Screw element with an axially asymmetric screw profile having at least two construction points located within the screw profile

Abstract

The present invention relates to a screw element having an axially asymmetric screw cross-sectional profile, which has at least two construction points located within the screw cross-sectional profile. The screw element according to the invention is suitable for use in an extruder having two drive shafts, which rotate in the same direction and at the same speed, in order to process or produce a plastic material as an extrudate. The present invention also relates to the arrangement of two identical or different screw elements according to the invention in an extruder having two drive shafts, which rotate in the same direction and at the same speed, the screw elements according to the invention being located opposite each other in pairs on the two drive shafts. The present invention further relates to an extruder equipped with two identical or different screw elements according to the invention and having drive shafts rotating in the same direction and at the same speed, the screw elements according to the invention being located opposite each other in pairs on the two drive shafts. In addition, the present invention relates to the use of the screw element according to the invention for processing or producing a plastic material.

Description

Technical Field

[0001] The present invention relates to a screw element with a non-axisymmetric screw cross-sectional profile, the cross-sectional profile having at least two construction points located within the screw cross-sectional profile. The screw element according to the invention is suitable for use in an extruder having two drive shafts, which rotate in the same direction and at the same speed, for the purpose of processing or producing a plastic substance in the form of an extrudate. The present invention also relates to the arrangement of two identical or different screw elements according to the invention in an extruder, the extruder having two drive shafts rotating in the same direction and at the same speed, wherein the screw elements according to the invention are located opposite each other in pairs on the two drive shafts. The present invention also relates to an extruder, which is equipped with two identical or different screw elements according to the invention and has two drive shafts rotating in the same direction and at the same speed, wherein the screw elements according to the invention are located opposite each other in pairs on the two drive shafts. In addition, the present invention relates to the use of the screw element according to the invention for processing or producing a plastic substance. Background Art

[0002] In an arrangement of two identical or different screw elements according to the invention in an extruder with two drive shafts rotating in the same direction and at the same speed, wherein the screw elements according to the invention are located in pairs opposite one another on the two drive shafts, the screw elements according to the invention located in pairs opposite one another on the two drive shafts partially but not completely clean one another.

[0003] The screw elements according to the invention are also suitable for use in extruders with more than two drive shafts, for example extruders with more than three or four drive shafts, or known annular extruders with eight to sixteen, in particular twelve drive shafts arranged annularly relative to one another. In this respect, identical or different screw elements according to the invention are arranged relative to one another on the drive shafts in a number corresponding to the number of drive shafts of the respective extruder.

[0004] Even in an arrangement of more than two identical or different screw elements according to the invention in an extruder with more than two drive shafts rotating in the same direction and at the same speed, wherein the screw elements according to the invention are located in pairs opposite to one another on the more than two drive shafts, the screw elements according to the invention located in pairs opposite to one another on the more than two drive shafts partially, but not completely, clean one another.

[0005] The screw cross-sectional profile is also referred to hereinafter as screw profile for short. In the context of the present invention, a construction point is understood to mean a point from which at least one arc of the screw profile is constructed and which is the center of the at least one arc. In this context, the center of an arc denotes a point which is the center of a circle, the associated arc being a subset of the circle.

[0006] The term "arc" means that it is not only a point on the screw profile, but that the arc has at least two points that are different from each other and have a non-zero angular spacing, wherein all points of the arc have the same center and the same radius, and the arc is that part of a circular line that belongs to a circular sector. The angular spacing is also referred to below as the center angle.

[0007] The two arcs that are directly adjacent to a particular arc are:

[0008] On the one hand, the arc before this particular arc,

[0009] On the other hand, the arc immediately following this particular arc.

[0010] Directly adjacent arcs have a common contact point. If the screw profiles can be distinguished at this contact point, the two arcs having this common contact point have different radii, because otherwise the two arcs having the same radius could combine to form a larger arc. If the screw profiles cannot be distinguished at this contact point, the two arcs having this common contact point have different radii or the same radius.

[0011] The drive shaft of the extruder which is equipped with screw elements, regardless of whether they are according to the invention or according to the prior art, is also referred to below as screw shaft.

[0012] Screw elements suitable for use in extruders with two drive shafts rotating in the same direction and at the same speed for the purpose of processing or producing plastic materials in the form of extrudates have long been known. For example, [1] = Klemens Kohlgrüber: Der gleichl ufige Doppelschnecnexteruder [Co-rotating twin-screw extruder] (Hanser Verlag, Munich, 2007) gives a detailed and good overview of the prior art related to such screw elements and extruders. "Extruder" is also referred to as "screw machine" hereinafter.

[0013] However, in the case of screw elements from the prior art, problems that frequently occur alone or in combination are:

[0014] - Insufficient mixing,

[0015] - an uneven force distribution occurs between the inner wall of the extruder housing and the flight flanks of the screw elements, in particular between the inner wall of the housing and the screw flight flank closest to the housing,

[0016] - the angle of the screw flight face closest to the housing cannot be freely selected,

[0017] - a uniform distribution of the extrudate cannot be ensured when the extruder is partially filled, wherein partial filling is understood in particular to mean when the actual output of the extrudate in one section of the extruder is lower than the maximum possible output through this section, preferably by at least 10% lower, particularly preferably by at least 20% lower, very particularly preferably by 25% to 75% lower, without pressure buildup,

[0018] - And in the past few years, the screw profile has not been based on a standard screw profile, such as the Erdmenger screw profile, with the result that the construction and manufacturing costs are increased.

[0019] FIG. 5 of US 4131371A discloses an Erlmenger screw profile whose center (83, 83') is not identical to the axis of rotation (84, 84') or the housing bore. Such a screw profile is referred to as eccentric. The three-thread Erlmenger screw profile disclosed in FIG. 5 of US 4131371A is eccentrically positioned so that exactly one screw thread facet 80 (or 80') forms a symmetrical and narrow gap relative to the housing inner wall, and the other two thread faces form the same but significantly larger gap relative to the housing inner wall. This type of positioning results in an uneven gap between the screw thread facet 80 (or 80') and the housing, which results in an uneven force distribution.

[0020] The two- and three-thread Erlmenger screw profiles also disclosed in US Pat. No. 4,131,371 A have only one thread face tip, i.e. they have a thread face angle of 0°. Such a thread face tip is mechanically unstable. Eccentrically positioned two-thread face Erlmenger screw profiles with a thread face angle greater than 0° will also have an uneven gap between the screw thread face and the housing, as a result of which an uneven force distribution will occur.

[0021] Likewise, EP 850738 A2 discloses eccentric triple-flight screw elements, all of whose screw flight flanks have a flight flank angle of 0° and are therefore mechanically unstable.

[0022] DE 3412258 A1 discloses eccentric three- and four-flight screw elements, all of whose screw flight flanks have a flight flank angle of 0° and are therefore mechanically unstable.

[0023] WO 2011116965A1 discloses screw elements, wherein the center of their cross-sectional profile is arranged eccentrically offset relative to the center of the housing hole and the rotation center of the conveying shaft. When the screw elements are positioned relative to each other on the conveying shaft, the profiles of the screw elements are completely peeled off from each other. With this arrangement, the purpose is to improve product quality and reduce the load peak of the torque on the support shaft, and thus fundamentally improve the cost-effectiveness of the extruder. This is also the case here, where this positioning - similar to US 4131371A - leads to uneven gaps between the screw flight facets and the housing, resulting in uneven distribution of forces. In addition, the fact that the screw elements are self-cleaning without restriction leads to relatively poor mass transfer, that is, only insufficient mixing is achieved.

[0024] WO 2011006516A1 discloses a screw element having at least two threads and wherein the first thread ridge cleans the inner wall of the extruder housing with a small gap and the second thread ridge cleans the inner wall of the extruder housing with a large gap. With this arrangement, the aim is to provide an unlimited self-cleaning multi-screw extruder, by means of which the product quality is significantly and effectively improved. Due to the unlimited self-cleaning of the screw elements, the result is a relatively poor mass transfer, i.e. only an insufficient mixing effect is achieved.

[0025] Therefore, even if screw elements according to WO 2011116965 A1 or WO 2011006516 A1 are used, it is not possible to solve the above-mentioned problems in a satisfactory manner.

[0026] The above explanation of WO 2011006516 A1 is also applicable to EP 0002131 A1 and EP 0788868 A1.

[0027] Figures 6 to 8 of DE 19718292A1 disclose a double-thread screw element, the deviation of the radius of the thread facet from the radius of the inner wall of the housing is much greater than the housing gap. This structure - similar to US 4131371 A - also leads to an uneven gap between the screw thread facet and the housing, resulting in an uneven force distribution. For the screw element disclosed in Figure 9 of DE 19718292A1, the same applies as explained above for WO 2011006516A1. In Figure 7 of DE19718292A1, the thread facet has a thread facet angle of 0°. As has been further explained above, such a thread facet end is mechanically unstable. Summary of the invention

[0028] It is therefore an object of the present invention to provide a screw element by means of which the above-mentioned problems can be solved.

[0029] In particular, it is an object of the present invention to provide a screw element which makes it possible:

[0030] When the screw element is used in an extruder having two or more drive shafts,

[0031] - Improved mixing,

[0032] - ensure uniform distribution of forces between the flight ridge or ridges of the screw element and the inner wall of the extruder housing,

[0033] - gentler handling of extrudates,

[0034] - To ensure a uniform distribution of the extrudate when the extruder is partially filled. Against this background, the flight land(s) of the screw elements according to the invention should be mechanically stable.

[0035] This object is achieved by the screw element proposed by the present invention.

[0036] In particular, the object is achieved by:

[0037] A screw element having a number Z of grooves,

[0038] Suitable for twin-shaft screw machines,

[0039] having two screw shafts SW1 and SW2 rotating in the same direction and at the same speed, whose rotation axes D1 and D2 are at an axial distance a and having two circular housing holes penetrating each other, each hole having the same housing inner radius rg and whose hole centers M1 and M2 are at the same distance as the axial distance a and whose hole centers M1 and M2 coincide with the cross-sectional centers of the respective rotation axes D1 and D2 of the screw shafts SW1 and SW2,

[0040] Therein, the screw elements have a screw profile which:

[0041] (1) Forming a closed convex line,

[0042] (2) consists only of arcs with radii less than or equal to the axial distance a, where directly adjacent arcs have different radii,

[0043] (3) having a first construction point K1 located within the screw profile,

[0044] (4) It is not axisymmetric about the first construction point K1,

[0045] (5) consists of at least 4, preferably 4 to 25, particularly preferably 4 to 17 arcs,

[0046] (6) having a second construction point K2 which does not coincide with the first construction point K1, wherein the second construction point K2 is located within the screw profile,

[0047] (7) It is not point-symmetrical or axis-symmetrical about the second construction point K2,

[0048] (8) having a rotation point DP which coincides with one of the hole centers M1 or M2 and is located on the path from the first construction point K1 to the second construction point K2,

[0049] (9) having exactly one main thread facet HK, wherein the main thread facet HK is formed by only one circular arc and the center of the circular arc is the second construction point K2, and wherein the contact points of the main thread facet HK and the two circular arcs directly adjacent to the main thread facet HK are the set of points of the screw profile that are farthest from the second construction point K2,

[0050] (10) having at least one groove, wherein one groove is formed by only one circular arc, the center of which is the first construction point K1, and one groove is an arc whose radius is the same as the core radius ri, and wherein, except for the corresponding common contact point, the distance between the two circular arcs directly adjacent to one groove and the first construction point K1 is greater than the circular arc of the groove,

[0051] (11) having a plurality of side faces, wherein the side faces are those regions of the screw profile whose arc centers are neither the first construction point K1 nor the second construction point K2,

[0052] (12) The groove is separated from the nearest point of the main thread land HK by at least one arc, which is the side surface.

[0053] The number Z of grooves is understood here to mean the number of grooves in the screw profile. The number Z of grooves is an integer natural number greater than or equal to 1. The number Z of grooves is preferably an integer from 1 to 4, and a number of grooves of 2 is particularly preferred.

[0054] According to the invention, preferably, the screw profile according to the invention is not point-symmetrical or is not point-symmetrical about the first construction point K1 , preferably, the screw profile according to the invention is not point-symmetrical about the first construction point K1 .

[0055] The arc forming the main flight land HK preferably has a center angle greater than 0°, and the arc forming the main flight land HK preferably has a center angle of 1° to 179°. As a result, compared with the prior art, when the screw element is used as intended, the main flight land HK, which is usually exposed to the maximum mechanical load, has a high mechanical stability.

[0056] According to the invention, the number of arcs of the screw profile according to the invention is preferably equal to the number of grooves Z multiplied by 4 or equal to the number of grooves multiplied by 4 and then increased by 1, that is to say the screw profile according to the invention

[0057] - when the number of grooves is Z=1, it preferably consists of exactly 4 arcs or exactly 5 arcs, particularly preferably consists of exactly 5 arcs,

[0058] - when the number of grooves is Z=2, preferably consists of exactly 8 arcs or exactly 9 arcs, particularly preferably consists of exactly 9 arcs,

[0059] - when the number of grooves is Z=3, preferably consists of exactly 12 arcs or exactly 13 arcs, particularly preferably consists of exactly 13 arcs,

[0060] For a number of grooves Z=4, it preferably consists of exactly 16 arcs or exactly 17 arcs, particularly preferably of exactly 17 arcs.

[0061] According to the invention, the second construction point K2 of the screw profile according to the invention is preferably located within a circle centered at the first construction point K1 and having a core radius ri as radius, wherein the core radius ri is the radius corresponding to the minimum distance from the first construction point K1 to a point on the screw profile.

[0062] According to the invention, the second construction point K2 of the screw profile according to the invention particularly preferably lies in a circle having the first construction point K1 as centre and a radius of at most 30%, very particularly preferably at most 20%, of the core radius ri.

[0063] Compared to the prior art, this achieves a situation in which the screw elements have a high mechanical stability when used as intended. This also makes it possible to handle the extrudate more gently than in the prior art.

[0064] The rotation point DP of the screw element according to the invention is preferably closer to the second construction point K2 than to the first construction point K1 , and particularly preferably the rotation point DP is located at the second construction point K2 .

[0065] The arc radius rHK of the main thread face HK preferably corresponds to the housing inner radius rg minus the main thread face clearance c_HK. In this case, the main thread face clearance c_HK is greater than 0. Here, the main thread face clearance c_HK is preferably 0.1% to 3.2%, preferably 0.2% to 2.6%, particularly preferably 0.3% to 2.0%, very particularly preferably approximately 0.8% to 1.4% of the housing inner radius rg. The main thread face clearance c_HK is particularly preferably constant over the entire main thread face height HK; thus, a shear gap with a constant distance is formed between the main thread face HK and the housing inner wall.

[0066] The arc forming the groove preferably has,

[0067] - when the number of grooves is Z=1, the center angle is 90° to 150°, preferably 95° to 140°, particularly preferably 100° to 130°,

[0068] - when the number of grooves is Z=2, the center angle is 5° to 50°, preferably 10° to 40°, particularly preferably 15° to 30°, wherein the center angles of the grooves may be the same or different, but are preferably the same,

[0069] - when the number of grooves is Z=3, the corresponding center angle is 3° to 30°, preferably 6° to 24°, particularly preferably 9° to 18°, wherein the center angles of the grooves may be the same or different, but are preferably the same,

[0070] When the number of grooves is Z=4, the corresponding center angle is 2° to 20°, preferably 4° to 16°, particularly preferably 6° to 12°, wherein the center angles of the grooves may be the same or different, but are preferably the same.

