Stator for eccentric screw pumps, eccentric screw pump, and production method

Abstract

The invention relates to a stator (3; 103) for a progressive cavity pump (1), comprising a stator body (15; 115) with a shell (19; 119) and an elastic inner lining (21; 121) with which the shell is provided. According to a first aspect, the shell and the inner lining are each made of a thermoplastic polymer material. According to a second aspect, the shell is made of a thermoplastic polymer material, the inner lining is made of a material with elastomer-like properties, and the stator body is manufactured in a two-component injection molding process or in a casting process with at least two stages. According to a third aspect, the shell has at least a section of a helical outer surface (31; 131) which is modified in certain areas by at least additional demolding surfaces (36; 136).Furthermore, according to a fourth aspect, a stator (3; 103) for a progressing cavity pump (1) is proposed, comprising an inner component or lining (21; 121) designed to interact with a rotor (4) of the progressing cavity pump (1) and made of a thermoplastic elastomer or a thermoplastic polyurethane. A progressing cavity pump and a method for manufacturing a stator for a progressing cavity pump are also proposed.

Description

AREA OF INVENTION

[0001] The invention relates to stators for progressive cavity pumps, to progressive cavity pumps with such stators, and to a method for manufacturing a stator for a progressive cavity pump. GENERAL STATE OF THE ART

[0002] Progressive cavity pumps are well-known. These pumps consist of a stator and a rotor that rotates eccentrically within a passage of the stator. Both the stator passage and the rotor are provided with helically wound surfaces, which, in conjunction with each other, form pumping chambers for the medium being pumped during operation of the progressive cavity pump.

[0003] Several stator designs for progressive cavity pumps have already been proposed.

[0004] For example, in a conventional design, the helical inner surface of the stator is formed within an elastomer body and is therefore elastically flexible. In this way, a sealing line can be created around each of the conveying chambers by appropriately dimensioning the stator and rotor geometry. This enables pressure to be maintained during the conveying of the medium. Furthermore, the elasticity of the stator's inner surface in such a design can help improve the wear behavior and service life of the stator, especially when conveying abrasive media containing, for example, sand or similar materials.

[0005] In the aforementioned conventional construction method, a steel tube is first manufactured and processed separately to produce the stator. An elastomer is injected into this steel tube to form the elastomer body and bond it to the steel tube. Prior to the elastomer injection, this process includes degreasing and sandblasting the steel tube, as well as applying a two-layer adhesion-enhancing coating as a pretreatment. This coating, consisting of a primer layer and an adhesion promoter layer, ensures a reliable, strong, and durable bond between the steel and the elastomer.

[0006] Furthermore, stators have been proposed in which a rigid shell is subsequently arranged around an elastomer body during the assembly of the stator in a detachable manner, without permanently bonding the elastomer body and the shell to each other.

[0007] Furthermore, conventional stator designs with a solid metal shell, such as steel, cast aluminum or cast steel, exist, which allow for a uniform wall thickness of the inner elastic material contained by the shell.

[0008] Furthermore, stators made entirely of elastomers or even of non-elastically flexible plastics such as PA (polyamide) or PTFE (polytetrafluoroethylene) – so-called solid stators – have already been proposed. Such stators thus have a hard, inflexible inner surface.

[0009] The previous, conventional method for manufacturing a stator for an eccentric screw pump with a supporting shell and the possibility of maintaining pressure or overcoming back pressure by forming a sealing line is therefore relatively complex and expensive.

[0010] For example, the production of the vulcanized elastomer body is already complex, energy-intensive, and costly. The production of the metallic sheath and its mechanical processing are also energy-intensive and expensive.

[0011] Furthermore, bonding the elastomer to the metal surface of the casing requires a multi-step, time-consuming pretreatment to achieve good adhesion between the two.

[0012] Furthermore, the stator, as a component of the progressive cavity pump, is typically subject to wear during operation. Therefore, repeated replacement of the stator may be necessary. The presence of the elastomer body, particularly its rigid bond with the steel tube casing, complicates the recycling of a worn stator. Even recycling an elastomer on its own is difficult.

[0013] Against this background, it would be desirable to have an improved design for a stator for an eccentric screw pump that is less complex and more economical to manufacture, and preferably also more sustainable with regard to the manufacturing process. BRIEF SUMMARY OF THE INVENTION

[0014] Against this background, it is therefore an object of the present invention to provide a stator for a progressive cavity pump that avoids or mitigates at least one, some, or all of the aforementioned disadvantages. Furthermore, a correspondingly improved progressive cavity pump and a correspondingly improved method for manufacturing a stator for a progressive cavity pump are to be provided.

[0015] According to the invention, this problem is solved by a stator for an eccentric screw pump with the features of claim 1 and / or by a stator for an eccentric screw pump with the features of claim 3 and / or by a stator for an eccentric screw pump with the features of claim 9 and / or by an eccentric screw pump with the features of claim 19 and / or by a method with the features of claim 20.

[0016] Accordingly, in a first aspect of the invention, a stator for a progressive cavity pump is proposed, comprising a stator body with a supporting shell and an elastic inner lining with which the shell is provided. The shell and the inner lining are each made of a thermoplastic polymer material.

[0017] According to a second aspect of the invention, a stator for an eccentric screw pump is provided, comprising a stator body having a supporting shell and an elastic inner lining with which the shell is provided, wherein the shell is formed with a thermoplastic polymer material, the inner lining is formed with a material having elastomer-like properties, and the stator body is manufactured in a two-component injection molding process or in a casting process of at least two stages.

[0018] Furthermore, according to a third aspect of the invention, a stator for an eccentric screw pump is proposed, comprising a stator body with a jacket and an elastic inner lining with which the jacket is provided on the inside, wherein the jacket has on the outside at least partially a helical surface-like outer surface, for example a double-start helical surface-like outer surface, which is modified in some areas at least by additional demolding surfaces.

