Modular eccentric screw pump

Abstract

The invention relates to an eccentric screw pump having a rotor forming a screw conveyor and a stator forming a worm pitch, the rotor rotating in the stator during the conveying operation. The stator comprises a stator housing (single piece or multi-piece), in which a stator bushing made of an elastic material is located, which forms the worm pitch. The stator bushing forms a protrusion on at least one side in the direction of the longitudinal axis of the pump, which protrudes from the stator housing to form a free force introduction surface. A force can be applied on the free force introduction surface, which compresses the stator bushing into the stator housing to cause a lateral elongation of the stator bushing there, which leads to a contraction of the worm pitch. The protrusion is surrounded by a movable support tube, which moves relative to the stator housing in the direction of the longitudinal axis of the stator housing for compression.

Description

TECHNICAL FIELD

[0001] The invention relates to an excentric screw pump having a stator which is adjustable mainly in the range of normal operation according to the invention.

[0002] The invention also relates to a method for operating a stator for adjusting such an excentric screw pump. BACKGROUND

[0003] Excentric screw pumps have a wide field of application.

[0004] Excentric screw pumps are the preferred mechanism at least when pumping highly viscous fluids whose consistency and / or solid content is difficult to control. For these reasons, excentric screw pumps are also used for the exploitation of natural resources.

[0005] Here, excentric screw pumps are particularly suitable for pumping fluids containing abrasive components. The pumping effect of an excentric screw pump is based on the principle of a mobile conveying chamber which is formed between a central screw conveyor and a worm screw pitch formed by the stator bushing with a double pitch.

[0006] However, within the range of normal operation, it is necessary to be able to compensate for any wear that can occur over time on the stator bushing. The worm screw pitch formed by the stator bushing should be able to be subsequently (re)contracted without leading to the disassembly of the excentric screw pump or the installation and removal of the stator bushing. Therefore, the worm screw pitch should be adjustable without the need for disassembly or without the need for removal. If not, each adjustment of the worm screw pitch would result in the pump being unavailable, which would go beyond normal maintenance times.

[0007] In addition, it can also be necessary to adjust the worm screw pitch for other reasons, for example in order to increase the prestress of the worm screw pitch formed by the stator bushing against the screw conveyor. This can be necessary in order to ensure better sealing in response to the specific viscosity of the fluid to be pumped.

[0008] Such setability can be achieved by avoiding a connection of the elastic stator bushing to the outer housing. If a pressure or compression force is applied to the elastic but incompressible (i.e. substantially constant volume) stator bushing in the direction of the longitudinal axis of the screw pump and at the same time a lateral elongation in the radially outward direction is prevented, a significant lateral elongation of the stator bushing in the radially inward direction occurs. As a result, the elastic stator bushing "grows" radially inward. As a result, the worm screw pitch formed thereby becomes narrower.

[0009] With this lateral elongation of the stator bushing, the interaction with the rotor screw, which is guided in the stator profile, i.e. the worm pitch, leads to an increasing overlap between the eccentric screw and the stator bushing with a contraction of the worm pitch. The increasing overlap can be used to increase the sealing of the conveying chamber or to compensate for the removal of material associated with wear.

[0010] In order to be able to exert a compression force in the manner described above and to have a long usable distance along which the compression can take place if necessary, it has been considered to use Figure 1 the structure shown.

[0011] An important component of this structure is the movable and fixed support tubes 6, 7. With the aid of Figure 1 a compression device, not shown in the drawing, a pressure D directed along the longitudinal axis L into the interior of the stator is exerted on the front annular surface S of the stator bushing 5 by means of the support tubes 6, 7. Similarly, it is also possible to exert a pulling force in the opposite direction.

[0012] The support tubes 6 and 7 prevent the stator bushing 5 from being displaced radially outwards when it is compressed in the region of its protrusion 19. Here, the fixed support tube 7 is usually equipped with an inner cone 10, into which the movable support tube 6 slides deeper with increasing compression force. Here, it is usually the case that the fixed support tube is stretched, for which considerable forces are required, which are more advantageous if they can be used to produce the lateral elongation of the stator bushing along the entire length. SUMMARY

[0013] Object of the invention

[0014] It is therefore the object of the present application to provide an adjustable eccentric screw pump in which, during adjustment over its length, a more effective displacement of the stator bushing in the radially inwards direction takes place.

