Improvements in Mills for Mixing India-rubber and other like Materials.
Year: 1894

page_text: Date of Application, 4th Dec., 1894-Accepted, 5th Jan., 1895
COMPLETE SPECIFICATION.
Improvements in Mills for Mixing India-rubber and other like
Materials.
A communication from abroad by JOSEPH EDWIN DAVIS, Treasurer, of
34, Baltimore Street, Lynn, in the State of Massachusetts, one of the United
States of America.
I ALFRED George Brookes of 55 and 56 Chancery Lane, in the County of
London, Chartered Patent Agent 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 :—
Mixing mills for rubber, and like material, as commonly constructed, contain two
cylindrical rolls driven in opposite directions, one at a speed considerably in excess
of the other, said rolls being rotated usually at speeds respectively of about eight
and fifteen rotations per minute.
The crude rubber is passed between these rolls, it clinging to the slow one, the
foreign substance or compound with which the rubber is to be mixed being
deposited between the rolls or upon the rubber clinging to the slow roll and
thereby thoroughly worked into and mixed with the rubber.
It is impossible for all of the compound to be taken up at once, and it is therefore
customary to provide an endless travelling apron to catch such portion or portions
of the compound as may escape unmixed from between the rolls and return the
same again to the top of the mill to be again passed one or more times between the
rolls, this operation being repeated until all of the compound is thoroughly worked
into or mixed with the rubber.
The endless carrier or apron which catches and returns the compound, as
described, usually travels upon three rollers, two of which are stationary while the
third is carried by a yoke pivoted in the frame of the machine, and held by hooks,
cords or other inflexible fastening devices in proper position to cause the apron to
hug one of the rolls, the fastening devices being released when necessary to permit
the said yoke and movable roller to be thrown down away from the rolls in order
that the rubber thereon may be removed.
Again it has been customary to so mount this endless carrier or apron that it
runs in contact with the faster of the two rolls, the rubber and compound as before
stated clinging to the slower roll.
This invention has for its object to improve mills of the class above described,
whereby the capacity of the mill and the thoroughness of the mixture of the
compound with the pure rubber are increased, and the operation and control of the
mill made more convenient and simple.
The invention therefore consists, first, in supporting the endless apron so that it
runs in contact and co-operation with the slow roll instead of the fast one, to
thereby obtain a more thorough mixture of the compound as will be hereinafter
described.
The invention also consists in pivoting the roller carrier by which the endless
apron is thrown against the roll in such manner that when in its position against
said roll, it stands at one side its dead centre, whereby the tension alone of the
apron is sufficient to automatically retain the said carrier in such position.
One of the other rollers, about which the said apron passes, is made to yield by
means of suitable springs, to enable the said carrier and its roller to be moved from
one to another of its positions past the intermediate dead centre and to exert the

page_text: proper tension upon the apron to retain the carrier in its position against the rolls
as described; also to permit the apron to adjust itself to the increasing diameter of
the layer of rubber or material upon the roll as the said layer thickens by
introduction of the foreign substance or compound.
The invention also comprehends various details of construction to be more fully
hereinafter described and set forth in the claims, one of which consists in
providing brushes to sweep or brush the compound from the endless apron upon
the mixing roll, and another in providing the apron with a rib running in suitable
annular grooves in the rollers, to prevent the apron creeping laterally in either
direction.
In the drawings
Fig. 1 represents, in end view, partially broken away, one form of rubber mixing
mill embodying the invention.
Fig. 2, a vertical section of the same taken on the dotted line -;
Fig. 3, a perspective detail shewing the rib upon the apron.
Figs. 4 and 44 sectional detail and partial top views respectively, shewing the
preferred construction of the brushes for cleaning the apron;
Fig. 5, a cross sectional detail shewing one of the boxes for the yielding
roller;
Fig. 5, a detail shewing top of one of the guides H, and
Figs. 6, 7, 8, and 9, diagrams illustrating the action of the apron runting on the
slow roll, to be referred to.
