Method and plant for separating infill for artificial grass surfaces

Abstract

Method of separating an infill (100) for artificial grass surfaces, wherein the infill (100) comprises a first granular material and a second granular material having a specific density different from the specific density of the first granular material, wherein said method comprises: - screening (810) the infill (100) to divide the infill (100) into a plurality of infill fractions having different granulometries, wherein the plurality of infill fractions comprises one or more mixed infill fractions (34, 35) each comprising the first and second granular material; - separating (820) each mixed infill fraction (34, 35) into a respective first infill sub-fraction (37) and a respective second infill sub-fraction (38), comprising pouring each mixed infill fraction onto a respective vibrating table (18) and running a flow of water having a flow direction (20) over the table (18), to move the second sub-fraction (38) in accordance with the flow direction (20) and to move the first sub-fraction (37) in a direction opposite to the flow direction (20).

Description

[0001] DESCRIPTION

[0002] Title: METHOD AND PLANT FOR SEPARATING INFILL FOR ARTIFICIAL GRASS SURFACES

[0003] Technical field of the invention

[0004] The present invention relates to a method and a plant of separating an infill for artificial grass surfaces, in particular an infill at the end of its service life.

[0005] State of the art

[0006] Artificial grass surfaces are known, for example for sports use (e.g. football fields, baseball fields, etc.), comprising an artificial grass carpet comprising a backing layer from which artificial filaments protrude that simulate natural grass. Typically, a layer of granular material, referred to as infill, is spread among the artificial filaments. With wear, the artificial grass carpet becomes damaged and must be replaced. Since the infill comprises several components (including the materials of the infill proper, the synthetic grass filaments detached from the rest of the grass carpet as a result of wear, and possible foreign bodies, such as stones and other contaminants not originally part of the artificial grass surface), it is advantageous to separate the infill into its different components, so as to allow recovery and recycling of the raw materials of which the infill is comprised.

[0007] Summary of the invention

[0008] The term "infill” refers generally, and unless otherwise specified, to a mixture of components differing from each other in the constituent material(s) and deriving from an infill used, or intended to be used, in artificial grass surfaces. The term infill may refer to such a mixture in any phase of the separation method of the present invention. Therefore, the same term "infill”, depending on the context or the considered phase of the method, may refer to mixtures differing from each other in presence and / or percentage content of the different components. For example, the term "infill” may comprise one or more infill fractions or one or more infill sub-fractions.

[0009] Typically, the infill comprises (in a non-negligible content, e.g. greater than or equal to 10% or greater than or equal to 20% by weight) a first granular material and a second granular material having a specific density different from (e.g. lower than) the specific density of the first granular material, and possibly artificial grass filaments (e.g. in a weight content lower than or equal to 5% or lower than or equal to 3%).

[0010] The first granular material is for example constituted by granules of sand or of another material similar to sand in granulometry and / or specific density, e.g. another inert material. Such material, in use, functions for example as a stabilizing material since it confers weight to the artificial grass carpet to be stabilized on the ground, and facilitates the upright maintenance of the artificial filaments to reproduce the appearance of natural grass.

[0011] The second granular material is for example constituted by granules comprising a matrix in polymeric material and a filler charge, such as granules in elastomeric compound derived from shredded tires (e.g. SBR rubber or Styrene Butadiene Rubber), granules in a polymeric material chosen from the group: polyvinyl chloride (PVC), polyurethane (PU), polyester (PE), polypropylene (PP) with charge in calcium carbonate and / or talc and / or cellulose and / or vegetal material, or granules in completely vegetal material (e.g. cork particles, coconut, nutshells, fruit stones, e.g. olive stones, etc.), or their mixtures. Such second granular material, in use, functions for example as a performance material since it improves the performance properties of the field for sports use (for example in terms of mechanical response of the surface). Artificial grass filaments are filaments which, following the wear of the artificial grass surface, detach from the support layer and mix with the other components of the infill.

[0012] The expression "to separate an infill or a fraction of infill” or similar expressions, unless otherwise specified, means to separate from the rest of the infill or fraction, at least partially, at least one component (e.g. first or second granular material, or the filaments or foreign bodies) constituting the infill, with a degree of purity greater than that possessed by the component in the infill before the separation. In other words, a selective separation of such component is provided. For example, the separated component can have a degree of purity, by weight and / or volume, greater than or equal to 70%, or greater than or equal to 90%.

[0013] The terms "upstream,” "downstream,” and similar expressions refer to the direction of the infill flow during the separation.

[0014] The Applicant has addressed the problem of separating an infill for artificial grass surfaces, in an effective manner, i.e. with a high degree of purity of at least one separated, and / or with a reduced footprint of the separation plant, and / or with a high separation capacity in terms of infill treated per unit of time.

[0015] According to the Applicant, the above-mentioned problem is solved by a method and a plant in accordance with the appended claims and / or having one or more of the following features.

[0016] According to an aspect the invention relates to a method of separating an infill for artificial grass surfaces, wherein the infill comprises a first granular material and a second granular material having a specific density different from the specific density of the first granular material.

[0017] Preferably the method comprises screening the infill to divide the infill into a plurality of infill fractions having different granulometries.

[0018] Preferably said plurality of infill fractions comprises one or more mixed infill fractions each comprising said first and second granular material.

[0019] Preferably the method comprises separating each mixed infill fraction into a respective first infill sub-fraction and a respective second infill sub-fraction.

[0020] Preferably said separating comprises pouring each mixed infill fraction onto a respective vibrating table and running a flow of water having a flow direction over said table, to move said second sub-fraction in accordance with said flow direction and to move said first sub-fraction in a direction opposite to said flow direction.

[0021] According to one aspect the invention relates to a plant for separating an infill for artificial grass surfaces.

