EP3610154B1 - Eccentric screw pump - Google Patents

Description

The present invention relates to an eccentric screw pump, in particular a wobble pump, according to the features of the preamble of claim 1.

State of the art

Eccentric screw pumps are pumps for pumping a variety of media, especially viscous, highly viscous and abrasive media such as sludge, liquid manure, petroleum and fats. Eccentric screw pumps known from the prior art are formed from a rotor and a stator, with the rotor being accommodated in the stator and moving eccentrically in the stator. For this purpose, the stator has an inner side that is coiled in the shape of a snail. From the movement of the rotor and the mutual contact of the stator and rotor in so-called sealing areas or sealing contact surfaces, migrating conveying chambers are formed between the stator and the rotor, by means of which liquid media can be transported along the stator. The rotor performs an eccentric rotary movement around the longitudinal axis of the stator or around the longitudinal axis of the progressing cavity pump. The outer worm, ie the stator, has, for example, the form of a two-start thread, while the rotor worm has only one thread. For example, progressing cavity pumps are suitable for pumping water, petroleum and a large number of other liquids. The shape of the pumping chambers is constant during the movement of the rotor within the stator, so that the pumped medium is not squeezed. With the right design, not only fluids but also solids can be pumped with progressing cavity pumps.

The pumping efficiency of an eccentric screw pump is particularly determined by the quality of the seal between the pressure chambers or pumping chambers of the stator and the profile of the displacing rotor, which is achieved in particular by the pressure chamber walls of the stator a preload in the sealing areas or in the area of the sealing contact surfaces can be pressed elastically onto the rotor. This initial overlap is necessary in particular in order to prevent the pump pressure that builds up when the eccentric screw pump is started from pressing the elastically deformable material of the stator radially outwards. If this overlap is missing, the frictional contact between the rotor and the stator is lost as a result of the pump pressure building up. However, this is necessary in order to prevent or minimize the overflow of the pumped medium to a pumping chamber with a lower pressure. Coverage means in particular that the outer dimensions of the rotor in the contact areas or along the sealing areas or sealing contact surfaces between the rotor and stator is larger than the inner dimensions of the stator.

A large number of eccentric screw pumps are known which have an unreinforced elastomer stator. These are usually progressing cavity pumps in which the stator is surrounded by a pressure medium. For example, in such eccentric screw pumps, one end of the stator is fixed within the eccentric screw pump, while the other end of the stator is arranged so that it can swing freely. This enables the stator to absorb the eccentric movement of the rotor-stator system. Furthermore, it is provided that the stator is surrounded by the pumped medium. In this type of pump, in particular, the conveying direction is selected in such a way that the conveying medium surrounding the stator has the pressure on the pressure side of the eccentric screw pump. The stator is pressed onto the rotor by the resulting pressure difference between the pumping chambers connected to the suction side and the pressure on the pressure side on the outer surface of the stator. Comparatively high pressures can thus be generated even with very soft stators. These eccentric worm pumps are referred to in particular as wobble pumps.

There are two types of wobble pumps. Some are articulated and others are non-articulated. In the case of wobble pumps without a joint, the axis of the flexible rubber stator describes a cylinder shape, ie the stator is pushed away to the side. In the case of wobble pumps with a joint, the eccentric movement between the rotor and stator (eccentricity) is compensated for by the fact that between the stationary axis of the drive shaft and the rotor worm a cardanic joint for torque transmission is arranged. In addition, the stator is flexibly clamped at the opposite end, which allows a further cardanic degree of freedom. The eccentricity e can be compensated for by the distance between these two cardanic degrees of freedom, each with an angle α. The axis of the stator essentially describes a cone shape.

A particular disadvantage is that due to the contact between the rotor and stator with overlap along the sealing areas or sealing contact surfaces, a high breakaway torque has to be overcome when the eccentric screw pump is started up. The drive used for the rotor must be dimensioned sufficiently to apply the appropriate force for breaking loose the eccentric screw pump and accelerating the eccentric screw pump over the low speed range.

through the U.S. 2,826,152 A discloses an eccentric screw pump that includes a stator with a bellows-shaped section that is fixed to the annular web by means of the housing. A rotor is provided within the stator and is operatively connected to the stator.

through the DE 2 139 949 A1 discloses a screw pump having a housing. Inside the housing, a shaft is provided with a sleeve-like part which contacts an inner sleeve portion of a flexible sleeve. The diameters of the two frictionally engaged surfaces are chosen so that an appropriate contact can take place.

through the U.S. 2,765,114 A another eccentric screw pump with a stator-rotor system is disclosed. An annular flange is associated with the stator and is clamped between the housing parts. The stator and rotor are designed in such a way that there is a frictional and sealing effect between them.

the U.S. 6,358,027 discloses a progressive cavity pump capable of draining fluid by axial displacement of the rotor at rest to facilitate pump starting.

description

The object of the invention is to provide an eccentric screw pump, in particular a wobble pump, whose starting when it is put into operation is improved.

The above object is achieved by an eccentric screw pump, in particular a wobble pump, which comprises the features in patent claim 1. Further advantageous configurations are described by the dependent claims.

The invention relates to an eccentric screw pump, in particular a wobble pump, for pumping fluid or free-flowing conveyed media from a suction side to a pressure side. The wobble pump comprises an inner pump part and an outer pump part, for example the wobble pump comprises a rotor as the inner pump part and a stator, in particular a wobble stator, as the outer pump part. According to an alternative embodiment, it can also be provided that the outer pump part is arranged to rotate, while the inner pump part is fixed. A further embodiment can provide that the inner and the outer pump part are arranged to rotate in opposite directions.

According to the preferred embodiment, the progressive cavity pump comprises a rotor and a stator. The rotor of the wobble pump is connected to a drive shaft and thus to the drive via a joint. Alternatively, the joint can also be connected directly to the motor shaft of the drive. The stator is designed to be flexible and is fixed on one side, particularly on the suction side, to the housing of the eccentric screw pump or pump housing, while the other end of the stator is arranged in a freely swinging manner within the pump housing and can thus absorb the eccentric movement of the rotor. In the following, only wobble pumps are preferably spoken of in order to describe such an eccentric screw pump.

