EP1522729A1 - Progressive cavity pump and stator for such a pump - Google Patents

Abstract

Eccentric spiral pump comprises an inner casing (2) made from wear-resistant elastic material in a cylindrical housing casing (1). An inner surface (3) of the inner casing or the inner casing has a rinsing direction and length on the side facing inward. A screw-like rotor (6, 8) inserted into the inner casing in a first axial position is also provided. An independent claim is also included for an elastomer stator for the eccentric spiral pump. Preferred Features: The inner casing is extended from its front in the radial or axial direction so that the front edge (24) of the rotor rotates eccentrically during the pump operation.

Description

The invention relates to an elongated delivery pump as an eccentric screw pump, consisting of a stator and a rotor. The stator can be a cylindrical outer shell, preferably made of metal, and one of this received or Hollow casing made of a "rigid-elastic" material with helical Have inner surface. He takes a corresponding helical or helical Rotor on. Stator and rotor have the same direction slopes. Also of relevance is the Stator itself, with "rigid-elastic" lining or elastomeric jacket.

Such pumps are for various applications, for example as Feed pump for mortar mixtures or other abrasive conveying fluid known, cf. DE-B 33 04 751 (KTO) with "conical bias" between stator and rotor, stronger becoming the exit MAS.

A metallic, mostly hardened rotor is operated in one of its slope or Wendel opposite direction driven rotating. Around the rotor at promotional Operation against the stator in a constant axial position (or position) Hold must from the input side drive shaft, if necessary above the rotor upstream equipment parts, such as clutch, driver, mixing tool or the like., One corresponding axial holding force can be applied. The axial holding force arises as "Reactio" by the conveyance and forward movement of the conveyed and the Rotation of the rotor in the stator conditioned "Actio" after the rotor against the slope its helix and against the slope of the helix of the inner lining of the stator (the inner shell) of the driving device (on the input side) is rotated.

The forces involved are great, on the one hand by the operating in the pump building up discharge pressure, on the other hand by the eccentric position of the rotor and in that the rotation in the relative direction of rotation of the rotor relative to the opposite slope of the screw flights the rotor against the conveying direction loaded axially out of the stator.

In order to facilitate the entry of the medium to be pumped ("conveying fluid") into the pump, The jacket (stator) is often funnel-shaped widened on the inlet side.

It has been shown that due to the high load in the elastomer part of the stator Significant signs of wear and tear can occur, often after surprisingly short operating time, for example 2 hours or less.

Also, a flat wear along the screw thread of the rotor can occur, so a general diameter reduction, which reduces the flow rate. This can be counteracted in a longitudinally split housing shell by a retightening (contraction) of axially extending housing segments, with a corresponding reduction in the capacity must be taken into account. Instead, even with one-piece (not split) housing shell and over the pump length remaining permanent winding cross section of the rotor, the clear cross-sectional area of the stator windings from the pump inlet to the pump outlet are steadily reduced, so be provided a certain "conicity", so that the bias between elastomeric Stator jacket and hardened rotor increases towards the outlet. This makes it possible to achieve a reduction in the drive power or an approximately constant delivery rate over longer operating times, cf. to DE-B 33 04 751 .

However, it turns out in practice that even with perfectly trained and assembled and matched drive system and at Compliance with the best bias in the jacket by retightening a multi-part housing or by choosing a taper in the stator, a faster Performance degradation and / or segregation (change in consistency) of the promoting medium - even with newly replaced stator or rotor - can occur, and can not be resolved by the steps shown. This leads to Complaints and complaints on the newly used rotors or Stators that qualify as faulty or insufficient, though they All specifications were met by the manufacturer and were correct. The Cause of the sudden reduction in performance or the cyclical Consistency change of the discharge side delivery fluid (in technical language the user named "thick / thin") could not be clarified. The manufacturer had Proper stators or rotors are delivered, the user also has them properly installed in his previously (still) functioning pump device. Nevertheless, the error symptoms described, in particular an axial Gutter in the elastomer of the stator, which extends from the suction side to the pressure side of the stator rejuvenated (or widened the other way around) and initially to an inappropriate or bad rubber compound or faulty processing of the elastomeric Close inside part of the stator jacket. Such unexpected errors at Use of nearly new building components (stator or rotor) should be avoided become.

The invention is based on the object to effectively remedy larger To ensure service life, a change in the consistency of the promoted Medium to prevent and sudden loss of capacity at near mint to avoid exchanged components.

