IMPROVEMENTS IN CASTING METALS UNDER PRESSURE, AND IN APPARATUS AND APPLIANCES THEREPOR
Year: 1869

page_text: LETTERS PATENT to Benjamin Joseph Barnard Mills, of 35, South-
ampton Buildings, in the County of Middlesex, Patent Agent, for
the Invention of "IMPROVEMENTS IN CASTING METALS UNDER PRESSURE,
AND IN APPARATUS AND APPLIANCES THEREPOR." -A communication
from abroad by John Joseph Charles Smith, of Somerville, and
Jesse Albert Locke, of Boston, both in the State of Massachusetts,
United States of America.
Sealed the 24th August 1869, and dated the 11th May 1869.
COMPLETE SPECIFICATION filed by the said Benjamin Joseph Barnard
Mills at the Office of the Commissioners of Patents, with his.
Petition and Declaration, on the 11th May 1869, pursuant to the
9th Section of the Patent Law Amendment Act, 1852.
TO ALL TO WHOM THESE PRESENTS SHALL COME, I, BENJAMIN
JOSEPH BARNARD MILLS, of 35, Southampton Buildings, in the County
of Middlesex, Patent Agent, send greeting.
WHEREAS I am in possession of an Invention for "IMPROVEMENTS
IN CASTING METALS UNDER PRESSURE, AND IN APPARATUS AND APPLIANCES
THEREFOR," and have petitioned Her Majesty to grant unto me, my
executors, administrators, and assigns, Her Royal Letters Patent for

page_text: the same, and have made solemn Declaration that the same has been
communicated to me from abroad by John Joseph Charles Smith, of
Somerville, and Jesse Albert Locke, of Boston, both in the State of
Massachusetts, United States of America.
NOW KNOW YE, that I, the said Benjamin Joseph Barnard Mills,
do hereby declare that the following Complete Specification, under my
hand and seal, fully describes and ascertains the nature of the said
Invention, and in what manner the same is to be performed, in and by
the following statement, that is to say :-
The principal object of this Invention is to cast brass, bronze, and
others of the refractory metals and metal compositions with the greatest
possible density and freedom from blow holes, and to produce perfect
sharp and well-defined fac similes of any desired pattern, whether the
said pattern be plain and simple or elaborately chased, engraved, or
finished in any manner.
The Invention is valuable for producing plain articles of any hard or
refractory metal with great rapidity and economy, and also for producing
by machinery fine and elaborate casts, such as heretofore have required
to be made or finished by hand at a high cost.
Certain parts of the Invention may be applied to apparatus of various
forms. The apparatus which is here selected for illustration, but to
which the Invention is not necessarily restricted, consists of a rotary
wheel or cylinder, on the periphery of which are arranged a series of
moulds, each formed of a pair of hinged metallic plates, which while
the casting is being performed are held firmly together between stationary
housings, suitable rollers being interposed between the rotary mould
plate and the stationary housings to reduce the friction. Each of the
mould plates is provided with one or more springs, which as the rotation
brings the moulds successively opposite recesses in the housings cause
the mould plates to separate with a sudden movement, causing a jar
which effectually detaches and discharges the casting. This effect is
assisted by pins which are driven inward as the mould plate is separated,
and in their retracted position form parts of the mould. The continued
rotation of the wheel carries the mould plates between converging planes,
which gradually close the moulds and conduct their rollers between the
parallel parts of the housings by which the plates are held to receive the
molten metal which is injected into the moulds from a cylinder or other
suitable reservoir by a sliding piston or plunger. A detachable non-