[0015] Solution according to the invention

[0016] According to the application, the solution to this object is achieved by the means of the application.

[0017] The point of departure is therefore an eccentric screw pump which comprises a rotor which forms a screw conveyor and a stator which forms a worm pitch, the rotor rotating in the stator during the conveying operation.

[0018] The stator comprises a stator housing which is of one piece or of several pieces, in the latter case possibly not only segmented or divided into several parts in the lateral direction but also segmented or divided into several parts in the direction of the stator longitudinal axis L. A stator bushing made of an elastic material, preferably a vulcanized material, is located in the stator housing. The stator bushing forms the worm pitch with its central cavity.

[0019] The stator sleeve forms a protrusion at least on one side along the longitudinal axis of the pump. This protrusion projects from the stator housing to form a free force introduction surface via which a force can be applied which compresses the stator sleeve into the stator housing. The compression takes place in such a way that a transverse elongation of the stator sleeve is produced (exactly) in the stator housing. This transverse elongation causes a worm pitch contraction.

[0020] In all these cases, the protrusion is surrounded at its outer circumference by a movable support tube. This movable support tube can be moved relative to the stator housing in the direction of the longitudinal axis of the stator housing during the compression.

[0021] According to the invention, the movable support tube or its circumferential jacket surface is arranged at least predominantly (preferably completely) in the recess of the stator sleeve in the radial direction. Ideally, only its radially protruding collar projects outward. In this preferred (complete) arrangement, the outer circumferential surface of the movable support tube is closed in the recess in a flat or smooth manner. There is at least substantially no change in diameter compared to the surrounding circumferential surface of the stator sleeve.

[0022] This eliminates the necessity of having to widen the fixed support tube during the insertion of the movable support tube and applying the corresponding force for this purpose.

[0023] In this way, it can be ensured more effectively that the elongation restriction (Dehnungsbehinderung) experienced by the stator sleeve during its compression results in a "growth" of the stator sleeve in the radially inward direction.

[0024] Thereby, an eccentric screw pump is obtained according to the invention which can be adjusted more precisely or more uniformly over its entire stator length.

[0025] At the same time, the eccentric screw pump according to the invention generally offers a long distance over which the stator sleeve can be compressed, resulting in an expanded adjustment range. In this regard, the movable support tube is preferably designed in such a way that its insertable length for compression is at least ¼, preferably at least ½, of the outer radius of the stator sleeve.

[0026] Optional improvements

[0027] As soon as the compression of the stator sleeve is only achieved by applying pressure to the free front annular surface available on the end face of the stator sleeve at the free end of the protrusion, there is a risk of undesirable inhomogeneity in the adjustment. If the necessary pressure becomes too high, the end face of the stator sleeve can be deformed very strongly in the immediate vicinity of the force introduction. A part of the compression effect that is actually required inside the stator housing thus "disappears".

[0028] Therefore, it proves particularly advantageous if the movable support tube is connected to the stator bushing material in a mating manner on its inner sheath surface under all circumstances. This connection is designed such that, in the event of shear stress, the corresponding compressive force is transmitted to the stator bushing individually or, in any case, primarily through said connection. This also necessitates protection in a separate location.

[0029] The connection of materials can be, in particular, an "adhesive connection by (internal) vulcanization," or it can be an actual bond or weld, such as a connection to the plastic layer of a support tube. The support tube may have a connecting aid, such as a hole / opening, into which the vulcanized material, ribs, or a particularly rough (e.g., knurled) inner surface is then inserted, thereby interlocking with the vulcanized material and forming a tight connection.

[0030] This special method allows the stator bushing to be compressed particularly well or uniformly during adjustment (even when very strong compression is required).

