IMPROVEMENTS IN MECHANICAL STOKING APPARATUS FOR BOILER AND OTHER FURNACES
Year: 1876

page_text: LETTERS PATENT to James Smith, Engineer to Messieurs Walter Crum and
Company, of Thornliebank, in the County of Renfrew, North Britain, for the
Invention of "IMPROVEMENTS IN MECHANICAL STOKING APPARATUS FOR
BOILER AND OTHER FURNACES."
Sealed the 28th March 1877, and dated the 9th October 1876.
PROVISIONAL SPECIFICATION left by the said James Smith at the Office
of the Commissioners of Patents on the 9th October 1876.
JAMES SMITH, Engineer to Messieurs Walter Crum and Company, of Thorn-
liebank, in the County of Renfrew, North Britain. "IMPROVEMENTS IN MECHANICAL
STOKING APPARATUS FOR BOILER AND OTHER FURNACES."
This Invention relates to improvements in mechanical stoking apparatus for
supplying fuel to and moving it inwards in boiler and other furnaces in a regular
manner, the object being to simplify the construction and working of the parts and
to render the apparatus more efficacious and satisfactory than heretofore, and less
liable to get out of order.
In carrying out the Invention a hopper is arranged at the mouth of each furnace
partly in the manner described in the Specification of Letters Patent granted to
the present applicant and dated 8 February 1875, (No. 466). The fuel may be
pushed inwards from the lower part of the hopper by screws as described in the
said earlier Specification, or as is now preferred by sliding or hinged plates or bars
made to reciprocate by means of one or more revolving cranks or eccentrics.
In one modification two bars, each about as long as and occupying one-half the
width of the furnace mouth, is pivoted by its middle on a vertical pin, and the
adjacent inner ends of the two bars are connected to the revolving crank or
eccentric, the bars being thereby inade to oscillate. The inner edge of the dead
plate forming the bottom of the hopper has cast on it a vertical flange or plate
extending downwards to the top of the fire-bars or grate, and perforated for the
admission of air. The fire-bars are of a step-like form, as viewed laterally, each
bar having three or other number of horizontal or nearly horizontal parts at slightly
different levels, the inner parts being lower. The entire set of fire-bars (or it might
be a single grated casting) is supported on two vertical rocking frames which allow
the bars to reciprocate inwards and outwards with very little friction. The
I Prine 621

page_text: reciprocating motion is given to the bars through a connecting rod, by a crank or
eccentric on the bottom end of a short vertical spindle carried in a transverse frame
bar, and driven by means of a worm wheel and worm from a transverse horizontal
shaft which may extend in front of a number of contiguous furnaces. The short
vertical spindle for working the fire-bars may also be fitted with the crank or
eccentric for working the lower movable part or parts of the hopper.
The fire-bars are by preference comparatively short, so that the fuel falls down
over their inner ends in a partially unconsumed condition, its combustion being
completed whilst it lies on the bottom of the flue, the usual fire-bridge being
dispensed with, or a sufficient space being left for it between the inner ends of the
fire-bars and the bridge if a bridge is used.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said James Smith in the Great Seal Patent Office on the 5th April 1877.
JAMES SMITH, Engineer to Messieurs Walter Crum and Company, of Thornlie-
bank, in the County of Renfrew, North Britain. "IMPROVEMENTS IN MECHANICAL
STOKING APPARATUS FOR BOILER AND OTHER FURNACES."
My said Invention relates to improvements in mechanical stoking apparatus for
supplying fuel to and moving it inwards in boiler and other furnaces in a regular
inanner, the object being to simplify the construction and working of the parts, and
to render the apparatus more efficacious and satisfactory than heretofore, and less
liable to get out of order.
In carrying out my present Invention a hopper is arranged at the mouth of each
furnace partly in the manner described in the Specification of earlier Letters Patent
granted to me and dated 8 February 1875 (No. 466). The fuel may be pushed
inwards from the lower part of the hopper by screws as described in my said earlier
Specification, or, as I now prefer, by sliding or hinged plates or bars made to
reciprocate by means of one or more revolving cranks or eccentrics.