page_text: conducting lining is applied to the interior of the cylinder each time
before it is filled, and serves the combined purposes of preventing the
molten metal setting or adhering to the metallic cylinder, and effectually
packing the joint between the moving piston and the cylinder. From
this reservoir the metal is forced through a contracted aperture directly
into the moulds, the gates of the latter being funnel-shaped so as to
cause no interruption to the passage of the metal. A continuous
pressure is applied to the metal within the cylinder during the casting
operation, and the partitions between the moulds being tapered to an
edge cause no perceptible interruption to the flow as they pass the
discharge orifice of the reservoir. The reservoir is mounted upon a
sliding bed provided at its forward end with a segmental plate or standard
which fits around the periphery of the cylinder so as to tightly close
the gates of the moulds and serves also as a mouthpiece for the injecting
cylinder. The sliding bed is held up to the cylinder by a screw and
spring, the latter permitting it to yield so as to avoid danger of breakage
in the event of any hard matters getting between the mouthpiece plate
and the cylinder. The injecting and pressing apparatus may be used
with equally good effect in connection with stationary moulds, the said
moulds being arranged either separately or in any number together, and
placed either horizontally or vertically, or in cases where it is desirable
to cast a number of small articles at one time, any number of moulds.
therefor may be placed together within a single flask or casing, and a.
single injecting reservoir may be used for all. The molten metal may
be made to enter the moulds horizontally or may be forced upward from.
the lower part, or introduced at top, as convenience or various circum-
stances may dictate. For casting a large number of small articles.
simultaneously, the stationary moulds are preferably arranged in a
vertical nest or series and the metal injected at bottom, the separate-
moulds or parts of moulds being provided with suitable grooves to form-
when united gates or sprues for the admission of the fluid metal. A
cluster or connected series of these moulds being placed together in their
flask or casing are supported and firmly compressed by a plate, which is
forced against the moulds by set screws tapped into the top, bottom, or-
side of the flask, in order that the moulds may resist the pressure of the
metal when injected, and not part or open at the joints and thereby
cause the formation of fins or seams in casting. The entire flask may-
then be enclosed in a tight box from which the air can be exhausted by
an air pump of large capacity, small perforations being formed in the

page_text: walls of the flask and in the body of the moulds to permit the escape
of air and gas from all parts of the latter. Whenever the air and gas
exhausting process is used, care must be taken that the joints of the
outer chest are all tightly closed, and the junction between the said
chest and the reservoir are luted with wet clay or other material to make
all air-tight.
As a material for the moulds themselves, steel or other metal may
sometimes be used to good advantage, especially for small moulds in a
rotary apparatus, such as is represented in Figures 1, 2, and 3 of the
Drawings, and herein-after more particularly described.
"
The great rapidity with which refractory metals chill and become
"set
causes difficulty in the use of metal moulds, even though the said
moulds may be heated prior to the introduction of the metal. This
rapid setting would afford insufficient time for applying pressure to the
metal unless this is done instantaneously by apparatus such as is herein
described, and even with the improved apparatus there is danger of the
formation of a skin on the surface of the metal, which with elaborate
or fine work may cause a mottled, streaked, seamed, or otherwise
defective appearance.
Again, if metal moulds are highly heated to
prevent to a certain extent the sudden chilling, the fluid metal will unite
with the moulds, especially the alloys of copper and tin, and even if
metal moulds could be used with advantage, the expense of making them
would forbid their use in cases where only a limited number of castings
are wanted of one and the same pattern, and in some cases the utter
impossibility of making them.
Where the diameter of the apparatus or the size of the flasks or mould
boxes or other circumstances will admit of it, it is better to form the
moulds of a composition which will combine the following qualities,
namely: First, non-conductibility to heat; second, sufficient strength,
density, and hardness to resist the pressure exerted on the fluid metal
to prevent the latter entering the pores under such pressure, and to avoid
danger of the fine lines and sharp corners being injured in necessary
handling, or crushed or flattened by the pressure; third, the presence of
numerous very small pores, which while they will not permit the
entrance of the molten metal under pressure will allow the withdrawal
of air and gas from the moulds.
The production of composition moulds combining the above qualities
constitutes and important part of this Invention. They may be made as

