Arrangement comprising an impeller and a cutting head for liquid of a pump containing solid matter

Abstract

The invention relates to an arrangement comprising an impeller (3) and a cutting head (1) for a pump containing a liquid containing solids, wherein the cutting head (1) is fixedly connected to the impeller (3) in an axial extension thereof for interaction with a cutting ring (3) and has a cutting head body (8) with a plurality of cutting segments (11) with cutting head cutting edges (13) for comminuting the solid, which cutting head cutting edges (13) extend radially away from the cutting head body (8), the impeller (3) has a plurality of blades (23) with leading edges (24) arranged at a distance from the cutting head cutting edges (13) and extending substantially parallel to the cutting head cutting edges (13), and the cutting head cutting edges (13) are arranged radially ahead of the leading edges (24) in the direction of rotation of the impeller (3).

Description

Technical field

[0001] The invention relates to an arrangement comprising an impeller and a cutting head for liquid containing solids of a pump, wherein the cutting head is fixedly connected to the impeller in axial extension of the same for interaction with a cutting ring and has a cutting head body with a plurality of cutting segments with cutting head cutting edges for comminuting the solid, which cutting head cutting edges extend radially away from the cutting head body. Background of the invention

[0002] Solid particles in liquids such as wastewater can clog pumps or pipelines. To prevent such blockages, so-called cutting devices are used, which are located upstream of the pump's intake to break down the solids contained in the liquid.

[0003] Cutting mechanisms known from the prior art often consist of a stationary part, called the cutting surface or cutting element, and a rotating part, called the cutting head. Depending on the application of the cutting mechanism, circular, conical, or cylindrical cutting surfaces can be used. The cutting surfaces, also called cutting screens, have openings through which the liquid flows towards an impeller of the pump. A flat or conical cutting surface is referred to as a cutting plate. A cylindrical cutting surface is called a cutting ring.

[0004] While the cutting action of such cutting units is good, at least when new, the cutting units themselves can become clogged, blocked by solids, or solids can accumulate in front of the pump's intake area, thus blocking it. Furthermore, a cutting unit installed upstream of the pump generally has a negative impact on the pump's efficiency and performance curve due to its influence on the flow into the pump.

[0005] US 2013 / 121811 A1 describes a shredder pump equipped with a motor that has a drive shaft and a housing connected to the motor, defining a bowl with an inlet for receiving waste material.

[0006] WO 2010 / 039858 A1 describes a pump for crushing solids in a liquid stream with a spiral casing, a rotating cutting unit with at least one blade parallel to an axis of rotation of the rotating cutting unit, an impeller arranged on an outer circumference of the rotating cutting unit and a stationary cutting unit with at least one blade parallel to the axis of rotation of the rotating blade.

[0007] EP 1344944 A1 describes a centrifugal pump with a comminution device upstream of the pump impeller for fibrous or lumpy impurities in the pumped fluid, wherein the comminution device is formed by a cutting head rotating with the pump impeller and provided with several cutting edges, and a cutting insert that is fixedly arranged in the housing of the centrifugal pump and interacts with the cutting head. Description of the invention

[0008] Starting from this situation, it is an object of the present invention to provide an arrangement comprising an impeller and a cutting head for liquid containing solids of a pump which is more reliable in operation compared to solutions known from the prior art, reduces maintenance and / or assembly effort and at the same time enables a high hydraulic efficiency of the pump.

[0009] The object of the invention is achieved by the features of the independent claims. Advantageous embodiments are specified in the dependent claims.

[0010] Accordingly, the problem is solved by an arrangement comprising an impeller and a cutting head for liquid containing solids of a pump, wherein The cutting head is fixedly connected to the impeller in axial extension of the same for interaction with a cutting ring and has a cutting head body with a plurality of cutting segments with cutting head cutting edges for comminuting the solid, which cutting head cutting edges extend radially away from the cutting head body, the impeller has a plurality of blades with leading edges arranged at intervals from the cutting head cutting edges and extending substantially parallel to the cutting head cutting edges, and the cutting head cutting edges are arranged radially ahead in the direction of rotation of the impeller and at least partially at the same axial height as the leading edges.