Referring to the drawings, in the embodiment of my invention there shewn,
A, A, represent two end frames of the mill, which may be of suitable shape and
construction to sustain the working parts.
The frames A, A, are provided with suitable horizontal guideways to receive the
boxes a, a, for the journals of the main rolls B and B', cylindrical in shape and of
any suitable or desired construction, they being provided with suitable means for
cooling, which not constituting an essential part of this invention, is neither shewn
nor described.
The journal boxes for the roll B are shewn as stationary, while the boxes for the
roll B' are made to slide in the horizontal guideways referred to and maintained in
adjusted position, by the usual set screws a¹, a¹.
In Fig. 1 s represents a main driving shaft provided with a spur wheel s¹ in mesh
with and driving the larger spur wheel 2, shewn as fast upon one of the end
journals of the roll B, the two rolls being geared together at the opposite end of the
machine by spur wheels and s', shewn in dotted lines Fig. 2, and of such relative
diameters that the speed of rotation of the roll B shall be preferably about double
that of the roll B', the relative speeds of the two rolls in usual practice being
fifteen rotations per minute for the roll B and eight for the roll B'.
It is evident, however, that the relative speed of rotation of the two rolls may be
varied to meet the various requirements, and that any suitable driving mechanism
other than that herein shewn may, so far as this invention is concerned, be
employed.
In accordance with one part of this present invention, there is provided an endless
apron C, the same being passed about three rollers c, c', and c², the roller e being
mounted in suitable fixed bearings on the front of the frame, as shewn.
The roller c', as herein shewn, is mounted in suitable journal boxes c', shewn in
dotted lines Fig. 2, the said boxes being fitted to slide on suitable guide ribs c³,
see Fig. 5. formed upon brackets bolted or otherwise secured to the rear of the
end frames, said boxes being drawn rearwardly by means of suitable springs, shewn
as close-coiled springs connected at one of their ends to the said boxes, and
at their opposite ends to the blocks cx threaded to receive the screws es loosely
mounted in suitable bearings on the said brackets and provided with prope:
means for adjustment shewn as hand wheels c¹0.
The roller c is journaled at its opposite ends in the side arms d of a yoke D, said
aide arms as herein shewn being provided at their lower ends with roller or other

page_text: suitable studs shewn in dotted lines Fig. 2, which enter and are adapted to move
in the elliptical or cam-shaped openings e in the cam plates e' at either end of the
machine and bolted or otherwise secured to the inner adjacent faces of the end
frames.
The top bar d of the yoke D is shewn as a substantially semi-cylindrical
member, bolted or otherwise secured at its ends to the inturned upper ends d³ of the
side arms d, said top bar being provided with conveniently located handles d' shewn
as arranged comparatively near each other, in practice about eighteen inches
apart, instead of being arranged at the extreme ends of the yoke as in the usual
practice.
In the full line position Fig. 2, it will be seen that the movable roller c² is thrown
to the left past the dead centre line drawn vertically through the fulcrum d¹,
the tension of the apron created by the springs at the rear of the machine acting
to retain the said roller and its yoke in the position shewn with the apron in close
contact with the roll B1 without the use of any fastening devices to retain said yoke
in such position.
When, however, it is necessary to throw the yoke down and away from the
roll B1 for any purpose, the operator grasps the handles d' and draws the yoke to
the right Fig. 2 about d' as a fulcrum, the said fulcrum at the same time sliding
along in the cam openings e into its dotted position, to enable the said roller c² to
more readily pass the dead centre point, the tension upon the apron and gravity
thereafter operating to throw the said roller and its yoke away from the roll B' and
down into its dotted position Fig. 2.
The springs which permit the yielding roller c¹ to slide bodily toward the front
of the machine, enable the apron to also move toward the front of the machine in
order that the roller c³ may rise and pass the dead centre line, which would
be impossible if both rollers c and c¹ were fixed, without straining the apron.