page_text: "
follows: Take fine clay of such kinds as will resist a considerable degree
of heat without glazing or melting on the surface. Said clay after it has
been well mixed and washed in the same manner as it is prepared for
pottery is made dry, so that it may be reduced to powder. When
reduced to powder it is moistened with water about as much as sand used
for ordinary moulding. The pattern if it is to be used for a number of
moulds ought to be of metal. For one or two impressions said pattern
may be of hard plaster of Paris or hard wood. If of either of these two
last-named materials it must be first coated with shellac varnish, the
pattern is then rubbed over with a little oil (preferably paraffine oil)
applied with a brush, so that it may be released easily from the moist
clay. After oiling the pattern is coated over with a fine paste-like "slip"
made of the same clay used for moulding. The pattern or a number of
them are placed in an iron or brass flask or frame suitable for the size
and thickness of the mould to be made and provided with a bottom and a
plunger or follower, and the flask is filled with the moist clay powder on
top of the pattern. Then the plunger or follower is placed in position
and the whole brought under a powerful press and subjected to a slowly
applied but high pressure, say, about 300 to 400 lbs. to the square inch;
thereby packing and pressing the loose powder into a compact and solid
block. After sufficient pressure is applied it is allowed to stand under
the press for a few minutes, so that the surplus moisture or water in the
"slip" may be absorbed by the more dry clay powder. The purpose of the
slip" is to unite the loose particles of the clay powder in direct contact
with the pattern to a fine and homogeneous mass. The flask may then
be removed from the press and the bottom taken off; this done the
pattern is easily taken out, and a mould will be found as perfect and
smooth as if made of wax or gypsum. If a mould is to be made con-
sisting of two or more parts the first part made is coated on the surface
coming in contact with the surface of the next part to be made with a
slight coat of collodion or thin shellac varnish, so as to make a partition
between the clay surfaces, and they may be separated without difficulty.
When the mould is completed it may be taken out of the flask or frame
and handled and carried without danger of breaking. The moulds
made are rendered dry by exposure to the influence of air or a gentle
heat. When most of the moisture is evaporated the moulds are placed
into furnaces similar to those used for burning pottery, and the heat
gradually raised until the moulds are red hot, which will burn them
about as hard as a soft brick or clay stone. When cooled off they are
68

page_text: ready for casting. As it is necessary to keep these moulds in the same
shape as when first made, and whereas articles made of clay are very
liable to warp during the process of drying and burning, unless it is done
with great care and waste of time, for the prevention of these evils it is
found best to use to one part of clay powder made of fresh or new clay,
another half of clay powder made of clay which has been previously
burnt, or of old clay moulds which have been used for casting; the
compound of these two different kinds of clay powder is very beneficial,
as it prevents the warping of the moulds, even if they are of a consider-
ably large size.
In the Drawings Figure 1 is a horizontal section of an apparatus
illustrating one mode of carrying out the Invention; Figure 2 is a
longitudinal section thereof, with part of the revolving wheel in cleva-
tion, part of it in section, and part entirely removed; Figure 3 is a
vertical transverse section, the stationary parts being represented in the
plane underneath by the line x, x, and the rotary mould wheel in the
plane of line y, y, Figure 2; Figure 4 is a section of a part of the
apparatus on a larger scale illustrating a mode of withdrawing air and
gas from the moulds prior to the injection of the metal or simultaneously
:therewith.
Similar letters of reference indicate corresponding parts in the several
views.
A, A, represent various parts of the stationary frame; B is a wheel
or cylinder attached to a shaft C, which is rotated by gearing D, E,
or other means; F, F, are mould plates hinged in pairs to the periphery
of the wheel, and so constructed that each pair will join, when closed, a
matrix to produce the article which it is desired to cast; ff, represent
pins employed to aid in the detachment and ejection of the casting
from the moulds, as previously explained. The inner ends of the said
pins are flush with the inner surface of the moulds when the latter
are closed. The outer faces of the hinged mould plates are furnished
with friction rollers G which bear against the housings H, so as to
hold the moulds in their closed condition to receive the metal;
h, h, represent recesses in the housings permitting the moulds to be
opened by the springs I, I, when the castings are to be discharged.
These recessesses begin with abrupt shoulders h¹ to permit the moulds
to open suddenly, and converge so as to conduct the friction rollers
gradually up to the parallel parts of the housings H. The reservoir for

