System and method for depalletizing and / or palletizing a palletized stack of layers of items

Abstract

The present invention relates to a system for depalletizing and / or palletizing a palletized stack of layers of items, in particular glass bottles. The invention also relates to an end effector for sweeping off a layer of items. The invention further relates to a method for depalletizing or palletizing a palletized stack of layers of items.

Description

[0001] System and method for depalletizing and / or palletizing a palletized stack of layers of items

[0002] The present invention relates to a system for depalletizing and / or palletizing a palletized stack of layers of items, in particular glass bottles. The invention also relates to an end effector for sweeping off a layer of items from a palletized stack of layers of items. The invention further relates to a method for depalletizing or palletizing a palletized stack of layers of items.

[0003] Industrial food production, such as beverage factories, use filling lines to package their products. Often glass bottles are used for packaging of beverages, such as beer or the like. For an efficient process, empty glass bottles are transported by conveyor belts to the filling station where the glass bottles are filled with a beverage. For feeding this empty packaging material, such as glass bottles, it is common that these are supplied in stacked layers on a pallet. The palletized layers of empty packaging, such as glass bottles, needs to be depalletized before the packaging can enter into the process and be transported to the filling station(s). The stacked items are typically separated by packaging sheets in between layers and the pallet is depalletized by taking off one layer at a time. Depalletizing can be done automatically by the use of robots or automatic systems. However these systems are heavy and need a lot of power to be operated.

[0004] The object of the present invention is therefore to provide an improved system for automatic depalletizing.

[0005] The present invention provides thereto a system for depalletizing and / or palletizing a palletized stack of layers of items, in particular glass, metal or plastic packaging containers, preferably empty, glass bottles, comprising:

[0006] - at least one movable plate, provided with first coupling elements;

[0007] - at least one robotic arm, comprising an (robotic) arm element and an end effector; said end effector comprising at least one sweeping element and further comprising second coupling elements, wherein the first and second coupling elements are complementary, the coupling elements are configured for automatic coupling and uncoupling of the robotic arm to the movable plate, in particular the second coupling elements are configured for automatic coupling and uncoupling of the robotic arm to the first coupling elements of the movable plate; wherein the robotic arm is configured for horizontally sweeping off one layer of items from the stack onto the at least one movable plate using at least the at least one sweeping element and / or wherein the robotic arm is configured for horizontally sweeping off one layer of items from the at least one moveable plate onto a position on a pallet (for palletizing), in particular by using at least the at least one sweeping element; and wherein the robotic arm is configured to move the at least one movable plate from a first resting area to a second resting area wherein the first area comprises a first position that aligns with the top layer of items of the stack and the second resting area comprises a second position at a substantially similar horizontal level of a downstream or upstream conveyor.

[0008] The system according to the present invention is suitable for depalletizing a palletized stack of a layers of items. These items can also be interpreted as articles or containers. Examples of items are (empty) glass beer bottles, champagne or wine bottles, oval glass containers, metal cans, jars, kegs, plastic sauce bottles, or the like. For de palletizing the items are in particular empty, but the system can also be used for palletizing full items, articles or containers. Suitable fields for use of this system are for example in food, paint or chemical industry.

[0009] The robotic arm of the system according to the present invention comprises an arm element and an end effector, as is typical for robotic arms. The arm element provides flexibility in degrees of freedom and the end effector provides the function of the robotic arm. In the system according to the present invention the end effector can be referred to as a sweeping tool. The end effector and the arm element can be connected to form an integrated robotic arm. Alternatively, the end effector and the arm element can be connected in such a way that the end effector can be disconnected from the arm element. Optionally the end effector can temporarily be replaced by a second end effector with different features, or to replace the end effector with a similar one during maintenance or repairs. Connecting and disconnecting in such an embodiment can be done manually or automatically.

[0010] The arm element is beneficial because it provides flexibility to the robotic arm. The robotic arm element is configured such that the end effector is able to reach the desired first and second position. Or if applied, multiple first and / or second positions.

[0011] Where in this document is referred to a coupling of the robotic arm and the movable plate, in particular a coupling between the end effector and the movable plate is meant.

[0012] The system according to the present invention is in particular advantageous for depalletizing empty and clean (new) cans, bottles and the like. The system can be used for depalletizing a pallet with empty bottles or cans and feeding the empty bottles or cans to a conveyor belt of a filling line for example. The system can typically be used for all items that have substantially the same height and have a substantially round, such as circular or octagonal, footprint. In order to be stacked on a pallet in layers it is beneficial if the items have the same height and in order to be swept horizontally on and off a plate it is beneficial when the footprint of the items is substantially round, such as circular or octagonal. While the movable plate is being repositioned from the first position to the second position, and vice versa, the movable plate and the robotic arm are coupled. The coupling of the movable plate and the robotic arm is typically done by coupling of the complementary coupling elements The movable plate is preferably uncoupled from the robotic arm during sweeping of a layer of items on or off the plate. The coupling elements allow for a quick coupling and uncoupling, for example the coupling and / or uncoupling takes less than 20 seconds, preferably 10 seconds, more preferably less than 5 seconds, even more preferably less than 2 seconds. The robotic arm is preferably further configured to move vertically downwards to uncouple the first and second coupling elements. This downward movement may be for example within the range of 10 - 50 mm, preferably 20-40 mm, even more preferably substantially 30 mm.

[0013] The system according to the present invention presents a solution for depalletizing which is maintenance-friendly due to the separate movable plate that is connectable to the robotic arm for each layer of items to depalletize. The movable plate and the robotic arm are connected by their coupling elements. Preferably, said coupling elements itself are static coupling elements. The coupling elements themselves are free from movable parts. This makes the configuration low cost and maintenance friendly. In case the coupling elements are static elements, the robotic arm moves the second coupling elements towards the first coupling elements and due to their mutual repositioning, as such form a coupling between the first and second coupling elements.

[0014] Another advantage of the present invention is that downstream conveyor belts, for example for feeding empty bottles to a filling line, can be reached in a variety of ways. Multiple downstream conveyor belts can be fed by using one system according to the present invention. The movable plate of the system according to the present invention can be uncoupled from the robotic arm while loaded with items (e.g. empty bottles). Due to this configuration, the downstream conveyor belts can be positioned above each other as well. Experiments have shown that it is possible to simultaneously provide four downstream filling lines with empty bottles by using the system according to the present invention.

[0015] Typically the system may use one single individual movable plate. Alternatively, the system may comprise multiple individual movable plates, that can be used for buffering capacity. The system allows for various floorplans according to the user’s wishes.

[0016] Since the system is suitable for depalletizing and / or palletizing pallets, it is preferred that the movable plate comprises a top surface with the same shape as a pallet, such as rectangular shape. The top surface is the surface where the layer of items can be placed, and may also be referred to as base plate of the movable plate. The dimensions of the top surface and / or of the plate will be typically slightly bigger than the size of the pallet to (de)palletize. Therefore, preferably the movable plate comprises a rectangular (base) plate.

