Improvements in or appertaining to Casting Metals.
Year: 1894

page_text: Date of Application, 6th Feb., 1894-Accepted, 7th Apr., 1894
Improvements in or appertaining to Casting Metals.
A communication by JOHN JOSEPH CHARLES SMITH, of Passaic, in the State of
New Jersey, and EUGENE C. SMITH, of Providence, in the County of
Providence and State of Rhode Island, both of the United States of America,
Manufacturer of Art Castings and Moulder respectively.
I, WILLIAM PHILLIPS THOMPSON F.C.S., M.I.M.E., of The Agency for
Foreign Patent Solicitors 6 Lord Street, Liverpool and 6, Bank Street,
Manchester, both in the County of Lancaster and 323 High Holborn, in the
County of Middlesex, Civil 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 :-
The object of the invention is the construction of a practical apparatus into
which molds that are to be filled with metal may be enclosed hermetically and air
tight so that a high vacuum may be obtained in the molds and so as not to involve
waste of time and labor.
In making the apparatus a new, useful and practical combination and arrange-
ment of the different parts was particularly contemplated so as to serve their
functions to the best advantage, save labor and produce results to a certainty.
Experience gained by long and practical use of casting machines constructed
differently from the present one has shown many great deficiencies in them.
Casting apparatus by means of which mechanical pressure is applied to the fluid
metal to force it in the molds, require very dense and strong molds and even with
such the molds crack from the sudden heat and force of the metal which only too
often will show objectionable fins or seams on the casting if the casting is not
spoiled altogether.
Furthermore, such former casting machines have been constructed to receive a
number of molds for every casting operation because the charging, closing and the
getting of the machine ready for a casting, takes so much labor on account of the
wrong combinations of the different parts. To fill a number of molds, each
probably containing five to ten pieces, generally results in a loss of several pieces-
sometimes half of them. Furthermore, when a number of molds, say only two, are
placed for one charge in the machine, it very often happens that the fluid metal
will force or bend one mold into the hollow part of the other, which increases the
thickness of one casting and diminishes the other opposite one.
This is a very
objectionable feature especially on light and very thin articles.
Therefore, in the construction of the new machine it is aimed to arrange every
part so that the machine can be charged, closed and discharged in the least time
possible so that more than one mold need not be cast or filled at every operation
and can be done with comparatively little work or loss of time.
Practice in casting "by means of machines made for application of mechanical
pressure" has taught that if molds are made of a material which has not enough
density to resist the pressure of the fluid metal, the castings will not present such a
smooth surface and such sharpness of lines as the mold really presents.
Mechanical pressure cannot be regulated to a nicety on account of the friction in
the cylinder but atmospheric pressure can be regulated to the exact required
pressure to be exercised on the metal. To obtain a perfectly sharp and smooth
casting by a vacuum only requires a fine but very porous mold.
"

page_text: '
Referring to the accompanying drawings which form a part or Speci
fication:-
Figure represents a vertical longitudinal section of the machine through the
centre.
Figure II is an elevation of the front.
Figures III and IV are respectively plan and sectional views of an angular
rubber rim used as an air-tight packing on a part of the machine.
Figure V is a plan of an asbestos washer also used as a fireproof packing.
Figures VI and VII are respectively a vertical section and a plan of an asbestos
tube, washer or ring used to line the main gate.
With a base or platform A is firmly connected an upright plate B at right angles.
The plate B is provided in the centre with a rib B to impart stiffness to the plate.
On the top of plate B is a horizontal extension R. This extension is provided
with a dovetail or T-slot R2 in its centre to receive a sliding bolt R³. To the
plate B, two side plates C are connected by means of hinges D so that the side
plates will open or close like doors. Each of said two plates has angular extensions
at the loose edge slotted to form hooks C2. With an upright movable plate E, the
base A, the upright B and the two side plates C, a box or case is formed which has
a given height and width. By moving the plate E either forward or backward the
depth of the box may be increased or diminished. The adjustment of the plate E
is facilitated by the attachment of an arm F which has a roller F2 at the end, the
same resting on the base A. The arm F prevents also the falling of plate E.
The top or cover of this box is formed by a plate G which is hinged at M to the
upper end of plate E. The plate G reaches over the horizontal extension R.
By means of the slot bolt R³, the top plate G can be fastened to the extension Rat
any desired place. As the plate G is fastened to plate E by means of hinge M, it
is evident that the depth of the box (i.e. the distance between plates B and E) can
be increased or diminished as it may be required according to the thickness of the
mold to be placed in the box for casting. The plate G can also be thrown back
on its hinge so as to open the box on top.
