Cutting ring for solid-laden fluid of a pump

Description

Technical area

[0001] The invention relates to a cutting ring for liquid of a pump loaded with solids, with a cutting ring base body forming an opening for cooperation with a cutting head, which cutting ring can be fixedly connected to the pump in the axial extension of an impeller of the pump, wherein a plurality of cutting teeth with respective at least outer cutting edges oriented in the direction of a suction side of the pump away from the impeller are provided on the cutting ring around the opening, and the cutting teeth extend axially outwards from the cutting ring base body at least in the direction of the suction side. Background of the invention

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

[0003] Cutting devices known from the state of the art often have 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 device, circular, conical, or cylindrical cutting surfaces can be used. The cutting surfaces, also called cutting screens, have openings through which the fluid flows toward a pump impeller. A flat or conical cutting surface is referred to as a cutting plate. A cylindrical cutting surface is called a cutting ring.

[0004] CN 210715160 U describes a cutting pump, in particular a radial gap adjustable cutting pump.

[0005] CN 208236728 U describes a water installation of sewage pumps, which belongs to the technical field of pumping equipment.

[0006] WO 2016 / 201436 A1 describes one or more techniques and / or systems for a cutting / grinding system that can be engaged with a pump.

[0007] 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 intake area, thereby blocking the intake area. Furthermore, a cutter installed upstream of the pump generally has a negative impact on the pump's efficiency and characteristic curve due to the impact on the inflow into the pump. Description of the invention

[0008] Based on this situation, it is an object of the present invention to provide a cutting ring for liquid loaded with solids in a pump, 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.

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

[0010] Accordingly, the object is achieved by a pump for liquid loaded with solids, with an impeller and a cutting ring, wherein the cutting ring has a cutting ring base body forming an opening for interaction with a cutting head, and is fixedly connected to the pump in the axial extension of an impeller of the pump, wherein on the cutting ring base body around the opening, a plurality of cutting teeth are provided, each with preferably inner cutting edges oriented axially in the direction of the impeller and at least outer cutting edges oriented in the direction of a suction side of the pump away from the impeller, the cutting teeth extend axially away from the cutting ring base body, preferably partly inwards in the direction of the impeller and partly outwards at least in the direction of the suction side, at least in the outwardly extending cutting teeth there is a radially outwardly extending material recess, and in a valley between two at least outwardly extending cutting teeth there is a radially outwardly extending axial recess in the cutting ring base body.

[0011] A key aspect of the proposed solution is the provision of a radially outwardly extending material recess and a radially outwardly extending axial recess. Through these measures, solids that may become stuck to the outer diameter of the cutting head and rotate during operation experience a cutting effect in every axial plane of the cutting mechanism formed by the cutting head and cutting ring. In particular, the material recess reduces the cutting surface, thereby reducing friction. This means less torque is required and the pump can be operated more reliably both during start-up and during regular operation. This penetration of the cutting edges is achieved in particular by the preferably pocket-shaped, outwardly extending axial recess, which is introduced radially outwards into the cutting ring base body.The pockets are preferably formed between the cutting teeth and in the form of axial recesses. During operation, the cutting edges of the rotating cutting head can thus sweep past the cutting edges of the stationary cutting ring on a cylindrical peripheral surface. In summary, the proposed cutting ring achieves a better and unobstructed flow to the pump inlet and a higher filtration efficiency.

[0012] A pump is generally a fluid-flow machine that uses rotary motion and dynamic forces to pump, primarily liquids. The pump is preferably designed as a centrifugal pump. In a centrifugal pump, in addition to the tangential acceleration of the liquid, the medium, 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 sewage pump.

[0013] During normal operation of the pump, a housing of a pump motor can be arranged above a pump housing, in which the impeller, driven by the motor via the motor shaft, is provided for conveying the fluid. The motor housing can be fixedly connected to the pump housing and / or designed as a single piece. Preferably, the motor shaft protrudes from the motor housing into the pump housing on a drive side and / or the impeller is fixedly connected to the motor shaft on the drive side.

