Method and injection mold for producing a rotor unit for an eccentric screw pump, as well as rotor unit, stator unit, and eccentric screw pump

Abstract

The aim of the invention is to produce a rotor unit (20) for an eccentric screw pump (10), wherein the rotor unit (20) has a helical rotor portion (22) which has an acting surface and is designed to interact, via the acting surface, with a stator portion (18) of the eccentric screw pump (10). This aim is achieved by carrying out the following steps: b) providing an injection mold (50) which has a rotor-portion mold part (52) at least for the area of the acting surface of the helical rotor portion (22), which mold part comprises a negative mold which integrally encloses the helical rotor portion (52); c) injection-molding the rotor unit (20) in the injection mold (50).

Description

[0001] Method and injection mold for producing a rotor unit for an eccentric screw pump as well as a rotor unit, a stator unit and an eccentric screw pump

[0002] BACKGROUND OF THE INVENTION

[0003] 1. Field of the invention

[0004] The present invention relates to a method and an injection mold for producing a rotor unit for an eccentric screw pump.

[0005] The invention further relates to a rotor unit, a stator unit and an eccentric screw pump.

[0006] 2. Description of the prior art Progressive cavity pumps are used in various industrial sectors, particularly in automated manufacturing, to discharge precisely defined quantities of a medium to be dosed, such as an adhesive.

[0007] Eccentric screw pumps comprise a stator whose inner wall is corrugated, similar to the internal thread of a double-start threaded nut. A helical rotor is rotatably mounted within this stator. The helical rotor and the inner wall of the stator are adapted to one another in such a way that enclosed, pocket-like cavities remain between the rotor and the stator. These cavities move in a longitudinal direction of the stator when the rotor rotates relative to the stator. By rotating the rotor, a medium to be metered can be pumped through the interaction of the rotor and stator according to the endless piston principle.

[0008] The delivery volume per unit of time depends not only on the rotor's speed relative to the stator, but also on the geometries of the rotor and stator, particularly their dimensions, the pitch of the helical shape and its diameter, as well as the rotor's eccentricity. With these types of progressive cavity pumps, dosing processes can be carried out with high precision and repeatability.

[0009] During operation of an eccentric screw pump, the rotor performs an eccentric movement around a central axis of rotation, which is imposed on the rotor by the thread-shaped inner wall of the stator.

[0010] Since the helical rotor is typically driven, a flexible coupling must be provided between the helical rotor and a corresponding drive component. Since the rotor (and also the stator) are constructed in several parts, we will refer to a rotor unit and a stator unit in the following, although in technical terms, the terms rotor and stator are usually abbreviated.

[0011] In previously known eccentric screw pumps, the rotor unit typically comprises a metallic or ceramic helical rotor section and a metallic or ceramic drive shaft. Between the metallic rotor section and the metallic drive shaft, either a flexible, deformable shaft or a joint is provided to enable the eccentric movement of the rotor section. Such a rotor unit is known, for example, from DE 20 2007 018 923 U1.

[0012] Furthermore, DE 20 2020 005 671 U1 describes a rotor unit in which the flexibly deformable flex shaft is made of a steel cable, the end of which is accommodated in the drive shaft of the rotor unit in such a way that a gap remains between the drive shaft and the steel cable, which allows radial movement of the flex shaft within the drive shaft and is filled with an elastic material. Although such a rotor unit appears well suited for many applications, it is complex to manufacture, and the gap around the steel cable represents a weak point in the design.

[0013] Another rotor unit is known from DE 198 13 999 C1 from 1999. In contrast to the multi-part metal rotor units commonly used today, this one was manufactured from a single piece of plastic using an injection molding process. However, it has been shown that the plastic rotor units proposed there did not achieve the desired dosing precision and durability. Overall, there are currently no plastic rotor units available on the market for high-precision progressing cavity pumps.

[0014] It has also been shown that the multi-part rotor units with a metallic rotor section previously used in high-precision eccentric screw pumps also have various problems.

[0015] In particular, the flexible shaft made of a different material located between the ("front") helical rotor section and a ("rear") drive section, and its attachment to the rotor section or the drive section, has an adverse effect, especially on the design of the pump inlet at the inlet of the helical rotor section into the stator unit. The material transition also represents a potential fracture point, which either leads to an earlier failure of the rotor or requires special attention during manufacturing.

[0016] In addition, the helical rotor section made of metal requires extensive machining in order to define its geometry with sufficiently high accuracy and to provide a sufficiently high surface quality.

