System and method for cleaning and sorting sheets

Abstract

System for food safe cleaning and sorting sheets of paper or plastic (3), comprising an infeed module (90), a scanning module (160), a sorting module (120), at least one cleaning module (150) and conveying means (200) connecting the infeed module, the scanning module, the cleaning module and the sorting module, wherein the infeed module is arranged to receive a stack of sheets and to remove a single sheet (3) from said stack and transfer said removed sheet to the conveying means (200), wherein the conveying means are arranged for moving the sheet (3) from the infeed module (90), to the cleaning module (150), to the scanning module (160) and to the sorting module (120), subsequently, wherein the cleaning module (150) comprises at least one cleaning unit arranged to clean at least one surface of said sheet, wherein the scanning module (160) is arranged to scan the sheet and generate scan imaging data of said sheet (3), wherein the system is arranged to, based on the scan data and one or more predefined damage threshold values, generate sorting data comprising at least information to assign a sheet (3) to one or more of at least two categories, wherein the sorting module (120) is arranged to receive sheets (3) from the scanning module (160) and sorting data and to, based on the sorting data, sort the sheets (3).

Description

[0001] SYSTEM AND METHOD FOR CLEANING AND SORTING SHEETS

[0002] The present invention relates to a system and method for cleaning and sorting sheets of paper or plastic.

[0003] In the production of beverage cans, as well as other cans, empty cans are typically produced in a can factory without attached lids. The open-topped cans are then transported to a separate filling factory. To save space, the open-topped cans are typically stacked, with interlayer sheets placed between each layer of cans. Such interlayer sheets are typically sheets of paper, cardboard or plastic. As the cans are transported without lids, it is preferable that contaminants are not introduced into the cans during transport, or at any other point during handling. The interlayer sheets are in principle suited for re-use, but may be damaged and / or contaminated after use. To select used interlayer sheets suitable for re-use, the sheets are typically sorted and checked by hand. In addition, to ensure the sheets are sufficiently clean to be food save, the sheets may be cleaned. However, this process is labour intensive, and does not always result in reliable sorting and / or cleaning.

[0004] It is a goal of the present invention, next to other goals, to at least partially solve at least one of the above mentioned problems and / or to provide an improved system for cleaning and sorting sheets of paper or plastic.

[0005] This goal, amongst other goals, is met by a system according to claim 1, more specifically by a system for food safe cleaning and sorting sheets of paper or plastic, comprising an infeed module, a scanning module, a sorting module, at least one cleaning module and conveying means connecting the infeed module, the scanning module and the cleaning module and the sorting module, wherein the infeed module is arranged to receive a stack of sheets and to remove a single sheet from said stack and transfer said removed sheet to the conveying means, wherein the conveying means are arranged for moving the sheet from the infeed module, to the cleaning module, to the scanning module and to the sorting module, subsequently, wherein the cleaning module is arranged to clean at least one surface of said sheet, wherein the scanning module is arranged to scan the sheet and generate scan imaging data of said sheet, wherein the system is arranged to, based on the scan data and one or more predefined damage threshold values, generate sorting data comprising at least information to assign a sheet to one or more of at least two categories, wherein the sorting module is arranged to receive sheets from the scanning module and sorting data and to, based on the sorting data, sort the sheets. Herein, food safe is defined as being sufficiently clean to meet the applicable standards for food safety. Food safe cleaning of sheets of paper and plastic in particular is defined as cleaning at least part of said paper or plastic sheets in such a way that contaminants that harm food safety are at least partially removed.

[0006] The above method beneficially allows for the automated cleaning of interlayer sheets of paper or plastic (“sheets”), as well as allowing for automated sorting of sheets based on predefined damage criteria, which can be expressed by damage threshold values. It will be appreciated that, while the above system is particularly effective for use with interlayer sheets, the above system can be used for any sort of sheets, not only interlayer sheets, or necessarily sheets of paper or plastic.

[0007] It will be appreciated that the above system can also be used only for cleaning, preferably food safe cleaning, sheets without also sorting the sheets, or alternatively for example for only sorting the sheets without cleaning the sheets. For such more limited applications, the cleaning module and / or the scanning module, and / or the sorting module can be omitted from the system. For example, a system without the scanning module and / or without the sorting module can be used for cleaning sheets. In another example, a system without the cleaning module can be used for scanning and sorting sheets. In yet another example, a system without the sorting module can be used for only scanning, and optionally also cleaning sheets. In yet another example, a system without the scanning module can be used for cleaning the sheets, and / or for sorting the sheets based on for example the total number of sheets provided to the system, instead of characteristics of individual sheets.

[0008] Preferably, the sheets are provided in a substantially horizontal orientation, and wherein the sheets travel through the system in a substantially horizontal trajectory. This allows for a simple layout of the system, and in particular a simple layout of the conveying means. In addition, this ensures that sheets arrive in the sorting module in the same orientation as the orientation in which the sheets are provided to the infeed module, improving further processing of the sheets.

[0009] Preferably, one of the at least two categories is representative for accepted sheets, and another one of the at least two categories is representative for rejected sheets. This allows for an efficient processing of the sheets, ensuring that at least a supply of accepted sheets is provided by the system for further processing. In addition, as mentioned above, the threshold values determining whether sheets are, for example, rejected or accepted can be adjusted. This allows the system to be configured for particular and varying applications and requirements. Preferably, the system is arranged to use image recognition technology to generate sorting data based on the scan imaging data. Image recognition provides a reliable and adjustable method for generating sorting data based on the scan imaging data, and does not require continuous human supervision during operation.

[0010] Preferably, the sorting data comprises information representative of one or more of: individual tear length, total tear length, number of tears, number of missing sheet corners, sheet shape, overall sheet length, overall sheet width, sheet circumference, holes, sheet edge damage, vertical variations, imprints, stains, sheet corner radius. Any one of the above characteristics represents types of damage that sheets may incur during use, handling, transportation, etcetera. In addition, for differing applications, different types and degrees of damage may or may not be acceptable. Providing the above plurality of optional information to be included in the sorting data allows for ample configurability and adjustability of the sorting system. In addition, different types of sheets, for example the aforementioned paper or plastic sheets, may incur damage in different ways and to different degrees. The above information types thus also allow the system to be reconfigured for different types of sheets.

[0011] The cleaning module preferably comprises at least one cleaning unit. Preferably, a cleaning unit comprises an antistatic cleaning unit, wherein the antistatic cleaning unit is arranged to change the electrical charge of the sheets passing through the cleaning module and / or particles or other objects or substances present on the surface of the sheets. Antistatic cleaning beneficially allows for the sheets to be cleaned without contacting the sheets with the cleaning unit. This beneficially helps to prevent cross contamination of sheets, wherein contaminants removed from one sheet by the cleaning unit are reapplied to any subsequent sheets.

