FR2474946A1 - EXTRUDER WITH A PENCIL BODY - Google Patents

Abstract

EXTRUDER WITH A SPINDLE BODY FOR IMPLEMENTATION OF THERMOPLASTS AND ELASTOMERS, IN WHICH AN ENDLESS SCREW TURNS, WHOSE THREADS ARE INTERRUPTED AT THE POINTS OF PENETRATION OF THE SPINDLES IN THE BODY. THE ENDS AND BEGINNINGS OF THE INTERRUPTED THREADS 3 OF THE SCREW 2 ARE ARRANGED FOLLOWING THE AXIS OF THE SCREW 2 AND AT THE SAME HEIGHT, BETWEEN THE PINS 4 FIXED ON THE BODY, SO THAT THE RADIAL INTERRUPTING FACES OF THE ENDS 10 AND 11 THREAD BEGINS ARE LOOKING AFTER THE SCREW AXIS.

Description

The present invention relates to an extruder with a pin body for

  the use of thermoplastics and elastomers, in which a worm rotates, and pins substantially

  equidistant along the circumference of the body are arranged radially

  the inner wall of the latter towards the axis of the worm, whose nets are interrupted where

pins enter the body.

  Extruders with a pin roll are described in German Offenlegungsschrift No. 22 35 784. The screw threads of these extruders are

  interrupted at the points where the pins enter the body through

  towards the wall of the latter. Such a design aims to ensure a perfect mixing and plasticizing effect of the material used. This design has the following drawback: there is practically no shearing of the material and the homogeneity of the mass to be used consequently leaves much to be desired. The material arriving on the pins is certainly divided and deflected, but there is no significant shear because the material, when it is gripped by a pin, can escape into the neighboring net without suffering

  significant shear between the screw thread and the pins. The con-

  known ception thus produces many partial flows and groups together

  by division and flow deflection, but no shear flow. The pins are scanned by many particles

  of the material, without any intense shear.

  The object of the invention is to improve an extruder with a pin body of the aforementioned type, so that the pins produce a shear gradient and consequently an excellent homogeneity of

the mass to implement.

  According to an essential characteristic of the invention, the

  mites and the beginnings of the interrupted threads of the worm are arranged along the axis of the latter at the same height, between the pins fixed on the body, so that the radial faces of interruption of the ends and beginnings of net are opposite

along the axis of the worm.

  As a result of the arrangement of the ends and the beginnings of the interrupted threads, so that the radial interruption faces are facing along the axis of the worm, the material is always subjected to significant shear when it is between a stationary pin and radial interrupt faces. This arrangement produces a very large active area for

  the transmission of high shear energy to the material.

  The material at this location is further stretched at high speed

  elevated through the narrow gap, without being able to escape.

  In the prior art, the material to be used can always

  days escape without significant constraint, when it comes into con-

  tact with the stationary pins. A high number of rows of

  Although the spindles produce good brewing, the shearing of

  riau, the main responsible for good homogeneity, is strongly

neglected.

  According to another characteristic of the invention, radial planes of pins are provided in the form of rings with upstream and downstream relative to the direction of flow of the material, short

parts of screws with several threads.

  The implementation of the principle of the invention, namely the

  facing the radial faces of interruption of the ends of net starts on a portion of plastification with multiple nets,

amplifies the effect of the invention.

  The series assembly of several plasticizing units of this

  type allows to obtain an excellent mixing action and

  tification with a very short extruder. The purchase price

  an extrusion unit is thus significantly reduced.

  In order to obtain a lower flow resistance in a plastification part of the type previously described, and according to another characteristic of the invention, the beginnings of the threads of the multi-threaded screw parts and the ends of the parts-of

  multi-threaded screws arranged downstream of the threadless zones, followed

  the direction of flow of the material are selected.

  Other features and advantages of the invention will be

  better understood using the detailed description below of a

  embodiment and the accompanying drawings in which Figure 1 is the longitudinal section of a single screw extruder according to the invention; Figure 2 is the longitudinal section of an extrusion part with two plastics units; FIG. 3 depicts debut and tip ends; Figure 4 schematically illustrates the principle of the invention; and Figure 5 schematically shows an embodiment according to

the prior art.

  A worm (2) carrying helical threads (3) is housed in an extruder body (1). Pins (4), locked by a screwing (5), passes through the body (1). Many pins (4) are arranged in the body (1) so that their axis is oriented on the axis of the worm (2). A greater or lesser number of pins may pass radially through the body to penetrate the extrusion chamber (6), depending on the diameters of the body and the worm. The pins (4) are arranged perpendicular to the axis of the worm (2) and constitute a pin plane. Several pin planes can be arranged with a given spacing, screw areas to

  one or more threads being disposed between the various broaching planes

  che. Fig. 2 shows an extruder part with two plastification zones (7). The latter consist of screw parts (8) and (9) with several threads, disposed immediately upstream

and downstream of a pin plane.

