ECCENTRIC SCREW PUMP WITH WORKING ENGAGEMENT AND IDLE ENGAGEMENT AND METHOD FOR CONTROLLING THE ECCENTRIC SCREW PUMP

Abstract

An eccentric screw pump for delivering solid-laden liquids includes a rotor and a stator within which the rotor is rotatably arranged. The rotor and stator are arranged and designed with respect to one another in such a way that at least one chamber is formed, which serves to transport the liquid. The eccentric screw pump has a drive motor for rotating the rotor, a control device for controlling the drive motor at least in a working state, in which the rotor is rotated, and an idle state, in which the rotor does not rotate, and an engagement unit, which is designed to set an engagement between the rotor and stator to an idle engagement in the idle state and to a working engagement in the working state. The idle engagement is less than the working engagement. A method for operating the eccentric screw pump is also disclosed.

Claims

1.-24. (canceled)

25. An eccentric screw pump for delivering solid-laden liquids, the eccentric screw pump comprising: a helically wound rotor; a stator having an inlet and an outlet and within which the rotor is arranged to be rotatable about a longitudinal axis of the stator, and which has a helical inner wall corresponding to the rotor; wherein the rotor and stator are arranged with respect to one another such that at least one chamber is formed which serves to transport the liquid, and the chamber is separated by a sealing line; a drive motor for rotating the rotor; a control device for controlling the drive motor at least in a working state, in which the rotor is rotated, and an idle state, in which the rotor does not rotate; and an engagement unit adapted to set an engagement between the rotor and stator to an idle engagement in the idle state and to a working engagement in the working state, wherein the idle engagement is less than the working engagement.

26. The eccentric screw pump according to claim 25, wherein the idle engagement is set such that contact between the rotor and stator is substantially free of tension.

27. The eccentric screw pump according to claim 25, wherein, in the working engagement, a substantially complete sealing line is formed between the rotor and stator.

28. The eccentric screw pump according to claim 25, wherein the engagement unit is adapted to adjust the engagement from the working engagement to the idle engagement in or before a run-down time period, wherein the run-down time period comprises a switch from the working state to the idle state.

29. The eccentric screw pump according to claim 25, wherein the engagement unit is adapted to adjust the engagement from the idle engagement to the working engagement in a run-in time period or thereafter, wherein the run-in time period comprises a switch from the idle state to the working state.

30. The eccentric screw pump according to claim 25, wherein the engagement unit comprises an electronic engagement control and an engagement drive actuated by the electronic engagement control to change an engagement.

31. The eccentric screw pump according to claim 25, wherein the engagement unit comprises a hydraulic path and a hydraulic drive which is coupled to the rotor and/or stator such that an engagement can be adjusted by applying a hydraulic pressure.

32. The eccentric screw pump according to claim 25, wherein the rotor has a tapering or conical form.

33. The eccentric screw pump according to claim 25, wherein the rotor has a varying eccentricity.

34. The eccentric screw pump according to claim 32, wherein the rotor tapers towards the outlet.

35. The eccentric screw pump according to claim 25, wherein the adjustment of the engagement from the working engagement to the idle engagement comprises an axial displacement of the rotor.

36. The eccentric screw pump according to claim 25, wherein the rotor is axially displaceable between a working position and an idle position.

37. The eccentric screw pump according to claim 25, wherein the stator comprises a supporting element and an elastomer part, and wherein the engagement comprises a pre-tension between the rotor and stator so that the working engagement is a working pre-tension and the idle engagement is an idle pre-tension.

38. The eccentric screw pump according to claim 37, wherein the stator is radially engageable in order to adjust the pre-tension between the working pre-tension and the idle pre-tension.

39. The eccentric screw pump according to claim 37, wherein two adjustment elements are arranged on the stator and have a variable mutual spacing, and wherein a mechanical coupling is established between the adjustment elements and the stator so that, by altering the relative distance between the two adjustment elements, it is possible to change a cross section and a length of an elastomer part of the stator.

