Pump unit for centrifugal pump and centrifugal pump

Abstract

To provide a pump unit for a centrifugal pump.SOLUTION: The pump unit comprises: a pump housing 2 and a rotor 10 arranged in the pump housing and rotatable about an axial direction A, the pump unit is designed for contactless magnetic levitation and contactless magnetic driving of the rotor, the pump housing has a bottom portion 3 and a cover 4, the bottom portion has the rotor having a cylindrical cup 31 for receiving the rotor and a substantially ring-shaped first sealing surface 5 for sealing interaction with the cover, and the cover has a substantially ring-shaped second sealing surface 6 designed for sealing interaction with the first sealing surface. One sealing surface is designed as a ribbed surface, whereas the other sealing surface is designed as a smooth surface. Furthermore, a centrifugal pump with such a pump unit is proposed.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a pump unit for a centrifugal pump for conveying a fluid according to the preamble of the independent claim. The present invention further relates to a centrifugal pump comprising such a pump unit. [Background technology]

[0002] A centrifugal pump is known which comprises a pump unit and a drive unit, in which a rotor is arranged in the pump unit and forms the impeller of the centrifugal pump. A stator is arranged in the drive unit. In the pump unit, the rotor can be contactlessly magnetically supported by the drive unit and contactlessly driven to rotate about an axial direction. Such a centrifugal pump is, for example, marketed by the applicant under the trade name Levitronix® BPS pump.

[0003] The stator and the rotor form an electromagnetic rotary drive. For example, in the case of the Levitronix® BPS pump, the electromagnetic rotary drive is designed according to the principle of a bearingless motor. The term bearingless motor means an electromagnetic rotary drive in which the rotor can be fully magnetically supported relative to the stator, where no separate magnetic bearings are provided. For this purpose, the stator is designed as a bearing and drive stator, being both the stator of the electric drive and the stator of the magnetic bearing. By means of the electrical windings of the stator, a magnetic rotating field can be generated which exerts on the rotor a torque which realizes its rotation about a desired axis of rotation defined by the axial direction, on the one hand, and a transverse force which is optionally adjustable on the rotor so as to make it possible to actively control or adjust its radial position, on the other hand. Thus, three degrees of freedom of the rotor can be actively adjusted, i.e. its rotational position and its radial position (two degrees of freedom). With regard to the other three degrees of freedom, namely its position in the axial direction and its tilt with respect to a radial plane perpendicular to the desired axis of rotation (two degrees of freedom), the rotor is passively magnetically supported or stabilized by reluctance forces, i.e. the rotor cannot be controlled. The absence of a separate magnetic bearing with a complete magnetic bearing of the rotor is the characteristic that gives the bearingless motor its name. In a bearing-driven stator, the bearing function cannot be separated from the drive function.

[0004] Of course, other designs of centrifugal pumps are also known in which the rotor is magnetically supported without contact, where, for example, a separate magnetic bearing for the rotor is provided, so that the magnetic bearing function is separated from the drive function, for example, a separate coil is provided for this purpose, with which only the bearing force for the rotor is obtained, this separate coil not contributing to the drive of the rotor.

[0005] Centrifugal pumps with a contactless, magnetically supported and driven rotor, for example a rotor designed according to the principle of a bearingless motor, have been found to have many applications. The absence of mechanical bearings makes such centrifugal pumps particularly suitable in applications where very delicate substances are conveyed, for example blood pumps, or where the demands in terms of purity are very high, for example in the semiconductor, pharmaceutical and biotechnology industries, or for conveying abrasive or corrosive substances that would cause mechanical bearings to fail very quickly, for example pumps for slurries, sulfuric acid, phosphoric acid or other chemicals in the semiconductor industry.

[0006] Figure 1 shows a representation of a centrifugal pump known from the state of the art, designed according to the bearingless motor principle. For example, this is a Levitronix® BPS pump. To allow a better understanding, a part is cut away in Figure 1 to make the inside of the centrifugal pump visible.

[0007] 1 and 2 are devices from the state of the art, the respective reference numbers are designated here with inverted commas or dashes.The centrifugal pump is generally designated by the reference number 200'.

[0008] The centrifugal pump 200' comprises a drive unit 100' and a pump unit 1'. To enable a better understanding, the pump unit 1' is shown in a cross-sectional representation in FIG.

[0009] A rotor 10' forming a wheel or impeller is arranged in the pump unit 1', by means of which the fluid is conveyed. The drive unit 100' comprises a motor housing 120' in which a stator 102' is arranged, which together with the rotor 10' forms an electromagnetic rotary drive for rotating the rotor about an axial direction A. The drive unit 100' is designed for contactless magnetic bearing of the rotor 10' according to the bearingless motor principle. For this purpose, the stator 102' is designed as a bearing-drive stator, by means of which the rotor 10' can be magnetically driven without contact for rotation about the axial direction A and also magnetically supported without contact relative to the stator 102', where the rotor 10' is passively magnetically stabilized in the axial direction A and also actively magnetically supported in a radial plane perpendicular to the axial direction A, which is indicated in FIG. 1 by the line E. The motor housing 120' has in one of its axial end faces, i.e. in the upper axial end face according to the present representation, a recess 121' into which the pump unit 1' can be inserted.

[0010] The electromagnetic rotary drive with the stator 102' and the rotor 10' is designed as a so-called temple motor. The stator 102' comprises a number of coil cores 125', here eight coil cores 125', each of which comprises a longitudinal leg 126' extending in the axial direction A from a first end, which is the lower end according to the representation in FIG. 1, to a second end, and a transverse leg 127' arranged at the second end of the longitudinal leg 126' in a radial plane E. Each transverse leg 127' extends radially from the associated longitudinal leg 126' towards the rotor 10' and is bounded by a radially inner end face. The coil cores 126' are arranged around the rotor 10' in the circumferential direction, so that the rotor 10' is arranged between the radially inner end faces of the transverse legs 127' of the coil cores 126'.

[0011] All first ends of the transverse legs 126' are connected to each other by a back iron 122' for conducting magnetic flux. At least one concentrated winding 160', 161' is provided on each longitudinal leg 126' and surrounds the respective longitudinal leg 126'. With regard to the number and arrangement of the concentrated windings 160', 161', many variations are known that are not described in detail here. For example, there is a winding 160' that is wound around exactly one longitudinal leg 126' and a winding 161' that is wound around exactly two longitudinal legs 126'.

[0012] These multiple longitudinal legs 126', which extend in the axial direction A and are reminiscent of the columns of a temple, are what give the temple motor its name.

[0013] The pump unit 1' comprises a pump housing 2' having an inlet 21' and an outlet 22' for a fluid, and further comprises a rotor 10' arranged in the pump housing 2' for conveying the fluid, which can be rotated about an axial direction A. The rotor 10' comprises a magnetic core 101' which magnetically interacts with a stator 102' to generate a torque and to generate a magnetic bearing force. For example, the magnetic core 101' is a permanent magnet ring or a permanent magnet disk.

[0014] It is also possible that the magnetic core 101' is designed in a permanent magnet-free manner, i.e. without permanent magnets. In this case, the rotor 10' is designed, for example, as a reluctance rotor. In this case, the magnetic core 101' of the rotor 10' is made, for example, of a soft magnetic material. Suitable soft magnetic materials for the magnetic core 101' are, for example, ferromagnetic or ferrimagnetic materials, such as, in particular, iron, nickel-iron, cobalt-iron, silicon-iron, mu-metal, etc.

[0015] Furthermore, it is possible to design the magnetically effective core 101' of the rotor 10' to include both ferromagnetic and permanent magnet materials. For example, the permanent magnets can be placed or inserted into a ferromagnetic base body. Such a design is advantageous, for example, when it is desired to save permanent magnet material to reduce the cost of large rotors.

[0016] Typically, the magnetic core 101' is completely surrounded by plastic. In other designs, the magnetic core 101' is completely surrounded within a sheath made of a ceramic material or a metallic material, for example stainless steel or titanium or tantalum.

[0017] Additionally, the rotor 10' includes a plurality of vanes 103' for conveying the fluid from the inlet 21' to the outlet 22'.

[0018] The pump housing 2' comprises a bottom part 3' and a cover 4' for closing the bottom part 3', wherein a sealing element 90', e.g. an O-ring or a flat seal, is provided between the bottom part 3' and the cover 4' to prevent leakage of fluid to the environment.

[0019] The bottom part 3' of the pump housing 2' has a cylindrical cup 31' for receiving the rotor 10'. The cup 31' is inserted into a recess 121' in the motor housing 120' so that the rotor 10', or more precisely the magnetically effective core 101' of the rotor 10', is arranged between the lateral legs 127' of the coil core 126'.

