WO2018162360A1

WO2018162360A1 - Eccentric spiral pump

Info

Publication number: WO2018162360A1
Application number: PCT/EP2018/055216
Authority: WO
Inventors: Norman Dicks; Oliver Stumpf
Original assignee: Seepex Gmbh
Priority date: 2017-03-07
Filing date: 2018-03-02
Publication date: 2018-09-13
Also published as: DE102017104768A1

Abstract

This is an eccentric spiral pump having - a stator (1) made from elastic or elastomeric material which defines a spiral interior chamber (11), - a stator housing (3) which surrounds the stator (1) and can be braced against the stator (1) in the radial direction, - a spiral rotor (2) which rotates eccentrically on the stator, wherein the interior chamber of the stator (1) has a setpoint geometry with a cross section which is constant over the length in the braced operating state. The pump is characterized in that, in the encompassed, pressureless state, the stator (1) has an oversize geometry which differs from the setpoint geometry with one or more oversize regions which are configured as material projections (13) beyond the setpoint geometry in the direction of the rotor and extend in each case over a limited length region.

Description

Cavity Pump

Description:

The invention relates to an eccentric screw with

a stator of elastic or elastomeric material defining a helical interior, a stator jacket surrounding the stator,

- An eccentrically rotating in the stator, helical rotor, wherein the interior of the stator has a desired geometry, wherein the desired geometry refers to the operation of the pump and thus the operating state. Such an eccentric screw pump is a pump from the group of rotary displacement pumps, which are used to convey a wide variety of media and in particular liquid media and also highly viscous liquids in various industrial sectors. The liquids to be delivered may also contain solids. The rotor is helically formed, with a relatively large pitch and flight depth and relatively small core diameter. It is arranged eccentrically in the stator or in the interior of the stator. The stator or its helical interior has a thread more than the rotor. The rotor abuts the inner surface of the stator via one or more uninterrupted sealing lines. The sealing lines separate conveying spaces from one another, which in the course of the rotation of the rotor from the suction side to the pressure side or from the inlet side to

Move the exit side (continuous). The sealing line and the sealing lines thus separate and seal the delivery chambers from each other, so that a sealing of the suction side of the stator relative to the pressure side takes place. The stator is made of an elastic material. Elastic material means in the context of the invention, in particular an elastomer, for. B. a (synthetic) rubber or a rubber mixture. Incidentally, composites of an elastic material (eg, elastomer) and another material, e.g. As metal, includes. Preferably, the stator jacket is formed as a longitudinally divided shell of a plurality of radially clamped shell segments, between which over the shell length extending separating gaps are formed. In such separation column z. B. Statorstege, which is externally connected to the rotor, z. B. are formed, which takes place via these engaging in the separating gaps Statorstege a rotationally fixed fixation of the stator in the stator jacket. The stator may be formed as a longitudinally divided stator and a plurality of stator segments, for. B. half shells, exist.

Such an eccentric screw pump with longitudinally divided stator and a longitudinally split stator shell of several shell segments is z. B. from DE 10 2008 021 920 A1. The stator jacket with its segments forms a stator clamping device, with which the stator can be tensioned in the radial direction against the rotor. In this way, the desired Vorspannmaß can be adjusted.

Eccentric screw pumps having such a structure have proven excellent in practice, and in particular against the background of the fact that the stator may be formed longitudinally divided, so that a particularly simple replacement of the stator without complete disassembly of the

Pump can be done. However, the pump is capable of further development, especially if it is to be designed for a high operating pressure. - This is where the invention starts. From DE 10 2015 104 549 A1 an eccentric screw pump is known, in which the friction forces occurring between rotor and stator are to be reduced, without jeopardizing the operational safety of the pump. For this purpose, it is proposed to provide the stator with friction-optimizing recesses. In an end region in which partially impermissible sealing lines are defined, the stator should be designed to prevent contact. This should only be claimed areas and sections of the sealing lines, which are also required for safe operation of the pump. Non-functional sealing line regions may be formed without contact between the stator and the rotor so as not to generate unnecessary friction.

The invention has for its object to provide an eccentric screw pump of the type described above, which can be used in an economical manner even at high operating pressures and can be designed for high operating pressures.

