Cutting screen with evenly distributed cutting surfaces

Abstract

The invention relates to a cutting screen (1) for use in wet shredders (2) with an inner edge region (4) and an outer edge region (6), 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 by a circumferential ratio (UV) that is the ratio of accumulated lengths of material sections AM (12) along a circumferential line to a circumference (U) belonging to the circumferential line, and wherein at least one continuous, curvature-free circumferential function F exists for the cutting screen (1) that maps circumferences U to a reference circumferential ratio RUV.wherein the circumferential ratio (UV) for each circumference U of a circle concentric to the working area (8) of the cutting screen (1) and lying within the working area (8) does not deviate from the reference circumferential ratio RUV = F(U) by more than 0.05, preferably 0.03, preferably 0.01 of the reference circumferential ratio (RUV) at the respective circumference.

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. 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, wherein the cutting screen has a working area between the inner and outer edge regions consisting of empty sections and material sections, the working area being designed to be swept by a cutting edge during operation. A circumferential line of a circle within a working area intersects material sections AM and empty sections AL. A circumferential ratio UV is the ratio of accumulated lengths of material sections AM along a circumferential line to a circumference U belonging to the circumferential line. For the cutting screen, there exists at least one continuous, curvature-free circumferential function F that maps circumferences U to a reference circumferential ratio RUV.A cutting screen according to the invention is characterized in that the circumferential ratio UV for each circumference U of a circle concentric to the working area of ​​the cutting screen and lying within the working area does not deviate from the reference circumferential ratio RUV = F(U) by more than 0.05, preferably 0.03, preferably 0.01 of the reference circumferential ratio at the respective circumference.

[0007] The invention is based on the understanding that the wear of a cutting edge rotating relative to the cutting screen depends significantly on the contact between the rotating cutting edge and the cutting screen. The cutting screen has a working area. The working area is the area swept by at least one cutting edge during operation. It can also be referred to as the effective surface. During operation, the rotating cutting edge rests against the cutting screen, more precisely against the material sections of the working area of ​​the cutting screen. The cutting edge of the cutting knife is pressed against the cutting screen by an adjusting mechanism with an actuating force. This actuating force acts on those sections of the cutting edge of the cutting knife that are in contact with material sections of the cutting screen.In contrast, different stress conditions exist on those sections of the cutting edge of the cutting blade that are located on empty sections of the cutting screen: Here, solids to be shredded during operation are cut through. Transverse forces act on the cutting screen, the magnitude of which depends on the type of solids (material, geometry, etc.).

[0008] The working area of ​​the cutting screen is circular. During operation, each position of the cutting edge covers both material sections and empty sections. When the cutting edge rotates, the circumferential ratio UV represents the ratio of material sections AM along a circumferential line of the cutting screen to the circumference U associated with that circumferential line. For a cutting edge whose rotation is concentric to the working area of ​​the cutting screen, each position along the cutting edge can be assigned a radius R, or – by multiplying the radius R by 2 × π – a circumference U. The circumferential ratio UV takes on values ​​between 0 and 1 for each circumference U. The larger the value of the circumferential ratio, the more frequently the cutting edge of the cutting blade makes contact with the cutting screen during each rotation.

[0009] Cutting edges of cutting knives and cutting screens are particularly susceptible to wear when the circumferential ratio assumes different values ​​for different positions (radii, circumferences) along a cutting edge. In particular, increased wear occurs when there are strongly varying circumferential ratios at adjacent positions along the cutting edge, i.e., when there are jumps in the circumferential ratio along the radius. According to the invention, it is therefore provided to avoid such jumps in the circumferential ratio along a cutting edge as far as possible. This means that at least one continuous and curvature-free circumferential function F exists that maps circumferences U to a reference circumferential ratio RUV (i.e.,(No sudden, wear-promoting jumps in the circumferential ratio occur) and the geometry of a cutting screen according to the invention is characterized in that the circumferential ratio UV for each circumference U of a circle concentric to the working area of ​​the cutting screen and lying within the working area deviates from the reference circumferential ratio RUV = F(U) by no more than 0.05, preferably 0.03, preferably 0.01 of the reference circumferential ratio at the respective circumference. Accordingly, the circumferential ratio UV deviates from the reference circumferential ratio RUV = F(U) by a maximum amount that lies within a tolerance band. Such a tolerance band is provided for metrological and manufacturing reasons. For example, the reference circumferential ratio can be a constant 0.5, i.e., regardless of the circumference (or(of the radius) approximately equal numbers of material sections and empty sections are provided on each circle concentric with the working area. However, for manufacturing and / or metrological reasons, a precisely measured circumferential ratio of exactly 0.5 for every circumference is not achievable. For example, manufacturing and / or metrological factors introduce noise, i.e., slight deviations from the reference circumferential ratio. In the example given, and for deviations of up to 0.05, circumferential ratios of up to 0.55 can be determined for some circumferences, while ratios of 0.45 can be determined for others. It should be understood that other reference circumferential ratios are also possible, and that, in particular, the reference circumferential ratio does not have to be a constant function, as in the example given. It can just as easily be another circumferential function F, provided it is continuous and free of curvature changes.