[0020] The pump unit 1' is attached to a motor housing 120', for example by means of a number of screws 11'.

[0021] In many applications, for example in the semiconductor industry, the pump unit 1', except for the magnetic core 101', is made of plastic, for example perfluoroalkoxy polymer (PFA) or polytetrafluoroethylene (PTFE), because these are plastics with very high chemical resistance. These plastics are practically inert materials, such as those frequently used in the semiconductor industry, which cannot be attacked by chemically very corrosive substances. In addition, PFA and PTFE are plastics of very high purity, because they have no additional substances and their molecular complexes are at least approximately inert. PFA is often preferred because it can be processed in injection molding processes.

[0022] The sealing element 90' for sealing between the bottom part 3' and the cover 4' is designed, for example, as an O-ring or a ring-shaped flat seal. Elastomers are preferred for the sealing element 90', in particular because they have very good restoring forces. Furthermore, in the semiconductor industry, where there are very high demands on purity, it is common to use perfluoroelastomers (FFPM) for the sealing element 90'. FFPMs are used in particular when very high heat and / or chemical resistance is required.

[0023] Even with these very new and high performance materials, leakage problems can occur, for example in the semiconductor industry, where the chemical resistance of the elastomers may be insufficient to ensure the continued and safe operation of the centrifugal pump, especially at high temperatures, where there are processes in which sulfuric acid has to be conveyed at temperatures of up to 220°C.

[0024] Another problem is outgassing of additives, for example in sealing elements. For example, in the semiconductor industry, even very small amounts of impurities can have fatal consequences, since the product produced can be unusable even with the smallest contamination. It should be noted here that the current semiconductor industry produces structures in the range of 5 nanometers or smaller. Therefore, purity is extremely important in the semiconductor industry.

[0025] Furthermore, creep of the sealing element or portions of the sealing element can lead to problems, for example, because the creep process can cause cracks or other damage in the sealing element.

[0026] Especially at high temperatures and / or cyclical processes involving frequent pressure or temperature changes, there is a risk of leakage that could allow very dangerous, corrosive or harmful fluids to escape into the environment surrounding the centrifugal pump. Summary of the Invention [Problem to be solved by the invention]

[0027] Starting from this state of the art, it is therefore an object of the invention to propose a pump unit with a rotor that can be magnetically levitated without contact for a centrifugal pump, which has improved operational reliability, in particular with regard to leakage and with regard to purity, and in addition, it is an object of the invention to propose a centrifugal pump with such a pump unit. [Means for solving the problem]

[0028] The subject matter of the invention which meets this object is characterized by the features of the independent claims.

[0029] Thus, according to the invention, a pump unit for a centrifugal pump for conveying a fluid is proposed, which pump unit comprises a pump housing with an inlet and an outlet for the fluid and a rotor arranged in the pump housing for conveying the fluid, the rotor being capable of being rotated about an axial direction, where the pump unit is designed for contactless magnetic levitation of the rotor and for contactless magnetic driving of the rotor, where the pump housing has a bottom part and a cover for closing the bottom part, where the bottom part has a cylindrical cup for receiving the rotor and a substantially ring-shaped first sealing surface for sealing interaction with the cover, where the cover has a substantially ring-shaped second sealing surface designed for sealing interaction with the first sealing surface, where one of these two sealing surfaces is designed as a ribbed surface with at least one radial sealing rib, which extends in the circumferential direction along the entire sealing surface, whereas the other of the two sealing surfaces is designed as a smooth surface.

[0030] This embodiment makes it possible to dispense with a separate sealing element between the bottom part and the cover, which would come into contact with the fluid during normal, i.e. fault-free, operation. The fluid to be conveyed therefore does not come into contact with any separate sealing element during normal, i.e. fault-free, operation, and therefore there is no risk of the fluid being contaminated by such a separate sealing element. By omitting such a separate sealing element 90' (Fig. 2), all problems caused by such a separate sealing element 90' in the known pump unit 1' are eliminated.

[0031] The omission of such a separate sealing element represents a significant improvement with regard to the purity of the fluid to be conveyed, and since the fluid cannot come into contact with such a separate sealing element during normal operation, there is also no risk of the fluid being contaminated by such a separate sealing element, for example due to leakage of additional substances through the sealing element, as may occur, for example, when using elastomeric seals.

[0032] Preferably, a radial reinforcing element is provided, designed in the shape of a ring, extending radially outwardly around the two sealing surfaces. The radial reinforcing element surrounding the two sealing surfaces radially outwardly is advantageous in terms of stabilizing the first and second sealing surfaces and thus preventing deformation of the sealing surfaces or relative movement of the two sealing surfaces relative to each other. This ensures to a large extent that there are no open gaps or other leakage paths between the two sealing surfaces, even in the case of high pressures in the pump housing. In addition, the radial reinforcing element is advantageous in terms of further reducing or even completely preventing creep of the bottom part or cover, in particular in the case of the pump housing being made of creep-prone plastics such as PFA or PTFE.

[0033] Preferably, a plurality of sealing ribs are provided in the first or second sealing surface designed as a ribbed surface, each of the sealing ribs extending completely along the entire circumference of the ribbed surface. Each of these sealing ribs is in contact with the second or first sealing surface designed as a smooth surface. This means that each sealing rib is in direct physical contact with the sealing surface designed as a smooth surface. The term "smooth surface" means in particular that this sealing surface does not have grooves or other recesses in which the sealing ribs can be engaged. The sealing ribs therefore rest on this unstructured smooth surface.

[0034] An embodiment is possible in which the first sealing surface is designed as a ribbed surface and the second sealing surface is designed as a smooth surface, i.e. the sealing ribs are provided on the bottom part and the second sealing surface, i.e. the surface of the cover, is designed as a smooth sealing surface without structuring.

[0035] Furthermore, embodiments are also possible in which the second sealing surface is designed as a ribbed surface and the first sealing surface is designed as a smooth surface, i.e. the sealing ribs are provided on the cover and the first sealing surface, i.e. the surface of the bottom part, is designed as a smooth sealing surface without structuring.

[0036] The term "radial sealing rib" means that the sealing rib has a radial extent perpendicular to the axial direction. As a result, the sealing rib can absorb radial forces. It is also possible, but not necessary, for the sealing rib to extend perpendicular to the axial direction. The sealing rib can also extend obliquely to the axial direction.

[0037] In a preferred embodiment, each sealing rib is in each case designed as a circular shape, i.e. as a circular ring extending in the circumferential direction along the entire sealing surface. This embodiment is preferred, although not essential. For example, embodiments are also possible in which each sealing rib is designed as an ellipse or as a spiral. For such pump units, the embodiment of a spiral construction is particularly advantageous, in which the pump housing is designed as a spiral.

[0038] Particularly preferably, each sealing rib is in each case designed as a closed sealing rib, which means that it has no beginning and no end, for example, each sealing rib is designed as a closed ring without beginning and no end in the circumferential direction.

[0039] The bottom part and the cover are connected to each other via a press fit, which is realized by pressing the respective sealing rib of the first or second sealing surface designed as a ribbed surface against the second or first sealing surface designed as a smooth surface, whereby a sealing connection is formed between the bottom part and the cover. The assembly of the cover and the bottom part is achieved by moving the cover and the bottom part relative to each other in the axial direction, so that the first and second sealing surfaces are pressed against each other, so that they sealingly interact. One advantage here is that the mounting direction when the cover and the bottom part are assembled is axial, and the sealing ribs do not extend in the mounting direction but in the radial direction, i.e. perpendicular to the mounting direction.

[0040] Preferably, the ribbed surface comprises a plurality of radial sealing ribs, for example three sealing ribs, each of the plurality of radial sealing ribs extending in the circumferential direction along the entire ribbed surface, where the sealing ribs are arranged next to one another in the axial direction and a valley is provided in each case between two adjacent sealing ribs, where each valley has a non-zero radial distance from the smooth surface, where each sealing rib has a height measured in the radial direction that is greater than the radial distance of the valley from the smooth surface. With this embodiment, a particularly good sealing effect can be achieved between the bottom part and the cover.

[0041] It is a preferred measure that the radial reinforcing elements are engaged in both the cover and the bottom part, so that they can reinforce both the cover and the bottom part, whereby undesired relative movements between the bottom part and the cover, for example due to deformations or even creep effects, can be further reduced.

