Rotor for an eccentric screw pump and method for the manufacture thereof

Abstract

A method of manufacturing a metallic rotor of an eccentric screw pump, comprising clamping a workpiece extending along a central longitudinal axis in a workpiece clamping device and removing material from the workpiece by cutting with a cutting tool. The invention further comprises not producing the surface of the rotor in a three-axis whirling process, using the cutting tool to produce the outer surface geometry of the rotor, advancing the cutting tool along an axis of advance that is parallel to the longitudinal axis of the rotor, and rotating the cutting tool about an axis of tool rotation that is parallel to the longitudinal axis of the rotor.

We claim: 
     
         1 . A rotor for an eccentric screw pump, the rotor having a helical geometry with a central worm axis that winds helically around a central longitudinal axis of the rotor, wherein the rotor is produced in a milling process in which a milling tool rotating about a tool rotation axis which is not parallel to a central longitudinal axis of the rotor is used for the machining production of the rotor from a workpiece. 
     
     
         2 . The rotor according to  claim 1 , wherein the rotor extends from a first end along a central longitudinal axis thereof to a second end, and a geometry of the rotor generated in the milling process is a helical geometry defined by at least one geometric parameter including:
 an eccentricity of a worm thread, defined as the distance between a central worm axis running in the center of a worm cross-sectional area and the center longitudinal axis;   a surrounding outer diameter of the helical geometry in relation to the central longitudinal axis;   an enveloping inner diameter of the helical geometry in relation to the central longitudinal axis;   an outer diameter of the helical geometry in relation to the central worm axis; and   a pitch of the central worm axis;
 wherein the at least one of the geometric parameters changes in the axial direction along the central longitudinal axis of the rotor, wherein the first end of the rotor is greater than at the second end of the rotor or the geometric parameter is different at one end of the rotor from a cross section of the rotor lying between the first and second ends in an axial direction. 
   
     
     
         3 . The rotor according to  claim 2 , wherein the at least one geometric parameter is changed continuously towards the second end of the rotor, starting from the first end of the rotor. 
     
     
         4 . The rotor according to  claim 2 , wherein the at least one geometric parameter starting from the first end of the rotor towards the second end of the rotor towards the second end of the rotor is first enlarged and then reduced in size, or is first reduced and then enlarged. 
     
     
         5 . The rotor according to  claim 2 , wherein the at least one geometric parameter is varied from the first end of the rotor to the second end of the rotor along the entire length of the rotor or along an axial section of the rotor with a single, double, or triple exponential dependence on the axial feed of the milling tool along the central longitudinal axis. 
     
     
         6 . The rotor according to  claim 2 , wherein:
 the helical geometry of a manufactured rotor has a non-circular cross section with respect to the central worm axis,   the helical geometry of the manufactured rotor has a non-point symmetrical cross section with respect to a point of symmetry located in the central worm axis;   at least one lubrication pocket is formed in the surface of the helical geometry of the manufactured rotor; or   an outer geometry of the rotor has at least one wear allowance section in which the outer geometry has axially protruding sections deviating from a continuous worm outer geometry.   
     
     
         7 . The rotor according to  claim 2 , wherein at least two of the geometric parameters are changed along the axial feed path of the milling tool such that:
 a first geometric parameter is increased and a second geometric parameter is increased or decreased in a proportional or exponential ratio to the increase of the first parameter; or   a first geometric parameter is increased and a second geometric parameter is increased or decreased in a non-correlated ratio to the increase of the first parameter.   
     
     
         8 . A stator for an eccentric screw pump comprising a stator cavity having a geometry according to the rotor according to  claim 2 . 
     
     
         9 . The use of a rotor according to  claim 1  as a stator core for manufacturing a stator in a master moulding process. 
     
     
         10 . An eccentric screw pump comprising a rotor according to  claim 1 . 
     
     
         11 . An eccentric screw pump comprising a stator according to  claim 8 . 
     
     
         12 . An eccentric screw pump of comprising:
 a rotor having a helical geometry with a central worm axis that winds helically around a central longitudinal axis of the rotor, wherein the rotor is produced in a milling process in which a milling tool rotating about a tool rotation axis which is not parallel to a central longitudinal axis of the rotor is used for the machining production of the rotor from a workpiece, or the rotor is manufactured in an additive manufacturing process comprising a laser sintering process or a laser melting process, in which a selective material application process or a selective material curing process is controlled on the basis of the geometric data of the rotor; and   a stator according to  claim 8 ;   wherein at least one geometric parameter of the rotor varying in a direction along the central longitudinal axis of the rotor and the at least one geometric parameter of the stator is varying along a central longitudinal axis of the stator are coincident geometric parameters.   
     
     
         13 . The eccentric screw pump according to  claim 12 , wherein the at least one geometric parameter of the rotor and the at least one geometric parameter of the stator change synchronously in a direction along the central longitudinal axis.