[0071] The screw profile according to the present invention can have a third construction point K3, wherein the screw profile is not axisymmetric or point-symmetric about the third construction point K3, wherein the third construction point K3 is a point that is at the same distance from the second construction point K2 as from the first construction point K1, and wherein the first construction points K1, K2 and K3 are located on a straight line, and K1, K2 and K3 are not the same.

[0072] The screw profile according to the invention can have one secondary flight land or a plurality of secondary flight lands NK i =NK1 to NK n , where each secondary thread face NK i It is formed by only one arc, the center of which is the first construction point K1 or the second construction point K2 or the third construction point K3. The subscripts i and n represent positive integers. The index n specifies the number of secondary thread facets NK1 to NK n . Secondary thread lands NK1 to NK nThe number n is preferably equal to the number of grooves Z.

[0073] If the screw profile according to the invention has at least one secondary flight land NK i , then the groove and the secondary thread edge NK i Since the groove - as explained above - is separated from the closest point of the main flight land HK by at least one arc - which is the side, the following holds true if the screw profile according to the invention has at least one secondary flight land NK i , the groove is not only separated from the nearest point of the main thread edge HK by at least one arc (which is the side), but also separated from the secondary thread edge NK i The closest points of the two sides are separated by at least one arc, which is the side.

[0074] Forming secondary thread land NK i The arc preferably has a central angle greater than 0°, forming the secondary thread edge NK i The arc preferably has a central angle of 1° to 179°. As a result, compared with the prior art, the secondary thread face NK i Has high mechanical stability, when the screw element is used as expected, the secondary flight land NK i The highest mechanical loads are usually experienced after the main thread land HK.

[0075] Forming secondary thread land NK i And in this case, the arcs in which neither of the two directly adjacent arcs is a main thread land HK particularly preferably have,

[0076] - when the number of grooves is 2, a center angle of 5° to 50°, preferably 10° to 40°, particularly preferably 15° to 30°,

[0077] - when the number of grooves is 3, a center angle of 3° to 30°, preferably 6° to 24°, particularly preferably 9° to 18°,

[0078] - When the number of grooves is 4, a center angle of 2° to 20°, preferably 4° to 16°, particularly preferably 6° to 12°, wherein on a plurality of secondary thread lands NK1 to NK n In the case of the secondary thread lands NK1 to NK n The central angles can be the same or different.

[0079] Forming secondary thread land NK i And one of the two directly adjacent arcs is the arc of the main thread land HK, in which case it is particularly preferred to have,

[0080] - a center angle of greater than 0° to 140°, preferably 5° to 110°, particularly preferably greater than 10° to 80°, when the number of grooves is Z=1,

[0081] - for a number of grooves Z=2, correspondingly a center angle of greater than 0° to 45°, preferably 5° to 30°, particularly preferably greater than 10° to 15°,

[0082] - for a number of grooves Z=3, correspondingly a center angle greater than 0° to 27°, preferably 2° to 18°, particularly preferably 4° to 9°,

[0083] - for a number of grooves Z=4, correspondingly a center angle greater than 0° to 18°, preferably 1° to 12°, particularly preferably 2° to 6°,

[0084] Among them, on multiple secondary thread edges NK1 to NK n In the case of the secondary thread lands NK1 to NK n The central angles can be the same or different.

[0085] For the screw profile according to the invention, one or more secondary flight lands NK may be provided. i =NK1 to NK n , it is also established that

[0086] -When the secondary thread land NK is formed i When the center of the arc is the first construction point K1, in addition to the secondary thread face NK i In addition to the corresponding common points of contact, each with a secondary thread edge NK i The two directly adjacent arcs have a smaller distance to the first construction point K1, or when forming the secondary thread land NK i When the center of the arc is the second construction point K2, it has a smaller distance to the second construction point K2, or when the secondary thread face NK is formed i When the center of the arc is the third construction point K3, it has a smaller distance to the third construction point K3,

[0087] -When the secondary thread land NK is formed i When the center of the arc is the second construction point K2, the secondary thread face NK is formed. i The arc of the thread is at a smaller distance from the second construction point K2 than the main thread edge HK.

[0088] The arc forming the main thread face HK is preferably the same as the arc forming the secondary thread face NK. i The arc of the secondary thread land NKi has the first construction point K1 as the center and its radius rNK corresponds to the housing inner radius rg minus the secondary thread land clearance c_NK.

[0089] The main thread land HK is formed and the two directly adjacent arcs are not the secondary thread land NK i The arc preferably has,

[0090] - for a number of grooves Z=1, a center angle of 90° to 150°, preferably 95° to 140°, particularly preferably 100° to 130°,

[0091] - when the number of grooves is Z=2, a center angle of 5° to 50°, preferably 10° to 40°, particularly preferably 15° to 30°,

[0092] - When the number of grooves is Z=3, the central angle is 3° to 30°, preferably 6° to 24°, and particularly preferably 9° to 18°; - When the number of grooves is Z=4, the central angle is 2° to 20°, preferably 4° to 16°, and particularly preferably 6° to 12°.

[0093] The arc forms the main thread land HK and one of the two directly adjacent arcs is the secondary thread land NK i The arc preferably has,

[0094] - a center angle of 10° to 150°, preferably 30° to 140°, particularly preferably 50° to 130°, for a number of grooves Z=1,

[0095] - when the number of grooves is Z=2, a center angle of 5° to 50°, preferably 10° to 40°, particularly preferably 15° to 30°, - when the number of grooves is Z=3, a center angle of 3° to 30°, preferably 6° to 24°, particularly preferably 9° to 18°,

[0096] For a number of grooves Z=4, a center angle of 2° to 20°, preferably 4° to 16°, particularly preferably 6° to 12°.

[0097] In particular, the two internal angles between the arc of the main thread face HK and the arc directly preceding the arc of the main thread face HK and having a common contact point with the arc of the main thread face HK and also the arc immediately following the arc of the main thread face HK and having a common contact point with the arc of the main thread face HK are from 130° to 180°, preferably from 135° to 180°, particularly preferably from 140° to 180°. In this respect, the two internal angles can be the same or different; preferably, they are different.

[0098] In the context of the present invention, the internal angle between two directly adjacent arcs is the angle between the tangents of the associated arcs which lie within the screw profile, wherein the tangents extend through a common contact point of the associated arcs.

[0099] In addition, in particular, the secondary thread land NKi The arc and the NK directly located on the secondary thread edge i The arc is in front of the secondary thread face NK i The arc of the arc has a common contact point and there is also an arc next to the secondary thread edge NK i The arc is connected with the secondary thread edge NK i The two internal angles between the arcs of the circle having a common contact point are from 130° to 180°, preferably from 135° to 180°, particularly preferably from 140° to 180°. In this respect, the two internal angles may be the same or different.

[0100] Most particularly, all interior angles between two directly adjacent arcs of the screw profile according to the invention are from 130° to 180°, preferably from 135° to 180°, particularly preferably from 140° to 180°.

[0101] Compared to the prior art, this also achieves a situation in which the screw elements have a high mechanical stability when used as intended. This also makes it possible to handle the extrudate more gently than in the prior art.

[0102] The side surface preferably has a radius corresponding to the axial distance a. More preferably, the arc forming the side surface has a center which is neither the first construction point K1 nor the second construction point K2 nor the third construction point K3.

[0103] Further preferably, the distance from the first construction point K1 to the second construction point K2 is 0.2% to 20%, preferably 0.4% to 15%, particularly preferably 0.6% to 10%, very particularly preferably 0.8% to 5% of the inner radius rg of the housing.

[0104] Further preferably, in the case of the screw profile according to the invention,

[0105] - when the number of grooves is Z=1, the smaller angle between the angle bisector of the groove and the connecting line between K1 and K2 is from 0° to 90°, preferably from 45° to 70°, and particularly preferably approximately 55°,

[0106] - when the number of grooves is Z=2, the smaller angle between the angle bisector of the groove (the arc point of the groove lying on the angle bisector of the groove is separated from the closest point of the main thread land HK by a smaller curve length) and the connecting line between K1 and K2 is from 110° to 160°, preferably from 125° to 145°, and particularly preferably approximately 135°,

[0107] - when the number of grooves is Z=3, the smaller angle between the angle bisector of the groove (the arc point of the groove lying on the angle bisector of the groove is separated from the closest point of the main thread land HK by a smaller curve length) and the connecting line between K1 and K2 is from 130° to 170°, preferably from 140° to 160°, and particularly preferably approximately 150°,

[0108] - When the number of grooves is Z=4, the smaller angle between the angular bisector of the groove (the arc point of the groove located on the angular bisector of the groove is separated from the nearest point of the main thread edge HK by a smaller curve length) and the connecting line between K1 and K2 is from 140° to 175°, preferably from 150° to 165°, and particularly preferably approximately 157.5°.

[0109] It can be seen from the above

[0110] the distance of the main thread land HK from the first construction point K1 at each point of the main thread land HK is greater than the core radius and therefore also greater than the distance between the groove and the first construction point K1,

[0111] - the distance of the main thread face HK from the second construction point K2 at each point of the main thread face HK is equal to or smaller than the housing inner radius rg,

[0112] - Each secondary thread land NK i On the relevant secondary thread land NK i The distance from the first construction point K1 at each point is greater than the core radius, and therefore the distance is also greater than the distance between the groove and the first construction point K1,

[0113] -Main thread face HK and secondary thread face NK i directly adjacent to each other and may have a common point of contact.

[0114] The screw element according to the invention makes it possible when the screw element is used in an extruder having two or more drive shafts.

[0115] - Improved mixing,

[0116] - ensure uniform distribution of forces between one or more flight lands of the screw element and the inner wall of the extruder housing,

[0117] - gentler handling of extrudates,

[0118] - Ensure that the extrudate is evenly distributed when the extruder is partially filled.

[0119] In this case, compared to the prior art, the screw elements, in particular the main flight lands HK and - if present - the secondary flight lands NK i Or secondary thread lands NK1 to NKn , most especially the main thread land HK, which has high mechanical stability.

[0120] This is surprising because, as described above, in the case of an arrangement of two identical or different screw elements according to the invention in an extruder with two drive shafts rotating in the same direction and at the same speed, wherein the screw elements according to the invention are located opposite each other in pairs on the two drive shafts, the screw elements according to the invention located opposite each other in pairs on the two drive shafts only partially but not completely clean each other. As described above, this also applies analogously to the arrangement of more than two identical or different screw elements according to the invention in an extruder with more than two drive shafts rotating in the same direction and at the same speed, wherein the screw elements according to the invention are located opposite each other in pairs on more than two drive shafts.

[0121] Until now, it has been assumed that screw elements which completely clean one another are necessary to achieve this goal.

[0122] However, surprisingly it has been found that with the screw elements according to the invention,

[0123] - better mixing action due to the return flow of the extrudate into the non-self-cleaning areas of the screw elements - uniform force distribution due to the shear gap with a constant distance between the main flight land HK and the inner wall of the housing, and

[0124] - In the case of partial filling, a more uniform distribution of the plastic mass is achieved due to the reflow of the extrudate in the non-self-cleaning areas of the screw elements.

[0125] This also enables gentler processing of the extrudate compared to the prior art.

[0126] When used in a screw machine, the main flight lands HK of the screw element according to the invention shorten the flow channel, which is formed in such a way that a uniform flow gap is formed along the housing wall. This leads to a uniform distribution of forces.

[0127] The screw elements according to the invention are suitable for being arranged in pairs and operating in screw machines having two drive shafts rotating in the same direction and at the same speed and having another screw element according to the invention having the same or different screw profile and having the same or different rotation point arrangement on the other screw shaft, wherein preferably screw elements according to the invention having the same screw profile are used. The screw elements according to the invention are similarly also suitable for use in screw machines having more than two drive shafts rotating in the same direction and at the same speed.

[0128] The screw elements according to the invention can be in the form of conveying, kneading or mixing elements, preferably in the form of conveying elements or kneading elements.

[0129] The invention therefore also relates to the arrangement of two identical or different screw elements according to the invention in a screw machine having two drive shafts rotating in the same direction and at the same speed, wherein the screw elements according to the invention are located opposite each other in pairs on the two drive shafts. Accordingly, the invention therefore also relates to the arrangement of more than two identical or different screw elements according to the invention in a screw machine having more than two drive shafts rotating in the same direction and at the same speed, wherein the screw elements according to the invention are located opposite each other in pairs on the more than two drive shafts.

[0130] The invention also relates to a screw machine equipped with two identical or different screw elements according to the invention and having two drive shafts rotating in the same direction and at the same speed, wherein the screw elements according to the invention are located on the two drive shafts in pairs opposite to each other. Accordingly, the invention also relates to a screw machine equipped with more than two identical or different screw elements according to the invention and having more than two drive shafts rotating in the same direction and at the same speed, wherein the screw elements according to the invention are located on the more than two drive shafts in pairs opposite to each other.

[0131] The screw profile according to the invention can be constructed in a simple manner from a reference screw profile; this reference screw profile is preferably a screw profile from the prior art, particularly preferably a so-called Ermenger profile, see [1], pages 249 to 253.

[0132] In this regard, the following holds

[0133] The core radius ri, the number of grooves Z and the outer radius ra of the screw profile according to the invention correspond to the core radius ri, the number of grooves Z and the outer radius ra of the reference screw profile.

[0134] as well as

[0135] The first construction point K1 of the screw profile according to the invention is identical to the first construction point K1 of the reference screw profile,

[0136] wherein the outer radius rfra of the reference screw profile is 0.2% to 10%, preferably 0.4% to 7.5%, particularly preferably 0.6% to 5%, very particularly preferably 0.8% to 2.5% smaller than the inner radius rg of the housing,

[0137] ●Among them

[0138] o If each of the reference screw profiles is at a reference distance rfa corresponding to the axial distance a, and

[0139] ○ If the reference screw profile rotates at its corresponding rotation reference point, then the rotation reference point 1 (rfDP1) and the rotation reference point 2 (rfDP2) rotate at the same speed and in the same direction of rotation

[0140] Two similar reference screw profiles then clean each other exactly in pairs.

[0141] A second construction point K2 is then inserted into this reference screw profile - as explained above - and if appropriate - as explained above - also a third construction point K3 is inserted. Starting from this second construction point K2 and, if present, also from the third construction point K3, at least one further arc is inserted into the screw profile, wherein the at least one further arc intersects the at least one arc already present in the reference screw profile and the portion of the at least one already present arc that has been "cut off" by the at least one further arc is replaced by the at least one further arc.

[0142] Furthermore, the invention relates to the use of a screw element according to the invention for processing or producing plastics materials.

[0143] In the context of the present invention, plastic substances are understood to mean:

[0144] Suspensions, pastes, glass melts, unfired ceramics, metal melts, plastics, plastic melts or solutions, polymer melts or solutions, elastomers, rubber melts or solutions.

[0145] Plastics, polymer solutions or polymer melts are preferably used, particularly thermoplastic polymers. The thermoplastic polymers used are preferably selected from at least one of the groups of polycarbonates, polyamides, polyesters (especially polybutylene terephthalate and polyethylene terephthalate), polylactides, polyethers, thermoplastic polyurethanes, polyacetals, fluoropolymers (especially polyvinylidene fluoride), polyether sulfones, polyolefins, especially polyethylene and polypropylene, polyimides, polyacrylates (especially polymethyl methacrylate), polyphenylene oxides, polyphenylene sulfides, polyether ketones, polyaryletherketones, styrene polymers (especially polystyrene), styrene copolymers (especially styrene-acrylonitrile copolymers), acrylonitrile-butadiene-styrene block copolymers and polyvinyl chloride. It is also preferred to use mixtures of the known listed polymers, which are understood by those skilled in the art to be combinations of two or more polymers. Particularly preferred are polycarbonates and mixtures containing polycarbonates, very particularly preferably polycarbonates, which are obtained, for example, by an interfacial process or a melt transesterification process.

