.

No. 443,110. Patented Deo. 23, 1890.

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N. W. PRATT.

AUTOMATIC STOKBR.

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ATTORNEY (No Model.) A 4 sheets-sheet s,

N.. W. PRATT. AUTOMATIC STOKBR.

No. 443,.110. 'Patented Deo. 2.3-, 1890. Z1-@f4 Q/ A TTORNEY.

I (N0 MOdGL) l 4 Sheets-Sheet 4.

N. W. PRATT. .AUTOMATIC STOKER.

Patented Deo. 23, 1890.

ATTORNEY.

UNITED STATES PATENT OFFICE.

NAT. V. PRATT, OF BROOKLYN, NEV YORK.

AUTOMATIC sToKER.

SPECIFICATION forming part of Letters Patent No. 443,11, dated December 23, 1890. Application filed December 23,1889. Serial No. 334.727. (No model.)

V.To @ZZ whom t may concern:

Be it known that I, NAT. YV. PRATT, a citizen of the United States, residing at Brooklyn,in the countyof Kings and State of New York, have invented certain new and useful Improvements in Automatic Stokers, of which the following is a specication.

My invention relates to chain-grate stokers; and it has for its object to adapt the furnace wherein such a stoker is used to exclude the access of cold air through the interstices that are usuallyleft between the moving sections of the grate and the furnace-walls or other parts of the furnace or ash-pit; also to adapt the construction of the furnace to obtaining a maximum efficiency of heat; also to promote convenient access to the furnace where it is required to pull the fire or to observe or regulate the same independent of the feeder; also to separate the residue of the fuel that has traveled the entire length of the furnace from the portions of fuel that may fall through the grate at intermediate points and be but partly consumed; also to crush and distribute the coal evenly upon the grate and apportion asuflicient amount of the body of coal toward the sides of the furnace to form a seal against the direct access of air above the grate; also to promote water circulation in the boiler and to protect the walls of the furnace by the introduction of water-pipes that lie proximate to the sides of the hre; and in order to enable others skilled in the art to which my invention appertains to understand and use the same, I will proceed to describe its construction in detail, explain its operation, and point out in the appended claims its novel characteristics.

Referring to the accompanying drawings, forming a part of this specication, and in which similar characters of reference indicate corresponding parts, Figure 1 is a sectional elevation of a water-tube boiler, showing the improvements applied thereto; Fig. 2, a transverse section of Fig. l on the line :c x, shown on an enlarged scale; Fig. 3, a front elevation of the lower portion of the boilerfront on the same scale as Fig. 2; Figs. 4 and 5, detail views of the feeder; Fig. 6, a detail view of the sprocket-wheels and their shaft at the rear end of the chain grate; Fig. 7, a horizontal section on the line 'y y of Fig. l;

Fig. 8, a sectional elevation of the furnace and ash-pit with the chain grate and feeder removed; and Fig. 9, a transverse section on the line z e', Fig. S.

A A are the inclined watentubes, and B the steam -drum, composing a well-known type of sectional boiler which I have chosen to illustrate in connectionwith myinvention, it of course being understood that the said invention is applicable likewise to any other type of boiler than the special form shown.

C is the furnace, located beneath the front or elevated ends of the water-tubes, and to which the draft is supplied from the point D through the sections of the graues.

E E are water-boxes at each side of the furnace-doors F, which form side walls for the doors and iuelose the receiving-space of the feeder above the doors.

To the water-boxes E, I connect the watertubes l l, which communicate with the inud- `drum G or any suitable lower portion of the boiler, and are slightly inclined to promote circulation extending through the furnace adjacent to the walls thereof and just above the grate-surface to form hre-backs for the fuel. The hand-holes 2, Fig. 3, afford access to these tubes for cleaning them. To the Water-boxes E, I also connect the uptake-pipes Il, which deliver the rip-current of water from the tubes l to the connecting-box I, intermediate to the headers and the steam-drum of the boiler, or to any suitable upper portion of the boiler.

The pulverized coal or ashes at the sides of the furnace are banked up against the tubes l to seal the sides of the grate, and in order to effectuate this purpose the tubes are made to converge from the front of the furnace toward the rear, as seen in Fig. 7, so that as the fuel is moved rearward and becomes consumed and diminished in bulk it is crowded toward the center of the furnace to compensate for the reduction and to maintain the depth at the. sides.