[0022] Preferably the plant comprises a granulometric screening device to divide the infill into a plurality of infill fractions having different granulometries.

[0023] Preferably said plurality of infill fractions comprises one or more mixed infill fractions each comprising said first and second granular material.

[0024] Preferably the plant comprises one or more densimetric separation devices, each densimetric separation device being connected to said granulometric screening device to separate a respective mixed infill fraction of said one or more mixed infill fractions into a respective first infill sub-fraction and a respective second infill sub-fraction.

[0025] Preferably each densimetric separation device comprises a vibrating table and a hydraulic circuit to generate a flow of water running over said table along a flow direction. The Applicant has discovered that, by separating the infill into at least two infill fractions with different granulometries (that is, having different grain size distributions, and typically substantially non-overlapping), of which at least one is a mixed fraction (that is, comprising both the first and the second granular material with non-negligible content, for example at least 5% or 10% each), it is possible to subject each mixed fraction to separation by means of a vibrating table with water flow (which performs a densimetric separation, that is, based on the specific density of the constituents of the infill fraction) with high separation effectiveness (e.g., in terms of the percentage of undesired material in each sub-fraction). Indeed, the granulometric subdivision reduces the grain size range of each mixed fraction. In other words, each mixed fraction comprises granules of more homogeneous size compared to the starting infill. Since the densimetric separation with water flow is based on the effect of the water drag (which depends on the suspension time of the granules in water), the reduction of the granulometric variation in each mixed fraction improves the dependence of the final effect (that is, the overall direction of movement of the granule) on the density of the granule, thereby improving the efficiency and / or effectiveness of the separation. On the contrary, the Applicant has found that water flow separation on an infill with a broad granulometric range provides incomplete or unsatisfactory separation.

[0026] The present invention instead allows obtaining, as empirically verified by the Applicant, a weight content of the first granular material in each first infill sub-fraction greater than 50% and a weight content of the second granular material in each second infill sub-fraction greater than 50%.

[0027] The present invention, in one or more of the aspects, may comprise the following preferred features.

[0028] Preferably said plant comprises a control system. Preferably the control system is programmed to execute one or more of the operations of the method of the present invention.

[0029] Preferably one or more of the operations of the present method is executed on a continuous flow of infill.

[0030] Preferably said infill fractions have respective contiguous and non-overlapping granulometric intervals.

[0031] Preferably said plurality of infill fractions comprises a first pure fraction comprising a weight content of said second granular material greater than 70%, more preferably greater than or equal to 80%, even more preferably greater than or equal to 90%, and possibly said artificial grass filaments.

[0032] Preferably said first pure fraction has a granulometric size greater than a granulometric size of said one or more mixed infill fractions.

[0033] Preferably said plurality of infill fractions comprises a second pure fraction comprising a weight content of said first granular material greater than 70%, more preferably greater than or equal to 80%, even more preferably greater than or equal to 90%.

[0034] Preferably said second pure fraction has a granulometric size greater than a granulometric size of said one or more mixed infill fractions.

[0035] In this way, the efficiency of the subsequent density separation of the mixed fractions is improved.

[0036] Preferably said mixed infill fractions (more preferably in a number less than or equal to three, even more preferably in a number of two and only two) have respective contiguous and non-overlapping granulometric size intervals.

[0037] Preferably said mixed infill fractions comprise a first mixed infill fraction and a second mixed infill fraction. Preferably said screening said infill is performed by means of a granulometric screening device.

[0038] Preferably said granulometric screening device comprises a feed inlet, a plurality of outlets and a plurality of screens each having a different granulometric size (i.e. the size of the openings, typically circular). Preferably said screens are arranged in an ordered sequence of decreasing granulometric size, more preferably in a vertically stacked sequence. Preferably said a plurality of screens comprises three and only three screens. In this way, high efficiency and effectiveness of separation is achieved, even in the case of wet infill.

[0039] Preferably a first screen of said plurality of screens has a granulometric size greater than or equal to 1000 m, more preferably greater than or equal to 1100 pm, and / or less than or equal to 2000 pm, more preferably less than or equal to 1800 pm.

[0040] Preferably said first pure fraction has a particle size greater than or equal to 1000 pm, more preferably greater than or equal to 1100 pm, and / or less than or equal to 3000 pm, more preferably less than or equal to 2500 pm.

[0041] Preferably a second screen of said plurality of screens has a granulometric size greater than or equal to 500 pm, more preferably greater than or equal to 600 pm, and / or less than or equal to 1200 pm, more preferably less than or equal to 1100 pm.

[0042] Preferably said first mixed fraction has a particle size greater than or equal to 500 pm, more preferably greater than or equal to 600 pm, and / or less than or equal to 2000 pm, more preferably less than or equal to 1500 pm.

[0043] Preferably a third screen of said plurality of screens has a granulometric size greater than or equal to 300 pm, more preferably greater than or equal to 350 pm, and / or less than or equal to 700 pm, more preferably less than or equal to 600 pm.

[0044] Preferably said second mixed fraction has a particle size greater than or equal to 300 pm, more preferably greater than or equal to 350 pm, and / or less than or equal to 1200 pm, more preferably less than or equal to 1100 pm.

[0045] Preferably said second pure fraction has a particle size less than or equal to 700 pm, more preferably less than or equal to 600 pm, even more preferably less than or equal to 500 pm.

[0046] Preferably said feed inlet is located upstream (and more preferably above) of said first screen. Preferably a first, second, and third outlet is located upstream of said first, second, and third screen. Preferably a fourth outlet is located downstream of said third screen.

[0047] Preferably it is provided discharging said first pure infill fraction from said first outlet, and / or discharging said first mixed infill fraction from said second outlet, and / or discharging said second mixed infill fraction from said third outlet, and / or discharging said second pure infill fraction from said fourth outlet.

