Improvements in Mechanical Stokers for Furnaces.
Year: 1898

page_text: Date of Application, 13th Dec., 1898-Accepted, 11th Feb., 1899
COMPLETE SPECIFICATION.
Improvements in Mechanical Stokers for Furnaces.
I, JOHN FREDERICK POOL, of No. 1527 Moyamensing Avenue, in the City of
Philadelphia, State of Pennsylvania, United States of America, Mechanical
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 objects of my invention are to burn with economy low grade fuels, to
avoid the formation of smoke, to automatically handle the fuel and ashes, and
to use fuel that will buru either from above or from below.
I will describe my invention with reference to the accompanying drawings,
of which:-
Fig. 1, represents a longitudinal section of a mechanical stoker constructed in
accordance with my invention;
Fig. 2, is a front view, and Fig. 3, a part plan and part horizontal section of
the same;
Fig. 4, is a side view of one of the movable grate bars;
Fig. 5, is a plan or top view of the same;
Fig. 6, is a side view of the upper end of one of the stationary grate bars;
Fig. 7, is a transverse section of one of the grate bars;
Fig. 8, is a section of one of the ash dumping plates drawn to a larger scale
than Fig. 1;
Fig. 9, is a transverse section on the line of the shaft carrying the ash dumping
plates, showing one of the said dumping plates and some of the grate-bar sup-
porting devices;
Fig. 10, is a sectional view of the connection employed between the operating
lever and the fuel feeding or grate operating device, such section being drawn
to a larger scale than Fig. 1:
Fig. 11, is a transverse section on the line - Fig. 10;
Fig. 12, is a transverse section on the line yy Fig. 10;
Fig. 13, is an enlarged view of the upper end of one of the movable grate bars,
showing its relation to the furnace front and dead plate; and
Fig. 14, is a similar view of the upper end of one of the fixed grate bars.
1 represents the upper portion of the furnace front and 2 the lower portion
of the same, the latter being offset inwardly in respect to the upper portion and
constituting a bearing for the heads 3 of the fixed grate bars 4ª, the heads 3
of the movable bars 4 being supported upon operating devices therefor, as here-
inafter described.
Both sets of bars have toes 5 at their lower ends and these toes have side walls
with horizontal bottoms which rest upon flanged collars 6 mounted upon a shaft 7
which is adapted to suitable bearings in the side walls of the furnace and is
capable of having motion of partial rotation imparted to it whenever such motion
becomes desirable.
One end of the shaft projects beyond one of the side walls of the furnace

page_text: and has secured to it a toothed segment 9 with which gears a worm or screw 10
on an inclined shaft 11 mounted in suitable bearings at the side of the furnace
and having at its upper end a hand wheel 12 whereby it may be turned in one
direction or the other so as to cause such movement of partial rotation of the
shaft 7 in either direction.
The collars 6 upon which the toes of the movable grate bars 4 rest are free
to turn on the shaft 7 and are preferably provided internally with a mass of
graphite or other heat resisting lubricant so that as the grate bars are moved,
these supporting collars can turn back and forth on the shaft and thereby lessen
the friction due to such movement.
The fixed grate bars 4" alternate with the movable grate bars 4 and the flanged
collars which support the said fixed grate bars are, by preference, secured to
the shaft 7, some of the said collars forming part of the ash dumping plates 13
suitably perforated or slotted, and when in their raised position forming a con-
tinuation of the upper surface of the grate bars as shown in Fig. 1. Those of
the collars 6 which form part of the dumping plates 13 are preferably split and
provided with ears which can be drawn together by means of a clamp bolt, as
shewn in Fig. 8, so that they may be tightened upon the shaft 7, and secured
by keys let into the shaft, thus causing the ash dumping plate to move with
the said shaft.
To brackets 15 on the upper portion of the front plate of the furnace is adapted
a shaft 16 which carries an eccentric 17 with strap 18 connected to a pin on a
right angled lever 19, the latter being suitably fulcrummed in a bracket 20 on
the front plate, so that, as the shaft 10 is rotated a swinging movement will be
imparted to the said lever.
Each of the arms of the lever 19 is forked for the reception of a block 21 which
is mounted so as to be free to turn with a transverse bolt 22 (Fig. 11) which is
adapted to bearings in the forked portion of the arm, both block and bolt being
perforated for the passage of a rod 23, which has, outside of the block 21, a
nut 24, and inside of the said block an adjustable clamp stop 25, so that by
adjusting the latter to different positions on the rod 23, more or less lost motion
of the block 21, between the nut 24 and the clamp stop, will be permitted, and
hence the extent of movement imparted to the rod 23 by the lever 19 can be
readily regulated.
Each of the stops 25 consists of a bolt 26 (Fig. 12) which has an opening for
the passage of the rod 23 and passes through a pair of washers 27 embracing
the opposite sides of the said rod, and acted upon by a handled nut 28, adapted
to the threaded end of the bolt 26, hence, by turning the said nut backwards,
the hold of the washers 27 upon the rod 23 can be loosened and the stop 25
adjusted to any desired position on the rod, to be again locked in position after
adjustment by screwing up the nut 28 and tightening the washers upon the rod.
One arm of the lever 19 is connected by its rod 23 to an arm .30 depending
from a rock shaft 31 which carries the heads 3 of the movable grate bars 4.
Each of the heads 3 has toothed racks 33 engaging with toothed segments 32
on the shaft 31, so that the bars 4 are constantly moved back and forth, the
heads 3 being just free from contact with the upper portion of the furnace front 2,
so that there is no frictional retardation of the movement of the bars. Continual
agitation of the bed of fuel lying upon the grate bars is thus effected to insure
the proper access of air thereto, to support combustion, and also to insure the
feeding of the mass of fuel downward on the grate bars, and thereby make room
for the fresh fuel at the upper ends of the said grate bars, and deliver the ashes
from their lower ends on to the plates 13, which can be swung downward at
intervals so as to dump the mass of ashes into the ash pit, or they can be swung
partially downwards so as to withdraw their ends to a greater or less distance
from the bridge wall and thus provide for a slow but continuous discharge of
ashes into the ash pit. The other arm of the lever 19 is connected by its rod 23
to an arm 34 on a rock shaft 35 mounted in suitable bearings in front of the

