EP3181908B1 - Multi-stage centrifugal pump having tension anchors made of sheet metal - Google Patents

Description

The invention relates to a multi-stage centrifugal pump with the features specified in the preamble of claim 1.

Centrifugal pumps of this type are known in numerous design variants; in this connection, reference is made in particular to the Grundfos CR series, which is available on the market in different sizes. All these pumps have in common that they have a foot part with which they stand on the ground or a foundation provided for this purpose during operation, and a head part which is designed as a motor chair or is provided for receiving a motor chair, via which a drive motor for the Pump can be connected. These are pumps in which the actual centrifugal pump and the drive motor essentially form independent units which are coupled to one another in the area of the motor chair. Standard motors are typically used, which are not specially designed for these pumps, but which can also be used in other drive applications. This centrifugal pump must therefore be designed so that it can absorb the drive motor attached to the head section and its reaction forces. The centrifugal pumps are designed in series, the head and foot parts of which correspond, but which differ in the number of pump stages arranged between them.

In known centrifugal pumps of this type, the pump stages are integrated between the head part and the foot part, the head part and the foot part are connected via tie rods that give the pump mechanical cohesion. For this purpose, four tie rods symmetrically distributed around the circumference of the pump stages are generally provided, which are formed from round material and are provided with an external thread at the ends. These tie rods are either fixed in threaded holes in the foot part or fastened there by means of nuts, the free ends of the tie rods being guided through corresponding bores in the head part on the head part side and being fixed there via nuts. The pump stages incorporated between the head part and foot part are thus clamped to one another via these tie rods, as a result of which the entire structure maintains its stability. The US 2008/0019831 A1 shows such a multi-stage centrifugal pump, which is designed as an inline pump.

A disadvantage of multi-stage centrifugal pumps of this type is that the tie rods are quite complex to assemble. So they must first be screwed into the foot section, after which the connection to the head section is made and finally the nuts on the head section are put on and tightened with the required torque. In addition, these helical tie rods are expensive and heavy. They protrude significantly from the side of the cylindrical pump body, so that they always form contact surfaces on which one can easily get caught with a tool or other objects. Due to the lateral protrusion over the pump body, bending moments on the head part and foot part are also effective, which can lead to undesired deformations.

Against this background, the invention has for its object to improve a multi-stage centrifugal pump of the type mentioned with regard to the tie rods and their attachment.

This object is achieved according to the invention by a multi-stage centrifugal pump with the features specified in claim 1. Advantageous embodiments of the invention are in the subclaims, the following description and the drawing. In this case, the features specified in the subclaims and the description, each individually but also in a suitable combination, can further develop the solution according to the invention.

The multi-stage centrifugal pump according to the invention is designed as an inline pump and has a foot part with a suction and a pressure connection and a head part, between which pump stages are integrated. The pump stages are surrounded by a ring channel through which the last pump stage is connected to the pressure connection. The head part and foot part are connected to each other via tie rods, which are fixed at one end to the head part and with the other end to the foot part, the tie rods being threaded at one end with which they are braced on the head part or on the foot part. According to the invention, the tie rods are formed at least in sections from sheet metal and each have at the other end, i.e. at the non-threaded end, at least one recess in the sheet metal, with which they are positively fixed at least in the pulling direction on the foot part or on the head part, and into which a projection provided on the foot or head part engages.

Basically, it does not matter whether the positive connection is made by means of the recess on the foot part side and the screw connection on the head part side or vice versa, but since the head part is more accessible, it is generally easier to provide the screw connection on the head part side.

It must be taken into account that the centrifugal pumps of the type in question have a foot part with which they stand on the floor or on a foundation, that is to say a component which carries the entire pump and the motor connected to it.

