EP3303844B1 - Impeller for a centrifugal pump and centrifugal pump - Google Patents

Description

The invention relates to an impeller for a centrifugal pump according to the preamble of claim 1 and a centrifugal pump according to the preamble of claim 12.

Centrifugal pumps are known in the art and have been used successfully in the process industry for many years. Process industry includes in particular the beverage industry, food technology, pharmacy and biochemistry.

Such centrifugal pumps basically have a housing provided with an inlet, an outlet, and a chamber provided in fluid communication with the inlet and the outlet in the housing. In the chamber, an impeller is rotatably received.

The patent literature has already considered many aspects of centrifugal pumps, including the design of this impeller.

From the NL 275 238 A For example, it is known to provide on the back of the impeller blades that serve the pressure regulation of the medium on the back of the impeller. A more extensive effect is not discussed and does not seem to exist.

There are applications in the above fields of application for centrifugal pumps are known in which media are pumped with fibrous and solid components.

A type of centrifugal pump that can be used in such applications is designed so that fibers and solid components can be crushed. The US 7 118 327 B2 proposes such a centrifugal pump, in which on the back of the impeller protruding structures are provided which mesh in structures which are provided on the housing.

The WO 2011/139223 A1 Take up this idea and suggest a slightly different solution. The back of the impeller is provided here with a plurality of projections. This added radial extent of the projections is in an interval of +/- 10%, +/- 25% up to +/- 40% of the radius of the impeller. This solution works without interlocking structures.

Out JP H-01 149592 U an impeller for a centrifugal pump is known, which is rotatably receivable in a chamber, so that a gap is provided between a rear side of the impeller and a housing wall. On the impeller several scrapers are arranged.

Out US 2010/061841 A1 a foam pump is known in which an additional outlet of the chamber is provided for cleaning and rinsing.

Out US 2014/0178190 A1 Furthermore, a centrifugal pump is known, are provided in the blade slots between a blade and a back plate of an impeller to achieve a homogeneous gas-liquid mixture.

It is an object of the invention to provide a centrifugal pump and an impeller for a centrifugal pump, is given by the structurally simple way, a higher compatibility for media that can form deposits.

This object is achieved by an impeller for a centrifugal pump with the features of the first claim and a centrifugal pump having the features of the twelfth claim. The dependent claims indicate advantageous developments of the invention.

The invention includes an impeller for a centrifugal pump having a housing, an inlet, an outlet, a chamber provided in fluid communication with inlet and outlet, the impeller being rotatably receivable in the chamber such that between a rear of the impeller and a housing wall a gap is provided. The rear side of the impeller has at least one scraper, which is materially connected to the impeller at a first location and a second location, the first location and the second location being at a distance from each other. This impeller is characterized in that at this distance, a cleanable gap between the scraper and the back of the impeller is created. This scraper eliminated upon rotation of the impeller deposition, which has formed, for example, when the impeller. The innocuous measure is achieved when so much deposit is eliminated that an unrestrained rotation of the impeller is reached. The cohesive connection of the scraper makes it possible to upgrade a standard impeller inexpensively for application of the centrifugal pump with solids forming media. Instead of special parts with small quantities, the use in large numbers manufactured standard parts is possible as a basis. The combination of scraper and impeller in two places, creating large-scale material connections, for example by welding, unnecessary. This simplifies the production and prevents in thermal processes distortion and distortion of the impeller by heat input. The space between scraper and impeller is dimensioned between the joints so that cleaning fluid, which is introduced with application-typical pressure in the centrifugal pump, reliably eliminates media residues.

The centrifugal pump has a housing on which an inlet and an outlet are arranged. Within the housing there is provided in fluid communication with inlet and outlet a chamber in which an impeller is rotatably received. Between a rear side of the impeller and a housing wall, a gap is formed. Deposition of the pumped medium in this gap is reduced to a harmless level by the back of the impeller has at least one scraper which is integrally connected at a first location and a second location with the impeller, wherein first location and second location have a distance from one another and at this distance a cleanable gap between the scraper and the back of the impeller is created. This scraper eliminated upon rotation of the impeller deposition, which has formed, for example, when the impeller. The innocuous measure is achieved when such an amount of deposit is eliminated that rotation of the impeller without braking contact with deposit is achieved. The cohesive connection of the scraper makes it possible to upgrade a standard impeller inexpensively for application of the centrifugal pump with solids forming media. Instead of special parts with small quantities, the use in large numbers manufactured standard parts is possible as a basis. The combination of scraper and impeller in two places, creating large-scale material connections, for example by welding, unnecessary. This simplifies the production and prevents in thermal processes distortion and distortion of the impeller by heat input. The space between scraper and impeller is dimensioned between the joints so that cleaning fluid, which is introduced with application-typical pressure in the centrifugal pump, reliably eliminates media residues. Advantageously, the gap is dimensioned so that the requirements for cleanability, which are formulated in the guidelines of the "European Hygienic Engineering & Design Group", the "EHEDG Guidelines" are met. The requirements are set out in document 2 " A method for the assessment of in-place cleanliness of food processing equipment "in the third edition ISBN 0 907503 17 9 executed.

