US2177179A - Stoker - Google Patents

Description

Oct 24, .1939'. s. J. HENDERSHOTT Er Al. 2,177,179

STOKER Filed March 19, 1937 ttomegs k 50 Y Small or house stok'ers Patented Oct. '24, 1939 UNITI-:D STATES PATENT OFFICE STOKER Silas J. Hendershott and Bert Coleman,

` Detroit, Mich.

Application March 19, 1937, seriaiNo. 131,867

s claims. (ci. 19a-213) Thisinvention relates to a stoker for feeding fuel from a hopper into a retort within the furnace and more particularly adapted for use in,l connection 5 naces. A -f An object of the present invention is to provide a screw forfeeding coal .from a hopper to the retort, which screw is so constructed as to permit the feeding of comparatively large lumps l without danger of clogging, and also to provide a screw which is so shaped as to effect a mixing of v the smallv and larged lumps of coal rather than arseparating of these operation.

I It is also an object to so feed the coal from the hopper to the retort that the coal will beevenly 4distributed throughout the retort with the small and large lu'mps so mixed asto give a better burning of the coal due to the fact that air penetration of the fuel bed is enhanced, thus preventing caking of the'coal within the retort. l

It is an object to so construct the screw feed as to cause the coal to be lifted thereby away from the feed tube through which the screw extends and the coal forced toward the axis of the screw to be fed freely in a longitudinal direction, vand it is also an object to provide a screw so constructed as to provide a greater space between the ights or turns of the screw, thereby permitting the feeding of lumps of greater size without unduly crushing these lumps, and thus permitting of the feeding of coal having a greater range in lump sizes.

' It is also an object to provide certain other new and useful features in the construction, arrangement andy combination of parts, all as hereinafter more fully described, reference being had to the accompanying drawing, in which- Figure lfis a plan view of a' stoker illustrative of an emboiment of the present invention; c Fig. 2 is\a side elevation with parts broken away and in section to more clearly show the construction;

with house fur- Fig. 3v is an enlarged detail of a feed screw illus- 45 trative of an embodiment of the invention and showing parts broken away and in section to disclose the construction, .and

' Fig. 4-is a transverse sectionfsubstantially upon the line 4-4` of Figure are usually provided with a hopper or bin into which the coal is-placed 'and a-etort located within the furnace with a tube connecting the -retort and hopper and containing a feed screw which is formed `with a lon- 55 gitudinal axial shaft,

to small stokers,

parts during the feeding' To give efficient operation of these small screw A feed stokers, the coal is usually graded in size; some taking only line coal and others being able to handle coal containing lumps of somewhat larger size, but in'any case it is necessary to grade 5 the coal to suit the particular stoker which is designed to feed that particular grade, and in any event the coal contains only comparatively small lumps as larger lumps cannot be fed by these small house stokers due to the limited -capacity' of 10 the screw feed and the construction of the screw which will in its operation, crush the larger lumps or will Vbecome clogged by them and prevent eilicient operation of the device. In those stokers which employ a feed screw4 having an axial shaft, 15

the tendency of the operation of the screw in feeding the coal along the feed tube, is to sepaa rate the small from the large lumps, the small sizes falling to the bottom of the tube and being carried along the tube and forced into the retort 20 at the 'forward end or entrance to the retort vso that the coal is not evenly distributed as to sizes throughout the retort, the smaller lumps pushing up through the retort at its forward end while the larger lumps are forced toward the rear end. This 25 uneven distribution chokes the flow of air through the coal inthe retort and annuneven fire is the result, these stokers commonly being provided with a blower which forces air. to the retort and through the coal contained therein. If the small- 30 er sizes or particles of coal are massed at th entrance end of the retort, the air will not pene-V trate this rather compact mass of ne lumps or particles and there will be a coking of the coal which will prevent the most ellicient burning of 35 the coal.

Asillustrative of an embodiment of the presentI invention, a stoker of conventional type is shown in the accompanying drawing, said stoker comprising a suitable hopper I into which the 40 coal is placed and the bottom of this hopper communicates through an opening 2 therein with the forward end of a feed tube 3 within which a feed screw 4 is positioned, this screw being of slightly less external diameter than the internalj diameter f of the feed tube. This feed tube 3 is connected at its end opposite the hopper, to the retort 5 which is enclosed within va suitable wind-box 6 connected by an air duct 'l to the casing 8 of a blowerv y 9, which casing and blower are located adiacent 50 the hopper I and associated with which blower is an electric motor l0' for driving the'blower. The y top of the wind-box 6 is open around the retort 5 and upon the retort is placedV an upwardly extending tuyre Il having slots or openings I2 ln 55 its inner wallso that air passing from the blower through the feed duct 1 and into the .wind chamber 6 will pass upwardly into the tuyre and out through the openings l2 into the coal bed within the retort and tuyre.

