US2359888A - Stoker - Google Patents

Description

{)ct 10, 1944. c B 2,359,888

STOKER Filed April 12, 1944 5 Sheets-Sheet [U H i i g R, i i W 3 i 2 E Q 5 i.i

iCF I O" I k INVENTOR. 6M4 w BY N Wad; A

, ATTORNEYS.

C. R. BARR STOKER 5 Sheets-Sheet 2 Filed Aprill2 1944 INVENTOR. m Q, 6%

BY ATTORNEYS.

b N RH Get. 10, 1944. c. R. BARIVQ 2,359,888

STOKER Filed April 12, 1944 5 Sheets-Sheet 3 Fri/ a I I I INVENTOR.

BY a I r .4 TTORNEYS.

c. R. BARR I 2,359,888

STOKER Filed April 12, 1944 5 Sheets-Sheet 4 QW N AHR I INVENTOR. W W. 6w

- A TTORNEYS.

ct. 1, 1944. c. R. BARR 2,359,888

STOKER Filed April 12, 1944 5 Sheets-Sheet 5 INVENTOR.

l l L./' BY Wad; a. M

A TTORNEYS.

Patented Oct. 10, 1944 UNITED STATES PATENT OFFICE STOKER Charles R. Barr, Pittsburgh, Pa.

Application April 12, 1944, Serial No.. 530,657

8 Claims. (Cl. 110-105) This invention relates to new and useful improvements in solid fuel stokers for burning coal, and the present application is a continuation-inpart of application Serial No. 357,127, filed September 1'7, 1940.

The invention consists of feeding measured increments of fuel to different areas of a fire box successively while maintaining a combustion atmosphere in the fire box chamber capable of consuming substantially all of the volatile or combustible products, before passing to the stack, to eliminate smoke.

The invention further contemplates the employment of a stationary grate above an air chamber capable of maintaining relatively low air pressure to uniformly deliver air through the grate bars, which together with the uniform distribution of the fuel throughout the fire box area sustains efiicient combustion and maintains a uniform thickness of fire bed on the grate bars. It is a primary object of the invention to. provide a method of stoking solid fuel which shall eliminate smoke in the stack and which shall be capable of controlling the rate of firing a boiler in accordance with a wide range of load demand.

It is a further object of the invention to provide a method of stoking fuel by feeding small increments and distributing the same uniformly throughout the fire box area independently of the rate or volume of fuel being delivered to the fire box.

It is still a further object of the invention to provide a method of stoking fuel which consists of establishing a series of divergent blasts through a wall of a fire box and delivering measured increments of fuel to different zones of the blast successively from one side of the blast to the other to thereby obtain a uniform distribution of the fuel to different areas of the fire box for maintaining the fire bed of substantially uniform thickness.

These and other objects of the invention will become more apparent from a consideration ofthe accompanying drawings constituting a part hereof in which like reference characters designate like parts and in which Fig. 1 is a rear elevational View of a stoker feed apparatus embodying the principles of this invention;

Fig. 2 is a side elevational View thereof;

Fig. 3 is cross-sectional views of the parts of a paddle conveyor;

Fig. 4 is a top plan view of the paddle conveyor diagrammatically illustrating the feeding of the fuel to the blast;

Fig. 5 is an end elevational View of the assembled paddle conveyor;

Fig. 6 is a top plan view of the fuel distributor plate showing the steam box and a portion of the conveyor housing in horizontal cross section;

Fig. '7 is a top plan View diagrammatically illustrating the distribution of the fuel in the fire box;

Fig. 8 is a vertical cross-sectional View, partially in elevation, illustrating the feeding of the solid fuel from a hopper to the distributor plate and into the fire box;

Fig. 9 is an end elevational view, partially cut away, of an adjustable crank pin drive;

Fig. 10 is a vertical section taken on the line I0l0 of Fig. 9;

Fig. 11 is a cross-sectional View. partially in elevation, taken along the line ll-Il of Fig. 9;

Fig. 12 is a cross-sectional view of a portion of the paddle conveyor drive taken on the line IVE-I2 of Fig. 2;

Fig. 13 is a vertical longitudinal section of a fire box and grate structure and blast chamber partially in elevation and partially cut away; and

Fig. 14, is a front elevational view of the paddle conveyor mechanism and blast nozzles.

With reference to Figs. 1 and 2 of the drawings, the structure therein illustrated comprises an integral casting l which may be attached to the front of a fire box by bolts extending through openings 2 around the periphery of the casting, and openings extending through a flanged face 3 of the casting which is attached to the front Wall 4, of the fire box in the manner shown in Fig. 8.

As shown in Figs. 2, 8, 13 and 14, a distributor plate 5 extends inwardly from the stoker casting and forms the sill of the fire box door. The fuel designated by the numeral 6 is fed through a hopper I, Fig. 8, attached to the top of the stoker casting, by a paddle conveyor generally designated by the numeral 8 to the distributor plate 5, the fuel dropping over a shoulder 9 of the casting into the path of a plurality of blast nozzles H3 communicating with a pressure chamber or steam box H, Fig. 6, the details of which will be hereinafter described.

