EP2643595A1 - Self-cleaning screw-type centrifugal wheel pump with recirculation behind the impeller - Google Patents

Abstract

The screw-type centrifugal wheel pump (1) comprises a pump housing (3) and a screw-type centrifugal wheel (20) arranged rotatably within the pump housing (3) and having a hub (21) and a blade (25), and comprises a rotatable drive shaft (33) connected to the screw-type centrifugal wheel (20), and comprises a cover plate (2) arranged between the screw-type centrifugal wheel (20) and a housing rear wall (23), wherein the cover plate (2) has a central opening (2g) through which the hub (21) or the drive shaft (33) runs, and wherein an interior space (37) is formed between the cover plate (2) and the housing rear wall (23), wherein a gap (2b) is formed between the central opening (2g) of the cover plate (2) and the hub (21) or the drive shaft (33), which gap is connected in fluid-conducting fashion to the interior space (37), wherein the cover plate (2) has at least one aperture (2a), which is arranged spaced apart from the central opening (2g), in order to generate a fluid flow (F1) which flows into the interior space (37) via the aperture (2a) and out of the interior space (37) again via the gap (2b).

Description

SELF-CLEANING SCREW CENTRIFUGE WHEEL PUMP WITH RECIRCULATION BEHIND THE SHAFT WHEEL

description

The invention relates to a Schraubenzentrifugalradpumpe, a

 5 Method of operating a centrifugal screw centrifugal pump and a cover plate for a centrifugal screw centrifugal pump.

Prior Art 0 Document CH 662 864 discloses a

 Schraubenzentrifugalradpumpe, wherein the Schraubenzentrifugalrad is rotatably mounted on a rotational axis. The

 Schraubenzentrifugalradpumpe has in the region of the connection between Schraubenzentrifugalrad and axis of rotation on a cavity 5. This very well-proven embodiment of a

 Schraubenzentrifugalradpumpe has the disadvantage that deposit within the cavity impurities and

 can accumulate. This results in increased wear and / or increased maintenance.

0 Presentation of the invention

It is an object of the present invention

 Form Schraubenzentrifugalradpumpe and to propose a method for cleaning a Schraubenzentrifugalradpumpe, the more advantageous with respect to the attachment of impurities

Have properties.

This object is achieved with a screw centrifugal pump having the features of claim 1. The dependent claims 2 to 19 relate to further advantageous embodiments. The object is further achieved with a method for self-cleaning a Schraubenzentrifugalradpumpe comprising the features of claim 20. The claims 21 and 22 relate to further advantageous method steps. The object is further achieved with a cover plate having the features of claim 23. The claims 24 to 30 relate to further advantageous

Embodiments. The problem is solved in particular with a

 A screw centrifugal wheel pump comprising a pump housing having a pump inlet opening and a housing rear wall arranged opposite the pump inlet opening, comprising a housing arranged rotatably within the pump housing

Schraubenzentrifugalrad with a hub and a blade, and comprising a rotatable drive shaft which with the

Screw centrifugal is connected, and comprising a

Cover plate which is arranged between the Schraubenzentrifugalrad and the rear wall of the housing, wherein the cover plate a

Center opening through which the hub or the drive shaft runs, and being between the cover plate and the

Rear wall of an interior space is formed, wherein the

Cover plate aligned to the pump inlet opening

Front side, and wherein the front side comprises a partial surface whose course so the back of the

 Schraubenzentrifugalrades adapted adapted that between the front of the cover plate and the back of the

Schraubenzentrifugalrades a gap of up to 3 mm is formed, wherein between the center opening of the cover plate and the hub or the drive shaft, a gap is formed, the fluid is conductively connected to the interior and the gap, wherein the cover plate has at least one aperture which spaced is arranged to the center opening, wherein the

Schraubenzentrifugalrades and the arrangement of the aperture are designed mutually adapted so that the back of the Schraubenzentrifugalrades the aperture is not covered or covered with a rotation of the Schraubenzentrifugalrades 360 ° only during a partial angle, and wherein the aperture fluid-conducting connection between the front and the interior formed to generate a fluid flow over the

 Breakthrough flows into the interior and flows through the gap back out of the interior.

The screw centrifugal pump according to the invention as well as the method according to the invention have the advantage that during the pumping operation a partial flow is formed, which differs from the

Front to the back of the cover plate flows and then along a central opening of the cover plate back to the front of the

Cover plate flows, so that forms a cleaning stream, which is possibly in the cavity located behind the cover plate or at least partially recycle accumulated impurities to the front of the cover plate, so that these impurities on the main flow of Schraubenzentrifugalradpumpe

can be promoted away. The screw centrifugal pump according to the invention comprises a rotatably mounted screw centrifugal wheel and a cover plate arranged directly next to the screw centrifugal wheel with a central opening, wherein a hub or a drive shaft of the screw centrifugal wheel preferably extends through the central opening. Between the center opening and the hub or the drive shaft, a fluid-conducting gap is formed. Rotating the helical centrifugal wheel in the direction of rotation causes a fluid to be conveyed along a main flow, with the result that a partial flow of the fluid through an opening spaced apart from the center opening to the rear of the

Cover plate flows, and that this partial flow then flows through the fluid-conducting gap back to the main flow, due to the prevailing between the aperture and the fluid gap gap pressure difference. This partial flow forms a purifying fluid flow, which in particular flows through the rear space of the cover plate and supplies any impurities present therein to the skin flow.

