Improvements in Moulds for Casting Metals.
Year: 1889

page_text: COMPLETE SPECIFICATION.
Improvements in Moulds for Casting Metals.
I ALFRED CLAYTON COLE of the firm of W. H. Cole and Company of 85 Grace-
church Street in the City of London Merchants do hereby declare the nature of this
invention which has been communicated to me from abroad by Charles Henry Wilder
of Natick in the County of Middlesex and State of Massachusetts United States of
America Gentleman and in what manner the same is to be performed to be particularly
described and ascertained in and by the following statement:
--
This Invention relates to an improvement in moulds from which to cast metal articles
and its object is to produce a mould such that its inner or moulding surface will not
be in any degree fused or fluxed by the contact of the molten metal, but will at all
times have and preserve a smooth and indestructible moulding face whereby not
only can more perfect castings be obtained than has heretofore been possible, but
also the same mould may be repeatedly used for producing castings.
The invention also includes a convenient form in which the mould can be made
to preserve it against accidental injury in handling all as hereinafter more fully set
forth and explained.
For the further explanation of this invention there is shewn in the accompanying
drawings at Figure 1, in section on the line 1. 1 Fig. 2. one part of a flask and one
part of a mould for a cylindrical casting, and a cylinder of cast metal in the mould
part of the casting which would be formed in the other part of the mould being above
the surface in the part of the mould shewn.
Figure 2 shews a transverse section on the line 2. 2. of Figure 1 of the flask
mould and casting.
The outer wall of flask is marked a the mould is marked at.
and the casting is marked a². The mould is represented in the drawing as being
composed of two parts, the inner portion a³ being formed of the improved mould
material and the outer portion of a strengthening or protecting material as herein-
after explained.
A layer of sand is represented as a between the mould and the outer wall of
the flask.
The customary dowels and sockets for joining adjacent portions of the mould are
represented at a and flanges a are provided on the edges of the flask to retain the
sand between the mould and flask.
The improved mould is formed of a mixture of pulverized coke and pulverized
graphite or as it is commercially known plumbago. In preparing this mixture each
of the substances is ground to as fine a powder as is readily practicable, the graphite,
as is well known being capable of a considerably finer reduction than the coke.
After the two substances have been thus ground they are united or incorporated
with each other mechanically in any convenient manner.
The function of the coke in the mixture thus formed is that which comes from its
refractory and infusible character; the function of the graphite is through its equally
refractory character, and through its much greater fineness of grain to fully permeate
and fill up the interstices that would otherwise occur among the grains of coke, thus
giving to the mixture as a whole a much more compact texture of grain and
consequently much greater capacity for exactly preserving and reproducing the form
of the article to be cast than would be possible if coke alone were employed.
As a mould if made in the ordinary manner by a pattern in a loose mixture is
readily disturbed and destroyed by handling in using this improved mixture for
moulding a permanent form is given to the mould by mixing with a suitable portion
of the coke and graphite mixture a suitable plastic cokable binder such as melted
pitch or tar in sufficient proportion to make the whole mass plastic.

page_text: The plastic mass thus obtained may be pressed or tamped around the article or
pattern duplicates of which the mould is intended to produce. When the interior
face of the mould has thus been given the desired form and after it has cooled in
order to make it permanent and convenient for repeated handling the mould is placed
within a suitable metal box or case and surrounded therein with sand.. This box is
then closed, placed in a heating furnace and subjected to heat at a temperature and
for a period sufficient to convert the binder into.coke.
The mould then after being allowed to cool may be repeatedly used in the ordinary
manner to furnish castings of the form originally impressed upon it.
The permanent or portable mould thus obtained will sometimes however be found
to lack the strength required to withstand the handling to which it may be subjected.
Therefore to meet this defect it is provided with an exterior or backing as follows:-
After the mixture of coke graphite and the binder has been pressed or tamped
upon the pattern a sufficient quantity of pulverized coke is mixed with an adhesive
cokable binder, thus forming a second plastic mass and this second mass is spread
over the back or outer portion of the mould formed of coke and graphite bound
together and the two are temporarily united under moderate pressure while the mass
of the backing is still plastic. The mould and backing are then placed in a sand
filled case and the whole is subjected to the coking operation in a furnace as before
described continuing this until the whole of the binder throughout the mass has been
converted into coke thereby producing a mould formed of a mixture of coke and
graphite and a backing for the mould formed of coke the whole integrally
united.
It will be understood that a mould so formed will be used in casting in the ordinary
manner the moulds being made sectional and provided with dowels and sockets or other
well known appropriate devices for uniting them in readiness for casting and a flask
and sand filling being applied in the usual manner.
Having now particularly described and ascertained the nature of the said inven
tion and in what manner the same is to be performed I declare that what I
claim is
1. As a new article of manufacture a permanent mould formed of coke graphite
and a coked binder as hereinbefore described.
2. As a new article of manufacture a permanent mould provided with an integrally
attached back the face of the said mould being formed of a mixture of coke graphite
and coked binder and the backing of said mould being formed of coke and a coked
binder the said mould and back being united all substantially as set forth.
Dated this 28th day of May 1889
J. H. JOHNSON & Co.,
47, Lincoln's Inn Fields, London, W.C., Agents.