[0010] Determining the perimeter-to-UV ratio of a cutting screen can be achieved, for example, by taking a transmitted light photograph of the screen and subsequently analyzing the image using a computer. In this analysis, transmitted light areas are considered empty areas, and shadow areas are considered material areas of the screen. The circular shape of the screen can be identified using standard computer methods based on the transmitted light image. However, the empty areas may also be oriented at an angle to the screen's axis of rotation. In such cases, instead of a transmitted light image, an image of the front surface of the screen should be used to determine the empty and material areas, and the analysis can then be performed using a reflected light photograph of the screen.

[0011] The working area, within which the circumference ratios deviate by no more than 0.05, preferably 0.03, preferably 0.01 from a reference circumference ratio, is designed to be swept by at least one cutting edge during operation. "Swept" here refers to a rotational relative movement of the cutting edge relative to the cutting screen. The cutting edge can be at least partially in contact with the cutting screen, or a narrow gap can be provided between the cutting edge and the cutting screen, in which shear forces occur during operation to break down the solids.

[0012] 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 from a material section to a blank section occurs in the circumferential direction. 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. Consequently, other ratios of material sections to blank sections are possible in edge areas, and the edge area-to-circumference ratio need not meet the requirements of a continuous, curvature-free function within a tolerance band.

[0013] Taking this definition of the working area into account, the circumference ratios of a cutting screen can be determined using a computer at various positions (radii, circumferences) within the working area and plotted against the circumference. A photographic image, such as a scan, is preferably used for the computer-aided evaluation of the geometric ratios of a cutting screen. Preferably, two different pixel states are discernible in the image, with material sections being detected in one pixel state (e.g., dark) and empty sections in the other (e.g., light). For example, a pixel can be captured at least in every hundredth of the radius of the outer boundary of the working area. A higher resolution is preferred.

[0014] Preferably, the cutting screen also has at least one continuous, curvature-free angular function G that maps circular angles φ to a reference radial ratio RRV, wherein a radial ratio (RV) is the ratio of all accumulated lengths of material sections (AM) along a radial cutting line (L) to the length of the cutting line L, wherein the cutting line L forms an angle φ ∈ [0°, 360°] with a radial horizontal cutting line, wherein the cutting line extends over the working area without protruding into the inner edge region and / or the outer edge region, and wherein the radial ratio (RV) for each radial cutting line with a circular angle φ ∈ [0°, 360°] does not deviate from the reference radial ratio RRV = G (φ) by more than 0.15, preferably 0.1. Advantageously, for such cutting screens, no sudden, strong changes in the radial ratio in the direction of travel occur during the rotation of the cutting edge relative to the cutting screen.This ensures smoother operation. Vibrations are minimized. There are fewer sudden, impulsive loads on the cutting edge of the cutting blade. This has a positive effect on wear resistance and extends maintenance intervals.

