HK1188275B - Self-cleaning screw-type centrifugal wheel pump with recirculation behind the impeller - Google Patents

Description

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

Technical Field

The invention relates to a screw-type centrifugal wheel pump (Schraubenzentrifurals radial pump), a method for operating a screw-type centrifugal wheel pump, and a cover plate for a screw-type centrifugal wheel pump.

Background

Document CH 662864 discloses a screw-type centrifugal wheel pump, in which a screw-type centrifugal wheel is rotatably supported at an axis of rotation. The screw-type centrifugal wheel pump has a cavity in the region of the connection between the screw-type centrifugal wheel and the axis of rotation. This embodiment of the screw-type centrifugal wheel pump, which has proven itself to be very suitable, has the disadvantage that dirt can be deposited and accumulate in the cavity. This results in increased wear and/or increased maintenance costs.

Disclosure of Invention

The object of the invention is to design a screw-type centrifugal wheel pump and to provide a method for cleaning a screw-type centrifugal wheel pump, which has more advantageous properties with regard to the deposition of dirt.

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

This object is achieved in particular with a screw-type centrifugal wheel pump, comprising: a pump housing having a pump flow inlet and a housing rear wall disposed opposite the pump flow inlet; comprising a helical centrifugal wheel rotatably arranged within a pump housing, with a hub and blades; and a rotatable drive shaft connected with the spiral centrifugal wheel; and a cover plate which is arranged between the screw-type centrifugal wheel and the housing rear wall, wherein the cover plate has a central opening through which the hub or the drive shaft extends, and wherein an interior space is formed between the cover plate and the housing rear wall, wherein the cover plate has a front side which is oriented toward the pump flow inlet, and wherein the front side comprises a partial surface which is designed to be matched to the rear side of the screw-type centrifugal wheel in such a way that a gap of up to 3mm is formed between the front side of the cover plate and the rear side of the screw-type centrifugal wheel, wherein a gap is formed between the central opening of the cover plate and the hub or the drive shaft, which gap is connected to the interior space and to the gap in a fluid-conducting manner, wherein the cover plate has at least one perforation (Durchbrechung) which is arranged at a distance from the central opening, wherein the arrangement of the screw-type centrifugal wheel and the perforation is, such that the rear side of the screw-type centrifugal wheel does not cover the perforations or covers the perforations only during a partial angle when the screw-type centrifugal wheel rotates through 360 °, and wherein the perforations form a fluid-conducting connection between the front side and the interior space in order to generate a fluid flow which flows into the interior space via the perforations and out of the interior space again via the gap.

The screw-type centrifugal wheel pump according to the invention and the method according to the invention have the advantage that during operation of the pump a partial flow is formed which flows from the front side to the rear side of the cover plate and then along the central opening of the cover plate back to the front side of the cover plate, so that a cleaning flow is formed which is able to convey dirt which may be located or deposited in the cavity behind the cover plate back at least partially back to the front side of the cover plate, so that this dirt can be conveyed away via the main flow of the screw-type centrifugal wheel pump.

The screw-type centrifugal wheel pump according to the invention comprises a rotatably mounted screw-type centrifugal wheel and a cover plate with a central opening arranged immediately beside the screw-type centrifugal wheel, wherein the hub or the drive shaft of the screw-type centrifugal wheel preferably extends through the central opening. A fluid-conducting gap is formed between the central bore and the hub or the drive shaft. The rotation of the helical centrifugal wheel in the direction of rotation causes the fluid to be conveyed along the main flow, which results in a partial flow of the fluid flowing via the perforations spaced apart with respect to the central opening to the rear side of the cover plate and, due to the pressure difference existing between the perforations and the fluid-conducting gap, the partial flow then flowing again via the fluid-conducting gap to the main flow. This partial flow forms a clean fluid flow which flows in particular through the space on the rear side of the cover plate and conveys to the main flow dirt which may be present therein.

The cover plate preferably extends on the side facing the centrifugal wheel or on the partial surface facing the centrifugal wheel, corresponding to the course of the rear surface of the centrifugal wheel, so that the partial surface preferably extends in a truncated cone or flat manner, wherein the partial surface can also have other extensions, for example a curved or polygonal course.

The object is further achieved, in particular, by a method for self-cleaning a screw-type centrifugal wheel pump having a rotatably mounted screw-type centrifugal wheel and a cover plate with a central opening, which is arranged with play on the rear side of the screw-type centrifugal wheel, wherein the cover plate has perforations which are spaced apart with respect to the central opening, wherein a hub or a drive shaft of the screw-type centrifugal wheel extends through the central opening such that a fluid-conducting gap is formed between the central opening and the hub or the drive shaft, wherein the arrangement of the screw-type centrifugal wheel and the perforations is designed to be adapted to one another such that the rear side of the screw-type centrifugal wheel does not cover the perforations during rotation of the screw-type centrifugal wheel or only covers the perforations during a partial angle Δ, wherein the screw-type centrifugal wheel is rotated in the direction of rotation and thereby conveys fluid along the main flow, wherein a partial flow F1 of the fluid flows via the perforations to the rear side of the cover plate, and wherein this partial flow then flows via the gap back to the main flow due to the pressure difference existing between the perforations and the gap.