[0017] SUMMARY OF THE INVENTION

[0018] It is therefore an object of the present invention to provide a method for producing a rotor unit for an eccentric screw pump that is improved over the previous manufacturing process. In particular, the method according to the invention is intended to provide a rotor unit that allows the creation of eccentric screw pumps with better metering properties, in particular higher metering precision, than previously possible. Furthermore, the effort required to manufacture the rotor unit is to be reduced.

[0019] Furthermore, it is an object of the invention to provide an injection mold with which such a rotor unit can be produced.

[0020] Finally, the present invention also aims to provide a rotor unit, a stator unit and an eccentric screw pump which are improved with respect to the prior art. With regard to the method, this object is achieved according to the invention by a method for producing a rotor unit for an eccentric screw pump, in which a) the rotor unit has a helical rotor section which has an active surface and is designed to cooperate with the active surface with a stator section of the eccentric screw pump, and / or b) the rotor unit has a shaft sealing section at which the rotor unit is rotatably and fluid-tightly sealed with respect to a base body component of the eccentric screw pump, with the following steps: c) providing an injection mold which

[0021] - at least for the area of ​​the active surface of the helical rotor section, a rotor section molded part comprising a negative mold integrally enclosing the helical rotor section, and / or

[0022] - a shaft sealing section molded part comprising a negative mold integrally enclosing the shaft sealing section of the rotor unit; c) injection molding of the rotor unit in the injection mold.

[0023] The inventors have recognized that an improved rotor unit is obtained if the helical rotor section and / or a shaft sealing section are manufactured directly in such a way that its effective surface is sufficiently smooth.

[0024] In a typical injection molding process, components such as the rotor unit are molded into two half-shells, the parting line of which runs longitudinally through the rotor unit, typically with the central longitudinal axis of the rotor unit in the parting line. This allows the rotor unit to be removed from the injection mold after injection molding by simply opening the two half-shells.

[0025] However, the inventors have now realized that such a manufacturing process is unsuitable for producing more precise rotor units. This is because the parting line between the two half-shells is almost inevitably reflected as a parting line, usually in the form of a small unevenness and / or a burr, on the surface of the rotor unit. This is the case even with very precisely manufactured injection molds.

[0026] The inventors have further recognized that this dividing line in the area of ​​the helical rotor section has a negative effect on the dosing precision of an eccentric screw pump with such a rotor unit and this is probably the reason why the plastic injection molding known from rotor units from DE 198 13 999 C1 has not been established to date.

[0027] Reworking the parting line, for example, using a milling or grinding machine to remove the parting line in the area of ​​the working surface, is only of limited help here. Firstly, reworking the parting line is complex due to the helical shape of the rotor section. Secondly, while reworking can smooth the surface, the geometric dimensions of the helical rotor section tend to become less precise.

[0028] The manufacturing method according to the invention therefore comprises an injection mold having a rotor section molded part, at least for the area of ​​the effective surface of the helical rotor section, which comprises a negative mold integrally enclosing the helical rotor section. The effective surface of the helical rotor section is thus produced without parting lines. In particular, post-processing to remove the parting line can be eliminated.

[0029] The inventors have therefore recognized that, despite the requirements of high-precision eccentric screw pumps, it is possible to deviate from the usual three-part design of the rotor unit and construct it as a single piece. In particular, the rotor unit can be manufactured as a single-piece injection-molded component, thus essentially reducing the manufacturing process to a single-step process.

[0030] The rotor unit can be made of thermoplastics, thermosets and / or elastomers.

[0031] Preferably, the rotor unit can be made of a polymer, in particular a polymer mixture.

[0032] The material of the rotor unit can therefore include one or more materials from the following group: PTFE, ETFE, PFA, FEP, PVDF, PE-UHMW, PPA, PEI, PAI, PEK, PEEK, PAEK, PEKEKK, LCP, PI, PBI, PPS, PSU, PES, POM, PU, ​​UP resins, EP resins, FEPM, FKM, FFKM, EPDM, HNBR, CSM, PUR, silicone, TPU, TPE-A, TPE-O, TPE-E.

[0033] Advantageously, the chemical and physical properties of the rotor unit, such as chemical resistance, abrasion resistance, sliding friction behavior, elasticity, etc., can be adapted to the respective dosing medium, in particular optimized accordingly, via the polymers, polymer mixtures used and their composition.

[0034] In particular, the materials of the rotor unit can be selected to meet one or more standards, depending on the application. Medical standards, such as FDA, Pharmacopoeia, 3A Sanitary Optional, and KTW, usually aim to prevent contaminants from the rotor units from migrating into the media being dosed.