[0017] The system is advantageous for factories or operational spaces where floor space is limited. The system according to the present invention is very compact. Due to the separate movable plate, the robotic arm, and more in particular the (robotic) arm element, can be relatively light and flexible. The (robotic) arm element of the system is preferably capable of lifting in between 300-700, more in particular 300 - 500 kgs. It is possible, but not necessary to use a robotic arm that can handle more weight, which saves costs and material. The relatively low lifting capability requirement has a beneficial effect on the cost of the robotic arm element itself, but also on the cost element during operation because due the amount of energy needed during operation is also less compared to conventional depalletizer systems, thus saving costs during operation. The robotic arm element can be chosen from several commercially available robotic arm elements. An example of a suitable and compatible arm element is a Fanuc M410 robotic arm element. The movable plate and (end effector of the) robotic arm may be uncoupled during sweeping off a layer of items onto the plate. The movable plate and the (end effector of the) robotic arm may be coupled while the movable plate is moved from the first position to the second position. This coupling and uncoupling is advantageous because it allows for the use of a lighter robotic arm, which reduces the energy consumption that is needed for operation of the system according to the present invention. Therefore, the end effector may have a weight in the range of 100-250 kgs, preferably 125-175 kgs, even more preferably in the range of 140- 160kgs.

[0018] The arm element of the robotic arm of the present invention can also be referred to as a robotic arm element.

[0019] The system comprises at least one sweeping element. Typically, the sweeping element may be part of an operational tool that is part of the robotic arm. Preferably the system comprises at least two sweeping elements, in particular two sweeping elements, that are positioned on opposite sides of part of the robotic arm, such as on opposite sides of an operational tool, wherein the sweeping elements are configured for facing each other in a closed position. In this case, a closed position is the position of the sweeping elements wherein a layer of items is placed onto the movable plate by the sweeping elements.

[0020] In an embodiment of the system according to the present invention, preferably the first position and second position are static positions and the pallet to be depalletized moves upward to align with the first position. This can be done by using a lift element. Such lift element moves the pallet with palletized layers of items vertically. In another embodiment, the first position is a dynamic position and / or the second position is a dynamic position. Furthermore, it is conceivable that a system comprises multiple second positions, for feeding multiple conveyor belts. It is also possible that the system comprises multiple first resting areas with first positions. In such an embodiment typically the system may also comprise multiple second resting areas with seconds positions. In such an embodiment multiple different items on different pallets can be fed into different filling lines while only one robotic arm is operational. Any combination is possible, such as multiple, preferably two, first resting positions and one second resting position or one first resting position and multiple, preferably two, second resting positions. Multiple first and / or second resting positions is advantageous because it gives a very flexible system for depalletizing or palletizing. This can lead to cost reductions.

[0021] Preferably the system is used for depalletizing. A pallet with new empty items, such as layers of jars, bottles or the like can be positioned next to a first resting area for depalletizing operation. However, the system can be used for palletizing as well. If programmed the correct way, it is even possible to use the system for simultaneous palletizing and depalletizing of items. However, using the system for palletizing and depalletizing simultaneously is not recommended due to the risk of contamination (via residues on the movable plate).

[0022] The system can be used for depalletizing at least one pallet with palletized stack of layers of items. The system can also be used for depalletizing more than one pallet and feeding one or multiple downstream stations (and thus multiple second resting areas), such as conveyors for filling lines.

[0023] In another example, the second position may be a position on a chain belt for example. The second resting area may comprise a transport system such as a chain belt, roller system or another type of conveyor. The system according to the present invention may be configured for sweeping off a layer of items onto at least one moveable plate wherein the second resting area comprises a chain belt for transporting the moveable plate towards a downstream or upstream station, such as a filling line, where sweeping off the layers of items from the moveable plate can be performed by a robotic arm according to the present invention.

[0024] Typically, the second position is preferably lower than the first position. In a preferred embodiment, the movable plate and the robotic arm are configured to be uncoupled during sweeping of the layer of items onto or from the movable plate. The advantage is that the movable plate and robotic arm do not have to move relative to each other while being coupled. This provides for a robust and cheaper construction.

[0025] In a preferred embodiment, the system comprises a first supporting element, in particular within the first resting area, for supporting the movable plate in the first position, aligned with the top layer of the stack of layers of items to be depalletized, and / or wherein the system comprises a second supporting element, in particular within the second resting area, for supporting the movable plate in the second position. The first and / or second supporting element may be an independent supporting element, such as a frame. Another example is that the support element may be integrated within a downstream conveyor belt system for example. The support element can also be an extension of a shaft system or the like. The advantage of a support element is that the support element can support and stabilize the movable plate while being loaded and unloaded, without the need of a coupling with a part of the robotic arm. This allows for a more lean and smaller robot to control the robotic arm. This is advantageous because it saves costs, since a cheaper robotic arm can be used and lighter robotic arms typically require less energy.

[0026] In an embodiment of the present invention, the system comprises a first supporting element. The first supporting element may comprise a framework with an in height movable top surface, said top surface at least corresponding to the surface of the movable plate. This in height movable top surface can be used within the first resting area, and / or the second resting area. Furthermore, a supporting element with an in height movable top surface can be used under the pallet to be depalletized. The first supporting element, if applied, is suitable for supporting the movable plate while being unloaded and / or loaded. Throughout this document, by unloading and loading, sweeping items from the plate (unloading) and on the plate (loading) is meant. It is conceivable that the system further comprises a second support element, in particular within the second resting area, comprising a top flat surface for supporting the at least one movable plate, said second support element positioned such that a layer of items can be swept from a movable plate on top of the support element to a downstream conveyor.

[0027] If more downstream conveyors are loaded with layers of items by the system according to the present invention, the system may have multiple resting areas. It is possible that the system comprises multiple first supporting elements and / or multiple second supporting elements.

[0028] The first and / or second supporting element, may have various shapes and sizes as long as it has a flat top surface for supporting the movable plate while being loaded and / or unloaded. For example, the top surface of the supporting element spans a surface that corresponds to the size of the movable plate. Preferably, the top surface of the second supporting element aligns with a downstream or upstream conveyor.

[0029] An important element of the present invention is that the movable plate can be easily coupled and uncoupled with the robotic arm. Therefore the system comprises coupling elements. There are various ways for the movable plate to be easily and without human interference coupled to the robotic arm.

