IMPROVEMENTS IN THE MANUFACTURE OF ARTICLES OF INDIA-RUBBER OR OTHER VULCANIZABLE GUM."
Year: 1881

page_text: "
LETTERS PATENT to Benjamin Joseph Barnard Mills, of the Firm of Harris
and Mills, of 23, Southampton Buildings, in the County of Middlesex, Patent
Agent, for an Invention of IMPROVEMENTS IN THE MANUFACTURE OF
ARTICLES OF INDIA-RUBBER OR OTHER VULCANIZABLE GUM." A communi-
cation from abroad by John Joseph Charles Smith and Hermann Gelpcke,
both of College Point, in the County of Queen's, and State of New York, in
the United States of America, India-rubber Manufacturers.
PROVISIONAL SPECIFICATION left by the said Benjamin Joseph Barnard
Mills at the Office of the Commissioners of Patents on the 31st August 1881.
BENJAMIN JOSEPH BARNARD MILLS, of the Firm of Harris and Mills, of 23,
Southampton Buildings, in the County of Middlesex, Patent Agent. "IMPROVE-
MENTS IN THE MANUFACTURE OF ARTICLES OF INDIA RUBBER OR OTHER
VULCANIZABLE GUM." A communication from abroad by John Joseph Charles
Smith and Hermann Gelpcke, both of College Point, in the County of Queen's,
and State of New York, in the United States of America, India Rubber
Manufacturers.
This Invention is applicable to the production of a great variety of articles of
india rubber, both for use and ornament.
Under one mode of carrying out the Invention a sheet of plastic composition
suitable for producing hard rubber by vulcanization is laid on a sheet of tin or
other ductile metal, and covered with tin foil to prevent cohesion to the follower..
The connected sheets are then placed between dies and pressed or struck up to the
required forin. In the case of hollow articles which are formed in two or more
parts a groove is made in the face of each die to produce a ridge of rubber where a
junction is to be made between the faces of the halves or parts when they are sub-
sequently placed together preparatory to vulcanization. Before placing the two
halves or parts together the foil is removed from their inner faces, where: the rubber
surfaces are to come in contact and form a union.

page_text: Where the design is too sharp or delicate to be produced through the medium of
ductile sheet metal inter-posed between the rubber and the die, rigid moulds of soft
metal are made and used in the following manner :-
A suitable alloy is made of sixty-six parts of lead, thirty parts of tin, and four
parts of antimony; this in a molten state is poured over a hard metal pattern
within a flask or curb, preferably made of wood. The molten metal while cooling
is stirred and worked by means of a trowel or paddle until it acquires a mushy
plastic consistency, when it is immediately placed under a press and subjected to
heavy pressure, which forces the plastic metal into all the interstices of the pattern.
When removed the mould is ready for use.
The moulds are heated before being filled, so that the rubber composition may
be rendered more plastic. If there are any very deep depressions in the matris,
fragments of the rubber composition are first pressed into these with the fingers,
carefully expelling all the air. A sheet of the rubber composition is then applied,
beginning at one edge and carefully rubbing and pressing it into all the parts of
the heated matrix, the air being thus driven before it so that none may be confined
beneath the rubber.
The whole face of the half mould is thus covered with a continuous and
impervious sheet of rubber composition, which being rendered very soft and plastic
by heat is pressed into close contact and cohesion with all parts of the matrix and
with the marginal face of the mould around the same.
A pair or set of moulds prepared and supplied with rubber composition in either
of the modes above described are then laid face to face and pressed together
with the necessary force to effect cohesion and union between the meeting surfaces
of rubber. To effect this a simple press is used in the case of the rigid moulds, but
with sheet metal moulds clamp dies are used approximating in shape to the original
dies by which the sheets were formed or struck up, and having straight margins in
parallel planes to bear on the marginal flanges of the sheet metal mould, so as to force
together and unite the corresponding marginal ribs or prominences on the meeting
faces of the rubber, and avoid distorting the object by pressing the moulded sheets
out of shape.