This is substantially a standard arrangement of stoker partsfthe feed screw 4 usually being a screw having a longitudinal axial shaft, but the present commotion includes a feed screw which fis devoid of an axial shaftextending throughout its length, butvas lshown in Figure 3 is cast or otherwise formed without a shaft formed with screw nights or turns, but is formed with these flights or turns only, they being of sumcient strength to form a rigid screw, the end flight being formed with a suitable head I3 to which the drive shaft Il is connected, this drive shaft having a worm wheel vl5 on its forward end to engage a worm on the shaft I6 of the blower 9, which shaft is driven by the motor i0 by means of a chain I1 or other suitable power transmitting mechanism.

The present feed screw which is shown in detail in Fig. 3 is formed with any desired number of turns of the blade or wall Il and this blade is lof a width radially of the screw, to extend from substantially the longitudinal axial line of the screw to its exterior diameter which is substantially the interior diameter of the feed tube within which it is designed to operate. This blade/is preferably of a substantially triangular shape in cross section with the apex of the triangle forming the inner edge of the blade, terminating substantially at the longitudinal axial line of the screw. 'I'his inner edge I9 of the blade is sharp or thin as compared with the outer side 20 of the blade which is of extended width and forms the peripheral'surface of the screw to run in close proximity to the wall of the feed tube), and the rear side or wall 2i of the blade lies in a substantially radial plane of the screw, that isfthe surface of this side of the blade extends at substantiallyright angles to the longitudinal axis of the screw. The opposite or forward side 22 of the blade is inclined outwardly and forwardly, meeting the peripheral surface of the blade in a substantially' sharp angle 2.3. Theblade I8 which constitutes the screw, is therefore self-supporting, that is, it is without an axial shaft or any part serving that purpose,

but the blade itself, being thick' and wide at its periphery, has suflicient strength to withstand the feeding strains of forcing the coal along the feed tube, the wide periphery of the blade lying close to the wall of the tube, and as the screw is turned the coal which drops in ibetween thefirst flights of the screw from the hopper, will bev fed along the tube and by reason of the forwardly inclined side 22 of\theblade, there will bea lifting effect of the blade upon the coal, tending to force the coal toward the axis of the screwpand thus vnot only lifting the nner particles from the bottom of the tube but also causing them to mix with the larger particles or lumps, thus maintaining the even distribution of large and small lumps so that when the coal enters the retort there will be no tendency for the smaller lumps to pack together at the entrance side of the retort and the coal will be evenly distributed throughout the length of the retort. Friction of the coal against the surface of the feed tube is reduced by the form of the screw blade which tends to lift the coal away from the bottom of the feed tube and `cause it to move'toward the axis of the screw,

jacent the longitudinal axis of the screw and fed n A t along without being crushed and without danger of blocking-the screw so that it will not turn.-

What we claim is:

1. A feed screw comprising a single helical blade of ya depth transversely of the screw substantially equal to one-half the diameter of the screw and having a forward face inclined forwardly in the direction of movement of the fuel and'arranged to Afeed, toward the axis of the screw. v

2. A feed screw comprising a single blade with :alsl

an outer edge face of extended width in the direction of the length of the screw and a forward side face inclined inwardly and rearwardly, said outer edge face meeting said forward side face' at an vacute angle, arranged so that rotation of the screw brings said forward face of said blade into contact with .the fuel andv operates to move., the fuel toward` the longitudinal axis of \the screw and feed the fuel without crushing .the lumps in the fuel and with a mixing action.

3. 'A feed screwcomprising a helical blade exltending in cross section of -said blade from the periphery to substantially the longitudinal axis of thescrew, said blade having forward and rear side faces meeting in an angle at substantially the longitudinal axis of the screw, and an outer pe" ripheral face of extended widthlongitudinally of the'screw,psaid forward side face being inclined inwardly and rearwardly from said peripheral face, said forward andv peripheral faces meeting in a sharp angle, arranged so that upon rotation of said screw saidy sharp forward angle of said blade cuts beneaththe fuel being fed by the screw and said inclined forward side of said blade tends to move the fuel toward the axis of the screw.

SILAS J.-HENDERSHO'IT.

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