STUFFING SCREW

Abstract

A stuffing screw (2) for use in an extruder system comprises a housing (7) and at least one conveying screw (5), which is mounted in a rotatable manner within the housing (7), wherein a conveying space is formed between an inner side of the housing (7) and the conveying screw (5). The stuffing screw (2) is characterized in that at least one portion of the inner side of the housing (7) is provided with one or more depressions, in particular in the form of a groove (13).

Claims

1. A stuffing screw comprising: a housing; and at least one conveying screw, which is mounted in a rotatable manner within the housing, wherein a conveying space is formed between an inner side of the housing and the conveying screw, and at least one portion of the inner side of the housing comprises one or more depressions extending radially outwardly away from the conveying screw.

2. The stuffing screw as claimed in claim 1, wherein each of the one or more depressions comprise a groove having a longitudinal direction and a cross-sectional dimension orthogonal to the longitudinal direction.

3. The stuffing screw as claimed in claim 1, wherein the conveying screw has a longitudinal axis and the housing comprises at least two depressions spaced apart from one another in the direction of the longitudinal axis of the conveying screw.

4. The stuffing screw as claimed in claim 2, wherein the groove runs parallel to the longitudinal axis of the conveying screw.

5. The stuffing screw as claimed in claim 2, wherein the groove runs helically with respect to the longitudinal axis of the conveying screw.

6. The stuffing screw as claimed in claim 5, wherein the conveying screw has at least one helically running thread disposed about the longitudinal axis thereof, and the direction of pitch of the thread is counter to the direction of pitch of the groove.

7. The stuffing screw as claimed in claim 6, wherein the groove and the thread define an angle () of 70 to 110 as seen in the direction of the longitudinal axis of the conveying screw.

8. The stuffing screw as claimed in claim 5, wherein the conveying screw has at least one helically running thread disposed about the longitudinal axis thereof, and the direction of pitch of the thread and the direction of pitch of the groove are identical.

9. The stuffing screw as claimed in claim 5, the pitch of the helically running groove is non-uniform.

10. The stuffing screw as claimed in claim 5, wherein the inner side comprises a plurality of spaced apart depressions, each depression comprising a helically running groove, wherein the helically running grooves comprise different directions of pitch, pitches and/or numbers of windings.

11. The stuffing screw as claimed in claim 2, further comprising a degassing outlet.

12. An extruder system comprising an extruder, and a stuffing screw as claimed in claim 2.

13. The extruder system as claimed in claim 12, wherein the stuffing screw further comprises a degassing outlet.

14. A method of degassing viscoelastic material conveyed in an extruder, the method comprising conveying, the viscoelastic material through the extruder system as claimed in claim 13, and degassing the viscoelastic material.

15. A conveying screw assembly comprising: a housing defining a longitudinal direction and a radial direction orthogonal to the longitudinal direction; and at least one conveying screw mounted in a rotatable manner within the housing for conveying material through the housing in the longitudinal direction of the housing, the conveying screw having a longitudinal axis parallel to the longitudinal direction of the housing; wherein the housing comprises an interior surface disposed towards and at least partially about the at least one conveying screw, wherein the interior surface comprises at least one groove extending along at least a portion of the interior surface and at an angle to the radial direction.

16. The conveying screw assembly according to claim 15, wherein the groove has a longitudinal dimension, and at least portions thereof run parallel to the longitudinal axis of the conveying screw or helically with respect to the longitudinal axis.

17. The conveying screw assembly according to claim 16, wherein the groove has a cross-sectional configuration orthogonal to the longitudinal direction, and the cross-sectional configuration comprises at least one of: a rectangular configuration; a triangular configuration; and a semi-circular configuration.

18. The conveying screw assembly according to claim 17, wherein the interior surface comprises a plurality of spaced apart helically running grooves, wherein the helically running grooves comprise different directions of pitch, pitches and/or numbers of windings.

