IMPROVEMENTS IN AND RELATING TO FURNACES
Year: 1881

page_text: LETTERS PATENT to John Henry Johnson, of 47, Lincoln's Inn Fields, in the
County of Middlesex, Gentleman, for an Invention of "IMPROVEMENTS IN
AND RELATING TO FURNACES." A communication from abroad by Michel
Perret, of Paris, in the Republic of France.
PROVISIONAL SPECIFICATION left by the said John Henry Johnson at the
Office of the Commissioners of Patents on the 30th August 1881.
JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
Gentleman. "IMPROVEMENTS IN AND RELATING TO FURNACES." A communication
from abroad by Michel Perret, of Paris, in the Republic of France.
This Invention of improvements in and relating to furnaces has reference chiefly
to the construction and arrangement of fire bars or grates for furnaces working
with or without a blast, whereby combustion is enabled to take place under more
favorable conditions than usual in furnaces provided with ordinary firebars or
grates.
The improved arrangement, hereinafter described, has the effect of preventing all
irregularities in the bars or grate, and of maintaining the metal at a uniform tem-
perature whereby the uniformity of the passages for the supply of air is ensured,
the clearing of the bars is facilitated, and the grate generally is preserved from
deterioration. A special arrangement of the furnace also enables pulverulent com-
bustibles to be consumed without wasting the finer particles of the fuel, as
bereinafter described.
In carrying out the said Invention when applied to a furnace with a forced
draught, for example, the grate is composed of a series of bars provided with webs
of considerable depth partially immersed in water in such a manner as to be con-
tinually cooled, whereby the bars are protected from rapid deterioration or burning.
For this purpose the bars are arranged in a strong case of sheet iron filled with
water to a certain height, and provided with suitable apertures for the admission
of the blast of air, which passes over the surface of the water, and thence between
the bars into the furnace. An aperture is also provided in the case for the purpose

page_text: of supplying the latter with water, and for ascertaining the level of the water
therein; and a third aperture serves for the removal of the small quantity of ash
that falls into the said water.
In order to prevent the bars from breaking under the strain resulting from the
difference between the expansion of the part of the firebars in direct contact with
the fire and that of the part cooled by the water, the cooled portion is divided by
one or more slots perpendicular to the plane of the grate.
The webs of the fire bars may be of a curvelinear, angular, or other suitable form,
and may be of such a shape as to dip into the water at one extremity only, in
which case the thickness of the metal is increased with the distance from the cooling
liquid, so as to provide a good conductor for carrying off the heat.
The cooling of the grate by chilling the clinkers or scoria at its surface prevents
the latter from adhering to the bars, and enables the said clinkers to be readily
removed from the upper side of the bars when the latter are close together, or from
their under side when they are wide apart. In the latter case the clinkers may be
pushed down by a suitable tool or by simply rocking the bars.
The firegrate is not necessarily constructed with bars, but inay be formed by a
metal plate of suitable thickness perforated with holes of convenient size, and
provided on its underside with pendant webs, ribs, or projections of such a depth
or length as to dip into water placed below them, sufficient space being provided
for the passage of air between the water and the surface upon which combustion
takes place.
The cooling resulting from the partial immersion of the grate preserves the
original form of the latter, and enables the area of the orifices therein for the
admission of air to be determined with precision, and also enables the area of these
orifices to be reduced to any required extent for the purpose of employing dry and
dusty combustibles.
However, when the size of these orifices is reduced beyond certain limits, say,
one twelfth of an inch for example, the air does not pass through readily, so that
extra pressure becomes necessary, which disturbs or lifts the fuel, whereby
irregularity in the supply of air is produced, and the furnace ceases to act properly.
This disadvantage is obviated, according to this Invention, even when extremely
small holes are employed, by simply graduating or tapering the orifices downwards
in such a manner as to enable the stream of air to spread out obliquely and act
upon a larger area, so as to be more thoroughly diffused among the combustibles.
-By-this-means-a-uniform-supply-of-air-through-thin-layers-of-fuel-may-be-obtained-
with a relatively small pressure.
This arrangement may also be applied to grates without a blast, and enables the
section of the air passages to be reduced by facilitating the introduction of the air
into the layers of fuel.
