Improvements in Mechanical Stokers.
Year: 1891

page_text: Date of Application, 3rd Sept., 1891
Complete Specification Left, 3rd June, 1892-Accepted 9th July, 1892
PROVISIONAL SPECIFICATION.
Improvements in Mechanical Stokers.
I, GILBERT LITTLE, 1 Metal Exchange Buildings Whittington Avenue
London, E.C., Engineer, do hereby declare the nature of this invention to be as
follows:-
My invention relates to improved means of feeding coal to furnaces from the
hoppers of mechanical stokers. Hitherto the coal has been fed from the hopper
into the furnace, by means of "sprinklers,' 'fan blades," revolving chains &
pushers."
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The object of the present invention is to effect the feeding of the coal from the
hopper into the furnace, by utilizing two or more spirals or other forms of conveyor.
To this end I construct an ordinary mechanical stoker hopper in which I place the
spirals or other forms of conveyors. The coal in the hopper is fed automatically
and continuously or intermittently, by the spirals or conveyors, on to the "dead-
plate" or moving grate, in any desired quantity. The coal as it is fed by the
spirals or conveyors into the mouth of the furnace, is coked, and the volatile gases
pass with the air over the incandescent coke. As the coal is coked it is carried
backward by the moving fire-bars, and more green coal is fed into the furnace by
the conveyors to be coked in turn.
I also apply a peculiar movement to the fire-bars which causes them to move up
and down all along the length of the grate, which breaks up the clinkers and allows
the air to pass freely thro' the fuel.
This peculiar movement or rocking motion is communicated to the fire bars,
by means of vertical levers which work backwards and forwards on angle shaped
supports, and operate the cross-bars which carry the fire-bars.
I also fit supports or guides to the fire-bars which obviate the "squeaking"
noise common to moving fire-bars.
This arrangement of mechanical stoker hopper with feeding spirals or conveyors,
and up & down movement of the fire-bars greatly facilitates the operation to be
performed, as the coal is spread by the spirals or conveyors in an even laver, any
desired thickness all across the grate.
The peculiar movement of the fire-bars allows the air and the gases to get better
incorporated, under the conditions most desired, to effect economy in the fuel, and
prevent the emission of smoke from the chimney; and the spirals are placed high
enough to admit of a large furnace door being fitted for hand firing.
Dated this 3rd day of September 1891.
GILBERT LITTLE.
COMPLETE SPECIFICATION.
Improvements in Mechanical Stokers.
I, GILBERT LITTLE, of 91 Windsor Road, Forest Gate, Essex, 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:-
My invention relates to improvements in mechanical stokers.
One of the objects of my said invention is to provide improved mechanism,
comprising spiral conveyors or the like, and employed for the purpose of feeding
fuel into furnaces, from hoppers secured to the boiler front for instance.
Another