In addition to the scraper, the compatibility of the centrifugal pump against solids-forming media can be increased in a further development by a further measure. The centrifugal pump has an inlet, an outlet, a housing formed by a bottom and a lid, a chamber provided in fluid communication with inlet and outlet, an impeller rotatably received in the chamber, and an impeller between a rear side and a housing wall provided gap. The media compatibility is increased by a spacer disposed between the lid and bottom and connected to the lid and bottom, and that an axial width of the gap is at least as large as an axial thickness of the spacer. The spacer element is dimensioned in its axial strength so that the formation of a deposit on the housing wall does not immediately lead to an increase of the gap and thus blockage of the impeller. An existing centrifugal pump can be retrofitted by subsequent insertion of a spacer and, where appropriate, replace other components, such as an extended shaft and made more compatible for solid-forming media. In the production of only a few additional, easy to produce components are necessary, so that this solution is very inexpensive.

With reference to the following figures, the invention, their developments and the representation of the advantages to be deepened.

Fig. 1:

Seitlicher Anblick einer Kreiselpumpe;

Fig. 2:

Schnitt durch eine Kreiselpumpe mit einem Laufrad in erster Bauform;

Fig. 3:

Detailansicht des Gehäuses mit einem Abstandselement zwischen Bauteilen des Gehäuses;

Fig. 4:

Ansicht eines Laufrades in einer zweiten Bauform;

Fig. 5:

Ansicht eines Laufrades in einer dritten Bauform;

Fig. 6:

Ansicht eines Laufrades in einer vierten Bauform;

Fig. 7:

Ansicht eines Laufrades in einer fünften Bauform;

Fig. 8:

Ansicht eines Laufrades in einer sechsten Bauform;

Fig. 9:

Ansicht eines Laufrades in einer siebten Bauform;

Fig. 10:

Ansicht eines Laufrades in einer achten Bauform;

Fig. 11:

Ansicht eines Laufrades in einer neunten Bauform;

Fig. 12:

Ansicht eines Laufrades in einer zehnten Bauform.

Show it:

Fig. 1:

Side view of a centrifugal pump;

Fig. 2:

Section through a centrifugal pump with an impeller in the first design;

3:

Detail view of the housing with a spacer between components of the housing;

4:

View of an impeller in a second design;

Fig. 5:

View of an impeller in a third design;

Fig. 6:

View of an impeller in a fourth design;

Fig. 7:

View of an impeller in a fifth design;

Fig. 8:

View of an impeller in a sixth design;

Fig. 9:

View of an impeller in a seventh design;

Fig. 10:

View of an impeller in an eighth design;

Fig. 11:

View of a runner in a ninth design;

Fig. 12:

View of a runner in a tenth design.

In Fig. 1 a centrifugal pump 1 is shown in a side view. The centrifugal pump 1 comprises a housing 2 which is provided with an inlet 3 and an outlet 4. Inlet 3 and outlet 4 are designed to be connected to a fluid guide arrangement, not shown, for example, a piping system. The housing 2 of the centrifugal pump 1 is supported by a lantern 5, the lantern 5 provides a connection to a motor assembly. The Motor assembly, usually comprising an electric motor, is located under a cover 6 and rests on feet 7. The housing 2 is constructed in several parts, wherein the parts are releasably connected together to allow easy maintenance, such as cleaning. In order to enable the detachable connection, a cover flange 8 and a bottom flange 9 are provided, which are releasably connected by means of screws 10.

