Cutting sieve with evenly distributed cutting surfaces

Abstract

Cutting screen (1) for use in wet shredders (2) with an inner edge region (4) and an outer edge region (6), the inner edge region (2) having a central recess (16) for receiving a rotating element, wherein the cutting screen (1) has a working area (8) between the inner and the outer edge regions (4, 6) consisting of empty sections (10) and material sections (12), wherein the working area (8) is designed to be swept by at least one cutting edge (11) during operation, characterized in that the material sections (12) are formed by: a first plurality of first material webs (36) extending spirally from the inside out; and a second plurality of second material webs (38) which extend in a curved, preferably spiral, direction opposite to the first material webs (36) from the inside out.

Description

[0001] The present invention relates to a cutting screen for use in wet shredders. The invention further relates to a wet shredder for shredding solids, wherein the wet shredder comprises a cutting screen.

[0002] Liquid or sludge-like media, sometimes containing solids, especially fibrous and / or fiber-containing solids, are processed in various industries, including food processing, pulp and paper production, and the operation of biogas or wastewater treatment plants. During the transport and / or processing of such media containing solids, a wide variety of plant components are used: pipelines, feed pumps, restrictors, etc. To prevent damage or blockage of these components, the media containing solids should not contain large solids or long fibers. Otherwise, downstream pumps, for example, can become blocked and / or pipes can be damaged. This can result in costly maintenance work and / or plant downtime. Wet shredders, also called macerators, and heavy solids separators are therefore frequently used at the beginning of the material flow through the plant. Heavy solids separators remove heavy solids (e.g.,Stones). Light solids, such as wood scraps, bones, hair, fibers, or food scraps, are shredded in a wet shredder. Various principles of wet shredders are known, e.g., twin-shaft shredders. The present application proposes a cutting screen for a wet shredder in which the shredding is carried out by a circular cutting screen arranged within the wet shredder, which is swept by at least one cutting blade rotating relative to the cutting screen. The cutting screen has openings of specific sizes. Light, floating solids are shredded between the cutting screen and the at least one cutting blade by shear forces until they are small enough to pass through the openings of the circular cutting screen.

[0003] The applicant markets generic shredding devices under the trademark RotaCut. WO 2012 / 032175 A1 describes the design of such a shredding device. An adjustment mechanism moves a second cutting element (cutting blade), which is movable relative to a first cutting element (cutting screen), in such a way that, in the event of wear on the cutting edges of the first cutting elements, the second cutting element remains in permanent contact with the first. This is ensured, in particular, by the use of a hydraulic cylinder. Preferably, the first cutting element is a cutting screen with a plurality of openings, the boundary edges of which form cutting edges.

[0004] The design of a cutting screen geometry presents several challenges. Depending on the intended application, the particle size must be appropriately selected to ensure that the shredded solids and fibers are sufficiently small for further processing. Simultaneously, the particle size must not be too small to guarantee a specific throughput. Materials resistant to chemicals processed during operation may be required. To maximize replacement intervals, the geometry should exhibit minimal wear during operation. The applicant offers cutting screens with various geometries, allowing the selection of the most suitable option for each specific application.To further increase efficiency, maximize maintenance intervals, and ensure a sustainable, durable product design, there is a need to further optimize the material and geometric properties of cutting screens for wet shredders. In particular, it has not yet been sufficiently considered that the shearing action of the cutting screen against the cutting edge of a cutting knife, and the varying contact conditions of the cutting edge on the screen, lead to locally uneven wear of the cutting knife along its edge. The cutting edge of the cutting knife wears unevenly. Consequently, the shearing action exerted by the cutting knife in combination with the cutting screen on solids also varies locally in the worn state. As a result, the shear performance decreases, and the throughput is reduced.

[0005] The object of the invention is therefore to provide a cutting screen with improved wear properties, which leads to improved, more uniform wear of the cutting edges of cutting knives during operation. Furthermore, it is an object of the invention to provide a system for comminuting solids in mixed fluids, which, when using the cutting screen, allows for the extension of maintenance intervals for changing the cutting screens and / or cutting knives.

