EP2148096B1 - Centrifugal pump - Google Patents

Description

Centrifugal pumps have a gap between the rotating impeller and the stationary pump member surrounding the impeller. In order to reduce leakage losses occurring at the gap from the impeller pressure side to the impeller suction side, gap seals are provided.

Such gap seals are made US 2006/0147328 A1 and US 2007/0160467 A1 known. The gap seals described therein are mounted on a stationary pump part which separates the impeller pressure side from the impeller suction side. Typically, despite the gap seal, there is still a gap between the stationary pump member and the relatively rotating impeller. The width of this gap can be designed so that no appreciable loss of leakage can occur, but then there is a risk of friction between the impeller and the gap seal, which can lead to wear of the friction partners involved and particularly unfavorable to a blocked pump. Accordingly, in the known centrifugal pumps, the dilemma is to have to accept a relatively high wear and a blockage of the pump or otherwise with a larger gap, although a lower wear but relatively large leakage losses either at a narrow, low leakage causing gap.

Out US 2001/0007632 A1 . BE 767 910 A1 . US 3,020,850 A such as GB 730,459 A Pumps are known in which the split ring seal is attached to each impeller side. This seal arrangement is advantageous in that no relative movement between the impeller and the seal takes place in the direction of rotation of the impeller. The wear of these seals is correspondingly lower.

Against this background, the invention has for its object to provide a centrifugal pump with a gap seal, which should be further improved in the wear characteristics at the lowest possible leakage from the impeller pressure side to the impeller suction.

This object is achieved by a centrifugal pump having the features specified in claim 1. Advantageous developments of the invention will become apparent from the dependent claims, the following description and the drawings.

The centrifugal pump according to the invention has at least one impeller and at least one sealing arrangement which is arranged between a housing wall of the pump housing and the impeller and thus seals the suction side of the impeller against the pressure side of the impeller. The seal assembly has a seal which is rotatably attached to the impeller.

That is, the sealing of the suction side of the impeller against the pressure side between the seal and the stationary housing wall or arranged on the housing wall sealing body, wherein the seal rotates with the impeller. Accordingly, there is no relative movement between the impeller and the seal in the direction of rotation of the impeller. An advantage of this embodiment is that the impeller in this way does not form a frictional partner with a fixed pump part, so that the impeller no abrasive wear subject. Next allows the inventive arrangement of the seal on the impeller in a particularly favorable manner to form the seal not only as a radial seal but particularly advantageous as an axial seal, which will be described in detail with the associated advantages in detail.

On the impeller, the seal is slidably disposed in the radial direction relative to the impeller. Particularly advantageously, the seal is mounted on the impeller so that it can move radially in any direction transverse to a central axis of the impeller substantially. This allows a narrow formation of the required gap between the seal rotating with the impeller and the fixed part of the seal assembly, since the seal is e.g. then, when a foreign body has penetrated into the gap or when the seal contacts the fixed part of the seal assembly due to a deflection of the impeller shaft, can perform a short-time increasing evasion movement of the gap. That is, by a radial displacement of the seal relative to the impeller, the radial distance of the seal from the fixed part of the seal assembly at the location where it contacts the fixed part or at which a foreign body is located, be increased so that it is favorable no abrasive wear on the seal and / or the fixed part of the seal assembly comes.

With the aim of further reducing the risk of abrasive wear, the invention further provides, in a further advantageous embodiment, for the seal to be designed to be flexible at least in sections. Accordingly, the seal preferably has elastic deformability, and preferably elastic flexibility, at least in a portion adjacent to the gap with the fixed part of the seal assembly. These are preferably a deformability transversely to its sealing surface with the fixed part of the seal assembly. This elasticity also allows a deflection movement of the seal in a deflection of the impeller shaft or in a foreign body penetrated into the seal assembly.