This object is achieved according to the teaching of claims 1 or 2 or 10 or 15. With the stator according to the invention itself, the solution is prepared. The Subclaims show alternative measures or advantageous additions.

At first, the described error solved by the invention appeared to be a problem the elastomer to be at the sealing points (the radially inwardly projecting Webs of the elastomeric helix) by an axially extending notch or Gutter early worn and thereby opened a channel for a return flow or a bad seal between the helical rotor and the inner surface reached the elastomeric lining of the outer shell. The cause is or was but not in the elastomer blend or its processing or incorporation, rather, it first had to be recognized where the actual cause of this occurred and was visible on a removed stator error symptom. To this described Rückflußrinne in the interior of the stator joined a close the exit end circumferentially in the stator or its elastomeric lining incised gutter.

Neither the axially extending, a backflow permitting groove, nor the Extensive notch at the outlet could be symptomatic of the User in the complaint usually described "thick-thin problem" attributed to the fact that a pump does not deliver the material promoted more consistently, but alternately promoted sections, the higher and higher had lower water content, so the thickened conveyor with little water content and the strongly segregated water content with little coarse-grained material at Outlet provided under pressure. Apparently a mistake in the area of Mixer or mortar.

Only an analysis of a larger environment of error symptoms could show that the error system passes through a chain of events that the caused demixing at the user, but not caused by a badly manufactured by the manufacturer pump or one of their replacement parts, or by the user incorrectly installed replacement parts, but by an axial Displacement of stator and rotor relative to each other. This axial displacement of the Rotor in the stator causes a at the front, pressure-side end of the rotor existing crescent-shaped end by the eccentric movement like a knife in the Engraving elastomer of the stator and how a sickle there described circumferential notch on the entire circumference of the elastomeric stator liner leaves. Due to this damaged area, it is due to high Temperatures of the elastomeric jacket (in the range of 60 ° C to 70 ° C) during operation favors that an axial piece of the elastomeric stator between the notch and the end (the pressure-side end) of the stator is deformed inwards and (fig spoken) radially collapses, whereby the Asked on the pressure side Passage cross-section is reduced. Due to the reduced passage cross-section Forms a higher pressure before the exit of the pump, which is not on the normal way out of the pump on the pressure side can escape through Dispensing of based on the outlet cross section too much subsidized conveying fluid. This too much conveyed material builds up such a high pressure before the (reduced) Outlet of the pump on that a backward flow is formed and the sealing line at the Inside the stator is damaged, leading to the suction side widening axial groove leads. So this was not on a bad quality of Elastomers as solid-elastic inner material or the inner lining of the External mantle of the stator due, but on an operational basis Overpressure situation, due to a drastic front sickle-shaped End of the helical rotor. The pressure situation described results in addition, the actually only observed consistency change at the outlet (MAS). The delivery fluid is segregated during delivery, so it forms chambers with elevated Water content and chambers with reduced water content, which the user as a poorly pumped pump considered and rated, for him first too much water and then promotes too much coarse-grained material.

The various power transmission points show in the course of permanent use a conveyor wear and tear. These cause that as a result of the beginning described axial forces (towards the drive side, ie opposite to the conveying direction) Loads on mechanical coupling points arise, which give way and not at be replaced with a rotor change. Mostly they are not all one hardened material, as it is the rotor for its flow rate. A Resulting backward displacement of the axial position of the rotor leads to a Intruding the crescent-shaped circumferential point of the rotor and the described groove-shaped, circumferential damage in the sealing elastomeric jacket. The The corresponding solution, on the other hand, seems as simple as it is convincing. Of the Area which is (or would) be damaged by the sickle-shaped edge of the rotor is omitted, without changing the pump in its actual length, ie without shorten the stator with its outer sheath or other conversions on site to have to meet. As a result, the rotor moves with its crescent-shaped edge in a free space. Thus, the edge does not receive a yielding countermeasure on which they shift the axial position of the stator with its elastomeric Inside could harm to trigger the chain of events that the user perceives as a "thick / thin" symptom.

Occur at the various power transmission wear and tear that in addition lead that the rotor due to the forces occurring counter to the conveying direction (to Drive side) is moved in the stator, so is the optimum Capacity important axial assignment of stator and rotor is no longer given.

There are various designs possible, such as the end face of the rotor end is released (claim 6 to claim 9, claim 12). These Exemptions (claim 3) should be with a "hollowing out" or a withdrawal or receding the elastomeric end portion. You can conical, comparable to the entrance side, or be chosen in other designs.