The stator is preferably designed to be flexible, for example it can consist of an elastomeric material. Alternatively, provision can be made for the stator to be made of a relatively rigid material, but with such thin walls that the material of the stator yields correspondingly, in particular when a force acts radially to the longitudinal axis of the stator.

During ongoing production operations, the stator and the rotor of the wobble pump are brought into contact along what are known as sealing lines or sealing areas, so that pumping chambers for the pumped medium that are separate from one another are formed. When the wobble pump is at rest, on the other hand, there is no sealing contact between the rotor and the stator, at least in some areas, in the sealing areas or in the area of the sealing contact surfaces. In contrast, the stator, which is also referred to below as the wobble stator, is at least partially and/or essentially completely surrounded by the pumped medium in an operating state of the wobble pump or working mode of the wobble pump. This causes pressure on the outer surface of the stator. The stator is pressed radially against the rotor and brought into sealing contact with it, particularly in the sealing areas or in the area of the sealing contact surfaces, as a result of which adjacent pumping chambers for the pumped medium are formed that are separate from one another.

Further advantageous configurations of the wobble pump are described below using a wobble pump in which the outer pump part is designed as a wobble stator and the inner pump part is designed as a rotor. It goes without saying It goes without saying that the person skilled in the art can apply this analogously to wobble pumps that have a static inner pump part and a rotating outer pump part or to wobble pumps in which the inner and outer pump parts are designed to rotate in opposite directions.

Provision is preferably made for play to be formed at least in regions along the sealing regions or sealing contact surfaces between the rotor and the stator when the wobble pump is in the idle state.

The flexible area on the wobblestator, which is responsible for compensating for the eccentricity, is one of the most heavily loaded areas of the wobblestator. Depending on the design of the stator clamping point, the constant bending of the wobble stator results in tensile or compressive forces or shearing forces in this area. Depending on the design of the stator clamping point, the operating torque and the axial force due to the differential pressure can also cause tensile, compressive or shear forces. The drive torque creates high shear stresses on the wobble stator. It is known that elastomers can withstand tensile and shear forces for a long time if the elastomeric material is "prestressed" or compressive stresses are introduced. It is also known that the drive torque and the resulting shear stresses increase as the delivery pressure of the pump increases. During operation of the wobble pump, which is clamped directly at the end, with medium and high pressures, pressure forces arise in addition to the loads mentioned on the flexible area of the wobble stator due to the differential pressure between the pressure and suction sides. These compressive forces serve to "preload" the material so that a long service life can be achieved in this operating state.

If wobble pumps according to the state of the art are operated with overlap between rotor and wobble stator at low pressures or in the pressureless state, this superimposed "preload" is missing, so that the elastomeric material of the wobble stator is damaged. Especially when wobble pumps start up with an overlap between the rotor and wobble stator, this leads to particularly severe material damage, since the hole breaking torque has to be endured without any "preload".

The eccentric screw pump according to the invention with a wobble stator and with play between the wobble stator and the rotor which is formed at least in certain areas in the idle state thus has flexible areas in the wobble stator which, at higher torque loads, have a higher pretension to match. Due to the play, the starting torque is approximately zero and the operating torque is also very low at small differential pressures.

For example, it is provided that the rotor has, at least in some areas, smaller external dimensions than the wobble stator has internal dimensions. Preferably, there is at least a minimum distance between the rotor and the wobble stator in the largely entire area of the sealing areas or sealing contact surfaces that separate the pumping chambers from one another during operation of the wobble pump.

According to a preferred embodiment of the invention, no sealing contact is formed between the rotor and the wobble stator in the idle state along an area that corresponds approximately between 50%-100% of the sealing areas or sealing contact surfaces. In particular, in this area there is play or a distance between the rotor and the wobble stator. In the remaining areas, there may be contact between the rotor and the wobble stator in the sealing areas or in the area of the sealing contact surfaces. It is even possible that in the remaining 0% to 50% of the sealing areas or sealing contact surfaces there is partial overlapping between the rotor and the wobble stator. This means that it would also be conceivable that in one embodiment of a wobble pump according to the present application between the rotor and the wobble stator in the sealing areas or in the area of sealing contact surfaces there is some play or distance and some overlap between the rotor and the wobble stator of the rotor-stator system is formed. This can arise in particular due to the manufacturing tolerances in the manufacture of the rotor and/or the wobble stator.

In the operating state, there is contact between the rotor and the wobble stator along the sealing areas or sealing contact surfaces. This contact is generated in particular by the pumped medium acting on the outer surface of the wobble stator. This is also referred to as overlapping, since the conveying medium acting from the outside on the outer lateral surface compresses the flexible wobble stator in such a way that it wants to assume a shape whose inner dimensions would be smaller than the outer dimensions of the rotor. As a result of the overlap, a contact, in particular a frictional contact, is established between the rotor and the wobble stator at least in regions, preferably along the entire entire length of the sealing regions or sealing contact surfaces. This frictional contact causes a physical separation from neighboring delivery chambers of the progressing cavity pump, as a result of which backflow of the delivery medium can be effectively prevented.

In one operating state, the wobble pump has a suction side with a suction-side pressure. The pumped medium entered the wobble pump via an inlet and is transported through the pumping chambers between the wobble stator and the rotor to the pressure side. Inside the wobble pump there is a first suction side pressure on the suction side and a second pressure side pressure on the pressure side.

If the pumped medium is transported through the wobble pump, the pressure builds up from the suction side towards the pressure side. In particular, when pumping the pumped medium within the rotor-stator system, pumping chambers are created which, depending on the current angle of rotation between the rotor and the wobblestator, essentially have either the suction pressure or the pumping pressure of the wobble pump. In the case of a single-stage wobble pump, you can see pumping chambers that have the suction-side pressure and other pumping chambers that have the pressure-side pressure in a snapshot. In the case of rotor-stator systems with more than one stage, there are also completely closed pumping chambers that have a pressure value between the pressure on the suction side and the pressure on the pressure side. This means that in the pressure side area of the wobblestator, there is no pressure difference between the inside of the stator and the outside of the stator. In the suction side area of the wobblestator, on the other hand, there is a pressure difference between the inside and outside of the wobblestator over a large part of the rotation angle.