[0019] The object of the invention described above is furthermore solved according to a fourth aspect of the present invention by a stator for an eccentric screw pump, comprising an inner component or inner lining which is provided for interaction with a rotor of the eccentric screw pump and is formed with a thermoplastic elastomer or a thermoplastic polyurethane.

[0020] Furthermore, an eccentric screw pump with a rotor and a stator designed according to the invention is provided. The stator is designed to interact with the rotor and accommodates the rotor at least partially.

[0021] Furthermore, the invention provides a method for manufacturing a stator for a progressive cavity pump, in particular for manufacturing a stator designed according to the invention. In the method according to the invention, a stator body is formed with a shell made of a thermoplastic polymer material, and the shell is provided with an inner lining made of a material with elastomer-like properties. The stator body is manufactured using a two-component injection molding process or a casting process with at least two stages.

[0022] One of the underlying ideas of the invention is that the formation of both the elastic inner lining and the shell with a thermoplastic polymer material enables a significant reduction in the effort, manufacturing time and energy input for the production of the stator.

[0023] By manufacturing the elastic inner lining or inner component with a thermoplastic material, significant energy savings can be achieved compared to the production and vulcanization of an elastomer body. Similarly, manufacturing the outer shell with a thermoplastic material instead of a metal allows for a considerable reduction in effort and energy consumption. The invention thus makes it possible to significantly reduce the CO₂ footprint (product carbon footprint, or PCF) and to produce the stator in a more sustainable and resource-efficient manner. Furthermore, by manufacturing both the outer shell and the inner lining with a thermoplastic material, a strong and reliable bond between these components can be achieved with minimal effort.

[0024] For example, according to one aspect of the invention, when using thermoplastic materials, particularly of the same type or material family, which are differentiated, for example, with respect to one or more mechanical properties of the materials for the shell and inner lining, the stator body with the solid bond between the shell and inner lining can be recycled as a single-material component. For example, the used stator body, preferably after cleaning, can be shredded and ground into granules suitable for further processing. Such granules can then be processed, for example, on a conventional injection molding machine like fresh plastic granules, or alternatively, for example, sold to a material compounder.In this way, the invention creates a stator for an eccentric screw pump with an elastic inner lining and good performance, which can also be equipped with improved recyclability.

[0025] The proposed design of the casing with a thermoplastic material offers the advantage of relatively free geometric design. This allows, for example, the casing to follow the internal geometry of the stator, such as a helical shape, thereby optimizing the wall thickness of the inner lining for further improvement in manufacturability and ensuring a more uniform appearance. Furthermore, this approach, particularly in combination with the thermoplastic inner lining (made, for example, from a thermoplastic elastomer or thermoplastic polyurethane), also reduces the weight of the finished stator. This helps to lower resource consumption during stator production and CO₂ emissions associated with shipping, and contributes to easier handling of the stator both during manufacturing and at the customer's site.

[0026] Manufacturing the stator body using a two-component injection molding process or a casting process with at least two stages allows for a good bond between the shell and the inner lining with minimal effort, particularly through injection molding of the shell and / or the inner lining separately. This also contributes to the economical and sustainable production of the stator. Furthermore, such injection molding or casting processes, especially through shell injection molding, allow for simple and wide variation of the shell geometry and, in particular, the adaptation of the shell geometry to the stator's inner geometry with little or no additional cost, offering the aforementioned advantages of good manufacturability and low component weight.

[0027] The demolding surfaces provided according to one aspect of the invention further facilitate the production of the stator body and contribute to even more economical and cost-effective manufacturing. In particular, the demolding surfaces make it possible to produce the stator body in a simply designed casting tool, especially a slideless two-plate tool. The demolding surfaces can preferably be arranged in such a way as to avoid undercuts which, without the provision of movable tool elements, would hinder easy separation of the tool plates in the parting plane.

[0028] According to a further aspect of the invention, the use of a thermoplastic elastomer or a thermoplastic polyurethane as a thermoplastic material for forming the inner component or inner lining contributes to the economical and sustainable production of the stator, particularly with a reduced CO₂ footprint, both on its own and especially in combination with the jacket made of the thermoplastic material. The thermoplastic elastomer or the thermoplastic polyurethane, in combination with a thermoplastic jacket, can each contribute to the advantageous recyclability of the stator.

[0029] The invention can, for example, enable a cost reduction of up to approximately 70 percent compared to the conventional method with an elastomer body that is firmly connected to a steel shell, and a reduction of the CO2 footprint or PCF of up to approximately 70 to 80 percent.

[0030] Advantageous embodiments and further developments of the invention will be found in the dependent claims and in the description with reference to the drawings.

[0031] In particular, the stator body is manufactured using a two-component injection molding process. This enables a reliable connection between the shell and the inner lining with minimal effort, economical and sustainable production, and a complex shell geometry with low additional costs. Furthermore, the possibility of a complex shell geometry improves manufacturability and reduces the weight of the stator, for example, by having the shell essentially follow the geometry of the inner lining or component.

[0032] In particular, in a further development, the shell and the inner lining form a direct bond. This simplifies the design and manufacturing of the stator body. A complex intermediate layer to improve the adhesion between the shell and the inner lining can be eliminated. A direct bond can be achieved, in particular, using the two-component injection molding process or the at least two-stage casting process, in which the shell and inner lining are injection molded separately.

[0033] According to one embodiment, the inner lining has a substantially uniform wall thickness. This advantageously enables improved production of the inner lining using an injection molding / casting process, particularly with a thermoplastic material such as a thermoplastic elastomer (TPE) or a thermoplastic polyurethane (TPU). A uniform, ideally constant, wall thickness is especially beneficial when processing TPE or TPU, as it prevents unfavorable material accumulation, void formation, and warpage. Furthermore, a uniform wall thickness avoids excessively long cooling times during injection molding of the inner lining, thus enabling a more economical manufacturing process.