The cover plate extends on the Schraubenzentrifugalrad the side facing or the

 Schraubenzentrifugalrad facing surface preferably according to the course of the back of the

Schraubenzentrifugalrades, so that the partial surface preferably frusto-conical or even, wherein the partial surface could also have a different shape, for example, a curved or polygonal course. The object is further achieved in particular with a method for self-cleaning a Schraubenzentrifugalradpumpe comprising a rotatably mounted Schraubenzentrifugalrad and a lower

Forming a gap on the back of the

Schraubenzentrifugalrades arranged cover plate with a

A central opening, wherein the cover plate has an opening which is spaced with respect to the center opening, wherein a hub or a drive shaft of the Schraubenzentrifugalrades passes through the central opening, so that forms a fluid-conducting gap between the center opening and the hub or the drive shaft, wherein the Schraubenzentrifugalrad and the arrangement of

 Through openings are adapted mutually adapted so that the back of the Schraubenzentrifugalrades the aperture is not covered during rotation of the Schraubenzentrifugalrades or only during a partial angle Δ is covered, wherein the Schraubenzentrifugalrad is rotated in the direction of rotation and thereby a fluid is conveyed along a main flow, wherein a Partial flow Fl of the fluid flows through the aperture to the back of the cover plate, and wherein this partial flow then flows through the gaps back to the main flow, due to the prevailing between the aperture and the gap pressure difference.

The object is further achieved, in particular, with a cover plate for a screw centrifugal pump, wherein the cover plate has a front side and a rear side, and wherein the cover plate has a center opening in its center, wherein the center opening adapted to pass through a rotational axis of the Schraubenzentrifugalrades and extends in the direction of the axis of rotation, and wherein the cover plate has at least one aperture which is spaced from the center opening, and wherein the aperture forms a fluid-conducting connection between the front and the back of the cover plate, and wherein the opening has an inlet opening towards the front, and wherein the front side has a recess, wherein the inlet opening is arranged in this recess, and wherein the inlet opening forms an inlet surface, which in the

Substantially parallel to the axis of rotation A runs.

The invention will be described below with reference to exemplary embodiments in detail.

Brief description of the drawings

The used to explain the embodiments

Drawings show:

Figure 1 is an axial section of a known from the prior art Schraubenzentrifugalradpumpe.

 Fig. La is a side view of the illustrated in Figure 1

 Screw centrifugal pump on away broken

 Outer housing;

 Fig. Lb is a plan view of an impeller;

 Fig. 2 in a longitudinal section a partial view of a

Screw centrifugal pump with an embodiment of a cover plate; Figures 3 to 5 differently extending apertures;

Fig. 6 is a plan view of a cover plate;

 7 is a perspective view of that shown in FIG

 Cover plate;

8 shows a section through the cover plate according to FIG. 6 along the line B-B;

 9 shows a section through a further embodiment of a cover plate;

 Fig. 10, 1 1 schematically a section through two more

 Embodiments of cover plates:

 12 is a side view of another embodiment of an impeller of a Schraubenzentrifugalradpumpe in away broken outer housing.

 FIG. 13 is a plan view of the impeller of FIG. 12. FIG

 illustrated centrifugal centrifugal pump;

 Fig. 14 is a plan view of another embodiment of a cover plate.

 Basically, the same parts are given the same reference numerals in the drawings.

Ways to carry out the invention

Fig. 1 shows an art known from the prior art, in the document CH 662 864 disclosed embodiment

Screw-centrifugal pump. Figure 1 shows an axial section through the Schraubenzentrifugalradpumpe 1 comprising a

Screw Centrifugal 20 with a hub 21 and a blade 25, comprising a drive shaft 33 which is fixedly connected to the hub 21, and comprising a behind the

In the housing rear wall 23 in the vicinity of the drive shaft 33, an outlet opening 36 is provided so that gases can escape, which are carried in the fluid and excrete against the impeller rotation center and pass through the impeller rear gap between the impeller hub 21 and rear wall 23 in the interior 37. The gap between the impeller hub 21 and the housing rear wall 23 is formed as a labyrinth, wherein both the hub side and the rear wall side labyrinth structure is interrupted by a transverse groove 38, so that a self-cleaning effect and no conveyed solids in the interior 37 and the

Outlet opening 36 reach.

 However, it has been shown that despite this measure

Impurities can get into the interior 37, with these impurities in the interior 37 deposit and

accumulate, so that at certain intervals cleaning the Schraubenzentrifugalradpumpe is required.