As already mentioned, it proves to be particularly advantageous if the seal is designed as an axial seal, wherein for the purposes of the invention an axial seal is to be understood as meaning a seal in which the seal takes place in the axial direction of the impeller, ie the sealing surfaces extend in the axial direction of the impeller. An embodiment is preferred in which the seal is arranged on a suction mouth of the impeller, wherein it has a hollow cylindrical portion which extends in the axial direction of the impeller. The suction mouth of the impeller is typically formed centrally on a front cover plate in the inflow direction of the impeller. At the edge of the cover disk delimiting the suction mouth, the seal is preferably mounted in such a way that the inner wall of the hollow cylindrical section, which preferably forms a sealing surface of the seal arrangement, is aligned substantially flush with the edge of the suction mouth.

Advantageously, in this case a sleeve-shaped stationary part of the seal arrangement, which is expediently arranged on the housing of the centrifugal pump or on the housing wall, engage in the hollow cylindrical portion of the seal.

The outer cross-section or outer diameter of the sleeve-shaped part of the seal assembly, which engages in the hollow cylindrical portion of the impeller-side arranged seal expediently corresponds to the inner cross-section or inner diameter of the hollow cylindrical portion of the seal, wherein a formed between the sleeve-shaped part and the hollow cylindrical portion of the seal gap may advantageously be relatively narrow. Accordingly, only relatively small leaks can occur at the gap. In view of these leaks, it also proves to be advantageous that the gap at least in one end portion extends in the inflow direction of the sucked by the pump liquid and is open to the hem and out, so that the resulting leakage liquid can be sucked directly on the suction mouth.

A particularly small gap width can be achieved if the impeller-side seal, as already described, at least partially flexible and / or this seal is displaceable in the radial direction relative to the impeller. These embodiments cause the impeller-side seal in the case of friction with the housing-side sleeve-shaped part of the seal assembly can escape this sleeve-shaped part in the radial direction, i. can move radially away from this part. The housing-side part of the seal assembly and the seal can align themselves so independently.

The ability of the impeller-side seal to be able to move in the radial direction of the impeller relative to the impeller also proves to be advantageous insofar as by such a displacement of the impeller-side seal, similar to a hydrodynamic sliding bearing, a narrowing in the radial direction gap between the impeller side and the housing side seal results. This wedge-shaped gap leads to a hydrodynamic pressure distribution in the gap, whereby a force is exerted on the radially movable impeller-side seal, which tends to move the hollow cylindrical portion of the seal again in a concentric position to the housing-side sleeve-shaped part of the seal assembly. Accordingly, the gasket is capable of returning to its normal position on its own.

The seal may be attached to the impeller advantageously with a preferably flexible mounting ring. This proves to be special expedient if a section of the impeller, preferably an axial end of the impeller surrounding the suction mouth, and a section of the seal which contacts this section or end have an at least substantially corresponding external cross section. The flexibility of the mounting ring makes it possible in this case advantageous that the mounting ring can be placed under strain in a simple manner around the contacting portions of the impeller and the seal and then exerts a clamping force on these sections, whereby the seal positively and / or non-positively on the Impeller is set.

To attach the seal to the impeller preferably has both an end of the seal and an axial end of the impeller on a radially outwardly cantilevered flange extension, wherein the two extensions for fixing together engage in an inner groove of the extension ring attached to the attachment. In this way, the seal is positively fixed not only in the radial direction but also in the axial direction of the mounting ring.

The attachment ring preferably holds the seal with radial play on the impeller. For example, the attachment ring may comprise an extension formed at the end of the seal, the extension having a small clearance in the radial direction to the attachment ring, which advantageously permits limited deflection movements of the sealing ring in the radial direction relative to the rotor.

Advantageously, the seal is rotatably connected via a positive connection with the impeller. This positive connection can be generated either directly between the seal and the impeller or on the mounting ring by the intervention of at least one engagement means in at least one corresponding receptacle for this engagement means, which is basically arbitrary, on which component or on which components Engagement means and on which component or which components receptacles are provided for these engagement means.

