EP4108927B1 - Cutting head of a pump - Google Patents

Description

The invention relates to a cutting head of a pump for liquids loaded with solids for interaction with a cutting ring, with a cutting head base body assigned to an impeller of the pump, on the circumferential surface of which a plurality of cutting segments are provided, each of which has axially extending cutting head cutting edges for comminuting the solids, each of which extends radially away from the cutting head base body.

Background of the invention

Admixtures of solids in liquids such as wastewater can clog pumps or pipes. To prevent such blockages, so-called cutting units are used, which are located in front of the suction area of the pumps in order to chop up the solids contained in the liquid.

Cutting devices known from the state of the art often have a fixed part, called a cutting surface or cutting element, and a rotating part, called a cutting head. Depending on the application of the cutting device, circular, conical or cylindrical cutting surfaces can be used. The cutting surfaces, also called cutting screens, have openings through which the liquid flows to an impeller of the pump. If the cutting surface is flat or conical, it is called a cutting plate. A cylindrical cutting surface is called a cutting ring.

EP 0120178 A1 describes a centrifugal pump for liquids containing solids such as scraps of fabric or other elongated objects, comprising a pump housing with an inlet opening and a rotating impeller, the impeller being provided with cutting devices which are provided with axially extending grooves of the inlet opening work together so that a cutting effect is created between both parts. This pump has a cutting head with cutting edges of different lengths.

WO 2012173488 A1 describes a liquid ring screw pump with an integrated grinder or shredder, comprising a pump housing with an inlet and an outlet and a rotatable helical screw rotor within the pump housing, the helical screw rotor being provided with the grinder or shredder at one end, namely at the inlet end of the pump housing.

US 7841550 B1 describes a cutting arrangement for positioning at the inlet end of a centrifugal pump used for pumping liquids and slurries containing solids, including various types of waste, and for cutting the solids into smaller pieces, which can then be processed for disposal. While the cutting effect of such cutters is good, at least when new, the cutters themselves can become clogged, blocked by solids, or solids can become lodged in front of the pump's suction area, thereby closing off the suction area. In addition, a cutter installed upstream of the pump usually has a negative effect on the pump's efficiency and characteristic curve due to the effect it has on the inflow into the pump.

Description of the Invention

Based on this situation, it is an object of the present invention to provide a cutting head for liquids of a pump loaded with solids, which is more reliable in operation than the solutions known from the prior art, reduces maintenance costs and at the same time enables a high hydraulic efficiency of the pump.

The object of the invention is solved by the features of the independent claim. Advantageous embodiments are specified in the subclaims.

Accordingly, the object is achieved by a pump for liquid loaded with solids, with an impeller and a cutting head for interacting with a cutting ring, with a cutting head base body assigned to an impeller of the pump, on the circumferential surface of which a plurality of cutting segments are provided, each of which has axially extending cutting head cutting edges for comminuting the solids, which each extend radially away from the cutting head base body and each extend from a liquid inlet side of the cutting head opposite the impeller essentially axially in the direction of the impeller, wherein at least two of the cutting head cutting edges have axial extensions of different lengths.

A key point of the proposed solution is that the different lengths of the cutting head cutting edges result in a higher and thus better pump characteristic. While the longer cutting head cutting edge can interact with the blades of the impeller, the shorter cutting head cutting edge also acts on the solid material, thereby achieving a better cutting result and less clogging of the pump. An even better cutting result can be achieved if, for example, one third of the cutting head cutting edges are longer to interact with the blades of the impeller and two thirds of the cutting head cutting edges are shorter. Preferably, to create rotational symmetry, at least two cutting head cutting edges are shorter and a multiple of these are longer.

A pump is generally a fluid machine that uses a rotary motion and dynamic forces to convey mainly liquids as a medium. The pump is preferably designed as a centrifugal pump. In a centrifugal pump, in addition to a tangential acceleration of the liquid, the medium, centrifugal force occurring in radial flow is used for conveying, so that such pumps are also referred to as centrifugal pumps. The pump can preferably be used for a hydraulic system in a building, for example as a sewage pump.