19. The conveying screw assembly according to claim 17, wherein: the interior surface comprises a plurality of spaced apart helically running grooves, wherein the helically running grooves are one of: regularly spaced or irregularly spaced, along the circumferential and axial directions of the interior surface; and the cross-sectional configuration for each groove is one of: the same as or different from the cross-sectional configuration of another groove; and for each groove, the cross-sectional configuration is one of: the same or different along the entire length of the groove.

Description

[0027] The invention will be explained in more detail hereinbelow with reference to exemplary embodiments illustrated in the drawings, in which:

[0028] FIG. 1 shows a schematic illustration of a first embodiment of an extruder system according to the invention;

[0029] FIG. 2 shows a schematic illustration of a second embodiment of an extruder system according to the invention;

[0030] FIG. 3 shows a schematic illustration of a third embodiment of an extruder system according to the invention;

[0031] FIG. 4 shows various possible way of integrating a stuffing screw in an extruder system according to the invention;

[0032] FIG. 5 shows a first groove shape for a stuffing screw according to the invention;

[0033] FIG. 6 shows a second groove shape for a stuffing screw according to the invention;

[0034] FIG. 7 shows a third groove shape for a stuffing screw according to the invention;

[0035] FIG. 8 shows a fourth groove shape for a stuffing screw according to the invention;

[0036] FIG. 9 shows a fifth groove shape for a stuffing screw according to the invention;

[0037] FIG. 10 shows a first groove progression for a stuffing screw according to the invention;

[0038] FIG. 11 shows a second groove progression for a stuffing screw according to the invention;

[0039] FIG. 12 shows a third groove progression for a stuffing screw according to the invention; and

[0040] FIG. 13 shows a fourth groove progression for a stuffing screw according to the invention.

[0041] An extruder system according to the invention has an extruder 1 and at least one stuffing screw 2 connected thereto. The extruder 1 comprises an extruder screw 3, which is mounted in an extruder housing 4 so as to be driven in rotation by a drive (not illustrated). The stuffing screw 2 comprises a conveying screw 5, which is mounted in a housing 7 so as to be driven in rotation by a drive 6. It is possible for the extruder 1 to have, for example, a single extruder screw 3 and for the stuffing screw 2 to have a single conveying screw 5, as is illustrated by way of example in FIGS. 1 and 2. It is likewise possible for the extruder 1 to be designed with a plurality of extruder screws 3 and for the stuffing screw 2 to be designed with a plurality of conveying screws 5. FIG. 3 shows, by way of example, the configuration of an extruder system according to the invention having two extruder screws 3 and two conveying screws 5. In configurations with more than one conveying screw 5, designs in which the screws are closely intermeshing and rotate in the same direction or in opposite directions are preferred according to the invention.

[0042] The stuffing screw 2 of an extruder system according to the invention may be provided as a feeding mechanism, via which a product and/or one or more additives are/is fed to the product already located in the extruder 1. FIG. 2 shows, by way of example, a corresponding configuration of an extruder system according to the invention having an inlet 8 in a housing 7 of the stuffing screw 2, the product being fed via said inlet,

[0043] The stuffing screw 2 may also be provided for the purpose of degassing the extruder 1 (cf. FIG. 1). In this case, the housing 7 of the stuffing screw is provided with an outlet 9 for connection to an extraction system 10.

[0044] In the annular product space formed between the extruder screw(s) 3 and the extruder housing 4, the product is transported in the direction denoted by the arrow 12, and possibly mixed, plasticated and compressed in the process, by the rotation of the extruder screw(s) 3, designed with helically running threads 11. The inner volume of the extruder housing 4 and the inner volume of the housing 7 of the stuffing screw 2 are connected to one another, and therefore a product which is fed via the stuffing screw 2 can be introduced into the extruder 1 and gas which has formed in the extruder 1 can be discharged via the stuffing screw 2.