The object is further achieved, in particular, by a cover plate for a screw-type centrifugal wheel pump, wherein the cover plate has a front side and a rear side, and wherein the cover plate has a central bore in its center, wherein the central bore is designed to be matched for the passage (durchritt) of the axis of rotation of the screw-type centrifugal wheel and extends in the direction of the axis of rotation, and wherein the cover plate has at least one perforation which is arranged at a distance from the central bore, and wherein the perforation forms a fluid-conducting connection between the front side and the rear side of the cover plate, and wherein the perforation has an inlet opening toward the front side, and wherein the front side has a recess (vertieff), wherein the inlet opening is arranged in the recess, and wherein the inlet opening forms an inlet face which extends approximately parallel to the axis of rotation a.

The present invention will be described in detail below with reference to examples.

Drawings

The accompanying drawings, which are used to illustrate embodiments, show:

fig. 1 shows an axial section through a screw-type centrifugal wheel pump known from the prior art;

fig. 1a shows a side view of the screw-type centrifugal wheel pump shown in fig. 1 with the outer casing removed;

FIG. 1b shows a top view of the running wheel;

fig. 2 shows a partial view of a screw-type centrifugal wheel pump with an embodiment of a cover disk in longitudinal section;

fig. 3 to 5 show different extensions of the perforations;

FIG. 6 shows a top view of the cover tray;

FIG. 7 is a perspective view of the cover tray shown in FIG. 6;

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

FIG. 9 shows a cross section through another embodiment of the lid panel;

figures 10, 11 show schematically a section through two further embodiments of the cover disc;

FIG. 12 shows a side view of another embodiment of a working wheel of a screw-type centrifugal wheel pump with the housing removed;

FIG. 13 shows a top view of the rotor of the screw-type centrifugal wheel pump shown in FIG. 12;

fig. 14 shows a top view of another embodiment of a cover tray.

In principle, identical components are provided with the same reference numerals in the figures.

Detailed Description

Fig. 1 shows an embodiment of a screw-type centrifugal wheel pump 1 known from the prior art and disclosed in the document CH 662864. Fig. 1 shows an axial section through a screw-type centrifugal wheel pump 1, which comprises: a screw-type centrifugal wheel 20 with a hub 21 and blades 25; comprises a drive shaft 33 fixedly connected with the hub 21; and a housing rear wall 23 arranged behind the screw-type centrifugal wheel 20; and a housing outer wall 3 circumferentially surrounding the helical centrifugal wheel 20. An outlet opening 36 is provided in the housing rear wall 23 in the vicinity of the drive shaft 33, through which gas, which is entrained in the conveying medium and separates (ausscheiden) against the center of rotation of the running wheel and passes through the gap at the back of the running wheel between the running wheel hub 21 and the housing rear wall 23 into the interior 37, can escape. The gap between the rotor hub 21 and the housing rear wall 23 is formed as a Labyrinth (Labyrinth), wherein the Labyrinth on both the hub side and the housing rear wall side is interrupted by means of the transverse groove 38, as a result of which a self-cleaning action is produced and no solid parts are carried along into the interior 37 and the outlet opening 36.

However, it has been shown that despite this measure, dirt can reach the interior 37, wherein this dirt can be deposited and accumulate in the interior 37, so that the screw-type centrifugal wheel pump needs to be cleaned at certain time intervals.

Fig. 1a shows a side view of the screw-type centrifugal wheel pump 1 shown in fig. 1 with the outer casing 3 removed. Fig. 1b shows an embodiment of a screw-type centrifugal wheel 20 in a top view, which is not disclosed in the document CH 662864 as such, but which is suitable for the screw-type centrifugal wheel pump 1 shown in fig. 1 and 1a, so that fig. 1, 1a and 1b are explained jointly. The screw-type impeller 20 of the screw-type centrifugal impeller pump 1 comprises a hub 21 with a sickle-shaped base part 30, to which blades 25 are connected, wherein a shaft 33 passes through a pressure-side housing wall 23 designed as a truncated cone (kegelstempf) and is connected to the hub 21. The housing wall 23 with the cone angle γ of between 5 ° and 70 ° is swept over by the end edge 28 of the pressure-side blade flank (Schaufelflanke)27 with a small gap 24. The blade 25 furthermore comprises a suction-side flank 39. The sickle-shaped base part 30 extends from the blade discharge tip (schaufelalestritstitz) 35 (end edge 26 to which it terminates) (auslauffen) in a sickle-shaped or spiral manner via a relatively large path around the pump axis up to the point 31 where the hub 21 has a relatively small radius R2. At the blade discharge tip 35, the hub 21 has a maximum radius R1. Thereby exposing a relatively large area of the housing wall 23 between the blade discharge tip 35 and the mentioned hub location 31 over a relatively large arc, which is suitably about 120. The exposure of housing wall 23 by a reduction of rotor hub radius R1 can be carried out as permitted by the material specifications, in order to still ensure sufficient strength of screw-type centrifugal wheel 20.

