EP3767105B1 - Stator for a helical gear pump - Google Patents

Description

The invention relates to a stator for an eccentric screw pump having a rotor.

Stators of the generic type have a continuous and coiled pump cavity formed by a lining made of an elastomer, in which an eccentrically mounted rotor rotates. Due to the eccentric mounting of the rotor, chambers are formed between it and the coiled lining as it rotates, which in a sense migrate from a suction side of the eccentric screw pump to its pressure side, so that a medium is pushed or conveyed in the axial direction through the pump or the stator .

Such stators can be used in eccentric screw pumps, in particular for pumping media such as plaster, mortar, oil, etc. In order to improve a delivery rate with stators of this type, according to, for example EP 0 358 789 A1 , DE 195 31 318 A1 , EP 1 522 729 B2 or DE 41 11 166 C2 provided to taper the lining conically starting from the suction side towards the pressure side. As a result, the elastic resilience of the lining is adapted to the conveying pressure, which increases continuously in the axial direction or conveying direction. Due to the conical shape of the stator, an adapted transition piece must also be used for the connection to the next component in the eccentric screw pump if the wall thickness of the jacket remains the same over the entire stator and this also adapts to the conical taper.

In addition, with such a conical taper, the forces acting on the lining are increased by the medium. If the medium has, for example, coarse material components, for example rocks, then these stress the lining more in an elastically less flexible and already tapered area, so that the lining wears faster overall.

The object of the invention is therefore to provide a stator with increased delivery capacity, which is easy to manufacture, has a high level of durability and can be easily integrated into an eccentric screw pump.

According to the invention it is provided that an average wall thickness of the lining of the stator starting from an end wall thickness, which is present in the area of a preferably cylindrical suction side of the stator, continuously, ie according to a continuous function of any degree, in the axial direction up to a lowest average Wall thickness is reduced, and that the mean wall thickness increases again at least in areas after reaching the lowest mean wall thickness, so that a preferably cylindrical widening is formed in the lining up to a pressure side of the stator. This means that the mean wall thickness of the lining, starting from the lowest mean wall thickness, increases again immediately after it has been reached, or after it has been reached, initially remains approximately constant over a certain range and only then increases again in order to develop the expansion in the lining .

This advantageously means that, in addition to adapting the mean wall thickness of the lining in the axial direction to the pump pressures acting in the pump cavity of the stator, a suitable transition can be created on the pressure side. The expansion allowed advantageously also a connection, for example via a conventional flange, to the next component of the eccentric screw pump. For example, the wall thickness can also be set as it prevails on the suction side, so that advantageously the same connections, e.g. flanges, can be used for both sides of the stator if the end wall thicknesses on the pressure side and on the suction side roughly match.

In addition, the lining becomes more flexible again towards the pressure side, as a result of which the conveyed medium, which is normally under high pressure on the pressure side, can stabilize. The pressure increases only slightly in the expansion of the pressure side when the lining becomes more flexible again. In contrast to this, the pumped medium experiences an increased pressure increase in the area of the increasingly hard lining due to the continuous reduction in the mean wall thickness in an area before the expansion, which is also desired for the pumping effect in this area. In the area of the expansion, however, there is no longer any increased pressure increase and the medium is thus stabilized. In the stator according to the invention, overall an optimized transfer of the conveyed medium into the next component of the eccentric screw pump can take place.

The structure of the stator can also achieve an improved retention function if, for example, the eccentric screw pump is switched off. The pumped medium can flow back in the pump cavity if a pressure difference between adjacent chambers in the pump cavity becomes too high. If a harder lining is chosen, the backflow only occurs at higher pressure differences between the chambers. The lining, which becomes harder in the axial direction, prevents the conveyed medium from increasing as the pressure increases at the same time there is also a backflow, ie higher pressure differences are possible before the conveyed medium flows back.

• im Bereich der Saugseite des Stators eine Vormischzone ausbildet zum Homogenisieren und/oder Zerkleinern des zu fördernden Mediums,
• im Bereich der Druckseite des Stators in der Aufweitung eine Stabilisierungszone ausbildet zum Stabilisieren und zum sanften Überleiten des geförderten Mediums in der Exzenterschneckenpumpe, und
• zwischen der Vormischzone und der Stabilisierungszone eine Hochdruckzone mit verminderter Rückströmung des Mediums ausbildet zum Erhöhen des Druckes im Pumpenhohlraum im Betrieb der Exzenterschneckenpumpe aufgrund der in axialer Richtung zumindest bereichsweise kontinuierlich abnehmenden mittleren Wandstärke und damit der zunehmenden Härte der Auskleidung, wobei der Druck in der Hochdruckzone gegenüber der Vormischzone und der Stabilisierungszone zumindest bereichsweise mit einem höheren Druckgradienten angepasst wird.