To solve this problem, the invention teaches in a generic eccentric screw pump of the type described above, that the stator in the unpressurized and preferably untensioned state has a deviating from the desired geometry oversize geometry with one or more Übermaßbereiche, as Materialvorhaltungen on the setpoint geometry out in the direction towards the rotor and thus are formed toward the interior and each extending over a limited length range. Such excess ranges are preferably dimensioned such that in the (strained)

Operating state at a predetermined operating pressure adjusts the desired geometry or at least approximates the actual geometry to the desired geometry.

The invention is initially based on the knowledge that the operation of a progressing cavity pump can be optimized when the stator is not manufactured with the ideal setpoint geometry, but with a deviating from the desired geometry oversize geometry, so that then sets the desired geometry only during operation , The desired geometry refers to the geometry that is ideal for an operating state. The desired geometry is given by the rotor shape (rotor outer geometry) and complementary to this. Does the rotor z. Example, a circular cross section, the stator interior has a desired geometry with a cross section in the form of a slot. As long as the rotor has a constant cross section over the length, the cross section (i.e., the cross sectional area and the cross sectional shape) of the stator interior is also constant over the length of the stator.

As a rule, with eccentric screw pumps there is a pressure difference between the pressure side and the suction side. The delivery pressure / internal pressure in the stator therefore increases from the suction side to the pressure side. The pressure increase is discrete (per chamber). Since the stator material is elastic, it is deformed by the internal pressure in the stator. Thus, the operating geometry deviates from the empty geometry. The deviation depends on the operating pressure. Higher pressure means greater deformation, means greater deviation between empty geometry and operating geometry. According to the invention, these considerations are already taken into account in the manufacture of the stator by the stator is equipped with an oversize geometry with corresponding Übermaßbereichen and consequently Vorvorungen material that sets the operating geometry and consequently as the operating geometry, the desired geometry.

The invention is particularly preferably used in an eccentric screw pump with a stator jacket which can be clamped (with a tensioning device) against the stator. By changing the tension of the stator, an external pressure can be exerted on the stator. By this external force, the stator is deformed. Depending on the exact design of the stator jacket and the stator clamping device, this introduction of force does not take place uniformly over the length and / or circumference of the stator. This is inventively counteracted that the stator is made in the manner described with the oversize geometry, so that a possibly uneven force application is counteracted by appropriately provided oversize.

Particularly preferably, the stator casing can be a longitudinally divided casing made up of a plurality of casing segments that can be braced in the radial direction, between which separating gaps extending over the casing length are formed. It can be z. B. to act two, three or four or more shell segments, which are distributed over the circumference. In the separation column, which are formed between the shroud segments, preferably engage Statorstege, which is externally connected to the stator, z. B. are formed as elastomeric webs. About this engaging in the separation column Statorstege a rotationally fixed fixation of the stator in the stator jacket in the clamped state. The elastomeric webs consequently absorb the torques transmitted to the stator during operation. Such a construction of the shell of several shell segments also influences the relationship between empty geometry and operating geometry and this is considered according to the invention. For the invention has now recognized that at high operating pressures or pump internal pressures there is a risk that the elastomeric material of the stator in areas of

As a result, separating gaps are pushed out, since the jacket segments or adjusting segments can not work optimally in these areas. Material pretensions are preferably provided in one or more of these areas in order to compensate for the deviations from the standard geometry or desired geometry resulting from pressure conditions (internal pressure in the stator, external pressure through the jacket) on the elastomer body. The Materialvorhaltungen are therefore provided in the areas in which a deflection of the elastomer and thus an interruption of the sealing line would be to be feared in a conventional stator. The material Vorhaltung are therefore particularly preferably provided in one or more areas of the stator, which are arranged in the assembled state in the region of the separation column. Therefore, they are particularly preferably arranged in the regions of the stator or the corresponding stator inner surface assigned to the stator webs. Overall, the stator or the stator geometry can be dimensioned taking into account an intended operating pressure such that in the clamped state and during operation at a predetermined operating pressure (essentially) sets the desired geometry, in which preferably the interior of the stator has a constant cross-section over the entire Length. In any case, the actual geometry in the operating state can be approximated to the desired geometry by such oversize regions as material pretensions. The optimal empty geometry (ie the actual geometry in the unstressed, pressureless state) can be determined for a given setpoint geometry by simulations and in particular tests, preferably taking into account a planned operating pressure.