At any convenient point or points which the form and nature of the article may
render most expedient, one or more openings are provided to admit water to the
interior of the object within the mould during vulcanization and permit the free
escape of air displaced by the water. If the form of the article makes it desirable
to have these apertures at the ends, they are provided either by the introduction of
metal tubes or by the formation of corresponding semitubular openings in the half
moulds, in which the rubber composition is laid and pressed continuously from the
inside to the outside and around the margin of the channel in the metal, so that
when the parts of the mould are brought together an unbroken duct will
provided to convey water to the interior without the possibility of it being
admitted to the slightest extent between the rubber composition and the face of
the mould.
In many cases the water duct can with less disfigurement of the finished article
be made in the centre of one or the other face of the mould. For this purpose a
metallic nipple is provided protecting from the face of the mould, so that the rubber
composition may be pressed around it to form a water tight joint, and opening to
the exterior, so as to conduct water to the interior of the object within the mould
without admitting moisture between the material and the face of the mould. A
second small aperture may be provided at what will be the uppermost part of the
mould when in the vulcanizer, so as to allow the free escape of displaced air as the
water flows in, but by locating the main aperture on top, the one opening is made
to serve for the admission of water and escape of air. The moulds require no
clamps or special fastenings to prevent their separation after they have once been
pressed together. The cohesion of the composition and its adhesion to the surfaces
of the mould prevent separation in handling, and while in the vulcanizer the

page_text: external water pressure tends to hold the parts together, as will presently be
described.
The moulds being thus charged and prepared are ready for the vulcanizer. This
is constructed with an interior chamber, which being filled with the charged moulds
is tightly closed with a cover secured against internal pressure, after which water
is forced in through a pipe, expelling the air and developing internal pressure,
which may be 100 lbs. to the square inch, more or less. The rigid moulds are
simply laid one on another as closely as possible so as to economize room.
sheet metal moulds, which are liable to bend out of shape when laid flat, and
especially under a superincumbent weight, are suspended from horizontal rods within
the vulcanizer. The water chamber is surrounded by a steam jacket for producing
the necessary heat for vulcanization.
The
The first effect of the heat is to render the rubber composition exceedingly plastic,
so that by the internal water pressure it is forced into close contact with all parts
of the matrix, and the most delicate and intricate designs are brought out with
sharpness and perfection. It will further appear that while the pressure per square
inch of the water within and around the mould is equal, the superior external
area causes the sum of pressure to be much greater on the outside than on the
inside, and hence the parts of the mould are held together with great force while in
the vulcanizer.
In many cases the shape of the article to be produced renders it necessary or
expedient to form the mould in more than two parts.
The Invention is very well adapted for manufacturing large hollow articles, such
as clock cases, without joints. For this purpose it is preferred to use a rigid mould
made in six or more pieces by pressure casting, as above described.

page_text: SPECIFICATION in pursuance of the conditions of the Letters Patent filed
by the said Benjamin Joseph Barnard Mills in the Great Seal Patent Office
on the 28th February 1882.
BENJAMIN JOSEPH BARNARD MILLS, of the Firm of Harris and Mills, of 23,
Southampton Buildings, in the County of Middlesex, Patent Agent. "IMPROVE-
MENTS IN THE MANUFACTURE OF ARTICLES OF INDIA-RUBBER OR OTHER
VULCANIZABLE GUM." A communication from abroad by John Joseph Charles
Smith and Hermann Gelpeke, both of College Point, in the County of Queen's,
and State of New York, in the United States of America, India-rubber
Manufacturers.
This Invention is applicable to the production of a great variety of articles of
india rubber, both for use and ornament.
Under one mode of carrying out the Invention a sheet of plastic composition
suitable for producing hard rubber by vulcanization is laid on a sheet of tin or
other ductile metal, and covered with tin foil to prevent cohesion to the follower.
The connected sheets are then placed between dies, and pressed or struck up to the
required form. In the case of hollow articles which are formed in two or more.
parts a groove is made in the face of each die to produce a ridge of rubber where a
junction is to be made between the faces of the halves or parts when they are
subsequently placed together preparatory to vulcanization. Before placing the two
halves together the foil is removed from their inner faces where the rubber surfaces
are to come in contact and form a union.