[0012] Preferably, the cleaning module is arranged after the infeed module. Having the cleaning module as the first module through which sheets fed into the system by the infeed module pass prevents contaminants from entering further into the system, improving overall cleanliness.

[0013] It will further be appreciated that the cleaning module described herein can also be used outside of the context of the system described herein, in different processes.

[0014] Preferably, a cleaning unit comprises at least one inlet for compressed gas, at least one nozzle comprising at least one outlet for expelling compressed gas, and at least one array of electrodes comprising at least one electrode arranged to generate an electric field, wherein at least part of the gas is electrically charged by the electric field. This cleaning unit thus allows for compressed gas to be directed against the sheets to remove at least some contaminants. The electric field further preferably at least partially electrically charges at least part of any contaminants on the sheets, and / or at least part of the sheets passing by the cleaning module. The electric charge reduces the adherence of at least some contaminants present on the sheets, allowing for improved removal of said at least some contaminants.

[0015] Preferably, the cleaning unit further comprises at least one suction inlet connected to a vacuum source for generating suction, wherein the at least one suction inlet is arranged to remove at least part of the expelled gas. This allows the expelled gas to collect contaminants from the sheet, which is then at least partially evacuated through the suction inlet. The suction inlet preferably connects to a filtering means to collect contaminants collected by the suction inlet.

[0016] Preferably, the at least one nozzle comprises a nozzle body rotatably arranged in the cleaning unit. The rotatable nozzle body allows the nozzle to move, in order to direct the gas expelled from the nozzle body across a larger area, increasing the coverage of the sheet by compressed gas, which improves the removal of contaminants from the sheet.

[0017] Preferably, the nozzle body comprises at least one outlet arranged in a direction that is offset from the axis of rotation of the nozzle body and at an oblique angle to said axis of rotation. This results in the compressed gas that exits the at least one outlet generating a force vector that induces a rotating motion in the nozzle body. This allows the rotating movement of the nozzle body to be at least partially induced by the gas exiting the nozzle body. Preferably, the rotating motion of the nozzle body is entirely induced by the gas exiting the nozzle body.

[0018] Preferably, the cleaning unit comprises a row of nozzles and at least one array of electrodes arranged substantially perpendicular to said row of nozzles. This allows for a compact arrangement of the cleaning unit.

[0019] Preferably, the at least one array of electrodes comprises one rod-shaped electrode. This simplifies the construction of the cleaning unit.

[0020] Preferably, at least one nozzle is arranged on a first side of a suction inlet, and wherein at least one electrode is arranged on a second side of said suction inlet, opposite the first side.

[0021] Preferably, wherein the at least one array of electrodes extends along substantially the entire width of the conveying means. Preferably, the width of the conveying means corresponds substantially to the width of sheets to be used in the system, said width being defined as the distance between the edges of the sheet in a direction perpendicular to the direction of travel of the sheet past the cleaning module. This ensures a complete coverage of the sheets by the at least one array of electrodes.

[0022] Preferably, the one or more suction inlets extend substantially along the entire width of conveying means. This ensures a complete coverage of the sheets by the one or more suction inlets, ensuring that contaminants are removed from substantially the entirety of at least one surface of the sheet.

[0023] Preferably, the system further comprises two longitudinal arrays of electrodes, preferably two rodshaped electrodes, being arranged on either side of the row of nozzles and substantially parallel to the conveying surface. As a result, the sheet is subjected to an electrical field both before and after passing the nozzles of the cleaning unit, improving the effectiveness of the cleaning of the sheet.

[0024] Preferably, the system comprises at least two suction inlets, and wherein at least one suction inlet is arranged on each side of the row of nozzles, wherein the at least one suction inlet is further arranged between an array of electrodes and the row of nozzles. This increases the proportion of the compressed gas expelled by the nozzles that is collected by the suction inlets. As the expelled gas collects contaminants from the sheet, increasing the amount of gas that is evacuated by the suction inlets increases the amount of contaminants removed from the sheet.

[0025] Preferably, electrode shrouds are arranged around each array of electrodes, enclosing said array of electrodes substantially at least three and at most five sides. This protects the electrodes, as well as operators in the vicinity of the electrodes.

[0026] Preferably, the system comprises one cleaning unit, said one cleaning unit being arranged above the trajectory of the sheets, wherein said cleaning module is arranged to substantially only clean the topside of sheets passing the cleaning module. This is beneficial for the described application of cleaning (interlayer) sheets, as only the top surfaces of the sheets collect contaminants, while the bottom surfaces of interlayer sheets remain sufficiently clean during use. Thus, cleaning only the top surface of sheets allows for a more economical processing of the sheets.

[0027] In another embodiment, the cleaning module comprises at least two cleaning units, wherein at least a first cleaning unit is arranged above the trajectory of the sheets passing the cleaning module, and wherein at least a second cleaning unit is arranged below the trajectory of the sheets passing the cleaning module, wherein the cleaning module is arranged to substantially clean both the topside and the underside of sheets passing the cleaning module. This beneficially allows both sides of the sheets to be cleaned.

[0028] Preferably, the cleaning unit further comprises a cover comprising at least two openings, arranged between the at least one nozzle and the conveying surface. Said cover preferably comprises a perforated plate, and / or a grille comprising wires. This cover prevents the sheets from entering the cleaning module, for example as a result from being sucked into the cleaning module.

[0029] Preferably, the distance between the cleaning unit and the conveying surface is adjustable. This allows the position of the cleaning unit relative to the conveying surface, and thus relative to sheets passing the cleaning unit, to be adjusted. Adjusting the position of the cleaning module also impacts the efficacy of the cleaning module in cleaning the sheets. In addition, some sheets may be bent or dented. Increasing the distance between the cleaning module and the conveying surface increases the clearance between the conveying surface and the cleaning module, through which the sheets pass. Increasing said clearance prevents sheets, in particular bent or dented sheets, from being caught between the cleaning module and conveying means.

[0030] Preferably, the system further comprises a double sheet detection module, arranged to receive a sheet, and wherein the double sheet detection module is arranged to determine whether a single sheet has been received from the infeed module or a stack of more than one sheets, wherein the double sheet detection module is further arranged to transfer a single sheet and reject a stack of more than one sheets, wherein the double sheet detection unit comprises an outlet for transferring single sheets and an outlet for expelling stacks of more than one sheet. If double sheets are allowed to pass further into the system, such as through the scanning module and / or sorting module, said double sheets may for example be caught in any of the mentioned modules, or elsewhere in the system.