According to another modification, the surface for supporting the combustible
materials may be formed by a series of bars provided with partially immersed webs,
as hereinbefore described, and having recesses formed in their sides so as to forin
holes in the shape of stars or crosses, for example, when the said bars are laid close
together side by side these holes are extremely small at the lower extremity at the
underside of the bars, but are enlarged towards the upper surface for the purpose of
allowing the air to pass out obliquely and penetrate every part of the fuel.
It has been ascertained by experience that the quantity of water evaporated
by coming in contact with the firebars is unimportant, even when hot air is
employed.
In lieu of cooling the bars by partially immersing them, as hereinbefore described,
the same result may be obtained by making the webs of the bars wider and
deeper, an arrangement which is more particularly applicable in the case of loco-
motive engine furnaces. Under these conditions the air acts as the refrigerating
agent.
In some cases steam from the boiler may be blown in between or underneath the
fire bars in such a manner as to cool the latter, which in this case are surrounded

page_text: by an atmosphere of steam in lieu of being partially immersed in water, as herein-
before described.
The possibility of employing heated air without risk of injuring the firebars is of
great importance when a blast is employed, as it enables the heat of the gases to be
utilized after the latter have done their work.
The heat may be extracted from the gases by various means. Metal tubes
presenting an extensive surface may be advantageously employed for this purpose.
The employment of very poor, dusty, or pulverulent combustibles on the
improved partially immersed grate or fire bars in conjunction with a blast is liable
to cause a part of the combustible materials or fuel to be carried away by the
draft, so as to retard the generation of heat, and necessitate frequent cleaning of
the flues.
In order to obviate this disadvantage a horizontal partition or shelf is arranged
above the fire bars, which deflects the products of immediate or first combustion into
a combustion chamber at the rear of the fire bars; this chamber is likewise covered
by a shelf or partition which deflects the gaseous products forwards on to the shelf,
hereinbefore described, above the fire bars.
In consequence of this arrangement the heaviest particles are deposited in a heap
in the combustion chamber at the back of the grate, where they are consumed as
they roll down the sides of the heap, whilst the lighter portions suspended in the
gaseous atmosphere are burnt at a very elevated temperature together with all the
combustible gases.
The whole of the combustible material carried away by the draft or blast of air
is thus consumed before reaching the flues, and in the case of boiler furnaces the
plates of the boiler are protected from the injurious action of the flame.
This arrangement is also applicable to furnaces in which foul or noxious gases
are consumed.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said John Henry Johnson in the Great Seal Patent Office on the
28th February 1882.
JOHN HENRY JOHNSON, of 47, Lincoln's Inn Fields, in the County of Middlesex,
Gentleman. "IMPROVEMENTS IN AND RELATING TO FURNACES." A communication
from abroad by Michel Perret, of Paris, in the Republic of France.
This Invention of improvements in and relating to furnaces has reference chiefly
to the construction and arrangement of fire bars or grates for furnaces working
with or without a blast, whereby combustion is enabled to take place under more
favorable conditions than is usual in furnaces provided with ordinary fire bars or
grates.
The firebars ordinarily employed heretofore are arranged at a certain distance
apart, calculated according to the nature of the fuel employed, the volume of air
to be admitted in a given period, and in general to the nature of the operations to
be performed by the furnace.
However, even when the furnace is designed with the greatest care, it soon
begins to depart from its normal rate of working, on account of the expansions
and the incrustations which change the area of the passages for the admission of
air beneath the fire bars, and also by reason of the rapid wearing away of the
said bars.
The later defect is particularly marked in furnaces with a forced draught, or
supplied with air under pressure, and is probably the cause of such furnaces being
seldom employed, notwithstanding the advantages which they present in many
instances.
The improved arrangement hereinafter described has the effect of preventing all
irregularities in the form of the bars or grate, and of maintaining the metal at an
even temperature, whereby the uniformity of the passages for the supply of air is
insured, the clearing of the bars is facilitated, and a grate generally is preserved
from deterioration. A special arrangement of the furnace also enables pulverulent
combustibles to be consumed without wasting the finer particles of the fuel as
hereinafter described.