The stator is pushed outwards by pressure differences between the pumping chambers; the pumped medium tries to push the stator outwards so that it can flow into a lower-pressure pumping chamber. This outward pressure is roughly the same anywhere on the stator. This radially outward pressure within the pumping chambers causes the elastomeric wobblestator to be forced radially outward. In order to compensate for the play that exists between the rotor and the wobblestator in the idle state and to prevent the radially outward-directed pressure within the pumping chambers from creating a gap in the sealing areas or in the area of the sealing contact surfaces between the rotor and the wobblestator that Transfer of pumped medium between the individual pumping chambers, and would thus allow a return flow of pumped medium to the suction side, is during operation of the wobble pump - as already described - the pressure side pressure of the pumped medium on the outer surface of the stator. The external pressure is thus applied by the pumped medium conveyed to the pressure side, so that the free end of the wobble stator, which is freely arranged within the pump housing, is flushed with the pressure on the pressure side and this results in a radial pressing of the stator on the rotor and a sealing contact between the stator and the rotor in the area of the sealing contact surfaces.

According to one embodiment of the invention, when the wobble pump is in the idle state, there is a first clearance between the rotor and the wobblestator on the suction side and a second clearance between the rotor and the wobblestator on the pressure side. In particular, the first game on the suction side is larger than the second game on the pressure side. In the idle state, there is no differential pressure between the suction side and the pressure side via the wobble pump.

Since the internal pressure of the pumped medium increases towards the pressure side, while the external pressure of the pressure medium is essentially the same everywhere on the outer lateral surface of the wobblestator, the wobblestator becomes in the area of the pressure side pressed less strongly on the rotor than on the suction side. In one embodiment, in which there is less play between the rotor and the wobblestator on the pressure side than on the suction side when at rest, this can be compensated for better so that the frictional contact between the wobblestator and the rotor along the sealing areas or sealing contact surfaces in the essentially the same everywhere. The geometry of the rotor and/or the wobblestator is therefore selected in such a way that the preload between the rotor and the wobblestator is reduced on the suction side compared to the pressure side.

For example, the clearance between the rotor and wobblestator can decrease substantially continuously along the sealing areas or sealing contact surfaces between the rotor and the wobblestator from the suction side to the pressure side in order to compensate for the pressure difference increasing from the suction side to the pressure side.

According to a further embodiment it can be provided that in the idle state of the wobble pump there is clearance between the rotor and the wobble stator on the suction side and a so-called overlap between the rotor and the wobble stator is provided on the pressure side.

In the idle state, in particular before the start of a pumping process, there is no delivery medium on the pressure side of the wobble pump, or the medium present has only a low differential pressure to the suction side of the wobble pump. Thus, no corresponding pressure acts on the outer surface of the wobble stator. At the start of the pumping process, pumped medium is conveyed to the pressure side of the wobble pump, which then presses on the outer surfaces of the wobble stator and thus causes the desired overlap or contact between the rotor and the wobble stator in the sealing areas or in the area of the sealing contact surfaces, so that the neighboring Pumping chambers are physically separated from each other.

Since at the beginning of the pumping process there is still no external pressure acting on the outer jacket surface of the wobblestator and there is therefore essentially play between the rotor and the wobblestator, such a Wobble pump no or only a very low breakaway torque, so that such a wobble pump compared to conventionally known wobble pumps in which at rest an overlap between the rotor and stator is formed, can be operated with a weaker drive.

According to one embodiment of the invention, an annular space, into which the pumped medium flows, is formed at least in regions on the pressure side between the wobble stator and the pump housing. The pumped medium in the annular space thus presses on the outer surface of the wobble stator with pressure on the pressure side.

Eccentric screw pumps with stators clamped on both sides are already known, in which pumping medium is used to generate sufficient contact pressure between the stator and rotor during operation. In this case, a dead space is formed in the supply line of the pumped medium to the stator and around the stator. Especially when pumping media that contain solid particles, contamination or the like, deposits can form within these dead spaces, which then block and/or destroy the corresponding components within a relatively short time.

Furthermore, progressing cavity pumps with stators clamped on both sides are described, which use a pressure transmission medium, the delivery medium on the pressure side and the pressure transmission medium surrounding the stator being separated by a piston or a membrane. However, this results in the disadvantage that a significantly more complicated structure is present here. In addition, a displaceable piston can also be blocked and/or destroyed by solid bodies. The same applies to flexible membranes. The problem mentioned does not exist with a wobble pump, since here the free end of the wobble stator is arranged to oscillate freely within the pumped medium on the pressure side.

In general, the following applies: the greater the pressure to be pumped by an eccentric screw pump, the greater the contact pressure that must prevail between the rotor and stator in order to ensure that the eccentric screw pump is adequately sealed guarantee. At the same time, however, these contact forces should not become too great in order to avoid unnecessary power loss and wear due to friction.

The prior art already provides a solution here, whereby the contact pressure between the rotor and a stator clamped on two sides can be adapted to the differential pressure. However, the differential pressure between the fluid on the pressure side and the interior of the stator is not the same everywhere. At the pressure-side region of the stator clamped at two ends, the pressure inside the stator clamped at two ends and the surrounding pressure of the pressure-side fluid are approximately the same. In the suction-side area of the stator clamped on two sides, the suction pressure is essentially the same inside the stator, which results in a very high pressure difference compared to the fluid on the pressure side. Due to the two-sided clamping of the stator in the pressure - and suction-side area of the stator, it is stabilized from both sides and the radial flexibility of the stator is limited in this area. A contact pressure results from the progression of the differential pressure and the radial stability of the stator. This is very uneven for stators clamped in on two sides, which leads to poor efficiency and to increased wear, particularly at specific points.

In the case of wobble pumps with a stator clamped on one side, the mobility of the stator is restricted on one side. In particular, the stator is clamped at the suction-side end and has limited mobility in this area. On the other hand, the wobble stator at the pressure-side end can move radially without restriction. If the contact pressure force is calculated as a function of differential pressure and radial stability, the wobblestator is evenly pressed against the rotor over large areas of the stator length due to an advantageous distribution of the contact pressure forces.