[0015] It is also preferred that the function (F) be convex, linear, or constant. In this case, the function (F) is not concave. The terms "convex" and "concave" refer here to a representation in which the circumferential ratio is plotted on the ordinate, increasing in the positive direction, and the radius is plotted on the abscissa, also in the positive direction. A constant function F advantageously exhibits uniform circumferential ratios for every radial position of the cutting blade within the working area. However, in specific applications, it may also be advantageous for the function F to be linear or convex. In particular, the wear of cutting edges on cutting blades at the inner or outer edge of the cutting screen may be greater if the cutting blade is forced against the screen by compressive forces, e.g., at the inner or outer edge. Similarly, the wear behavior at the outer edge may be greater than at the inner edge, depending on the application.For example, larger solids are more likely to be broken down at the outer edge than at the inner edge due to centrifugal force, resulting in greater shear stresses. Advantageously, such differences in wear behavior along a cutting edge can be compensated for by a suitable design of a cutting screen whose circumferential ratio does not deviate from the reference circumferential ratio RUV by more than 0.05, preferably 0.03, preferably 0.01, where the reference circumferential ratio follows a convex or linear function.

[0016] 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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. In this case, the circumferential ratio UV decreases towards the radial outside, because a constant number of second material ribs with constant widths faces an increasing circumference towards the radial outside. Radially outside, the friction between the cutting edge of the cutting blade 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 increased wear during shearing.Then it is advantageous to compensate for the friction-related wear caused by the contact of the cutting screen to the cutting edge of the cutting knife by keeping it radially lower on the outside than in the middle of the cutting screen.

[0021] However, it is also preferred that the second material webs taper radially outwards. Ball passages are then larger with increasing radius.

[0022] It is equally preferred that the second material webs taper radially inwards. In this case, for example, an almost constant circumference ratio can be achieved for all circumferences within the working area. This is advantageous for achieving uniform comminution. Furthermore, radially outer areas are thus made thicker than radially inner areas. This is advantageous because, due to centrifugal force, heavier solids, which can potentially cause more wear than lighter particles, tend to accumulate radially outwards. The radially outer areas are advantageously thicker and therefore more robust than radially inner areas.

[0023] 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.

[0024] 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.

[0025] 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 if they provide cutting angles in a range of 10° to 30°, preferably in a range of 15° to 25°, and preferably 20°.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] Preferably, the cutting screen has one or more elements for positioning and / or securely fixing the cutting screen in a wet shredder.

[0030] The problem is solved in a further 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 it. 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.

[0031] A preferred system is one in which the number of first material ribs of the cutting screen is not divisible by the number of cutting knives. Typically, one, two, three, four, or six cutting knives are used in a wet shredder, preferably with even spacing. Using a number of first material ribs that is not divisible by the number of cutting knives is advantageous for preventing vibrations of the wet shredder during operation.

[0032] 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.

[0033] In contrast to the prior art, 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. They show:

[0034] Fig. 1 a perspective view of a preferred embodiment of a cutting screen according to the invention in a system for crushing solids with a representation of a cutting blade of a wet crusher; Fig. 2a a frontal view of a first cutting screen from the prior art; Fig. 2ba developmental representation of the first cutting screen from the prior art with an evaluation of the circumference ratio; Fig. 2c a developmental representation of the first cutting screen from the prior art with an evaluation of the radial ratio; Fig. 3a a frontal view of a second cutting screen from the prior art; Fig. 3b a developmental representation of the second cutting screen from the prior art with an evaluation of the circumference ratio; Fig. 3c a developmental representation of the second cutting screen from the prior art with an evaluation of the radial ratio; Fig. 4a a frontal view of a third cutting screen from the prior art; Fig. 4b a development diagram of the third cutting screen from the prior art with an evaluation of the circumference ratio; Fig. 4c a developmental representation of the third cutting screen from the prior art with an evaluation of the radial ratio; Fig. 5a a frontal view of a first embodiment of a cutting screen according to the invention; Fig. 5b a developmental representation of the first embodiment of a cutting sieve according to the invention with an evaluation of the circumference ratio; Fig. 5c a developmental representation of the first embodiment of a cutting screen according to the invention with an evaluation of the radial ratio; Fig. 6a a frontal view of a second embodiment of a cutting screen according to the invention; Fig. 6b a developmental representation of the second embodiment of a cutting sieve according to the invention with an evaluation of the circumference ratio; Fig. 6c a developmental representation of the second embodiment of a cutting screen according to the invention with an evaluation of the radial ratio; Fig. 7a a frontal view of a third embodiment of a cutting screen according to the invention; Fig. 7ba developmental representation of the third embodiment of a cutting sieve according to the invention with an evaluation of the circumference ratio; Fig. 7c a developmental representation of the third embodiment of a cutting screen according to the invention with an evaluation of the radial ratio; Fig. 8a a cutting screen according to the invention in a system with four cutting blades and a hidden rotor; Fig. 8b a cutting screen according to the invention in a system with four cutting blades and an integrated rotor; and Fig. 9 a wet shredder with a built-in cutting screen.

