METHOD FOR CONTROLLING AN ECCENTRIC SCREW PUMP WITH WORKING AND RESTING POSITION

Description

[0001] The disclosure relates to a progressive cavity pump for conveying liquids loaded with solids, comprising a helically wound rotor, a stator with an inlet and an outlet in which the rotor is rotatably arranged about a longitudinal axis of the stator, and which has a helically shaped inner wall corresponding to the rotor, wherein the rotor and stator are arranged and configured relative to each other such that at least one chamber is formed which serves for conveying the liquid, and the chamber is separated by a sealing line. The progressive cavity pump has a drive motor for rotating the rotor and a control device for controlling the drive motor at least in an operating state in which the rotor is rotating and in a rest state in which the rotor does not rotate. The invention relates to a method for controlling a progressive cavity pump.

[0002] Progressive cavity pumps of the type mentioned above have been known for several years and are used in particular for the gentle conveying and metering of liquids containing solids, abrasive liquids, or generally liquids with high viscosity. They utilize a single- or multi-start helical rotor, which is arranged in and rotates within a corresponding two- or multi-start chamber of a stator. The appropriate design of the rotor's outer profile and the stator's inner profile creates a constriction, in particular a sealing line, which seals at least one chamber, but preferably individual chambers of a plurality of chambers, against each other. The rotor and stator can be in direct contact with each other, forming a sealing line, or they can have a sealing gap separating the chambers within the constriction.Typically, the rotor is designed as a single-start worm and the stator as a double-start worm with a double pitch, which results in the sealing of the individual chambers.

[0003] A screw pump is known from DE2632716, which has a conical screw and a conical pressure jacket. In this embodiment, the screw has a taper of approximately 30°, which is intended to increase the delivery pressure over a short screw length. The screw and pressure jacket are axially adjustable relative to each other by means of a sleeve in which the pressure jacket is axially movable. This is intended to maintain a constant pressure by displacing the pressure jacket under the influence of the fluid pressure on an annular portion of the pressure jacket within the pump. A disadvantage of this known system is that it is solely designed to maintain the constant increased pressure generated by the reduction in cross-sectional area in the delivery direction of the conical pump gap and does not allow for axial displacement depending on other influencing factors.

[0004] A screw pump with a conical stator and rotor is also known from AT223042. In this screw pump, the rotor can be axially adjusted relative to the stator by means of a screw sleeve inserted between the rotor and the output shaft. With the pump stationary, a user manually rotates the sleeve through a handhole using a tool. This compensates for both jamming and excessive play between the stator and rotor caused by stator swelling or wear of the rotor and / or stator.

[0005] US Patent 2,527,673 A relates to a progressive cavity pump with a rotor and a stator, which is particularly suitable for pumping small quantities of liquid, e.g., water. In one embodiment of the pump, the rotor is automatically disengaged from the stator when the pump stops operating. This is intended to prevent overloading during start-up. A spring is provided to ensure that when the pump comes to a standstill and the discharge pressure decreases, the rotor is moved to a position where it no longer has direct contact with the stator.

[0006] From DE102015112248A1, an eccentric screw pump is known in which the gap geometry between the rotor and stator can be changed by adjusting the stator preload. An increased preload causes compression of the stator, which is designed as an elastomer component, and can thereby reduce the gap geometry. However, a disadvantage of this eccentric screw pump is that the elastomer thicknesses of the stator vary both circumferentially and longitudinally due to its geometry, and therefore an increased preload leads to uneven elastic deformation. Reliable operation of the eccentric screw pump is therefore not guaranteed, and the uneven gap geometry can cause locally increased wear with this type of adjustment.

[0007] A similar progressive cavity pump is known from DE 10 2014 112 552 A1. This progressive cavity pump has at least one stator made of an elastic material and a rotor rotatable within the stator. The stator is at least partially surrounded by a stator shell, which is a longitudinally split shell consisting of at least two shell segments and forms a stator clamping device with which the stator can be clamped radially against the rotor. The stator clamping device has one or more movable actuating elements that adjust and clamp the stator onto the shell segments. This pump is characterized by the fact that the stator clamping device has one or more actuators that are connected to or equipped with actuating elements for automated positioning of the stator.

[0008] Conical progressive cavity pumps are also known, as these allow for both simple assembly and adjustment of the rotor relative to the stator in case of wear. Such a progressive cavity pump is known, for example, from WO 2010 / 100134 A2. This document proposes, in order to prevent or compensate for wear, a progressive cavity pump with a conical rotor designed such that all individual chambers have the same volume. If wear phenomena, particularly cavitation, occur during operation, it is possible to axially shift the rotor relative to the stator so that the chamber volumes are equal again and a tight seal is achieved.

[0009] Another adjustment method is disclosed in DE102014117483A1. An adjustable pump unit for a positive displacement pump, in particular for a progressive cavity pump or a rotary lobe pump, is intended to be adaptable to a wide variety of operating conditions and pumping tasks. For this purpose, the pump unit is at least partially made of an electrically and / or temperature-active material and / or coupled or equipped with at least one electrically and / or temperature-active element for its adjustment.Preferably, parameters of the positive displacement pump are set by means of a control device and an electro- and / or temperature-active pump unit coupled to it, and preferably the elastomer body or the elastomer lining is at least partially formed from an electroactive material and / or coupled or equipped with at least one electroactive means, and the elastomer body or the lining and / or the at least one electroactive means can be replaced as sensors, wherein its.

[0010] Measurement signals for measurement acquisition and / or processing are transmitted to a control device of the positive displacement pump.