The centrifugal pump 1 is in Fig. 2 shown in a sectional view. The housing 2 comprises a cover 11 with the cover flange 8 and a bottom 12 with the bottom flange 9. cover flange 8 and bottom flange 9 are arranged indirectly and or indirectly touching and connected together by suitable securing means, in the example shown with the screws 10. cover 11th and bottom 12 define a chamber 13 in which an impeller 14 is rotatably received. The impeller may be designed in a semi-open design by a blade 16 or a plurality of blades 16 is disposed on a disc-shaped base body 15 on a side facing the inlet 3 of the disk-shaped base body 15.

The impeller 14 is rotatably supported about an axis of rotation R in a flying arrangement of a pump shaft 17, which in turn is rotatably mounted on a motor shaft 18. With a feather key 19, which is arranged engaging in pump shaft 17 and motor shaft 18, a security against rotation of the waves can be effected against each other. The pump shaft 17 passes through the transition into the chamber 13, a seal assembly which is designed as a mechanical seal and, for example, a mounted on the pump shaft 17 rotating seal ring 20 and disposed in the housing stationary seal ring 21 comprises. This seal arrangement can also be designed as a flushed mechanical seal, for example, according to the type DE 203 16 570 U1 ,

Between a housing wall 23, which is formed on the bottom 12, and a rear side 22 of the impeller 14, which faces the housing wall 23, a gap 24 is formed with a gap width S. In applications of the centrifugal pump 1, in which solids-forming media reach the chamber 13, solids can deposit on the housing wall 23 and / or the back 22. The run of the impeller 14 is made difficult or impossible if these deposits have used up the gap width S. On the back 22 is therefore a scraper 25 or a plurality of such scrapers 25 are arranged, which are designed so that deposition of solid on the housing wall 23 by scraping is reduced so far that the gap 24 is free enough to allow free rotation of the impeller 14.

Alternatively or in addition to the scraper 25, a spacer element 26 between the cover 11 and the bottom 12, advantageously between the cover flange 8 and bottom flange 9 may be provided. With this, the centrifugal pump 1 can be converted for applications in which solid formation in the gap 24 is expected or observed. The gap width S is increased by this distance element 26 beyond the standard dimension. Between the spacer 26 and the lid 11, a first seal 27 is provided. A second seal 28 is located between bottom 12 and the spacer element 26. First seal 27 and second seal 28 provide a secure seal of the chamber 13 against the environment 29 of the centrifugal pump 1. Advantageously, the seal 27 and 28 are designed and set to hygienic standards, for example, DIN 11864.

The chamber 13 may have a peripheral channel 30 which extends in the axial direction as a cylindrical extension in the direction of the motor assembly. It can be designed in the circumferential direction as a spiral channel. The seals 27 and 28 and the spacer 26 may be arranged as a spatial boundary of this peripheral channel 30.

The Fig. 3 shows an exploded view of the housing 2 with the spacer 26. The spacer 26 is formed as a ring with a central annular opening 31. Through this annular opening 31, a portion of the bottom 12 dives through.

On a side facing the cover flange 8 side of the spacer 26, a ring opening 31 surrounding the first groove 32 is provided. This groove serves to receive the first seal 27. A second groove 33, also surrounding the annular opening 31, is formed on a side of the spacer element 26 facing the bottom flange 9. It cooperates with a third groove 34 which is formed on the bottom flange 9 by the second and third grooves 33 and 34 together receive the second seal 28. The third groove 34 is designed so that it receives a seal according to the hygienic requirements, if Lid flange 8 and 9 bottom flange without the spacer 26 are connected directly to each other.

The lid flange 8 has a collar 35 which extends in an axial direction toward the bottom. The collar has on its radially inner side a first inner surface 36. This is adapted to cooperate with an edge surface 37 of the bottom flange 9. If the centrifugal pump 1 assembled without spacer 26, the collar 35 engages around the bottom flange 9 and first inner surface 36 and edge surface 37 effect in this case, a centering of the lid 11 and bottom 12 to each other.

The spacer 26 has an edge portion 38 which is formed as an axially offset in the direction of the bottom flange 9 ring. By this offset, an outer surface 39 is formed on the spacer element 26. This outer surface 39 causes with the first inner surface 36 together a radial orientation, in particular a substantial centering of the spacer 26 with respect to the cover flange 8. On the bottom flange 9 facing side of the spacer 26 of the edge portion 38 extends in the axial direction beyond the spacer 26 addition and has a second inner surface 40. The second inner surface 40 together with the edge surface 37 together a substantially concentric alignment of spacer 26 and bottom flange 9 to each other.