According to the invention, the tie rods are formed at least in sections from sheet metal, preferably all of sheet metal except for the threaded part at one end. The tie rods should go as far as possible be made of sheet metal, that is, the threaded part should be as short as necessary. The sheet metal part should therefore bridge the entire area between the head part and foot part or end immediately in front of the head or foot part, where the threaded part then joins. Such tie rods formed from sheet metal can be produced inexpensively, for example by laser cutting or punching, which is particularly advantageous in the case of large quantities. The connection is made positively on one side by means of the at least one recess, either on the foot part or on the head part, preferably on the foot part, so that the thread is arranged on the head part side and screwed there with a nut. The extensive design of the tie rods made of sheet metal has the further advantage that they can be matched to the outer contour of the pump stages, as a result of which the radial size in the area of the pump stages can be significantly reduced. As a result, the moment loads on the head and foot sections known in prior art designs can also be significantly reduced. In addition, the design of the tie rods made of sheet metal also enables an aesthetically significantly more appealing design than was the case according to the prior art, in which the clamping bolts protrude radially like foreign bodies. The dimensioning of the tie rods depends on the forces to be absorbed and the tensile strength of the material used. However, they should advantageously be dimensioned at least in such a way that the tie rods are inherently stable. This can also be supported, for example, in that the tie rods have a curvature which is adapted to the curvature of the pump body, that is to say they are bent about their longitudinal axis. Such a curvature makes it possible to apply the tie rods to the pump body formed by the pump stages in the region of the pumps with virtually no spacing, so that, which is particularly advantageous, they have the same temperature level as the pump body. Centrifugal pumps with tie rods that are at least partially made of sheet metal are, for example, from the EP2143959 A1 or the JP2001041187 A known.

According to the invention, the end formed from sheet metal is fixed by means of at least one recess into which a projection provided on the foot or head part engages. If the recess lies completely within the sheet, a pin-like or hook-like projection is to be provided on the foot or head part side in order to obtain a positive connection in the pulling direction. Such a pin can, for example, lie within an anchor recess of the foot part or can also be molded onto the foot part at a suitable location.

In the following, the recesses are designated as anchor recesses, which are provided and determined for positive locking, that is, for anchoring the end of a tie rod formed from sheet metal. In contrast to this, the recesses in the end of a tie rod formed from sheet metal are referred to below only as recesses. It can either be recesses in the form of holes in the sheet or lateral recesses. Finally, the recesses in the head part in which the ends of the tie rods on the head part are fixed are referred to below as hole recesses. It can be holes, bores or laterally open recesses.

It is particularly advantageous if, according to a development of the invention, the tie rods each have a recess on at least one long side. Then a form-fitting fixation in the head or foot part can take place by designing a corresponding anchor recess which has an area in which the tie rod can be inserted and a further area in which a counter part engages in this recess. This state can be achieved, for example, by swiveling, shifting or rotating.

It is particularly advantageous if lateral recesses are provided on both longitudinal sides of the tie rod, preferably on same height, then a particularly even application of force into the tie rod takes place.

In principle, it is conceivable to also form the threaded end of the tie rod from sheet metal, in which further material is applied to the sheet metal base body either by folding or by application, into which a thread is then cut or embossed. According to a further development of the invention, however, it is advantageously provided that the tie rods are provided with a threaded bolt at their threaded end, which is connected to the part of the tie rod formed from sheet metal by welding.

In order to fix the threaded end of the tie rod in the head part or foot part, hole recesses are provided according to the invention, through which the threaded ends of the tie rods are guided and fixed and braced there by means of a nut. This attachment is advantageously carried out on the headboard side, the headboard advantageously being designed as a motor chair. This is the same component that not only closes the pump stages upwards, but also forms the motor mount. The hole recesses can be open on the side, so that it is not necessary to insert the threaded ends of the tie rods through them, but that they can also be inserted from the side, for example. This facilitates automated assembly in particular.

The part of the pump clamped between the foot part and head part advantageously has a cylindrical section, for example formed by a tube, which forms the return channel from the pressure side back to the foot part. According to a development of the invention, it is provided that the parts of the tie rods formed from sheet metal are adapted to the curvature of this cylindrical section, that is to say to theirs Deform longitudinal axis. Such a deformation makes it possible to apply the tie rods almost flush to this cylindrical section, if this is desired. Alternatively, the tie rods can also be arranged at a distance, and this arrangement can also result in a technically and optically advantageous design.