[0030] In an embodiment, the first coupling elements of the movable plate are positioned on the top surface of the movable plate, comprising protrusions, protruding from the top surface of the movable plate. The first coupling elements may extend away from the top surface while being attached to at least one side of the base plate of the movable plate. Said protrusions being complementary to the second coupling elements of the robotic arm. The first coupling element may be shaped in the form of a T-shaped protrusion. The T-shape may be made from tubes, rods or steel hollow pipes with a circular or rectangular or square cross-section. A second coupling element, for example also T-shaped or comprising a plate with a protruded rod element, may abut the first coupling element such that while the robotic arm moves the movable plate and the robotic arm can remain coupled. In a preferred embodiment, the first and second coupling elements are static coupling elements. For example, the first coupling element may comprise a protruding plate protruding from a base plate of the movable plate and further comprising a rod or pin that extends from the protruding plate 3b towards and partly over the surface of the base plate. Preferably said pin or rod is in parallel with the top surface of the base plate. In this embodiment, the second coupling element may comprise a curved surface positioned on top of a sweeping element. Alternatively, the second coupling element may comprise two pins that are positioned in parallel to one another and also in parallel with the top surface of the base plate. In a coupled state, the two pins of the second coupling element support the pin or rod from the first coupling element. This is a cost-effective and efficient way for a stable coupling and carrying of the movable plate with the robotic arm. The complementary first and second coupling elements allow for a coupling between the robotic arm and the movable plate. By coupling it can be understood that the movable plate and the robotic arm are limited in their relative mutual movement. This allows for a stable movement and dislocation of a layer of items positioned on the movable plate. In particular, in a coupled state, the movement of the movable plate vertically away from the robotic arm is limited. Furthermore, the horizontal movement of the movable plate with respect to the robotic arm can be limited.

[0031] Wherein this document reference is made to coupled state, it should be interpreted as that mutual movement of the movable plate and at least part of the robotic arm, for example an operational tool comprising the sweeping elements, is limited.

[0032] Preferably, the first coupling elements are positioned on two opposite sides of the movable plate. In case guiding elements are applied, the first coupling elements may be positioned on (or attached to) the movable plate on the same sides as the guiding elements. Preferably, four first coupling elements are positioned protruding from the top surface and / or attached to the sides of the movable plate. In this embodiment where four first coupling elements are applied the movable plate is rectangular of shape. The four first coupling elements, if applied, may be attached to two opposite sides of the movable plate. This is advantageous because this leaves the other two sides of the movable plate open and free for a smooth sweeping operation by the sweeping elements. Furthermore, four first coupling elements positioned on two opposite sides provide for a relative easy coupling by the first and second coupling elements.

[0033] In a preferred embodiment, the second coupling elements are positioned such that, in a coupled state, the second coupling elements are positioned in between the guiding elements, if applied, and the first coupling elements.

[0034] In another embodiment, the first coupling elements of the movable plate are positioned on the bottom surface of the movable plate.

[0035] It is also possible that the first coupling elements of the movable plate are coupling surfaces or recesses in the movable plate and that the second coupling elements lift or grip the movable plate on said coupling surfaces. For example, by using hooks as second coupling elements

[0036] Another example is that the first and second complementary coupling elements comprise a gripping element. The gripping element may be combined with coupling surfaces and / or through holes and / or anchors to be gripped.

[0037] The first and second complementary coupling elements may comprise a male and female coupling element. Another example is that the first and second complementary coupling elements comprise at least one hook element and a hook receiving element. The hook-receiving element may be a protrusion that protrudes from the movable plate, either from the upper surface or from the bottom surface. The hook receiving element may further be a rod shaped element.

[0038] Combinations of first and second coupling elements are presented here. The first element may be a hook element and the complementary second element may comprise a rod shaped element, (see figures)

[0039] The first element can be rod shaped and second element can be hook shaped. The first element can be hook shaped and second element can be hook shaped.

[0040] In an embodiment, the first and / or second coupling element comprises an (electronic) magnetic element. At least one of the coupling elements may comprise a magnetic element for a magnetic coupling. The magnetic element may comprise a magnet, preferably an electro magnet, which can be controlled for coupling and decoupling of the movable plate to the robotic arm. It is possible that both the first and second coupling elements comprise a magnet. Alternatively, only one of the first and second coupling elements comprise a magnet and the other comprises a magnetic surface to which the magnet can be coupled, at least temporarily.

[0041] Any magnetic coupling element can be combined with other embodiments, such as a hook element, or a protrusion from the movable plate.

[0042] In a preferred embodiment, the first coupling element comprises a coupling surface on the bottom side of the movable plate and wherein the second coupling element comprises a hook element configured for abutting the coupling surface on the bottom side of the movable plate. In such an embodiment, the hooks are configured to lift the movable plate.

[0043] To avoid that items fall off the movable plate, especially while the plate is moved from one position to another, several measures can be taken. First of all, due to precision of the robotic arm and the coupling the movable plate will be kept substantially horizontal while loading, unloading and while moving. Second, it is possible to have an anti-slip coating, that provides a resistance that can be overcome during sweeping movements during loading and unloading of the plate , but the resistance provides sufficient resistance to avoid glass bottles or cans to slide over the surface during movement of the plate. Furthermore, it is possible to add other precautionary measures, such as guiding elements. In an embodiment, the movable plate comprises a base plate and guiding elements. The guiding elements are in particular suitable for guiding the layer of items during sweeping of a layer of items onto or from the movable plate. Simultaneously, the guidance elements may prevent items from falling off. For example, the guidance elements may comprise longitudinal bars, which are positioned perpendicular to the top surface of the movable plate. The guidance elements have the advantage of stabilising and preventing the layers of items to fall off during loading and / or unloading and during movement from first to second position.

[0044] The movable plate can be provided with adjustable guidance elements, such that the mutual distance in between the adjustable guidance elements can be increased or decreased. This allows for handling of pallets in various sizes, in particular various widths.

[0045] In a preferred embodiment, the guiding elements are positioned on opposite sides of the base plate and wherein the movable plate is positioned such by the robotic arm that the guiding elements are positioned substantially perpendicular to the sweeping elements during sweeping of a layer of items onto or from the movable plate. During loading and unloading, the sweeping elements may provide for guidance on a first pair on opposite sides of the layer of items, while the guidance elements, if applied, may form a guidance on a second pair of opposite sides of the layer to be swept. Said first and second pair of sides mutually enclose an angle, such that they together may form a substantially rectangular shape. This configuration provides for a robust and effective guidance and stabilisation during movement. During movement of the movable plate, for example from the first to the second position, the sweeping elements may function as guiding elements as well. The sweeping elements are kept in a position relative to the plate and items on the plate to prevent items to fall or roll off the plate during movement. To this end, the sweeping element may comprise at least one bar.

[0046] It is preferred that the sweeping elements are hingedly connected to the robotic arm. The advantage thereof is that a hinge construction is a robust and cheap way to reposition the sweeping elements relative to a layer of items to be swept.