During regular operation of the pump, a housing of a motor of the pump can be arranged above a pump housing in which the fluid supplied by the motor via the motor shaft driven impeller is provided for conveying the fluid, wherein the housing of the motor can be fixedly connected to the pump housing and/or designed as a single piece. Preferably, the motor shaft projects from the housing of the motor into the pump housing on a drive side and/or the impeller is fixedly connected to the motor shaft on the drive side.

The liquid preferably comprises water or another liquid medium such as waste water. The fluid can comprise solids such as impurities of any kind, in particular faeces, sediments, dirt, sand, or even smaller pieces of wood, brushwood, textiles or rags or the like. The housing of the motor and/or the pump housing is preferably made of metal, in particular cast iron or stainless steel, and/or plastic.

The cutting ring is preferably designed with a disk-like cutting head base body with an opening through which the cutting head is guided. The cutting head base body can preferably be connected to the impeller of the pump, for example by screwing it. The cutting head can also be designed as one piece with the impeller, for example from a metal or a plastic. The cutting segments preferably extend radially away from the cutting head base body and/or are arranged at regular intervals and/or designed as one piece with the cutting head base body. The axially extending cutting head cutting edges are preferably provided radially on the outside of the cutting segments and preferably cooperate with cutting teeth of the cutting ring to chop up the solid material. By rotating the motor shaft, for example, a textile caught by the cutting head cutting edges of the cutting body can come into engagement with the cutting teeth as a solid material, so that the textile is chopped up and as a result the pump cannot clog.

According to the invention, the at least two cutting head cutting edges extend from the liquid inlet side in the direction of the impeller. If the pump has more than two cutting head cutting edges, all cutting head cutting edges extend from the liquid inlet side in the direction of the impeller. Particularly preferably, at least one cutting head cutting edge extends over the entire extent between the liquid inlet side and the opposite side associated with the impeller. The axially extending The cutting head cutting edge preferably does not extend to the side associated with the impeller and is shortened accordingly. The cutting segments extend from the cylindrical peripheral surface, preferably in a triangular manner in an axial plan view, to the radial edge of the cutting head. The different lengths of the axial extension are preferably ≥ 30%, 40%, 50%, 60% or 70%. Essentially axial means in particular that, for example, a draft angle can be included and/or the cutting head cutting edges can extend pivoted by 3%, 5% or 10% from the axial. Furthermore, the cutting head cutting edge can be designed in the form of a serrated edge. A shorter cutting head cutting edge is preferably provided between two longer cutting head cutting edges.

According to a preferred development, a first part of the cutting head cutting edges extends from the liquid inlet side essentially over the entire axial extent of the cutting head and a second part of the cutting head cutting edges extends from the liquid inlet side only over a part of the entire axial extent of the cutting head. The second part can, for example, only extend over half of the first part. Preferably, the second part extends over a part such that the second part of the cutting head cutting edges cannot interact with the blades of the impeller.

According to another preferred development, the other part of the second part of the axial extension is designed to be free of cutting head cutting edges. In the region free of cutting head cutting edges, the cutting head preferably has a smaller radial outer diameter than in the region in which cutting head cutting edges are provided.

According to a further preferred development, the cutting segment tapers in the other part of the second part of the axial extension towards a side of the cutting head facing the impeller, in particular in the form of a drop. The cutting segment tapers in particular in its radial extension from the cutting head cutting edge towards the circumferential surface of the cutting head base body. The cutting segment preferably merges smoothly, in particular linearly, into the cutting head base body, whereby flow optimization is achieved.

According to another preferred development, the cutting head has a circumferential cylinder-like collar on its side axially facing the impeller, which ends flush with the cutting head cutting edges in terms of its radial outer diameter. The collar preferably falls away, in axial sectional view, in the manner of a circular segment or exponentially from the side facing the impeller towards the cutting head base body. Particularly preferably, the collar, which is in particular designed like a collar, tapers in diameter away from its side facing the impeller and merges into the cutting head base body in particular in a flowing manner. Preferably, the collar has the same radial diameter as the cutting head cutting edges or cutting segments and/or is designed in one piece with the cutting head cutting edges or cutting segments that extend over the entire axial extent and/or are longer and/or merges into them in a flowing manner.

