Improved Grate Bars for Boilers and other Applications.
Year: 1896

page_text: Date of Application, 3rd Mar., 1896
PROVISIONAL SPECIFICATION.
Improved Grate Bars for Boilers and other Applications.
I, BENJAMIN ARTHUR THOMAS 8 Robert Road Handsworth Staffordshire,
Mechanical Engineer do hereby declare the nature of this invention to be as
follows:-
Improvements in grate bars, by casting small tapered fillets or ribs from " thick
& upwards & of square triangular or circular form, in elevation, to a hollow bar,
the top edges of which are hollowed out between the junction of the fillets or ribs
to it. These fillets or ribs are of such thickness & so spaced apart according to
the character of the fuel used & the top edges of the main body of the bar
hollowed out as described, so that the amount of air opening to the fuel can be
made equal to the space occupied by the grate bars, thus providing nearly double
the amount of air for the fuel & so improving general combustion, than is possible
with ordinary hollow bars while 1 retain the following advantages which a hollow
bar possesses over a solid grate bar.
Air passing from the front end to the back of the hollow bars & out beyond the
bridge is superheated and produces combustion of such combustible gasses &
suspended carbon or smoke as may have escaped from the fire through lack of
oxygen; it also prevents the bars from getting too hot & warping or burning &
obviates the adherence of clinkers to them-thus increasing the life & efficiency of
the grate.
Dated this 2nd day of March 1896.
BENJAMIN ARTHUR THOMAS.
Improved Grate Bars for Boilers and other Applications.
I, BENJAMIN ARTHUR THOMAS Engineer, residing at 8 Robert Road,
Handsworth, Staffordshire do bereby 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 embraces improvements in grate or fire bars and their accessories,
for stationary, locomotive, marine boilers and other applications such as, heating,
annealing, puddling furnaces, brewers kettles and the like, whereby a larger
percentage of air can be obtained and so directed and distributed through the fuel
as to improve the efficiency of primary combustion (that is the combustion of the
fuel on the grate) while also providing secondary combustion of such gasses as may
escape from the grate. The construction of my grate or firebars obviates the
adherence of cliukers to them and increases their strength and durability.
To elucidate the advantages of my invention, I will briefly make a comparison
with it of existing methods.

page_text: Solid grate or firebars soon burn and warp under lieavy firing, their upper
surfaces often get red hot and the clinkers readily stick to them and are very
diflicult to remove as they often practically weld to them. They usually have a
larger percentage of bar or "dead" surface than of air space.
follow grate or firebars having longitudinal hollows or openings through which
air passes, while obviating some of the disadvantages of clinkering and having
other advantages, take up too much of the air space necessary for primary
combustion, their upper surfaces are usually from 1 to 14" wide and upwards-
1 being about the minimum width requisite to embrace the opening and thickness
of metal on each side of it; so that taking a set of such hollow grate bars, of
only in width, spaced apart (as wider air spaces would waste fuel by allowing
considerable of it to fall into the ashpit) it will readily be seen that 66 per cent.
of the grate surface is taken up by the bars (which may be termed dead surface)
and only 33 per cent. of air space is provided. By my construction of grate or
fire bar these proportions of bar surface to air space can nearly be reversed, nir
space being increased (without having recourse to wide air spaces) so that better
draught and hence more oxygen is provided for the combustion of the fuel.
Fig. 1, represents a transverse section, through A. B. (see Fig. 2, Sheet 1) of a
Cornish boiler furnace showing a set of one arrangement of my fire or grate bars
in position.
Fig. 2, represents a longitudinal section C. D. Fig. 1, through the boiler furnace
showing the grate bars in elevation and the front and back bearers & bridge in
section and the secondary combustion chamber and bridge d and d'.
Fig. 3, represents a transverse section through G. H. see Fig. 2, showing the
bridge and hack bearers in section.
Fig. 4, is a sectional plan through the flue at E. F. Fig. 1, looking down on the
grate.
Fig. 5, is a transverse section on an enlarged scale through I. J. see Fig. 6,
Sheet 2.
Fig. 6, is a plan of Fig. 5, with the grate bars broken off.
Fig. 7, is an elevation of the grate bars broken off.
Fig. 8, is a transverse section, indicating some of the variations, in unbroken
and dotted lines, that may be made in the body and side ribs or fillets of the bar.
Fig. 9, is a transverse section through a couple of my grate bars, which are more
particularly adapted for fine fuel.
Fig. 10, is an elevation, broken off, of Fig. 9.
Fig. 11, represents the grate bars made in balves and spaced apart.
Fig. 12, represents the grate bars made in halves and connected together.
Fig. 13, represents a part internal elevation of one of the halves in Fig. 12.
Fig. 14, is a half section showing the side ribs or fillets connected together on
their outer extremities.
Fig. 15, is a part plan of Fig. 14.
Like letters refer to similar parts.
By a reference to the drawings it will be seen how retain the feature of a
hollow fire-bar, by providing longitudinal openings such as h, and 2, through
which air passes and keeps the bars from getting too hot, thus preventing them
from burning and warping and providing in the metal of the grate-bars a reduc
tion in temperature, which is unfavorable for the adherence of clinkers. As a ho
piece of iron wont weld to a cold piece, in a similar manner hot clinkers wont stick
and weld on to a comparatively cool grate-bar.
The air which passes through the longitudinal openings, extracts the heat from
the grate-bars and passing into the combustion chamber D, heyond the bridge
provides hot air to complete combustion of such of the gases as may escape fron
ike grate and also of the suspended particles of carbon which form the smoke
The amount of air passing through the bars may be regulated by a damper.
The tubular part or body of the grate or fire-bar, may be of any convenient depth
or width, preferably shaped after the manner shown in Fig. 5, but the shape may