[0011] Furthermore, WO2018130718A1, the applicant's patent, discloses a progressive cavity pump that allows axial adjustment of the rotor. This patent reveals various structural possibilities for enabling axial adjustment of the rotor and stator relative to each other. Moreover, this patent demonstrates the advantage of temporarily widening the sealing gap between the rotor and stator during operation to allow a controlled leakage flow. This reduces friction between the rotor and stator, thereby minimizing wear. The leakage flow can also be advantageously used for cooling. For example, this makes it possible to set a larger gap during start-up of the progressive cavity pump to minimize friction in dry conditions.It is also possible to operate the progressive cavity pump in an energy-saving manner by adjusting it to the optimal overall efficiency, taking into account the volumetric efficiency and friction losses. However, only a slight increase in the constriction is recommended for shear-sensitive media.

[0012] Even though this progressive cavity pump has already proven its worth, there is still a need to further improve progressive cavity pumps and adapt them to specific fields of application.

[0013] The invention solves the problem in an eccentric screw pump of the type mentioned at the outset by a method according to independent claim 1 for controlling an eccentric screw pump with a feed unit which is configured to set a feed between rotor and stator to a rest feed in the rest state and to a working feed in the working state, wherein the rest feed is less than the working feed.

[0014] The invention is based on the understanding that in a progressive cavity pump that remains stationary for extended periods, such as several hours, days, or even weeks, relaxation of the elastomer material of the stator can occur at the contact points between the rotor and the stator, sometimes even resulting in creep. In progressive cavity pumps with an elastomer stator, a preload is applied between the rotor and stator to ensure sufficient sealing and corresponding pumping performance during operation, where considerable back pressures can occur. The stator is typically made of a flexible material that can yield, particularly under continuous load.This causes indentations to form on the stator at the contact points between the rotor and stator when the pump is at rest, which can have a detrimental effect during operation of the progressive cavity pump, especially during start-up. When starting a progressive cavity pump that has been stationary for an extended period, it must overcome not only the typical starting torque caused by friction, but also the ridge at the edges of the indentation in the stator material formed by the prolonged contact. This is particularly disadvantageous when motors with limited torque are used as the drive motor.The invention therefore proposes reducing the preload between the rotor and stator at rest by changing the feed rate from the working feed rate to the rest feed rate, and similarly from a working preload to a rest feed rate, and then increasing it back to a working preload in the operating state. This significantly reduces or completely eliminates the problem of relaxation in elastomeric stators at rest. Furthermore, it offers advantages during the normal start-up of the progressive cavity pump. If the preload has already been reduced from the working preload (working feed rate) to the rest feed rate by changing the feed rate, the progressive cavity pump can be started with the rest feed rate. After one or more revolutions, particularly when initial fluid is being pumped, the preload can be increased back to the working preload by changing the feed rate.In this way, starting the progressive cavity pump is also simplified and possible with low torque. Crucially, in the present invention, and unlike the proposal in WO 2018 / 130718 A1, the gap between the rotor and stator is reduced in the resting state. In particular, after the progressive cavity pump has finished operating, the gap is reduced from the operating gap to the resting gap.

[0015] According to the invention wird Delivery is automatically set to standby delivery in idle mode and automatically set to work delivery in working mode.

[0016] In other embodiments, the stator can also be designed as a solid stator and preferably made of a metallic material, but these are not covered by the wording of the independent claim. In such a case, no preload is applied between the rotor and stator during operation; instead, a sealing line that is as complete or continuous as possible is established. During operation, the rotor and stator heat up, which can lead to expansion. Since the rotor and stator are generally made of different materials, their thermal expansion can differ. With close contact between the rotor and stator and a largely complete sealing line, stresses can occur during cooling after operation, which can result in deformation of the components, even leading to the rotor seizing in the stator.By reducing the contact between rotor and stator in the rest state and setting it to a rest position according to the invention proposed here, the close contact is broken and a gap is set between rotor and stator, so that the described problem of deformation and seizing cannot occur.

[0017] The resting preload is lower than the operating preload. Preferably, the resting preload is reduced by 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100% compared to the operating preload. In a preferred embodiment, the resting preload is set such that the contact between the rotor and stator is largely stress-free. (Largely) stress-free is understood to mean a state in which the rotor is in contact with the stator only due to its weight, and no preload exists between the rotor and stator due to the feed rate.

[0018] Preferably, no complete sealing line is formed during the rest position. In contrast, a complete sealing line between the rotor and stator is preferably formed during the operating position. During the rest position, the progressive cavity pump does not form a completely tight seal, and fluid can flow from the inlet to the outlet or vice versa through the progressive cavity pump.

[0019] The control unit, preferably an electronic control unit, is preferably part of the progressive cavity pump, but need not necessarily be integrated into a housing with it. An external control unit can also be provided, which, for example, is part of or connected to a control station. The progressive cavity pump preferably has a housing to which, or in which, a control box containing the electronic control unit is attached.

[0020] The feed unit is designed according to the invention to adjust the feed between rotor and stator to the rest position in the rest position and to the working position in the operating position. According to the invention, this is done automatically. Die The delivery unit is designed to receive a stop signal for the progressive cavity pump and, in response to receiving the stop signal, to reduce the delivery speed from the operating speed to the idle speed. It is also designed to receive a start signal for the progressive cavity pump and, in response to receiving the start signal, to increase the delivery speed from the idle speed to the operating speed.

[0021] In one variant, the electronic control unit is designed to control both the drive motor and the preload. In this case, the electronic control unit can include the delivery unit, which can, for example, be implemented as a software module.

[0022] The delivery unit can also include an electronic delivery control unit and preferably a delivery drive, which is controlled by the electronic delivery control unit to change the delivery direction. In such an embodiment, the control unit for controlling the drive motor and the delivery control unit do not have to be located in the same place. It is also conceivable that, in a simple embodiment, the control device for the drive motor is formed by permanently wired switches.