Fig. 2 shows an exemplary embodiment of a screw-type centrifugal wheel pump 1 according to the invention in longitudinal section. The screw-type centrifugal wheel pump 1 includes: a pump housing 3 with an inlet port 3a or pump flow inlet 3a, an outlet port (Auslass)3b and a housing interior 3 c; and furthermore comprises a hub 21, which is connected to blades 25, which are only schematically illustrated and shown in dashed lines, and which is configured here as a screw-type centrifugal wheel 20 and which is rotatably supported via a drive shaft 33 which is rotatable about an axis a. The connection between the drive shaft 33 and the hub 21 is only schematically shown. The blades 25 and the hub 21 are preferably designed (as shown in fig. 1a and 1 b) as a single, common component or as a blade centrifuge wheel 20. In the exemplary embodiment shown, the screw-type centrifugal wheel pump 1 furthermore comprises a conical inner housing 4 with an inlet opening 4a and a spacer ring 5. The screw-type centrifugal wheel pump 1 furthermore comprises a housing rear wall 23 with a discharge opening 36 and a seal 6. The outlet opening 36 is used for maintenance purposes and is normally closed from the outside by means of a plug during operation of the screw-type centrifugal wheel pump 1. During the rotation of the vane centrifugal wheel 20, a main flow F is generated, which is guided via the inlet opening 3a to the outlet opening 3 b. The main flow F to be delivered comprises a fluid, preferably water and possibly a gas such as water vapour, wherein the screw-type centrifugal wheel pump 1 is used in a preferred application for delivering contaminated water, whereby the main flow F may also comprise solids, such as excrements, sand, gravel, fabric, fibres, plastic parts, etc.

The screw-type centrifugal wheel pump 1 furthermore comprises a cover plate 2, which is arranged directly behind the hub 21 or the screw-type centrifugal wheel 20 in the direction of extension of the axis a. The cover 2 has a front side 2h and a rear side 2i, wherein the front side 2h comprises a partial surface 2k, which is designed to be matched to the rear side 25a of the screw-type centrifugal wheel 20 in such a way that a gap 24 of up to a maximum of 3mm is formed between the front side 2h of the cover 2 and the rear side 25a of the screw-type centrifugal wheel 20. Preferably, the gap 24 has a width in the range between 0.5mm and 2 mm. The gap 24 is furthermore designed so narrowly that solids, for example fabrics present in waste water (such as ladies' socks), cannot penetrate into the gap 24 or are very likely to wrap around the hub. The narrow gap 24 furthermore produces a shearing action on the solids located in the gap 24, so that they are mechanically comminuted and conveyed towards the main flow F. In a preferred embodiment, at least one of the surfaces oriented toward the gap 24 is formed, either rough or provided with projecting teeth, for example, in order to improve the mechanical comminution of the solids located in the gap 24. A gap 24 wider than 3mm, for example 5mm or wider, would have a number of disadvantages. On the one hand, mechanical comminution of the solids is no longer ensured due to the wide gap 24. Furthermore, a wide gap 24 will significantly reduce the efficiency of the screw-type centrifugal wheel pump 1. The front face 2h in the exemplary embodiment shown comprises a partial surface 2k running in a substantially truncated cone, which is designed to match the rear face of the screw-type centrifugal wheel 20, wherein the partial surface 2k has a central bore 2g in its center, wherein the central bore 2g runs parallel to the axis a. The hub 21 extends through the central bore 2g, so that a gap 2b extending in the direction of the axis a is configured between the central bore 2g and the hub 21. The hub 21 furthermore has a projection (auskraging), which partially covers the partial surface 2k, so that a gap 24, which in the illustrated embodiment extends transversely with respect to the axis a, is formed between the hub 21 and the partial surface 2 k. The cover plate 2 has at least one perforation 2a, which is arranged at a distance from the central opening 2g, wherein the perforation 2a forms a fluid-conducting connection between the front side 2h and the rear side 2i of the cover plate 2. During operation of the pump or during rotation of the screw-type centrifugal wheel 20 in the direction of rotation R, the fluid has a higher pressure in the region of the perforations 2a than in the region of the central opening 2g, as a result of which a partial flow F1 is produced by a portion of the main flow F flowing as a partial flow F1 through the opening 2a to the rear face 2i of the cover plate 2 into the interior 37 and then via the gap 2b and the gap 24 back into the main flow F. This partial flow F1 causes the dirt present in the interior 37 to be transported out of it and to be conveyed to the main flow F.