According to another preferred development, the cutting head base body is designed in a cylinder-like manner, the cutting segments extend radially away from the cylinder-like peripheral surface and the cutting head cutting edges protrude up to the outer diameter of the cutting head, in particular the collar. If the first part of the cutting head cutting edges extends from the liquid inlet side essentially over the entire axial extent of the cutting head, this preferably means that the cutting head cutting edges extend up to the collar. The cutting head is preferably connected to the impeller in a force-fitting and/or form-fitting manner.

According to a further preferred development, the cutting segments, in particular in a radial plan view, extend in the direction of rotation of the cutting head non-linearly, in particular concavely and/or in the shape of a circular segment, radially away from the cutting head base body to the respective cutting head cutting edge and/or in the direction of rotation of the cutting head linearly radially away from the cutting head base body to the cutting head cutting edge. The non-linear, in particular concavely and/or in the shape of a circular segment in the direction of rotation of the cutting head enables flow optimization and thus an improvement in the efficiency of the pump.

According to another preferred development, the cutting segments and/or the cutting head cutting edges are bevelled on the liquid inlet side of the cutting head opposite the impeller, in particular all the way around the cutting head. The bevelling, for example at an angle of 15°, allows further flow optimization to be achieved.

Preferably, the pump has a cutting ring provided in a fixed position on the pump with a plurality of cutting teeth which cooperate with the cutting head cutting edges to crush the captured solid material.

Such a pump enables better flow in the inlet area of the impeller, which results in a higher pump characteristic curve, since disruption of the flow between the blades or the blade channels formed by them is reduced compared to designs known from the prior art. The cutting head cutting edges of different lengths described above better retain solids of larger diameters until they are sufficiently crushed by the external cutting ring, so that a better cutting result and a lower risk of clogging is achieved.

Short description of the drawings

The invention is explained in more detail below with reference to the accompanying drawings using preferred embodiments.

Fig. 1

eine Pumpe in einer Teilschnittansicht gemäß einem bevorzugten Ausführungsbeispiel der Erfindung,

Fig. 2

einen Schneidkopf der Pumpe in zwei perspektivischen Ansichten gemäß dem bevorzugten Ausführungsbeispiel der Erfindung,

Fig. 3

einen Schneidring der Pumpe in zwei perspektivischen Ansichten (oben) sowie in einer Schnittansicht (unten) gemäß dem bevorzugten Ausführungsbeispiel der Erfindung, und

Fig. 4

ein Laufrad und den Schneidkopf der Pumpe in einer perspektivischen Ansicht (links) und in einer Draufsicht (rechts) gemäß dem bevorzugten Ausführungsbeispiel der Erfindung.

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 (above) and in a sectional view (below) 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 plan view (right) according to the preferred embodiment of the invention.

Detailed description of the implementation examples

Fig. 1 shows a pump in a partial sectional view according to a preferred embodiment of the invention. The pump, designed as a sewage submersible motor pump, has a cutting mechanism upstream of an impeller 3 comprising a cutting head 1 and a cutting ring 2, which in Figs. 2 to 4 are shown. The cutting ring 2 and impeller 3 of the pump do not necessarily have to be designed as described below. This means that the cutting ring 2 and impeller 3 can be designed differently than described below.

The partial sectional view of the Fig. 1 shows a part of a pump housing 4 of the pump, above which a housing (not shown) for a motor of the pump is provided during regular operation of the pump. The motor drives the impeller 3 via a motor shaft (not shown), through which liquid loaded with solids can be sucked in from a suction side 5 formed below the pump housing 4. In this respect, the terms axial and radial used below each refer to the axial extension of the motor shaft.