[0045] The stuffing screw 2 can be connected to the extruder 1 in any desired orientation. FIG. 4 shows various orientations for the stuffing screws 2. In addition to vertically downward or upward and horizontally (to the right or left), it is also possible for the stuffing screw to be oriented obliquely upward or obliquely downward (as seen in relation to the direction of gravity in each case). Horizontal or vertical (in particular vertically upward) arrangements are preferred. FIGS. 1 to 3 show embodiments in which the stuffing screw 2 is arranged in each case perpendicularly in relation to the longitudinal axis of the extruder 1. As an alternative to this, of course, it is also possible for the stuffing screw 2 to be connected to the extruder 1 such that Its longitudinal axis encloses with the longitudinal axis of the extruder 1 an angle which, rather than being 90, is between 0 and <90, for example 45.

[0046] Should a plurality of stuffing screws 2 be combined on an extruder 1, then they can be provided at different axial positions as seen in relation to the longitudinal axis of the extruder 1. It is also possible for a plurality of stuffing screws 2 to be arranged is with different radical orientations at one axial position of the extruder 1 (cf, FIG. 4), so as to increase, for example, the free flow cross sections available.

[0047] FIGS. 5 to 9 show, schematically, different cross sections with which the grooves 13 of stuffing screws 2 according to the invention (here, by way of example, with two conveying screws 5 with the same direction of rotation) can be formed. FIG. 5 here shows a rectangular cross section for the grooves 13, and FIGS. 6 and 7 show triangular cross sections for the grooves 13. The triangular cross sections are not Isosceles, wherein, in the case of the embodiment of FIG. 6, the longer, flatter limb is located at the rear in the direction of rotation of the conveying screws 5 (petering out in the direction of rotation), whereas, in the case of the embodiment of FIG. 7, the shorter, steeper limb is located at the rear in the direction of rotation of the conveying screws 5 (falling away in the direction of rotation). Of course, it is also possible for the triangular cross section of the grooves 13 to be isosceles or equilateral. The cross section of the grooves 13 in the case of the embodiment of FIG. 8 is curved and, in particular, in the form of part of a circle. FIG. 9, in addition, also shows the possibility of forming the grooves 13 with irregular spacings and/or a non-uniform cross section (in respect of the dimensions and/or in respect of the cross-sectional shape).

[0048] FIGS. 10 to 13 show various possible progressions of grooves 13 of stuffing screws 2 according to the invention. The embodiment of FIG. 10 provides for the grooves 13 to be oriented parallel to the longitudinal axis 15 of the stuffing screw 2 or of the conveying screw 5. This is a straightforward and therefore technically cost-effective solution, in particular in the case of a combination with the groove shape according to FIG. 6, it is also possible, however, for the parallel arrangement to be distinguished by agglomerates which are formed in the grooves 13 being removed to particularly good effect. This can reduce the risk of caking in the grooves 13 or of the grooves 13 gradually blocking up.

[0049] In the case of the embodiment of FIG. 11, the grooves 13 of the stuffing screw 2 run helically, to be precise with the same direction of pitch (right-hand direction) as the likewise helically running threads 14 of the conveying screw 5. The grooves 13 and the threads 14 therefore run more or less parallel.

[0050] In contrast to this, the embodiment of FIG. 12 makes provision for the helically running grooves 13 to have a direction of pitch which is counter to that of the threads 14 of the conveying screw 5. Provision is preferably made here for the angle enclosed by the grooves 13 and the threads 14 over the longitudinal axis 15 of the stuffing screw 2 to range between 70 and 110.

[0051] FIG. 13, finally, shows a combination of grooves 13 which cross over as a result of opposite directions of pitch.

LIST OF REFERENCE SIGNS

[0052] 1 Extruder

[0053] 2 Stuffing screw

[0054] 3 Extruder screw

[0055] 4 Extruder housing

[0056] 5 Conveying screw

[0057] 6 Drive

[0058] 7 Housing

[0059] 8 inlet

[0060] 9 Outlet

[0061] 10 Extraction system

[0062] 11 Thread

[0063] 12 Transporting direction

[0064] 13 Groove

[0065] 14 Thread

[0066] 15 Longitudinal axis