With such a structure, it can preferably also be achieved that the stator due to the axial course of the mean wall thickness of the lining

• Forms a premixing zone in the area of the suction side of the stator for homogenizing and / or comminuting the medium to be conveyed,
• in the area of the pressure side of the stator in the widening a stabilization zone is formed for stabilization and for the gentle transfer of the conveyed medium in the eccentric screw pump, and
• Between the premixing zone and the stabilization zone, a high pressure zone with reduced backflow of the medium is formed to increase the pressure in the pump cavity during operation of the eccentric screw pump due to the mean wall thickness, which is continuously decreasing in the axial direction, at least in some areas, and thus the increasing hardness of the lining, with the pressure in the high pressure zone being opposite the premixing zone and the stabilization zone is at least partially adapted with a higher pressure gradient.

The stator is therefore divided into different axially spaced zones by the targeted course of the mean wall thickness, the transition preferably being defined by the mean wall thickness of the lining remaining constant at least in the premixing zone and / or in the stabilization zone. As a result, when it enters the stator and / or when it exits the stator, the conveyed medium can advantageously be adapted to the changed, tapering shape of the lining in the high-pressure zone or the resulting changed delivery rate of the stator.

The mean wall thickness can also be constant in parts of the high pressure zone. For example, it can be provided that the mean wall thickness of the lining in a first high pressure area of the high pressure zone decreases continuously in the axial direction down to the lowest mean wall thickness, the first high pressure area adjoining the premixing zone, and approximately constant in a second high pressure area of the high pressure zone the smallest mean wall thickness remains.

A zone is therefore advantageously available to the medium in which it can be homogenized or comminuted on the suction side and / or stabilized on the pressure side. Depending on the application and the conveyed medium, the respective zone can be set in a targeted manner by selecting a corresponding axial extent or an axial width as well as the wall thickness of the lining in the respective zone. The medium can then be "prepared" in the respective zone for the next area in the stator or in the eccentric screw pump.

For example, the lining in the high-pressure zone is less stressed when the flexibility decreases, since the medium has already been comminuted or homogenized in the premixing zone. The lining in the high pressure zone therefore wears less. The medium is stabilized in the stabilization zone so that a smoother transition or a smoother exit from the stator can be achieved.

For the tapering of the lining, it is preferably provided that the lining of the stator tapers conically in the axial direction, with the mean wall thickness of the lining starting from the end mean wall thickness in the axial direction at least in some areas, for example in the high pressure zone or in parts of the high pressure zone, decreases linearly in the direction of the pressure side or also following a non-linear function. This results in a linear taper that is easy to manufacture or a taper according to a non-linear function is created, which is preferably formed in that the outer surface of the lining tapers linearly or following a non-linear function, preferably with a constant pump diameter in the pump cavity.

Alternatively, it can also be provided that the lining of the stator tapers in the axial direction, at least in some areas, in that a contour of the outer surface of the lining, starting from the end average wall thickness to the lowest average wall thickness, more and more towards a contour of the inner surface of the lining, which is designed as a double helical thread approximates. This increases the tapering and thus the adaptation of the average wall thickness to the pressure acting in the pump cavity, the tapering then also being visible from the outside, since the jacket preferably also adapts to this two-thread shape of the outer surface.

In particular, this type of tapering can be provided in the first high pressure area of the high pressure zone, so that a transition between the preferably cylindrical premixing zone and the second high pressure area of the high pressure zone can occur, with the jacket in the second high pressure area being adapted to the double shape of the outer surface. As a result, there is a transition from the cylindrical cross-section to the coiled cross-section, the mean wall thickness remaining constant in the second high-pressure area. As a result, a type of hybrid stator is formed from a cylindrical premixing zone and a coiled high pressure zone in the second high pressure area. The first high pressure area then acts as a transition with a lining that becomes correspondingly harder due to the continuous adjustment of the mean wall thickness.

