Modular eccentric screw pump

Abstract

Eccentric screw pump (1) with a rotor forming a conveying screw (2) and a stator (3) forming a screw flight, in which the rotor rotates during conveying operation, wherein the stator (3) comprises a (one- or multi-part) stator housing (4) in which a stator lining (5) made of an elastomeric material is located, which forms the screw flight, wherein the stator lining (5) forms (at least) on one side in the direction along the longitudinal axis (L) of the pump a projection (19) which protrudes from the stator housing (4) in such a way that a free force application surface is formed, over which a force can be applied which compresses the stator lining (5) into the stator housing (4), so that a transverse expansion of the stator lining (5) occurs there, which leads to a narrowing of the screw flight, wherein the projection (19) is encompassed by a movable support tube (6). is,which (for the purpose of compression) can be displaced in the direction along the longitudinal axis (L) of the stator housing (4) relative to the stator housing (4), wherein the mobile support tube (6) is arranged in a recess of the stator lining (5), characterized in that the stator lining (5) has a recess (25) in the area of ​​the projection (19), into which the mobile support tube (6) is vulcanized over the entire bottom of the recess (25) or attached to it by gluing or welding, so that an outer circumferential surface of the mobile support tube (6) is flush with the outer circumferential surface of the stator lining (5).

Description

[0001] The invention relates to an eccentric screw pump with a stator that is predominantly adjustable during regular operation according to the preamble of claim 1.

[0002] It also concerns a method for the operational adjustment of the stator of such an eccentric screw pump. TECHNICAL BACKGROUND

[0003] Progressive cavity pumps have a wide range of applications.

[0004] They are a preferred choice, not least where highly viscous fluids with a difficult-to-control consistency and / or containing solids need to be pumped. For these reasons, progressive cavity pumps are also used in the extraction of mineral resources.

[0005] Progressive cavity pumps are ideally suited for pumping fluids containing abrasive components. Their pumping action is based on the principle of migrating pumping chambers, which form between the central screw and the double-pitch screw channel formed by the stator lining.

[0006] Nevertheless, there is a need to be able to compensate for any wear that may occur on the stator lining after some time during regular operation. Such a subsequent (re-)narrowing of the screw channel formed by the stator lining should be possible without disassembling the progressive cavity pump or removing and installing the stator lining. The screw channel should therefore be adjustable without disassembly or removal. If this were not the case, every adjustment of the screw channel would result in the pump being unavailable outside of normal maintenance hours.

[0007] Furthermore, being able to adjust the screw pitch can be advantageous for other reasons, such as increasing the preload with which the screw pitch formed by the stator lining bears against the conveying screw. This may be necessary to ensure a better seal in response to a specific viscosity of the fluid being pumped.

[0008] Such adjustability is achieved by omitting the connection between the elastomeric stator lining and the outer casing. If a compressive force is applied to the elastomeric, but incompressible (i.e., essentially volume-constant), stator lining along the longitudinal axis of the screw pump, and its radial outward expansion is simultaneously restricted, a significant radial inward expansion of the stator lining occurs. The elastomeric stator lining thus "grows" radially inward. Consequently, the screw flight it forms becomes narrower.

[0009] The interaction with the rotor screw, which is guided in the stator contour (i.e., the screw channel), results in a greater overlap of the eccentric screw and the stator lining with such lateral expansion of the stator lining as the screw channel narrows. This increased overlap can be used either to improve the sealing of the conveying chamber or to compensate for wear-related material loss.

[0010] In order to be able to apply a compression force in the aforementioned manner and to have a large path available along which compression can be carried out if necessary, consideration has already been given to the following: Fig. 1. To use the schematically shown construction.

[0011] An essential component of this construction is the mobile and stationary support tubes 6, 7. Using the support tubes 6, 7, a [missing information] is employed in Fig. In the compression device (not shown), a compressive force D directed along the longitudinal axis L towards the interior of the stator is applied to the end ring surface S of the stator lining 5. Similarly, a tensile force can also be applied in the opposite direction.