  The multi-threaded embodiment of the plasticization zones (7) significantly increases the high shearing action of the material to be used between the radial faces of the nets.

opposite.

  Whenever the radial faces (10) and (11) of thread interruption facing the rotating screw (2) pass in front of a spindle

  fixed, the material is subjected between these faces and the pin to a shear-

  importantly, multiplied by the multiple nets of

- plasticization.

  FIG. 5 represents, in a stylized and developed form, a mounting according to the prior art, in which a continuous helical thread, like the one of FIG. 4, is interrupted in order to create a free space for the fixed pins ( 14). When the radial interrupt face (13) passes the pin (14), the material can freely escape on the other side without shearing. When the radial face (12) of the new beginning of thread passes in front of the spindle (14), the screw continuing its rotation, the material can again escape in the opposite direction, without being requested.

in shear.

  A comparison of the operation shown diagrammatically in FIGS. 4 and 5 illustrates the remarkable shearing action produced by the

assembly according to the invention.

  The plasticization zones (7) according to the invention may for example be produced by simply fitting the parts with several threads (8) and (9), made separately, on a core with appropriate locking by keys. The separate embodiment of the parts (8) and (9) of the worm and the intermediate non-threaded area has a great advantage because more or less significant wear phenomena can occur. Thus the first areas of plasticization (7) are much more stressed than the following because the material is colder and therefore much more abrasive at the entrance. Another advantage of producing the screw in the form of interchangeable areas lies in the production. Parts of relatively small volume can be produced as parts

  economic precision moldings.

  Depending on the material to be used, it may be necessary to produce more or less significant shear energy in the material and consequently to provide a greater or lesser number of

homogenisation zones (7).

  Experience shows, for example, that the number of threads in the screw zones (8) and (9) must be the following, depending on the size of the extruder: extruder 90 2 extruder extruder 150 3 thread extruder 200 4 nets

extruder 250 5 threads.

  It has been found useful to respect a determined relationship between the length of the screw zones (8) and (9) and the diameter of the pins (4). A ratio of the length of the screw area (8) to the spindle diameter (4) of 1/1 to 1/2 is particularly effective, ie in the case of screw areas (8) having a length of 0.2 D, the pins or the unthreaded area between the zones (8) and (9) must have a length of 0, 1 to 0.2 D (D = diameter of the screw

unending).

  Experience shows that when implemented by a geo-

  metie of nets and pins according to the invention, the mixture of

  Cold chop is divided with minimal strength and stretched between pins and nets, to form long partial flows. It

  results in a remarkable homogeneity of the rubber mixture.

  The use of the zones of plasticization simultaneously makes it possible to cut the intermediate flow parts with one or two very high nets and a high flow per turn, without fear of heterogeneities,

  such as irregular distributions of temperature.

  A comparative test on an extruder equipped with a body

  cylinders according to the patent application of the Federal Republic of Germany

  Germany published under the number 22 35 784 gave the following results.

  The extruder is equipped with 10 successive pin planes. The rubber mixture to be used, which is substantially at ambient temperature, is introduced into the extruder and then

  homogeneity is determined after passing said pin planes.

  An extruder according to the invention is then fed with a material having the same viscosities and temperatures. After the passage of five zones of plasticization (7), the rubber mixture already has a homogeneity comparable to that of the material used in the extruder according to the prior art, with ten planes of

  successive pins and a double length.

  This comparative test shows that an extruder according to the invention can be made with a length 50% less than that of a

  extruder according to the prior art, or that flow rates markedly higher than

  are possible in the case of the same length, without any

  risk of heterogeneity of the material.

  Of course, various modifications may be made by those skilled in the art to the principle and devices that have just been described by way of non-limiting examples, without departing from the scope of the invention.

Claims (4)

claims   1. Extruder with a pin body for the implementation of thermoplasts and elastomers, in which a worm rotates and pins substantially equidistant according to the circumference of the body are arranged radially of the inner wall of this   last to the axis of the worm, whose nets are internally   broken at the places where the pins enter the body, said extruder being characterized in that the ends and the beginnings of the threads (3) interrupted of the worm are arranged along the axis of the latter at the same height, between the pins (4) fixed to the body, so that the radial faces of interruption of the ends (10) and the beginnings (11) of the net are opposite along the axis of the worm.   2. Extruder according to claim 1, characterized in that the radial faces facing interruption of the ends (10) and the beginnings (11) net belong to two separate parts of the screw (8, 9), each having a length axial thread of about 1/5 D and between which is disposed a non-threaded portion, having a   length about 1/5 D (D = diameter of the worm).   An extruder according to claim 2, characterized in that the thread start (15) of the multi-threaded screw parts (8) and the ends (16) of the threads of the multi-threaded screw parts (9) arranged in downstream of the unthreaded part following the direction   flow of the material, are appointed.   4. Extruder according to claim 2, characterized in that the   screw parts (8) and (9), as well as screw parts to one or more   nets, arranged between the plastification zones (7), are   made in the form of separate and interchangeable parts.