[0042] Another preferred embodiment is that the smooth surface is designed to have a frustoconical shape. For example, if the first sealing surface is designed as a smooth surface, it can be designed to have a frustoconical shape, so that it tapers when viewed in the mounting direction. Thus, with a corresponding embodiment of the second sealing surface, the thickness of the press-in between the bottom part and the cover can be adjusted by the depth to which the cover is pressed axially into the first sealing surface. Furthermore, it is also possible to readjust the press-in after long operation. In this way, for example, creep effects over time can be compensated. Furthermore, it is easier and more material-friendly to separate the cover from the bottom part again, for example by maintenance work.

[0043] Furthermore, preferably, a ring-shaped safety seal is arranged radially between the two sealing surfaces on the one hand and the radial reinforcing element on the other hand, which safety seal prevents leakage of fluid between the bottom part and the cover in case of a failure. During normal, i.e. fault-free, operation of the pump unit, this safety seal is not in contact with the fluid and has no sealing function. However, in case of a failure or malfunction, as a result of which the sealing effect between the first and second sealing surfaces is not fully ensured, this safety seal can effectively prevent fluid contamination and leakage of fluid. For example, in the semiconductor industry, such a failure can have disastrous consequences, since it can lead to material reject, e.g. wafers, which can generate very high costs. Furthermore, for example in the case of corrosive chemicals, leakage of fluid can lead to serious danger for the environment.

[0044] However, the safety seal may be located elsewhere, for example radially outward relative to the radial reinforcing element, etc. In embodiments using a safety seal, it is only important that the safety seal cannot come into contact with the fluid being conveyed during normal, i.e. fault-free, operation.

[0045] In some applications it is advantageous if an axial reinforcing element for absorbing axially acting forces is provided on the cover, where the axial reinforcing element is arranged so as to position the cover in the axial direction between the axial reinforcing element and the bottom part.

[0046] Thus, preferably, a support structure is provided which can be connected to the axial stiffening element, the support structure being arranged such that the pump housing can be clamped between the axial stiffening element and the support structure in the axial direction. Preferably, the support structure is made of a metallic material, so that the support structure has a high stability. The support structure can be designed, for example, as a metallic mounting ring which can be arranged around the cylindrical cup of the bottom part and firmly connected to the axial stiffening element, for example by means of screws.

[0047] In a preferred embodiment, the motor housing of the centrifugal pump forms the support structure and the axial stiffening element is designed to be attached to the motor housing of the centrifugal pump, for example by means of screws, so that the pump housing is sandwiched between the axial stiffening element and the motor housing.

[0048] This axial stiffening element is advantageous, for example, when high pressures are to be generated by the pump unit or when fluids are to be conveyed at high temperatures, or in the case of large pump units generating high flow rates and / or suction heads, as it provides the pump unit with a higher stability and thus makes it possible in particular to resist possible creep effects caused by axial forces.

[0049] The axial reinforcing element preferably comprises a metallic base body, for example made of stainless steel, and a sheath made of plastic, the base body being enclosed by the sheath.

[0050] The axial reinforcing element may furthermore be designed to have a spring effect, for example by means of a spring washer, which allows a readjustment of the sealing force between the first and second sealing surfaces.

[0051] If the pump unit is designed with axial reinforcing elements, it is advantageous from a construction point of view for the axial reinforcing elements to be designed as a single piece together with the radial reinforcing elements.

[0052] According to another preferred embodiment, the bottom part comprises a ring-shaped groove bounded by a radially inner wall and a radially outer wall, wherein the cover is designed to be sealingly engaged in the groove, wherein the radially inner wall or the radially outer wall forms the first sealing surface.

[0053] In another preferred embodiment, a ring-shaped recess is provided in the cover extending radially inwardly adjacent to the second sealing surface, and the ring-shaped groove is separated from the second sealing surface by a ring-shaped web, so that in the operating condition the pressure of the fluid against the web reinforces the sealing interaction of the first and second sealing surfaces. With this embodiment, the pressure of the fluid in the pump housing can be used to generate an additional radially outward force in the operating condition, which increases the sealing effect between the two sealing surfaces.

[0054] As already mentioned, embodiments are also possible in which the first sealing surface is designed as a smooth sealing surface and the second sealing surface is designed as a ribbed surface.

[0055] Of course, embodiments are also possible in which the first sealing surface is designed as a ribbed surface.

[0056] Preferably, the radial reinforcing element is designed as a metal ring enclosed by a plastic sheath, particularly preferably made of rustproof steel or stainless steel.

[0057] In a particularly preferred embodiment, the outlet for the fluid is arranged in the bottom part of the pump housing, which means that the fluid is preferably discharged from the bottom part of the pump housing.

[0058] Furthermore, the invention proposes a centrifugal pump for conveying a fluid, which comprises a pump unit designed according to the invention and a drive unit with a motor housing in which a stator is arranged, the stator together with the rotor forming an electromagnetic rotary drive for rotating the rotor about the axial direction, whereby the drive unit is designed for contactless magnetic levitation of the rotor.

[0059] Preferably, the stator is designed as a bearing-drive stator, by which the rotor can be magnetically driven without contact and can be magnetically levitated relative to the stator without contact, the rotor being passively magnetically stabilized in the axial direction and also actively magnetically levitated in a radial plane perpendicular to the axial direction, wherein the motor housing has a recess in the axial end face and a cylindrical cup of the pump housing is inserted into the recess.

[0060] Particularly preferably, the electromagnetic rotary drive is designed as a temple motor, the stator having a number of coil cores, each of which has a longitudinal leg extending axially from a first end to a second end and a transverse leg arranged in a radial plane at the second end of the longitudinal leg, the transverse legs extending radially from the longitudinal legs, the coil cores being arranged around the rotor in the circumferential direction, so that the rotor is arranged between the transverse legs of the coil cores, and at least one concentrated winding is provided on each longitudinal leg, at least one concentrated winding surrounding each longitudinal leg.

[0061] Further advantageous arrangements and embodiments of the invention emerge from the dependent claims.

[0062] In the following, the invention will be explained in more detail with reference to examples and also with reference to the drawings. [Brief description of the drawings]

[0063] [Figure 1] FIG. 1 is a perspective, partially cut-away view of a centrifugal pump according to the state of the art; [Diagram 2] FIG. 2 is a cross-sectional view showing a pump unit of the centrifugal pump of FIG. 1. [Diagram 3] 1 is a cross-sectional view showing a first embodiment of a pump unit according to the present invention. [Figure 4] FIG. 4 is an exploded view similar to FIG. [Diagram 5] FIG. 5 shows detail I of FIG. [Figure 6] 11A-11C are cross-sectional views showing different variants for the sealing rib; [Figure 7] FIG. 13 is a cross-sectional view showing a variation for the sealing surface. [Figure 8] FIG. 11 is a cross-sectional view showing a variation for the first embodiment. [Figure 9] FIG. 9 is an exploded view similar to FIG. [Figure 10] FIG. 4 is a cross-sectional view showing a second embodiment of a pump unit according to the present invention. [Figure 11] FIG. 11 is an exploded view similar to FIG. [Figure 12] FIG. 11 is a cross-sectional view showing a variation for the second embodiment. [Figure 13] FIG. 13 is an exploded view similar to FIG. [Figure 14] FIG. 11 is an exploded cross-sectional view showing a third embodiment of a pump unit according to the present invention. [Figure 15] FIG. 11 is an exploded cross-sectional view showing a fourth embodiment of a pump unit according to the present invention. [Figure 16] FIG. 10 is an exploded cross-sectional view showing a fifth embodiment of a pump unit according to the present invention. [Figure 17] A cross-sectional view showing a sixth embodiment of a pump unit according to the present invention. [Figure 18] FIG. 18 is an exploded view similar to FIG. [Figure 19]1 is a schematic cross-sectional view showing an embodiment of a centrifugal pump according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0064] As already explained above, Fig. 1 shows a centrifugal pump 200' having a contactless magnetically supported and contactless magnetically driven rotor 10' known from the state of the art. Fig. 2 shows a pump unit 1' of this centrifugal pump 200' as a cross-sectional representation.

[0065] As a representation similar to Figure 2, Figure 3 shows a first embodiment of a pump unit according to the invention, designated in its entirety by the reference number 1. To enable a better understanding, Figure 4 also shows the first embodiment of the pump unit 1 in an exploded view.

[0066] The pump unit 1 is designed for a centrifugal pump 200 (see FIG. 19) for conveying a fluid and comprises a pump housing 2 having an inlet 21 and an outlet 22 for the fluid. A rotor 10 (not shown in FIG. 4) for conveying the fluid is arranged in the pump housing 2 and forms a wheel or impeller of the pump unit 1 and thus of the centrifugal pump 200. The rotor 10 can be rotated about a desired axis of rotation defining an axial direction A.

