Toothed disc cleaner

Abstract

The invention relates to a toothed disc cleaner for pre-cleaning pre-comminuted plastic waste, in particular plastic flakes, in the course of plastic recycling, comprising two mutually facing cleaning tools, at least one of which is rotated by a rotary drive, wherein each cleaning tool has a working surface provided with cleaning teeth, and an annular working gap for pre-cleaning the plastic waste is delimited between the working surfaces lying opposite each other. The cleaning teeth of the working surfaces lying opposite each other mesh together in a mutually spaced manner. The toothed disc cleaner additionally comprises an inlet, which opens centrally into the working gap and which comprises a feed device for feeding the plastic waste to be cleaned, and an outlet, which is provided on the outer edge of the working gap and through which the plastic waste pre-cleaned in the working gap is discharged. The width of the working gap narrows radially outward starting from the inlet in a first section, and the width of the working gap is constant in a second section arranged radially outside of the first section.

Description

[0001] Toothbrush cleaner

[0002] The invention relates to a toothed disc cleaner for pre-cleaning pre-shredded plastic waste, in particular plastic flakes, in the course of plastic recycling, comprising two mutually facing cleaning tools, at least one of which is rotationally driven by a rotary drive, wherein the cleaning tools each have a working surface provided with cleaning teeth, wherein an annular working gap for pre-cleaning the plastic waste is defined between the mutually opposing working surfaces, and wherein the cleaning teeth of the opposing working surfaces mesh with one another at a distance from one another, further comprising an inlet opening centrally into the working gap with an input device for inputting the plastic waste to be cleaned, and an outlet provided on the outer edge of the working gap, through which outlet the plastic waste pre-cleaned in the working gap is discharged.

[0003] Plastic waste, such as PET beverage bottles, blister packs made of PET (deep-drawn PET films), plastic waste made of polyolefins, etc., must be cleaned during recycling. Very high quality standards must be met. Permissible contaminants are in the ppm range. The toothed disc cleaner in question here is used for the pre-cleaning of such plastic waste. A main cleaning process can then take place. For pre-cleaning, the plastic waste is first pre-shredded, particularly into plastic chips or flakes. Shredding can be carried out, for example, in a shredder (rotor with knives and counter-blades and screen basket). The desired flake size is created via a hole diameter in the screen basket. The separation of metals from the plastic waste usually takes place in a pre-sorting process using magnetic and eddy current separators.Before the plastic waste is shredded, it is often sorted by color and / or type of plastic.

[0004] The surfaces of plastic waste, including production waste, contain a variety of extrinsic contaminants, such as adhesive labels made of paper, plastic films, or metal foils, printed ink layers (possibly with printed sealants), metallized surfaces, deposits of clay, sand, grease, oil, and various food residues. The focus of recycling into high-quality polymers, equivalent to primary plastics, is the virtually residue-free removal of firmly adhered (extrinsic) coatings, whether with printing inks, metallically vapor-deposited surfaces, or adhesion promoters (adhesives).

[0005] For example, traditional washing technologies using cold or hot process water are used for cleaning. However, hot melt adhesives, printing inks, and metal vapor deposition, for example, are not completely removed. Complete removal is defined as residual contamination of less than 10 ppm, which only causes minimal VOCs (Volatile Organic Components) during further thermal processing, such as extrusion or melting. In traditional hot caustic soda washes, printing inks, for example, are only removed if specially adapted surfactants are used for the caustic soda and the flakes are penetrated in the wash solution for a long time. The removal of hot melt adhesives is also problematic. The residual adhesion levels of at least less than 100 ppm required by the market are generally not achieved.This becomes noticeable in the application of the recyclates, namely through gels in the film or a yellow tint. Other serious consequences are outgassing during granule extrusion or during further processing in LSP (Liquid State Polymerization), which condenses PET in a high vacuum. The consequences of inadequate purification from merely "clean" compared to "highly pure" severely restrict the use of recyclates and thus their marketing. At the same time, demands on the quality of the polymers are increasing, comparable to those of primary plastics. Products made from recyclates must be largely free of color impurities, various VOCs that burden degassing and melt filtration in the extruder, and extrinsic contamination, as such residual impurities can lead to adverse changes in the polymer properties in terms of mechanics and processing, as well as to undesirable color and odor changes.