[0035] Figure 1 shows a first embodiment of a cutting screen 1 for use in wet shredders 2 (cf. Figure 9) 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 the 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, five, or six cutting edges, may also be provided during operation, as is particularly evident in Figure 9The 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 Figure 9 The machine housing 15 shown is arranged. In particular, a drive shaft 18 for rotary driving of the cutting blade 14 is arranged through an inner recess 16 in the inner edge region 4 of the cutting screen 1.

[0036] The wet chopper 2 in Figure 9It 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. Figure 9 The wet shredder 2 is 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.

[0037] Liquid, fibers, 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 screen 1, which further reduce the size of the solids or fibers until they can pass through the empty sections 10.

[0038] 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 the 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.

[0039] 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.

[0040] 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 solids-laden fluid as a result of a torque provided by the drive 26.

[0041] For cutting screens 1 known from the prior art, it has been shown that the wear of the cutting blades 14 varies at different positions along the cutting edge 11. With unevenly worn cutting blades 14, the shear forces between the cutting edges 11 and the cutting screen 1 differ along the length of the cutting edges 11. The operation of the wet shredder 2 is then less efficient, and maintenance work to replace the cutting blades 14 is required. Cutting screens 1 known from the prior art, which lead to uneven wear of the cutting blades 14 during operation, are described in the Figure 2a , 3a and 4a shown. Figure 2a , Figure 3a and Figure 4a The illustrations show the cutting screens 1 as seen in a photograph. Empty sections 10 are shown in dark, material sections 12 in light.

[0042] The previously known cutting sieves 1 show in the Figure 2a , 3a and 4a Each cutting screen 1 has an inner edge region 4, an outer edge region 6, and a working area 8 with empty sections 10 and material sections 12. The inner edge region 6 has an inner recess 16 designed to accommodate a drive shaft 26 for the rotary drive of at least one cutting blade 14 during operation. The cutting screens 1 also have an outer edge region 6. The outer edge region 6 is covered with material around its entire circumference. It also has positioning elements 30 for positively locking the cutting screen 1 within a wet shredder 2. These positioning elements 30 are designed as bores 32.

[0043] Based on the Figures 2b to 2c The following describes how to determine the circumference ratio and the radial ratio: For the in Figure 2a The depicted cutting sieve 1 shows the Figure 2b and 2c A developmental representation. Using computer-aided methods, each pixel of the Figure 2a With a known angular position φ and a known radius R, a Cartesian coordinate is assigned, where the respective radius is plotted on the ordinate and the angular position φ multiplied by a constant K is plotted on the abscissa. Empty sections 10 near the center of the circle cover a larger angular range in this view than empty sections 10 of similar size farther from the center of the circle, so that the representation of the empty sections 10 in the development view of the Figure 2b , 2c is distorted. Figure 2bThe figure also shows the course of the circumferential ratio UV for a radius range of approximately 60 mm to approximately 210 mm. The circumferential ratio UV is the ratio of the accumulated lengths of material sections 12 along a circumferential line to a circumference U belonging to that circumferential line. The circular cutting screen 1 is depicted. Figure 2a in a transaction representation in Figure 2b A size ratio can be determined by the fact that in Figure 2bIn a first step, along a horizontal line 34 from the left end of the development representation to the right end of the development representation, the lengths along the horizontal line 34 that run along the lightly depicted material sections 12 are summed. In a second step, the sum thus calculated is divided by the length of the horizontal line 34. This division is the circumference ratio of the horizontal line 34, where the horizontal line is assigned a value corresponding to its position on the ordinate of the representation. Figure 2b a radius is assigned.

