EP2818722B1 - Centrifugal pump - Google Patents

Description

The invention relates to a centrifugal pump with several pump stages. There are multi-stage centrifugal pumps are known in which a plurality of pump stages, each consisting of a pump impeller and a surrounding spiral housing, are arranged between a head part and a foot part, wherein the wheels are arranged on a common shaft. In this case, head part and foot part, including the pump stages, are connected to one another via external tie rods in the form of screws.

Such a centrifugal pump typically has four screws, which extend on the outside along the pump stages. Embodiments are known in which the spiral housings in the region of the pump stages form the outer jacket or those in which a liquid return takes place within the housing, typically to the foot part, which have an outer jacket which forms an annular channel between the outer sides of the spiral housing and the outer jacket. via which the conveying fluid flows from the head part to the foot part or optionally also vice versa ( EP 2 112 380 A1 ).

Both versions have in common that the screws, with which the head and foot part are clamped, including the pump stages or, where appropriate, the surrounding outer sheath, abut in the region of the head and foot, but have a certain distance in the pump stages. The latter causes the temperature of the screws of the pumped liquid and thus also that of the volute casing or the outer shell can deviate not insignificant, which leads to thermal stresses within the centrifugal pump. Such thermal stresses can lead to premature wear or failure of the pump.

Another disadvantage of this design is that depending on the number of pump stages not only shaft and possibly outer sheath must be provided in different lengths, but that the head and foot connecting screws must be available in different lengths to order depending on the number Pump steps to connect the head and foot sections, including the pump stages.

In that regard, the cheaper DE 37 29 673 A1 known construction, in which an axial end of the outer shell, which comprises the pump stages, is fixed to the head part and the other axial end to the foot part and the mechanical connection between the head part and the foot part is formed by the outer shell itself. In this case, the outer shell is connected by insertion of a respective ring form-fitting manner with the foot part and with the head part, each having a radial inwardly directed flange-like projection which is screw-mounted respectively on the headboard or footboard. In this known construction arise due to the free lengths of the comparatively long tie rods and their partially spaced arrangement areas that are outside the temperature level of the pump.

Out WO 01/83996 A1 is a submersible pump to the prior art, in which the above-described thermal problems do not occur due to the system, because the entire pump is surrounded by the pumped liquid.

Based on the state of the art DE 37 29 673 A1 the invention has the object, a multi-stage generic centrifugal pump in such a way that thermal stresses within the pump are largely avoided, or at least reduced.

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

The centrifugal pump according to the invention has a plurality of pump stages, which are arranged axially between a head part and a foot part. It also has an outer sheath surrounding the pump stages circumferentially. In this case, an axial end of the outer shell is attached to the head part and the other axial end of the foot part of the centrifugal pump, wherein the mechanical connection between the head part and the foot part is formed by the outer shell.

The basic idea of the solution according to the invention is therefore to use the outer casing, which is generally present anyway, for clamping the pump stages between the head part and the foot part. The outer jacket thus forms the mechanical connection between the headboard and footboard. The axial ends of the outer shell are therefore fixed according to the invention, but preferably releasably attached to the foot and the headboard indirectly or directly. In this way, the otherwise required tie rods can be omitted. The outer shell is, if this forms the annular return channel within the centrifugal pump, always with the temperature level of the pumped liquid acted on, so that thermal stresses are largely avoided because the outer jacket and pump stages and head and foot always have the same temperature level. In embodiments that have the outer sheath only for fastening purposes, in which therefore no annular channel is formed, the outer sheath is expediently formed adjacent to the pump stages, ie adjacent to the outside of the spiral housing, in order to produce a heat-conducting connection to these, if possible.

In this case, the outer shell is connected by incorporation of at least one ring form-fitting manner with the foot part and / or the head part. The advantage of such a connection, in which the positive connection is formed by a typically open ring incorporated between the components, is that the components are quite easy to assemble, since they are tolerated without the ring diameter that they are plugged into each other. Only by interposing this ring, the actual positive connection occurs. It is particularly advantageous that the forces over almost the entire circumference are introduced uniformly from the foot part or head part to the outer shell or vice versa by the ring. The fact that the components abut each other over almost the entire circumference, at least when they are, which is likely to be the case, made of metal, a very good heat transfer between the components, so it is assumed that a uniform temperature level within the centrifugal pump can. The incorporated between the components ring is not designed as a closed ring but as an open ring, so that it can be mounted by slightly expanding also on components that are larger than the inner diameter of the ring or can be incorporated into components that are smaller than the Outer diameter of the ring, if this is compressed accordingly. Instead of the one-piece ring can also be a multipart Ring use find what can be advantageous in terms of mounting.