page_text: have a number of variations without departing from the purport of the invention,
some of which are indicated by the unbroken and dotted lines on Fig. 8.
It will be observed that the upper surface (a) see Fig. 5, is shown wide,
although it may be wider or narrower; this bar or "dead" surface is more than
counterpoised, by the longitudinal air spaces (s) which are shown wide, but
may be wider or narrower. Similar proportions of bar or "dead" surface and air
space being observed in the structure and spacing of the side ribs or fillets, herein-
after described; the object being to have, as previously intimated, a maximum of
air space and minimum of bar surface, without sacrificing the strength and
durability of the grate and without having air spaces so wide that the fuel would
not be properly supported.
The design shown in Fig. 5, is for average fuel & it will be noticed that there is
about 54% of air provided, to about 46 % (per cent.) of bir or "dead"
surface. By increasing the air spices to & retaining the same bar surfaces,
62 per cent. of air space would be provided, almost doubling the amount of air
space provided by ordinary hollow bars, as previously intimated.
By the shaping of the sides (9) and (g) which may vary in inclination to each
other (or may form straight lines tapering the body of the bar from top to bottom
or vice versa) it will be seen that considerable width can be provided in the body of
the bar (without encroaching on the air space for primary combustion) thus
providing lateral stability and giving a large upper surface for the action of the air
passing through the longitudinal openings of the bars, which reduces the temperature
of the metal right under the fire, while the sides of the bar are also cooled, which
in turn reduce the temperature of the side ribs or fillets connected thereto.
The body of the bar may be made deeper or wider at the back end than the
front or vice versa, or it may be fish-bellied-that is curved at the bottom.
The webs or sides of the body of the grate-bar, may be made with corrugations
or A shaped grooves. The longitudinal openings may be partitioned vertically
or horizontally to provide more than one travel for the air and the webs of the
body of the bar may have lateral outlets for the passage of part of it up through
the fuel. In certain applications such as locomotive or vertical boilers, annealing
furnaces and the like, the air passing through the longitudinal openings, may be
diverted to the ash-pit or outside if desirable.
The side ribs or fillets (f) are preferably shaped in the manner shown, cast on
or attached to the body of the bar with level upper surfaces and set at any suitable
angle to the body of the bar.
They are shown " wide at the top in Figs. 6, and 7, with air spaces
adjacent (both of which may be made wider or narrower) and are tapered from top
to bottom in order to provide a clearance for falling ashes and a freer access for
the air to the fuel. They may be tapered inwards or outwards in plan and be
connected together on their outside edges in pairs or series with straight, circular
or triangular pieces (viewed in plan) tapered downwards. They may be corru-
gated or formed with A shaped grooves. The upper surfaces may be undulated or
may incline from the body of the bar forming Vor U shaped surfaces with the
adjacent grate bars. It will be observed that the side ribs or fillets not only
enable a maximum provision of air space for the grate, hut also act as stiffeners to
the bars, resisting all tendencies to warp with the heat. They preferably extend
from top to bottom of the body of the bar thus providing a stronger attachment and
a larger surface subject to the cooling influence of the longitudinal air opening of
the body of the bar: but the ribs or fillets may be terminated at any suitable
point between the top & bottom of the grate-bar, and may be varied in form,
some of which variations are indicated by the unbroken and dotted lines on
Fig. 8.
The front end (a) of the grate-bars may be shaped as shown. but varies
according to the application. They may have single or double front bearers or
dead plates.
The bearing at the back is preferably as shown, for flue boilers, but may be