[0044] This procedure is used for a large number of horizontal lines 34 in Figure 2brepeated, each with a different assigned radius. In the example shown here, at least one pixel image is acquired radially along the length of an outer radius R of the cutting screen at every hundredth of the length of the outer radius R. A profile of circumferential ratios is then determined across the radius in steps of at least one circumferential ratio per hundredth of the length of the outer radius R. Finer resolutions, i.e., a denser pixel density and / or the determination of more circumferential ratios than described here, are also preferred. In a further step, the pairs of circumferential ratio and corresponding radius values ​​are plotted in a diagram or generated using computer-aided methods. Linear interpolation is performed between the individual measurements to represent a curve. Such a diagram is shown in Figure 2b, shown on the right. The curved lines between the development representation and the course of the circumference ratio illustrate the radius range for which the evaluation was carried out here. For the circular cutting screen 1, this diagram shows a wave-like course of the circumference ratio against the radius. It is evident that in this case, no continuous, curvature-free circumference function F exists that maps circumferences U to a reference circumference ratio RUV in such a way that the circumference ratio UV for each circumference U (or, when dividing the respective circumference by 2 x π: each radius) of a circle concentric with the cutting screen and lying within the working area does not deviate from the reference circumference ratio RUV by more than 0.05, preferably 0.03, preferably 0.01. For this reason, the in Figure 2a The illustrated cutting sieve does not represent a cutting sieve according to the invention, but is to be regarded as a comparative example.

[0045] Preferably, the described analysis is carried out using computer-aided methods. A corresponding photographic image can, for example, be divided into empty sections 10 and material sections 12 using pixel analysis. The described development of the geometry, as in Figure 2b and Figure 2c The diagram shown serves for illustration and can be used to determine a circumference ratio or the distribution of circumference ratios along different radii or circumferences, but this is not mandatory. Using a suitable computer program, for example, the center point of the cutting screen 1 can be determined, calculations of circumference ratios for different radii can be performed, the working area 8 can be delineated from the inner boundary area 4 and the outer boundary area 6, and the distribution of circumference ratios along different radii or circumferences can be plotted at a suitable resolution. Figure 2bIt can be seen that no corresponding continuous, curvature-free circumference function F exists to which the circumference ratio UV for every circumference U of a circle concentric to the cutting screen 1 and lying within the working area 8 deviates by no more than 0.05, preferably 0.03, preferably 0.01. A corresponding test can just as well be carried out using a computer program, for example by examining the minima and maxima of the plotted circumference ratio.

[0046] In Figure 2c Below the development diagram is a graphical evaluation of the radial ratio RV for the cutting screen 1. Figure 2aThe evaluation is analogous to the evaluation of the circumference ratio, with the difference that vertical lines 35 are considered instead of horizontal lines 34. The evaluation shown here extends from an inner boundary 37 of the circle to an outer boundary 39. Along a vertical line 35, the ratio of material sections 12 to the length of the vertical line 35 is the radial ratio RV. Such a radial ratio RV can be determined for angles from 0° to 360°. Figure 2c The maxima and minima of the radial ratio are marked. These lie below 0.2 and above 0.5, respectively. A continuous, curvature-free function G that maps circular angles to a reference radial ratio RRV, where the radial ratio RV for each radial intersection line with a circular angle between 0° and 360° does not deviate from the reference radial ratio RRV by more than 0.15, preferably 0.1, does not exist.

[0047] Figure 3a Figure 1 shows another previously known circular cutting screen 1 with first, spiral material ribs 36 that run from an inner edge region 4 to an outer edge region 6 in a mathematically positive direction of rotation. The cutting screen 1 also has second material ribs 38 that abut the first material ribs 36 without crossing them. A development view of the cutting screen 1 is shown. Figure 3a show the Figure 3b and 3c Analogous to the analysis used for the Figures 2a-2c As described, the circumference ratio UV for different radii of the cutting screen 1 is Figure 3a determined and in the Figure 3b shown. The course of the circumferential ratio is less wavy than the circumferential ratio of the cutting sieve 1. Figure 2aNevertheless, the course of the circumferential ratio varies along different radii (or circumferences) such that no continuous, curvature-free circumferential function F exists that maps circumferences U to a reference circumferential ratio RUV such that the circumferential ratio UV for each circumference U of a circle concentric with the cutting screen 1 and lying within the working area 8 does not deviate from the reference circumferential ratio RUV by more than 0.05, preferably 0.03, preferably 0.01. For this reason, the Figure 3a The depicted cutting sieve does not represent a cutting sieve according to the invention.