For the positive insertion of the ends of the tie rods, anchor recesses are preferably provided in the foot part, each of which has an insertion part and a holding part. The insertion part is designed in such a way that an end of a tie rod formed from sheet metal can be passed through this insertion part until the recesses on the long sides lie within these anchor recesses. Then by moving or pivoting a tie rod with its sheet metal part end can be transferred from the insertion part of an anchor recess into the holding part, in which the tie rod is positively held at least in the direction of its longitudinal axis and in which the material surrounding the anchor recesses laterally into the recesses of the sheet metal part end of the tie rod engages. The transfer from the insertion part into the holding part can advantageously be carried out by radial displacement or in a simple manner by pivoting, as will be described in detail below.

The anchor recesses are advantageously designed such that the holding parts connect radially on the outside to the insertion parts, so that the cylindrical section of the component surrounding the pump stages positively secures the ends of the tie rods, which lie in the neck parts of the anchor recesses, so that they no longer fit in can reach the area of the insertion parts in which they can be pushed through for assembly or disassembly purposes.

It is particularly advantageous if the anchor recesses are arranged in a circle around the longitudinal central axis of the pump, preferably in the foot part, and their insertion parts are covered by a component of the pump, for example a pump stage or the circumferential jacket, for the positive fixing of the tie rod located in the holding part. The tie rods are advantageously arranged symmetrically around the longitudinal center and axis of rotation of the pump; three, four or more tie rods can be provided.

It is structurally particularly favorable if the anchor recesses are arranged in an axial wall, preferably of the foot part. In this arrangement, the actual foot part can consist of a plate made, for example, of cast iron and a part adjoining it at the top can also be made of cast iron, that is, as a one-piece component with the plate or, if appropriate, also as a sheet metal construction.

According to an alternative embodiment of the invention, the insertion parts of the anchor recesses are arranged in a radial wall and the holding parts of the anchor recesses are preferably arranged in an axial wall of the foot part. Such an arrangement has the advantage that the tie rods can be inserted from the side and can be positively fixed, for example, by pivoting. This results in a very simple and at the same time reliable assembly. The holding parts of the anchor recesses can alternatively also be provided in a corresponding recess or cutout in the radial wall, typically in the circumferential side thereof.

Both the head part and the foot part are advantageously designed as a cast metal part, the foot part being designed to set up the pump on a foundation, typically on the floor is and the head part is designed to receive an electric motor driving the pump. These components can then be used for a whole series of pumps, only the tie rods and the pump stages incorporated between them or the surrounding pipe forming the return channel having to be adapted to the number of pump stages. According to the invention, the pump is designed as an inline pump and has a suction connection and a pressure connection in the foot part, the pump stages being surrounded by an annular channel through which the last pump stage is connected to the pressure connection in the foot part. On the outer channel wall, the tie rods can either be adjacent or preferably arranged at a short distance. In this case, the foot part with its suction and pressure connection can be designed as a cast part, but it is also possible, for example, for only one plate which forms the actual foot part to be made of cast iron and the rest of the foot part of sheet metal.

It is particularly expedient if the tie rods are made of sheet metal except for the threaded end part, that is to say the sheet metal part of the tie rod extends from the foot part to the head part or to just before it. In this way, on the one hand, cost-effective production and, on the other hand, an optically and technically preferred construction can be realized, in which the tie rods rest almost flush on the pump body, which is otherwise cylindrical there. It is particularly advantageous if the tie rods are made in one piece and, in particular, are also inherently stable, since then they can be incorporated relatively easily in largely automated assembly processes.

The foot part advantageously has a pot-shaped structure, the anchor recesses then advantageously being arranged where the pot bottom merges into the pot wall. The insertion part of the anchor recesses in the wall and the holding part in the floor can then be provided, for example. The anchor recess then extends in both areas. If the foot part is liquid-carrying and for this reason the inside of the pot wall cannot be provided with anchor recesses, the pot base can protrude radially beyond the pot wall in order to accordingly arrange anchor recesses on the outside.