page_text: molten metal consists of a cylinder J provided with a piston K, which
may be moved by a screw K', or by a lever in order to force the metal
out through the detachable thimble or nozzle L. A funnel j may be
formed upon or employed in connection with the reservoir J when it is
to be used in a horizontal position. The nozzle L passes into a mouth-
piece or guard plate M which serves to close the gates of the moulds,
and is rigidly attached to or forms a part of the bed N which supports
the cylinder J. The bed N is adapted to slide, and is held up to its
work by a screw O and spring P. Under the ordinary working of tho
machine the gates will be tightly closed so as to prevent any escape of
metal from the moulds until it is firmly set, but in the event of a
fragment of metal or other matter passing between the periphery of the
wheel and the guard plate M, the latter will yield, and thus avoid injury
to the apparatus; R, R, represent the tapering partitions between the
gates F of the moulds F. The said partitions converge to edges so as to
cause but momentary obstruction in passing the nozzle L, and to impart
a funnel shape to the gates or sprues.
The reservoir may be used in vertical position, as shown in Figure 4,
and the funnelj (Figure 2) dispensed with, the metal being introduced
into the open upper end of the cylinder, and the piston K afterwards
placed upon it. j represents the detachable non-conducting lining with
which the inner surface of the reservoir is coated prior to each time of
charging it with molten metal. F2, F2, represent moulds of the clay
composition herein-before described; S, S, plates, and T, T, set screws
by which the said moulds are firmly pressed and held together so as to
resist the pressure of the entering metal, and prevent any opening of the
joints. The plates S, S, may serve as the mould flask, or they may be
placed within a separate flask, and the latter enclosed in an outer air-
tight casing or box U from which air and gas are withdrawn prior to or
during the casting operation through pipes v, V, by means of a powerful
air pump, or for some classes of work the air-tight box and exhausting
process may be dispensed with, For some kinds of casting, especially
in iron and steel, moulds of iron and steel may be used with good
success, but it is very essential that such metal moulds be so arranged
that the fluid iron or steel is injected as directly as possible, and without
first passing through too long a space of gates or sprues before the
mould is reached by the metal. The reason why this should be done is
this, if fluid refractory metals come in direct contact with other metal

page_text: surfaces they chill and set more suddenly than those who are not
acquainted with this property have an idea of, even if those surfaces
should have been previously made red hot. The consequence of this
action is that the casting will show streaks and an uneven surface; but
if the moulds are filled directly from the injecting cylinder (avoiding the
passing of the fluid metal over a long distance in the gates), and the
strong pressure is brought to bear on the metal in the filled mould instan-
taneously before it has had time to form a hard skin or surface a very
good and sharp impression is thus obtained. Iron and steel moulds used
in this manner ought to be oxidized or rusted on the surface to a certain
extent. These rusted or oxidized surfaces are somewhat non-conductile,
and serve also to prevent the adhering of the injected metal to the
moulds.
When the suitable moulds are mado they. are put in a metal box
or flask, and an iron follower employed to press and hold the moulds
firmly together by means of the set screws, as illustrated in Figure 4,
just as the style of the machine may be, so as to resist the pressure of the
injected metal without parting at the joints. When this is done the
cylinder or injecting vessel J is provided on the inside with a non-
conducting lining.
The lining of the cylinder is performed as follows:-Take some fine
fire-proof clay or kaolin free from sand grit, and thoroughly blend
the same with about one-half the quantity of good plumbago; then
mix with water so as to form a paste. The cylinder is heated to about
200 degrees of Fahrenheit, and with a brush the aforesaid paste is applied
on the inside of the cylinder to a uniform thickness of about one-cighth of
an inch, the heat of the iron cylinder drying the paste as applied. This
done the cylinder is further heated to evaporate all moisture from the
lining and is then ready for further operation. The surface of the piston K
coming in contact with the fluid metal is coated in a similar manner.
This lining of the cylinder serves several useful purposes; it serves to
pack the space or joint between the cylinder and piston, and prevents
the intrusion of the metal between the two, which intrusion would
certainly and rapidly clog their parts, and stop the operation, as the
heat of the fluid metal will at once expand the cylinder more than the
piston, and admit the metal between them at the joint. It should be
explained that the plunger or piston K fits the cylinder, and is therefore
larger than the internal diameter of the lining, and that at every