[0011] A key aspect of the proposed solution lies in the leading cutting edges of the cutter head, which improves flow in the impeller area and thus achieves a higher pump performance curve. Solids that have passed through the cutting element formed by the cutting ring and cutter head do not directly encounter the leading edges. This prevents fibrous components from wrapping around the leading edges and clogging the pump. Leading edges extending essentially parallel to the cutting edges of the cutter head specifically means that the cutting edges of the cutter head and the leading edges extend parallel to each other or are angled at ≤ 2°, 5°, or 10° relative to each other.

[0012] A pump is generally defined as a fluid machine that uses rotary motion and dynamic forces to pump predominantly liquids as the medium. Preferably, the pump is designed as a centrifugal pump. In a centrifugal pump, in addition to the tangential acceleration of the liquid, the centrifugal force occurring in radial flow is used for pumping, so such pumps are also referred to as centrifugal pumps. The pump is preferably used for a building's hydraulic system, for example, as a wastewater pump.

[0013] In normal operation of the pump, a motor housing can be arranged above a pump housing, in which the impeller, driven by the motor via the motor shaft, is provided for pumping the fluid. The motor housing can be fixedly connected to the pump housing and / or be a single unit. Preferably, the motor shaft projects from the motor housing into the pump housing on one drive side and / or the impeller is fixedly connected to the motor shaft on the drive side.

[0014] The fluid preferably comprises water or another liquid medium such as wastewater. The fluid may also include solids such as impurities of any kind, in particular feces, sediments, dirt, sand, or even small pieces of wood, brush, textiles, rags, or the like. Preferably, the motor housing and / or the pump housing is made of metal, in particular cast iron or stainless steel, and / or plastic.

[0015] The cutting edges of the cutting head are arranged at least partially at the same axial height as the leading edges. Preferably, the axial extent of the cutting head's cutting edges is greater than the axial extent of the leading edges.

[0016] Preferably, the cutting head is screwed to the impeller and thus fixed to it, meaning the cutting head and impeller are designed as two parts. Alternatively, the cutting head and impeller can be manufactured as a single piece, for example, from a metal or plastic. "Radially leading the leading edges in the direction of rotation of the impeller" means, in particular, that the leading edges and the cutting edges of the cutting head are not on a radial line, but are fixed in front of them in the direction of rotation, for example, by a few degrees or millimeters.

[0017] The cutting segments extend radially away from the cutting head body and are preferably arranged at regular intervals and / or integrally formed with the cutting head body. Preferably, the axially extending cutting edges of the cutting head are provided radially outside the cutting segments. These edges interact with the cutting teeth of the cutting ring to shred the solid material. For example, a textile material captured by the cutting edges of the cutting head can be brought into contact with the cutting teeth by a rotational movement of the motor shaft, thus shredding the textile and preventing the pump from becoming clogged.

[0018] According to a preferred embodiment, the cutting edges of the cutting head extend substantially axially. Substantially axial means, in particular, that, for example, a draft angle can be included and / or that the cutting edges of the cutting head can be pivoted by ≤ 3%, 5%, or 10% from the axial plane. Furthermore, the cutting edge of the cutting head can be designed in the form of a serrated edge.

[0019] In a preferred embodiment, the cutting edges of the cutting head are arranged leading the inlet edges by an angle α ≥ 1.5°, 2.5°, 5°, or 10°, and in particular α ≤ 2.5°, 5°, 10°, 15°, 20°, 30°, or 45°. Furthermore, angles of, for example, α ≥ 15° or 20°, and in particular α ≤ 60°, 75°, or 90°, are also conceivable. As previously explained, such a design results in improved flow in the impeller area and an improved pump characteristic curve. Moreover, solids that have passed through the cutting element formed by the cutting ring and cutting head do not directly impact the inlet edges, thus preventing fibrous components of the solids from wrapping around the inlet edges and clogging the pump.