The one-sided clamping of the stator takes place at the end, for example directly via an annular widening formed at the free end of the stator. Alternatively, starting from the free end area, a rim can be formed, which is used to fasten the stator to the pump housing. The pressure difference of the wobble pump during operation results in a high axial force on the stator in the opposite direction to the conveying direction, ie directed away from the drive of the rotor. With end-side, one-sided clamping, especially with direct end-side Clamping or clamping at the end with a flange creates a compressive stress in the elastomer at the highly stressed bending point due to the axial force. This is advantageous for the service life of the stator material. In contrast to known wobblestators with overlapping, the clamping point of the wobblestator is less heavily loaded in the wobble pump according to the invention, since the torque is only applied when a superimposed compressive stress is formed.

In general, wobble stators are limited in their speed. In particular, wobble stators can only be operated at lower speeds, since excessive speeds result in strong vibrations that can damage parts of the wobble pump. It has been proven that clearance between the rotor and the wobble stator results in lower vibrations. A wobble pump according to the invention can thus be operated at higher speeds than conventionally known wobble pumps. This advantageous reduction in the vibrations results from the lower drive torques due to the play formed between the rotor and the wobble stator, since the oscillatable system is less strongly excited in the rotational direction. Especially with variable-speed pumps with a given output, such as solar pumps, only low differential pressures can be overcome at high speeds. This means that in the case of wobble pumps with play formed between the rotor and the wobble stator in the idle state, there is only a small drive torque. The excitation of the oscillatable system is thus even lower.

The advantage of a wobble stator described here with play in relation to the rotor also lies in the fact that such a stator can be made shorter than a stator clamped in at two ends. Since there is no second clamping point, the inlet side and the pressure connection can be accommodated in the same installation space of the pump housing. In particular, the pressure connection can be implemented at least partially in the stator area.

Furthermore, it is advantageous that such a wobble pump can be installed without any effort, since the rotor, in contrast to rotor-stator systems, Coverage, can be introduced largely without friction into the internal thread of the wobble stator.

According to one embodiment, the wobble stator can have a spiral-shaped outer contour, which corresponds in particular to the spiral-shaped inner contour. Such a wobble stator can be produced more cost-effectively, since less material is required and the vulcanization time is shortened due to the reduced wall thickness, so that production is faster and more stators can therefore be produced in a defined period of time. In addition, the stability of such a wobble stator is more uniform in the circumferential direction.

Furthermore, a joint for a wobble pump is described, which comprises a reinforced elastomer part. Various articulated shafts for eccentric screw pumps in the form of fiber or wire-reinforced plastic or elastomer bodies are known. These serve to compensate for the eccentric movement between a fixed stator and a fixed drive shaft. The disadvantage of the articulation designs known from the prior art is that a large, flexible length is required to compensate for the axial offset. As a result, there is a tendency for lateral vibrations at higher speeds. These vibrations reduce the life of the joint and result in unwanted noise and harmful vibrations. In addition, an internal support structure in the form of a shaft, a tube, a spring or a granulate is required to transmit significant pressure forces (in the conveying direction away from the motor). All of these support structures result in undesirable friction and wear in and/or on the joints.

If the joint described in more detail below is used in conjunction with a wobble pump, only an angle α must be compensated for instead of an axis offset e. Tests have shown that 0.5 to 1.5 times the outside diameter as the free bending length is sufficient to compensate for an angular offset of 1° to 2° that is common in wobble pumps. This short length of the joint results in fewer vibrations, which also leads to increased efficiency, a longer service life for the components and higher possible maximum speeds.

For particularly high loads, the advantageous vibration properties and the ability to transmit compressive forces of the short joint body, which is only subject to angular deflection, can be combined with the inner support bodies known from the prior art or with additional outer support bodies. Supporting bodies can be e.g. a sphere, granules, a spiral spring, a cylindrical shaft piece or a flexible elastomer or plastic body. The combination of support body with a lubricant is recommended here. In addition, a more or less viscous supporting liquid can also be used.

The joint comprises an at least partially movable central part which is formed from a reinforced elastomeric or plastic material. The reinforcement of the elastomer or plastic material is preferably formed by a fiber reinforcement or wire reinforcement integrated into the material. According to one embodiment, the actual articulated body consists of a commercially available hydraulic hose or another suitable hose with an internal reinforcing structure. The hose or hydraulic hose consists, for example, of a flexible material, for example elastomer or the like, which is reinforced in one or more layers with reinforcements that are preferably crossed in the shape of a cross. The reinforcement can be made of steel, plastic fibers or textile fibers.

The center piece is bordered on both sides by connecting pieces for fastening the rotor and/or the drive shaft. According to one embodiment, a connecting piece is attached to each of the two free ends of the hose piece. The two connection pieces are preferably designed with retaining grooves in the axial direction and/or possibly also in the radial direction. The connecting pieces preferably have an n-edged area, where n corresponds to the number of jaws on the hose press used later (hose presses usually have six or eight jaws). The connecting pieces each comprise, for example, a sleeve for holding the respective end of the hose piece. The sleeves are compressed using a hose press so that the hose is fixed between the two connectors. The n-edged area on the connecting piece is angled with the jaws of the Align hose press. After pressing, a secure connection is created between the respective connection piece and the respective sleeve and thus also a secure connection between the respective connection piece and the respective free end of the hose piece.

Alternatively, instead of an n-edged area on the connection piece, a thin cylindrical area can also be used. During the pressing process, this thin area can then also be brought into the n-edged shape.

Preferably at least two sleeves are pressed simultaneously in a suitable jaw construction. Due to the n-edged compression between the sleeve and the connection piece, a higher moment can be permitted for the construction, since a relative movement between the hose and sleeve as well as between the hose and the connection piece must take place at the same time for the hose to slip. The n-edged shape on the outside can also be used as a gripping surface for tools, for example if detachable threads are used to connect to the neighboring parts.

To protect the free ends of the hose piece, for example from environmental influences such as penetrating fluid or the like and/or to strengthen the bond between hose and sleeve or hose and connector piece, a sealing and/or adhesive compound can also be used, which is particularly effective between the free ends of the hose piece and the respective sleeve is introduced.

An alternative embodiment can provide for the use of commercially available metallic inserts for injection molded parts instead of the two connection pieces or in connection with one connection piece. In this case, the n-edged connection between the connection piece and the sleeve can possibly be dispensed with. Also, in one embodiment, grub screws may be used herein to provide external threads.