The cutting head 1 is fixedly connected to the impeller 3, in particular in a force-fitting and/or form-fitting manner by means of a cutting head screw 6, and rotates accordingly with the impeller 3 during operation of the pump. The cylinder-like cutting ring 2 enclosing the cutting head 1 is, in contrast, fixedly connected to the pump housing 4 by means of a plurality of 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 liquid sucked 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 rotary movement of the cutting head 1 relative to the cutting ring 2 causes solids contained in the liquid to be broken down before they reach the impeller 3.

Fig. 2 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 cylinder-like, rotationally symmetrical cutting head base 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.

Four cutting segments 11 arranged at regular intervals are provided on the peripheral surface 10 of the cutting head base body 8 and are designed as one piece with the cutting head base body 8. The cutting segments 11 each extend radially away from the cutting head base body 8. Furthermore, all cutting head base bodies 8 extend axially in the direction of the impeller 3 from a liquid inlet side 12 of the cutting head 1 opposite the impeller 3 and facing the suction side 5, thus forming axially extending cutting head cutting edges 13.

While the cutting segments 11 or their cutting head cutting edges 13 arranged 180° opposite each other on the left and right in the left figure extend axially of equal 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 or their cutting head cutting edges 13 do not extend axially from the liquid inlet side 12 to the side 14. In other words, two cutting head cutting edges 13 each have a different axial extension than the other two cutting head cutting edges 13, since a first part of the cutting head cutting edges 13 extends from the liquid inlet side 14 essentially or over the entire axial extension of the cutting head 1 and a second part of the cutting head cutting edges 13 extends from the liquid inlet side 14 only over a part of the entire axial extension of the cutting head 1.

In other words, the second part of the cutting segments 11 is shortened by approximately half compared to the first part, with the cutting segments 11 arranged opposite one another being identical. The shortened part of the cutting segments 11 of the axial extension is free of cutting head cutting edges 13. The shortened cutting segments 11 have a constant radial diameter up to approximately half the axial extension of the cutting head 1 and then taper in a drop-shaped manner towards the side 14 facing the impeller 3. On its side 14 axially facing the impeller 3, the cutting head 1 has a circumferential cylinder-like collar 15 which is designed in one piece with the cutting head base body 8 and which, in terms of its radial outer diameter, is flush with the cutting head cutting edges 13. The collar 15 tapers in its diameter from the side 14 towards the liquid inlet side 12, merging evenly into the cutting head base body 8.

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 head cutting edge 13. In contrast, 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 head cutting edge 13. The same applies to the drop-shaped taper of the shortened cutting segments 11.

For further flow optimization, the cutting segments 11 and the cutting head cutting edges 13 are beveled on the liquid inlet side 12 of the cutting head 1 opposite the impeller 3, as can be seen from Fig. 2 can be seen. To chop the To remove the captured solid matter, the above-described cutting head 1 with its cutting head cutting edges 13 can interact with the cutting ring 2 provided stationary on the pump and having a plurality of cutting teeth 16 as described below.

Fig. 3 shows a cutting ring 2 of the pump in two perspective views (above) and in a sectional view (below) according to the preferred embodiment of the invention. The cutting ring 2 has a ring-like cutting ring base body 18 forming an opening 17. In 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 of the pump by means of three cutting ring screws 7 grouped around the opening 17 in the axial extension of the impeller 3.

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

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

The outwardly extending cutting teeth 16 are shown in the sectional view below in the Fig. 3 below the disk-like cutting ring base body 18, while the inwardly extending cutting teeth 16 are shown in the sectional view above the cutting ring base body 18. The perspective illustration at the top right in Fig. 3 corresponds to this representation and shows the view on the Cutting ring 2 seen from the suction side 5, while the perspective illustration at the top left shows the view of the cutting ring 2 seen from the pump housing 4.

At least in the outwardly extending cutting teeth 16, a material recess 20 extending radially outward in the direction of rotation of the impeller 4 is introduced behind the cutting edge 19. Such a material recess 20 is also introduced in the inwardly extending cutting teeth 16. This means that the outer diameter of the cutting teeth 16 extending in a ring shape around the opening 17 in a wave-like or sinusoidal manner around the opening in plan view is the same, while the inner diameter in the area of the material recess 20 is larger than an area of the cutting teeth 16 without a material recess.