[0006] EP 2 094 462 B1 discloses a process for separating cellulose and other adhering substances during the recycling of waste plastics, particularly mixed plastics. In this process, films and pieces of thicker plastic parts from possibly pre-sorted plastic waste are mechanically pre-shredded into flakes or particles of a predetermined size. The shredded material is fed into a disc refiner together with water without first producing a compacted material or an agglomerate from the flakes. Contaminants are largely abraded from the flakes by the interacting discs of the disc refiner and subsequently present as separate substances that can be separated from the plastic parts using a suitable separation process. A similar process is known from EP 2 094 461 B1.

[0007] With these known processes, satisfactory primary cleaning of plastic waste can be achieved in most cases. However, the toothed disc refiner used in this process is less suitable for pre-cleaning of plastic waste. Pre-cleaning, however, can be crucial for the final result of the cleaning process. Furthermore, highly fluctuating input consistencies of the plastic waste and water can lead to an uneven distribution of the flakes, thus not always achieving complete cleaning.

[0008] EP 2 734 302 B1 discloses a further method for removing contaminants from plastic scrap using a disc refiner. The disc refiner is not a toothed disc refiner, but rather has a plurality of cleaning ribs extending between an inner and outer edge of the cleaning surfaces on the cleaning discs, wherein a plurality of cleaning webs extending transversely to the direction of extension of the cleaning ribs are arranged between at least some adjacent cleaning ribs. At least one flank of the cleaning ribs is inclined or curved relative to the axial direction of the respective cleaning disc, and the cleaning webs each rise in a ramp-like manner and have a lower height than the cleaning ribs.This ensures minimal mechanical stress on the plastic chips during cleaning by pulling them between the discs, especially between the cleaning ribs, and prevents them from kinking, folding, or bunching up, which can lead to inadequate cleaning. This process is also particularly suitable for the main cleaning of plastic chips.

[0009] Furthermore, EP 3 057 751 B1 discloses a device and a method for cleaning plastic, in particular plastic scrap, during plastic recycling. A toothed disc refiner is used, comprising a central inlet for introducing the plastic to be cleaned into the working gap and an outlet provided at the outer edge of the working gap for the cleaned plastic together with abraded impurities and water. The outlet has an outlet pipe through which water is pumped, flowing laterally past the working gap and directed tangentially to the working gap during operation. This water exerts a suction effect on the working gap, so that the cleaned plastic is conveyed into the outlet pipe. In this way, in addition to the input and cleaning consistency, the discharge consistency can also be flexibly adjusted, in particular independently of the cleaning consistency.In order to achieve maximum energy efficiency and cleaning effect, it is therefore possible to set a high solid consistency in the working gap and, at the same time, to set a suspension with a low solid consistency that is easy to convey or pump downstream of the working gap.

[0010] The aforementioned methods and devices are particularly suitable for the main cleaning of plastic waste. The described methods and devices are only partially suitable for pre-cleaning. Another problem arises with fluctuating feed consistencies, i.e., fluctuating solid content of the plastic waste when it is fed into the working gap together with a process fluid, such as water. In such cases, an uneven distribution of the plastic waste can occur, which in turn can have undesirable effects on the cleaning result.

[0011] Based on the explained prior art, the invention is therefore based on the object of providing a toothed disc cleaner for pre-cleaning pre-shredded plastic waste, which enables reliable and complete pre-cleaning at any time.

[0012] The invention solves the problem by the subject matter of independent claim 1. Advantageous embodiments can be found in the dependent claims, the description and the figures.

[0013] For a toothed disc cleaner of the type mentioned at the outset, the invention solves the problem in that the width of the working gap narrows radially outwards starting from the inlet in a first section and that the width of the working gap is constant in a second section arranged radially outside the first section.

[0014] As explained at the beginning, the toothed disc cleaner is used for pre-cleaning pre-shredded plastic waste, for example, plastic flakes or plastic shreds shredded from plastic film. In principle, the plastic flakes can be produced by shredding thin-walled hard plastics or film, etc. The contaminants to be removed can, in particular, be surface deposits, such as cellulose, label residue, organic contaminants, etc. The toothed disc cleaner according to the invention comprises two mutually facing cleaning tools, which can, for example, be cleaning discs. At least one of the cleaning tools is driven in rotation by means of a rotary drive, so that a relative rotation occurs between the cleaning tools. The cleaning tools each have a working surface provided with cleaning teeth.The working surfaces are ring-shaped, in particular circular, with an annular, in particular circular, working gap being defined between the opposing working surfaces. The cleaning teeth of the opposing working surfaces engage with each other at a distance from each other. The cleaning tools thus form a male tool and a female tool. The teeth on the working surfaces are individual teeth and are therefore not connected to each other by ribs or the like. It is possible for the cleaning tools to be axially adjusted relative to each other using a corresponding adjusting device, whereby the width of the working gap can be adjusted. The pre-cleaning gap is formed by the distance between the cleaning teeth, in particular their side flanks and apex surfaces.