[0067] The direction perpendicular to the axial direction A is designated as the radial direction. In the following, the term "axial" is used in its commonly accepted sense of "axially" or "in the axial direction". The term "radial" is used in its commonly accepted sense of "radially" or "in the radial direction".

[0068] The pump unit 1 is designed for contactless magnetic levitation of the rotor 10 and for contactless magnetic drive of the rotor 10. This can in particular be realized in a manner analogous to that described on the basis of figures 1 and 2. The pump unit 1 according to the invention can therefore be designed in a manner analogous to that of the pump unit 1' of figure 2 with regard to magnetic levitation and magnetic drive. For this purpose, the rotor 10 of the pump unit 1 comprises a magnetically effective core 101, designed for example as a permanent magnet ring or disk and surrounded by a plastic sheath.

[0069] Furthermore, the rotor 10 comprises a number of vanes 103 for conveying the fluid from the inlet 21 to the outlet 22. The vanes 103 are arranged on a plastic sheath of the magnetically effective core. The vanes 103 are preferably made of plastic and can be designed, for example, as a single piece with the plastic sheath. Of course, it is also possible to manufacture the individual vanes 103 or the entire vane 103 in a separate manufacturing process and connect the vanes 103 to the plastic sheath of the magnetically effective core 101, for example by a welding process.

[0070] The impeller formed by the rotor 10 with the vanes 103 is preferably designed as a radial impeller which is approached by the fluid from the inlet 21 in the axial direction A and deflects the fluid radially.

[0071] The pump housing 2 comprises a bottom part 3 and a cover 4 for closing the bottom part 3, where the bottom part 3 has a cylindrical cup 31 for receiving the rotor 10. The cup 31 is preferably designed and arranged so that it can be inserted into a recess of the drive unit 100 (Fig. 19). In particular, this can be achieved in a manner similar to that described with reference to Fig. 1. The cup is thus arranged and designed so that it can be inserted into a recess 121' (Fig. 1) in the motor housing 120' of the drive unit 100', the magnetically effective core 101 being arranged between the lateral legs 127' of the coil core 125'.

[0072] An important feature for the operational safety of the pump unit 1 is a reliable sealed connection between the bottom part 3 and the cover 4, in order to make it possible to reliably prevent leakage of fluid from the interior of the pump housing 2 to the outer space of the pump housing between the bottom part 3 and the cover 4. Furthermore, this sealed connection must be ensured even at high temperatures, e.g. up to 220° C. and / or at high pressures and / or in the case of chemically very aggressive fluids, such as sulfuric acid.

[0073] According to the invention, for this purpose the bottom part 3 has a substantially ring-shaped first sealing surface 5 for sealing interaction with the cover 4, and the cover 4 has a substantially ring-shaped second sealing surface 6 designed for sealing interaction with the first sealing surface 5. For this purpose one of the two sealing surfaces 5 or 6 is designed as a ribbed surface having at least one radial sealing rib 7 extending in the circumferential direction along the entire sealing surface 5 or 6, whereas the other of the two sealing surfaces 6 or 5 is designed as a smooth surface.

[0074] In the embodiment represented by Figures 3 and 4, the first sealing surface 5, i.e. the sealing surface 5 of the bottom part 3, is designed as a smooth surface and the second sealing surface 6, i.e. the sealing surface 6 of the cover 4, is designed as a ribbed surface.

[0075] For a better understanding, FIG. 5 further shows an enlargement of detail I of FIG. 4 so that the sealing interaction of the first sealing surface 5 and the second sealing surface 6 can be better appreciated.

[0076] Preferably, the ribbed surface comprises a number of radial sealing ribs 7 (in a first embodiment, precisely three), each of which extends completely along the entire ribbed surface, where the individual sealing ribs 7 are arranged next to each other in the axial direction A. Each sealing rib 7 is designed as a closed circular-shaped ring. Each radial sealing rib 7 is designed to allow absorbing radial forces. For this purpose, preferably but not necessarily, the sealing ribs 7 are aligned perpendicularly or at right angles to the axial direction A. Also possible are embodiments in which the sealing ribs 7 are arranged obliquely on the sealing surface 5 or 6, i.e. at an angle different from 90° to the axial direction A. It only makes sense that the radial sealing ribs 7 have a sufficient radial extension to allow absorbing radial forces.

[0077] It will be understood that the number of three sealing ribs 7 should be considered as an example: more than four or less than three sealing ribs 7 can also be provided on the sealing surface 5 or 6 designed as a ribbed surface.

[0078] In both the first embodiment of the pump housing 1 according to the invention and in all other embodiments described later, a variant is also possible in which the first sealing surface 5 is designed as a ribbed surface and the second sealing surface 6 is designed as a smooth surface. In all embodiments, both of these embodiments are therefore always possible, i.e. the respective sealing rib 7 is provided on the bottom part 3 and the second sealing surface on the cover 6 is designed as a smooth surface, and the respective sealing rib 7 is provided on the cover 4 and the first sealing surface 5 on the bottom part 3 is designed as a smooth surface. Figure 15 shows by way of example an embodiment in which the sealing rib 7 is arranged in the first sealing surface 5, i.e. in the sealing surface 5 of the bottom part 3.

[0079] The expression that one of the sealing surfaces 5, 6 is designed as a "smooth surface" means that this surface does not have any indentations or recesses, such as grooves, into which the sealing rib 7 can be engaged. Of course, it is also possible for a smooth surface to be plastically or elastically deformed by the sealing rib 7 (see for example FIG. 5), but a sealing surface 5 or 6 designed as a smooth surface is not provided with a texture or structure, in particular with grooves, into which the sealing rib 7 can be engaged. The sealing effect between a sealing surface 5 or 6 designed as a ribbed surface and a sealing surface 6 or 5 designed as a smooth surface is based on the pressure of the sealing rib 7 against the smooth surface and not on the sealing rib 7 being engaged in a groove or other recess.

[0080] The pump housing 2 is preferably made of plastic. Suitable plastics are, for example, perfluoroalkoxy polymers (PFA) or polytetrafluoroethylene (PTFE), since they have a very high chemical resistance and are not attacked or decomposed by chemically very corrosive substances, such as, for example, sulfuric acid. In addition, PFA and PTFE are particularly high-purity plastics, in which additives are used and whose molecular complexes are chemically very stable, i.e. resistant to corrosive substances.

[0081] The outlet 22 for the fluid is preferably arranged in the bottom part 3 of the pump housing 2. In particular, the outlet 22 is arranged between the cup 31 and the first sealing surface 5 in the axial direction A. This means that according to the present representation (e.g. Fig. 3, Fig. 4), the outlet 22 is arranged below all sealing ribs 7, regardless of whether the sealing ribs 7 are arranged in the second sealing surface 6 (e.g. Fig. 4) or in the first sealing surface (Fig. 15).

[0082] The sealing rib 7 is preferably an internal part of the first sealing surface 5 or the second sealing surface 6. The sealing rib 7 can for example be made in an injection molding process. For example, if the cover 4 and the bottom part 3 are made in an injection molding process, the sealing rib 7 can be made in the course of this injection molding process depending on the corresponding design of the injection mold or tool. However, it is also possible to make the sealing rib 7 by a subtractive machining process. For example, the sealing rib 7 can be machined from the first sealing surface 5 or the second sealing surface 6 by a machining process, for example a milling process.

[0083] The sealing interaction between the first sealing surface 5 and the second sealing surface 6 is based on a press fit between the cover 4 and the bottom part 3 which is explained in more detail on the basis of FIG.

[0084] According to a preferred embodiment, the pump unit 1 further comprises a radial reinforcing element 8 designed as a ring shape and extending radially outwardly around the two sealing surfaces 5, 6. Preferably, the radial reinforcing element 8 is designed as a metal ring completely surrounded by a plastic sheath. For the metal ring, corrosion-resistant steel or stainless steel is preferred. For the plastic sheath, a plastic having high chemical resistance is preferred. Examples of such suitable plastics are PTFE, PFA, ECTFE (ethylene chlorotrifluoroethylene), PP (polypropylene), ETFE (ethylene tetrafluoroethylene), PE (polyethylene). Alternatively, it is also possible to make the radial reinforcing element 8 entirely from a strong or stable plastic.

