The apparatus represented in Figs. 1, 2, 3, and 4 is the invention of
Messrs. Taylor & Wailes, and is designed for casting metallic objects
in annular form, its arrangement being slightly varied according to the
nature of the objects to be cast. In all cases where a special form is
to be given to the outer or inner circumference of the object, or where
it is desired to exert a pressure on the circumference, such form or
pressure is obtained by the introduction of a core which may be expanded
or contracted as need may be. For this purpose an expansible, metallic
core is employed, the arrangement of which is shown in Figs. 1 and 2,
and which is so fashioned that the inner circumference of the ring to be
cast may receive the desired form. This core is formed of the pieces, g,
g', made of cast-iron or any other material which fuses with difficulty,
and which are placed in the revolving mould in such a way that after the
cooling of the pieces the parts, g, recede by the shrinkage of the piece
and thus free the core. The parts, g, of the core are in the shape of
circular segments, and are united at their external circumference by a
flange, along with which they form a shoulder piece for the casting.
As a consequence of the rapid revolution of the mould, these parts are
pressed by centrifugal force against the molten metal which is run into
the mould.
[Illustration: CENTRIFUGAL METAL MOULDING APPARATUS.]
The plan, Fig. 2, shows the arrangement of the parts, g, g', and allows
it to be seen that the pieces, g', act as wedges against the segments,
g, and push these out so as to form a perfect circle. The molten metal
cannot become oxidized in the mould, since it is shut off from contact
with the external air by the cap, C, which covers it. Oxidation may,
however, be further prevented by passing some deoxidizing or neutral gas
into the mould. For this purpose the mould is filled before the casting
is done with some such gas as illuminating gas, carbonic acid, nitrogen,
or hydrogen.
This improved process of casting may also be employed for objects which
do not possess an exactly annular section. The moulds are then arranged
eccentrically in a frame which is made to revolve rapidly during the
cooling of the metal In this way the pieces are less strongly compressed
at the places where they are nearest the center of rotation than a the
points where the radius is greater.
Figs. 3 and 4 show section and plan of an apparatus of this kind. The
sand moulds are arranged in the frame, a b which revolves about the
axle, c. In the moulds there are iron cores, h, which press the metal
during rotation and thereby produce compact pieces.
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