In this case, the tubular outer jacket is formed from sheet metal. This is formed radially widened at its axial ends, as this an equally simple and effective attachment is possible, on the other hand, the assembly is very simple when z. B. results in a funnel-shaped receptacle, which allows easy mounting on the outer circumference of the pump stages. The expansion can be carried out radially outward or radially inward or in both directions, advantageously by plastic shaping, such as rollers, deep drawing, upsetting, flanging or the like.

The attachment of the outer shell in the head part or in the foot part is carried out according to the invention in that the foot part and / or on the head part at least partially circumferential radially inwardly directed projection is provided. This projection is expediently designed so that the axial, optionally flared, end of the outer shell is still just passed and only after integration of the ring of the desired fit, in particular in the axial direction occurs. Such a projection is to be formed by a separate, single or multi-part, annular component, which is screw-mounted on the head or foot. Thus, such a projection may be 360 ° circumferentially formed when it is formed by a flange which is screw-mounted on the head part or the foot part typically on an axial end face.

Such a flange may be formed in one piece, but also in several parts. In the latter case, it is advantageous if the individual flange parts are identical, z. B. by two identical flange halves.

Advantageously, the ring, which produces the positive connection between the head part and outer shell or foot part and outer shell, be formed in several parts. Then it is appropriate to divide the ring so that all parts are identical, z. B. to provide two identical ring halves.

In addition to any grooves for the integration of O-rings between the outer shell and headboard or outer shell and foot, the outer shell advantageously at least one end has a circumferential and radially outwardly open groove, which serves for the integration of the ring, with which the positive connection between the outer shell and Headboard or outer sheath and footboard is made. Since the outer sheath is formed from sheet metal, such a groove can be formed by a molding in this area.

In addition, head and foot also advantageously have a circumferential, but radially inwardly open groove for receiving the ring, which is advantageously arranged so that it is opposite in the installed position of the groove at the end of the outer shell or from the outer shell to the headboard or footboard seen in front of the radially expanded end of the outer shell is arranged. This arrangement ensures that the ring to be incorporated therein holds the flared end of the outer shell in a form-fitting manner within the head part or foot part. Such a groove can be formed by screwing a flange to an axial side of the head or foot part.

Preferably, interlocking means are provided at the axial end of the outer jacket, which hold the outer jacket against rotation on the foot part or on the head part. Such positive locking means can by a tongue and groove arrangement in the region of the flared portion on the outer circumference of the outer shell and on the corresponding inner side of the be provided corresponding recording of the headboard or footboard. For example, in the widened part of the outer jacket, axially parallel recesses can be distributed over the circumference, which engage in corresponding projections in the associated receptacle from the head part or foot part. These components provide a rotationally fixed connection between the headboard and outer shell or foot and outer shell.

Fig. 1

in stark vereinfachter perspektivischer Darstellung eine Ansicht eines erfindungsgemäßen Kreiselpumpenaggregates mit unterschiedlichen Befestigungen von Kopfteil und Fußteil,

Fig. 2

in perspektivischer Darstellung eine Ausführung der Befestigung eines axialen Außenmantelendes am Fußteil,

Fig. 3

die Verbindung der Fig. 2 in Explosionsdarstellung,

Fig. 4

einen Längsschnitt durch die Verbindung nach Fig. 2,

Fig. 5

in stark vergrößerter Darstellung die Einzelheit V in Fig. 4,

Fig. 6

eine alternative Befestigung in Darstellung nach Fig. 5 und

Fig. 7

eine weitere Ausführung in Darstellung nach Fig. 5.

The invention is explained in more detail with reference to embodiments shown in the drawing. Show it:

Fig. 1

in a greatly simplified perspective view of a view of a centrifugal pump assembly according to the invention with different fasteners of the headboard and footboard,

Fig. 2

a perspective view of an embodiment of the attachment of an axial outer shell end to the foot part,

Fig. 3

the connection of the Fig. 2 in exploded view,

Fig. 4

a longitudinal section through the connection after Fig. 2 .

Fig. 5

in a greatly enlarged view the detail V in Fig. 4 .