Alternatively or additionally, a pocket-like axial depression 22 extending radially outward is introduced into the cutting ring base body 18 in a valley 21 between at least two outwardly extending cutting teeth 16. In the present case, pocket-like axial depressions 22 are introduced into both the valleys 21 between the outwardly and inwardly extending cutting teeth 16. The depressions 22 extend from the valley bottom radially outward, deepening so that the cutting ring base body 18 is flattened radially outward 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.

As can be seen particularly from the figure below in Fig. 3 As can be seen, the outer cutting edge 19 of a valley 21 between two outwardly extending cutting teeth 16 and the inner cutting edge 19 of a valley 21 between two inwardly extending cutting teeth 16 overlap in the axial direction. In this way, there is no radially circumferential collar on a cutting surface of the cutting ring 2 formed by the cutting edges 19 that is not interrupted by a cutting edge 19. In the direction of rotation of the impeller 3, a cutting angle of the cutting edge 19 flattens outwards from the cutting ring base body 18 to a tip of the cutting tooth 16.

A cutting angle of the outer cutting teeth 16 or the outer cutting edges 19, facing the cutting head cutting edges 13, is 55°, whereby 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 flatter and is 20° on the outside and 10° on the inside. Each cutting tooth 16 projects outwards from the cutting ring base body 18 by at least 17 mm, whereby the inner cutting teeth 16 extend further axially away from the cutting ring base body 16 than the outer cutting teeth 16. The cutting teeth 16 are also radially "sharpened", namely flattened on the outside by 37° and on the inside by 33° compared to the disk-like cutting ring base body 16 towards the opening 17. Other cutting angles and dimensions are also conceivable.

Fig. 4 shows a closed two-channel impeller 3 and the cutting head 1 of the pump in a perspective half-open view on the left and in a half-open plan view on the right according to the preferred embodiment of the invention. The cutting head 1 is further provided with the Fig. 4 not shown impeller 3 stationary in axial extension of the same for interaction with the also in Fig. 4 not shown cutting ring 2. The cutting head 1 is designed as previously described with cutting head base body 8 with the plurality of cutting segments 11, each with axially extending cutting head cutting edges 13 for comminuting the solid material, wherein cutting head cutting edges 13 extend radially away from the cutting head base body 8.

The disk-like impeller 3 has, in the usual way, two helical blades 23, each of which extends from an inlet 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 can be seen particularly on the right. The blades 23 are axially enclosed on the one hand by a radially extending support disk 26 on the motor side with a hub (not shown) for receiving the motor shaft of the pump and on the other hand by a radially extending cover disk 27 on the suction side, so that the axially extending blades 23 are provided between the support disk 26 and cover disk 27 arranged parallel to one another. At the radially outer edge, the impeller 3 is open radially between the support disk 26, cover disk 27 and two adjacent blades 23 in a rectangular manner in a lateral plan view.

As is particularly evident from Fig. 4 As can be seen on the left, the cutting head cutting edges 13 are arranged at a distance from the inlet edges 24. Furthermore, the inlet edges 24 are provided spaced radially outwards from the inner edge of the impeller opening 25. In addition, the cutting head cutting edges 13 are arranged radially ahead in the direction of rotation of the impeller 3 and in particular radially overlapping the inlet edges 24, as indicated by the angle α in Fig. 4 indicated on the right. In other words, the entry edges 24 of the impeller 3 and cutting head cutting edges 13 do not lie on a radial line. The angle α is, for example, ≤ 2.5°, 5° or 10° and in particular α ≤ 2.5°, 5°, 10°, 15°, 20°, 30° or 45°. The cutting head cutting edges 13 and the entry edges 24 extend parallel to one another. Radially overlapping means in particular that the entry edges are at least partially arranged at the same axial height and/or at least partially in a common radial plane as the cutting head cutting edges. Preferably, the axial extent of the cutting head cutting edges is greater than the axial extent of the entry edges.

