DE102022127309A1 - 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 - Google Patents

Abstract

In order to produce a rotor unit (20) for an eccentric screw pump (10), 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), the following steps are carried out: b) 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 molded part (52) which comprises a negative mold which integrally encloses the helical rotor section (52); c) injection molding of the rotor unit (20) in the injection mold (50).

Description

BACKGROUND OF THE INVENTION

1. Field of the invention

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

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

2. Description of the state of the art

Progressive cavity pumps are used in various industrial sectors, particularly in automated manufacturing, to dispense precisely defined quantities of a medium to be dosed, such as an adhesive.

For this purpose, eccentric screw pumps comprise a so-called stator, the inner wall of which is corrugated like the internal thread of a two-start threaded nut. A helical rotor is rotatably mounted in this stator. The helical rotor and the inner wall of the stator are adapted to one another in such a way that closed, pocket-like cavities remain between the rotor and the stator, which move in a longitudinal direction of the stator when the rotor rotates relative to the stator. By rotating the rotor, a medium to be dosed can be conveyed through the interaction of the rotor with the stator according to the endless piston principle. The delivery volume per unit of time depends not only on the speed of the rotor relative to the stator, but also on the geometries of the rotor and stator, in particular their dimensions, the pitch of the helical shape and its diameter, as well as the eccentricity of the rotor.

With such eccentric screw pumps, dosing processes can be carried out with high precision and a high degree of repeatability.

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.

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

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 then provided to enable the eccentric movement of the rotor section. Such a rotor unit is known, for example, from the DE 20 2007 018 923 U1 known.

In addition, the DE 20 2020 005 671 U1 a rotor unit is described 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 enables a radial movement of the flex shaft within the drive shaft and is filled with an elastic material. Although such a rotor unit seems well suited for many applications, this rotor unit is complex to manufacture and the gap around the steel cable represents a weak point in the construction.

Another rotor unit is from the DE 198 13 999 C1 from 1999. In contrast to the multi-part metal rotor units that are common today, this one was made 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 on the market for high-precision eccentric screw pumps.

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.

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 unfavourable 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 possible break point, which could lead to an earlier failure of the rotor or requires special attention during production.

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

SUMMARY OF THE INVENTION

It is therefore the object of the present invention to provide a method for producing a rotor unit for an eccentric screw pump, which is improved compared to the previous manufacturing method. In particular, the method according to the invention is intended to provide a rotor unit that allows eccentric screw pumps to be created with better dosing properties, in particular higher dosing precision than before. The effort required to manufacture the rotor unit is also intended to be reduced.

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

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.

• a) die Rotoreinheit einen wendelförmigen Rotorabschnitt aufweist, der eine Wirkoberfläche hat und dazu eingerichtet ist, mit der Wirkoberfläche mit einem Statorabschnitt der Exzenterschneckenpumpe zusammenzuarbeiten, und/oder
• b) die Rotoreinheit einen Wellendichtabschnitt aufweist, an dem die Rotoreinheit gegenüber einem Grundkörperbauteil der Exzenterschneckenpumpe drehbar und fluiddicht abgedichtet wird, mit folgenden Schritten:
• c) Bereitstellen einer Spritzgussform, die
  • - zumindest für den Bereich der Wirkoberfläche des wendelförmigen Rotorabschnitts ein Rotorabschnitt-Formteil aufweist, das eine den wendelförmigen Rotorabschnitt einstückig umschließende Negativform umfasst, und/oder
  • - ein Wellendichtabschnitt-Formteil aufweist, welches eine den Wellendichtabschnitt der Rotoreinheit einstückig umschließende Negativform umfasst;
• c) Spritzgießen der Rotoreinheit in der Spritzgussform.

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 sealed in a rotatable and fluid-tight manner relative to a base body component of the eccentric screw pump, with the following steps:
• c) Providing an injection mould which
  • - 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
  • - has a shaft sealing section molded part which comprises a negative mold which integrally encloses the shaft sealing section of the rotor unit;
• c) Injection molding of the rotor unit in the injection mold.