The arrangement of the screw-type centrifugal wheel pump 20 and the perforations 2a is designed to be adapted to one another in such a way that the rear side 25a of the screw-type centrifugal wheel pump 20 does not cover the perforations 2a or only covers the perforations during a partial angle Δ when the screw-type centrifugal wheel pump 20 is rotated through 360 °.

In an advantageous embodiment, the helical centrifugal wheel 20 can be designed as shown in fig. 12 and 13. Fig. 12 shows a pump housing 3 in which a cover plate 2 and a helical centrifugal wheel 20 are arranged. The hub 21 is connected to a circular base part 30, wherein the blades 25 are connected to the base part 30 via their end edges 28. The screw-type centrifugal wheel 20 comprises a tip edge 26, a pressure-side blade flank 27, as well as a suction-side flank 39 and a blade discharge tip 35. Fig. 13 shows a top view of a screw-type centrifugal wheel 20, wherein the base part 30 is of circular design and has a maximum radius R1 with respect to the axis a. Fig. 13 shows by way of example a possible arrangement of openings or perforations 2a in relation to a screw-type centrifugal wheel 20. In this arrangement, the perforations 2a are not covered by the helical centrifugal wheel 20 or by the rear face 25a of the helical centrifugal wheel 20, so that the perforations 2a are always open. In this case, a flow in the direction of rotation R of the spiral-type centrifugal wheel 20 is advantageously produced in the region of the perforations 2a in order to hinder or prevent solid contaminants from entering the perforations 2 a. A fluid-conducting connection is formed between front surface 2h and interior space 37 via perforations 2a, so that a fluid flow F1 is produced, which flows into interior space 37 via perforations 2a and out of interior space 37 again via gap 2 b.

In a further advantageous embodiment, the helical centrifugal wheel 20 can be designed as shown in fig. 1a and 1 b. The hub 21 of the screw-type centrifugal wheel 20 comprises a sickle-shaped base part 30, wherein the blades 25 are arranged on the sickle-shaped base part 30 and the sickle-shaped base part 30 has a maximum radius R1 and a minimum radius R2 with respect to the axis of rotation a. The sickle-shaped base part 30 is designed to extend with respect to the perforations 2a in such a way that the rear side 25a of the screw-type centrifugal wheel 20 does not cover the perforations 2a with a minimum radius R2, wherein the rear side 25a of the screw-type centrifugal wheel 20 covers the perforations 2a during a partial angle Δ when the screw-type centrifugal wheel 20 is rotated through 360 °. The perforations 2a are thus temporarily covered during each revolution of the helical centrifugal wheel 20. This embodiment has the advantage that a flow in the direction of rotation R of the helical centrifugal wheel 20 is advantageously produced in the region of the perforations 2a in order to hinder or prevent solid dirt from entering the perforations 2 a. Another advantage is seen therein that solid dirt that has accumulated at the entry of the bore hole 2a is mechanically removed by the hubs 21, 30 that move onto the bore hole 2a (if the dirt protrudes beyond the front face 2 h).

Furthermore, the drive shaft 33 can also be placed to the front, so that the gap 2b is formed at least partially or also only between the cover plate 2 and the drive shaft 33.

The cover plate 2 has at least one perforation 2a and preferably at least two perforations 2 a. Advantageously, the perforations 2a are arranged symmetrically about the axis a in the partial surface 2 k. The perforations 2a can be designed in a number of possibilities. The perforations 2a shown below in fig. 2 are shown enlarged in fig. 3. A flow F2 flows at the front face 2h of the lid plate 2. The opening 2 comprises an inlet opening 2l, the cross-section of which is configured as an inlet face 2 m. The partial flow F1 flows through the perforations 2a to the rear face 2i of the cover plate 2. Diverting the partial flow F1 when flowing into the perforation 2a achieves the advantage that the solids located in the flow F2 can be hindered from flowing into the perforation 2 a. The partial stream F1 is thus at least partially cleaned of solids, since the solids are at least partially retained in the flow F2 and carried away therefrom.

Like the housing rear wall shown in fig. 1a, the cover plate 2 can have a cone angle γ in the range between 5 ° and 70 °.

Fig. 4 shows another embodiment of the perforation 2. In contrast to the embodiment shown in fig. 3, the perforations 2a shown in fig. 4 are arranged to extend in such a way that the partial flow F1 is diverted in such a way that it undergoes a partial backflow with respect to the flow F2 occurring at the front side 2h of the cover plate 2. The perforations 2a extend at least partially opposite to the direction of rotation of the helical centrifugal wheel 20 as shown in fig. 4. The perforation 2a extending in this way has the advantage that the solids cannot reach the rear face 2i of the cover plate 2 through the perforation 2a as well.