[0020] According to a further preferred embodiment, the impeller has an opening within which the cutting head is arranged, and the leading edges are spaced radially outwards from the edge of the opening. Preferably, this spacing is ≥ 2, 5, 10, 15, or 20 mm. Such spacing also contributes to improved flow in the impeller area and an improved pump characteristic curve.

[0021] In a preferred embodiment, the number of cutting head edges is equal to, not equal to, or twice the number of blades and / or leading edges. In other words, preferably one cutting head edge is assigned to each leading edge. If the cutting head has axially different lengths of cutting head edges, the longer cutting head edges preferably correspond to the number of blades, while the shorter cutting head edges, viewed axially, do not reach the blades. In such a case, the number of longer cutting head edges is preferably equal to the number of blades and / or leading edges. The leading edges preferably extend in the axial direction.

[0022] According to a further preferred embodiment, the impeller has a support disc with a hub for receiving a pump motor shaft on the motor side and a cover disc with a suction side on the suction side, with the blades located between the support disc and the cover disc. In this configuration, the impeller is preferably designed as a closed, two-channel impeller. Alternatively, the impeller can also be designed as an open impeller, as known from the prior art. The impeller is preferably fixedly connected to the motor shaft by a force-fit and / or positive-locking connection. The support disc and / or cover disc are preferably circular and arranged parallel to each other, while the blades extend radially outwards in a helical fashion between the opening and an outer edge of the impeller.If the cutting head has four cutting segments with cutting head cutting edges on the outside, with opposite segments being recessed, the radial position of the cutting head on the hub is preferably chosen such that the continuous cutting segments are located in the area of ​​the two leading edges of the impeller.

[0023] According to a preferred embodiment, at least two of the cutting head edges have axial extensions of different lengths, and the cutting head edge with the longer axial extension is spaced apart from the leading edge. The different lengths of the cutting head edges result in a higher and thus improved pump performance curve. While the longer cutting head edge can interact with the impeller blades, the shorter cutting head edge also acts on the solid material, resulting in better cutting performance and reduced pump clogging. Even better cutting performance can be achieved if, for example, one-third of the cutting head edges are longer to interact with the impeller blades, and two-thirds are shorter.Preferably, at least two cutting head edges are made shorter and a multiple of these longer. The cutting head is also preferably designed to be rotationally symmetrical. Furthermore, the cutting head edge can be designed in the form of a serrated edge. A shorter cutting head edge is preferably positioned between two longer cutting head edges.

[0024] The object of the invention is further achieved by a pump with a pump housing and an arrangement within the pump housing as described above, wherein a cylindrical sealing gap is provided between a suction side of the impeller and the pump housing for radial sealing of the impeller. According to a preferred embodiment, the pump has a cutting ring fixed to the pump or the cutting ring and an arrangement as described above, wherein, for radial sealing, the cutting ring at least partially surrounds the impeller to form a conical sealing gap. The proposed sealing gaps ensure reliable sealing of the pump. A shaft seal and / or a gap ring can be provided in the sealing gap. The shaft seal preferably has a sealing lip which rests on the impeller and is preferably pressed radially onto the impeller by a coil spring and / or worm spring.The shaft seal can be firmly seated in the pump housing and / or is preferably designed as a radial shaft seal. A V-ring seal, preferably made of nitrile rubber, can also be provided.

[0025] In a preferred further development of the aforementioned pump and / or the cutting ring fixed to the pump, and the previously described arrangement, the cutting ring has a plurality of cutting teeth that interact with the cutting edges of the cutting head to comminute the captured solid. Such a pump enables improved flow in the impeller inlet area, resulting in a higher pump performance curve, since, compared to prior art designs, flow disturbances between the blades or the blade channels formed by them are reduced. The previously described cutting edges of varying lengths better retain solids of larger diameter until they are sufficiently comminuted by the outer cutting ring, thus achieving improved cutting performance and a reduced risk of clogging. Brief description of the drawings

[0026] The invention is explained in more detail below with reference to the accompanying drawings and by way of preferred embodiments.

