Screw element having an axially asymmetrical screw profile which has at least two construction points located within the screw profile

A screw element having a number of grooves Z, suitable for a twin-shaft screw machine:

• having two screw shafts SW1 and SW2 that rotate in the same direction and at the same speed, axes of rotation D1 and D2 of which are at an axial distance a, and
• having two circular housing bores which penetrate one another, each of which has an identical housing inner radius rg and bore centers M1 and M2 of which are at a distance which is equal to the axial distance a, and the bore centers M1 and M2 of which coincide with the respective axes of rotation D1 and D2 of the screw shafts SW1 and SW2,
• wherein the screw element has a screw profile which:
• (1) forms a closed convex line,
• (2) is composed only of circular arcs the radius of which is less than or equal to the axial distance a, wherein directly adjacent circular arcs have a different radius,
• (3) has a first construction point K1 which lies within the screw profile,
• (4) is not axisymmetric in relation to the construction point K1,
• (5) is composed of at least 4 circular arcs,
• (6) has a second construction point K2 which does not coincide with the construction point K1, wherein the construction point K2 lies within the screw profile,
• (7) is not point-symmetric or axisymmetric in relation to the construction point K2,
• (8) has a point of rotation DP which coincides with one of the bore centers M1 or M2 and which lies on a path from the construction point K1 to the construction point K2,
• (9) has exactly one main flight land HK, the main flight land HK is formed from only one circular arc and the center of this circular arc is the construction point K2, and wherein the set of points of the screw profile that are furthest away from the construction point K2 comprise an end point of a circular arc preceding the main flight land HK, the main flight land HK, and a starting point of a circular arc succeeding the main flight land HK,
• (10) has at least one groove, wherein a groove of the at least one groove is formed from only a single circular arc the center of which is the construction point K1, and a radius of the groove of the at least one groove is the same as a core radius ri, and wherein a circular arc preceding the groove of the at least one groove and a circular arc succeeding the groove of the at least one groove, apart from an end point of the circular arc preceding the groove of the at least one groove and a starting point of the circular arc succeeding the groove of the at least one groove, have a greater distance from the construction point K1 than the circular arc of the groove of the at least one groove,
• (11) has a plurality of flanks, wherein flanks are those regions of the screw profile the circular arcs of which have a center which is neither the construction point K1 nor the construction point K2, and
• (12) the groove of the at least one groove is separated from the closest point of the main flight land HK by at least one circular arc, which is a flank,
• wherein a radius rHK of the circular arc of the main flight land HK corresponds to a housing inner radius rg reduced by a main flight-land clearance c_HK.