The perforations 2a shown above in fig. 2 are shown enlarged in fig. 5. A recess 2c is arranged on the front side 2h of the cover plate 2, which leads to the bore 2a, wherein the bore 2a forms an inlet opening 2l with an inlet surface 2m, such that the inlet opening 2l is arranged in the recess 2 c. The inlet openings 2l or inlet faces 2m can be arranged in different ways, however advantageously as shown in fig. 5, such that the partial flow F1 is diverted and undergoes at least partial backflow with respect to the flow F2 occurring at the front face 2h of the cover plate 2. The inlet opening 2l arranged in this way has the advantage that the solids cannot reach as well through the perforations 2a to the rear face 2i of the cover plate 2. As shown in fig. 5, the entry surface 2m is arranged in an advantageous embodiment such that it extends parallel or approximately parallel to the axis a. As shown in fig. 5, the entry faces 2m are preferably arranged in a back-to-back orientation with respect to the direction of rotation R. The axis a itself is not shown in fig. 5, however the direction of extension of the axis a is shown. As shown in fig. 5, the entry surface 2m is arranged in a further advantageous embodiment such that it extends perpendicularly or approximately perpendicularly to the direction of rotation R of the drive shaft 33, wherein the entry surface 2m is arranged opposite to the direction of rotation R.

Fig. 6, 7 and 8 show an embodiment of the cover plate 2 in a perspective view in a top view and in a section along the section line B-B. In an advantageous embodiment, the recess 2c can be formed (as shown in fig. 6 and 7) at least in part by a bore running substantially perpendicularly or perpendicularly to the axis a. Fig. 6 shows the course of the axis a and the preferred direction of rotation R. It can therefore be seen from fig. 6 that the entry face 2m extends parallel to the axis a and perpendicular to the direction of rotation R. Fig. 8 shows in section the cover plate 2 with a front face 2h, a rear face 2i and a central opening 2 g. The perforations 2a are arranged in a partial surface 2k which extends in a truncated or substantially truncated conical manner, wherein the perforations 2a are always arranged at a distance from the central opening 2 g. The perforations 2a may also (as shown in fig. 3) extend perpendicularly or substantially perpendicularly with respect to the partial surface 2k or, as shown in fig. 4, transversely with respect to the partial surface 2 k.

Depending on the respectively used spiral centrifugal wheel 20, a differently large partial surface 2k is covered by the rear side 25a of the spiral centrifugal wheel 20. In the case of the application of the screw-type centrifugal wheel 20 shown in fig. 1a and 1b, a part of the surface, designated by 2k in fig. 6, for example of the front face 2h, can be covered in the manner explained with reference to fig. 1a and 1 b. In the case of the application of the screw-type centrifugal wheel 20 shown in fig. 12 and 13, for example, the partial surface of the front face 2h, which is designated by 2k2 in fig. 6, is continuously covered.

In an advantageous embodiment, as shown in fig. 6 to 8, the cover plate 2 has a circumferentially extending recess, in particular a helically extending recess 2d, which advantageously begins to extend along the partial surface 2h in the region of the central bore 2 g. The recesses 2d advantageously extend helically from the inside outwards in the direction of rotation R as shown in fig. 6. This embodiment has the advantage that the contamination which is conveyed by means of the partial flow F1 via the central opening 2g or the gap 2b to the front face 2h of the cover plate 2 is conveyed along the recess 2d towards the periphery of the partial surface 2 k. The hub 21 rotating in the direction of rotation R on the partial surface 2k or the helical centrifugal wheel 20 rotating in the direction of rotation R furthermore assists dirt in the recess 2d or at the partial surface 2k to move in the direction of rotation R and to be conveyed outwards with respect to the partial surface 2k until it reaches the main flow F and is taken up by it and carried away. The arrangement of the perforations 2a as shown in fig. 6 to 8 is therefore particularly advantageous. As can be seen in particular from fig. 6, the dirt is displaced substantially in the direction of rotation R, wherein the perforations 2a are arranged in the recesses 2c and the entry surface 2m is oriented away from the direction of rotation R, so that the dirt (even if it flows through the recesses 2c) is conveyed to the main flow F due to the flow behavior and the direction of movement of the dirt, hardly or not at all, through the perforations 2 a.

As shown in fig. 7 and 8, the cover plate 2 can furthermore have a recess 2f running along the edge region, which is provided in particular for receiving an O-ring and thus for sealing.

Fig. 9 shows a further exemplary embodiment of a cover plate 2 in cross section, which differs from the cross section shown in fig. 8 but has a flat extended partial surface 2k or 2k 2. By the cover plate 2 according to fig. 9 also having a recess 2c leading into the opening 2a, the cover plate 2 is otherwise designed analogously to the embodiment shown in fig. 8. Fig. 6 discloses a top view of the cover plate 2 shown in fig. 9, provided that the helically running recesses 2d are not taken into account. The cover plate 2 shown in fig. 9 may, however, also have a helically extending recess 2d, so that a plan view of this embodiment would appear as shown in fig. 6. The cover plate 2 shown in fig. 9 furthermore has a central opening 2g and a front side 2h and a rear side 2 i. The front surface 2h or the partial surface 2k can extend with a plurality of possibilities, whereby for example it is curved (as schematically shown in cross section in fig. 10) or angular (as schematically shown in cross section in fig. 11). In the most preferred embodiment, part of the surface (as shown in fig. 8) extends in a truncated cone shape.

