Improved Apparatus for Effecting the Casting of Metals in Vacuo.
Year: 1892

page_text: Date of Application, 20th July, 1892-Accepted, 20th Aug., 1892
COMPLETE SPECIFICATION.
Improved Apparatus for Effecting the Casting of Metals in Vacuo.
1, WILLIAM SPEIRS SIMPSON, of 49 Battersea Park Road, Surrey, Engineer,
do hereby declare the nature of this invention and in what manner the same is to
be performed to be particularly described and ascertained in and by the following.
statement :-
My invention relates to an improved method of casting metals under a vacuum,
and has for its object the production of castings which are sharper and cleaner and
are more homogeneous, soft, and ductile than those made in the ordinary manner of
casting under atmospheric pressure.
In carrying out my invention, I enclose an ordinary box or flask in which the
mould is formed in an air tight chamber in which a vacuum is produced by any
suitable means, so that when the metal is poured it fills all the cavities and
interstices of the mould undisturbed by the generation of any vapour or gas.
In connection with the chamber enclosing the moulding box I use a subsidiary
chamber (air tight) containing a ladle or a crucible in which is placed the metal
previous to its being poured into the mould, a vacuum is formed in this subsidiary
chamber and thus the molten metal is exposed to an exhausting action which has
the effect of taking off all the gases and vapours contained in the fluid and
rendering the metal dead as far as any tendency to ebullition is concerned.
The ladle or crucible holding the metal is connected to a suitable hand turning
gear on the exterior of the chamber by means of air tight connections, and when the
exhaustion of the contents of the ladle is considered sufficiently complete the metal
may be emptied into the mould. In some cases, I separate the main chamber
containing the moulding box and the subsidiary chamber containing the ladle by
means of a thin plate of metal or metal diaphragm which forms an air tight division
between the two chambers until it is inclted by the hot metal being poured over it
when the ladle is emptied. The object of this diaphragm is to enable the
exhaustion of the main chamber to be carried on previous to and independently of
the exhaustion of the subsidiary chamber; however if the exhausting power is
sufficiently large, this diaphagin may be dispensed with and both chambers
exhausted at once.
The exhaustion may be obtained by means of air pump ejections or the like
acting directly
extensive scale, on the chambers but where the operation is carried on to any
employ a large vessel or series of comparatively large vessels
which are kept continually exhausted and which can be placed in communication
with any of the chambers and thus produce a rapid and complete exhaustion of the
moulding box and ladle of metal. Suitable spy holes fitted with glass or other
transparent material are formed in the top of the chamber containing the moulding
box, so that an attendant can observe the metal in the "risers" of the moulding
box, and control the ladle accordingly. Similar spy holes are formed in the sub-
sidiary chamber containing the ladle for observing the behaviour of the metal in
the ladle, and while pouring. The subsidiary chamber may be of any desired form
preferable where convenient spherical or semi-spherical and with ribs inside which
stiffen it and at the same time retain the lining of refractory material.
I sometimes arrange the chambers, so that the act of placing the subsidiary -
chamber on the cover of the main chamber can render the joint formed by the
fusible metal plate air tight.
Figures and 2 of the annexed drawings are longitudinal sections of the
apparatus.

page_text: igure transverse section.
Figure 4 similar section with stirrer.
An ordinary moulding box A is placed in the chamber B which has a removable
cover C making an air tight joint with the top of the chamber and allowing the
moulding box to be placed in position and removed, this lid has a hole D in it over
the part of the box where the metal is poured, and also two spy holes E, E,
arranged to give a view of the "risers in the moulding box. A subsidiary
chamber F with a movable lid or cover F' is arranged so as to fit over the hole D,
and the ladle or crucible G is placed in a suitable cradle or frame H which is hung
on a spindle I passing through a stuffing box J in the side of the chamber
the end of the spindle I being fitted with a handle or wheel I to control the tilting
of the ladle.
A plate of metal K sufficiently strong to resist the pressure of the atmosphere
but of a nature to be easily fused by the impact of the melted metal is placed
between the chamber B and the subsidiary chamber F, and an air tight joint is
made at this point by means of packing rings kept in place by the chamber F.
The object of this fusible plate is to separate the two chambers till the time the
metal is poured, so that the lower chamber B can be exhausted by means of the
pipe connections L while the subsidiary chamber F is exhausted by means of a
pipe connection M and when any gases cease to be given off the ladle is tilted
over, the metal melts the fusible plate and flows into the moulding box and com-
pletely fills the mould, the moulding box being also in a vacuum.
The interior of the subsidiary chamber is provided with ribs N, N, N, N, which
serve to strengthen it against the pressure of the atmosphere and also to retain
the lining in position. The cover F¹ of the subsidiary chamber is secured by
bolts or clay and may be loosely hinged for the convenience of turning back.
A spy hole is provided on top of the chamber F to enable the progress of the
metal to be observed, and this spy hole like the others is of course air tight.
When the process of exhaustion is sufficiently rapid, the fusible plate R may be
dispensed with and both the main and subsidiary chambers exhausted at the
same time.
The lower chamber B may be made to open on the top, or at the end, or at the
side or sides, the most convenient for the class of work being moulded and any
suitable means of exhausting may be used. It is obvious that one or more sub-
sidiary chambers F may be employed in connection with the lower chamber B.
One method I employ to stir the molten metal is as follows:-
A rod P entering the chamber at the top through a stuffing box Q and having
at the end of the rod inside the crucible or ladle C a knob or ball R. The stirrer
is connected to a lever S outside the chamber, the lever being pivoted to an arm T
cast, in the chamber itself. A slot U is made in the lever to enable the striker to
move up and down.
The method of working is exactly the same as an ordinary hand pump the down-
ward movement of the handle S raising the stirrer P out of the molten metal V in
the crucible at the same time of course displacing the metal, ou moving the handle
or lever up again it causes the stirrer to strike the molten metal, if this is done
two or three times it has the effect on the molten metal as though it were being
knocked with a hammer or violently stirred thus imparting a fibrous nature to the
molten metal.
Having now particularly described and ascertained the nature of this inven-
tion and in what manner the same is to be performed declare that what I
claim is :-
―
1. The apparatus shown in the annexed drawings, consisting of an upper vessel
with ladle and a lower vessel with mould, the two vessels being separated by a
fusible diaphragm, as described.
2. Arranging a ladle of molten metal in chamber and placing the mould in

page_text: another chamber exhausting the air from both chambers, and providing the upper-
vessel with appliances for turning the contained ladle therein for the fluid metal to-
run into the lower vessel, as and for the purposes set forth.
Dated this 20th day of Jul. 1905
H. GARDNER,
Patent Agent, 166, Fleet Street, London.
Agent for the said William Speirs Simpson..
H. GARDNER,
Patent Agent, 166, Fleet Street, London.
Agent for the said William Speirs Simpson..