In this context, a preferred embodiment provides that at least one engagement means is formed on a suction mouth side facing the seal, which is in engagement with a corresponding engagement means on the impeller. That is, the positive connection is made here directly between the seal and the impeller. Thus, e.g. recesses may be formed on an annular end surface of the gasket contacting the impeller, while corresponding protrusions are formed on an impeller side contact surface which engage with the gasket side recesses and fix the gasket against rotation relative to the impeller, preferably maintaining a certain radial mobility remains. Of course, it is also possible that the projections are provided on the sealing side and the recesses on the impeller side.

In addition, it may also be advantageous to form in the inner groove of the fastening ring at least one radially oriented projection, which engages in a corresponding radial recess of suction mouth and / or seal. Conversely, it is typically also possible to provide at least one radially aligned recess in the inner groove of the fastening ring, into which recess a radially aligned projection of suction mouth and / or seal engages. In both cases, a rotational movement of the seal is prevented relative to the impeller of the mounting ring. This is particularly advantageous when the mounting ring is made of an elastic material, such as rubber, since in the torque transmission from the impeller to the seal may possibly shocks from the impeller on the seal may occur, the noise caused thereby by the elastic material of the Mounting ring are damped.

In a further preferred embodiment of the centrifugal pump according to the invention, it is provided to non-rotatably connect the seal to the suction mouth by virtue of frictional engagement. Thus, the impeller-side and the sealing-side contact surface and possibly also a fixing ring serving for fastening the seal to the impeller can each be designed to form a frictional connection.

In particular, when the centrifugal pump according to the invention is a low-pressure pump, the seal and the fastening ring can be advantageously formed as an integral component. Accordingly, an annular portion is provided at an axial end of the seal, which includes an axial end of the impeller circumferentially. Preferably, the portion forming the seal and the portion of the component forming the fastening ring are in this case made of an elastic material.

Fig. 1

ein schematisch dargestelltes Ausführungsbeispiel eines Lauf- rads einer Kreiselpumpe mit einer daran angeordneten Dich- tungsanordnung in einem Längsschnitt,

Fig. 2

das Ausführungsbeispiel nach Fig. 1 in einer perspektivischen Explosionsdarstellung,

Fig. 3

ein schematisch dargestelltes zweites Ausführungsbeispiel eines Laufrads einer Kreiselpumpe mit einer daran angeord- neten Dichtungsanordnung in einem Längsschnitt,

Fig. 4

das Ausführungsbeispiel nach Fig. 3 in einer perspektivischen Explosionsdarstellung,

Fig. 5

ein schematisch dargstelltes drittes Ausführungsbeispiel eines Laufrads mit einer daran angeordneten Dichtungsanordnung in einem Längsschnitt,

Fig. 6

das Ausführungsbeispiel nach Fig. 5 in einer perspektivischen Explosionsdarstellung,

Fig. 7

ein schematisch dargestelltes viertes Ausführungsbeispiel ei- nes Laufrads mit einer daran angeordneten Dichtungsanord- nung in einem Längsschnitt, und

Fig. 8

das Ausführungsbeispiel nach Fig. 7 in einer perspektivischen Explosionsdarstellung.

The invention is explained in more detail with reference to exemplary embodiments illustrated in the drawings. In the drawings show:

Fig. 1

1 shows a schematically illustrated embodiment of a running wheel of a centrifugal pump with a sealing arrangement arranged thereon in a longitudinal section,

Fig. 2

the embodiment according to Fig. 1 in a perspective exploded view,

Fig. 3

2 shows a schematically illustrated second exemplary embodiment of an impeller of a centrifugal pump with a sealing arrangement arranged thereon in a longitudinal section,

Fig. 4

the embodiment according to Fig. 3 in a perspective exploded view,

Fig. 5

3 shows a schematic dargstelltes third embodiment of an impeller with a sealing arrangement arranged thereon in a longitudinal section,

Fig. 6

the embodiment according to Fig. 5 in a perspective exploded view,

Fig. 7

a schematically illustrated fourth embodiment of an impeller with a sealing arrangement arranged thereon in a longitudinal section, and

Fig. 8

the embodiment according to Fig. 7 in a perspective exploded view.