[0035] In addition, due to the polymer material of the rotor unit, heat transfer from the rotor section to the rubber of the stator section is reduced during operation, which also reduces corresponding thermal expansion. This enables more precise dosing and reduces fluctuations in dosing accuracy. Wear on the rubber in the stator unit is also reduced. The material of the rotor unit can advantageously be selected to achieve the lowest possible friction compared to the material of the stator unit, for example, an elastomer. The material pairing of the rotor unit and stator unit can therefore be selected to optimize friction.

[0036] By using a plastic rotor unit, a tribologically optimized compound can be advantageously used. Additionally, a compound blend of two or more polymers can further improve abrasion resistance.

[0037] The individual polymers and / or polymer blends can advantageously be doped with an additive that serves to improve the abrasive and tribological properties. Such an additive is preferably added to the polymers and / or polymer blends at a concentration of 1–30 percent by weight. Individual additives or several additives can be added, each in a mixing ratio of 1–30 percent by weight based on the polymer mass.

[0038] By applying a suitable additive, particularly a nanoscale additive extracted from the rotor unit through abrasion, continuously renewed rolling elements form between the rotor section and the stator section, acting as an intermediate layer in the tribological contact area. This reduces the coefficient of friction, particularly permanently, thereby reducing wear on the rotor unit and, above all, the vertical wear on the corresponding stator elastomer.

[0039] The additive used may include one or more from the following group: TiC, TiO2, CNT, MWCNT, fumed silica, layered silicates, molybdenum sulfide, PTFE, graphite, carbon black, AI(OH)3, BaSO4, UH-PE, AI2O3, boron nitride, aramid, silanes, calcium oxide, magnesium oxide, polyol esters, stearates,

[0040] Although the simple production in a single injection molding step offers significant advantages, the plastic rotor unit according to the invention can be subsequently coated with DLC, ta-C, ceramic coatings, or other coatings. This can, for example, provide wear protection or increase service life. Due to the plastic injection molding process, the rotor unit is also metal ion-free, preventing the carryover of inhibiting metal compounds.

[0041] The outer diameter of the helical rotor section can be 1 mm to 50 mm.

[0042] Preferably, the helical rotor section is removed from the rotor section molding by a screwing movement.

[0043] This combination of rotary and linear motion allows the rotor unit to be removed from the fully enclosing negative mold despite the helical shape of the rotor section. It does not matter whether the rotor section molded part is unscrewed from the rotor unit or whether the rotor unit is unscrewed from the rotor section molded part.

[0044] Such a screwing movement for removing the rotor unit from the injection mold is unusual and complex compared to opening half-shell molded parts. However, subsequent machining would be significantly more difficult.

[0045] While it would be conceivable to design the rotor section mold as a lost mold that would be destroyed to remove the component, this would not be a cost-effective solution due to the surface quality requirements of the helical rotor section. Instead, the screwing motion allows the rotor section mold to be reused multiple times.

[0046] The inventors have also recognized that the principle of parting line-free production can also be applied to a rotor unit having a shaft sealing section at which the rotor unit is rotatably and fluid-tightly sealed against a base body component of the eccentric screw pump, so that the injection mold has a shaft sealing section molded part which comprises a negative mold that integrally encloses the shaft sealing section of the rotor unit.

[0047] A progressing cavity pump always has a pump inlet chamber through which the rotor unit extends. The stator unit is located on one side of the pump inlet chamber, and the drive section for the rotor unit is located on the other. The medium to be metered exits the pump inlet chamber toward the stator unit. However, the pump inlet chamber must be sealed toward the drive side.

[0048] For this purpose, the rotor unit rotates with the shaft sealing section, for example, in a ring seal. Here, too, it has been shown that a shaft sealing section without parting lines is advantageous, as it allows for a better sealing effect.

[0049] In addition, the contact surface between the shaft seal section and the seal can be wetted with suitable triboadditives. These triboadditives build a permanent lubricating film and reduce frictional resistance even in the shaft seal section, thus increasing the service life of the rotor unit and the eccentric screw pump as a whole. Wetting with triboadditives is technically impossible for metal shafts, and run-in depressions quickly develop in the seal area.

[0050] According to the invention, a rotor unit can be produced by injection molding, in which either the helical rotor section or the shaft sealing section, or both at the same time, are designed to be free of parting lines.

