Improvements in or relating to Furnaces.
Year: 1899

page_text: Date of Application, 20th Mar., 1899-Accepted, 13th May, 1899
COMPLETE SPECIFICATION.
Improvements in or relating to Furnaces.
I, MAX ZAHN, Manufacturer, of Querfurter Chausee 4, Artern, Thuringia, in the
Empire of Germany, 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:-
In all mechanically worked furnaces in which the feeding is effected by a
travelling grate or the like, the combustible material is introduced in such a manner
that it travels in the direction of the current of gases produced by the combustion.
Such an arrangement is attended with the drawback that the fresh fuel will take
fire with difficulty. First, because the surface of contact with the burning or
incandescent portion is too small, and secondly, because the heated gases evolved
from the burning material do not pass over the fresh charge.
The consequence of such arrangement is therefore the production of only a
small amount of combustible gases which require a large quantity of air for its
total combustion.
On the other hand the fuel which has been burnt forms a layer on the grate which
becomes thinner towards the end, and through which an unnecessary quantity of
air passes.
The result of such an arrangement, as is seen from the above explanation, is
on the one hand a production of a small quantity of gas requiring air, and on the
other hand a production of much gas with a great quantity of surplus air. In
other words the mechanically working furnaces as known at the present time are
worked with too much surplus air, and consequently do not give the best results
possible.
In order to remedy this drawback the fuel in a furnace constructed according
to the present invention does not travel in the direction of the escaping gases, but
against them. In such an arrangement the fresh fuel is heated by the flames
striking against it, resulting in a much more energetic production of combustible
gases, which can take up from the accidentally introduced or surplus air the
oxygen contained in it. In other words a more rapid ignition of the fuel and a
more advantageous combustion is obtained.
There are however cases in which such a movement of the fuel against the
current of the gases is not possible, or for various reasons not advisable. In such
cases an arrangement is provided which will prevent the entrance of surplus air
by forcing the burnt material, mechanically, into a layer or layers of gradually
increasing thickness.
Both these arrangements may be introduced in one and the same furnace, assist-
ing each other in their effects.
In the following description several methods are explained of feeding mechani-
cally operated grates, and it should be observed that in all cases either the principle
of the fuel travelling against the current of heated gases, or the formation of thicker
layers of the burnt fuel, or a combination of the two principles are employed.
In Figure 1 of the accompanying drawings longitudinal, horizontal and trans-
verse sections of such an arrangement are shown.