[0048] In Figure 3c The course of the radial ratio RV over the angle φ from 0° to 360° for the cutting screen 1 of the Figure 3aThe extrema are shown and are approximately 0.1 and greater than 0.4. A continuous, curvature-free trigonometric function G that maps circular angles φ to a reference radial ratio RRV, such that the radial ratio RV does not deviate from the reference radial ratio RRV by more than 0.15, preferably 0.1, does not exist.

[0049] Analogous to the one in Figure 3a The example shown demonstrates the Figure 4a Another embodiment of a previously known cutting screen. It differs, among other things, in the central recess for receiving a shaft, in the design of the working area, and in the positions of the positioning bores. Based on the graphical analysis of the circumferential ratios along various radii in Figure 4b , which are shown on the transaction display Figure 4b Based on this, a visual analysis of the graph clearly shows that the cutting screen 1 of the Fig. 4aThe graph does not represent a cutting screen 1 according to the invention. It exhibits discontinuities and changes in slope.

[0050] An analysis of the radial ratios RV of the cutting screen 1 from Figure 4a along angular positions from 0° to 360° is in Figure 4c The extreme values ​​differ from each other by more than 0.3. There is no constant function and no other continuous, curvature-free function G that maps circular angles φ to a reference radial ratio RRV such that the in Figure 4c The radial ratio RV shown would not deviate from the reference radial ratio RRV by more than 0.15, preferably 0.1.

[0051] In contrast, the cutting screen 1 has the geometry as in Figure 5aFigure 1 shows a cutting screen 1 according to the invention. It also has an inner edge region 4, an outer edge region 6, and a working region 8 consisting of empty sections 10 and material sections 12, the working region 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 webs 38 that run in the opposite direction to the first material webs 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.

[0052] 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.

[0053] The cutting screen 1 has a thickness that is small compared to the diameter of the cutting screen 1. A page 42 (cf. Figure 1The 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.

[0054] Analogous to the one in the Figure 2a and 2b The described procedure for determining the circumference ratios UV or the course of the circumference ratio UV along different circumferences or radii is in the Figure 5b an unfolded representation of the cutting screen 1 according to the Figure 5aand a plotted progression of the circumferential ratio UV along the radius is shown. The progression of the circumferential ratio UV over the radius is shown for the cutting screen 1 according to Figure 5a significantly more uniform than for cutting sieves 1 according to the Figure 2a , 3a or 4a The course shows only very minor irregularities and no large jumps or changes in gradient over a longer period.

[0055] There exists a continuous, curvature-free circumference function F that maps circumferences U to a reference circumference ratio RUV such that the circumference ratio UV for each circumference of a circle concentric with the cutting screen 1 and lying within the working area 8 does not deviate from the reference circumference ratio RUV = F (U) by more than 0.05, preferably 0.03, preferably 0.01. Such a function F is in Figure 5bThe function F is shown as a dashed line. Here, the function F is a constant function. Equally, another function F' could be used, for example, a linear function with a small slope, which also fulfills the criteria of continuity, freedom from changes in curvature, and the distance of the circumference ratio UV from another reference circumference ratio RUV' = F'(U). The essential point is that at least one such function F exists. In operation, a cutting edge 11 is used when employing the in Figure 5aThe cutting screen shown is subjected to similar, approximately identical stresses along the length of the cutting edge 11 during one revolution, because the duration of contact with material sections 12 of the cutting screen 1 is approximately the same at every position of the cutting edge 11 during one revolution. Advantageously, the wear of the cutting edges 11 of the cutting blades 14 is therefore approximately the same at the various positions along the length of the cutting screen 1. The shearing effect is thus independent of the radial position along the cutting edge 11, even in advanced operating and wear conditions. Replacement of the cutting edge 11 is required less frequently, i.e., maintenance intervals are extended and system downtime is reduced. System efficiency increases. Fewer consumable parts (especially cutting blades 14) are required.

[0056] Another embodiment of a cutting sieve 1 according to the invention shows the Figure 6a 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.

[0057] 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.