[0146] Other preferred feed materials are rubber. Used rubber is preferably selected from at least one of the group of styrene-butadiene rubber, natural rubber, butadiene rubber, isoprene rubber, ethylene-propylene-diene rubber, ethylene-propylene rubber, butadiene-acrylonitrile rubber, hydrogenated nitrile rubber, butyl rubber, halogenated butyl rubber, chloroprene rubber, ethylene-vinyl acetate rubber, polyurethane rubber, thermoplastic polyurethane, gutta-percha, arylate rubber, fluorinated rubber, silicone rubber, vulcanized rubber and chlorosulfonyl polyethylene rubber. The combination of two or more listed rubbers, or the combination of one or more rubbers and one or more plastics is certainly possible.

[0147] These thermoplastics and elastomers can be used in pure form or as a mixture with fillers and reinforcing agents, such as in particular glass fibers, as a mixture with one another or with other polymers, or as a mixture with customary polymer additives.

[0148] In a preferred embodiment, the additive is added to the plastic material, in particular to the polymer melt and the mixture of the polymer melt. The additive can be added to the extruder in solid, liquid or solution form together with the polymer, or at least some or all of the additive is fed into the extruder via a side stream.

[0149] Additives can provide a variety of properties for polymers. The additives can be, for example, colorants, pigments, processing aids, fillers, antioxidants, reinforcing agents, ultraviolet light absorbers and light stabilizers, metal passivators, peroxide scavengers, alkaline stabilizers, nucleating agents, benzofurans and indolones with stable or antioxidant effects, mold release agents, flame retardant additives, antistatic agents, dyes and melt stabilizers. Examples of these include carbon black, glass fiber, clay, mica, graphite fiber, titanium dioxide, carbon fiber, carbon nanotubes, ionic liquids and natural fibers. BRIEF DESCRIPTION OF THE DRAWINGS

[0150] The invention will be explained in more detail by way of the following examples (but not limited thereto) with reference to the accompanying drawings. All figures were created using a computer program.

[0151] In order to create or describe a screw profile or element, it is advantageous to use dimensionless properties in order to simplify the transferability to screw elements or extruders of different sizes. Suitable as a reference variable for geometric variables such as, for example, length, radius or gap is the axial distance a, since this variable cannot be changed on the extruder. For the dimensionless axial distance A, A=a / a=1 holds. The dimensionless inner shell radius RG is calculated as RG=rg / a, where rg is the inner shell radius. For the dimensionless screw outer radius RA of the screw profile, it can be derived that RA=ra / a, where ra is the screw outer radius. The dimensionless core radius RI of the screw profile is calculated as RI=ri / a, where ri is the core radius. The dimensionless gap C between the screw flight facet and the shell is calculated as C=c / a, where c is the gap of the screw flight facet relative to the shell. The corresponding dimensionless gap of the main thread facet HK is denoted by C_HK, and the secondary thread facet NK is denoted by C_HK. i The corresponding dimensionless gap is denoted by C_NK. For the dimensionless radius R, R=r / a holds accordingly.

[0152] In these figures, all geometric variables are used in their dimensionless form on the right side of the corresponding figure. All angles are reported in radians or degrees.

[0153] Figure 1a shows a screw profile according to the prior art with a number of grooves Z=1, and Figure 1b Shows the eccentric displacement Figure 1a The screw profile.

[0154] In the context of the present invention, being in an eccentric displacement is understood to mean that the first construction point K1 of the screw profile is not located in the rotation point. The first construction point K1 is the point which is the center of the arc or arcs forming the groove or grooves.

[0155] Figure 2a shows a screw profile according to the invention having a number of grooves Z=1, and Figure 2b Shows the eccentric displacement Figure 2a The screw profile.

[0156] Figure 3a A further screw profile according to the invention is shown with a number of grooves Z=1, and Figure 3b Shows the eccentric displacement Figure 3a The screw profile.

[0157] Figure 4a A further screw profile according to the invention is shown with a number of grooves Z=1, and Figure 4b Shows the eccentric displacement Figure 4a The screw profile.

[0158] Figure 5a shows a screw profile according to the prior art with a number of grooves Z=2, and Figure 5b Shows the eccentric displacement Figure 5a The screw profile.

[0159] Figure 6a A screw profile according to the invention having a number of grooves Z=2 is shown, and Figure 6b Shows the eccentric displacement Figure 6a The screw profile.

[0160] Figure 7a A further screw profile according to the invention is shown with a number of grooves Z=2, and Figure 7b Shows the eccentric displacement Figure 7a The screw profile.

[0161] Figure 8a A further screw profile according to the invention is shown with a number of grooves Z=2, and Figure 8b Shows the eccentric displacement Figure 8a The screw profile.

[0162] Figure 9a A further screw profile according to the invention is shown with a number of grooves Z=2, and Figure 9b Shows the eccentric displacement Figure 9a The screw profile.

[0163] Fig.10a A further screw profile according to the invention is shown with a number of grooves Z=2, and Fig.10b Shows the eccentric displacement Fig.10a The screw profile.

[0164] Fig.11a1 shows a screw profile according to the prior art with a number of grooves Z=3, Fig.11a2 Shows Fig.11a1 A magnified view of the details around the screw thread edge (arc 6). Fig.11b1 shows the eccentric displacement from Fig.11a1 The screw profile, and Figure 11b2 Shows Fig.11b1 An enlarged view of the details around the screw thread land (arc 6).

[0165] Fig.12a1 shows a screw profile according to the invention having a number of grooves Z=3, Fig.12a2 Shows Fig.12a1 The main thread face HK (arc 6a) and the secondary thread face NK i (Arc 6) Enlarged details around it, Figure 12b1 The screw profile of FIG. 12a is shown in an eccentric displacement, and Figure 12b2 Shows Figure 12b1 The main thread face HK (arc 6a) and the secondary thread face NK i Zoomed in detail around (arc 6).

[0166] Fig.13a1 shows a screw profile according to the prior art with a number of grooves Z=4, Fig.13a2 An enlarged view of the detail around the screw flight land (arc 6) is shown, and Figure 13b1 Shows the eccentric displacement Fig.13a1 The screw profile, and Figure 13b2 Shows Figure 13b1 Magnified view of the detail around the screw flight land (arc 6).

[0167] Fig.14a1 shows a screw profile according to the invention with a number of grooves Z=4, Fig.14a2 Shows Fig.14a1 The main thread face HK (arc 6a) and the secondary thread face NK i (Arc 6) Enlarged details around it, Figure 14b1 Shows the eccentric displacement Fig.14a1 The screw profile, and Figure 14b2 Shows Figure 14b1 The main thread face HK (arc 6a) and the secondary thread face NK i Zoomed in detail around (arc 6).

[0168] Fig.15 The screw profile according to the invention is shown as a pair of two identical screw profiles with Figure 2b The number of grooves is Z=1.

[0169] Fig.16 The screw profile according to the invention is shown as a pair of two identical screw profiles with Figure 6b The number of grooves is Z=2.

[0170] Fig.17 The screw profile according to the invention is shown as a pair of two identical screw profiles with a number Z=3 of grooves from FIG. 12 b .

[0171] Fig.18 The screw profile according to the invention is shown as a pair of two identical screw profiles with a number Z=4 of grooves from FIG. 14 b .

[0172] Fig.19 Shown according to Fig.16The screw profile of the present invention acts as a pair of conveying elements.

[0173] Fig. 20 Shown from Figure 5a A screw profile with a number of grooves Z=2 in , as a pair of two identical screw profiles. DETAILED DESCRIPTION

[0174] Figures 1 to 14 have essentially the same structure, which will be described in detail below. Each figure has a first construction point K1, and the origin of the x / y coordinate system is also located in the first construction point K1. In addition to the first construction point K1, the figure can also have a second construction point K2, and in addition, a third construction point K3 can also be provided. The arc of the screw profile is identified by a thick solid line, and the thick solid line is provided with a corresponding arc number. The arc is numbered continuously in a counterclockwise direction, that is to say, it has a mathematically positive direction meaning. In this regard, when the arc passes through in a mathematically positive direction, the starting point of the arc is the first point of the arc, and the end point is the last point of the arc. The center of the arc is represented by a small circle. The center of the arc is connected to both the starting point and the end point of the associated arc by a thin solid line. The dimensionless screw outer radius RA is represented by a thin dotted line, and its value is reported as four significant digits in the lower right corner of the figure. The dimensionless housing inner radius RG is represented by a thin solid line, and its value is also reported as four significant digits in the lower right corner of the figure. On the right side of the figure, for each arc, the associated dimensionless radius R, the associated center angle α, the associated dimensionless x-coordinate Mx of the arc center M, the associated dimensionless y-coordinate My of the arc center M, the associated dimensionless x-coordinate Ax of the arc start point AP and the associated dimensionless y-coordinate Ay of the arc start point AP are reported in each case as four significant digits. This information clearly defines the screw profile. In addition, in each of these figures, the dimensionless screw outer radius RA and the dimensionless housing inner radius RG are reported.

[0175] Figures 15 to 18 In each case the dimensionless inner radius of the shell RG is reported, and Fig. 20 Reported in are the dimensionless reference housing inner radius RFRG and the dimensionless reference screw outer radius RFRA.

[0176] exist Fig.15 and 17 In each of the two, for both the left-hand and right-hand screw profiles, the arcs are numbered consecutively in a mathematically positive manner, and in Fig.16 and 18 In each of , the arcs are numbered consecutively in a mathematically positive manner for the left-hand screw profile and the arcs are numbered consecutively in a mathematically negative manner for the right-hand screw profile.

[0177] Figure 1a : Figure 1a A screw profile according to the prior art with a number of grooves Z = 1 is shown. Dimensionless screw outer radius RA = 0.61. Dimensionless housing inner radius RG = 0.66. The first construction point K1 is located at the center M1 of the housing bore and thus at the associated rotation point DP1.

[0178] This embodiment is disadvantageous because the gap between the housing and the screw flight flank (arc 2) is large, resulting in poor cleaning of the housing.

[0179] Figure 1b : Figure 1b The screw profile is obtained by making the Figure 1a The displacement is achieved so that the end point of arc 2 corresponding to the starting point of arc 3, the first construction point K1 and the second construction point K2 are located on a straight line. The second construction point K2 is located at the center M1 of the housing bore and therefore at the associated rotation point DP1. The end point of arc 2 corresponding to the starting point of arc 3 is located on the dimensionless screw outer radius RA. The dimensionless screw outer radius RA = 0.65. The dimensionless housing inner radius is RG = 0.66.

[0180] According to Figure 1a Compared to the embodiment of the embodiment of the invention, this embodiment has a narrow gap between the housing and the end point of the arc 2, which leads to good cleaning of the housing. However, this embodiment is disadvantageous because the gap between the housing and the screw flight ridge (arc 2) is not constant and this leads to a converging or diverging channel between the housing and the screw flight ridge (arc 2) depending on the direction of rotation. When the screw profile rotates clockwise about the second construction point K2, the polymer mass is pressed into the converging channel between the housing and the screw flight ridge (arc 2), as a result of which a large compressive force acts on the screw element, which can move the screw element far enough away from the rotation point DP1 that the screw element comes into contact with the housing and / or the directly adjacent screw element, and this leads to mechanical wear of the screw element.

[0181] Figure 2a : Figure 2a A closed screw profile according to the invention is shown, which has a number of grooves Z=1 and consists of 5 arcs. The dimensionless inner housing radius is RG=0.66. The dimensionless outer screw radius RA=0.61. The secondary flight land NK i The dimensionless gap of (arc 2) relative to the housing is C_NK=0.05.

[0182] The screw profile includes a first construction point K1, which is located at the center M1 of the housing bore and thus at the associated rotation point DP1. The screw profile is not axisymmetric or point-symmetric about the first construction point K1. The first construction point K1 is the center of the arc 2. The arc 2 has a dimensionless radius R_2=0.61, which is identical to the dimensionless screw outer radius RA. The center angle is α_2=0.8186≈46.9°. The arc 2 represents the secondary flight facet NK i , because, apart from the common contact point, the two directly adjacent arcs 1 and 2a have a smaller distance to the first construction point K1. The first construction point K1 is the center of the arc 4. The arc 4 has a dimensionless radius R_4=0.39, which is the same as the dimensionless core radius RI. The center angle is α_4=1.9217≈110.1°. The arc 4 represents a groove, because, apart from the common contact point, the two directly adjacent arcs 1 and 3 have a larger distance to the first construction point K1.

[0183] The screw profile includes a second construction point K2, which does not coincide with the first construction point K1 and is located within the screw profile and also within a circle whose center is the first construction point K1 and whose dimensionless radius is the same as the dimensionless core radius R1. The screw profile is not axisymmetric or point-symmetric about the second construction point K2. The second construction point K2 is the center of the arc 2a. The arc 2a has a dimensionless radius R_2a=0.65, which is slightly smaller than the dimensionless inner shell radius RG=0.66. The center angle is α_2a=1.0799≈61.9°. The arc 2a represents the main thread face HK, because, except for the common contact point, the two directly adjacent arcs 2 and 3 have a small distance to the second construction point K2.

[0184] The distance between the second construction point K2 and the first construction point K1 is approximately 0.121 times the dimensionless inner radius RG of the housing. The smaller angle between the angle bisector of the groove (arc 4) and the connecting line between K1 and K2 is 55.1°. The first construction point K1, the second construction point K2 and the center of the arc 1 are located on a line.

[0185] The arcs 1 and 3 represent the side faces. The dimensionless radii R_1 and R_3 of the two arcs 1 and 3 are respectively R_1=R_3=1.00. The centers of the two arcs are different from the first construction points K1 and K2 in each case.

[0186] Main thread face HK (arc 2a) and secondary thread face NK i (Arc 2) contact each other. The main thread face HK and the secondary thread face NK i Each is separated from the groove by a side surface.

[0187] Figure 2b : Figure 2bThe screw profile is obtained by making the Figure 2a The displacement is achieved so that the second construction point K2 is located at the center M1 of the housing hole and therefore at the associated rotation point DP1. The dimensionless housing inner radius is RG=0.66. The dimensionless screw outer radius RA=0.65. Arc 2a has a dimensionless radius R_2a=0.65, which is the same as the dimensionless screw outer radius RA. The dimensionless clearance of the main thread face HK (arc 2a) relative to the housing is C_HK=0.01. The first construction point K1, the second construction point K2 and the center of arc 1 are located on a line.

[0188] This embodiment is advantageous because it has a constant narrow gap between the housing and the main thread land HK (arc 2a), which leads to good cleaning of the housing. This embodiment is also advantageous because the length of the converging or diverging channel (depending on the direction of rotation) between the housing and the main thread land HK (arc 2) is significantly shorter than that according to Figure 1b Thus, when rotating clockwise, a converging channel is generated between the housing and the main thread land HK (arc 2a), and when rotating counterclockwise, a diverging channel is generated.

[0189] Figure 3a : Figure 3a A closed screw profile according to the invention is shown, which has a number of grooves Z=1 and consists of 5 arcs. The dimensionless inner housing radius is RG=0.66. The dimensionless outer screw radius RA=0.61. The secondary flight land NK i The dimensionless gap of (arc 2) relative to the housing is C_NK=0.05.