The movement of the apron bodily toward the front of the machine and the
sliding movement of the roller c¹ is reduced to a minimum by providing the sliding
fulcrum d for the yoke D, for were the said fulcrum fixed, said yoke in swinging
about said fulcrum from one to another side of its dead centre line would take up
and require a much greater length of apron.
The apron C is preferably of a width equal to the length of the rolls B, B', and
is provided in the present instance with a single longitudinal rib c¹, which runs in
grooves c2 in the rollers c, c', and c², which prevent the apron creeping in either
direction, although more than one rib may be employed if desired.
To brush any compound from the apron and to keep the latter always clean,
the top bar d² of the yoke D is provided with one or more, preferably a series of,
independent brushes as E, see Fig. 4 which bear upon the apron as the latter
moves through the yoke said brushes E being acted upon and pressed against the
apron by means of suitable springs as e² I have herein shewn two such springs
for each brush, the euds of adjacent brushes being overlapped as at e Fig. 4ª to
thereby break joints and present as it were a single continuous brush.
H, H, represent lateral guide plates shaped to enter between the rolls at the
top of the mill to prevent the rubber working out at the ends of the machine.
As herein shewn and preferably, the guides H, H, are each fitted to and adapted
to slide vertically in suitable brackets h, h, bolted or otherwise secured to the end
frames, said brackets being provided with adjusting screws h', by which to effect
vertical adjustment of said guides.
To prevent the compound working off the ends the roll B', said rolls are
provided with end collars b, said collars as herein shewn, being formed in segments
preferably two in number bolted together by bolts & shewn in dotted lines Fig. 2,
embracing the end of the roll.
M represents a table arranged beneath the machine to catch and support the
endless apron when the latter is slackened by throwing back of the yoke.
The operation of the mill is as follows
The screws a' are first slackened, to permit the rolls B and B₁ to separate

page_text: sufficiently to draw in the crude rubber deposited in lumps or large pieces in
the space between the rolls from the top, said rubber being drawn between the
rolls and worked into a sleeve or layer surrounding and hugging the slow roll B',
as shewn by the heavy black line Fig. 6.
During this time the yoke D is maintained in its dotted position Fig. 2 with the
apron removed from the roll.
After the rubber has been rolled into a proper layer about the rolls B', and the
rolls pressed together by means of the screws a¹ until the said layer or sleeve of
rubber is of suitable thickness, the operator throws the yoke into its full line
position Fig. 2, in which position it is automatically held, without fastening
devices, by the springs, with the endless apron C in contact with the rubber
layer or sleeve surrounding the rotating roll B' the said apron being thereby
caused to travel in the same direction as said roll, see arrows Fig. 2.
The compound or foreign substance or material with which the rubber is to be
mixed is then thrown in between the oppositely rotating rolls and is more or less
worked into the rubber at the pinch between the rolls, the excess of compound
which cannot be taken up at once, working or dropping through upon the
travelling apron C beneath, which carries it around in contact with the layer of
rubber upon the roll, and again deposits it upon the top of the said roll, to be passed
once more between the rolls and worked into the rubber, this operation being
repeated until all of the compound is thoroughly worked into the rubber.
The brushes E act to brush all the compound carried up by the endless apron
off onto the rubber coated roll.
As the compound is worked into the rubber, the space between the rolls remaining
fixed, the coating or sleeve surrounding the roll B' is necessarily lengthened,
owing to the additional material incorporated with it during the mixing operation,
the said sleeve so lengthened tending to droop or sag away from the roll at the
underside.
The travelling apron, however, being in contact with the sagging sleeve of
rubber takes the sag or slack along with it to the upper side of the roll as in
Fig. 7, when it is lapped over upon itself as shewn in Fig. 8, so that it passes
through the pinch between the rolls in three thicknesses instead of one as in
machines as now constructed, the three thicknesses being thoroughly worked
together into a single thickness.