Where the design is too sharp or delicate to be produced through the medium of
ductile sheet metal interposed between the rubber and the die, rigid moulds of soft
metal are made and used in the following manner :-
A suitable alloy is made of sixty six parts of lead, thirty parts of tin, and four
parts of antimony; this in a molten state is poured over a hard metal pattern
within a flask or curb preferably made of wood. The molten metal while cooling
is stirred and worked by means of a trowel or paddle until it acquires a mushy
plastic consistency, when it is immediately placed under a press and subjected to
heavy pressure, which forces the plastic metal into all the interstices of the pattern.
When removed the mould is ready for use.
The moulds are heated before being filled, so that the rubber compositions may
be rendered more plastic. If there are any very deep depressions in the matrix,.
fragments of the rubber composition are first pressed into these with the fingers,
carefully expelling the air. A sheet of the rubber composition is then applied,
beginning at one edge and carefully rubbing and pressing it into all parts of the
heated matrix, the air being thus driven before it so that none may be confined
beneath the rubber. The whole face of the half mould is thus covered with a
continuous and impervious sheet of rubber composition, which being rendered very
soft and plastic by heat is pressed into close contact and cohesion with all parts of
the matrix and with the marginal face of the mould around the same.
A pair or set of moulds prepared and supplied with rubber composition in either
of the modes above described are then laid face to face and pressed together with
the necessary force to effect cohesion and union between the meeting, surfaces of
rubber. To effect this a simple press is used in the case of the rigid moulds, but
with sheet metal moulds clamp dies are used, approximating in shape to the
original dies by which the sheets were formed or struck up, and having straight
margins in parallel planes to bear on the marginal flanges of the sheet metal

page_text: moulds, so as to force together and unite the corresponding marginal ribs or
prominences on the meeting faces of the rubber, and avoid distorting the object by
pressing the moulded sheets out of shape.
At any convenient point or points which the form and nature of the article may.
render most expedient, one or more openings are provided to admit water to the
interior of the object within the mould during vulcanization and permit the free
escape of air displaced by the water. If the form of the article makes it desirable
to have these apertures at the ends, they are provided either by the introduction
of metal tubes or by the formation of corresponding semitubular openings in the
half moulds in which the rubber composition is laid and pressed continuously from
the inside to the outside and around the margin of the channel in the metal, so
that when the parts of the mould are brought together an unbroken duct will be
provided to convey water to the interior without the possibility of its being
admitted to the slightest extent between the rubber composition and the face of
the mould.
In many cases the water duct can with less disfigurement of the finished article
be made in the centre of one or the other face of the mould. For this purpose a
metallic nipple is provided projecting from the face of the mould, so that the
rubber composition may be pressed around it to form a water-tight joint, and
opening to the exterior, so as to conduct water to the interior of the object within
the mould without admitting moisture between the material and the face of the
mould. A second small aperture may be provided at what will be the uppermost
part of the mould when in the vulcanizer, so as to allow the free escape of displaced
air as the water flows in, but by locating the main aperture on top the one opening
is made to serve for the admission of water and escape of air. The moulds require
no clamps or special fastenings to prevent their separation after they have onco
been pressed together. The cohesion of the composition and its adhesion to the
surfaces of the mould prevent separation in handling, and while in the vulcanizer
the external water pressure tends to hold the parts together, as will presently be
described. The moulds being thus charged and prepared are ready for the
vulcanizer. This is constructed with an interior chamber, which being filled with
the charged moulds is tightly closed with a cover secured against internal pressure,
after which water is forced in through a pipe, expelling the air and developing
internal pressure, which may be 100 lbs. to the square inch, more or less. The
rigid moulds are simply laid one on another as closely as possible, so as to
economize room.