[0027] The drawings show Fig. 1 a pump in a partial sectional view according to a preferred embodiment of the invention, Fig. 2 a cutting head of the pump in two perspective views according to the preferred embodiment of the invention, Fig. 3 a cutting ring of the pump in two perspective views (top) and in a sectional view (bottom) according to the preferred embodiment of the invention, and Fig. 4 an impeller and the cutting head of the pump in a perspective view (left) and in a top view (right) according to the preferred embodiment of the invention. Detailed description of the implementation examples

[0028] Fig. 1Figure 1 shows a pump in a partial sectional view according to a preferred embodiment of the invention. The pump, designed as a submersible wastewater pump, has a cutting unit upstream of an impeller 3, comprising a cutting head 1 and a cutting ring 2, which are arranged in Figures 2 to 4 The cutting head 1, cutting ring 2, and impeller 3 of the pump are shown. They do not necessarily have to be designed as described below. This means that while the pump has the cutting head 1 described below, cutting ring 2 and impeller 3 may be designed differently. The same applies to cutting ring 2 and impeller 3.

[0029] The partial section view of the Fig. 1Figure 1 shows a portion of the pump housing 4, above which, during normal operation of the pump, a housing (not shown) for the pump's motor is located. The motor drives the impeller 3 via a motor shaft (not shown), through which liquid containing solids can be drawn from a suction port 5 located below the pump housing 4. Therefore, the terms axial and radial used below refer to the axial extent of the motor shaft.

[0030] The cutting head 1 is fixedly connected to the impeller 3, in particular by means of a force-fit and / or form-fit connection via a cutting head screw 6, and rotates with the impeller 3 during pump operation. The cylindrical cutting ring 2, which surrounds the cutting head 1, is fixedly connected to the pump housing 4 by means of multiple cutting ring screws 7. A radial seal is provided between the cutting ring 2 and the impeller 3. The cutting head 1 projects into the suction side 5, so that the liquid drawn in from the suction side 5 first flows through a gap provided between the cutting head 1 and the cutting ring 2, and is then conveyed through the impeller 3. The rotational movement of the cutting head 1 relative to the cutting ring 2 comminutes any solids contained in the liquid before they reach the impeller 3.

[0031] Fig. 2Figure 1 shows the cutting head 1 of the pump in two perspective views according to the preferred embodiment of the invention. On the left, the cutting head 1 is shown in a perspective top view from the suction side 5, while on the right, the cutting head 1 is shown in a perspective top view from the side associated with the impeller 3. The cutting head 1 has a cylindrical, rotationally symmetrical cutting head body 8 made of metal, through which a bore 9 extends axially for receiving the cutting head screw 6 for fastening to the impeller 3.

[0032] Four regularly spaced cutting segments 11 are provided on the circumferential surface 10 of the cutting head body 8. These cutting segments are integrally formed with the cutting head body 8. Each cutting segment 11 extends radially away from the cutting head body 8. Furthermore, all cutting head bodies 8 extend axially from a liquid inlet side 12 of the cutting head 1, opposite the impeller 3 and facing the suction side 5, towards the impeller 3, thus forming axially extending cutting edges 13.

[0033] While the cutting segments 11 and their cutting head cutting edges 13, arranged opposite each other by 180° in the left figure, extend axially of the same length, namely from the liquid inlet side 12 of the cutting head 1 facing the suction side 5 to essentially the opposite side 14 facing the impeller 3, the two cutting segments 11 and their cutting head cutting edges 13, arranged at a distance of 90° between them, do not extend axially from the liquid inlet side 12 to the side 14.In other words, each pair of cutting head edges 13 has a different axial extension compared to the other two cutting head edges 13, since a first part of the cutting head edges 13 extends substantially or over the entire axial extension of the cutting head 1 from the liquid inlet side 14, and a second part of the cutting head edges 13 extends only over a part of the entire axial extension of the cutting head 1 from the liquid inlet side 14.

