IMPROVEMENTS IN CASTING METALS
Year: 1872

page_text: LETTERS PATENT to Alexander Melville Clark, of 53, Chancery Lane,
+
in the County of Middlesex, Patent Agent, for the Invention of
** IMPROVEMENTS IN CASTING METALS."-A communication from abroad.
by Joseph Louis Cumin and Louis François Achille Martel, both
of Paris, France.
Sealed the 21st February 1873, and dated the 9th September 1872.
PROVISIONAL SPECIFICATION left by the said Alexander Melville
Clark at the Office of the Commissioners of Patents, with his
Petition, on the 9th September 1872.
I, ALEXANDER MELVILLE CLARK, of 53, Chancery Lane, in the
County of Middlesex, Patent Agent, do hereby declare the nature of
the said Invention for "IMPROVEMENTS IN CASTING METALS," to be as
follows:-
Castings made in sand moulds, in the ordinary manner have hitherto
been rough and imperfect in detail, owing to the air which is unable to
escape quickly enough becoming confined in the recesses of the mould,
and thereby impairing the casting by forming air bubbles and pitting
the surface with holes. By means of the present Invention this defect

page_text: may be entirely avoided in castings of all kinds, all the details of the
pattern being faithfully reproduced without requiring to be afterwards
trimmed or finished by.hand.
This Invention consists in casting in vacuo; that is to say, the moment
the metal is filled in the mould is put in communication with a receiver
or chamber in which a vacuum has been formed, so that the air con-
tained in the mould is immediately exhausted therefrom through the
pores of the mould. For this purpose the latter, or that portion of it.
which is next the pattern, must be composed of a substance sufficiently
fine to retain the impression of the most minute details of the pattern,
and at same time prevent the penetration of the fused metal into the
body of the mould, which would take place by the atmospheric pressure
if the mould be made in sand only.
For fusible metals, such as type metal, the mould may be made of fine
plaster, dried.
For less fusible metals, such as brass and bronze, I use plaster
moulds to which has been added nearly equal proportions of plumbago
and alumina, or other fine amorphous substance, the mould being dried
by heating to a red heat, to render the hydrated sulphate of lime
anhydrous.
For more refractory metals, as cast iron and steel, which would be
liable to decompose the sulphate of lime, sand moulds are employed, the
interior surface of which is formed of a thin layer of plumbago, alumina,
or other suitable anhydrous substance.
Two methods of filling-in the metal may be employed in carrying out
this process of casting in vacuo:-1st, by pouring the metal into the
mould in the usual way, and 2ndly, by decantation, which is effected by
enclosing the mould, if it be porous, in a metal jacket furnished with two
tubes, one communicating with the exhausted receiver, and the other
immersed in the fused metal, in which it is carried down to the bottom.
This method of casting in vacuo may be applied to sand moulds, and
to chills or metallic moulds; but in the latter case it is evident that the
method of automatic decantation only can be employed.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent,
filed by the said Alexander Melville Clark in the Great Seal Patent
Office on the 8th March 1873.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, ALEXANDER
MELVILLE CLARK, of 53, Chancery Lane, in the County of Middlesex,
Patent Agent, send greeting.
WHEREAS Her most Excellent Majesty Queen Victoria, by Her
Letters Patent, bearing date the Ninth day of September, in the year of
our Lord One thousand eight hundred and seventy-two, in the thirty-sixth
year of Her reign, did, for Herself, Her heirs and successors, give and
grant unto me, the said Alexander Melville Clark, Her special licence
that I, the said Alexander Melville Clark, my executors, administrators,
and assigns, or such others as I, the said Alexander Melville Clark,
my executors, administrators, and assigns, should at any time agree with,
and no others, from time to time and at all times thereafter during the
term therein expressed, should and lawfully might make, use, exercise,
and vend, within the United Kingdom of Great Britain and Ireland,
the Channel Islands, and Isle of Man, an Invention for "IMPROVEMENTS
IN CASTING METALS," a communication to me from abroad by Joseph Louis
Cumin and Louis François Achille Martel, both of Paris, France, upon
the condition (amongst others) that I, the said Alexander Melville Clark,
my executors or administrators, by an instrument in writing under my,
or their, or one of their hands and seals, should particularly describe and
ascertain the nature of the said Invention, and in what manner the
same was to be performed, and cause the same to be filed in the Great
Seal Patent Office within six calendar months next and immediately
after the date of the said Letters Patent.
NOW KNOW YE, that I, the said Alexander Melville Clark, do
hereby declare the nature of the said Invention, and in what manner
the same is to be performed, to be particularly described and ascertained
in and by the following statement (that is to say) :-
Castings made in sand moulds in the ordinary manner have hitherto
been rough and imperfect in detail, owing to the air which is unable to
escape quickly enough becoming confined, and so preventing the metal
taking the exact form of the mould, thereby impairing the casting by
forming air bubbles, and pitting the surface with holes. By means of
.

page_text: the present Invention this defect may be entirely avoided, and art
subjects, moulds of steel or other hard metal, and castings of all kinds
may be obtained with all the details of the pattern faithfully reproduced,
without requiring to be afterwards finished by hand.
The Invention consists in casting in vacuo, that is to say, at the
moment the metal is run into the mould the latter is put in communica-
tion with an exhausted receiver or chamber, in which a vacuum has been.
formed, so that the air contained in the mould is immediately exhausted
therefrom through the pores of the mould. For this method of casting
it is necessary that the mould, or that portion of it which is next the
pattern, should be composed of a substance sufficiently fine to retain the
impression of the most minute details of the pattern, and at same time
prevent the penetration of the molten metal into the body of the mould,
which would take place under the influence of the vacuum if the mould
be made in sand only.
For fusible metals, such as type metal, the mould may be made of fine
plaster, dried.
For less fusible metals, such as brass and bronze, I use plaster moulds
to which has been added nearly equal proportions of plumbago and
alumina, or other fine amorphous substance, the mould being dried by
heating to a red heat, to render the hydrated sulphate of lime anhydrous.
For refractory metals, such as cast iron and steel, instead of using
sand moulds, which are not sufficiently resistant to withstand the sudden
introduction of the molten metal, it is preferable to employ moulds of
earthenware, said moulds being shells enclosed in sand.
Two methods of running-in the metal may be employed in carrying
out this process of casting in vacuo:-1st, by pouring the metal into the
mould in the usual way, and 2ndly, by a method which I term decanta-
tion, which is effected by enclosing the mould, if it be porous, in a metal
jacket furnished with two tubes, one communicating with the exhausted
receiver, and the other dipping down into the melted metal.
This method of casting in vacuo may be applied in connection with
sand moulds, and to chills, or metallic moulds; but in the latter case
it is evident that the above method of automatic decantation only can
be employed.

page_text: Having described the nature of the Invention, and in what manner
the same is to be performed, I declare that what I claim as the
Invention to be protected by the herein-before in part recited Letters
Patent is, the mode of casting in vacuo, as described, applicable to all
kinds of metals, whether in porous or metallic moulds or chills, and
whether by running or pouring in the metal in the ordinary way, or by
the method above described termed decantation.
In witness whereof, I, the said Alexander Melville Clark, have here-
unto set my hand and seal, this Seventh day of March, in the
year of our Lord One thousand eight hundred and seventy-three.