[0085] The radial reinforcing element 8 stabilizes the two sealing surfaces 5, 6, so that they remain in good sealing contact with each other even when the pressure inside the pump housing 2 is high. The radial reinforcing element 8 contributes to avoid relative movements between the two sealing surfaces, which in the worst case could lead to the opening of a gap through which fluid could escape from the pump housing 2. Another function of the radial reinforcing element 8 is to resist creep of the bottom part 3 or the cover 4. Furthermore, the radial reinforcing element 8 can also be designed to exert a radial spring effect towards the sealing surfaces 5, 6 to influence the press-fit between the sealing surfaces 5, 6. This makes it possible to adjust the press-fit between the cover 4 and the bottom part 3 if the bottom part 3 or the cover 4 is for example distorted.

[0086] Preferably, the radial reinforcing element 8 is arranged to be engaged in both the cover 4 and the bottom part 3, so that the radial reinforcing element 8 is engaged in the axial direction A over the entire boundary surface at which the bottom part 3 and the cover 4 are in contact with each other. For this purpose, a circumferential groove 42 (Figure 4) is provided in the cover 4 and a circumferential groove 32 is provided in the bottom part 3, where the circumferential grooves 32, 42 are arranged in such a way that they are aligned with respect to each other to form a gap for the radial reinforcing element 8 which will surround the radial reinforcing element 8 in the assembled state of the pump housing 2 (Figure 3).

[0087] However, embodiments without radial reinforcing elements 8 are also possible (see for example figures 17, 18).

[0088] The press-fit between the cover 4 and the bottom part 3 is depicted in the enlarged view of detail I in Fig. 5. As already mentioned, each radial sealing rib 7 is designed to be in the shape of a circular ring, where the individual sealing ribs 7 are arranged next to each other in the axial direction A. A valley 71 is provided between each two adjacent sealing ribs 7, where each valley 71 has a radial distance R from the sealing surface, which in this case is the first sealing surface 5, designed as a smooth surface.

[0089] Each sealing rib 7 has a peak 72, which denotes the point of the sealing rib 7 farthest from an adjacent valley 71, measured in a radial direction. Each sealing rib 7 has a height H, which denotes the vertical distance measured in a radial direction between the peak 72 and the adjacent valley 71. The peak 72 is connected to each of the adjacent valleys via a wall 73.

[0090] The height H of the sealing rib refers to the state in which the cover 4 has not yet been assembled with the bottom part 3, i.e. for example as represented in Fig. 4. After the cover has been assembled with the bottom part, i.e. for example in the state represented in Fig. 3, the sealing rib 7 penetrates into the smooth surface by a penetration depth T, for example due to deformation of the first sealing surface 5 designed as a smooth surface. The penetration depth T therefore indicates the difference, measured in the radial direction, between the position of the peak 72 and the non-deformed area of ​​the smooth surface opposite one of the valleys 71.

[0091] To assemble the pump housing 2 from the bottom part 3 and the cover 4, the cover 4 is preferably integrally assembled to the bottom part 3 in a mounting direction M until it brings the first sealing surface 5 into sealing interaction with the second sealing surface 6. This state is reached when the cover 4 is placed on the bottom part 3, where the mounting direction M is the axial direction A. After the cover 4 has been connected to the bottom part 3 via a press fit, the cover 4 is fixed to the bottom part 3, for example by means of a number of fixing screws 13 which pass through the cover 4 and engage into the bottom part 3 in the axial direction A.

[0092] Due to the fact that the sealing rib 7 is designed as a radial sealing rib 7 having a height H and the mounting direction M is the axial direction A, the sealing rib 7 extends transversely to the mounting direction M, for example perpendicularly to the mounting direction M. For example, this is an advantageous design over sealing elements extending in the mounting direction, such as, for example, axial sealing elements.

[0093] The strength of the press-fit between the cover 4 and the bottom part 3 is determined, inter alia, by the radial distance R, the height H and the penetration depth T, where the penetration depth T is determined, inter alia, by the material properties of the materials from which the cover 4 and the bottom part 3 are made.

[0094] In practice, it has been found that the height H is at least the same as the radial distance R, and preferably is greater than the radial distance R. The penetration depth T can also be (at least approximately) zero, so that the sealing rib 7 is in contact with the smooth surface. However, it is preferred that the penetration depth T is greater than zero, so that the sealing rib 7 penetrates into the smooth surface, which in this case is the first sealing surface 5. The radial distance R can be (at least approximately) zero, but preferably the radial distance R is greater than zero, i.e. the diameter of the cover 4 measured at the valley 71 is less than the inner diameter of the smooth surface, which in this case is the first sealing surface 5.

[0095] The radial distance R is preferably not smaller than zero. If the radial distance R is smaller than zero, the diameter of the cover 4 measured at the valley 71 is larger than the inner diameter of the smooth surface, in this case the first sealing surface 5. If the radial distance is smaller than zero, this has a negative effect on the separability of the cover 4 and the bottom part 3. Such a separation may be necessary, for example because it is necessary to replace the rotor 10.

[0096] It is advantageous in particular for the manufacture of the cover 4 with the sealing rib 7 (or alternatively, of course, also for the manufacture of the bottom part 3 with the sealing rib 7) that the connection angle α between the valley 71 and the wall 73 is in each case at least 90°, preferably greater than 90°, so that an undercut of the transition area between the wall 73 and the valley 71 is avoided in each case. This is particularly advantageous when the sealing rib is manufactured by an injection molding process.

[0097] As regards the profile of the sealing rib 7, with reference to its cross section shown in Figure 5 as a cross section in the axial direction A, a circular profile is preferred since this facilitates joining or separating the cover 4 and the bottom part 3. Furthermore, a profile is preferred such that the two walls 73 of the sealing rib 7 connecting its peak 72 to two adjacent valleys 71 are symmetrical with respect to the peak 72.

[0098] FIG. 6 exemplarily shows four different variants for the embodiment of the profile of the sealing rib 7 in a cross section in the axial direction A. The uppermost sealing rib 7 according to this representation has a substantially triangular profile. The second sealing rib 7 from the top side according to this representation has a rectangular profile at its radially inner end, i.e. at the arrangement of the valleys 71. The radially outer end of the sealing rib 7 is designed to have a semicircular profile that adjoins a rectangular profile in the radial direction. The third sealing rib 7 from the top side according to this representation has a substantially rectangular profile, in which each of the corners facing the first sealing surface 5 has a chamfered surface. The lowermost sealing rib according to this representation has a rectangular profile without a chamfered surface.

[0099] It will be appreciated that a myriad of other profiles are possible for the sealing ribs 7. In some embodiments, all of the sealing ribs 7 have the same profile at the sealing surface 5 or 6. In other embodiments, the sealing ribs 7 have at least two different profiles at the sealing surface 5 or 6.

[0100] 7 shows a variant for the embodiment of the sealing surfaces 5 and 6. In this variant, the sealing surface 5 or 6 (here, exemplarily, the first sealing surface 5) designed as a smooth surface is frustoconical, i.e. designed as a shell surface of a truncated cone. The surface normal vector of the first sealing surface 5 is therefore not oriented perpendicular to the axial direction but encloses at an angle that is not 90° to the axial direction A. Here, the truncated cone is aligned so as to taper in the installation direction M. This means that the diameter enclosed by the sealing surface 5 in a direction perpendicular to the axial direction A decreases when viewed in the direction of the rotor 10. The first sealing surface 5 therefore forms a kind of funnel that tapers when viewed from the cover 4 in the direction of the rotor 10.

[0101] Preferably, but not necessarily, the second sealing surface 6, here designed as a ribbed surface with sealing ribs 7, is also designed to be frustoconical. The second sealing surface 6 is designed as a shell surface of a truncated cone, which is more acute than the truncated cone forming the first sealing surface 5 with its shell surface. According to this embodiment, the first sealing surface 5 and the second sealing surface 6 enclose a non-zero clearance angle β. As represented in FIG. 7, the clearance angle β is the angle between the first sealing surface 5, designed as a smooth surface, and a straight line passing through all the valleys 71 of the second sealing surface 6. To ensure that the radial sealing effect is adequately maintained, the clearance angle β is at most 60°, preferably less than 30°.

[0102] Furthermore, preferably, but not necessarily, the sealing ribs 7 have various heights H as represented in Fig. 7. The height H of each of the sealing ribs 7 decreases as the space enclosed by the ribbed surface, in this case the second sealing surface 6, becomes narrower. According to the representation in Fig. 7, the uppermost sealing rib 7 has the largest height H, and according to this representation the lowermost sealing rib 7 has the smallest height H.