[0031] It will be appreciated that the double sheet detection unit described herein can also be used outside of the context of the system described herein, for example in other processes where it is beneficial to have the capability to detect double sheets.

[0032] It will further be appreciated that multiple relative positions of the cleaning module, double sheet detection module and scanning module are possible, each with different advantages and disadvantages. For example, if the cleaning module is positioned after the double sheet detection module, instead of before the double sheet detection module, it can be prevented that double sheets enter the cleaning module, reducing the risk of double sheets being caught between the conveying surface and the cleaning module. This then allows the cleaning module to be positioned closer to the conveying surface, improving the cleaning action of the cleaning module.

[0033] Preferably, the double sheet detection module is arranged between the cleaning module and the scanning module, wherein the double sheet detection module is arranged to transfer single sheets to the scanning module. This prevents double sheets from being transferred to the scanning module and beyond. As the scanning module can only properly scan single sheets, it is only possible to generate accurate sorting data from single sheets. 4

[0034] Preferably, the double sheet detection module comprises an electrode and a sensor arranged on opposite sides of the trajectory of a sheet passing through the double sheet detection module, wherein said electrode is arranged to transmit an electric signal to a sheet or a stack comprising more than one sheets passing through the double sheet detection unit, and wherein said sensor is arranged to measure the electric signal transmitted through the sheet or stack comprising more than one sheet, and wherein the double sheet detection module is arranged to transfer or reject the sheet or stack comprising more than one sheet based on the measured electric signal. Preferably, the electric signal comprises an electric current with a predetermined input voltage, and wherein the sensor is arranged to measure the voltage of the electric current transmitted through the sheet or stack comprising more than one sheet, and wherein the double sheet detection module is arranged to transfer a sheet or a stack comprising more than one sheets if the measured voltage exceeds a predetermined threshold voltage value, and reject a sheet or a stack comprising more than one sheet if the measured voltage is lower than the threshold voltage value. Preferably, the threshold voltage value is set lower than the input voltage minus the voltage drop of a single sheet, and higher than the input voltage minus the voltage drop of a stack comprising two sheets. This provides a simple and reliable means to determine whether single or double (or triple, quadruple, etcetera) sheets pass through the double sheet detection module.

[0035] Preferably, the double sheet detection module comprises a conveying track to transfer accepted (i.e. single) sheets through the double sheet detection module, and a diversion track to divert rejected sheets away from the conveying track. Thus, a continuous track for single sheets through the double sheet detection module is provided. This simplifies the system, and in particular the double sheet detection module.

[0036] Preferably, the double sheet detection module comprises diversion means to divert sheets from the conveying track to the diversion track. This allows double sheets to be diverted from the main conveying track. Preferably, the diversion means comprises a movable flap extending along the width of the conveying track, wherein the movable flap is movable between a closed position, wherein sheets traveling on the conveying track pass by the movable flap, and an open position wherein the movable flap extends into the trajectory of sheets traveling on the conveying track to divert sheets traveling on the conveying track to the diversion track. This provides a simple and reliable means to divert double sheets from the main conveying track.

[0037] Preferably, the system further comprises a stacking unit to stack sheets on a pallet, wherein the diversion track is arranged to transfer sheets to the stacking unit. Having the diverted, rejected, double sheets be stacked onto a pallet allows for easy and efficient removal of double sheets from the system.

[0038] Preferably, the infeed module comprises one or more engaging means for engaging a top sheet of a collection of one or more sheets in the infeed module, wherein the infeed module is further arranged to transfer sheets engaged by the engaging means to the conveying means.

[0039] It will be appreciated that the infeed module described herein can also be applied outside of the context of the system described herein, for purposes other than the cleaning and sorting of sheets.

[0040] Preferably, the engaging means comprise one or more movable suction devices arranged to engage a top sheet of a stack of sheets in the infeed module and to lift the top sheet upwards. Suction devices provide a reliable means to engage the flat surface of a sheet.

[0041] Preferably, the infeed module further comprises an infeed nozzle comprising an inlet and an outlet for pressurized gas, arranged to direct a jet of pressurized gas against an edge of the lifted top sheet to release any additional sheets adhering to the lifted top sheet. This improves the separation of the top sheet from sheet below.

[0042] Preferably, the nozzle comprises an electrode arranged to generate an electric field, wherein at least part of the gas passing through the infeed nozzle is electrically charged by the electric field. This electrically charged gas, as well as optionally the electric field, electrically charges the sheets, reducing the adherence between the sheets, thereby allowing for better separation of the sheets.

[0043] Preferably, the one or more movable suction devices are arranged to travel between a lowered position and a lifted position, and wherein the system is configured to activate the jet of pressurized gas only after the one or more movable suction devices have moved towards the lifted position. Preferably, the system is configured to lift and lower the one or more movable suction devices cyclically, and to activate and deactivate the jet of pressurized gas cyclically, wherein the jet of pressurized gas is deactivated after lifting the one or more movable suction devices. This reduces the consumption of pressurized gas, and prevents a flow of pressurized gas from disturbing the operation of the infeed module when the pressurized gas is not beneficial to separate the sheets.

[0044] Preferably, the infeed module comprises at least one pushdown member arranged adjacent to the one or more movable suction devices, wherein the at least one pushdown member comprises a tip extending downwards to a point higher than the location of a movable suction device when the movable suction device is in the lowered position, and to a point lower than the location of a movable suction device when the movable suction is in the lifted position. This pushdown member induces a bend in the engaged top sheet, as well as in any sheets adhering to the top sheet. This helps to separate the top sheet from any sheets below.

[0045] Preferably, the infeed module comprises at least two pushdown members arranged on opposing sides of the one or more movable suction devices. This improves the separating action of the bend applied to the top sheet, as well as to any sheets adhering to the top sheet.

[0046] Preferably, the one or more movable suction devices are arranged on a carrier, wherein the carrier is slidably arranged in the infeed module to move to and from the conveying means, wherein the infeed module further comprises an actuator arranged to move the carrier to and from the conveying means. This simplifies the infeed module, and increases the speed and efficiency of the infeed process.

[0047] Preferably, all sheets transferred to the scanning module are further transferred to the cleaning module. This ensures that the sheets introduced into the system by the infeed module are cleaned as soon as possible, to prevent contaminants from spreading into the system beyond the cleaning module.

[0048] Preferably, the system comprises at least two sorting modules, wherein a first sorting module is arranged to receive sheets from the cleaning module and, based on the sorting data, retain a sheet or transfer a sheet, wherein a second sorting module is arranged to receive transferred sheets from the first sorting module and, based on the sorting data, retain a sheet or transfer a sheet. This allows for sorting modules with substantially identical hardware to be used. Preferably, if the second sorting module is the last sorting module, the second sorting module retains all sheets it receives. Preferably, either one of the first or the second sorting module is arranged to, based on the sorting data, retain rejected sheets and transfer accepted sheets, and wherein the other one of the first or the second sorting module is arranged to, based on the sorting data, retain accepted sheets and transfer rejected sheets.