[0048] Preferably said granulometric screening device comprises a vibration system structured to vibrate, more preferably at ultrasonic frequencies (e.g. greater than 20 kHz) said screens. In this way the screening is promoted.

[0049] Preferably said granulometric screening device comprises a first cleaning system for screens structured to mechanically tap each screen of said plurality of screens, more preferably at ultrasonic frequencies. In this way the screens are kept clean even in the case of wet infill, i.e. infill not dried.

[0050] Preferably said granulometric screening device comprises a second cleaning system comprising, for at least a screen of said plurality of screens, more preferably for each screen, a perforated sheet arranged below said screen and supporting a plurality of plastic beads (having a diameter greater than the holes of the screen), more preferably made of plastic material (e.g. silicone), wherein said vibration system is structured to vibrate said perforated sheet. In this way, the beads are kept in continuous motion by bouncing between the perforated sheet and the upper screen, thus keeping said screen clean even in the case of wet infill.

[0051] Preferably said second cleaning system comprises, for at least one of said screens, more preferably for each screen, a plurality of nozzles to spray pressurized water onto an upper surface of said respective screen. In this way the screening is facilitated and the relative screen is kept clean, even in the case of wet infill.

[0052] Preferably each first sub-fraction comprises a weight content of said first granular material greater than 70%, more preferably greater than or equal to 80%, even more preferably greater than or equal to 90%.

[0053] Preferably each second sub-fraction comprises a weight content of said second granular material greater than 70%, more preferably greater than or equal to 80%, even more preferably greater than or equal to 90%, and possibly said artificial grass filaments.

[0054] Preferably said separating each mixed infill fraction is performed by means of a respective densimetric separation device.

[0055] Preferably each densimetric separation device comprises a first and a second outlet, wherein each densimetric separation device is configured to move said respective first infill sub-fraction toward said first outlet and said respective second infill sub-fraction toward said second outlet.

[0056] Preferably said vibrating table is micro-perforated at opposite ends along said flow direction. In this way, at the ends, the water falls below the table, whereas the sub-fractions reach the respective outlets.

[0057] Preferably said vibrating table is inclined with respect to a horizontal plane, wherein said flow direction forms, with its projection on a horizontal plane, an angle greater than or equal to 2° and less than or equal to 10°, more preferably less than or equal to 5°. In this way, the water flow is easily generated.

[0058] Preferably, said pouring each mixed infill fraction comprises pouring said mixed fraction onto a central portion of said respective vibrating table.

[0059] Preferably the method comprises separating said artificial grass filaments from said infill, more preferably from one or more of said infill fractions, even more preferably from said first pure fraction, and / or from one or more of said second sub-fractions, for example from each of said second sub-fraction. The present method and device for separating filaments are considered an invention in their own right, regardless of the other separation steps and devices described herein.

[0060] Preferably the plant comprises a (and more preferably only one) filament separation device.

[0061] Preferably said separating said artificial grass filaments is performed by means of a (and more preferably only one) filament separation device.

[0062] Preferably said filament separation device comprises a tank filled with water (in use) and a screw conveyor (helical screw) at the bottom of said tank.

[0063] Preferably said filament separation device comprises one or more pushing devices located at the water surface and configured to generate a surface water flow. Preferably each pushing device is a wheel equipped with radial blades and rotatable around a horizontal axis. Preferably said blades dip into the water to a depth greater than or equal to 40 cm and / or less than or equal to 80 cm.

[0064] Preferably the method comprises introducing said infill (or said first pure fraction, and / or one or more of said second sub-fractions) into a tank filled with water and collecting, e.g. by means of said screw conveyor, a first final infill fraction that settles at the bottom of the tank.

[0065] Preferably said method comprises pushing, e.g. by generating a surface water flow by said pushing devices, said filaments (and any other residues) that float or remain suspended near the water surface.

[0066] The Applicant has discovered that the combination of densimetric separation and the subsequent filament separation operation synergistically achieves an efficient separation of the filaments. The Applicant has observed that the filaments, being lightweight, tend to naturally follow the second granular material during densimetric separation. Therefore, the second infill sub-fractions (in addition to the first pure fraction) substantially contain all the filaments, and consequently, it is not necessary to carry out the filament separation operation from the first infill sub-fraction(s), nor from the second pure fraction. The subsequent filament separation through flotation exploits the density difference between the filaments and the second granular material. This combination thus constitutes an independent aspect of the present invention.

[0067] The Applicant has discovered that the smaller and lighter filaments remain suspended (during the finite time interval in which the separation occurs) just below the water surface, typically at a depth of several tens of centimeters, while the larger and heavier filaments float on the surface. The rotating wheels equipped with paddles are thus able to intercept the floating material down to an adequate depth and push it toward one end of the tank. The first final fraction of the mixture, which is instead collected at the bottom of the tank, therefore comprises almost exclusively (apart from any residuals) the second granular material.

[0068] Preferably the plant comprises a first draining device for draining said infill, more preferably said second pure fraction and / or one or more of said first sub-fractions, more preferably each first sub-fraction. Preferably said first draining device is located downstream of said granulometric screening device and / or said one or more densimetric separation devices.

[0069] Preferably is provided, more preferably after said screening and / or said separating each mixed fraction and / or separating the artificial grass filaments, draining said infill, more preferably said second pure fraction and / or one or more of said first sub-fractions, more preferably each first sub-fraction, to obtain a second final drained fraction (more preferably comprising at least 95% or 99% by weight of the first granular material).

[0070] Preferably the plant comprises a second draining device for draining said infill, more preferably said first pure fraction and / or one or more of said second sub-fractions, even more preferably said first final infill fraction. Preferably said second draining device is located downstream of said one or more densimetric separation devices and / or of said filament separation device.

