Abstract:
A treatment element to treat material in a multi-shaft worm machine has an outer contour with at least one outer contour portion, the associated evolute of which is a quantity of at least three points, each of the points lying outside the longitudinal axis and within the outer radius of the treatment element and two respective adjacent points having a spacing from one another, which is less than half the core radius. The treatment element ensures high flexibility during the adjustment of shear and/or extensional flows on the material to be treated.

Description:
REFERENCES TO RELATED APPLICATIONS 
     This application claims the priority of European Patent Application, Serial No. 09 012 358.9, filed Sep. 29, 2009, pursuant to 35 U.S.C. 119(a)-(d), the content of which is incorporated herein by reference in its entirety as if fully set forth herein. 
     FIELD OF THE INVENTION 
     The invention relates to a treatment element for treating material in a multi-shaft worm machine, in particular in a two-shaft worm machine, comprising
         a longitudinal axis M,   a respective core radius R i  having the longitudinal axis M as the centre point and an outer radius R a ,   an outer contour A(φ) running about the longitudinal axis M, wherein   φ is the angle about the longitudinal axis M and   R i ≦D A (φ)≦R a  applies to a spacing D A (φ) of the outer contour A(φ) from the longitudinal axis M.       

     Furthermore, the invention relates to a multi-shaft worn′ machine, in particular a two-shaft worm machine with
         a housing,   at least two housing bores, which penetrate one another and are parallel to one another,   at least two shafts arranged concentrically in the housing bores,
           which are rotatably drivable about associated rotational axes, in particular are rotatably drivable in the same direction, and   which have an axial spacing a of the rotational axes,   a plurality of treatment elements for treating material,   which are non-rotatably arranged one behind the other in an axial direction on the at least two shafts, and   which are configured to tightly mesh with one another.   
               

     BACKGROUND OF THE INVENTION 
     A two-shaft worm machine with single-threaded treatment or worm elements is known from DE 1 180 718 A. The outer contour of the worm elements is composed of circular arcs in cross-section. The active flank located in the rotational direction has an outer contour, which is composed of three circular arcs, the centre points of which are either located on the outer radius or on the longitudinal axis of the worm elements. The drawback is that the worm elements only allow a small flexibility in the adjustment of the shear and/or extensional flows acting on the material to be processed. 
     SUMMARY OF THE INVENTION 
     The invention is based on an object of developing a treatment element of the generic type in such a way that a high flexibility is provided in the adjustment of the shear and/or extensional flows acting on the material to be processed. 
     This object is achieved by a treatment element, in which
         the outer contour A(φ) has at least one outer contour portion A(Δφ), which runs along an angle portion Δφ,
           which has a continuously changing spacing D A (Δφ) from the longitudinal axis M, wherein R i &lt;D A (Δφ)&lt;R a , and   which has an associated evolute E,
               which is a quantity of n points P(i) where i=1 to n and n≧3,   wherein each of the points P(i) lies outside the longitudinal axis M and within the outer radius R a , and   wherein two respective adjacent points P(i) and P(i+1) have the spacing Δr(i) from one another, which is less than R i /2.   
               
               

     It was recognized according to the invention that the treatment elements known from the prior art, with the same ratio of the outer radius to the core radius, have the same angle of intersection of the active flank curve with the crest curve. The inner radius of the housing bores is greater by the radial play than the outer radius of the treatment elements. A geometrically similar form of the wedge between the inner contour of the housing and the active flank curve is therefore always produced with a constant ratio of the radial play to the outer radius. As the shear and/or extensional flows prevailing in the wedge substantially depend on the geometrical form thereof, they can only be adjusted by the angle of intersection of the active flank curve with the crest curve. As the angle of intersection only depends on the ratio of the outer radius to the inner radius, the adjustment of the shear and/or extensional flows is only possible to an extremely limited extent by means of the geometry of the wedge. 
     In comparison, the treatment element according to the invention—viewed in cross section or in a cross sectional projection—has at least one outer contour portion A(Δφ j ), the associated evolute E j  of which is a quantity of n points P(i) wherein i=1 to n and n≧3, in particular n≧4 and, in particular n≧5, wherein each of the points P(i) lies outside the longitudinal axis M of the treatment element and within the outer radius R a  thereof. Two adjacent respective points P(i) and P(i+1) have a spacing Δr(i) from one another, which is smaller than R 1 /2, in particular smaller than R i /4, in particular smaller than R 1 /6, and in particular smaller than R 1 /8. Adjacent points P(i) and P(i+1) belong to adjacent involute curves E′(i) and E′(i+1). The involute curves E′(i), wherein i=1 to n together form the outer contour portion A(Δφ j ) belonging to the evolute E j . 
     The index j characterizes the number of evolutes. The at least one outer contour portion A(Δφ j ) forms at least one part of a flank of the treatment element, the associated wedge being flexibly adjustable by means of the type and arrangement of the evolute E j . Correspondingly, the shear and/or extensional flows that can be produced by the treatment element can be flexibly adapted to the material to be treated by the means of the type and arrangement of the evolute E j . 
     The evolute E j  of the associated outer contour portion A(Δφ j ) running in a plane is the location or the curve of the centre points of curvature or the centre points of the circle of curvature. The outer contour portion A(Δφ j ) belonging to the evolute E j  is also called the involute. A notional rod with the length of the axial spacing a is unwound on the evolute E j  to construct the outer contour, the first rod end defining the outer contour portion A i (Δφ ji ) of one treatment element and the second rod end defining an associated outer contour portion A i+1  (Δφ ji+i ) of the further treatment element, which tightly mesh with one another when installed in a multi-shaft worm machine. 
     A high measure of degrees of freedom for the construction of the treatment element according to the invention is provided by the type, arrangement and number of evolutes so the outer contour portions (Δφ j ) can be varied with respect to their curvature, length and their angles of intersection over broad ranges. The wedges between the flanks and the inner contour of the housing can therefore be extremely flexible in design. As the shear and/or extensional flows prevailing in these wedges substantially influence the quality of the material to be processed, the quality can be optimized by the treatment element according to the invention and adapted to predetermined requirements. The at least one outer contour portion A(Δφ j ), in this case, in particular forms a part of the active flanks lying in the rotational direction. 
     The treatment element may be configured as a kneading element or kneading disc and have a constant outer contour in the direction of the longitudinal axis M. A plurality of kneading elements may be assembled with different offset angles about the longitudinal axis M with respect to kneading blocks. The kneading blocks may be produced in one part or be assembled from individual kneading elements. 
     Furthermore, the treatment element can be configured as a worm element, the outer contour of which is screwed in the direction of the longitudinal axis M by a constant and/or continuous function. The screwing can basically take place in the two rotational directions about the longitudinal axis M, so the worm element selectively has a conveying or retaining effect. Depending on the geometry of the worm element, the outer contour can optionally be understood as a cross sectional projection. 
     Furthermore, the treatment element may be configured as a transition element, which, in the direction of the longitudinal axis M, has a starting outer contour and an end outer contour, which are different, and change in the direction of the longitudinal axis M according to a continuous function in such a way that the starting outer contour continuously passes into the end outer contour. 
     The treatment element according to the invention can therefore be used with associated further treatment elements in any tightly meshing multi-shaft worm machines, in particular in two-shaft worm machines which can be rotatably driven in the same or opposite directions. The adjacent, tightly meshing treatment elements in this case form a treatment element group, the treatment elements of which were constructed by unwinding the notional rod of the length a on a common evolute E j  or a plurality of common evolutes E j . 
     The invention is furthermore based on the object of developing a multi-shaft worm machine of the generic type in such a way that a high flexibility is produced in the adjustment of the shear and/or extensional flows acting on the material to be processed. 
     This object is achieved by a multi-shaft worm machine having, in which
         at least two treatment elements arranged directly next to one another are configured such that each treatment element comprises
           a longitudinal axis M,   a respective core radius R i  having the longitudinal axis M as the centre point and an outer radius R a ,   an outer contour A(φ) running about the longitudinal axis M, wherein
               φ is the angle about the longitudinal axis M and   R i ≦D A (φ)≦R a  applies to a spacing D A (φ) of the outer contour A(φ) from the longitudinal axis M,   
               