This folding and doubling operation takes place at each two or three rotations
of the roll B', according to the quantity of compound worked into the rubber and
the rapidity with which it is incorporated therewith, dependent more or less
upon the separation of the rolls, said folding or doubling operation, due solely to
running the endless apron on the slow roll B' to which the rubber adheres, being
of the utmost importance as it enables the compound to be worked into the rubber
in much less time than has hitherto been possible.
This is for the reason that when the compound is rolled upon the rubber it
mixes with the latter at first only for a short depth in from the outer face of the
rubber, that portion of the rubber next the roll receiving at first little or none of
the compound.
As the outer surface of the rubber layer becomes more or less filled with the
compound at the very first, decreasing its richness, its ability to take compound
correspondingly lessens, rendering it more difficult for the rolls to force the
compound thereafter through to the inner and richer portions of the said layer;
but by folding over or doubling the layer every few rotations of the roll, as in
the present invention, the richer outer portions of the rubber layer which
receive at first little or none of the compound, are interposed between and worked
into adjacent faces of the layer which have at first received the compound, the latter
being thereby introduced at different lines in the thickness of the layer and more
thoroughly and quickly incorporated therewith.
This is illustrated in Fig. 9 where the heavily shaded portions of the rubber
layer represent the portions which have received the compound, the lighter

page_text: shaded portions representing the pure or rich rubber which has yet to receive the
compound.
It will be seen from this figure that by the folding operation described the rich
portions are interposed between portions which have already received compound,
thereby making it possible to more thoroughly distribute the compound through the
entire thickness of the layer.
In practice it is found that by running the apron on the slow roll, the compound
may be incorporated with the rubber in at least one quarter less time than when the
apron is run on the fast roll.
The spring e permits the apron to move towards and from the peripheral surface
of the roll B' according as the rubber layer thereon is of greater or less thickness,
thereby avoiding injury to the apron usually caused by stretching of the same
beyond its normal length.
This invention is not restricted to the particular construction of mill herein used
to illustrate this invention; nor is the invention otherwise restricted to the particular
construction and arrangement of parts shewn, for while I consider the construction
shewn an excellent one, yet the same may be varied more or less without departing
from the spirit and scope of the invention.
Having now particularly described and ascertained the nature of the said inven-
tion, and in what manner the same is to be performed, I declare that what I
claim is :-
1. In a mixing mill for rubber and like material, the use of two rolls, and means
to rotate the same in opposite directions, one at a higher speed than the other
whereby the material adheres to the latter, and an endless apron moving in contact
with and in the same direction as the slow moving roll or the material thereon to
act upon said material, substantially as described.
2. In a mixing mill for rubber and the like the use of two rolls, and means
to rotate the same, and an endless apron and movable and yielding rollers
over which said apron is passed, the former movable towards and from one of
said rolls and the latter yielding to permit such movement, substantially as
described.
3. In a mixing mill for rubber and like material the use of two rolls, and means
to rotate the same, and an endless apron adapted to travel in contact with one of
said rolls or the layer of material thereupon, and two or more rollers over which
said apron travels, and springs to retain one of said rollers in normal position
whereby said roller may yield to accommodate changes in position of said apron,
substantially as described.
4. In a mixing mill for rubber and the like, the use of two rolls and means to
rotate the same, and an endless apron; a yoke; a cam opening in which the fulcrum
thereof is movable; a roller carried by said yoke and over which said apron is
passed; and a yielding roller also for said apron whereby the said apron is enabled
to change its position to permit said yoke to be moved from one to another side of
its dead centre line, substantially as described.
5. In a mixing mill for rubber and the like, a frame; two rolls and means
to rotate the same, and an endless apron; a pivoted yoke; a roller carried
thereby, and a roller on said frame, over which said apron is passed; and one or
more brushes on and movable with said yoke to sweep said apron, substantially as
described.
Dated the 1st day of December 1894
WM. BROOKES & SON,
55 & 56, Chancery Lane, London, Agents for the Applicant.