Fig. 6

an alternative attachment in representation after Fig. 5 and

Fig. 7

another embodiment in illustration after Fig. 5 ,

In the illustrated centrifugal pump 1 is a multi-stage inline pump. The centrifugal pump 1 is intended for upright operation and has a foot part 2, to which an outer jacket 3 connects at the top, the upper end of which is received by a head part 4 is, which also forms a motor chair for the above arranged electric drive motor 5. The construction of in Fig. 1 The pump shown corresponds to the basic structure of such vertical multi-stage high-pressure centrifugal pumps of inline design, as they are manufactured and offered for example by the company Grundfos under the type designation CR or CRE.

The cast foot part 2 has an integrally formed therewith lower plate 6, which forms the actual foot of the centrifugal pump 1 and with which the centrifugal pump 1 rests on the ground and can be screwed via holes located in the plate 6 with the bottom. The foot part 2 has, moreover, the shape of a cylindrical tube 7 with a vertical axis, which faces away from its opposite two oppositely disposed connecting flanges 8 and 9, one of which forms the suction port and the other the pressure port of the pump 1. Via the suction connection, the liquid to be delivered passes into the foot part 2 and from there successively into the vertically adjoining pump stages, each consisting of a spiral housing and an impeller. In this case, the arrangement is such that the output of a lower volute casing is conductively connected to the input of the overlying pump stage and the output of the last, ie uppermost, pump stage is connected via an annular channel with the pressure port in the foot part 2. The annular channel is defined by the peripheral sides of the Fig. 1 invisible spiral housing on the one hand and the outer shell 3 cylindrical in this area on the other hand limited. The wheels of all pump stages sit on a common shaft, which is driven by the head part 4 of the centrifugal pump 1 arranged drive motor 5.

Although the present invention is described with reference to a vertical multi-stage centrifugal pump, it is not limited to the vertical arrangement.

The coaxial with the axis of rotation and shaft of the centrifugal pump arranged outer jacket 3 has the shape of a cylindrical tube, but is for attachment in the head part 4 and in the foot part of the second formed widened at the axial ends. The variants described below, in each of which the axial upper end of the foot part and the lower end of the outer shell 3 engaging therewith are shown, can be used in the same way for the connection between the head part and outer shell. Advantageously, the same types of connections and components are selected for both connections. However, this is not absolutely necessary, it may optionally be different compounds, as exemplified in Fig. 1 is shown.

When using the FIGS. 3 to 5 illustrated embodiment, the axial end of the outer shell 3 is expanded radially outward. The outer shell 3 formed from sheet metal is compressed there to a circumferential bead 10. The tubular part 7 of the foot part 2 is stepped cylindrical to its axial upper end. It has an inner part 11 which limits the circumferential axial surface 12 inwards. On the annular surface 12 holes 13 are arranged distributed, which serve to receive fastening screws 14, which serve to define a flange 15 having an annular cylindrical shape with an inwardly radially projecting bead 16. As in particular in Fig. 5 is visible, serves the superior inner part 11 for guiding the axial end of the outer shell 3 on the inside. There, a circumferential groove for an O-ring 17 is provided, with which the outer shell 3 with respect to the inner part of the 11th and thus sealed against the foot part 2. The outer circumference of the bead 10 at the end of the outer shell 3 is slightly smaller than the inner circumference of the bead 16 on the flange 15, so that the flange 15 can be pushed over the end of the outer shell.

In order to achieve a positive connection between these components, a ring 18 is provided. This ring 18 is, as in particular from Fig. 3 seen, open, so that after the flange 15 has been pushed over the end of the outer shell 3, it is so far increased in diameter by bending resiliently that it can be pushed over the bead 10. This ring 18 then springs back and frictionally engages the cylindrical part of the outer shell 3 on the outside. Now, if the flange 15 is fastened by means of the screws 14 in the holes 13 and thus on the foot 2, this ring 18 is pushed between the beads 10 and 16, as it is in Fig. 5 is shown. The beads 10 and 16 have for this purpose corresponding inclined surfaces, so that the ring 18 can create a force fit between these beads. This ring 18 now forms a positive connection between the flange 15 and the flared end of the outer shell 3 and thus defines this form-fitting and non-positive in the foot part 2.

It can be seen that this results in a very uniform application of force over the entire circumference. Also lie through the ring 18, which is formed of spring steel, the metallic flange 15, the outer shell formed from sheet metal shell 3 and the cast foot part 2 closely and thermally conductive to each other, so that they always have about the same temperature level during operation.