[0034] In a further development, the outer shell is connected to the inner lining on the inside via a connecting surface that is at least partially helical in shape, and which can be designed in particular as a double-start helical surface. In this way, a stator body is created in which the shell and inner lining can be handled together as a single unit, and the inner lining is reliably mechanically supported and pressure-resistant by the outer shell.

[0035] In particular, the outer shell has at least a section of a helical surface, especially a double-turn helical surface. With a shell wound in this way, and thus with such an outer surface, a substantially uniform wall thickness of the inner lining / component can be achieved, which is advantageous for the manufacturing process, and at the same time, a wall thickness of the shell itself can also be achieved, at least to a largely uniform degree. Such a relatively complex shape of the shell is comparatively easy and cost-effective to achieve with a thermoplastic material, thus facilitating the production of the inner lining with a uniform wall thickness from a TPE or TPU.

[0036] In one embodiment of the invention, the outer casing can be stiffened by stiffening ribs, which are preferably integral to the casing. This further improves the mechanical support function of the casing. The stiffening ribs can, for example, extend along the length of the stator body.

[0037] In one embodiment, the outer contour of the shell can be designed such that the stator body can be manufactured in a slideless two-plate mold. In this embodiment, manufacturability in a slideless two-plate mold can be enabled, in particular, by a defined number, shape, and size of demolding surfaces provided on the outside of the shell.

[0038] In particular, the helical outer surface can be modified in certain areas by at least additional demolding surfaces. Such demolding surfaces facilitate economical, cost-effective production of the stator body and help to avoid complex molds, for example, for injection molding. For instance, the demolding surfaces can be arranged so that the stator body can be manufactured in a slide-less, two-plate mold and demolded without undercuts.

[0039] According to one embodiment, the demolding surfaces are essentially flat or at least partially flat. This allows for simple demolding surfaces that can also be used for other purposes, in particular for engaging mechanical tools or for engaging transport or holding devices. However, instead of a flat demolding surface, it is possible for the demolding surfaces to be non-flat, provided that the shape of the demolding surface, viewed from the parting line of the forming tool, prevents undercuts. For example, in another embodiment, the demolding surfaces can be curved, and in particular, formed from parallel generating elements.

[0040] According to a further development, the wall thickness of the shell is reduced in the area of ​​the demolding surfaces compared to other areas of the shell where it has a helical outer surface. Since this reduction in shell thickness is limited to the demolding surfaces, excessively uneven shell thickness is prevented. At the same time, the resources required for shell production can be limited, resulting in a lighter stator that is also more efficient to manufacture.

[0041] In a further embodiment, with respect to a central plane of the stator in which a longitudinal axis of the stator lies, the demolding surfaces are arranged on both sides of the central plane on the outer surface of the shell. The central plane can, in particular, correspond to a parting line of a forming tool, such as an injection mold. In a further embodiment, the demolding surfaces can be arranged adjacent to the central plane. In a further embodiment, it can be provided that the outer surface of the shell is provided with stiffening ribs and that the demolding surfaces are arranged adjacent to at least one of the stiffening ribs.

[0042] In a further development, two or more demolding surfaces are provided on the outside of the casing on both opposite longitudinal sides of the stator.

[0043] According to a further embodiment, the demolding surfaces are designed and arranged in such a way that the demolding surfaces or at least some of these for handling the stator or the casing or both during the manufacture of the stator, or for handling the stator during its assembly on a rotor of the progressive cavity pump, or for such handling operations in combination The demolding surfaces can be used for various purposes. They can be equipped with additional functions and serve as an assembly aid when installing the stator into the pump and / or as a handling aid during manufacturing. In particular, the demolding surfaces can be suitable or intended as contact surfaces for a handling tool or device, or for an assembly tool. Handling during manufacturing can be automated, for example, using a robot. Additionally or alternatively, the demolding surfaces can also serve as an aid for manual assembly with or without tools, or for manual handling with or without a handling device.

[0044] In particular, the inner lining is made of a thermoplastic elastomer or a thermoplastic polyurethane. This choice of material for the inner lining enables more economical and sustainable stator production, especially by reducing the product carbon footprint. Furthermore, the thermoplastic elastomer or thermoplastic polyurethane, in combination with a thermoplastic jacket, can improve the stator's recyclability.

[0045] In one embodiment, the sheath is made of a polyamide, a polypropylene, or a thermoplastic polyurethane.

[0046] According to further training, it is planned that the inner lining is made of a thermoplastic elastomer and the jacket of a polypropylene; or that the inner lining is made of a thermoplastic elastomer and the jacket of a polyamide; or that the inner lining is made of a thermoplastic polyurethane and the jacket of a polyamide; or that the inner lining is made of a soft thermoplastic polyurethane and the jacket of a hard thermoplastic polyurethane.

[0047] This allows for a wide variety of exemplary material combinations to create an economical, sustainable stator for a progressive cavity pump, adapted to a wide range of applications, such as the medium being pumped and / or the stator's resistance to contact with that medium. Furthermore, the aforementioned material combinations for the casing and inner lining can significantly improve recyclability.

[0048] In an alternative embodiment of the invention, the inner lining can be formed with a cross-linked elastomer, and in particular, the shell can be formed with a polyamide. For example, by using an injection molding process, such as a two-component injection molding process or a two-stage injection molding process, it can be achieved that the inner lining, as an elastomer component, is directly bonded to the shell, thus forming a direct bond without the interposition of one or more adhesion-promoting layers. This, in turn, simplifies the manufacturing process, avoiding numerous processing steps for the shell as well as the need for complex shell preparation to ensure good adhesion. Coating agents for adhesion promotion are also advantageously eliminated.A stator body can thus be manufactured with a direct plastic-rubber composite. This can be produced independently of the shell geometry, for example, even with a cylindrical shell. The direct plastic-rubber composite is particularly feasible using a suitable combination of the thermoplastic material for the shell and the elastomer for the inner lining, with a polyamide being particularly preferred for the shell. Such a design, in turn, enables the production of a stator in a more economical and sustainable manner.