[0103] An advantage of such a conical embodiment of the sealing surfaces 5 and 6 is that the press-in, and in particular the strength of the press-in, can be adjusted by means of the fastening screw 13. The more the cone surrounded by the second sealing surface 6 is pressed into the cone surrounded by the first sealing surface 5 in the mounting direction M by turning the fastening screw 13, the stronger the press-in between the cover 4 and the bottom part 3 becomes.

[0104] Furthermore, this embodiment has the advantage that the press fit can be retightened in case of long term creep, for example of the cover 4 and / or the bottom part 3 .

[0105] In addition, the conical embodiment of the sealing surfaces 5, 6 allows easier separation of the cover 4 from the bottom part 3. The risk of breakage when separating the cover 4 from the bottom part 3 in the reverse direction of the mounting direction M is significantly reduced.

[0106] Other geometries of the substantially ring-shaped sealing surfaces 5, 6 are also possible, for example the two sealing surfaces 5, 6 can be designed to enclose an ellipsoid or even to enclose a helical structure, the latter being preferred in those embodiments in which the pump housing 2 is designed as a volute casing.

[0107] Figure 8 shows, as a cross-sectional view similar to figure 3, a variant of the first embodiment of the pump unit 1 according to the invention. To enable a better understanding, figure 9 also shows this variant in an exploded view.

[0108] In the variants represented in figures 8 and 9, a ring-shaped safety seal 20 is additionally provided, which prevents leakage of fluid between the bottom part 3 and the cover 4 in the event of a fault. The safety seal 20 is arranged in the axial direction A in the contact surface between the bottom part 3 and the cover 4. The safety seal 20 is arranged in the radial direction on the one hand between the two sealing surfaces 5, 6 and also between the radial reinforcing elements 8, i.e. the safety seal 20 is arranged radially outward with respect to the first sealing surface 5 and the second sealing surface 6. As a result, the safety seal 20 does not come into contact with the fluid in a fault-free operating state of the pump unit 1. Due to the sealing interaction of the first sealing surface 5 with the second sealing surface 6, the fluid cannot penetrate as far as the safety seal 20, so that, conversely, there is no risk of the fluid being contaminated by the safety seal 20.

[0109] If, however, a fault occurs during operation, as a result of which the sealing effect between the two sealing surfaces 5, 6 is not ensured to a sufficient degree, then on the one hand the safety seal 20 prevents an unintended or uncontrolled escape of fluid from the pump housing 2, so that, for example, corrosive or other dangerous fluids cannot seep into the environment or into the external space of the pump housing 2. If such a fault occurs, then on the other hand the safety seal 20 prevents the infiltration of substances from the outside into the internal space of the pump housing, which could lead to a contamination of the fluid and thus to unusability of the fluid or of products processed with the fluid, such as, for example, wafers in the semiconductor industry.

[0110] Such failures, which may render the sealing effect of the two sealing surfaces 5, 6 insufficient, are due, for example, to creep effects, and in particular long-term creep effects, or pressure-induced and / or temperature-induced deformations, for example of the cover 4 or the bottom part 3.

[0111] The safety seal 20 is preferably designed as a ring-shaped flat seal.

[0112] The safety seal 20 is preferably made of a plastic, such as a plastic that is typically used to seal hot and / or chemically aggressive fluids. For example, the safety seal 20 may be made of the same plastic as the pump housing 2. For example, the safety seal 20 may be made of PTFE. In this case, the safety seal 20 is preferably made of ePTFE (expanded PTFE), in particular because ePTFE has better elastic properties than PTFE.

[0113] Of course, it is also possible to use known elastomers for the safety seal 20. Furthermore, it is also possible for the safety seal to be designed as a radial O-ring or an axial O-ring.

[0114] Fig. 10, as a view similar to Fig. 3, shows a cross-sectional view of a second embodiment of a pump unit 1 according to the invention. To enable a better understanding, Fig. 11 also shows the second embodiment in an exploded view.

[0115] In the following, only the differences with respect to the first embodiment are considered. The equivalent and same parts relating to the second embodiment are indicated with the same reference signs as in the first embodiment. In particular, the reference signs have the same meaning as already explained in relation to the first embodiment. It will be understood that all the above descriptions of the first embodiment and variants apply in the same manner or similarly in the same manner to the second embodiment.

[0116] In a second embodiment of the pump unit 1, an axial stiffening element 9 capable of absorbing forces acting in the axial direction A is additionally provided on the cover 4. Here, the axial stiffening element 9 is designed as an annular disk-shaped plate which surrounds the inlet 21 and rests on the cover 4, so that the cover 4 is arranged between the axial stiffening element 9 and the bottom part 3.

[0117] Furthermore, a number of fastening screws 12 are provided, each of which extends in the axial direction A completely through the axial reinforcement element 9 and the pump housing 2, so that in this representation each fastening screw 12 projects downwards from the pump housing 2 in the axial direction A. The fastening screws 12 are designed to be engaged in the drive unit 100 (FIG. 19) when the pump unit 1 is assembled with the drive unit 100 to form the centrifugal pump 200. For this purpose, a threaded portion in which the fastening screws 12 are engaged is preferably provided in the motor housing of the drive unit 100, which can be designed, for example, similar to the motor housing 120′ of FIG. 1.

[0118] The clamping screws 12 are arranged radially outwardly with respect to the radial reinforcing element 8. By means of the clamping screws 12, the pump housing 2 can be clamped between the drive unit 100 and the axial reinforcing element 9, which allows a significant increase in the stability of the pump housing in the axial direction A. This increased stability is particularly advantageous in applications where very high pressures occur in the pump unit 1 or where the fluid is conveyed at very high temperatures, for example above 200° C., or where the pump unit 1 is designed with very large dimensions. The axial reinforcing element allows creep caused by axial forces to be resisted more effectively.

[0119] As a variant, it is also possible to design the axial stiffening element 9 with a spring effect, for example by means of a spring washer, so that it exerts a spring force, which is advantageous with the aim of further reducing creep of the component in the axial direction A. In this way, it is also possible to readjust the sealing force when the two sealing surfaces 5, 6 interact.

[0120] The term "axial reinforcing element 9" should be understood as meaning that the axial reinforcing element 9 is capable of absorbing axial forces. However, this does not necessarily mean that the axial reinforcing element 9 must be arranged perpendicular to the axial direction A, as shown for example in figures 10 and 11. Embodiments are also possible in which the axial reinforcing element is designed obliquely to the axial direction A.

[0121] Preferably, the axial reinforcing element 9 is designed as a metal plate completely surrounded by a plastic sheath. For the metal plate, corrosion-resistant steel or stainless steel is preferred. For the plastic sheath, a plastic with high chemical resistance is preferred. Examples of such suitable plastics are PTFE, PFA, ECTFE (ethylene chlorotrifluoroethylene), ETFE (ethylene tetrofluoroethylene), PP (polypropylene), PE (polyethylene). Alternatively, it is also possible to make the axial reinforcing element 9 entirely from a high-strength or stable plastic.

[0122] Fig. 12, as a similar view to Fig. 10, shows a cross-sectional view of a variant of a second embodiment of a pump unit 1 according to the invention. To enable a better understanding, Fig. 13 additionally shows this variant in an exploded view.

[0123] 12 and 13, the axial reinforcing element 9 is designed in a single piece with the radial reinforcing element 8. Thus, a single-piece reinforcing element 98 is provided which forms both the axial reinforcing element 9 and the radial reinforcing element 8.

[0124] The single-part reinforcing element 98 comprises an axial reinforcing element 9 designed as an annular disk-shaped plate arranged on the cover 4 surrounding the inlet 21, so that the cover 4 is arranged between the axial reinforcing element 9 and the bottom part 3. The single-part reinforcing element 98 further comprises a ring-shaped reinforcing element 8 designed as a ring and extending radially outwardly around the two sealing surfaces. The radial reinforcing element 8 is arranged in a circumferential groove 32 in the bottom part 3. The single-part reinforcing element 98 further comprises a ring-shaped connection area 89 connecting the axial reinforcing element 9 to the radial reinforcing element 8. The ring-shaped connection area 89 adjoins the radially outer edge of the axial reinforcing element 9 and is designed to radially outwardly surround the cover 4 and be in close contact with it.

[0125] Preferably, the single-piece reinforcing element 98 is designed to have a metal base body completely surrounded by a plastic sheath. The metal base body is preferably made of corrosion-resistant steel or stainless steel. The plastic sheath is preferably made of a plastic with high chemical resistance. Examples of such suitable plastics are PTFE, PFA, ECTFE (ethylene chlorotrifluoroethylene), ETFE (ethylene tetrafluoroethylene), PP (polypropylene), PE (polyethylene). Alternatively, the single-piece reinforcing element 98 can be made entirely from high-strength or stable plastic.