[0049] Preferably, the system comprises at least three sorting modules, wherein the second sorting module is arranged to transfer sheets, based on the sorting data, to the third sorting module, wherein the third sorting module is arranged to, based on the sorting data, retain a sheet or transfer a sheet. This increases the categories of sheets that can be sorted to three.

[0050] In an embodiment, the system may comprise more than three interconnected sorting modules, wherein a first sorting module is arranged to receive sheets from the cleaning unit and, based on the sorting data, retain a sheet or transfer a sheet to a second sorting module, wherein the second sorting module and at least two subsequent sorting modules are arranged to receive sheets from another sorting module and, based on the sorting data, retain a sheet or transfer a sheet. In this way, theoretically any number of sorting modules can be used to sort the sheets into as many categories.

[0051] Preferably, the two or more sorting modules are arranged in series. This allows for a simple arrangement of the system.

[0052] Preferably, at least one sorting module is configured to retain rejected sheets and at least one sorting module is configured to retain accepted sheets, and wherein the one or more additional sorting modules may be selectively configured to retain accepted or rejected sheets, wherein the configuration of individual sorting modules may be changed during sorting. This allows one or more sorting modules to serve as a buffer for another sorting module when it is full. While the full sorting module is emptied, the buffer module takes over the role of the full module in the sorting process. When the full module is emptied, it may retake the sorting role from the buffer module, or alternatively become the buffer module.

[0053] Preferably, the system is configured to categorize the scanned sheets into two or more categories in the sorting data, and wherein each sorting module may be selectively configured to retain any category of sheets.

[0054] Preferably, at least one sorting module is arranged to stack retained sheets onto a pallet. Preferably, all sorting modules are arranged to stack retained sheets onto a pallet. This allows for an efficient emptying of the sorting module, as all sheets can be taken out of the sorting module in a single operation.

[0055] Preferably, the system further comprises an outfeed conveyor arranged to receive pallets from the one or more sorting modules and transfer the pallets to a pallet outfeed. This provides a single collection point for pallets, allowing for a compact arrangement of the system.

[0056] In an embodiment, the outfeed conveyor is further arranged to receive pallets from the double sheet detection module and transfer the pallets to a pallet outfeed.

[0057] Preferably, the system further comprises a pallet dispenser module arranged to receive one or more pallets and dispense the pallets to the one or more sorting modules. This allows for an automated provision of empty pallets to the sorting modules, so that the sorting modules can continue to sort sheets and stack said sheets onto pallets.

[0058] Preferably, the system further comprises a pallet shuttle conveyor arranged to transfer pallets from the pallet dispenser to the one or more sorting modules. The shuttle conveyor is preferably arranged for movement of pallets in more than one direction. This provides for a flexible means of moving pallets using the shuttle conveyor.

[0059] Preferably, the pallet shuttle conveyor is further arranged to transfer pallets from the pallet dispenser to the double sheet detection module. This allows for an automated provision of empty pallets to the double sheet detection module.

[0060] Preferably, the infeed module is arranged to transfer empty pallets to the pallet dispenser. This allows emptied pallets to then be reused in the system, for example in the double sheet detection module or a sorting module. Preferably, the shuttle conveyor is arranged to transfer pallets from the infeed module to the pallet dispenser

[0061] In a preferred embodiment, the shuttle conveyor is arranged to receive pallets from the double sheet detection module and transfer the pallets to a pallet outfeed. This allows for an efficient removal of double sheets from the double sheet detection unit.

[0062] Preferably, the system further comprises one or more top frame dispensers arranged adjacent to the outfeed conveyor, wherein the one or more top frame dispensers are arranged to apply a top frame to a stack of sheets. This allows for an automated application of top frames to the stacks of sheets. Said top frames serve to protect the stacks of sheets during handling.

[0063] It will be appreciated that the pallet dispenser, pallet shuttle conveyor, either in combination or separately, can also be used outside of the context of the system described herein.

[0064] Another aspect relates to a method for food safe cleaning and sorting sheets of paper or plastic, using a system as described above.

[0065] The description is further elucidated by means of the following figures:

[0066] Figure 1 : shows an overview of the sorting system;

[0067] Figures 2A-C: show the infeed module 90 in different perspectives;

[0068] Figure 3: shows sheets 3 being fed into the sorting line;

[0069] Figure 4: shows a side view of the double sheet detection module;

[0070] Figure 5: shows a top view of the cleaning module;

[0071] Figure 6: shows a side view of the cleaning module;

[0072] Figure 7: shows a cross section of the cleaning module in perspective;

[0073] Figure 8: shows a cross section of the cleaning module from the side; and Figures 9A-C: show an overview of a sorting module.

[0074] Figure 1 shows an overview of the sorting system 1. The shown embodiment comprises two parallel sheet sorting lines 300a, b, each comprising a conveyor 200 comprising a sheet loading point 10 where stacks of sheets to be sorted are loaded into the sorting system, preferably these stacks of sheets are held on a pallet. The pallets of sheets 2 are then transferred towards the infeed module 90, where individual sheets 3 are taken from the top of the stack. The sheets 3 are then transferred towards the cleaning module 150 which cleans the sheets 3. The cleaned sheets are then transferred by the conveyor 200 towards the double sheet detection module 100. In some cases, multiple sheets remain stuck together, and more than one sheet may be taken off from the top of the stack in the infeed module 90. These double sheets, or in some cases more than two sheets that are stuck together, are recognized by the double sheet detection module 100 and removed from the conveyor 200. Cleaned, single sheets 3 are then transferred by the conveyor 200 from the double sheet detection module 100 to the scanning module 160 where both the top side and the bottom side of each sheet are scanned, preferably by means of one or more cameras imaging the sheets 3 to obtain scans. Image recognition technology is then used on the scans of the top and bottom of each sheet to identify different types of damage, and the system then quantifies the identified damage. Based on the quantified damage and one or more threshold values for the different types of damage, each scanned sheet 3 is categorized in one or more of at least two categories. For example, sheets may be simply categorized in “accepted” if the damage is within limits, or “rejected” when the damage exceeds one or more damage limits. In other examples, sheets may be categorized in more than two categories, for example based on types of damage, or levels of damage, or other characteristics. The scan data is then compiled into sorting data containing the mentioned information, and sent to the sorting modules.