FIG. 1 a shows a side view of that shown in FIG

Screw centrifugal wheel pump 1 at away broken

Outer housing 3. Figure lb shows in a plan view

 Embodiment of a Schraubenzentrifugalrades 20, which is not disclosed in such document CH 662864, but which is shown for the in Figures 1 and la

Screw centrifugal impeller 1 would be suitable, therefore, the figures 1, la and lb are explained together. The Schraubenzentrifugalrad 20 of the Schraubenzentrifugalradpumpe 1 comprises a hub 21 with a crescent-shaped base part 30, with which a blade 25 is connected, wherein an axis 33, the pressure-side, designed as a truncated housing wall 23 penetrates and is connected to the hub 21. The one

 Taper angle γ between 5 ° and 70 ° having housing wall 23 is swept by the end edge 28 of the pressure-side blade edge 27 with a small clearance 24. The blade 25 also includes a suction side flank 39. The crescent-shaped base portion 30 extends from the blade exit tip 35 into which the end edge 26 terminates, helically over a relatively long distance about the pump axis, to a point 31 at which Hub 21 has a relatively small radius R2. At the blade outlet tip 35, the hub 21 has the largest radius Rl. As a result, a relatively large area of the housing wall 23 is exposed over a relatively large arc δ, which is expediently approximately 120 °, between the blade outlet tip 35 and the aforementioned hub point 31. The exposure of the housing wall 23 by reducing the

Wheel hub radius Rl can go as far as the

allow material technical parameters to the

 Schraubenzentrifugalrad 20 still a sufficient to ensure strength.

FIG. 2 shows in a longitudinal section an embodiment of a screw centrifugal pump 1 according to the invention

Screw centrifugal impeller pump 1 comprises a pump housing 3 with inlet opening 3a or pump inflow opening 3a, outlet 3b and housing interior 3c, and further comprises a hub 21, which is connected to a blade 25 shown only schematically and dashed and thereby a Schaufelzentrifugalrad 20th forms, and which about a rotatable about an axis A.

Drive shaft 33 is rotatably mounted. The connection between the drive shaft 33 and the hub 21 is shown only schematically. The blade 25 and the hub 21 are preferably, as shown in Figure la and lb, as a single, common part or as

Vane centrifugal 20 designed. In the illustrated

Embodiment, the Schraubenzentrifugalradpumpe 1 also comprises a conical inner housing 4 with inlet opening 4a and a spacer ring 5. The Schraubenzentrifugalradpumpe 1 also comprises a housing rear wall 23 with a

 Outlet opening 36 and a seal 6. The outlet opening 36 is for maintenance purposes and is during operation of the

Schraubenzentrifugalradpumpe 1 usually closed with a plug from the outside. While rotating the

Schaufelzentrifugalrades 20, a main flow F is generated, which leads via the inlet opening 3a to the outlet 3b. The sponsored

Mainstream F comprises a fluid, preferably water and possibly gases such as water vapor, wherein the screw centrifugal wheel pump 1 in a preferred use for conveying

contaminated water is used, so that the main stream F may also include solids, such as feces, sand, gravel, textiles, fibers, plastic parts, etc.

The screw centrifugal pump 1 also comprises a cover plate 2, which is arranged in the direction of the axis A directly behind the hub 21 and the Schraubenzentrifugalrades 20. The cover plate 2 has a front side 2h and a rear side 2i, wherein the front side 2h comprises a partial surface 2k whose course in such a way the back 25a of

Schraubenzentrifugalrades 20 adapted adapted that between the front side 2h of the cover plate 2 and the rear side 25a of the screw centrifugal wheel 20, a gap 24 is formed of a maximum of up to 3 mm. Preferably, the gap 24 has a width in the range between 0.5 mm and 2 mm. Among other things, the gap 24 is designed to be so narrow that solids, for example fabrics that occur in sewage, such as women's stockings, can not penetrate into the gap 24 or can even wrap around the hub. The narrow gap 24 also creates a

Shearing action on itself within the gap 24 located

Solids, so that they are mechanically crushed and conveyed to the main flow F out. In a preferred

Embodiment is at least one of the gap 24 out

aligned surfaces, rough or designed, for example, with protruding teeth designed to improve mechanical comminution of located in the gap 24 solids. A gap 24 wider than 3mm, for example 5mm or wider, would have several disadvantages. On the one hand, due to the wide gap 24, the mechanical comminution of solids would no longer be guaranteed. In addition, a wide gap 24 would significantly reduce the efficiency of the Schraubenzentrifugalradpumpe 1. The front side 2h in the illustrated embodiment comprises a substantially frusto-conical running

