Improved Method of Casting Metals in Moulds.
Year: 1890

page_text: Date of Application, 24th Sept., 1890
Complete Specification Left, 24th July, 1891-Accepted, 12th Sept., 1891
PROVISIONAL SPECIFICATION.
Improved Method of Casting Metals in Moulds.
We, THOMAS STURGEON of Ilkley in the County of York Engineer and
THOMAS PHILLIP CHRISTOPHER CRAMPTON of 10 and 11 Cursitor Street
Chancery Lane W.C. in the County of Middlesex Electrical Engineer do hereby
declare the nature of our said invention to be as follows:-
:-
Our improved method of casting metal in moulds consists in so arranging the
moulds that before the metal is allowed to flow into the mould, the mould is
subjected to the action of a vacuum by which means the air is exhausted from
the mould.
The liquid metal is now allowed to flow into the mould and as all the air is
exhausted from the mould and the metal has atmospheric pressure upon it, the
metal should be pressed well up into every corner and crevice in the mould and
thus insure a good solid casting.
The best method of putting our invention into practice is as follows:-
The mould is prepared in the usual manner except that it is unnecessary to
make special arrangements (as at present) to allow the air to escape.
A luting of plastic fire clay or other suitable material is then used over the top
and under the bottom of the moulding boxes and round the joints and in such
other places as may be necessary to prevent a leakage of air into the mould. One
portion of the mould is fitted with a conical shaped opening leading into the
interior of the mould. Another portion of the mould is arranged so that it can
be readily put into communication with a large hermetically sealed chamber in
which a more or less perfect vacuum is constantly maintained by means of an air
pump.
The communication between the hermetically sealed chamber and the mould
can be closed by means of a plug of suitable refractory material.
The ladle or other vessel in which the metal is carried to the mould is furnished
with a funnel shaped opening at the bottom which is closed by a plug of refractory
material but so arranged that it can be readily withdrawn.
The action is as follows:-
The funnel shaped opening or nozzle at the underside of the ladle is inserted
into the conical opening leading into the mould and if necessary quickly luted
round with plastic material. A communication is now opened between the mould
and the vacuum chamber and the air is thus exhausted or drawn off from the
mould. This communication is closed by means of the plug. The plug in the
ladle is now withdrawn and the metal runs into the mould with the full force of
the atmosphere behind it. In this way very solid castings should be made perfectly
free from blow holes.
Instead of using ordinary foundry sand for the moulds we may use moulds
formed of some refractory material in a plastic state and then dried..
Dated 24th Santambon 1000
GEO. DOWNING,
Agent for Applicants.
COMPLETE SPECIFICATION.
Improved Method of Casting Metals in Moulds.
5 We THOMAS STURGEON of Ilkley in the County of York Engineer and
THOMAS PHILLIP CHRISTOPHER CRAMPTON of 10 and 11 Cursitor Street
Chancery Lane in the County of Middlesex Electrical Engineer do hereby
['rice 8d.]

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:
declare the nature of our said invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:-
Our improved method of casting metal in moulds consists essentially in
subjecting the mould to the action of a vacuum and thereby exhausting the air
from the mould before the metal is allowed to flow into it.
The liquid metal is then allowed to flow into the mould and as all the air has
beer exhausted from the mould and the metal has atmospheric pressure upon it,
the metal will be pressed well up into every corner and crevice in the mould, a
good solid casting will be obtained and the risk of flaws due to blowholes will be
removed or minimised.
In the accompanying drawings we shew illustrations of the best methods that
we are at present acquainted with for putting our invention into practice.
In Figure 1. a a² are respectively the upper and lower portions of a moulding
box specially prepared for making castings in accordance with our invention. An
outside view of this moulding box is given in Figure 2.
In Figure 3 we shew a plan of the top portion of the box,
Figure 4 being a plan of the lower portion.
Similar letters of reference shew the same parts in these four views.
b, is the top plate or cover which is planed true. The edges of the boxes are
also planed true so that when the top plate and boxes are clamped together by
means of the bolts and wing nuts c. c. c which fit in the slots d. d. d the joints may
be made air tight by means of a little white lead previously put on the planed
-edges. e. e, are the steady pins in the snugs f. f. at the sides of the boxes. The
funnel shaped vessel g, Figure 1 is made by preference of crucible clay and is
clamped, air-tight, on to the top plate b. The orifice at the bottom of this vessel
is closed by the plug h. This plug consists of any suitable refractory material
preferably of an iron core covered by a coating of crucible clay and it is made
to fit or luted so as to be air tight in the orifice. On to the top plate b is also
_clamped, air tight, the pipe leading to the vacuum chamber. Where possible
this pipe should be of the same material as the casting to be made as it becomes
filled with the metal. For instance if the metal is cast iron this pipe should also
be of cast iron so that when it is done with the pipe with what metal is left inside
it may be broken up and remelted.
The length of the pipe i should be sufficient to allow the melted metal to run up
until the column balances the atmospheric pressure on the metal in the vessel g.
For cast iron a rise of about 5 feet above the highest level in the vessel 9, should
be sufficient. k. k. is the dried sand mould with the passages and m, leading
respectively to the vessel g, and the vacuum pipe i.
When all the joints are made good and the plug h, in its place, the pipe i, is put
into communication with the vacuum chamber which should be hermetically sealed
and in which a more or less perfect vacuum should be constantly maintained by
means of an air pump condenser or other suitable means, all the air will then be
withdrawn from the mould. The melted metal is then poured into the vessel
and
the plug . withdrawn but this plug must not be withdrawn until there is sufficient
metal in the vessel g. not only to thoroughly fill the mould but also to allow for its
rising in the pipe i.
The mould should be dried before use. The communication between the mould
and the vacuum chamber might be closed by means of a plug of suitable refractory
material but we prefer to use the pipe i, as herein before described.
In Figures 5 and 6 we shew modifications of the arrangement for putting our
invention into practice. In Figure 5 instead of the plug, for closing the orifice
at the bottom of the conical vessel g. we use a disc n, of some fusible material so
that shortly after the molten metal is poured into the conical vessel, this disc
will melt in the thin part in the centre owing to the heat of the metal above it and
allow the metal to run into the mould. The thickness of the disc and the material