Fig. 1

in stark vereinfachter perspektivischer Darstellung ein erstes Ausführungsbeispiel einer Kreiselpumpe gemäß der Erfindung,

Fig. 2

die Kreiselpumpe nach Fig. 1 in Explosionsdarstellung,

Fig. 3

das Fußteil der Pumpe nach Fig. 1 von unten mit festgelegtem Zuganker,

Fig. 4

die Anordnung gemäß Fig. 3 schräg von oben,

Fig. 5

ein anderes Ausführungsbeispiel der Kreiselpumpe in Darstellung nach Fig. 1,

Fig. 6

die Pumpe nach Fig. 5 mit Fußteil im Teilschnitt und einem Zuganker in Einführstellung,

Fig. 7

die Pumpe gemäß Fig. 5 in Explosionsdarstellung,

Fig. 8

das Fußteil der Pumpe gemäß der Pumpe nach Fig. 5 in perspektivischer Ansicht schräg von vorne und oben,

Fig. 9

das Fußteil gemäß Fig. 8 in um 90° gedrehter Ansicht gegenüber Fig. 8,

Fig. 10

das Fußteil gemäß Fig. 8 in perspektivischer Ansicht von unten und

Fig. 11

zur Verdeutlichung des konstruktiven Aufbaus in Seitenansicht eine vergleichbar aufgebaute Kreiselpumpe im Längsschnitt mit angeschlossenem Elektromotor.

The invention is explained in more detail below with reference to the embodiment shown in the drawings. Show it:

Fig. 1

in a greatly simplified perspective view, a first embodiment of a centrifugal pump according to the invention,

Fig. 2

the centrifugal pump after Fig. 1 in exploded view,

Fig. 3

the foot part of the pump Fig. 1 from below with fixed tie rod,

Fig. 4

the arrangement according to Fig. 3 diagonally from above,

Fig. 5

another embodiment of the centrifugal pump in illustration Fig. 1 ,

Fig. 6

the pump after Fig. 5 with foot section in partial section and a tie rod in the insertion position,

Fig. 7

the pump according to Fig. 5 in exploded view,

Fig. 8

the foot part of the pump according to the pump Fig. 5 in perspective view diagonally from the front and above,

Fig. 9

the foot part according to Fig. 8 in a view rotated by 90 ° Fig. 8 ,

Fig. 10

the foot part according to Fig. 8 in perspective view from below and

Fig. 11

a side view of a comparable centrifugal pump with a connected electric motor to illustrate the construction.

When using Fig. 1 shown centrifugal pump 1 is a multi-stage centrifugal pump of the inline type (see also Fig. 11 ). It has a foot part 2, which is provided with its underside for installation on the floor or a corresponding foundation. The foot part 2 essentially has the shape of a rectangular plate, which has four fastening recesses 3 at its corners, with which the foot part 2 can be screw-fastened to the foundation, in which corresponding cap screws are passed through these recesses 3 and anchored in the foundation. The foot part 2 has a circular receptacle 4, which is provided for receiving a component having a suction connection 5 and a pressure connection 6, which receives pump stages which adjoin it at the top and are closed at the top by a cover part 7. A cylindrical tube section 8 is arranged between the cover part 7 and the component receiving the suction and pressure connection 5, 6, which surrounds the pump stages at a distance and forms an annular channel via which the liquid emerging at the end of the last pump stage is led to the pressure connection 6. The pump is closed at the top by a head part 9, which at the same time forms a motor chair for an electric motor which can be flanged there.

The component having the suction and pressure connection 5, 6, the adjoining pump stages, the pipe section 8 surrounding this and the cover part 7 are clamped between the foot part 2 and the head part 9 in a positive and non-positive manner, namely by four symmetrically about the longitudinal - and axis of rotation 10 of the pump arranged tie rods 11. These tie rods 11 are made of sheet metal and have an elongated narrow shape, they are bent about their longitudinal axis, corresponding to the curvature of the pipe section 8, so that they look like this Fig. 1 it can be seen to continue this outwards. The tie rods 11 have a lower end 12, which is also made of sheet metal, and an upper end 13, which is formed by an externally threaded bolt 14, which is welded to the upper end of the sheet metal part of the tie rod 11 is. Towards the lower end 12, the sheet metal section 15 is provided with two recesses 16 on its long side, which are arranged at the same height, the underside of which is recessed inward by 90 ° and the upper side of which runs obliquely to the outer edge of the sheet metal section 15. To anchor these lower ends 12 of the tie rods 11, four anchor recesses 18 are provided in the base part 2, specifically at the edge of the receptacle 4, in the axial wall 17, the contour of which is best shown in Fig. 4 is recognizable.