In the figures, an impeller 4 driven by an impeller 2 of a centrifugal pump is shown in each case. At a front, i. At a side facing away from the impeller shaft 2 cover plate 6 of the impeller 4, a suction port 10 is formed at one axial end 8. At the axial end 8 of the impeller 4, a seal 12 is arranged. The seal 12 is formed of an elastic material, preferably rubber. It has a hollow cylindrical portion 14 in the form of a base body 14, which is aligned axially and concentrically to a central axis A of the impeller 4. The main body 14 forms an inflow channel to the suction mouth 10 of the impeller. 4

At the end remote from the impeller 4 of the base body 14 engages a rigid, sleeve-shaped portion 16 of a sealing member 18 with a small clearance, ie, forming a comparatively narrow Gaps, in the main body 14 a. The sealing member 18 is fixedly arranged on a housing wall, not shown in the figures of a pump housing also not shown and forms an inlet to the suction port 10 of the impeller 4. Together, the impeller-side seal 12 and the sleeve-shaped portion 16 of the housing wall sealing member 18 form a seal assembly, the the suction side of the impeller 4 seals against the pressure side of the impeller 4. Due to the narrow design of the gap between the main body 14 of the seal 12 and the housing wall sealing member 18 can flow only a small amount of liquid from the pressure side of the impeller 4 to the suction side, wherein it proves to be particularly advantageous that the gap between the base body 14 and the sleeve-shaped portion 16 of the sealing member 18 concentric with the central axis A of the impeller 4 extends directly in the direction of the suction mouth 10 of the impeller 4, so that the leaked liquid can be sucked in again by the impeller 4 again.

The axial end 8 of the impeller 4 to the suction port 10 is formed in a flange, wherein a, a contact surface for the seal 14 forming end portion is radially expanded. The end of the seal 8, which is to be brought to bear on the end 8 of the impeller 4, is also expanded in the radial direction, the inner and outer diameter of this extension 21 corresponding to the corresponding diameters of the extension 19 formed at the end 8.

The attachment of the seal 12 at the end 8 of the impeller 4 by means of a mounting ring 20. The mounting ring 20 is made of elastic material, preferably rubber. On its inside a circumferential groove 22 is formed. For attachment of the seal 12 at the end 8 of the impeller 4, the fixing ring 20 is circumferentially so placed around the end 8 of the impeller 4 and the seal 12 that the formed at the end of the extension 19th and formed on the seal 12 extension 21 engage together in the groove 22 of the mounting ring 20 so that the mounting ring 20 includes these extensions 19 and 21 both axially and radially, wherein in the radial direction between the seal-side extension 21 and the circumferential inner wall of the Nut 22 is a small game. If necessary, this play allows a deflection movement of the seal 12 relative to the sleeve-shaped section 16 of the sealing part 18 transversely to the central axis A of the running wheel 4.

The seal 12 is fixed by the mounting ring 22 in both the radial and in the axial direction at the end 8 of the impeller 4. In order to prevent a rotational movement of the seal 12 relative to the impeller 4 about its central axis A, six projections 24 are formed on the outer end face of the end 8 of the impeller 4 evenly distributed over the circumference of this end face extending in the axial direction. Corresponding to these projections 24 six recesses 26 are formed at the front end of the seal 12 formed on the extension 21, in which the projections 24 engage positively.

That in the 3 and 4 illustrated embodiment corresponds essentially to the in the Fig. 1 and 2 illustrated embodiment, wherein, however, at the end faces of the formed at the end 8 extension 19 and the seal-side extension 21 no axially aligned projections 24 and recesses 26 are formed. Instead, at the end 8 formed on the extension 19 circumferentially six evenly distributed over the circumference radially aligned recesses 28 and formed on the seal 12 formed on the extension 21 also six evenly distributed over the circumference radially aligned recesses 30, wherein the position and Size of the recesses 28 and 30 are the same. Corresponding to the extensions 19 and 21 formed recesses 28 and 30 are on the inner circumference of the groove 22 of the mounting ring 20 evenly distributed over the inner circumference six projections 32 are formed. The projections 32 extend radially inwardly. In the assembled state, the projections 32 of the mounting ring 20 positively engage both in the recesses 28 of the extension 19 as in the recesses 30 of the extension 21 and thus prevent a rotational movement of the seal 12 relative to the impeller. 4