40. The eccentric screw pump according to claim 25, wherein the stator is a solid stator and the working engagement is selected such that a sealing line is formed and the idle engagement is selected such that a gap is formed between the rotor and stator.

41. A method for controlling an eccentric screw pump, the method comprising the steps of: providing an eccentric screw pump comprising: a helically wound rotor; a stator having an inlet and an outlet and within which the rotor is arranged to be rotatable about a longitudinal axis of the stator, and which has a helical inner wall corresponding to the rotor, wherein the rotor and stator are arranged with respect to one another such that at least one chamber is formed which serves to transport the liquid, and the chamber is separated by a sealing line; a drive motor for rotating the rotor; a control device for controlling the drive motor at least in a working state, in which the rotor is rotated, and an idle state, in which the rotor does not rotate; and an engagement unit adapted to set an engagement between the rotor and stator to an idle engagement in the idle state and to a working engagement in the working state, wherein the idle engagement is less than the working engagement; operating the eccentric screw pump in a working state by rotating the rotor within the stator of the eccentric screw pump with a working engagement between the rotor and stator; outputting a stop signal and, in response to the stop signal: stopping the rotation and switching to the idle state of the eccentric screw pump; and reducing the engagement between the rotor and stator from the working engagement to the idle engagement.

42. The method according to claim 41, wherein a run-down time period is defined by a time from the stop signal being output to a rotational standstill of the rotor, and the reduction in the engagement from the working engagement to the idle engagement takes place substantially at least partly during or following the run-down period.

43. A method according to claim 41, wherein the reduction in the engagement between the rotor and stator from the working engagement to the idle engagement comprises an axial displacement of the rotor from a working position into an idle position.

44. The method according to claim 41, wherein the reduction in the engagement between the rotor and stator from the working engagement to an idle engagement comprises altering a relative distance between two adjustment elements on the stator for changing a cross section and a length of an elastomer part of the stator.

45. The method according to claim 43, wherein the working position and the idle position are spaced apart between 1/50 and ¼ of a pitch of the rotor.

46. The method according to claim 42, further comprising the steps of: outputting a start signal; and in response to the start signal, beginning the rotation of the rotor and switching from the idle state to the working state of the eccentric screw pump.

47. The method according to claim 46, further comprising the step of, in response to the start signal: increasing the engagement between the rotor and stator from the idle engagement to the working engagement in a run-in time period or thereafter.

48. The method according to claim 47, wherein a run-in time period is defined by a time from the start signal being output to a setpoint speed of the rotor being reached, and the increase in the engagement from the idle engagement to the working engagement takes place at least partly during or following the run-in time period.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Further advantages, features, and details of the invention are revealed in the description below of the preferred embodiments and with reference to the drawing, in which:

[0038] FIG. 1 shows a schematic cross section through an eccentric screw pump according to a first exemplary embodiment;

[0039] FIG. 2a shows a schematic cross section through an eccentric screw pump perpendicularly to the longitudinal axis when set in working engagement;

[0040] FIG. 2b shows a schematic cross section along the longitudinal axis according to FIG. 2a;

[0041] FIG. 2c shows a schematic cross section perpendicularly to the longitudinal axis according to FIG. 2a;

[0042] FIG. 3a shows a schematic cross section through an eccentric screw pump perpendicularly to the longitudinal axis when set in idle engagement;

[0043] FIG. 3b shows a schematic cross section along the longitudinal axis according to FIG. 3a;

[0044] FIG. 3c shows a schematic cross section perpendicularly to the longitudinal axis according to FIG. 3a;

[0045] FIG. 4 shows a schematic cross section through an eccentric screw pump according to a second exemplary embodiment;

[0046] FIG. 5 shows a schematic cross section through an eccentric screw pump according to a third exemplary embodiment;

[0047] FIG. 6 shows a schematic cross section through an eccentric screw pump according to a fourth exemplary embodiment with a working engagement;