In carrying out the said Invention when applied to a furnace supplied with air
under pressure, for example, the grate is composed of a series of bars provided
with webs of considerable depth partially immersed in water in such a manner as
to be continually cooled, whereby the bars are protected from rapid deterioration
or burning. For this purpose the bars are arranged in a strong case of sheet iron
filled with water to a certain height, and provided with suitable apertures for the
admission of air, which passes over the surface of the water and is delivered thence
between the bars into the furnace. An aperture is also provided in a case for the
purpose of supplying the latter with water, and for ascertaining the level of the
water therein, and the third aperture serves for the removal of the small quantity
of ash that falls into the said water.
In order to prevent the bars from breaking under the strain resulting from the
difference between the expansion of the part of the fire bars in direct contact with
the fire and that of the part cooled by the water, the cooled portion is divided by
one or more slots perpendicular to the plane of the grate, so as to compensate for
the inequality of the expansion. The webs of the fire bars may be of a curvi-
linear, angular, or other suitable form, and may be of such a shape as to dip into
the water at one extremity only.
The cooling of the grate has the effect of chilling the clinkers or scoria at its
surface, and thus prevents the said clinkers or scoria from adhering to the bars.

page_text: The clinkers or scoria may then be readily removed from the upper side of the
grate when the bars are close together, or from the underside when they are wide
apart. In the latter case the clinkers may be pushed down by a suitable tool or
by simply rocking the bars.
The fire grate is not necessarily constructed with bars, but may be formed by a
metal plate of suitable thickness, perforated with holes of convenient size, and
provided on its underside with pendant webs, ribs, or projections of such a depth or
length as to dip into water placed below them, sufficient space being provided for
the passage of air between the water and the surface upon which combustion takes
place.
The cooling resulting from the partial immersion of the grate preserves the
original form of the latter, and enables the area of the orifices therein for the
admission of air to be determined with precision, and also enables the area of these
orifices to be reduced to any required extent for the purpose of employing dry and
pulverulent or dusty combustibles.
However, when the size of these orifices is reduced beyond certain limits, say
one twelfth of an inch for example, the air does not pass through readily, so that
extra air pressure becomes necessary, which disturbs or lifts the fuel, whereby
irregularity in the supply of air is produced and the furnace ceases to act properly.
This disadvantage is obviated according to this Invention, even when extremely
small holes or passages are employed, by simply graduating or tapering the orifices
inwards and downwards in such a manner as to enable the stream of air to spread
out obliquely and act upon a larger area, so as to be more thoroughly diffused
among the combustibles. By this means a uniform supply of air through thin
layers of fuel may be obtained with a relatively small pressure. This arrangement
may also be applied to the grates of furnaces working without a blast, and enables
the section of the air passages to be reduced by facilitating the introduction of the
air into the layers of fuel.
It has been ascertained by experience that the quantity of water evaporated by
coming into contact with the fire bars is unimportant, even when hot air is
employed.
In lieu of cooling the bars by partially immersing them, as hereinbefore described,
the same result may be obtained by making the webs of the bars wider and
deeper, an arrangement which is more particularly applicable in the case of
locomotive engine furnaces. Under these conditions the air acts as the refrigerating
agent.
In some cases steam from the boiler may be blown in between or underneath
the bars in such a manner as to cool the latter, which in this case are surrounded
by an atmosphere of steam in lieu of being partially immersed in water, as herein-
before described.
The possibility of employing heated air without risk of injuring the fire bars is
of great importance in the case of furnaces supplied with air under pressure, as it
enables the latent heat of the gases generated in the furnace to be utilized after
these gases have done their work, the gases in question not being required for
producing a draught in the chimney in furnaces of this description. The heat may
be extracted from the gases by various means. Metal tubes presenting an extensive
surface may be advantageously employed for this purpose.
And in order that the said Invention may be fully understood I shall now proceed
more particularly to describe the same, and for that purpose shall refer to the
several Figures on the annexed Sheet of Drawings, the same letters of reference
indicating corresponding parts in all the Figures.
Figure 1 of the accompanying Drawing represents in elevation, transverse section,
and plan, an improved fire bar constructed according to this Invention.