[0006] The problem is solved by a cutting screen with the features of independent claim 1. Such a cutting screen has an inner edge region and an outer edge region, the inner edge region having a central recess for receiving a rotating element, wherein the cutting screen has a working area between the inner and outer edge regions consisting of empty sections and material sections, and wherein the material sections are formed from first material ribs extending helically from the inside out, and second material ribs running in the opposite direction to the first material ribs, and wherein the working area is designed to be swept by a cutting edge during operation. Advantageously, the first material ribs support the second material ribs. The helical shape of the first material ribs is advantageous for a uniform distribution of material and empty sections in both the circumferential and radial directions.

[0007] The working area of ​​the cutting screen is round. During operation, one position of the cutting edge covers both material sections and empty sections.

[0008] The working area is bounded by an inner and an outer boundary. The inner and outer boundaries each follow the inner and outer radii, respectively, where the cutting screen is just outside the range of motion of a cutting blade during operation. Preferably, the inner and outer boundaries run along the smallest and largest radii, respectively, where at least one transition occurs in the circumferential direction from a material section to a blank section. Edge areas outside the working area can, for example, be completely filled with material or be provided with bores for centering pins or for fixing elements, such as screws.

[0009] Furthermore, a cutting screen is preferred in which the working area comprises at least 30%, preferably 40%, 50%, 60%, 70%, or 80% of the front surface of the cutting screen and at most 95%, preferably 90%, 85%, 80%, or 70% of the front surface of the cutting screen. The front surface is the circular area enclosed by the circular shape of the cutting screen and consists essentially of the inner and outer edge regions, as well as the working area arranged radially between them. The front surface includes areas with material and areas without material, e.g., empty sections, bores for fixing the cutting screen, and / or a passage for a drive shaft to drive a cutting blade. By defining a lower limit of at least 30%, preferably 40%, 50%, 60%, 70%, or 80% of the area, it is advantageously ensured that the volumetric throughput through the cutting screen is sufficiently large.By defining an upper limit of at most 95%, preferably 90%, 85%, 80%, 70% of the front surface, it is ensured that sufficient possibilities for clamping and fixing the cutting screen can be provided at the outer edge area and that a passage for a drive shaft can be provided at the inner edge area.

[0010] In a further preferred embodiment or aspect of the invention, the inner edge region of the cutting screen comprises a central recess for receiving a rotating element, wherein the material sections are formed by a first plurality of first material ribs extending spirally from the inside out; and a second plurality of second material ribs extending in a curved, preferably spiral, direction opposite to the first material ribs from the inside out, wherein the first material ribs, the second material ribs, the inner edge region, and the outer edge region enclose material-free empty sections. The term "spiral" here refers to a curve.which runs around a point and, depending on the viewer's perspective, moves away from or towards this point. In particular, the term here is not limited to the form of Archimedean spirals and also includes, for example, circular involutes. The material ribs of this embodiment form material sections. Opposing first and second material ribs advantageously support each other. In the further aspect of the invention mentioned here, it is specifically disclosed and claimed that a cutting screen for use in wet shredders has an inner edge region and an outer edge region, wherein the cutting screen has a working area between the inner and outer edge regions consisting of empty sections and material sections, wherein the working area is designed to be swept by at least one cutting edge during operation, and wherein the inner edge region has a central recess for receiving a rotating element.wherein the material sections are formed by a first plurality of first material ribs extending spirally from the inside out; and a second plurality of second material ribs extending in a curved, preferably spiral, direction opposite to the first material ribs from the inside out, wherein the first material ribs, the second material ribs, the inner edge region, and the outer edge region enclose material-free empty sections. The preferred embodiments described below explicitly relate to both the first and the further aspects of the invention.

[0011] Preferably, the first material webs extend in an involute shape, particularly in a circular involute shape. Because of the constant pitch of circular involutes, such an embodiment is particularly uniform.

[0012] Furthermore, it is preferred that the second material webs intersect the first material webs. The spaces between the first and second material webs then form empty sections. Depending on the number, slope, size of the material webs and other design parameters, a suitable ball passage size can be determined for the respective application.

[0013] In a preferred embodiment, the second material ribs have a substantially constant width from the radial inside to the radial outside; that is, they preferably do not taper towards the radial outside or radial inside. Radially outside, the friction between the cutting edge of the cutting knife and the cutting screen is then lower. Depending on the medium being cut, this can be advantageous. For example, heavier solids can accumulate radially outside due to centrifugal force, causing higher wear during shearing. In this case, it is advantageous to compensate by keeping the friction-induced wear from the contact between the cutting screen and the cutting edge of the cutting knife lower radially outside than in the center of the cutting screen.

