Improvements in and connected with Hot-air Fire-bridges for Furnaces.
Year: 1899

page_text: Date of Application, 14th Apr., 1899 -Accepted, 17th June, 1899
COMPLETE SPECIFICATION.
Improvements in and connected with Hot-air Fire-bridges for
Furnaces.
I, OTTO THOST, of Zwickau, in the Kingdom of Saxony, German Empire,
Manufacturer, 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:-
This invention has reference to hot air fire-bridges by means of which highly
heated air is passing into the space where further combustion of the fuel gases
takes place, so that the same are completely burnt up, whereby a perfect consump-
tion of the fuel and the fuel gases is effected.
An essential feature of my invention is a novel device, specially constructed for
the purpose, whereby the fire-brick bridge heretofore necessarily employed in
similar furnaces, is dispensed with. This novel device I prefer to call a grate
bar too, although it is of peculiar form. The novel grate bars rest upon an iron
construction behind the grate forming with these bars an air-chamber provided
with a device for regulating the admission of air. These bars may also be directly
cast on the common grate-bars, and these may easily replace old grate-bars in
ordinary and reverberatory furnaces.
The invention is illustrated in the accompanying drawings, in which:
Figure represents a vertical section through the body of the furnace;
Figure 2 shows a cross section on line 22 of Fig. 1.
Figure 3 represents a cross section on line 3 3 of Figure 1, showing an inside
lining of the furnace of the furnace made of fire-brick,
Figure 4 is a detail perspective view of the new grate-bar.
Figure 5 shows the novel grate-bar cast on a common grate bar in front eleva-
tion, while some brick-work is shown in section; and
Figure represents a cross-section of Figure 5 on line 66 partly in elevation.
Similar letters of reference denote like parts in all of the drawings.
The construction of the novel grate bar is plainly shown in Figure 1, and in
detail perspective view in Figure 4. In side elevation the bar resembles a quad-
rant provided with a narrower downward extension 6 cut off slantingly. Both
sides of the bar are hollowed out so that if two bars are laid together, there is
formed a channel f serving as an air passage. On the arc of the quadrant there
are provided small orifices or openings c, of which four are shown in Figures 1
and 4. These openings care relatively small in comparison to air-chanuel f.
The bars are made of iron, preferably cast of fire-proof material, or hardened
by a suitable process.
The grate-bars form the top part of an air-chamber a, located behind the
space through which the ashes fall. This air chamber is formed by enlarging
the fire-bridge, as shown in Figure 1. The inside walls a¹ of the air-chamber
are preferably made of iron and the vertical wall has, about in its centre, an
extension upon which rests the rectangular shoulder of the bar b. An iron

page_text: girder with extensions on both sides serves by its inside extension as a
support for the rectangular shoulder 3 of bar b, while the outside extension g
acts as a support for the ends of the common grate bars h. The air-chamber a
has in front a device for regulating the admission of air. This device may be
of any suitable construction. In Figure 1 a plain door-like cover is shown, whose
top part is attached to the lower portion of the girder g, while the bottom part
is provided with a chain so that the admission of air may be regulated from
the outside.
As is plainly shown in Figure 1 the grate bars bare so mounted that they
extend considerably higher up than the usual bars h, forming in this manner
the fire-bridge, which in former construction is made of brick-work, thus entirely
dispensing with the latter here. This arrangement has the advantage that the
air issuing from the openings e enters the space of combustion where the fuel
gases are actually somewhat compressed; that is in the place where air is most
needed.
The air enters the air-chamber a through the regulating device d and passes
into the channels f and the hollow portions of the bars b, and issues into the
space of combustion through the openings c. Since the bars are always glowing
during the operation of the furnace, the air is overheated within them and passes
in this condition into the space of combustion, mixing these with the fuel gases
and igniting same, so that they burn as a clear long body of flame, whirling on
in the continuation of the flue. Since the openings are relatively small in
comparison to the channel f the overheated air passing through them is rather
flowing through as soon as a good draft is established, and by the many openings
it is well distributed and mixed with the fuel gases.
In order to effect a further mixing of overheated air with the fuel gases the
flue may be provided at a small distance from the fire-bridge with a lining e of
fire brick (chamotte) see Figures 1 and 3.
In places where the construction of the air chamber a is impossible or incon-
venient for want of room or other reasons, I prefer to use grate bars having
the novel bar b cast directly on the usual bar, forming then an integral part
thereof; see Figures 5 and 6. Only the last or inside section of the grate adjoin-
ing to the brick work fire-bridge where the hot air fire-bridge is to be formed,
need be composed of such bars, Fig. 5. The usual bars composing the last section
are in this instance simply replaced by these novel bars, which can be done at
moderate expense. The ends of the bars embodying the novel feature from the
same air channels and hollow spaces and have the same openings
c as above
described if mounted side by side. For the purpose of regulating the admission
of the air in this instance, two bars are cast each with a hook on which a
cover dis suspended, Figure 5. By means of this cover the admission of air is
regulated as above described. It is plainly seen that with this arrangement the
combustion of the fuel gases is also effected.
Thus I have produced a hot air fire-bridge, which effects the combustion of
the fuel gases, and dispenses with the brick work fire-bridge.
Having now particularly described and ascertained the nature of my said
invention, and in what manner the same is to be performed, I declare that what
I claim is:
1. A hot air fire-bridge for effecting the combustion of fuel gases located at the
inside end of the grate and composed of grate bars mounted side by side and
resembling in side elevation a quadrant provided each with a narrow downward
extension and hollowed out on both sides, hollow air spaces between each pair of
bars air channels formed by the downward extensions of the bars and small air-
discharge orifices on the are of the quadrant, means for supporting the bars and
a device for regulating the admission of air, substantially as described.
2. In a hot air fire-bridge grate bars each resembling in side elevation a quad-

page_text: rant provided with a narrow downward extension which forms with the base of
the two rectangular shoulders and cut off slantingly and hollowed out on both
sides so that each pair of bars laid side by side forms a hollow air space between
the bodies of the bars and small discharge orifices on the arc and a chanuel
between the extensions, substantially as described.
3. A hot air-fire bridge for effecting the combustion of fuel gases located at
the inside end of the grate and composed of grate bars mounted side by side
and resembling in side elevation a quadrant provided each with a narrow down-
ward extension and hollowed out on both sides, hollow air spaces between each
pair of bars, air channels formed by the downward extensions of the bars and
small air-discharge orifices on the arc of the quadrant, an air-chamber formed by
enlarging the fire-bridge having on its inside vertical wall an extension acting
as a support for the grate-bars, an iron girder with extensions on both sides, whose
inside extensions act as the other support for the grate bars, and a device for
regulating the admission of the air into the air-chamber, substantially as described.
Dated this 14th day of April 1899.
GEO. H. RAYNER,
37, Chancery Lane, London, Agent for the Applicant.