When a mold Z is placed in the box to be filled with metal it is placed against
the plate B. The plate E is then moved against the mold and by means of the
screws J which have their fulera in two removable cross bars X, the mold can be
held together firmly.
The cross bars are provided with angular hooks X2 at the end and serve also
by means of the hooks C² to hold or lock the sides C firmly to the edges of
plate E.
By the arrangement and combination of the parts so far described a firm case or
On top
mold box is formed which can be opened and closed in less than a minute.
It is attached to the
of the plate G is a funnel-shaped metal receptacle K.
plate G by means of a swivel bolt N and a lock bolt K. This metal receptacle
has an arm or extension K³ on one side and a hinge joint L on the other. One
part of the hinge joint L is formed by an attachment to the swivel joint N.
At the end of the hinge joint L is an upright post T to which a cross bar or lever P
is hinged at O, forming a joint at that point. At the centre point where the
lever P crosses the metal receptacle K is a vertical stem O, jointed to lever Pat
that place. This vertical stem O is almost of an inch thick and has an asbestos
covering O. The metal receptacle, when thrown upward on its hinge L, is open
at the narrow end. The receptacle is provided with an asbestos lining S on the
inside. The bottom of the receptacle is formed by plate G when the receptacle is
resting thereon.
By means of a hole S through the plate G, at the centre of the receptacle
communication is established from the receptacle to the interior of the case and
-molds enclosed therein for casting. The diameter of the hole S is almost of ar
inch smaller than the diameter of the stem O so that the stem will fully cover the
hole when resting on it, and for centering the stem it may have a slight boss at its

page_text: lower end to enter the hole S.
16
An asbestos washer S² almost of an inch thick
and about larger than the inside of the receptacle at its narrow end is interposed
between the plate G and the edge of the narrow end of the receptacle. The hole
in said washer is of the same size as the hole S in plate G. When the washer is in
position, the hole in it must coincide with the hole S in plate G. The hole S is
lined with a short tube or ring S³ of asbestos of the shape shown in Figure VII.
One edge of said ring has a little flange St to prevent it from slipping through the
hole. The flange of short tube S³ serves also as a good air tight junction with the
hole in the washer, when the stem O rests over it.
It has now been described how the case is rendered perfectly air tight so that the
required vacuum can be created in the molds enclosed in the case. On the three
(top and side) edges. of the upright plate B a narrow rubber packing strip Y (a
little more than semi-circular in cross-section) is embedded. The flat surface of the
packing strip projects about of an inch over the surface of the edges of the
plate. A similar packing strip Y is also embedded on the top edge of the plate E
but not at the side edges or the bottom edges of said plate. These three edges are
provided with a different style of packing which is done as will now be described.
To the outer surface of plate E is attached near the edges a rubber rim of the
angular shape shown by plan and cross-section in Figures III and IV. This rubber
packing rim E2 is of the exact size of plate E but the angular edges flare out a little
as shown by the drawings.
The side plates or doors C being hinged to upright plate B, if closed, will press
against the rubber packing at the edges of plate B and when locked by the screw
bars a press also against the flaring flanges of the rubber rim E2. The lower flange
of rubber rim E² forms a good junction with the platform or base A. The adoption
of this peculiar shaped packing rim E2 is for this reason. The plate E has to be
moved a little forward yet by means of screws J after the sides C are locked so as
to press the two halves of the mold firmly together but if a similar packing to that
on the edges of plate B were used the plate E could not be moved after the box is
locked. When a vacuum is created in the case, the pressure of the atmosphere.
will act on the flanges of the rim and close the corners hermetically. When the top.
plate G is brought down to close the top, the case is already firmly locked and no
further moving of the lower parts takes place; therefore the top edges of plates E
and B are also closed air tight by the packing at those two edges. So far the
Fermetical closing of the mold case is automatic and requires no special time or
labor. Only the top and bottom edges of the two side plates or doors C remain to
be sealed which it is preferred to do at every operation of casting by luting those
joints with plastic clay or soft putty as it has been found in practice that rubber
packings at those junctures are not very reliable. This luting up is done very
quickly and effectively. It is shown that the base A is a little wider than the
body of the machine and when the doors C are closed a sharp corner C4 is formed
A similar
which is quickly sealed by smearing a little clay or putty in that corner.
corner C is formed by the edges of the plate & and the upper edges of the plates C
which is also luted in the same manner.