[0014] However, it is also preferred that the second material webs taper radially outwards. Ball passages are then larger with increasing radius.

[0015] It is equally preferred that the second material ridges taper radially inwards. This is advantageous for achieving uniform comminution.

[0016] Furthermore, radially outer areas are thus made thicker than radially inner areas. This is advantageous because, due to centrifugal force, heavier solid particles, which can potentially cause more wear than lighter particles, tend to accumulate radially outwards. The radially outer areas are therefore advantageously thicker and thus more robust than radially inner areas.

[0017] It is preferred that the second material webs run from the inner edge region to the outer edge region. Within the working area, they then intersect the first material webs. Advantageously, this avoids T-joints. From a structural mechanics perspective, this is beneficial.

[0018] Cutting angles are defined by the second material ribs intersecting each straight line extending radially outward from the center of the cutting screen. In operation, one or more straight cutting blades extending radially outward from the center are typically used. Preferably, the cutting screen is designed to define cutting angles in a range of 10° to 30°, preferably 15° to 25°, and more preferably 20°, when interacting with the cutting edge. Cutting angles in this range result in particularly reliable comminution of the solids to be processed.

[0019] However, it is also possible, and equally preferred, that the cutting blades are not arranged on a straight line extending radially outward from the center of the cutting screen. Preferably, the cutting edges of the cutting blades are arranged at an angle to a central axis that is perpendicular to a plane of the cutting screen and passes through its center. The distance of a cutting edge to the central axis is particularly preferred to be less than 3 cm, 2 cm, 1 cm, or 0.5 cm. Cutting screens with such angled cutting blades are particularly preferred, as they provide cutting angles in a range of 10° to 30°, preferably in a range of 15° to 25°, and preferably 20°.

[0020] Particularly preferred is any cutting angle in the range of 10° to 30°, preferably in the range of 15° to 25°, and preferably 20°. In the case of curves of the second material web, this can enclose various cutting angles with the straight line or with the cutting blade along the radius. If all cutting angles are in a similar range, particularly in the range of 10° to 30°, preferably in the range of 15° to 25°, and preferably approximately 20°, then the cutting effect is advantageously less dependent on the radial position of the solid to be comminuted.

[0021] Preferably, and depending on the application, the ball passage diameters of the empty sections lie within a range from a lower limit of 5 mm, 10 mm, 15 mm, 20 mm, or 25 mm to an upper limit of 25 mm, 30 mm, 35 mm, 40 mm, or 50 mm. For typical applications, this range is advantageously suited to ensure that only sufficiently comminuted solids are processed further in the subsequent plant elements and that an efficient volumetric throughput is maintained. Within this range, an optimum ball passage size can be achieved for the respective application. It should be understood that several different ball passage diameters may also be present within a cutting screen, which, for example, are smaller radially inward than radially outward.

[0022] Preferably, the first and second material ribs have a hard surface and a tough core. The terms "hard" and "tough" are used comparatively in the context of this disclosure. This means that the core, i.e., the interior material of the first and second material ribs, is tougher than the surface of the material ribs.

[0023] Preferably, the cutting screen has one or more elements for positioning and / or securely fixing the cutting screen in a wet shredder.

[0024] The problem is further solved in another aspect by a system for comminuting solids in mixed fluids, comprising a cutting screen according to the first aspect of the invention and at least one cutting blade. Preferably, the working area of ​​the cutting screen is swept by the at least one cutting blade during its rotation and is at least partially in contact with the at least one cutting blade. The cutting blade is configured to rotate about an axis of rotation during operation. This axis of rotation can be arranged offset from a central axis. A rotational axis of the at least one cutting blade is particularly preferred to be coaxial with a central axis of the working area. A central axis of the cutting screen is also preferably coaxial with the rotational axis of the at least one cutting blade.A system is preferred in which the number of first material ribs of the cutting screen is not divisible by the number of cutting blades.

[0025] Typically, a wet shredder uses one, two, three, four, or six cutting blades, preferably evenly distributed. Using a number of first material ribs that is not divisible by the number of cutting blades is advantageous for preventing vibrations of the wet shredder during operation.