[0015] As explained, the toothed disc cleaner according to the invention serves for pre-cleaning the pre-shredded plastic waste. The focus is therefore not on generating friction on the surfaces of the plastic waste, but on forming a suspension of the plastic waste and the detached contaminants, such as paper labels, into isolated cellulose fibers. Accordingly, there is a distance between the meshing teeth. This distance can exist in any possible axial position, i.e., even with the smallest adjustable width of the working gap, so that the teeth of the opposing cleaning tools, in particular their tooth flanks, never come into direct contact. It is conceivable that the cleaning tools can be adjusted so that, for example, the apex surfaces of the cleaning teeth can come into contact with the base of the opposing cleaning tool, but not the side flanks of the cleaning teeth.This forces the plastic waste to be pre-cleaned over the tooth flanks, which can improve the pre-cleaning result. The rotation axis of the at least one rotatably driven cleaning tool, in particular the cleaning disc, can simultaneously be the axis of symmetry of the cleaning tool, in particular the cleaning disc. An electric drive, for example, can be used as the rotary drive.

[0016] The toothed disc cleaner also has an inlet that opens centrally into the working gap, particularly in the axial direction of the cleaning discs when the cleaning tools are designed as cleaning discs, which simultaneously forms the axis of rotation. An inlet device is provided for introducing the plastic waste to be cleaned into the working gap via the inlet. The inlet device can feed the plastic waste together with a process fluid, such as water, into the working gap. A corresponding fluid feed device can be provided for this purpose. However, a separate feed of the process fluid, such as water, into the working gap is also possible via a separate fluid feed device. After introduction into the working gap, the plastic waste is pre-cleaned between the opposing work surfaces in the working gap.The plastic waste, such as plastic flakes, is sheared between the cleaning tools and thus distributed evenly in the working gap. The plastic waste passes through the rows of teeth formed by the cleaning teeth, causing further shearing of, for example, film packages or fibers such as ropes, and the formation of a suspension of organic deposits. Printing inks or metallized surfaces, for example, are not or only slightly removed during the pre-cleaning process, but cellulose or similar materials are.During the cleaning process, the plastic waste is transported radially outwards from the central inlet in the working gap and reaches the outlet provided at the outer edge of the working gap, through which the plastic waste is discharged together with the detached organic deposits and the process liquid for further processing, in particular a main cleaning.

[0017] According to the invention, the width of the working gap narrows radially outwards from the central inlet in a first section, and the width of the working gap is constant in a second section arranged radially outside the first section. The first section and the second section can in particular be a first annular section and a second annular section. The inlet zone formed by the first section serves to receive the quantity of plastic waste material at the inlet. The working gap in the first section, which is initially wider and then narrows outwards, results in homogenization and even distribution of the plastic waste, even if the inlet consistency, i.e. the proportion of plastic waste per unit of time and / or per volume of process liquid, fluctuates considerably.This homogenization and even distribution is crucial for the subsequent cleaning success. Only if the plastic waste is distributed as evenly as possible. (r ' md are transported outwards to the outlet in isolated sections along the rows of teeth formed by the opposing cleaning teeth, optimal cleaning can be achieved.

[0018] The second section, in which the working gap width remains constant, continues to be of crucial importance. Only the combination of the narrowing first section and the constant second section produces the optimum cleaning result. The first section ensures the necessary homogenisation and equalisation of the plastic waste, while the second section, with a constant working gap width, ensures sufficient physical stress on the plastic waste for an optimum cleaning effect. In this way, the plastic waste, in particular plastic flakes, are aligned parallel to the flanks of the cleaning teeth in the inlet zone formed by the first section, preventing any accumulation or clumping of plastic waste, which would be detrimental to the cleaning process. The necessary processing of the plastic waste for pre-cleaning takes place in the working zone formed by the second section.

[0019] Plastic flakes produced from plastic films, in particular, are difficult to dose for cleaning because they have a high dry and wet volume and a low bulk density. Due to the inventive design of the working gap with the first section and the inlet zone formed thereby, the cleaning tools can easily accommodate even sinusoidally fluctuating doses, for example, without clogging. The inventive design of the working gap also reliably breaks up sandwich or film packages produced, for example, during the shredding of plastic films. During the pre-cleaning process, organic adhesions or cellulose in particular are removed from the plastic waste without causing significant destruction of the plastic waste, which could significantly complicate subsequent separation of the suspension components and main cleaning.The pre-shredding of plastic waste is particularly important because the unfolding of accordion-folded plastic flakes by the cleaning tools according to the invention and the dissolution of film packages into individual flakes can lead to an elongation of the pre-shredded plastic waste. In practice, for example, an average grain size of the pre-shredded plastic waste of no more than 50 mm has proven effective. For example, flake sizes no larger than twice the height of the cleaning teeth may be suitable. With the toothed disc cleaner according to the invention, a cleaning result of the plastic waste with less than 200 ppm of extrinsic residual contamination is possible even during the pre-cleaning phase. A subsequent main cleaning process can then reliably achieve the high purity levels of the recyclates currently required.