The hole S in the top plate G is hermetically closed by the stem O resting over
said hole on top of the flange of the lining ring S2. The lower edge of the metal
receptacle finds an air tight packing by pressing on the outer edge of the washer S³.
A weight W at the end of lever P holds the valve stem down firmly.
From the description so far given of this apparatus, it will be seen that it
presents a series of novel and useful combinations for the purpose of saving labor
and time.
1
1st: The case or box for receiving the molds is so constructed that by the novel
combination of the different and required parts, it may be closed hermetically
with the greatest facility and effect, so that a good vacuum can be produced in the
molds.
2nd: The upper part of the apparatus consisting of the metal receptacle with its
closing valve is so constructed by a new combination of the required parts that it

page_text: •
can be quickly adjusted to receive a charge of metal and hold the same against the
suction of the vacuum until the proper moment when the metal is allowed to flow
into the molds. After a cast is made, the receptacle can be detached easily and
quickly from the casting and the remaining surplus of metal discharged.
The apparatus is operated as follows:-
The molds that are used are made of the composition and in the manner above
referred to. The molds are made of the exact size of the inside of the case in
height and width.' The thickness or depth of the mold however depends on the
shape of the casting to be made. As stated, the back plate E is movable to adjust
it to the thickness of the mold. The mold is provided with a vertical main entrance
gate U, the position of which has to correspond with the hole S in plate G. From
the main gate one or more smaller branches run to the different articles formed in
the mold.
The proper manner of cutting the gates required is well known to artisans in the
line of cutting. The molds must be perfectly dry if, good, sharp castings are
wanted. The mold is placed vertically in the apparatus against the plate B; then
plate E is pushed forward against the mold; then the side plates are closed and
locked by the cross screw bars X and then the mold is firmly closed together by
bringing the screws J to act against plate E. After this, the top plate G is
brought down and fastened by the sliding bolt R³. The next step is to bring the
metal receptacle in position. The description and drawings show that the receptacle
is connected to plate G by means of the swivel bolt and its hinge at point L which
permits the raising of the receptacle and the laying of it back.
It can also be
turned sideways on the swivel bolt. It is desirable, as will be shown, that the
receptacle have both these motions.
This
By raising the receptacle the hole S is free so that the asbestos washer S2 may
be placed on the plate G in such a way that the hole in washer corresponds, to the
hole S in plate G. Then the asbestos tube or ring S3 is slipped into the hole S so
that the flange on the ring will rest on the edge of the hole in the washer.
done, the receptacle is brought down and fastened by bolt K. The receptacle is
lined with a non-conductor of heat, to which the washer forms a non-heat conducting
bottom. The washer serves also as a fireproof packing at the joins of the
receptacle with the plate G. The hole S lined as aforesaid forms the inlet of
the fluid metal to the molds. This inlet is closed by raising the stem over it.
It is held down air-tight by the weight w acting on the lever P. The corners C³
and C³ are next luted as described before, which makes the apparatus ready for
casting.
Shortly before filling the metal receptacle with fluid metal, the air is well
exhausted out of the mold by means of a good vacuum pump attached to the pipe P²
which enters the case near the bottom of plate B. The air finds an easy passage
through the pores of the mold to the pipe P2. The working of the pump is kept up
during the act of filling the receptacle, also until the metal has filled the mold and
has become fully set.
When the metal receptacle has received sufficient metal to fill the mold with a
surplus for a head, then the valve stem O is lifted only about one inch when the
pressure of the atmosphere will quickly force the metal into the mold and fill every
cavity of it. The valve stem O should never be raised too much or out of the
metal until the mold is filled or else the air will rush into the mold with the metal
and spoil the casting.
As soon as the surplus of metal left in the receptacle has become set, the
receptacle must be quickly detached so that the gate may be easily broken before
the metal cools sufficiently to attain its full strength. To detach the receptacle the
lock bolt K², is loosened then the receptacle turned sideways on its swivel bolt N
by means of lever K³, so that the gate is sheered off and then the lever is lifted and
the receptacle thrown back on its hinge. The stem O must be drawn and before
the surplus metal left in the receptacle shrinks on it. After this the mold and
castings are removed from the case.

page_text: The form of mold which it is preferred to use with the above-described apparatus
will now be described and the process employed for producing such molds.
The object of the second part of the invention is the production of a mold for
casting metals, by means of which the most delicate outlines and designs of a finely
hand-wrought pattern can be perfectly reproduced in a mold taken from such a
pattern.