[0014] The liquid preferably comprises water or another liquid medium, such as wastewater. The fluid may comprise solids such as contaminants of any kind, in particular feces, sediment, dirt, sand, or even small pieces of wood, brushwood, textiles, or rags, or the like. The motor housing and / or the pump housing are preferably made of metal, in particular cast iron or contoured stainless steel, and / or plastic.

[0015] The cutting ring base body is preferably ring-shaped and / or made of metal, in particular of a hard metal. The cutting head can be inserted into the particularly circular opening, so that by rotating the cutting head, cutting head cutting edges can interact with cutting edges of the cutting ring to comminute the solid material. Preferably, the plurality of cutting teeth are provided with respective inner cutting edges oriented axially in the direction of the impeller and / or outer cutting edges oriented towards the suction side of the pump away from the impeller, wherein the cutting teeth extend axially away from the cutting ring base body, partly inwards towards the impeller and partly outwards towards the suction side. The cutting teeth are preferably grouped in a cylindrical manner around the opening.The material recess and / or the depression can be machined subsequently, for example by milling, or already introduced during the manufacture of the cutting ring, for example by means of an appropriately designed casting mold. Preferably, an inner diameter in the region of the material recess is larger than in the region in which no material recess is provided. The cutting edges are preferably designed free of the material recess. More preferably, a contour of the material recess follows, in particular parallel to a contour of the cutting edge. This results in a uniformly wide and thus also uniformly stable cutting surface. Furthermore, a cutting ring collar can be provided on the inside of the cutting ring, which transitions from the cutting ring base body in an axially tapered manner into the inner cutting teeth.Preferably, a material recess extending radially outwards is provided in all cutting teeth, and / or a radially outwards extending axial depression is provided in all valleys.

[0016] According to a preferred embodiment, the material recess is provided behind the cutting edge in the direction of rotation of the impeller. The cutting edge is preferably formed without a material recess, making it correspondingly stable and resistant even to larger solids. On the other hand, the material recess in the area of ​​the cutting tooth behind the cutting edge in the direction of rotation allows the cutting tooth material to be optimized and thus made more cost-effective.

[0017] According to another advantageous development, inner and outer cutting teeth are provided, and the outer cutting edge of a valley between two outwardly extending cutting teeth and the inner cutting edge of a valley between two inwardly extending cutting teeth axially overlap. With such a design, no radially circumferential collar, uninterrupted by a cutting edge, is formed on a cutting surface of the cutting ring formed by the cutting edges. Solids that become trapped on the outer diameter of the cutting head and rotate during operation are thus subjected to a cutting action in every axial plane of the cutting mechanism formed by the cutting ring and cutting head.

[0018] According to another preferred development, inner and outer cutting teeth are provided and the inner and outer cutting edges extend axially in a wave-like or sinusoidal manner around the opening and / or the cutting ring base body is flattened radially outwards in the valley. For this purpose, the inner and outer cutting edges preferably extend inwards and outwards in the direction of the normal to the cutting ring base body. Preferably, each valley corresponds axially to a cutting tooth and / or a recess provided opposite on the cutting ring base body, so that, for example, a valley and / or a recess is provided on the inside of the cutting ring base body and a cutting tooth extends on the outside. Preferably, the cutting ring base body is flattened radially outwards in the valley on the side on which the valley is enclosed between two adjacent cutting teeth.

[0019] According to another advantageous development, inner and outer cutting teeth are provided, and the inner cutting edge and the outer cutting edge are formed around the opening in the axial extension between a tip of an outer cutting tooth and a tip of an inner cutting tooth. The opening can be circumferentially enclosed by a cutting edge. Preferably, the inner cutting teeth extend axially beyond a cylindrical collar on the cutting head when installed.

[0020] According to another preferred embodiment, the slope of the cutting edge tapers outwards from the cutting ring base body to a tip of the cutting tooth in the direction of rotation of the impeller. In other words, external cutting teeth in particular are preferably designed such that the cutting angle becomes increasingly flatter towards the outside. Coarse solids thus experience a certain cutting effect at the end of the teeth, but can slide off again unhindered. Smaller or sufficiently pre-shredded solids, on the other hand, penetrate deeper into the cutting mechanism formed by the cutting ring and cutting head and are reliably shredded by the increasingly steep cutting angle, passing through the cutting mechanism towards the impeller. Inner and outer cutting teeth can have the same or different cutting angles.