[0020] As explained, a process fluid, such as water, is usually also supplied to the working gap. The inventive design of the toothed disk cleaner enables significantly lower process fluid temperatures compared to the prior art, as well as a drastic reduction in the use of NaOH or surfactant additives.

[0021] According to one embodiment, the second section can directly adjoin the first section. In this way, the transition between the inlet zone formed by the first section and the working zone formed by the second section is optimized. According to a further embodiment, the second section can extend to the outer edge of the working gap. The first section and the second section can together cover the entire working gap. However, it would also be conceivable to provide an inlet section, for example, between the inlet and the first section, on which inlet section, for example, no cleaning teeth are arranged.

[0022] The working surfaces of the cleaning tools, which have the cleaning teeth, can be conical in the first section and parallel to each other in the second section. This allows for a particularly simple design of the first and second sections.

[0023] According to a further embodiment, the cleaning teeth on the surface sections of the working surfaces of the cleaning tools forming the first section can be arranged at a greater distance from one another than on the surface sections of the working surfaces of the cleaning tools forming the second section. The density of the cleaning teeth per unit area is therefore lower in the first section than in the second section. This further simplifies the infeed of the plastic waste and further improves the homogenization, uniformization, and separation of the plastic waste, while in the working zone formed by the second section, the closer-together cleaning teeth ensure particularly effective pre-cleaning.

[0024] The cleaning teeth of the cleaning tools can each have the shape of a shark fin in a side view. Furthermore, it can be provided that a leading flank of the cleaning teeth of the cleaning tools during the relative rotation of the cleaning tools is arranged at an angle of between 30° and 60° relative to the working surface supporting the cleaning teeth. It can also be provided that a trailing flank of the cleaning teeth of the cleaning tools during the relative rotation of the cleaning tools is arranged at an angle of between 70° and 90° relative to the working surface supporting the cleaning teeth.When reference is made to a leading or trailing flank, this refers to the relative rotation of the cleaning tools. For example, a non-rotating cleaning tool (stator) also has leading and trailing flanks due to the relative rotation to an opposite, rotating cleaning tool (rotor). The angle to the working surface is measured in the shortest direction in each case. This design of the cleaning teeth, in particular the flatter bevel of the leading tooth flanks, enables particularly effective pre-cleaning with simultaneous optimization of the energy consumption of the toothed disc cleaner. The oblique design advantageously leads to extended surface contact of the flexible plastic waste, in particular plastic flakes, which are aligned parallel, particularly in the second section, i.e. the working zone, and thus to effective pre-cleaning.This also allows a targeted pumping action to be created, effectively transporting the plastic waste from the inlet through the working gap to the outlet, specifically conveying the plastic waste sequentially from toothed ring to toothed ring to the outside. The cleaning teeth, moving through the suspension of plastic waste and cleaning fluid, generate a flow determined by their shape. The angled design of the aforementioned tooth flanks allows a targeted pumping action to be achieved. Furthermore, the energy consumption of the toothed disc cleaner can be reduced through an optimal hydrodynamic design of the tooth flanks.

[0025] According to a further embodiment, at least one radially outer side flank of the cleaning teeth can be designed to be oblique with respect to the working surface carrying the cleaning teeth. Furthermore, opposite side flanks of intermeshing cleaning teeth can be spaced parallel to one another. Correspondingly, the opposite, i.e. radially inner, side flank of the cleaning teeth can also be designed to be oblique with respect to the working surface. The side flanks of a cleaning tooth can, for example, be mirror-symmetrical to one another, in particular in at least one rotational position of the cleaning tools relative to one another. The oblique arrangement can, for example, be at an angle between 10° and 30° to the respective working surface, again measured in the shortest direction. The cleaning teeth of a cleaning tool can have the same height.This applies to both cleaning tools, whereby the cleaning teeth of both cleaning tools can also be the same height. The cleaning teeth form a line so that plastic waste, especially plastic flakes, can align parallel to the side flanks of the cleaning teeth. The aforementioned design of the side flanks of the cleaning teeth can further improve the pumping effect. It can also further optimize the cleaning effect.