Sub-surface 2k, the course of the back one

Schraubenzentrifugalrad 20 is adapted adapted, wherein the partial surface 2k in the center thereof has a central opening 2g, wherein the central opening 2g extends parallel in the direction of the axis A. The hub 21 extends through the central opening 2g, so that between the center opening 2g and the hub 21, a gap 2b extending in the direction of the axis A is formed. The hub 21 also has a projection which partially covers the partial surface 2k, so that between the hub 21 and the sub-surface 2k, a gap 24 running transversely with respect to the axis A is formed. The cover plate 2 has at least one opening 2a, which is arranged at a distance from the center opening 2g, wherein the opening 2a forms a fluid-conducting connection between the front side 2h and the rear side 2i of the cover plate 2. During the pumping operation, or during the rotation of the Schaufelzentrifugalrades 20 in

Direction of rotation R, the fluid in the region of the opening 2a has a higher pressure than in the region of the central opening 2g, whereby a partial flow Fl is generated by a part of the

Main stream F flows as a partial flow Fl through the opening 2a to the back 2i of the cover plate 2 in the interior 37, and then flows through the gap 2b and the gap 24 back into the main flow F. This partial flow Fl causes contaminants, which are located in the interior 37, are conveyed out of this and the skin flow F are supplied.

The Schraubenzentrifugalrad 20 and the arrangement of

Opening 2a are designed to be mutually adapted so that the back 25a of the Schraubenzentrifugalrades 20, the aperture 2a is not covered or upon rotation of the

Screw centrifugal wheel 20 to 360 ° only during one

Partial angle Δ covered.

In an advantageous embodiment, the

Schraubenzentrifugalrad 20 as shown in Figures 12 and 13 to be configured. Figure 12 shows a pump housing 3 in which a cover plate 2 and a Schraubenzentrifugalrad 20 is arranged. The hub 21 is connected to a circular base part 30, wherein the blade 25 is connected via the end edge 28 with the base part 30. The Schraubenzentrifugalrad 20 includes a

Figure 13 shows the Schraubenzentrifugalrad 20 in a plan view, wherein the base member 30 is circular and with respect to the axis A has a maximum radius Rl. FIG. 13 shows, by way of example, a possible arrangement of an opening or an opening 2a with respect to the screw centrifugal wheel 20. In this arrangement, the opening 2a does not pass through the helical centrifugal wheel 20 or through the rear side 25a of FIG

Schraubenzentrifugalrades 20 covered, so that the opening 2a is constantly open. In this case, we advantageously in the region of the opening 2a a flow in the direction of rotation R of

Screw Zentrifugalrades 20 generated to complicate the entry of solid impurities in the opening 2a or prevent. Through the aperture 2a, a fluid-conducting connection between the front side 2h and the inner space 37 is formed in order to produce a fluid flow F1, which flows over the

Opening 2a flows into the interior 37 and flows back out of the interior 37 via the gap 2b.

In a further advantageous embodiment, the

Schraubenzentrifugalrad 20 as shown in Figures la and lb be configured. The hub 21 of the Schraubenzentrifugalrades 20 includes a crescent-shaped base portion 30, wherein the blade 25 is disposed on the crescent-shaped base portion 30 and the crescent-shaped base portion 30 with respect to the axis of rotation A has a maximum radius Rl and a minimum radius R2. The crescent-shaped base part 30 is extending with respect to the opening 2a in such a way designed such that the rear side 25a of the Schraubenzentrifugalrades 20, the aperture 2a at the minimum radius R2 is not covered, wherein the back 25a of the Schraubenzentrifugalrades 20, the aperture 2a covered during rotation of the Schraubenzentrifugalrades 20 by 360 ° during a partial angle Δ. The

 Aperture 2a is thus during each rotation of the

Screw centrifugal wheel 20 briefly covered. These

Design has the advantage that in the field of

Opening 2a advantageously a flow in the direction of rotation R of the Schraubenzentrifugalrades 20 is generated to complicate the entry of solid impurities in the opening 2a or prevent. Another advantage is the fact that solid impurities, which are located at the inlet of the

Affixing aperture 2a, are removed mechanically through the through the aperture 2a moving hub 21,30, if the impurities protrude over the front side 2h.

The drive shaft 33 could also be further advanced, so that the gap 2 b is formed at least partially or exclusively between the cover plate 2 and the drive shaft 33. The cover plate 2 has at least one opening 2a and preferably at least two openings 2a.

Advantageously, the openings 2a in the Teiloberiläche 2k arranged symmetrically with respect to the axis A. The

Openings 2a can be configured in a variety of ways. The opening 2a shown in Figure 2 below is shown in Figure 3 enlarged. At the front 2h of the cover plate 2 flows a flow F2. The opening 2 comprises an inlet opening 21 whose cross section has an entrance surface 2m formed. The partial flow Fl flows through the opening 2a to the back 2i of the cover plate 2. The partial flow Fl is at

Inflowing into the opening 2a deflected, which gives the advantage that located in the flow of F2 solids difficult to flow into the opening 2a. The partial flow Fl is thereby at least partially cleaned of solids because the solids at least partially remain in the flow F2 and be carried away by this.

The cover plate 2 could, similar to the housing rear wall shown in Figure la, have a cone angle γ in the range between 5 ° and 70 °.