The release of the connection takes place in the reverse direction, ie after loosening the screws 14, the flange 15 is first lifted up until the ring 18 is accessible. This is then bent, pushed over the bead 10 at the end of the outer shell 3, after which the outer sheath 3 can be pulled off the foot part 2 upwards.

In the case of Fig. 6 illustrated embodiment, the axial end of the outer shell 3 is widened radially inwardly and there has a circumferential bead 19 which rests against the inner part 11 under inclusion of this component sealing O-ring 17. The outer casing 3 is cylindrical on its outer side to the end, but has a circumferential in cross-section semicircular groove 20 which is provided for the integration of the ring 18, the positive connection between the end of the outer shell 3 and the foot part 2 with the flange 21st forms, which also has a radially inwardly projecting and encircling bead 22 which, however, in contrast to the bead 16 extends directly to the outside of the outer shell 3. Outer casing side of the ring 18 is positively fixed in the groove 20, flange side by the bead 22nd

In the case of Fig. 7 illustrated embodiment, the outer shell 3 is formed widened at its axial end 23, but not compressed, as in the embodiments described above. The outer casing 3 therefore also has essentially the same material thickness in the widened region 23 as in the remaining region. This flared end 23 of the outer sheath 3 is located in a circumferential groove 24 in the axial surface 12. Also, the transition between the groove 24 and the inner part 11, which supports the axial end of the outer sheath 3 radially inwardly, adapted accordingly. The seal between the outer shell 3 and the foot also takes place here by an O-ring 17, which lies in a circumferential groove on the outer circumference of the inner part 11 and which rests against the inside of the outer shell 3. A flange 25 is fastened by means of screws 14 in holes 13 under inclusion of the ring 18 and thus defines the outer shell 3 in the foot part 2. The flange 25 has an outward here obliquely grading form. On the inside, it has a bead 26, with which it holds the ring 18 positively but also non-positively.

In all the above embodiments, the assembly of the compound takes the form that first the respective flange is pushed over the axial end of the outer shell, after which the ring 18 is pushed onto this end and the axial end is brought into its intended position in the foot part 2. Then, the flange is fastened by means of the screws 14 in the holes 13, after which the connection is positive and non-positively fixed. The release takes place in reverse order.

LIST OF REFERENCE NUMBERS

1

rotary pump

2

footboard

3

outer sheath

4

headboard

5

drive motor

6

Plate of 2

7

cylindrical tube of 3

8th

flange

9

flange

10

bead

11

inner part

12

surface

13

drilling

14

screw

15

flange

16

bead

17

O-ring

18

ring

19

Bead ( Fig. 6 )

20

Groove ( Fig. 6 )

21

Flange ( Fig. 6 )

22

Bead ( Fig. 6 )

23

expanded end ( Fig. 7 )

24

Groove ( Fig. 7 )

25

Flange ( Fig. 7 )

26

Bead ( Fig. 7 )

Claims (5)

1. A centrifugal pump (1) with several pump stages, which are arranged axially between a head part (4) and a foot part (2), and with an outer casing (3) which peripherally surrounds the pump stages, wherein an axial end of the outer casing (3) is fastened on the head part (4) and the other axial end on the foot part (2), and the mechanical connection between the head part (4) and the foot part (2) is formed by the outer casing (3), wherein the outer casing (3) is connected with a positive fit for the foot part and/or the head party by way of integrating at least one ring (18) and that the foot part (2) and/or the head part (4) comprises a radially inwardly projection or bulge (16; 22; 26), which is formed by a flange (15, 21, 25) which is screw-fastened on the head part (4) or on the foot part (2), characterised in, that the ring (18) formed from sheet metal, the metallic flange (15), the outer casing (3) formed from sheet metal and the head part (4) consisting of cast metal bear on one another in a tight and thermally conductive manner wherein the flange (15; 21; 25) is fastened via screws (14) on bores of the head part (4) or the foot part (2).
2. A centrifugal pump according to claim 1, characterised in that the outer casing (3) is designed in a radially widened manner at least at one end.
3. A centrifugal pump according to claim 1 or 2, characterised in that the flange is designed in a multi-part manner, preferably comprises two identical flange halves.
4. A centrifugal pump according to one of the preceding claims, characterised in that the ring (18) is designed in a multipart manner, preferably has two identical ring halves.
5. A centrifugal pump according to one of the preceding claims, characterised in that the outer casing (3) at least at one end is provided with a peripheral and radially outwardly open groove (20).

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