[0031] Significantly, the eccentric screw pump is designed such that the movable support tube can be inserted into the stator housing itself for compression, and its outer diameter is smaller than the minimum inner diameter of the section of the stator housing that can be inserted. In this way, the number of parts in the eccentric screw pump is kept as small as possible, which reduces manufacturing workload.

[0032] However, it is particularly advantageous if the support tube is inserted into a fixed support tube that is fastened to the end face of the stator housing for compression, and its outer diameter is inherently smaller than the minimum inner diameter of the available insertion section of the fixed support tube.

[0033] The fixed support tube can then be secured or screwed onto the end face of the stator housing. In this way, the stator housing used for constructing a non-adjustable eccentric screw pump can also be used unchanged to construct an adjustable eccentric screw pump. This also applies if the stator housing—unlike the movable support tube—has a polygonal net cross-section instead of a circular one inside.

[0034] Preferably, the fixed support tube has a first radial flange, and one or more compression mechanisms, typically in the form of traction mechanisms, engage with the first radial flange. If traction mechanisms are used, they are advantageously designed as screws. With the aid of such a radial flange, forces for compressing the stator bushing can be applied particularly easily without requiring structural changes to the stator housing.

[0035] In most cases, the movable support tube has a second radial flange, with one or more of the compression mechanisms engaging with the second radial flange. In this way, the movable support tube can particularly easily participate in applying the force required to compress the stator bushing.

[0036] The screws can be equipped with nuts or rigid hexagonal heads, for example, which can be tightened manually by means of a spanner, if desired. Alternatively, they can also be supported by an actuating mechanism which drives them in the manner of a planetary gear by means of a sun gear which works according to the planetary gear principle. Ideally, the drive is electric. The nuts on the screws or the screws themselves are thereby turned.

[0037] At least in the case where particularly large forces have to be applied for compression purposes, the movable support tube or the second radial flange, respectively, is preferably designed in such a way that, upon compression, the forces, preferably even the majority of the forces, are additionally introduced into the stator bushing also via the front annular surface on the free end face of the protrusion. In some cases it is advantageous if even substantially the entire force can be introduced.

[0038] Independent of the previously claimed content, a method for contracting the worm pitch formed by the elastic stator bushing of an eccentric screw pump is claimed. The contraction according to the method is achieved by compression of the stator bushing in the direction of the stator longitudinal axis, which is supported via its outer circumference in the radial direction by the stator housing. Here, the compression force is exerted on the protrusion formed by the stator bushing, which protrudes at the end face by the actual stator housing. The method according to the invention is characterized in that the compression force acts at least partially, but not only insignificantly, on the protrusion by means of shear stress, which engages with its outer circumferential surface. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 A concept previously considered is shown.

[0040] Figure 2 An overview of an eccentric screw pump is shown in its entirety.

[0041] Figure 3 A stator of an eccentric screw pump according to the invention is shown.

[0042] Figure 4 An enlarged cross section of Figure 3 is shown. DETAILED DESCRIPTION

[0043] SUMMARY

[0044] Figure 2 An eccentric screw pump 1, which forms the basis of the invention, is shown in its entirety.

[0045] The main components of this eccentric screw pump 1 are a suction housing 11 and a pump section 12 which is in fluid communication with it.

[0046] An inlet 13 for the medium to be conveyed is formed on the suction housing 11.

[0047] The conveyed medium is output via an outlet 14 arranged at the end of the pump section 12.

[0048] Preferably, the modular construction is chosen, even if this modular construction is not mandatory from a patent law perspective. The pump motor 15 is then connected to the suction housing 11 by means of a flange. The pump motor 15 drives the rotor by means of a force transmission 16, often a cardan joint, which will be described in more detail later.

[0049] The pump section is formed by a stator 3, which has a rotor rotating therein.

