Cylinder for rubber mixing mill

Cylinder for rubber mixing mill, consisting of a hollow cylinder 1 and two flange-journals 2, 3 and driven by a hydraulic motor 21 with a hollow shaft. The hollow cylinder has longitudinal channels 4 provided with solid rods 8 fastened in the two flanges. The temperature regulation of the cylinder is provided by a crossed dual circuit. The temperature regulating fluid circulates in longitudinal channels 4 then cools the inner wall 19 of the hollow cylinder before being evacuated along the axis of the cylinder.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention relates to machines that are used in the making of rubber 
mixtures. 
2. Description of the Related Art 
Most of the raw materials used in the rubber industry are solids which 
exhibit very irregular physical properties (balls of latex, isoprene 
plates, pellets of additives, powdered carbon black) and their unit 
masses, for example, vary from about a hundred kilograms to a few 
micrograms. Before being able to shape these products with accuracy, it is 
necessary to mix them thoroughly and make them plastic. These operations 
are successively performed in mixing mills of two types: (1) internal 
mixers which are closed and where two rotors having complementary shapes 
mix the rubbers and their fillers (such as carbon black); and (2) roller 
mixing mills consisting of rotating cylinders with parallel axes, between 
which the mixtures of products are made to pass several times in 
succession to homogenize them and change their physical properties 
(rheology, elasticity, etc.). 
When the mixtures get to roller mixing mills, they must be rapidly cooled. 
Further, the material temperature must be regulated during the 
homogenization process. 
The cylinders of current roller mixing mills are bulky parts which, with or 
without a central channel, can weigh 7 tons. Their length including 
journals exceeds 2 meters, and their diameter is on the order of 700 mm. 
The cylinders have numerous longitudinal channels (parallel to the 
cylinder axis) drilled from end to end and connected at their ends (see 
for example patent DE 23 15 669) to make possible a circulation of the 
temperature regulating liquid from one of the journals. 
SUMMARY OF THE INVENTION 
This invention has as an object to provide a rubber mixing mill cylinder 
that makes it possible to considerably improve the heat exchanges between 
said mixing mill cylinder and the mixtures, and also improve its 
mechanical strength. 
For such a cylinder, this invention proposes a temperature regulating 
circuit which comprises longitudinal channels distributed regularly near 
the outside surface of the cylinder, in which the heat exchanging liquid 
circulates. At least some of the longitudinal channels are provided with 
solid rods to convert their sections for flow of the liquid into annular 
sections. 
Another aspect of the invention relates to a rubber mixing mill cylinder 
consisting of at least three parts, a hollow cylinder and two 
flange-journals, wherein the hollow cylinder and the flange-journals are 
assembled by the rods fastened at each end in a flange-journal, in which 
the rods pass through the flange-journals and hollow cylinder in at least 
some of the longitudinal channels that are also used for the circulation 
of the heat exchanging liquid for thermal regulation. 
The fastening of the rods is performed preferably by two nuts screwed onto 
each rod end after having heated the rod to a temperature higher than the 
maximum expected temperature reached during the operation of the mixing 
mill. 
The role of the hot-mounted rods in the longitudinal channels is thus 
twofold: on the one hand, they convert a circular channel section into an 
annular section--which is very favorable for heat exchange since it 
increases the circulation speed at the same flow rate and promotes the 
change of type of flow--, and on the other hand, due to their thermal 
contraction, they act as braces between the two flanges and over the 
entire periphery of the hollow cylinder, which causes an axial compressive 
prestressing of the hollow cylinder and considerably increases its 
stability. 
Another advantage of the invention is that it makes it possible to make 
only the two flange-journals of forged steel having excellent mechanical 
strength, while using molded cast iron for the actual cylinder which is 
stressed principally in radial compression. 
The invention also permits considerable savings in weight. The cylinder has 
a weight on the order of 12 tons whereas a solid cylinder of equivalent 
geometry would have a weight greater than 17 tons; this savings in weight 
obviously brings about a savings of materials and a reduction of 
temperature lag. 
The circulation of the temperature regulating liquid in the channels is 
performed by distributing the flows. But the fact of having a hollow 
cylinder with separate flange journals makes it possible to design much 
more hydrodynamic connections than when it is necessary to drill a single 
bulky part, and to be able to do it much more easily. 
Preferably, the temperature regulating circuit of the cylinder according to 
the invention is dual, i.e., with halves of the dual circuit being placed 
at opposite ends relative to the axis of the cylinder, which makes 
possible opposite flows in adjacent longitudinal channels. 
