IMPROVEMENTS IN THE MANUFACTURE OF IRON SLEEPERS FOR RAILWAYS, PART OF WHICH IMPROVEMENTS IN THE PREPARATION OF IRON ARE APPLICABLE TO OTHER PURPOSES
Year: 1872

page_text: PROVISIONAL SPECIFICATION left by William Alexander Lyttle at
the Office of the Commissioners of Patents, with his Petition, on
the 15th June 1872.
I, WILLIAM ALEXANDER LYTTLE, of the Grove, Hammersmith, in the
County of Middlesex, Engineer, do hereby declare the nature of the said
Invention for "IMPROVEMENTS IN THE MANUFACTURE OF IRON SLEEPERS FOR
RAILWAYS, PART OF WHICH IMPROVEMENTS IN THE PREPARATION OF IRON ARE
APPLICABLE TO OTHER PURPOSES," to be as follows:—
I construct the sleepers of cast iron formed in any of the various
existing shapes adopted for iron sleepers, and I render this cast iron
less brittle by annealing in any of the present well-known ways, but
more particularly by means of the process of cementation with sesqui-
oxide of iron now followed in rendering cast iron malleable. By a
short treatment under the latter process the brittleness of the iron is
sufficiently diminished for the purpose of railway sleepers. If the pig
iron used for such castings is much charged with silicon, sulphur,' or
phosphorus, it will be rendered more suitable for the production of a
good result under the subsequent annealing of the casting if is
subjected for a short time to the process known as refining, care
being taken that neither the temperature nor the blast of the refinery
furnace shall be such as to commence the oxidation of the carbon,
technically known as "boiling." The object to be kept in view in

page_text: this modified refining is to burn out as much as possible of the other
impurities, and yet preserve the fluidity of the iron by retaining in
it the carbon. If the refining is not checked in time the iron will be
rendered unfit for casting, and the beat and duration of the refining
process must be determined experimentally for each particular quality
of pig iron.
Iron of suitable quality refined in the foregoing way, cast into thin
bars or slabs and then thoroughly decarbonized by the well-known
process of cementation in hematite or other sesqui-oxide of iron, or
other mineral oxides now used for the same purpose, may be subjected
to heating, rolling, and treatment such as would follow a process of
puddling in the making of wrought iron. When, however, this com-
bined process of refining and decarbonizing is to be followed by
subsequent working of the mass as wrought iron, the refining should
be carried as far as possible short of very active boiling. In any case
the presence of quicklime in contact with the iron in the refinery
is an advantage, and quicklime in powder may also be mixed with
the powdered hematite or otlier mineral used for cementation. When
this is done it will be advisable to calcine the mixture occasionally in a
reverberatory furnace so as to reburn the lime.
The process of annealing or cementation may either be conducted as
at present, or ovens may be constructed as follows, for the purpose
of rendering it easier to deal with large quantites of castings in a con-
tinuous manner. For this purpose I employ either a series of ovens
made and heated like those known as Hoffman's kilns for burning
bricks, or a long arched tramway furnace through which peculiar
trucks laden with the castings undergoing cementation are slowly
passed and annealed.
When an arched tramway furnace is employed it should be provided
with sliding or rolling iron doors at the middle and at the two ends,
and the half at which the trucks with the castings enter should be
devoted to firing, whilst the other half should be used as the chamber
in which the castings are allowed to cool slowly down. The latter
I shall call the annealing section, and the former the firing section.
If the firing is done by allowing the flames of furnaces at the sides
of the archway to enter it and traverse it freely like a horizontal flue,
the exit for the flames into the vertical chimney should be close to the
entrance end.

page_text: The annealing section should be cut off from the firing section by
means of sliding doors of double iron plates, between which water may
be allowed to circulate so as to keep the doors from being burned. If,
on the other hand, the flame is not allowed to enter the archway, but
heats it through the fire-bricks of flues, as in the ovens used by potters,
it may be desirable to divide the firing section into several divisions,
in the same way as the firing and annealing sections are divided, so as
to enable the castings to be subjected to increasing heat in two or more
augmenting stages. This archway should be provided with an iron
tramway, and the castings to be fired should be loaded interstratified
with the required powder of cementation on wheeled trucks of iron
without springs, the tops of which should carry a thick layer of fire-
clay slabs. The sides of the trucks should fit as closely as possible
to the sides of the archway, and should be carried downwards outside
the wheels towards the tramway, terminating in a perfectly horizontal
plate of iron extending the whole length of the truck on both sides.
This plate is intended to run in a trough projecting from the sides of
the archway, and filled with sand or sand and powdered plaster of Paris,
or any other infusible powder. By this means flame cannot pass down
by the sides underneath the trucks. The ends of the trucks should be
made of unequal height so as to overlap each other, and the wheels may
have friction rollers, and may be lubricated with powdered plumbago.
By lengthening the archway beyond the annealing section the trucks
when cooled down below redness may, if desired, be run into a portion
of archway forming the air passage leading to the various furnaces, and
the air would thus take up the residual heat of the trucks and their
castings, and so become a hot blast or hot draught.
The processes herein-before proposed for the manufacture of iron
sleepers are also available for the production of all the various heavy
iron articles now shaped by forging, such as, amongst other applications,
the ribs and girders used in roofing, bridge, and ship building, and the
ironwork of the wheels and frames of railway carriages.