In order to bring the outer surface closer to the two-thread inner surface, it is preferably provided that there is a B dimension of the lining starting from the end average wall thickness in the axial direction, at least in some areas, for example in the high pressure zone or in parts of the high pressure zone, continuously reduced in the direction of the pressure side and an A dimension of the lining remains constant at the same time. As a result, the manufacturing process according to this alternative can be simplified.

It is preferably also provided that the mean wall thickness of the lining increases abruptly or continuously after reaching the lowest mean wall thickness and possibly after remaining constant at the lowest mean wall thickness (see second high pressure area) in order to develop the pressure-side expansion. A continuous increase enables a smoother transition between the high pressure zone and the stabilization zone as well as easier production. Nevertheless, an abrupt transition can also be provided in order, for example, to promote stabilization and to keep a further increase in pressure of the conveyed medium within limits.

It is preferably also provided that an inside diameter of the jacket corresponds to an outside diameter of the lining, so that the jacket rests flat against the outer surface of the lining over the entire stator and thus assumes the conical or the coiled course corresponding to the outer surface Has constant material thickness. The jacket consists of a harder material than the lining, preferably steel. As a result, the jacket surrounding the lining can be easily adapted to the tapering shape of the lining, for example by means of a forming process.

Fig. 1

einen Stator gemäß einer ersten Ausführungsform;

Fig. 1a

eine Schnittansicht des Stators gemäß Fig. 1;

Fig. 2

einen Stator in einer weiteren Ausführungsform;

Fig. 2a, 2b

Schnittansichten des Stators gemäß Fig. 2;

Fig. 3

eine weitere Ausführungsform eines Stators.

The invention is explained in more detail below on the basis of exemplary embodiments. Show it:

Fig. 1

a stator according to a first embodiment;

Fig. 1a

a sectional view of the stator according to Fig. 1 ;

Fig. 2

a stator in a further embodiment;

Figures 2a, 2b

Sectional views of the stator according to Fig. 2 ;

Fig. 3

another embodiment of a stator.

In Figure 1 a stator 1 is provided which has a tubular jacket 2, which is preferably made from a steel tube, for example by forming. The jacket 2 encloses an elastically resilient lining 3, the inner surface 4 of which has a coiled or helical contour K4, with a double helical thread being formed. A pump cavity 5 is thereby formed in the interior of the stator 1, into which a rotor 6 ( Figure 1a ) is inserted, the rotor 6 being designed in the manner of a single-start coarse thread and possibly resting against the elastically flexible lining 3 under prestress. The eccentrically mounted rotor can rotate in the pump cavity 5.

The stator 1 has a suction side 7 and a pressure side 8, and when the stator 1 is installed together with the rotor 6 in an eccentric screw pump (not shown), the medium to be conveyed, for example mud, mortar or plaster, is placed in chambers on the suction side 7 is conveyed through the pump cavity 5 in the axial direction X to the pressure side 8 when the rotor 6 is set in rotation. The pressure in the pump cavity 5 increases steadily towards the pressure side 8, so that a lower pressure acts on the elastically flexible lining 3 on the suction side 7 than on the pressure side 8.

As executed in Figure 1 the lining 3 is designed conically on its outer surface 9, an average wall thickness W of the lining 3 from a position near the suction side 7 of the stator 1 in the axial direction X to the pressure side 8 initially continuously, ie according to a constant function, decreases. A contour K9 of the outside 9 runs from the position near the suction side 7 in the axial direction X, linearly descending at least in some areas, ie according to a linear function. This ensures that the elastic resilience of the lining 3 on the suction side 7 is higher than, for example, in the middle area of the stator 1 or in the area of the stator 1 with the smallest wall thickness WM. The lining 3 becomes harder and harder towards the pressure side 8 (approximately linear).

The conical taper can be set in such a way that a mean pump diameter DP remains the same over the entire stator 1, so that no adaptation of the rotor 6 is necessary either. For this purpose, only the outer surface 9 is tapered in the axial direction X towards the pressure side 8. In principle, however, a continuous adaptation of the mean pump diameter DP, in particular a conical taper towards the pressure side 8, can also be provided.

Starting from the smallest wall thickness WM of the lining 3, the stator 1 has a widening 10 towards the pressure side 8, through which the mean wall thickness W is increased to an end wall thickness WE. The end wall thickness WE on the suction side 7 preferably corresponds to the end wall thickness WE on the pressure side 8. As a result, the elastic flexibility and the hardness of the lining 3 on the end faces of the stator 1 are approximately identical.