[0048] FIG. 7 shows a schematic cross section through an eccentric screw pump according to the fourth exemplary embodiment with an idle engagement;

[0049] FIG. 8 shows a schematic cross section through an eccentric screw pump according to a fifth exemplary embodiment;

[0050] FIG. 9 shows a schematic cross section through an eccentric screw pump according to a sixth exemplary embodiment;

[0051] FIG. 10 shows a schematic cross section through an eccentric screw pump according to a seventh exemplary embodiment;

[0052] FIG. 11 shows a schematic cross section through an eccentric screw pump according to an eighth exemplary embodiment; and

[0053] FIG. 12 shows a graph.

DETAILED DESCRIPTION OF THE EMBODIMENTS

[0054] An eccentric screw pump 1 has a stator 2 and a rotor 4. The stator has a central axis L1, which extends centrally through an inner cavity 6 of the stator 2. The stator 2 has an inner wall 8, which delimits the cavity 6 and is formed from an elastomer material. The inner contour of the wall 8 is formed such that it defines a double-threaded helix. The rotor 4 likewise has a helical shape overall, wherein the pitch of the helix form of the stator 2 is double the pitch of the rotor 4. Individual chambers 5 are thus formed, which are separated by a constriction 7.

[0055] The stator 2 furthermore has an inlet 10 and an outlet 12. The inlet 10 is connected to an inlet housing 14, which has an inlet flange 16 on which an inlet pipe 18 is flange-mounted. The outlet 12 is furthermore provided with an outlet housing 20, which has an outlet flange 22 on which an outlet pipe 24 is flange-mounted.

[0056] The embodiment shown in FIG. 1 relates to a stationary eccentric screw pump, which is, in particular, installed in the system in a fixed manner. The inlet pipe 18 may merge into a further pipeline, for example, waste water pipeline, and the outlet pipe 24 may merge into another further pipeline or a collecting tank.

[0057] A drive shaft 26 extends through the inlet housing 14, which drive shaft 26 is connected to the rotor 4 via a first Cardan joint 28 and communicates with a driven shaft 32 of a gear system 34 via a second Cardan joint 30. Instead of such a drive shaft 26 having two Cardan joints 28, 30, it is likewise preferable to use a thin flexible shaft which enables the eccentric drive. The gear system 34 is connected, on the input side, to a drive motor 36 which, according to this exemplary embodiment, is designed as an electric motor. However, the drive motor 36 may also be connected directly to the driven shaft 32, without an interconnected gear system 34. The drive motor 36 may also be arranged at a spacing, or axially offset, from the driven shaft 32 and/or the gear system 34 and may communicate therewith, for example, via a belt drive. As a further alternative, the drive motor 36 is designed as a hydraulic machine 204 (c.f., FIG. 6), for example, as a Gerotor motor.

[0058] The eccentric screw pump 1 has an engagement unit 39 for adjusting the engagement between the rotor 4 and stator 2. According to this exemplary embodiment (FIG. 1), the engagement unit 39 is designed such that the stator 2 is axially displaceably mounted. The stator 2 is displaceable along the longitudinal axis L1, as indicated by the arrow 38. To this end, the stator 2 is received in portions of the inlet housing 14 and the outlet housing 20 which are sealed with a seal 40, 42. For the displacement of the stator 2, the engagement unit 39 has a contact portion 44, which may communicate with an engagement drive (not shown in FIG. 1) which is provided for this purpose.

[0059] FIGS. 2a, 2b, and 2c and 3a, 3b, and 3c illustrate the alteration to the engagement, i.e., also an adjustment of the constriction 7, with reference to a schematic illustration.