In one modification two bars, each about as long as and occupying one-half of the
width of the furnace mouth, are pivoted each by its middle on vertical pins, and the
two adjacent inner ends of the two bars are connected to the revolving crank or
eccentric, the bars being thereby made to oscillate. The fire-bars are of a step-like
form, as viewed laterally, each bar having three or other number of horizontal or
nearly horizontal parts at slightly different levels, the inner parts being lower. The
fire-bars are supported on two vertical rocking fraines, which allow the bars to
reciprocate inwards and outwards by the action of revolving cranks or eccentrics
with very little friction; or instead of all the bars being supported and moved in
this way there may be arranged alternately with reciprocating bars stationary bars
supported by transverse bearers at their outer and inner ends. The inner vertical
rocking frame in each furnace may in some cases be dispensed with, the inner ends
of the reciprocating bars being arranged to rest and slide upon the inner transverse
bearer.
The fire-bars are by preference comparatively short, and in some cases the fuel
falls down over the inner ends in a partially unconsumed condition, its con-
bustion being completed whilst it lies on the bottom of the flue, the usual fire-bridge
being dispensed with, or a sufficient space being left for it between the inner ends
of the fire-bars and the bridge if a bridge is used.
Instead of separate oscillating bars being used for the primary propulsion of the
fuel inwards from the bottom of the hopper, the reciprocating fire-bars may have
suitable pieces cast or fixed on their outer ends for that purpose.
And in order that my said Invention and the manner of performing the same
may be properly understood I hereunto append a Sheet of explanatory Drawings,
to be herein-after referred to, and representing the modifications of my mechanical

page_text: stoking apparatus which I now believe to be most advantageous in practice. In
these Drawings the same reference numerals are used to mark the saaic or like parts
wherever they are repeated.
Figure 1 of the Drawings is a front end elevation showing my apparatus as fitted
to a cylindrical boiler, certain parts being supposed to be removed to show details
that would otherwise be hid; Figure 2 is a longitudinal vertical section corre-
sponding to Figure 1, and Figure 3 is a plan of the grate surface.
Each hopper 1 is formed by a pair of vertical side plates 2 cast with flanges by
which they are bolted to the front end of the boiler, and formed with ribs sup-
porting an inclined front plate 3 which can be easily removed at any time to give
direct access to the fire. The inner side or back of the hopper is formed by a
vertical plate 4 sliding in vertical guides, and serving as a door under which the
fuel passes from the hopper into the furnace. This door plate 4 is suspended by
chains from pulleys 5 on a horizontal shaft G which can be turned by a hand
wheel 7, and has fixed on it a ratchet wheel 8 with which a catch can be engaged
so as to hold the door plate in any desired position. At the bottom of the hopper 1
there are fixed three hollow castings or air boxes 9, one in the middle and a smaller
one at each side, and these castings have their inner ends curved down and
perforated for the admission of the air to the fire.
The reciprocating fire-bars are of two kinds, those 10 under the middle air box 9
being of the kind shewn separately in end and side elevation in Figure 4, whilst
those 11 which are at the two spaces between the air boxes 9 are formed, as shown
separately in Figure 5, with a double stepped part 12, which by its reciprocation
propels the fuel from the bottom of the hopper 1 into the furnace. The top surfaces
of the parts 12 are made broad enough to cover the spaces between the bars, whilst
ribs are cast on the sides of the vertical web to subdivide the passages for air. The
stationary bars 13 which alternate with the reciprocating bars 10, 11, are of the
kind shown separately in Figure 6, and are held at their front ends on a checked
flange formed on a transverse bearer 14, the under sides of their ends being checked
to engage with the flange which thus prevents them from moving longitudinally.