           wherein
           the outer contour A(φ) has at least one outer contour portion A(φ), which runs along an angle portion A T ,
               which has a continuously changing spacing D A (Δφ) from the longitudinal axis M, wherein R i &lt;D A (Δφ)&lt;R a , and   which has an associated evolute E,
                   which is a quantity of n points P(i) where i=1 to n and n≧3,   wherein each of the points P(i) lies outside the longitudinal axis M and within the outer radius R a , and   wherein two respective adjacent points P(i) and P(i+1) have the spacing, and   
                   
               the sum of the core radius R i  and the outer radius R a  substantially equals the axial spacing a.   
               

     By means of the at least two treatment elements according to the invention, the wedges between the flanks and the inner contour of the housing may be flexibly varied, whereby the shear and/or extensional flows exerted can be optimally adapted to the material to be processed. The at least two treatment elements are configured and arranged in such a way that they tightly mesh and form a corresponding treatment element group. This is achieved in that the sum of the outer radius R a  and the core radius R i  substantially corresponds to the axial spacing a. Substantially this means that the axial retraction b, which is conventional in practice, is disregarded. If the axial retraction b is taken into account, the sum of the outer radius R a  and the core radius R i  corresponds to the difference of the axial spacing a and the axial retraction b. 
     The at least two treatment elements of the treatment element group were constructed on at least one common evolute E j  by unwinding a notional rod with the length of the axial spacing a or the axial spacing a less the axial retraction b. 
     Depending on the type, arrangement and evolute E j , the treatment elements of the treatment element group may be symmetrical, for example axially and/or rotationally symmetrical, or non-symmetrical and/or congruent or non-congruent. Moreover, the at least two treatment elements may be developed in accordance with the configurations according to the invention. 
     Further features, details and advantages of the invention emerge from the following description of a plurality of embodiments with the aid of the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic view of a two-shaft worm machine configured as a two-shaft extruder according to first embodiment, 
         FIG. 2  shows a horizontal part longitudinal section through the two-shaft worm machine in  FIG. 1 , 
         FIG. 3  shows a vertical cross section through the two-shaft worm machine according to the section line in  FIG. 1  with two tightly meshing treatment elements configured as kneading elements in a first rotational position, 
         FIG. 4  shows a vertical cross section through the two-shaft worm machine in accordance with the section in  FIG. 1  with two tightly meshing treatment elements configured as kneading elements in a second rotational position, 
         FIG. 5  shows a perspective view of a plurality of treatment elements according to  FIG. 3 , 
         FIG. 6  shows a construction diagram to illustrate a first construction step of treatment elements in  FIG. 3 , 
         FIG. 7  shows a construction diagram to illustrate a second construction step of the treatment elements in  FIG. 3 , 
         FIG. 8  shows a construction diagram to illustrate a third construction step of the treatment elements in  FIG. 3 , 
         FIG. 9  shows a perspective view of a plurality of tightly meshing treatment elements configured as worm elements according to a second embodiment, 
         FIG. 10  shows a vertical cross section according to  FIG. 3  with treatment elements according to a third embodiment, 
         FIG. 11  shows a construction diagram for illustrating the construction steps of the treatment elements in  FIG. 10 , 
         FIG. 12  shows a vertical cross section according to  FIG. 3  with treatment elements according to a fourth embodiment, 
         FIG. 13  shows a construction diagram for illustrating a first construction step of the treatment elements in  FIG. 12 , 
         FIG. 14  shows a construction diagram to illustrate a second construction step of the treatment elements in  FIG. 12 , 
         FIG. 15  shows a construction diagram to illustrate a third construction step of the treatment elements in  FIG. 12 , 
         FIG. 16  shows a vertical cross section according to  FIG. 3  with treatment elements according to a fifth embodiment, 
         FIG. 17  shows a vertical cross section in accordance with  FIG. 3  with treatment elements according to a sixth embodiment, 
         FIG. 18  shows a vertical cross section according to  FIG. 3  with treatment elements according to a seventh embodiment, 
         FIG. 19  shows a vertical cross section according to  FIG. 3  with treatment elements according to an eighth embodiment, 
         FIG. 20  shows a vertical cross section according to  FIG. 3  with treatment elements according to a ninth embodiment, 
         FIG. 21  shows a vertical cross section according to  FIG. 3  with treatment elements according to a tenth embodiment, 
         FIG. 22  shows a vertical cross section according to  FIG. 3  with treatment elements according to an eleventh embodiment, 
         FIG. 23  shows a vertical cross section according to  FIG. 3  with treatment elements according to a twelfth embodiment, 
         FIG. 24  shows a vertical cross section according to  FIG. 3  with treatment elements according to a thirteenth embodiment, 
         FIG. 25  shows a vertical cross section according to  FIG. 3  with treatment elements according to a fourteenth embodiment, 
         FIG. 26  shows a vertical cross section according to  FIG. 3  with two-threaded treatment elements according to a fifteenth embodiment, 
         FIG. 27  shows a construction diagram to illustrate the construction steps of the treatment elements in  FIG. 26 , 