[0049] In an embodiment of the fourth aspect, the stator can further comprise a supporting shell, wherein the shell is manufactured as a separate component and the inner component is contained within the shell, or the shell is connected to the inner lining to form a stator body. Preferably, the shell is made of a thermoplastic polymer material, in particular a polyamide, a polypropylene, or a thermoplastic polyurethane.

[0050] In various forms of the fourth aspect, it may be provided that the inner lining or inner component is made of a thermoplastic elastomer and the jacket of a polypropylene; or that the inner lining or inner component is made of a thermoplastic elastomer and the jacket of a polyamide; or that the inner lining or inner component is made of a thermoplastic polyurethane and the jacket of a polyamide; or that the inner lining or inner component is made of a soft thermoplastic polyurethane and the jacket of a hard thermoplastic polyurethane.

[0051] In a further development of the fourth aspect of the invention, the outer shell can have a helical surface-like outer surface at least in sections, and the helical surface-like outer surface can be modified in certain areas at least by additional demolding surfaces.

[0052] The stators proposed according to the invention can each be used, for example, as a construction material stator, whereas a variety of other applications of the stators proposed according to the invention for the most diverse conveyed media as well as the most diverse progressive cavity pumps and applications are also possible and useful. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] The invention is described in more detail with reference to exemplary embodiments shown in the accompanying drawings.

[0054] The accompanying drawings are included to facilitate a further understanding of this invention and are incorporated into and form part of this description. The drawings illustrate embodiments of this invention and, together with the description, serve to explain the principles of the invention. Other embodiments of this invention and many of its intended advantages are easily understood when they are better understood by reference to the following detailed description. The elements of the drawings are not necessarily drawn to the same scale. Identical reference numerals denote correspondingly similar parts. Fig. 1 shows an eccentric screw pump according to an exemplary embodiment in a schematically simplified side view; Fig. 2 shows a stator for the eccentric screw pump of the Fig. 1according to the exemplary embodiment in a side view; Fig. 3 shows the stator of the Fig. 2 in a view in a cross-sectional AA as in Fig. 2 indicated; Fig. 4 shows the stator of the Fig. 2 in a view in a longitudinal section BB, as in Fig. 2 indicated; Fig. 5 shows the stator of the Fig. 2 in a view in another cross-section CC, as in Fig. 4 indicated; Fig. 6 shows the stator according to the embodiment of the Fig. 2 in a first perspective view; Fig. 7 shows a detail D of the perspective view from Fig. 6 Fig. 8 shows another perspective view of the stator in accordance with the embodiment of the Fig. 2 Fig. 9 shows a stator for an eccentric screw pump such as that of the Fig. 1 according to another embodiment in a side view; Fig. 10 shows the stator of the Fig. 9 in a view in a longitudinal section FF, as in Fig. 9indicated; Fig. 11 shows the stator of the Fig. 9 in a view in a cross-section EE, as in Fig. 9 indicated; Fig. 12 shows the stator of the Fig. 9 in a view in another cross-section GG, as in Fig. 10 indicated; Fig. 13 shows the stator of the Fig. 9 in a first perspective view; and Fig. 14 shows another perspective view of the stator of the Fig. 9 .

[0055] In the figures, identical reference numerals denote identical or functionally similar components unless otherwise indicated. All directional terms, such as "top", "bottom", "left", "right", "above", "below", "horizontal", "vertical", "back", "front", and similar terms, are used for explanatory purposes only and are not intended to restrict the embodiments to the specific arrangements shown in the drawings. DETAILED DESCRIPTION OF THE INVENTION

[0056] In Fig. 1Figure 1 shows a schematically simplified side view of a progressive cavity pump 1. The progressive cavity pump 1 has a stator 3 which, in the illustrated embodiment, is coupled to a housing 6 on the supply side. As schematically indicated by arrow 64, the housing 6 provides the supply of a pumped medium to an input side of the stator 3. On the output side, the pumped medium is discharged into a Fig. 1 The material is pumped out in the direction indicated by arrow 66. However, it is understood that the eccentric screw pump 1 of the Fig. 1 is shown in an exemplary and illustrative manner and that the stator 3, which is described in more detail below, and its variants can be used in an analogous way in other types of progressive cavity pumps 1.

[0057] The stator 3 is an elongated component with a longitudinal direction L. Along the direction L, the stator 3 has a passage 13 with a helically wound inner surface, in Fig. 1 (Not shown in detail.) In passage 13, a rotor 4 with a helically wound outer surface is arranged. During operation of the progressive cavity pump 1, the rotor 4 can rotate eccentrically in passage 13 of the stator 3. A drive 10, comprising, for example, an electric motor, serves to drive the rotor 4.

[0058] A stator 3 according to an exemplary embodiment, which is located in the eccentric screw pump 1 of the Fig. 1 which can be used is in the Figs. 2 to 8 illustrated.

[0059] The stator 3 is formed with a stator body 15. The stator body 15 is tube-shaped and has a supporting, tubular shell 19, which is provided on the inside with an elastic inner lining 21. While the shell 19 thus has a mechanical support function and is made of a relatively rigid material, the inner lining 21 is made of a material with elastomer-like properties. Along the longitudinal direction L of the stator, the stator body 15 is provided with the passage 13, which accommodates the rotor 4. A helically wound inner surface 91 of the inner lining 21 surrounds the passage 13, interacts with the rotor 4 during operation, and is located in the Figs. 3 to 5 The inner surface 91 is located in the Figures 2 to 8 The illustrated embodiment is wound in a two-start helical or helix shape.