[0190] The screw profile includes a first construction point K1, which is located at the center M1 of the housing bore and thus at the associated rotation point DP1. The screw profile is not axisymmetric or point-symmetric about the first construction point K1. The first construction point K1 is the center of the arc 2. The arc 2 has a dimensionless radius R_2=0.61, which is identical to the dimensionless screw outer radius RA. The center angle is α_2=0.6946≈39.8°. The arc 2 represents the secondary flight face NK i , because, apart from the common contact point, the two directly adjacent arcs 1 and 2a have a smaller distance to the first construction point K1. The first construction point K1 is the center of arc 4. Arc 4 has a dimensionless radius R_4=0.39, which is the same as the dimensionless core radius RI. The center angle is α_4=1.9217≈110.1°. Arc 4 represents a groove, because, apart from the common contact point, the two directly adjacent arcs 1 and 3 have a larger distance to the first construction point K1.

[0191] The screw profile includes a second construction point K2, which does not coincide with the first construction point K1 and is located within the screw profile and is also located within a circle, the center of which is the first construction point K1 and the dimensionless radius of which is the dimensionless core radius RI. The screw profile is not axisymmetric or point-symmetric about the second construction point K2. The second construction point K2 is the center of the arc 2a. The arc 2a has a dimensionless radius R_2a=0.65, which is slightly smaller than the dimensionless inner shell radius RG=0.66. The center angle is α_2a=1.1594≈66.4°. The arc 2a represents the main thread face HK, because, except for the common contact point, the two directly adjacent arcs 2 and 3 have a small distance to the second construction point K2.

[0192] The distance between the second construction point K2 and the first construction point K1 is approximately 0.091 times the inner radius RG of the housing. The smaller angle between the angle bisector of the groove and the connecting line between K1 and K2 is 35.0°. The line between the first construction point K1 and the center of the arc 1 and the line between the second construction point K2 and the starting point of the arc 3 are approximately parallel.

[0193] Arcs 1 and 3 represent the side faces. The radii of the two arcs are respectively R_1=R_3=1.00. The centers of the two arcs are different from the first construction points K1 and K2 in each case.

[0194] Main thread face HK (arc 2a) and secondary thread face NK i (Arc 2) contact each other. The main thread edge and the secondary thread edge NK i Each is separated from the groove by a side surface.

[0195] Figure 3b : Figure 3b The screw profile is obtained by making the Figure 3a The displacement is achieved so that the second construction point K2 is located at the center M1 of the housing bore and therefore at the associated rotation point DP1. The dimensionless housing inner radius is RG=0.66. The dimensionless screw outer radius is RA=0.65. The arc 2a has a dimensionless radius R_2a=0.65, which is equal to the dimensionless screw outer radius RA. The dimensionless clearance of the main thread face HK (arc 2a) relative to the housing is C_HK=0.01.

[0196] This embodiment is advantageous because it has a constant narrow gap between the housing and the primary thread land HK (arc 2a), which results in good cleaning of the housing. This embodiment is also advantageous because the housing and the secondary thread land NK i The length of the converging or diverging channel (depending on the direction of rotation) between (arcs 2) is substantially less than Figure 1bThus, when rotating clockwise, a converging channel is created between the housing and the main thread land HK (arc 2a), and when rotating counterclockwise, a diverging channel is created.

[0197] Figure 4a : Figure 4a A closed screw profile according to the invention is shown, which has a number of grooves Z=1 and consists of 5 arcs. The dimensionless inner housing radius is RG=0.66. The dimensionless outer screw radius is RA=0.61. The secondary flight land NK i The dimensionless clearance of (arc 2) relative to the housing is C_NK=0.05. Here, the center of arc 1 is the same as the starting point of arc 3.

[0198] The screw profile includes a first construction point K1, which is located at the center M1 of the housing bore and thus at the associated rotation point DP1. The screw profile is not axisymmetric or point-symmetric about the first construction point K1. The first construction point K1 is the center of the arc 2. The arc 2 has a radius R_2=0.61, which is identical to the dimensionless screw outer radius RA. The center angle is α_2=0.5238≈30.0°. The arc 2 represents the secondary flight face NK i , because, apart from the common contact point, the two directly adjacent arcs 1 and 2a have a smaller distance to the first construction point K1. The first construction point K1 is the center of arc 4. Arc 4 has a dimensionless radius R_4=0.39, which is the same as the dimensionless core radius RI. The center angle is α_4=1.9217≈110.1°. Arc 4 represents a groove, because, apart from the common contact point, the two directly adjacent arcs 1 and 3 have a larger distance to the first construction point K1.

[0199] The screw profile includes a second construction point K2, which does not coincide with the first construction point K1 and is located within the screw profile and is also located within a circle, the center of which is the first construction point K1 and the dimensionless radius of which is the core radius RI. The screw profile is not axisymmetric or point-symmetric about the second construction point K2. The second construction point K2 is the center of the arc 2a. The arc 2a has a dimensionless radius R_2a=0.65, which is slightly smaller than the dimensionless inner shell radius RG=0.66. The center angle is α_2a=1.2966≈74.3°. The arc 2a represents the main thread face HK, because, except for the common contact point, the two directly adjacent arcs 2 and 3 have a small distance to the second construction point K2.

[0200] The distance between the second construction point K2 and the first construction point K1 is approximately 0.077 times the dimensionless inner radius RG of the housing. The smaller angle between the angle bisector of the groove and the connecting line between K1 and K2 is 15.0°. Figure 1a In contrast, the size and position of arc 3 remain unchanged.

[0201] Arcs 1 and 3 represent the side faces. The dimensionless radius of the two arcs is respectively R_1=R_3=1.00. The centers of the two arcs are different from the first construction points K1 and K2 in each case.

[0202] Main thread face HK (arc 2a) and secondary thread face NK i (Arc 2) contact each other. The main thread face HK and the secondary thread face NK i Each is separated from the groove by a side surface.

[0203] Figure 4b : Figure 4b The screw profile is obtained by making the Figure 4a The displacement is achieved so that the second construction point K2 is located at the center M1 of the housing bore and therefore at the associated rotation point DP1. The dimensionless housing inner radius is RG=0.66. The dimensionless screw outer radius is RA=0.65. The arc 2a has a radius R_2a=0.65, which is the same as the dimensionless screw outer radius RA. The dimensionless clearance of the main thread face HK (arc 2a) relative to the housing is C_HK=0.01. The center of circle 1 corresponds to the starting point of circle 3.

[0204] This embodiment is advantageous because it has a constant narrow gap between the housing and the primary thread land HK (arc 2a), which results in good cleaning of the housing. i The length of the converging or diverging channel (depending on the direction of rotation) between (arc 2) is significantly smaller than that according to Figure 1b Thus, when rotating clockwise, a converging channel is created between the housing and the main thread land HK (arc 2a), and when rotating counterclockwise, a diverging channel is created.

[0205] Figure 5a : Figure 5a A screw profile according to the prior art with a number of grooves Z = 2 is shown. The dimensionless screw outer radius is RA = 0.61. The dimensionless housing inner radius is RG = 0.66. The first construction point K1 is located at the center M1 of the housing bore and thus at the associated rotation point DP1.

[0206] This embodiment is disadvantageous because the gaps between the housing and the first thread flank (arc 2 ) and also between the housing and the second thread flank (arc 6 ) are large, resulting in poor cleaning of the housing.

[0207] Figure 5b : Figure 5b The screw profile is obtained by making the Figure 5aThe displacement is achieved so that the smaller angle between the angular bisector of arc 8 and the connecting line between the first construction point K1 and the second construction point K2 is 135°. The second construction point K2 is located at the center M1 of the housing bore and therefore at the associated rotation point DP1. The end point of arc 6, which corresponds to the starting point of arc 7, is located on the dimensionless screw outer radius RA. The dimensionless screw outer radius is RA=0.65. The dimensionless housing inner radius is RG=0.66.

[0208] According to Figure 5a Compared to the embodiment of , this embodiment has a narrow gap between the housing and the end point of the arc 6, which leads to good cleaning of the housing. However, a disadvantage of this embodiment is that the gap between the housing and the second thread face (arc 6) is not constant, and this leads to a converging or diverging channel between the housing and the second thread face (arc 6) depending on the direction of rotation. When the screw profile rotates clockwise about the second construction point K2, the polymer mass is pressed into the converging channel between the housing and the second thread face (arc 6), as a result of which a large compressive force acts on the screw element, which can move the screw element far enough away from the rotation point DP1 that the screw element comes into contact with the housing and / or the directly adjacent screw element, which leads to mechanical wear of the screw element.

[0209] Figure 6a : Figure 6a A closed screw profile according to the invention is shown, which has a number of grooves Z=2 and consists of 9 arcs. The dimensionless inner radius of the housing is RG=0.66. The dimensionless outer screw radius is RA=0.61. The dimensionless clearances of the first secondary thread facet NK1 (arc 2) and the second secondary thread facet NK2 (arc 6) relative to the housing are C_NK=0.05, respectively.

[0210] The screw profile includes a first construction point K1, which is located at the center M1 of the housing bore and thus at the associated rotation point DP1. The screw profile is not axisymmetric or point-symmetric about the first construction point K1. The first construction point K1 is the center of the arc 2. The arc 2 has a dimensionless radius R_2=0.61, which is identical to the dimensionless screw outer radius RA. The center angle is α_2=0.3509≈20.1°. The arc 2 represents the secondary flight face NK i , because apart from the common contact point, the two directly adjacent arcs 1 and 3 have a small distance to the first construction point K1. The first construction point K1 is the center of the arc 6. The arc 6 has a radius R_6=0.61, which is the same as the dimensionless screw outer radius RA. The center angle is α_6=0.0001≈0.006°. The arc 6 represents the secondary thread face NK i, because, apart from the common contact point, the two directly adjacent arcs 5 and 6a have a smaller distance to the first construction point K1. The first construction point K1 is the center of arc 4. Arc 4 has a radius R_4=0.39, which is the same as the dimensionless core radius RI. The center angle is α_4=0.3509≈20.1°. Arc 4 represents a groove, because, apart from the common contact point, the two directly adjacent arcs 3 and 5 have a larger distance to the first construction point K1. The first construction point K1 is the center of arc 8. Arc 8 has a radius R_8=0.39, which is the same as the dimensionless core radius RI. The center angle is α_8=0.3509≈20.1°. Arc 8 represents a groove, because, apart from the common contact point, the two directly adjacent arcs 1 and 7 have a larger distance to the first construction point K1.

[0211] The screw profile includes a second construction point K2, which does not coincide with the first construction point K1 and is located within the screw profile and is also located within a circle, the center of which is the first construction point K1 and the radius of which is the dimensionless core radius. The screw profile is not axisymmetric or point-symmetric about the second construction point K2. The second construction point K2 is the center of the arc 6a. The arc 6a has a dimensionless radius R_6a=0.65, which is slightly smaller than the dimensionless inner shell radius RG=0.66. The center angle is α_6a=0.3618≈20.7°. The arc 6a represents the main thread face HK, because, except for the common contact point, the two directly adjacent arcs 6 and 7 have a small distance to the second construction point K2.

[0212] The distance between the second construction point K2 and the first construction point K1 is approximately 0.100 times the dimensionless housing inner radius RG. The smaller angle between the angle bisector of the groove and the connecting line between K1 and K2 is 135.0°, and the arc point of the groove located on the angle bisector of the groove is separated from the closest point of the main thread land HK by a smaller curve length.

[0213] Arcs 1, 3, 5 and 7 represent side faces. The dimensionless radii of the four arcs are respectively R_1=R_3=R_5=R_7=1.00. The centers of the four arcs are different from the first construction points K1 and K2 in each case.

[0214] The main thread land HK (arc 6a) and the second secondary thread land NK2 (arc 6) are in contact with each other. The main thread land HK, the first secondary thread land NK1 (arc 2) and the second secondary thread land NK2 (arc 6) are each separated from the groove by a side surface.

[0215] Figure 6b : Figure 6b The screw profile is obtained by making the Figure 6aThe screw profile is shifted. This shift is achieved so that the second construction point K2 is located in the center M1 of the housing bore and therefore at the associated rotation point DP1. The dimensionless housing inner radius is RG=0.66. The dimensionless screw outer radius is RA=0.65. The arc 6a has a dimensionless radius R_6a=0.65, which is the same as the dimensionless screw outer radius RA. The dimensionless clearance of the main thread face HK (arc 6a) relative to the housing is C_HK=0.01.

[0216] This embodiment is advantageous because it has a constant narrow gap between the housing and the main thread land HK (arc 6a), which leads to good cleaning of the housing. Figure 5b Compared with the shell and the secondary thread face NK i The length of the converging or diverging passage (depending on the direction of rotation) between (arc 6) is practically equal to zero. Thus, when rotating clockwise, a converging passage is created between the housing and the main thread land HK (arc 6a), and when rotating counterclockwise, a diverging passage is created.

[0217] Figure 7a : Figure 7a A closed screw profile according to the invention is shown, which has a number of Z=2 grooves and consists of 9 arcs. The dimensionless inner radius of the housing is RG=0.66. The dimensionless outer radius of the screw is RA=0.61. The dimensionless clearances of the first secondary flight face NK1 (arc 2) and the second secondary flight face NK2 (arc 6) relative to the housing are C NK=0.05 respectively.

[0218] The screw profile includes a first construction point K1, which is located at the center M1 of the housing bore and thus at the associated rotation point DP1. The screw profile is not axisymmetric or point-symmetric about the first construction point K1. The first construction point K1 is the center of the arc 2. The arc 2 has a dimensionless radius R_2=0.61, which is identical to the dimensionless screw outer radius RA. The center angle is α_2=0.3509≈20.1°. The arc 2 represents the secondary flight facet NK i, because, apart from the common contact point, the two directly adjacent arcs 1 and 3 have a smaller distance to the first construction point K1. The first construction point K1 is the center of arc 6. Arc 6 has a dimensionless radius R_6=0.61, which is the same as the dimensionless screw outer radius RA. The center angle is α_6=0.0837≈4.8°. Arc 6 represents the secondary thread face NKi, because, apart from the common contact point, the two directly adjacent arcs 5 and 6a have a smaller distance to the first construction point K1. The first construction point K1 is the center of arc 4. Arc 4 has a dimensionless radius R_4=0.39, which is the same as the dimensionless core radius RI. The center angle is α_4=0.3509≈20.1°. Arc 4 represents the groove, because, apart from the common contact point, the two directly adjacent arcs 3 and 5 have a larger distance to the first construction point K1. The first construction point K1 is the center of arc 8. The arc 8 has a dimensionless radius R_8=0.39, which is identical to the dimensionless core radius RI. The center angle is α_8=0.3509≈20.1°. The arc 8 represents a groove, since, apart from the common contact point, the two directly adjacent arcs 1 and 7 have a greater distance to the first construction point K1.

[0219] The screw profile includes a second construction point K2, which does not coincide with the first construction point K1 and is located within the screw profile and is also located within a circle, the center of which is the first construction point K1 and the radius of which is the dimensionless core radius RI. The screw profile is not axisymmetric or point-symmetric about the second construction point K2. The second construction point K2 is the center of the arc 6a. The arc 6a has a dimensionless radius R_6a=0.65, which is slightly smaller than the dimensionless inner shell radius RG=0.66. The center angle is α_6a=0.2731≈15.6°. The arc 6a represents the main thread face HK, because, except for the common contact point, the two directly adjacent arcs 6 and 7 have a small distance to the second construction point K2.

[0220] The distance between the second construction point K2 and the first construction point K1 is approximately 0.091 times the dimensionless housing inner radius RG. The smaller angle between the angle bisector of the groove and the connecting line between K1 and K2 is 135.0°, and the arc point of the groove located on the angle bisector of the groove is separated from the closest point of the main thread land HK by a smaller curve length.

[0221] Arcs 1, 3, 5 and 7 represent side faces. The radii of the four arcs are respectively R_1 = R_3 = R_5 = R_7 = 1.00. The centers of the four arcs are different from the first construction points K1 and K2 in each case.