[0026] It is also preferred that the number of secondary material ribs is not divisible by the number of cutting blades. This is also advantageous for avoiding inherent vibrations of the wet shredder during operation.

[0027] Preferred embodiments of the cutting screen according to the invention are explained with reference to the accompanying figures. It should be understood that the cutting screen according to the first aspect of the invention and the system according to the second aspect of the invention have the same and similar sub-aspects, as set out in particular in the dependent claims. Therefore, for further developments of the second aspect of the invention, reference is made in full to the further developments of the first aspect of the invention.

[0028] They show: Fig. 1 A perspective view of a preferred embodiment of a cutting screen according to the invention in a system for comminuting solids with a representation of a cutting blade of a wet shredder Fig. 2 a frontal view of a first embodiment of a cutting sieve according to the invention Fig. 3 a frontal view of a second embodiment of a cutting screen according to the invention Fig. 4 a frontal view of a third embodiment of a cutting screen according to the invention Fig. 5a a cutting screen according to the invention in a system with four cutting blades and a hidden rotor; Fig. 5b a cutting screen according to the invention in a system with four cutting blades and an integrated rotor; and Fig. 6. A wet shredder with built-in cutting screen

[0029] Fig. Figure 1 shows a first embodiment of a cutting screen 1 for use in wet shredders 2 (see Figure 1). Fig. 6) with an inner edge region 4, an outer edge region 6, wherein the cutting screen 1 has a working area 8 between the inner edge region 4 and the outer edge region 6, consisting of empty sections 10 and material sections 12, the working area 8 being designed to be swept by a cutting edge 11 during operation. The cutting edge 11 is a separate component of the wet shredder 2 or part of a system 3 consisting of a cutting screen 1 and at least one cutting knife 14 and is shown here for illustration. The cutting edge 11 moves relative to the cutting screen 1 in a circular direction of movement 13, the circular shape of the direction of movement 13 being concentric to that of the cutting screen 1. It should be understood that more than one cutting edge, e.g., two, three, four, or five cutting edges, may also be provided during operation, as is particularly evident in the Fig. 5a and Fig. Figure 5b shows that the cutting performance and throughput of the medium being processed are thus increased. The cutting edge 10 is the edge of a cutting knife 14 facing the cutting screen 1. The cutting knife 14 is in operation in a Fig. 6 machine housing 15 shown. In particular, a drive shaft 18 for rotary driving of the cutting knife 14 is arranged through an inner recess 16 in the inner edge region 4 of the cutting screen 1.

[0030] The wet chopper 2 in Fig. 6 also features a fluid inlet 20, a fluid outlet 22, an opening unit 24, a drive 26, a rotor 46, a heavy material separator 27, and a hydraulic adjustment unit 28. The hydraulic adjustment unit 28 is located between the cutting screen 1 and the drive 26 and is not shown in detail here. During operation, the fluid inlet 20 is connected to a feed and the fluid outlet 22 to a discharge. These can be designed, for example, as pipes or hoses. Furthermore, the opening unit 24 is in a closed state during operation. Fig. Figure 6 shows the wet shredder 2 not in operation, and the opening unit 24 is shown in an open position for better visibility of the cutting screen 1. During operation, high-density solids entering the wet shredder 2 will sink due to gravity and collect in the heavy material separator 27.

[0031] Liquid and low-density solids entering the wet shredder 2 are forced upwards through the cutting screen 1. Large solids cannot easily pass through the empty sections 10 of the cutting screen 1 due to their geometric dimensions. Free-floating fibers are cut to a statistical, average length by rotating the cutting blades 14. The rotation of the cutting blades 14 relative to the cutting screen 1 generates shear forces between the cutting blades 14 and the cutting screen 1, which further reduce the size of the solids or fibers until they can pass through the empty sections 10.

[0032] Solids that could pass through the cutting screen 1 uncompressed are reduced to a statistical geometric mean by randomly occurring cutting processes. This degree of comminution, or statistical geometric mean, depends, among other things, on the number of cutting blades 14, the rotational speed of the cutting blades 14, the flow velocity, and the geometric design of the cutting screen 1.

[0033] At fluid outlet 22, the fluid loaded with solids or fibers is in a state where the geometric dimensions of the solids are more uniform and smaller than at fluid inlet 20. This allows the solid-laden fluid to be processed more effectively in subsequent system components, thus protecting these components. High-density solids can be, for example, stones or metals. Low-density solids can be, for example, textiles, hair, biological waste, leaves, grasses, bones, or the like.