Each anchor recess has an insertion part 19 and a holding part 20 which are matched to the lower end 12 of a tie rod. The insertion part 19 is dimensioned such that it corresponds to the cross-sectional area of the sheet metal section 15, that is to say that a tie rod 11 can be inserted and passed through the insertion part 19 from above into the insertion part 19. This lower end 12 is inserted so far into the insertion part 19 until the recesses 16 are arranged at the level of the anchor recess 18, then the tie rod 11 is displaced radially outward in the anchor recess 18, so that the comparatively narrow web part 21, which is between the Recesses 16 is formed in the sheet metal section 15, into which the holding part 20 of the anchor recess 18 passes, as a result of which the tie rod 11 is positively fixed in the foot part 2 in the pulling direction 22. The holding part 20 of the armature recess 18, which is arranged in the axial wall 17 of the receptacle 4, is continued in the radial wall 23 of the receptacle 4 in accordance with the obliquely upwardly extending recesses 16, so that the tie rod in this position outside the actual receptacle 4, namely is arranged radially offset.

The receptacle 4, which is provided in terms of its dimensions for receiving the component receiving the suction and pressure connection 5, 6, can still receive this component after incorporating the tie rods 11, but with the effect that by incorporating the component into the receptacle 4 the insertion parts 9 of the anchor recesses 18 are closed and thus the lower ends 12 of the tie rods 11 are positively fixed within the foot part 2.

As soon as the tie rods 11 are positively fixed within the base part 2, the remaining pump parts, in particular the pump stages, the pipe section 8 and the cover part 7, can be incorporated, after which the head part 9 is placed on from above. The upper ends 13, that is to say the threaded bolts 14, pass through hole recesses 24 in the head part 9, which are arranged in alignment with the anchor recesses 8 arranged in the foot part 2, so that after the head part is put on, the bolts 14 projecting through the hole recesses 24 underneath Intermediate washers provided with nuts 25 and braced. This gives the entire centrifugal pump 1 a closed and stable structure, whereby, in particular, from Fig. 1 it can be seen that the tie rods 11 rest against the otherwise cylindrical pump body at only a small distance, so that overall a slim outer contour is created with practically no projections in the radial direction.

When using the 5 - 10 The embodiment variant shown are incorporated into the base part 2a of the suction connection 5 and the pressure connection 6. There the pipe section 8, which delimits the ring channel to the outside, extends between the foot part 2a and the head part 9a. The structure in detail results in particular from Fig. 7 . In this construction, the head and foot parts 9a, 2a, which are made of cast iron, are not lined with stainless steel sheet, as in the previously described embodiment, but form parts of the flow channels. The basic structure is similar, but the receptacle 4a is closed, that is to say without a recess on the inside. This is necessary to ensure the tightness with respect to the pipe section 8. The anchor recesses 18a surrounding the receptacle 4a are provided here, which are arranged on the outside of the receptacle 4a and which have a radial insertion part 19a and an axial holding part 20a. The radial insertion part 19a of an armature recess 18a lies in a radial wall 23a, which surrounds the receptacle 4a at a distance and receives the pressure and suction connections 5, 6. At its upper end, this radial wall 23a merges into an axial wall 17a, which, however, is not part of the receptacle 4a, but rather forms an outer shoulder.