[0021] According to another advantageous development, inner and outer cutting teeth are provided, and two, three, four, six, or eight cutting teeth are provided, which are oriented alternately outward and inward. More cutting teeth can also be provided. Preferably, the number of outwardly directed cutting teeth corresponds to the number of cutting segments of the cutting mechanism extending in this area, although other ratios are also possible.

[0022] According to another preferred embodiment, the cutting ring base body is disk-shaped, and the cutting teeth extend axially away from the base surface. The cutting ring is preferably made of a metal, in particular a hard metal. The cutting edges can be reinforced. It is also conceivable for the cutting edges and / or the cutting teeth to be designed to be replaceable, so that they can be replaced after they become worn.

[0023] According to another advantageous development, the pitch of the cutting edge in the direction of rotation of the impeller is steeper than the pitch against the direction of rotation, so that the pitch of the cutting edge that interacts with the cutting head is flatter. In the direction of rotation of the impeller, the pitch of the cutting edge is preferably 20° on the outside and 10° on the inside. The pitch and the cutting angle of the outer cutting edges is preferably 55° against the direction of rotation, i.e. on the side interacting with the cutting head, while the cutting angle of the inner cutting edges, in contrast, is preferably 52.5°. In a radial side view, each cutting tooth is thus preferably triangular in shape. Each cutting tooth preferably projects at least 17 mm outwards. The cutting teeth can also be radially 'sharpened', for example, flattened towards the opening by 37° on the outside and 33° on the inside relative to the disc-like cutting ring base body.According to another preferred embodiment, the inner cutting tooth extends further axially away from the cutting ring base body than the outer cutting tooth.

[0024] Advantageously, the pump has a cutting head which is connected to the impeller in a rotationally fixed manner and has a plurality of cutting head teeth which cooperate with the cutting edges to crush the captured solid material.

[0025] Such a pump enables improved flow in the impeller inlet area, resulting in a higher pump characteristic curve, as disruption of the flow between the blades or the blade channels formed by them is reduced compared to prior art designs. The proposed cutting ring provides a cutting effect on solids that adhere to the outer diameter of the cutting head and rotate during operation in every axial plane of the cutting mechanism, thus achieving better cutting results and reducing the risk of clogging. Short description of the drawings

[0026] The invention is explained in more detail below with reference to the attached drawings using preferred embodiments.

[0027] The drawings show Fig. 1 shows a pump in a partial sectional view according to a preferred embodiment of the invention, Fig. 2 shows a cutting head of the pump in two perspective views according to the preferred embodiment of the invention, Fig. 3 shows 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 shows 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

[0028] Fig. 1 shows a pump in a partial sectional view according to a preferred embodiment of the invention. The pump, designed as a submersible sewage pump, has a cutting mechanism upstream of an impeller 3 comprising a cutting head 1 and a cutting ring 2, which Figs. 2 to 4are shown. The cutting head 1 or impeller 3 of the pump do not necessarily have to be designed as described below. This means that the pump can, for example, have the cutting head 1 described below, but the impeller 3 can be designed differently than described below.

[0029] The cutting head 1 does not have to be designed as described below, although this is certainly possible.

[0030] The partial sectional view of the Fig. 1shows part of a pump housing 4 of the pump, above which, during regular operation of the pump, a housing (not shown) for a pump motor is provided. The motor drives the impeller 3 via a motor shaft (not shown), through which liquid laden 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 refer to the axial extent of the motor shaft.

[0031] The cutting head 1 is fixedly connected, in particular non-positively and / or positively, to the impeller 3 by means of a cutting head screw 6, and rotates accordingly with the impeller 3 during operation of the pump. The cylindrical cutting ring 2, which encloses the cutting head 1, is 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 sucked-in liquid from the suction side 5 first flows through a gap provided between the cutting head 1 and the cutting ring 2, before being conveyed through the impeller 3. The rotational movement of the cutting head 1 relative to the cutting ring 2 crushes any solids contained in the liquid before they reach the impeller 3.

