US2566419A - Locomotive stoker - Google Patents

Description

Sept. 4, 1951 J. KANE LOCOMOTIVE STOKER Filed March 22, 1948 INVENTOR JOHN KANE Attorney Patented Sept. 4, 1951 UNITED STATES PATENT OFFICE LOGOMOTIVE, STOKER John Kano, Erie, Pa., assignor to Read Standard Corporation, a corporation of Delaware Application- March 22, 1948, Serial No. 16,160

4 Claims.

My invention relates generally to stokers, and more particularly to locomotive stokers of the type that convey coal from a source of supply, as from a tender bin, to the firebox throu h the usual firing opening in the locomotive boiler backhead. from. which point the coal is scattered over the fire by jets of fluid under pressure In certain stokers of this type it is customary to employ a screw conveyor rotating in an inclined riser conduit for advancing the coal to the distributing Jets It is characteristic of such a conveying system that more coal is advanced by the screw conveyor along one side of the conduit than along the other. Thus, if the winding of the screw thread is such that it advances coal when the conveyor screw turns in counter-clockwise direction, more coal is advanced along the right side of the conduit than along the left side.

In the absence of corrective measures, this results in the delivery of a preponderance of coal to the right side of the distributor jet with con sequent heavier firing along the right side of the firebox. This condition has been remedied by tapering the final flight of the screw conveyor and terminating the forward end of the screw a distance rearward of the upright face of the distributor jet to provide a zone in which a head of coal builds up and is pushed forward over the distributor jet. At the same time, this zone provides a mass of coal that can be acted upon by vanes disposed between the forward end of the screw conveyor and the distributor jet, and which vanes are preferably adjustable for directing the coal in a desired path to the distributor jet.

The nature of a screw conveyor is such that it effects a pushing action on the head of coal in the aforesaid zone during only a portion of each revolution, so that an intermittent feed of coal to the distributor jet results. If the coal is dry, it will, when the normal angle of repose is exceeded, drop forwardly in front of the distributor jet in a flowing stream and even though there is a slight time interval until another stream of coal flows in front of the distributor jet, no particularly objectionable firing conditions result therefrom. This is especially true at the higher rates of firing when the interval between successive deliveries of coal to the distributor jet is shortened.

It has been found, however, that when wet coal is conveyed, particularly wet slack coal, the coal particles adhere to each other, so that when the normal angle of repose of the coal is reached, the coal does not start to flow in front of the distributor jet, but builds up into a sizable agglomerated mass before it breaks oil and drops in front of the distributor jet. This, condition tends to create objectionable smoke and makes it necessary for the fireman to observe the fire more closely and to manipulate and adjust the stoker controls more frequently to maintain optimum firing conditions.

I have found that these objections can be largely overcome and it is accordingly an object of the present invention to provide an improved locomotive stoker discharge unit of the type employing a screw conveyor operating in a stoker discharge conduit, in which a more continuous delivery of coal to the stoker distributor jet is attained than in prior constructions, whereby more uniform distribution of coal over the grate is obtained while minimizing objectionable black smoke.

A further object is to provide a stoker discharge unit. of the character just described that will effect such more continuous delivery of coal to the stoker distributor jet without impairing substantial uniform delivery of coal to the distributor jet, with respect to the amount of coal delivered to the left and right sides thereof.

Another object is to provide a stoker discharge unit of the character described which will di integrate and loosen a conglomerate mass of coal and facilitate its advancement to the Stoker distributor jet.

These and other objects of the invention accordingly reside in the particular construction of the parts and their novel relation one with another, as will become apparent from the following description when read in connection with the accompanying drawing, in which Figure 1 is a fragmentary central vertical section throu h the rear portion of a locomotive with the novel stoker discharge unit app thereto and shown in similar section, with parts depicted in elevation;

Figure 2 is a sectional view taken on the line 2-2 of Figure 1; and

Figure 3 is a fragmentary central vertical section of a modification of the novel stoker discharge unit, with parts thereof shown in elevation.