[0012] The support tubes 6 and 7 prevent the stator lining 5 from deflecting radially outwards in the area of ​​its overhang 19 during compression. The stationary support tube 7 is often equipped with an internal cone 10 into which the mobile support tube 6 is inserted deeper with increasing compression. The stationary support tube is typically stretched in the process, requiring considerable forces that would be more beneficial if they were available to generate transverse expansion of the stator lining along its entire length.

[0013] DE 20 2007 013 820 U1 describes a device for pumping a free-flowing substance. US 2009 / 0 288 818 A1 describes an electric submersible well pump. DE 10 2016 117 910 A1 and DE 10 2017 107 962 B3 each describe a progressive cavity pump.

[0014] FR 1 284 388 A1 describes a machine for transporting mortar, cement or similar products under pressure, consisting of a conical screw conveyor tapering in the direction of transport, housed in a casing with a filling hopper, which also tapers in its part containing the screw conveyor, and which opens into a transport pipe.

[0015] DE 10 2008 021 920 A1 describes an eccentric screw pump with at least one stator made of an elastic material and a rotor mounted in the stator, wherein the stator is at least partially surrounded by a stator shell, and wherein the stator is a longitudinally split stator consisting of at least two stator partial shells. TASK OF INVENTION

[0016] Accordingly, the object of the invention is to create an adjustable progressive cavity pump in which, during its adjustment over its length, a more efficient displacement of the stator lining in a radially inward direction is achieved. INVENTIONAL SOLUTION

[0017] According to the invention, this problem is solved using the means of the first main claim.

[0018] The starting point is therefore an eccentric screw pump with a rotor forming a conveying screw and a stator forming a screw thread, in which the rotor rotates during conveying operation.

[0019] The stator comprises a one-piece or multi-piece stator housing – in the latter case, possibly segmented not only transversely but also along the longitudinal axis L of the stator, or divided into several parts. This housing contains a stator lining made of an elastomeric, preferably vulcanized, material. The central cavity of the stator lining forms the worm gear.

[0020] The stator lining forms a projection along at least one side of the pump's longitudinal axis. This projection extends from the stator housing in such a way that it creates a free force application surface. A force can be applied across this surface, compressing the stator lining into the stator housing. This compression occurs in such a way that a transverse expansion of the stator lining also occurs within the stator housing. This transverse expansion causes a narrowing of the worm gear.

[0021] In all of this, the protrusion is enclosed on its outer circumference by a movable support tube. During compression, the movable support tube can be displaced along the longitudinal axis of the stator housing relative to the stator housing.

[0022] According to the invention, the mobile support tube, or its circumferential surface, is arranged, at least predominantly, preferably completely, within a recess of the stator lining when viewed in the radial direction. Ideally, only its radially projecting collar protrudes outwards. In the preferred, complete arrangement within the recess, the outer circumferential surface of the mobile support tube is flush or smooth. In this case, there is – at least substantially – no change in diameter compared to the surrounding outer circumferential surface of the stator lining.

[0023] This eliminates the need to expand the stationary support tube during the insertion of the mobile support tube and to exert corresponding forces for this purpose.

[0024] In this way, it is more efficiently ensured that the expansion constraint experienced by the stator lining during compression leads to a “growth” of the stator lining in a radially inward direction.

[0025] According to the invention, an eccentric screw pump is thus obtained which can be adjusted more precisely or more evenly over its entire stator length.

[0026] At the same time, the progressive cavity pump according to the invention usually offers a particularly long stroke by which the stator lining can be compressed, thus resulting in an increased adjustment range. If desired, the mobile support tube is preferably designed such that it has an insertion length usable for compression of at least 1 / 4, preferably at least 1 / 2, of the outer radius of the stator lining. OPTIONAL REFINITIONS

[0027] As long as the compression of the stator lining is achieved solely by applying pressure to the free end ring surface available at the free end of the overhang on the end face of the stator lining, there is a risk of undesirable inconsistencies in the adjustment. If the required pressure becomes too high, the end face of the stator lining deforms significantly in the immediate vicinity of the force application. This results in a loss of some of the compression effect that is actually needed within the stator housing.