The paddle conveyor 8 consists of a shaft E2 of square shape that extends the entire width of the stoker and is driven by a ratchet wheel [3, Fig. 2, that is actuated by a pawl I4 carried by an oscillating bracket I5 that is operated by a link l6 connected to a rocking lever ll. One arm of the lever I! is connected by a, link I8 to an adjustable crank pin I9 that is mounted on a flanged hub 25 on the end of the drive shaft 20. Shaft 20 is driven through gear transmission 2I, Fig. 1, which in the form shown comprises a standard automobile forward four-speed and reverse transmission with a shift lever 22. The transmission is connected to a gear reducer 23 that is driven by a motor 24. By means of the gear transmission 2|, the paddle conveyor shaft I2 can be driven at four selected speeds, the purpose of which will be hereinafter described. By means of the .pawl and ratchet drive and the adjustable crank pin I9, the paddle conveyor shaft I2 can be driven over a wide range of speeds by adjusting the center of the crank pin I9. I

The construction of the adjustable drive mechanism will become more clear from a description of Figs. 9, 10 and 11 of the drawings. sists of a flanged hub 25 having teeth 26 milled therein for receiving the toothed face '2'! of the crank pin block 28 on which crank pin I9 is mounted or with which it is integrally formed. The block 28 is provided with grooves 29 and 30 for receiving complementary shaped projecting tongues or faces of clamping plates 3| and 32, which are fastened by bolts 33 to the flanged hub 25.

The crank pin block 28 may be adjusted radially with respect to the center of the flanged hub or main drive shaft by unclamping the block and moving it radially with the teeth 26 and 21 in coacting relation by lifting the block out of engagement with the teeth of the flanged hub 25 and placing it to the adjusted position where it is again clamped by the plates 3| and 32. By this adjustment the thrust of the rocker arm or lever I1 is varied to vary the throw of the pawl I 4, which varies the angular motion of the ratchet wheel I3 and correspondingly changes the angular or rotary movement of the paddle conveyor shaft I2.

To prevent damage to the paddle conveyor, shaft I2 is driven by a pair of friction disks 34 and 35 of conical shape which engage complementary shaped faces of the ratchet wheel I3. If for any reason an obstruction, such as a steel bar would pass into the paddle conveyor, no damage would be done as the conveyor would stall and permit the drive disks 34 and 35 to revolve in ratchet wheel I3 without imparting movement to the paddle conveyor shaft.

It will be noted that the distributor plate is provided with recesses 36, Figs. 4 and 6, to impart a more or less directional force to the blast and the fuel passing thereover, the degree of flare or diversion being in accordance with the position of the recess near the center or ends of the dis-' tributor plate.

Distribution to the sides of the fire box is further facilitated by the horns or end brackets 31. As shown in the several figures of the drawings, there are five blast nozzles I0 communicating with a steam box or steam chamber II closed at one end by plug 38 and communicating by a steam line 39 with a source of blast pressure or steam. Each nozzle I0 is regulated by a needle valve 40 having a hand wheel 4I extending to the rear of the stoker casting, as shown in Fig. 1.

One of the primary features of the invention is the construction and operation of the paddle wheels 8, which as shown in Fig. 3 have their square central openings I 2a ofiset angularly with respect to the axes of the paddles or blades 8a, so that when assembled on the square shaft I2 the It conblades are staggered as shown in Figs. 5, 8, 13 and 14 of the drawings.

There are four sets of paddle wheels assembled as shown in Fig. 4 which when viewed from the end gives the conveyor the appearance of Fig. 5, there being sixteen individual blades, of which only one is in the vertical position at any time. By means of this arrangement of paddles, a very small quantity of the powdered coal or slag or lump coal is delivered to a predetermined zone on the distributor plate at one time. This relatively small quantity of fuel becomes entrained in the blast of the particular nozzle or nozzles that are in alignment with the blade that delivers the fuel and is spread forward as shown in Figs. 4, 7, 8 and 13. Because of this advancing of the fuel to the distributor plate in small increments, it is blown into the fire box and completely scattered, resulting in complete combustion of the finer particles before they reach the fire bed, and the larger particles become distributed uniformly over the fire bed area, as shown in Figs. 7, 8 and 13 of the drawings, thereby assuring a bed of substantially uniform thickness throughout the entire fire box at the front, rear and sides thereof. Even the larger particles of the fuel are ignited before they reach the fire bed and they will not form clinkers as is the case when lump fuel is piled up and subjected to a slow distillation.

As shown in Fig. 13 the grate bars 42 are located above the air chamber 43 which is connected to an air blast or blower 44 to maintain about 2 pounds pressure beneath the grate. A valve 45 regulates the volume of air supplied.

Because of the distribution of the fuel gradually and successively in small quantities from one end of the distributor plate to the other and then again from the same end to the other, resulting in a corresponding gradual distribution from one side of the fire box to the other, the volatile products of combustion are consumed between successive charges and every portion of the bed has reached a red heat before a succeeding charge of fuel is delivered thereto.