[0075] Scanned sheets 3 are then transferred towards, in the shown embodiment, three sorting modules 120. The sorting modules 120 receive the sorting data, and, based on said sorting data either retain a sheet or transfer a sheet to a subsequent sorting module 120. The sorting modules are therefore flexible in which category of sheets each sorting module retains. For example, the first sorting module 120A may retain and stack rejected sheets and transfer accepted sheets to the second sorting module 120B. The second sorting module may then retain and stack accepted sheets. In this example, no sheets are thus transferred to the third module 120C. However, the sorting modules may be configured such that one of the three sorting modules 120 serves as an overflow module 120. For example, if one of the sorting modules 120 approaches full, meaning that the stack of sheets 3 approaches the maximum stack size, additional sheets 3 may be transferred to the overflow module 120, such that the full sorting module 120 may be emptied. The emptied sorting module 120 may after emptying then function as the overflow module 120 when another sorting module 120 reaches the maximum stack size.

[0076] The sorting modules 120 are arranged to stack retained sheets 3 onto pallets 2. In addition, the sorting modules 120 are arranged to transfer pallets 2 of sheets 3 to the outfeed conveyor 400 by means of transfer conveyors 40, which are preferably drive chain conveyors 40. Pallets 2 are transferred by the outfeed conveyor 400 towards the outfeed point 30 where the pallets 2 may be removed from the system, for example by a forklift (not shown). Optionally, top frame dispensers 130 may be arranged next to the outfeed conveyor 400 to place a top frame onto the stacks of sheets 3 being transferred on the outfeed conveyor 400. In the shown embodiment, the top frame dispensers 130 are robot arms 130 provided with a stack of top frames to place onto the stacks of sheets 3. Optionally, a wrapping station 30 may be arranged on the outfeed conveyor to apply a plastic wrapping to the stacks of sheets 3 being transferred on the outfeed conveyor 400.

[0077] Optionally, a pallet shuttle 80a, b may be provided for each sorting line 300a, b, in combination with a pallet dispenser 70a, b. The pallet dispenser 70 provides empty pallets 2 which are transported on the pallet shuttle 80, which is in the shown embodiment a conveyor similar in arrangement to the outfeed conveyor 400, towards the sorting modules 120. The pallet dispenser 70 receives stacks of empty pallets 2 through the pallet dispenser infeed 701a, b. The double sheet detection module 90 is additionally coupled to the pallet shuttle 80, and is arranged to transfer full pallets 2 containing stacks of removed double sheets onto the pallet shuttle 80. These pallets 2 are then transferred by the pallet shuttle towards the double sheet outfeed 81a, b to be removed, for example using a forklift. The infeed module 90 may additionally be connected to the pallet shuttle 90, and arranged to transfer emptied pallets onto the pallet shuttle 80, so that a new pallet with sheets 2 to be sorted may be loaded into the infeed module 90. The emptied pallets 2 may be transferred to the pallet outfeed 81 and removed, or into the pallet dispenser 70 to be reused to stack sorted sheets 3 onto in the sorting modules 120.

[0078] Figures 2A-C show the infeed module 90 in different perspectives. In figure 2 A the infeed module 90 is shown from the side. The infeed module 90 comprises a pallet lift 97 arranged to receive a pallet 2 of sheets 3 and to lift said pallet of sheets upwards to gradually feed the sheets 3 into the infeed mechanism. A pallet 2 is shown on the pallet lift 97, as well as a pallet outline 2’, shown in an uppermost position towards which it can be lifted by the pallet lift 97. The infeed mechanism comprises two movable primary suction devices 91, which are arranged to move up and down in direction Dp. The primary suction devices are preferably suction cups 91 which are connected to a vacuum source. The primary suction devices 91 move downwards onto the top sheet 3 of a provided stack of sheets 3 and connect to the top sheet through suction. The primary suction devices 91 then move upwards to pull the sheet 3 upwards and off the stack. Secondary suction devices 93 are provided, which are preferably suction cups that are connected to a vacuum source. When a sheet 3 is pulled off the stack by the primary suction devices 91, the secondary suction devices 93 are arranged to connect to the lifted sheet 3. When the secondary suction devices 93 connect to the sheet 3, the primary suction devices 91 may disconnect from the sheet. The secondary suction devices 93 are attached to a movable carrier 95 which is arranged to slide back and forth in direction Din. When a sheet 3 is lifted up by the suction devices 91, connected to the secondary suction devices 93 and then disconnected from the primary suction devices 91, the carrier 95 moves towards the conveyor (not shown) to push the top sheet 3 into the conveyor. An actuator 96 is connected between the carrier 95 and the frame of the infeed module to move the carrier 95. The actuator 96 in the shown embodiment is comprised by a pneumatic cylinder, but other types of linear actuators known in the art may also be applied.

[0079] A nozzle 94 is provided to direct a jet of pressurized gas, preferably air, towards the edge of a lifted sheet 3. Preferably, the jet of pressurized gas is electrically charged to reduce static electricity buildup in the sheets and particles and other materials adhering to the surface of the sheets 3. The jet of pressurized gas being directed at the edge of the lifted sheet 3 serves to separate the top sheet 3 from any sheets 3 that may inadvertently stick to the top sheet, thereby helping to prevent more than one sheet being fed into the conveyor at a time.

[0080] Two pushdown members 92 are also provided on opposite sides of the two primary suction devices 91. In the perspective shown in figure 2 A, the pushdown members 92 overlap with the primary suction devices 91. The pushdown members 92 are arranged to protrude downwards below the maximum height of the primary suction devices 91. Thus, the pushdown members push the outsides of a sheet 3 downwards as the sheet is lifted by the primary suction devices 3, thereby applying a curvature to the sheet 3. This bending additionally helps to separate the top sheet 3 from any sheets stuck to the bottom of the top sheet 3.

[0081] Figure 2B shows a top view of the infeed module 90. The pushdown members 92 can be seen to be provided on opposing sides of the primary suction devices 91. The secondary suction devices 93 can be seen to be provided at the same mutual distance as the pushdown members 92. As the pushdown members 92 are provided in a fixed position, the parts of the lifted sheet 2 contacting the pushdown members 92 is also at a constant height for each lifting cycle. Placing the secondary suction devices 93 as far apart as the pushdown members 92 therefore ensures that the contact points on each sheet 2 where the secondary suction devices 93 engage the sheet are at approximately the same height for each cycle, meaning each sheet lifting operation. This improves reliability of the engagement of the secondary suction devices 93 with the sheets 3. Conveying means 971 are also shown to be provided, and arranged to transfer empty pallets in a direction perpendicular to the infeed direction Din, in the present embodiment the conveying means 971 are arranged to transfer empty pallets onto the pallet shuttle (not shown).

[0082] Figure 2C shows a rear view of the infeed module 90. In particular the conveying means 971 are shown in more detail. The other components are as described above.