[0051] Preferably, it is further provided that the rotor unit has a flexible shaft section which is arranged between the shaft sealing section and the helical rotor section and enables a radial movement of the helical rotor section relative to the shaft sealing section, and that the injection mold has a flexible shaft section molded part which comprises a negative mold enclosing the flexible shaft section.

[0052] In contrast to the rotor section molding, the negative mold of the flexible shaft section molding does not have to enclose the flexible shaft section in one piece. It can have a parting plane in the usual way, for example, in the longitudinal direction.

[0053] The flexible shaft section molded part can specify a smaller cross-section for the flexible shaft section than for the cross-section of another section of the rotor unit, particularly the helical rotor section. This is because a corresponding taper in the area of ​​the flexible shaft section can achieve the flexibility of the rotor unit required for the eccentric movement of the rotor section.

[0054] The transition between the flexible shaft section and its adjacent sections can be continuous, for example, through a conical taper and a conical thickening. Due to the design, this achieves a flat, consistent deflection angle with the helical rotor section. In contrast, a multi-part rotor unit with universal joints has two distinct bending points. The same applies to multi-part rotor units with flexible shafts due to the flexible shaft connection heads.

[0055] By appropriately selecting the length-to-diameter ratio of the flexible shaft section, both flexibility and elasticity can be influenced. The diameter of the flexible shaft section of the rotor unit can range from 1 mm to 30 mm. The eccentric deflection can range from 0.05 mm to 30 mm.

[0056] In addition to the geometric values, the flexibility and elasticity of the flex shaft section can be changed by changing the polymer used.

[0057] The flexibility of a flex shaft section of the rotor unit can therefore also be achieved by the material properties of the one-piece rotor unit at the flex shaft section being different from other sections.

[0058] This can be achieved, for example, through multi-component injection molding. This involves changing the composition of the injection material during the injection molding of the one-piece rotor unit. This allows the flexible shaft section to be produced with a more flexible material than other sections of the rotor unit.

[0059] In this case, the cross-section of the flexible shaft section does not need to be tapered, which means that the volume of the pump inlet chamber does not need to be increased unnecessarily.

[0060] Preferably, the rotor unit is cast as a one-piece plastic injection-molded component using a multi-component injection molding process. Another possibility is to subsequently subject at least one section of the base material of the rotor unit to a processing step that modifies the material properties there, such as doping, plasma treatment, or similar.

[0061] Preferably, it is further provided that the flexible shaft section has a higher flexibility than the drive shaft section and / or the helical rotor section.

[0062] It is preferably further provided that the flexible shaft section is produced with a non-circular, in particular polygonal, preferably hexagonal, cross-section.

[0063] A non-circular cross-section on the flexible shaft section of the rotor unit creates a stirring motion in the pump inlet chamber of the eccentric screw. This can be advantageous for certain dosing media to maintain their viscosity or achieve better homogenization of the medium. It can also prevent the dosing medium from permanently settling inside the inlet chamber and / or on the flexible shaft section. In conjunction with the radial eccentric movement, a non-circular cross-section allows any adhering dosing medium to "flake off" more easily.

[0064] A thickened section in front of the helical rotor section can also interrupt the laminar flow of the medium to be metered and achieve better homogenization. A specially designed pump inlet section can be provided on the rotor unit for this purpose.

[0065] Preferably, it is provided that the rotor unit has a drive section which is designed to be coupled to a drive of the eccentric screw pump and to be driven in rotation by this, wherein the drive section has a bearing surface on which the rotor unit is rotatably mounted in the eccentric screw pump, and that the injection mold has a bearing section mold part which comprises a negative mold enclosing the drive section of the rotor unit.

[0066] Preferably, the drive shaft section includes a driver, via which the rotor unit can be positively driven in a rotary motion. Preferably, the flexible shaft section is designed such that the helical rotor section can execute an eccentric movement with an amplitude of at least 5%-10% of the diameter of the rotor section relative to a central axis defined by the drive shaft section.

[0067] This can be achieved, for example, by adapting the geometry of the rotor unit, in particular by adjusting the diameter or length of the flexible shaft section.

[0068] For mechanical reasons, the rotor units, which have often been constructed in three parts, have a thickening at the transition between the front rotor component and the flexible shaft component, which hinders the flow of material into the inlet of the stator unit.

[0069] It is therefore preferably provided that the rotor unit has a transition section between the flexible shaft section and the helical rotor section, which transition section has a maximum diameter that is smaller than a maximum diameter of the helical rotor section.