The gap width S of the gap 24 in the axial direction is at least as large as an axial thickness D of the spacer element 26. Advantageously, cover 11, bottom 12 and spacer 26 are designed so that the gap width S is increased by the thickness D by installing the spacer element 26 , This is done by the arrangement according to Fig. 3 achieved, in which the annular disk-shaped spacer element with its thickness D between the cover flange 8 and the bottom flange 9 can be mounted.

The scraper 25 may include features according to one or more of the following types of designs and may be combined with one or more features of the design of the back surface 22 of the impeller 14.

In Fig. 4 a view is shown on the back 422 of an impeller 414. This is structured with elevations and depressions, for example by machining steps during production. The structuring comprises circular arranged circumferential grooves 441, which alternate with circular peripheral webs 442 in the radial direction. The circumferential webs 442 are interrupted by radial grooves 443, so that the circumferential webs 442 extend only part of the circumference. The radial grooves 443 extend straight from a center of the impeller 414, but can also be curved, as shown in subsequent developments. On the peripheral webs 442 at least one scraper 425 is attached cohesively. If impeller 414 and scraper 425 made of stainless steel, the material bond is preferably effected by welding. The material connection with the scraper 425 is provided on at least a first and a second of the furthest from the impeller 414 points 444 and 445 of the circumferential webs 442 created. The scraper 425 bridges the circumferential grooves 441. This bridging also creates a gap between scraper 425 and impeller 414. This gap is dimensioned to meet the application-specific hygiene requirements. This is met, for example, when the walls bounding the gap collide at a right angle or a larger angle and the maximum distance between scraper 425 and impeller 414 is a few millimeters. The distance is advantageously such that the specifications of the above-mentioned document with the ISBN 0 907 503 17 9 are met. The scraper 425 extends radially outwardly in a radial extent from an area near a hub 446 of the impeller 414 and extends on a circumferentially-curved tooth 447 of the impeller 414. The bend of the tooth 447 results in a bend of the scraper 425. The scraper 425 completely covers the radius of the impeller 414.

In Fig. 5 a slightly modified form of impeller 514 is shown. The rear side 522 here also has a structuring in the form of circular circumferential grooves 541 and circumferential webs 542, which are interrupted in their circular course by radial grooves 543 extending substantially in the radial direction. The radial grooves 543 are straight and may extend from a center of the hub 546. The scraper 525 extends straight from the hub 546 and extends to one of the teeth 547. This and the rectilinear curve results in only an extension of the scraper 525 in the radial direction of the impeller 514, which does not reach the full radius. In particular, the inner part of the impeller 514 is covered. The scraper 525 has lower recesses 549 on its side facing the impeller 514. On its side facing away from the impeller 514 upper recesses 550 are arranged. The Upper recesses 550 improve the action of the scraper, deposits in the gap 24 are even better eliminated. The lower recesses 549 enlarge the gap 548 between scraper 525 and impeller 514, so that it can be easily cleaned and the centrifugal pump 1 fulfills hygienic requirements easier. The scraper 525 is integrally connected to the crests of the circumferential webs 542 at at least a first location 544 and a second location 545.

The execution after Fig. 6 shows an impeller 614, which also has on its rear side 622 in the radial direction alternating and circular circumferential grooves 641 and peripheral webs 642. These are interrupted by radially extending radial grooves 643. The scraper 625 is segmented in this embodiment and includes at least a first segment 651 and a second segment 652. Each of the segments 651 and 652 has a first location 644 and a second location, respectively Point 645 with two, preferably adjacent, circumferential webs 642 integrally connected to form a gap 648. The segments 651 and 652 are staggered in the radial and circumferential directions to increase the summed radial coverage by the scraper 625 and to increase the scraping action to remove deposits. Segments may be near the hub 646 and disposed on a tooth 647 or a plurality of teeth 647. The summed radial coverage through the segments can be more than 60% to achieve a good effect with less expensive manufacturing.