[0083] Figure 3 shows sheets 3 being fed into the sorting line by the infeed module 90 in more detail. In the figure a top sheet 3a has been picked up and lifted upwards by the primary suction devices 91. The pushdown members 93 can be seen to push the sides of the lifted sheet 3a downwards to induce a bend in the sheet. A second sheet 3b is shown to partially adhere to the top sheet 3a. The bending action of the pushdown members, as well as the jet of pressurized gas directed at the edge of the sheet 3a help to release the second sheet 3b from the top sheet 3a. Below the second sheet 3b, the stack of sheets to be sorted 3b is shown. The pushdown members 92 are provided with wheels 921 which are rotatably connected to the pushdown members 92. The wheels allow the sheets to roll over the pushdown members 92. Figure 4 shows a side view of the double sheet detection module 100. Sheets 3 arrive from the infeed module 90 past centring means 20, 21 arranged to centre sheets 2 on the conveyor 200. The sheets 3 additionally pass a double sheet sensor (not shown). The double sheet sensor comprises an electrode arranged to contact a passing sheet 3 on either the top or the bottom of the sheet, and a sensor arranged to contact the sheet 3 on the side opposite the electrode. An electrical current is applied to the sheets 3, and the voltage drop is measured by the sensor. If the voltage drop is higher than a threshold value, it is determined that a stack of more than one sheet passes the sensor. The sheets 3 then pass by a flap 104 which is arranged to selectively open and close. If the flap 104 is closed, sheets 3 travel over the flap through the double sheet detection module, and onwards to the scanning module 160. If the flap 104 opens, for example after being triggered to do so by the sensor sensing that a stack of more than one sheet 3 has arrived, the flap 104 opens into the trajectory of sheets traveling on the conveyor 200 to direct a passing stack of more than one sheet onto the diversion conveyor 102. The diversion conveyor 102 directs sheets to below the double sheet detection module conveyor 101 onto a pallet 2 which is arranged on a pallet lift 103. In the figure, a pallet 2 is shown in the lowermost position, and a pallet 2’ is shown in the uppermost position. The diverted sheets 3 impact the stacking stop 105 to arrange the sheets in a stack on the pallet 2, which is gradually lowered as more diverted sheets 3 are stacked onto the pallet 2. When the pallet is full, conveying means 107, which are arranged perpendicular to the trajectory of the sheets 3, transfer the full pallet out of the double sheet detection module 100 and onto the pallet shuttle 80 (not shown). The double sheet detection module conveyor 101 transfers sheets 3 that are not diverted through the double sheet detection module and further into the sorting line. A hold down member 106 is provided to push passing sheets 106 onto the conveyor 101.

[0084] Figure 5 shows a top view of the cleaning module 150. Sheets 3 are received from the double sheet detection module 100 on the conveyor 200 on the right side of the cleaning module 150. Additional centring means 20 are arranged on both sides of the conveyor 200 to centre passing sheets 3 on the conveyor 200. The centring means 20 each comprise an endless belt 21 which is arranged around pulleys 22. The cleaning unit 1500 spans across the entire width of the conveyor 200, as well as across the entire width of the sheets 3.

[0085] Figure 6 shows a side view of the cleaning module 150. The cleaning unit 1500 is arranged above the conveyor 200. A separator provided with holes 152, in the present embodiment a grille 152 is provided between the cleaning unit 1500 and the conveyor 200. Sheets 3 to be cleaned pass between the conveyor 200 and the separator 152. Electrodes 151a, b are provided, which generate an electric field to eliminate static charge in the sheets 3 and / or any particulates, dirt, dust, or other objects that may adhere to the surface of the sheets 3. The cleaning unit 1500 is adjustable in height along direction De.

[0086] Figure 7 shows a cross section of the cleaning unit 1500 in perspective view. A row of nozzle bodies 154 is provided, which are arranged to rotate. Each nozzle body 154 comprises two nozzle arms 154a, which each comprise a nozzle 155. The nozzles are aimed in a direction with a component perpendicular to the axis of rotation of the nozzle bodies, so that jets of gas expelled from the nozzles 155 induce a rotating motion in the nozzle bodies 154. The nozzles 154 are additionally aimed towards the conveyor 200, and thus the sheets 3 passing underneath the cleaning unit 1500 on the conveyor 200, in order to direct jets of gas onto the sheets 3. The cleaning unit 1500 comprises inlets for pressurized gas 153 to feed the nozzles 154.

[0087] Figure 8 shows a cross section of the cleaning unit 1500 seen from the side. The nozzle bodies 154 are provided in a nozzle compartment 158, which is enclosed by nozzle compartment shroud 158b, separating the nozzle compartment 158 from the suction compartment 153b. Suction inlets 153a, b are provided on each side of the nozzle compartment 158, and are arranged to suck in particles, dirt, dust or other objects on the surface of sheets 3 passing underneath the cleaning unit 1500. The suction inlets 153a, b comprise slits running along substantially the entire width of the cleaning module, preferably at least the entire width of the sheets 3 to be cleaned. Suction outlets 153 are provided on the top of the cleaning unit 1500, and connect to the suction inlets 153a, b through the suction compartment 153c. A vacuum source is attached to the suction outlets 153 to evacuate the mentioned particles etc.

[0088] Figures 9A-C show an overview of a sorting module 120. Figure 9A shows a side view of a sorting module 120. Sheets 3 are received on the left side, either from the scanning module 160 or cleaning module 150, or from a prior sorting module 120. The sorting module 120 is provided with a movable flap 121, which may open to divert a sheet 3 onto the pallet 2 below. If the flap 121 is closed, sheets will pass through the sorting module 120 without being retained by the sorting module 120. If, in an example, a sorting module 120 is the last in a series of sorting modules 120, the flap 121 may remain open to ensure that any sheets not retained prior are retained by the last sorting module 120. An actuator 121a is provided to move the flap 121. A pallet 2 is provided in the sorting module to receive retained sheets 3. A pallet lift 125 is provided to raise the pallet upwards so that it may receive sheets 3, and gradually downwards as the stack of sheets 3 on the pallet 2 grows. Diverted sheets 3 impact a sheet stop 122, so that sheets being placed on the stack are aligned in at least a first direction. Conveying means 126, preferably endless chains or belts, are provided to transfer pallets 2, preferably with a stack of sheets 3, out of the sorting module 120. Figure 9B shows a top view of a sorting module 120 as well as a transfer conveyor 40. A movable alignment member 123 is provided to push against retained sheets 3 to align the sheets in a second direction perpendicular to the first direction. The movable alignment member 123 is preferably slidably mounted, and movable in direction Da by actuator 124. Pallets 2 are transferred onto the transfer conveyor 40 by the conveying means 126. The transfer conveyor then transfers the pallets onto the outfeed conveyor 400 (not shown) using conveying means 41, which are also preferably endless chains or belts. A movable pallet alignment member 42 is provided to align the pallets against pallet stop 45. The pallet alignment member 42 is mounted using linear guides 44 and movable by actuator 43 in direction Dar. Figure 9C shows a perspective view of a sorting module 120, showing the components as described above.