In an advantageous embodiment, the cover plate 2 is designed as a cast part, wherein the recess 2c and advantageously also the perforations 2a or the inlet opening 2l already form part of the cast part that has not yet been machined. To complete the cover plate 2, it is then primarily necessary to machine the front side 2h, in particular by chip-removing machining. A cover plate 2 produced from a casting designed in this way has the advantage that no or only very little additional expenditure is incurred during production, since a chip-removing machining of the cover plate 2 is absolutely necessary. The cover plate 2 shown in fig. 6 to 8, which comprises two recesses 2c with perforations 2a, can therefore be produced (compared to a cover plate 2 without perforations 2a) with a negligibly small additional cost. The casting has a thickness between 2 and 10 mm. However, the cover plate 2 may also be made of a metal plate.

The method according to the invention makes possible a self-cleaning of the screw-type centrifugal wheel pump 1. The screw-type centrifugal wheel pump 1 has a rotatably mounted screw-type centrifugal wheel 20 and a cover plate 2 which is arranged immediately beside or behind the screw-type centrifugal wheel 20 and has a central opening 2g, wherein a hub 21 of the screw-type centrifugal wheel 20 or a shaft 33 which supports the screw-type centrifugal wheel 15 extends through the central opening 2g, so that a fluid-conducting gap 2b is formed between the central opening 2g and the hub 21 or the shaft 33. If the screw-type centrifugal wheel 20 is rotated in the direction of rotation R and thus conveys the fluid along the main flow F, a partial flow F1 of the fluid flows via the perforations 2a spaced apart from the central opening 2g to the rear face 2i of the cover plate 2 and then via the gap 2b to the main flow F again (due to the pressure difference existing between the perforations 2a and the gap 2b) after this partial flow F1. This partial flow F1 may convey dirt located in the space behind the cover plate 2 back to the main flow F. The cover plate 2 advantageously has on its front side 2h at its partial surface 2k a helically extending recess 2d, wherein the helically extending recess 2d extends from the inside to the outside in the direction of rotation R, so that the partial flow F1 exiting from the gap 2b and any dirt present therein is conveyed to the main flow F via the helically extending recess 2 d.

In the exemplary embodiment shown, the cover plate 2 and the housing rear wall 23 are always shown as separate components. The cover plate 2 and the housing rear wall 23 can also be designed in one piece, for example by being produced from a single component, for example a casting. Such a single casting (which comprises both the cover plate 2 and the housing rear wall 23) has the advantage that it can be produced cost-effectively and no sealing is required between the cover plate 2 and the housing rear wall 23. This makes particularly low-maintenance embodiments possible.

Fig. 14 shows a further exemplary embodiment of the cover plate 2 already shown in fig. 6 in a top view. The opening 2a or the entry face 2m in turn extends parallel to the axis a, wherein, unlike in fig. 6, the opening 2a or the entry face 2m extends at an angle α relative to a straight line L extending radially through the axis a, wherein the angle α preferably has a value in the range of +/-60 degrees.

Claims (34)

1. A screw-type centrifugal wheel pump (1) comprising: a pump housing (3) having a pump flow inlet (3a) and a housing rear wall (23) opposite the pump flow inlet (3 a); comprising a screw-type centrifugal wheel (20) rotatably arranged within the pump housing (3) with a hub (21) and blades (25); and a drive shaft (33) rotatable about an axis of rotation (A) and connected with the helical centrifugal wheel (20); and a cover plate (2) which is arranged between the screw-type centrifugal wheel (20) and the housing rear wall (23), wherein the cover plate (2) has a central opening (2g) through which the hub (21) or the drive shaft (33) extends, and wherein an interior space (37) is formed between the cover plate (2) and the housing rear wall (23), wherein the cover plate (2) has a front side (2h) which is oriented toward the pump flow inlet (3a), and wherein the front side (2h) comprises a partial surface (2k) which is oriented so as to be adapted to the rear side (25a) of the screw-type centrifugal wheel (20) in such a way that a first gap (24) of up to 3mm is formed between the front side (2h) of the cover plate (2) and the rear side (25a) of the screw-type centrifugal wheel (20), wherein a second gap (2b) is formed between the central opening (2g) of the cover plate (2) and the hub (21) or the drive shaft (33), which second gap is fluidically connected to the interior space (37) and to the first gap (24), wherein the cover plate (2) has at least one perforation (2a), which is arranged at a distance from the central opening (2g), wherein the arrangement of the helical centrifugal wheel (20) and the perforation (2a) is designed to be adapted to one another in such a way that the rear side (25a) of the helical centrifugal wheel (20) does not cover or covers the perforation (2a) only during a partial angle when the helical centrifugal wheel (20) rotates through 360 °, and wherein the perforation (2a) forms a fluid-conducting connection between the front side (2h) and the interior space (37), to generate a fluid flow (F1) which flows into the interior (37) via the perforations (2a) and flows out of the interior (37) again via the second gap (2 b).