The sheet metal moulds, which are liable to bend out of shape when laid flat,
and especially under a superincumbent weight, are suspended from horizontal rods
within the vulcanizer. The water chamber is surrounded by a steam jacket for
producing the necessary heat for vulcanization.
The first effect of the heat is to render the rubber composition exceedingly plastic,
so that by the internal water pressure it is forced into close contact with all parts
of the matrix, and the most delicate and intricate designs are brought out with
sharpness and perfection.
It will further appear that while the pressure per square inch of the water within
and around the mould is equal, the superior external area causes the sum of pressure
to be much greater on the outside than on the inside, and hence the parts of the
mould are held together with great force while in the vulcanizer.
In many cases the shape of the article to be produced renders it necessary or
expedient to form the mould in more than two parts.
The Invention is very well adapted for manufacturing large hollow articles, such
as clock cases, without joints. For this purpose it is preferred to use a rigid mould
made in six or more pieces by pressure casting, as above described.
And in order that the said Invention may be more clearly understood and readily
carried into effect. I will proceed, aided by the accompanying Drawings, more fully.
to describe the same.

page_text: DESCRIPTION OF THE DRAWINGS.
Figure 1 represents a sheet of tin, a sheet of raw rubber composition, and a tin
foil covering in juxta position, adapted for introduction between dies, by which
they are pressed into the necessary shape to form a half or other part of any desired
hollow article, one half of the tin foil sheet being removed to expose the subjacent
rubber and metal sheets; Figure 2 is a longitudinal section showing the said sheets
between dies and pressed into shape to constitute one half of a hollow brush body;
Figure 3 is a face view of the front and back portions of the brush body formed
between dies, after the manner represented in Figure 2, and prepared to be placed
together for vulcanizing; Figure 4 is a longitudinal section showing the parts
placed between a pair of clamp dies suitably formed to press the meeting surfaces
together and cause them to cohere while preserving the shape of the hollow body;
Figure 5 is a transverse section of the same showing the clamp-dies closed and the
hollow body compressed between them; Figures 6 and 7 are respectively a longi-
tudinal and a transverse section of a rigid two-part vulcanizing mould adapted for
forming hair brush bodies; Figures 8 and 9 are respectively a longitudinal and a
transverse section of a four-part vulcanizing mould adapted for making brush
bodies of another kind; Figures 10, 11, and 12 are respectively a horizontal
section and longitudinal and transverse vertical sections of a six part vulcanizing
nould adapted for forming a clock case; Figures 13 and 14 are respectively
longitudinal and transverse vertical sections of the vulcanizer charged, closed, and
filled.
Referring to Figures 1 and 2, 1 represents a sheet of plastic composition adapted
for the production of hard rubber by vulcanization; 2 represents a sheet of block
tin or other ductile metal, to which the sheet 1 of rubber composition is applied
preparatory to placing them between forming dies; 3 represents a sheet of tin foil
or other very thin metal, which in practice covers the exposed face of the sheet 1 of
rubber composition to prevent its cohesion to the face of the die follower, with which
it would otherwise come in contact.
The metallic sheet 2 serves to receive the required form, together with the rubber,
and to retain the said form, preventing the distortion of the body of plastic rubber
after removal from the dies; said sheet 2 thus constitutes, after pressure between
the dies 4, 5, as represented in Figure 2, a mould of such shape as it has acquired
from the said-dies-
The two halves of a brush body thus formed are shown in Figure 3, the tin
foil 3 being removed from such portions of the rubber surfaces as are to come
together.
The parts being thus prepared are laid together face to face, as shown in
Figure 4, and placed between clamp dies 6, 7, connected by hinges 8, and provided
with handles 9, 9, for opening and closing them. The clamp dies 6, 7, are formed
on their inner faces to correspond with the moulds which are shaped between the
dies 4, 5, as already described with reference to Figures 2 and 3, and in the present
illustration are made to constitute the front and back portions of a hollow brush
body. The dies 6, 7, being closed are pressed together with any necessary force
to unite the rubber surfaces by a press of common construction; 10, 10, represent
apertures or tubes for the admission of water to the interior of the hollow articles
within the mould, and the escape of displaced air therefrom.