         FIG. 28  shows a vertical cross section according to  FIG. 3 , with two-threaded treatment elements according to a sixteenth embodiment, 
         FIG. 29  shows a vertical cross section according to  FIG. 3 , with two-threaded treatment elements according to a seventeenth embodiment, 
         FIG. 30  shows a vertical cross section according to  FIG. 3 , with three-threaded treatment elements according to an eighteenth embodiment, 
         FIG. 31  shows a vertical cross section according to  FIG. 3 , with single-threaded treatment elements according to a nineteenth embodiment, 
         FIG. 32  shows a construction diagram to illustrate the construction steps of the treatment elements of  FIG. 31 , 
         FIG. 33  shows a vertical cross section accord ng to  FIG. 3 , with single-threaded treatment elements according to a twentieth embodiment, 
         FIG. 34  shows a construction diagram to illustrate the construction steps of the treatment elements in  FIG. 33 , and 
         FIG. 35  shows a vertical cross section according to  FIG. 28 , with eccentrically arranged treatment elements according to a twenty first embodiment. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first embodiment of the invention will be described below with reference to  FIGS. 1 to 8 . A two-shaft worm machine  1  configured as a two-shaft extruder has a housing  2  consisting of a plurality of housing portions  3 ,  4 ,  5 ,  6  arranged one behind the other and designated housing sections. Configured in the housing  2  are a first housing bore  7  and a second housing bore  8  penetrating the latter, the associated axes  9 ,  10  of which run parallel to one another. In the penetration region of the housing bores  7 ,  8 , the housing portions  3  to  6  have an upper first interstice  11  and a correspondingly configured lower second interstice  12 . 
     Shafts  13 ,  14 , which can be rotatably driven by a drive motor  15 , are arranged in the housing bores  7 ,  8  concentrically with respect to the respectively associated axis  9 ,  10 . A branch gearing  16  is arranged between the shafts  13 ,  14  and the drive motor  15 , a clutch  17  being in turn arranged between the drive motor  15  and the branch gearing  16 . The shafts  13 ,  14  are driven in the same direction, in other words in the same rotational directions  18 ,  19  about the axes  9 ,  10 . The axes  9 ,  10  are accordingly also designated rotational axes. 
     Arranged on the first housing portion  3  adjacent to the branch gearing  16  is a material feed  20  in the form of a funnel, through which plastics material to be prepared or processed can be fed into the housing bores  7 ,  8 . The material is conveyed in a conveying direction  21  from the first housing portion  3  to the last housing portion  6  through the housing  2  and leaves the worm machine  1 , for example, through a nozzle plate  22  closing off the housing  2 . 
     The worm machine  1 , one behind the other in the conveying direction  21 , has a feed zone  23 , a melting zone  24 , a mixing zone  25  and a pressure build-up zone  26 . Arranged on the shafts  13 ,  14  configured as toothed shafts are—one behind the other in the conveying direction  21  respectively associated with one another pair-wise, first worm elements  27 ,  28 , first kneading elements  29 ,  30 , second kneading elements  31 ,  32  and second worm elements  33 ,  34 , in each case as treatment elements. Both the worm elements  27 ,  28 ,  33 ,  34  and the kneading elements  29 ,  30 ,  31 ,  32  mesh with one another, in other words are configured to be tightly meshing. The worm elements  27 ,  28  arranged next to one another pair-wise in each case form a first treatment element group  35 . Accordingly, the kneading elements  29 ,  30  or  31 ,  32  and the worm elements  33 ,  34 , in each case pair-wise, form further treatment element groups  36 ,  37  and  38 . 
     A treatment element group  37  consisting of the kneading elements  31 ,  32  will be described in detail below with the aid of  FIGS. 3 to 8 . Only one treatment element group is shown in  FIGS. 3 and 4  for reasons of clarity. The kneading elements  31 ,  32  of the following treatment element groups  37 , for example, have an offset angle about the respective longitudinal axis M of 30°. The kneading elements  31 ,  32  are configured to be single-threaded and congruent with respect to one another. This means that the kneading elements  31 ,  32  can be made congruent by displacement and/or rotation about their respective longitudinal axis M 1  or M 2 . The longitudinal axes M 1  and M 2  are concentric with respect to the associated rotational axes  9 ,  10  of the shafts  13 ,  14 . In a cross sectional plane running perpendicular to the longitudinal axes M 1 , M 2 , the kneading elements  31 ,  32  in each case have an outer contour A 1 (φ), A 2 (φ) running about the associated longitudinal axis M 1 , M 2 , wherein φ is the angle about the respective longitudinal axis M 1 , M 2  and is between 0≦φ≦360°. As the kneading elements  31 ,  32  are congruent with one another, their outer contours A 1 (φ) and A 2 (φ) are identical. Inasmuch as it is unimportant to distinguish the outer contours A 1 (φ) and A 2 (φ) below and the longitudinal axes M 1  and M 2 , these are designated together by A(φ) or M. 
     The outer contours A(φ) have, relative to their respective longitudinal axis M, which serve as centre points, a minimum core radius R i  and a maximum outer radius R a . The outer radius R a  is smaller by a radial play &lt;S r &gt; than the inner radius R b  of the housing bores  7 ,  8 . As the kneading elements  31 ,  32  are configured to be tightly meshing, the sum of the core radius R i  and the outer radius R a  substantially equals the axial spacing a of the rotational axes  9 ,  10 . This substantially means that a slight axial retraction b is disregarded. If this is taken into account, the sum of the core radius R i  and the outer radius R a  is equal to the difference of the axial spacing a and axial retraction b. The axial retraction b is disregarded below. 