The tie rods 11 themselves are designed in exactly the same way as in the embodiment described above. You will be here, however, as especially in Fig. 6 can be seen, inserted obliquely from the outside and above through the insertion part 19a, i.e. the armature recess part in the radial wall 23a, until the recesses 16 or the web 21 of the tie rods 11 are arranged at the level of the holding parts 20a of the armature recesses 18a. Then the tie rod 11 is pivoted obliquely upwards until it lies parallel to the pipe section 8 at a distance and the threaded bolt 14 engages in the laterally open hole recess 24a, opposite the upper end of which it is incorporated as in the previous embodiment Washer screwed to a nut 25 and thus fixed. With the pivoting in of the tie rod 11, for example about an axis running tangentially to the upper edge of the foot part 2a, the narrow sheet metal section 21 between the recesses 16 reaches the area of the holding part 20a of the anchor recess 18a in the axial wall 17a, as a result of which the parts projecting from it Sheet metal section 15 enter into a positive connection in the pulling direction 22 and in the opposite direction. The tie rod 11 is held in this position by the threaded bolt 14 fixed by means of the nut 25, with which the upper end 14 of the tie rod 11 is fastened to the head part 9a.

The holding part 20a of an armature recess 18a is provided in the above-described embodiment in the axial wall 17a, but this part of the armature recess 18a can also be provided in the radial wall 23a if it is dimensioned accordingly and one which is matched to the lower end 12 of the tie rod 11 , ie has a corresponding recess or recess in the shape.

The main advantage of the arrangement described above is that the pump can be built almost completely from the foot part 2a to the head part 9a, after which the tie rods 11 are finally inserted into the anchor recesses 18a and pivotally secured there by pivoting. The corresponding tension between the foot part 2a and the head part 9a is then applied by tightening the nut 25 with the intended torque. This design is therefore particularly advantageous for an at least partially automated assembly.

Based on Fig. 11 the basic structure of such a centrifugal pump with drive is shown, which, like the break line in horizontal Direction clarifies, stands for multi-stage centrifugal pumps with virtually any number of pump stages. To drive the centrifugal pump, a drive motor 26 in the form of an electric motor is attached to the head part 9a, which is designed as a motor chair at the upper end, the shaft 27 of which is connected in a rotationally fixed manner to a shaft 28 of the centrifugal pump 1 by a coupling. On the drive shaft 28 of the centrifugal pump, according to the number of stages, centrifugal wheels 29 are arranged in a rotationally fixed manner, which together with guide devices 30 fixed to the housing form the pump stages.

The liquid is pumped through the (in Fig. 11 (not visible) Suction port 5 to the suction mouth of the lowest pump stage and from there it goes from pump stage to pump stage with pressure increase upwards, where it emerges within the head part 9a and is led down again via an annular channel 31 to the foot part and there to the pressure connection 6.

Reference symbol list

1

Centrifugal pump

2, 2a

the foot part

3rd

Mounting recesses

4, 4a

admission

5

Suction connection

6

Pressure connection

7

the lid part

8th

Pipe section

9, 9a

the headboard

10th

Axis of rotation, longitudinal central axis

11

Tie rod

12

lower end of 11

13

upper end of 11

14

Threaded bolt

15

Sheet metal section

16

Recesses

17, 17a

axial wall of 4

18, 18a

Anchor recess

19, 19a

the introductory part of 18

20, 20a

the holding part of 18

21

Bridge part of 11

22

Direction of pull

23, 23a

radial wall of 4

24.24a

Perforations

25th

mother

26

Electric motor

27th

Motor shaft

28

Pump shaft

29

Gyro wheels

30th

Guides

Claims (16)