Referring to Figures 6 and 7; 11, 12, represent the respective members of
a rigid two-part mould within which hollow articles are formed preparatory to
vulcanization.
Prior to the filling of these moulds the moulds and the rubber composition are
both heated in order to make the composition more soft and plastic, and permit
the pressing of it into all the cavities of the mould. If there be any deep depres-
sions or undercut cavities or intricate designs of any kind, these are first carefully

page_text: filled with fragments of the plastic composition pressed in with the fingers so as to
completely expel the air, after which the entire face of the mould is covered with.
a sheet of rubber, as shown at 1c, which is laid thereon with great care, beginning
at one edge and pressing it closely in with the fingers so as to drive all the air
before it until the other edge of the mould is reached. The face of the mould is
thus completely covered with a continuous and impervious sheet of rubber com-
position in close contact with all parts of the matrix without any air between.
The rubber is carried above the margin of the matrix all round, as shown at 1.
The two parts of the mould thus prepared are laid face to face and pressed together,
the projecting edges 1d of the rubber composition coming together and forming a
perfect union, so that the hollow rubber body thus formed will confine the water
which is forced into its cavity preparatory to vulcanization, and prevent the
entrance of any water between the rubber and the face of the mould. An inwardly
projecting nipple to admit water to the interior of the hollow article is shown
at 12. Around this the plastic rubber is carefully pressed so as to form a perfectly
water tight joint. The parts being then placed and pressed together, the charged
mould is ready for the vulcanizer, which will be hereinafter described; 11° represent
projections on the face of the mould cap to produce depressions in the face of the
brush body to indicate where it is to be drilled for the reception of bristles.
In many instances the shape of the article to be produced renders it impracticable
to form it within a rigid mould of two parts, as illustrated in Figures 6 and 7.
In such case the mould is made in four or more parts, as circumstances may
require Figures 8 and 9 illustrate the application of the Invention to the making
of brush bodies having deep cavities in their sides to receive the fingers. The
form shown in this illustration is especially intended for a flesh brush, but is well
adapted for many kinds of brushes to be grasped by the hand; 13 represents the
base of the mould, the interior surface of which is formed and adapted to impart
any desired shape and ornamentation to the back of the brush. On the base are
formed end pieces 13º, and to it are applied side pieces 14, 14, made separable to
permit the removal of the finished hard rubber article from the mould, said side.
pieces being provided with inwardly projecting ridges 14ª for the purpose of
producing cavities in the sides of the brush to afford an effective hold to the fingers
and thumb of the user. The side pieces 14 are connected to the base 13 by
dowels 14b.
15 represents the cap of the mould, the inner surface of which forms the face of
the brush body, said surface having, as in the other illustrations, small projec-
tions 11ª properly arranged to produce depressions in the face of the brush body
to indicate where it is to be drilled to receive the tufts of bristles. In the centre.
of the cap.15 is applied the nipple 12ª to admit water to the interior preparatory to
and during vulcanization. The cap 15 is held in proper position on the base by
dowels 15. This mould is shown empty for clearness of representation, but the
manner of filling it will be clearly understood from the description above given
with reference to the moulds 11, 12. The base 13 and side pieces 14, 14, being:
placed together and properly heated, a sheet of plastic rubber composition in a
warm state is laid over the ornamented surface of the base, beginning with one
side and carefully pressing out the air before it with the fingers, as before described,
and the warm plastic composition is in like manner pressed carefully into the
cavities beneath the projecting ridges 14ª of the side pieces, and around the said-
ridges as well as around the interior faces of the end pieces of the base until the
entire base and sides of the mould are completely covered with the composition
which has been pressed into close contact with all parts of the surface, and is carried
up completely to the upper part of the base all around. The inner surface of the
cap 15 of the mould is then in like manner covered with plastic rubber, which is
pressed thoroughly over all parts of the interior surface of the heated mould cap,
and closely around the nipple 12", so as to prevent any passage of water around
said nipple beneath the rubber..