By maintaining a uniform thickness of fire bed, as illustrated in Figs. 8 and 13 of the drawings, the air passes uniformly between the grate bars upwardly through the fire bed and will support combustion throughout the entire fire box area. The intermittent relatively small charges of fuel to different portions of the grate or fire box area are thus efficiently consumed and the volatile gases are burnt before the succeeding charge is delivered by the paddle and blast to the portion of the fire bed to which it is directed. This method of firing maintains a clear atmosphere in the fire box free of smoke. As a consequence, complete combustion results and no combustible gases reach the stack.

One of the features of the staggered paddle conveyor in conjunction with the adjustable ratchet drive and speed transmission is the degree to which the feeding of the fuel may be regulated to meet any firing conditions that circumstances may require.

If the boiler load is constant, the device is set to feed the required amount of fuel by adjusting crank pin I9 to the position which rotates the square shaft I2 at a desired speed to deliver the fuel to the distributor plate 5.

When abnormal conditions arise, the quantity of the fuel delivered may be doubled or quadrupled by merely shifting the transmission lever 22 without adjusting the feed crank I9. Such an arrangement is ideal for institutions where it is desirable to quickly bring up temperatures throughout large buildings in the mornings and which have a much less and constant heat requirement during the clay or night.

I have found in actual practice that the method of feeding as herein disclosed permits the burning of run-of-mine or slag fuels at substantial savings in fuel cost. Also, where a mixed lump and powdered fuel is available it may be freely used without putting it through crushers as the apparatus will feed the powdered fuel along with the lump coal.

I am aware that stokers employing blast for distributing fuel have heretofore been proposed, but none of these practice the method of my invention of feeding successive charges of fuel in small quantities over a wide distributing area, with the result that in the operation of such prior devices the fuel is piled up or concentrated on different portions of the fire box grate.

My method to a great extent possesses the firing qualities of powdered fuel delivered through burner nozzles without the detrimental features of crushing and the hazards of explosion and this result is attributable to the conveying of relatlvely small quantities of fuel to the blast to be distributed over a wide area of the fire box, which causes both the vertical and horizontal areas of the fire box to be substantially filled with a luminous fiame.

I claim:

1. The method of firing solid fuel in a fire box to maintain a fire bed of substantially uniform thickness throughout the fire box area, which comprises slowly feeding measured quantities of fuel successively from the one side entirely across to the other through the fire box opening and simultaneously blowing the fuel forward and across the fire box area.

2. The method of firing solid fuel in a fire box to maintain a fire bed of substantially uniform thickness throughout the fire box area, which comprises maintaining a constant blast in a plane parallel with and above the fire bed and intermittently and slowly feeding measured quantities of the fuel successively from the one side entirely across to the other of said blast.

3. The method of firing solid fuel in a fire box having an aerated grate to maintain a fire bed of substantially uniform thickness throughout the entire grate area which comprises admitting air from beneath the fire box uniformly through the grates, slowly feeding measured quantities of fuel from the one side entirely across to the other through the fire box openin in successive intermittent charges, and simultaneously blowing the fuel forward and across the fire box area.

4. The method of firing solid fuel in a fire box having an aerated grate to maintain a fire bed of substantially uniform thickness throughout the entire grate area which comprises admitting air from beneath the fire box uniformly through the grates, slowly feeding measured quantities of fuel from the one side entirely across to the other through the fire box opening in successive intermittent charges at a speed regulated to maintain a predetermined temperature in the fire box, and simultaneously blowing the fuel forward and across the fire box area to obtain a uniform deposit of the fuel on the fire bed.

5. The method of feeding and distributing in a horizontal plane, lump or powderous materials or both, which comprises slowly feeding the material in small measured volumes successively from the one side entirely across to the other side of a laterally diverging blast to simultaneously blow the fuel forward and across the fire box area, and

regulating the total volume of the materials feeding stream by varying the speed of feeding while maintaining a constant unit increment of feed.

6. The method of firing solid fuel in a fire box which comprises building a fire bed of substantially uniform thickness over the entire grate area of the fire box and slowly charging measured quantities of fuel in small increments from the one side forward and entirely across to the other side of the fire box area at a rate to maintain a predetermined firing temperature and a uniform depth of the fire bed throughout the fire box area.

'7. The method of firing solid fuel in a fire box which comprises maintaining air under pressure in excess of atmospheric pressure beneath the entire grate area and slowly charging measured quantities of fuel in small increments above said grate forward and from one side to the other successively to different areas of the fire box to at all times maintain an efficient combustion atmosphere in the fire box and a uniform depth of the fire bed on the supporting grate.

8. The method of firing solid fuel in a fire box having a fuel supporting grate above an air chamber, which comprises maintainin air pressure in excess of atmospheric pressure in said air chamber beneath the entire grate area to provide a forced draft through the grate upward into the fire box, maintaining a blast above the grate transversely of said forced draft and slowly charging measured quantities of fuel above the grate in small increments successively from the one side entirely across to the other side of said transverse blast to distribute the fuel forward and across the fire box area to at all times maintain an effi cient combustion atmosphere in the fire box and a uniform depth of fire bed on the supporting grate.

CHARLES R. BARR.

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