page_text: In this construction the fuel is introduced through a feeding funnel or hopper 1
and a shoot 2 on to the travelling grate 3 upon which it travels against the current
of heated gases, the burnt fuel heaping up more or less towards the discharged end
by the sides of the furnace being provided with inclined plates 4 of, say, sheet
iron. The material which is thus forced into a smaller space in the course of its
movement must therefore form a thicker layer. The burnt out fuel and slack
leave the fire-chamber through the opening 5, which is provided with a screen or
damper to prevent surplus air from entering:
Here
In the furnace represented in Figure II in longitudinal and cross section, the
fuel is introduced through a hopper and passages 2 into the grate 3 at the point x,
and is moved along to y in a horizontal direction. At the grate takes an upward
curve, on which the fuel is carried upwards towards the discharge end z.
a portion of it slips back, whereby it becomes heaped up between y and z.
there is a screen or damper in the opening 5, the slack or burnt fuel.being dis-
charged at this point."
At z
In the furnace represented by Figure III in three similar sections to Figure I
the fuel is introduced at the front through the opening 1. The travelling grate 3
is an inclined stepped grate, and moves the fuel downwards. In its course the
burning fuel meets a wedge-shaped projection 4 which divides it as it
forcing it to both sides and heaping it up. The burnt slack drops into the ash-pit
passes on,
through an opening 5.
Whereas, in the different methods of construction as represented by Figures I, II,
and III, the movement of the fuel is produced by the movement of the whole
grate Figure IV represents in longitudinal cross section a construction in which
a stationary horizontal grate is employed.
The fuel is introduced at the front 1, falls at r on to the grate 3 and is carried
forward on it to the rear s.
Underneath this grate and towards each side of it are rails or bars a and b.
These rails carry cross bars b, which are provided with teeth q, which teeth pass
between the grate bars when moved upwards. The bars a and b are connected at c
to an eccentric f, and at d by means of the bolts with the movable. joints. k.
These joints are fastened by means of the bolt i on to a bridge which serves as
a support to the grate-bars."
When the eccentrics f are revolved in the direction of the arrow the teetli q
are so actuated, that they push the fuel from the front r towards the back s. At s
a stationary plate t forms a continuation of the grate on which the burnt material
accumulates.
In thus accumulating there the fuel still on the grate is forced into a thicker
layer as it approaches the end of the grate.
If the teeth q are all of the same size the fuel will travel slower in proportion
as it approaches the point s, the bars a and b having a greater upward movement
at e than at d and hence also the teeth q which are moved by the said bars.
By making the teeth, as in the illustration given in the drawing, longer at e
than those at d, the rate of travelling of the fuel at the beginning will be
accelerated. It is possible however to make, for instance, the teeth somewhere
between c and d shorter, in consequence of which the heaping up of the fuel
between rand s will be effected.
As will therefore be seen by giving the teeth 9 varying lengths it is possible
to impart to the fuel at any point required on the grate any travelling velocity,
whereby the depth of the layers at such places may be regulated.
A somewhat similar arrangement of a stepped grate is shown in Figure V.
Between the grate bars are arranged slides q which are connected by means of
rods P with levers a and b which are pivoted at the points c and c¹ and connected
by bars d and and rods e with eccentrics f f. When the eccentrics revolve
the slides are reciprocating between the grate bars thereby pushing the fuel
downwards. Inasmuch as the levers are pivoted at the points c and c it follows
that the slides ¹ move a smaller distance the lower they are placed as regards

page_text: the grate. The travelling of the fuel is hence retarded and so it becomes heaped up
or accumulated in proportion as it is automatically moved towards the lower part
of the grate.
On this
Below the lowest bar is a plate t to which is fixed an operating rod u.
plate the lowest portions of the fuel accumulates. By advancing this plate more
or less beyond the lowest grate bar it is possible to effect the accumulation or heap-
ing up
of the fuel by means of the slides q' to any desired height of the grate.
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. The method of feeding mechanically worked furnaces consisting in causing
the fuel to travel through the combustion chamber in a direction opposite to that
of the heated gases in order to secure an efficient ratio between the quantity of air
introduced and that of the gases evolved, substantially as described.
2. The method of feeding mechanically worked furnaces with fuel, whereby the
fuel is moved along and heaped up towards the exit end as it passes through the
combustion chamber in order to prevent the undesired entry of air through the
partly or wholly consumed residue of the fuel, substantially as described.
3. The method of feeding mechanically worked furnaces with fuel consisting
in causing the fuel to travel through the combustion chamber in a direction
opposite to that of the heated gases, and causing it to be heaped up towards its exit
end substantially as described.
4. A combustion chamber comprising a horizontally travelling grate, and means
for feeding fuel thereto, whereby said fuel will be moved in a direction contrary
to that of the combustion gases, and inclined plates above the grate surface to
cause the fuel to be compacted and heaped up as it passes through the combustion
chamber, substantially as described.
5. A modification of the apparatus described comprising an upwardly curved
grate surface upon which the fuel is fed and travels and by reason of the upward
inclination of the grate accumulates towards the exit end substantially as described.
6. A modification of the apparatus described comprising a travelling grate on
which the fuel is divided by a wedge shaped projection and forced into deeper
layers on both sides, substantially as described.
7. A modification of the apparatus described comprising a stationary horizontal
grate on which the fuel is moved forward by means of forwarding teeth passing
between the grate bars and means for operating said teeth, in combination with a fuel
accumulation plate at the end of the grate substantially as described.
8. A modification of the apparatus described comprising a stationary stepped
grate, on which the fuel is moved forward by slides, reciprocated between the
grate-bars, with an accumulation plate at the bottom, substantially as described.
9. The complete furnace grate substantially as described or illustrated in
Figure 1, or Figure 2, or Figure 3, or Figure 4, or Figure 5, of the accompanying
drawings.
Dated this 20th day of March 1800