According to the sectional view in Figure 1a an A dimension A and a B dimension B can be specified for the stator 1, each representing the thickness of the lining 3 in a Z-direction Z or in a Y-direction Y. In order to achieve the conical tapering of the lining 3 in the axial direction X, it is provided according to this embodiment that both the A dimension A and the B dimension B decrease continuously in the axial direction X from the corresponding position. As a result, the mean wall thickness W is continuously reduced down to the minimum wall thickness WM. Since the jacket 2 rests flat against the lining 3, preferably is adhered or vulcanized, its inner diameter D is also continuously reduced. An outer diameter E of the lining 3 thus corresponds to the inner diameter D of the jacket 2.

Due to the conical tapering of the lining 3 starting from the suction side 7 and the subsequent widening 10 on the pressure side 8, the stator 1 is divided into three zones V, H, S or areas:
In a premixing zone V, which begins on the suction side 7 of the stator 1, there is a relatively low pressure in the pump cavity 5 . This premixing zone V is therefore suitable for crushing or pre-compacting a coarse-grained medium, for example mortar, plaster or sludge, which may still contain coarse material components, for example rocks, and mixing it evenly into a homogeneous medium .

Due to the high elastic resilience in this premixing zone V, the forces acting during the comminution of these coarse material constituents can be absorbed by the lining 3 without the lining 3 being damaged significantly beyond normal wear. This is supported by the fact that in the premixing zone V there are still low pressures in the pump cavity 5 and these are only very different increase slightly. This ensures optimal mixing.

The mean wall thickness W in the premixing zone V is constant at the end wall thickness WE. From a certain position in the axial direction X, the premixing zone Z changes into a high pressure zone H, this being initiated by a reduction in the mean wall thickness W of the lining 3. The reduction in the mean wall thickness W reduces the elastic resilience of the lining 3. At the same time, the pressure in the pump interior 5 increases in the axial direction X, so that the conveyed medium also acts on the lining 3 with higher forces. However, since the conveyed medium has already been comminuted and homogenized in the premixing zone V, the lining 3 in the high-pressure zone H is less stressed because the material constituents of the medium tend to have smaller particle sizes.

At the same time, due to the lower elastic resilience of the lining 3 in the high pressure zone H or decreasing in the axial direction X, a higher delivery rate can be achieved, since the material of the lining 3 has an ever increasing resistance to a backflow over the sealing line between the rotor 6 and the lining 3 of the stator 1 provides for the medium to be conveyed. The pressure increases more in the high pressure zone H due to the decreasing mean wall thickness W or the increasing hardness of the lining 3 than in the premixing zone V. elastic resilience of the lining 3 a crushing of coarse material constituents still present. However, these occur only sporadically and have decreased very sharply up to the minimum wall thickness WM, so that one that goes beyond normal wear and tear Damage to the lining 3 can be largely avoided.

The backflow behavior of the stator 1 can be improved by the conical structure of the high pressure zone H. The conveyed medium can flow back if a pressure difference between adjacent chambers in the pump cavity 5 becomes too high. If a harder lining 3 is selected, the backflow only occurs at higher pressure differences between the chambers. The lining 3, which becomes harder in the axial direction X, also prevents backflow as the pressure of the pumped medium in the pump cavity 5 increases, i.e. higher pressure differences are possible before the pumped medium flows back.

Starting from the minimum wall thickness WM, a stabilization zone S follows in the axial direction X in the stator 1 and is located in the area of the pressure side 8 or the widening 10. In the stabilization zone S, the mean wall thickness W of the lining 3 is increased again and then runs constant, so that the elastic flexibility of the lining 3 increases again or the hardness of the lining 3 decreases again. As a result, as in the premixing zone V, there is a slight pressure build-up in the pump cavity 5 on the outlet side.

In the transition area to the next component of the eccentric screw pump, i.e. on the pressure side 8 of the stator 1, there is reduced wear and the pumped medium is stabilized before the transition to the next component.

Furthermore, by increasing the average wall thickness W to the end wall thickness WE in the area of the widening 10, a connection, for example via a flange, to the next component of the eccentric screw pump can be established to be provided. On the suction side 7 and the pressure side 8 of the stator 1, with the same end-side wall thicknesses WE, identical or standardized flanges or connections can advantageously be used. Due to the external shape of the stator 1, it can be clearly recognized in which orientation the stator 1 is to be mounted in the eccentric screw pump.