An advantage of using a joint between the rotor and the drive is that the rotor can thus be positioned within the stator that the clearance between stator and rotor is the same everywhere along the pressure areas.

A further embodiment of a wobble pump can provide that the rotor-stator system has an inlet-side end section in which an inlet funnel free of sealing lines is formed between the stator and the rotor along a funnel length, the helical inner peripheral surface of the stator being in a central main section of the rotor Stator system and is formed in the inlet-side end portion. In particular, the inlet funnel is designed in such a way as in the application with the reference number DE 10 2016 009 028 is described.

Such an inlet funnel, which on the one hand comprises a continuation of the helical inner peripheral surface of the stator and on the other hand is free of sealing lines, achieves advantageous flow effects.

According to one embodiment, the invention thus relates to eccentric screw pumps with an unreinforced elastomer stator, with the delivery medium surrounding the stator serving as pressure medium in order to create the sealing contact between the rotor and stator during ongoing pump operation. If necessary, the stator can also be supported by inserts of a largely rigid material, with the flexible one-sided clamping point having to be retained.

In particular, when the wobble pump is started up, a certain differential pressure arises, as a result of which the wobble stator is pressed onto the rotor by the delivery medium acting on the wobble stator from the outside with pressure on the pressure side, resulting in a real separation of the pressure side from the suction side of the wobble pump due to the forced solid-body contact between the rotor and the stator. This offers various advantages. On the one hand, a wobble pump according to the invention with a gap between the stator and rotor can easily break away, since there is still no differential pressure when the wobble pump is at a standstill. The differential pressure between the interior and the exterior of the wobble stator only builds up with increasing speed and thus closes the sealing contact at so-called sealing areas or sealing contact surfaces.

Since in wobble pumps known from the prior art with overlap, in which the stator is also surrounded by pumped medium during operation, the friction torques are significantly increased at speeds below the usual operating range for the corresponding wobble pump, correspondingly powerful drives are required for the commissioning of such wobble pumps necessary. In contrast, a wobble pump according to the invention with play between rotor and stator can be operated with a significantly smaller drive. One reason for this is that at low speeds, the differential pressures that lead to high torques cannot be built up. This means that in the wobble pumps according to the invention the necessary drive torque is significantly lower than in wobble pumps with an overlap between the rotor and the wobble stator due to the play or distance formed at least in certain areas between the rotor and the wobble stator. Furthermore, with a wobble pump according to the invention, there is an improvement in the efficiency or the overall efficiency in a large part of the pump characteristics map.

The wobble pump according to the invention can thus be used advantageously as a photovoltaically operated water pump. In this case, breaking loose of the wobble pump and accelerating the wobble pump over the low speed range are critical, since the motor torque available is lower compared to mains-connected pumps. The amount of energy available and thus the driving force also depends on the amount of light available and/or the angle of incidence of the solar radiation. In particular, the position of the sun plays an important role. The sun's rays, which are still weak and falling very obliquely on the photovoltaic panels in the morning, provide little energy, which again leads to reduced engine torque.

character description

• Figur 1 zeigt eine erfindungsgemäße Exzenterschneckenpumpe in einem Ruhezustand.
• Figur 2 zeigt eine erfindungsgemäße Exzenterschneckenpumpe in einem Betriebszustand.
• Figur 3 zeigt eine weitere Darstellung einer erfindungsgemäßen Exzenterschneckenpumpe in einem Betriebszustand.
• Figur 4 zeigt die auf die Exzenterschneckenpumpe im Betriebszustand wirkenden Kräfte.
• Figur 5 zeigt eine erste Ausführungsform einer endseitigen Befestigung des Stators einer Exzenterschneckenpumpe.
• Figur 6 zeigt eine zweite Ausführungsform einer endseitigen Befestigung des Stators einer Exzenterschneckenpumpe.
• Figur 7 zeigt eine perspektivische Darstellung einer ersten Ausführungsform eines Gelenks.
• Figur 8 zeigt eine Schnitt- Darstellung der ersten Ausführungsform eines Gelenks gemäß Figur 8.
• Figur 9 zeigt eine perspektivische Darstellung eines Zwischenproduktes bei der Herstellung der ersten Ausführungsform eines Gelenks gemäß Figur 7.
• Figur 10 zeigt eine Schnitt- Darstellung des Zwischenproduktes bei der Herstellung der ersten Ausführungsform eines Gelenks gemäß Figur 7.
• Figur 11 zeigt ein Anschlussstück eines Gelenks gemäß Figur 7.
• Figur 12 zeigt eine perspektivische Darstellung einer zweiten Ausführungsform eines Gelenks.
• Figur 13 zeigt eine Schnitt- Darstellung der zweiten Ausführungsform eines Gelenks gemäß Figur 12.
• Figur 14 zeigt ein Bauteil der zweiten Ausführungsform eines Gelenks gemäß Figur 12.

In the following, exemplary embodiments are intended to explain the invention and its advantages in more detail with reference to the attached figures. The proportions of the individual elements to one another in the figures do not always correspond to the real ones Size proportions as some shapes are simplified and other shapes are exaggerated relative to other elements for clarity.

• figure 1 shows an eccentric screw pump according to the invention in a state of rest.
• figure 2 shows an eccentric screw pump according to the invention in an operating state.
• figure 3 shows a further representation of an eccentric screw pump according to the invention in an operating state.
• figure 4 shows the forces acting on the progressing cavity pump in the operating state.
• figure 5 shows a first embodiment of an end attachment of the stator of an eccentric screw pump.
• figure 6 shows a second embodiment of an end attachment of the stator of an eccentric screw pump.
• figure 7 shows a perspective view of a first embodiment of a joint.
• figure 8 shows a sectional representation of the first embodiment of a joint according to FIG figure 8 .
• figure 9 shows a perspective representation of an intermediate product during the production of the first embodiment of a joint according to FIG figure 7 .
• figure 10 shows a sectional representation of the intermediate product during the production of the first embodiment of a joint according to FIG figure 7 .
• figure 11 shows a connecting piece of a joint according to FIG figure 7 .
• figure 12 shows a perspective view of a second embodiment of a joint.
• figure 13 shows a sectional representation of the second embodiment of a joint according to FIG figure 12 .
• figure 14 shows a component of the second embodiment of a joint according to FIG figure 12 .