[0060] In the exemplary embodiment of the Fig. 2-8The outer shell 19 and the inner lining 21 are each made of a thermoplastic material and are directly bonded to each other without the need for an interposed, separately applied adhesion-enhancing layer. The thermoplastic material of the inner lining 21 is a thermoplastic elastomer (TPE) or a thermoplastic polyurethane (TPU), while the thermoplastic material of the outer shell 19 is, in particular, a polyamide (PA), a polypropylene (PP), or a thermoplastic polyurethane (TPU). By forming the supporting outer shell 19 from a thermoplastic material and using a thermoplastic elastomer or thermoplastic polyurethane for the relatively soft inner lining 21, a strong and reliable bond between the outer shell 19 and the inner lining 21 can be achieved.

[0061] For example, in variants of the embodiment of the Fig. 2-8 The following material combinations are provided for the casing 19 and the inner lining 21 of the stator body 15: the outer shell 19 is made of PP, the inner lining 21 of TPE; or the outer shell 19 is made of PA, the inner lining 21 of TPE; or the outer shell 19 is made of PA, the inner lining 21 of TPU; or the outer shell 19 is made of TPU, the inner lining 21 also of TPU.

[0062] In this process, the material of the outer shell 19 is designed to be relatively rigid and hard by appropriately adjusting the thermoplastic materials, while the material of the inner lining 21 is designed to be relatively soft and elastically compliant. With suitable dimensioning of the rotor 4, this allows the rotor 4 to form a sealing line with the inner surface 91 of the inner lining 21 around the pumping chambers that form between the inner surface 91 and the rotor 4, enabling the progressive cavity pump 1 to build up and maintain pressure. Due to its relatively rigid and hard design, the outer shell 19 fulfills its mechanical support function for the inner lining 21 and ensures pressure stability.

[0063] In one of the exemplary embodiments mentioned above, the inner lining 21 is made of a soft thermoplastic polyurethane and the outer shell 19 of a hard thermoplastic polyurethane. Thus, such a stator 3 can be considered to be made of a single material, in this case TPU. Such a stator 3 can be easily cleaned at the end of its service life, i.e., when the wear of the stator 3 exceeds a tolerable level, recycled as a whole, and, for example, shredded and processed into reusable thermoplastic granules. The other thermoplastic material combinations mentioned above can also prove advantageous with regard to recyclability.

[0064] The inner lining 21 has the inner surface 91 on its inside and is radially externally connected to a substantially helical surface-like connecting surface 28, similar to the inner surface 91, see Fig. 3 and 4 , connected to the inside of coat 19. Figs. 3-5 further illustrate that the inner lining 21 has a substantially uniform, and therefore at least largely constant, wall thickness t21, which is schematically indicated in the figures.

[0065] The outer shell 19 also has a helical outer surface 31, which in the illustrated embodiment is again designed with two threads. The outer surface 31 essentially follows the connecting surface 28 and the inner surface 91 parallel to each other. In this way, the outer shell 19 also has a wall thickness t19 that is essentially uniform and largely constant over large parts of the outer shell 19. This saves material and thus resources and, like the uniform wall thickness t21 of the inner lining 21, contributes to good manufacturability.

[0066] The Fig. 2Figures 6 to 8 illustrate the outer surface 31 in various views. Here, the outer surface 31 is divided into several sub-surfaces designed as helical sections, some of which are designated 32, 33, 34, and 35 by way of example. In a longitudinal section, sub-surface 32 is a summit surface, sub-surface 33 a first inclined, falling flank, sub-surface 34 a valley surface, and sub-surface 35 a second inclined, rising flank of one of the helical threads of the outer contour of the stator body 15. One or both of the end regions of the stator body 15 can be connected or terminated with geometries, for example in the form of stepped cylindrical end sections 16 and / or 17, see Figure 6. Fig. 2 , 6 and 8 , provided whose outer surfaces are not part of the helically shaped outer surface 31.

[0067] In the embodiment shown in the figures, the outer surface 31, designed as a double-start screw surface, is modified in a multitude of sub-areas by the introduction of surface sections 36 that deviate from the screw surface shape.

[0068] To manufacture the stator 3, the stator body 15 is produced in a two-component injection molding process or in a casting process with at least two stages, which in particular includes two separately guided injection molding steps.

[0069] A two-component injection molding process for manufacturing the stator body 15 can be advantageously and economically carried out in a slideless two-platen mold, for example, as a transfer process. In this case, the two-platen mold has, for instance, two cavities: a first for forming the inner lining 21 and a second for forming the shell 19. After injection molding the inner lining 21, it can be transferred from the first to the second cavity and overmolded there with the intended material to form the shell 19, as described above. In a variant of the embodiment, it can instead be provided that, in a two-component injection molding process, the shell 19 is first injection molded, followed by the inner lining 21, with which the shell 19 is then filled. The use of a two-component injection molding process makes it easier to achieve a good, reliable bond between the shell 19 and the inner lining 21.

[0070] While the material intended for the production of the inner lining 21 exhibits elastic compliance as described above, a more rigid, solid mechanical behavior is desired for the shell 19. To prevent the helical outer surface 31, together with the rigid material properties of the shell 19, from hindering the separation of the tool plates of a simple, slideless two-plate mold due to undercuts, such undercuts, viewed in the direction of the central plane M, are eliminated by the surface sections 36. The central plane M forms the parting line of the mold. Thus, the surface sections 36 serve as demolding surfaces, enabling the use of a simple mold for producing the shell 19 and thereby contributing to a reduction in manufacturing costs.

[0071] The wall thickness t19 of the shell 19 is reduced in the area of ​​the demolding surfaces 36 compared to other areas of the shell 19, where it has the unmodified helical outer surface 31. This is illustrated by way of example and schematically simplified form. Fig. 3 in cross-section AA. For example, in the area of ​​the demolding surfaces, the wall thickness t19 can be reduced to about 50 percent of the wall thickness of the shell 19 in areas of unmodified helical outer surface 31.