In the in the FIGS. 5 and 6 illustrated embodiment, projections 19 or 21 projections or recesses are formed neither on the front side nor on the peripheral side of the extensions. Here, the rotationally fixed arrangement of the seal 12 at the end 8 of the impeller 4 by means of adhesion. For this purpose, the end and peripheral surfaces of the extensions 19 and 21 as well as the side contacting the region of the groove 22 of the mounting ring 20 form a friction pair, which prevents rotation of the seal 12 relative to the impeller 4.

Similarly, in the in the FIGS. 7 and 8 illustrated embodiment, the seal 12 at the end 8 of the impeller 4 rotatably fixed by frictional engagement. However, here is a seal 12 'is provided, in which a hollow cylindrical body 14' and a mounting ring 20 'form an integral component, that are firmly connected to each other.

LIST OF REFERENCE NUMBERS

2

- Impeller shaft

4

- Wheel

6

- cover disc

8th

- The End

10

- Suction mouth

12, 12'-

poetry

14, 14'-

Section, basic body

16

- Section

18

- sealing part

19

- Extension

20, 20'-

fixing ring

21

- Extension

22

- groove

24

- Head Start

26

- recess

28

- recess

30

- recess

32

- Head Start

A

- central axis

Claims (13)

1. A centrifugal pump with at least one impeller (4) and with at least one sealing arrangement arranged between the impeller (4) and a housing wall, said sealing arrangement sealing the suction side of the impeller (4) with respect to the pressure side of the impeller (4) and comprising a seal (12) which is fastened on the impeller (4) in a rotationally fixed manner, characterised in that the seal (2) is displaceable in the radial direction relative to the impeller (4).
2. A centrifugal pump according to one of the preceding claims, characterised in that the seal (12) is designed in a flexible manner at least in sections.
3. A centrifugal pump according to one of the preceding claims, characterised in that the seal (12) is arranged on a suction port (10) of the impeller (4) and comprises a hollow-cylindrical section (14) which extends in the axial direction.
4. A centrifugal pump according to claim 3, characterised in that a stationary part (16) of the sealing arrangement, said part being designed in a sleeve-like manner, engages into the hollow-cylindrical section (14) of the seal (12).
5. A centrifugal pump according to one of the preceding claims, characterised in that the seal (12) is fastened on the impeller (4) with a fastening ring (20).
6. A centrifugal pump according to claim 5, characterised in that the fastening ring is designed in a flexible manner.
7. A centrifugal pump according to claim 6, characterised in that an end of the seal (12) as well as the end (8) of the suction port (10) comprise an outwardly projecting, flange-like widening (19, 21) which for fastening, together engage into an inner groove (22) of the fastening ring (20) applied around the widenings (19, 21).
8. A centrifugal pump according to one of the claims 6 or 7, characterised in that the fastening ring (20) holds the seal (12) on the impeller (4) with radial play.
9. A centrifugal pump according to one of the preceding claims, characterised in that the seal (12) is connected to the impeller (4) in a rotationally fixed manner by way of a positive-fit.
10. A centrifugal pump according to claim 9, characterised in that at least one engagement means is formed on a side of the seal (12), said side facing the suction port (10), and this at least one engagement means is in engagement with corresponding engagement means on the impeller (4).
11. A centrifugal pump according to claim 9, characterised in that at least one radially aligned projection (32) is formed in the inner groove (22) of the fastening ring (20), and this projection engages into corresponding radial recesses (28, 30) of the suction port (10) and/or seal (12).
12. A centrifugal pump according to one of the claims 1 to 7, characterised in that the seal (12) is connected to the suction port (10) in a rotationally fixed manner by way of a non-positive fit.
13. A centrifugal pump according to one of the preceding claims, characterised in that the seal (12) and the fastening ring (20) are designed as an integral component.

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