[0028] In light of this, it has proven particularly advantageous if the mobile support tube is bonded to the stator lining, at least on its inner surface. This connection is designed such that the respective compression force can be transferred to the stator lining solely or predominantly via this connection, generating shear stresses. This also provides protection on its own.

[0029] The material-bonded connection can be, in particular, an "adhesive bond through (in-)vulcanization," or alternatively, bonding in the true sense or welding, for example, with a plastic layer of the support tube. The support tube can have joining aids, such as holes / openings into which material penetrates and is later hardened by vulcanization, ribs, or a particularly rough, e.g., knurled, inner surface that thus interlocks and intimately bonds with the vulcanized material.

[0030] This special method allows the stator lining to be compressed particularly well and evenly during the adjustment process, even when extremely strong compression is required.

[0031] It can be advantageous to design the progressive cavity pump so that the mobile support tube for compression can be inserted into the stator housing itself, and that its outer diameter is smaller than the smallest inner diameter of the section of the stator housing available for insertion. This minimizes the number of components in the progressive cavity pump, thus reducing manufacturing costs.

[0032] However, it is particularly advantageous if the support tube for compression is inserted into a stationary support tube attached in front of the end face of the stator housing, and if its outer diameter is inherently smaller than the smallest inner diameter of the section of the stationary support tube available for insertion.

[0033] The stationary support tube is then fixed or screwed onto the front face of the stator housing. In this way, the same stator housings used for non-adjustable progressive cavity pumps can be used to build adjustable progressive cavity pumps. This also applies if these stator housings – unlike the mobile support tube – have a polygonal, rather than a circular, internal cross-section.

[0034] Preferably, the stationary support tube has a first radial flange to which one or more compression elements are attached, usually in the form of tension elements. If tension elements are used, they are advantageously designed as threaded rods. Such a radial flange makes it particularly easy to apply forces for compressing the stator lining without requiring any structural modifications to the stator housing.

[0035] The mobile support tube typically features a second radial flange to which one or more of the aforementioned compression elements are attached. This allows the mobile support tube to be particularly easily involved in applying the forces required to compress the stator lining.

[0036] These threaded rods can be equipped with nuts or rigid hexagonal heads, which can be tightened manually with a wrench as needed. Alternatively, they can also carry actuators driven by a type of planetary gear via a sunburst gear, similar to a planetary gearbox. Ideally, the drive is motorized. This then rotates nuts on the threaded rods or the threaded rods themselves.

[0037] At least where particularly high forces are required for compression, the mobile support tube or the second radial flange is preferably designed such that, during compression, force is also introduced into the stator lining via the annular surface on the free end face of the projection, preferably even the greater part of the force. In some cases, it is advantageous to introduce essentially the entire force in this way.

[0038] Independently of the claims made previously, protection is also claimed for a method for narrowing the screw channel formed by the elastomeric stator lining of a progressive cavity pump. The narrowing according to the method is achieved by compressing the stator lining, which is supported radially along its outer circumference by a stator housing, in the direction of the stator's longitudinal axis. The compression force is applied to a projection formed by the stator lining extending from the end face of the actual stator housing. The method according to the invention is characterized in that the compression force is applied, at least partially, to a greater than negligible extent by means of a shear stress acting on one of the projection's circumferential surfaces. LIST OF FIGURES The Fig. Figure 1 shows a concept that was previously considered. The Fig. Figure 2 shows an overview of an eccentric screw pump as a whole. The Fig. Figure 3 shows the stator of an eccentric screw pump according to the invention. The Fig. Figure 4 shows a close-up from Fig. 3. PREFERRED EXECUTION EXAMPLE OVERVIEW

[0039] The Fig. Figure 2 shows the eccentric screw pump 1, which forms the basis of the invention, as a whole.