     The construction of the outer contours A(φ) and their course will be described in detail below. The outer contours A(φ) have a spacing D A (φ) from their longitudinal axis M, in each case, for which there applies in each case: R i ≦D A (φ)≦R a . The outer contours A(φ) have a crest A(Δφ K ), a base A(Δφ G ) and two flanks A(Δφ F1 ) and A(Δφ F2 ). The angle portions Δφ K , Δφ G  and Δφ F  are designated the crest angle, base angle and flank angle. This is illustrated in  FIG. 8 . 
     The first flank A(Δφ F1 ) is composed of a first outer contour portion A(Δφ 1 ) with an angle portion Δφ 1  and a transition portion A(Δφ T ) with a transition angle Δφ T  and forms an active flank of the kneading element  31 ,  32  in the respective rotational direction  18 ,  19 . The second flank A(Δφ F2 ) corresponds to a second outer contour portion A(Δφ 2 ) with an angle portion Δφ 2  and forms a passive flank of the kneading element  31 ,  32  lying counter to the respective rotational direction  18 ,  19 . The outer contour portions A(Δφ 1 ) and A(Δφ 2 ) have a continuously changing distance D A (Δφ 1 ) and D A (Δφ 2 ) from the respective longitudinal axis M, for which in each case R i &lt;D A (Δφ)&gt;R a . This is illustrated in  FIG. 7 . 
     The outer contour portions A(Δφ 1 ) and A(Δφ 2 ) have an associated evolute E, which is a quantity of three points P(i), wherein i=1 to 3. The points P(i) lie outside the respective longitudinal axis M and inside the outer radius R a . 
     The construction of the outer contour portions A(Δφ 1 ) and A(Δφ 2 ) is illustrated in  FIG. 6 . To speak figuratively with respect to the construction thereof, a notional rod with the length of the axial spacing a is unwound on the evolute E, the first rod end defining the first outer contour portion A(Δφ 1 ) of one kneading element  31  and the second rod end defining the second outer contour portion A(Δφ 2 ) of the other kneading element  32  and vice versa. In other words, the notional rod is unrolled on a polygon course formed by the point P (1) to P(3), wherein the rod ends lie on the core radius R i  or the outer radius R a  at the beginning. The unrolling is ended when the rod end originally lying on the core radius R i  impinges on the outer radius R a . Unrolling is taken to mean that the notional rod is rotated about the point P(1) until the rod impinges on the next point of the polygon course, in other words on P(2). The notional rod is then rotated about the point P(2), until the rod impinges on the next point, in other words P(3). The notional rod is then rotated about the point P(3) until the rod end impinges on the outer radius R a . This unrolling is illustrated in  FIG. 6 , the notional rod being shown in individual positions while the unwinding is shown by dashed lines. 
     The outer contour portions A(Δφ 1 ) and A(Δφ 2 ) are therefore formed by three circular arcs, the associated centre points of which are the points P(1) to P(3). Adjacent points of the points P(1) to P(3) have a constant spacing Δr(i)=Δr from one another. This means that the radii of adjacent circular arcs, which are also called involute curves E′(1) to E′(3), differ by the spacing Δr(i)=Δr. The spacing Δr is less than R i  and less than R 1 /2. In particular, the spacing Δr may also be smaller than R i /4, in particular smaller than R i /6, and, in particular, smaller than R i /8. The circular arcs belonging to the points P(1) to P(3) have constant angles at centre Δε(i)=Δε. The angles at centre Δε(i)=Δε are less than 60°. In particular, the angle at centre Δε can also be smaller than 45° and in particular smaller than 30°. 
     Because of the constant spacings Δr and the constant angles at centre Δε, the points P(1) to P(3) lie on a continuous and differentiable curve in the form of a circle, which has a direction of curvature remaining the same. 
       FIG. 7  illustrates the further construction of the first flank portion A(ΔφF 1 ). The first flank portion A(Δφ F1 ) is composed of the first outer contour portion A(Δφ 1 ) and the transition portion A(Δφ T ) with the transition angle Δφ T . The transition portion A(Δφ T ) is a circular arc about the centre point M T  with the transition radius R T . The centre point M T  is produced from the contact point of the outer radius R a  and the second outer contour portion A(Δφ 2 ). The transition radius R T  corresponds to the axial spacing a. To speak figuratively, the notional rod with the length of the axial spacing a—once the rod end impinges on the outer radius R a —is pivoted about this contact point, in other words about the centre point M T , until the rod crosses the longitudinal axis M. The movable rod end then comes to rest on the core radius R i . 
       FIG. 8  illustrates the construction of the crest A(Δφ K ) and the base A(Δφ G ). The crest A(Δφ K ) is a circular arc with the longitudinal axis M as the centre point and a radius corresponding to the outer radius R a . The base A(Δφ G ) is also a circular arc with the longitudinal axis M as the centre point and a radius corresponding to the core radius R i . To speak figuratively, the notional rod, once this has impinged on the longitudinal axis M, is rotated about the latter, until the rod ends again impinge on their starting points. The crest angle Δφ K  therefore corresponds to the base angle Δφ G . 
     As the rod ends in each case define one of the outer contours A 1 (φ) or A 2 (φ), the process described has to be repeated again in order to define the complete outer contour A 1 (φ) or A 2 (φ) for each of the kneading elements  31 ,  32 . Because of the fact that the outer contour portions A(Δφ 1 ) and A(Δφ 2 ) are formed on a common evolute E or have a common evolute E, the outer contours A 1 (φ) and A 2 (φ) resulting from the construction process are congruent. This means that the construction process described above does not have to be repeated for this special case, as both kneading elements  31 ,  32  are already constructed thereby. 