Referring to Figure 1, the numeral 10 design, nates a locomotive boiler firebox of conventional design provided with a grate II and a backhead I2. A stoker I3, only so much of which is shown. as is necessar for a complete understanding of the invention, communicates at its forward or discharge end with the lower portion of the firing opening M formed in the boiler backhead IQ of a conduit section 2t extending rearwardly toward the locomotive tender. 7

The lower portion of the riser conduit is tubular, but the upper portion or discharge mouth- 2| flares laterally. The floor portion 22 of the conduit discharge mouth 2| is preferably made detachable and is provided at its forward end in the firing opening l4 with a pressure fluid distributor jet head 23. A distributing plate 24 is in detachable engagement-with the distributor jet'head 23. Coal-is. elevated through the, riser conduit l6 by a screw conveyor 25 and is forced over the distributor jet head 23' onto the distributing plate 24 from which it is projected in aerial paths over the firein the firebox by blasts of pressure fluid emitted from jet openings (not shown) in the'fro nt face 26 of the distributor jet head 23. 7

In stoking devices of the character described and illustrated in the drawing, itihas been found in'practice that the screw conveyor has a tend:-

ency to advance more coal along one side of the riser conduit |6than along its oppositeside,

in turn resulting in an uneven discharge ofcoal 1 over the distributor jethead 23 onto the distributing plate 24, whereupon more coal is spread over one side of the firebox than the other, establishing troublesome fire conditions.

This conditionhas been overcome in prior constructionsby tapering the final flight of the screw conveyor and terminating the forward end thereof a sufiicient distance rearward of the spill edge of the distributor jet head to provide a zone in which a head of fuel can accumulate,

and by providing adjustable deflecto members 21 at the sides of the flaring mouth portion 2| of the riser conduit l6 that act on the head of coal to-direct or.regulate delivery thereof to the distributing plate 24, as shown, for example, in U. S. Patent 2,075,158. r i

It is characteristicof a screw conveyor, however, to exert a pushing action on thehead of coal during onlya portion of each revolution so that an intermittent feed of coal to the distribu tor jet head results. Aspreviously explained, this is .not particularly objectionable with dry coal especially at the higher rates of firing. Wet coal, particularly wet slack coal, because of the .adherence of the particles has a tendency to build up beyond the normal angle, of repose of the coal,

and then breaks off in an agglomerated mass in front of the jet openings of the distributor jet head.

The present invention corrects this condition by providing a more continuous delivery of coal to the distributor jet head and minimizes any tendency of the coal to pack in the mouth portion of the stoker riser conduit. As shown in Figure 1, the screw conveyor 25 has amain conveyor flight 28 terminating short of the forward end of the conveyor screw hub 29. On the forward end of the hub 29 are a plurality of radially extending blades 30, the details of which are herein after more fully described.

The location of the blades 30 is important, and

as shown they are disposed in the zone where the head of coal accumulates, just rearward of a plane that defines the normal angle of repose of the coal before breaking over the spill edge of the distributor jet head 23. This angle is approximately 45 and the blades are disposed in the head of coal as close to the normal angle of 'repose of the coal as the clearance between the outer edges of the blades 30 and the short top wall 3| of the discharge mouth 2| permits.

' The distance between the blades 30 and the forward end of the conveyor flight 28 is determined by the space required to build up a sufficient'head of coal for the blades 30 to operate in. This distance may vary, depending on the pitch of the conveyor flight 28, the extent of expansion of the mouth portion 2|, and other factors, but of course is readily determinable for any particular set of conditions.

The four blades 30 areequidistantlyspaced fromeach other and radiatefrom the, hub29 in a common plane at right angles with respect to the axis of the hub 29 and have a radius preferably as nearly. as large as the radius of the conveyor flight 28 as the clearancesirrthe mouth portion 2| permit. The blades 30 are pitched in the same direction as the conveyor flight 28, and preferably though not necessarily at an angle of approximately 45. Eachblade thus exerts a slicing and pushing action,on the head of coal close to the front face'thereof, pre venting any excessive building up of an a glomerated mass of coal beyond itsnormal angle of repose, and pushes the coal onto ,thedistribut ing plate 24 over the spill edge of the distributor jet head 23 in a more, continuous stream than in prioristokers of the screw conveyor type,

The blades 30 flare outwardlyfrom the hub 29 to present an increasingly larger .coal push,- ing surface from the hub.29 outwardly to the periphery of the blades 30. Theblades 30 are proportioned so as toprovide a space between the trailing edge of one blade andthe leading edge of the next blade considered in a plane normal to the axis of the conveyor screw hub 29 that is approximately equalto the width of a blade 30, or in other words, the blades. fail to overlap by a distance equal to approximately the width of a blade. The factor determining the spacing between the blades, is the free passage of coal to the distributing plate 24 without plugging in the mouth portion 2|.. The spacing set forth above has been found most satisfactory in practice, however, the spacing may be increased or decreased to some extent depending on the cross sectional area available to passage of coal in the mouth portion 2| adjacent the blades 30. V H