[0040] The main components of such an eccentric screw pump 1 are the suction housing 11 and the pump section 12 which is in flow communication with it.

[0041] The suction housing 11 has an inlet 13 for the medium to be pumped.

[0042] The pumped medium is discharged via the outlet 14 located at the end of the pump section 12.

[0043] The preferred design is a block construction, even though this is not mandatory under patent law. The pump motor 15 is then flanged to the suction housing 11. The pump motor 15 drives the rotor, which will be described in more detail below, via the usually cardan-type drive train 16.

[0044] The pump section is formed by the stator 3 with the rotor rotating inside it.

[0045] The rotor is formed by an eccentric screw 2, which can be classified as a round-threaded screw. Compared to a normal screw, the eccentric screw has a larger pitch, a greater thread depth, and a smaller core diameter. The stator 3 is designed to complement the rotor. It forms a "screw thread," but with twice the pitch length and an additional thread. This arrangement creates a series of conveying chambers 17 between the stationary stator 3 and the rotor, which rotates eccentrically within it. The conveying chambers 17 move continuously and without changing shape from their inlet side, formed by the trumpet 18 at the suction housing 11, to their outlet side, i.e., to the outlet 14. This pressurizes and conveys the medium contained in the conveying chambers 17.

[0046] The speed of movement of the pumping chambers 17 towards the outlet side, and thus the theoretical pump delivery rate, can be controlled via the rotational speed of the rotor.

[0047] In addition to the number of stator windings, the tightness of the contact line between rotor and stator influences the suction capability and the achievable delivery pressure of the pump. THE DESIGN BASED ON THE INVENTION

[0048] The Fig. 3 already shows the Fig. 2. Pump section 12 mentioned, however without showing the eccentric screw.

[0049] Clearly visible in the Fig. 3 is the stator 3. It consists of the stator housing 4, which can optionally be divided here, and in which the stator lining 5 is located. The stator lining 5 has no, or at least essentially no, frictional connection with the inner surface of the stator housing 4 on its outer circumferential surface. The stator housing 4 therefore does not impede the compression of the stator lining 5, which will be explained in more detail later.

[0050] Also clearly visible in the figure is the fact that the stator lining 5 protrudes from the stator housing 4 on the left side, forming a projection 19. This projection 19 lies, at least substantially, radially within the mobile support tube 6. The smaller portion usually lies within the stationary support tube 7.

[0051] A compression device 8 is connected to the support tubes 6 and 7. This device comprises the first radial flange 20 of the stationary support tube 7 and the second radial flange 21 of the mobile support tube 6. The first radial flange 20 can be attached to the stationary support tube 7 or directly to the stator housing 4. The second radial flange 21 is typically connected to the mobile support tube 6, preferably by welding. The distance between the two radial flanges 20 and 21 is adjustable. Ideally, a tension element 22 is provided for this purpose, preferably in the form of a threaded rod. As can be seen here, in this specific case, the first radial flange 20 has an internal thread for anchoring the threaded rod. The second radial flange 21 can have through holes through which the respective threaded rod passes, in order to be screwed to it on the other side with an actuating nut 23.It is noteworthy that the radial flange 21 – either on its own or with the aid of a bolted-on ring element – ​​is also capable of applying compressive forces acting from left to right to the free end ring surface of the stator lining 5 in the area of ​​the projection 19. Such a configuration is optional.

[0052] To the Fig. 3 and Fig. Figure 4 clearly shows the special positioning of the mobile support tube according to the invention. The stator lining 5 has a recess 25 on its outer circumferential surface, which in many cases is purely annular in shape. It then usually has a straight cylindrical base and end walls extending radially outwards at right angles to it. Preferably, the recess 25 is long and shallow. The amount by which said base extends along the longitudinal axis L is then preferably at least 7.5 times, better at least 10 times, greater than the amount by which each end wall of the recess 25 extends radially outwards.