The inner ends of the stationary bars 13 rest on the top of an inner transverse
bearer 15 without check of any kind. All the reciprocating bars 10, 11, rest upon
two rocking frames 16, 17, which are shown separately in Figures 7 and 8, the bars
having notches 18 formed on their under sides to catch upon the top transverse
horizontal bars of the rocking frames 16, 17. The levers or arms of the inner
rocking frame 17 are formed with journals which are supported in bearings fixed
to the bottom of the flue. The levers or of the outer rocking frame 16 are
forked at their lower ends to rest on pins 19 carried by brackets or standards.
The reciprocating motion is imparted to the bars by the front rocking frame 16
which is moved by an adjustable connecting rod 20 proceeding from a crank 21 on a
vertical spindle carried by the front transverse bearer 14. The spindle of the
crank 21 has fixed on its upper end a worm wheel 22 which is driven by a worm 23
on a revolving horizontal shaft 24 carried in front of the boiler in bearings fixed to
or formed on the front bearer 14, and driven by means of a pulley 25 and belt, or
in any other convenient way.
A more compact mode of arranging the worm shaft 24, worm wheel 22, and
crank spindle 21, is shown in Figure 9. The whole of the fire-bars 10, 11, 13, at
the part within the furnace are shaped in plan, as shown in Figure 3, that is, so as
to form narrow air spaces between then, which spaces are of a slightly increasing
width towards the inner end. Air is also admitted from the ash-pit through
notches in plates or bars 26 fixed at the extreme sides of the grate space.
The reciprocating action of the alternate bars 10, 11, combined with the step-
like configuration, as seen in Figures 4, 5, 6, causes the fuel to progress along the
grate surface towards the inner ends of the bars, and on reaching those ends the
more or less consumed fuel falls over upon the bottom of the flue where its
combustion is completed.
The length of the fire-bars may be advantageously varied to suit the kind of

page_text: fuel used. Thus for the softer or more bituminous coals the bars should be shorter
and the combustion be less completely effected upon them, whilst for harder coals
the bars may be longer. The quantity of air admitted to the fuel which has fallen
over the inner ends of the fire-bars may be regulated by a plate under the inner
bearer 15, or by simply maintaining a sufficient heap of ashes under the bearer.
The condition of the fire can be seen at any time on opening a small sight hole
door 29 in the hopper slide or door plate 4. A flat casing 30 is formed in the
plate 4 round the sight hole, and has access at the top and bottom for air, which
passes thence into the furnace through perforations indicated by dotted circles in
Figure 1, and tends to keep the plate cool.
Whilst I prefer to have the fire-bars step-shaped as herein-before described, they
may with nearly the same results be made straight and with an inclination the
same as the general inclination of the stepped bars.
Having thus particularly described my said Invention, and the manner of per-
forming the same, have to state that I do not restrict myself to the precise details
herein described or delineated, but that what I believe to be novel and original, and
claim as the Invention secured to me by the herein-before in part recited Letters
Patent is,-
1. The arranging or combining together of the parts of mechanical stoking
apparatus for boiler and other furnaces, substantially in the improved manner herein
described and delineated.
2. The applying or using of the longitudinally reciprocating step surfaced or
inclined grate bars (10, 11,) alone or alternated with stationary bars (13) as herein-
before described.
3. The forming on or fixing to the reciprocating bars or some (11) of them, the
upper stepped parts (12) for propelling the fuel inwards from the bottom of the
hopper, as herein-before described.
4. The supporting of the reciprocating bars (10, 11,) on two rocking frames (16, 17,)
or partly on one rocking frame (16) and partly on a fixed bar (15), as herein-before
described.
In witness whereof, I, the said James Smith, have hereunto set my hand
and seal, this Fourth day of April, in the year of our Lord One thousand
eight hundred and seventy-seven.
Witness,
EDMUND HUNT,
Patent Agent,
Glasgow.
JAMES SMITH. (L.S.)