The ledges J .l of fire-brick overhanglthe tubes l in the furnace and prevent accumulation of ashes behind and around the said tubes, exposing only the sides of the latter that are in direct contact with the moving fuel.

3 are sleeves that support the fire-brick ICO of the bridge-wall K at those portions which the tubesl intersect, and the latter are thereby left free to their movements of lineal expansion-without rupture to the wall.

L and M are overhanging radiating blocks composed of fire-brick, and these being placed at an angle to the tire are adapted to absorb and radiate the heat, so as to intensify the temperature of the furnace. 'lhe radiatingsurface L is by its inclined position adapted to receive the heat from the body of the lire, assuming a glowing temperature, an d to transmit the same tothe fresh fuel beneath it with sufficient intensity to ignite the same at an earlier period than would be the case should the direct heat of the fire be employed to ignite the incoming fuel.

The chain grate N is composed of interlocking links having any well-known or suitable form of construction, and it is operated over sprocket-wheels t 5 in the usual manner, the power being applied to the shaft t5 of the wheels 4. The chain grate travels over supporting-rollers T, that extend at suitable intervals beneath the links between the side frames 8 8, that carry the sprockctwheel shafts and form a carriage for the grate and its operating mechanism. 'lhe carriage S is provided with truck-wheels il, that fit a flanged track, upon which the grate may be rolled out bodily from the interior of the furnace.

The upper edges of the side frames S S are inwardly flanged, as shown in Fig. 2, to close the spaces that would otherwise be left at the sides of the grate-links, upon which the fire rests, and there are plates 10 built int-o the side walls overhanging the flanges 11 of the frame 8 adjacent to them and above which the tubes 1 are located. The plates 10 being parallel with the flanges 11 effectually close the sides of the furnace from the spaces exterior to the side frames 8, and I here remark that the inclined position of the plates 10 and of the flanges 11 permit their surfaces to be brought closely together when the grate-truck is pushed back, affording a practicallyT tight joint throughout the adjacent surfaces.

The rear sprocket-wheel shaft 12, as more fully appears in Fig. G, is furnished with a cylinder 13, enveloping it and extending between the sprocket-wheels, so as to fill the spaces as far as possible that would otherwise permit passage of cold air into the furnace at the reversing-point of the grate. The spaces exterior to the frames 8, adjacent to the side walls and opposite to the sprocket-wheels 5, are also filled by flanged caps 18, that abut against the counter-surfaces 20, Fig. 7, of the bridge-wall and have recesses 19, that inclose the hubs of the sprocket-wheels.

Below the grate-truck l employ one or more ash-pan trucks 14, (two being shown,) that are withdrawn upon suitable trucks beneath and between the tracks of the grate. There is a partition-plate 15, that depends from the caps 18 of the grate-frame between the lower or returning links of the grate and the top of the ash-pan 1l, and there is also a partition 1U beneath inthe ash-pan that corresponds in position with the plate 15 when theash-truck is in place. A separation is thereby formed between the body of the ash-pit and the chamber 17 to prevent passage of draft, and the ashes are precipitated into the chamber 17 as the grate revolves, the perfectly-consumed residue being received in a separate compartment from that of the imperfectly-consumed coals that form a considerable percentage of the ash dropping at intermediate points from the fire.

l is the feeding-hopper that is provided at its neck with a feeding and crushing device 21. The casing 22 of the feeder forms the crown of the furnace-door casing, and the furnace-doors F swing on a fulcrum at 23, Figs. 1, 3, and 5. The doors are fixed to the shaft 21, having a suitable hand-lever at the side, by which the doors are raised, and the weight of the doors is eounterbalanced by a. weight 29, connected by a chain to the lever 2S, the latter having a position relative to the draft of the weight., whereby the doors are held in either their open or closed position bythe gravity of the weight. Access is therefore obtained to the fire independently of the feeding device and without the necessity of removing any of the parts pertaining thereto, as llas been the case with the forms of mechanism used heretofore. The interior of the casing 22 is cylindrical, and the feeder 21 rotates therein in the direction of the arrow, Fig. et. 'lhe feeder is composed of blades that form pockets 25, which fill from the hopper by the gravitation of the coal into them. Stich lumps of the coal as may be larger than the intended size are caught between the edges of the blades and the adjacent edges of the easing 22 and broken, and the portions are successively discharged or showered upon the grate as the pockets come opposite the opening 2G. It is to be observed that the neck of the hopper and the opening 26 are sufficiently apart with relation to the blades of the feeder to cut off ingress of air at all positions of the feeder. The blades, moreover, are arranged spirally, as shown in Fig. et, whereby their rotation in the direction of the arrow will tend to spread the fuel toward the sides of the furnace, since thebulk would naturally tend to pass through the center of the hopper. The spiral form is, however, made of sufficient pitch to more than equalize the said tendency, inasmuch as it is desired to apportion the coal largely to the side of the furnace, for the purposes hereinbefore stated.