[0026] At least one of the edges between the leading or trailing flanks and side flanks and / or at least one of the edges between the leading or trailing flanks and / or side flanks and a crest surface of the cleaning teeth can be rounded. The aforementioned advantageous effects are thereby further enhanced, while friction, which is not primarily desired, is reduced, particularly during pre-cleaning.

[0027] In a further embodiment, the cleaning tools can be made of cast stainless steel. Cast stainless steel, for example, based on an alloy with high Brinell hardness, produces a comparatively rough surface, including that of the cleaning teeth, due to the process. In particular, the surface hardness of cast stainless steel is so high that mechanical stress from the plastic waste does not lead to a loss of roughness. This ensures that the cleaning teeth can continue to perform their cleaning function even over long periods of time.

[0028] As explained, at least one of the cleaning tools, and preferably both cleaning tools, can be a cleaning disc. The cleaning disc can, for example, be circular in shape. It can, for example, be constructed from several circular ring segments. The axial direction then simultaneously forms the direction of rotation of the at least one cleaning disc. The inlet can then open into the working gap in the axial direction of the at least one cleaning disc.

[0029] According to a further embodiment, it can be provided that the input device comprises a liquid supply device through which a liquid can be fed directly into the input device and / or that a liquid supply device is assigned to the working gap through which a liquid can be fed directly into the working gap. The input device can, for example, comprise a conveyor screw that conveys the plastic waste to the inlet. By means of a liquid supply device of the input device, a process liquid, such as water, can be introduced directly into the input device, for example the screw flight of a conveyor screw, in particular via suitable nozzles. As explained, it would also be conceivable, however, for a liquid supply device to be assigned to the working gap through which liquid can be fed directly into the working gap.For example, a conveyor screw could be designed as a hollow shaft screw and process fluid, such as water, could be introduced directly into the working gap via the hollow shaft. Of course, other additional or alternative ways of introducing the process fluid, in particular other nozzles for direct introduction into the working gap, would also be possible. The invention also achieves the object through the use of a toothed disc cleaner according to the invention for the pre-cleaning of plastic fakes pre-shredded from plastic films. The toothed disc cleaner according to the invention is particularly suitable for the pre-cleaning of plastic flakes pre-shredded from plastic films. Cleaning results of less than 200 ppm of extrinsic residual contamination can be achieved even with the pre-cleaning. It is important to maintain suitable solid consistencies in the working gap, for example less than 5 wt.-% for plastic flakes pre-shredded from plastic films. For PET or rigid plastics in material transport, the solids consistency can be selected somewhat higher, for example, no more than 10 wt. Immediate process fluid removal is also important to prevent recontamination due to excessively long retention of the cleaned plastic waste. As mentioned, grain sizes of the pre-shredded plastic waste of no more than 50 mm have proven practical when using a toothed disc cleaner according to the invention.

[0030] An embodiment of the invention is explained in more detail below with reference to the figures. They show schematically:

[0031] Figure 1 shows a cleaning disc of a toothed disc cleaner according to the invention in a perspective view,

[0032] Figure 2 shows the cleaning disc from Fig. 1 in a plan view,

[0033] Figure 3 is a sectional view along a toothed disc cleaner according to the invention, and

[0034] Figure 4 shows two detailed views of a cleaning disc of the toothed disc cleaner according to the invention. Figure 5 shows a toothed disc cleaner according to the invention in a schematic, partially sectioned view.

[0035] Figure 6 shows the toothed disc cleaner according to Figure 5 with an input device for inputting plastic waste to be cleaned according to a first embodiment,

[0036] Figure 7 shows the toothed disc cleaner according to Figure 5 with an input device for inputting plastic waste to be cleaned according to a second embodiment,

[0037] Figure 8 shows the toothed disc cleaner according to Figure 5 with an input device for inputting plastic waste to be cleaned according to a third embodiment, and

[0038] Figure 9 shows a toothed disc cleaner according to the invention in a schematic sectional view with an outlet according to a further embodiment.

[0039] Unless otherwise stated, the same reference symbols in the figures refer to the same objects.

[0040] Figures 1 and 2 show a cleaning tool 10 of a toothed disc cleaner according to the invention, in this case a circular ring-shaped cleaning disc 10, which can, for example, also be constructed from several circular ring segments. The cleaning disc 10 has a circular ring-shaped working surface 12 on which a plurality of cleaning teeth 14 are arranged. The cleaning disc 10 forms a central inlet 16 for plastic waste to be pre-cleaned, for example plastic flakes from pre-shredded plastic films. An outlet 18 for the pre-cleaned plastic waste is formed on the outer edge of the cleaning disc 10. Connected to the inlet is an inlet device for introducing the plastic waste to be cleaned. The plastic waste can be introduced, for example, together with a process liquid, such as water.