[0034] The cutting blades 14 wear down, particularly at their cutting edges 11. The cutting screen 1 also wears down in the edge region. The hydraulic adjusting unit 28 is designed to press the cutting edges 11, even when in use and showing partial wear, with an axial force towards or against the cutting screen 1. At the points of contact between the cutting edges 11 and the cutting screen 1, or at narrow gaps between the cutting edges 11 and the cutting screen 1, shear forces are exerted on the fluid containing solids as a result of a torque provided by the drive 26.

[0035] Another embodiment of a cutting sieve 1 according to the invention shows a top view of a cutting sieve 1 in Fig. 2. It also has an inner edge region 4, an outer edge region 6, and a working area 8 consisting of empty sections 10 and material sections 12, the working area 8 being designed to be swept by a cutting edge 11 during operation. The material sections 12 are formed, firstly, by first, spiral material ribs 36, which extend from the inner edge region 4 to the outer edge region 6 of the cutting screen 1 in the mathematically negative direction of rotation. In the embodiment shown here, five such first material ribs 36 are present. In the embodiment shown here, the first material ribs 36 extend in a circular involute shape. This is advantageous in order to maintain a constant cutting angle between the second material ribs 38 along the radius. Secondly, material sections 12 are formed by second material ribs 38 that rotate in the opposite direction to the first material ribs 36.In the embodiment shown here, 23 such second material webs 38 are present. The second material webs 38 taper from radially outside to radially inside. In other embodiments, the material sections can consist of other elements or of material webs that have a different orientation.

[0036] Empty sections 10, free of material, are enclosed by the first material ribs 36, the second material ribs 38, the inner edge region 4, and the outer edge region 6. The various material sections 12 together form a lattice structure 40. During operation, only those comminuted solids and / or fibers smaller than at least one of the empty sections 10 pass through the lattice structure 40. Additionally, comminution to a statistical average degree of comminution takes place, even of solids and / or fibers that are already smaller in at least one dimension than empty sections of the lattice structure at the fluid inlet 20. When the cutting screen 1 is swept by a straight cutting edge 11 of a cutting knife 14, cutting angles of approximately 20° are enclosed between the second material ribs 38 and the cutting edge 11.The embodiment shown here does not have centering bores 32 for positioning the cutting screen 1. Instead, the cutting screen 1 can be placed on a support surface inside the machine housing 15 of the wet shredder 2 at its outer edge region 6. A second surface is lowered onto the other side of the cutting screen 1 and tightened using a screw connection, thus securing the cutting screen 1 by friction. However, bores 32 for positive-locking positioning and securing can also be provided. Inside the circle is a recess 16 for receiving a drive shaft 18, the drive shaft 18 being designed to rotate cutting blades 14 relative to the cutting screen 1.

[0037] The cutting screen 1 has a thickness that is small compared to the diameter of the cutting screen 1. A page 42 (cf. Fig. 1) The cutting screen 1 is in contact with the cutting edge 11 of the cutting knife 14 during operation and is designed to shear solids in conjunction with the cutting edge 11. The other side 44 of the cutting screen 1, facing away from the cutting edge 11, is a mirror image of the first side 42. The second side 44 is subjected to less mechanical stress from shear forces. If the first side 42 of the cutting screen 1 becomes worn, the second, unworn side 44 can be used for shearing in conjunction with the cutting edge 11 after the cutting screen 1 is turned over.

[0038] When using a cutting screen geometry as in Fig. Figure 2 shows that the cutting edges wear evenly. The shearing effect is therefore independent of the radial position along the cutting edge 11, even in advanced operating and wear conditions. This means that the cutting edge 11 requires replacement less frequently, extending maintenance intervals and reducing system downtime. System efficiency increases, and fewer consumable parts (especially cutting blades 14) are required.