The inventors have recognized that an improved rotor unit can be 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.

In a conventional injection molding process, components such as the rotor unit are injection molded in two half-shells, the parting plane of which runs lengthways through the rotor unit, typically in such a way that the central longitudinal axis of the rotor unit lies in the parting plane. This means that the rotor unit can be removed from the injection mold after injection molding by simply opening the two half-shells.

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

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 dosing precision of rotor units from the DE 198 13 999 C1 known plastic injection molding has not yet established itself.

Reworking the parting line, for example in a milling or grinding machine, which removes the parting line in the area of the active surface, only helps to a limited extent here. On the one hand, reworking the parting line is complex due to the helical shape of the rotor section. On the other hand, although the surface can be smoothed by reworking, the geometric dimensions of the helical rotor section become less precise as a result of the reworking.

The manufacturing method according to the invention therefore comprises an injection mold which has a rotor section molding at least for the area of the active surface of the helical rotor section, which comprises a negative mold which integrally encloses the helical rotor section. The active surface of the helical rotor section is thus produced without any parting lines. In particular, this eliminates the need for post-processing to remove the dividing line.

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

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

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

The material of the rotor unit can therefore comprise 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.

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, and in particular optimized accordingly, via the polymers, polymer mixtures used and their composition.

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, KTW, usually aim to prevent harmful substances from the rotor units from entering the media to be dosed.

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 lower when running, which also reduces the 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.

Advantageously, the material of the rotor unit can be selected so that the lowest possible friction is achieved 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.

By using a plastic rotor unit, a tribologically optimized mixture (compound) can be used. In addition, a compound blend of two or more polymers can further improve the abrasion resistance.

The individual polymers and/or polymer mixtures can advantageously be doped with an additive that serves to improve the abrasive and tribological properties. Preferably, such an additive is mixed into the polymers and/or polymer mixtures at a weight ratio of 1-30 percent. Both individual additives and several additives can be added, each in a mixing ratio of 1-30 percent by weight based on the polymer mass.

By using a suitable additive, particularly a nanoscale additive, which is extracted from the rotor unit by abrasion, constantly renewed rolling elements are formed between the rotor section and the stator section, which act as an intermediate layer in the tribological contact area. This reduces the coefficient of friction, particularly permanently, which reduces wear on the rotor unit and, above all, height wear on the corresponding stator elastomer.

The additive used may comprise one or more of the following group: TiC, TiO2, CNT, MWCNT, fumed silica, layered silicates, molybdenum sulphide, PTFE, graphite, carbon black, Al(OH)3, BaSO4, UH-PE, Al ₂ O ₃ , boron nitride, aramid, silanes, calcium oxide, magnesium oxide, polyol esters, stearates,

Although the simple production in a single injection molding step offers great 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 the service life.

Due to the plastic injection molding process, the rotor unit is also free of metal ions, so that no carryover of inhibiting metal compounds occurs.

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

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

This combination of rotary and linear movement allows the rotor unit to be removed from the completely 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.

Such a screwing movement to remove the rotor unit from the injection mold is unusual and, compared to opening half-shell molded parts, complex. However, subsequent processing would be significantly more difficult.

It would be conceivable to design the rotor section molding as a lost mold that is destroyed when the component is removed. However, due to the requirements for the surface quality of the helical rotor section, this would not be an economically viable solution. Instead, the screwing movement allows the rotor section molding to be used multiple times.

The inventors have also recognized that the principle of parting line-free production can also be applied to a rotor unit which has 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 which integrally encloses the shaft sealing section of the rotor unit.

An eccentric screw 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 area for the rotor unit is located on the other side. The medium to be dosed emerges from the pump inlet chamber towards the stator unit. However, the pump inlet chamber must be sealed towards the drive side.

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 this enables a better sealing effect to be achieved.

In addition, the contact surface between the shaft sealing section and the seal can be wetted using suitable triboadditives. These triboadditives build up a permanent lubricating film and reduce the frictional resistance in the area of the shaft sealing section, thereby increasing the service life of the rotor unit and the eccentric screw pump as a whole. Wetting metal shafts with triboadditives is not technically possible and run-in depressions quickly form in the area of the seals.

