SCREW TO BE USED IN AN EXTRUDER AND EXTRUDER

Abstract

A screw to be used in an extruder has a modular structure so that it can be adapted very flexibly to new tasks and conditions. The modular structure of a screw contains a rod-shaped mandrel and individual screw components which are slidable onto the mandrel. The components perform the classic functions of the screw during the extrusion process, such as conveying, kneading, mixing or shearing of the plastic to be guided into and through the plant.

For transmission of the occurring high torque, the components are connected with the mandrel so that they positively engage and are axially braced in addition. The connection is to be performed such that it can be released by simple means.

Claims

1. Screw to be used in an extruder, the screw having a mandrel and a segment borne by the mandrel, characterized in that the segment and the mandrel have a cyclically asymmetric profile shaft connection.

2. Screw according to claim 1, characterized in that the profile shaft connection has a whole multiple of local maximum values of the radius of the connection between the mandrel and the screw as compared to the cyclically symmetric screw segments.

3. Screw according to one of claim 1 or 2, the profile shaft connection having a contour with two profile flanks, the extruder screw having a direction of rotation determined by construction, characterized in that one profile flank, in particular the profile flank of the mandrel which faces the segment in the direction of rotation, is steeper in the radial direction than the other profile flank.

4. Screw to be used in an extruder, the screw having a mandrel and a segment borne by the mandrel, with the segment and the mandrel having a profile shaft connection, in particular screw according to one of the above claims, characterized in that the profile shaft connection is a polygonal profile shaft connection with curved flanks.

5. Screw according to claim 4, characterized in that a flank is convexly curved in the direction of the segment.

6. Screw according to one of claim 4 or 5, characterized in that a flank is concavely curved in the direction of the segment.

7. Screw according to one of claims 4 through 6, the mandrel having a polygonal contour, characterized in that the polygonal contour is harmonic.

8. Screw according to one of claims 4 through 6, the mandrel having a polygonal contour, characterized in that the polygonal contour is disharmonic.

9. Screw to be used in an extruder, the screw having a mandrel and a segment borne by the mandrel, the segment and the mandrel having a profile shaft connection, in particular screw according to one of claims 1 through 3, characterized in that the profile shaft connection is a spline shaft connection.

10. Screw to be used in an extruder, the screw having a mandrel and a segment borne by the mandrel, the segment and the mandrel having a profile shaft connection and the profile shaft connection being embodied in the form of an axially asymmetric toothed shaft connection with one tooth, the tooth having a right and a left tooth flank, in particular screw according to one of claims 1 through 3, characterized in that the tooth flanks have a curvature.

11. Screw according to claim 10, a tooth segment having a tooth contour, characterized in that the tooth contour is harmonic.

12. Screw according to claim 10, a tooth segment having a tooth contour, characterized in that the tooth contour is disharmonic.

13. Screw to be used in an extruder, the screw having a mandrel and a segment borne by the mandrel, the segments and the mandrel being connected by a cyclically symmetric profile shaft connection, wherein the profile shaft connection is an axially asymmetric toothed shaft connection, a tooth pitch having a tooth contour, in particular screw according to one of the above claims, characterized in that the tooth contour of the mandrel deviates from a fifth-degree polynomial in the direction perpendicular to the contour by maximally one hundredth of a tip circle diameter of the mandrel.

14. Screw according to claim 13, characterized in that a left point of a tooth contour is described by the polynomial, the left point being positioned on the tip circle diameter of the mandrel and the left point bordering on the left flank of a first tooth.

15. Screw according to one of claim 13 or 14, characterized in that a right point of a tooth contour is described by the polynomial, the right point being located on the tip circle diameter of the mandrel and the right point bordering on the left flank of a second tooth.

16. Screw according to one of claims 13 through 15, characterized in that a lowest point of a tooth contour is described by the polynomial, the point being located on the root circle diameter of the mandrel within a range between 55% and 90%, preferably within a range between 65% and 83% and particularly preferably within a range between 75% and 79% in the circumferential direction on a radius between the radius of the left point and the radius of the right point.

17. Screw according to one of claims 13 through 16, characterized in that at the left point, the gradient of the radius in the direction of circumference lies within a range between 0.1 and 0.1, preferably between 0.05 and 0.05 and particularly preferably has a value of 0.

18. Screw according to one of claims 13 through 17, characterized in that at the lowest point, the gradient of the radius in the direction of circumference is 0.

19. Screw according to one of claims 13 through 18, characterized in that at the right point, the gradient of the radius in the direction of circumference lies within a range between 10 and , preferably between 100 and and particularly preferably has a value of .

20. Screw to be used in an extruder, the screw having a mandrel and a segment borne by the mandrel, the segment and the mandrel having a profile shaft connection with a disharmonic contour, in particular screw according to one of the above claims, characterized in that the profile shaft connection has an axially symmetric contour, the contour of the mandrel having a concave recess, with respect to an else cylindrical shape of a mandrel surface area, with a harmonic shape of a contour of the recess, the harmonic contour of the recess being associated with the else cylindrical shape of the mandrel surface area by a disharmonic transition at the tip circle of the mandrel.

21. Screw according to claim 20, characterized in that the profile shaft connection is cyclically symmetric.

22. Screw according to one of claim 20 or 21, characterized in that the harmonic contour of the recess corresponds to a portion of a contour of an ellipse.