Claims

Claims1. System for food safe cleaning and sorting sheets of paper or plastic, comprising an infeed module, a scanning module, a sorting module, at least one cleaning module and conveying means connecting the infeed module, the scanning module, the cleaning module and the sorting module, wherein the infeed module is arranged to receive a stack of sheets and to remove a single sheet from said stack and transfer said removed sheet to the conveying means, wherein the conveying means are arranged for moving the sheet from the infeed module, to the cleaning module, to the scanning module and to the sorting module, subsequently, wherein the cleaning module comprises at least one cleaning unit arranged to clean at least one surface of said sheet, wherein the scanning module is arranged to scan the sheet and generate scan imaging data of said sheet, wherein the system is arranged to, based on the scan data and one or more predefined damage threshold values, generate sorting data comprising at least information to assign a sheet to one or more of at least two categories, wherein the sorting module is arranged to receive sheets from the scanning module and sorting data and to, based on the sorting data, sort the sheets.

2. System according to claim 1 , wherein one of the at least two categories is representative for accepted sheets, and another one of the at least two categories is representative for rejected sheets.

3. System according to any of the preceding claims, wherein the system is arranged to use image recognition technology to generate sorting data based on the scan imaging data, and wherein the sorting data comprises information representative of one or more of: individual tear length, total tear length, number of tears, number of missing sheet corners, sheet shape, overall sheet length, overall sheet width, sheet circumference, holes, sheet edge damage, vertical variations, imprints, stains, sheet corner radius.

4. System according to any of the preceding claims, wherein a cleaning unit comprises an antistatic cleaning unit, wherein the antistatic cleaning unit is arranged to change the electrical charge of the sheets passing through the cleaning module and / or particles or other objects or substances present on the surface of the sheets.

5. System according to any of the preceding claims, wherein a cleaning unit comprises at least one inlet for compressed gas, at least one nozzle comprising at least one outlet for expellingcompressed gas, and at least one array of electrodes comprising at least one electrode arranged to generate an electric field, wherein at least part of the gas is electrically charged by the electric field.

6. System according to claim 5, wherein the cleaning unit further comprises at least one suction inlet connected to a vacuum source for generating suction, wherein the at least one suction inlet is arranged to remove at least part of the expelled gas.

7. System according to any of the preceding claims 5-6, wherein the at least one nozzle comprises a nozzle body rotatably arranged in the cleaning unit, wherein the nozzle body comprises at least one outlet arranged in a direction that is offset from the axis of rotation of the nozzle body and at an oblique angle to said axis of rotation.

8. System according to any of the preceding claims 5-7, wherein the cleaning unit comprises a row of nozzles and at least one array of electrodes arranged substantially perpendicular to said row of nozzles.

9. System according to claim 8, wherein the at least one array of electrodes comprises one rodshaped electrode.

10. System according to claim 9, wherein at least one nozzle is arranged on a first side of a suction inlet, and wherein at least one electrode is arranged on a second side of said suction inlet, opposite the first side.

11. System according to any of the preceding claims 5-10, wherein the at least one array of electrodes extends along substantially the entire width of the conveying means.

12. System according to claim 11, wherein the one or more suction inlets extend substantially along the entire width of the conveying means.

13. System according to any of the preceding claims 8-12, comprising two longitudinal arrays of electrodes, preferably two rod-shaped electrodes, being arranged on either side of the row of nozzles and substantially parallel to the conveying surface.

14. System according to at least claim 6 and 13, comprising at least two suction inlets, and wherein at least one suction inlet is arranged on each side of the row of nozzles, wherein theat least one suction inlet is further arranged between an array of electrodes and the row of nozzles.

15. System according to any of the preceding claims 5-14, wherein the cleaning unit is a unilateral cleaning unit arranged on one side of the trajectory of the sheets passing the cleaning module, and wherein the cleaning unit is arranged to substantially clean a single side of the sheet.

16. System according to any of the preceding claims 5-15, wherein the cleaning unit further comprises a cover comprising at least two openings, arranged between the at least one nozzle and the conveying surface.

17. System according to any of the preceding claims, wherein the distance between the cleaning unit and the conveying surface is adjustable.

18. System according to any of the preceding claims, comprising one cleaning unit, said one cleaning unit being arranged above the trajectory of the sheets, wherein said cleaning unit is arranged to substantially only clean the topside of sheets passing the cleaning module.

19. System according to any of the preceding claims 1-17, wherein the cleaning module comprises at least two cleaning units, wherein at least a first cleaning unit is arranged above the trajectory of the sheets passing the cleaning module, and wherein at least a second cleaning unit is arranged below the trajectory of the sheets passing the cleaning module, wherein the cleaning module is arranged to substantially clean both the topside and the underside of sheets passing the cleaning module.

20. System according to any of the preceding claims, further comprising a double sheet detection module, arranged to receive a sheet, and wherein the double sheet detection module is arranged to determine whether a single sheet has been received from the infeed module or a stack of more than one sheets, wherein the double sheet detection module is further arranged to transfer a single sheet and reject a stack of more than one sheets, wherein the double sheet detection unit comprises an outlet for transferring single sheets and an outlet for expelling stacks of more than one sheet.

21. System according to claim 20, wherein the double sheet detection module is arranged between the cleaning module and the scanning module, wherein the double sheet detection module is arranged to transfer single sheets to the scanning module.

22. System according to any of the preceding claims 20-21, wherein the double sheet detection module comprises an electrode and a sensor arranged on opposite sides of the trajectory of a sheet passing through the double sheet detection module, wherein said electrode is arranged to transmit an electric signal to a sheet or a stack comprising more than one sheets passing through the double sheet detection unit, and wherein said sensor is arranged to measure the electric signal transmitted through the sheet or stack comprising more than one sheet, and wherein the double sheet detection module is arranged to transfer or reject the sheet or stack comprising more than one sheet based on the measured electric signal.

23. System according to claim 22, wherein the electric signal comprises an electric current with a predetermined input voltage, and wherein the sensor is arranged to measure the voltage of the electric current transmitted through the sheet or stack comprising more than one sheet, and wherein the double sheet detection module is arranged to transfer a sheet or a stack comprising more than one sheets if the measured voltage exceeds a predetermined threshold voltage value, and reject a sheet or a stack comprising more than one sheet if the measured voltage is lower than the threshold voltage value.