According to a further embodiment of the stator 1, which is shown in FIG Figure 2 is shown, the reduction in the mean wall thickness W in the axial direction X is achieved by continuously adapting the outer surface 9 of the lining 3 to the coiled inner surface 4 of the lining 3. The outer surface 9 accordingly also forms a two-start coarse thread from a certain axial position. Since the jacket 2 rests flat against the outer surface 9 of the lining 3 or is adhered or vulcanized to it, the jacket 2 also follows the shape of the double helical thread of the inner surface 4 from a certain axial position.

This also divides the stator 1 in the axial direction X into a premixing zone V, a high pressure zone H and a stabilization zone S, with an approximately constant average wall thickness W, which corresponds to the end average wall thickness WE, being formed in the premixing zone V. As a result, a high elastic resilience of the lining 3 is achieved over a certain area, whereby the medium provided via the suction side 7 can be comminuted or mixed or homogenized without damaging the lining 3 significantly beyond normal wear.

From a certain axial position, the mean wall thickness W of the lining 3 decreases continuously (dotted line in Fig. 2 ), whereby, as already mentioned, this is achieved in that the outer surface 9 of the lining 3 is attached to the double-helix thread formed by the inner surface 4 is continuously adjusted. This also causes a continuous tapering of the lining 3 in the axial direction starting from the suction side 7 in the direction of the pressure side 8. In contrast to the embodiment in Figure 1 However, the reduction in the mean wall thickness W or the increase in hardness takes place according to a different, steeper course, which increases the pumping effect even more, since there is an increased increase in pressure.

Also in the embodiment according to Figure 2 a high pressure zone H is formed by the continuous tapering of the lining in the axial direction X, in which the elastic resilience of the lining 3 continuously decreases while the pressure in the pump cavity 5 increases at the same time take place, with the liner 3 being prevented from being damaged due to the even lower pressure in the pump cavity 5. In the further axial course, the conveyed medium is further homogenized, so that in the area of the minimum wall thickness, low-wear conveyance can be achieved with maximum conveying capacity at the same time.

Starting from the lowest wall thickness WM, the mean wall thickness W increases in the embodiment according to FIG Figure 2 in the area of the widening 10 and then remains constant, so that a stabilization zone S is also formed here. In this, the pressure in the pump cavity 5 increases only slightly due to the low flexibility, so that a low-wear and smooth transition with a stabilized medium to the next component in the eccentric screw pump can be provided. Here, too, the end wall thickness WE on the pressure side 8 corresponds to the end wall thickness WE on the suction side 7 in order to create an identical connection on both end sides of the stator 1.

According to the sectional views in Figures 2a and 2b corresponding to the embodiment in Fig. 2 are assigned, it can be seen that the A dimension A and the B dimension B are adapted differently to form the continuous tapering of the lining 3 in the axial direction X. Figure 2a shows the section through the stator 1 in the premixing zone V, the A dimension A and the B dimension B at this axial position with the dimensions A, B in Figure 1a essentially coincide with the first embodiment. In Figure 2b the section through the stator 1 in the high pressure zone H, ie after the taper, is shown. The A dimension A is compared to the situation in the premixing zone V (see Sect. Figure 2a ) stayed the same. Only the B dimension B has decreased compared to the situation in the premixing zone V. The continuous tapering of the lining 3 in the axial direction is thus achieved solely by adjusting the B dimension.

The semiaxes HA1, HA2 of the jacket 2 and the lining 3 behave in a corresponding manner. A first semiaxis HA1 pointing in the Z direction remains constant in the axial direction X, while a second semiaxis pointing in the Y direction is constant HA2 is continuously tapered. Since the jacket 2 rests flat against the lining 3, the semiaxes HA1, HA2 of the jacket 2 (inner surface) and the lining 3 (outer surface) correspond.

This also results in the two-thread coiled outer contour K9 of the stator 1, which is visible from the outside due to the simultaneous adaptation of the shape of the jacket 2 to the outer surface 9 of the lining 3. With this configuration, the subdivision of the stator 1 into different zones V, H, S can still be supported, since the elastic flexibility can be optimally adapted to the pressure conditions in the pump cavity 5 due to the coiled wall thickness adjustment in the axial direction.