[0072] The representation of the wall thicknesses t21 and t19 in the figures is intended as an illustration, whereby the actual wall thickness in the axially normal cross-sections and the axially parallel longitudinal section may be distorted due to the helical surface shapes.

[0073] To remove the undercuts that would hinder easy separation of the forming tool, the demolding surfaces 36 - see Fig. 2, 3 , 6-8- with respect to the central plane M of the stator 3, in which the stator longitudinal axis L also lies, the demolding surfaces 36 are arranged on both sides of the central plane M on the outer side of the shell 19 and are each adjacent to the central plane M. Here, on the outer side of the shell 19, two or more demolding surfaces 36 are provided on each of two opposite longitudinal sides 45 and 46 of the stator 3. In particular, for each passage of the unmodified helical surface, on the basis of which the outer surface 31 is formed, through the central and parting plane M, one demolding surface 36 is provided on each side of the central plane M.

[0074] The demolding surfaces 36 can be designed, for example, with a rounded or curved shape, or essentially flat. In the exemplary embodiment of the Figs. 2 to 8 , see for example Figs. 6 to 8The demolding surfaces 36 each exhibit a slight curvature, but are each formed from parallel generating lines perpendicular to the central plane M. Different, planar or non-planar configurations of the demolding surfaces 36 are conceivable, provided they are suitable for preventing undercutting near the central plane M.

[0075] The demolding surfaces 36 on both longitudinal sides 45 and 46 are designed and arranged such that the demolding surfaces 36, or at least some of them, can be used for handling the stator 3, the stator body 15, or the shell 19, or both, during the manufacture of the stator 3 and / or for handling the stator 3 during its assembly on the rotor 4. For example, the demolding surfaces 36, or some of them, can facilitate the removal of the finished stator body 15 from the mold after injection molding of the shell 19.

[0076] For example, the demolding surfaces 36 can serve as contact surfaces for an assembly tool or handling tool or means. Fig. 3A tool or means 55 for assembly or handling is shown schematically and purely as an example. The demolding surfaces 36 can thus be well suited, for example, to automatically remove the finished injection-molded stator body 15 from the mold, for instance, using a robot and a gripper as a handling means 55. Furthermore, the demolding surfaces 36 can simplify the screwing of the stator 3 onto the rotor 4, either manually or using the assembly tool 55, at the customer's site. A flat or at least partially flat design of the demolding surfaces 36 can be advantageous for their use in assembly and / or handling, as described above, although this is not mandatory, and differently shaped, e.g., slightly curved, demolding surfaces 36 can also be equally suitable for facilitating assembly and / or handling.

[0077] Although it is preferable to provide the demolding surfaces 36 as explained above in order to enable simple and economical manufacturing, in another variant of the above with reference to Figs. 2 to 8 In the described embodiment, the demolding surfaces 36 are missing and a more complex forming tool is used.

[0078] In another variant of the above, with reference to Figs. 2 to 8In the described embodiment, the stator body 15 can be manufactured using a two-stage casting process instead of a two-component injection molding process. First, the outer shell 19 is manufactured separately from the selected material by injection molding, and the finished shells 19 are subsequently injection-molded with the inner lining 21. Thus, the inner lining 21 is formed within the shell 19 by injection molding from the selected thermoplastic material, in particular TPE or TPU. Alternatively, in yet another variant of the embodiment, the inner lining 21 can first be manufactured separately from the selected thermoplastic material, in particular TPE or TPU, and the finished inner linings 21 can then be provided with the outer shell 19 in a separate operation by injection molding.

[0079] In the above embodiments, the outer shell 19 preferably forms a direct bond with the inner lining 21, in which a specially applied adhesion promoter layer between the outer shell 19 and the inner lining 21 is not required.

[0080] In further variations of the above with reference to Figs. 1-8In the illustrated embodiment, the inner lining 21, instead of being permanently and adhesively connected to the shell 19, can be detachably arranged within a shell. For this purpose, an inner component 21, designed as described above for the inner lining 21 but used as a separate component, is manufactured. The material for forming the inner component is a thermoplastic elastomer or a thermoplastic polyurethane, from which the inner component is produced by injection molding. The resulting inner component is then received as a separate part within a supporting shell without an adhesive connection to it. The shell can be made of a thermoplastic material as described above, or alternatively, of a metal. For example, in this variant, such a shell can be geometrically shaped essentially as described above. Figs. 1-8The described design may be intended to allow the outer shell to be opened or disassembled in order to insert the inner component made of TPE or TPU into the shell.

[0081] In another embodiment of the invention, the outer shell 19, as in the embodiments described above, is formed from a thermoplastic, preferably relatively hard, plastic material, while the inner lining 21, unlike in the embodiments described above, is formed with a cross-linked elastomer. A suitable polyamide can be selected as the thermoplastic material for the outer shell 19, for example, a polyamide available from Evonik Industries under the name VESTAMID®. The inner lining 21 is thus formed with a rubber material, for example, a synthetic rubber. In this embodiment, the outer shell 19 is first injection-molded from the thermoplastic material selected for it, and then the inner lining 21 is introduced into the outer shell 19 by injection molding the elastomer.In this way, the inner lining 21 is formed during injection molding and can bond with the shell 19 during the crosslinking or vulcanization of the elastomer. Thus, in this embodiment of the invention, the stator body is also manufactured using a two-component injection molding process or a two-stage casting process. Here, the composition of the thermoplastic material of the shell 19 is selected such that the inner lining 21 forms a strong bond with the supporting shell 19, enabling a direct plastic-rubber bond and eliminating the need for a separately applied adhesion promoter layer.