[0039] Another embodiment of a cutting sieve 1 according to the invention shows the Fig. 3. Here, the second material webs 38 do not taper. They have a uniform web width from radially inside to radially outside. Only in the area of ​​the intersections with the first material webs 36 are they locally widened such that the empty sections 10 enclosed by the first material webs 36 and the second material webs 38 have rounded corners. Such rounded corners are due to manufacturing constraints, and the radius of curvature can be, for example, and preferably, 0.1 mm, 0.5 mm, 1 mm, 1.5 mm, 3 mm, 4.5 mm, or 6 mm. In the example shown here, a number of webs is provided for both the first material webs 36 and the second material webs 38, namely five and 23 respectively, which is not divisible by the number of cutting blades when, for example, two, three, or four cutting blades are used.

[0040] It should be understood that in other embodiments a different number of first material webs 36 and / or second material webs 38 may be used. Preferably, the number of first material webs 36 and / or second material webs 38 is chosen such that, when divided by the number of cutting blades 14 used, the result is not an integer.

[0041] In comparison to the embodiment made of Fig. 2 is the inner edge region 4 of the embodiment in Fig. 3 larger. Radially inside, the empty sections 10 are smaller than radially outside. When constructing the cutting screen 1, the number of first material webs 36 and second material webs 38 is specified by specifying a predetermined pitch of the spirals or involutes and by specifying the widths of the first material webs 36 and second material webs 38.

[0042] Empty sections 10 resulting from such a design specification, which are too small to be manufactured with a production machine, e.g., a laser cutting machine or a milling tool, in particular empty sections 10 at the inner edge region 4, are preferably removed before a production order is placed. That is, for a production order, such small empty sections 10 are not removed from a blank, and instead these areas are formed as material sections 12. Preferably, empty sections 10 are not considered for a production order, i.e., not removed from the blank, if they are so small that clogging of the cutting screen 1 is to be expected during operation. Instead, a material section 12 is preferably provided in this area. The size of such an area, i.e.,The size below which a material section 12 is provided instead of an empty section 10 depends on the application and, in particular, on the solids-laden medium to be shredded. This advantageously prevents clogging and avoids the cutting blade 14 repeatedly passing over a blockage, thus preventing faster wear.

[0043] This ensures that at an empty section 10b, the minimum ball passage diameter of all empty sections 10 is greater than a predetermined value, i.e., that the cutting screen 1 is permeable to balls (shown here as circular) with a diameter of at least 30 mm. In other embodiments, however, other minimum ball passage diameters can be chosen, e.g., 25 mm, 20 mm, 15 mm, 10 mm, or 5 mm. Similarly, another empty section 10a is the empty section that a (fictitious) ball with a maximum diameter cannot pass through. This value is 40 mm here, but in other embodiments it can also be, for example, 35 mm, 30 mm, 25 mm, 20 mm, or 15 mm, always being greater than or equal to the minimum ball passage diameter.The choice of the size of the empty sections 10, the minimum ball diameter and the maximum ball diameter depends on the process, in particular on the medium to be crushed and the requirements for a degree of crushing of the medium.

[0044] Another embodiment of a cutting sieve according to the invention is described in Fig. 4 shown.

[0045] The ones here in the Fig. 2, Fig. 3 and Fig. The four illustrated embodiments with spirally extending first material webs 36 and opposing second material webs 38 each represent one possible embodiment. The empty sections 10 are approximately rectangular with rounded edges. Other embodiments differ, for example, in the number of first and / or second material webs 36, 38, in the degree of taper of the first and / or second material webs 36, 38, and / or in the types and / or pitches of the spiral shapes. Other embodiments have round, triangular, polygonal, and / or teardrop-shaped empty sections 10 and / or freeform empty sections 10. Combinations of differently shaped empty sections 10 are also possible. Fig. Figure 5a shows a system 3 consisting of a cutting screen 1 with a grid structure 40 and four cutting blades 14a, 14b, 14c, 14d. The four cutting blades 14a, 14b, 14c, 14d are arranged circumferentially, each offset by 90°. The cutting edges 11 of the cutting blades 14 are arranged at an angle to a central axis, i.e., an axis that passes through the center of the circular central recess 16 and is perpendicular to the cutting screen 1. The cutting blades 14a, 14b, 14c, 14d, or their imaginary extensions, do not intersect the central axis. The cutting blades 14a and 14b are not aligned but parallel to each other. The cutting blades enclose cutting angles of approximately 20° with the second material ribs 38.