According to Figure 3 is compared to the embodiment in Figure 2 it is provided that a width VB of the premixing zone V in the axial direction X is increased compared to the previous embodiments. It can thus be determined in a targeted manner, for example as a function of the area of application of the stator 1, over which extent a low-wear homogenization or mixing of the conveyed medium is to take place. As a result, the amount of coarse material particles in the high pressure zone H can be reduced and the wear on the lining 3 can thus be influenced in a targeted manner. The width SB of the stabilization zone S can also be adjusted accordingly in order to give the medium a sufficiently large area for stabilization and thus to optimize the transition, for example as a function of the area of application. A width HB of the high pressure area H can also be selected accordingly in order to define the area in which the delivery rate is to be increased by a corresponding adaptation of the pressure gradient. This can be done in mutual coordination with the course of the mean wall thickness W in order to achieve a corresponding pressure increase along the conveying direction.

The widths VN, HB, SB can also in the first exemplary embodiment according to FIG Fig. 1 can be set variably accordingly.

In Fig. 3 it is also provided that the high pressure zone H is divided into two high pressure areas H1, H2. In a first high pressure area H1 of the high pressure zone H, the mean wall thickness W initially decreases continuously in the axial direction X until the lowest mean wall thickness WM is reached. In the second high pressure area H2 of the high pressure zone H, the mean wall thickness W remains approximately constant at the lowest mean wall thickness WM. Subsequently, the mean wall thickness W of the lining 3 increases again starting from the lowest mean wall thickness WM towards the pressure side 8 of the stator 1, so that the widening occurs on the pressure side 8 10 forms in the lining 3.

With this structure, a type of “hybrid stator” is provided, which is formed from a cylindrical stator in the premixing zone V and a two-flight coiled stator in the second high pressure area H2 of the high pressure zone H. The mean wall thicknesses W within the two hybrid components (cylindrical stator in the premixing zone V and two-flight helical stator in the second high-pressure area H2) are different but constant in each case. The transition between the two hybrid components is ensured by the continuous adjustment of the mean wall thickness W in the first high pressure area H1, which at the same time also adjusts the hardness of the lining as in the first design variants in Fig. 1 and Fig. 2 is achieved. The widening 10 is formed in the stabilization zone S by continuously adapting the mean wall thickness W.

List of reference symbols

1

stator

2

coat

3

lining

4th

Inner surface of the liner 3

5

Pump cavity

6th

rotor

7th

Suction side

8th

Print side

9

External surface of the liner 3

10

Widening

A.

A dimension

B.

B dimension

D.

Inner diameter of the jacket 1

E.

Liner outer diameter 3

DP

mean pump diameter

H

High pressure zone

H1

first high pressure area of high pressure zone H

H2

second high pressure area of high pressure zone H

HB

Width of the high pressure zone H

HA1

first semiaxis

HA2

second semiaxis

K4

Contour of the inner surface 4 of the lining 3

K9

Contour of the outer surface 9 of the lining 3

S.

Stabilization zone

SB

Width of the stabilization zone

V

Premix zone

VB

Width of the premixing zone V

W.

medium wall thickness

WE

end wall thickness

WM

smallest wall thickness

X

axial direction

Y Z

Y, Z direction

Claims (15)

1. Stator (1) for a helical gear pump comprising a rotor (6), said stator (1) comprising an elastically yielding lining (3) with an exterior surface (9), the lining (3) being enclosed by a rigid housing (2),

   whereby an interior surface (4) of the lining (3) forms a double-threaded high-helix screw and borders a pump cavity (5) extending in the axial direction (X) for receiving the rotor (6) of the helical gear pump,

   said lining (3) of said stator (1) tapering in the axial direction (X) at least in certain regions, whereby, to that end, an average wall thickness (W) of the lining (3), starting from a wall thickness (WE) at the end which exists in the region of a suction side (7) of the stator (1), continuously decreases in the axial direction (X) at least in certain regions until a smallest average wall thickness (WM) is reached,

   characterised in that

   the average wall thickness (W) of the lining (3) starting from the smallest average wall thickness (WM) increases again, at least in certain regions, towards a discharge side (8) of the stator (1) so that a widening (10) in the lining (3) is formed towards the discharge side (8) of the stator (1).
2. Stator (1) according to claim 1, characterised in that due to the axial progression of the average wall thickness (W) of the lining (3)