A mold for this purpose should resist exposure to the heat necessary for drying
it, and also the heat of the melted metals poured into it, without being fractured
or cracked. At the same time, such molds should be porous enough to admit a
free escape of the gases. usually generated by fluid metals.
The invention consists of a mold composed of plaster of Paris and non-melting
fibre, such as fibre of asbestos. The invention is carried out in the following
manner:
Fine, short asbestos fibre or pulp is mixed with water to about the consistency
of a thick, creamy, but still flowing mass being well stirred and mixed. Plaster
of Paris is then mixed with water in the usual way known to those skilled in the
working of plaster. To two parts of this plaster mixture about one part of the
asbestos mixture is added. Both are then well stirred together to form a uniform
mass which is applied to, and cast on, the pattern from which a mold is to be taken
in substantially the same manner as in making a plaster mold. The making of the
second half or other parts of a mold is performed in the same manner as above.
When the molds are formed as stated, they are placed in a drying oven and
exposed to a moderate heat, say, 250 to 300 F. for about ten to twelve hours more
or less so as to evaporate the greater portion of the moisture and render the molds
at least apparently dry. Then the heat is slowly increased to about 1000 degrees
or a low red heat, and this heat is retained for two or three hours, more or less,
when the molds are allowed to cool off slowly. They are then ready to receive
the casting.
By the foregoing means, a perfect mold in every respect is produced; practically
useful for producing small sharp castings, also castings of considerable surface but
very thin and light in body.
Furthermore with this invention, a material for molds is obtained of sufficient
strength to permit the use of elastic rubber patterns having many deep and fine
undercuts in their designs. The elastic patterns can be drawn from a mold made
of this composition without breaking away the deep undercuts in the design. This
cannot be done by any other process of molding known to my correspondents.
Molds made of their composition of plaster of Paris and asbestos fibre-can be
used for casting metals in them with most satisfactory results, either by pressure
applied to the fluid metal by some one of the known patented contrivances, or by
means of simply pouring the metal into the mold as is done ordinarily in using
sand or loam molds.
If the molds are to be filled with metal by pressure, the heat for drying them
is not brought to so high a degree; but when the metal is to be poured, as in the
ordinary way, of casting metal, the molds must be perfectly free from moisture and
the sulphur and crystal water contained in the plaster which can only be fully
removed by a low red heat.
All other combinations of plaster and other materials which are known to my
correspondents for making molds could not resist exposure to a low red heat without
cracking and crumbling into pieces.
The manner in which the molds are made is simple and efficient.
In order to convey a clear idea of the novelty and utility of the invention, a few
facts will here be stated concerning the use of molds made of plaster of Paris mixed
with sand, burnt clay, dust or ashes (in the ordinary manner) into which fluid metals
such as Brittania, zinc, brass (or other metals into which copper enters largely)
sterling silver or gold could be cast successfully. For a practical useful mold such
compositions could be used only for metals melting at a low degree of heat.
It is well known by those skilled in the art of casting metals, that metals (even

page_text: those melting at as low a heat as 600 F.) cannot be cast successfully and sharp in
a plaster of Paris mold, or the compositions mentioned, unless the fluid metal is
forced into the mold by pressure.
Such mechanical pressure is indispensable if the mold is of pure plaster, or the
compositions above mentioned because a mold made of such compositions will not
stand the heat required to expel all moisture and sulphuretted crystal water
contained in the plaster without cracking and crumbling to pieces. Therefore,
mechanical pressure must be applied to overcome counteractions of gases and
vapors generated by the heat of the fluid metal.
The above only applies to metals melting at a low heat. Metals melting at a
high heat, say, 1000 to 2000 degrees, cannot be cast in plaster molds, or molds
made of the mentioned compositions, even with mechanical pressure because the
heat of the metal acts on the fine surface of the mold and destroys it, consequently
a rough casting is the result.
A few explanations may be here made concerning molds made of pure plaster,
or mixtures of sand, ashes, loam, etc. with plaster. It is well known that the
crystallization of a portion of the water, used in the mixing of ground calcined
plaster, gives it the property of setting, or hardening into a solid mass.
It is also known that this crystallized water cannot be fully expelled from the
plaster until about 800° or 900° F. is applied, but when subjected to this heat the
plaster cracks and crumbles in pieces.
In order to overcome this trouble, resort has been had to the mixture of sand,
brick-dust, ashes, etc., with the plaster to produce a mold that would stand the
heat necessary for expelling the crystal water and sulphur in the plaster and render
it fit to receive metal castings that melt at a high heat. A great many experiments
have been made by my correspondents with such mixtures with plaster for molds,
but they have never met with satisfactory or practical results, nor has any one else
to their knowledge.