     The outer contour portions A(Δφ 1 ) and A(Δφ 2 ) are curved over their respective angle portions Δφ 1  and Δφ 2  and have no straight part portions. Moreover, the outer contours A 1 (φ) or A 2 (φ) have a uniform direction of curvature. 
     As can be seen from  FIGS. 3 and 4 , the evolutes E which are the same and associated with the kneading elements  31 ,  32  can be moved into one another by a linear displacement by the axial spacing a in the direction thereof. The sum of the spacings of the evolutes E or the curves, on which the points P(i) of the evolutes E lie, from the contact point B in the direction of the axial spacing a in each rotational position is substantially equal to the axial spacing a, whereby the kneading elements  31 ,  32  are tightly meshing. 
     The wedge K a  between the inner contour of the housing bores  7 ,  8  and the active flank A(Δφ F1 ) and the corresponding wedge K p  between the inner contour of the passive flank A(Δφ F2 ) can be flexibly adjusted in the kneading elements  31 ,  32  according to the invention, whereby the shear and/or extensional flows can be optimally adapted to the plastic material to be processed. The active angle α a  of intersection of the crest A(Δφ K ) and the active flank A(Δφ 1 ) is 0°. The passive angle α p  of intersection of the crest A(ΔφK) and the passive flank A(Δφ F2 ) is greater than 0°. 
     Since the spacing of the evolutes E of the kneading elements  31 ,  32  in every rotational position corresponds to the axial spacing a, the kneading elements  31 ,  32  are tightly meshing and have a common tangent in their respective contact point B. 
     A second embodiment of the invention will be described below with reference to  FIG. 9 . In contrast to the previous embodiment, the treatment elements  31   a ,  32   a  are configured as worm elements. The outer contours A 1 (φ) and A 2 (φ) correspond to the first embodiment, wherein the latter are screwed along the respective rotational axis  9 ,  10  with a constant and continuous function. With regard to the further mode of functioning, reference is made to the first embodiment. 
     A third embodiment of the invention will be described below with reference to  FIGS. 10 and 11 . The kneading elements  31   b  and  32   b  are neither congruent with respect to one another nor symmetrical. The kneading elements  31   b ,  32   b  in each case have two evolutes E j , wherein j=1 and 2. Each of the evolutes E j  is a quantity of 3 points P j (i) wherein I=1 to 3. The first evolute E 1  is a polygon course formed from the points P 1 (1) to P 1 (3), adjacent points of the points P 1 (1) to P 1 (3) having different spacings Δr(i). The second evolute E 2  corresponds to that of the first embodiment. The outer contour portions A 1 (Δφ 11 ) and A 2 (Δφ 12 ) are formed by unwinding the notional rod at the first evolute E 1 . In accordance with the first embodiment, the transition portion A 1 (Δφ T1 ) is then formed by pivoting the notional rod about the centre point M T1 . By rotating the notional rod about the centre point M, the crest A 2 (Δφ K2 ) and the base A 1 (Δφ G1 ) are then formed in accordance with the first embodiment. 
     A further half rotation of the notional rod now follows. The notional rod is firstly unwound on the second evolute E 2 , so the outer contour portions A 1 (Δφ 21 ) and A 2 (Δφ 22 ) are formed. By pivoting the notional rod about the centre point M T2 , the transition portion A 2 (Δφ T2 ) is then formed analogously to the first embodiment. By rotating the notional rod about the centre point M, the base A 2 (Δφ G2 ) and the crest A 1 (Δφ K1 ) are formed and the outer contours A 1 (φ) and A 2 (φ) are closed. The outer contour portions A 1 (Δφ 11 ) and A 2 (Δφ 12 ) are therefore produced on the evolute E 1 , whereas the outer contour portions A 1 (Δφ 21 ) and A 2 (Δφ 22 ) are produced on the evolute E 2  that is different therefrom. Accordingly, the wedges K a1  and K a2  or the wedges K p1  and K p2  and the angles α a1  and α a2  of intersection or the angles α p1  and α p2  of intersection are also configured differently. With regard to the further mode of functioning and construction, reference is made to the previous examples. 
     A fourth embodiment of the invention will be described below with reference to  FIGS. 12 to 15 . In contrast to the previous examples, the evolute E is a continuous and differentiable curve in the form of a circular arc about the centre point M E . Viewed mathematically, this evolute E can be formed in that a limit transition toward zero is carried out for the angle at centre Δε in accordance with the first embodiment. The spacing Δr of the points P(i) then passes into the arc length ds and the angle at centre Δε passes into the change of the tangent direction dε. The evolute E therefore has the radius of curvature R E =ds/dε. The evolute E is therefore a circular arc with an infinite number of points P(i), wherein i=1 to ∞ in the limit transition. The construction of the flanks A(Δφ F1 ) and A(Δφ F2 ) according to  FIGS. 13 and 14  takes place in accordance with the first embodiment, wherein the evolute E—as already stated—is a circular arc. As the outer contour portions A(Δφ 1 ) and A(Δφ 2 ) have the same evolute E, the kneading elements  31   c  and  32   c  are congruent with respect to one another. The kneading elements  31   c  and  32   c  are, however, non-symmetrical. The active angle of intersection α a =0°. Accordingly, the passive angle of intersection α p &gt;0°. The wedges K a  and K p  can thus be flexibly adapted to the plastics material to be processed. With regard to the further mode of functioning and construction, reference is made to the previous embodiments. 