In the embodiment according to Fig. 7 the impeller 714 has a smooth rear side 722, in which structuring is dispensed with, as in the examples shown so far. The scraper 725, of which several may be distributed along the periphery for better performance and easier balancing of the impeller 714, extends straight in the radial direction. Its upper edge 753, which faces away from the back 722, is smooth without elevations or depressions. On the opposite side of the upper edge 753 in the axial direction of the scraper 725 has at least one lower recess 749 through which a gap 748 between the back 722 and the scraper 725 is created. This intermediate space 748 extends between a first location 744 and second location 745, at which a material connection between the back 722 and the scraper 725 is created. The radial extent of the scraper 725 begins at a distance A from the hub 746 and extends to one of the teeth 747, with more than two-thirds of the radius of the impeller 714 are covered in order to achieve a good cleaning effect. In this case, the scraper 725 can span a free space 754 between two adjacent teeth 747.

In the Fig. 8 illustrated embodiment largely corresponds to the basis Fig. 7 explained embodiment. With the smooth back 822 of the impeller 814, a scraper 825 is firmly bonded. Notwithstanding the embodiment according to Fig. 7 is the upper edge 853 of the scraper 825 is structured by upper recesses 850, for example, wave-like. As a result, a good cleaning performance is generated.

In Fig. 9 Embodiment of the impeller 914 is shown, the features of the embodiment according to Fig. 4 to Fig. 6 with features of execution Fig. 7 combined. The rear side 922 of the impeller 914 is structured in this embodiment by incorporated circular circumferential grooves 941, which alternate with circular peripheral webs 942 in concentric sequence. Straight radial grooves 943 interrupt circumferential grooves 941 and circumferential ridges 942. The radial grooves 943 are straight, but are inclined against the radial direction. They can also be offset to the radial direction and follow a secant. The scraper 925 has as in the execution Fig. 7 a smooth upper edge 953. On its side facing the rear side 922 at least one lower recess 949 is provided, which extends between a first location 944 and a second location 945. At locations 944 and 945, the scraper 925 is integrally connected to the upper edges of two circumferential webs 942. The circumferential groove 941 provided between the first and second locations 944 and 945 and the lower recess 949 create a clearance 948 between scraper 925 and impeller 914, which is particularly easy to clean. The scraper 925 is straight shaped and extends over part of the radius of the impeller 914, preferably more than 50% of that radius.

The Fig. 10 shows an impeller 1014, which in many parts that in Fig. 9 equivalent. In particular, the back 1022 has at least one circumferential groove 1041 and a peripheral ridge 1042. Furthermore, at least one straight radial groove 1043 may be provided, which extends partially or advantageously entirely between the hub 1046 and a tooth root 1055. At least one rectilinear scraper 1025 extending in the radial direction is at a first location 1044 and one second location 1045 cohesively connected to the back 1022. Between the locations 1044 and 1045, the scraper 1025 has a lower recess 1049, so that a space 1048 is created between the back 1022 and the scraper 1025. It can be provided over the longitudinal extent of the scraper 1025 further lower recesses and other locations with cohesive connection. This gap 1048 is increased by one or more than one circumferential groove 1041 and therefore easier to clean. The upper edge 1053 of the scraper 1025 facing away from the rear side 1022 has at least one upper recess 1050, which improves the cleaning action of the scraper 1025.

In Fig. 11 is a very cost effective and at the same time shown in terms of removal of deposit highly effective execution of the scraper 1125. The 1125 scraper is made from a perforated sheet cut into strips, each strip giving a scraper 1125. The pitch of the perforated plate can be made at the height of the holes, so that in a simple manner, the gap 1148 and lower recesses 1149 and upper recesses 1150 arise. The perforated plate can be like in Fig. 11 be shown bent and with its curvature following the course of the tooth 1147 integrally attached to at least a first location 1144 and a second location 1145. A very good function of the scraper 1125 is observed when it covers at least 75% of the radius of the impeller 1114. The backside 1122 can be made smooth or textured, the structuring being more costly but having a better cleaning effect. The structuring may be in the form of at least one circumferential groove 1141 and a peripheral ridge 1142 and may include at least one radial groove 1143.

The execution in Fig. 12 shows an impeller 1214, which in its design of the basis Fig. 11 explained impeller 1114 by the shape of the scraper 1225 deviates. The scraper 1225 is rectilinear and extends from the hub 1246 except for a tooth 1247 of the impeller 1214, covering at least 75%.

The aforementioned scrapers 25, 425, 525, 625, 725, 825, 925, 1025, 1125 and 1225 are preferably designed and arranged such that they are balanced with respect to the axis of rotation of the centrifugal pump 1, so that additional means for balancing the impeller 14th , 414, 514, 614, 714, 814, 914, 1014, 1114 and 1214 can be omitted.