The invention initially relates to embodiments in which the rotor has a constant over the length of the cross section (area and shape), z. B. a constant over the length of a circular cross-section. Then the

Nominal geometry of the stator interior on a constant over the length cross-section (area and shape), z. As a constant over the length slot shape. Alternatively, however, the invention also includes embodiments in which the rotor has a continuously increasing or decreasing cross-section over the length and therefore has a conical geometry. In this case, the interior of the stator in the desired geometry on a continuously increasing or decreasing over the length cross-section (area and shape). Even with such geometries, the inventive oversize geometry can be realized.

The invention is preferably realized in an eccentric screw pump, the stator casing of which consists of a longitudinally divided casing of several casing segments. Similarly, pumps may be used whose stator jacket is formed by several hold-downs as segments. However, the invention also includes embodiments in which the stator jacket is optionally formed in one piece, for. B. as a slotted tube having only a separation gap.

In addition, it is preferably provided that the stator in the manner already described as a longitudinally divided stator of a plurality of stator segments, for. B. consists of several elastomeric shells. In this case, dividing planes result between the stator segments, which for example can run parallel to the length of the stator. In accordance with the invention, the behavior of these parting planes (separating gaps in the elastomer), taking into account the factors mentioned above (internal pressure and shape of the shell segments), can be taken into account as an influencing factor from the relationship between empty geometry and operating geometry in the determination of the ideal target geometry in the operating state. There is z. For example, the possibility of excessive ranges in the areas of the parting planes / separation gaps in the elastomer

deliberately to renounce. Alternatively, the invention also includes embodiments with a one-piece stator, since such a one-piece stator can also be combined with a described longitudinally split stator jacket or also with a slotted stator jacket. In any case, the stator is preferably formed separately from the stator jacket and consequently arranged detachably or non-destructively interchangeable within the stator jacket. In principle, conceivable within the scope of the invention, however, are embodiments in which the stator is vulcanized into the stator jacket.

As already mentioned, the invention is particularly preferably used in pumps in which the stator jacket (in the radial direction) can be clamped against the stator. Alternatively, however, embodiments are also included in which a voltage of the stator is realized in another way, for. B. via intermediate elements (eg., Hydraulic cushion) or otherwise. Such possibilities of tension are z. B. from DE 10 2014 1 12 552 A1.

The oversize regions according to the invention extend as material projections only over limited length regions of the stator, so that only local elastomer precautions are provided. In the area of these local Materialvorhaltungen the cross-sectional area of the stator interior is less than the cross-sectional area in other areas without such Materialvorhaltungen and in particular less than the nominal cross-section during operation.

In a preferred embodiment, the material projections in the region of the suction side are dimensioned smaller than in the region of the pressure side, because on the suction side lower corrections are required during operation.

Particularly preferred in the context of the invention, a stator is used, which has a non-constant thickness over the circumference, d. H. the stator has a non-constant and therefore varying wall thickness along its length. Looking at such a stator, a longitudinal section in a certain peripheral region, the stator has in this longitudinal section over the length of a non-constant and consequently (periodically) varying thickness. Such stators are to be distinguished from stators with over the circumference and the length of constant wall thickness, which are also used in practice (eg as Equal Wall Stator). In such a stator, the thickness is also constant over the length viewed in a single longitudinal section. However, the material projections according to the invention are particularly preferably used in a stator with wall thickness that is not constant over the circumference, and particularly preferably in such (circumferential) areas of the stator with a small wall thickness. In this case, the invention has recognized that the problem of avoidance of the material described above in areas with large wall thickness is less critical than in areas with low wall thickness, so that particularly preferred material Vorhaltung are provided in areas of low wall thickness. The dimensioning of the material pretensions can consequently be effected as a function of the wall thickness provided at the respective location, in particular the respective circumferential position.