page_text: upper plate of the furnace front, the said rock shaft having near each end a
segment 36 secured to the shaft 35 by means of a clamping bolt 37, the said seg-
ments being connected by means of rods 38 to a pusher plate 39 which forms
part of the bottom of a fuel hopper 40 extending across the upper front plate of
the furnace.
The forward end of the pusher plate 39 carries antifriction rollers 39* bearing
upon a dead plate 41, which, extends into the upper portion of the furnace and
is in contact at its lower end with the heads 3" of the stationary grate bars 4ª,
so that there is a constant feeding or pushing forward of the fresh fuel from
the bottom of the hopper, first onto the dead plate, and then onto the upper ends
of the grate bars, the fuel being maintained upon the dead plate for a sufficient
length of time to insure the comparatively slow distillation therefrom of the
more volatile gases, which gases passing through the highly heated products
of combustion arising from the incandescent fuel on the grate, are ignited and
consumed so as to prevent the formation of smoke.
The dead plate 41 rests upon the heads of the stationary grate bars 3ª and upon
an angle bar 42 extending transversely across the front of the furnace, and the
said plate can, when the occasion arises, be readily lifted from the tops of the
grate bars so as to permit of the withdrawal of any one of the latter when it
becomes burnt out or otherwise in need of repair or replacement.
The inner end of the dead plate is supported free from contact with the heads
of the movable grate bars, and hence does not retard the movement of the same.
Each of the grate bars is of inverted U-shape with slotted top and vertical
side walls as shewn in Fig. 7 and the upper portion of each of the side walls of
each grate bar is reduced in thickness at and near the top, this reduction in
thickness preferably extending throughout the depth of the top member of the
bar, so that while the lower portions of the side walls of adjoining bars may be
in contact with each other the upper portions of the said side bars are separated
by a space sufficient to permit of the lateral expansion and "growth due to
the heating of this portion of the grate bar, without causing the bars to bind upon
each other as to interfere with the movement of the movable bars of the grate.
The upper portion of each of the contracted side walls of each grate bar is also
slotted transversely, as shewn at 43, Figs. 4, 5 and 7, so as to provide for longi-
tudinal contraction and expansion of the upper surface of the bar without caus-
ing the same to buckle or otherwise become distorted, the slots 43 gradually
increasing in depth from each end of the bar towards the centre of the same, as
shewn in Fig. 4.
The heads of the fixed bars of the grate have lugs 46 engaging with the bear-
ing bar or portion 2 of the furnace front upon which the said grate bar heads
are supported.
My improved stoker can be used in connection with a furnace having either
natural, induced, or forced draft, the ash pit doors fitting snugly to the lower por-
tion of the front plate of the furnace and the heads of the grate bars being of
box-like form and fitting snugly against each other so that there is no undue
leakage when the air is maintained under pressure in the ash pit.
As all portions of the bed of fuel are subjected to the same degree of agitation
and receive the same supply of air, it follows that the combustion is regular
and uniform throughout the entire mass of fuel upon the grate, so that the
maximum heating value of the fuel is obtained, and fuels of inferior quality can
be successfully used, the provision of the dead plate at the upper end of the
grate bars enabling me to partially coke or distill the volatile gases from the
green fuel before the latter reaches the air supplying portion of the grate where
active combustion begins, hence the formation of smoke, such as is due to the
rapid distillation of volatile gases from a mass of green fuel thrown upon a
highly heated body of incandescent fuel, is effectually prevented in my furnace,
and the fuel, of whatever character, is burned without any, or with a minimum
production of smoke.