[0222] The main thread land HK (arc 6a) and the second secondary thread land NK2 (arc 6) are in contact with each other. The main thread land HK, the first secondary thread land NK1 (arc 2) and the second secondary thread land NK2 (arc 6) are each separated from the groove by a side surface.

[0223] Figure 7b : Figure 7b The screw profile is obtained by making the Figure 7a The displacement is achieved so that the second construction point K2 is located at the center M1 of the housing bore and therefore at the associated rotation point DP1. The dimensionless housing inner radius is RG=0.66. The dimensionless screw outer radius is RA=0.65. The dimensionless radius of the arc 6a is R_6a=0.65, which is the same as the dimensionless screw outer radius RA. The dimensionless clearance of the main thread face HK (arc 6a) relative to the housing is C_HK=0.01.

[0224] This embodiment is advantageous because it has a constant narrow gap between the housing and the primary thread land HK (arc 6a), which results in good cleaning of the housing. This embodiment is also advantageous because the housing and the secondary thread land NK i The length of the converging or diverging channel (depending on the direction of rotation) between (arcs 6) is significantly smaller than that according to Figure 5b Thus, when rotating clockwise, a converging channel is created between the housing and the main thread land HK (arc 6a), and when rotating counterclockwise, a diverging channel is created.

[0225] Figure 8a : Figure 8a A closed screw profile according to the invention is shown, which has a number of grooves Z=2 and consists of 9 arcs. The inner radius of the housing is RG=0.61. The dimensionless outer screw radius is RA=0.58. The dimensionless clearance of the first secondary flight face NK1 (arc 2) and the second secondary flight face NK2 (arc 6) relative to the housing is C_NK=0.03.

[0226] The screw profile comprises a first construction point K1, which is located at the center M1 of the housing bore and thus at the associated rotation point DP1. The screw profile is not axisymmetric or point-symmetric about the first construction point K1. The first construction point K1 is the center of the arc 2. The arc 2 has a dimensionless radius R_2=0.58, which is identical to the dimensionless screw outer radius RA. The center angle is α_2=0.5079≈29.1°. The arc 2 represents the secondary flight face NK i, because apart from the common contact point, the two directly adjacent arcs 1 and 3 have a small distance to the first construction point K1. The first construction point K1 is the center of the arc 6. The arc 6 has a dimensionless radius R_6=0.58, which is the same as the outer radius RA of the screw. The center angle is α_6=0.0320≈1.9°. The arc 6 represents the secondary thread face NK i , because, in addition to the common contact point, the two directly adjacent arcs 5 and 6a have a smaller distance to the first construction point K1. The first construction point K1 is the center of arc 4. Arc 4 has a dimensionless radius R_4=0.42, which is the same as the dimensionless core radius RI. The center angle is α_4=0.5079≈29.1°. Arc 4 represents a groove, because, in addition to the common contact point, the two directly adjacent arcs 3 and 5 have a larger distance to the first construction point K1. The first construction point K1 is the center of arc 8. Arc 8 has a dimensionless radius R_8=0.42, which is the same as the dimensionless core radius RI. The center angle is α_8=0.5079≈29.1°. Arc 8 represents a groove, because, in addition to the common contact point, the two directly adjacent arcs 1 and 7 have a larger distance to the first construction point K1.

[0227] The screw profile includes a second construction point K2, which does not coincide with the first construction point K1 and is located within the screw profile and is also located within a circle, the center of which is the first construction point K1 and the dimensionless radius of which is the dimensionless core radius RI. The screw profile is not axisymmetric or point-symmetric about the second construction point K2. The second construction point K2 is the center of the arc 6a. The arc 6a has a dimensionless radius R_6a=0.60, which is slightly smaller than the inner radius RG=0.61 of the housing. The center angle is α_6a=0.4895≈28.0°. The arc 6a represents the main thread face HK, because, except for the common contact point, the two directly adjacent arcs 6 and 7 have a small distance to the second construction point K2.

[0228] The distance between the second construction point K2 and the first construction point K1 is approximately 0.055 times the inner radius RG of the housing. The smaller angle between the angle bisector of the groove and the connecting line between K1 and K2 is 135.0°, and the arc point of the groove located on the angle bisector of the groove is separated from the closest point of the main thread face HK by a smaller curve length.

[0229] Arcs 1, 3, 5 and 7 represent side faces. The dimensionless radii of the four arcs are respectively R_1=R_3=R_5=R_7=1.00. The centers of the four arcs are different from the first construction points K1 and K2 in each case.

[0230] The main thread land HK (arc 6a) and the second secondary thread land NK2 (arc 6) are in contact with each other. The main thread land HK, the first secondary thread land NK1 (arc 2) and the second secondary thread land NK2 (arc 6) are each separated from the groove by a side surface.

[0231] Figure 8b : Figure 8b The screw profile is obtained by making the Figure 8a The screw profile is shifted. This shift is achieved so that the second construction point K2 is located at the center M1 of the housing bore and therefore at the associated rotation point DP1. The dimensionless housing inner radius is RG=0.61. The dimensionless screw outer radius is RA=0.60. The arc 6a has a dimensionless radius R_6a=0.60, which is the same as the dimensionless screw outer radius RA. The dimensionless clearance of the main thread face HK (arc 6a) relative to the housing is C_HK=0.01.

[0232] This embodiment is advantageous because it has a constant narrow gap between the housing and the primary thread land HK (arc 6a), which results in good cleaning of the housing. This embodiment is also advantageous because the housing and the secondary thread land NK i The length of the converging or diverging passages (depending on the direction of rotation) between (arcs 6) is substantially less than Figure 5b Thus, when rotating clockwise, a converging channel is created between the housing and the main thread land HK (arc 6a), and when rotating counterclockwise, a diverging channel is created.

[0233] Figure 9a : Figure 9a A closed screw profile according to the invention is shown, which has a number of grooves Z=2 and consists of 10 arcs. The dimensionless inner radius of the housing is RG=0.66. The dimensionless outer screw radius is RA=0.61. The dimensionless clearance of the first secondary thread face NK1 (arc 2) and the second secondary thread face NK2 (arc 6) relative to the housing is C_NK=0.05.

[0234] The screw profile includes a first construction point K1, which is located at the center M1 of the housing bore and thus at the associated rotation point DP1. The screw profile is not axisymmetric or point-symmetric about the first construction point K1. The first construction point K1 is the center of the arc 2. The arc 2 has a dimensionless radius R_2=0.61, which is identical to the dimensionless screw outer radius RA. The center angle is α_2=0.0550≈3.2°. The arc 2 represents the secondary flight face NK i, because apart from the common contact point, the two directly adjacent arcs 2a and 3 have a small distance to the first construction point K1. The first construction point K1 is the center of the arc 6. The arc 6 has a dimensionless radius R_6=0.61, which is the same as the dimensionless screw outer radius RA. The center angle is α_6=0.0837≈4.8°. The arc 6 represents the secondary thread face NK i , because, in addition to the common contact point, the two directly adjacent arcs 5 and 6a have a smaller distance to the first construction point K1. The first construction point K1 is the center of arc 4. The radius of arc 4 is R_4=0.39, which is the same as the dimensionless core radius RI. The center angle is α_4=0.3509≈20.1°. Arc 4 represents a groove, because, in addition to the common contact point, the two directly adjacent arcs 3 and 5 have a larger distance to the first construction point K1. The first construction point K1 is the center of arc 8. Arc 8 has a radius R_8=0.39, which is the same as the dimensionless core radius RI. The center angle is α_8=0.3509≈20.1°. Arc 8 represents a groove, because, in addition to the common contact point, the two directly adjacent arcs 1 and 7 have a larger distance to the first construction point K1.

[0235] The screw profile includes a second construction point K2, which does not coincide with the first construction point K1 and is located within the screw profile and also within a circle, the center of which is the first construction point K1 and the dimensionless radius of which is the dimensionless core radius RI. The screw profile is not axisymmetric or point-symmetric about the second construction point K2. The second construction point K2 is the center of the arc 2a. The arc 2a has a dimensionless radius R_2a=0.564, which is less than the dimensionless screw outer radius RA=0.61. The center angle is α_2a=0.3577≈20.5°. The arc 2a represents the secondary thread face NK i , because, except for the common contact point, the two directly adjacent arcs 1 and 2 have a smaller distance to the second construction point K2, and the arc 6a has a larger distance to the second construction point K2. The second construction point K2 is the center of the arc 6a. The arc 6a has a dimensionless radius R_6a=0.65, which is slightly smaller than the dimensionless inner shell radius RG=0.66. The center angle is α_6a=0.2731≈15.6°. The arc 6a represents the main thread face HK, because, except for the common contact point, the two directly adjacent arcs 6 and 7 have a smaller distance to the second construction point K2, and the arc 2a has a smaller distance to the second construction point K2.

[0236] The distance between the second construction point K2 and the first construction point K1 is approximately 0.091 times the dimensionless housing inner radius RG. The smaller angle between the angle bisector of the groove and the connecting line between K1 and K2 is 135.0°, and the arc point of the groove located on the angle bisector of the groove is separated from the closest point of the main thread land HK by a smaller curve length.

[0237] Arcs 1, 3, 5 and 7 represent side faces. The dimensionless radii of the four arcs are respectively R_1=R_3=R_5=R_7=1.00. The centers of the four arcs are different from the first construction points K1 and K2 in each case.

[0238] The main thread land HK (arc 6a) and the second secondary thread land NK2 (arc 6) are in contact with each other. The main thread land HK, the first secondary thread land NK1 (arc 2) and the second secondary thread land NK2 (arc 6) are each separated from the groove by a side surface.

[0239] Figure 9b : Figure 9b The screw profile is obtained by making the Figure 9a The screw profile is shifted. This shift is achieved so that the second construction point K2 is located at the center M1 of the housing bore and therefore at the associated rotation point DP1. The dimensionless housing inner radius is RG=0.66. The dimensionless screw outer radius is RA=0.65. The arc 6a has a dimensionless radius R_6a=0.65, which is equal to the dimensionless screw outer radius RA. The dimensionless clearance of the main thread face HK (arc 6a) relative to the housing is C_HK=0.01.

[0240] This embodiment is advantageous because it has a constant narrow gap between the housing and the primary thread facet HK (arc 6a), which results in good cleaning of the housing. Furthermore, this embodiment is advantageous because it has a constant gap between the housing and the first secondary thread facet NK1 (arc 2a). This embodiment is also advantageous because the length of the converging or diverging channels (depending on the direction of rotation) between the housing and the secondary thread facets NK (arc 2) and the second secondary thread facets NK2 (arc 6) is significantly shorter than the length of the converging or diverging channels (depending on the direction of rotation) according to the embodiment. Figure 5b Thus, when rotating clockwise, a converging channel is created between the housing and the main thread land HK (arc 6a), and when rotating counterclockwise, a diverging channel is created.

[0241] Fig.10a : Fig.10a A closed screw profile according to the invention is shown, which has a number of grooves Z=2 and consists of 10 arcs. The dimensionless inner radius of the housing is RG=0.66. The dimensionless outer radius of the screw is RA=0.61. The clearances of the first secondary thread face NK1 (arc 2) and the second secondary thread face NK2 (arc 6) relative to the housing are C_NK=0.05.

[0242] The screw profile comprises a first construction point K1, which is located at the center M1 of the housing bore and therefore at the associated rotation point DP1. The screw profile is point symmetrical about the first construction point K1. The first construction point K1 is the center of arc 2. Arc 2 has a dimensionless radius R_2=0.61, which is identical to the dimensionless screw outer radius RA. The center angle is α_2=0.0837≈4.8°. Arc 2 represents the secondary flight facet NK1, since, apart from the common contact point, the two directly adjacent arcs 2a and 3 have a smaller distance to the first construction point K1. The first construction point K1 is the center of arc 6. Arc 6 has a dimensionless radius R_6=0.61, which is identical to the dimensionless screw outer radius RA. The center angle is α_6=0.0837≈4.8°. Arc 6 represents the secondary thread facet NK2, since, apart from the common contact point, the two directly adjacent arcs 5 and 6a have a smaller distance to the first construction point K1. The first construction point K1 is the center of arc 4. Arc 4 has a dimensionless radius R_4=0.39, which is identical to the dimensionless core radius RI. The center angle is α_4=0.3509≈20.1°. Arc 4 represents a groove, since, apart from the common contact point, the two directly adjacent arcs 3 and 5 have a greater distance to the first construction point K1. The first construction point K1 is the center of arc 8. Arc 8 has a dimensionless radius R_8=0.39, which is identical to the dimensionless core radius RI. The center angle is α_8=0.3509≈20.1°. Arc 8 represents a groove, since, apart from the common contact point, the two directly adjacent arcs 1 and 7 have a greater distance to the first construction point K1.

[0243] The screw profile includes a second construction point K2, which does not coincide with the first construction point K1 and is located within the screw profile and is also located within a circle, the center of which is the first construction point K1 and the dimensionless radius of which is the dimensionless core radius RI. The screw profile is not axisymmetric or point-symmetric about the second construction point K2. The second construction point K2 is the center of the arc 6a. The arc 6a has a dimensionless radius R_6a=0.65, which is slightly smaller than the dimensionless inner shell radius RG=0.66. The center angle is α_6a=0.2731≈15.6°. The arc 6a represents the main thread face HK, because, except for the common contact point, the two directly adjacent arcs 6 and 7 have a small distance to the second construction point K2.

[0244] The screw profile includes a third construction point K3, which has the same distance to the first construction point K1 as the second construction point K2, and wherein the first construction points K1, K2 and K3 are located on a straight line, and K1, K2 and K3 are not the same. The screw profile is not axisymmetric or point-symmetric about the third construction point K3. The third construction point K3 is the center of the arc 2a. The arc 2a has a dimensionless radius R_2a=0.65, which is slightly smaller than the dimensionless inner radius RG=0.66 of the shell. The center angle is α_2a=0.2731≈15.6°. The arc 2a represents the secondary thread face NK3, because, except for the common contact point, the two directly adjacent arcs 2 and 3 have a smaller distance to the third construction point K3.

[0245] The distance between the second construction point K2 and the first construction point K1 is approximately 0.091 times the dimensionless housing inner radius RG. The smaller angle between the angle bisector of the groove and the connecting line between K1 and K2 is 135.0°, and the arc point of the groove located on the angle bisector of the groove is separated from the closest point of the main thread land HK by a smaller curve length.

[0246] Arcs 1, 3, 5 and 7 represent side faces. The dimensionless radii of the four arcs are respectively R_1=R_3=R_5=R_7=1.00. The centers of the four arcs are different from the first construction points K1 and K2 in each case.

[0247] The main thread land HK (arc 6a) and the second secondary thread land NK2 (arc 6) are in contact with each other. The main thread land HK, the first secondary thread land NK1 (arc 2) and the second secondary thread land NK2 (arc 6) are each separated from the groove by a side surface.

[0248] The screw profile is not axisymmetric about the first construction point K1 , but is point-symmetrical. In this way, the screw profile can be constructed particularly easily.

[0249] Fig.10b : Fig.10b The screw profile is obtained by making the Fig.10a The screw profile is shifted. This shift is achieved so that the second construction point K2 is located at the center M1 of the housing bore and therefore at the associated rotation point DP1. The dimensionless housing inner radius is RG=0.66. The dimensionless screw outer radius is RA=0.65. The arc 6a has a dimensionless radius R_6a=0.65, which is the same as the dimensionless screw outer radius RA. The dimensionless clearance of the main thread face (arc 6a) relative to the housing is C_HK=0.01.