[0050] The rotor is formed by an eccentric screw 2, which can be classified as a round thread screw. In comparison to a normal screw, the eccentric screw has a greater lead, a greater thread depth and a smaller core diameter. The stator 3 is designed to be complementary to the rotor. It forms a "worm pitch" with twice the length of the lead and an additional pitch. By this arrangement, a series of conveying chambers 17 is formed between the stationary stator 3 and the rotor rotating eccentrically therein. These conveying chambers 17 move continuously and without changing shape from their inlet side on the suction housing 11, which is formed by a horn 18, to their outlet side, i.e. the outlet 14. The medium in the conveying chambers 17 is thereby pressurized and conveyed.

[0051] The speed of movement of the conveying chambers 17 in the direction of the outlet side and thus the theoretical pump delivery can be controlled by the rotational speed of the rotor.

[0052] In addition to the number of stator windings, the tightness of the contact line between rotor and stator also influences the suction capacity of the pump and the achievable conveying pressure.

[0053] Configuration according to the invention

[0054] Figure 3 A pump section 12 is shown, which has been designed according to the Figure 2 explanation, but the eccentric screw is not shown.

[0055] In Figure 3 , the stator 3 can be clearly seen. The stator 3 consists of a stator housing 4, which is optionally divisible here, in which a stator bushing 5 is located. On its outer peripheral surface, the stator bushing 5 has no connection or at least substantially no force-fitting connection to the inner surface of the stator housing 4. The stator housing 4 thus does not prevent the compression of the stator bushing 5, which will be described in more detail below.

[0056] Also clearly visible according to the drawing is that the stator bushing 5 protrudes from the stator housing 4 on the left side and forms a protrusion 19 there. This protrusion 19 is located at least substantially radially within the movable support tube 6. A generally smaller part is located within the fixed support tube 7.

[0057] The compression device 8 is connected to the support tubes 6 and 7. This includes a first radial flange 20 of the stationary support tube 7 and a second radial flange 21 of the movable support tube 6. The first radial flange 20 can be fastened to the stationary support tube 7 or directly to the stator housing 4. The second radial flange 21 is usually connected, preferably welded, to the movable support tube 6. The distance between the two radial flanges 20 and 21 is adjustable. Ideally, a traction mechanism 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 screw. The second radial flange 21 can have a through-hole through which the corresponding screw passes in order to be screwed on the other side with an actuating nut 23.

[0058] It is worth noting at this point that the radial flange 21, as such or by means of a ring mechanism screwed in, can also exert a pressure which here acts from left to right in the region of the protrusion 19 on the free front annular surface of the stator bushing 5. This design is optional.

[0059] In Figure 3 and Figure 4 the special position of the movable support tube according to the invention can be seen very clearly. The stator bushing 5 has a recess 25 on its outer peripheral surface which in many cases is designed as a pure annular cylinder. This recess 25 has mainly a straight cylindrical base and an end face wall extending radially outwards at right angles thereto. Preferably, the recess 25 is long and flat. The amount by which the base extends along the longitudinal axis L is preferably at least 7.5 times greater, better still at least 10 times greater, than the amount by which each end face wall of the recess 25 extends radially outwards.

[0060] The actual tube portion of the movable support tube 6 is placed in this recess 25, so that in the ideal case there is no transition to the outer peripheral surface of the stator bushing 5 in the sense of a perceptible, i.e. substantial, diameter jump.

[0061] Ideally, the movable support tube 6 is vulcanized into the stator bushing 5 or fastened thereto by adhesion or in the broadest sense "welding", i.e. - preferably over the entire base of the recess 25 - a shear-resistant connection exists between the inner surface of the circumference of the movable support tube and the elastomer of the stator bushing 5 which rests on it from the inside, which goes beyond a pure frictional connection. It can be useful to implement this shear-resistant connection over a particularly long length, for example over a length parallel to the longitudinal axis L which is at least 1 / 2 or better still even at least 2 / 3 of the outer diameter of the stator bushing.

[0062] Optionally, there is Figure 4The fixed support tube 7 is visible in the middle. It is particularly advantageous that the circular cross section is chosen for better uniformity when the support tube 6 is compressed, while the stator housing 4 has a polygonal cross section. This difference makes it possible to catch the fixed support tube 7, which also usually has a circular cross section.