[0071] Preferably is provided draining said first pure fraction and / or one or more of said second sub-fractions, even more preferably said first final infill fraction, to obtain a first final drained fraction (more preferably comprising at least 95% or 99% by weight of the second granular material).

[0072] Preferably each draining device comprises a vibrating micro-perforated inclined screen.

[0073] Preferably is provided introducing said infill into each draining devices at a lower portion of a micro-perforated inclined screen and moving said infill up along said screen by vibrating said screen.

[0074] In this way, the infill loses a significant amount of water during the time required to travel up the vibrating screen. Preferably it is provided collecting said first and / or second final drained infill fraction. Preferably it is provided filtering said water discharged from each densimetric separation device and / or from said filament separation device and / or from each draining device, and / or said water sprayed by the second cleaning system in said granulometric separation device, and more preferably to reuse said water for separating said infill.

[0075] Preferably said plant comprises a hydraulic circuit comprising a filtering device comprising one or more hydraulic filters, more preferably sock hydraulic filters, and a hydraulic pump, wherein said hydraulic circuit fluidly connects each densimetric separation device, and / or said filament separation device and / or said granulometric separation device and / or each draining device, with said filtering device.

[0076] Preferably said sock hydraulic filters comprise meshes suitable for retaining solid particles having granulometric sizes greater than or equal to 20 m, and / or less than or equal to 200 pm.

[0077] In this way, it is possible to filter the water used for separating the filaments, and / or in the water-based separation tables, and / or for cleaning the screens, and / or coming from the draining devices, and to retain the very fine solid part (sludge). The clarified water can then be reused in the plant.

[0078] Preferably the method comprises, more preferably before said granulometric screening, pre-screening said infill to separate a waste fraction, more preferably having a granulometric size greater than or equal to 2.5 mm, more preferably greater than or equal to 3 mm.

[0079] Preferably, the plant comprises, more preferably upstream of said granulometric screening device, a pre-screening device comprising a screen, more preferably vibrating and / or inclined relative to a horizontal plane, more preferably having a granulometric size greater than or equal to 2.0 mm, more preferably greater than or equal to 2.5 mm, and / or less than or equal to 30 mm, more preferably less than or equal to 25 mm. Preferably, the pre-screening device comprises a container downstream of the screen to collect the infill and a screw conveyor at the bottom of the container. In this way the infill is cleaned of stones or other foreign bodies larger than the typical size of the infill. Moreover, the container acts as a buffer to continuously feed the plant, possibly evening out the infill over time, for example by mixing infills coming from different fields, in order to maintain the properties of the infill to be separated constant over time. Preferably the plant comprises an infill handling system to generate a flow of said infill along the plant.

[0080] Preferably, the infill handling system comprises a plurality of mechanical handling devices distributed along a path, to generate a flow of infill along said path, more preferably a substantially continuous flow. Preferably, said mechanical handling devices are active (i.e., motorized) and / or passive (i.e., non-motorized). Preferably, said active mechanical handling devices are selected from the group consisting of elevators (e.g., bucket elevators), screw conveyors, and belt conveyors. Preferably, said passive mechanical handling devices are connecting pipes and / or chutes.

[0081] Preferably the method comprises removing said infill from an artificial grass carpet before said granulometric screening and / or said densimetric separating and / or said separating said artificial grass filaments.

[0082] Brief Description of the Figures

[0083] Figure 1 shows a schematic of a plant according to the present invention;

[0084] Figure 2 schematically and partially shows a perspective view of a plant according to the present invention;

[0085] Figure 3 schematically shows a perspective view of a granulometric screening device of a plant according to the present invention;

[0086] Figure 4 schematically shows a perspective view of a water-flow densimetric separation device of a plant according to the present invention;

[0087] Figure 5 schematically shows a perspective view of a filament separation device of a plant according to the present invention;

[0088] Figure 6 schematically shows a perspective view of a filtering device of a plant according to the present invention;

[0089] Figure 7 schematically shows a perspective view of a draining device of a plant according to the present invention; Figure 8 shows an exemplary flow chart of a separation method according to the present invention.

[0090] Detailed description of some embodiments of the invention

[0091] The features and advantages of the present invention will be further clarified by the following detailed description of some embodiments, provided by way of example and not limitation of the present invention, with reference to the accompanying figures.

[0092] In the figures, the number 1 indicates a plant for separating an infill for artificial grass surfaces according to the present invention. More specifically, the plant 1 is configured to separate the infill into its different components, with a desired degree of purity, for example at least 90% by weight, or at least 95% by weight, or at least 99% by weight of each component.

[0093] Exemplarily the infill comprises a first granular material consisting of sand grains, having a granulometric size between approximately 100 m and 1400 pm.

[0094] Exemplarily the infill comprises a second granular material consisting of SBR rubber granules, optionally recycled (e.g., obtained from shredded used tires). Exemplarily the second granular material has a granulometric size between 800 pm and 2500 pm.

[0095] Exemplarily the infill may also comprise dust, i.e., granular material with a smaller granulometric size than sand, for example less than 50 pm, and / or small stones or other foreign objects, generally having a size greater than 3000 pm. Exemplarily the infill also comprises artificial grass filaments, for example made of polypropylene (PP) and / or polyethylene (PE). Exemplarily the artificial filament has a mass per unit length of approximately 2000 dtex.

[0096] It is noted that the plant of the present invention may also be used for separating other mixtures of granular material in which there is an overlap in the granulometric size ranges of granules made of different materials.

[0097] Exemplarily the plant 1 comprises a removal device (not shown) for removing the infill from an artificial grass carpet. The removal device is not further described or illustrated, as it may be of the type described, for example, in patent

[0098] IT202000004087A1.

[0099] Alternatively, the plant 1 may not comprise the removal device and may be configured to process infill that has already been removed from the respective artificial grass carpet.