page_text: operation the cylinder must be relined or recoated, as such lining is
detached from the cylinder J, and pushed in advance of the piston K at
every forward movement of the latter, the effect of which is to close the
joint, and prevent the intrusion of the metal between the piston and side
of the cylinder, as above stated. No matter how high the pressure is
on the fluid metal, not a drop can leak out, the detached lining will
pack the joint so much the more closely. The importance of this
detachable lining can scarcely be over estimated since it forms by its
non-conducting property the only practicable means for preventing the
chilling or rapid setting, and also the adhering of the molten metal
which would arrest the forward motion of the piston, and preclude any
successful operation. Those acquainted with the nature of refractory
metals know how rapidly they chill and set if they come in contact with
another metal surface, even if said surface is made red hot, and it
requires several minutes time to fill the cylinder and perform the
operation of injecting. This lining serves also to prevent the direct
contact of the fluid metal with the surface of the cylinder, which would
soon spoil the cylinder by the excessive heat of a mass of molten metal,
even if the other aforesaid advantages were not of such great importance.
The nozzle or thimble L (if made of metal) is lined in the same manner
as the cylinder itself. The discharge orifice of the said nozzle is then
stopped with a clay plug or tamp capable of resisting a pressure of six
or eight pounds to the square inch. The office of the plug or tamp
is to prevent the gradual passage of the metal into the moulds. All
being in readiness, and the cylinder J charged with molten metal in
quantity somewhat in excess of the capacity of the moulds to be filled
and placed in proper position, a pressure of from 30 to 60 lbs. to the
square inch, and sometimes more may be applied to the metal by either
a screw, lever, or other means; but experience will soon indicate to the
practical operator the proper amount of pressure for various kinds of
casting. When pressure is applied to the metal the plug will yield and
pass along in the main gate, giving the metal free passage into the
moulds. When the casting is performed and the metal is set the
cylinder is readily detached by breaking the metal in the gate at the
junction of the thimble and the moulds. This ought to be dono
immediately after the casting is done, and before the metal in the gate
has acquired its full strength by cooling off. The remaining head of
metal in the cylinder is casily removed after cooling.

page_text: The operation of the rotary apparatus represented in Figures 1, 2, and 3
may be described as follows:-Any number of the reservoirs J, K, L, may be
prepared for use by coating their inner surfaces, with a suitable non-conduct.
ing paste, and filling them with molten metal, the nozzle L being closed
with a clay plug to prevent the escape of metal. The cylinder J being placed
in the position shewn in the Drawings, the wheel B is set in motion, and
then pressure is applied to the piston K so as to cause a continuous
discharge of molten metal through the nozzle L. The small clay plug or
stopper in the nozzle being driven out with the first discharge of metal
may pass into one of the moulds and cause the production of a single
imperfect casting, but after this a continuous jet of pure molten metal is
kept up. The metal is thus injected and compressed into each mould as
the rapid rotation of the wheel carries it in front of the nozzle. The
guard plate M prevents the escape of any of the metal until it has had
time to become set, and as the bearing rollers G of each mould reach the
shoulders of the recesses the springs I cause the mould plates to
separate instantaneously with a concussion which discharges the casting
from the mould, or if the jar should be insufficient the driving of the pins
finwards through the mould plates insures the detachment of the casting.
The continued rotation of the wheel carries the rollers up the
converging faces of the recesses h until they pass between the parallel
faces of the housings H so as to effect the tight reclosure of the moulds
in readiness for filling. For casting articles of larger weight than a
quarter of a pound the motion of the wheel may preferably be inter-
mittent instead of continuous. Where from the character or size of the
castings to be produced, the particular metal or alloy used therein, or
other circumstances it is found desirable to employ moulds of the clay
composition in connection with the rotary apparatus, as illustrated in
Figure 4, the said composition moulds may be arranged and secured in
the several flasks or mould chambers completely around the periphery
of the wheel before the casting operation begins. The injecting reservoir
J being then charged and set in position and pressure applied to the
piston K a number of large compressed castings may be produced by
a single revolution of the wheel, or in some cases it will be practicable to
employ the composition moulds in continuous or repeated operation in
the manner first described. While selecting to illustrate various parts
of the Invention the preferred styles or types thereof it is not proposed to
restrict it thereto so long as the same results are obtained by means