[0058] Out of Figure 5c It is also evident that the cutting sieve 1 is made of Figure 5a exhibits a more uniform distribution of the radial ratio RV along angles φ from 0° to 360° than previously known cutting screens. Extreme values ​​of a plotted evaluation of the unwound cutting screen 1 are greater than 0.2 and less than 0.4, respectively. Consequently, the cutting screen 1 is made of Figure 5aA continuous, curvature-independent function G that maps reference radial ratios RRV to angles φ, wherein the reference radial ratio does not deviate from the radial ratio by more than 0.15, preferably 0.1. In the example shown here, the function G can be, for instance, a constant function that assigns a reference radial ratio RRV of 0.3 to each angle φ. A corresponding tolerance band for a deviation of 0.15 ranges from 0.15 to 0.45. For a permissible deviation of 0.1, a tolerance band of 0.2 to 0.4 is used. The in Figure 5c All the radial ratios shown lie within these two tolerance bands.

[0059] In comparison to the embodiment made of Figure 5a is the inner edge region 4 of the embodiment in Figure 6alarger. 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.

[0060] 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 comminuted. This advantageously prevents clogging and avoids the cutting blade 14 repeatedly passing over a blockage, thus preventing faster wear.

[0061] 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.

[0062] Within the working area 8, there exists a curvature-free, continuous function F that maps perimeters U to a reference perimeter ratio such that, for all perimeter ratios within the working area, the difference between the perimeter ratio and the reference perimeter ratio is less than 0.05, preferably 0.03, preferably 0.01. An example of such a function F is shown in the Figure 6b indicated by dashed lines. Analogous to the functions of circumference ratios UV versus different radii R described above, the representation of the Figure 6b based on an evaluation of the unfolding representation of the cutting screen 1 from Figure 6a The transaction diagram is also in Figure 6bdepicted.

[0063] The in Figure 6b The function F shown is convex. It should be understood that it is not necessary to define the function F mathematically using parameters and / or mathematical operators. A function is generally characterized by the fact that it assigns exactly one function value (here: a theoretical reference circumference ratio RUV) to each element of a set (here: the set of possible circumferences U of concentric circles within the working area 8). This applies to the function F indicated by the dashed line in Figure 6b This function F is continuous. It has no abrupt jumps.

[0064] It should be understood that the measured values ​​of the circumferential ratio UV, or the interpolated course of the measured values, can indeed exhibit jumps. If discrete measured values ​​are recorded to determine the circumferential ratio UV, and linear interpolation is performed between the measured values, such a measured course of the circumferential ratio UV will inevitably exhibit jumps. However, such discontinuities are unacceptable for a cutting screen 1 according to the invention, as is the case, for example, in Figure 6a depicted, so small that the difference to a continuous, curvature-free function F is less than 0.05, preferably 0.03, preferably 0.01. In other words, a tolerance band with an extent of 0.1, preferably 0.06, preferably 0.02 exists around such a function F. All circumferential ratios UV of circles concentric to the cutting screen 1 within the working area 8 of the cutting screen 1 according to the invention lie within the tolerance band.

[0065] Advantageously, the contact times of the cutting screen 1 with the at least one cutting edge 11 along the cutting edge 11 are approximately the same for all points per revolution. For the in Figure 6b In the depicted curve, the graph is degressive radially outwards within the working area 8, i.e., radially outwards, the contact times between cutting screen 1 and cutting edge 11 per revolution are longer than radially inwards.

[0066] In Figure 6c is a representation of the radial ratio RV for the cutting element 1 from Figure 6a depicted. Analogous to the radial ratio used for the in the Figure 5a As described in the embodiment shown in Figure 5c, all values ​​lie within a tolerance band around a function G that maps angles φ to a reference radial ratio continuously and without curvature changes, where the tolerance band is narrower than 0.2.

[0067] Another embodiment of a cutting sieve according to the invention is described in Figure 7adepicted. In the Figure 7b is an unwound cutting sieve according to the embodiment shown in Figure 7a and an evaluation of the circumference ratio UV is shown. It is evident that there are hardly any fluctuations in the circumference ratio and that it is essentially constant along the radius R within the working area 8. In Figure 7c The course of the radial ratio RV for the cutting screen 1 is Figure 7a The radial ratio RV fluctuates within a tolerance band that is less than 0.2.

[0068] The ones here in the Figure 5a , 6a and 7aThe 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 feature round, triangular, polygonal, and / or teardrop-shaped empty sections 10 and / or have freeform shapes as empty sections 10. Combinations of differently shaped empty sections 10 are also possible.

[0069] In Figure 8aA system 3 consisting of a cutting screen 1 with a grid structure 40 and four cutting blades 14a, 14b, 14c, 14d is shown. 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 runs through the center point of the circular central recess 16 and 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.