[0023] According to the invention ist However, it is designed so that the delivery unit automatically reduces the delivery speed from the working position to the resting position when the drive motor switches from the working state to the resting state. For example, if an operator presses a start button on the progressive cavity pump, the electronic control unit controls the drive motor so that it switches from the resting state to the working state and the rotor rotates. Simultaneously and automatically, the delivery speed is increased. die The delivery unit switches the delivery from the rest position to the working position. If an operator then activates a switch to stop the progressive cavity pump, or if this is triggered by a higher-level control unit, the electronic control unit controls the drive motor in such a way that the rotor rotation is stopped and the drive motor switches from the working state to the rest position. Simultaneously, the delivery unit automatically controls the delivery so that it is reduced from the working position to the rest position.

[0024] The feed unit is designed to adjust the feed rate from the working feed rate to the rest feed rate within or after a settling-down period. This settling-down period encompasses the transition from the working state to the rest state. For example, the settling-down period is defined from the point at which a stop signal is received until the rotor comes to a complete standstill. Typically, it takes several to a few rotor revolutions from receiving a stop signal until the rotor comes to a complete standstill. Preferably, the feed rate is reduced from the working feed rate to the rest feed rate within this settling-down period.According to the invention, the feed unit is designed to adjust the feed from the working position to the resting position when the rotor has come to a complete standstill, particularly immediately thereafter, or after a first predetermined rest period following complete standstill. For example, the feed from the working position to the resting position can be adjusted within 1, 2, 3, 4, 5, 10, 15, 20, 30, or 60 seconds, or within 1, 2, 3, 5, 10, 20, or 30 minutes. It may be advantageous not to adjust the feed from the working position to the resting position immediately after the rotation has ceased and complete standstill has been reached, since it is possible that the progressive cavity pump will restart shortly thereafter and the rotor will begin rotating again.To avoid reducing the delivery rate every time a pumping process is briefly interrupted, a predetermined initial rest period can be implemented. This period must elapse before the delivery rate is reduced from the operating rate to the rest rate. This is particularly useful if the pump is designed for a higher operating pressure.

[0025] Conversely, the feed unit is designed to adjust the feed rate from the idle position to the working position within or after a start-up period. The start-up period encompasses the transition from the idle state to the working state. If the progressive cavity pump is in the idle state and the feed rate is reduced from the working position to the idle position, and the pump is then started so that the rotor is to rotate, the feed rate is also increased from the idle position to the working position. The start-up period can be defined as a time range beginning with the receipt of a start signal until a target speed is reached. Preferably, the feed rate is also increased from the idle position to the working position within this start-up period.It is also possible to increase the feed rate from the resting preload to the working feed rate only when the target speed has been reached, or to additionally wait a period of time, for example 1, 2, 3, 5, or 10 seconds after reaching the target speed before increasing the feed rate to the working feed rate.

[0026] The electronic delivery control system can receive a start signal from a higher-level control center and send a release signal to the control center when the delivery system is in standby mode. Alternatively, the start and stop signals can simply be passed through, and the electronic delivery control system can receive them independently of the control center or the electronic control unit for the drive motor, automatically adjusting the delivery system according to the operating status.

[0027] In another alternative, the feed unit is hydraulically operated. This is particularly preferred if the drive motor is also hydraulically operated. For example, in this case, the feed unit comprises a hydraulic path through which a hydraulic fluid can be received, as well as a hydraulic drive coupled to the rotor and / or stator for adjusting the feed rate.

[0028] In a preferred embodiment, the rotor is tapered and preferably has a conical shape. Alternatively, the rotor can also have varying eccentricities. Preferably, the rotor tapers towards the outlet. It is also preferred that the eccentricities decrease or increase towards the outlet. The reverse configuration is also possible, in which the rotor tapers towards the inlet and the eccentricities increase or decrease towards the inlet.

[0029] In both variants, the feed rate can be adjusted by axially shifting the rotor and stator relative to each other. For example, if the rotor and stator are conical, the rotor can be shifted towards the tapered end of the stator to increase the feed rate. Similarly, the stator can be shifted towards the widening end of the rotor to increase the feed rate. Of course, it is also possible to shift both the rotor and stator. However, shifting the rotor can offer certain structural advantages. For instance, when shifting the stator, it is essential to ensure that the stator remains sealed to adjacent housing components. Adjusting the rotor can be easily achieved, for example, using the methods described in WO 2018 / 130718. These methods can also be combined.

[0030] In a further preferred embodiment, the stator is radially adjustable to set the feed rate between the working and rest positions. This embodiment is based on the idea that the feed rate between the rotor and stator can also be set or increased by radially compressing the stator. For this purpose, the stator may comprise a support element and an elastomeric part, wherein the support element fully encloses the elastomeric part, at least partially. The support element is preferably made of a metal and radially supports the elastomeric part. To further influence the radial feed rate, the stator may also be provided with two adjusting elements, for example, at the axial end faces of the stator, which are variable in distance from each other.A mechanical coupling and / or connection is preferably provided between the adjusting elements and the stator, such that the cross-section and length of the stator's elastomeric portion can be altered by changing the relative distance between the two adjusting elements. For example, when the two adjusting elements are moved towards each other, the elastomeric portion is axially compressed, resulting in radial expansion of the elastomeric portion both radially outwards and radially inwards. Since the support element is located radially outwards, the axial compression of the elastomeric portion only causes a radially inwards expansion of the elastomeric portion, thus increasing the preload between the rotor and stator. Conversely, the preload can be reduced again by positioning the adjusting elements further apart.Preferably, the axial length of the elastomer part is selected such that the rest preload is set without compression of the elastomer part or with the adjusting elements in a neutral position.