     A fifth embodiment of the invention will be described below with reference to  FIG. 16 . The kneading elements  31   d  and  32   d  are configured in accordance with the fourth embodiment and have an evolute E, which is a continuous and differentiable curve in the form of a circular arc. The ratio of the outer radius R a  to the core radius R i  equals 1.55. The crest angle Δφ K =20° and the active angle of intersection α a =0°. The passive angle of intersection α p &gt;0°. The associated wedges K a  and K p  can thus be flexibly adapted to the plastics material to be processed. Reference is made to the preceding examples with regard to the further mode of functioning and construction. 
     A sixth embodiment of the invention will be described below with reference to  FIG. 17 . The kneading elements  31   e  and  32   e  are configured in accordance with the fourth embodiment and have an evolute E, which is a continuous and differentiable curve in the form of a circular arc. The ratio of the outer radius R a  to the core radius R i  equals 1.55. The crest angle Δφ K =80°. The active angle of intersection α a =0°. The passive angle of intersection α p &gt;0°. The associated wedges K a  and K p  can thus be flexibly adapted to the plastics material to be processed. With regard to the further mode of functioning and construction, reference is made to the previous embodiments. 
     A seventh embodiment of the invention will be described below with reference to  FIG. 18 . The kneading elements  31   f  and  32   f  are configured in accordance with the fourth embodiment and have an evolute E, which is a continuous and differentiable curve in the form of a circular arc. The ratio of the outer radius R a  to the core radius R i  equals 1.55. The crest angle Δφ K =20°. The active angle of intersection associated with the active flank A(Δφ F1 ) is α a =15°. The passive angle of intersection associated with the passive flank A(Δφ F2 ) is α p =20°. The associated wedges K a  and K p  can thus be flexibly adapted to the plastics material to be processed. With regard to the further mode of functioning and construction, reference is made to the previous embodiments. 
     An eighth embodiment of the invention will be described below with reference to  FIG. 19 . The kneading elements  31   g  and  32   g  are configured in accordance with the fourth embodiment and have an evolute E, which is a continuous and differentiable curve in the form of a circular arc. The ratio of the outer radius R a  to the core radius R i  equals 1.55. The crest angle Δφ K =20°. The active angle of intersection associated with the active flank A(Δφ F1 ) is α a =5°. The passive angle of intersection associated with the passive flank A(Δφ F2 ) is α p =10°. The associated wedges K a  and K p  can thus be flexibly adapted to the plastics material to be processed. With regard to the further mode of functioning and construction, reference is made to the previous embodiments. 
     A ninth embodiment of the invention will be described below with reference to  FIG. 20 . The kneading elements  31   h  and  32   h  are configured in accordance with the fourth embodiment and have an evolute E, which is a continuous and differentiable curve in the form of a circular arc. The ratio of the outer radius R a  to the core radius R i  equals 1.55. The crest angle Δφ K =20°. The active associated angle of intersection α a =5°. The passive angle of intersection α p =20°. The associated wedges K a  and K p  can thus be flexibly adapted to the plastics material to be processed. With regard to the further mode of functioning and construction, reference is made to the previous embodiments. 
     A tenth embodiment of the invention will be described below with reference to  FIG. 21 . The kneading elements  31   i  and  32   i  are configured in accordance with the fourth embodiment and have an evolute E, which is continuous and differentiable curve in the form of a circular arc. The ratio of the outer radius R a  to the core radius R i  equals 1.55. The crest angle Δφ K =20°. The active angle of intersection α a =10°. The passive angle of intersection α p =10°. Because of the same angles α a  and α p  of intersection, the kneading elements  31   i  and  32   i  are congruent and symmetrical. The associated wedges K a  and K p  are configured the same. With regard to the further mode of functioning and construction, reference is made to the previous embodiments. 
     An eleventh embodiment of the invention will be described below with reference to  FIG. 22 . The kneading elements  31   j  and  32   j  are configured in accordance with the fourth embodiment and have an evolute E and a continuous and differentiable curve in the form of a circular arc. The ratio of the outer radius R a  to the core radius R i  equals 1.55. The crest angle Δφ K =0°. The crest A(Δφ K ) therefore degenerates to a single point, the centre point M T . The angle α a  of intersection associated with the active flank A(Δφ F1 ) is maximal. The angle α p  of intersection associated with the passive flank A(Δφ F2 ) is also maximal. Because of the same angles α a  and α p  of intersection, the kneading elements  31   j  and  32   j  are congruent and symmetrical. The associated wedges K a  and K p  can thus be flexibly adapted to the plastics material to be processed. With regard to the further mode of functioning and construction, reference is made to the previous examples. 
     A twelfth embodiment of the invention will be described below with reference to  FIG. 23 . The kneading elements  31   k  and  32   k  are configured in accordance with the fourth embodiment and have an evolute E and a continuous and differentiable curve in the form of a circular arc. The ratio of the outer radius R a  to the core radius R i  equals 1.55. The crest angle Δφ K =100°. The active angle α a  of intersection is maximal. The passive angle α p  of intersection is also maximal. Because of the same angles α a  and α p  of intersection, the kneading elements  31   k  and  32   k  are congruent and symmetrical. The passive flank A(Δφ F2 ) is formed from the outer contour portion A(Δφ 2 ) and a further transition portion A(Δφ T2 ), in contrast to the previous embodiments. The second transition portion A(Δφ T2 ) is produced as a circular arc about the centre point M T2  with the transition radius R T , which corresponds to the axial spacing a. The associated wedges K a  and K p  may thus be flexibly adapted to the plastics material to be processed. 
