Year: 1887

page_text: Date of Application, 28th Mar., 1887
Complete Left, 20th Dec., 1887
Complete Accepted, 20th Jan., 1888
I, ROBERT MARSHALL, of Endrick Bank, Honor Oak Park, in the County of
Surrey, Engineer, do hereby declare the nature of this invention to be as follows:-
My invention has for its object the application to steam boiler and other furnaces
of simple and effective means whereby the air supply is caused to pass in thin strata
immediately beneath the underside of the firebars, so as to become heated to such an
extent by radiation from the firegrate before coming in coming in contact with the
fuel, so as to add considerably to the intensity of the temperature of the furnace, and
effect the combustion of the fuel with a minimum production of smoke. By this
means the steaming capacity of a boiler is increased and as a consequence, for the
same production of steam a higher evaporative efficiency is attained.
For this purpose, according to one arrangement, I place close underneath the
firebars, a plate or shelf in such a way that the air, before coming in contact with the
fuel, must pass from the front end of the furnace forward underneath the said plate
to near the inner end of the furnace, where it rises up and then passes backward
again in the narrow space between the upper surface of the plate and the bottoms of
the fire bars, in order to rise through these and enter into combustion with the fuel.
By this means the air in passing in a thin stratum beneath the furnace bars becomes
highly heated on its way to the fuel, and an intense and consequently perfect
combustion results.
The distance between the undersides of the bars and the plate may be so arranged
or regulated, that, when required, a tool can be introduced below the bars for slicing
or pricking them from beneath as well as above. The ashes &c. in accumulating
upon the plate may be raked off from time or they may be discharged as presently
described.
A door may be provided for gaining access to the space above the plate, and for
regulating the heat this door may be more or less opened so as to admit a certain

page_text: quantity of cold air directly into the space. Or the door may be made with pivotted
louvre blades for this purpose. The said plate, as also the opening below it through
which the air enters, may also be made with louvre blades or with openings provided
with slides, so that the quantity of air admitted beneath the plate can be regulated,
and also instead of causing the whole body of air to travel forward beneath the plate,
a portion thereof may be admitted through the plate. Also by opening the louvre
blades of the plate occasionally any deposit of ashes upon them may be discharged
into the space below.
A jet of steam is, by preference, employed in combination with this method of air
supply, the jet being so arranged as to accelerate the current of air in the narrow
space under the bars on which it will also have a cooling action.
In the case of steam boilers having internal flues in which the firebars extend
inwards beyond the end of the boiler, the firebridge being formed in a chamber
externally thereto, I sometimes dispense with the before mentioned plate, and bring
the firebars down to within a very short distance of the bottom of the internal
flue.
The air supply to the furnace is made to enter a flue at the front of the boiler that
passes underneath the same to the inner end, where it communicates with a space
below the fire bridge, so that the air rises in this space and then passes backward
again in the narrow space between the underside of the firebars and the bottom
of the internal boiler flue, which, in this case, serves in lieu of the before described
plate.
My above described invention is applicable with particular advantage to marine
boilers and locomotive engines.

page_text: I, ROBERT MARSHALL, of Endrick Bank, Honor Oak Park, in the County of
Surrey, 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 has for its object the application to steam boiler and other furnaces
of simple and effective means whereby the air entering beneath the grate is caused to
pass only in restricted quantity up through the front part of the grate, while the
greater part enters freely up through the back part of the grate the arrangement
being such that the limited supply of air to the front part of the grate is made to pass
in a comparatively thin stratum close against the underside of the grate bars so as to
become heated to such an extent by radiation from the burning fuel before passing
among the same, and thus to produce a more perfect combustion thereof, while at the
same time owing to the limited quantity of air passing in at that part of the furnace
as compared with the quantity of fresh fuel on the grate, only the lower part of the
fuel is maintained in a state of perfect combustion by the entering air, the upper
part being subjected to a process of distillation, the volatile constituents given off being
made to travel forward over the fuel on the inner part of the grate, where they
enter into combustion with the excess of air passing up through the fuel at that
part.
The means I employ for the above purpose, consist mainly in the arrangement of a
plate under the front part of the furnace grate, within a short distance from the
underside of the bars, the narrow space between the two being open either at the
inner end of the plate, or at the outer end or both combined, or slits or openings
capable of being regulated by slides or louvre blades may be formed in the plate itself
for the entrance of air, the action in either case being that while air can pass freely
to the inner part of the fire grate underneath the said plate, only a restricted quantity
of highly heated air will pass up through the front part of the fire grate.
The accompanying drawings shew various constructions of furnaces for carrying
my above described invention into effect. Fig. 1 shows a longitudinal section of one
arrangement and Fig. 2 shows a part front view and part transverse section of the
same.
A is the before mentioned plate, fixed at a small distance from the undersides of
the front part of the furnace bars, and extending right across the furnace being
supported by angle irons B. B. on the sides of the furnace. The space between the
plate A and the bars is closed by a flap C, hinged either to the plate A as shewn or
to the front of the furnace, so that by opening this flap more or less a certain quantity
of air may be admitted directly into the space, while when it is closed, the whole of