[0060] Whilst FIGS. 2a-2c show an engagement between the rotor 4 and stator 2, which corresponds to a working engagement and in which there is contact between the rotor 4 and stator 2, FIGS. 3a-3c illustrate an idle position with a widening so that a gap S is established. FIG. 2b shows a section along the longitudinal axis L1, as is also illustrated in FIG. 1. The rotor 4 is in a maximum upper position with respect to FIGS. 2a-2c, which can be seen, in particular, with reference to FIGS. 2a and 2c, which each show sections perpendicularly to the longitudinal axis L1. FIG. 2a shows a section near to the inlet 10 and FIG. 2c shows a section at the outlet 12. As can be seen in particular with reference to FIGS. 2a and 2c, the rotor 4 abuts against an inner wall 9 of the stator 2 with a portion of its circumferential surface 3. A sealing line D is formed in the constriction 7 as a result of the contact. The working engagement, which here is a working pre-tension between the rotor 4 and stator 2, ensures that the sealing line D is substantially continuous during operation. It is generally provided that the rotor 4 is positioned in the stator 2 in such a way that a pre-tension is produced in the radial direction. The stator 2 is formed from a flexible material, in particular, such as an elastomer. A pre-tension in the radial direction consequently results in an elastic deformation of the stator 4 in the region of the sealing line D, in particular, at points with a more punctiform contact or a smaller contact surface compared to points with a more planar contact.

[0061] As a result of an axial adjustment of the rotor 4, which is of conical design overall in this exemplary embodiment, it is possible to widen the constriction 7 and thus reduce a radial pre-tension from the working engagement or working pre-tension to the idle engagement or idle pre-tension or even to establish a gap S instead of a sealing line D. The reduction in the engagement is achieved by a displacement of the rotor 4 in the direction of the conical widening, i.e., to the left with reference to FIGS. 2a-3c. The constriction 7 is thus widened and the idle engagement (c.f., FIGS. 3a-3c) may be set.

[0062] The working position PA and the idle position PR of the rotor 4 relative to the stator 2 are shown in FIG. 2b and FIG. 3b, respectively. In this exemplary embodiment, the working position PA and the idle position PR are spaced apart by ¼ of the pitch of rotor 4 (the pitch is understood to be the distance between two crests or two roots in section). This distance is generally sufficient to ensure a reliable idle engagement. As can be easily seen from FIGS. 2a-2c, a high pressure prevails in particular at points at which the contour of the rotor runs counter to the contour of the stator (in FIG. 2b, in particular, at the points which are denoted by 7, D in the lower region). In the idle state of the eccentric screw pump, when the rotor 4 is not driven by the drive motor 36, a relaxation or, in the worst case, a creep of the material of the stator 2 may occur in particular at these points. This results in changes to the internal geometry of the stator 2, in particular, such as indentations in the material of the stator 2, which do not recede immediately after operation resumes. Although these indentations usually recede again during operation, this may take several minutes or hours. The start of the operation is particularly problematic, when the drive motor 36 not only has to overcome the breakaway torque due to the friction between the rotor 4 and stator 2, but the rotor 4 also has to move out of the depression(s) or indentation(s) which have formed. For this reason, the invention provides that the engagement, and therefore also the pre-tension between the rotor 4 and stator 2, is set to the idle engagement or idle pre-tension in the idle state and to the working engagement or working pre-tension in the working state, wherein the idle engagement or idle pre-tension is less than the working engagement or working pre-tension.

[0063] In this exemplary embodiment (FIGS. 2a-3c), the eccentricity e1, e2 is constant, whereas the diameter D1, D2 of the rotor 4 decreases in the direction of the outlet 12. This means that e1 and e2 are identical, whereas D1 is greater than D2. However, embodiments are also included, in which the diameter is constant, i.e., D1 is identical to D2, and the eccentricity changes, i.e., for example, e1 is greater than e2. This has a corresponding effect during the axial displacement. It is likewise possible that both the diameter and the eccentricity are altered over the length.

[0064] The engagement and therefore the pre-tension may also be adjusted in that the stator 2 is squeezed in the axial direction in order to thereby generate a radial widening of the stator 2. To this end, adjustment elements (not shown here) may be provided, for example, at axial end faces of the stator, which adjustment elements have a variable mutual spacing, wherein a mechanical coupling and/or connection is established between the adjustment elements and the stator so that, by altering the relative distance between the two adjustment elements, it is possible to change the cross section and the length of the elastomer part of the stator. The adjustment elements may be formed, for example, as circular pressure plates, which are connected to one another via tension rods. It is also possible to integrate electroactive polymers in the stator 2, which bring about a radial expansion of the stator 2 when a voltage is applied.