page_text: substantially equivalent. For an example the pressure of steam or
condensed air may be applied to act on the piston, or steam or
condensed air may even be used to exercise direct pressure on the fluid
metal if the cylinder is in vertical position and the end of the cylinder
closed, although practical experience has proved that the mechanical
pressure is the most reliable and least complicated. It is also proposed
in some cases to use a form of double flask, or a flask with two or more
chambers connected by suitable gates, so that the molten metal may
be placed in one and the moulds in the other or others, so that the
I compression casting" can be performed by forcing the metal out of
the first chamber or the reservoir into the moulds, which are arranged
and secured in the other chambers.
Another modification consists in the employment of a horizontal
reservoir with its discharge aperture at or near the highest part as the
metal need not entirely fill the reservoir; when the piston is retracted
no metal will be discharged until the piston moves, even if the plug or
tamp be dispensed with, but to prevent cooling and oxidation it is
preferable to use the plug in this case also. As a substitute for the
clay plug or tamp a sliding rod or other form of valve may be employed
being adjusted to resist any pressure below a certain degree, and where
the pressure exceeds that degree to yield and open the way between the
reservoir and moulds.
It will be apparent that some of the principal parts of the Invention,
as for example the injecting process and apparatus, the material for t! e
moulds, the manner of securing the moulds within the flask, and the
exhausting process are not in any manner restricted in their use to the
rotary apparatus which has been more particularly described in con-
nection with Figures 1, 2, and 3 of the Drawings, but may be used
equally well with stationary or detached flasks of any description. In
practice it is rarely found necessary to employ the atmospheric ex-
haustion in connection with the compression of the metal, but its use
is found advantageous in cases where it is especially necessary to produco
castings of the most compact and solid character with entire freedom
from blow holes throughout. In these cases it is preferable to use the
stationary rather than the rotary moulds so that the exhaustion may be
effected through a simple pipe conuected to the air-tight chest within
which the flask is enclosed. When the injecting reservoir is placed in
a vertical position the use of a thimble L separate from the reservoir

page_text: J facilitates the removal of the reservoir by slipping it off vertically
when the metal has become set. The superincumbent mass of metal
remaining in the reservoir might render this difficult or impossible
if the lower end of the reservoir itself were contracted or formed with
an inwardly projecting flange or shoulder. If said thimble is made
of iron or other metal it ought to be divided longitudinally into two
parts, so that the same may be readily detached from the metal in the
central gate, and the head left in the cylinder after casting. Continued
practice has proved that the best manner of making said thimble is
to form or make it by pressing moist clay into a suitable mould, and
after forming to burn it hard in the manner that brick or pottery
is burnt, and to use a new thimble at every operation of casting.
Such mineral thimbles are strong enough, cheaply made, and easily
detached by breaking them in pieces after casting. Practical founders
know that if a mould could be used of a material more dense than sand
or sand loam a more perfect and sharp mould could be made, and
there would not be so great liability of the sharp lines of the mould
being washed by the inflowing metal, but they are also aware that if
a mould is made so dense by ramming and stamping, or by the use of
dense material, the gases generated and the air in the moulds will not
be ejected by the mere pressure obtained by the weight of the metal
itself; the consequence is that the metal is blown out of the mould
and the casting is useless. The use of the compression process applied
to refractory metals as above described enables the use of moulds of
great density and of materials which will take a very finc and sharp
impression of the patterns by great pressure applied to the material
formed into moulds. By providing separate injecting vessels for the
reception of the molten metal previous to its introduction into the
mould and having a high pressure to bear on the fluid metal in the very
act of its very rapid filling of the moulds, the elimination of the gases
generated and the air in the moulds is compelled to take place through
very fine pores and the small orifices made at the joints of the moulds,
and as the pressure is kept on the metal until it is well set and solid
such a thing as blowing will never, or very seldom take place, but
the metal is compelled to fill every cavity of the mould, producing a
perfect, sharply defined, and smooth surface.
Moulds made of clay composition in the manner already described are
especially well adapted to be used with this compressing casting
apparatus. Moulds to be used for another more simple method of casting