1. A multistage centrifugal pump which is designed as an inline pump, with a foot part (2), which comprises a suction connection and a delivery connection (5, 6), with a head part (9) and with pump stages which are integrated therebetween, said pump stages being surrounded by an annular channel by way of which the last pump stage is connected to the delivery connection (6), wherein the head part (9) and the foot part (2) are connected via tie rods (11) which are arranged on the outer channel wall of the annular channel and which with one end (13) are fastened on the head part (9) and with the other end (12) are fastened on the foot part (2), wherein the tie rods (11) are provided with a thread at one end (13) in each case, with which thread they are tightened on the head part (9) or on the foot part (2), characterised in that the tie rods (11) are formed at least in sections from sheet metal, and in each case at the other end (12) comprise at least one recess (16) in the sheet metal, with which recess (16) they are positively fixed on the foot part (2) or on the head part (9), at least in the pulling direction (22) and into which a projection which is formed on the foot part or head part engages.
2. A centrifugal pump according to claim 1, characterised in that the tie rods (11) comprise a recess (16) in each case on at least one longitudinal side.
3. A centrifugal pump according to claim 1 or 2, characterised in that the tie rods (11) comprise recesses (16) in each case on both longitudinal sides, preferably at the same height.
4. A centrifugal pump according to one of the preceding claims, characterised in that the tie rods (11) at their end (13) which is provided with a thread comprise a threaded bolt (14) which is connected to the part (15) of the tie rod (11) which is formed from sheet metal, by way of welding.
5. A centrifugal pump according to one of the preceding claims, characterised in that hole recesses (24) are provided in the foot part (2) or in the head part (9), preferably in the head part (9), through which recesses (24) the ends (13) of the tie rods (11) which are provided with a thread are led, and there are fixed and tightened by a nut (25) in each case, wherein the head part (9) is preferably designed as a motor stool.
6. A centrifugal pump according to one of the preceding claims, characterised in that the pump (1) between the foot part (2) and the head part (9) comprises a cylindrical section (8), and that the parts (15) of the tie rods (11) which are formed from sheet metal have a curvature which is adapted to the curvature of this cylindricalsection.
7. A centrifugal pump according to one of the preceding claims, characterised in that tie recesses (18) are provided in the foot part (2) or in the head part (9), preferably in the foot part (2), and each comprise an introduction part (19) and a holding part (20), wherein the introduction part (19) is designed such that an end (12) of a tie rod (11) can be led through, and the holding part (20) is designed such that the end (12) of the tie rod (11) can be brought into the holding part (20) by way of preferably radial displacement and/or by pivoting at the height of its at least one recess (16), and the tie rod (11) is positively held at least in the direction (22) of its longitudinal axis.
8. A centrifugal pump according to claim 7, characterised in that the tie recesses (18) are arranged in a circular manner around the longitudinal middle axis (10) of the pump (1), preferably in the foot part (2), and their introduction parts (19) are covered by a component of the pump (1), for the positive fixation of the tie rods (11).
9. A centrifugal pump according to claim 8, characterised in that the holding parts (20) connect radially outwards onto the introduction parts (19) of the tie recesses (18), and a cylindrical section of the component positively fixes the ends (12) of the tie rods (11) in the tie recesses (18).
10. A centrifugal pump according to one of the preceding claims 7-9, characterised in that the tie recesses (18) are arranged in an axial wall (17), preferably of the foot part (2).
11. A centrifugal pump according to one of the preceding claims 7-10, characterised in that the introduction parts (19a) of the tie recesses (18a) are arranged in a radial wall (23a), and the holding parts (20a) of the recesses (18a) are arranged in an axial or radial wall (23a), preferably of the foot part (2a).
12. A centrifugal pump according to one of the preceding claims, characterised in that the head part (9) and/or the foot part (2) is designed as a metallic cast part, wherein the foot part (2) is designed for placement of the pump (1) on a foundation, in particular on the floor, and the head part (9) is designed for receiving an electric motor driving the pump (1).
13. A centrifugal pump according to one of the preceding claims, characterised in that the tie rods (11) are arranged at a distance to the outer channel wall of the annular channel.
14. A centrifugal pump according to one of the preceding claims, characterised in that the part (15) of a tie rod (11) which is formed from sheet metal extends from the foot part (2) to the head part (9) or to directly in front of this.
15. A centrifugal pump according to one of the preceding claims 7-14, characterised in that the foot part (2, 2a) comprises a pot-like structure, and the tie recesses (18, 18a) are arranged in the region, in which the pot base merges into the pot wall.
16. A centrifugal pump according to one of the preceding claims, characterised in that the tie rods (11) are designed in a single-piece manner and preferably in an intrinsically stable manner.

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