[0041] In Figure 3, the cleaning disc 10 shown in Figures 1 and 2 is depicted as a lower cleaning disc 10 together with an upper cleaning tool 20, in this case an upper cleaning disc 20. The upper cleaning disc 20 is also circular in shape and has a circular working surface 22. A plurality of cleaning teeth 24 are located on the working surface 22 of the upper cleaning disc 20. By means of a rotary drive, at least one of the cleaning discs 10, 20 can be driven to rotate about its axis, so that a corresponding relative rotation is generated between the cleaning discs 10, 20.The upper cleaning disc 20 is largely identical to the lower cleaning disc 10, with the difference that the rows of teeth formed by the cleaning teeth 24 are each arranged radially offset from the rows of teeth formed by the cleaning teeth 14 of the lower cleaning disc 10, so that the cleaning teeth 14 and 24 mesh with each other at a distance from one another, as can be seen in Figure 3. Figure 3 also shows that opposite side flanks 26, 28 of the meshing cleaning teeth 14, 24 are spaced parallel to one another. It can also be seen that the side flanks 26 of the cleaning teeth 14 and the side flanks 28 of the cleaning teeth 24 are each mirror-symmetrical and are arranged at an angle to the working surface 12 or 22 supporting the cleaning teeth 14 or 24, for example at an angle between 10° and 30°.Particularly in Figure 3 it can also be seen that the working surfaces 12 and 22 of the cleaning discs 10 and 20, starting from the inlet 16, taper towards one another in a radially outward direction in a first section, such that the working gap formed between the working surfaces 12, 22 narrows radially outward in this first section, starting from the inlet 16. In a second section adjoining the first section and continuing to the outlet 18, the working surfaces 12 and 22 of the cleaning discs 10 and 20 are arranged parallel to one another, so that the width of the working gap is constant in this second section. In Figure 2, the circular dividing line between the first section, which is located radially inward in Figure 2, and the second section, which is located radially outward, is shown at reference numeral 30 for illustrative purposes.Figures 1 and 2 also show that the cleaning teeth 14 are arranged at a greater distance from one another on the surface section of the working surface 12 forming the first section than on the outer surface section of the working surface 12 forming the second section. The tooth density of the cleaning teeth 14 is therefore lower in the first section than in the second section. This is also the case for the upper cleaning disc 20.

[0042] The design of the toothed disc cleaner according to the invention will be explained in more detail with reference to Figure 4. First, in the right-hand view of Figure 4, in which only the lower cleaning disc 10 is shown in section, the cone angle 32 of the conical arrangement of the working surfaces 12 and 22, respectively, is shown in the first section. The left-hand view in Figure 4 represents a sectional view along the line AA in the right-hand view of Figure 4. In particular, one of the cleaning teeth 14 can be seen there in a sectional view, wherein the direction of rotation of the cleaning disc 10 runs from left to right in the left-hand view of Figure 4. A flank 34 of the cleaning tooth 14, which leads in the course of the relative rotation of the cleaning discs 10, 20 to one another, is arranged relative to the working surface 12 at an angle 36 between 30° and 60°, in the present case of 45°.A trailing flank 38 of the cleaning tooth 14, which trails during the relative rotation of the cleaning discs 10, 20, is arranged at an angle 40 relative to the working surface 12 between 80° and 90°, in this case approximately 85°. The apex surface 42 of the cleaning tooth 14 can be formed parallel to the working surface 12.

[0043] Edges between the various surfaces of the cleaning tooth 14, in particular the leading and trailing flanks 34, 38 and the apex surface 42 and / or between the leading and trailing flanks 34, 38 and the side flanks 26 and / or between the side flanks 26 and the apex surface 42, can be rounded. All cleaning teeth 14 and 24 can be configured as shown in Figure 4 as an example for one of the cleaning teeth 14.

[0044] It should also be mentioned that the cleaning discs 10, 20 can each be manufactured as a stainless steel casting.

[0045] In Figure 5, cleaning discs 10, 20, which can be configured, for example, as explained for Figures 1 to 4, are arranged in a cleaning housing 44 so as to be rotatable relative to one another. During operation, a rotary drive 46 can, for example, drive the cleaning disc 20 via a rotary shaft 48, so that the cleaning discs 10, 20 rotate relative to one another. The working gap between the cleaning discs 10, 20 can be adjusted via an adjusting device 50 comprising an adjusting drive 52 and an adjusting element 54.