[0065] FIG. 4 shows an exemplary embodiment which is modified with respect to FIG. 1, wherein similar elements are denoted by the same reference signs. In this regard, please refer to the above description of the first exemplary embodiment (FIG. 1) in its entirety. With regard to the pre-tension between the rotor 4 and stator 2, please refer to FIGS. 2a-3c.

[0066] In contrast to the first exemplary embodiment, in this exemplary embodiment (FIG. 4), the engagement unit 39 is designed such that the rotor 4 is axially displaceable, specifically together with the complete drive train 25, which, according to this exemplary embodiment, consists of the drive shaft 26, the gear system 34, and the drive motor 36, even though all three of these elements are optional. In this regard, the arrow 37 indicates that the drive motor 36 is also displaced. To this end, the housing 46 of the gear system 34 is displaceably mounted in a portion 48 of the inlet housing 14 which is opposite the inlet 10 of the stator 2 and is sealed with respect to the surrounding environment by a seal 50. In the event that a gear system 34 is not present, the drive motor 36 may also be mounted directly on the portion 48 or by means of a motor mount.

[0067] For the purpose of displacing the rotor 4 in the axial direction, a separate engagement drive 52 is provided, which may displace the drive train 25 (or only the drive motor 36 in the event that a gear system 34 is not provided) for example via a spindle drive 54 (shown merely schematically) such that the engagement between the rotor 4 and stator 2 may be adjusted from the working engagement to the idle engagement and vice versa.

[0068] To this end, an electronic engagement control 53 is preferably connected to an electronic control device 58 of the eccentric screw pump 1 or the drive motor 36 via a signal line 56. The drive motor 36 is moreover connected to the electronic control device 58 via a signal line 60. The electronic control device 58 may be, for example, part of a control centre or receives via a receiving or input interface 200, via which control or regulating data are input or received, and is designed to execute the control or regulation depending on this control or regulating data. For example, a setpoint volume or a difference between a setpoint volume and an actual volume may be input into the electronic control device 58 via this input interface 200. In this case, the input interface 200 may be a user interface or an interface to a superordinate unit, for example a control centre. Additionally or alternatively, an input connection 202 may be provided for connecting a sensor, switch, and/or superordinate control unit. The electronic engagement control 53 receives a start signal from the electronic control unit or directly from a superordinate unit, which start signal has the effect of starting the drive motor 36 and controls the engagement device 52 automatically on the basis thereof, which then sets the engagement to the working engagement. The electronic engagement control 53 likewise receives a stop signal, which has the effect of stopping the drive motor 36 and controls the engagement drive 52 automatically on the basis thereof, which then sets the engagement to the idle engagement.

[0069] In other embodiments, the electronic control unit 58 and the engagement control 53 may also be integrated in one control.

[0070] FIG. 5 shows a further exemplary embodiment, which is essentially similar to the exemplary embodiment of FIG. 4. Identical and similar elements are in turn denoted by the same reference signs, so please refer to the above description in its entirety. It should be understood that the electronic control unit 58 described with reference to FIG. 4 is likewise provided in the eccentric screw pump 1 according to FIG. 5.