page_text: the air supply enters beneath the plate A and after passing beyond the inner end
thereof, part of it rises up through the back part of the grate bars, while a smaller
portion passes backward in the space between A and the front part of the grate bars,
becoming highly heated and then rising up between the bars to enter into combustion
with the thin laver of incandescent fuel on the bars.
The air supply passing up through the back part of the grate bars, being more than
will enter into combustion with the solid fuel there situated, will partly pass through
the same becoming highly heated, and will impinge upon and enter into combustion
with the combustible gases that are passing forward from fuel on the front part of the
furnace.
In the arrangement shewn in section and front view at Figs. 3 and 4, the plate A
is not fixed, but can be slid in and out upon the angle iron bearings B, being provided
with a handle E for this purpose.
By this means the effect of the
according to the position of the plate.
front.
plate upon the combustion can be modified
The flap C is in this case fixed on the furnace
The heating capacity of an existing furnace may be further increased by forming
an extension as indicated by the dotted lines at D so that the part extending from the
commencement of the bars to the end of the extension then serves as a deal plate for
the reception of the fresh fuel that is subjected to the distilling operation the dead plate
being formed either with or without holes for the passage of air through it from the
space between it and the plate A.
Figs. 5 and 6 shew perspective views to an enlarged scale of the plate A formed
with an opening F, which can be more or less closed by a slide moved by a
handle G so as to admit more or less air from below into the space between the plate
and the bars.
Figs. 7 and 9 shew respectively a longitudinal section and a cross section of an
arrangement in which the plate A is formed into a hollow or double dead plate
the upper surface A' being formed with slits or perforations as shewn in plan at
Fig. 8.
In this arrangement the whole of the air supply to the front part of the furnace is
admitted through the flap C; a similar opening closed by a flap might however also
be provided at the inner end of the hollow dead plate, the flap being worked by a
handle from the front.
Fig. 10 shews a longitudinal section and Fig. 11 a plan of an arrangement in which
the box shaped dead plate A is formed to carry the front bars H, the air supply to
which is regulated by the flap C.
Fig. 12 shews a vertical section of a locomotive fire box with this invention
applied thereto, the plate A being in this case arranged to be slid upon angle iron
supports I by means of the handle E either into the position shewn, or into the
opposite position on the other side of the fire box, according to the direction in
which the engine is travelling, the fresh fuel must in this case be thrown either on
the front part or on the back part of the grate, according to the position of the
plate A.
Or, instead of arranging the plate A to shift as described it may fixed in the
position under the front end of the grato, and a second plate A² Fig. 13, be fixed
below it, extending from the back end of the fire box just above the flap J to within
a certain distance of the front end, so that when the engine is running forward the
air supply entering through J passes first forward underneath A² and then back again
underneath A, into the furnace, while on running backward the air supply entering
through the flap K passes directly underneath A to the furnace.
Or in place of the fixed plate A' the flap J instead of opening outwards as usual
may be arranged to open inwards, and be considerably extended in length as
shewn in dotted lines at Fig. 13, so that when raised it will serve in lieu of the
plate A².
Fig. 14 shews the invention applied to a vertical steam boiler, the opening with flap C
being omitted in this case.

page_text: Having now particularly described and ascertained the nature of this invention and
in what manner the same is to be performed, we declare that what we claim is :—
1. Enclosing the underside of the front part of a furnace by a plate in such manner that.
the air supply to the inner part of the furnace passes beneath such plate while a small
portion of the air supply is made to pass into the narrow space between the said
plate and the furnace bars or perforated or slotted dead plate, substantially as herein
described.
2. In furnaces constructed as set forth in the preceding claim, arranging the
plate A in combination with a flap C for admitting more or less air from the front
into the space between the plate and the underside of the bars, air being at the same
time admitted into such space at the inner end of the plate A, substantially as herein
described with reference to Figs. 1 to 4 of the drawings.
3. Constructing the plate A to be slid more or less from beneath the furnace bars,
substantially as described with reference to Figs. 3 and
of the drawings.
4. Constructing the plate A with openings closed by a slide or slides or with
inoveable louvre blades for the admission of a regulated quantity of air into the space
above the plate, substantially as herein described with reference to Figs. 5 and 6.
Dated this 19th day of December 1887.
ABEL & IMRAY,
Agents for the Applicant.