[0070] With regard to the injection mold, the object according to the invention is achieved by an injection mold for producing a rotor unit for an eccentric screw pump, wherein the rotor unit has a helical rotor section, characterized in that the injection mold has, at least for the region of the active surface of the helical rotor section, a rotor section molded part which comprises a negative mold enclosing the helical rotor section in one piece.

[0071] Such an injection mold can be used to produce the rotor unit according to the invention with a helical rotor section that is free of parting lines without any post-processing.

[0072] Preferably, it is provided that the injection mold has one of the additional molded parts that was explained above with regard to the manufacturing method or is listed in claims 2 to 8. With regard to the rotor unit, the object of the invention is achieved by a rotor unit for an eccentric screw pump, with a helical rotor section that has an active surface and is designed to cooperate with the active surface with a stator section of the eccentric screw pump, wherein the helical rotor section is designed as a one-piece injection molded part, wherein the active surface of the helical rotor section is designed to be free of parting lines and without parting line post-processing areas.

[0073] Such a rotor unit is suitable for eccentric screw pumps for high-precision dosing. In particular, an examination of the active surface of the helical rotor section reveals that it was produced without parting lines using an injection molding process with a one-piece, enclosing negative mold.

[0074] The one-piece rotor unit manufactured according to the invention even increases dosing accuracy compared to known multi-part rotor units. The inventors recognized that the universal joints, steel cables, or flexible springs of the multi-part rotor units, due to their design, cause intrinsic play, which impairs dosing accuracy. In flexible shafts with springs, the system pressure built up by the eccentric screw pump axially pulls or compresses the springs, depending on the direction of flow. In addition, the applied torque compresses or stretches the spring depending on the direction of rotation. This creates a tracking error with respect to the angle of rotation, which negatively impacts dosing accuracy. This is not the case with the rotor unit according to the invention.

[0075] It is preferably provided that the rotor unit has a shaft sealing section at which the rotor unit is sealed rotatably and fluid-tightly with respect to a base body component of the eccentric screw pump, and that the shaft sealing section is designed to be free of parting lines and without parting line remachining areas.

[0076] Preferably, it is provided that the rotor unit has one of the additional sections which were explained above with regard to the manufacturing method or are listed in claims 2 to 8. With regard to the stator unit, the object according to the invention is achieved by a stator unit for an eccentric screw pump, with a sleeve-shaped base body and a stator section located in the sleeve-shaped base body, which stator section is designed to receive a helical rotor section of a rotor unit, wherein the sleeve-shaped base body is produced in one piece from plastic using an injection molding process, wherein the sleeve-shaped base body has an integrally formed, radially projecting locking nose which is designed to secure the stator unit against rotation within the eccentric screw pump, and / or the sleeve-shaped base body has an inner wall with integrally formed adhesion elevations.

[0077] The adhesion protrusions can impart a roughness with a mean roughness of at least Ra = 0.4 pm to the inner wall, at least in sections. In particular, the mean roughness can be between Ra = 0.4 pm and Ra = 6.5 pm.

[0078] The rubber stator section can be molded particularly well into the sleeve of such a stator unit. This eliminates the need for intermediate steps such as sandblasting, grinding, scraping, or activating the inner wall.

[0079] With regard to the eccentric screw pump, the object according to the invention is achieved by an eccentric screw pump with a rotor unit according to one of claims 11 to 12 and / or a stator unit according to one of claims 12 to 13.

[0080] Since the moving mass of a polymer rotor unit is significantly lower compared to multi-part metal versions, the progressing cavity pump can be designed smaller and / or lighter in terms of drive power, bearing design and / or pump body size.

[0081] BRIEF DESCRIPTION OF THE DRAWINGS

[0082] In the following, exemplary embodiments of the invention are explained in more detail with reference to the drawings. In these drawings:

[0083] Figure 1 shows a longitudinal section through an eccentric pump according to the invention; Figure 2 shows a plan view of a rotor unit according to the invention for use with the eccentric screw pump shown in Figure 1;

[0084] Figure 3 is a side view of the rotor unit of Figure 2;

[0085] Figure 4 is a perspective view of the rotor unit from Figures 2 and 3 in a casting mold shown only schematically for producing the rotor unit;

[0086] Figure 5a is a plan view of a sleeve of a stator unit for use in the eccentric screw pump shown in Figure 1;

[0087] Figure 5b a side view of the sleeve;

[0088] Figure 5c shows a longitudinal section of the sleeve along the section line AA shown in Figure 5a;

[0089] Figure 5d shows a cross-section of the sleeve along the section line BB shown in Figure 5b;

[0090] Figure 6 is a perspective view of the sleeve.