The rotation is imparted to the grate-shaft 6 and also to the feederlby mechanism substantially alike. The said mechanism consists in each case of a worm-gear 30, having the teeth on the side of its periphery, a worm 31 engaging therewith, a ratchetwheel 32 on the worm-shaft, and a rock-arm 33, fulerumed on said shaft, bearing a pawl that en- IOO ITO

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gages with a greater or less number of teeth of the ratchet, according to thelength of stroke given to the rock-arm. The actuating-stroke is derived from any suitable source of given speed as the eccentrics 3e, and said stroke is varied by the adjustment of the eccentricrods at greater or less-distance from the fulcruni of the lever 33. The relative automatic speeds of the feeder and the grate are thereby Varied, according to requirements of the fire.

What I claim as my invention, and desire to secure by Letters Patent, is-

1. The combination,with a chain Stoker, of a furnace the side walls whereof converge in the direction of motion of the grate, whereby the fuel is concentrated during its passage and combustion.

2. The combination, with a boiler-furnace and a chain stoker, of water-circulatin g pipes extending longitudinally at the sides of the furnace adjacent the surface of the grate to form portions of the side walls for retaining the fuel, said pipes connecting at their respective ends with a lower portion of the boiler and with an upper portion thereof to promote circulation, substantially as described.

3. The combination, with achain Stoker, of water-circulating pipes extending longitudinally and adjacent to the furnace walls at or nearthe surface of the grate, said pipes converging toward the direction of the lineal movement of the grate, for the purposes specitied.

4. The combination, with a boiler-furnace and a chain stoker, of the water-boxes E, form- .ing side walls of the fuel-receiving chamber,

water-circulating pipes extending longitudinally and adjacent the furnace-walls and the surface of the grate and connected to a rear and lower portion of the boiler, and uptakepipes, as H, con necting with a front and upper portion of the boiler, adapted for the purposes specified.

5. The combination of a furnace and a removable chain-grate frame therein, the adjacent surfaces whereof form joints inclined with reference to the direction in which the grate is inserted or withdrawn from the f urnace, for the purpose set forth.

6. In a chain grate, the combination of the side frames composing a grate-truck inclined at the upper edges toward the rear of the furnace, andsurfaces, as the plates l0, that incline correspondingly to the upper edges of the side frames and project from the furnace side walls to form a joint that is closed by the backward movement of the grate-truck, as described.

7 The combination, with a chain stoker wherein a space is left at the reversing-point of the links adjacent the bridge-wall, of an ash-pan adapted to receive the deposits from intermediate portions of the grate, and having a partitioned compartment beneath said reversing-point of the links to receive the ashes precipitated adjacent the bridge-wall.

S. The combination, with a chain stoker wherein a space is leftat the reversing-point of the links adjacent the bridge-wall, of a partition-plate located vertically beneath the reversing-point of the links, an ash-pan extending beneath the grate and beneath the said space, and a partition-plate within the ashpan adapted to form a continuation of the first-named partition-plate when the grate and the ash-pan are in place, substantially as and for the purposes specified.

t). The combination, in a chain stoker, with the sprocket-wheels and shaft at the reversing-point of the links, of cylinders enveloping the said shaft at the exposed spaces of the same between the sprocket-wheels, said cylinders having a diameter whereby they occupy the spaces intervening between the shaft and the inner surfaces of the links, adapted for the purposes specified.

NAT. XV. PRATT.

Witnesses;

H. F. PARKER, CHAs. HANIMNN.

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