An approximately cylindrical recess of the elastomeric material, one of the helical Shape of the inner surface following, but greatly expanding radially outward shape is just as possible as any other radially outwardly widening design the relocating in operation sickle-shaped edge portion of the rotor to grant a free space.

This clearance leads to a "non-occurring damage" to the sealing Elastomer material, but at the same time ensures that a certain reduction in the effective for the pressure build-up length of the pump, when physically equal permanent length. Such a percentage reduction of pressure levels up to may be half a stage (claim 3), is compensated according to the invention by an increasing conical bias, as explained above, on the remaining pressure levels. This can be a performance of the pump and its Replacement parts are ensured, which complement each other in a combinatorial way (claim 5), but also alone by creating the appropriate design of the Elastomerstators (claim 10, claim 15) such a combinatorial effect prepared as a replacement or replacement part.

With respect to the rotor or the components driving this rotor, axially in front of Pump on the suction side MES (the motor drive, the mixing spiral and others Couplings) and axially after the pump (a pressure flange or pump end, which serve as spacers), no changes must be made. These Components can stay the same. Likewise, the way of installation of the pump can be the same remain, their axial position remain unchanged and there is no need Operating and handling instructions are given to systematically eliminate errors that occur. They are already avoided by you Occurrence is either delayed or completely prevented.

One in itself in the drive mechanisms and in front of the actual pump Error generation is caused by a change in the stator jacket on the pressure side counteracted, which is actually the one neuralgic point at which a maximum arises at pressure and must be guided and held by sealing lines, or until here should also be built. This loss of capacity can but by be compensated that a reinforced conical design of the interior to do so contributes to the remaining pressure levels along the length of the pump the Reducing the power to compensate or with a slightly reduced Power the pump to continue operating, avoiding any in operation constructive error symptom whose cause research is complex.

Creating a clearance symbolizes avoidance of a harmful Touching the crescent-shaped circumferential edge (also called peripheral edge) at a rotating movement of the rotor with respect to the elastomeric, ie compliant and softer inner coat of contrast, much stiffer Outer jacket of the stator.

The clearance symbolizes an axial extent and a radial extent for a Reduction of the strength of the elastomeric lining (claim 3, claim 4, Claim 14), or conversely spoken, a widening of the worm gear in the radial direction on a predetermined axial piece near the exit on the Pressure side of the stator.

A damaging wear can also be avoided by the clearance is understood that no pressure contact this sickle-shaped cutting Front edge arises when a (light) touching contact is allowed and not the optimum of a pure exemption or avoidance of any touch is complied with (claim 10). There will always be a time when the axial drive connection is so severely worn or shortened axially that a Crescent-shaped pressure-side end of the rotor under radial pressure touching the The elastomeric jacket will touch and cut into it, only the time until this can be delayed so far that an acceptable wear of the Drive connection no adverse conveying properties on the screw pump Has.

On the front side, a circumferential sealing web (claim 16) and axially projecting and be formed radially far outward on the elastomeric end face, in its axial Extension, however, is substantially less than 2% of the axial length of a stator slope (a screw stage or a stage of the "thread"), on the other He has a completely different task, that of the axial and radial sealing of the Connection point of the stator to the advanced functional parts, without having to the crescent-shaped end of the rotor or a geometry of the rotor functional would be related. When installing the stator, the sealing bar becomes so strong compressed until the stiffer outer sheath with a metallic pressure side Recording comes into contact (claim 9).

A reduction of the A-measure in the conveying direction in the still pressure-loaded Section of the screw pump (claim 5) refers to a respective Gradient level in terms of their beginning and end. The clear width of the Inner sheath continues to be reduced substantially uniformly per level. With this increase in the effect of conicity, that is, a more soaring Preload on the pressure-effective section, with a removal of each Preload in the exit-side Rückversetzungs-, in particular Widening portion (the feared engagement of the crescent-shaped cutting action of Rotor end), may have a length of at least 2%, preferably between 5% and 10%, be compensated up to a half step length insofar as the against crescent cutting action secured stator in a pump practically the same Achieve performance, despite a shortened axial pressure stroke, after the Outer jacket as such should remain unchanged in its physical total length.