[0047] Preferably, the sweeping element can be configured to abut against (one side of) the layer of items to be swept, said sweeping element being hingedly connected to the robotic arm. In this embodiment, the sweeping element may be configured to hinge outwards with respect to the robotic arm. The sweeping element may comprise at least one bar, such as a rectangular shaped element. In an embodiment, the sweeping element comprises a sweeping position and an open position, in particular wherein the sweeping position and the open position mutually enclose an angle. The sweeping position and open position may comprise an angle of substantially 90 degrees. This provides for a safe operation, wherein the sweeping element can be positioned over the layer of items to be swept and then consequently decrease the mutual distance between two sweeping elements from the open position to their sweeping positions. Preferably the system comprises two sweeping elements and the mutual distance between the sweeping elements is larger in the open position than in the sweeping position.

[0048] In the open position, the sweeping elements can be in parallel with the upper surface of the base plate of the movable plate. In this case, the open position of the sweeping elements can allow for the end effector to approach a stack of items more closely.

[0049] In an embodiment it is possible that the second coupling elements are integrated with the sweeping elements. For example, each second coupling element may comprise two rods that are positioned in parallel and extend in a direction parallel to a base plate of the movable plate. In another embodiment, each second coupling element may comprise at least one curved surface, integrated or provided onto a sweeping element, for engaging with the first coupling element. For example, the first coupling element is a rod and the second coupling element is a curved plate that receives the rod

[0050] Preferably, the sweeping elements further comprises a rectangular bar. A rectangular bar can provide a protective barrier to prevent items to fall off the movable plate during movement. Such a rectangular bar, if applied, has preferably at least the same width of the layer of items to depalletize. The width of the rectangular bar can have a similar width as the base plate of the movable plate, or, preferably, the width of the rectangular bar is smaller than the width of the base plate of the movable plate of the system according to the present invention. If integrated coupling elements are applied, the integrated second coupling element may be positioned on top of the rectangular bar, spanning a surface perpendicular to the plane of the rectangular bar. A safe and hygienic material is preferred for the movable plate. So, preferably the movable plate may comprise a polymer base plate, in particular a flat base plate comprising a polymer material. The plate may comprise a metal frame, for example made from aluminium, or steel, such as inox 316, inox 304 or a combination thereof. At least the top surface of the movable plate can be manufactured from a polymer material, preferably polyethylene, for example PE / UHMPE or HDPE. Any attached or additional coupling elements can be made of other suitable materials such as a polymer, or a metal.

[0051] Typically, layers of items are separated by packing sheets. Therefore, it would be advantageous if the system can also pick up these packing sheets in between sweeping operations. In an embodiment of the system according to the present invention, the robotic arm also comprises picking elements, such as suction cups, for picking packing sheets that are present in between the layers of items. The picking elements for picking packing sheets may comprise suction cups, or hooks, or pins or the like. The packing sheets may be picked and dropped at a drop off location. Experiments have shown that 4 suction cups are easy to work with, also 5 or 6 suction cups showed good results. Therefore it is preferred that if applied, the end effector of the robotic arm comprises at least 4 picking elements.

[0052] The packaging sheet can be picked before sweeping off a layer of items. Preferably, this is done before sweeping off the layer of items from the movable plate to a downstream conveyor belt. This has the advantage that the packaging layer can provide stability to the layer of items on the movable plate.

[0053] In the open position of the sweeping elements, the sweeping elements may be positioned in parallel above the movable plate. This position allows for the end effector to approach the packaging sheets closely, so that the picking elements can easily pick the packaging sheet.

[0054] In a preferred embodiment, the system according to the present invention is provided with gripping means for gripping a packaging sheet, in particular a packaging sheet that is positioned under a layer of items to be swept. The gripping means may grip the packaging layer while the sweeping elements sweep off the layer of items that is positioned on that packaging layer. This prevents the packaging sheet to move along with the layer of items and keeps the packaging sheet at its position.

[0055] Preferably the picking elements are positioned above the movable plate in a coupled position of the robotic arm and the movable plate. Preferably the picking elements are configured for holding a packing sheet above a layer of items on the movable plate, especially during movement of the plate from a first to a second position. In this case, the picking sheet is positioned above the layer of items on the plate while a loaded movable plate is moved from a first position to a second position. This is advantageous because in this configuration the packing sheet forms a shield over the layers of items, which is typically empty bottles or cans with an open top. This way the packing sheet prevents dust or other parts from accidentally entering the items on the movable plate.

[0056] Typically layers of glass bottles, jars and the like are stacked with packing sheets in between and optionally a wrap around it. Before depalletizing the wrap must be taken off. Downside of this is that the outer item of a layer can fall off really easily. In case of glass bottles this is not beneficial in terms of cost and it also brings a safety risk. For a safe working environment it is preferred that the pallet to be depalletized is shielded, such that items that are on the sides of the pallet remain on the pallet and do not fall off. Especially in case of glass bottles or jars it is advantageous that the risk of falling and breaking of the items is reduced. To this end, it is possible to place the pallet within a shaft. In an embodiment, the system comprises at least one shaft comprising at least three upright walls at least partly surrounding the palletized stack of layers of items. Preferably the shaft comprises four walls, of which one wall can be opened to allow a pallet to enter (and / or leave) the shaft.

[0057] Preferably, the shaft, if applied, comprises a lift element to lift the pallet to be depalletized such that the top layer of the pallet to depalletize is positioned above the shaft. In case the layer of items is put in the position above the shaft, the layer of items can be swept onto the movable plate of the system of the invention.

[0058] The pallet that is depalletized can be removed from its position by an operator or an automatic device. It is also possible that the system of the invention is configured for disposal and / or dislocation of the pallet that is depalletized. This can be done for example by integrated pallet hooks in the robotic arm.

[0059] Preferably, the robotic arm may further comprise secondary coupling elements configured for automatic coupling and uncoupling with at least one pallet, for example wherein the secondary coupling elements comprise at least one pallet hook. In particular two pallet hooks, which are configured for picking up the pallet on opposite sides of the pallet. By automatic coupling it is meant that no manual operation is necessary for the system to pick up a depalletized pallet. The embodiment comprising pallet hooks is beneficial in case the user has a low budget and cannot afford separate pallet transport and / or in case the capacity is relatively low.

[0060] The invention also may relate to the use of a system according to the present invention for depalletizing and / or palletizing layers of items, such as cans, jars or bottles.

[0061] Preferably the system according to the present invention is provided with safety measures for a safe operation of the system. The system may comprise at least one safety switch, provided on the robotic arm, to safely start the repositioning of the movable plate and to guard safe movement of the plate and to check that the movable plate safely is positioned in the second resting area.