[0091] DESCRIPTION OF PREFERRED EMBODIMENTS

[0092] Figure 1 shows schematically an eccentric screw pump, designated overall by the reference numeral 10.

[0093] The eccentric screw pump 10 comprises a base body 12 in which a pump supply chamber 14 is arranged. The pump supply chamber 14 can be supplied with the medium 17 to be discharged via an inlet 15.

[0094] At its output end (Figure 1 above), the eccentric screw pump 10 has a stator unit 16, the details of which are explained below with reference to Figures 5a-d and Figure 6. However, an essential element of the stator unit 16 is a stator section 18, which is shaped similarly to a double-start internal thread and projects into a passage space of the stator unit 16.

[0095] The eccentric screw pump 10 further comprises a rotor unit 20. As shown in Figures 2 and 3, the rotor unit 20 is an elongated component that is essentially rotationally symmetrical. According to the invention, the rotor unit 20 is manufactured as a one-piece plastic injection-molded part, specifically in a single step, as explained further below, without any post-processing steps.

[0096] The rotor unit 20 initially has a helical rotor section 22, which extends into the stator unit 16. The shape of the helical rotor section 22 and the stator section 18 are coordinated over half the pitch of the rotor unit in such a way that small pockets 24 form between the two components, in which the medium 17 to be discharged is received. In the area of ​​the stator section 18, the helical rotor section 22 interacts with the stator unit 16 with its outer surface 26.

[0097] Furthermore, the rotor unit 20 has a transition section 28, which adjoins the helical rotor section 22. In the assembled state of the eccentric screw pump 10, the transition section 28 is thus arranged in the pump supply chamber 14.

[0098] In the illustrated embodiment of the rotor unit 20, the transition section 28 is further followed by a flexible shaft section 30. However, the helical rotor section 22 can also be directly connected to the flexible shaft section 30.

[0099] As can be seen from Figures 2 and 3, the flex shaft section 30 has a smaller cross-section than the transition section 28 or the helical rotor section 22. As a result, the flex shaft section 30 is more flexible than the other sections of the rotor unit 20 and thus allows an eccentric movement of the helical rotor section 22. Furthermore, the flex shaft section 30 has a hexagonal cross-section.

[0100] The rotor unit 20 further includes a shaft sealing section 32. The shaft sealing section 32 connects directly or indirectly to the flexible shaft section 30.

[0101] At the shaft sealing section 32 of the rotor unit 20, the pump supply chamber 14, through which the rotor unit 20 extends, is sealed fluid-tight relative to the base body 12. In the present embodiment, two (or three or more if necessary) sealing rings 34 are therefore located on the shaft sealing section 32, allowing a fluid-tight but rotatable passage of the rotor unit 20.

[0102] Finally, the rotor unit 20 also has a drive section 36, which is arranged at the bottom in Figure 1.

[0103] The drive section 36 comprises a bearing surface 38, on which the rotor unit 20 is mounted relative to the base body 12 of the eccentric screw pump 10 via a rolling bearing 40. This fixes the rotor unit 20 to a rotational axis 42.

[0104] In addition, the drive section 36 has a circumferential flange 37 as a stop at the transition to the shaft sealing section 32, via which the axial position of the rotor unit 20 is fixed in the direction of the drive section 36 after insertion into the eccentric screw pump 10.

[0105] At its end, the drive section 36 also has a driving structure, here in the form of two circular segment teeth 44, with which a drive motor (not shown here), usually a stepper motor, drives the rotor unit 20 in rotation.

[0106] The eccentric screw pump 10 operates in such a way that the rotation of the rotor unit 20 via the drive motor also causes the helical rotor section 22 to rotate. This then causes the pockets 24 containing the medium 17 to be discharged to move from the pump supply chamber 14 toward the outlet of the stator unit 16. The more flexible flex shaft section 30 enables the helical rotor section 22 to perform an eccentric movement around the rotation axis 42, which is determined by the interaction of the helical shape of the rotor section 22 and the stator unit 16.

[0107] The rotor unit 20 according to the invention is manufactured using a plastic injection molding process, which is explained below, particularly with reference to Figure 4.

[0108] Figure 4 shows the rotor unit 20 in a perspective view within a schematically illustrated injection mold 50, which comprises several molded parts 52, 54, 56a, 56b, 58, and 60a, 60b. The molded part most relevant to the present invention is the rotor section molded part 52, in which the helical rotor section 22 is cast. The rotor section molded part 52 integrally encloses the helical rotor section 22. This means, in particular, that no parting plane is arranged between two half-shell molded parts on the rotor section 22.