Another advantageous feature of the temperature regulating circuit of the 
cylinder according to the invention is that the heat exchanging fluid for 
thermal regulation, after having regulated the external surface of the 
hollow cylinder by passing through the annular longitudinal channels, 
circulates along the inside wall of said hollow cylinder and thus provides 
thermal homogenization before being evacuated via the axis of the 
cylinder. 
According to yet another feature, the two parts of the temperature 
regulating circuit have a common central collector part followed by dual 
outlets that pass through both ends of said cylinder and in the axis of 
the cylinder. 
To drive the cylinder according to the invention, a hydraulic motor is 
used. This hydraulic motor has a hollow output shaft making it possible 
for one of the two inlet-outlets of the temperature regulating circuit to 
pass through it. 
The field of application of the invention relates mainly to mixing mills 
for rubbers but can also be applied to any other product, particularly 
mixers for paper pulp.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The cylinder according to the invention consists of a hollow cylinder part 
1 and two flange-journals 2 and 3. 
The hollow cylinder part is drilled with 40 longitudinal channels 4 (FIGS. 
1 and 2) which extend into each flange-journal at 5 and 6 (FIGS. 4 and 5). 
Bolts 7 are used to hold the flange journals and cylinder part in place 
for the machining and assembly of the device. Each channel is provided 
with a solid rod 8, both ends of which are fastened to one of 
flange-journals 2 and 3. 
The fastening of the rods 8 is performed by two nuts 9 screwed onto 
opposite ends of the rod after having heated the rods to a temperature 
higher than the expected maximum temperature of use (FIGS. 4 and 5). 
The temperature regulating circuit includes two (first and second) axial 
inlets 10 and 11 that are coaxial with two (first and second) axial 
evacuation ducts 12 and 13. Each axial inlet is part of a temperature 
regulating circuit constituted as follows. At an end of each of the two 
axial inlets, the distribution of the fluid is provided by a distribution 
circuit including 10 passages 14 which extend into a circular groove 15 
(FIGS. 4 and 5) which feeds 20 longitudinal channels 4 (FIG. 2), i.e., 
alternating ones of the 40 channels 4 such that temperature regulating 
liquid flows in opposite direction in adjacent channels 4, thereby forming 
an inlet circuit. At the outlet of each of the channels 4, evacuation is 
provided by outlet circuits including evacuating passages 16 which connect 
to the channels 4 and come out in a circular groove 17. Sealing bushings 
150 force the heat exchanging liquid, after having passed through annular 
channels 4, to enter the evacuation passages 16 before reaching circular 
groove 15. Groove 17 is itself connected to an internal flow passage 
circuit which is composed of 10 longitudinal grooves 18 and an annular 
passage 19 (FIG. 3). This annular passage 19 thermally regulates the inner 
wall of the hollow cylinder. Finally, the two annular passages 19 extend 
to a common collector part 20 at the center of the hollow cylinder, from 
which the heat exchanging liquid is evacuated through the axial ducts 12 
and 13. 
The design of this dual temperature regulating circuit, coupled with the 
sharp reduction of temperature lag of the cylinder, makes it possible to 
notably improve the thermal characteristics of heating and temperature 
regulation. 
By way of example, in the case of a 20.degree. C. heat exchanging fluid 
being water and having a 30 m.sup.3 /hour fluid flow rate, 1.5 min instead 
of the conventional 15 min were enough to cool a cylinder from 40.degree. 
to 24.degree. C. Conversely, 50 sec instead of the conventional 240 was 
sufficient to heat a cylinder from 30.degree. to 50.degree. C. where the 
heat exchanging fluid was at 60.degree. C. Moreover, while the heat 
exchanging fluid had flow rates on the order of 30 m.sup.3 /hour, higher 
flow rates are also possible. 
The crossed flow (i.e., in alternating channels 4) of the temperature 
regulating fluid provides a high thermal homogeneity of the hollow 
cylinder. 
Finally, the design of this cylinder in three parts connected by elastic 
rods 8 allows temperature changes greater than 20.degree. C. per minute, 
whereas fear of thermal fatigue previously prohibited changes greater than 
1.degree. C. per minute. 
FIG. 6 shows a half section of a flange-journal 3 with hydraulic motor 21 
with a hollow output shaft for driving the cylinder. The design of this 
hollow shaft motor makes it possible for the temperature regulating 
circuit to pass through the motor shaft. 
Obviously, numerous modifications and variations of the present invention 
are possible in light of the above teachings. It is therefore to be 
understood that within the scope of the appended claims, the invention may 
be practiced otherwise than as specifically described herein.