Improvements in Crucible Melting Furnaces.
Year: 1896

page_text: Date of Application, 18th Jan., 1896
Complete Specification Left, 27th June, 1896-Accepted, 1st Aug., 1896
PROVISIONAL SPECIFICATION.
Improvements in Crucible Melting Furnaces.
I, WILLIAM KIRKHAM, of 22, Bhinsworth Street, Attercliffe, Sheffield, in the
County of York, Furnace Builder and Contractor, do hereby declare the nature of
my said invention to be as follows:-
The ordinary method employed in the construction of crucible melting furnaces,
sometimes called pot hole furnaces, has been in use for melting steel in the Sheffield
district with little variation for upwards of a hundred years and the portion of the
furnace which undergoes the most rapid deterioration is the brickwork and lining,
forming the furnace chamber or hole, in which the crucible pots are placed during
the process of melting.
The body of the furnace, which is rectangular, is built of firestone or firebrick,
an oval mould or building box is then employed and a lining of ground gannister
is rammed round the space between the rectangular walls and the mould, leaving
an oval furnace chamber of the required size. This gannister lining is finished off
with several courses of firebrick at the top and closed in with a metal plate having
a square hole, through which the furnace is fed with coke and through which the
crucibles are placed in, and taken out.
The bottom of the furnace chamber herein described is provided with metal
bearers and fire bars, with an ash pit below. A flue runs from the back of the
furnace chamber into the stack and a movable cover consisting of a quarry or large
fire brick fitted with an iron frame is employed for covering the square hole in the
top of the furnace above referred to.
A number of holes such as are herein described are built in continuous rows side
by side on or about the floor level, part of the furnace chamber and fire bars being
accessible from the cellars below the floor.
As these furnaces are worked continuously for many hours at an intense heat
and when not working are suddenly cooled down by the inrush of cold air from
the cellars through the ash pit and furnace into the flues and stack, a rapid
deterioration takes place, necessitating repair and re-lining every four or five
weeks. After each repair considerable time is lost in drying the new work which
has to be gradually heated up to the proper temperature, during which a con-
siderable amount of expansion takes place having a tendency to thrust the walls
and floor out of shape necessitating periodical repairs and rebuilding of the whole
of the lower portion of the furnace.
The object of my invention is to overcome these disadvantages, which I effect in
the following manner, viz. :-
Instead of building each furnace chamber with rectangular walls, as herein
previously described, I place an oval shaped perforated metallic casing over each
fire grate.
This casing I construct in segments which I secure together with
straps or bolts on the outside, so as to allow for expansion and contraction. I line
the inside of this casing with special silica fire bricks, formed in segments. On the
outside of the metallic casing near the top, I rivet angle irons on which to rest
filling in plates, to cover the spaces between each furnace chamber. The space
below these plates forming a passage for the circulation of air all round the so
called furnace casing, these spaces are supplied with air from the cellars through
openings formed in the brickwork and they are likewise provided with outlets

page_text: gradually heated up to the proper temperature, during which a considerable.
amount of expansion takes place having a tendency to thrust the walls and floor
out of shape necessitating periodical repairs and rebuilding of the whole of the
lower portion of the furnace.
The object of my invention is to overcome these disadvantages, which I effect
in the following manner, viz. :-
The nature of my invention will be better understood on reference to the
accompanying sheet of drawings, in which,
Figs. 1, 2, and 3 represent sectional views of a crucible melting furnace constructed
in the ordinary manner.
Figs. 4, 5, and 6 are sectional views of a similar furnace constructed by my
improved method.
Figs. 1 and 4 being sections taken on the line A. B. as shewn in Figs. 2
and 5.
Figs. 2 and 5 being sections taken on the line C. D. as shewn in Figs. 1
and 4.
Fig. 3 being a section taken on the line E. F. Figs. 1 and 2.
Fig. 6 being a section taken on the line G. H. Figs. 4 and 5.
Fig. 7 is a side elevation of the oval-shaped metallic casing employed in my new
method of construction.
>
Fig. 8 is an end elevation of the saine, half in section showing the fire-brick.
lining.
Fig. 9 being a plan of the same.
The same letters refer to similar parts throughout the several views.
Instead of building each furnace chamber with rectangular walls, as herein
previously described, I place an oval shaped perforated metallic casing, a, over
each fire grate, b. This casing 1 construct in segments which I secure together
with straps or bolts, c, d, on the outside, so as to allow for expansion and contraction..
I line the inside of this casing with special silica fire bricks, e, formed in segments.
On the outside of the metallic casing near the top, I rivet angle irons, f, f, on
which to rest filling in plates, g, to cover the spaces between each furnace chamber.
The space, h, below these plates forming a passage for the circulation of air all
round the so called furnace casing, these spaces are supplied with air from the
cellars through openings, i, formed in the brickwork and they are likewise pro-
vided with outlets, j, communicating with the flues, k, into the stack. The space
above the plates and the furnace floor, is filled in with dry material and the furnace
casings are gathered in and topped off with several courses of fire brick, l, the
whole being covered with plates, m, in the usual way.
1
With a view to decreasing the damaging effect of the cold air rushing through
the furnace when cooling down, I provide doors or shutters, n, to the ash pits and
air passages and likewise dampers, o, in the flue or chimney of the furnace, by which
means a large amount of heat can be retained in the brickwork of the furnace
which will tend to considerable economy of fuel in re-lighting and getting up fresh
heats as well as to the diminution of wear and tear caused from the sudden
expansion and contraction of the brickwork.
It will thus be seen that by my new mode of construction and appliances the
furnace chamber is built quite independently of the side and end walls and that
less bricks will be required, the repairs and renewals can be more easily and quickly
executed, the wear and tear will be less rapid and the liability to distortion reduced
to a minimum.
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. In a crucible melting furnace, constructing over each fire grate an independen
pot hole or furnace chamber with a perforated metallic casing, lined with fire brick
or other suitable refractory material, and so arranged and covered in as to form