24. System according to claim 23, wherein the threshold voltage value is set lower than the input voltage minus the voltage drop of a single sheet, and higher than the input voltage minus the voltage drop of a stack comprising two sheets.

25. System according to any of the preceding claims 20-24, wherein the double sheet detection module comprises a conveying track to transfer accepted sheets through the double sheet detection module, and a diversion track to divert rejected sheets away from the conveying track.

26. System according to claim 25, wherein the double sheet detection module comprises diversion means to divert sheets from the conveying track to the diversion track.

27. System according to claim 26, wherein the diversion means comprises a movable flap extending along the width of the conveying track, wherein the movable flap is movable between a closed position, wherein sheets traveling on the conveying track pass by themovable flap, and an open position wherein the movable flap extends into the trajectory of sheets traveling on the conveying track to divert sheets traveling on the conveying track to the diversion track.

28. System according to any of the preceding claims 25-27, further comprising a stacking unit to stack sheets on a pallet, wherein the diversion track is arranged to transfer sheets to the stacking unit.

29. System according to any of the preceding claims, wherein the infeed module comprises one or more engaging means for engaging a top sheet of a collection of one or more sheets in the infeed module, wherein the infeed module is further arranged to transfer sheets engaged by the engaging means to the conveying means.

30. System according to claim 29, wherein the engaging means comprise one or more movable suction devices arranged to engage a top sheet of a stack of sheets in the infeed module and to lift the top sheet upwards.

31. System according to any of the preceding claims 29-30, wherein the infeed module further comprises an infeed nozzle comprising an inlet and an outlet for pressurized gas, arranged to direct a jet of pressurized gas against an edge of the lifted top sheet to release any additional sheets adhering to the lifted top sheet.

32. System according to any of the preceding claims 29-31, wherein the nozzle comprises an electrode arranged to generate an electric field, wherein at least part of the gas passing through the infeed nozzle is electrically charged by the electric field.

33. System according to any of the preceding claims 29-32, wherein the one or more movable suction devices are arranged to travel between a lowered position and a lifted position, and wherein the system is configured to activate the jet of pressurized gas only after the one or more movable suction devices have moved towards the lifted position.

34. System according to claim 33, wherein the system is configured to lift and lower the one or more movable suction devices cyclically, and to activate and deactivate the jet of pressurized gas cyclically, wherein the jet of pressurized gas is deactivated after lifting the one or more movable suction devices.

35. System according to any of the preceding claims 29-34, wherein the infeed module comprises at least one pushdown member arranged adjacent to the one or more movable suction devices, wherein the at least one pushdown member comprises a tip extending downwards to a point higher than the location of a movable suction device when the movable suction device is in the lowered position, and to a point lower than the location of a movable suction device when the movable suction is in the lifted position.

36. System according to claim 35, comprising at least two pushdown members arranged on opposing sides of the one or more movable suction devices.

37. System according to any of the preceding claims 29-36, wherein the one or more movable suction devices are arranged on a carrier, wherein the carrier is slidably arranged in the infeed module to move to and from the conveying means, wherein the infeed module further comprises an actuator arranged to move the carrier to and from the conveying means.

38. System according to any of the preceding claims, wherein all sheets transferred to the scanning module are further transferred to the sorting module.

39. System according to any of the preceding claims, comprising at least two sorting modules, wherein a first sorting module is arranged to receive sheets and, based on the sorting data, retain a sheet or transfer a sheet, wherein a second sorting module is arranged to receive transferred sheets from the first sorting module and, based on the sorting data, retain a sheet or transfer a sheet.

40. System according to at least claims 2 and 39, wherein either one of the first or the second sorting module is arranged to, based on the sorting data, retain rejected sheets and transfer accepted sheets, and wherein the other one of the first or the second sorting module is arranged to, based on the sorting data, retain accepted sheets and transfer rejected sheets.

41. System according to any of the preceding claims 39-40, comprising at least three sorting modules, wherein the second sorting module is arranged to transfer sheets, based on the sorting data, to the third sorting module, wherein the third sorting module is arranged to, based on the sorting data, retain a sheet or transfer a sheet.

42. System according to any of the preceding claims 39-41, comprising more than three interconnected sorting modules, wherein a first sorting module is arranged to receive sheetsfrom the cleaning unit and, based on the sorting data, retain a sheet or transfer a sheet to a second sorting module, wherein the second sorting module and at least two subsequent sorting modules are arranged to receive sheets from another sorting module and, based on the sorting data, retain a sheet or transfer a sheet.

43. System according to any of the preceding claims 39-42, wherein the two or more sorting modules are arranged in series.

44. System according to any of the preceding claims 41-43, wherein at least one sorting module is configured to retain rejected sheets and at least one sorting module is configured to retain accepted sheets, and wherein the one or more additional sorting modules may be selectively configured to retain accepted or rejected sheets, wherein the configuration of individual sorting modules may be changed during sorting.

45. System according to any of the preceding claims 41-44, wherein the system is configured to categorize the scanned sheets into two or more categories in the sorting data, and wherein each sorting module may be selectively configured to retain any category of sheets.

46. System according to any of the preceding claims, wherein at least one sorting module is arranged to stack retained sheets onto a pallet.

47. System according to claim 46, wherein all sorting modules are arranged to stack retained sheets onto a pallet.

48. System according to any of the preceding claims 46-47, further comprising an outfeed conveyor arranged to receive pallets from the one or more sorting modules and transfer the pallets to a pallet outfeed.

49. System according to any of the preceding claims 46-48, further comprising a pallet dispenser module arranged to receive one or more pallets and dispense the pallets to the one or more sorting modules.

50. System according to claim 49, further comprising a pallet shuttle conveyor arranged to transfer pallets from the pallet dispenser to the one or more sorting modules.

51. System according to at least claims 28 and 50, wherein the pallet shuttle conveyor is further arranged to transfer pallets from the pallet dispenser to the double sheet detection unit.

52. System according to at least claim 28 and any of the preceding claims 50-51, wherein the shuttle conveyor is arranged to receive pallets from the double sheet detection module and transfer the pallets to a pallet outfeed.

53. System according to any of the preceding claims 50-52, wherein sheets are provided to the infeed module on a pallet, and wherein the infeed module is arranged to transfer empty pallets to the pallet dispenser.

54. System according to any of the preceding claims 48-53, further comprising one or more top frame dispensers arranged adjacent to the outfeed conveyor, wherein the one or more top frame dispensers are arranged to apply a top frame to a stack of sheets.

55. Method for food safe cleaning and sorting sheets of paper or plastic, using a system according to any of the preceding claims.

Images