A combination of helical formation and conical expansion of the Mantels in the output range offers a lightweight manufacturing technology (claim 8). Of the Screw shell is no longer tapered conically towards the pressure end, but slightly or more expanded, retains its basic snail shape but at and additionally receives a conically widening form. As a result, the runs Conicity in the direction of pressure in this endangered by the crescent-shaped engagement Section as "counter-conicity", in the sense of an expansion and not a rejuvenation of the clear space defined by the helical inner surface of the elastomeric Inner sheath is formed (claim 19).

This "widened conicity" can be compared with one of these "reducing conicity" or such a clear space, the axially forward, so contrary to the conveying direction (claim 8), or immediately before the beginning of Gegenkonizität ("widening" conicity) is. The expansion extends in radial Direction on an axial piece, so that both directions together one Reducing the wall thickness of the elastomeric inner lining in this axially short Reach piece on the exit side.

Instead of a paraphrase of reducing the wall thickness of the elastomeric Inner lining (elastomeric jacket), can also be due to a widening of the interior be spoken, based on the screw flights, which the helical or helical inner wall justified (claim 15).

A cylindrically designed expansion, retraction or wall thickness reduction (Claim 6, claim 16) can directly into a circumferentially extending sealing ridge on Pass over the forehead.

Also a combination of widened helix and downstream cylindrical or conical widening without helix is possible, as well as the Combination of cylindrical and conical expansion section with an axial Offset from each other (claim 6 and claim 7).

Figur 1

zeigt im Längsschnitt eine Pumpe gemäß einem Beispiel der Erfindung, mit Stator 1,2 und Rotor 6.

Figur 2a, Figur 2b

zeigen im Figurenteil 2a im Längsschnitt einen nicht konischen Stator für eine Exzenterschnecken-Pumpe, im Figurenteil 2b einen Querschnitt durch diesen Stator.

Figur 3a

zeigt einen intakten Kupplungsbereich zwischen einem eintrittsseitigen Ende 8 des Rotors 6 und einem vorgelagerten Mischwerkzeug mit Antrieb, die selbst nicht dargestellt ist.

Figur 3b

zeigt den Kupplungsbereich nach betriebs-bedingtem Verschleiß v an Eingriffsstellen.

Figur 4a, Figur 5a, Figur 6a

zeigen verschiedene Ausführungsformen des Stators gemäß weiteren Beispielen der Erfindung.

Figur 4b, Figur 5b, Figur 6b

zeigen jeweils die entsprechenden Stirnansichten am Austrittsende der Statoren.

The invention will be explained in more detail with reference to schematic drawings of several embodiments. These embodiments illustrate and supplement the invention.

FIG. 1

shows in longitudinal section a pump according to an example of the invention, with stator 1, 2 and rotor 6.

Figure 2a, Figure 2b

in the figure part 2a in longitudinal section a non-conical stator for an eccentric screw pump, in the figure part 2b a cross section through this stator.

FIG. 3a

shows an intact coupling region between an inlet end 8 of the rotor 6 and an upstream mixing tool with drive, which itself is not shown.

FIG. 3b

shows the coupling area after operational wear v at points of intervention.

Figure 4a , Figure 5a, Figure 6a

show various embodiments of the stator according to further examples of the invention.

FIG. 4b, FIG. 5b, FIG. 6b

each show the corresponding end views at the outlet end of the stators.

The eccentric screw pump has in the example, as can be seen from Figure 1, a outer cylindrical elongated housing 1 of a predetermined diameter and predetermined length. The housing may e.g. Made of steel. In the case is a hollow cylindrical shell, e.g. made of highly wear-resistant rubber or the like. Elastomer material firmly attached, the inner surface 3 a helical Contour for the formation of a double-flighted double-flighted screw channel having. At the inlet end face MES the screw channel is conical expanded, as shown at 4, to the entrance of one to the exit side MAS promoting medium as fluid, e.g. a mix of water and one Additive to facilitate. The stator can be axially slotted or multi-piece, which not shown separately.

In the inner jacket of the stator 2 is a screw 6, e.g. made of hardened steel, used. The pitch direction 7 is the same for stator and rotor. The longitudinal axis 11 the coiled rotor section is opposite to the central axis 10 of the Worm threads of the stator (the axis of rotation of the rotor) radially offset by 2 * e, resulting in the eccentricity 9 (or "e").

On the inlet side MES, the rotor 6 is extended beyond the stator start at 8 to enter the axis 10 to form a screw head 17 (Fig. 3a), over which the rotor in a the slope direction of stator and rotor driven opposite sense can be. The outlet opening 5 of the stator of the pump is on the Exit side MAS specially trained. Further details below.