[0100] The plant 1 comprises an infill handling system 2 (Fig. 2) for generating a substantially continuous flow of infill along a path of the plant 1. Exemplarily the infill handling system 2 comprises a plurality of mechanical handling devices distributed along the path, including, for example, a plurality of bucket elevators 3a, 3b and screw conveyors 4, as well as a plurality of connecting pipes (not shown in Figure 2 for clarity, to better display the devices located behind them). Exemplarily the plant 1 comprises a pre-screening device 5 (Fig. 2) comprising a vibrating screen 6, inclined with respect to a horizontal plane and having granulometric size approximately equal to 2.5 mm. Exemplarily the prescreening device 5 comprises a container 7 downstream of the screen 6 to collect the infill. Exemplarily the container 7 comprises a horizontal screw conveyor (not visible in Figure 2) positioned at the bottom to transport the infill to an outlet 8 connected to an additional screw conveyor 9.

[0101] Downstream of the pre-screening device 5, the plant 1 comprises a granulometric screening device 10.

[0102] Exemplarily the granulometric screening device 10 (Fig. 3) comprises a feed inlet 11 consisting of a through-opening located at the top and connected to the pre-screening device 5 via the screw conveyor 9.

[0103] Exemplarily the granulometric screening device 10 comprises three screens, each having a different granulometric size, vertically stacked in an ordered sequence with decreasing granulometric size from top to bottom, where the first screen (having openings with a granulometric size of approximately 1200 m or approximately 1400 pm or approximately 1600 pm) is positioned at the top, followed, from top to bottom, by a second screen (having openings with a granulometric size of approximately 700 pm or approximately 800 pm or approximately 1000 pm), and a third screen (having openings with a granulometric size of approximately 400 pm or approximately 500 pm). The choice of the granulometric size of the three screens is made each time based on the granulometric size composition of the infill. Exemplarily the granulometric screening device 10 comprises, from top to bottom, a first outlet 13a, a second outlet 13b, a third outlet 13c, and a fourth outlet 13d, arranged laterally and respectively positioned at a vertical level just above the vertical level of the first, second, and third screens, respectively. The fourth outlet 13d is positioned at a vertical level just below the vertical level of the third screen.

[0104] Exemplarily the outlets 13a, 13b, 13c, and 13d are in direct flow communication with respective screw conveyors 9. Exemplarily the granulometric screening device 10 comprises a first cleaning system (not shown) for the screens, configured to mechanically tap each screen at ultrasonic frequencies.

[0105] Exemplarily the granulometric screening device 10 comprises a second cleaning system (not shown) comprising, for one or more of the screens (for example, at least for the lower screen), a perforated sheet comprising holes with a diameter of 20-30 mm, arranged below the respective screen and supporting a plurality of plastic beads (having a diameter larger than the holes of the sheet).

[0106] Exemplarily the second cleaning system comprises for each screen a plurality of nozzles to spray pressurized water onto the upper surface of each screen.

[0107] Exemplarily the granulometric screening device 10 comprises a vibration system (not shown) structured to vibrate the entire structure, including the screens and optionally each perforated sheet, at ultrasonic frequencies.

[0108] Downstream of the granulometric screening device 10, the plant 1 comprises a first 15a and a second 15b densimetric separation device distinct from each other.

[0109] Exemplarily the first 15a and second densimetric separation device 15b comprise a respective inlet 16 at one end of a respective screw conveyor 12, in communication with, respectively, the second 13b and third 13c outlet of the granulometric screening device 10.

[0110] Exemplarily each densimetric separation device 15a, 15b comprises (Fig. 4) a vibrating table 18, a first outlet 21 , and a second outlet 22.

[0111] Exemplarily, each densimetric separation device 15a, 15b comprises a hydraulic circuit 19 configured to generate a water flow flowing over the table 18 along a flow direction 20. Exemplarily the hydraulic circuit 19 comprising a plurality of nozzles distributed above the table 18 and oriented parallel to the table. Exemplarily the vibrating table 18 is micro-perforated (not shown in Figure 4) at opposite ends along the flow direction 20.

[0112] Exemplarily the vibrating table 18 is inclined with respect to a horizontal plane, wherein the flow direction 20 forms with its projection on a horizontal plane an angle (of an adjustable value, for example between 2° and 5°).

[0113] Each densimetric separation device 15a, 15b comprises (Fig. 4) a first outlet 21 and a second outlet 22, advantageously arranged on the same side of the device. To this end, the densimetric separation device 15a, 15b comprises an additional table 17 positioned below the table 18 and parallel and fixed to it. In this way, the additional table 17 collects the material falling from the end of the table 18 opposite the said outlets 21 , 22 and, thanks to its vibration, moves it toward the second outlet 22. Consequently, the second outlet 22 is positioned at a lower level than the first outlet 21. Exemplarily each respective first outlet 21 of the first 15a and second densimetric separation device 15b is in direct flow communication with a first bucket elevator 3a at a respective lower inlet.

[0114] Exemplarily the respective second outlet 22 of the first 15a and second densimetric separation device 15b is in direct flow communication with a second bucket elevator 3b at a respective lower inlet.

[0115] Downstream of the second bucket elevator 3b, the plant 1 comprises a filament separation device 23.

[0116] Exemplarily, the filament separation device 23 (Fig. 5) comprises a tank 24 and a screw conveyor (not visible) for collection at the bottom of the tank 24 to convey the material to a first outlet arranged at the bottom.

[0117] A screw conveyor 25 connects the upper outlet of the second bucket elevator 3b with an inlet 28 of the filament separation device 23, positioned above the tank.

[0118] The device 23 comprises, at one end of the tank 24, a second overflow outlet arranged superiorly.

[0119] Exemplarily the filament separation device 23 comprises four (as shown in Figure 2) or two (as shown in Figure 5) pushing devices 26 arranged in an upper portion of the tank. Exemplarily each pushing device 26 is a wheel equipped with radial blades 27 and rotatable around a horizontal axis, parallel to each other. Exemplarily the blades 27 reach to a depth of approximately 65 cm.