page_text: metal under pressure, but applicable only to the casting of larger pieces
of one face, are made in the same manner, only it is preferable to use
instead of ordinary clay the clay composition used for black lead
crucibles or for good fire tiles. The only necessary difference in the
manner of forming the mould is as follows:-The iron box or frame is
first filled with clay powder, and the pattern is then placed with face
down. The reason for doing so is that the clay mould is left in the iron
box and the bottom of the box is not removeable, therefore the pattern
must be placed on top of the powder that it may be taken out after the
impression is produced. The iron box or flask used for the clay mould
ought to be of the outside size and shape of the dic or mould to be cast
in metal, and the bottom ought to be provided with a hole or slot for the
purpose presently to be seen. When the pattern is removed the clay
mould is made dry; after drying and while still in the iron box it is
placed in a muffle furnace, and the heat gradually raised until the
mould and iron box are brought to a temperature nearly equal to that
of the metal to be cast in it; while this is done the metal to be used is
melted in another furnace. Then the clay mould is taken out of the
furnace and filled with so much of the fluid metal as is necessary to
make the articles, allowing a small surplus to be acted on by the follower.
The surplus of metal is kept from overflowing by an iron collar or frame
which extends above the clay moulds. When so far filled the follower
is put on top of the fluid metal and then the whole is placed under a
screw or lever press. During the time required to perform the filling
of the mould and placing under the press, the fluid metal becomes
"mushy" or semi-fluid, and if pressure is applied the metal will take a
perfectly sharp impression of the mould. When the whole is cooled off
the casting is removed out of the iron collar or box by driving something
through the hole left for that purpose in the bottom of the box. The
alloys of copper and tin are most favorable for this process of casting,
but it may also be employed for other refractory metals and metal
compositions with good success. The use of clay in this method of
producing moulds for dies and other single faced castings greatly
reduces the care and skill required and the risk of loss involved in
making such castings. In forming metal moulds with metal patterns,
there is great danger of the injury or destruction of the pattern to be
copied by the molten metal adhering to it. It is well known that
moulds have been made of clay when in a plastic state for different
purposes, and also that clay mixed with sand is used for making