     Reference is made to the previous embodiments with regard to the further mode of functioning and construction. 
     A thirteenth embodiment of the invention will be described below with reference to  FIG. 24 . The kneading elements  31   l  and  32   l  have two evolutes E 1  and E 2 , which are configured in accordance with the fourth embodiment and are a continuous and differentiable curve in the form of a circular arc. The kneading elements  31   l  and  32   l  are accordingly not congruent, but symmetrical. The ratio of the outer radius R a  to the core radius R i  equals 1.55. The crest angle Δφ K =0°. The crest A(ΔφK) therefore degenerates to a single point, the centre point M T . The angles α a1  and α p1  and α a2  and α p2  of intersection are the same, so the same wedges K a1  and K p1  and K a2  and K p2  are produced. With regard to the further mode of functioning and construction reference is made to the previous embodiments. 
     A fourteenth embodiment of the invention will be described below with reference to  FIG. 25 . The kneading elements  31   m  and  32   m  have two evolutes E 1  and E 2 , which are configured in accordance with the fourth embodiment and are a continuous and differentiable curve in the form of a circular arc. The kneading elements  31   m  and  32   m  are accordingly not congruent, but symmetrical. The ratio of the outer radius R a  to the core radius R i  equals 1.55. The crest angle Δφ K =120°. The angles α a1  and α p1  and α a2  and α p2  of intersection are the same, so the same wedges K a1  and K p1  and K a2  and K p2  are produced. The evolutes E 1  and E 2  have a common tangent T, so the outer contour portions A 1 (Δφ 11 ) and A 1 (Δφ 21 ) and A 2 (Δφ 12 ) and A 2 (Δφ 22 ) pass into one another in a continuous and differentiable manner. With regard to the further mode of functioning and construction, reference is made to the previous embodiments. 
     A fifteenth embodiment of the invention will be described below with reference to  FIGS. 26 and 27 . The kneading elements  31   n  and  32   n  are two-threaded. The kneading elements  31   n  and  32   n  have four evolutes E 1  to E 4 , which are continuous and differentiable curves in the form of circular arcs. The kneading elements  31   n  and  32   n  are congruent. The outer contour A 1 (φ) of the kneading element  31   n  is composed of the outer contour portion A 1 (Δφ 11 ) unwound on the evolute E 1 , the outer contour portion A 1 (Δφ 21 ) unwound on the evolute E 2 , the transition portion A 1 (Δφ T11 ) about the centre point M T11 , the outer contour portion A 1 (Δφ 31 ) unwound on the evolute E 3 , the outer contour portion A 1 (Δφ 41 ) unwound on the evolute E 4  and the transition portion A 1 (Δφ T21 ) about the centre point M T21 . The outer contour A 2 (φ 2 ) of the kneading element  32   n  is produced with the aid of the evolutes E 1  to E 4  accordingly, wherein the transition portions A 2 (Δφ T12 ) and A 2 (Δφ T22 ) have the centre points M T12  and M 22 . The active angles α a1  and α a2  of intersection equal 0°. The passive angles α p1  and α p2  of intersection are the same and greater than 0°. Accordingly, the active wedges K a1  and K a2  and the passive wedges K p1  and K p2  are the same. With regard to the further mode of functioning and construction, reference is made to the previous embodiments. 
     A sixteenth embodiment of the invention will be described below with reference to  FIG. 28 . The kneading elements  31   o  and  32   o  are two-threaded in accordance with the fifteenth embodiment and have four evolutes E 1  to E 4  in the form of circular arcs. The kneading elements  31   o  and  32   o  are not congruent, but symmetrical. The outer contour A 1 (φ) of the treatment element  31   o  is composed of the outer contour portion A 1 (Δφ 11 ) unwound on the evolute E 1 , the crest A 1 (Δφ K1 ) about the centre point M 1 , the outer contour portion A 1 (Δφ 21 ) unwound on the evolute E 2 , the outer contour portion A 1 (Δφ 31 ) unwound on the evolute E 3 , the crest A 1 (Δφ K2 ) about the centre point M 1  and the outer contour portion A 1 (Δφ 41 ) unwound on the evolute E 4 . The evolutes E 2  and E 3  and E 1  and E 4  in each case have a common tangent T 1  and T 2 , so the outer contour portions A 1 (Δφ 21 ) and A 1 (Δφ 31 ) and A 1 (Δφ 41 ) and A 1 (Δφ 11 ) pass into one another in a continuous and differentiable manner. The outer contour A 2 (φ) of the treatment element  32   o  is formed in accordance with the evolutes E 1  to E 4 , the outer contour portions A 2 (Δφ 12 ) and A 2 (Δφ 22 ) being connected by the base A 2 (Δφ G1 ) and the outer contour portions A 2 (Δφ 32 ) and A 2 (Δφ 42 ) by the base A 2 (Δφ G2 ). The active angle α a1  of intersection and the passive angle α p1  of intersection of the treatment element  31   o  are about 33°. The active angle α a2  of intersection and the passive angle α p2  of intersection of the treatment element  32   o  are 0°. Consequently, the wedges K a1  and K p1  are the same. The same applies to the wedges K a2  and K p2 . With regard to the further mode of functioning and construction, reference is made to the previous embodiments. 
     With reference to  FIG. 29 , a seventeenth embodiment of the invention will be described below. The kneading elements  31   p  and  32   p  are two-threaded. The kneading elements  31   p  and  32   p  are not congruent, but symmetrical. The kneading elements  31   p  and  32   p  have four evolutes E 1  to E 4 , which are, in each case, continuous and differentiable curves. The evolutes E 1  to E 4  form an astroid, which can be described by the following equations:
 