[0120] The tank 24 is provided with a water discharge outlet located below the second outlet.

[0121] Exemplarily the plant 1 comprises a first draining device 29a arranged downstream of the first bucket elevator 3a. A screw conveyor 31 a connects the upper outlet of the first bucket elevator 3a with an inlet of the first draining device.

[0122] Exemplarily the plant 1 comprises a second draining device 29b arranged downstream of the filament separation device 23.

[0123] A screw conveyor 31 b exemplarily connects the first outlet of the filament separation device 23 with an inlet of the second draining device 29b.

[0124] Exemplarily, each draining device 29a, 29b (fig. 7) comprises a polyurethane screen 30, vibrating and inclined relative to the horizontal (e.g., at an angle between 2° and 5°). The screen 30 is micro-perforated with holes having a diameter of approximately 500 pm on the upper surface of the screen 30, wherein the cross-section of each hole enlarges moving towards the lower surface of the screen 30 (to prevent any solid particles from getting stuck in the holes). Beneath the screen 30, there is a water collection tank equipped with a submersible pump for sending the water to the filtering device 41.

[0125] Exemplarily each draining device 29a, 29b comprises an outlet for the infill material at the upper end of the screen 30. Exemplarily the plant 1 comprises a hydraulic circuit 40 comprising a filtering device 41 , a hydraulic pump (not shown), and a piping system. Exemplarily the filtering device 41 (schematically shown in fig. 6) comprises three hydraulic sock filters 45. Exemplarily the piping system fluidly connects each densimetric separation device 15a and 15b, the filament separation device 23, the granulometric separation device 10, and each draining device 29a and 29b with the hydraulic sock filters 45.

[0126] Exemplarily the hydraulic sock filters 45 comprise fabrics suitable for retaining solid particles having granulometric sizes greater than or equal to 20 pm and less than or equal to 200 pm.

[0127] In use, the plant 1 allows carrying out a method of separating an infill 100 according to the present invention, described below with reference to fig. 8.

[0128] Exemplarily the first screen has a granulometric size equal to 1400 pm, the second screen equal to 800 pm, and the third screen equal to 500 pm.

[0129] Optionally the method initially comprises removing the infill from an artificial turf carpet.

[0130] Exemplarily the method comprises pouring the infill 100 from above onto the grid 6 of the pre-screening device 5 to granulometrically pre-screen the infill in order to separate a reject fraction 110 having granulometric size greater than 2.5 mm from the infill 100. Exemplarily, the thus cleaned infill 120 is collected in the container 7 downstream of the grid 6, then conveyed towards the outlet 8 at the bottom of the container and subsequently sent from the pre-screening device 5 to the granulometric screening device 10 by means of the screw conveyor 9.

[0131] Exemplarily the method comprises, by means of the granulometric screening device 10, granulometrically screening 810 the infill 120 to subdivide the infill into four infill fractions 33, 34, 35, 36 with different granulometries and having respective contiguous and non-overlapping granulometric ranges.

[0132] To this end, after passing through the feeding inlet 11 , the infill 120 exemplarily impacts in sequence the three screens of the granulometric screening device 10.

[0133] The fraction of infill that does not pass through the through openings of the first screen corresponds to a first pure fraction 33 and exits from the first outlet 13a.

[0134] The fraction of infill that passes through the through openings of the first screen but does not pass through the through openings of the second screen corresponds to a first mixed fraction 34 and exits from the second outlet 13b.

[0135] The fraction of infill that passes through the through openings of the second screen but does not pass through the through openings of the third screen corresponds to a second mixed fraction 35 and exits from the third outlet 13c.

[0136] The fraction of infill that passes through the third screen and exits from the fourth outlet 13d corresponds to a second pure fraction 36.

[0137] Exemplarily the first pure fraction 33 comprises a weight content of the second granular material greater than or equal to 90% or 95%, and possibly the artificial grass filaments. Exemplarily the first pure fraction 33 has a granulometric size greater than or equal to 1400 pm and less than or equal to 2500 pm.

[0138] Exemplarily the first pure fraction 33 is moved from the granulometric screening device 10 directly to the filament separation device 23 via the screw conveyor 42, the bucket elevator 3b, and the screw conveyor 25.

[0139] Exemplarily the second pure fraction 36 comprises a weight content of the first granular material greater than or equal to 90% or 95%. Exemplarily, the second pure fraction 36 has a granulometric size less than or equal to 500 pm. Exemplarily the second pure fraction 36 is moved from the granulometric screening device 10 to the first dripping device 29a by means of the screw conveyor 43.

[0140] Exemplarily the first 34 and second 35 mixed fractions each comprise the first and second granular materials and typically the artificial grass filaments.

[0141] Exemplarily the first mixed fraction 34 has a granulometric size greater than or equal to 800 m and less than or equal to 1400 pm. Exemplarily the second mixed fraction 35 has a granulometric size greater than or equal to 500 pm and less than or equal to 800 pm.

[0142] Exemplarily the first 34 and second 35 mixed fractions are moved from the granulometric screening device 10 to the respective densimetric separation devices 15a, 15b by means of the respective screw conveyors 17a and 17b.

[0143] Exemplarily the method comprises separating 820 each mixed fraction of infill 34, 35 into a respective first sub-fraction of infill 37 and a respective second sub-fraction of infill 38 having different specific densities, for example by means of the respective densimetric separation devices 15a, 15b.

[0144] Exemplarily, each mixed fraction of infill 34, 35 is poured onto a central portion of the respective vibrating table 18, on which a water flow with a flow direction 20 runs. The second sub-fraction 38 moves in the same direction as the flow 20 towards the second outlet 22, and the first sub-fraction 37 moves in the opposite direction to the flow 20 towards the first outlet 21.