[0053] The actual tube part of the mobile support tube 6 is inserted into this recess 25 - ideally in such a way that there is no transition in the sense of a noticeable, i.e. significant, diameter jump to the surrounding outer circumferential surface of the stator lining 5.

[0054] Ideally, the mobile support tube 6 is vulcanized into the stator lining 5 or attached to it by bonding or welding in such a way that – preferably across the entire bottom of the recess 25 – a shear-resistant connection, exceeding a purely frictional connection, is provided between the inner surface of the circumference of the mobile support tube and the elastomer of the stator lining 5 bearing against it from the inside. It may be advantageous to implement this shear-resistant connection over a particularly long length, for example, a length parallel to the longitudinal axis L of at least 1 / 2 or, better yet, at least 2 / 3 of the outer diameter of the stator lining.

[0055] The in Fig. The stationary support tube 7, which can be identified as 4, is optional. It is particularly advantageous if, for reasons of better uniformity during compression, a circular cross-section is chosen for the support tube 6, while the stator housing 4 has a polygonal cross-section. This difference is then accommodated by the stationary support tube 7, which itself usually also has a circular cross-section.

[0056] Turning back to Fig. 3, so it is easy to understand how the compression device 8 works.

[0057] By tightening the actuating nut 23 and, if necessary, loosening the locking nut 24 beforehand, the first radial flange 20 and the second radial flange 21 are moved towards each other. Since the mobile support tube 6 is positively connected to the second radial flange 21, it is inserted into the stationary support tube 7 in a direction parallel to the longitudinal axis L. It is also noteworthy that the stator lining is generally not hollow anywhere, but is completely supported everywhere in the radially outward direction. In this respect, too, it differs from that of Fig. 1 previous solution shown.

[0058] The mobile support tube 6 transmits a shear stress on its inner surface to the stator lining 5 located inside it. This stress propagates within the stator lining 5 into the area of ​​the stator housing 4. However, the end of the stator lining 5 furthest from the housing is rigidly clamped and therefore cannot move along the longitudinal axis L. Consequently, lateral expansion occurs within the stator lining in the area of ​​the stator housing 4. This radial expansion is prevented by the stator housing 4. As a result, a considerable radial expansion occurs in the inward direction. This narrows the worm gear. The shear-resistant connection between the inner surface of the mobile support tube 6 and the portion of the stator lining 5 located within it, as described above, allows for a very uniform force transmission into the stator lining 5.

[0059] As a rule, at least one section of the worm gear lies in the area beneath the mobile support tube 6, which has a maximum clear diameter and therefore forms a region where the wall of the stator lining is very thin. Nevertheless, this thin section does not collapse even during compression, because it is prevented from doing so by its connection to the inner surface of the mobile support tube 6.

[0060] During compression, force can also be introduced via the annular surface S of the stator lining 5 in the region of the free end of the projection 19. Often this is even the predominant part of the force introduced for compression.

[0061] It should also be noted that the effect of narrowing the screw thread can be reversed. Due to its design, the compression device 8, with the aid of the mobile support tube 6, can also transmit tensile forces to the stator lining 5. The described shear-resistant connection between the inner surface of the mobile support tube 6 and the portion of the stator lining 5 located within it is particularly advantageous in this regard. This connection effectively introduces a shear stress, which in turn leads to a high tensile stress along the further length of the stator lining 5. REFERENCE MARK LIST 1 eccentric screw pump 2 eccentric screw 3 Stator 4 Stator housings 5 Stator lining 6 mobile support tubes 7 stationary support tube 8 Compression device 9 Overhang 10 Inner cone 11 Suction housings 12 Pump section 13. Admission for the medium to be funded 14 Outlet for the medium to be promoted 15 Pump motor 16 Powertrain 17 Funding Chamber 18 Trumpet 19 Overhang 20 first radial flange of the stationary support tube 21 second radial flange of the mobile support tube 22 Tensioning element, preferably in the form of a threaded rod 23 Actuating nut 24 locking nuts 25 Exclusion 26 Ring organ L Longitudinal axis of the eccentric screw pump or the eccentric screw and the stator D pressure force S face ring surface H area in which, in a non-inventive variant, a hollow lying of the stator lining can be observed