[0070] The four cutting blades 14a, 14b, 14c, 14d are partially enclosed and held by a rotor 46. Figure 8aThe rotor 46 is not shown for better illustration of the cutting blades 14a, 14b, 14c, 14d. The same system 3 with rotor 46 shown is in Figure 8b 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 (see figure). Figure 9 ) 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.

Claims

1. Cutting screen (1) for use in wet shredders (2) with an inner edge region (4) and an outer edge region (6), 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 the fact that a circumference ratio (UV) is the ratio of accumulated lengths of material sections A M (12) along a perimeter line to a perimeter (U) belonging to the perimeter line, UV = ∑ U A M U and wherein for the cutting screen (1) there exists at least one continuous, curvature-free circumferential function F which maps perimeters U to a reference circumferential ratio RUV: F: U → RUVwherein the circumferential ratio (UV) for each circumference U of a circle concentric to the working area (8) of the cutting screen (1) and lying within the working area (8) does not deviate from the reference circumferential ratio RUV = F(U) by more than 0.05, preferably 0.03, preferably 0.01 of the reference circumferential ratio (RUV) at the respective circumference.

2. Cutting screen (1) according to claim 1, wherein a radial ratio (RV) is the ratio of all accumulated lengths of material sections (A) M ) (12) along a radial section line L to the length of the section line L, wherein the section line L forms an angle φ with a radial horizontal section line, wherein the section line extends over the working area (8) without protruding into the inner boundary area (4) and / or the outer boundary area (6), RV = ∑ L A M L where for the cutting sieve (1) there exists at least one continuous, curvature-free angular function G that maps circular angles φ to a reference radial ratio RRV: G: φ → RRV and wherein the radial ratio (RV) for each radial section line with a circular angle φ ∈ [0°, 360°] does not deviate from the reference radial ratio RRV = G(φ) by more than 0.15, preferably 0.

1.

3. Cutting screen (1) according to any of the preceding claims, wherein the function (F) is convex, linear or constant.

4. 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).

5. Cutting screen (1) according to one of the preceding claims, the inner edge region having a central recess (16) for receiving a rotating element, wherein the material sections (12) are formed by a first plurality of first material ribs (36) extending spirally from the inside out; and a second plurality of second material ribs (38) extending in a curved, preferably spiral, direction opposite to the first material ribs (36) from the inside out, wherein the first material ribs (36), the second material ribs (38), the inner edge region (4, 6) and the outer edge region (6) enclose material-free empty sections, wherein the first material ribs preferably extend in an involute shape, preferably in a circular involute shape, wherein the second material ribs (38) preferably intersect the first material ribs (36).

6. Cutting sieve (1) according to claim 5, wherein the second material webs (38) do not taper radially outwards or inwards.

7. Cutting sieve (1) according to claim 5, wherein the second material webs (38) taper radially outwards or radially inwards.

8. Cutting sieve (1) according to one of claims 5 to 7, 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 claims 5 to 8, wherein the cutting screen (1) is configured to enclose cutting angles in a range of 10° to 30°, preferably in a range of 15° to 25°, preferably of 20° when interacting with the cutting edge (11), wherein preferably each cutting angle is in a range of 10° to 30°, preferably from 15° to 25°, preferably at 20°.

10. Cutting sieve (1) according to one of the preceding claims, wherein the ball passage diameters of the empty sections (10) are in a range from a lower limit of 5 mm, preferably 10 mm, 15 mm, 20 mm, 25 mm to an upper limit of 25 mm, preferably 30 mm, 35 mm, 40 mm.

11. Cutting sieve (1) according to one of the preceding claims, characterized by the fact 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).

12. 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).

13. 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).

14. System (3) according to claim 13, wherein the working area (8) of the cutting screen (1) is swept over by the at least one cutting blade (14) when the at least one cutting blade (14) rotates and is at least partially in contact with the at least one cutting blade (14), wherein preferably the axis of rotation of the at least one cutting blade (14) is coaxial to a central axis of the working area (8) and / or to a central axis of the cutting screen (1).

15. System (3) according to one of claims 13 to 14, wherein the number of first material webs (36) and / or the number of second material webs (38) is not divisible by the number of cutting blades (14) in an integer way.

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