Figure 2 represents in side elevation and transverse sections a bar for immersion
at one part of the web only. The transverse sections, which are taken through
different parts of this bar, shew how the thickness of the web increases in proportion.

page_text: with the distance from the cooling liquid, so as to provide a good conductor for
carrying off the heat, and thus preserve the bar from becoming excessively heated.
Figure 3 represents inside elevation and transverse section a bar constructed
according to a modification of the preceding type, and consisting in forming the
web of the bar in the form of a trapezium or of a triangle, the latter being indicated
by the dotted lines in the same Figure.
Figure 4 is a plan of a portion of a series of partially immersed bars having
recesses formed in their sides, so as to constitute between them holes (which may
be in the shape of stars or crosses, for example), when the said bars are laid close
together side by side. These holes are extremely small at the lower extremity at
the underside of the bars, but are enlarged towards the upper surface for the
purpose of allowing the air to pass out obliquely and. penetrate every part of the
fuel.
Figure 5 is a transverse section of several of these bars, shewing the shape of
the holes. To allow of expansion and contraction the webs may have a slot or
slots in them; one such slot is shewn in Figure 1; and
Figure 6 illustrates in side elevation and transverse section a fire bar similar to
the bars illustrated in Figures 1, 2, and 3, but provided with two slots or openings
in the web for the purpose described.
Figures 7 and 8. illustrate in longitudinal and transverse section respectively a
furnace constructed according to this Invention and arranged for burning pulverulent
fuel.
The employment of very poor, dusty, or pulverulent combustibles on the
improved partially immersed grate or fire bars in conjunction with a blast is
liable to cause a part of the combustible materials or fuel to be carried away by
the draft, so as to retard the generation of heat and necessitate frequent cleaning
of the flues..
In order to obviate this disadvantage a horizontal partition or shelf A,
Figures 7 and 8, is arranged above the fire bars, which deflects the products of
immediate or first combustion into a combustion chamber B at the rear of the fire
bars. This chamber is likewise covered by a shelf or partition C, which deflects
the gaseous products forwards on to the shelf A above the fire bars.
In consequence of this arrangement the heavier particles are deposited in a heap
in the chamber B at the back of the grate, where they are consumed as they roll
down the sides of the heap, whilst the lighter portions suspended in the gaseous_
atmosphere are burnt at a very elevated temperature together with all the
combustible gases.
The whole of the combustible material carried away by the draught or blast of
air is thus consumed before reaching the flues, and in the case of boiler furnaces the
plates of the boiler are protected from the injurious action of the flame.
This arrangement is also applicable to furnaces in which foul or noxious gases
are consumed.
Having now described and particularly ascertained the nature of the said
Invention, and the manner in which the same is or may be used or carried into
effect, I would observe in conclusion that what I consider to be novel and original,
and therefore claim as the Invention secured to me by the hereinbefore in part
recited Letters Patent is,
First. In furnaces, the employment of fire bars or equivalent supports for the
fuel, having a web or webs or a projection or projections from their undersides to
be acted upon by a cooling medium, substantially as hereinbefore described with
reference to the accompanying Drawings.
Second. In furnaces, the employment of fire bars or equivalent supports for the
fuel, having a web or webs or a projection or projections from their underside, the
same being divided by transverse slots or openings to allow of the unequal
expansion of the metal, substantially as herein before described and illustrated in
the accompanying Drawings.
Third. In furnaces, the employment of a grate or support for the fuel, having

page_text: air passages made flaring or widened at their upper extremities, substantially as
and for the purpose hereinbefore described and illustrated in the accompanying
Drawings.
Fourth. In furnaces, the combination with a grate or fuel supporting surface
of the construction herein before described and claimed, of means for admitting hot
air beneath the grate or surface together with or without a blast, substantially as
and for the purpose described.
Fifth. The arrangement described, with reference to and shown in Figures 7
and 8 of the accompanying Drawings, for burning poor, dusty, or pulverulent fuel.
In witness whereof, I, the said John Henry Johnson, have to this my
Specification set my hand and seal, this Twenty eighth day of February,
One thousand eight hundred and eighty two.
J. HENRY JOHNSON. (L.S.).