[0250] This embodiment is advantageous because it has a constant narrow gap between the housing and the main thread land (arc 6a), which results in good cleaning of the housing. This embodiment is also advantageous because the length of the converging or diverging channel (depending on the direction of rotation) between the housing and the main thread land (arc 6) is significantly shorter than that according to Figure 5b Thus, when rotating clockwise, a converging channel is generated between the housing and the main thread land HK (arc 6a), and when rotating counterclockwise, a diverging channel is generated.

[0251] Figure 11a: Fig.11a1 shows a screw profile according to the prior art with a number of grooves Z=3, and Fig.11a2 Shows Fig.11a1 Detail around the arc 6 of FIG. 6 . The dimensionless outer screw radius is RA=0.54. The dimensionless inner housing radius is RG=0.584. The first construction point K1 is located at the center M1 of the housing bore and thus at the associated rotation point DP1.

[0252] This embodiment is disadvantageous because the gaps between the housing and the first thread ridge (arc 2), between the housing and the second thread ridge (arc 6), and between the housing and the third thread ridge (arc 10) are large, resulting in poor housing cleaning.

[0253] Figure 11b: Fig.11b1 The screw profile is obtained by making the Fig.11a1 The screw profile is shifted; Figure 11b2 Shows Fig.11b1 6. The displacement is achieved so that the smaller angle between the angular bisector of the arc 8 and the connecting line between the first construction point K1 and the second construction point K2 is 150°. The second construction point K2 is located at the center M1 of the housing bore and therefore at the associated point of rotation DP1. The end point of the arc 6, which corresponds to the start point of the arc 7, is located on the dimensionless screw outer radius RA, while the start point of the arc 6 is not located on the dimensionless screw outer radius RA. The dimensionless screw outer radius is RA=0.58. The dimensionless housing inner radius is RG=0.584.

[0254] According to Fig.11a1 Compared to the embodiment of the embodiment of the present invention, this embodiment has a narrow gap between the housing and the end point of the arc 6, which leads to good cleaning of the housing. However, a disadvantage of this embodiment is that the gap between the housing and the second thread facet (arc 6) is not constant, and this leads to a converging or diverging channel between the housing and the second thread facet (arc 6) depending on the direction of rotation. Thus, when rotating clockwise, a converging channel is generated between the housing and the main thread facet HK (arc 6), and when rotating counterclockwise, a diverging channel is generated.

[0255] Figure 12a: Fig.12a1 A closed screw profile according to the invention is shown, which has a number of grooves Z=3 and consists of 13 arcs, and Fig.12a2 Shows Fig.12a1 The enlarged view of the details around the arc 6 and arc 6a. The dimensionless inner radius of the housing is RG = 0.584. The dimensionless outer radius of the screw is RA = 0.54. The dimensionless clearances of the first secondary thread face NK1 (arc 2), the second secondary thread face NK2 (arc 6) and the third secondary thread face NK3 (arc 10) relative to the housing are C_NK = 0.044.

[0256] The screw profile comprises a first construction point K1, which is located at the center M1 of the housing bore and therefore at the associated rotation point DP1. The screw profile is not axisymmetric or point-symmetric about the first construction point K1. The first construction point K1 is the center of arc 2. Arc 2 has a dimensionless radius R_2=0.54, which is identical to the dimensionless screw outer radius RA. The center angle is α_2=0.2726≈15.6°. Arc 2 represents the secondary flight facet NK1, since, apart from the common contact point, the two directly adjacent arcs 1 and 3 have a smaller distance to the first construction point K1. The first construction point K1 is the center of arc 6. Arc 6 has a dimensionless radius R_6=0.54, which is identical to the dimensionless screw outer radius RA. The center angle is α_6=0.0501≈2.9°. Arc 6 represents the secondary thread facet NK2, since, apart from the common contact point, the two directly adjacent arcs 5 and 6a have a smaller distance to the first construction point K1. The first construction point K1 is the center of arc 10. Arc 10 has a dimensionless radius R_10=0.54, which is identical to the dimensionless screw outer radius RA. The center angle is α_10=0.2726≈15.6°. Arc 10 represents the secondary thread facet NK3, since, apart from the common contact point, the two directly adjacent arcs 9 and 11 have a smaller distance to the first construction point K1. The first construction point K1 is the center of arc 4. Arc 4 has a dimensionless radius R_4=0.46, which is identical to the dimensionless core radius RI. The center angle is α_4=0.2726≈15.6°. Arc 4 represents the groove, since, apart from the common contact point, the two directly adjacent arcs 3 and 5 have a larger distance to the first construction point K1. The first construction point K1 is the center of the arc 8. The arc 8 has a radius R_8=0.46, which is the same as the dimensionless core radius RI. The center angle is α_8=0.2726≈15.6°. The arc 8 represents a groove, because, in addition to the common contact point, the two directly adjacent arcs 7 and 9 have a greater distance to the first construction point K1. The first construction point K1 is the center of the arc 12. The arc 12 has a radius R_12=0.46, which is the same as the dimensionless core radius RI. The center angle is α_12=0.2726≈15.6°. The arc 12 represents a groove, because, in addition to the common contact point, the two directly adjacent arcs 1 and 11 have a greater distance to the first construction point K1.

[0257] The screw profile includes a second construction point K2, which does not coincide with the first construction point K1 and is located within the screw profile and is also located within a circle, the center of which is the first construction point K1 and the dimensionless radius of which is the dimensionless core radius RI. The screw profile is not axisymmetric or point-symmetric about the second construction point K2. The second construction point K2 is the center of the arc 6a. The arc 6a has a dimensionless radius R_6a=0.58, which is slightly smaller than the dimensionless inner shell radius RG=0.584. The center angle is α_6a=0.2282≈13.1°. The arc 6a represents the main thread face HK, because, except for the common contact point, the two directly adjacent arcs 6 and 7 have a small distance to the second construction point K2.

[0258] The distance between the second construction point K2 and the first construction point K1 is approximately 0.073 times the inner radius RG of the housing. The smaller angle between the angle bisector of the groove and the connecting line between K1 and K2 is 150.0°, and the arc point of the groove located on the angle bisector of the groove is separated from the closest point of the main thread face HK by a smaller curve length.

[0259] Arcs 1, 3, 5, 7, 9 and 11 represent side faces. The dimensionless radii of the six arcs are respectively R_1=R_3=R_5=R_7=R_9=R_11=1.00. The centers of the six arcs are different from the first construction points K1 and K2 in each case.

[0260] The main thread face HK (arc 6a) and the secondary thread face NK2 (arc 6) are in contact with each other. The main thread face HK (arc 6a), the first secondary thread face NK1 (arc 2), the second secondary thread face NK2 (arc 6) and the third secondary thread face NK3 (arc 10) are each separated from the groove by a side surface.

[0261] Figure 12b: Figure 12b1 The screw profile is obtained by making the Fig.12a1 The screw profile is shifted; Figure 12b2 Shows Figure 12b1 6 and an enlarged view of the details around the arc 6a. This displacement is achieved so that the second construction point K2 is located at the center M1 of the housing hole and therefore at the associated rotation point DP1. The inner radius of the housing is RG=0.584. The dimensionless outer screw radius is RA=0.58. The arc 6a has a dimensionless radius R_6a=0.58, which is the same as the dimensionless outer screw radius RA. The dimensionless clearance of the main thread face HK (arc 6a) relative to the housing is C_HK=0.004.

[0262] This embodiment is advantageous because it has a constant narrow gap between the housing and the main thread facet HK (arc 6a), which leads to good cleaning of the housing. This embodiment is also advantageous because the length of the converging or diverging channel (depending on the direction of rotation) between the housing and the main thread facet (arc 6) is substantially smaller than in the embodiment according to FIG. 11b. Thus, when rotating clockwise, a converging channel is created between the housing and the main thread facet HK (arc 6a), and when rotating counterclockwise, a diverging channel is created.

[0263] Figure 13a: Fig.13a1 shows a screw profile according to the prior art with a number of grooves Z=4, and Fig.13a2 Shows Fig.13a1 Detail around the arc 6 of FIG. 6 . The dimensionless outer screw radius is RA=0.52. The dimensionless inner housing radius is RG=0.554. The first construction point K1 is located at the center M1 of the housing bore and thus at the associated rotation point DP1.

[0264] This embodiment is disadvantageous because the gaps between the shell and the first thread edge (arc 2), between the shell and the second thread edge (arc 6), between the shell and the third thread edge (arc 10), and between the shell and the fourth thread edge (arc 14) are large, resulting in poor cleaning of the shell.

[0265] Figure 13b: Figure 13b1 The screw profile is obtained by making the Fig.13a1 The screw profile is shifted; Figure 13b2 Shows Figure 13b1 6. The displacement is achieved so that the smaller angle between the angular bisector of the arc 8 and the connecting line between the first construction point K1 and the second construction point K2 is 157.5°. The second construction point K2 is located at the center M1 of the housing bore and therefore at the associated rotation point DP1. The end point of the arc 6, which corresponds to the start point of the arc 7, is located on the dimensionless screw outer radius RA, while the start point of the arc 6 is not located on the dimensionless screw outer radius RA. The dimensionless screw outer radius is RA=0.55. The dimensionless housing inner radius is RG=0.554.

[0266] According to Fig.13a1 Compared to the embodiment of the embodiment of the present invention, this embodiment has a narrow gap between the housing and the end point of the arc 6, which leads to good cleaning of the housing. However, this embodiment is disadvantageous because the gap between the housing and the second thread land (arc 6) is not constant and this leads to a converging or diverging channel between the housing and the second thread land (arc 6) depending on the direction of rotation. Thus, when rotating clockwise, a converging channel is generated between the housing and the main thread land HK (arc 6), and when rotating counterclockwise, a diverging channel is generated.

[0267] Figure 14a: Fig.14a1 A closed screw profile according to the invention is shown, which has a number of grooves Z=4 and consists of 17 arcs; Fig.14a2 Shows Fig.14a1 The enlarged view of the details around the arc 6 and arc 6a. The dimensionless inner radius of the housing is RG = 0.554. The outer radius of the screw is RA = 0.52. The clearances of the first secondary thread face NK1 (arc 2), the second secondary thread face NK2 (arc 6), the third secondary thread face NK3 (arc 10) and the fourth secondary thread face NK4 (arc 14) relative to the housing are C_NK = 0.034.

[0268] The screw profile comprises a first construction point K1, which is located at the center M1 of the housing bore and therefore at the associated rotation point DP1. The screw profile is not axisymmetric or point-symmetric about the first construction point K1. The first construction point K1 is the center of arc 2. Arc 2 has a dimensionless radius R_2=0.52, which is identical to the dimensionless screw outer radius RA. The center angle is α_2=0.2289≈13.1°. Arc 2 represents the secondary flight facet NK1, since, apart from the common contact point, the two directly adjacent arcs 1 and 3 have a smaller distance to the first construction point K1. The first construction point K1 is the center of arc 6. Arc 6 has a dimensionless radius R_6=0.52, which is identical to the dimensionless screw outer radius RA. The center angle is α_6=0.0381≈2.2°. Arc 6 represents the secondary thread facet NK2, since, apart from the common contact point, the two directly adjacent arcs 5 and 6a have a smaller distance to the first construction point K1. The first construction point K1 is the center of arc 10. Arc 10 has a dimensionless radius R_10=0.52, which is identical to the dimensionless screw outer radius RA. The center angle is α_10=0.2289≈13.1°. Arc 10 represents the secondary thread facet NK3, since, apart from the common contact point, the two directly adjacent arcs 9 and 11 have a smaller distance to the first construction point K1. The first construction point K1 is the center of arc 14. Arc 14 has a dimensionless radius R_14=0.52, which is identical to the dimensionless screw outer radius RA. The center angle is α_14=0.2289≈13.1°. Arc 14 represents the secondary thread facet NK4, since, apart from the common contact point, the two directly adjacent arcs 13 and 15 have a smaller distance to the first construction point K1. The first construction point K1 is the center of arc 4. Arc 4 has a dimensionless radius R_4=0.48, which is the same as the dimensionless core radius. The center angle is α_4=0.2289≈13.1°. Arc 4 represents a groove, since, apart from the common contact point, the two directly adjacent arcs 3 and 5 have a greater distance to the first construction point K1. The first construction point K1 is the center of arc 8. Arc 8 has a dimensionless radius R_8=0.48, which is the same as the dimensionless core radius. The center angle is α_8=0.2289≈13.1°. Arc 8 represents a groove, since, apart from the common contact point, the two directly adjacent arcs 7 and 9 have a greater distance to the first construction point K1. The first construction point K1 is the center of arc 12. The arc 12 has a dimensionless radius R_12=0.48, which is the same as the dimensionless core radius. The center angle is α_12=0.2289≈13.1°. The arc 12 represents a groove, because, apart from the common contact point, the two directly adjacent arcs 11 and 13 have a greater distance to the first construction point K1. The first construction point K1 is the center of the arc 16. The arc 16 has a dimensionless radius R_16=0.48, which is the same as the dimensionless core radius. The center angle is α_16=0.2289≈13.1°.The arc 16 represents a groove, since, apart from the common contact point, the two directly adjacent arcs 1 and 15 have a greater distance to the first construction point K1 .

[0269] The screw profile includes a second construction point K2, which does not coincide with the first construction point K1 and is located within the screw profile and is also located within a circle, the center of which is the first construction point K1 and the dimensionless radius of which is the dimensionless core radius. The screw profile is not axisymmetric or point-symmetric about the second construction point K2. The second construction point K2 is the center of the arc 6a. The arc 6a has a dimensionless radius R_6a=0.55, which is slightly smaller than the dimensionless inner shell radius RG=0.554. The center angle is α_6a=0.1950≈11.2°. The arc 6a represents the main thread face HK, because, except for the common contact point, the two directly adjacent arcs 6 and 7 have a small distance to the second construction point K2.

[0270] The dimensionless distance between the second construction point K2 and the first construction point K1 is approximately 0.051 times the dimensionless inner radius RG of the housing. The smaller angle between the angle bisector of the groove and the connecting line between K1 and K2 is 157.5°, and the arc point of the groove located on the angle bisector of the groove is separated from the closest point of the main thread face HK by a smaller curve length.

[0271] Arcs 1, 3, 5, 7, 9, 11, 13 and 15 represent side faces. The dimensionless radii of the eight arcs are respectively R_1=R_3=R_5=R_7=R_9=R_11=R_13=R_15=1.00. The centers of the eight arcs are different from the first construction points K1 and K2 in each case.

[0272] The main thread face HK (arc 6a) and the second secondary thread face NK2 (arc 6) are in contact with each other. The main thread face HK, the first secondary thread face NK1 (arc 2), the second secondary thread face NK2 (arc 6), the third secondary thread face NK3 (arc 10) and the fourth secondary thread face NK4 (arc 14) are each separated from the groove by a side surface.

[0273] Figure 14b: Figure 14b1 The screw profile in is obtained by shifting the screw profile from FIG. 14 a; Figure 14b2 Shows Figure 14b16 and an enlarged view of the details around the arc 6a. This displacement is achieved so that the second construction point K2 is located at the center M1 of the housing hole and therefore at the associated rotation point DP1. The dimensionless housing inner radius is RG=0.554. The dimensionless screw outer radius is RA=0.55. The arc 6a has a dimensionless radius R_6a=0.55, which is the same as the dimensionless screw outer radius RA. The dimensionless clearance of the main thread face HK (arc 6a) relative to the housing is C_HK=0.004.

[0274] This embodiment is advantageous because it has a constant narrow gap between the housing and the main thread facet HK (arc 6a), which results in good cleaning of the housing. This embodiment is also advantageous because the length of the converging or diverging channel between the housing and the main thread facet (arc 6) (depending on the direction of rotation) is substantially smaller than the embodiment according to FIG. 13b. Thus, when rotating clockwise, a converging channel is created between the housing and the main thread facet HK (arc 6a), and when rotating counterclockwise, a diverging channel is created.