According to the invention, a rotor unit can be produced by the injection molding process 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.

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.

In contrast to the rotor section molded part, the negative mold of the flexible shaft section molded part does not have to enclose the flexible shaft section in one piece. This is because it can have a parting plane in the usual way, for example in the longitudinal direction.

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, in particular the helical rotor section. This is because the flexibility of the rotor unit required for the eccentric movement of the rotor section can be achieved by appropriate tapering in the area of the flexible shaft section.

The transition between the flexible shaft section and its neighboring 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 to the helical rotor section. In contrast, a multi-part rotor unit with universal joints has two clear bending points. The same applies to multi-part rotor units with flexible shafts due to the connection heads of the flexible shafts.

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

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

The flexibility of a flexible shaft section of the rotor unit can therefore also be achieved by making the material properties of the one-piece rotor unit at the flexible shaft section different from other sections.

This can be achieved, for example, by multi-component injection molding. During the injection molding of the one-piece rotor unit, the composition of the injection material is changed. This allows the flexible shaft section to be produced with a more flexible material than other sections of the rotor unit.

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.

It is therefore preferably provided that the rotor unit is cast as a one-piece plastic injection-molded component in a multi-component injection molding process.

Another possibility is to subsequently subject the base material of the rotor unit in at least one section to a processing step that changes the material properties there, such as doping, plasma treatment or similar.

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.

Preferably, it is further provided that the flexible shaft section is produced with a non-circular, in particular polygonal, preferably hexagonal, cross-section.

A non-circular cross-section on the flexible shaft section of the rotor unit causes a stirring movement in the pump inlet chamber of the eccentric screw. This can be advantageous for certain dosing media in order to maintain their viscosity or to achieve better homogenization of the medium. It can also prevent dosing medium from settling permanently 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.

A thickening in front of the helical rotor section can also interrupt a laminar flow of the medium to be dosed and achieve better homogenization. For this purpose, a specially designed pump inlet section can be provided on the rotor unit.

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 the latter, 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.

Preferably, the drive shaft section comprises a driver, via which the rotor unit can be positively driven in a rotary movement.

Preferably, the flexible shaft section is designed such that the helical rotor section can perform 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.

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.

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.

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

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 at least for the region of the active surface of the helical rotor section, a rotor section molded part which comprises a negative mold integrally enclosing the helical rotor section.

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 post-processing.

Preferably, the injection mold comprises one of the additional mold parts explained above with respect to the manufacturing method or listed in claims 2 to 8.

With regard to the rotor unit, the object according to the invention is achieved by a rotor unit for an eccentric screw pump, with 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, 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.

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 shows that it was produced without parting lines in an injection molding process with a one-piece enclosing negative mold.

The one-piece rotor unit manufactured according to the invention even increases the dosing accuracy compared to known multi-part rotor units. This is because the inventors have recognized that the cardan joints, steel cables or flexible springs of the multi-part rotor units cause an intrinsic play due to their design, which impairs the dosing accuracy. In the case of flexible shafts with springs, the springs are pulled or compressed axially by the system pressure built up by the eccentric screw pump, depending on the direction of delivery. In addition, the torque introduced compresses or pulls the spring depending on the direction of rotation. This creates a lag error with regard to the angle of rotation, which has a negative effect on the dosing accuracy. This is not the case with the rotor unit according to the invention.

Preferably, it is provided that the rotor unit has a shaft sealing section at which the rotor unit is sealed in a rotatable and fluid-tight manner relative 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 post-processing areas.

Preferably, the rotor unit comprises one of the additional sections explained above with respect to the manufacturing method or 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 is designed to receive a helical rotor section of a rotor unit, wherein the sleeve-shaped base body is made 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.

The adhesion elevations can impart a roughness with a mean roughness value of at least Ra = 0.4 µm to the inner wall, at least in sections. In particular, the mean roughness value can be between Ra = 0.4 µm and Ra = 6.5 µm.