[0063] When returning to Figure 3 , it is easy to understand how the compression device 8 works.

[0064] By tightening the actuating nut 23 and loosening the locking nut 24, which can have been done beforehand, the first radial flange 20 and the second radial flange 21 are moved towards each other. Since the movable support tube 6 is connected to the second radial flange 21 in a force-fitting manner, it is inserted into the fixed support tube 7 in a direction parallel to the longitudinal axis L. It is also worth noting that the stator bushing is not usually lying flat anywhere, but is fully supported everywhere in the radially outward direction. In this respect, it also differs from the earlier solutions shown in Figure 1 .

[0065] The movable support tube 6 thus transfers shear stress on its inner surface to the stator bushing 5 located inside it. Inside the stator bushing 5, this shear stress propagates into the area of the stator housing 4. However, the end of the stator bushing 5 facing away is clamped firmly and thus cannot move in the direction of the longitudinal axis L. Therefore, a lateral elongation occurs in the stator bushing in the area of the stator housing 4. In the radially outward direction, this lateral elongation is prevented by the stator housing 4. Therefore, a significant lateral elongation occurs in the radially inward direction. The worm pitch is thus contracted. The shear-resistant connection between the inner surface of the movable support tube 6 and the part of the stator bushing 5 located therein, which has been described above, allows the force to be introduced into the stator bushing 5 very uniformly.

[0066] Here, at least a part of the worm pitch is usually located in the area below the movable support tube 6, which has the largest net diameter and thus forms an area in which the wall of the stator bushing is very thin. However, even this thin section does not collapse when compressed, since the collapse is prevented by the connection to the inner surface of the movable support tube 6.

[0067] As part of the compression, it is also possible to introduce a force through the stator bushing 5 in the area of the free end of the protrusion 19. This is usually even the main part of the force introduced for compression.

[0068] It should also be noted that the effect of the worm pitch contraction can also be reversed. That is, by virtue of its corresponding design, the pulling force can also be transmitted to the stator bushing 5 via the compression device 8 by means of the movable support tube 6. Here, the said shear stress connection between the inner surface of the movable support tube 6 and the portion of the stator bushing 5 located therein has a particularly advantageous effect. This is because the shear stress can be introduced very well, which leads to a high tensile stress in the further course of the stator bushing 5.

[0069] Reference signs

[0070] 1 eccentric screw pump

[0071] 2 eccentric screw or screw conveyor

[0072] 3 stator

[0073] 4 stator housing

[0074] 5 stator bushing

[0075] 6 movable support tube

[0076] 7 fixed support tube

[0077] 8 compression device

[0078] 9 protrusion

[0079] 10 inner cone

[0080] 11 suction housing

[0081] 12 pump section

[0082] 13 inlet for the medium to be conveyed

[0083] 14 outlet for the medium to be conveyed

[0084] 15 pump motor

[0085] 16 force transmission train

[0086] 17 conveying chamber

[0087] 18 horn

[0088] 19 protrusion

[0089] 20 first radial flange of the fixed support tube

[0090] 21 second radial flange of the movable support tube

[0091] 22 traction mechanism, preferably in the form of a screw

[0092] 23 actuating nut

[0093] 24 lock nut

[0094] 25 recess

[0095] 26 annular means

[0096] L longitudinal axis of the eccentric screw pump or of the eccentric screw and stator

[0097] D pressure

[0098] S front annular surface

[0099] H area in which, in variants not according to the application, the lying of the stator bushing can be observed

Claims

1. An eccentric screw pump (1) having a rotor forming a screw conveyor (2) and a stator (3) forming a worm pitch, wherein, during conveying operation, the rotor rotates in the stator, wherein, The stator (3) includes a single-piece or multi-piece stator housing (4), a stator bushing (5) made of elastic material is located in the stator housing, the stator bushing forming a worm gear pitch, wherein the stator bushing (5) forms a protrusion (19) at least on one side along the longitudinal axis (L) of the pump, the protrusion (19) extending from the stator housing (4) to form a free force-introducing surface, through which a force can be applied to the stator bushing ( 5) Compressed into the stator housing (4) to cause a lateral elongation of the stator bushing (5) therein, which results in a contraction of the worm pitch, wherein the protrusion (19) is surrounded by a movable support tube (6) which is movable relative to the stator housing (4) in a direction along the longitudinal axis (L) of the stator housing (4) for the purpose of compression, characterized in that the movable support tube (6) is arranged in a recess of the stator bushing (5).