 x=c ·(cos( t )) n  
 
 y=d ·(sin( t )) n  
 
with the factors c and d and the exponent n, wherein c&gt;d and n=3. The outer contour A 1 (φ) of the kneading element  31   p  is composed of the outer contour portion A 1 (Δφ 11 ) unwound on the evolute E 1 , the outer contour portion A 1 (Δφ 21 ) unwound on the evolute E 2 , the outer contour portion A 1 (Δφ 31 ) unwound on the evolute E 3  and the outer contour portion A 1 (Δφ 41 ) unwound on the evolute E 4 . The evolutes E 1  to E 4  in each case have, pair-wise, common tangents T 1  to T 4 , so the outer contour portions A 1 (Δφ 11 ) to A 1 (Δφ 41 ) pass into one another in a continuous and differentiable manner. The outer contour A 2 (φ) of the kneading element  32   p  is comprised accordingly. The active angle α a1  of intersection and passive angle α p1  of intersection of the kneading element  31   p  are the same, so the wedges K a1  and K p1  are also the same. The same applies to the active angle α a2  of intersection and passive angle α p2  of intersection and the corresponding wedges K a2  and K p2  of the kneading element  32   p . The angles α a2  and α p2  of intersection are, however, smaller than the angles α a1  and α p1  of intersection. The crests and bases of the kneading elements  31   p  and  32   p  are degenerated to single points. With regard to the further mode of functioning and construction, reference is made to the previous embodiments.
 
     An eighteenth embodiment will be described below with reference to  FIG. 30 . The kneading elements  31   q  and  32   q  are triple-threaded. The kneading elements  31   q  and  32   q  are congruent and symmetrical. They have three evolutes E 1  to E 3 , which are in each case continuous and differentiable curves and together form a tricuspoid. The outer contour A 1 (φ) of the kneading element  31   q  is composed of the outer contour portion A 1 (Δφ 11 ) unwound on the evolute E 1 , the outer contour portion A 1 (A T21 ) unwound on the evolute E 2 , the outer contour portion A 1 (Δφ 31 ) unwound on the evolute E 3  and the outer contour portions A 1 (Δφ 41 ) to A 1 (Δφ 61 ) formed with a corresponding unwinding process. As the evolutes E 1  to E 3  in each case have, pair-wise, a common tangent T 1  to T 3 , the outer contour portions A 1 (Δφ 11 ) to A 1 (Δφ 61 ) pass into one another in a continuous and differentiable manner. The active angles α a1  and α a2  of intersection and the passive angles α p1  and α p2  of intersection are the same size, so corresponding wedges K a1 , K a2 , K p1  and K p2  are produced. The outer contour A 2 (φ) of the kneading element  32   q  is formed in accordance with the kneading element  31   q . With regard to the further functioning and construction, reference is made to the previous embodiments. 
     A nineteenth embodiment of the invention will be described below with reference to  FIGS. 31 and 32 . The kneading elements  31   r  and  32   r  are single-threaded. They are congruent, but not symmetrical. The kneading elements  31   r  and  32   r  have an evolute E, which is a continuous and differentiable curve in the form of a spiral. The spiral can be described by the equation
 
ρ= k·t   n  
 
wherein ρ is the radius, k is a constant and t is the angle (in polar coordinates) of the spiral. The kneading elements  31   r  and  32   r  have a crest angle Δφ K =20°. The active angle of intersection α a =0°. The passive angle of intersection α p1 &gt;0°. The exponent n equals 2.5. The spiral-shaped evolute E is additionally rotated through 180°. With regard to the further mode of functioning and construction, reference is made to the previous embodiments, in particular the fourth embodiment.
 
     A twentieth embodiment of the invention will be described below with reference to  FIGS. 33 and 34 . The kneading elements  31   s  and  32   s  are single-threaded and not congruent. The kneading elements  31   s  and  32   s  have two evolutes E 1  and E 2 , which in each case form a continuous and differentiable curve in the form of a spiral. The crest angle Δφ K =20°. Accordingly, the base angle Δφ G =20°. The active angle of intersection α a1 =20°. The active angle of intersection α a2  equals 10°. The exponent n=1.0. The spiral evolutes E 1  and E 2  are rotated through 120° and 100°. With regard to the further mode of functioning and construction, reference is made to the previous examples, in particular the third and nineteenth embodiments. 
     A twenty-first embodiment of the invention will be described below with reference to  FIG. 35 . The kneading elements  31   t  and  32   t  are configured in accordance with the sixteenth embodiment. In contrast to the previous embodiments, the kneading elements  31   t  and  32   t  with their longitudinal axes M 1  and M 2  are arranged eccentrically with respect to the associated rotational axes  9  and  10 . The longitudinal axes M 1  and M 2  therefore have a spacing e from the associated rotational axes  9  and  10 , which characterizes the eccentricity. Because of the eccentric arrangement, the shape of the wedges K a1  and K p1  or wedges K a2  and K p2  and the size of the angles α a1  and α p1  or α a2  and α p2  of intersection depend on the rotational position of the kneading elements  31   t  and  32   t . The spacing e along the rotational axes  9 ,  10  may be constant or vary. Moreover, the angle at which the kneading elements  31   t  and  32   t  are eccentrically moved out may be constant or vary. With regard to the further mode of functioning, reference is made to the previous embodiments. In particular, the treatment elements  31 ,  32  to  31   s ,  32   s  described in the previous embodiments may also be eccentrically arranged in accordance with the twenty first embodiment.