The rubber stator section can be molded particularly well into the sleeve of such a stator unit. An intermediate step for roughening the inner wall, such as sandblasting, grinding, scratching, or activating, can therefore be omitted.

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.

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

BRIEF DESCRIPTION OF THE DRAWINGS

• 1 einen Longitudinalschnitt durch eine erfindungsgemäße Exzenterpumpe;
• 2 eine Draufsicht auf eine erfindungsgemäße Rotoreinheit zur Verwendung der in 1 gezeigten Exzenterschneckenpumpe;
• 3 eine Seitenansicht der Rotoreinheit aus 2;
• 4 eine perspektivische Ansicht die Rotoreinheit aus den 2 und 3 in einer nur schematisch dargestellten Gussform zur Herstellung der Rotoreinheit;
• 5a eine Draufsicht auf eine Hülse einer Statoreinheit zur Verwendung in der in 1 gezeigten Exzenterschneckenpumpe;
• 5b eine Seitenansicht der Hülse;
• 5c einen Longitudinalschnitt der Hülse entlang der in 5a gezeigten Schnittlinie A-A;
• 5d einen Querschnitt der Hülse entlang der in 5b gezeigten Schnittlinie B-B;
• 6 eine perspektivische Ansicht der Hülse.

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

• 1 a longitudinal section through an eccentric pump according to the invention;
• 2 a plan view of a rotor unit according to the invention for use in 1 shown eccentric screw pump;
• 3 a side view of the rotor unit 2 ;
• 4 a perspective view of the rotor unit from the 2 and 3 in a casting mould shown only schematically for producing the rotor unit;
• 5a a plan view of a sleeve of a stator unit for use in the 1 shown eccentric screw pump;
• 5b a side view of the sleeve;
• 5c a longitudinal section of the sleeve along the 5a shown section line AA;
• 5d a cross-section of the sleeve along the 5b shown section line BB;
• 6 a perspective view of the sleeve.

DESCRIPTION OF PREFERRED EMBODIMENTS

1 shows schematically an eccentric screw pump, generally designated by the reference numeral 10.

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

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

The eccentric screw pump 10 further comprises a rotor unit 20.

As the 2 and 3 show, 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, namely in one step, without post-processing steps, as will be explained further below.

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 with one another over half the pitch of the rotor unit in such a way that small pockets 24 are formed 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.

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.

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

As can be seen from the 2 and 3 As can be seen, the flexible shaft section 30 has a smaller cross-section than the transition section 28 or the helical rotor section 22. As a result, the flexible 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 flexible shaft section 30 has a hexagonal cross-section.

The rotor unit 20 further comprises a shaft sealing section 32. The shaft sealing section 32 is directly or indirectly connected to the flexible shaft section 30.

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 exemplary embodiment, two (or three or more if necessary) sealing rings 34 are therefore located on the shaft sealing section 32, which allow the rotor unit 20 to pass through in a fluid-tight but rotatable manner.

Finally, the rotor unit 20 has a drive section 36, which 1 is arranged at the bottom.

The drive section 36 comprises a bearing surface 38 on which the rotor unit 20 is mounted via a rolling bearing 40 relative to the base body 12 of the eccentric screw pump 10. The rotor unit 20 is thereby fixed to a rotation axis 42.

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.

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.

The eccentric screw pump 10 works 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 with the medium 17 to be discharged to move from the pump feed chamber 14 towards 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 about the axis of rotation 42, which is caused by the interaction of the helical shape of the rotor section 22 and the stator unit 16.

The rotor unit 20 according to the invention is manufactured in a plastic injection molding process, which is described below primarily on the basis of the 4 is explained.

4 shows the rotor unit 20 in a perspective view within a schematically illustrated injection mold 50, which comprises several mold parts 52, 54, 56a, 56b, 58 and 60a, 60b.

The most relevant molded part for 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 encloses the helical rotor section 22 in one piece. This means in particular that no parting plane between two half-shell molded parts is arranged on the rotor section 22.

The injection mold 50 is therefore specially designed so that, as indicated by the rotation arrow 62 in 4 As indicated, the rotor section molding 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.