[0034] In other words, the second part of the cutting segments 11 is shortened by approximately half compared to the first part, with the opposing cutting segments 11 being identical. The shortened portion of the cutting segments 11 along their axial extent is free of cutting head edges 13. The shortened cutting segments 11 have a constant radial diameter up to approximately half the axial extent of the cutting head 1 and then taper in a teardrop shape towards the side 14 facing the impeller 3. On its axially facing side 14, the cutting head 1 has a circumferential cylindrical collar 15, which is integrally formed with the cutting head body 8 and whose radial outer diameter is flush with the cutting head edges 13.The collar 15 tapers in diameter from side 14 towards the liquid inlet side 12, transitioning uniformly into the cutting head body 8.

[0035] Facing the direction of rotation of the cutting head 1, the cutting segments 11 extend concavely radially away from the cutting head base body 8 towards the respective cutting edge 13 of the cutting head. Conversely, facing away from the direction of rotation of the cutting head 1, the cutting segments 11 extend linearly radially away from the cutting head base body 8 towards the cutting edge 13 of the cutting head. The same applies to the teardrop-shaped taper of the shortened cutting segments 11.

[0036] For further flow optimization, the cutting segments 11 and the cutting head cutting edges 13 are chamfered on the liquid inlet side 12 of the cutting head 1 opposite the impeller 3, as shown in the figure. Fig. 2This can be seen. To crush the captured solid, the aforementioned cutting head 1 with its cutting head cutting edges 13 can interact with the cutting ring 2, which is fixed to the pump, and which has a plurality of cutting teeth 16, as described below.

[0037] Fig. 3 Figure 1 shows a cutting ring 2 of the pump in two perspective views (top) and in a sectional view (bottom) according to the preferred embodiment of the invention. The cutting ring 2 has a ring-shaped cutting ring base body 18 forming an opening 17. In the Fig. 1 In the installed state shown, the cutting head 1 is guided through the opening 17. As previously described, the cutting ring 2 is fixed in place to the pump housing 4 by means of three cutting ring screws 7 grouped around the opening 17, in axial extension of the impeller 3.

[0038] At regular intervals, a plurality of cutting teeth 16 are provided around the opening 17 on the rotationally symmetrical cutting ring base body 18, with respective inner cutting edges 19 oriented axially towards the impeller 3 and outer cutting edges 19 oriented away from the impeller 3 towards the suction side 5 of the pump, wherein the cutting edges 19 interact with the cutting head cutting edges 13 of the same when the cutting head 1 is rotated.

[0039] Three cutting teeth 16 extend axially away from the cutting ring base body 18 inwards towards the impeller 3 into the pump housing 4, and three cutting teeth 16 extend outwards towards the suction side 5 outwards from the pump housing 4, as also in Fig. 1indicated. Likewise, four, eight, twelve or more cutting teeth 16 can be provided, oriented alternately outwards and inwards. In axial extension, between the tip of an outer cutting tooth 16 and the tip of an inner cutting tooth 16, an inner cutting edge 19 and an outer cutting edge 17 are formed around the opening 17.

[0040] The outwardly extending incisors 16 are shown in the sectional view below in the Fig. 3 The cutting ring base body 18 is shown below the disc-shaped cutting ring body 18, while the inwardly extending cutting teeth 16 are shown above the cutting ring base body 18 in the sectional view. The perspective view is shown at the top right in Fig. 3corresponds to this representation and shows the view of the cutting ring 2 as seen from the suction side 5, while the perspective illustration in the upper left shows the view of the cutting ring 2 as seen from the pump housing 4.

[0041] At least in the outwardly extending cutting teeth 16, a radially outwardly extending material recess 20 is provided behind the cutting edge 19 in the direction of rotation of the impeller 4. A similar material recess 20 is also provided in the inwardly extending cutting teeth 16. This means that the outer diameter of the cutting teeth 16, which extend in a wave-like or sinusoidal pattern around the opening 17 in a top view, is the same, while the inner diameter in the area of ​​the material recess 20 is larger compared to an area of ​​the cutting teeth 16 without a material recess.

