Improvements in Under-feed Furnaces.
Year: 1895

page_text: Date of Application, 28th Feb., 1895-Accepted, 24th May, 1895
[Communicated from abroad by James Garden, 283, North 15th Street, of the
City of Portland, County of Multnomah and State of Oregon, United States
of America, Manufacturer of Furnaces.]
Improvements in Under-feed Furnaces.
1, WILLIAM PHILLIPS THOMPSON, F.C.S., M.I.M.E., of The Agency for
Foreign Patent Solicitors, 31, High Holborn, in the County of Middlesex,
6, Lord Street, Liverpool, and 6, Bank Street, Manchestor, both in the County
of Lancaster, and Lower Temple Street, Birmingham, in the County of Warwick,
Civil Engineer, do hereby declare the nature of this invention and in what manner
the same is to be performed, to be particularly described and ascertained in and
by the following statement :-
The primary object of my invention is to so construct a furnace in combination
with an under-feed mechanical stoker, that the air may be supplied to the furnace
at the point of combustion, while, at the same time, the gases formed may be
prevented from returning or escaping otherwise than through the flue or stack
designed therefor.
A further object is to provide simple and efficient means whereby the fuel may
be uniformly fed and more completely and perfectly distributed to the furnace
from beneath, while at the same time it is prevented from clogging.
To these ends, my invention consists in the combination of elements hereinafter
more particularly described and definitely claimed.
In the drawings,
Figure 1 is a longitudinal, vertical sectional view of a furnace embodying the
features of my invention.
Figure 2 is a transverse, vertical sectional view of said furnace taken upon the
line 2-2 Figure 1.
Figure 3 is an enlarged plan view in detail of a dead-plate employed in said
furnace.
Figure 4 is a side view of the same.
Figure 5 is a transverse sectional view thereof.
Figure 6 is an enlarged plan view of the fuel conduit and tuyores, showing my
improved auxiliary ram located in the former.
Figure 7 is a longitudinal vertical sectional view thereof.
Figure 8 is a detail view showing a modified form of pushing device.
Figure 9 is an enlarged sectional view in detail, taken upon the line 8-8,
Figure 6, viewed in the direction of the arrow there shown, and
Figure 10 is a like view taken upon the line 9-9 Figure 7.
Referring to the drawings, a, Figures 1 and 2, represents what is commonly
known as a **
water leg" boiler, to which is applied my improved furnace, having
the usual fire-box b. In front of the furnace and beneath the fire level is placed
a feeding ram c, Figure 1, which consists of the usual plunger or pusher d enclosed
within a suitable cylinder and connected by means of a rod, as shown, with a steam
piston or other suitable means for reciprocating the same. A hopper e is placed
above and in communication with the cylinder or fuel conduit. That portion f
of the fuel conduit which is within the furnace is, preferably, of a concave or
trough shape in cross-section and is extended back through the middle of the
fire-box to a point at or near the rear of the latter. It is also preferably inclined

page_text: substantially as shown in Figures 1 and 7.
Within the front of the furnace and
above the forward part of the conduit, is placed a plate or shield which is intended,
by contact therewith, to prevent the fuel from being drawn back with tho backward
stroke of the pusher as hereinafter described. The fuel conduit for which I make
no claim, may be made of cast-iron, fire-brick or other suitable material.
Within the fuel condnit I place a rod or bar which is loosely secured in
position so as to permit of a longitudinal movement thereof by means of staples A¹
which form guides therefor. The rod is preferably jointed, as shown at h
Figure 7, and the lower or forward end is provided with a lug as shown having an
elongated opening therein through which is inserted a bolt which serves to
connect the bar h with the cylindrical pusher d so as to permit of a slight joint-like
movement between the two. Rigidly attached to the bar h is one or more
blocks of cast-iron or other suitable material, which are intended to act as
auxiliary pushers or distributors to advance the coal ahead of the main or primary
pusher d and thus prevent it from being clogged and packed in the conduit, which
1 have found in practice to be a serious and in most cases fatal obstacle in the use
of the primary ram alone. The blocks are made to conform substantially to
the shape of the bottom of the conduit, and, in longitudinal section, are sub-
stantially triangular as shown in Figure 7, the rear face being sloped toward the
front of the furnace, while the forward one is vertical or substantially so except
at the bottom where it is inclined forward like the share of a plough.
Upon each side of the fuel conduit is an air-chamber i, better shown in Figures 2
and 9, the two uniting at the front in a common passage-way j Figures 6, 7 and 10,
which is connected in turn with a suitable fan or air-compressor. Openings i
Figure 6, are formed in the top of the casing into which are fitted a series of
movable tuyeres & Figures 6, 7 and 9, the construction of which is well known;
anid tuyeres being secured in place by means of a rod ¹ passed through staples
formed thorein. By means of this device air may be forced into and thoroughly
mixed with the fresh fuel at the point of combustion.
As the air is forced into the furnace through the means described, a buck or
downward pressure is produced which is sufficient to force the air and gas
downwardly through the ordinary grate heretoforo employed and thence into the
furnace room. This objectionable feature often becomes so serious as to destroy
the grate bars in a few moments, besides causing the escape of the noxious gases
in such a way as to cause inconvenience if not positive injury to the attendants.
In order to obviate this objection I have, in my improved construction, dispensed
with the usual grate and in lieu thereof I have sealed or closed the space occupied
thereby preferably by placing upon each side of the tuyores a dead-plate 7 of cast
iron which is supported upon suitable flanges or lugs in such a manner as to enable
it to be readily romoved. Each dead-plate is provided with ribs l', which serve
to strengthen the plate, while those upon the top permit a sufficient amount of
ashes to accumulate to protect the plates from the beat of the furnace. By means
of suitable doors in the front of the furnace upon a levol with the dead-plates, the
asbes may be readily removed.
The operation of my improved feeding devico is as follows:-The fuel being
fed into the hopper e falls into the conduit as the pusher dis withdrawn for that
purpose. The pusher is then advanced which movement serves to push the fuct
back somewhat into the conduit. This act is repeated until a considerable quantity
is accumulated in the furnace. Upon the withdrawal of the main pusher, the fuel
is caused to lodge against the shield 9 which enables the block to pass beneath
it; whereupon, with the next forward movement of the pusher a portion of the
fuel is forced further back by means of the auxiliary pusher-block h. The same
action is caused in turn in connection with the block until the furnace is supplied
with fuel to its normal limit. With each movement of the pusher d, the auxiliary
pushers, of which it is obvious there may be an indefinite number, serve, by their
action, to cause a complete distribution of the fuel while they prevent it from
becoming clogged in the throat of the conduit.