[0275] 1 to 14 show screw profiles with a number of grooves Z from 1 up to and including 4, wherein the dimensionless screw outer radius RA of the screw profile has different discrete values. The screw element according to the invention is not limited to these discrete values ​​of the screw outer radius. If the first construction point K1 is located at the center M1 of the housing bore and therefore at the associated rotation point DP1, a screw profile with a number of grooves of 1 or a number of grooves of 2 can have a dimensionless screw outer radius in the range of RA=0.57 to RA=0.67, preferably in the range of RA=0.59 to RA=0.65, and if the first construction point K1 is located at the center M1 of the housing bore and therefore at the associated rotation point DP1, a screw profile with a number of grooves of 3 can have a screw outer radius in the range of RA=0.515 to RA=0.56, preferably in the range of RA=0.525 to RA=0.55. If the first construction point K1 is located at the center M1 of the housing bore and thus at the associated rotation point DP1 , a screw profile having four grooves can have an outer screw radius in the range RA=0.51 to RA=0.535, preferably in the range RA=0.515 to RA=0.53.

[0276] If the first construction point K1 is located in the center M1 of the housing bore and therefore in the associated rotation point DP1, the dimensionless screw outer radius RA is 0.2% to 10%, preferably 0.4% to 7.5%, particularly preferably 0.6% to 5%, very particularly preferably approximately 0.8% to 2.5% smaller than the dimensionless housing inner radius RG. That is, if the first construction point K1 is located in the center M1 of the housing bore and therefore in the associated rotation point DP1, the secondary thread land NK iThe dimensionless clearance C_NK between the housing and the dimensionless housing inner radius RG is 0.2% to 10%, preferably 0.4% to 7.5%, particularly preferably 0.6% to 5%, very particularly preferably approximately 0.8% to 2.5%. n In the case of , these secondary thread lands can have the same or different dimensionless clearances C_NK.

[0277] If the second construction point K2 is located in the center M1 of the housing bore and therefore at the associated point of rotation DP1, the dimensionless outer screw radius RA is 0.1% to 3.2%, preferably 0.2% to 2.6%, particularly preferably 0.3% to 2.0%, very particularly preferably approximately 0.4% to 1.4% smaller than the dimensionless inner housing radius RG. That is to say, if the second construction point K2 is located in the center M1 of the housing bore and therefore at the associated point of rotation DP1, the dimensionless gap C_HK between the main thread land HK and the housing is 0.1% to 3.2%, preferably 0.2% to 2.6%, particularly preferably 0.3% to 2.0%, very particularly preferably approximately 0.4% to 1.4% of the dimensionless inner housing radius RG.

[0278] The distance of the second construction point K2 from the first construction point K1 and the smaller angle between the angular bisector of the groove (the arc point of the groove lying on the angular bisector of the groove is separated from the closest point of the main thread facet HK by a smaller curve length) and the connecting line between K1 and K2 make it possible to adapt the position of the main thread facet HK and the size of its center angle and thus the screw profile or the screw element having this screw profile to the processing task in the twin-shaft screw machine. Thus, for example, in accordance with Figure 6a In the case of a profile, the distance (0.1 times the inner housing radius) and the smaller angle (135°) between the angle bisector of the groove (the arc point of the groove lying on the angle bisector of the groove and the closest point of the main thread land HK are separated by a smaller curve length) and the connecting line between K1 and K2 have been selected so that the arc 6 hardly exists anymore. Figure 7a In the example, the distance between K1 and K2 has been reduced to 0.091 times the inner radius of the housing, with the result that the center angle of arc 6 increases and the center angle of arc 6a representing the main thread land HK decreases. Figure 6a If the distance between K1 and K2 increases to more than 0.1 times the inner radius of the housing, arc 6 will disappear completely from the screw profile. In this case, the intersection point between arcs 5 and 6a will have to be determined in order to be able to determine the center angle of arcs 5 and 6a. The above applies analogously to screw profiles with a number of grooves Z=3 or a number of grooves Z=4.

[0279] If the screw profile has a secondary thread face NK formed by an arc centered at the second construction point K2 or the third construction point K3i , then the position of the second construction point K2 or the third construction point K3 and the secondary thread edge NK i The radius of the arc makes the secondary thread face NK i Able to adapt to the processing tasks of twin-shaft screw machines. Figure 9a In the embodiment, the arc 2a centered at the second construction point K2 forms the corresponding secondary thread face NK i .exist Figure 9a In the case where the radius of arc 2a is reduced, the center angle of arc 2a will increase. In the case where the radius of arc 2a is small enough, arc 2 will completely disappear from the screw profile. In this case, in order to be able to determine the center angle of arcs 2a and 3, it will be necessary to determine the intersection point between arcs 2a and 3. Fig.10a In the figure, the arc 2a centered at the third construction point K3 forms the corresponding secondary thread face NK i .exist Fig.10a In the example above, if the radius of arc 2a is reduced, the center angle of arc 2a will increase. In the case where the radius of arc 2a is small enough, arc 2 will completely disappear from the screw profile. In this case, it will be necessary to determine the intersection point between arcs 1 and 2a in order to be able to determine the center angle of arcs 1 and 2a.

[0280] 1 to 14 show screw profiles with a number of grooves from Z=1 up to and including Z=4, wherein the distance between the first construction points K1 and K2 of the screw profile has different discrete values. The screw element according to the invention is not limited to these discrete values. The distance from the first construction point K1 to the second construction point K2 is 0.2% to 20%, preferably 0.4% to 15%, particularly preferably 0.6% to 10%, and very particularly preferably 0.8% to 5% of the dimensionless inner radius RG of the housing.

[0281] 1 to 14 show screw profiles with a number of grooves ranging from Z=1 to Z=4 and including Z=4, wherein the screw profile has different discrete values ​​for the smaller angle between the angle bisector of the groove and the connecting line between K1 and K2, whose arc points on the angle bisector of the groove are separated from the closest point of the main flight face HK by a smaller curve length. The screw element according to the invention is not limited to these discrete values. When the number of grooves is Z=1, the smaller angle between the angle bisector of the groove and the connecting line between K1 and K2 is in the range of 0° to 90°, preferably in the range of 45° to 70°, and particularly preferably approximately 55°. When the number of grooves is Z=2, the smaller angle between the angle bisector of the groove and the connecting line between K1 and K2, whose arc points on the angle bisector of the groove are separated from the closest point of the main flight face HK by a smaller curve length, is in the range of 110° to 160°, preferably in the range of 125° to 145°, and particularly preferably approximately 135°. When the number of grooves is Z=3, the smaller angle between the angle bisector of the groove and the connecting line between K1 and K2 is in the range of 130° to 170°, preferably in the range of 140° to 160°, and particularly preferably in the range of approximately 150°, and the arc point of the groove located on the angle bisector of the groove is separated from the closest point of the main thread face HK by a smaller curve length. When the number of grooves is Z=4, the smaller angle between the angle bisector of the groove and the connecting line between K1 and K2 is in the range of 140° to 175°, preferably in the range of 150° to 165°, and particularly preferably approximately 157.5°, and the arc point of the groove located on the angle bisector of the groove is separated from the closest point of the main thread face HK by a smaller curve length.

[0282] Figures 1 to 14 show screw profiles with a number of grooves from Z = 1 to Z = 4 and including Z = 4, wherein the center angle of the arc of the groove forming the screw profile has different discrete values. The screw element according to the invention is not limited to these discrete values. When the number of grooves is Z = 1, the arc of the groove forming the groove has a center angle of 90 ° to 150 °, preferably 95 ° to 140 °, and particularly preferably 100 ° to 130 °. When the number of grooves is Z = 2, the arc of the groove forming the groove each has a center angle of 5 ° to 50 °, preferably 10 ° to 40 °, and particularly preferably 15 ° to 30 °. When the number of grooves is Z = 3, the arc of the groove forming the groove each has a center angle of 3 ° to 30 °, preferably 6 ° to 24 °, and particularly preferably 9 ° to 18 °. When the number of grooves is Z = 4, the arc of the groove forming the groove each has a center angle of 2 ° to 20 °, preferably 4 ° to 16 °, and particularly preferably 6 ° to 12 °.

[0283] 1 to 14 show screw profiles with a number of grooves from Z=1 up to and including Z=4, wherein the center angles of the arcs forming the main thread facets HK have different discrete values. The screw element according to the invention is not limited to these discrete values. For example, in the first case, one of the two adjacent arcs of the main thread facet HK can be a secondary thread facet NK. i In the second case, for example, neither of the two directly adjacent arcs of the main thread face HK is the secondary thread face NK. i . In the first case, when the number of grooves is Z=1, the arc forming the main thread face HK has a center angle of 10° to 150°, preferably 30° to 140°, particularly preferably 50° to 130°. In the second case, when the number of grooves is Z=1, the arc forming the main thread face HK has a center angle of 90° to 150°, preferably 95° to 140°, particularly preferably 100° to 130°. In the first case, when the number of grooves is 2, the arc forming the main thread face HK has a center angle of 5° to 50°, preferably 10° to 40°, particularly preferably 15° to 30°. In the second case, when the number of grooves is 2, the arc forming the main thread face HK has a center angle of 5° to 50°, preferably 10° to 40°, particularly preferably 15° to 30°. In the first case, when the number of grooves is 3, the arc forming the main thread land HK has a center angle of 3° to 30°, preferably 6° to 24°, particularly preferably 9° to 18°. In the second case, when the number of grooves is 3, the arc forming the main thread land HK has a center angle of 3° to 30°, preferably 6° to 24°, particularly preferably 9° to 18°. In the first case, when the number of grooves is 4, the arc forming the main thread land HK has a center angle of 2° to 20°, preferably 4° to 16°, particularly preferably 6° to 12°. In the second case, when the number of grooves is 4, the arc forming the main thread land HK has a center angle of 2° to 20°, preferably 4° to 16°, particularly preferably 6° to 12°.

[0284] 1 to 14 show screw profiles having a number of grooves ranging from Z=1 to Z=4 including Z=4, wherein secondary flight lands NK1 to NK n The central angle of the arc of the screw element has different discrete values. The screw element according to the invention is not limited to these discrete values. For example, in the first case, the secondary thread face NK i One of the two directly adjacent arcs can be the main thread edge HK. In the second case, it may be the case that, for example, the secondary thread edge NK i In the first case, when the number of grooves is Z=1, a secondary thread face NK is formed. iThe central angle of the arc is greater than 0° to 140°, preferably greater than 0° to 110°, and particularly preferably greater than 0° to 80°. In the first case, when the number of grooves is Z=2, the secondary thread edge NK is formed i The arc has a central angle greater than 0° to 45°, preferably greater than 0° to 30°, particularly preferably greater than 0° to 15°. In the second case, when the number of grooves is Z=2, the secondary thread face NK is formed i The arc has a center angle of 5 to 50°, preferably 10 to 40°, particularly preferably 15 to 30°. In the first case, when the number of grooves is Z=3, the secondary thread edge NK is formed i The arc has a central angle greater than 0° to 27°, preferably greater than 0° to 18°, particularly preferably greater than 0° to 9°. In the second case, when the number of grooves is Z=3, the secondary thread face NK is formed i The arc has a center angle of 3 to 30°, preferably 6 to 24°, particularly preferably 9 to 18°. In the first case, when the number of grooves is Z=4, the secondary thread land NK is formed i The arc has a central angle greater than 0° to 18°, preferably greater than 0° to 12°, particularly preferably greater than 0° to 6°. In the second case, when the number of grooves is Z=4, the secondary thread face NK is formed i The arc of a circle has a center angle of 2 to 20°, preferably 4 to 16°, particularly preferably 6 to 12°.

[0285] Fig.15 : shows a screw profile according to the invention, which has a Figure 2b The number of grooves is Z = 1, as a pair of two identical screw profiles. Fig.15 By copying from Figure 2b The arcs 1, 2, 2a, 3 and 4 of the housing and screw profile in the positive x-axis direction are obtained by shifting the copies by an axial distance. The copied and shifted arcs are given the references 1', 2', 2a', 3' and 4'. Arc 2a of the left-hand screw profile is not cleaned by the right-hand screw profile. Arc 2a' of the right-hand screw profile is not cleaned by the left-hand screw profile. The screw profile is not completely self-cleaning.

[0286] Fig.16 : shows a screw profile according to the invention, which has a Figure 6b The number of grooves is Z = 2, as a pair of two identical screw profiles. Fig.16 is obtained by copying Figure 6b and shift it axially in the positive x-axis direction by a distance, and by copying Figure 6bArcs 1, 2, 3, 4, 5, 6, 6a, 7 and 8 of the screw profile are mirrored at point K2 on the x-axis and rotated 90° clockwise in point K2 and the copies are shifted by the axial distance in the positive x-axis direction. The copied and shifted arcs are given the labels 1', 2', 3', 4', 5', 6', 6a', 7' and 8'. Arc 6a of the left-hand screw profile is not cleaned by the right-hand screw profile. Arc 6a' of the right-hand screw profile is not cleaned by the left-hand screw profile. The screw profile is not completely self-cleaning.

[0287] Fig.17 : shows a screw profile according to the invention with a number Z=3 of grooves from FIG. 12b as a pair of two identical screw profiles. Fig.17 is obtained by copying arcs 1, 2, 3, 4, 5, 6, 6a, 7, 8, 9, 10, 11 and 12 from the housing and screw profile in Figure 12b and shifting the copies by this axial distance in the positive x-axis direction. The copied and shifted arcs are given the designations 1', 2', 3', 4', 5', 6', 6a', 7', 8', 9', 10', 11' and 12'. Arc 6a of the left-hand screw profile is not cleaned by the right-hand screw profile. Arc 6a' of the right-hand screw profile is not cleaned by the left-hand screw profile. The screw profile is not completely self-cleaning.

[0288] Fig.18 : shows a screw profile according to the invention with a number Z=4 grooves from FIG. 14b as a pair of two identical screw profiles. Fig.18 This is obtained by copying the housing from Figure 14b and shifting it an axial distance in the positive x-axis direction, and copying arcs 1, 2, 3, 4, 5, 6, 6a, 7, 8, 9, 10, 11, 12, 13, 14, 15 and 16 from the screw profile in Figure 14b, mirroring the copied arcs at point K2 on the x-axis and rotating them 135° clockwise at point K2, and shifting the copies by the axial distance in the positive x-axis direction. The copied and shifted arcs are given the designations 1', 2', 3', 4', 5', 6', 6a', 7', 8', 9', 10', 11', 12', 13', 14', 15' and 16'. Arc 6a of the left-hand screw profile is not cleaned by the right-hand screw profile. Arc 6a' of the right-hand screw profile is not cleaned by the left-hand screw profile. The screw profile is not completely self-cleaning.

[0289] Fig.19 :shows the Fig.16The screw profile of the invention is in the form of a pair of conveying elements with rotation axes D1 and D2, which are at a dimensionless axial distance A from each other and are located at the same height on the drive shaft AW1 and the drive shaft AW2. The dimensionless inner radius of the housing is RG=0.66, and the dimensionless outer radius of the screw is RA=0.65. The dimensionless gap between the main thread face HK of the conveying element and the inner wall of the housing is C_HK=0.01. The dimensionless length of the conveying element is 1.2 times the dimensionless axial distance A. The dimensionless pitch of the conveying element is T=1.2, wherein the dimensionless pitch is understood to mean the quotient of the axial length required for the screw profile to rotate by an angle of 6.2832=360° and the axial distance a. The housing is illustrated by hatching on the left and right sides of the two conveying elements. A possible calculation grid is also illustrated on the surface of the two conveying elements, which can be used to calculate the flow in twin-shaft and multi-shaft extruders. For the force fit between the drive shaft AW (such as drive shaft AW1 or drive shaft AW2) and the screw element, a tongue and groove system or an arrangement of multiple interlocking teeth can be used. The arrangement of multiple interlocking teeth can be configured as a trapezoid or a wave shape and symmetrical or asymmetrical respectively.

