IM- PROVEMENTS IN THE GRATE BARS AND OTHER PARTS OF STEAM BOILER AND OTHER FURNACES
Year: 1870

page_text: PROVISIONAL SPECIFICATION left by Thomas Lishman at the Office
of the Commissioners of Patents, with his Petition, on the 6th June
1870.
I, THOMAS LISHMAN, of Stockton-on-Tees, in the County of Durham,
Engineer, do hereby declare the nature of the said Invention for "IM-
PROVEMENTS IN THE GRATE BARS AND OTHER PARTS OF STEAM BOILER AND OTHER
FURNACES," to be as follows:-
The main objects of my said Invention are economy of fuel and
prevention of smoke in steam boiler and other furnaces. The said
Invention relates to the employment of hollow or tubular fire-bars which
support the fuel in the furnace, and at the same time conduct a supply
of air to the back of the furnace to combine with the unconsumed
carbon at that point; also to the devices used in combination with these
bars for regulating the supply of air to the furnace and through the bars.
By this Invention I am not only enabled to effect a great saving of fuel,
while ensuring a more perfect combustion thereof, and preventing the
production of smoke, but I diminish the first cost of the furnace, and
obviate the necessity for frequent repairs, while obtaining an increased
useful effect from the furnace.

page_text: For the purpose of the said Invention I place in the furnace the
required number of the hollow or tubular grate bars, into which air is
admitted at the front of the furnace. The air thus admitted passes
through the said bars and escapes therefrom at the bridge, thus bringing
a quantity of oxygen to combine with the unconsumed carbon which
would otherwise pass away as smoke. The air is heated in passing
through the bars. This oxygen and carbon in combining pass away
under the boiler as flame and a great heat is developed.
The said fire-bars are pipes or tubes preferably of cast iron in one or
a number of lengths or sections, with square or rectangular heads or
bearing pieces to rest on the dead plate and bearing plates; the aperture
for the escape of the air is made in the head; or the said bars may be
provided with elbow pieces open at their upper ends near the top of the
bridge. The heads or bearing pieces are wider than the body of the bar,
so that when the said bars are in place there will be the usual space
between them.
No air is admitted at the front of the furnace below the fire-bars, as in
an ordinary furnace, the mouth of the ash-pit being closed by an iron
door or plate. At the front of the furnace I regulate the quantity of
air admitted above and through the fire-bars. For this purpose I place
at the mouth of the furnace a plate having a number of apertures or
slots, and over this plate I place a sliding plate, also having similar
apertures or slots. By adjusting this sliding plate the apertures are
opened or closed, and the area for the admission of air is thus increased
or diminished at pleasure. I also for a like purpose provide the furnace
doors with apertures, which are covered by adjustable slotted plates; by
turning these plates the apertures in the doors are more or less uncovered,
and the admission of air is increased or diminished accordingly.
I prefer to place on the bridge a block of cast iron or fire-brick, which
is perforated with a number of small holes. These holes divide the air
and gas as they pass over the bridge into a number of small streams,
and ensure the more perfect combination of the oxygen and carbon at
that point.