DE1273789B - Kneading and mixing device for the continuous preparation and processing of plastic masses - Google Patents

Description

Kneading and mixing device for continuous preparation and processing of plastic masses The invention relates to a kneading and mixing device for the continuous preparation and processing of plastic, especially ethers thermoplastic masses with a conical tapered screw acting as a kneading organ, whose housing is displaceable in the axial direction.

Processing is to be understood as a process in which the individual Components of a mixture due to the introduction of predominantly mechanical forces like this intimately and evenly brought into connection and distributed with one another that no more agglomerates are present and the mass to be processed as a result of Friction heating that occurs during this process after exiting the machine is obtained homogeneously.

One of the kneading devices serving to solve this problem was the core of a cylindrical screw, starting in the material filling zone, is eccentric arranged to the screw axis. The volumetric efficiency of such a screw however, it is unfavorable and the desired kneading effect cannot be influenced.

Furthermore, machines are both cylindrical and conical Known snails that are generally multi-corrugated, predominantly double-corrugated. These so-called twin-screw mixers are divided into those with intermeshing, partially interchangeable kneading tools and in machines whose screws are only touch in the tip circle. A special feature of both machine types is to emphasize that the kneading intensity, also called specific energy input, is almost constant for a given product, i.e. it is independent of the shape of the The kneading organs can hardly be varied unless the screws or screw parts have been replaced will.

Knetzoxie is also known to remedy this disadvantage to connect a valve or a valve point that can be changed in its gap width. At one - e.g. Narrowing of the throttle gap increases the flow resistance at this point, a higher pressure than the original one is required to overcome it. This increased pressure is planted more or less depending on the useful volume of the kneading zone quickly in the direction of the filling zone, with the one located in this area Material is compressed more strongly. The torque also increases accordingly on the screw shafts and thus the specific energy input into the mass, d. This means that the kneading intensity can be adjusted by regulating the kneading zones downstream Throttle points are influenced indirectly.

The disadvantage of these designs can be seen in the fact that in the Preparation of highly viscous, shear-sensitive masses, such as plasticizer-free PVC with a high k-value regulates the kneading intensity by means of the kneading zones downstream throttling points because of the poor flowability of these thermoplastics in connection with their low temperature stability is very difficult. The reason is that in the processing of such masses the effect of the kneading tool and housing wall structurally determined, unchangeable kneading gap predominates and the variable throttle gap only has corrective properties. Therefore, e.g. when changing to a different material recipe, in general two, but mostly three parameters (dosage, throttle gap, screw speed) can be changed if certain technological material properties are observed should be. Since each parameter allows three settings (starting position, less, More), result from changing two parameters depending on the experience of the operating personnel up to nine, with a change of three, however, twenty-seven possible variations.

There are also proposals known according to which the screw is conical is designed and displaceable in the axial direction, but these machines are unable to knead the material to be processed.

This is where the invention comes in, which aims at a machine the aforementioned defects do not adhere and which works according to the single-screw principle, which increases the effort, susceptibility to failure and maintenance compared to multi-screw systems to decrease.

According to the invention, in a kneading and described above Mixing device which is limited within a by a continuous web Worm gear located, in a known manner eccentric to the screw axis arranged core divided and towards the concentric web with opposite eccentricity offset.

This results in adjacent narrow and wide kneading gaps, whose plane of separation lies transversely to the screw axis, causing bending stresses be avoided.

This subdivision also has the effect that the to-be-processed Material is kneaded not only against the cylinder wall, but also within a Ganges from the zone with high pressure to the one next to it with low pressure must partly drain. This process takes place alternately as seen in the conveying direction once with the current and once against it, which advantageously makes it more intense Kneading and mixing effect is achieved.

The cylinder is moved axially from the zero position starting out, an enlargement of the gap cross-sections, whereby the surface contents the narrow gaps change more in percentage than those of the wide gaps. Reduced accordingly the compression ratio of each half-aisle and thus the kneading intensity, d. In other words, with otherwise the same operating conditions, the specific energy input decreases. This effect follows the measure described without delay over the entire length of the kneading part, causing thermal damage to the material to be processed can be prevented with certainty.

The object of the invention is in the drawings, for example shown. Fig. 1 shows a longitudinal section through the kneading and mixing device, Fig. 2 is a plan view of the kneading and mixing device with a horizontal partial section, Abt, 3 shows a cross section through the kneading and mixing device.