   - a premixing zone (V) is formed in the region of the suction side (7) of the stator (1) for homogenising and/or crushing the medium to be transported,

   - a stabilising zone (S) is formed in the widening (10) in the region of the discharge side (8) of the stator (1) for stabilising and smoothly transitioning the medium to be transported in the helical gear pump, and

   - a high pressure zone (H) is formed between the premixing zone (V) and the stabilising zone (S) for increasing the pressure in the pump cavity (5) in operation of the helical gear pump due to the average wall thickness (W) continuously decreasing in the axial direction (X) at least in certain regions.
3. Stator (1) according to claim 2, characterised in that the average wall thickness (W) of the lining (3) remains the same in the premixing zone (V) and/or in the stabilising zone (S).
4. Stator (1) according to claim 2 or 3, characterised in that the average wall thickness (W) of the lining (3) continuously decreases in the axial direction (X) in a first high pressure region (H1) of the high pressure zone (H) and remains approximately constant at the smallest average wall thickness (WM) in a second high pressure region (H2) of the high pressure zone (H), the first high pressure region (H1) being adjacent to the premixing zone (V).
5. Stator (1) according to one of the above claims, characterised in that the lining (3) of the stator (1) conically tapers in the axial direction (X), where, to that end, the average wall thickness (W) of the lining (3) decreases linearly or in a manner following a non-linear function in the axial direction (X) in the direction of the discharge side (8) starting from the average wall thickness (WE) at the end.
6. Stator (1) according to claim 5, characterised in that the exterior surface (9) of the lining (3) tapers linearly or in a manner following a non-linear function, so as to reach the decrease, linear or following a non-linear function, of the average wall thickness (W) starting from the average wall thickness (WE) at the end.
7. Stator (1) according to one of the claims 1 through 4, characterised in that the lining (3) of the stator (1) tapers in the axial direction (X) in that a contour (K9) of the exterior surface (9) of the lining (3) starting from the average wall thickness (WE) at the end towards the smallest average wall thickness (WM) more and more approaches a contour (K4) of the interior surface (4) of the lining (3) designed as double-threaded high-helix screw.
8. Stator (1) according to claim 7, characterised in that, starting from the average wall thickness (WE) at the end, a B measure (B) of the lining (3) continuously decreases in the axial direction (X) in the direction of the discharge side (8), while, at the same time, an A measure (A) of the lining (3) remains constant.
9. Stator (1) according to claim 7 or 8, characterised in that a first half-axis (HA1) of the housing (2) remains constant in the axial direction (X), and a second half-axis (HA2) of the housing (2) which is perpendicular in relation to the first half-axis (HA1) continuously decreases in the axial direction (X).
10. Stator (1) according to one of the claims 7 through 9, characterised in that the contours (K9) of the exterior surface (9) of the lining (3), in the region where the average wall thickness (W) corresponds to the wall thickness (WE) at the end, are approximately round, and, in the region where the average wall thickness (W) corresponds to the smallest average wall thickness (WM), run in parallel with the contours (K4) of the interior surface (4) of the lining (3) designed as double-threaded high-helix screw.
11. Stator (1) according to one of the above claims, characterised in that the average wall thickness (W) in the widening (10) at the discharge side (8) corresponds to the wall thickness (WE) at the end at the suction side (7).
12. Stator (1) according to one of the above claims, characterised in that the average wall thickness (W) of the lining (3) increases abruptly or continuously upon reaching the smallest average wall thickness (WM) so as to form the widening (10) at the discharge side.
13. Stator (1) according to one of the above claims, characterised in that an average pump diameter (DP) of the pump cavity (5) also tapers, at least in certain regions, in the axial direction (X) towards the discharge side (8), preferably in linear fashion, or remains constant in the axial direction (X) across the entire stator (1).
14. Stator (1) according to one of the above claims, characterised in that an interior diameter (D) of the housing (2) corresponds to an exterior diameter (E) of the lining (3) so that the housing (1) lies flat ion contact with the exterior surface (9) of the lining (3) across the entire stator (1), where the housing (2) is adapted by deformation to a contour (K9) of the exterior surface (9).
15. Stator (1) according to one of the above claims, characterised in that the housing (1) exhibits a material thickness that remains constant in the axial direction (X).

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