page_text: object of my said invention is to provide improved means for imparting movement
to fire-bars so that they are caused to move the fuel along the grate from the end
at which it is fed in by the feeding devices and to break up the clinkers.
It is an important feature of the apparatus hereinbefore referred to that it acts
with a minimum of noise and that its arrangement on the boiler front is such as to
leave each furnace front sufficiently exposed to enable a large fire-door of the usual
type to be provided therein so that haud-firing may be adopted at any time when
the driving-mechanism of the mechanical feeders is stopped.
In order that my said invention may be clearly understood I will now proceed-to
describe the same with reference to the accompanying drawings, in which
Figure 1 is an elevation of the front end of a Lancashire boiler fitted with
mechanical stoking devices according to my invention.
Figure 2 is a longitudinal section of Figure 1 and shows the interior of one of
the flues and the fuel feeding devices in connection with the said flue.
Figure 3 is a plan of one of the hoppers, and of certain of its appurtenances
hereinafter fully described.
Like letters of reference indicate corresponding parts throughout the drawings.
A is the boiler shell A' the boiler front, B B are the flues, and C C are the luel
hoppers secured to the boiler front. DD are screw conveyors, working in
cylindrical recesses C' formed in the lower portion of each hopper. The said
recesses are provided in order that the weight of the fuel in the hoppers may not
rest upon the conveyors so as to render them difficult to work. E is a driving
shaft provided with bevel wheels E¹ which gear with and drive bevel wheels D¹
secured to the spindles D2 of the conveyors which spindles turn in bearings
formed in the lower part of each hopper. F F are casings which protect the
wheels D' the shaft E and the wheels E' from dust and dirt. The said shaft may
be rotated intermittently or continuously by any suitable means; in the present
example it is driven intermittently by a ratchet, and the said ratchet is operated by
the crank shaft H hereinafter described. G G are short spouts which guide the
fuel from the conveyors on to the dead-plate.
His a crank-shaft supported in suitable bearings in castings secured to the
boiler front. The said shaft H is arranged as hereinafter described to operate the
fire-bars and is rotated by any suitable gearing. The said gearing is contained in
and protected by the casing J in the arrangement shown in the drawings and
is driven by the chain K from a shaft rotated by any suitable motor.
Cranks H H are provided upon the shaft H, and connecting rods L are connected
at L' to the said cranks and at L² to bearers M M' which extend across in front of
each furnace and are arranged to move in a manner hereinafter explained; it will
be seen that in front of each furnace there are four cranks and two bearers. The
upper bearers M are connected with the cranks H', and are supported at their ends
by the upper ends of rocking arms N, journals being formed on the ends of the
bearers for reception in bearings in the said rocking arms, and the lower bearers M¹
are connected with the cranks H² and similarly supported at their ends by the
upper ends of rocking arms O. The lower ends of all the rocking-arms are formed
so as to encircle knife-edge bearings P upon which they are supported; the said
bearings are firmly secured in the casting I.
QQ are the fire-bars; R is a fire-bar bearer suitably fixed in the flue. The
inner ends Q' of the fire-bars are supported by the said fixed bearer, and are so formed
that they may slide endwise thereon in the manner hereinafter described; the
opposite end of each fire-bar is so shaped that it may be conveniently supported
upon one or other of the movable bearers M, M', the said ends of the bars being
notched as at Q³ to cause them to be retained in proper engagement with the said
movable bearers.
S is a perforated pipe from which jets of steam may be delivered below the
fire-bars to prevent them from becoming overheated.
T is the fire-door, which is of the normal size and situated in the usual position,
which are great advantages.

page_text: The operation of the said apparatus will now be described with reference to one
only of the two furnaces as the operation is exactly similar for each :-
The hopper C is filled with fuel by any suitable mechanical or other means; the
said fuel gravitates to the lower portion of the hopper and into the ends of the con-
veyors which protrude from the cylindrical recesses C', whence it is fed either
continuously or intermittently by the conveyors D on to the spout G and thence
on to the dead plate and the ends Q2 of the fire-bars. The fuel, as it is fed into
the mouth of the furnace is coked and then carried backward along the grate by the
action of the fire-bars. The said fire-bars are operated by the movable bearers M M'
which, by the rotation of the crank shaft H and the action of the connecting-rods L
are caused to move with the rocking arms N and O in the arc of a circle about the
knife-edge bearings upon which the lower ends of the said rocking-arms bear as
aforesaid. As the ends Q2 of the bars reciprocate, and also rise and fall, during
their movement in the arc of a circle, the ends Q₁ of the fire-bars slide upon the
bearer R and also move up and down. The cranks H¹ and H' are so set that the
ends Q of the fire-bars controlled by one of the pairs of cranks and the corre-
sponding bearer M or M¹ will descend and move towards the front of the boiler as
the fire-bars controlled by the other bearer rise and move away from the boiler
front. Thus every time that one set of bars descend the fuel is lifted from them by
other bars which are ascending and moving forward, so that the clinkers are
broken up and the whole of the fuel on the bars is steadily fed towards the back
end of the grate whilst being consumed'; the residue falls from the end of the grate
into the ashpit as shown in the drawings.
By the use of two or more conveyors to each grate which are operated at suitable
speeds, and by imparting the aforesaid rising and falling movement to alternate
fire-bars or alternate groups of fire-bars an even and uniform layer of fuel of any
desired thickness may be spread upon the grate, and the combustion of the fuel
may be effected economically and without the emission of smoke, and the fire bars
are self-cleaning, that is to say clogging of the air-spaces between them is prevented
by the aforesaid movement of the bars.
I wish it understood that the foregoing description is given by way of example,
and that I do not limit this invention to the details nor to the arrangements
of parts as herein before set forth, as these may be varied without departing from
my said invention.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. The combination with a fuel hopper of two or more spiral conveyors or the
like arranged substantially as hereinbefore described, for the purpose specified.
2. The movable fire-bars constructed arranged and operated in the manner
herein before described for the purposes specified.
3. Mechanism for imparting movement to fire-bars, substantially as hereinbefore
described.
4. The improved mechanical stoker arranged and operating substantially as
hereinbefore described with reference to the accompanying drawings.
Dated this 3rd day of June 1892.
HASELTINE, LAKE & Co.,
45, Southampton Buildings, London, W.C., Agents for the Applicant.