[0109] The injection mold 50 is therefore specially designed such that, as indicated by the rotation arrow 62 in Figure 4, the rotor section molded part 52 is screwed down from the helical rotor section after the injection molding process by a combined rotary and linear movement (like a cork from a corkscrew) in order to remove the rotor unit 20 from the injection mold.

[0110] As the next molded part, the injection mold 50 has a transition section molded part 54, into which the transition section 28 is cast. The transition section molded part 54 is also shown here as a single piece. However, the transition section 28 does not necessarily have to be designed without parting lines, so two half-shell molded parts can also be used here in a known manner.

[0111] The injection mold 50 further comprises two flexible shaft section mold parts 56a, 56b, which abut one another at a parting plane 64 and form the flexible shaft section 30.

[0112] The flexible shaft section molded parts 56a, 56b usually also have a central injection opening, which is not shown here. However, this can also be arranged on the transition section molded part 54.

[0113] If the transition section molded part 54 is also designed as a half-shell molded part, as explained, the corresponding half-shell parts can be combined with the flexible shaft section molded parts 56a, 56b.

[0114] As a further element, the injection mold 50 has a shaft sealing section molded part 58, which integrally encloses the shaft sealing section 32 of the rotor unit 20. This allows the shaft sealing section 32 to be cast without parting lines. Finally, the injection mold 50 has two drive section molded parts 60a, 60b, which form the drive section 36 as half-shell molded parts.

[0115] After the injection molding filling process, the rotor unit 20 is preferably removed from the injection mold 50 in a sequence, after which the rotor section molding 52 is unscrewed before the two flexible shaft section moldings 56a, 56b, which can then be separated laterally. After removing the two flexible shaft section moldings 56a, 56b, the shaft seal section molding 58 is then pulled off toward the distal end of the rotor unit 20. The order of the drive section moldings 60a, 60b is arbitrary, since they can be removed at the end or at any other time independently of the other moldings.

[0116] Figures 5a to 5d and Figure 6 show a stator unit 16 according to the invention.

[0117] The stator unit 16 comprises a mostly cylindrical sleeve 70 as a base body, inside which the stator section 18 (see Figure 1) is arranged. The stator section 18 is typically made of a rubber, in particular a rubber compound, and interacts with the helical rotor section 22 of the rotor unit 20, as explained above, to generate the pumping action of the eccentric screw pump 10.

[0118] According to the invention, the sleeve 70 of the stator unit 16 is designed as a one-piece plastic injection-molded component. This allows for a special shape of the sleeve 70.

[0119] Thus, the sleeve 70 of the stator unit 16 has a one-piece, radially projecting locking lug 72, which is designed to engage a recess in the housing 12 of the eccentric screw pump 10 (see Figure 1). This secures the inserted stator unit 16 against rotation within the eccentric screw pump 10.

[0120] In addition, the sleeve 70 has a ridge 76 formed as integrally formed protrusions on its inner wall 74. The ridge 76 thus ensures a roughness with a mean roughness of at least Ra = 0.4 on the inner wall 74 of the sleeve 70. The protrusions allow the rubber stator section 18 to be directly attached to the inner wall 74 of the sleeve 70 after injection molding without any further surface treatment. This is done in a subsequent injection molding step.

[0121] In addition to providing an enlarged adhesion surface for the stator section 18, the adhesion elevations also provide a positive locking mechanism against rotation between the sleeve 70 and the stator section 18.

[0122] The corrugation 76 can run completely around the circumference as shown, but it can also be present only in sections.

[0123] As can be seen particularly from Figure 5c, the ribbing 76 extends axially completely through the sleeve 70 in the illustrated embodiment. This is advantageous with regard to production by injection molding, since it allows a central core of a stator injection mold to be easily removed axially. Of course, more complex adhesion elevations can also be provided. For example, the ribbing 76 can be interrupted in the axial direction in order to create a positive locking connection between the sleeve 70 and the stator section 18 in the axial direction as well.

