Improvements in Segmental Fire Bars and Grates for Boiler Furnaces.
Year: 1889

page_text: Date of Application, 10th Apr., 1889
Complete Specification Left, 10th Jan., 1890-Accepted, 15th Feb., 1890
PROVISIONAL SPECIFICATION.
Improvements in Segmental Fire Bars and Grates for Boiler
Furnaces.
I NICHOLAS DOWNING Railway Street Norton Road Stockton-on-Tees Durham,
Ironfounder do hereby declare the nature of this invention to be as follows:-
My invention relates to improvements in Fire-Bars used in Vertical Boilers and
which are made in segments or parts and which when put together for use form a
circle, made up in the following manner.
A square is formed inside the circle, the diagonals of which are nearly equal to the
diameter of the circle; this leaves four segments outside the square to complete the
circle.
The square is filled up with single Fire-bars of a suitable length and the segments
on each side of the square are usually cast in one piece with the Fire-bars, and with
provision on two of them for carrying the single Fire-bars used to fill the
up square,
the consequence is, that these segments have to be extremely heavy as they have not
only to withstand the heat of the fire but have to support the square of single Fire-
bars as well & owing to their being made all in one piece the expansion & contraction
is unequal, this causes the bars to break off before being worn out and the whole
segment has to be taken out; the extra weight of metal also interferes with the
air-space.
The object of my invention is to overcome these disadvantages and is accomplished
in the following manner. I divide the circle as described above, but the segments on
each side of the square I make in 3 pieces, one in the form of an open frame and the
other in the form of two light gratings forming the Fire-bars. The open segments
have provision on two of them for carrying the single bars which make up the square,
the open frame segments are put in first and are underneath the Fire-bars and are
thus removed from the excessive heat of the fire, and are kept cool by the air passing.
underneath the Fire-grate, they will consequently need much less metal for the same
strength than if they formed part of the Fire-bars, and as the gratings resting on
these open frames do not need to be so strong there is a greater margin left for
air space.
Dated this oth day of April 1609.
COMPLETE SPECIFICATION.
Improvements in Segmental Fire Bars and Grates for Boiler
Furnaces.
I, NICHOLAS DOWNING, of 2 Oxford Terrace, Norton Road, Stockton-on-Tees, in
the County of Durham, Ironfounder, 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 the arrangement and construction of fire-bars specially
designed for use in vertical boilers of the donkey type, which fire-bars are grouped
together in sections or separate parts of the furnace grating.
The usual mode of providing fire-bars for vertical boilers consists in dividing the
furnace grating into sections or parts which when put together form a circle to fit the
boiler shell, and is made up of a square, the diagonals of which are slightly less than
the diameter of the circle, and four segments outside the square to complete the
circle, which are fitted up with separate gratings. The square is filled up
detached fire-bars, and the segmental gratings outside of the square are cast in one
with