[0126] The single-piece embodiment of the radial reinforcing element 8 with the axial reinforcing element 9 as a single-piece reinforcing element 98 has the advantage of being particularly simple and therefore cost-effective to produce. In addition, the single-piece reinforcing element 98 gives the pump unit 1 a particularly high robustness, for example because the cover 4 is completely surrounded and supported along its radially outer circumferential surface, as a result of which creep effects can be further reduced. This is also particularly advantageous in applications in which high-temperature fluids are conveyed.

[0127] It will be understood that the variant using a single-piece reinforcing element 98 is also suitable for all other embodiments of the pump unit 1 according to the invention.

[0128] FIG. 14, as an exploded view similar to FIG. 11, shows a cross-sectional representation of a third embodiment of a pump unit 1 according to the invention.

[0129] In the following, only the differences from the embodiment described above will be considered. The equivalent parts related to the third embodiment are indicated with the same reference signs as in the embodiment described above. In particular, the reference signs have the same meaning as already explained in relation to the above embodiment. It will be understood that all the previous explanations related to the embodiments and variants apply in the same manner or similarly in the same manner to the third embodiment.

[0130] The third embodiment of the pump unit 1 according to the invention is similar in design to the second embodiment (FIG. 11), but in the third embodiment the circumferential groove 32 in the bottom part of the second embodiment is replaced by a ring-shaped groove 33 which, with respect to its width measured in the radial direction, is significantly larger than the circumferential groove 32 of the second embodiment.

[0131] The ring-shaped groove 33 is bounded in the radial direction by a radially inner wall 331 and a radially outer wall 332, where the radially outer wall 332 is arranged radially outward with respect to the radially inner wall 331. The width of the ring-shaped groove 33 is therefore the radial distance between the radially inner wall 331 and the radially outer wall 332. The radially inner wall 331 forms a first sealing surface 5 of the bottom part 3, where the first sealing surface 5 is designed as a smooth sealing surface.

[0132] The cover 4 of the third embodiment is designed with a ring-shaped axial end region 44 which is engaged in the ring-shaped groove 33. The ring-shaped axial end region 44 is bounded in the radial direction by a radially inner surface 441 and a radially outer surface 442, where the radially outer surface 442 is arranged radially outward with respect to the radially inner surface 441. The radially inner surface 441 of the axial end region 44 forms the second sealing surface 6 of the cover 4, designed here as a ribbed surface with sealing ribs 7.

[0133] When the axial end region 44 of the cover 4 is engaged in the ring-shaped groove 33 in the bottom part, the first sealing surface 5 formed by the radially inner wall 331 and the second sealing surface 6 formed by the radially inner surface 441 interact sealingly.

[0134] The width of the ring-shaped groove 33 is dimensioned such that the ring-shaped radial reinforcing element 8 can be engaged in the ring-shaped groove 33, so that the radial reinforcing element 8 is radially arranged between the axial end region 44 and the radially outer wall 332.

[0135] The ring-shaped groove 33, the axial end region 44 and the radial extension of the radial reinforcing element 8 are dimensioned such that a press fit is achieved between the cover 4 and the bottom part 3 and such that the first sealing surface 5 comes into sealing interaction with the second sealing surface 6.

[0136] According to a third embodiment variant of the pump unit 1, not represented in the drawings, the first sealing surface 5, i.e. the sealing surface 5 of the bottom part 3, is designed as a ribbed surface with sealing ribs 7 and the second sealing surface 6, i.e. the sealing surface 6 of the cover 4, is designed as a smooth surface. Thus, in this variant, the radially inner wall 331 of the ring-shaped groove 33 is designed as a ribbed surface and the radially inner surface 441 of the axial end region 44 is designed as a smooth surface.

[0137] FIG. 15, as an exploded view similar to FIG. 11, shows a cross-sectional representation of a fourth embodiment of a pump unit 1 according to the invention.

[0138] In the following, only the differences with respect to the embodiments described above will be considered. The same equivalent parts relating to the fourth embodiment are indicated with the same reference signs as in the embodiments described above. In particular, the reference signs have the same meaning as already explained in relation to the embodiments described above. It will be understood that all the above explanations relating to these embodiments and variants apply in the same manner or in a similar manner to the fourth embodiment.

[0139] As already mentioned above, the pump housing 1 according to the invention is possible both in an embodiment in which the first sealing surface 5 of the bottom part 3 is designed as a smooth surface and the second sealing surface 6 of the cover 4 is designed as a ribbed surface with sealing ribs 7 and in an embodiment in which the first sealing surface 5 of the bottom part 3 is designed as a ribbed surface with sealing ribs 7 and the second sealing surface 6 of the cover 4 is designed as a smooth surface, and this applies in particular to all embodiments described in this specification.

[0140] A fourth embodiment of the pump unit 1 according to the invention shows, by way of example, an embodiment in which the first sealing surface 5 is designed as a ribbed surface. The fourth embodiment is designed similarly to the second embodiment (FIG. 11). However, in the fourth embodiment the first sealing surface 5, i.e. the sealing surface of the bottom part 3, is designed as a ribbed surface with sealing ribs 7. The second sealing surface 6, i.e. the sealing surface of the cover 4, is designed as a smooth surface.

[0141] FIG. 16, as a cross-sectional view similar to FIG. 10, shows a cross-sectional view of a fifth embodiment of a pump unit 1 according to the invention.

[0142] In the following, only the differences with respect to the embodiments described above will be considered. The same equivalent parts relating to the fifth embodiment are indicated with the same reference signs as in the embodiments described above. In particular, the reference signs have the same meaning as already explained in relation to the embodiments described above. It will be understood that all the above explanations relating to these embodiments and variants apply in the same manner or in a similar manner to the fifth embodiment.

[0143] A fifth embodiment of a pump unit 1 according to the invention (FIG. 16) is designed similarly to the second embodiment (FIG. 10).

[0144] In the fifth embodiment, a ring-shaped recess 45 is provided in the cover 4 and extends radially inwardly adjacent to the second sealing surface, where the ring-shaped recess 45 is separated radially outwardly from the second sealing surface 6 by a ring-shaped web 46. A radially inner boundary surface 461 of the web 46 forms the radially outer boundary of the recess 45. A radially outer boundary surface of the web 46 forms the second sealing surface 6, i.e. the sealing surface 6 of the cover 4, which is here designed as a ribbed surface with sealing ribs 7. The ring-shaped recess 45 is therefore arranged at the same height as the sealing surfaces 5 and 6 in the axial direction A. In the operating state of the pump unit 1, the ring-shaped recess 45 is of course also filled with fluid, so that the pressure of the fluid exerts a radially outward force on the web 46, thereby reinforcing the sealing interaction of the first sealing surface 5 and the second sealing surface 6.

[0145] In all the above-described embodiments and variants, the outlet of the pump housing is provided in the bottom part 3. In particular, the outlet 22 is always arranged below the sealing rib 7 according to the present representation, i.e. in the axial direction A, between the cylindrical cup 31 and the two sealing surfaces 5 and 6. This is also a preferred embodiment, i.e. it is also preferred that all sealing ribs 7 are arranged above the outlet 22 (according to the representations of Figures 3, 4, 8-16). However, embodiments are also possible in which the separation surface between the cover 4 and the bottom part 3 is arranged significantly closer to the cylindrical cup 31 in the axial direction A, so that the outlet 22 is located above the sealing rib 7 according to the present representation. For example, the outlet 22 can be arranged in the cover 4.

[0146] Fig. 17 shows a sixth embodiment of a pump unit 1 according to the invention in a cross-sectional view similar to that of Fig. 3. To enable a better understanding, Fig. 18 further shows the sixth embodiment of the pump unit 1 in an exploded view.

[0147] In the following, only the differences with respect to the embodiments described above will be considered. The same equivalent parts relating to the fifth embodiment are indicated with the same reference signs as in the embodiments described above. In particular, the reference signs have the same meaning as already explained in relation to the embodiments described above. It will be understood that all the above explanations relating to these embodiments and variants apply in the same manner or in a similar manner to the fifth embodiment.

[0148] The sixth embodiment of the pump unit 1 according to the invention is designed similarly to the first embodiment (FIGS. 3, 4). In contrast to the first embodiment, no radial reinforcing elements 8 are provided in the sixth embodiment. Thus, the circumferential grooves 32, 42 (FIG. 4) provided in the first embodiment are also absent in the sixth embodiment.