[0290] As an alternative, from Fig.16 The screw profile according to the invention can also be in the form of a pair of kneading elements or a pair of mixing elements.

[0291] As is known, conveying elements are characterized in that (see, for example, [1], pages 227-248) the screw profile has a continuous spiral turn and a continuous portion in the axial direction. In this case, the conveying element can be right-handed or left-handed. The pitch of the conveying element is preferably in the range of 0.1 to 10 times the axial distance, and the axial length of the conveying element is preferably in the range of 0.1 to 10 times the axial distance.

[0292] As is known, kneading elements are characterized in that (see, for example, [1], pages 227-248) the screw profile is continued in an offset manner in the axial direction in the form of kneading disks. The arrangement of the kneading disks can be right-handed, left-handed or neutral. The axial length of the kneading disks is preferably in the range of 0.05 to 10 times the axial distance. The axial distance between two adjacent kneading disks is preferably in the range of 0.002 to 0.1 times the axial distance.

[0293] As is known (see, for example, [1], pages 227-248), the mixing elements are formed by conveying elements with openings on the screw flight edges. The mixing elements can be right-handed or left-handed. Their pitch is preferably in the range of 0.1 to 10 times the axial distance, and the axial length of the elements is preferably in the range of 0.1 to 10 times the axial distance. The openings are preferably in the form of U-shaped or V-shaped grooves, which are preferably arranged in counter-conveying or axially parallel manner.

[0294] The sequence of screw elements on the drive shaft AW consisting of conveying elements and / or kneading elements and / or mixing elements is called a spiral configuration. All screw elements on the drive shaft AW and the drive shaft AW itself together form the screw shaft SW. The first drive shaft is denoted AW1 and the first screw shaft is denoted SW1. The second drive shaft is denoted AW2 and the second screw shaft is denoted SW2.

[0295] The screw profile according to the invention can be obtained particularly easily from a reference screw profile which is axisymmetric about the first construction point K1. This axisymmetric reference screw profile is characterized by

[0296] the dimensionless core radius RG, the number Z of grooves and the dimensionless outer radius RA of this axisymmetric reference screw profile correspond to the dimensionless core radius RG, the number Z of grooves and the dimensionless outer radius RA of the screw profile according to the invention, and

[0297] the first construction point K1 of this axisymmetric reference screw profile is identical to the first construction point K1 of the screw profile according to the invention,

[0298] ● In the case of an odd number Z of grooves, this axisymmetric reference screw profile is axisymmetric with respect to the x-axis or y-axis,

[0299] ● In the case of an even number of Z grooves, this axisymmetric reference screw profile is axisymmetric with respect to the x-axis and the y-axis, and ● Two similar axisymmetric reference screw profiles clean each other exactly in pairs

[0300] o If these axisymmetric reference screw profiles have a reference distance RFA corresponding to the axial distance A, and

[0301] o If, in the case of an odd number Z of grooves, these axisymmetric reference screw profiles are not rotated relative to each other on their respective reference axes of rotation RFD1 and RFD2, and

[0302] o If, in the case of an even number Z of grooves, these axisymmetric reference screw profiles are rotated relative to each other on their respective reference rotation axes RFD1 and RFD2 by an angle of π / Z = 180° / Z, and

[0303] o If these axisymmetric reference screw profiles rotate on their respective reference rotation axes RFD1 and RFD2 at the same speed and in the same direction of rotation.

[0304] therefore,

[0305] - Figure 1a A reference screw profile is shown, which is axisymmetric about the first construction point K1 and for Figure 2a, Figure 3a or Figure 4a The screw profile according to the invention has a number of grooves Z=1.

[0306] - Figure 5a A reference screw profile is shown, which is axisymmetric about the first construction point K1 and for Figure 6a , Figure 7a , Figure 9a or Fig.10a The screw profile according to the invention has a number Z=2 grooves.

[0307] FIG. 11 a shows a reference screw profile which is axisymmetric about the first construction point K1 and has a number of grooves Z=3 for the screw profile according to the invention according to FIG. 12 a .

[0308] FIG. 13 a shows a reference screw profile which is axisymmetric about the first construction point K1 and has a number of grooves Z=4 for the screw profile according to the invention according to FIG. 14 a .

[0309] - Figure 5a A reference screw profile is shown, which is axisymmetric about the first construction point K1 and for Figure 7a The screw profile according to the invention has a number of grooves Z=2. The arcs 1 to 5, the arc 8 and the first construction point K1 are respectively identical. Therefore, the dimensionless core radius RI, the number of grooves Z and the dimensionless outer radius RA of the axisymmetric reference screw profile and the screw profile according to the invention are in each case of the same size. Therefore, the rotation points of the axisymmetric reference screw profile and the rotation points of the screw profile according to the invention correspond.

[0310] For example, in order to Figure 5a The reference screw profile (which is axisymmetric about the first construction point K1) is converted into Figure 7aAccording to the screw profile of the invention, the arc 6a representing the main thread face HK must be inserted between the arcs 6 and 7 to become an axisymmetric reference screw profile, it is necessary to adjust the arcs 6 and 7 accordingly. The radius of the arc 6a is selected so that it is equal to the dimensionless inner shell radius RG=0.66 minus the dimensionless gap C_HK=0.01. The center of the arc 6a is located at the second construction point K2. The position of the second construction point K2 is selected so that the smaller angle between the groove angle bisector and the connecting line between K1 and K2 is 135.0°, the smaller angle between the arc points located on the groove angle bisector is separated from the closest point of the main thread face HK by a smaller curve length, and the distance between the first construction points K1 and K2 is equal to 0.06. The new end point of the arc 6 is generated by the intersection of the arc 6a with the old arc 6. The starting point of the arc 6a is the same as the end point of the arc 6. The new starting point of the point 7 on the circle is generated by the intersection of the arc 6a with the old arc 7. The end point of arc 6a is identical to the start point of arc 7. The start point, end point and center of arcs 6, 6a and 7, respectively, now being known, make it possible to calculate the corresponding center angles.

[0311] Fig. 20 A pair of reference screw profiles are shown, which have a number of grooves Z = 2. The reference screw profile, which is symmetrical about the left-hand axis of the first construction point K1, corresponds to the screw profile according to Figure 5a The axisymmetric profile shown. The axisymmetric reference screw profile of the right-hand axis represents a copy of the reference screw profile of the left-hand axis and is therefore also axisymmetric,

[0312] ● its copy has been mirrored on the x-axis, and

[0313] ● It has been rotated clockwise by an angle of π / 2 = 180° / 2 = 90° at the origin of the x / y coordinate system, and

[0314] • It is displaced in the positive x-direction by a dimensionless reference axial distance RFA, which corresponds to the dimensionless axial distance A.

[0315] By means of this process, arc 1 of the reference screw profile of the left-hand axis, axisymmetric about the first construction point K1, has been transformed into arc 1' of the axisymmetric reference screw profile of the right-hand axis. The same applies analogously to arcs 2 to 8, from which arcs 2' to 8' are generated. The first construction point K1 is identical to the rotational reference point RFD1. The first construction point K1', which is offset by a reference axial distance in the positive x-direction, is identical to the rotational reference point RFD2. If the axisymmetric reference screw profiles rotate at the same speed and in the same direction of rotation on their respective reference rotation axes RFD1 and RFD2, the axisymmetric reference screw profiles of the left-hand axis and the right-hand axis clean each other in pairs.

[0316] exist Fig. 20In the embodiment, the reference screw outer radius RFRA is identical to the reference housing inner radius RFRG = 0.61. The reference screw outer radius RFRA is 0.2% to 10%, preferably 0.4% to 7.5%, particularly preferably 0.6% to 5%, very particularly preferably 0.8% to 2.5% smaller than the housing inner radius RG.

[0317] At a given dimensionless axial distance A, corresponding to the dimensionless reference axial distance RFA, a reference screw profile can be easily constructed according to the method disclosed in [1], pages 95 to 109.

Claims

1. A screw element having a number Z of grooves, Suitable for twin-shaft screw machines having two screw shafts SW1 and SW2 rotating in the same direction and at the same speed, with their rotation axes D1 and D2 being at an axial distance a, and having two circular housing holes penetrating each other, each having the same housing inner radius rg, and whose hole centers M1 and M2 are at a distance equal to the axial distance a, and whose hole centers M1 and M2 coincide with the cross-sectional centers of the respective rotation axes D1 and D2 of said screw shafts SW1 and SW2, in, The screw element has a screw profile, which: - forming a closed convex line, - consists only of arcs with a radius less than or equal to the axial distance a, wherein directly adjacent arcs have different radii, - having a first construction point K1 located within the screw profile, - is not axisymmetric about the first construction point K1, - consists of at least 4 arcs, - having a second construction point K2 which does not coincide with the first construction point K1, wherein the second construction point K2 is located within the screw profile, - is not point-symmetrical or axis-symmetrical about the second construction point K2, - has a rotation point DP which coincides with one of the hole centers M1 or M2 and is located on the path from the first construction point K1 to the second construction point K2, - has exactly one main thread facet HK, which is formed by only one circular arc, the center of which is the second construction point K2, and wherein the contact points of the main thread facet HK and the two circular arcs directly adjacent to the main thread facet HK are the set of points of the screw profile that are farthest from the second construction point K2, - having at least one groove, wherein a groove is formed by only one corresponding circular arc, the center of which is the first construction point K1, and a groove is a circular arc with the same radius as the core radius ri of the screw profile, and wherein, apart from the corresponding common contact point, two circular arcs directly adjacent to a groove are at a greater distance from the first construction point K1 than the circular arc of the groove, - has a plurality of side faces, wherein the side faces are those regions of the screw profile whose arc has its center neither at the first construction point K1 nor at the second construction point K2, The groove is separated from the closest point of the main thread land HK by at least one arc of a circle, the at least one arc of a circle being a flank.

2. The screw element according to claim 1, wherein The circular arc forming the main thread land HK has a central angle greater than 0°.

3. The screw element according to claim 1 or 2, wherein: The screw element is not point-symmetrical or is not point-symmetrical about the first construction point K1 .

4. The screw element according to claim 1 or 2, wherein: The number of arcs of the screw profile is equal to the number of grooves Z multiplied by 4 or equal to the number of grooves Z multiplied by 4 and then increased by 1.

5. The screw element according to claim 1 or 2, wherein: The second construction point K2 of the screw profile lies within a circle having the first construction point K1 as center and the core radius ri as radius.

6. The screw element according to claim 1 or 2, wherein: The rotation point DP of the screw element is located closer to the second construction point K2 than to the first construction point K1 .

7. The screw element according to claim 1 or 2, wherein: The arc radius rHK of the main thread land HK corresponds to the housing inner radius rg and reduces the main thread land gap c_HK.

8. The screw element according to claim 1 or 2, wherein the arc forming the groove - when the number of grooves is Z=1, has a center angle of 90° to 150°, - when the number of grooves is Z=2, correspondingly, they have a central angle of 5° to 50°, wherein the central angles of the grooves are the same or different, - when the number of grooves is Z=3, correspondingly, they have a central angle of 3° to 30°, wherein the central angles of the grooves are the same or different, When the number of grooves is Z=4, the center angle is 2° to 20° accordingly.

9. The screw element according to claim 1 or 2, wherein: The screw profile has a third construction point K3, wherein the screw profile is not axisymmetric or point-symmetric about the third construction point K3, wherein the third construction point K3 is a point that is at the same distance from the second construction point K2 as from the first construction point K1, and wherein the first construction points K1, K2 and K3 are located on a straight line, and K1, K2 and K3 are not the same.

10. The screw element according to claim 1 or 2, wherein: The screw profile has a secondary flight land NK or a plurality of secondary flight lands NK1 to NK n , where each secondary thread face NK i It is formed by only one circular arc, the center of which is the first construction point K1 or the second construction point K2 or the third construction point K3.

11. The screw element according to claim 1 or 2, wherein: Groove and secondary thread land NK i The closest points of the two surfaces are separated by at least one arc, wherein the at least one arc is a side surface.

12. The screw element according to claim 1 or 2, characterized in that The point of rotation DP of the screw profile is the second construction point K2 .

13. The screw element according to claim 1 or 2, wherein: It is suitable for being arranged and operated in pairs in a screw machine with another screw element having the same or a different screw profile and having the same or a different arrangement of the points of rotation on the other screw shaft.

14. The screw element according to claim 1 or 2, wherein The core radius ri, the number of grooves Z and the outer radius ra of the screw profile correspond to the core radius ri, the number of grooves Z and the outer radius ra of the reference screw profile. and The first construction point K1 of the screw profile is identical to the first construction point K1 of the reference screw profile, in, The reference screw outer radius rfra is 0.2% to 10% smaller than the housing inner radius rg, in, - if the reference screw profile has a reference distance rfa corresponding to the axial distance a, and - if the reference screw profiles rotate at the same speed and in the same direction of rotation with their respective reference rotation points rfDP1 and rfDP2, Two similar reference screw profiles then clean each other exactly in pairs.

15. The screw element according to claim 2, wherein: The circular arc forming the main thread land HK has a central angle of 1° to 179°.

16. The screw element according to claim 3, wherein The screw element is not point-symmetrical about the first construction point K1 .

17. The screw element according to claim 4, wherein Screw profile of the screw element - when the number of grooves is Z=1, it consists of exactly 4 arcs or exactly 5 arcs, - when the number of grooves is Z=2, it consists of exactly 8 arcs or exactly 9 arcs, - when the number of grooves is Z=3, it consists of exactly 12 arcs or exactly 13 arcs, When the number of grooves is Z=4, it consists of exactly 16 arcs or exactly 17 arcs.

18. The screw element according to claim 6, wherein The rotation point DP is located on the second construction point K2.

19. The screw element according to claim 8, wherein the arc forming the groove - when the number of grooves is Z=1, has a center angle of 95° to 140°, - when the number of grooves is Z=2, correspondingly, they have a central angle of 10° to 40°, wherein the central angles of the grooves are the same or different, - when the number of grooves is Z=3, correspondingly, they have a central angle of 6° to 24°, wherein the central angles of the grooves are the same or different, When the number of grooves is Z=4, the central angle is 4° to 16° accordingly.

20. The screw element according to claim 8, wherein the arc forming the groove - when the number of grooves is Z=1, it has a central angle of 100° to 130°, - when the number of grooves is Z=2, correspondingly, they have a central angle of 15° to 30°, wherein the central angles of the grooves are the same or different, - when the number of grooves is Z=3, correspondingly, they have a central angle of 9° to 18°, wherein the central angles of the grooves are the same or different, When the number of grooves is Z=4, the center angle is 6° to 12° accordingly.

21. The screw element of claim 14, wherein the reference screw outer radius rfra is 0.4% to 7.5% smaller than the housing inner radius rg.

22. The screw element of claim 14, wherein the reference screw outer radius rfra is 0.6% to 5% smaller than the housing inner radius rg.

23. The screw element of claim 14, wherein the reference screw outer radius rfra is 0.8% to 2.5% smaller than the housing inner radius rg.

24. An extruder having two or more drive shafts rotating in the same direction and at the same speed, wherein: The extruder is equipped with two or more identical or different screw elements according to any one of claims 1 to 23.

25. Use of a screw element according to any one of claims 1 to 23 for processing or producing plastic substances.

Images