Identical reference symbols are used for elements of the invention that are the same or have the same effect. Furthermore, for the sake of clarity, only reference symbols are shown in the individual figures that are necessary for the description of the respective figure. The illustrated embodiments only represent examples of how the device according to the invention can be designed and do not represent any final limitation.

figure 1 shows a schematic view of an eccentric screw pump 1, in particular a wobble pump 2, in a state of rest and figure 2 shows the eccentric screw pump 1 in an operating state AZ. The eccentric screw pump 1 comprises an elastomeric stator 3 with an inner side which is coiled in the shape of a snail and a rotor 4 . The stator 3 has one more thread than the rotor 4 . The rotor 4 is accommodated in the stator 3 . The rotor 4 and the stator 3 form the rotor-stator system 11. The rotor-stator system 11 is arranged in the pump housing 6, with an annular space 12 being formed between the pump housing 6 and the outer lateral surface of the stator 3.

The rotor 4 is coupled to the drive shaft 7 of a drive (not shown), for example an electric motor, and rotates about the longitudinal axis of the stator or about the longitudinal axis L of the eccentric screw pump 1 and at the same time performs a circular translation determined by the eccentricity e of the rotor-stator Systems 11. This means that the rotor 4 moves eccentrically in the stator 3.

The rotor 4 is coupled to the drive shaft 7 via a universal joint 5 . The cardanic joint 5 compensates for the eccentric movement or eccentricity e between the rotor 4 and the stator 3 by torque transmission. The free end 8 of the stator 3, which is opposite the cardanic joint 5, is fixed on one side to the pump housing 6 of the eccentric screw pump 1, in particular flexibly clamped. This leaves another gimbal degree of freedom to. The eccentricity e can be compensated for by the distance between these two cardanic degrees of freedom, each with an angle α. During ongoing production, the axis of the stator essentially describes a cone shape.

The free end 8 of the stator 3 has, for example, an annular widening 9 for fixing to the pump housing 6, which is held on the pump housing 6, for example by clamping. If necessary, the annular widening 9 can serve as a flange 10, via which the stator 3 can be connected to the pump housing 6, for example screwed.

The stator 3 and the rotor 4 are dimensioned such that in a first idle state according to RZ figure 1 of the eccentric screw pump 1 along the at least two sealing contact surfaces 14 between the rotor 4 and the stator 3 at least in some areas a game 100 or distance is formed. In particular, the rotor 4 has, at least in some areas, smaller external dimensions A(4) than the stator 3 has internal dimensions I(3).

In the operating state AZ of the eccentric screw pump 1 according to figure 2 The pumped medium FM enters the eccentric screw pump 1 via an inlet 15 and is transported by the moving pumping chambers FR formed by the movement of the rotor 4 and the mutual contact of the stator 3 and rotor 4 on the sealing contact surfaces 14 from the suction side S to the pressure side D of the eccentric screw pump 1 transported in the conveying direction TR. The pumped medium FM is discharged from the eccentric screw pump 1 via the outlet 16 and fed to its further use or processing.

If the conveying medium FM is pumped through the progressing cavity pump 1 ( figure 2 ), the pumped medium FM in the pumping chambers FR formed between the rotor 4 and the stator 3 causes a radially outward pressure on the stator 3, as a result of which the elastically deformable material of the stator 3 is pressed radially outward. In order to ensure adequate sealing of the pumping chambers FR, conventionally known wobble pumps have an overlap between the stator and the rotor when at rest. That is, there is a bias voltage between the stator and the rotor. In particular, this achieves that the outer dimensions of the rotor are larger than the inner dimensions of the elastomeric stator.

In the illustrated eccentric screw pump 1 in the form of a wobble pump 2, the pressure of the pumped medium FM(FR) within the pumping chambers FR is counteracted in the operating state AZ via the pumped medium FM(D) already pumped to the pressure side D. In particular, the pumped medium FM(D), which has the pressure on the pressure side, flows around the stator 3 protruding into the pressure side area D and in doing so presses the stator 3 against the rotor 4. Due to the play 100 formed between the stator 3 and the rotor 4 in the idle state RZ, the starting of the eccentric screw pump 1 without the disadvantageous high starting torque of wobble pumps with overlap between rotor and stator formed in the agitation state. The conveying effect can then start with a very low value and be increased with the increase in the conveyed medium FM(D) conveyed by the eccentric screw pump 1 .

In particular, the pressure exerted on the stator 3 by the pumped medium FM(D) presses the latter against the rotor 4 in the area of the at least two sealing contact surfaces 14, as a result of which the individual pumping chambers FR are securely spatially separated from one another. Due to the solid-state contact between the rotor 4 and the stator 3 formed in the operating state AZ, a real separation of the pumping chambers FR and a separation between the suction side S of the eccentric screw pump 1 and the pressure side D of the eccentric screw pump 1 is achieved.

A significant advantage of such an eccentric screw pump 1 or wobble pump 2 is, in particular, that when the eccentric screw pump 1 is transferred from a standstill or from the idle state RZ to an operating state AZ, due to the play between the rotor 4 and the stator 3 in the idle state RZ, at least in certain areas 100 when starting the eccentric screw pump 1, less effort is required to overcome the breakaway torque.

figure 3 shows a further stylized representation of an eccentric screw pump according to the invention 1 and figure 4 shows the on the progressing cavity pump 1 forces acting in operating state AZ. In figure 3 the flexible area 20 of the stator 3 is marked at the free end area 8 . Due to the RZ between rotor 4 and stator 3 in the idle state (cf figure 1 ) Formed game 100, the rotor-stator system 11 in the idle state RZ on no bias. Thus, when starting the eccentric screw pump 1, the starting torque is approximately zero and the operating torque is also low at small differential pressures between the suction side S and the pressure side D. It increases with increasing flow rate up to the discharge side pressure p(D). The flexible region 20 of the stator 3 has a correspondingly higher preload at higher torque loads due to the increasing differential pressure between the suction side S and the pressure side D.