A conicity k is due to a black, increasing edge area of the helical screw represented in Figure 1, which with a rising Contact pressure from the input side 4 to the output side 5 is operated to the rising discharge pressure and the sealing lines to delineate the Delivery chambers better in the elastomeric stator shell 2 form. Such Delivery chambers are in the upper portion of Figure 1 between the Screw channel (through the inner wall forming 3 of the elastomeric lining 2 formed) and the outer wall of the elongated coil 6 illustrates. Also above are the sealing lines of the chambers in cross section through the short black Overlap strip represents that do not overlap even in operation, but by yielding the elastomeric material formed by pressure Create sealing effect to the stator, as well as the continuous zone k opposite.

The axial direction is denoted by z, as the conveying direction, the two Axes 10,11 offset eccentrically and can be seen with the offset 9.

In addition to cylindrical coordinates with z for axial direction and r for the radial Direction to be worked.

Mention should be made of the length of a slope or a step, which is denoted by L1 in Figure 2a , visible on a double-flighted helix of the stator, wherein the associated inner wall 3 forms a clear interior I, in which no rotor is used in this figure.

For an optimal delivery and lowest possible wear is an accurate Adjustment and adjustment of pump parts required. This includes having an axial Position z1 of the rotor relative to the stator during pump operation as possible is maintained exactly. This requires in terms of very high, axially against the Direction of z forces acting on the rotor a very high holding force, the over the drive side must be applied to the rotor, causing wear on the the driving force transmitting parts favors. The consequences are by comparing the Figures 3a and 3b illustrates. Left is an intact coupling between the Screw head 17 and the driver 16,18 an upstream mixing tool 15 (shown only partially). Right is the same clutch in the worn State shown. The consequence of the wear is that the rotor z1 its position relative to the stator has changed by the offset 19, whereby it against the Conveying direction has migrated into the stator. The measure .DELTA.z corresponds to the Offset 19 and the wandering of the one provided with a recording Schneckenkopfs 17 in the coupling 18 on the driver 16 of the mixing tool 15, wherein in particular the locations indicated in Figure 3b with v wear of a axial removal of the non-hardened driver tool against the hardened Steel of the rotor subject.

Figures 2 show the stator in a normal training. The inlet end 4 is flared, while the worm gear is unchanged as far as in the direction perpendicular to the axis 10 extending plane 22, in which the outlet-side opening 5 'of the shell 2 is located. If, in this casing, a rotor such as the rotor 6 according to FIG. 1 is in its working position z1 and driven in rotation, it performs a considerable flexing work on the elastomer casing 2 surrounding it. At this, a crescent-shaped edge 24 is correspondingly involved in the output-side end face 25 of the rotor 6, since in the shell of Figure 2a, the worm threads continue unchanged to the mantle end face in the plane 22. The crescent-shaped end edge 24 works thereby, when the offset .DELTA.z becomes larger, in the material of the shell, and causes a corresponding notch or even a cut. These can have a radial depth of up to 3 mm and more. The jacket elastomer becomes hot, up to 60 ° to 70 ° Celsius and bulges, folds a little way inwards, and reduces the outlet cross-section of the opening 5 for the conveyed medium (conveying fluid).

It could be determined that this would increase the consistency of the subsidized Mixed cyclically changed, caused by an increased pressure on the pressure side and damage to the stator by an axially forming groove, which the coiled circumferentially extending sealing lines breaks through. Already after a short time the pump can become unusable.

As shown in FIGS. 1 and 4 to 6 , the occurrence of such damage can be effectively avoided. The outlet opening 5 of the shell 2 is widened compared to an assumed regular screw surface course and thus precludes a pressure-exerted touch the crescent-shaped end edge 24 of the rotor with the jacket 2 during operation, preferably even if the rotor due to wear of parts in the drive path (s 3) changes its predetermined regular axial position z1 relative to the stator counter to the conveying direction (by offset 19 or Δz in FIG. This creates a state as it is pictorially represented as clearance or exemption G. The crescent-shaped edge 24 shown in section as a sharp, less than 180 ° having cutting edge, does not touch the elastomeric sheath 2, but a distance is provided.