[0046] Various options for introducing plastic waste to be pre-cleaned into the toothed disc cleaner will be explained with reference to Figures 6 to 8. In Figure 6, the inlet comprises an inlet screw 58 driven by a screw drive 56, to which, on the one hand, plastic waste 62 to be pre-cleaned is fed via an inlet opening 60 and, on the other hand, a cleaning liquid 66, such as water, is fed by means of a pump 64. The cleaning liquid can generally be added via a screw inlet, even via several inlets, into the inlet screw 58 downstream of the inlet, via a hollow shaft of the inlet screw 58 and / or via inlet nozzles in the cleaner housing 44. The inlet screw 58 conveys the plastic waste 62 together with the cleaning liquid 66 centrally into the working gap formed between the cleaning discs 10, 20.The pre-cleaned plastic waste is discharged via the outlet 18 for further processing, as shown in Figure 6 at reference numeral 68.

[0047] The embodiment according to Figure 7 differs from the embodiment according to Figure 6 only in that instead of the feed screw 58, an feed hopper 70 is provided, which has a plurality of feed nozzles 72 at its upper edge, for example distributed at regular intervals. Cleaning liquid 66 supplied by the pump 64 is introduced into the feed hopper 70 via the feed nozzles 72, for example in the form of a liquid jet onto an inner wall of the feed hopper 70, in which the fed plastic waste 62 is located. Via a connection 74, the plastic waste 62, together with the cleaning liquid 66, are in turn fed centrally into the working gap between the cleaning disks 10, 20. Such a feed device is known, for example, from EP3 423 203 Bl.

[0048] In the embodiment according to Figure 8, an inlet tank 76 is provided with a stirring device 78 arranged therein, into which the plastic waste 62 and the cleaning liquid 66 are fed. In the inlet tank 76, the plastic waste 62 is stirred with the cleaning liquid 66. Via a pump 80, the plastic waste 62 mixed with the cleaning liquid 66 is in turn fed centrally into the working gap between the cleaning discs 10, 20, as illustrated in Figure 8 at 82.

[0049] Figure 9 shows an example of an outlet of a toothed disc cleaner according to the invention, with Figure 9 only showing the cleaner housing 44 of the toothed disc cleaner in section with the outlet. The design shown in Figure 9 corresponds, for example, to the design described in EP 3 057 751 B1. The embodiment shown in Figure 9 can be combined with any of the previously explained embodiments.

[0050] In the example shown, an outlet pipe 84 is connected tangentially to the outlet 18 of the toothed disc cleaner with respect to the working gap between the cleaning discs 10, 20. Via a flange 86, the outlet pipe 84 can be connected directly or via another pipe to a separating device, in which the pre-cleaned plastic is separated from the contaminants abraded in the working gap. At the end of the outlet pipe 84 facing away from the flange 86 or the separating device, in the example shown, a nozzle pipe 88 is connected to a pump 90, in particular a liquid pump 90, for example a water pump 90, such as a centrifugal pump.

[0051] During operation of the toothed disc cleaner, the plastic pre-cleaned in the working gap, together with abraded contaminants and the cleaning fluid, is drawn by centrifugal force through the outlet 18 into the outlet pipe 84. At the same time, the fluid pump 90 introduces fluid, such as water, through the nozzle pipe 88 in the conveying direction of the suspension emerging from the working gap to the separating device in the form of a directed fluid jet into the outlet pipe 84, as illustrated in Figure 9 at reference numeral 92. The directed fluid jet thus runs tangentially to the working gap, just like the outlet pipe 84. The fluid jet transports the mixture of cleaning fluid and pre-cleaned plastic, as well as abraded contaminants, located in the outlet pipe 84 to the separating device, as illustrated in Figure 9 at reference numeral 94.The liquid jet exerts a suction effect on the working gap according to the principle of a jet pump, such that the suspension of pre-cleaned plastic, abraded contaminants, and cleaning fluid is drawn from the working gap into the outlet pipe 84. At the same time, the discharge consistency, i.e., the consistency in the outlet pipe 84, can be adjusted as required by the liquid jet. A solids pump is therefore not required, nor is a pump sump.