The invention can basically be implemented with different stator and rotor geometries. Thus, the invention is preferably used in a stator for use, the interior of which - in the desired geometry - in cross section has the shape of a slot formed by two semicircles, which are connected to each other via corresponding parallel lines. In such a stator, the wall thickness in the region of the semicircular ends of

Recess less than in the region of the straight line, so that the material Vorvorungen are preferably provided in the region of the semicircular geometry. It may be expedient to dimension the material projections in the region of the semicircles greater than in the region of the connecting straight line. However, this consideration may be combined with other considerations, so that z. B. in a region of the semicircular geometry then still dispensed with a material provision, when this area coincides with a parting plane of a longitudinally divided stator. Incidentally, in the overall design then the construction of the stator shell of z. B. several shell segments and associated therewith the possibly existing separation gaps between the shell segments considered.

In principle, the invention also covers stators with a stator geometry differing from the slot geometry described. So z. B. a slot-shaped cross-section may be provided, in which the ends are not exactly semicircular, but have a measure beyond the semicircle, so that a quasi bone-like structure is created (see, eg, EP 0 381 413 A2). In addition, geometries can be used which deviate completely from the slot shape. For example, reference is made to DE 602 107 and WO 2004/031584 A1.

The invention is not only the eccentric screw pump described, but in particular also a rotor / stator combination, which has a stator on the one hand and a rotor on the other hand, wherein the stator is made in the manner described with oversize geometry. Consequently, the rotor / stator combination is also independently protected.

In addition, the subject of the invention is a stator of such a rotor / stator combination or for such a pump. That is, the stator with oversize geometry is also placed under protection, since such a stator according to the invention can be used in practice without modifying the rotor and the other pump parts.

The stator can be made of elastomeric material z. B. by injection molding ("injection molding") or molding ("compression molding") produce. The elastic material may be z. B. an elastomer, for. B. a synthetic rubber or a rubber mixture act. But there are also composites of an elastomer and another material, eg. As metal, includes.

Overall, in the context of the invention, a geometry optimization to increase the pressure-related use limit and increase efficiency by the Elastomervorhaltungen described. Such a stator is particularly preferably used in connection with eccentric screw pumps, which on the one hand have a clampable stator jacket and, on the other hand, a longitudinally divided stator.

The pump according to the invention or the stator according to the invention can be designed for a high operating pressure or a high internal pump pressure. By the material Vorvorungen is prevented that a pressure-induced deformation leads to an interruption of the sealing line. The formation of backflows is avoided or at least significantly reduced, so that such a backflow does not have to be compensated by an increased delivery. This can z. B. suction-side overclamps and associated temperature increases can be avoided. Overall, eccentric screw pumps can be operated with a high differential pressure. Furthermore

There is an improvement in the overall efficiency, since z. B. the clamping on the suction side can be reduced by the Elastomervorhaltungen.

In the following the invention will be explained in more detail with reference to a drawing showing only one exemplary embodiment. 1, the empty geometry of the Statorinnenraums with Materialvorhaltungen invention, the subject of Fig. 3a in a modified embodiment and a schematically simplified cross-section through a stator with a material according to the invention ,

In the figures, an eccentric screw pump is shown, which has in its basic structure a stator 1 made of an elastic or elastomeric material and a rotating in the stator 1, helical rotor 2, wherein the stator 1 is surrounded by a stator shell 3. Furthermore, the pump has a pump housing 4, which (depending on the operating direction) is referred to as a suction housing. In addition, the pump has a connection piece 5, which is also referred to as a discharge nozzle. Not shown is also provided drive, the drive via a

only indicated coupling rod 6 operates on the rotor 2. The coupling rod 6 is connected via coupling joints on the one hand to the rotor 2 and on the other hand to a drive shaft, not shown, wherein of the coupling joints only the rotor-side hinge 7 is shown.

The stator 1 is formed in the illustrated embodiment as a longitudinally divided stator, so that it consists of two stator sub-shells 1 a, 1 b, which are formed in the embodiment as half shells, each covering an angle of 180 °. Longitudinal means along the stator longitudinal axis L or parallel to this. The separating cut between the partial shells consequently runs along or parallel to the longitudinal axis L.