[0145] The first sub-fraction of infill 37 has a density greater than a predetermined threshold value, and the second subtraction of infill 38 has a density lower than the first sub-fraction 37.

[0146] Exemplarily each first sub-fraction 37 comprises a weight content of the first granular material greater than or equal to 90% or 95%. Exemplarily each of the two first sub-fractions 37 is conveyed toward the first draining device 29a, through the bucket elevator 3a and then by means of the screw conveyor 31 a.

[0147] Exemplarily each second sub-fraction 38 comprises a weight content of the second granular material greater than or equal to 90%, and possibly the artificial grass filaments. Exemplarily each of the two second sub-fractions 38 is conveyed toward the filament separation device 23 through the bucket elevator 3b and then by means of the screw conveyor 25.

[0148] Exemplarily the method comprises separating 830 the artificial grass filaments 32 from the first pure infill fraction 33 and from each second sub-fraction 38 by means of the filament separation device 23. Exemplarily the artificial grass filaments 32 constitute about 2-3% by volume and less than 1 % by weight of the material fed into the filament separation device 23.

[0149] Exemplarily the first pure infill fraction 33 and each second sub-fraction 38 are fed to the inlet 28 of the filament separation device 23 by means of the screw conveyor 25.

[0150] Exemplarily the rotating blades 27 of the thrust devices 26 push toward the outlet 14 the artificial grass filaments 32 (and possibly other residues) that float or remain suspended near the free surface of the water. The artificial grass filaments 32 are subsequently collected in a container (not shown) by means of the screw conveyor 44.

[0151] The fraction of infill that settles at the bottom of the tank 24 is therefore free of artificial grass filaments and is conveyed by the collection screw (not visible in the figures) located at the bottom of the tank 24 toward an outlet of the device 23 and from there transported to the draining device 29b by means of the screw conveyor 31 b. This fraction of infill exiting the device 23 corresponds to the first final infill fraction 39.

[0152] Exemplarily the method comprises dripping 850 the second pure fraction 36 and the first sub-fractions 37 by means of a first dripping device 29a. To this end, the second pure fraction 36 together with the first sub-fractions 37 are fed into the first dripping device 29a by means of the screw conveyor 31a, at a lower end of the respective inclined microperforated screen 30.

[0153] Exemplarily the method comprises draining 840 the first final infill fraction 39 by means of a second draining device 29b. Exemplarily, the second pure fraction 36 together with the first sub-fractions 37 are fed into the second draining device 29b by means of the screw conveyor 31b, at a lower end of the respective inclined microperforated screen 30. Exemplarily the infill is made to ascend along the screen 30 by means of vibration of the screen 30.

[0154] Exemplarily from the first 29a and the second draining device 29b, respectively, a first final drained fraction 300 and a second final drained fraction 200 are collected at the outlet (e.g., in respective containers, not shown), the first final drained fraction 300 consisting substantially (for example at least 95% or 99% by weight) of the first granular material, and the second final draining fraction 200 consisting substantially of the second granular material, both wet but associated with a modest amount of water.

[0155] Exemplarily the method further comprises filtering 860 the water 400 used in the steps of granulometrical ly screening 810, separating 820 each mixed infill fraction, separating 830 the artificial grass filaments, draining 840 the first final infill fraction, and draining 850 the second pure fraction 36 and the first sub-fractions 37.

[0156] The water 400 to be filtered is pumped into the inlet of the sleeve filters 45, at respective tops of the sleeve filters 45 (fig. 6), and flowing downward along the filters 45, the very fine solid part 401 is retained and discarded through replacement of the filters 45 themselves. Exemplarily, it is possible to detect when the filters 45 are clogged via a pressure gauge, so as to carry out their replacement. Exemplarily, the filtered water is reused in the aforementioned steps 810, 820, 830, 840, and 850 of the infill separation method, with minimal water consumption. Exemplarily, the aforementioned steps of the separation method are controlled by a control system (not shown), suitably configured by an operator.

Claims

CLAIMS1. Method of separating an infill (100) for artificial grass surfaces, wherein the infill (100) comprises a first granular material and a second granular material having a specific density different from the specific density of the first granular material, wherein said method comprises:- screening (810) the infill (100) to divide the infill (100) into a plurality of infill fractions having different granulometries, wherein said plurality of infill fractions comprises one or more mixed infill fractions (34, 35) each comprising said first and second granular material;- separating (820) each mixed infill fraction (34, 35) into a respective first infill sub-fraction (37) and a respective second infill sub-fraction (38), wherein said separating (820) comprises pouring each mixed infill fraction onto a respective vibrating table (18) and running a flow of water having a flow direction (20) over said table (18), to move said second sub-fraction (38) in accordance with said flow direction (20) and to move said first sub-fraction (37) in a direction opposite to said flow direction (20).

2. Method of separation according to claim 1 , wherein said infill fractions have respective contiguous and nonoverlapping granulometric intervals, wherein said plurality of infill fractions comprises a first pure fraction (33) comprising a weight content of said second granular material greater than 70% and having a granulometric size greater than or equal to 1000 pm, wherein said plurality of infill fractions comprises a second pure fraction (36) comprising a weight content of said first granular material greater than 70% and having a granulometric size less than or equal to 700 pm, wherein said mixed infill fractions have respective contiguous and non-overlapping granulometric size intervals, wherein said mixed infill fractions comprise a first mixed infill fraction (34) and a second mixed infill fraction (35), wherein said first mixed fraction (34) has a granulometric size greater than or equal to 500 pm and / or less than or equal to 2000 pm, wherein said second mixed fraction (35) has a granulometric size greater than or equal to 300 pm and / or less than or equal to 700 pm, and wherein said screening (810) said infill (100) is performed by means of a granulometric screening device (10).