A further axial backward displacement by more than Δz according to FIG. 3b would be shown in FIG lead to an even further shifted to the right axial position of the rotor 2, connected with a possibly pending (stressful) touch, despite one expanded design of the outlet opening 5. A pure touch itself is still not harmful, just one that with additional pressure load to one Cutting effect in the elastomer leads, which then axially to the pressure side lying portion of the elastomer jacket to unwanted displacements would cause radially inward. But even this radial shift inward can at the outwardly in thickness greatly reduced elastomeric shell 2 a piece be done far, if the exit-side end face of the rotor and her obvious Cutting edge but should exert pressure on the elastomeric sheath, it is radially still set back and opens a larger cross section at the outlet MAS.

It can be seen from FIG. 1 that the area of the reduction of the jacket wall thickness 2 near the end face at the outlet MAS is not a big axial stretch, but one significant radial expansion of the outlet opening 5. To compare the lengths can be referred to a level L1 of Figure 2a as a comparison object, from which several along the total length L of the stator by the elastomeric Inner lining are provided.

For the definition of a taper k according to FIG. 1, a change in the clear dimension of the interior by indicating the percentage reduction, corresponding to one percentage reinforcement or thickening of the elastomeric sheath 2 indicated become. This indication can also extend to the A measure and the C measure according to Figure 2b as being indicated changing in the course of the z-direction. The both dimensions A and C define the largest and smallest dimension of the interior, being the largest and the smallest distance of the inner surface of the elastomeric Lining 2 in section correspond to Figure 2a.

The shape of the widening 5 of the end MAS of the stator can be different be.

In FIG. 5 , the widening 5a is conically shaped approximately in accordance with the widening at the entry end 4. The plan view of the flared end is shown in FIG. 5b.

A similar plan view results in the embodiment according to FIG. 6 , in which the widening 5b has a stepped design. This corresponds to a substantially cylindrical retraction of the elastomer wall 2 '.

The embodiment according to FIG. 4 corresponds with the widening 5c substantially to the shape shown in FIG. 1, with an additional screw portion in the z5 section. FIG. 4b shows the corresponding plan view.

Despite the seemingly identical views, Figure 5b shows a slope at the Expansion or extension 5a, Figure 6b, a cylindrical recess 5b, or a plan view of an end-face, radially directed surface and the figure 4b a Combination of a conical expansion connected with a helical Leak 5c at a conicity other than that to the expansion section of the Length z5 led (in the previously stored area and the previous levels). A Such snail-like training associated with a conical or even cylindrical design can also be described as having a conical shape is maintained, with inverted conicity, so one that a pressure load relaxed, or not created and directed to the outside, towards a thinner wall thickness 2 'of the elastomeric shell 2, or significantly and more so is widened conically, that gap distances between a crescent-shaped edge 24th according to Figure 1 and the inner surface of the expansion 5 even with a built-rotor can be seen.

All embodiments additionally have a frontally arranged circumferential web-shaped seal 21, for sealing attachment to others Intermediate sections (intake) in the transition section to the delivery hose on the Pressure side. This circumferential ridge 21 is radially far outward on the elastomeric Inner sheath arranged near the rigid housing or outer sheath 1. It extends in the axial direction by far less than 2% of a step length L1, and has none Influence on the protection of the inner wall of the elastomer lining 2 against a of Rotor caused damage. When installed, this bridge becomes practical completely compressed.

To illustrate the axial extension and the radial widening, a group of reference symbols is shown in FIG. 6a , such that the residual wall thickness 2 'which arises after introduction of a cylindrical recess 5b or a cylindrical expansion 5b preferably matches a radial thickness of the circumferential web just explained 21. The axial extent z5 of the retraction or widening, generally to be described as "clearance G" of Figure 1, shall be related to the length L1 of a step (a thread). The size of the radial expansion r5 corresponds to a shape along the axial distance z5 on which the expansion r5 takes place. It does not have to be constant, but, as can be seen from FIGS. 5a and 4a , can vary circumferentially and also assume different values in the longitudinal direction z.

In the axial direction z5 the widening or widening should be to the exemption of the Mantels from the end edge of the rotor at least 2%, preferably above 3%, or 5% to 10% of a stage L1 of the stator screw 3 amount. For better understanding is shown in Figure 2 such a stage. At a step length of e.g. 110 mm the lower limit of the extension is about 2 mm to 4 mm, but may also be 5 mm to 11 mm and more, up to half a step.

The occurring reduction of the pump-effective length of the stator is compensated by a corresponding increase in the bias voltage k between the rotor and stator. The conicity can be seen in the sectional view through inclined connecting lines 21 in FIGS. 5a, 6a . They correspond to the illustrated conicity k, which ensures an increased bias to the pressure side. The change in taper takes place in an advantageous manner by continuous change of the A-measure. The percentage reduction of this level per level should be at least 0.4%.