[0071] According to this exemplary embodiment (FIG. 5), the rotor 4 is in turn arranged to be displaceable with respect to the stationary stator 2. However, in this exemplary embodiment, the drive motor 36 is likewise stationary and non-displaceable. Overall, the drive shaft 26 is in turn coupled to the driven shaft 32 of the drive motor 36 via a Cardan joint 30. To enable a displacement of the rotor 4 and drive shaft 26, the driven shaft 32 is axially displaceably mounted in the gear system 34, in particular, in a driven gear 68 of the gear system 34. The driven gear 68 is coupled to the driven shaft 32 by an axially displaceable shaft-hub connection. The gear system 34 is therefore equipped with a gear 68 which is designed as a hollow shaft and in which the driven shaft 32 may be displaced. Alternatively, the driven gear 68 may also be displaceable in the gear system 34 and rigidly connected to the driven shaft 32. The driven shaft 32 is in turn guided through a seal 70 so that liquid cannot penetrate into the gear system 34 from the drive inlet housing 14. A drive 52 (c.f., FIG. 4) may in turn be arranged on an outwardly lying portion 72 of the driven shaft 32 in order to enable the axial displacement of the driven shaft 32 and therefore the rotor 4.

[0072] A further embodiment of the invention, which is based on the previous embodiments, is shown in FIG. 6. Identical and similar elements are denoted by the same reference signs as those in the previous exemplary embodiments, so, in this regard, please refer to the above description in its entirety.

[0073] In FIGS. 6 and 7, the eccentric screw pump 1 is firstly not designed as a stationary pump, but is part of an agricultural trailer, which supports a slurry tanker 206. The slurry tanker 206 is connected to the inlet pipe 18. The outlet pipe 24 is connected to a spreader 208 and a dribble bar linkage 210. A particularly preferred embodiment is thus formed, which may also be implemented with the other embodiments of eccentric screw pumps 1 disclosed herein. An eccentric screw pump is particularly suitable for delivering slurry, since slurry contains solid substances and is therefore not easily pumpable.

[0074] A further difference from the previous exemplary embodiments is that the drive motor 36 here is designed as a hydraulic machine 204. The hydraulic machine 204 may be connected to a hydraulic source (not shown, see FIGS. 8 and 9 for this) of the agricultural trailer via a supply line and a return line (not shown) and thus supplied with hydraulic medium under pressure.

[0075] In one example, the hydraulic machine 204, like the drive motor 36 according to the exemplary embodiment of FIG. 4, may be displaceably mounted on the pump housing 14 and axially displaced via a drive 52 in order to bring the rotor 4 into the working position PA (FIG. 6) and the idle position PR (FIG. 7) in order to thereby be able to set the working engagement or working pre-tension and the idle engagement or idle pre-tension. The engagement drive 52 is then in turn connected to the electronic engagement control 53 (not shown in FIGS. 6, 7). The hydraulic machine 204 may be driven solely via the supplied pressure so that the electronic control device 58 does not actuate the hydraulic machine 203 directly, but rather a hydraulic pump (not shown here) for supplying a hydraulic pressure.

[0076] In FIGS. 6 and 7, a hydraulic driven shaft 212 is displaceably mounted in the hydraulic machine 204. The hydraulic driven shaft 212 is then in turn connected to the drive shaft 26 via the second Cardan joint 30. The hydraulic driven shaft 212 is accordingly displaceably mounted in a hollow shaft of the hydraulic machine.

[0077] FIGS. 8 and 9 show two variants, in which the drive motor is designed as a hydraulic machine 204 and the engagement unit 39 is of purely hydraulic design. An engagement unit 39 of hydraulic design may be advantageously used in the embodiment described with reference to FIGS. 6 and 7.

[0078] A hydraulic pump 220 forms a hydraulic pressure source here. This is connected to a first hydraulic line 226 and a second hydraulic line 228 via a directional valve 224 and supplies these lines with hydraulic pressure. The first hydraulic line 226 leads to the hydraulic machine 204, which, in the exemplary embodiment shown here, is firstly connected to a gear system 34. The gear system 34, as described with reference to FIG. 5, is equipped with a hollow shaft through which the driven shaft 32 extends in an axially displaceable manner. As soon as the directional valve 224 switches, hydraulic medium is delivered and the hydraulic machine 204 drives the driven shaft 32.