2. A screw-type centrifugal wheel pump according to claim 1, characterized in that the first gap (24) has a width in the range from 0.5mm to 2 mm.

3. A screw-type centrifugal wheel pump according to any one of the preceding claims 1-2, wherein the partial surface (2k) extends substantially in the shape of a truncated cone.

4. Spiral-type centrifugal wheel pump according to any of the preceding claims 1-2, characterized in that the cover plate (2) has at least two perforations (2 a).

5. A screw-type centrifugal wheel pump according to any one of the preceding claims 1-2, wherein the through-hole (2a) has an inlet opening (2i) towards the front face (2h), the front face (2h) has a recess (2c), and the inlet opening (2i) is arranged in this recess (2 c).

6. A screw-type centrifugal wheel pump according to claim 5, characterized in that the inlet opening (2l) is configured as an inlet face (2m) which extends substantially parallel to the axis of rotation (A).

7. A screw-type centrifugal wheel pump according to claim 5, wherein the recess (2c) is at least partly configured by a hole extending substantially perpendicular to the axis of rotation (A).

8. A screw-type centrifugal wheel pump according to claim 5, characterized in that the cover plate (2) is constituted by a casting, and the recess (2c) has formed a part of the casting in the raw state.

9. A screw-type centrifugal wheel pump according to any one of claims 1-2, wherein the perforations (2a) extend perpendicularly or substantially perpendicularly with respect to the partial surface (2 k).

10. The screw-type centrifugal wheel pump according to any one of claims 1 to 2, characterized in that the perforations (2a) extend transversely with respect to the partial surface (2 k).

11. Spiral-type centrifugal wheel pump according to any of claims 1-2, characterized in that the cover plate (2) is composed of a metal plate.

12. The screw-type centrifugal wheel pump according to any one of the preceding claims 1 to 2, characterized in that the screw-type centrifugal wheel (20) has a direction of rotation (R) and the perforations (2a) extend opposite to the direction of rotation (R) of the screw-type centrifugal wheel (20).

13. A screw-type centrifugal wheel pump according to any one of the preceding claims 1-2, characterized in that the screw-type centrifugal wheel (20) has a direction of rotation (R), an entry face (2m) formed by the entry opening (2l) of the perforation (2a) extending substantially parallel to the axis of rotation (A) and facing away from the direction of rotation (R).

14. The screw-type centrifugal wheel pump according to any one of the preceding claims 1 to 2, characterized in that the hub (21) of the screw-type centrifugal wheel (20) comprises a circular base piece (30), the blades (25) being arranged on the circular base piece (30), and the circular base piece (30) being arranged concentrically to the axis of rotation (a) and having a maximum radius (R1), wherein the maximum radius (R1) is matched with respect to the perforation (2a) such that a back face (25a) of the screw-type centrifugal wheel (20) does not cover the perforation (2 a).

15. The screw-type centrifugal wheel pump according to any one of claims 1 to 2, the hub (21) of the screw-type centrifugal wheel (20) comprises a sickle-shaped base part (30), the blades (25) are arranged on the sickle-shaped base part (30), and the sickle-shaped base part (30) has a maximum radius (R1) and a minimum radius (R2) with respect to the axis of rotation (A), wherein the sickle-shaped base part (30) is designed to extend in relation to the perforations (2a), such that the rear face (25a) of the screw-type centrifugal wheel (20) does not cover the perforation (2a) with the smallest radius (R2), and the back (25a) of the screw-type centrifugal wheel (20) covers the perforation (2a) during a partial angle (delta) when the screw-type centrifugal wheel (20) is rotated by 360 °.

16. A screw-type centrifugal wheel pump according to any one of the preceding claims 1-2, characterized in that the partial surface (2k) has a helically extending recess (2d) which extends outwards along the partial surface (2k) substantially in the area of the central bore (2 g).

17. The screw-type centrifugal wheel pump (1) according to claim 5, characterized in that the screw-type centrifugal wheel (20) has a direction of rotation (R) and an entry face (2m) formed by the entry opening (2l) of the perforation (2a) extends substantially parallel to the axis of rotation (A) and away from the direction of rotation (R).

18. The screw-type centrifugal wheel pump (1) according to claim 16, wherein the screw-type centrifugal wheel (20) has a direction of rotation (R) and the helically extending recess (2d) extends from inside to outside in the direction of rotation (R).