For a better understanding below are some definitions used explained. Thus, the number of stages of the stator is equal to stator length divided by the slope its worm threads. The conicity of the stator screw results from the difference the C and A measures entry MES and exit MAS, with the reduction evenly distributed over the number of gradients. The mean of the A-measure per level results from the A-measure at the entrance of the level diminished by the A-measure at the exit of the stage. In this sense, here is below the percentage Reduction of the A-measure per step The A-measure-difference per step multiplied by 100 and divided by the A-measure understood at the entrance of the stage.

As is apparent from both FIG. 1 and FIGS. 5a and 6a, this reduces the A dimension in the conveying direction, ie in the direction of the stator output MAS.

A segregation, ie a consistency change of the conveyed medium, as well How an early wear of the pump parts can be done in a very simple way and with the Possibility of avoiding an accepted reduction of the To compensate pump performance.

Claims (19)

Eccentric screw pump with an inner shell (2) made of wear-resistant and elastic material in a one- or multi-part cylindrical housing shell (1); wherein an inner surface (3) of the shell (2) or the inner shell (2) on its inwardly facing side (3) is helical shaped with a predetermined pitch direction and length; with a helically or helically shaped rotor (6, 8) with the same pitch direction (7) inserted into the shell in a first axial position (z1) and with radial eccentricity (9) and held in this position on the drive side (15, 16) like the stator (2); wherein an outlet opening (5) of the stator (2) is widened from its front end on a portion of the axial conveying length radially outwards so that - in pumping operation rotating - front edge (24) of the near the outlet opening located rotor end (23) - preferably also with a wear-related axial displacement (1 9, Δz) of the rotor - with respect to the inner surface (3) of the stator without contact or free (G) can rotate. Eccentric screw pump with a stator of a one-piece cylindrical housing (1) and an inner shell (2) made of elastomeric material, whose inner surface (3) around the longitudinal axis (10; z) helically or helically extending, and with a helical, elongated rotor (6) which is arranged with its central axis (11) opposite the longitudinal axis (10) of the stator by a predetermined amount (9, e) radially offset in a given axial position (z) relative to the stator in this, the same pitch direction as the inner casing has - and the pitch direction of the inner surface (3) of the inner shell opposite - rotatably driven and from a drive side (8) in the given axial position (z) is held; in which the inner casing (2) is hollowed out or widened by its exit-side end (22) both in the radial and in the axial direction to such an extent that an exit-side end edge (24) of the rotor (6) during a pump operation - the inner surface (3) of the jacket (2) not loading - eccentrically rotated; to compensate for a loss of power over a distributed over the remaining length of the stator decrease of a largest clearance (A-dimension) of the inner surface (3) formed screw channels in the stator (2) is provided (stronger "conicity"). Eccentric screw pump according to claim 1 or 2, characterized in that by radial and axial retraction of an exit-side end face (22) of the stator shell (2) generated clearance (G) of the exit-side peripheral edge (24) of the rotor (6) axially against the conveying direction on a Length portion (z5), which is at least 2% of an axial length of a stator slope (screw stage L1), in particular above 3%, between 5% and 10% or up to a half stage. Eccentric screw pump according to claim 3, characterized in that the rear offset (cavity or widening) is dimensioned so that the clearance (G) is maintained even with a wear-related axial offset (19, .DELTA.z) of the rotor (6). Eccentric screw pump according to one of the preceding claims, characterized in that to compensate for by the backward displacement of a portion (z5) of the output-side end face (22) of the stator (2) and the consequent shortening of its at least one effective worm gear loss occurring power loss (I) a reduction of the clear width of the screw channel (A-dimension reduction) in the conveying direction per pitch (L1) of the stator shell (2) of at least 0.4% is provided; or (ii) a clear width of the inner jacket per stage (L1) is reduced by more than substantially 0.4%, whereby the inside width of the inlet opening (4) to the outlet opening (5) is reduced substantially continuously. Eccentric screw pump according to claim 1 or claim 2, wherein the Expansion has a substantially cylindrical mold portion has (5b). Eccentric screw pump according to claim 1 or claim 2 or claim 6, wherein the expansion (5) of the pressure-side opening substantially has conical mold section (5 a), in particular with an im significant conical extension as inlet cone (4) on the entrance side (MES) of the stator or the pump. Eccentric