FIG. 4 shows a further exemplary embodiment of an opening 2a. In contrast to the embodiment shown in FIG. 3, the opening 2a shown in FIG. 4 is arranged to run in such a way that the partial flow F1 is deflected with respect to the flow F2 occurring at the front side 2h of the cover plate 2 such that it undergoes a partial flow reversal. The opening 2a extends as shown in Figure 4 at least partially opposite to the direction of rotation R of

Schraubenzentrifugalrades 20. The running such

 Opening 2a has the advantage that solids can pass through the opening 2a to the back 2i of the cover plate 2 less effectively.

The opening 2a shown at the top in FIG. 2 is shown enlarged in FIG. On the front side 2h of the cover plate 2, a recess 2c is arranged, which opens to the opening 2a, wherein the opening 2a forms an inlet opening 21 with inlet surface 2m, so that the inlet opening 21 in the Recess 2c is arranged. The inlet opening 21 or the inlet surface 2m may be arranged in various ways, but advantageously as shown in Figure 5 such that the partial flow Fl is deflected and with respect to the at

Front 2h of the cover plate 2 occurring flow F2 undergoes an at least partial flow reversal. The like

arranged inlet opening 21 has the advantage that solids can pass less well through the opening 2a to the back 2i of the cover plate 2. As shown in FIG. 5, in an advantageous embodiment, the entrance surface 2m is arranged in such a way that it runs parallel or substantially parallel to the axis A. As illustrated in FIG. 5, the entry surface 2m is preferably arranged so as to be oriented away from the direction of rotation R. In Figure 5, not the axis A per se, but the course of the axis A is shown. As shown in Figure 5, the entrance surface 2m in a further advantageous

Embodiment arranged such that it is perpendicular or substantially perpendicular to the rotational direction R of the drive shaft 33, wherein the entrance surface facing away from 2m to

Rotation direction R is arranged.

Figures 6, 7 and 8 show an embodiment of a

Cover plate 2 in plan view, in perspective view and in a section along the section line B-B. In an advantageous

Embodiment, the recess 2c, as shown in Figures 6 and 7, at least partially by a substantially

are formed perpendicular or perpendicular to the axis A extending bore. FIG. 6 shows the course of the axis A and the preferred direction of rotation R. From FIG. 6 it can thus be seen that the entrance surface 2m is parallel to the axis A and perpendicular to the axis A Rotation direction R runs. Figure 8 shows in section the cover plate 2 with front 2h, back 2i and center opening 2g. In the frusto-conical or substantially frusto-conical shape

extending part surface 2k, the openings 2a are arranged, wherein the openings 2a are always spaced from the center opening 2g are arranged. The apertures 2a could also, as shown in FIG. 3, extend perpendicularly or substantially perpendicularly with respect to the partial surface 2k, or, as shown in FIG. 4, extend transversely with respect to the partial surface 2k. Depending on the screw centrifugal wheel 20 used in each case, a differently sized partial surface 2k is covered by the rear side 25a of the screw centrifugal wheel 20. Using the illustrated in the figures la and lb

 Screw centrifugal wheel 20 could be covered, for example, the partial surface of the front side 2h designated by 2k in FIG. 6, in the manner described with reference to FIGS. 1a and 1b. By using the helical centrifugal wheel 20 shown in FIGS. 12 and 13, for example, the partial surface of the front side 2h designated by 2k2 in FIG. 6 could be permanently covered. In an advantageous embodiment, the cover plate 2, as shown in Figures 6 to 8, extending in the circumferential direction recess, in particular a spirally extending recess 2d, which advantageously extends in the region of the central opening 2g along the part surface 2h to the outside.

Advantageously, the recess 2d extends as shown in Figure 6 in the direction of rotation R spiral from inside to outside. These

Embodiment has the advantage that a pollution, which with the help of the partial flow Fl via the center opening 2g or the gap 2b is conveyed to the front side 2h of the cover plate 2, is conveyed along the recess 2d against the periphery of the partial surface 2k out. The over the sub-surface 2k rotating in the direction of rotation R hub 21 and the in

Rotation direction R rotating Schraubenzentrifugalrad 20 also helps to move in the depression 2 d or on the sub-surface 2 k pollution in the direction of rotation R to move and with respect to the part surface 2 k against the outside until the pollution reaches the skin stream F, and detected by this and carried away becomes. Particularly advantageous is thus an arrangement of

Opening 2a as shown in Figures 6 to 8.

In particular, from Figure 6 it can be seen that the contamination is moved substantially in the direction of rotation R, wherein the

Opening 2a is disposed in a recess 2c and the inlet surface 2m facing away from the direction of rotation R is aligned so that dirt, even if they flow through the recess 2c, due to the flow conditions and the

Direction of movement of the contaminants hardly or not at all by the opening 2a flow but the

Main current F are supplied.