19. Spiral-type centrifugal wheel pump according to any of the preceding claims 1-2, characterized in that the cover plate (2) has at least two perforations (2a), wherein at least two perforations (2a) are arranged symmetrically with respect to the rotation axis (a).

20. A screw-type centrifugal wheel pump according to claim 5, characterized in that the cover plate (2) is constituted by a casting, and the recess (2c) and the inlet opening (2l) have formed a part of the casting in the raw state.

21. A method for self-cleaning a screw-type centrifugal wheel pump (1), the screw-type centrifugal wheel pump (1) having a rotatably mounted screw-type centrifugal wheel (20) and a cover plate (2) with a central bore (2g) which is arranged on a rear side (25a) of the screw-type centrifugal wheel (20) with a first gap (24) being formed, wherein the cover plate (2) has perforations (2a) which are spaced apart with respect to the central bore (2g), wherein a hub (21) or a drive shaft (33) of the screw-type centrifugal wheel (20) extends through the central bore (2g) such that a second fluid-conducting gap (2b) is formed between the central bore (2g) and the hub (21) or the drive shaft (33), wherein the arrangement of the screw-type centrifugal wheel (20) and the perforations (2a) is designed so as to be adapted to one another, such that a rear side (25a) of the screw-type centrifugal wheel (20) does not cover the perforations (2a) during a rotation of the screw-type centrifugal wheel (20) or only covers the perforations (2a) during a partial angle (Δ), wherein the screw-type centrifugal wheel (20) is rotated in a direction of rotation (R) and thereby conveys a fluid along a main flow (F), wherein a partial flow (F1) of the fluid flows via the perforations (2a) to a rear side (2i) of the cover plate (2), and wherein, due to a pressure difference existing between the perforations (2a) and the second gap (2b), the partial flow (F1) thereafter flows via the first gap (24) and the second gap (2b) back to the main flow (F).

22. Method according to claim 21, characterized in that the cover plate (2) has on its front side (2h) a helically extending recess (2d), wherein the helically extending recess (2d) extends from the inside outwards in the direction of rotation (R) such that the partial flow (F1) emerging from the second gap (2b) is fed to the main flow (F) via the helically extending recess (2 d).

23. The method according to claim 21 or 22, characterized in that the partial flow (F1) is diverted as it flows into the perforations (2a) in order thereby to separate solids from the partial flow (F1).

24. Cover plate (2) for a screw-type centrifugal wheel pump, wherein the cover plate (2) has a front side (2h) and a rear side (2i), and wherein the cover plate (2) has a central bore (2g) in its center, wherein the central bore (2g) is designed to be adapted to the passage of an axis of rotation (A) of the screw-type centrifugal wheel (20) and extends in the direction of the axis of rotation (A), and wherein the cover plate (2) has at least one perforation (2a) which is arranged at a distance from the central bore (2g), and wherein the perforation (2a) forms a fluid-conducting connection between the front side (2h) and the rear side (2i) of the cover plate (2), and wherein the perforation (2a) has an inlet opening (2l) toward the front side (2h), and wherein, the front face (2h) has a recess (2c), wherein the inlet opening (2l) is arranged in the recess (2c), and wherein the inlet opening (2l) forms an inlet face (2m) which extends substantially parallel to the axis of rotation (A).

25. The cover plate (2) according to claim 24, characterized in that at least one partial surface (2k) of the front face (2h) extends substantially frustoconical or substantially flat.

26. The cover sheet (2) according to claim 24 or 25, characterized in that the cover sheet (2) has at least two perforations (2 a).

27. The cover plate (2) according to any one of claims 24 to 25, characterized in that the recess (2c) is at least partially configured by a hole extending substantially perpendicular to the rotation axis (a).

28. The cover plate (2) according to any one of claims 24 to 25, characterized in that the cover plate (2) consists of a casting and the recess (2c) has formed a part of the casting in the raw state.

29. The cover sheet (2) according to any one of claims 24 to 25, wherein the perforations (2a) extend perpendicularly or substantially perpendicularly with respect to the front face (2 h).

30. The cover sheet (2) according to any one of claims 24 to 25, wherein the perforations (2a) extend transversely with respect to the front face (2 h).

31. The cover plate (2) according to claim 25, characterized in that the partial surface (2k) has a helically extending recess (2d) which extends outwards along the partial surface (2k) starting substantially in the region of the central hole (2 g).

32. Cover plate (2) according to any one of claims 24 to 25, characterized in that the screw-type centrifugal wheel pump is a screw-type centrifugal wheel pump according to any one of claims 1 to 20.

33. The cover plate (2) according to claim 24 or 25, characterized in that the cover plate (2) has at least two perforations (2a), wherein at least two perforations (2a) are arranged symmetrically with respect to the rotation axis (a).

34. The cover plate (2) according to any one of claims 24 to 25, characterized in that the cover plate (2) consists of a casting and the recess (2c) and the inlet opening (2i) have formed a part of the casting in the raw state.