Since the stator 3 is only fixed to the pump housing 6 on one side, the mobility of the stator 3 is only restricted on one side. If the contact pressure force F is calculated as a function of the differential pressure Δp and the radial stability rS, the result is a largely uniform contact pressure of the stator 3 on the rotor 4 between the pressure side D and the suction side S.

Due to the play 100 formed between the rotor 4 and the stator 3 in the idle state RZ (compare in particular Figures 1 and 2 ) only slight vibrations occur, so that a wobble pump 2 with a correspondingly designed rotor-stator system 11 can be operated at higher speeds than conventionally known wobble pumps. Because of the play formed in the idle state RZ, there are in particular fewer excitations of the oscillatable system in the rotational direction. As a result, wobble stators 3 according to the invention can advantageously be used in variable-speed eccentric screw pumps 1 with a predetermined output, for example solar-powered wobble pumps 2, in which only small differential pressures Δp can usually be overcome at higher speeds.

figure 5 shows a first embodiment of an end attachment of the stator 3 of an eccentric screw pump 1 and figure 6 shows a second embodiment of an end attachment of the stator 3 of an eccentric screw pump 1. According to FIG figure 5 embodiment shown, the stator 3 has an annular widening 9 at its free end region 8, via which the stator 3 is fixed to the pump housing 6. For example, the annular widening 9 as a flange 10 to screw the stator 3 to the pump housing 6 or the like.

According to the figure 6 In the embodiment shown, the free end area 8 of the stator 3 has a rim structure 17 which extends in the direction of the opposite end area 13 on the suction side and which encloses the stator 3 in some areas, with an annular space 19 being formed between the outer lateral surface of the stator 3 and the rim structure 17, which is in fluid communication with the annular space 12 formed between the stator 3 and the pump housing 6 as described above. The brim structure 17 extending in the direction of the opposite end area 13 on the suction side transitions into a free end area 18 . The free end area 18 is fixed to the pump housing 6, in particular the stator 3 is fastened to the pump housing 6 in a central area 6M of the pump housing 6 via the free end area 18 of the flange structure 17. FIG.

With the two in the Figures 5 and 6 In the embodiments shown, the stator 3 can in each case be almost completely surrounded by the conveying medium FM from the suction-side end area 8 to the pressure-side end area 13 (compare in particular figure 2 ).

figure 7 shows a perspective view of a first embodiment of a cardanic joint 5, 5a and figure 8 shows a sectional view. figure 9 shows a perspective representation of an intermediate product 5*, 5a* during the production of the first embodiment of a universal joint 5, 5a according to FIG Figure 7 and Figure 10 shows a sectional view. figure 11 shows a connecting piece 60 of a joint 5, 5a according to FIG figure 7 .

The joint 5, 5a includes an internally reinforced elastomer part 50. Tests have shown that 0.5 to 1.5 times the outer diameter dA as the free bending length LB is sufficient to compensate for an angular offset α of 1 to 2° that is usual in wobble pumps 2. This short length of the joint 5, 5a results in fewer vibrations, which also leads to an increased efficiency of the wobble pump 2, a longer service life for the components of the wobble pump 2 and higher possible maximum speeds of the wobble pump 2.

For special embodiments, e.g will. Internal support bodies can be e.g. a sphere, granules, a spiral spring, a cylindrical shaft piece or a flexible elastomer or plastic body. The combination of support body with a lubricant is recommended here. In addition, a more or less viscous supporting liquid can also be used.

The elastomeric part 50 of the joint 5a preferably consists of a commercially available hydraulic hose or other suitable hose with an internal reinforcing structure. The internal reinforcing structure can be formed, for example, by means of reinforcements interlocked in the shape of a cross in one or more layers. The reinforcement can be formed from metal fibers or wires, plastic fibers and/or textile fibers or the like. A connecting piece 60 is fastened to each of the two free ends of the hose piece 51 forming the elastomer part 50 . The two connecting pieces 60 are preferably designed with retaining grooves 62 in the axial direction and/or possibly also in the radial direction and may have further retaining means (not shown) for fastening and fixing in and/or on the free end areas of the hose piece 51. The connecting pieces 60 preferably have an n-edged attachment area 63, where n corresponds to the number of jaws of the hose press used later (hose presses usually have six or eight jaws). The connecting pieces 60 are in particular assigned a sleeve 52 for holding the respective end of the tube piece 51 (cf Figures 9 and 10 ). The sleeves 52 are compressed using a hose press, in particular the sleeves 53 compressed in this way (cf Figures 7 and 8 ) has an outer contour, at least in some areas, which corresponds to the outer contour of the n-sided contact area 63 of the respective connection piece 60 . In this way, the tube piece 51 is fixed between the two connection pieces 60 . The n-edged area 63 on the connecting piece 60 must be aligned at an angle with the jaws of the hose press. After pressing, a secure connection between the respective connection piece 60 and the respective sleeve 53 and thus also a secure connection between the respective connection piece 60 and the respective free end of the hose piece 51.

Preferably, at least two sleeves 52 are pressed simultaneously in a suitable die design. A higher moment can be permitted for the construction due to the n-edged compression between the sleeve 52 and the connection piece 60, since a relative movement between the hose piece 51 and a sleeve 52 and also between the hose piece 51 and that of the sleeve 52 is required for the hose piece 51 to slip associated connector 60 must take place simultaneously. The n-edged outer contour of the n-edged contact area 63 can also be used as a working surface for tools if, for example, detachable threads are used as a connection to the adjacent parts, in particular the rotor 4 and/or the drive shaft 7 (cf Figures 1 and 2 ) be used. Alternatively, instead of an n-edged outer contour of the connection piece 60, a thin cylindrical area can also be used. During the pressing process, this thin area can then also be brought into the n-edged shape.

To protect the free ends of the tube piece 51, for example against environmental influences such as penetrating fluid or the like and/or to strengthen the bond between tube piece 51 and sleeves 52, 53 or tube piece 51 and connection pieces 60, a sealing compound and/or adhesive compound can also be used be used, which is introduced in particular between the free ends of the hose piece 51 and the respective sleeve 52, 53.

figure 12 shows a perspective view of a second embodiment of a cardanic joint 5, 5b and figure 13 shows a sectional representation. figure 14 shows a component 65 of the second embodiment of a cardanic joint 5b according to FIG figure 12 . This embodiment envisages using a commercially available metallic insert for injection-molded parts 66 as component 65 . The n-edged connection between the connection piece 60 and the pressed sleeve 52 can possibly be dispensed with here. In the exemplary embodiment shown, the connecting piece 60 is in the form of a threaded pin 64 with an internal thread for attachment to the rotor 4 and/or the drive shaft 7 (cf Figures 1 and 2 ) educated.