page_text: moulds to be used for casting large bells and other heavy bronze and
brass castings so as to give strength to the sand that it may resist the
pressure of a great mass of metal. Now those acquainted with the
art of forming moulds and other things of plastic clay, know that it is
very difficult and almost impossible to press plastic clay into deep
cavities of a pattern, especially if the pattern is made of metal or other
material of great density, because the air will always be more or less
confined in the cavities and prevent the admission of the clay to produce
a sharp and perfect impression. Another disadvantage and that not
the least is that clay used in the plastic kneadable state will shrink. very
much, thereby reducing the size and changing the form of the article to
be moulded, further an article formed or moulded of plastic clay is very
liable to warp and get out of shape by handling, and during the process
of drying. But by using a moist clay powder and forming it into a
compact mass by high pressure, those difficulties are entirely obviated,
by using first a coating of "slip" applied over the pattern with a brush,
the clay is brought into every cavity of the pattern at the commence-
ment. Then the moist clay powder, being first in a loose state, attaining
its strength and hardness gradually by the pressure slowly applied,
permits of the easy escape of the air from the cavities of the pattern and
throughout the whole mass and produces a perfect and sharp impression.
Further, by using moist clay powder, and making it a compact block by
means of high pressure, the mould is, when formed comparatively to a
mould made of plastic clay, in a greatly advanced state of dryness, may
be handled and carried about without getting out of shape, and as it
contains not one-fourth part as much water as plastic clay it is almost
entirely relieved from shrinkage and adapted to retain the shape and
size first given in making. Further, by mixing with fresh new clay
powder one half of powder made of burnt clay the mould is relieved
from liability to warp and crack during the process of drying and
burning. The application of "slip" made of clay as a facing closes the
pores and unites the clay powder into a fine and plastic mass where it
comes in direct contact with the pattern. The "slip" is rendered quickly
plastic by absorbtion of the surplus of water it contains by the com-
paratively dry clay powder in the rear. Now, as the application of slowly
applied pressure is believed to be new in this connection, it is proper to
explain its importance. If an attempt is made to form the loose
moist clay powder into a compact and solid mass, as a good mould
must be by means of stamping and ramming as it is done in the

page_text: ordinary way of moulding, it would naturally take a great deal of labor,
but after removing the pattern the mould would be of insufficient and
unequal compactness and imperfect impression, and further when the
mould was removed from the flask it would not properly hold together in
burning, but fall to pieces as if the mould had been made of a number of
layers of clay. If high pressure should be applied by means of machinery
in a sudden manner, or with a momentum the same results would occur.
But, if pressure is applied slowly and gradually, the loose particles of
the clay powder are gradually and firmly united into a solid compact
mass of uniform density entering perfectly and sharply into every cavity
of the pattern. The labor required to form a mould in the manner
described is but little more than in forming a mould in the ordinary
way of moulding. It is well known that building blocks, bricks, and
other such like articles have been formed of moist clay powder by
means of high pressure, but the application of the principle in the
manner described to the formation of moulds for casting is believed to
effect a result which is new in the art to which it pertains.
Having thus described the nature of the said Invention, and the
mode in which the same may be carried into effect, I would have it
understood that it is not desired to restrict the Invention in any of its
various parts to the precise details herein shown and described, as such
may be varied without departing from the peculiar character of thic
Invention; but what I do claim is,―
First. An injecting vessel or cylinder provided with a piston or
plunger and a detachable lining of nonconducting material employed
in combination with one or a series of moulds for casting metals.
Second. The provision in said cylinder of a temporary closable but
self-opening communication with the moulds, substantially as set forth.
Third. The injecting cylinder J and detachable thimble or nozzle L
employed substantially as described in combination with a mould box
for casting metals under pressure.
Fourth. A series of hinged moulds arranged around a revolving wheel
or cylinder, and adapted for the injection of the fluid metal at the
periphery of the wheel, and the discharge of the castings automatically,
substantially as herein described.

page_text: Fifth. The tapering or thin edged partitions between the gates or
sprues adapted to pass the discharge orifice of the injecting cylinder
without seriously obstruct ing flow of metal.
Sixth. The mouth piece or guard plate L, operating substantially as
described in combination with a series of moulds passing in succession
an injecting vessel for the purpose stated.
Seventh. The combination of one or more separate injecting vessels
having non-conducting detachable linings, with a series of moulds
passing in succession the mouth or opening for the emission of the fluid
metal from the said injecting vessels.
Eighth. The arrangement of a series of moulds having consecutive
orifices or gates, one or more slabs or followers S, set screws T, and
enclosing box U, substantially as described.
Ninth. The combination of an air exhausting apparatus with the
moulds For F, slabs or plates S, and enclosing box U, substantially as
described.
Tenth. A mould formed of moist clay powder under high but slowly
applied pressure for use in casting metals, substantially as described.
In witness whereof, I, the said Benjamin Joseph Barnard Mills,
have hereunto set my hand and scal, this Tenth day of May,
in the year of our Lord One thousand eight hundred and sixty-
nine.