2. An eccentric screw pump (1) having a rotor forming a screw conveyor (2) and a stator (3) forming a worm gear pitch, wherein, during conveying operation, the rotor rotates in the stator, wherein, The stator (3) includes a single-piece or multi-piece stator housing (4), and a stator bushing (5) made of elastic material is located in the stator housing. The stator bushing forms a worm gear pitch, wherein the stator bushing (5) forms a protrusion (19) at least on one side along the longitudinal axis (L) of the pump. The protrusion (19) extends from the stator housing (4) to form a free force-introducing surface through which a force can be applied to compress the stator bushing (5) into the stator housing (4) to produce the desired effect. The stator bushing (5) is laterally elongated, which causes a contraction in the worm pitch, wherein the protrusion (19) is surrounded by a movable support tube (6), which is movable relative to the stator housing (4) in a direction along the longitudinal axis (L) of the stator housing (4) for compression purposes, characterized in that the movable support tube (6) is connected to the stator bushing (5) in a material-fit manner on its inner sheath surface, such that the compressive force can be transmitted to the stator bushing (5) by generating shear stress through the connection.

3. The eccentric screw pump (1) according to claim 1, characterized in that, The movable support tube (6) is connected to the stator bushing (5) in a material-fitting manner on its inner sheath surface, so that compressive force can be transmitted to the stator bushing (5) by generating shear stress through the connection.

4. The eccentric screw pump (1) according to any one of claims 1 to 3, characterized in that, The movable support tube (6) is inserted into the stator housing (4) itself for compression, and the outer diameter of the movable support tube (6) is smaller than the minimum inner diameter of the section of the stator housing (4) that can be inserted.

5. The eccentric screw pump according to any one of claims 1 to 3, characterized in that, The movable support tube (6) is inserted into the fixed support tube (7) fastened to the end face of the stator housing (4) for compression, and the outer diameter of the movable support tube (6) is smaller than the minimum inner diameter of the fixed support tube (7) that can be inserted.

6. The eccentric screw pump (1) according to claim 5, characterized in that, The fixed support pipe (7) has a first radial flange (20), and one or more traction mechanisms (22) engage with the first radial flange (20).

7. The eccentric screw pump (1) according to claim 6, characterized in that, The traction mechanism (22) is designed as a screw.

8. The eccentric screw pump (1) according to any one of claims 1 to 3, characterized in that, The movable support tube (6) has a second radial flange (21), and one or more compression mechanisms engage with the second radial flange (21).

9. The eccentric screw pump (1) according to claim 8, characterized in that, One or more compression mechanisms engage with the second radial flange (21) in the form of a traction mechanism (22).

10. The eccentric screw pump (1) according to claim 9, characterized in that, The traction mechanism (22) is designed as a screw.

11. The eccentric screw pump (1) according to claim 8, characterized in that, The second radial flange (21) is designed such that, during compression, the second radial flange (21) also introduces force on the free end face of the protrusion (19) via the front annular surface (S).

12. A method for reducing the pitch of a worm gear, the worm gear pitch being formed by an elastic stator bushing (5) of an eccentric screw pump (1), the reduction being achieved by compression of the stator bushing (5), the stator bushing (5) being radially supported on its outer circumference via a stator housing (4) in the direction of the stator longitudinal axis (L), wherein, A compressive force is applied to the protrusion (19), which is formed on the stator bushing (5) extending from the stator housing (4) at its end face. The protrusion (19) is characterized in that the compressive force is applied to the protrusion (19) at least in part by means of shear stress, and the protrusion (19) engages with one of its circumferential surfaces.

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