The rubber composition is also brought up to the margin of the cavity in the.

page_text: mould cap, so as to present all around a projecting edge ready to unite with
the projecting margin of the filling of the base of the mould when the parts are
brought together.
The cap being then placed on the base and pressed down forms a perfect union,
any necessary pressure being applied for this purpose.
The charged mould is then ready for the vulcanizer.
The Invention is of great value and importance for the moulding of hollow
rubber articles of large size in solid metal moulds under the application of internal
water pressure.
For the purpose of illustrating this application of the Invention a mould for clock
cases is shown in Figures 10, 11, 12, the said moulds being in practice 18 or 20
inches long, or of any desirable size; one of the merits of the present Invention
being that its use is not limited to articles of small size.
16 represents the front of the mould, the interior surfaces of which are made
with any desired configuration and ornamentation. The ends 17, 17, are connected
with the front by mitre joints, and firmly secured thereto by bolts 18, 18, the said
end plates being formed in correspondence with the front or in any suitable way,
and ornamented as desired.
The ornamental or irregular parts of the mould being connected together are
covered with the plastic rubber composition; the mould and composition being
hented as before explained, and the mode of applying the rubber to the mould
being substantially similar. Great care is always necessary to press the rubber
into close contact with all parts of the surface and expel all air from beneath it.
The intelligent and skilled operator will readily understand from the character
and shape of each mould where and in what manner it is necessary to apply the
first fragments of rubber, and subsequently the continuous sheets, so as to perfectly
exclude all air from between the rubber and the surface of the mould. The
coating or charging of the mould being thus accomplished, the rubber composition
will be in one continuous body all over the surface, and the mould is ready for the
application of the top, bottom, and back plates 19, 20, 21. These being covered
with sheet rubber composition which adheres to all the surfaces, are pressed into
place and secured by screws 22. Nipples to admit water to the interior of the
hollow body and permit the escape of the displaced air are shown at 120, 12º, as
before.
A vulcanizing vessel such-as-is-used-in-carrying out this Invention is illustrated
in Figures 13 and 14. It is constructed with an interior water chamber 23,
the walls 24 and bottom 24ª of which are completely surrounded by a steam
jacket 25.
26 represents a pipe admitting water to the interior chamber 23, and 26ª a pipe
for the escape of displaced air.
These pipes are provided with stop cocks 27, 27ª, and the pipe 26 is connected
with a force pump 28 for producing water pressure within the chamber 23. 29 is
a pipe for admitting steam to the steam space 25, said pipe being governed by a
stop cock 30.
31 represents the cap or cover which is secured to the body of the vulcanizer by
bolts 32, adapted to sustain the heavy internal pressure applied to the water in the
chamber 23. Within the cover 31 is a steam space 33, connected by a duct 34 with
the main steam space 25 surrounding the vulcanizing chamber.
In operation the various moulds having been charged with rubber composition
in any of the modes hereinbefore described, are placed in the vulcanizing
chamber 23, the rigid moulds being stacked compactly in the bottom of the
vulcanizing chamber to any necessary height, as shown at 35, 35. The moulds
which are formed of ductile.metal plates as described with reference to Figures 1, 2,
and 3 are suspended within the chamber, as shown at 36, by means of rods 37,
and suitable hooks 38; a simple aperture 38a formed in one end of the mould
plate 2, Figures 1 and 3, affording convenient means of suspension from said.
hooks,

page_text: The vulcanizing chamber being thus completely stocked with material may be
filled with water through the pipe 26, either before or after the application of the
cap or cover 31.
The nipples 12 already described being carefully placed uppermost in all the
moulds, the water will pass freely within the hollow articles in said moulds, and
all the contained air being displaced by such water will escape therefrom, all the
air passing out of the vulcanizing chamber 23 as the latter fills with water.
The cover 31 being secured in position, a water pressure of 100 lbs. to the square
inch, more or less, is produced within the vulcanizing chamber 23 by means of the
force pump 28, and this pressure acting on the exterior surface of all the moulds
holds them together with great force, while at the same time the pressure of the
water in the interior of the hollow body forces the material into close and intimate
contact with all parts of the interior surfaces of the mould.