[0062] Safety is important for the operation of the system according to the present invention. There are several options conceivable to ensure that the layer of items is safely swept off and moved from the first position to a second position. In an embodiment the system may be provided with sensors to check if the first and second coupling elements are properly coupled. An additional safety coupling can be made for example at two opposite sides of the movable plate. For safety reasons, the system can be provided with a safety programmable logic controller (PLC). It can be conceivable that two or more, for example four, couplings of the first and second coupling elements are independently connected with a safety PLC.

[0063] The present invention further relates to an end effector for sweeping off a layer of items to depalletize a stack of items for use in a system according to the invention. The end effector may be referred to as sweeping tool. The end effector according to the present invention may comprise at least one sweeping element, preferably two positioned on opposite sides of the tool, and further comprising second coupling elements, wherein the second coupling elements are complementary to first coupling elements of a movable plate according to the present invention. The (second) coupling elements are configured for automatic coupling and uncoupling of the end effector to first coupling elements of the movable plate. When the end effector is connected to the arm element of the robotic arm, the robotic arm is configured for horizontally sweeping off one layer of items from the stack onto the at least one movable plate using at least the at least one sweeping element.

[0064] In combination, the robotic arm is preferably configured to move the at least one movable plate from a first resting area to a second resting area wherein the first area comprises a first position that aligns with the top layer of items of the stack and the second resting area comprises a second position at a substantially similar horizontal level of a downstream or upstream conveyor.

[0065] The system according to the invention may further comprise at least one automated guided vehicle (AGV). The at least one automated guided vehicle may be used for transport of at least one moveable plate. During transport the moveable plate may comprise a layer of items. The movable plates can be moved to other sides of a factory and may omit the need for long and inconvenient conveyor belt systems.

[0066] The at least one moveable plate of the system according to the present invention may be provided with two side frames, wherein the side frames of two moveable plates are mutually stackable. The two optional side frames are preferably positioned at the same side as the optional guiding elements and, if applied, these are positioned on two opposite sides of the movable plate. This is an advantageous positioning because it leaves the sides open and free of any obstacles for the sweeping operation. The frames are advantageous for stacking the plates for a longer period of time, in particular stacking of multiple moveable plates while items are positioned on the moveable plate. It is conceivable that all moveable plates are mutually stackable. The advantage of stackable moveable plates is that the movable plates can be used for storage as well. This increases the flexibility of the system even further. There is more flexibility in the layout of the operation wherein the system is used. The moveable plates may be stacked and transported while each moveable plate carries a layer of items, such that transport systems such as conveyor belts or bottle lines become at least partly obsolete. The flexibility of the layout of the operational space increases due to the use of stackable moveable plates (for example by moveable plates provided with side frames wherein the side frames of two moveable plates are mutually stackable). This may also reduce turnover time. Another advantage is that vertical spaces can be used more efficiently. Further, the moveable plates may be used as a buffer wherein the items buffered onto the moveable plates are protected from dust or other undesired particles falling into the items, such as bottles, because there is another moveable plate on top. Preferably, a packing layer is placed on top of the upper layer of items, or alternatively an empty moveable plate may be used as a top layer.

[0067] In an embodiment, the system comprises moveable plates comprising stackable frames wherein these stackable moveable plates can be placed onto a pallet. The pallet with a stack of moveable plates may be autonomously transported, for example by an automated guided vehicle, or manually transport, for example by a forklift truck, to the desired location. This embodiment increases the flexibility of the system as explained above. At least one of the moveable plates in the stack of moveable plates, preferably all moveable plates, may comprise a layer of items, such as bottles. The moveable plates may comprise a layer of items during transport and / or when used as a buffer.

[0068] The invention further relates to a method for depalletizing and / or palletizing a pallet. The method according to the present invention is a method for palletizing and / or depalletizing at different height levels, in particular by using a device according to the present invention, comprising the following steps: a) Sweeping off the top layer of items or a layer of items from a first position to a movable plate; b) Coupling the movable plate with a robotic arm; c) Moving and positioning of the movable plate to a second position by the robotic arm that is coupled to the movable plate; d) Uncoupling the movable plate and the robotic arm; e) Sweeping off the layer of items from the movable plate; f) Coupling the movable plate and the robotic arm; g) Moving and positioning the movable plate to the first position and uncouple the movable plate and the robotic arm; h) Repeating steps a-h until the pallet is depalletized or palletized.

[0069] Depalletizing comprises bringing the movable plate to a first position, which is next to a top layer of a pallet, sweeping the top layer of items to the movable plate and then bringing the loaded movable plate to a second position, said second position being next to a downstream conveyor. The movable plate is then unloaded by sweeping off the layer of items to the downstream conveyor.

[0070] Palletizing comprises bringing the movable plate to a first position, which is next to an upstream conveyor, sweeping the layer of items from the conveyor to the movable plate and then bringing the loaded movable plate to a second position, which is next to a pallet to be palletized. The movable plate is then unloaded by sweeping off the layer of items on top of the pallet. Optionally with a packing sheet in between.

[0071] Uncoupling of the movable plate and the robotic arm may comprise the steps of moving at least part of the robotic arm vertically downwards, such that the mutual distance between the first and second coupling element increases. This allows for a advantageous position to sweep off the items on the movable plate, if present.

[0072] The method is advantageous because it provides more flexibility for the user and it uses less floor space than other methods wherein large systems are installed.

[0073] The same advantages apply to the method as are for the device of the present invention.

[0074] The method can also be used for palletizing a layer pallet. In such an embodiment, the first position may comprise a feeding conveyor belt for feeding items, such as empty or filled bottles. The second position may comprise a position on a pallet and / or on top of a moveable plate positioned on a pallet.

[0075] Preferably, the movable plate and the robotic arm are uncoupled during sweeping of the layer of items onto or from the movable plate. This allows for the use of a light and therefore low-cost and energy use friendly robotic arm for operation of the method.

[0076] In case a pallet comprises packing sheets in between layers of items on the pallet, it is preferred that the method further comprises the step of picking up a packing sheet, wherein the packing sheet is positioned above the layer of items during repositioning of the movable plate from the first position to the second position.

[0077] The method further includes preferably the step of dropping the packing sheet later on.

[0078] Preferred embodiments of the invention are set out in the non-limitative set of clauses presented below.

[0079] Clauses

[0080] 1 . System for depalletizing a palletized stack of layers of items, in particular empty containers, comprising: at least one movable plate, provided with first coupling elements; at least one robotic arm, comprising an arm element and an end effector; said end effector comprising at least one sweeping element and further comprising second coupling elements, wherein the first and second coupling elements are complementary, the (second) coupling elements are configured for automatic coupling and uncoupling of the robotic arm to first coupling elements of the movable plate; wherein the robotic arm is configured for horizontally sweeping off one layer of items from the stack onto the at least one movable plate using at least the at least one sweeping element, preferably at least two sweeping elements; and wherein the robotic arm is configured to move the at least one movable plate from a first resting area to a second resting area wherein the first area comprises a first position that aligns with the top layer of items of the stack and the second resting area comprises a second position at a substantially similar horizontal level of a downstream or upstream conveyor. 2. System according to clause 1 , wherein the movable plate and the robotic arm are configured to be uncoupled during sweeping of the layer of items onto or from the movable plate.