[0042] Alternatively or additionally, a radially outwardly extending, pocket-like axial recess 22 is formed in the cutting ring body 18 in a valley 21 between at least two outwardly extending cutting teeth 16. In the present case, pocket-like axial recesses 22 are formed in the valleys 21 between both the outwardly and inwardly extending cutting teeth 16. The recesses 22 extend radially outward from the valley floor, so that the cutting ring body 18 is radially flattened outwardly in the valley 21. The material recesses 20 and valleys 21 are provided on all cutting teeth 16 or between them and can be produced by milling or by a corresponding casting mold of a metal cutting ring 2.

[0043] As can be seen in particular from the image below in Fig. 3As can be seen, the outer cutting edge 19 of a valley 21 overlaps in the axial direction between two outwardly extending cutting teeth 16, and the inner cutting edge 19 of a valley 21 overlaps in the axial direction between two inwardly extending cutting teeth 16. Thus, on a cutting surface of the cutting ring 2 formed by the cutting edges 19, there is no radially circumferential collar that is not interrupted by a cutting edge 19. In the direction of rotation of the impeller 3, the cutting angle of the cutting edge 19 flattens outward from the cutting ring base body 18 towards a tip of the cutting tooth 16.

[0044] The cutting angle of the outer cutting teeth 16, or the outer cutting edges 19, facing the cutting head cutting edges 13, is 55°, while the cutting angle of the inner cutting teeth 16 is 52.5°. In the direction of rotation of the impeller 3, the cutting angle is shallower, measuring 20° on the outside and 10° on the inside. Each cutting tooth 16 projects at least 17 mm outwards from the cutting ring body 18, with the inner cutting teeth 16 extending further axially away from the cutting ring body 18 than the outer cutting teeth 16. The cutting teeth 16 are also radially chamfered, namely flattened at 37° on the outside and 33° on the inside relative to the disc-shaped cutting ring body 18 towards the opening 17. Other cutting angles and dimensions are also conceivable.

[0045] Fig. 4Figure 1 shows a closed two-channel impeller 3 and the cutting head 1 of the pump in a perspective, half-opened view on the left and in a half-opened top view on the right, according to the preferred embodiment of the invention. The cutting head 1 is furthermore fixed to the impeller 3 in axial extension thereof for interaction with the in Fig. 4 The cutting ring 2 (not shown) is connected. The cutting head 1 is designed as described above with a cutting head base body 8 with a plurality of cutting segments 11, each with cutting head cutting edges 13 extending in particular axially for comminuting the solid, wherein the cutting head cutting edges 13 extend radially away from the cutting head base body 8.

[0046] The disc-shaped impeller 3 has, in the conventional manner, two helical-shaped blades 23, each extending from an leading edge 24 facing the cutting head 1 at a central impeller opening 25 to the outer radial edge of the impeller, as shown in Fig. 4 This is particularly evident on the right. The blades 23 are axially enclosed on one side by a radially extending support disk 26 on the motor side, with a hub (not shown) for receiving the pump's motor shaft, and on the other side by a radially extending cover disk 27, so that the axially extending blades 23 are positioned between the support disk 26 and cover disk 27, which are arranged parallel to each other. At its radially outer edge, the impeller 3 is open in a rectangular shape between the support disk 26, the cover disk 27, and two adjacent blades 23 in a side view.

[0047] As particularly from Fig. 4As can be seen on the left, the cutting head cutting edges 13 are arranged opposite the inlet edges 24. Furthermore, the inlet edges 24 are spaced radially outwards from the inner edge of the impeller opening 25. In addition, the cutting head cutting edges 13 are arranged radially ahead of the inlet edges 24 in the direction of rotation of the impeller 3, as indicated by the angle α in Fig. 4 As indicated on the right. In other words, the leading edges 24 of the impeller 3 and the cutting head cutting edges 13 do not lie on a radial line. The angle α is, for example, ≤ 2.5°, 5°, or 10°. The cutting head cutting edges 13 and the leading edges 24 extend parallel to each other.