[0031] The invention solves the aforementioned problem by means of a method of the aforementioned und The method, as defined in independent claim 1, is for controlling a progressing cavity pump according to one of the preferred embodiments of a progressing cavity pump described above. The method comprises the steps of: operating the progressing cavity pump in a working state, comprising rotating a rotor in a stator of the progressing cavity pump with a working position between the rotor and stator; issuing a stop signal and, in response to the stop signal, terminating the rotating drive and switching to a rest state of the progressing cavity pump; and reducing the position between the rotor and stator from the working position to a rest position.

[0032] It should be understood that the progressive cavity pump and the method according to the invention have the same and similar sub-aspects, as set out in particular in the dependent claims. Therefore, for preferred features of the method and their advantages, reference is made in full to the above description.

[0033] The stop signal can be provided, for example, by an operator of the progressing cavity pump, a higher-level control unit, a program component of the progressing cavity pump's electronic control unit, or similar. An operator can, for instance, issue the stop signal via a button or remote control, which is then received by the progressing cavity pump's electronic control unit and / or its drive motor. Alternatively, a higher-level control system, such as a plant control system, a control room, or the control system of a vehicle to which the progressing cavity pump is attached, can issue the stop signal. It is also possible that the progressing cavity pump's electronic control unit itself contains an operating schedule that initiates the pump's operation according to predetermined criteria, such as a time schedule.A stop signal can also be issued, for example, by a sensor of the progressive cavity pump or an upstream or downstream unit.

[0034] The steps of stopping the rotary drive and reducing the feed rate can be performed simultaneously or partially or completely sequentially. They preferably follow immediately after and in response to the output of the stop signal.

[0035] According to the invention, the progressive cavity pump remains in a position corresponding to its resting position until it is next started. This means that the progressive cavity pump is always stored in its resting position when switched off. This achieves the advantages mentioned above and, in particular, prevents relaxation due to a pre-tensioned contact between the rotor and stator.

[0036] To reduce the feed rate from the working feed rate to the rest feed rate, an axial position between the rotor and stator is changed, and in particular the rotor and / or stator is moved from a working position to a rest position, the working position and the rest position are spaced at least 1 / 50, 1 / 40, 1 / 30, 1 / 10, 1 / 5, or 1 / 4 of the rotor pitch. It is preferred that the rest feed rate is lower than the working feed rate. Preferably, the rest feed rate is reduced by 10, 20, 30, 40, 50, 60, 70, 80, 90, or 100% compared to the working feed rate.

[0037] According to the invention, the method comprises the weiteren Steps: Outputting a start signal and, in response to the start signal: initiating the rotational drive of the rotor and switching from the rest state to the operating state of the progressive cavity pump. According to the invention, the method, in response to the start signal, comprises: increasing the feed rate between the rotor and stator from the rest position to the operating position. Again, the steps of initiating the rotational drive and increasing the feed rate can be executed simultaneously, or partially or completely sequentially.

[0038] Embodiments of the invention are now described below with reference to the drawings. These drawings are not necessarily intended to represent the embodiments to scale; rather, where this serves for clarification, the drawings are presented in a schematic and / or slightly distorted form. With regard to additions to the teachings directly apparent from the drawings, reference is made to the relevant prior art. It should be noted that numerous modifications and changes concerning the form and detail of an embodiment can be made without deviating from the general idea of ​​the invention. The general idea of ​​the invention is not limited to the exact form or detail of the preferred embodiments shown and described below, nor is it limited to an object that would be restricted compared to the object claimed in the claims.For the sake of simplicity, identical or similar parts, or parts with identical or similar functions, are referred to below using the same reference numerals. Further advantages, features, and details of the invention will become apparent from the following description of the preferred embodiments and from the drawings; these are shown in: . Fig. 1 a schematic cross-section through an eccentric screw pump according to a first embodiment; Fig. 2a a schematic cross-section through an eccentric screw pump perpendicular to the longitudinal axis with the working position set; Fig. 2b a schematic cross-section along the longitudinal axis according to Figur 2a ; Fig. 2c a schematic cross-section perpendicular to the longitudinal axis according to Figur 2a ; Fig. 3a a schematic cross-section through an eccentric screw pump perpendicular to the longitudinal axis with the rest position set; Fig. 3b a schematic cross-section along the longitudinal axis according to Figur 3a ; Fig. 3c a schematic cross-section perpendicular to the longitudinal axis according to Figur 3a ; Fig. 4 a schematic cross-section through an eccentric screw pump according to a second embodiment; Fig. 5 a schematic cross-section through an eccentric screw pump according to a third embodiment; Fig. 6 a schematic cross-section through an eccentric screw pump according to a fourth embodiment with working feed; Fig. 7 a schematic cross-section through an eccentric screw pump according to the fourth embodiment with rest position; Fig. 8 a schematic cross-section through an eccentric screw pump according to a fifth embodiment; Fig. 9 a schematic cross-section through an eccentric screw pump according to a sixth embodiment; Fig. 10 a schematic cross-section through an eccentric screw pump according to a seventh embodiment; Fig. 11 a schematic cross-section through an eccentric screw pump according to an eighth embodiment; and in Fig. 12 a diagram.

[0039] An eccentric screw pump 1 comprises a stator 2 and a rotor 4. The stator has a central axis L1 that 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 elastomeric material. The inner contour of the wall 8 is shaped to define a double-start helix. The rotor 4 is also helical overall, with the pitch of the helix of the stator 2 having twice the pitch of the rotor 4. This creates individual chambers 5, which are separated by a constriction 7.

[0040] The stator 2 further comprises an inlet 10 and an outlet 12. The inlet 10 is connected to an inlet housing 14, which has an inlet flange 16 to which an inlet pipe 18 is flanged. The outlet 12 is further equipped with an outlet housing 20, which has an outlet flange 22 to which an outlet pipe 24 is flanged.