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

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.

There is usually also a central injection opening on the flexible shaft section moldings 56a, 56b, which is not shown here. However, this can also be arranged on the transition section molding 54.

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.

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. As a result, the shaft sealing section 32 is 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.

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 taken apart from the side. After the two flexible shaft section moldings 56a, 56b have been removed, the shaft seal section molding 58 is then pulled off in the direction of the distal end of the rotor unit 20. The order of the drive section moldings 60a, 60b is arbitrary, since these can be removed at the end or at any other time independently of the other moldings.

In the 5a to 5d as well as 6 a stator unit 16 according to the invention is shown.

The stator unit 16 comprises a mostly cylindrical sleeve 70 as a base body in the interior of which the stator section 18 (cf. 1 ) is arranged. The stator section 18 is typically made of a rubber, in particular a rubber mixture, and interacts with the helical rotor section 22 of the rotor unit 20 as explained above to produce the pumping action of the eccentric screw pump 10.

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

Thus, the sleeve 70 of the stator unit 16 has an integrally formed, radially projecting locking lug 72 which is designed to engage in a recess in the housing 12 of the eccentric screw pump 10 (cf. 1 ). This secures the inserted stator unit 16 against twisting within the eccentric screw pump 10.

In addition, the sleeve 70 has a corrugation 76 on its inner wall 74 as integrally formed adhesion elevations. The corrugation 76 thus ensures a roughness with a mean roughness value of at least Ra = 0.4 on the inner wall 74 of the sleeve 70.

Due to the adhesion elevations, the stator section 18 made of rubber can be attached directly to the inner wall 74 of the sleeve 70 after injection molding without a further surface treatment step. This takes place in a further injection molding step.

In addition to an enlarged adhesion surface for the stator section 18, the adhesion elevations also represent a positive-locking anti-twisting device between the sleeve 70 and the stator section 18.

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

As is particularly evident from 5c As can be seen, the corrugation 76 in the embodiment shown extends axially completely through the sleeve 70. This is advantageous with regard to production using the injection molding process, since a central core of a stator injection mold can thus be easily removed axially. Of course, more complex adhesion elevations can also be provided. For example, the corrugation 76 can be interrupted in the axial direction in order to create a positive locking between the sleeve 70 and the stator section 18 in the axial direction as well.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 202007018923 U1 [0008]
• DE 202020005671 U1 [0009]
• DE 19813999 C1 [0010, 0021]

Claims (14)

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 sealed in a rotatable and fluid-tight manner with respect to a base body component (12) of the eccentric screw pump (12), with the following steps: c) providing an injection mold (50) which - has a rotor section molding (52) at least for the area of the active surface of the helical rotor section (22), which comprises a negative mold which integrally encloses the helical rotor section (52), and/or - has a shaft sealing section molding (58) which has a Shaft sealing section (32) of the rotor unit (20) comprises a negative mold that integrally encloses it; d) injection molding of the rotor unit (20) in the injection mold (50). 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 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 driven in rotation 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 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 has a maximum diameter that is smaller than a maximum diameter of the helical rotor section (22), and that b) the injection mold (50) has a transition section molding (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 enclosing the helical rotor section (22) in one piece. 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) which are in the Claims 2 until 7 are listed. 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 be connected to 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 active surface of the helical rotor section (22) is designed free of parting lines and without parting line post-processing areas. Rotor unit after 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 relative to a base body component (12) of the eccentric screw pump (10), and that b) the shaft sealing section (32) is designed to be free of parting lines and without parting line post-processing areas. Rotor unit (20) according to one of the Claims 10 or 11 , characterized in that the rotor unit (20) has one of the additional sections which are in the Claims 2 until 7 are listed. 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) and designed to receive a helical rotor section (22) of a rotor unit (20), characterized in that c) the sleeve-shaped base body (70) is manufactured in one piece from plastic using an injection molding process, 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 elevations (76). Eccentric screw pump with a rotor unit (20) according to one of the Claims 10 until 12 and/or a stator unit (16) according to Claim 13 .

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