[0081] 3. System according to clause 1 or 2 , comprising a first supporting element, in particular within the first resting area, for supporting the movable plate in the first position, aligned with the top layer of the stack of layers of items to be depalletized, and / or wherein the system comprises a second supporting element, in particular within the second resting area, for supporting the movable plate in the second position.

[0082] 4. System according to any of the previous clauses, wherein the system comprises a first supporting element, comprising a framework with an in height movable top surface, said top surface at least corresponding to the surface of the movable plate.

[0083] 5. System according to any of the previous clauses, further comprising a second supporting element, in particular within the second resting area, comprising a top flat surface for supporting the at least one movable plate, said second supporting element positioned such that a layer of items can be swept from a movable plate on top of the supporting element to a downstream conveyor.

[0084] 6. System according to any of the previous clauses, wherein the first and second complementary coupling elements comprise a gripping element.

[0085] 7. System according to any of the previous clauses, wherein the first and second complementary coupling elements comprise a male and female coupling element.

[0086] 8. System according to any of the previous clauses, wherein the first and second complementary coupling elements comprise at least one hook element and a hook receiving element, such as a rod shaped element.

[0087] 9. System according to any of the previous clauses, wherein the first and / or second coupling element comprises an (electronic) magnetic element. 10. System according to any of the previous clauses, wherein the first coupling element comprises a coupling surface on the bottom side of the movable plate and wherein the second coupling element comprises a hook element configured for abutting the coupling surface on the bottom side of the movable plate.

[0088] 11 . System according to any of the previous clauses, wherein the movable plate further comprises a base plate and guiding elements, for guiding the layer of items during sweeping of a layer of items onto or from the movable plate.

[0089] 12. System according to clause 11 , wherein the guiding elements are positioned on opposite sides of the base plate and wherein the movable plate is positioned such by the robotic arm that the guiding elements are positioned substantially perpendicular to the sweeping elements during sweeping of a layer of items onto or from the movable plate.

[0090] 13. System according to any of the previous clauses, wherein the sweeping element is configured to abut against the layer of items to be swept, said sweeping element being hingedly connected to the robotic arm.

[0091] 14. System according to any of the previous claim clauses s, wherein the sweeping element comprises a sweeping position and an open position, in particular wherein the sweeping position and the open position mutually enclose an angle.

[0092] 15. System according to any of the previous clauses, wherein the movable plate comprises a polymer base plate, in particular a flat base plate comprising a polymer material.

[0093] 16. System according to any of the previous clauses, wherein the robotic arm also comprises picking elements, such as suction cups, for picking packing sheets that are present in between the layers of items. 17. System according to any of the previous clauses, wherein the system comprises at least one shaft comprising at least three upright walls at least partly surrounding the palletized stack of layers of items.

[0094] 18. System according to any of the previous clauses, wherein the robotic arm further comprises at least one pallet hook, configured for automatic coupling and uncoupling with at least one pallet.

[0095] 19. System according to any of the previous clauses, wherein the system comprises multiple first resting positions and / or multiple second resting positions.

[0096] 20. End effector for sweeping off a layer of items to depalletize a stack of items for use in a system according to any of the previous clauses.

[0097] 21 . Method for palletizing and / or depalletizing at different height levels, in particular by using a system according to any of the clauses 1 - 19 or by using an end effector according to claim 20, comprising the following steps: a) Sweeping off the top layer of items from a first position to a movable plate; b) Coupling the movable plate with a robotic arm; c) Moving and positioning of the movable plate to a second position by the robotic arm that is coupled to the movable plate; d) Uncoupling the movable plate and the robotic arm; e) Sweeping off the layer of items from the movable plate; f) Coupling the movable plate and the robotic arm; g) Moving and positioning the movable plate to the first position and uncouple the movable plate and the robotic arm; h) Repeating steps a-h until the pallet is depalletized.

[0098] 22. Method according to clause 21 , wherein the movable plate and the robotic arm are uncoupled during sweeping of the layer of items onto or from the movable plate.

[0099] 23. Method according clause 21 or 22, further comprising the step of picking up a packing sheet, wherein the packing sheet is positioned above the layer of items during repositioning of the movable plate from the first position to the second position, and preferably dropping the packing sheet later on.

[0100] The invention will be further elucidated by means of non-limiting exemplary embodiments illustrated in the following figures, in which:

[0101] - Figure 1 shows an embodiment of the system according to the present invention;

[0102] - Figure 2a shows an embodiment of a part of the robotic arm and a movable plate in coupled state.

[0103] - Figure 2b shows an uncoupled view of the embodiment of figure 2a.

[0104] - figure 3a shows a perspective top view of an embodiment of a part of a robotic arm according to the present invention.

[0105] - figure 3b shows a perspective bottom view of the embodiment of figure 3a.

[0106] - Figure 4 shows an embodiment of a shaft for the system according to the present invention

[0107] - Figure 5a shows a perspective view of an embodiment of a part of the robotic arm and a movable plate according to the present invention.

[0108] - Figure 5b shows a side view of the embodiment shown in figure 5a in a coupled state.

[0109] - Figure 5c shows a top view of the embodiment shown in figure 5a in a coupled state.

[0110] - Figure 6 shows a perspective view of an embodiment of the present invention comprising one robotic arm and two first resting areas.

[0111] Within these figures, similar reference numbers correspond to similar or equivalent elements or features.

[0112] Figure 1 shows an embodiment of a system 1 for depalletizing a palletized stack of layers of items, in particular glass bottles. The system 1 comprises a movable plate 2, provided with first coupling elements 3 (not shown, see figure 2). The movable plate 2 comprises a rectangular shaped base plate. The movable plate 2 shown further comprises guiding elements 4, which are located on opposite sides and on the top surface of the movable plate. Examples of embodiments of the coupling elements 3 are further shown in figures 2a and 5a. The system 1 further comprises a robotic arm 5, comprising two sweeping elements 6a, 6b. The sweeping elements 6a, 6b comprise second coupling elements 7 (not shown, see figure 2). The first and second coupling elements are complementary. The coupling elements are shown in a coupled state. The robotic arm 5, comprising an arm element 5” and an end effector 5’, can move the movable plate from the first resting area to a second resting area. In the shown embodiment, the robotic arm 5 swept a layer of items 11 from the pallet 12 to the movable plate 2. Then the robotic arm 5 is coupled to the movable plate 2. The figure shows the coupled state of the robotic arm 5 and the movable plate 2. In the embodiment and state shown in figure 1 , the robotic arm 5 is in a state wherein the movable plate 2 is moved from a first resting area 8 to a second resting area 9 wherein the first area 8 comprises a first position 8a that aligns with the top layer of items of the stack 8b and the second resting area 9 comprises a second position 9b at a substantially similar horizontal level of a downstream or upstream conveyor 10.