[0041] In the Fig. 1 The embodiment shown is a stationary progressive cavity pump, which is particularly well installed in a system. The inlet pipe 18 can connect to another pipeline, for example a wastewater pipeline, and the outlet pipe can connect to another pipeline or a collection tank.

[0042] A drive shaft 26 extends through the inlet housing 14 and is connected to the rotor 4 via a first universal joint 28 and to an output shaft 32 of a gearbox 34 via a second universal joint 30. Instead of such a drive shaft 26 with two universal joints 28, 30, it is equally preferred to use a thin flexible shaft, which allows for eccentric drive. The gearbox 34 is connected on the input side to a drive motor 36, which, according to this embodiment, is designed as an electric motor. However, the drive motor 36 can also be connected directly to the output shaft 32 without an intermediate gearbox 34. The drive motor 36 can also be arranged remotely or axially offset from the output shaft 32 and / or the gearbox 34 and be connected to it, for example, via a belt drive. Alternatively, the drive motor 36 can be a hydraulic machine 204 (see [reference]). Fig. 6 ) trained, for example as a gerotor motor.

[0043] The eccentric screw pump 1 has a feed unit 39 for adjusting the feed between rotor 4 and stator 2. According to this embodiment ( Fig. 1 The feed unit 39 is designed such that the stator 2 is mounted for axial displacement. The stator 2 is displaceable along the longitudinal axis L1, as indicated by arrow 38. For this purpose, the stator 2 is received in sections of the inlet housing 14 and the outlet housing 20, which are sealed with a seal 40, 42. To displace the stator 2, the feed unit 39 has an engagement section 44, which is connected to a feed drive provided for this purpose (in Fig. 1 (not shown) may be related.

[0044] The Fig. 2a, 2b und 2c Figures 3a, 3b and 3c illustrate the change in delivery, that is also a change in the narrowing 7, using a schematic representation.

[0045] While the Fig. 2a - 2c The diagram illustrates a positioning between rotor 4 and stator 2 that corresponds to a working position and in which contact exists between rotor 4 and stator 2. Fig. 3a - 3c a rest position with an extension, so that a gap S is set. Fig. 2b shows a section along the longitudinal axis L1, as also in Fig. 1 The rotor 4 is shown in its maximum upper position relative to the Fig. 2a - 2c , which is particularly evident from the Fig. 2a und 2c This can be seen as showing sections perpendicular to the longitudinal axis L1. Fig. 2a shows a cut close to entrance 10 and Fig. 2c a cut at outlet 12. As can be seen in particular from the Fig. 2a und 2c As can be seen, a section of the rotor 4's circumferential surface 3 rests against an inner wall 9 of the stator 2. This contact forms a sealing line D in the constriction 7. The working feed, which in this case is a working preload between rotor 4 and stator 2, ensures that the sealing line D is essentially continuous during operation. Typically, the rotor 4 is positioned axially within the stator 2 such that a preload in the radial direction results. The stator 2 is made of a flexible material, such as an elastomer. A preload in the radial direction consequently leads to elastic deformation of the stator 4 in the region of the sealing line D, particularly at points of contact or with a smaller contact area compared to areas with more extensive contact.

[0046] By axially adjusting the rotor 4, which in this embodiment is conically shaped, it is possible to widen the constriction 7 and thus reduce the radial preload from the working position or working preload to the rest position or rest preload, or even to set a gap S instead of a sealing line D. The reduction of the position is achieved by moving the rotor 4 in the direction of the conical widening, that is, with respect to the Fig. 2a - 3c to the left. This widens the constriction 7, and the rest delivery (cf. Fig. 3a-3c ) will be set.

[0047] In Fig. 2b are the work position PA and in Fig. 3b The rest position PR of the rotor 4 is shown relative to the stator 2. In this embodiment, the working position PA and the rest position PR are spaced 1 / 4 of the pitch of the rotor 4 (the pitch being understood as the distance between two peaks or two valleys in cross-section). This distance is generally sufficient to ensure a reliable rest position. As can easily be seen from Fig. 2a-2c This is particularly noticeable at points where the rotor contour runs counter to the stator contour (in Fig. 2b High pressure is present, particularly at the points marked 7 and D in the lower section. When the progressive cavity pump is at rest, and the rotor 4 is not driven by the drive motor 36, relaxation or, in the worst case, creep of the stator 2 material can occur, especially at these points. This results in changes to the internal geometry of the stator 2, such as indentations in the stator 2 material, which do not immediately disappear after operation is resumed. Although these indentations usually disappear during operation, this can take several minutes or hours. The start of operation is particularly problematic, as the drive motor 36 must not only overcome the breakaway torque due to friction between the rotor 4 and stator 2, but also move the rotor 4 out of the indentation(s).For this reason, the invention provides that the feed and thus also the preload between rotor 4 and stator 2 is set to the rest feed or rest preload in the rest state and to the working feed or working preload in the working state, wherein the rest feed or rest preload is less than the working feed or working preload.

[0048] The eccentricity e1, e2 is in this embodiment ( Fig. 2a-3c The diameter D1, D2 of the rotor 4 decreases towards the outlet 12. That is, e1 and e2 are identical, while D1 is larger 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 larger than e2. The effect on axial displacement is then corresponding. It is also possible for both the diameter and the eccentricity to vary along the length.