In order to give an idea of the novelty and utility of this invention, it is desired
to state that it has been the aim of founders and artisans to use molds made of
plaster, or compositions of the same for casting metals, especially brass, bronze,
German and sterling silver, gold, etc., because the most delicate outlines and design
of a given pattern can be more accurately and sharply reproduced in a plaster
mold, than in a mold made of sand or loam.
My correspondents are fully aware that metals melting at a low degree of heat
are cast in pure plaster molds. Such metals as type-metal, tin, Brittania, and zinc
have been cast in plaster molds with success, but the metal had to be forced into the
molds by mechanical pressure. Sterling silver and some low melting brass
compositions have been cast in plaster molds by pressure, but the results with these
metals were never satisfactory or practical, even though cast under pressure. The
molds could not withstand the heat necessary to dry them perfectly and effectually,
consequently they cracked when the red-hot metal was injected. They also became
soft and the pressure on the metal caused it to penetrate into the mold, producing
a rough casting and obliterating all fine outlines and design.
By using the mixture of plaster of Paris and asbestos as specified, a strong and
fine mold is produced and one which will answer all purposes such as withstanding
.heat, pressure, &c.
The short fine fibre holds the plaster together and its fire-proof qualities enables
the mold to stand the heat necessary for drying without cracking or crumbling.
This composition yields a mold into which the metal can be poured the same as in
a dry sand mold. The metal lies perfectly to the surface of the mold and produces
a casting as perfect in every detail as the original patterns.
A mold made and burnt in the manner described, retains all the most delicate
outlines, and the material being such a poor conductor of heat, the mold does not
chill rapidly; consequently very thin castings of considerable surface can be made
to perfection.
These molds can also be filled with metal forced in by pressure and produce

page_text: better castings in every respect than with molds made of plaster, or mixtures of
sand, ashes, etc. with plaster.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, as communicated to me by
my foreign correspondents I declare that what I claim is:
1. In a casting apparatus, the combination of the base plate A, the upright
plate B fixed thereto, the movable top plate G and the hinged side plates C hinged
to plate B and forming with the base and top plates sharp corners for the purpose.
of luting, substantially as set forth.
2. The combination of the base plate A, the upright plate B fixed thereto, the
hinged side plates C, the adjustable plate E, the hinged top plate G, the edges of
plates B, C, and E being suitably channelled or grooved to receive packing,.
substantially as and for the purposes set forth.
the
3. The combination of the base plate A, the fixed and adjustable plates B,
side plates C, and the flanged packing plate E2 arranged and adapted to operate:
substantially as set forth.
4. The combination of the base plate A, fixed upright plate B, hinged side
plates C having hooks C, adjustable upright plate E, screws J and cross bars X,.
arranged and adapted to operate, substantially as set forth.
5. The combination of the base plate A, upright plate B, side plates C, adjustable
upright plate E having arm F provided with roller F2, substantially as and for the
purposes set forth.
6. The combination of the base plate A, upright plate B, suitable side plates,
adjustable upright plate E and top plate G hinged to said plate E, substantially as
and for the purposes set forth.
7. In combination with a suitable mold casing, a hinged top plate therefor, a
metal receptacle K having lever K³ hinged to said top plate and lock bolt. K²
substantially as and for the purposes set forth.
8. The combination in a casting apparatus with a suitable mold casing, of a
movable top plate, a metal receptacle and its lever connected to said plate by a
hinge and swivel, an upright arm T on said lever, valve stem O, cross lever P and
weight W., substantially as and for the purposes set forth.
9. In a casting apparatus, the combination of the top plate G, the asbestos tube
or ring S³, the asbestos washer S2 and the metal receptacle hinged to said top plate,.
substantially as set forth.
10. A mold to receive metal castings consisting of a mixture of asbestos fibre, or
pulp, with plaster of Paris, substantially as described.
11. A mold to receive metal castings consisting of a mixture of non-melting fibres.
and plaster, substantially as described.
12. The method of making molds herein described consisting in mixing asbestos.
fibres or pulp with water to the desired consistency, mixing plaster with water,.
then adding said mixtures together and thoroughly mixing them forming said
mixture into the desired shape of the mold and then baking said mold, substantially
as specified.
Dated this 5th day of February 1894.
WM. P. THOMPSON & Co.,
Agents.