In the present case, as previously stated, two blades 23 are provided, while the cutting head 1 leading through the impeller opening 25 has four cutting head cutting edges 13. Of the four cutting head cutting edges 13, however, only the cutting head cutting edges 13 of the non-shortened cutting segments 11 interact with the blades 23. In the axial direction, the shortened cutting segments 11 are provided on the suction side in front of the blades 23, so that there is no transfer of the cutting head cutting edges 13 of the shortened cutting segments 11 with the blades 23. If, for example, eight cutting segments 11 are provided in an alternative embodiment, 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 in that the cutting ring 2 at least partially encloses the impeller to form a conical sealing gap.

The embodiments described are merely examples which can be modified and/or supplemented in many ways within the scope of the claims.

list of reference symbols

cutting head 1 cutting ring 2 wheel 3 pump housing 4 suction side 5 cutting head screw 6 cutting ring screw 7 cutting head body 8 drilling 9 peripheral surface 10 cutting segment 11 liquid inlet side 12 cutting head cutting edge 13 Page 14 federal government 15 cutting tooth 16 opening 17 cutting ring base body 18 cutting edge 19 material recess 20 valley 21 deepening 22 shovel 23 leading edge 24 impeller opening 25 support disc 26 cover plate 27

Claims (10)

1. Pump for liquid loaded with solids with a cutting head (1) for interaction with a cutting ring (2) and with an impeller (3), wherein

   the cutting head (1) has a cutting head base body (8) which is assigned to the impeller (3) of the pump, wherein a plurality of cutting segments (11) are provided on a circumferential surface (10) of the cutting head base body (8), the cutting segments (11) each have axially extending cutting head cutting edges (13) for comminuting the solids, the cutting segments (11) each extend radially away from the cutting head base body (8) and the cutting segments (11) each extend from a fluid inlet side (12) of the cutting head (1) arranged opposite the impeller (3) essentially axially in the direction of the impeller (3), and

   at least two of the cutting head cutting edges (13) comprise axial extensions of different lengths.
2. Pump according to the previous claim, wherein a first part of the cutting head cutting edges (13) extends from the fluid inlet side (12) substantially over an entire axial extension of the cutting head (1) and a second part of the cutting head cutting edges (13) extends from the fluid inlet side (12) only over a part of the entire axial extension of the cutting head (1).
3. Pump according to the previous claim, wherein the another part of the second part of the axial extension is designed free of cutting head cutting edges (13).
4. Pump according to any of the previous two claims, wherein the cutting segment (11) taper in particular in tear drop shape in the another part of the second part of the axial extension towards a side (14) of the cutting head (1) facing the impeller (3).
5. Pump according to any of the previous claims, wherein the cutting head (1) has a circumferential cylindrical collar (15) on its side axially facing the impeller (3), which collar is flush with the cutting head cutting edges (13) with respect to its radial outer diameter.
6. Pump according to the previous claim, wherein the collar (15) tapers in diameter away from its side facing the impeller (3) and merges into the cutting head base body (8).
7. Pump according to any of the previous claims, wherein the cutting head base body (8) is cylindrical in shape, the cutting segments (11) extend radially away from the cylindrical circumferential surface (10) and the cutting head cutting edges (13) project up to the outer diameter of the cutting head (1).
8. Pump according to any of the previous claims, wherein the cutting segments (11) extend at least one of non-linearly radially away from the cutting head base body (8) in direction of rotation of the cutting head (1) towards the respective cutting head cutting edge (13) and linearly radially away from the cutting head base body (8) towards the cutting head cutting edge (13) in direction of rotation of the cutting head (1) away from the cutting head base body (8).
9. Pump according to any of the previous claims, wherein at least one of the cutting segments (11) and the cutting head cutting edges (13) are beveled on the fluid inlet side (12) of the cutting head (1) opposite the impeller (3).
10. Pump according to any of the previous claims and with the cutting ring (2) provided stationary on the pump with a plurality of cutting tooth (16) which cooperate with the cutting head cutting edges (13) for comminuting the captured solids.

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