page_text: piece with the fire-bars in and with extensions provided on two of them at opposite
sides of the square for carrying the detached fire-bars which occupy the square; the
consequence is that the metal in these segmental gratings is unevenly distributed,
and they are prematurely destroyed by unequal expansion and contraction which
causes the long and relatively thin bars to break off from the heavier rim before they
would be burnt through by the heat of the furnace; the extra bulk of metal to
enable the bars to resist the strains of unequal expansion and contraction also reduces
the air space.
The object of my invention is to remove these defects in the segmental parts of
the furnace grating by dividing the circle into the usual sections with the square
filled up as usual with detached fire-bars, but the gratings outside of the square I
make in two halves supported by and fitted into the frames or cross bars, by which
construction parts of different thickness and differently exposed to the heat of the
furnace are detached from each other and with the metal more equally distributed in
each separate casting a more equal expansion and contraction is obtained with an
increase of air space between the bars which are reduced in thickness. The frames
or rims into which the segmental gratings are fitted have provision on two of them
in the form of channel shaped cross bars for supporting the bars which occupy the
square ; these frames are put in first and aro underneath the gratings, and are thus
protected from the excessive heat of the fire and are kept cool by the air drawn in
through the fire grate, they consequently need much less metal for the same strength
and durability than if they formed one casting with the fire-bars according to the
designs hitherto in use, and as the gratings rosting on these frames do not need to be
so strong as when forming one casting with them, their thickness is reduced and more
air space is obtained.
And in order that my invention may be fully understood and readily carried into
effect I will now proceed to describe the same by referring to the accompanying
drawings which illustrate the mode of applying my invention to furnaces of vertical
donkey boilers. Figure 1 is a plan of a segmental section of a furnace grate as at
present constructed; Figure 2 is a plan view of the furnace grate constructed
according to my invention with half the fire-bars removed; Figure 3 is a sectional
view taken on line AA of Figure 1; and Figure 4 is a similar view showing the
segmental sections of the grate placed on the slope. Figures 5 and 6 are views of the
segmental grates constructed according to my invention; and Figure 7 illustrates a
modification of my invention showing how I cut the circumferential rim away, and
extend the segmental gratings to the ring attached to the furnace shell.
Figure 1 illustrates the heavy and unweildly form of a segmental fire grating as at
present in use for completing the circular area of the furnace grating, in this style of
fire grating it will be observed that long thin fire bars and a relatively heavy outside
rim are cast in one piece, the bars being also more exposed to the heat of the furnace
than the rim, the expansion and contraction is consequently unequal, and causes the
bars to break off before they would be burnt through by the heat, when the whole
segment has to be taken out, and perhaps other parts of the furnace grating
disturbed; also the extra thickness of the bars to resist the strains due to unequal
expansion reduces the air space.
In Figures 2 and 3 the furnace grate is shown as a complete circle enclosed within
a rim which is divided into four detached segments a¹ a² as a', two of which a¹ and a³
are cast in a piece with the channel cross bars 61 6³, respectively to which cross bars
are hooked on the tie bars c for the purpose of holding the grating together.
The detached fire-bars in the centre are supported on the two cross bars 6' 62 in the
manner shown. The other segmental frames a³ a which complete the circumference
of the rim fit in between the segmental frames a¹ a³, and are supported at each end
from the cross bars 6 and frames a¹ a³, and also rest on the ring attached to the
furnace shell. The segmental grates ele are of the forms shown in Figures 5 and 6,
that two half grates occupy each segmental area enclosed between the
rim a¹ a a³ a', and the cross bars b¹ or the tie bars c upon which they are
supported,
BO

page_text: This arrangement facilitates their removal and replacement in case of fracture.
Small openings or holes are cast in the channel cross bars 616 to admit currents of
air through the bottom which tends to increase the combustion of the furnace and to
keep the cross bars cool. Figure 4 illustrates how the segmental gratings may be
placed on the slope to admit air more freely to the furnace by the tendency to
accumulate the fuel on the lower level of the central area. Figure 7 illustrates a
modification of my invention in which the rim which extends all round the grating
as described with reference to Figure 2 is cut away, the channel cross bars 6 being
cast with crossheads a which are short lengths of the circular rim which if completed
would enclose the whole grating, instead of which the segmental grates fextend to
the boiler shell and fit in hetween the crossheads a and a to complete the circle, in all
other respects the grating is constructed as already described with reference to
Figure 2.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is carried into effect, I declare that what I
claim is
Firstly-In the circular furnace gratings of vertical boilers the use and
construction of segmental gratings consisting of detached parts which are preferably
halves fitted together in a detached frame upon which they rest at one or both sides,
substantially as and for the purpose as hereinbefore described with reference to the
accompanying drawings.
SecondlyThe combination of parts as a whole constructed, arranged, and fitted
together as circular furnace gratings for effecting the purposes hereinbefore described
with reference to the accompanying drawings.
11
1
G. J. CLARKSON,
Stockton-on-Tees, Agent for the Applicant.