[0032] Fig. 2shows 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 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.

[0033] On the circumferential surface 10 of the cutting head base body 8, four regularly spaced cutting segments 11 are provided, which are designed integrally 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 fluid 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.

[0034] While the cutting segments 11 and their cutting head cutting edges 13 arranged opposite one another by 180° in the left-hand 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 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, two cutting head cutting edges 13 each have a different length of axial extension compared to 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 substantially 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.

[0035] In other words, the second part of the cutting segments 11 is shortened by approximately half compared to the first part, whereby the oppositely arranged cutting segments 11 are each identically designed. The shortened part of the cutting segments 11 of the axial extent is free of cutting head cutting 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 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, cylindrical collar 15 which is designed in one piece with the cutting head base body 8 and whose radial outer diameter is flush with the cutting head cutting edges 13.The collar 15 tapers in diameter from the side 14 towards the fluid inlet side 12 into the cutting head base body 8, smoothly merging.

[0036] 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.

[0037] 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. 2can be seen. To crush the captured solid material, 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.

[0038] Fig. 3 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 an annular 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.

[0039] At regular intervals on the rotationally symmetrical cutting ring base body 18 around the opening 17, a plurality of cutting teeth 16 are provided 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, wherein the cutting edges 19 interact with the cutting head cutting edges 13 of the cutting head 1 when the cutting head 1 rotates.

[0040] Three cutting teeth 16 extend axially away from the cutting ring body 18 in the direction of the impeller 3 inwards into the pump housing 4 and three cutting teeth 16 extend outwards out of the pump housing 4 in the direction of the suction side 5, as in Fig. 1indicated. 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 disc-like cutting ring body 18, while the inwardly extending cutting teeth 16 are shown in the sectional view above the cutting ring body 18. The perspective illustration top right in Fig. 3corresponds to this illustration and shows the view of the cutting ring 2 as seen from the suction side 5, while the perspective illustration top left shows the view of the cutting ring 2 as seen from the pump housing 4. At least in the outwardly extending cutting teeth 16, a radially outwardly extending material recess 20 is made in the direction of rotation of the impeller 4 behind the cutting edge 19. Such a material recess 20 is also made in the inwardly extending cutting teeth 16. This means that the outer diameter of the cutting teeth 16, which extend in a ring shape around the opening 17 in a wave-like or sinusoidal manner in plan view, is the same, while the inner diameter in the area of ​​the material recess 20 is larger than in an area of ​​the cutting teeth 16 without a material recess.

[0041] In addition, a radially outwardly extending pocket-like axial recess 22 is formed in 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 recesses 22 are formed in both the valleys 21 between the outwardly and inwardly extending cutting teeth 16. The recesses 22 extend radially outward from the valley floor, 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.

[0042] As can be seen particularly from the figure below in Fig. 3As 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. 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, a cutting angle of the cutting edge 19 tapers outward from the cutting ring base body 18 to a tip of the cutting tooth 16.

[0043] The cutting angle of the outer cutting teeth 16 or the outer cutting edges 19, facing the cutting head cutting edges 13, is 55°, whereas 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, amounting to 20° on the outside and 10° on the inside. Each cutting tooth 16 projects at least 17 mm outward from the cutting ring base body 18, with the inner cutting teeth 16 extending axially further from the cutting ring base body 16 than the outer cutting teeth 16. The cutting teeth 16 are also radially sharpened, namely flattened to 37° on the outside and 33° on the inside relative to the disc-like cutting ring base body 16 toward the opening 17. Other cutting angles and dimensions are also conceivable.

[0044] Fig. 4shows 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 fixed 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 a cutting head base body 8 having a plurality of cutting segments 11, each with axially extending cutting head cutting edges 13 for comminuting the solid material, wherein the cutting head cutting edges 13 extend radially away from the cutting head base body 8.