The cover plate 2, as shown in Figures 7 and 8, also a running along the edge region recesses 2 f

have, which is intended in particular for receiving an O-ring and thus for sealing. FIG. 9 shows in a section a further exemplary embodiment of a cover plate 2 which, in contrast to the section shown in FIG. 8, however, has a flat part surface 2k or 2k2. Otherwise, the cover plate 2 is configured similar to the 8 embodiment in that the cover plate 2 according to FIG. 9 also has a recess 2c which opens into an opening 2a. Insofar as the spiral-shaped depression 2d is thought away, FIG. 6 reveals a plan view of the cover plate 2 shown in FIG

However, cover plate 2 could also be a spiral running

Well 2d, so that a plan view of this

Embodiment as in Figure 6 would look like. The cover plate 2 shown in Figure 9 also has a central opening 2g and a front 2h and a back 2i. The front side 2h or the partial surface 2k can run in a variety of ways, for example curved, as shown schematically in a section in FIG. 10, or edged, as shown schematically in a section in FIG. In the most

preferred embodiment, the partial surface, as shown in Figure 8, frusto-conical.

In an advantageous embodiment, the cover plate 2 as

Cast formed, wherein the recess 2c and

Advantageously, the opening 2a or the inlet opening 21 already part of the still unprocessed

 Casting form. For the completion of the cover plate 2, it is then still essentially necessary to machine the front side 2h, in particular by removing machining machining. A cover plate 2 made of a casting designed in this way has the advantage that during production no or only very little additional costs result, since the chip-removing machining of the

Cover plate 2 is required anyway. The cover plate 2 shown in Figures 6 to 8, comprising two recesses 2c with

Openings 2a, thus, in comparison to cover plates 2 without Openings 2a, are manufactured with negligible additional costs. The casting should not have a thickness between 2 and 10 mm. However, the cover plate 2 could also be made of a metal sheet. The inventive method allows self-cleaning a Schraubenzentrifugalradpumpe 1. In this case, the

Schraubenzentrifugalradpumpe 1 a rotatably mounted

Schraubenzentrifugalrad 20 and an immediately adjacent

or behind the Schraubenzentrifugalrad 20 arranged cover plate 2 with a central opening 2g, wherein a hub 21 of the Schraubenzentrifugalrades 20 or a Schraubenzentrifugalrad 15 superposed axis 33 passes through the central opening 2g, so that between the center opening 2g and the hub 21 or the axis 33 a Fluid conducting gap 2b forms. If that

Schraubenzentrifugalrad 20 is rotated in the direction of rotation R and thereby a fluid is conveyed along a main flow F, then a partial flow Fl of the fluid via a relative to the

Center opening 2g spaced aperture 2a to the back 2i of the cover plate 2 and flow this Teilstrom Fl then flow over the gap 2b back to the main flow F, due to the prevailing between the aperture 2a and the gap 2b

Pressure difference. This partial flow Fl promotes any impurities in the space behind the cover plate 2 again to the main flow F. Advantageously, the cover plate 2 on the front side 2h at the part surface 2k a spiral

extending recess 2d, wherein the spiral

extending recess 2d in the direction of rotation R from the inside to the outside, so that the outgoing from the gap 2b partial flow Fl and possibly located therein impurities on the spiraling depression 2d is supplied to the main flow F.

In the illustrated embodiments, the cover plate 2 and the housing rear wall 23 are always shown as separate parts. The cover plate 2 and the housing rear wall 23 could also be designed in one piece, for example by being made of a single part, for example a cast part. Such a single casting, comprising both the cover plate 2 and the housing rear wall 23, has the advantage that this

is inexpensive to produce, and that between the cover plate 2 and the rear wall 23 no seal is required. This allows a particularly low-maintenance embodiment.

FIG. 14 shows a plan view of a further exemplary embodiment of the cover plate 2 already shown in FIG. 6. The opening 2a or the entrance surface 2m again runs parallel to the axis A, wherein the opening 2a or the entry surface 2m, in contrast to FIG extending through the axis A extending line L inclined at an angle α, wherein the angle α preferably has a value in the range of + / - 60 degrees.

