Agitating – Rubber or heavy plastic working – Stirrer is through-pass screw conveyor
Patent
1994-08-09
1996-01-02
Cooley, Charles E.
Agitating
Rubber or heavy plastic working
Stirrer is through-pass screw conveyor
366 90, 366307, 366322, B29B 742
Patent
active
054802270
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a national phase of PCT/EP93/03507 filed 11, Dec. 1993, and based, in turn, upon German national application P42 44 312.1 filed 28 Dec. 1992 under the International Convention.
FIELD OF THE INVENTION
The invention relates to a screw-type extruder in whose cylinder, receiving at least one endless screw, bores are provided for receiving pins arranged in radial planes, projecting into the conveying area, the axes of the pins being arranged tangentially to the cylinder wall or close to the tangents and parallel thereto.
BACKGROUND OF THE INVENTION
A screw-type extruder of this kind has become known from DE 40 10 540 C1.
Screw-type extruders serve for plastifying and homogenization of the mass to be extruded, a process involving strong heating and depending on the nature of the mass. In the case of cross-linkable/vulcanizable masses this heating limits the throughput rate of the extruder, since cross-linking and/or vulcanization are not allowed to occur in the extruder. Among the technical means achieving the required plastification with a minimum heating of the mass, in practice two principles have been found to be particularly effective, namely the so called transfer mix according to DE 27 31 301 A1/DE 27 31 438 A1 and the pin extruder with radial pins according to DE 22 35 784 B2 and others. Radial pins with an active conveying or mixing action, e.g. according to DE 36 13 612 A1 are substantially more sensitive from the mechanical point of view than simple radial pins and have therefore not been introduced in practice.
However besides the natural wear, the biggest disadvantage of pins radially projecting into the cylinder is that the pins even when new, but especially after a certain wear, are subject to breakage. Such pin breakages are costly, since they do not only damage the machine but also create product problems because they cannot be covered by the product liability insurance of the manufacturers and result in rejects or high control costs.
The extruder according to DE 40 39 942 C1 which is supposed to combine the advantages of the transfer mix and of the radial-pin extruder has also the same problems and in addition is also very expensive.
The tangential-pin extruder according to DE 40 10 540 C1 avoids the breaking danger due to the different, namely, tangential arrangement of the pins, lowers the manufacturing costs compared with the transfer mix and allows for an intensive tempering of the pins, which makes possible a higher rotational speed of the screw and thereby higher throughput rates of the extruder. These pins, however, also do not have an active conveying effect. A disadvantage similar to the radial-pin extruders is that self-cleaning does not occur without problems. The insertion and removal of the conveyor screw is possible only when the pins have been pulled out from the inner cylinder space.
OBJECTS OF THE INVENTION
It is an object of the invention avoids the disadvantages of the state of the art.
It is another object of the invention to provide a screw-type extruder with a high plastifying output which can be manufactured in a simple and cost-efficient manner, and which has the advantage of improved self-cleaning conditions and is fully secured against pin breakage.
SUMMARY OF THE INVENTION
The invention consists in that the pins are arranged in areas where the screw is provided with a core bead and the cylinder is provided with an annular recess in its inner wall. The pins are arranged outside a (theoretical) cylinder enveloping the backs of the screw webs. The pins traverse diagonally the radial plane area in which the ring bead and the annular recess are located.
This screw-type extruder can be manufactured in a simple way because the production of annular recesses in the cylinder and ring beads on the screw does not create problems and is cost-efficient. The pins are located in slanted bores of the cylinder of the screw-type extruder, their production requiring considerable less expense than the production of
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Cooley Charles E.
Dubno Herbert
Krupp Maschinentechnik GmbH
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