[0149] Furthermore, a centrifugal pump 200 for conveying a fluid by means of a pump unit 1 is proposed according to the invention, whereby the pump unit 1 is designed according to the invention. Fig. 19 shows an embodiment of a centrifugal pump 200 according to the invention in a schematic cross-sectional view. The centrifugal pump 200 comprises a drive unit 100 with a motor housing. To allow a better overview, the motor housing is not shown in Fig. 19. However, the drive unit 100 can be designed in the same way, for example similar to a drive unit 100' with a motor housing 120' represented in Fig. 1, whereby a recess 121' is provided in the motor housing 120' and a cylindrical cup 31 of the bottom part 3 of the pump housing 1 is inserted into the recess 121'.

[0150] A stator 102 is arranged in the motor housing, which together with the rotor 10 forms an electromagnetic rotary drive for rotating the rotor 10 about the axial direction A, where the drive unit 100 is designed for contactless magnetic levitation of the rotor 10.

[0151] Preferably, the stator 102 is designed as a bearing-drive stator, by means of which the rotor 10 can be magnetically driven without contact and can be magnetically levitated without contact relative to the stator 102, in which the rotor is passively magnetically stabilized in the axial direction A and actively, i.e. controllably, magnetically levitated in a radial plane E perpendicular to the axial direction.

[0152] Particularly preferably, the electromagnetic rotary drive with the rotor 10 and the stator 102 is designed as a temple motor, in which the stator 102 has a number of coil cores 125, each of which has a longitudinal leg 126 extending in the axial direction A from a first end to a second end and a transverse leg 127 arranged at the second end of the longitudinal leg 126 in the radial plane E. The transverse leg 127 extends radially inwards from the longitudinal leg 126 towards the rotor 10.

[0153] The first ends, or lower ends according to the present disclosure, of all of the longitudinal legs 126 are connected to each other by a back iron 122 for conducting magnetic flux.

[0154] The coil core 125 is circumferentially disposed about the rotor 10 such that the rotor 10 is disposed between the lateral legs 127 of the coil core 125. At least one concentrated winding 160 is provided on each longitudinal leg 126 such that at least one concentrated winding 160 surrounds each longitudinal leg 126.

[0155] The rotating electromagnetic fields necessary for the magnetic drive and magnetic levitation of the rotor 10 are generated by the concentrated windings 160. Using these concentrated windings 160, such a rotating electromagnetic field is thus generated in operation in a manner known per se, so as to exert a torque on the rotor 10 and also to exert an optionally adjustable transverse force radially on the rotor 10, so that the radial position of the rotor 10, i.e. its position in the radial plane E perpendicular to the axial direction A, is actively controlled or adjusted. With regard to the other three degrees of freedom, i.e. its position in the axial direction and its tilt with respect to the radial plane E perpendicular to the desired axis of rotation (two degrees of freedom), the rotor 10 is passively magnetically levitated or stabilized by magnetic reluctance forces, i.e. the rotor 10 cannot be controlled.

Claims

1. A pump unit for a centrifugal pump for conveying a fluid, comprising a pump housing (2) having an inlet (21) and an outlet (22) for said fluid, and a rotor (10) arranged in said pump housing (2) for conveying said fluid, which can be rotated about an axial direction (A), said pump unit being designed for contactless magnetic levitation of said rotor (10) and for contactless magnetic driving of said rotor (10), said pump housing (2) having a bottom part (3) and a cover (4) for closing said bottom part (3), said bottom part (3) comprising a cylindrical cup (31) for receiving said rotor (10), 1. A pump unit having a substantially ring-shaped first sealing surface (5) for sealing interaction with said cover (4), said cover (4) having a substantially ring-shaped second sealing surface (6) designed for sealing interaction with said first sealing surface (5), characterized in that one of said two sealing surfaces (5, 6) is designed as a ribbed surface with at least one radial sealing rib (7), said at least one radial sealing rib (7) extending in the circumferential direction along the entirety of said sealing surface (5, 6), whereas the other of said two sealing surfaces (6, 5) is designed as a smooth surface.

2. 2. A pump unit according to claim 1, wherein a radial reinforcing element (8) designed in the shape of a ring is provided, extending radially outwardly around said two sealing surfaces (5, 6).

3. 3. A pump unit according to claim 1, wherein the ribbed surface comprises a plurality of radial sealing ribs (7), each of which extends in a circumferential direction along the entire ribbed surface, the sealing ribs (7) being arranged adjacent to one another in the axial direction (A), a valley (71) being provided in each case between two adjacent sealing ribs (7), each valley (71) having a radial distance (R) from the smooth surface that is not zero, and each sealing rib (7) having a height (H), measured in the radial direction, that is greater than the radial distance (R) of the valley (71) from the smooth surface.

4. A pump unit according to any one of claims 2 to 3, wherein the radial reinforcing element (8) is engaged in both the cover (4) and the bottom part (3).

5. 5. A pump unit according to any one of claims 1 to 4, wherein the smooth surface is designed to have a frusto-conical shape.

6. 6. The pump unit according to claim 1, wherein a ring-shaped safety seal (20) is arranged radially between the two sealing surfaces (5, 6) on the one hand and the radial reinforcing element (8) on the other hand, the safety seal (20) preventing leakage of the fluid between the bottom part (3) and the cover (4) in case of a malfunction.

7. 7. A pump unit according to claim 1, wherein an axial reinforcing element (9) for absorbing forces acting in the axial direction (A) is provided on the cover (4), the axial reinforcing element (9) being arranged to position the cover (4) between the axial reinforcing element (9) and the bottom part (3) in the axial direction (A).

8. 7. A pump unit according to claim 6, wherein the axial reinforcing element (9) is formed in one piece with the radial reinforcing element (8).

9. 9. A pump unit according to any one of claims 1 to 8, wherein the bottom part (3) comprises a ring-shaped groove (33) bounded by a radially inner wall (331) and a radially outer wall (332), the cover (4) being designed to be sealingly engaged in the groove (33), the radially inner wall (331) or the radially outer wall (332) forming the first sealing surface (5).

10. 10. A pump unit according to any one of claims 1 to 9, wherein a ring-shaped recess (45) is provided in the cover (3) extending radially inwardly adjacent the second sealing surface (6), said ring-shaped recess (45) being separated from the second sealing surface (6) by a ring-shaped web (46), so that in operating conditions the pressure of the fluid against the web (46) reinforces the sealing interaction of the first sealing surface (5) and the second sealing surface (6).

11. 11. A pump unit according to any one of the preceding claims, wherein the first sealing surface (5) is designed as the smooth sealing surface and the second sealing surface (6) is designed as the ribbed surface.

12. 12. Pump unit according to any one of claims 2 to 11, characterized in that the radial reinforcing element (8) is designed as a metal ring enclosed by a sheath of plastic material.

13. 13. A centrifugal pump for conveying a fluid, comprising a pump unit (1) designed according to any one of claims 1 to 12 and a drive unit (100) with a motor housing in which a stator (102) is arranged, said stator (102) together with said rotor (10) forming an electromagnetic rotary drive for rotating said rotor (10) about said axial direction (A), said drive unit (100) being designed for contactless magnetic levitation of said rotor (10).

14. 14. The centrifugal pump according to claim 13, wherein the stator (102) is designed as a bearing and driving stator, by means of which the rotor (10) can be magnetically driven without contact and can be magnetically levitated without contact with respect to the stator (2), the rotor (10) is passively magnetically stabilized in the axial direction (A) and also actively magnetically levitated in a radial plane (E) perpendicular to the axial direction (A), and the motor housing has a recess in its axial end face, into which a cylindrical cup (31) of the pump housing (1) can be inserted.

15. The electromagnetic rotary drive is designed as a temple motor, the stator (102) has a plurality of coil cores (125), each of the plurality of coil cores (125) having a longitudinal leg (125) extending in the axial direction (A) from a first end to a second end, and a transverse leg (127) arranged at the second end of the longitudinal leg (126) in the radial plane (E), the transverse leg (127) being arranged at the second end of the longitudinal leg (126), the transverse leg (127) being arranged at the second end of the longitudinal leg (126) in the radial plane (E ...

15. The centrifugal pump of claim 14, wherein the coil core (125) extends radially from the lateral legs (127) of the rotor (10), the coil core (125) is arranged circumferentially around the rotor (10) such that the rotor (10) is arranged between the lateral legs (127) of the coil core (125), and at least one concentrated winding (160) is provided on each longitudinal leg (125), the at least one concentrated winding (160) surrounding each of the longitudinal legs (126).

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