3. Method of separation according to anyone of the preceding claims, wherein each first sub-fraction (37) comprises a weight content of said first granular material greater than 70%, wherein each second sub-fraction (38) comprises a weight content of said second granular material greater than 70%, wherein said separating (820) each mixed infill fraction (34, 35) is performed by means of a respective densimetric separation device (15a, 15b) comprising said respective vibrating table (18), wherein said vibrating table (18) is inclined with respect to a horizontal plane, wherein said flow direction (20) forms, with its projection on a horizontal plane, an angle greater than or equal to 2° and less than or equal to 10°.

4. Method of separation according to anyone of the preceding claims, wherein said infill (100; 33; 38) comprises artificial grass filaments, wherein the method comprises separating (23) said artificial grass filaments (32) from said infill (100; 33; 38) by means of:- introducing said infill (100; 33; 38) into a tank (24) filled with water;- pushing said filaments (32) that float or remain suspended near the water surface, andcollecting a first final infill fraction (39) that settles at the bottom of the tank, and wherein the method comprises, after said screening (810) and said separating (820) each mixed fraction, draining (840, 850) said infill (100; 36, 37; 39) to obtain a first (300) and / or a second final drained fraction (200) by introducing said infill (100; 36, 37; 39) into one or more draining devices (29a, 29b) at a lower portion of a micro-perforated inclined screen (30) and moving said infill (100; 36, 37; 39) up along said screen (30) by vibrating said screen (30), and wherein the method comprises collecting said first (300) and / or second final drained infill fraction (200).

5. Plant (1) for separating an infill (100) for artificial grass surfaces, wherein said plant comprises:- a granulometric screening device (10) to divide the infill (100) into a plurality of infill fractions having different granulometries, wherein said plurality of infill fractions comprises one or more mixed infill fractions (34, 35) each comprising said first and second granular material.- one or more densimetric separation devices (15a, 15b), each densimetric separation device (15a, 15b) being connected to said granulometric screening device (10) to separate a respective mixed infill fraction of said one or more mixed infill fractions (34, 35) into a respective first infill sub-fraction (37) and a respective second infill sub-fraction (38), wherein each densimetric separation device (15a, 15b) comprises a vibrating table (18) and a hydraulic circuit (19) to generate a flow of water running over said table (18) along a flow direction (20).

6. Plant (1) for separating according to claim 5, wherein said granulometric screening device (10) comprises a feed inlet (11), a plurality of outlets, and a plurality of screens each having a different granulometric size and arranged in a vertically stacked sequence of decreasing granulometry, wherein a first screen of said plurality of screens has a granulometric size greater than or equal to 1000 m and / or less than or equal to 2000 pm, wherein a second screen of said plurality of screens has a granulometric size greater than or equal to 500 pm and / or less than or equal to 1200 pm, wherein a third screen of said plurality of screens has a granulometric size greater than or equal to 300 pm and / or less than or equal to 700 pm, wherein said feed inlet (11 ) is located upstream of said first screen, wherein a first (13a), second (13b), and third (13c) outlet is located upstream of said first, second, and third screen respectively, and wherein a fourth outlet (13d) is located downstream of said third screen, wherein said granulometric screening device (10) comprises a vibration system structured to vibrate said plurality of screens at ultrasonic frequencies, wherein said granulometric screening device (10) comprises a first cleaning system for said plurality of screens structured to mechanically tap each screen of said plurality of screens at ultrasonic frequencies, wherein said granulometric screening device (10) comprises a second cleaning system comprising, for each screen, a perforated sheet arranged below said each screen and supporting a plurality of plastic beads, wherein said vibration system is structured to vibrate said perforated sheet, and wherein said second cleaning system comprises, for each screen, a plurality of nozzles to spray pressurized water onto an upper surface of said respective screen.

7. Plant (1) for separating according to anyone of claims from 5 to 6, wherein each densimetric separation device (15a, 15b) comprises a first (21) and a second outlet (22), wherein each densimetric separation device (15a, 15b) is configured to move said respective first infill sub-fraction (37) toward said first outlet (21) and said respective second infill sub-fraction (38) toward said second outlet (22), wherein said vibrating table (18) is micro-perforated at opposite ends along said flow direction (20), wherein said vibrating table (18) is inclined with respect to a horizontal plane,wherein said flow direction (20) forms, with its projection on a horizontal plane, an angle greater than or equal to 2 and less than or equal to 10°.

8. Plant (1) for separating according to anyone of claims from 5 to 7, comprising a filament separation device (23) comprising a tank (24) filled with water, a screw conveyor at the bottom of said tank, and one or more pushing devices (26) located at the water surface and configured to generate a surface water flow, wherein each pushing device (26) is a wheel equipped with radial blades (27) and rotatable around a horizontal axis, wherein said blades (27) dip into the water to a depth greater than or equal to 40 cm and / or less than or equal to 80 cm.

9. Plant (1) for separating according to anyone of claims from 5 to 8, comprising a first (29a) and a second draining device (29b) located downstream of said one or more densimetric separation devices (15a, 15b), wherein each draining device (29a, 29b) comprises a vibrating micro-perforated inclined screen (30).

10. Plant (1) for separating according to anyone of claims from 5 to 9, comprising a hydraulic circuit (40) comprising a filtering device (41) comprising one or more sock hydraulic filters (45), and a hydraulic pump, wherein said hydraulic circuit (40) fluidly connects each densimetric separation device (15a, 15b), and / or said filament separation device (23) and / or said granulometric separation device (10) and / or each draining device (29a, 29b), with said filtering device (41), wherein said sock hydraulic filters (45) comprise meshes suitable for retaining solid particles having granulometric sizes greater than or equal to 20 pm, and / or less than or equal to 200 pm.

Images