[0049] Furthermore, the feed rate and thus the preload can also be adjusted by pressing the stator 2 in the axial direction to generate a radial expansion of the stator 2. For this purpose, adjusting elements (not shown here) can be provided, for example, at axial end faces of the stator, with variable distances between them. A mechanical coupling and / or connection exists between the adjusting elements and the stator, so that by changing the relative distance between the two adjusting elements, a change in the cross-section and length of the elastomeric part of the stator can be achieved. The adjusting elements can, for example, be designed as circular pressure plates connected to each other by means of tie rods. It is also possible to integrate electroactive polymers into the stator 2, which cause a radial expansion of the stator 2 when a voltage is applied.

[0050] Fig. 4 shows an opposite Fig. 1 modified embodiment, wherein similar elements are designated with the same reference numeral. In this respect, full reference is made to the above description of the first embodiment ( Fig. 1 ) Reference is made to the preload between rotor 4 and stator 2. Figuren 2a bis 3c referred.

[0051] In contrast to the first embodiment, in this embodiment ( Fig. 4 The feed unit 39 is designed such that the rotor 4 is axially displaceable, together with the complete drive train 25, which, according to this embodiment, consists of the drive shaft 26, the gearbox 34, and the drive motor 36, even though all three elements are optional. Arrow 37 indicates that the drive motor 36 is also displaced. For this purpose, the housing 46 of the gearbox 34 is slidably mounted in a section 48 of the inlet housing 14 opposite the inlet 10 of the stator 2 and sealed against the environment by a seal 50. If no gearbox 34 is present, the drive motor 36 can also be mounted directly or by means of a motor mount on the section 48.

[0052] To move the rotor 4 in the axial direction, a separate feed drive 52 is provided, which can move the drive train 25 (or only the drive motor 36 if no gearbox 34 is provided) via, for example, a spindle drive 54 (shown only schematically) so that the feed between rotor 4 and stator 2 can be adjusted from the working feed to the rest feed and vice versa.

[0053] An electronic feed control 53 is preferably connected to an electronic control unit 58 of the progressive cavity pump 1 or the drive motor 36 via a signal line 56. The drive motor 36 is also connected to the electronic control unit 58 via a signal line 60. The electronic control unit 58 can, for example, be part of a control room or receive control or regulation data via a receive or input interface 200, and is configured to execute the control or regulation based on this control or regulation data. For example, a target volume or a difference between a target volume and an actual volume can be entered into the electronic control unit 58 via this input interface 200.The input interface 200 can be a user interface or an interface to a higher-level unit, such as a control room. Additionally or alternatively, an input port 202 can be provided for connecting a sensor, switch, and / or higher-level control unit. The electronic delivery control 53 receives a start signal from the electronic control unit or directly from a higher-level unit, which starts the drive motor 36 and automatically controls the delivery drive 52 based on this signal, which then sets the delivery to the working position. Likewise, the electronic delivery control 53 receives a stop signal, which stops the drive motor 36 and automatically controls the delivery drive 52 based on this signal, which then sets the delivery to the standby position.

[0054] In other embodiments, the electronic control unit 58 and the delivery control 53 can also be integrated into a control unit.

[0055] Fig. 5 shows a further embodiment, which is fundamentally similar to the embodiment shown. Fig. 4 Identical and similar elements are again marked with the same reference symbols, so that the above description applies in full. It should be understood that the elements with reference to Fig. 4 described electronic control unit 58 also applies to the eccentric screw pump 1 according to Fig. 5 is planned.

[0056] According to this embodiment ( Fig. 5 In this embodiment, the rotor 4 is again arranged to be displaceable relative to the stationary stator 2. However, in this embodiment, the drive motor 36 is also stationary and not displaceable. The drive shaft 26 is again coupled to the output shaft 32 of the drive motor 36 via a universal joint 30. To allow displacement of the rotor 4 and drive shaft 26, the output shaft 32 is mounted axially displaceably in the gearbox 34, specifically in an output gear 68 of the gearbox 34. The gear 68 is coupled to the output shaft 32 by an axially displaceable shaft-hub connection. The gearbox 34 is thus equipped with a gear 68 designed as a hollow shaft, in which the output shaft 32 can be displaced. Alternatively, the gear 68 can also be displaceably mounted in the gearbox 34 and rigidly connected to the output shaft 32.The output shaft 32 is guided by a seal 70, so that no fluid can penetrate from the drive inlet housing 14 into the gearbox 34. A drive 52 (see figure) can be attached to an external section 72 of the output shaft 32. Fig. 4 ) be arranged to allow the axial displacement of the output shaft 32 and consequently of the rotor 4.

[0057] In Fig. 6 Another embodiment is shown, based on the previous embodiments. Identical and similar elements are provided with the same reference numerals as in the previous embodiments, and therefore full reference is made to the above description.

[0058] In Fig. 6 and 7The progressive cavity pump 1 is not initially designed as a stationary pump, but is part of an agricultural trailer that carries a slurry tanker 206. The slurry tanker 206 is connected to the inlet pipe 18. The outlet pipe 24 is connected to a distributor 208 and a trailing hose boom 210. This forms a particularly preferred embodiment, which can also be implemented with the other embodiments of progressive cavity pumps 1 disclosed herein. A progressive cavity pump is particularly suitable for conveying slurry, since slurry contains solid components and is therefore not easily pumpable.

[0059] Another difference from the previous embodiments is that the drive motor 36 is designed here as a hydraulic machine 204. The hydraulic machine 204 can be connected to a hydraulic source (not shown; see [reference]) via a supply and a return line (not shown). Fig. 8 and 9) of the agricultural trailer and thus be supplied with hydraulic fluid under pressure.