Claims

[1] Eccentric screw pump (1) with a rotor forming a conveying screw (2) and a stator (3) forming a screw flight, in which the rotor rotates during conveying operation, wherein the stator (3) comprises a (one- or multi-part) stator housing (4) in which a stator lining (5) made of an elastomeric material is located, which forms the screw flight, wherein the stator lining (5) forms (at least) on one side in the direction along the longitudinal axis (L) of the pump a projection (19) which protrudes from the stator housing (4) in such a way that a free force application surface is formed, over which a force can be applied which compresses the stator lining (5) into the stator housing (4), so that a transverse expansion of the stator lining (5) occurs there, which leads to a narrowing of the screw flight, wherein the projection (19) is supported by a mobile support tube (6) encompassed iswhich (for the purpose of compression) can be displaced in the direction along the longitudinal axis (L) of the stator housing (4) relative to the stator housing (4), wherein the mobile support tube (6) is arranged in a recess of the stator lining (5), characterized by , that the stator lining (5) has a recess (25) in the area of ​​the overhang (19) into which the mobile support tube (6) is vulcanized over the entire bottom of the recess (25) or is attached to it by gluing or welding, so that an outer circumferential surface of the mobile support tube (6) is flush with the outer circumferential surface of the stator lining (5). [2] Eccentric screw pump (1) according to the preamble of claim 1 or according to claim 1, characterized by, that the mobile support tube (6) is materially connected to the stator lining (5) at its inner surface, such that it can transmit compression force to the stator lining (5) via said connection, generating shear stresses. [3] Eccentric screw pump (1) according to claim 1 or 2, characterized by , that the mobile support tube (6) is inserted into the stator housing (4) itself for compression and that its outer diameter is smaller than the smallest inner diameter of the section of the stator housing (4) available for insertion. [4] Eccentric screw pump (1) according to claim 1 or 2, characterized by , that the mobile support tube (6) is inserted into a stationary support tube (7) attached in front of the end face of the stator housing (4) for compression and that its outer diameter is smaller than the smallest inner diameter of the section of the stationary support tube (7) available for insertion. [5] Eccentric screw pump (1) according to claim 4, characterized by , that the stationary support tube (7) has a first radial flange (20) to which one or more tension elements (22) are attached, ideally designed as threaded rods. [6] Eccentric screw pump (1) according to one of the preceding claims, characterized by , that the mobile support tube (6) has a second radial flange (21) on which one or more compression elements preferably in the form of tension elements (22) are applied, which are ideally designed as threaded rods. [7] Eccentric screw pump (1) according to claim 6, characterized by , that the second radial flange (21) is designed such that, during compression, it also introduces force into the protrusion (19) via the annular surface (S) on the free end face. [8] Method for narrowing the screw thread formed by the elastomeric stator lining (5) of a progressive cavity pump (1) by compressing the stator lining (5), which is supported radially over its outer circumference by a stator housing (4), in the direction of the stator longitudinal axis (L), wherein the compression force is applied to a projection (19) formed by the stator lining (5) projecting (at its end face) from the stator housing (4), wherein the compression force is applied (at least partially, more than just insignificantly) by means of a shear stress on the projection (19) acting on one of its circumferential surfaces, characterized by , that the stator lining (5) has a recess (25) in the area of ​​the overhang (19), into which the mobile support tube (6) is vulcanized over the entire bottom of the recess (25) or is attached to it by gluing or welding, so that an outer circumferential surface of the mobile support tube (6) is flush with the outer circumferential surface of the stator lining (5).

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