The cock 27 being closed to confine the water within the vulcanizing chamber,
steam is introduced to the surrounding space 25 and the top space 33 in the cover
through the pipe 29, and duct 34. The heat from the steam is quickly conducted
through the water and the metal moulds within the vulcanizing chamber. The
requisite heat for vulcanization is thus developed and is maintained for the
requisite time to produce hard rubber. It will be apparent that the first effect of
the heat is to soften the rubber composition within the moulds, and by expansion
of the water to press the material with still greater force in contact with the mould
surfaces, the result of which is a very sharp and perfect reproduction of the most
intricate and elaborate designs, and this pressure is maintained until vulcanization
is completed.
39 is a pipe for taking water of condensation from the steam space 25. The end
of the said pipe is closed by a valve 40.
It is well known that hollow articles (generally of small size) have been
vulcanized by filling the interior with water, plugging it up, and then placing the
mould under water, the surface of which is exposed directly to the steam employed
to produce heat and pressure within the vulcanizer. This mode has been found
uncertain in its results, because the steam afforded only an elastic and variable
external pressure, and the internal pressure produced by simply heating the
confined body of water contained in the hollow article within the mould was not
sufficient to force the material into sufficiently close contact with all parts of the
matrix. Hence it was impossible to produce delicate and elaborate designs with
sharpness and perfection, but this result is effectually attained by the improved
mode now devised, in which water is forced under a heavy initial pressure into the
vulcanizing chamber, both around and within the hollow articles, completely filling
the vulcanizer, and being confined without contact of air or steam (which forms an
elastic cushion), the pressure being increased by the heat requisite for vulcanization,
which heat is applied by steam acting not on the surface of the water, but through
the iron walls of the interior vulcanizing chamber.
The present Invention will thus be seen to constitute an important improvement
on what has gone before in the manufacture of hollow articles of hard rubber.
The Invention is also clearly distinguished from a mode heretofore devised of
vulcanizing hollow articles in soft rubber under both internal and external pressure,
inasmuch as the plastic and cohesive nature of the hard rubber composition,
especially when hot, adapts the meeting surfaces to cohere and form a perfect
union, and exclude water from between the material and the face of the mould
without requiring an external sack or envelope to exclude water, or clamps to hold
the parts of the mould together.
It is also well known that solid articles have been moulded by covering the body
of composition on both sides with sheet metal, and compressing between dies. An
important distinction in the present improvement consists in the stamping or
pressing of the respective halves or parts of hollow articles between foil and sheet
inetal, removing the foil from the inner face so far as necessary, pressing the two

page_text: inner faces together so as to cause the rubber surfaces to unite, and then
vulcanizing under pressure.
Having thus described the nature of the said Invention, and the mode in which
the same is carried into effect, I would have it understood that what I claim is,―
First. The process of making hollow articles of rubber or other vulcanizable gum
by pressing the separate halves or parts in suitable moulds or dies between sheet
metal and foil, then removing the foil from surfaces which are to be joined together,
uniting the parts under pressure, and vulcanizing the hollow articles in water
under pressure, the water being admitted to the interior to prevent collapsing.
Second. The process of forming hollow articles of rubber or other vulcanizable
gum which consists in pressing plastic rubber composition into the parts of the
mould while they are in a heated state, placing them together so as to cause
cohesion between the margins of the rubber in the respective parts of the mould,
and then vulcanizing under water pressure admitted to the interior of the article as
well as to the outside of the mould.
Third. The process of vulcanizing articles of rubber or other vulcanizable gum
which consists in placing them together with their moulds in a tightly closed vessel,
completely filling said vessel with water under pressure, and subjecting the whole
to the necessary degree of heat for a proper length of time.
In witness whereof, I, the said Benjamin Joseph Barnard Mills, have hereunto
set my hand and seal, this Twenty seventh day of February, in the year
of our Lord One thousand eight hundred and eighty two.