[0060] The hydraulic machine 204, like the drive motor 36, can be used in an example according to the embodiment of the Fig. 4 The rotor 4 is slidably mounted on the pump housing 14 and axially displaced via a drive 52 to move it into the working position PA ( Fig. 6 ) and the resting position PR ( Fig. 7 ) to be able to adjust the working delivery or working preload and resting delivery or resting preload. The delivery drive 52 is then in turn connected to the electronic delivery control 53 (in Fig. 6 , 7(not shown). The hydraulic machine 204 can be driven solely by the provided pressure, so that the electronic control unit 58 does not directly control the hydraulic machine 203, but rather a hydraulic pump (not shown here) to provide hydraulic pressure.

[0061] In the Fig. 6 and 7 A hydraulic output shaft 212 is slidably mounted in the hydraulic machine 204. The hydraulic output shaft 212 is then, in turn, connected to the drive shaft 26 via the second cardan joint 30. The hydraulic output shaft 212 is therefore slidably mounted in a hollow shaft of the hydraulic machine.

[0062] The Figuren 8 and 9We now show two variants in which both the drive motor is designed as a hydraulic machine 204 and the feed unit 39 is purely hydraulically designed. A hydraulically designed feed unit 39 can be advantageously used with regard to the Figuren 6 and 7 described embodiment can be used.

[0063] A hydraulic pump 220 forms a hydraulic pressure source. This pump is connected via a directional control valve 224 to a first hydraulic line 226 and a second hydraulic line 228, supplying them with hydraulic pressure. The first hydraulic line 226 leads to the hydraulic machine 204, which in the embodiment shown here is initially connected to a gearbox 34. The gearbox 34 is configured as described in the following diagram. Fig. 5 The device is described as being equipped with a hollow shaft through which the output shaft 32 is axially displaceable. As soon as the directional control valve 224 switches, hydraulic fluid is pumped and the hydraulic machine 204 drives the output shaft 32.

[0064] The feed unit 39 comprises the second hydraulic line 228 and a hydraulic actuator 230, which forms the feed drive 52. The hydraulic actuator 230 is a hydraulic lifting cylinder 232 with a cylinder chamber 234 and a piston 236, which is connected to the output shaft 32, preferably via an intermediate axial bearing, and can axially displace the output shaft 32. A return spring 238 is provided on the side opposite the cylinder chamber 234, which returns the piston 236 to its original position relative to the cylinder chamber 234. Fig. 8 The return spring 238 therefore serves to set the feed to the rest position, and the feed to the working position can be set via the pressure in the cylinder chamber 234.

[0065] In the second hydraulic line 228 a throttle 240 is provided, which serves to reduce the volume flow slightly in order to achieve the desired travel speed and thus time for the movement from the rest position to the working position and vice versa.

[0066] According to the invention, the feed is always automatically adjusted to the working feed and the resting feed. As soon as the directional control valve 224 switches, hydraulic pressure is supplied to the hydraulic machine 204, which subsequently drives the rotor 4, and also to the hydraulic drive 230, which then adjusts the feed to the working feed. If the directional control valve 224 is switched so that the hydraulic machine is stationary, the return spring 238 ensures that the feed is adjusted to the resting feed.

[0067] Fig. 9 shows a similar variant to Fig. 8 Identical and similar elements are marked with the same reference symbols. Therefore, the above description applies in full.

[0068] Unlike Fig. 8 is in Fig. 9 No hydraulic machine 204 is provided that is fixedly arranged on the inlet housing 14, but the hydraulic machine 204 is designed according to the embodiment shown in the example above. Fig. 4 The hydraulic drive 230 of the feed unit 39 acts directly on the hydraulic machine 204 to move it and thus adjust the feed.

[0069] Even in the exemplary embodiment according to Fig. 10 The rotor 4 is displaceable, while the stator 2 is fixed in the inlet housing 14 and the outlet housing 20. According to this embodiment, the drive shaft 26 is formed in two parts, comprising a first part 74 and a second part 76. The two parts 74 and 76 are telescopically inserted into one another, and an expansion element 80 is formed in a recess 78 in the first part 74 between the two parts 74 and 76. The expansion element 80 serves to allow a change in the axial length of the drive shaft 26 by displacing the second shaft part 76 relative to the first shaft part 74. The expansion or reduction of the expansion element 80 enables the rotor 4 to be displaced. For example, the expansion element 80 can comprise a spindle, a piston, a movable magnetic core, electroactive polymers, or the like, which, when actuated, enable movement.An electrical connection can be established via the output shaft 32 or implemented inductively and / or wirelessly. A sliding contact is also a possibility.

[0070] Fig. 11 Figure 1 shows an embodiment of the eccentric screw pump 1, which again allows a displacement of the rotor 4 relative to the stator 2. In this embodiment, the drive shaft 26 is again as in the first four embodiments of the Figuren 1 , 4 , 5 and 6 The drive shaft 26 is formed in one piece. The drive shaft 26 is connected to the output shaft 32 by means of a cardan joint 30.

[0071] In the embodiment according to Fig. 11 The shaft stub 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 telescopically inserted into one another, and in the part 84 is an expansion element 80, corresponding to the expansion element 80 according to Fig. 10 , formed. Alternatively, it can also be provided that a drive engages at the front face 88 of the rotor 4, which axially displaces the rotor 4.

[0072] Even though the electronic control unit 58 and the delivery control 53 are shown only as examples in the embodiment shown in accordance with Fig. 4 As shown, it should be understood that they can also be present in the other embodiments. Likewise, each embodiment can be equipped with a hydraulic feed unit 39 as shown in the Figuren 8 and 9shown, be equipped, even if the drive motor 36 is not designed as a hydraulic machine 204.

[0073] Based on a Fig. 12 The diagram shown now describes the relationship between the operating state, the resting state, the operating position FB, and the resting position F0. The upper diagram plots the position F, and the lower diagram plots the rotational speed n of rotor 4, both over time t.