[0113] In the figure a pallet 12 is shown which is located on a lift element 13. The pallet 2 is depalletized and the last layer of glass bottles 11 is shown on the movable plate 2.

[0114] In the figure a frame 8’ is present in the first resting area 8, which defines the first position 8a on the top surface of the frame 8’. The embodiment of the system 1 shown further shows a frame 9’ which is positioned in the second resting area 9, of which the top surface defines the second position 9b.

[0115] Figure 2a shows a coupled state of a part of an embodiment of an end effector 5’ of the robotic arm and a movable plate 2. Figure 2b shows an uncoupled view of the embodiment of figure 2a. In both figures the top surface of the movable plate is empty.

[0116] In the shown embodiment, the movable plate 2 comprises first coupling elements 3, which are hook like elements in this embodiment. The first coupling elements 3 protrude from the top surface of the movable plate 2a upwards. The hooks 3 are positioned on the corners of the movable plate 2. The coupling elements 3 are divided over two opposite sides 14, 15 of the movable plate 2. The movable plate 2 further comprises two guiding elements 4a, 4b that are positioned on opposite sides 14, 15 respectively. This is an advantageous positioning because it leaves the sides 16, 17 open and free of any obstacles for the sweeping operation.

[0117] In the shown embodiment, the end effector 5’ of the robotic arm comprises two sweeping elements 6a, 6b. In figure 2a, the sweeping elements 6a, 6b are shown in a coupled state wherein the sweeping elements 6a, 6b are in a sweeping position. This is also the position that is maintained while the plate 2 is moved by the robotic arm 5 from the first position to the second position. The shown embodiment further shows second coupling elements 7, which are rod shaped elements. The second coupling elements 7 are positioned in between the guiding element 4a, 4b and the second coupling elements 3. This is visible in figure 2a. In figure 2b the sweeping elements 6a, 6b are shown in a n open position. The sweeping elements 6a, 6b is are hingedly connected to the part of the robotic arm 5’. The shown embodiment further shows pallet hooks 18.

[0118] Figure 3a shows a perspective top view of an embodiment of an end effector 5’ of a robotic arm according to the present invention. Figure 3b shows a perspective bottom view of the embodiment of figure 3a.

[0119] The shown embodiment in figures 3a, 3b show an example of an end effector of a robotic arm 5”. This embodiment comprises two sweeping elements 6a, 6b. The sweeping elements 6a, 6b are hingedly connected to the end effector 5” of the robotic arm. The end effector 5” of the robotic arm is further provided with suction cups 19 as picking elements for picking a packing sheet.

[0120] Figure 4 shows an embodiment of a shaft 20 for the system according to the present invention. The shaft comprises four walls 21 ,22,23,24 which enclose a space for a pallet 12. It is possible to place a lift element within the shaft (not shown). The lift element 13 as shown in figure 1 can be placed in a shaft 20 like shown for example. The walls surround ta space for the pallet 12. To allow a pallet 12 to enter, the door 21 can be split into two parts 21a, 21 b. This could also be a slidable door, or a hinged door in one part, whatever suits the user. The shaft further comprises an extended element 25 , where empty pallets and / or packing sheets can be dropped. Figure 5a shows an embodiment of a part of an embodiment of a system for depalletizing a palletized stack of layers of items, in particular glass bottles. The figure shows a movable plate 2, provided with first coupling elements 3. The movable plate 2 comprises a rectangular shaped base plate 2a. The first coupling elements 3 comprises a protruding plate 3b protruding from the base plate 2a and further comprising a rod or pin 3a that extend from the protruding plate 3b towards and partly over the surface of the base plate 2a.

[0121] The movable plate 2 shown further comprises guiding elements 4, which are located on opposite sides and on the top surface of the movable plate. The figure further shows an example of an end effector 5’, comprising two sweeping elements 6a, 6b. The sweeping elements 6a, 6b comprise second coupling elements 7. The first and second coupling elements are complementary. The second coupling elements 7 in this embodiment shown comprises two rods 7a, 7b, that extend in parallel and in parallel with the base plate 2a of the movable plate 2. The second coupling elements 7 are integrated with the sweeping elements 6a, 6b.

[0122] The rod or pin 3a and the plate 3b in combination with the pins 7a, 7b of the second coupling element 7 limit mutual movement of the movable plate 2 with respect to the operational tool 5’ of the robotic arm. The protruding plate 3b limits the movement of the movable plate 2 relative to pins 7a, 7b of the secondary coupling element 7. This prevents that the movable plate would slide off in horizontal direction H. to the base plate 2, due to blocking of the pins 7a, 7b in case of an unexpected rotation. Perpendicular to the horizontal and vertical direction, into the paper, the relative movement is also limited, because the two pins 7a, 7b support and take pin 3a with them in the same direction. The two pins 7a, 7b of the second coupling element 7, support the rod or pin 3a in an upward movement in vertical direction. Due to the limiting in movement, the mutual plate and operational tool of the robotic arm are temporarily coupled. So, the coupling elements are shown in a coupled state in figures 5a, 5b and 5c. In this state, the robotic arm 5 can move the movable plate 2 from the first resting area to a second resting area.

[0123] The sweeping elements 6a, 6b can be put in an open or a closed position, due to the hinge 6c. The figures 5a, 5b, 5c show the closed position. Only part of an embodiment of the robotic arm of the system is shown. The figure shows the operational tool 5’ that is part of the robotic arm 5. The robotic arm used preferably has its base on the ground level and can move the operational tool 5’ shown freely to any desired position.

[0124] In this embodiment, the guiding elements 4 are situated on opposite sides of the base plate. On either side of a guiding element 4, first coupling elements 3 are positioned. In an uncoupled state, two opposite sides of the base plate are provided with two guiding elements and first coupling elements and the other two sides are free from any obstacles. Items are swept onto the base plate of the movable plate by at least one of the sweeping elements 6a, 6b. Each sweeping element is provided with a rectangular bar 6d. In a coupled state, the items are protected and guided on the base plate by the two guiding elements 4 and the bars of the two sweeping elements 6a, 6b.

[0125] In the embodiment shown, the robotic arm is provided with picking elements, in this case suction cups 19. These can pick up any packaging sheets that are in between layers of items to depalletize.