[0079] The engagement unit 39 comprises the second hydraulic line 228 and a hydraulic drive 230, which forms the engagement drive 52. The hydraulic drive 230 is a hydraulic lifting cylinder 232 here, having a cylinder chamber 234 and a piston 236, which is, in turn, connected to the driven shaft 32, preferably with an interconnected axial bearing, and may displace the driven shaft 32 axially. On the side opposite the cylinder chamber 234, a restoring spring 238 is provided, which loads the piston 236 to the left with reference to FIG. 8. The restoring spring 238 serves accordingly to set the engagement to the idle engagement, and the engagement may be set to the working engagement via the pressure in the cylinder chamber 234.

[0080] In the second hydraulic line 228, a throttle 240 is provided, which serves to reduce the volume flow somewhat in order to achieve the desired movement speed and therefore gain time for the movement from the idle position into the working position and vice versa.

[0081] In this embodiment, the engagement is always automatically set to the working engagement and the idle engagement. As soon as the directional valve 224 switches, hydraulic pressure is supplied to the hydraulic machine 204, which consequently drives the rotor 4, but also to the hydraulic drive 230, which then sets the engagement to the working engagement. If the directional valve 224 is switched such that the hydraulic machine is stationary, the return spring 238 ensures that the engagement is set to the idle engagement.

[0082] FIG. 9 shows a similar variant to that in FIG. 8 and identical and similar elements are denoted by the same reference signs. In this regard, please refer to the above description in its entirety.

[0083] In contrast to FIG. 8, a hydraulic machine 204, arranged in a fixed manner on the inlet housing 14, is not provided in FIG. 9, but rather the hydraulic machine 204, along the lines of the exemplary embodiment according to FIG. 4, is itself displaceably arranged in the inlet housing 14. The hydraulic drive 230 of the engagement unit 39 acts directly on the hydraulic machine 204 here in order to displace this and thereby set the engagement.

[0084] The rotor 4 is also displaceable in the exemplary embodiment according to FIG. 10, whereas the stator 2 is received in a stationary manner in the inlet housing 14 and the outlet housing 20. According to this exemplary embodiment, the drive shaft 26 is designed in two parts and has a first shaft part 74 and a second shaft part 76. The two shaft parts 74, 76 are pushed telescopically one inside the other and an expansion element 80 is formed between the two shaft parts 74, 76, in a recess 78 in the first shaft part 74. The expansion element 80 serves to enable the axial length of the drive shaft 26 to be changed via a displacement of the second shaft part 76 with respect to the first shaft part 74. A displacement of the rotor 4 is enabled via the expansion of the expansion element 80 or a reduction in the expansion element 80. For example, the expansion element 80 may comprise a spindle, a piston, a movable magnetic core, electroactive polymers, or the like, which enable a movement as a result of an actuating procedure. An electrical connection may be realized via the driven shaft 32 or implemented inductively and/or via radio. A sliding contact may also be considered.

[0085] Finally, FIG. 11 shows an exemplary embodiment of the eccentric screw pump 1, which in turn enables a displacement of the rotor 4 with respect to the stator 2. In this exemplary embodiment, the drive shaft 26 is again formed in one part, as in the first four exemplary embodiments of FIGS. 1, 4, 5, and 6. The drive shaft 26 is connected to the driven shaft 32 by means of a Cardan joint 30.

[0086] In the exemplary embodiment according to FIG. 11, the shaft journal 82, which connects the Cardan joint 28 to the rotor 4, is formed in two parts and has a first part 84, which is rigidly connected to the rotor 4, and a second part 86, which is connected to the Cardan joint 28. The parts 84 and 86 are pushed telescopically one inside the other and an expansion element 80, corresponding to the expansion element 80 according to FIG. 10, is formed in the part 84. Alternatively, it may also be provided that a drive acts on the end face 88 of the rotor 4, which drive displaces the rotor 4 axially.

[0087] Although the electronic control device 58 and the engagement control 53 are only shown by way of example in the exemplary embodiment according to FIG. 4, it should be understood that they may also be present in the other exemplary embodiments. Likewise, each exemplary embodiment may be equipped with a hydraulic engagement unit 39 as shown in FIGS. 8 and 9, even if the drive motor 36 is not designed as a hydraulic machine 204.