23. Screw according to one of claims 20 through 22, characterized in that the harmonic contour of the recess corresponds to a portion of a contour of a circle.

24. Screw according to one of claims 20 through 23, characterized in that the harmonic contour of the recess corresponds to a portion of a polygon.

25. Screw according to one of the above claims, characterized in that the mandrel has an undercut proximate to the root-circle diameter.

26. Screw according to one of the above claims, characterized in that the segment has an undercut proximate to the root circle.

27. Screw according to one of the above claims, the mandrel and the segment each having a tip-circle diameter and a root-circle diameter, characterized in that the tip-circle diameter of the segment is larger than the root-circle diameter of the mandrel.

28. Screw according to one of the above claims, the mandrel and the segment each having a tip-circle diameter and a root-circle diameter, characterized in that the root-circle diameter of the segment is larger than the tip-circle diameter of the mandrel.

29. Screw according to one of the above claims, characterized in that the profile shaft contour of the segment is radially larger by at the most one hundredth of the tip circle diameter of the mandrel; preferably, by at the most one thousandth.

30. Screw according to one of the above claims, the profile shaft contour having edges, characterized in that the edges are rounded.

31. Extruder having a screw according to one of the above claims.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0166] In the following, the invention will be explained in more detail by means of two examples of embodiment with reference to the drawings wherein:

[0167] FIG. 1 schematically shows a cross-section of a screw to be used in an extruder, the screw having a cyclically asymmetric profile shaft connection with positive engagement,

[0168] FIG. 2 schematically shows a cross-section of a screw to be used in an extruder, the screw having a polygonal shaft connection with positive engagement, having a disharmonic polygonal contour with convexly curved polygonal flanks,

[0169] FIG. 3 schematically shows a cross-section of a screw to be used in an extruder, the screw having an axially asymmetric toothed shaft connection with positive engagement, having a disharmonic shaft contour and a harmonic tooth contour, and

[0170] FIG. 4 schematically shows a cross-section of a screw to be used in an extruder, the screw having a profile shaft connection to a mandrel with concave recesses, wherein the contour of the recesses is harmonic.

DETAILED DESCRIPTION OF THE DRAWINGS

[0171] The extruder screw 1 in FIG. 1 has a mandrel 2 and a segment 3. The extruder screw can rotate about an axis 4 for conveying, kneading, mixing or shearing a plastic.

[0172] The mandrel 2 and the segment 3 are interconnected by a releasable profile shaft connection with positive engagement, wherein the segment 3 can be axially slid onto the mandrel 2.

[0173] The profile shaft connection of the extruder screw 1 is cyclically asymmetric and has a mandrel profile 5.

[0174] The extruder screw 1 has two spirals. The cyclically asymmetric profile shaft connection is designed such that the segment 3 cannot be slid onto the mandrel circumference at a faulty angle, which in turn ensures that the adjacent segments also cannot be positioned at a non-fitting peripheral angle.

[0175] The extruder screw 10 in FIG. 2 has a mandrel 11 and a segment 12. The extruder screw 10 can rotate about an axis 13 for conveying, kneading, mixing or shearing a plastic.

[0176] The mandrel 11 and the segment 12 are interconnected by a releasable polygonal shaft connection with positive engagement, wherein the segment 12 can be axially slid onto the mandrel 11.

[0177] The polygonal shaft connection of the extruder screw 10 is cyclically symmetric and has a disharmonic polygonal profile 14 with convexly curved flanks.

[0178] The extruder screw 20 in FIG. 3 has a mandrel 21 and a segment 22. The extruder screw 20 can rotate about an axis 23 for conveying, kneading, mixing or shearing.

[0179] The mandrel 21 and the segment 22 are interconnected via a positively engaging, axially asymmetric, releasable toothed shaft connection wherein the segment 22 can be slid axially onto the mandrel 21.

[0180] The toothed shaft connection of the extruder screw 20 has a cyclically symmetric tooth pitch 28 and a disharmonic profile.

[0181] Each tooth segment 26 has a left tooth flank 24 and a right tooth flank 25. The transition between the left tooth flank 24 and the right tooth flank 25 is at the lowest point 30 of the tooth contour 29.

[0182] The tooth contour 29 of each cyclically symmetric tooth segment 26 starts at a left point 27, leads to the lowest point 30 via the right tooth flank 25 and to the right point 31 via the left tooth flank 24.

[0183] The left tooth flank 24 and the right tooth flank 25 have a curved contour.

[0184] The left tooth flank 24 and the right tooth flank 25 are asymmetric.

[0185] The left tooth flank 24 has a steeper contour than the right tooth flank 25.

[0186] The mandrel preferably rotates in the direction of the steeper tooth flank. In this embodiment, this is the direction of the left tooth flank 24. That is, in this embodiment, the preferred direction of rotation is counterclockwise.

[0187] The extruder screw 40 in FIG. 4 has a mandrel 41 and a segment 42. The extruder screw 40 can rotate about an axis 43 for conveying, kneading, mixing or shearing of a plastic.

[0188] The mandrel 41 and the segment 42 are interconnected via a positively engaging releasable profile shaft connection, wherein the segment 42 can be axially slid onto the mandrel 41.

[0189] The profile shaft connection of the extruder screw 40 is cyclically symmetric and has twelve recesses 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56.

[0190] The recesses 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56 have a harmonic concave contour 57 with a disharmonic transition to the else cylindrical mandrel surface area 60 at the transition points 58, 59.