This longitudinally divided configuration of the elastomeric stator 1 makes it possible to disassemble and assemble the stator 1 when the suction housing 4, the discharge nozzle 5 and the rotor 2 are mounted.

The stator shell 3 is also formed in the illustrated embodiment as a longitudinally divided shell and it has a plurality of shell segments 8. These may be two, three, four or more shell segments 8. In the figures, an embodiment with four sheath segments 8 is shown. This stator jacket 3 with its jacket segments 8 forms a Statorspannvorrichtung or Statoreinstellvorrichtung, with which on the one hand the longitudinally divided stator 1 fix and seal and on the other hand, a desired voltage or bias of the stator 1 can be adjusted. This adjustment can be done with known from the prior art measures. This is z. Reference is made, for example, to DE 10 2008 021 920 A1 and DE 10 2014 1 12 550 A1.

The stator 1 and its stator shells 1 a, 1 b have on the outside projecting stator bars 9, which extend over the entire stator length or at least almost the entire stator length and which z. B. externally formed on the stator 1, z. B. can be vulcanized. These stator webs 9 engage in the assembled state in separating gaps 10 and spaces between the individual shell segments 8, so that they are clamped between two adjacent shell segments 8 and thus form a rotation and absorb the torques during operation.

The stator 1 has a helical interior 1 1, in which the rotor 2 rotates. The rotor 2 is also helical, wherein the rotor 2 has a smaller number of turns than the stator 1 and as the interior 1 1 of the stator 1. In the illustrated embodiment, the rotor 2 is catchy and the stator 1 and its interior 1 1 zweigängig formed.

The rotor 2 is in operation via one or more uninterrupted sealing lines on the inner surface of the stator 1, said sealing lines separate delivery spaces from each other in the course of the rotation of the rotor from the suction side S to the pressure side D out (continuously).

The stator 1 has in this embodiment, a desired geometry, which has a constant cross-section over the length in the clamped operating state. In the illustrated embodiment, this cross-section is formed at any point of the stator slot-shaped, wherein such a slot 12a, b composed of two half circles 12a and two connecting lines 12b.

In the prior art, such a stator is manufactured with the appropriate desired geometry, d. H. the stator already has the desired geometry in the unloaded state. According to the invention, a stator 1 is now provided which, in the unstressed, pressureless state, has an oversize geometry deviating from the desired geometry with one or more oversize regions 13, which as material projections 13 extend beyond the desired geometry SG in the direction of the rotor and consequently toward the interior are formed and each extending only over a limited length range. These oversize areas, which serve as material projections 13 during operation under pressure, are shown in FIGS. 3 and 4.

The Materialvorhaltungen / Übermaßbereiche 13 are dimensioned so that approaches the actual geometry to the desired geometry SG or particularly preferably the desired geometry is set in the clamped operating condition at a given operating pressure. The embodiment according to the invention therefore has the advantage that the desired geometry SG, which is designed for optimum operation, is not set under pressure in the unassembled state, but only in the assembled and tensioned state. This is achieved by the material projections 13, which are arranged in particularly critical areas of the stator 1. Thus, material projections 13 may be arranged in particular in areas of the stator, which are assigned to one or more separating gaps 10 between two shell segments 8, so that a deflection of the elastomeric material in this area can be compensated by the material provision.

These are always only local Materialvorhaltungen 13, which do not extend over the entire length of the stator, but only over locally limited lengths. It can be seen in the figures that the