Claims

A screw centrifugal wheel pump (1) comprising  Pump housing (3) having a Pumpenemströmöffnung (3a) and a Pumpenemströmöffnung (3a) opposite arranged rear housing wall (23), comprising a within the pump housing (3) rotatably arranged  Screw centrifuge wheel (20) having a hub (21) and a blade (25), and comprising a rotatable drive shaft (33) which is connected to the screw centrifugal (20), and comprising a cover plate (2) which between the Screw centrifugal gear (20) and the rear housing wall (23) is arranged, wherein the cover plate (2) has a central opening (2g) through which the hub (21) or the drive shaft (33) extends, and wherein between the cover plate (2) and  Housing rear wall (23) an interior space (37) is formed, wherein the cover plate (2) facing the Pumpenemströmöffnung (3a) directed towards the front (2h), and wherein the front side (2h) comprises a partial surface (2k) whose course so the back (25a) of the Schraubenzentrifugalrades (20) adapted adapted that between the front (2h) of the cover plate (2) and the back (25a) of the  Schraubenzentrifugalrades (20) a gap (24) of up to 3 mm is formed, wherein between the central opening (2g) of the cover plate (2) and the hub (21) or the  Drive shaft (33) has a gap (2b) is formed, the fluid conducting to the interior (37) and the gap (24)  is connected, wherein the cover plate (2) at least one  Opening (2a) which spaced from the Center opening (2g) is arranged, wherein the Schraubenzentrifugalrades (20) and the arrangement of  Opening (2a) are designed mutually adapted so that the back (25a) of the Schraubenzentrifugalrades (20) the aperture (2a) is not covered or covered by a rotation of the Schraubenzentrifugalrades (20) by 360 ° only during a partial angle, and wherein the  Opening (2a) forms a fluid-conducting connection between the front side (2h) and the inner space (37) to produce a fluid flow (Fl), over the  Opening (2 a) flows into the interior (37) and flows back out of the interior (37) via the gap (2 b). 2. Centrifugal centrifugal pump according to claim 1, characterized in that the gap (24) has a width in the range of 0.5 mm to 2 mm. 3. Centrifugal centrifugal pump according to one of  preceding claims, characterized in that the partial surface (2k) is substantially frusto-conical. 4. Centrifugal centrifugal pump according to one of  preceding claims, characterized in that the cover plate (2) has at least two openings (2a), wherein the at least two openings (2a) are arranged in particular symmetrically with respect to the axis of rotation (A). 5. Centrifugal centrifugal pump according to one of preceding claims, characterized in that the opening (2a) to the front (2h) towards a Inlet opening (21), that the front side (2h) has a recess (2c), and that the inlet opening (21) in this recess (2c) is arranged. 6. screw centrifugal pump according to claim 5, characterized in that the inlet opening (21) a  Entry surface (2m) is formed, which is substantially parallel to the axis of rotation (A). 7. Centrifugal screw pump according to one of claims 5 to 7, characterized in that the recess (2c) is at least partially formed by a substantially perpendicular to the axis of rotation (A) extending bore. 8. centrifugal centrifugal pump according to claim 5 or 6,  characterized in that the cover plate (2) consists of a casting, and that the recess (2c) and  Advantageously, the inlet opening (21) already forms part of the unprocessed casting. 9. Schraubenzentrifugalradpumpe according to one of claims 1 to 5, characterized in that the opening (2a) perpendicular or substantially perpendicular with respect to the partial surface (2k) extends. 10. Centrifugal screw pump according to one of  Claims 1 to 5, characterized in that the Opening (2a) transversely with respect to the part surface (2h) extends. 1 1. Centrifugal centrifugal pump according to one of  Claims 1 to 7 or 9 to 10, characterized in that the cover plate (2) consists of a metal sheet. 12. Schraubenzentrifugalradpumpe after one of  preceding claims, characterized in that the opening (2a) opposite to the direction of rotation (R) of the Schraubenzentrifugalrades (20). 13. Centrifugal centrifugal pump according to one of  The preceding claims, characterized in that the Schraubenzentrifugalrad (20) has a direction of rotation (R), and that by the inlet opening (21) of the opening (2a) formed entrance surface (2m) substantially parallel to the axis of rotation (A) and facing away from the direction of rotation (R) runs. 14. Schraubenzentrifugalradpumpe after one of  preceding claims, characterized in that the hub (21) of the screw centrifugal wheel (20) comprises a circular base part (30), that the blade (25) on the  circular base part (30) is arranged, and that the circular base part (30) is arranged concentrically to the rotation axis (A) and has a maximum radius (Rl), wherein the maximum radius (Rl) with respect to the Aperture (2a) is adapted such that the back (25a) of the Schraubenzentrifugalrades (20), the aperture (2a) is not covered. 15. Centrifugal screw pump according to one of  Claims 1 to 12, characterized in that the hub (21) of the Schraubenzentrifugalrades (20) comprises a sickle-shaped base part (30) that the blade (25) on the  crescent-shaped base part (30) is arranged, and that the crescent-shaped base part (30) with respect to the rotation axis (A) has a maximum radius (Rl) and a minimum radius (R2), wherein the crescent-shaped base part (30) with respect to the opening (2a) is designed such that the rear side (25 a) of the Schraubenzentrifugalrades (20) the  Opening (2a) at the minimum radius (R2) not covered, and that the back (25a) of the  Schraubenzentrifugalrades (20) the aperture (2a) during a rotation of the Schraubenzentrifugalrades (20) by 360 ° during a partial angle (Δ) covered. 