[0082] In the case of the previously described embodiment with a stator body 15 formed with a direct plastic-rubber composite, the geometry of the shell 19 and inner lining 21 can be described as above with reference to the Figs. 1-8The described design is analogous to the embodiment with a thermoplastic inner lining 21, for example made of TPE or TPU. However, in variants of the direct plastic-rubber bond, the thermoplastic shell 19 can instead be designed as a substantially cylindrical tube with a cylindrical connecting surface to the inner lining. In such a case, the wall thickness of the elastomeric inner lining thus varies.

[0083] In the Figs. 9 to 14 A stator 103 is shown according to a further embodiment. Except for the differences described below, the stator 103 is designed like the one in the Figs. 2 to 8 illustrated stator 3, and can be used in an exemplary eccentric screw pump 1, as in Fig. 1Illustrated, they are used essentially analogously to stator 3. Elements and features of stator 103 that correspond to those of stator 3 are provided with reference numerals formed from the reference numerals of the features of stator 3 and adding 100 to each of them.

[0084] Stator 103 differs from stator 3 in particular in that a jacket 119 of stator 103, formed from a thermoplastic polymer material such as polyamide, polypropylene, or a hardened TPU, is provided with external stiffening ribs 178, 179, 180, and 181, which extend substantially parallel to the longitudinal axis L of the stator on the stator body 115 and thus on the stator 103. The stiffening ribs 178-181 stiffen the stator 103 against bending about a transverse axis and increase its resistance to mechanical forces along the longitudinal axis L of the stator.

[0085] The stiffening ribs 178-181 are manufactured in one piece with the shell 119 during the production of the shell 119, in particular by injection molding by overmolding an inner lining 121 or, for example, during the injection molding of the shell 119 before the injection molding of the same with the inner lining 121, and are thus made of the same thermoplastic material as the shell 119.

[0086] The stiffening rib 181 is additionally formed with a radially extending recess 185, in particular a round blind hole, which can be used, for example, for fastening or connecting purposes, such as by means of a screw. The recess 185 is surrounded by a hollow cylindrical widening of the rib 181, which is also laterally stiffened in a direction transverse to a main extension direction of the stiffening rib 181 by additional transverse ribs 182 in order to transfer any loads at the location of the recess 185 into the shell 119.

[0087] The four stiffening ribs 178-181 are arranged at intervals of essentially 90 degrees around the stator's longitudinal axis L, as seen in the cross-section of the stator 103, and extend radially outwards. Although four stiffening ribs 178-181 are used for the example of the Figs. 9-14As shown in the present illustration, it is understood that variants of this embodiment may have more or fewer stiffening ribs. For example, only two stiffening ribs arranged approximately 180 degrees opposite each other could be provided, or more than four stiffening ribs could be provided, for example six or eight, which are arranged particularly evenly distributed around the stator circumference.

[0088] The inner lining 121 is, in the case of the stator 103, according to the embodiment of the Figs. 9-14 injection molded from a thermoplastic polymer material with elastomer-like properties, preferably a TPE or a TPU.

[0089] In the exemplary embodiment of the Figs. 9-14The median plane M, which coincides with a parting line of a forming tool, in particular an injection mold, for a stator body 115 formed with the shell 119 and the inner lining 121, lies centrally within each of the stiffening ribs 180 and 178 arranged at opposite angles of 180 degrees, see Fig. 13 , 9 and 11 .

[0090] Except for the area of ​​the ribs 180, 178, the demolding surfaces 136 are arranged on an outer surface 131 of the shell 119 in a manner analogous to the demolding surfaces 36 in order to eliminate undercuts in the direction of view towards the central and parting plane M. With the exception of the demolding surfaces 136, the areas of the stiffening ribs 178-182 and the recess 185, the outer surface 131 is arranged analogously to the embodiment of the Fig. 2-8 , essentially shaped like helical surfaces, in Figs. 9-14again, a double-threaded helical surface. A helical surface on which the outer surface 131 is based is therefore modified both by the ribs 178-182 and by the demolding surfaces 136.

[0091] The sectional views of the Fig. 10 and 11 They also make it clear that a wall thickness t121 of the shell 121, as in the embodiment of the Fig. 2-8 , is essentially constant, which improves the manufacturability of the inner lining 121, especially from TPE or TPU, and that a wall thickness t119 in the area of ​​the demolding surfaces 136 is reduced compared to other areas of the shell 119, in which its outer surface 131 is designed in a helical manner, essentially analogous to what is described above for the wall thickness t19.

[0092] The stator 103 can be modified in variants of the same as described above for the variants of the stator 3, and can furthermore be formed in yet another embodiment alternatively with a plastic-rubber direct composite as also described above for a variant of the stator 3.

[0093] Although the invention has been fully described above with reference to preferred embodiments, it is not limited to these, but can be modified in many different ways. List of reference symbols

[0094] 1 Eccentric screw pump 3, 103 Stator 4 Rotor 6 Housing 10 Drive 13, 113 Through-hole (stator) 15, 115 Stator body 16, 116 End section (stator body) 17, 117 End section (stator body) 19, 119 Shell 21, 121 Inner lining or inner component 28, 128 Connecting surface 31, 131 Outer surface (shell) 32, 132 Outer surface part (shell) 33, 133 Outer surface part (shell) 34, 134 Outer surface part (shell) 35, 135 Outer surface part (shell) 36, 136 Demolding surface 45, 145 First longitudinal side (stator) 46, 146 Second longitudinal side (stator) 55 Handling or assembly tool 64 Feed of conveyed material 66 Conveying direction 178, 179 Stiffening rib 180, 181 Stiffening rib 182 Transverse rib 185 Recess 91, 191 Inner surface (stator) t19, t119 Wall thickness (shell) t21, t121 Wall thickness (inner lining) L Stator longitudinal axis (stator) M Middle plane (stator)

Claims

1. Stator (3; 103) for an eccentric screw pump (1), comprising a stator body (15; 115) having a supporting shell (19; 119) and an elastic inner lining (21; 121) with which the shell (19; 119) is provided, wherein the shell (19; 119) and the inner lining (21; 121) are each formed with a thermoplastic polymer material.