page_text: Instead of employing the bar in the position shown, it may be placed beneath
the conduit as indicated in dotted lines in Figure 7, and connected through 'a
longitudinal slot in the conduit with the auxiliary pusher blocks; or a sprocket
chain having buckets or blocks thereon as indicated in Figure 8 may be mounted
upon suitable drums at the respective ends of the conduit beneath which they
are placed so as to connect the chain with the blocks in the couduit, and connected
by means of a bar with the pusher d so as to be actuated thereby.
In lieu of the cast metal dead-plates the bottom of the furnace may be built up
solidly with fire-brick ;-thus leaving no opening corresponding to the usual ash-pit
beneath; but I prefer the construction shown as it may the more readily be
repaired.
I have found in practice that by employing the auxiliary pushing device and
closing the furnace to the admission of air except through the tuyeres, that the
most satisfactory results may be obtained. The fuel is uniformly and evenly
distributed which insures satisfactory combustion.
It is obvious that the pushers may be made to act continuously and auto-
matically and that the auxiliary pushers may be used with a worm-feed or may be
operated by means of a can or its equivalent. In any event, the clogging in the
throat of the furnace may be prevented and a complete distribution accomplished
by the use of the auxiliary pusher; and I do not wish to be confined to any special
means for operating it.
My improved device is especially applicable to marine work; and may be used
to excellent advantage by sealing the front of the furnace and employing an
over-blast in connection therewith.
Having now particularly described and ascertained the nature of my said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
:-
1. The combination with a furnace having an under-feed conduit, of means for
introducing the fuel to the couduit, a longitudinally movable auxiliary pusher
arranged within the conduit, and means for actuating said pusher lengthwise of
said conduit, substantially as described.
2. The combination with a closed, sealed or gratoless furnace, of an under-feed
conduit, means for introducing the fuel thereto, a supplementary pusher for
distributing the same thorein, a series of tuyeres in operative proximity to said
conduit, and means for forcing the air into said tuyores whereby the fuel may
be evenly distributed, and a back-flow of the gases avoided, substantially as
described.
3. The combination with a grateless furnace, of a fuel conduit, main and
supplementary pushers for forcing and distributing the fuel therein, means for
actuating said pushers and means for forcing air into said furnace in operative
proximity to said conduit and through and between the fresh fuel to the point of
combustion, substantially as described.
4. The combination with a furnace, of a fuel conduit for feeding the fuel
thereto from beneath, a hopper in operative connection therewith, a ram for
forcing the fuel into the furnace when delivered from said hopper, means for
actuating said ram, a bar attached to said ram and extending lengthwise of the
conduit and one or more feeding blocks or auxiliary pushers attached to said bar,
substantially as described.
5. The combination with a furnace, of a fuel conduit for feeding the fuel thereto
from beneath, a hopper in operative connection therewith, a ram for forcing the
fuel into the furnace when delivered from said hopper, means for actuating said
ram, a supplemental pushing device in operative connection with said ram and
arranged to extend into the rear of the furnace, and a shield in connection with
the forward end of the conduit for engaging the fuel and preventing its withdrawal
with the backward movement of the auxiliary pushing or distributing device,
substantially as described.

page_text: 6. The combination with a furnace, or a rearwardly and upwardly inclined fuel
conduit, a ram for feeding the fuel thereto aud a jointed bar attached to said rain
and connected with one or more pusher blocks arranged in said conduit,
substantially as described.
7. The combination with a furnace, of an under-feed fuel conduit, a ram for
forcing the fuel therein, an auxiliary pushing or distributing device, means for
actuating the same, means for forcing air into said furnace adjacent to said fuel
conduit, and dead-plates arranged upon the sides of the furnace adjacent to the
openings through which the air is introduced, substantially as described.
Dated this 28th day of February 1895.
W. P. THOMPSON & Co.,
31, High Holborn, London, W.C., Patent Agents for the Applicant.