Claims

PATENT CLAIMS Method for producing a rotor unit (20) for an eccentric screw pump (10), a) wherein the rotor unit (20) has a helical rotor section (22) which has an active surface and is designed to cooperate with the active surface with a stator section (18) of the eccentric screw pump (10), and / or b) wherein the rotor unit (20) has a shaft sealing section (32) at which the rotor unit (20) is rotatably and fluid-tightly sealed with respect to a base body component (12) of the eccentric screw pump (12), comprising the following steps: c) providing an injection mold (50) which, at least for the region of the active surface of the helical rotor section (22), has a rotor section molding (52) which comprises a negative mold enclosing the helical rotor section (52) in one piece, and / or a shaft sealing section molding (58),which comprises a negative mold integrally enclosing the shaft sealing section (32) of the rotor unit (20); d) injection molding the rotor unit (20) in the injection mold (50). A method for producing a rotor unit (20) for an eccentric screw pump (10) according to claim 1, characterized in that a) the helical rotor section (22) is removed from the rotor section molded part (52) by a screwing movement. Method for producing a rotor unit (20) for an eccentric screw pump (10) according to one of the preceding claims, characterized in that a) the rotor unit (20) has a flexible shaft section (30) which is arranged between the shaft sealing section (32) and the helical rotor section (22) and enables a radial movement of the helical rotor section (22) relative to the shaft sealing section (32), and in that b) the injection mold has a flexible shaft section molded part (56a, 56b) which comprises a negative mold enclosing the flexible shaft section (30). Method for producing a rotor unit (20) for an eccentric screw pump (10) according to claim 3, characterized in that a) the flexible shaft section (30) is produced with a non-circular, in particular polygonal, preferably hexagonal, cross-section.Method for producing a rotor unit (20) for an eccentric screw pump (10) according to one of the preceding claims, characterized in that a) the rotor unit (20) has a drive section (36) which is designed to be coupled to a drive of the eccentric screw pump (10) and to be rotationally driven thereby, wherein the drive section (36) has a bearing surface (38) on which the rotor unit (20) is rotatably mounted in the eccentric screw pump (10), and in that b) the injection mold (50) has a bearing section molded part which comprises a negative mold enclosing the drive section (36) of the rotor unit (20). Method for producing a rotor unit (20) for an eccentric screw pump (10) according to one of the preceding claims, characterized in that a) the rotor unit (20) is cast as a one-piece plastic injection-molded component in a multi-component injection molding process. Method for producing a rotor unit (20) for an eccentric screw pump (10) according to one of the preceding claims, characterized in that a) the rotor unit (20) has a transition section (28) between the flexible shaft section (30) and the helical rotor section (22), which transition section has a maximum diameter that is smaller than a maximum diameter of the helical rotor section (22), and in that b) the injection mold (50) has a transition section molded part (54) which comprises a negative mold enclosing the transition section of the rotor unit (20).Injection mold (50) for producing a rotor unit (20) for an eccentric screw pump (10), wherein the rotor unit (20) has a helical rotor section (22), characterized in that the injection mold (50) has, at least for the region of the active surface of the helical rotor section (22), a rotor section mold part (52), which comprises a negative mold integrally enclosing the helical rotor section (22). Injection mold according to claim 8, characterized in that the injection mold (50) has one of the additional mold parts (54, 56a, 56b, 58, 60a, 60b) listed in claims 2 to 7.Rotor unit (20) for an eccentric screw pump (10), with a) a helical rotor section (22) which has an active surface and is designed to cooperate with the active surface with a stator section (18) of the eccentric screw pump (10), b) wherein the helical rotor section (22) is designed as a one-piece injection-molded part, characterized in that. c) the effective surface of the helical rotor section (22) is free of parting lines and Parting line reworking areas are formed. Rotor unit according to claim 10, characterized in that a) the rotor unit (20) has a shaft sealing section (32) at which the rotor unit (20) is rotatably and fluid-tightly sealed against a base body component (12) of the eccentric screw pump (10), and that b) the shaft sealing section (32) is formed without parting lines and without parting line reworking areas. Rotor unit (20) according to one of claims 10 or 11, characterized in that the rotor unit (20) has one of the additional sections listed in claims 2 to 7.Stator unit (16) for an eccentric screw pump (10), with a) a sleeve-shaped base body (70) and b) a stator section (18) located in the sleeve-shaped base body (70), which stator section is designed to receive a helical rotor section (22) of a rotor unit (20), characterized in that c) the sleeve-shaped base body (70) is produced in one piece from plastic by injection molding, wherein the sleeve-shaped base body (70) has an integrally formed, radially projecting locking nose (72) which is designed to secure the stator unit (16) against rotation within the eccentric screw pump (10), and / or. The sleeve-shaped base body (70) has an inner wall (74) with integrally formed adhesion protrusions (76). An eccentric screw pump with a rotor unit (20) according to one of claims 10 to 12 and / or a stator unit (16) according to claim 13.

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