[0048] As previously described, two blades 23 are provided, while the cutting head 1, which extends through the impeller opening 25, has four cutting edges 13. However, only those of the full-length cutting segments 11 interact with the blades 23. In the axial direction, the shortened cutting segments 11 are positioned upstream of the blades 23 on the suction side, so that there is no transmission of the cutting edges 13 of the shortened cutting segments 11 to the blades 23. If, in an alternative embodiment, for example, eight cutting segments 11 are provided, the impeller 3 expediently has four blades 23. For radial sealing of the impeller 3, a cylindrical sealing gap (not shown) is provided between the suction side 5 of the impeller 3 and the pump housing 4.A further seal is formed by the cutting ring 2 at least partially enclosing the impeller 3 to form a conical sealing gap.

[0049] The described embodiments are merely examples that can be modified and / or supplemented in various ways within the scope of the claims. The scope of protection of the invention is defined by the following claims. Reference symbol list

[0050] Cutting head 1 Cutting ring 2 balance bike 3 Pump housing 4 suction side 5 Cutting head screw 6 Cutting ring screw 7 Cutting head base 8 Drilling 9 Perimeter area 10 Cutting segment 11 Liquid entry side 12 Cutting head cutting edge 13 Page 14 Federal 15 Incisor 16 opening 17 Cutting ring base body 18 Cutting edge 19 Material recess 20 valley 21 in-depth 22 shovel 23 Entrance edge 24 Wheel opening 25 support disc 26 Cover plate 27

Claims

1. An arrangement comprising an impeller (3) and a cutting head (1) for liquid in a pump charged with solids, the cutting head (1) being fixedly connected to the impeller (3) in the axial extension thereof to interact with a cutting ring (2) and a cutting head main body (8) comprising a plurality of cutting segments (11) comprising cutting head cutting edges (13) for breaking up the solids, which cutting head cutting edges (13) extend radially away from the cutting head main body (8), the impeller (3) comprising a plurality of blades (23) having inlet edges (24) that are arranged at a distance from the cutting head cutting edges (13) and extend substantially in parallel with the cutting head cutting edges (13), characterized in that the cutting head cutting edges (13) are arranged to be radially leading in the rotational direction of the impeller (3) and to be at the same axial height as the inlet edges (24) at least in part.

2. The arrangement according to the preceding claim, wherein the cutting head cutting edges (13) are arranged to lead in relation to the inlet edges (24) by the angle α > 1.5°, 2.5°, 5°, or 10°.

3. The arrangement according to any one of the preceding claims, wherein the cutting head cutting edges (13) each extend substantially axially.

4. The arrangement according to any one of the preceding claims, wherein the impeller (3) comprises an impeller opening (25), within which the cutting head (1) is arranged, and the inlet edges (24) are arranged to be at a distance radially outward from the edge of the impeller opening (25).

5. The arrangement according to any one of the preceding claims, wherein the number of cutting head cutting edges (13) is equal to, not equal to, or double the number of blades (23) and / or inlet edges (24).

6. The arrangement according to any one of the preceding claims, wherein the impeller (3) comprises a mounting disk (26) comprising a hub for receiving a motor shaft of the pump on the motor side and a cover disk (27) on the intake side, and the blades (23) are provided between the mounting disk (26) and the cover disk (27).

7. The arrangement according to any one of the preceding claims, wherein at least two of the cutting head cutting edges (13) have axial extensions of different lengths and the cutting head cutting edge (13) is arranged at a distance from the inlet edge (24) by the longer axial extension.

8. A pump comprising a pump housing (4) and an arrangement according to any one of the preceding claims arranged in the pump housing (4), wherein a cylindrical sealing gap is provided for radially sealing the impeller (3) between an intake side (5) of the pump and the pump housing (4).

9. The pump according to the preceding claim and comprising a cutting ring (2) fixedly provided on the pump or comprising the cutting ring (2) and an arrangement according to any one of the preceding claims, wherein, for the radial sealing, the cutting ring (2) surrounds the impeller (3) at least in part to form a conical sealing gap.

10. The pump according to any one of the two preceding claims and / or comprising the cutting ring (2) fixedly provided on the pump and an arrangement according to any one of the preceding claims, wherein the cutting ring (2) comprises a plurality of cutting teeth (16) interacting with the cutting head cutting edges (13) to break up the collected solids.

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