page_text: of which it is formed should be such that it will not melt too rapidly so as to allow
time for the conical vessel to be supplied with the necessary quantity of metal
before it gives away.
In Figure 5 is also shewn the method of clamping the
conical vessel down on to the top plate. b. b. is the top plate. o. o. are the studs.
p. p. the clamps pressing on to the flange formed at the bottom of the conical vessel
and block up at their other ens by the pieces 1. J. A ring, or bush r. r. of fire
clay or other suitable material is inserted in the hole in the top plate to preserve it
from injury.
9.
In the arrangement shewn in Figure 6 we dispense with the conical vessel and
use the bent pipe. One end of this bent pipe is clamped air-tight on to the top
plate b. of the moulding box a portion of which is shewn in section in Figure 6.
The other end, which projects beyond the edge of the moulding box and hangs
downwards is closed by a fusible disc t. attached air-tight to the face on the pipe
by a luting of white lead. The ladle containing the melted metal u. u is inserted
under the end of this pipe and then raised up until the fusible disc t. is sufficiently
submerged in the metal. On the centre of this disc giving away, owing to the
heat imparted by the metal, the liquid metal will be forced into the mould by
atmospheric pressure.
In Figure 7 we shew the application of our invention to casting steel ingots.
v. v. is the ingot mould which is closed at the top and bottom by the plates wo¹ w²
the joints being made air tight. . . is the ladle containing the liquid steel.
y. y. is the bent pipe (similar to that shewn in Figure 6 at s. s.) and it is closed at
the end by the fusible disc z.
These pipes, together with the vacuum pipes, should be made of the same material
that is to be cast, so that when the casting is finished and the pipes are consequently
done with, they may (with the metal which has lodged in them) be broken up and
melted over again.
a. a. a. a. Figure 7 is the pipe leading to the vacuum chamber.
In some cases the fusible disc t. Figure 6 might be dispensed with and the outer
end of the pipe left open. The ladle containing the metal u. u. would then be raised
till the pipe is submerged a sufficient depth before a cominunication is opened to
the vacuum chamber. On this communication being opened the air in the mould
is withdrawn and the metal rushes in. This arrangement however would only do
where the capacity of the vacuum chamber is greatly in excess of that of the mould
and thus capable of creating instantaneously an approximate vacuum in the mould.
We therefore prefer to adopt the plan described of closing the orifice of the tube
by the fusible disc t, Figure 6.
The fusible disc may be made of cast iron or of metal the same as that which is
to be cast provided it is made sufficiently thin in the centre to give way at the
proper time.
Having now particularly described and ascertained the nature of our said
invention and in what manner the same is to be performed we declare that what
we claim is -
1. The employment in the casting of metals in moulds, of a mould in which a
vacuum has been established.
2. The various methods or apparatus for casting metals in moulds in which a
vacuum has been or may be established substantially as herein before described and
illustrated in the accompanying drawings.
DCT.... 1901
GEO. DOWNING,
8, Quality Court, London, W.C., Agent for Applicants.