[0052] List of reference symbols

[0053] 10 cleaning disc

[0054] 12 work surface

[0055] 14 cleaning teeth

[0056] 16 Entrance

[0057] 18 Outlet

[0058] 20 cleaning discs

[0059] 22 work surface

[0060] 24 cleaning teeth

[0061] 26 side flanks

[0062] 28 side flanks

[0063] 30 dividing line

[0064] 32 cone angles

[0065] 34 Leading flank

[0066] 36 angles

[0067] 38 Trailing edge

[0068] 40 angles

[0069] 42 vertex surface

[0070] 44 Cleaner housing

[0071] 46 rotary drive

[0072] 48 Rotating shaft

[0073] 50 V creation device

[0074] 52 Adjustment drive

[0075] 54 Adjustment element

[0076] 56 Worm drive

[0077] 58 Feed screw

[0078] 60 inlet opening

[0079] 62 plastic waste

[0080] 64 Pump

[0081] 66 Cleaning fluid

[0082] 68 Arrow

[0083] 70 entry funnels

[0084] 72 feed nozzles

[0085] 74 Connection

[0086] 76 Entry tank

[0087] 78 Stirring device

[0088] 80 Pump Arrow Outlet pipe Flange Nozzle pipe Pump Arrow Arrow

Claims

Claims 1. A toothed disc cleaner for pre-cleaning pre-shredded plastic waste, in particular plastic flakes, during plastic recycling, comprising two mutually facing cleaning tools (10, 20), at least one of which is rotationally driven by a rotary drive (46), wherein the cleaning tools (10, 20) each have a working surface (12, 22) provided with cleaning teeth (14, 24), wherein an annular working gap for pre-cleaning the plastic waste is defined between the opposing working surfaces (12, 22), and wherein the cleaning teeth (14, 24) of the opposing working surfaces (12, 22) mesh with one another at a distance from one another, further comprising an inlet (16) opening centrally into the working gap, having an input device for inputting the plastic waste to be cleaned, and an outlet (18) provided at the outer edge of the working gap,through which the plastic waste pre-cleaned in the working gap is discharged, characterized in that the width of the working gap narrows radially outwards starting from the inlet (16) in a first section and that the width of the working gap is constant in a second section arranged radially outside the first section.

2. Toothed disc cleaner according to claim 1, characterized in that the second section directly adjoins the first section.

3. Toothed disc cleaner according to one of the preceding claims, characterized in that the second section extends to the outer edge of the working gap. Toothed disc cleaner according to one of the preceding claims, characterized in that the working surfaces (12, 22) of the cleaning tools (10, 20) having the cleaning teeth (14, 24) are arranged conically in the first section and parallel to one another in the second section. Toothed disc cleaner according to one of the preceding claims, characterized in that the cleaning teeth (14, 24) are arranged on the surface sections of the working surfaces (12, 22) of the Cleaning tools (10, 20) are each arranged at a greater distance from one another than on the surface sections of the working surfaces (12, 22) of the cleaning tools (10, 20) forming the second section. Toothed disc cleaner according to one of the preceding claims, characterized in that a flank (34) of the cleaning teeth (14, 24) of the cleaning tools, which flank leads during the relative rotation of the cleaning tools (10, 20), is arranged at an angle (36) of between 30° and 60° relative to the working surface (12, 22) carrying the cleaning teeth (14, 24). Toothed disc cleaner according to one of the preceding claims, characterized in that a trailing flank (38) of the cleaning teeth (14, 24) of the cleaning tools during the relative rotation of the cleaning tools (10, 20) is arranged at an angle (40) of between 70° and 90° relative to the working surface (12, 22) carrying the cleaning teeth (14, 24).Toothed disc cleaner according to one of the preceding claims, characterized in that at least one radially outer side flank (26, 28). the cleaning teeth (14, 24) are formed obliquely with respect to the working surface (12, 22) carrying the cleaning teeth (14, 24). Toothed disc cleaner according to one of the preceding claims, characterized in that opposing side flanks (26, 28) of intermeshing cleaning teeth (14, 24) are spaced parallel from one another. Toothed disc cleaner according to one of the preceding claims, characterized in that the cleaning tools (10, 20) are stainless steel castings. Toothed disc cleaner according to one of the preceding claims, characterized in that at least one of the cleaning tools (10, 20) is a cleaning disc (10, 20). Toothed disc cleaner according to claim 11, characterized in that the inlet (16) opens into the working gap in the axial direction of the at least one cleaning disc (10, 20).Toothed disc cleaner according to one of the preceding claims, characterized in that the feed device comprises a liquid supply device through which a liquid can be fed directly into the feed device and / or that a liquid supply device is assigned to the working gap through which a liquid can be fed directly into the working gap. Use of a toothed disc cleaner according to one of the preceding claims for the pre-cleaning of plastic flakes pre-shredded from plastic films.

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