[0074] Initially, approximately at the origin of the coordinate systems, the rotational speed n = n0 = 0 and the feed rate F is set to the rest position F0. The fact that the value F0 is not on the abscissa here does not necessarily mean that the rest position or rest preload is positive; rather, rotor 4 and stator 2 may not touch at all or only marginally, so that stator 2 is completely or substantially stress-free. In any case, the rest position or rest preload F0 should be chosen such that essentially no relaxation or creep of material from stator 2 occurs at contact points with stator 2, or a sufficiently large gap is set if it is a solid stator.

[0075] At time tn1, a start signal is output, for example via the input interface 200. In response, the electronic control unit 58 activates the drive motor 36, which in turn drives the rotor 4, causing it to begin rotating. The rotational speed n of the rotor 4 increases until it reaches the target speed nN, which is achieved at time tn2. At this point, the operating state (with respect to rotational speed) is also reached. The time interval between tn1 and tn2 can be referred to as the start-up time, ramp-up time, or start-up time. In the Fig. 12 In the illustrated embodiment, the feed rate F is partially increased from the rest position F0 to the working position FB within the start-up time range. This is performed automatically by the feed unit 39, also in response to the start signal. A time interval is provided between time tn1 and time tF1, at which the feed unit 39 begins to increase the feed rate F, for example, by axially adjusting the rotor 4. This is not strictly necessary; it could also be provided that times tn1 and tF1 coincide, or that tF1 precedes tn1. The latter is particularly preferred when the rotor 4 is placed on the stator 2, and the weight of the rotor 4 on the stator 2 causes some relaxation at the contact points. In this case, it is preferred, for example, to first move the rotor 4 axially a short distance before starting its rotation.Preferably, time tF1 occurs after time tn2, preferably offset by a predetermined waiting time of, for example, 1, 2, 3, 5, or 10 seconds. Fig. 12 It can also be seen that the gradient of the feed rate is lower than the gradient of the rotational speed. This is also not necessary, and these parameters can be adjusted and selected according to the operating mode, pump fluid, material, and material pairing.

[0076] Once the progressive cavity pump 1 has been operating at working speed FB since time tF2, a stop signal is output at time tn3, for example, again via input interface 200. However, it can also be an automatically generated stop signal, for example, due to the time difference between tn2 and tn3 or due to a sensor signal. From this point on, the rotational speed n of the rotor 4 is reduced again by the electronic control unit 58 and falls at the same gradient with which it had increased. This is not mandatory, and the gradients can differ. In particular, it is often preferred that standstill is reached as quickly as possible. After the rotational speed n has almost returned to zero, the feed unit 39 reduces the feed rate F from the working speed FB to the rest speed F0.The rest position F0 is reached at time tF4, which lies after time tn4. The period between tn3 and tn4 can be referred to as the run-down time interval. In the embodiment shown here, the change in the position F from the working position FB to the rest position F0 therefore lies partially within the run-down time interval. The intervals can also completely overlap; tF3 can coincide with tn3, and tF4 with tn4. Time tF3 can also be before time tn3 or after time tn4. It is also conceivable and preferred if time tF4 is before or after time tn3 and / or before or after time tn4.

[0077] A latency can also be implemented between tn3 and tF3 in case a start signal is received shortly after the stop signal is issued (at tn3). This latency can be defined according to the specific application and can be several seconds or minutes.

Claims

1. A method for controlling an eccentric screw pump (1), having - a helically wound rotor (4), - a stator (2), having an inlet (10) and an outlet (12), in which the rotor (4) is arranged rotatably about a longitudinal axis (L1) of the stator (2), and which has a helical inner wall (8) corresponding to the rotor (4), wherein rotor (4) and stator (2) are arranged and formed with respect to one another such that at least one chamber (5) is formed which serves to transport the liquid, and the chamber (5) is separated by a sealing line (D), - a drive motor (36) for rotating the rotor (4), - a control device (58) for controlling the drive motor (36) at least in a working state, in which the rotor (4) is rotated, and an idle state, in which the rotor (4) does not rotate, - and having an engagement unit (39) which is adapted to adjust a preload (F) between rotor (4) and stator (2) to an idle preload (F0) in the idle state and to a working preload (FB) in the working state, wherein the idle preload (F0) is lower than the working preload (FB); the method comprising: - operating the eccentric screw pump in a working state, comprising: - rotating the rotor in the stator of the eccentric screw pump with the working preload (FB) between rotor and stator; - outputting a stop signal and, in response to the stop signal: - stopping the rotating and switching to an idle state of the eccentric screw pump; and - automatically reducing the preload between rotor and stator from the working preload to the idle preload (F0); - outputting a start signal and, in response to the start signal: - starting the rotating of the rotor and switching from the idle state to the working state of the eccentric screw pump, in response to the start signal: - automatically increasing the preload between rotor and stator from the idle preload (F0) to the working preload (FB) in a run-in time period.

2. The method according to claim 1, wherein a run-down time period is defined from a point in time of the outputting of the stop signal to a rotational standstill of the rotor and the reduction of the preload from the working preload to the idle preload takes place at least partially during or subsequent to the run-down time period.

3. The method according to any one of claims 1 to 2, wherein the reduction of the preload between rotor and stator from the working preload to the idle preload comprises: axial displacement of the rotor from a working position into an idle position.

4. The method according to any one of claims 1 to 3, wherein the reduction of the preload between rotor and stator from the working preload to an idle preload comprises: changing a relative distance between two adjustment elements on the stator for changing the cross section and the length of an elastomer part of the stator.

5. The method according to claim 3, wherein the working position and the idle position are spaced apart by at least 1 / 30 of the pitch of the rotor.

6. The method according to any one of claims 1 to 5, wherein the idle preload is reduced by 20% relative to the working preload.