[0045] The disc-like impeller 3 has, in the usual way, two helical blades 23, each extending 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 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 lateral plan view.

[0046] As is particularly evident from Fig. 4As can be seen on the left, the cutting head cutting edges 13 are arranged at a distance from the leading edges 24. Furthermore, the leading edges 24 are provided radially outwardly spaced 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 leading edges 24, as indicated by the angle α in Fig. 4indicated 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° and in particular α ≤ 2.5°, 5°, 10°, 15°, 20°, 30° or 45°. The cutting head cutting edges 13 and the leading edges 24 extend parallel to one another. Radially overlapping means in particular that the leading 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 extension of the cutting head cutting edges is greater than the axial extension of the leading edges.

[0047] In the present case, as previously explained, two blades 23 are provided, while the cutting head 1 passing 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 transmission 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 3 to form a conical sealing gap.

[0048] The described embodiments 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 balance bike 3 Pump housing 4 suction side 5 Cutting head screw 6 Cutting ring screw 7 Cutting head body 8 drilling 9 circumferential area 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 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

1. Pump for a solids-loaded fluid, comprising an impeller (3) and a cutting ring (2), wherein the cutting ring (2) comprises a cutting ring base body (18) forming an opening (17) for cooperation with a cutting head (1) and is stationarily connected to the pump in axial extension of the impeller (3), wherein a plurality of cutting teeth (16) with respective at least outer cutting edges (19) oriented away from the impeller (3) in the direction of a suction side (5) of the pump are provided at the cutting ring base body (18) around the opening (17), the cutting teeth (16) extend axially outwardly from the cutting ring base body (18) at least in the direction of the suction side (5), in a valley (21) between two at least outwardly extending cutting teeth (16), a radially outwardly extending axial depression (22) is provided in the cutting ring base body (18), characeterized in that at least in each of the outwardly extending cutting teeth (16) a radially outwardly extending material recess (20) is formed.

2. Pump according to the previous claim, wherein the material recess (20) is provided in direction of rotation of the impeller (3) behind the cutting edge (19).

3. Pump according to any of the previous claims, comprising inwardly extending inner cutting teeth and (16) and outer cutting teeth (16), wherein 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 (19) overlap axially.

4. Pump according to any of the previous claims, with inwardly extending inner cutting teeth (16) and outer cutting teeth (16), wherein the inner and outer cutting edges (19) extend axially wave-like or sinusoidally around the opening (17) and / or the cutting ring base body (18) is radially flattened in the valley (21) outwardly.

5. Pump according to any of the previous claims, with inwardly extending inner cutting teeth and (16) and outer cutting teeth (16), wherein in an axial extension between a tip of an outer cutting tooth (16) and a tip of an inner cutting tooth (16) around the opening (17) the inner cutting edge (19) and the outer cutting edge (19) are respectively formed.

6. Pump according to any of the previous claims, wherein in the direction of rotation of the impeller (3), an axial slope of the cutting edge (19) flattens outwardly from the cutting ring base body (18) to a tip of the cutting tooth (16).

7. Pump according to any of the previous claims, with inwardly extending inner cutting teeth and (16) and outer cutting teeth (16) and two, three, four, six or eight cutting teeth (16) oriented alternately outwardly and inwardly.

8. Pump according to any of the previous claims, wherein the cutting ring base body (18) is configured disc-like and the cutting teeth (16) extend axially away from the bottom face of the cutting ring base body (18).

9. Pump according to any of the previous claims, wherein an axial cutting angle of the cutting edges (19) in the direction of rotation of the impeller (3) is shallower than the cutting angle opposite to the direction of rotation.

10. Pump according to any of the previous claims, comprising inner cutting teeth (16) and outer cutting teeth (16), wherein the inner cutting teeth (16) extend axially away from the cutting ring base body (18) to a greater extent than the outer cutting teeth (16).

11. Pump comprising a cutting ring according to any of the previous claims and comprising the cutting head (1) connected torque-proof to the impeller (3), wherein the cutting head (1) comprises a plurality of cutting head cutting edges (13) which cooperate with the cutting edges (19) in chopping the grasped solid material.