Stator 1 in the illustrated embodiment over the length has a non-constant wall thickness W1, W2. Such stators 1 with non-constant wall thickness are known from the prior art, they are widely used in practice. Particularly preferably, the material projections 13 are provided in such a stator in the range of low wall thicknesses W1. There is also the possibility that material pretensions are dimensioned larger in the area of low wall thickness W1 than in areas with greater wall thickness W2. An exemplary embodiment is shown in Fig. 3a. It can be seen that the material projections 13a are provided as a function of the orientation of the stator geometry or of the oblong hole, wherein the configuration illustrated in FIG. 3a preferably relates to the divided stator jacket illustrated in FIG. So z. B. for the position "90 °" in Fig. 3 can be seen that the Materialvorhaltungen 13 are particularly pronounced in the areas which are associated with the two top and bottom separating columns of the stator, wherein the stator jacket and the separation column in Fig. 3a These are also the areas in which the stator has a particularly small wall thickness The shape of the material provision 13 varies depending on the orientation of the oblong hole, taking into account the described specifications 2, even in the 0 ° position or the 180 ° position in the area of the semicircles and consequently to provide right and left of the oblong hole material Vorhaltung.In the specific embodiment is in these areas despite the existing separation column of the stator shell on waived such Materialvorhaltungen, since in this Berei Chen also the parting planes between the Statorhalbschalen themselves are provided, which are otherwise indicated in Fig. 3b.

Incidentally, it is shown in FIG. 3b that a plurality of material projections 13 are provided in different length regions of the stator, which, however, are optionally dimensioned differently. Thus, it can be seen that the material projections 13 are dimensioned smaller in the area of the suction side S than in the region of the pressure side D. The thickness of the material projections 13 can consequently decrease from the pressure side D to the suction side S or increase from the suction side S to the pressure side D.

Claims

claims:

1. progressing cavity pump with at least

a stator (1) of elastic material defining a helical interior (11),

a stator jacket (3) surrounding the stator (1),

- An eccentrically rotating in the stator, helical rotor (2), wherein the interior of the stator (1) has a desired geometry for operation, characterized in that the stator (1) in the unpressurized state deviating from the desired geometry oversize geometry with one or a plurality of oversize regions, which are formed as Materialvorhaltungen (13) beyond the desired geometry (SG) out in the direction of the rotor (2) back and each extending over a limited length range.

2. Eccentric screw pump according to claim 1, characterized in that the interference regions are dimensioned so that the actual geometry approaches the desired geometry in the operating state at a predetermined operating pressure, preferably the desired geometry (SG) is set.

3. Eccentric screw pump according to claim 1 or 2, characterized in that the interior of the stator (1) has a constant over the length

Has cross section or a continuously increasing or decreasing over the length of the cross section.

4. Eccentric screw pump according to one of claims 1 to 3, characterized in that the stator jacket (3) against the stator (1) can be clamped, preferably in the radial direction is clamped.

5. Eccentric screw pump according to claim 4, characterized in that the stator jacket (3) as a longitudinally divided jacket consists of several braceable in the radial direction sheath segments (8), between which over the shell length extending separating gaps (10) are formed, in which preferably Statorstege (9 ), the outside of the stator (1) connected z. B. are formed.

6. Eccentric screw pump according to claim 5, characterized in that the interference regions in one or more regions of the separating gaps (10), preferably the stator webs (9) associated regions of the stator (1) and the stator inner surface are arranged.

7. Eccentric screw pump according to one of claims 1 to 6, characterized in that the stator (1) as a longitudinally divided stator of a plurality of stator segments (1 a, 1 b), z. B. half shells, consists.

8. Eccentric screw pump according to one of claims 1 to 7, characterized in that the Materialvorhaltungen in the region of the suction side (S) are smaller than in the region of the pressure side (D) are dimensioned.

9. Eccentric screw pump according to one of claims 1 to 8, characterized in that the stator (1) over the circumference of a non-constant

Wall thickness, wherein the Materialvorhaltungen (13) in the region of low wall thickness (W1) are provided or wherein the Vorvorungen material in the region of low wall thickness (W1) are formed stronger than in the region of greater wall thickness (W2).

10. Rotor / stator combination for an eccentric screw pump according to one of claims 1 to 9, consisting of a rotor (2) and a stator (1), wherein the stator (1) in the unpressurized state deviating from the desired geometry oversize geometry with one or has a plurality of interference regions, which are formed as material Vorhaltung beyond the desired geometry in the direction of Statorinnenraums and each extending only over a limited length range.

1 1. Stator for an eccentric screw pump according to one of Claims 1 to 9, characterized in that the stator (1) has an oversize geometry deviating from the desired geometry (SG) with one or more oversize regions which are shown as material projections (13) via the desired geometry (SG) in FIG Direction are formed toward the interior and extend only over a limited length range.