screw pump according to claim 1 or claim 2 or claim 7, wherein on a piece (z5) of the axial length near the exit side (MAS) the Helical inner surface (3) radially outward and axially forward extended to the pressure side (5c), in particular against a substantially steadily decreasing the radial dimension of the inner surface (3) said axial piece (z5) starting near the input side of the stator or the pump. Eccentric screw pump according to claim 1 or 2, wherein a pressure-side Front end of the stator carries an annular elastomeric web (21), for sealing when installing the stator, compared to a pressure-side recording. Elastomerstator for an eccentric screw pump according to one of the preceding claims, with a in a substantially cylindrical housing (1) can be introduced or arranged there jacket (2) made of elastomeric material whose inner surface (3) is helical, for receiving a in the elastomeric sheath in a predetermined axial position and with predetermined radial eccentricity (9) can be inserted under bias and on the drive side in this position sustainable (16,18) helical rotor (6); wherein an outlet opening (5; 5a, 5b, 5c) of the stator (2) is widened from its front end and the axial conveying direction or expands circumferentially to - in pumping operation - a circumferentially rotating end edge (24) at the rotor end ( 23) of an inserted rotor (6) - preferably also at an axial offset (1 9, Δz) of the rotor, relative to the stator - without contact or without significant pressure contact to the inner surface (3) of the elastomeric jacket (2) to rotate. Elastomer stator according to claim 10, wherein the cylindrical housing as circumferentially continuous shell in one piece, or with at least one axial Slot provided or provided with a plurality of axial slots is multi-part. Elastomerstator according to claim 10, wherein the extension or Expansion (5a, 5b, 5) on the pressure-side front end of the stator substantially cylindrical, conical or helical, or a combination of such Has sections. Elastomerstator according to claim 10, wherein the stator on its front side Input side has a particular conical widening (4). An elastomeric stator according to claim 10, wherein the axially-backward length (z5) the expansion (5) greater than 2%, preferably 5% and less than 50% of the axial Length (L1) of one step of the helical gear of the stator is (stator pitch). An elastomeric stator for an eccentric screw pump, comprising a substantially rigid outer shell and an inner shell (2) arranged therein made of elastomeric material that is more flexible with respect to the outer shell, whose inner surface (3) is helically or helically shaped around a longitudinal axis (10) a helical or helical, eccentric rotor (6), which in a predetermined axial position (z1) against the stator shell can be introduced into this, and is held by a drive side in its axial position (18,16,17), wherein the elastomeric inner jacket (2) from its exit-side forehead back (z5) (i) in the axial direction (ii) axially further forward of a helical inner surface (3) (to the MES inlet side) in the radial direction (r5) is reduced to provide an outlet side end edge (24) of the rotor (6) in pump operation clearance (G), and wherein the helical inner surface (3) from the front end side substantially decreases in its inner dimension substantially steadily, until before Reduced trained (r5, z5) wall thickness of the elastomeric sheath (2). Elastomerstator according to claim 15 or claim 10, wherein the output side (MAS) a circumferential web (21) is formed of elastomeric material, the axially protruding, in particular between it (21) and the beginning of the first, itself Axial one piece (Z5) extending radial expansion (R5,5b) in significant cylindrical reduction of the wall thickness of the elastomer jacket (2) is present. An elastomeric stator according to claim 16 or claim 6 (without reference to claim 1) or claim 2), wherein a residual wall thickness (2 ') of the elastomeric Inner shell in the region of the radial expansion (5b) is substantially the same has radial strength, as the output side (MAS) protruding circumferential Footbridge (21). Elastomerstator according to claim 15, wherein the inner dimension of the helical Inner surface (3) per stage decreases by at least 0.4%, up to the radial Expansion (5,5a, 5b, 5c). An elastomeric stator for an eccentric screw pump, comprising a substantially rigid outer shell and an inner shell (2) arranged therein made of elastomeric material that is more flexible with respect to the outer shell, whose inner surface (3) is helically or helically shaped around a longitudinal axis (10) a helical or helical, eccentric rotor (6) which is held in a first axial position (Z1) in the stator shell from a drive side (18,16,17), wherein the compliant inner shell (2) near its exit-side end of a Gegenkonizität (5,5a, 5b, 5c), which causes a wall thickness reduction to the front, measured against a wall thickness of the inner shell (2) before the start of Gegenkonizität.

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