[0088] The relationship between the working state, the idle state, the working engagement FB and the idle engagement F0 is now described with reference to a graph shown in FIG. 12. The engagement F is plotted against time t in the top graph, the speed n of the rotor 4 is plotted against time tin the bottom graph.

[0089] At the start, approximately at the origin of the coordinate systems, the speed n=n0=0 and the engagement F is set to the idle engagement F0. The fact that the value F0 is not on the x-coordinate here shall not necessarily mean that the idle engagement or idle pre-tension is positive; rather, the rotor 4 and stator 2 may not be touching one another, or may be only marginally touching one another, so that the stator 2 is completely or substantially without tension. In any case, the idle engagement or idle pre-tension F0 should be selected such that a relaxation and creep of the material of the stator 2 do not occur at contact points of the stator 2, or a sufficiently large gap is established if the stator is a solid stator.

[0090] At a time tn1, a start signal is output, for example via the output interface 200. In response to this, the electronic control device 58 actuates the drive motor 36 and this drives the rotor 4, which begins to rotate. The speed n of the rotor 4 increases to the setpoint speed nN, which is reached at the time tn2. The working state (with respect to the speed) is also reached here. The time period between tn1 and tn2 may be described as the run-in time period, ramp-up time period, or start-up time period. In the exemplary embodiment shown in FIG. 12, the engagement F is increased from the idle engagement F0 to the working engagement FB partly within the run-in time period. This is carried out automatically by the engagement unit 39, likewise in response to the start signal. A time interval is provided between the time tn1 and a time tF1 at which the engagement unit 39 begins to increase the engagement F, for example, via an axial adjustment of the rotor 4. This is not compulsory; it may likewise be provided that the times tn1 and tF1 coincide, or tF1 is before tn1. The latter case is particularly preferred if the rotor 4 lies against the stator 2 and a certain relaxation at the contact points occurs due to the weight force of the rotor 4 on the stator 2. In this case, it is preferred, for example, to firstly displace the rotor 4 a short distance axially before the rotation of the rotor 4 is started. The time tF1 is preferably after the time tn2, preferably offset by a predetermined wait time of, for example, 1, 2, 3, 5 or 10 seconds. It can furthermore be seen from FIG. 12 that the gradient of the engagement is less than the gradient of the speed. This is also not a requirement and these gradients may be adapted and selected according to the type of operation, the pump fluid, the material and the material pairing.

[0091] After the eccentric screw pump 1 has been operating with the working engagement FB in the working state from the time tF2, a stop signal is output at the time tn3, for example, in turn via the input interface 200. However, this may also be an automatically generated stop signal, for example, based on the time difference between tn2 and tn3 or based on a sensor signal. From that time, the speed n of the rotor 4 is reduced again by the electronic control device 58 and drops here with the same gradient as that with which it had also increased. This is also not compulsory and the gradients may differ. In particular, it is often preferred if the standstill is reached as quickly as possible. After the speed n has almost reached the value 0 again, the engagement unit 39 reduces the engagement F from the working engagement FB to the idle engagement F0. The idle engagement F0 is then achieved at the time tF4, which is after the time tn4. The time period between tn3 and tn4 may be described as the run-down time period. In the exemplary embodiment shown here, the change in the engagement F from the working engagement FB to the idle engagement F0 is therefore realized partly within the run-down time period. The periods may also overlap entirely; tF3 may coincide with tn3 and tF4 may coincide with tn4. The time tF3 may also be before the time tn3 or after the time tn4. It is also conceivable and preferred if the time tF4 is before or after the time tn3 and/or before or after the time tn4.

[0092] A latency may also be provided between tn3 and tF3 if a start signal is received again shortly after the stop signal is output (at tn3). This latency may be specified according to the particular application and may amount to several seconds or minutes.