page_text: Having thus described the nature of my invention, I wish it to be understood
that I do not limit myself to the exact construction illustrated, as many changes
within the knowledge of those skilled in the art may be made therein without
departing from the main features of my invention, for instance, the front plate
may be made without the inward offset; the grate bars may be supported upon
a special bearing extending across the furnace inside of the front plate; the
rock shaft 31 may also be inside the furnace, and the heads and toes of the grate
bars may be cast with the said bars, instead of being cast separable and bolted
thereto; the ash dumping plate may be made without perforations or in the form
of a grate, and may be carried by a shaft independent of that which supports the
toes of the grate bars, and many other immaterial variations of this character
may be made without departing from my invention, but I declare that what I
claim is:-
1st. In a mechanical stoker the combination of the front plate of the furnace
having a transverse opening therein with the grate bars supported at their upper
and lower ends in such position with respect to said opening that any one or
more of the said bars may be withdrawn from above through the said opening
in the front plate of the furnace, without affecting the position of any of the
other bars, substantially as herein before described.
2nd. In a mechanical stoker, the combination of the front plate of the furnace
having its lower portion offset inwardly in respect to the upper portion, a trans-
verse opening being formed between the upper and lower portion of the furnace
front with the grate bars supported at their upper and lower ends and capable
of being withdrawn from above through the said opening between the upper
and lower portions of the furnace front, substantially as herein before described.
3rd. In a mechanical stoker, the combination of alternating fixed and mov-
able grate bars, a fixed support for the upper ends of the fixed bars, and devices
for reciprocating the movable bars, the said reciprocating devices also serving
to support the upper ends of the movable bars free from contact with the fixed
bearing, substantially as hereinbefore described.
4th. In a mechanical stoker, the combination of inclined grate bars and sup-
ports therefor, with a dead plate forming an upward continuation of the grate
bars, a furnace front having an opening through which the grate bars can be
withdrawn, and provision for mounting the dead plate so that it can be
raised above the heads of the grate bars in order to permit of such withdrawal,
substantially as hereinbefore described.
5th. In a mechanical stoker, the combination of alternating fixed and mov-
able grate bars, with a dead plate forming an upward continuation of the said
bars, the said dead plate resting upon the heads of the fixed grate bars, but being
free from contact with the heads of the movable bars, substantially as herein-
before described.
6th. In mechanism for reciprocating the grate bar or pusher plate of a mech-
anical stoker, the combination of the vibrated lever, with a power transmitting
rod having stops between which the end of the lever plays, one of the said stops
being adjustable on the rod and comprising a bolt perforated for the passage of
the rod, washers strung on the said bolt and embracing the opposite sides of
the rod, and a nut adapted to the threaded portion of the rod and bearing upon
one of the said washers, substantially as herein before described.
7th. A grate bar for furnaces having an inverted U-shape in cross section,
the opposite side walls of the bar being reduced in thickness at and near the
top, whereby the lower portions of the side walls of adjoining bars may be in
contact without restricting the lateral expansion and growth of the upper portion
of the bar, substantially as hereinbefore described.
Sth. A grate bar for furnaces consisting of a slotted or perforated body or
central portion, and detachable head and toe portions, the entire grate bar,
with its head and toe portions having vertical side walls, and all of the parts

page_text: of the bar having the upper portions of said side walls reduced in thickness,
substantially as herein before described.
9th. A grate bar for furnaces having an inverted U-shape in cross section,
the upper member being slotted or perforated, vertical side walls reduced in
thickness at and near the top, and transverse slots extending through the upper
portions of the said side walls, substantially as herein before described.
10th. In a mechanical stoker, the combination of the inclined grate bars,
an ash dumping structure forming a continuation of the said grate bars, a
shaft located under the lower ends of the grate bars and to which the said ash
dumping structure is secured, and provision for moving the said shaft whereby
the ash dumping structure will swing down and away from the bridge wall,
substantially as hereinbefore described.
11th. In a mechanical stoker, the combination of the grate bars, ash dumping
plates having collars which serve also as supports for the lower ends of the grate
bars, and a shaft to which the said collars are secured, substantially as herein-
before described.
Dated this 13th day of December 1898.
JOHNSONS & WILLCOX,
47, Lincoln's Inn Fields, London, W.C., Agents.