Alternatively, grub screws can be used to provide external threads for attachment to rotor 4 and/or drive shaft 7 .

The invention has been described with reference to preferred embodiments. It will be apparent to those skilled in the art that modifications or variations can be made to the invention without thereby departing from the scope of the following claims.

reference list

1

progressing cavity pump

2

wobble pump

3

stator, wobble stator

4

rotor

5, 5a, 5b

gimbal

5*, 5a*

intermediate

6

pump housing

6M

central area of the pump housing

7

drive shaft

8th

free end, free end area, suction-side end area

9

annular widening

10

flange

11

rotor-stator system

12

annular space

13

suction-side end area

14

sealing contact surface

15

inlet

16

outlet

17

brim structure

18

free end area of the brim structure

19

annular space

20

flexible area

50

internally reinforced elastomer part

51

piece of tubing

52

sleeve

53

compressed sleeve

60

fitting

62

retaining grooves

63

n-edged touchdown area

64

grub screw

65

component

66

commercially available metallic insert for injection molded parts

100

Game

A(4)

Outside dimensions of the rotor

AZ

operating condition

D

pressure side; print side area

there

outer diameter

Δp

differential pressure

f

pressing force

FM

conveying medium

FM(D)

to the pressure side D

FM(FR)

conveying medium located in conveying chambers

FR

conveyor room

I(3)

Internal dimensions of the stator

L

longitudinal axis

LB

free bending length

rS

radial stability

RZ

hibernation

S

suction side

TR

conveying direction

Claims (15)

1. An eccentric screw pump (1) for pumping fluid or free-flowing conveying media (FM) from a suction side (S) to a pressure side (D), the eccentric screw pump (1) comprising a rotor (4) and a stator (3), wherein the stator (3) is designed to be flexible and is secured to the pump housing (6) on one side, in particular on the suction side (S), wherein the rotor (4) is connected to a drive shaft (7) via a joint (5), wherein the eccentric screw pump (1) can assume an idle state (RZ) and an operating state, characterized in that in the idle state (RZ) of the eccentric screw pump (1), no sealing contact is formed at least in some regions between the rotor (4) and the stator (3) in sealing regions (14), wherein in the operating state (AZ) of the eccentric screw pump (1), the stator (3) is surrounded at least in some regions and/or essentially completely by the conveying medium (FM), wherein, in the operating state (AZ), the rotor (4) and the stator (3) are brought into contact along the sealing regions (14) by means of the conveying medium (FM) acting on outer jacket surfaces of the stator from the outside.
2. The eccentric screw pump (1) according to claim 1, wherein, in the idle state (RZ), a play (100) is formed at least in some regions in the sealing regions (14) between the rotor (4) and the stator (3).
3. The eccentric screw pump (1) according to claim 1 or 2, wherein, in the idle state (RZ), no sealing contact or a play (100), respectively, is formed between the rotor (4) and the stator (3) in a region between 50% - 100% of the sealing regions (14), and wherein, in the operating state (AZ), an overlap between the rotor (4) and the stator (3) is formed in the sealing regions (14) .
4. The eccentric screw pump (1) according to one of the preceding claims, wherein a first play (100) is formed between the rotor (4) and the stator (3) in the first idle state (RZ) of the eccentric screw pump (1) on the suction side (S), and wherein a second play (100) is formed between the rotor (4) and the stator (3) on the pressure side (D).
5. The eccentric screw pump (1) according to one of claims 1 to 3, wherein a play (100) is formed between the rotor (4) and the stator (3) in the first idle state (RZ) of the eccentric screw pump (1) on the suction side (S), and wherein an overlap is formed between the rotor (4) and the stator (3) on the pressure side (D).
6. The eccentric screw pump (1) according to claim 4, wherein the first play (100) is formed to be larger than the second play (100).
7. The eccentric screw pump (1) according to one of claims 4 or 6, wherein the play (100) decreases essentially continuously along the sealing regions (14) between the rotor (4) and the stator (3) from a section side (S) of the eccentric screw pump (1) to a pressure side (D) of the eccentric screw pump (1).
8. The eccentric screw pump (1) according to one of the preceding claims, wherein the conveying medium (FM), which at least partially surrounds the stator (3) in an operating state (AZ), has the pressure side pressure (p(D)).
9. The eccentric screw pump (1) according to one of the preceding claims, wherein the stator (3) is secured to the pump housing (6) on one side directly via a free end region (8) of the stator (3).
10. The eccentric screw pump (1) according to claim 9, wherein, for securing to the pump housing (6), the free end region (8) of the stator (3) has an annular widening (9), or wherein the free end region (8) of the stator (3) for securing to the pump housing (6) is formed as flange (17).
11. The eccentric screw pump (1) according to one of the preceding claims, wherein the joint (5) has a central part (50), which is formed so as to be at least partially movable and which is made of a reinforced elastomer or plastic material.
12. The eccentric screw pump (1) according to claim 11, wherein the reinforcement of the elastomer or plastic material is formed by means of a fiber reinforcement or wire reinforcement integrated in the material.
13. The eccentric screw pump (1) according to claim 11 or 12, wherein the central part (50) is limited on both sides by means of connecting pieces (60) for fastening the rotor (4) and/or the drive shaft (7).
14. The eccentric screw pump (1) according to one of the preceding claims, wherein the stator (3) has a screw thread-shaped inner circumferential surface and comprises an inlet funnel for the conveying medium (FM) on the end region (8) of the stator (3), which is secured on one side, wherein the inlet funnel comprises a continuation of the screw thread-shaped inner circumferential surface of the stator (3) and is formed so as to be free from sealing lines with respect to the rotor (4).
15. The eccentric screw pump (1) according to one of the preceding claims, wherein at least one solar module is assigned to the eccentric screw pump (1), wherein the drive can be operated by means of solar power.

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