2. Stator for an eccentric screw pump according to claim 1, characterized by the fact that the stator body (15; 115) is manufactured using a two-component injection molding process.

3. Stator (3; 103) for an eccentric screw pump (1), comprising a stator body (15; 115) having a supporting shell (19; 119) and an elastic inner lining (21; 121) with which the shell (19; 119) is provided, wherein the shell (19; 119) is formed with a thermoplastic polymer material, the inner lining (21; 121) is formed with a material having elastomer-like properties and the stator body (15; 115) is manufactured in a two-component injection molding process or in a casting process of at least two stages.

4. Stator for an eccentric screw pump according to one of the preceding claims, characterized by the fact that the outer shell (19; 119) forms a direct connection with the inner lining (21; 121).

5. Stator for an eccentric screw pump according to one of the preceding claims, characterized by the fact that the inner lining (21; 121) is formed with a substantially uniform wall thickness (t21; t121).

6. Stator for an eccentric screw pump according to one of the preceding claims, characterized by the fact that the outer shell (19; 119) is connected on the inside to the inner lining (21; 121) at least in sections in a helical surface, in particular in a two-way helical surface.

7. Stator for an eccentric screw pump according to one of the preceding claims, characterized by the fact that the outer shell (19; 119) has at least a section of a helical outer surface (31; 131), in particular a two-turn helical outer surface (31; 131).

8. Stator for an eccentric screw pump according to claim 7, characterized by the fact that the helical outer surface (31; 131) is modified in certain areas at least by additional demolding surfaces (36; 136).

9. Stator (3; 103) for an eccentric screw pump, comprising a stator body (15; 115) having a shell (19; 119) and an elastic inner lining (21; 121) with which the shell (19; 119) is provided on the inside, wherein the shell (19; 119) has on the outside at least in sections a helical outer surface (31; 131) which is modified in areas at least by additional demolding surfaces (36; 136).

10. Stator for an eccentric screw pump according to claim 8 or 9, characterized by the fact that the demolding surfaces (36; 136) are each essentially flat or at least sectionally essentially flat, or that the demolding surfaces (36; 136) are each curved, and in particular are formed from generating elements parallel to each other.

11. Stator for an eccentric screw pump according to one of claims 8 to 10, characterized by the fact thatin the area of ​​the demolding surfaces (36; 136) the wall thickness (t19; t119) of the shell (19; 119) is reduced compared with other areas of the shell (19; 119) where it has the helical outer surface (31; 131).

12. Stator for an eccentric screw pump according to one of claims 8 to 11, characterized by the fact that with respect to a central plane (M) of the stator (3; 103) in which a longitudinal axis (L) of the stator lies, the demolding surfaces (36; 136) are arranged on both sides of the central plane (M) on the outside of the shell (19; 119) and in particular that the demolding surfaces (36) are arranged adjacent to the central plane (M) or the shell (119) is provided on the outside with stiffening ribs (178-181) and the demolding surfaces (136) are arranged adjacent to at least one of the stiffening ribs (178, 180).

13. Stator for an eccentric screw pump according to one of claims 8 to 12, characterized by the fact thatOn the outside of the shell (19; 119) on both opposite longitudinal sides (45, 46; 145, 146) of the stator (3; 103) two or more of the demolding surfaces (36; 136) are provided.

14. Stator for an eccentric screw pump according to one of claims 8 to 13, characterized by the fact that The demolding surfaces (36; 136) are designed and arranged such that the demolding surfaces (36; 136) or at least some of them are usable for handling the stator (3; 103) or the shell (19; 119) or both during the manufacture of the stator (3; 103) or for handling the stator (3; 103) during its assembly on a rotor (4) of the progressive cavity pump (1) or for such handling operations in combination, in particular as suitable or provided as contact surfaces for a handling tool (55) or an assembly tool (55).

15. Stator for an eccentric screw pump according to one of the preceding claims, characterized by the fact thatthe inner lining (21; 121) is formed with a thermoplastic elastomer or a thermoplastic polyurethane.

16. Stator for an eccentric screw pump according to one of the preceding claims, characterized by the fact that the sheath (19; 119) is made of a polyamide or a polypropylene or a thermoplastic polyurethane.

17. Stator for an eccentric screw pump according to one of the preceding claims, characterized by the fact thatthe inner lining (21; 121) is formed with a thermoplastic elastomer and the jacket (19; 119) with a polypropylene; or that the inner lining (21; 121) is formed with a thermoplastic elastomer and the jacket (19; 119) with a polyamide; or that the inner lining (21; 121) is formed with a thermoplastic polyurethane and the jacket (19; 119) with a polyamide; or that the inner lining (21; 121) is formed with a soft thermoplastic polyurethane and the jacket (19; 119) with a hard thermoplastic polyurethane.

18. Stator for an eccentric screw pump according to claim 4 or one of claims 5 to 14 in conjunction with claim 4, characterized by the fact that the inner lining (21; 121) is formed with a cross-linked elastomer and in particular that the shell (19; 119) is formed with a polyamide.

19. Eccentric screw pump (1) with a rotor (4) and a stator (3; 103) according to one of the preceding claims, wherein the stator (3; 103) is designed to interact with the rotor (4) and accommodates the rotor (4) at least section by section.

20. Method for manufacturing a stator (3; 103) for an eccentric screw pump (1), in particular a stator (3; 103) according to one of claims 1 to 18, wherein a stator body (15; 115) of the stator (3; 103) is formed with a jacket (19; 119) made of a thermoplastic polymer material and the jacket (19; 119) is provided with an inner lining (21; 121) made of a material with elastomer-like properties, wherein the stator body (15; 115) is manufactured in a two-component injection molding process or in a casting process of at least two stages.

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