[0046] The four cutting blades 14a, 14b, 14c, 14d are partially enclosed and held by a rotor 46. Fig. In Figure 5a, the rotor 46 is not shown to better illustrate the cutting blades 14a, 14b, 14c, 14d. The same system 3 with the rotor 46 shown is in Fig. 5b shown. Each cutting blade 14 is arranged in a groove 48 of the rotor 46. The rotor 46 is rotated by means of the drive shaft 18 (cf. Fig. 6) causes the cutting blades 14a, 14b, 14c, 14d to sweep over the working area 8. In other embodiments, more or fewer than four cutting blades 14 may be provided, e.g. three cutting blades 14 or six cutting blades 14, wherein the rotor 46 is adapted accordingly to the number of cutting blades 14. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] WO 2012 / 032175 A1

[0003]

Claims

[1] Cutting screen (1) for use in wet shredders (2) with an inner edge region (4) and an outer edge region (6), the inner edge region (2) having a central recess (16) for receiving a rotating element, wherein the cutting screen (1) has a working area (8) between the inner and outer edge regions (4, 6) consisting of empty sections (10) and material sections (12), wherein the working area (8) is designed to be swept by at least one cutting edge (11) during operation, characterized by , that the material sections (12) are formed by: a first plurality of first material webs (36) extending spirally from the inside out; and a second plurality of second material webs (38) which extend in a curved, preferably spiral, direction opposite to the first material webs (36) from the inside out. [2] Cutting sieve (1) according to claim 1, wherein the first material webs (36) extend in an involute shape, preferably in a circular involute shape. [3] Cutting screen (1) according to one of the preceding claims, wherein the working area (8) comprises an area of ​​at least 30%, preferably 40%, 50%, 60%, 70%, 80% of a front surface of the cutting screen (1) and of at most 95%, preferably 90%, 85%, 80%, 70% of the front surface of the cutting screen (1). [4] Cutting sieve (1) according to one of the preceding claims, wherein the second material ribs (38) cross the first material ribs (36). [5] Cutting sieve (1) according to one of the preceding claims, wherein the second material webs (38) do not taper radially outwards or inwards. [6] Cutting sieve (1) according to one of the preceding claims, wherein the second material webs (38) taper radially outwards. [7] Cutting sieve (1) according to one of the preceding claims, wherein the first material webs (36) taper radially inwards. [8] Cutting sieve (1) according to one of the preceding claims, wherein the second material webs (38) extend continuously from the inner edge region (4) to the outer edge region (6). [9] Cutting screen (1) according to one of the preceding claims, wherein the cutting screen (1) is designed to enclose cutting angles in a range of 10° to 30°, preferably in a range of 15° to 25°, preferably 20° when interacting with the cutting edge (11). [10] Cutting screen (1) according to claim 9, wherein each cutting angle is in a range of 10° to 30°, preferably from 15° to 25°, preferably at 20°. [11] Cutting sieve (1) according to one of the preceding claims, wherein the ball passage diameters of the empty sections (10) are in a range of 5 mm, preferably 10 mm, 15 mm, 20 mm, 25 mm to 25 mm, preferably 30 mm, 35 mm, 40 mm. [12] Cutting sieve (1) according to any one of the preceding claims, characterized by , that the cutting sieve (1) has a higher hardness on the surface of the first and second material ribs (36, 38) than in the interior of the first and second material ribs (36, 38). [13] Cutting screen (1) according to one of the preceding claims, wherein the outer edge region (6) has bores (32) for positioning and / or fixing the cutting screen (1) in a wet shredder (2). [14] System (3) for comminuting solids in mixed fluids, comprising a cutting screen (1) according to one of the preceding claims and at least one cutting knife (14). [15] System (3) according to claim 14, wherein the working area (8) of the cutting screen (1) is swept over by the at least one cutting knife (14) when the at least one cutting knife (14) rotates and is at least partially in contact with the at least one cutting knife (14). [16] System (3) according to one of claims 14 and 15, wherein the axis of rotation of the at least one cutting blade (14) is coaxial to a central axis of the working area (8). [17] System (3) according to one of claims 14 to 16, wherein the axis of rotation of the at least one cutting knife (14) is coaxial to a central axis of the cutting screen (1). [18] System (3) according to any one of claims 14 to 17, wherein the number of first material webs (36) is not divisible by the number of cutting blades (14) by an integer. [19] System (3) according to any one of claims 14 to 18, wherein the number of second material webs (38) is not divisible by the number of cutting blades (14).

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