The application of the invention has been described with reference to a centrifugal pump, but is also applicable in a self-priming centrifugal pump. A self-priming property can be achieved by connecting a pumping stage, such as a liquid ring pumping stage, upstream of the inlet and a return line. Such a return line between a suction area of a liquid ring pumping stage and the part of the centrifugal pump in which pumped fluid is under pressure is, for example, in US Pat DE 10 2007 032 228 A1 described.

Claims (13)

1. An impeller for a centrifugal pump (1), having a housing (2), an inlet (3), an outlet (4), a chamber (13) provided in the housing (2) in fluidic contact with the inlet (3) and the outlet (4), wherein the impeller (14, 414, 514, 614, 714, 814, 914, 1014, 1114, 1214) can be rotatably accommodated in the chamber (13) in such a manner that a gap (24) is provided between a rear side (22, 422, 522, 622, 722, 822, 922, 1022, 1122, 1222) of the impeller (14, 414, 514, 614, 714, 814, 914, 1014, 1114, 1214) and a housing wall (23), wherein the rear side of the impeller (14, 414, 514, 614, 714, 814, 914, 1014, 1114, 1214) has at least one scraper (25, 425, 525, 625, 725, 825, 925, 1025, 1125, 1225) which is integrally bonded with the impeller (14, 414, 514, 614, 714, 814, 914, 1014, 1114, 1214) at a first location (444, 544, 644, 744, 944, 1044, 1144) and a second location (445, 545, 645, 745, 945, 1045, 1145), and wherein the first location (444, 544, 644, 744, 944, 1044, 1144) and the second location (445, 545, 645, 745, 945, 1045, 1145) are spaced apart from each other,
   characterized in that a cleanable intermediate space (548, 648, 748, 948, 1048, 1148) is created in said space between the scraper (25, 425, 525, 625, 725, 825, 925, 1025, 1125, 1225) and the rear side (22, 422, 522, 622, 722, 822, 922, 1022, 1122) of the impeller (548, 648, 748, 948, 1048, 1148).
2. The impeller according to Claim 1, characterized in that the scraper has bottom recesses (549, 749, 949, 1049, 1149) on a side facing the impeller.
3. The impeller according to Claim 1 or 2, characterized in that the rear side of the impeller has a structure in the form of circular peripheral grooves (441, 541, 641, 941, 1041, 1141) and peripheral webs (442, 542, 642, 942, 1042, 1142).
4. The impeller according to any one of the preceding claims, characterized in that a radial extension of the scraper starts at a distance (A) from the hub.
5. The impeller according to any one of the preceding claims, characterized in that the scraper is designed and arranged so that it is balanced relative to a rotary axis (R) of the centrifugal pump.
6. The impeller according to any one of the preceding claims, characterized in that a structure of the rear side of the impeller comprises at least one radial groove (443, 543, 643, 943, 1043, 1143) extending in a radial direction.
7. The impeller according to any one of the preceding claims, characterized in that the scraper entirely covers a radius of the impeller.
8. The impeller according to any one of the preceding claims, characterized in that the scraper has top recesses (550, 850, 1050, 1150) on a side facing away from the impeller.
9. The impeller according to any one of the preceding claims, characterized in that the scraper is designed segmented and comprises at least one first segment (651) and one second segment (652).
10. The impeller according to any one of the preceding claims, characterized in that the scraper is designed bent.
11. The impeller according to Claim 10, characterized in that the curvature of the bent scraper follows the contour of a tooth (447, 547, 647, 747, 1147, 1247) of the impeller.
12. A centrifugal pump having a housing (2), an inlet (3), an outlet (4) and a chamber (13) provided in the housing (2) in fluidic contact with the inlet (3) and the outlet (4), characterized in that the centrifugal pump comprises the impeller (14, 414, 514, 614, 714, 814, 914, 1014, 1114, 1214) rotatably accommodated in the chamber according to any one of Claims 1 to 11, and a gap (24) is provided between the rear side (22, 422, 522, 622, 722, 822, 922, 1022, 1122) of the impeller and a housing wall (23).
13. The centrifugal pump according to Claim 12, characterized in that the housing (2) is formed by a cover (11) and a floor (12), wherein a spacing element (26) is arranged between the cover (11) and the floor (12) and is connected to the cover (11) and the floor (12), and an axial width (S) of the gap is at least as large as an axial thickness (D) of the spacing element (26).

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