[0126] Figure 6 shows an embodiment of a system 30 according to the present invention with multiple first resting areas 38 and one second resting area 39. From the second position 39a in the second resting area 39, two downstream lines can be filled with items. The system 30 comprises two shafts 40 for feeding pallets with stacked layers of items. The system 30 further comprises a third resting area for a stack of pallets 45. This can be done manually as in this embodiment or with an automatic palletizer (not shown). The figure shows a robotic arm 35 with an end effector 35’ and an arm element 35”. The arm element 35”enables the robotic arm to reach all first and second positions 39a, 38a. The end effector 35’ allows for sweeping a layer of items with the sweeping elements 36a, 36b. The end effector 35’ can be coupled with the movable plate 32. The coupling elements are not shown in this figure, any coupling elements as shown in the previous figures can be used. The end effector 35’is further provided with a frame 37 for picking elements such as suction cups (not shown). The second position 39a is aligned with two downstream conveyor belts 51 , 52. Empty and clean articles can be swept from the second position of the movable plate in the direction D1 , D2 to the downstream conveyor belts 51 , 52 respectively. From there the empty articles are transported to the filling lines in directions F1 ,F2 respectively. The system can also be used for palletizing, wherein the directions D1 ,D2,F1 and F2 would be reversed.

[0127] It will be clear that the invention is not limited to the exemplary embodiments which are illustrated and described here, but that countless variants are possible within the framework of the attached claims, which will be obvious to the person skilled in the art. In this case, it is conceivable for different inventive concepts and / or technical measures of the above-described variant embodiments to be completely or partly combined without departing from the inventive idea described in the attached claims.

[0128] The verb 'comprise' and its conjugations as used in this patent document are understood to mean not only 'comprise', but to also include the expressions 'contain', 'substantially contain', 'formed by' and conjugations thereof.

Claims

Claims1 . System for depalletizing a palletized stack of layers of items or palletizing layers of items, in particular empty containers, comprising:- at least one movable plate, provided with first coupling elements;- at least one robotic arm, comprising an arm element and an end effector; said end effector comprising at least one sweeping element and further comprising second coupling elements, wherein the first and second coupling elements are complementary, the coupling elements are configured for automatic coupling and uncoupling of the robotic arm to the movable plate, in particular the second coupling elements are configured for automatic coupling and uncoupling of the robotic arm to the first coupling elements of the movable plate; wherein the robotic arm is configured for horizontally sweeping off one layer of items from the stack onto the at least one movable plate using at least the at least one sweeping element, preferably at least two sweeping elements and / or wherein the robotic arm is configured for horizontally sweeping off one layer of items from the at least one moveable plate onto a position on a pallet; and wherein the robotic arm is configured to move the at least one movable plate from a first resting area to a second resting area wherein the first area comprises a first position that aligns with the top layer of items of the stack and the second resting area comprises a second position at a substantially similar horizontal level of a downstream or upstream conveyor.

2. System according to claim 1 , wherein the movable plate and the robotic arm are configured to be uncoupled during sweeping of the layer of items onto or from the movable plate.

3. System according to claim 1 or 2 , comprising a first supporting element, in particular within the first resting area, for supporting the movable plate in the first position, aligned with the top layer of the stack of layers of items to be depalletized, and / or wherein the system comprises a second supportingelement, in particular within the second resting area, for supporting the movable plate in the second position.

4. System according to any of the previous claims, wherein the system comprises a first supporting element, comprising a framework with an in height movable top surface, said top surface at least corresponding to the surface of the movable plate.

5. System according to any of the previous claims, further comprising a second supporting element, in particular within the second resting area, comprising a top flat surface for supporting the at least one movable plate, said second supporting element positioned such that a layer of items can be swept from a movable plate on top of the supporting element to a downstream conveyor.

6. System according to any of the previous claims, wherein the first and second complementary coupling elements comprise a gripping element.

7. System according to any of the previous claims, wherein the first and second complementary coupling elements comprise a male and female coupling element.

8. System according to any of the previous claims, wherein the first and second complementary coupling elements comprise at least one hook element and a hook receiving element, such as a rod shaped element.

9. System according to any of the previous claims, wherein the first and / or second coupling element comprises an (electronic) magnetic element.

10. System according to any of the previous claims, wherein the first coupling element comprises a coupling surface on the bottom side of the movable plate and wherein the second coupling element comprises a hook element configured for abutting the coupling surface on the bottom side of the movable plate.11 . System according to any of the previous claims, wherein the movable plate further comprises a base plate and guiding elements, for guiding the layer of items during sweeping of a layer of items onto or from the movable plate.

12. System according to claim 11 , wherein the guiding elements are positioned on opposite sides of the base plate and wherein the movable plate is positioned such by the robotic arm that the guiding elements are positioned substantially perpendicular to the sweeping elements during sweeping of a layer of items onto or from the movable plate.

13. System according to any of the previous claims, wherein the sweeping element is configured to abut against the layer of items to be swept, said sweeping element being hingedly connected to the robotic arm.

14. System according to any of the previous claims, wherein the sweeping element comprises a sweeping position and an open position, in particular wherein the sweeping position and the open position mutually enclose an angle.

15. System according to any of the previous claims, wherein the movable plate comprises a polymer base plate, in particular a flat base plate comprising a polymer material.

16. System according to any of the previous claims, wherein the robotic arm also comprises picking elements, such as suction cups, for picking packing sheets that are present in between the layers of items.

17. System according to any of the previous claims, wherein the system comprises at least one shaft comprising at least three upright walls at least partly surrounding the palletized stack of layers of items.

18. System according to any of the previous claims, wherein the robotic arm further comprises at least one pallet hook, configured for automatic coupling and uncoupling with at least one pallet.

19. System according to any of the previous claims, wherein the system comprises multiple first resting positions and / or multiple second resting positions.

20. End effector for sweeping off a layer of items to depalletize a stack of items for use in a system according to any of the previous claims or for sweeping a layer of items from a conveyor belt for palletizing said items onto a pallet.21 . Method for palletizing and / or depalletizing at different height levels, in particular by using a system according to any of the claims 1 - 19 and / or by using an end effector according to claim 20, comprising the following steps: a) Sweeping off the top layer of items from a first position to a movable plate; b) Coupling the movable plate with a robotic arm; c) Moving and positioning of the movable plate to a second position by the robotic arm that is coupled to the movable plate; d) Uncoupling the movable plate and the robotic arm; e) Sweeping off the layer of items from the movable plate; f) Coupling the movable plate and the robotic arm; g) Moving and positioning the movable plate to the first position and uncouple the movable plate and the robotic arm; h) Repeating steps a-h until the pallet is depalletized or palletized.

22. Method according to claim 21 , wherein the movable plate and the robotic arm are uncoupled during sweeping of the layer of items onto or from the movable plate.

23. Method according claim 21 or 22, further comprising the step of picking up a packing sheet, wherein the packing sheet is positioned above the layer of items during repositioning of the movable plate from the first position to the second position, and preferably dropping the packing sheet later on.

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