page_text: similar to the front bearing for vertical and locomotive boilers. It will be
observed that the, back end (a) of the grate bars is formed with end plates which
close the spaces between the body of the bars and are rebated over the back
bearer to prevent ashes from falling into the hollow bridge: but the grate bars
may fit into recesses of the upper part of the bridge. Provision is made for the
expansion of the grate bars fongitudinally and laterally. The end plates may bu
loose and fitted in grooves as shown at (a) Figs. 6 and 7. The grate bars may be
adapted for rocking to stir up the fuel or for oscillating or damping (that is
revolving in hearings to drop the clinkers into the ash pit). In Fig. 9, the side
rilis are shown projecting hetween each other and if arranged for rocking the fuel
is thoroughly stirred up. The grate-bars shown in Fig. 11, may fit back to back
or he spacuff any anitable distance apart with a longitudinal air space wider at the
bottom than the top. When the grate-bars are made in halves after the manner
shown in Fig. 12, inside ribs (i) may he spaced at any suitable distance apart;
they provide rigidity and also give a zigzag travel to the air passing through the
longitudinal opening & being cooled by the air, in turn cool the bully & ribs of the
grate-bar. They may be connected together with bults, as shown, or other
suitable means. It will he noticed that a space is provided under the ribs (i)
through which a rod may he passed to push any dust or accumulations into the
chamber (d) from whence it ena he removed as in the ease of the other longitudinal
openings && of the other designs. The parts forming the top and
bottom of the bar may be rebated over each other or may form a straight flush
joint.
The pieces (k) connecting the side ribs or fillets together, are preferably on the
outer edge of the ribs and of the form shown, but may vary in number and form,
connecting the side rils or fillets, when spaced further apart.
The bridge bearers for flue boilers are preferably in two parts an upper and a
lower, as shown on Figs. 2 and 3 (Sheet 1) so that they can be introduced into a
boiler flue without disturbing the front bearers and frames for the doors and also
that the upper part (4) may have freedom to move in the recess of the lower
hearer () as the grate bars expand or contract. The top and bottom plates
of (7) may he connected together by ribs as shown on Figs. 2 and 3-the top plate
being rebated to receive the upper end of the grate-bars, as shown at (a') Fig. 2.
But the front of the upper bearer (2) may have pockets ur recesses into which the
ends of the grate bars may project, openings being provided through which the air
from the interior of the grate-bars may pass into the combustion chamber (d).
The back of the upper hearer may have a flange to keep the firebricks in
position.
The lower bridge bearer (2) Figs. 2 and 3 has a recess on its upper surface in
which the upper part (7) has freedom to move. The grate-bars may take their
main bearing on the front raised surface of the bearer (1) as shown, hut may have
a bevilled bearing or a hook like bearing on a circular shaped projection of the
lower plate of the upper bearer (57). The bearers for locomotive, vertical, builurs
annealing furuuces and the like vary with local conditions.
The upper and lower bridge bearers are hollow; the former to allow of the
passage of air from the interior of the grate-bars into the secondary combustion
chamber (d) and the latter to allow accumulations of ashes to be raked out of the
combustion chamber (d) while the boilers are at work. The front opening of the
lower bridge bearer is closed by a specially shaped door such as (e) see Figs. I
and 2-it may be drawn out or pushed into position by the rake or a rod and
always ensures a complete closure of the opening. Doors with hinges may be
used but the form shown is preferable in most cases, as the hinges are liable to
clog, through falling ashes and dust from the grate, or work hard through
expansion.
The front and back bearers may be connected together with the rods (e) sc
Figs. 1 and 2.
The secondary bridge (d) may be at any suitable distance from the first bridge

page_text: sufficient room being allowed to prevent choking of the air passage through (62) by
cinders and clinkers which may be pushed over the bridge.
Forced or induced draught inay be applied to the grates, the front of the boilers.
being adapted accordingly.
The grate-bars may be adapted for mechanical stoking.
Having now particularly described and ascertained the nature of my said inven-.
tion and in what manner the same is to be performed, I declare that what I
claim is :
1. A hollow grate or fire-bar having a tubular body with a longitudinal opening.
or openings, in conjunction with side ribs or fillets so arranged as to add to its
lateral strength and durability, while providing a maximum amount of air space for
primary combustion and a minimum amount of grate-bar surface, though securing
secondary combustion and provision for the reduction of the temperature of the
grate or fire-bar, so as to obviate burning and warping and the adhesion of clinkers
to the surface of the fire-bars.
2. A hollow grate or fire-bar so arranged with the upper portion of the tubular
part or body of the bar tapered or inclined, so as to give a minimum amount of bar
surface and a maximum of air space, in conjunction with side ribs or fillets.
3. A hollow grate or fire-bar in conjunction with side ribs or fillets, which
reciprocate or project between the side ribs of the adjacent bar, siugly, in pairs, or
in series.
4. A hollow grate or fire-bar, arranged in sections, in conjunction with side ribs.
or fillets, either spaced apart or connected together by bolts or other suitable.
means.
5. A hollow grate or fire-bar in conjunction with side ribs or fillets which are
connected together with pieces, substantially as described.
6. Hollow back bearers, for the grate or fire-bars, in which the upper portion.
has freedom to move in a recess of the lower portion, as the grate-bar expands or
contracts, and with a door such as (c) in the lower portion, to allow for cleaning.
out the secondary combustion chamber. Tie rods being provided to connect the-
front and back bearers. Substantially as described.
Dated this 28th day of November 1896.
BENJAMIN ARTHUR THOMAS..