16. Centrifugal centrifugal pump according to one of  preceding claims, characterized in that the partial surface (2h) has a spirally extending recess (2d), which extends substantially in the region of the central opening (2g) starting along the part surface (2h) to the outside. 17. Screw centrifugal wheel pump (1) comprising a  Cover plate (2) according to one of the preceding claims, comprising a pump housing (3) with a  Pumpeneinströmöffnung (3a) and comprising a Screw centrifugal wheel (20) having a hub (21) and / or a drive shaft (33), the cover plate (2) being located on a side (25a) opposite the pump inflow opening (3a) the screw centrifugal wheel (20) and immediately behind the Schraubenzentrifugalrad (20) is arranged, and wherein between the central opening (2g) of the cover plate (2) and the hub (21) and / or the drive shaft (33), a gap (2b) is formed , 18 screw centrifugal (1) according to claim 1 1 in combination with one of claims 5 to 8, characterized in that the Schraubenzentrifugalrad (20) has a direction of rotation (R), and that by the  Inlet opening (21) of the opening (2a) formed  Entry surface (2m) substantially parallel to the  Rotation axis (A) and facing away from the direction of rotation (R). 19 screw centrifugal (1) according to claim 1 1 or 12, characterized in that the spirally extending recess (2d) in the direction of rotation (R) from inside to outside. 20. Method for self-cleaning a  Screw centrifugal wheel pump (1) comprising a rotatably mounted screw centrifugal wheel (20) and a cover plate (2) with a center opening (2g) forming a gap (24) on the rear side (25a) of the screw centrifugal wheel (20), the cover plate (2) a  Opening (2a), which with respect to the Center opening (2g) is spaced, wherein a hub (21) or a drive shaft (33) of the Schraubenzentrifugalrades (20) through the central opening (2g) extends, so that between the Center opening (2g) and the hub (21) or the drive shaft (33) forms a fluid-conducting gap (2b), wherein the  Screw centrifugal wheel (20) and the arrangement of  Opening (2 a) are configured mutually adapted so that the back (25 a) of the Schraubenzentrifugalrades (20) the aperture (2 a) during rotation of the  Schraubenzentrifugalrades (20) is not covered or only during a partial angle (Δ) is covered, the  Schraubenzentrifugalrad (20) is rotated in the direction of rotation (R) and thereby a fluid along a main flow (F) is conveyed, with a partial flow (Fl) of the fluid through the opening (2a) to the back (2i) of the cover plate (2) flows, and wherein this partial flow (Fl) then over the  Columns (2b, 24) flows back to the main flow (F), due to the prevailing between the aperture (2a) and the gap (2b) pressure difference. 21. The method according to claim 20, characterized in that the cover plate (2) on the front side (2h) a  2d), wherein the spirally extending recess (2d) runs in the direction of rotation (R) from inside to outside, so that the partial flow (F1) emerging from the gap (2b) via the spiral-shaped depression (2d) is the main flow (F) is supplied. 22. The method according to claim 20 or 21, characterized characterized in that the partial flow (Fl) is deflected when flowing into the opening (2a), thereby separating solids from the partial flow (Fl). 23. cover plate (2) for a Schraubenzentrifugalradpumpe, in particular according to one of claims 1 to 19, wherein the cover plate (2) has a front (2h) and a back (2i), and wherein the cover plate (2) in its center a central opening (2g), wherein the central opening (2g) for the passage of an axis of rotation (A) of the  Schraubenzentrifugalrades (20) adapted and extends in the direction of the axis of rotation (A), and wherein the cover plate (2) at least one aperture (2a) which is spaced from the central opening (2g) is arranged, and wherein the aperture (2a) is a fluid conductive connection between the front (2h) and the back (2i) of the  Cover plate (2) is formed, and wherein the opening (2a) to the front (2h) toward an inlet opening (21), and wherein the front side (2h) has a recess (2c), wherein the inlet opening (21) in this recess ( 2c) is arranged, and wherein the inlet opening (21) an entrance surface (2m) is formed, which is substantially parallel to the axis of rotation (A). 24. cover plate (2) according to claim 23, characterized  characterized in that at least a partial surface (2k) of the front side (2h) is substantially frusto-conical or substantially flat. 25. cover plate (2) according to claim 23 or 24, characterized  characterized in that the cover plate (2) at least two Openings (2 a), wherein the at least two openings (2 a) are arranged in particular symmetrically with respect to the axis of rotation (A). 26. cover plate (2) according to one of claims 23 to 25, characterized in that the recess (2 c) at least partially by a substantially perpendicular to  Rotary axis (A) extending bore is formed. 27. cover plate (2) according to one of claims 23 to 26, characterized in that the cover plate (2) consists of a casting, and that the recess (2 c) and  Advantageously, the inlet opening (21) already forms part of the unprocessed casting. 28. cover plate (2) according to any one of claims 23 to 27, characterized in that the opening (2a) is perpendicular or substantially perpendicular with respect to the front side (2h). 29. cover plate (2) according to one of claims 23 to 27, characterized in that the opening (2a) transversely with respect to the front side (2h) extends. 30. Cover plate (2) according to one of claims 23 to 29, characterized in that the partial surface (2h) has a spirally extending recess (2d) which substantially in the region of the central opening (2g) starting along the partial surface (2h) after Outside runs.