One for the continuous kneading and mixing of plastic masses made of powdery or pasty plastics with or without filler content The kneading and mixing device has an externally cylindrical housing 1, the bore of which into a temperature-controllable conical section 2 and a cylindrical section 3 is divided. A work spindle 4 is mounted on the same axis as the housing 1, which consists of a cylindrical part 5 provided with helical flights and one with helical threads, conically tapering part 6 consists of the work spindle is stored in a manner known per se in the transmission housing 7, which also does not contains illustrated gears. To the task of the starting materials is a through the housing wall 1 through the funnel 8 provided in the area of the zone 5 joins. The substances escaping from zone 5 in the conveying direction enter the part 6 designed as a kneading screw. In the area of each aisle is the Core designed so that it is related to the screw axis, at least two eccentric to this has offset parts and following the screw thread alternately one narrow kneading gap 12 and a wide gap 13 forms. Due to the eccentric offset However, there is a wider gap 14 next to the narrow kneading gap 12 and next to the wide one Gap 13 a narrow kneading gap 15. The materials to be processed flow, the -screw following, the kneading gap 12, are partly in gap 14 urges, flow on in Knetspaitldi and are partly displaced in gap 13. This process causes In addition to the actual kneading, intensive mixing in the conveying direction and against it. The energy required for this is generated by the drive motor 16 - and via a reduction gear 7 initiated into the work spindle 4, from where it is by means of kneading part 6 in the for Plasticizing required frictional heat is implemented. Conversely, there is a certain one Temperature at constant speed and constant throughput of a certain corresponds to the average viscosity of the plastic material, this is applied to the housing 1 transmitted torque measured in the manner of a rotational viscometer and used for Control of the energy introduced, thus the desired kneading intensity and thus the permitted temperature. For this purpose, the housing is 1 in a front cross member 17 and a rear cross member 18 around its axis rotatably mounted that the axial thrust of the housing arising in the conveying direction 1 is supported on the Lagerl9 located in the Traversel7 and the traverse 17 of Tie rods 20 is held.

These tie rods 20 are z. B. stored in the transmission housing 7, on the transmission side End designed as a threaded spindle 21 and by means of worm drive 22 via a handwheel 23 or an adjusting motor 24 displaceable in the axial direction, the housing 3 is taken over the cross member 17 through the bearings 19 and 25. The filling side The housing 3 is supported in the radial direction, for. B. in a 3-point storage that is located in the traverse 18, such that the housing 3 on two rollers 26 rests and is caught by a spring-loaded roller27. Rotating along of the housing 3 upon rotation of the work spindle 4 filled with mass is in the Way prevents a stop 28 fixedly connected to the housing 3 from contacting the pressure element of a load cell 29 or a similar device applies, which in turn is connected to the traverse 18. The contact pressure generated at the load cell 29 is displayed in a measuring instrument 30 and / or registered. The measuring instrument30 can be provided with a maximum and / or minimum contact in a manner known per se the value that is set when the machine is operating automatically corresponding control impulse to the adjusting motor24, which via the worm drives22 the housing 3 moves in the axial direction until the through the conical Training of the kneading part 6 resulting torque change again with the the measuring instrument 30 covers predetermined value. In addition, it is appropriate Extension of the threaded spindle 21 possible, the housing 3 for the purpose of cleaning to retract completely from the work spindle 4.

Claims (2)

Patent claims: 1! Kneading and mixing device for continuous Preparation and processing of plastic, in particular thermoplastic, masses with a cone-shaped tapered screw acting as a kneading element, its housing in the axial direction. is shiftable, d a by c h g e'-indicates that the inside a snail bounded by a continuous web located in the ganges, divided in a known manner and arranged eccentrically to the screw axis core offset towards the concentric web with opposite eccentricity is. 2. kneading and mixing device according to claim 1, characterized in that that a measuring device (28, 29, 30) for the by the kneading screw (6) on the im Machine frame around its axis rotatably mounted housing (1) transmitted torque is provided that a deviation from a predetermined target value by axial Moving the housing (1) by means of the adjusting motor (24) compensates. Considered publications: German Patent Specifications No. 860 261, 1 030 555.