The screw conveyor 25 is preferably, though not necessarily provided atits forward end with an additional flight 32 in. order to provide a more continuous feed of coal to the blades 30. In Figure 3 is shown a modified form of the invention identical in all respects to the prefer: red form, except that the. screw conveyor ,3? is provided with a single flight 34 throughout. The single flight 34 is in some instances preferred, where, for example, a double flight restricts the area through the riser conduit to the extent of causing congestion of the, coalinthe region of the double flight, and where it is preferable to alleviate this condition by theuse of a single flight screw than to make other alternations in the stoker, as for example, by decreasing the feeding of coal to the lower end of the screw conveyor or increasing the pitch between the double flight portion of the screw conveyor.

I claim:

1. A coal discharge unit of a locomotive stoker comprising an inclined discharge conduit provided at its upper end with an axially directed discharge opening, the lower forward edge of said conduit providing a ledge over which the coal discharges, and a conveyor screw provided with a hub mounted in said discharge conduit, a plurality of blades carried for rotation by and projecting radially from the forward end of said hub rearwardly adjacent said ledge, and a con veyor flight wound about said hub for the major portion of its length and terminating at distance rearward of said blades to provide a zone in which a head of coal will form, said blades being pitched in the same direction as said conveyor flight and being of a width to fall short of overlapping each other whereby each of said blades slices off and pushes ahead a portion of the advancing head of coal.

2. A coal discharge unit of a locomotive stoker comprising an inclined riser conduit having an expanded mouth portion, said conduit being provided at its upper end with an axially directed discharge opening the lower forward edge of said conduit providing a ledge over which the coal discharges, and a conveyor screw in said conduit having a hub extending into said expanded mouth portion, a plurality of blades carried for rotation by and projecting radially from the forward end of said hub rearwardly adjacent said ledge, a conveyor flight wound about said hub for the major portion of its length and terminating a distance rearward of said blades to provide a zone in which a head of coal will form, said blades being pitched in the same direction as said conveyor flight and being of a width to fall short of overlapping each other whereby each of said blades slices off and pushes ahead a portion of the advancing head of coal.

3. A coal discharge unit of a locomotive stoker comprising an inclined riser conduit having an expanded mouth portion, said conduit being provided at its upper end with an axially directed discharge opening the lower forward edge of said conduit providing a ledge over which the coal discharges and a conveyor screw in said conduit having a hub extending into said expanded mouth portion, a plurality of blades carried for rotation by and projecting radially from the forward end of said hub at a point so that said blades will lie immediately rearward of a plane defining the normal angle of repose of the coal at said discharge ledge of the conduit, a conveyor flight wound about said hub for the major por-- tion of its length and terminating a distance rearward of said blades sufficient to provide a head of coal in said expanded mouth portion to envelop said blades, said blades being pitched in the same direction as said conveyor flight and being of a width to provide longitudinal passages therebetween of approximately the width of said blades, whereby each of said blades slices off and pushes ahead a portion of the advancing head of coal.

4. A coal discharge unit of a locomotive stoker comprising an inclined riser conduit, said conduit being provided at its upper end with an axially directed discharge opening, the lower forward edge of said conduit providing a ledge over which the coal discharges, and a conveyor screw in said conduit having a hub, a plurality of blades carried for rotation by and projecting radially from the forward end of said hub rearwardly adjacent said ledge so that said blades will lie immediately rearward of a plane defining the normal angle of repose of the coal at said discharge ledge of the conduit, a main conveyor flight wound about said hub for the major portion of its length and terminating a distance rearward of said blades to provide a zone in which a head of coal will form, said blades being pitched in the same direction as said main conveyor flight and being of a width to fall short of overlapping each other whereby each of said blades slices off and pushes ahead a portion of the advancing head of coal JOHN KANE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,254,393 Clendon Jan. 22, 1918 1,713,719 Severson May 21, 1929 1,828,116 Lower Oct. 20, 1931 2,000,469 Lippert May 7, 1935 2,056,368 Roesch Oct. 6, 1936 2,073,792 Gray Mar. 16, 1937 2,115,464 Kirby Apr. 26, 1938 2,127,693 McCanless et al. Aug. 23, 1938 2,151,575 Ward Mar. 21, 1939 2,186,404 Carter Jan. 9, 1940 FOREIGN PATENTS Number Country Date 86,240 Germany Apr, 8, 1896

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