Conveying device for a web, corresponding packaging machine and packaging material manufacturing line

Abstract

It is described a conveying device (15) for a web (4) fed along a conveying path (P), comprising a plurality of electroadhesive elements (18) comprising an outer electroadhesive gripping surface (19) configured to adhere to the web (4), wherein at least two electroadhesive elements (18) of the plurality of electroadhesive elements (18) are activatable to generate at least a first electric field (E1) and a second electric field (E2).

Description

TECHNICAL FIELD

[0001] The present invention relates to a conveying device for conveying a web. The present invention further relates to a packaging machine for producing sealed packages from a web of packaging machine as well as a packaging material manufacturing line for producing the web of packaging material provided with said conveying device.BACKGROUND ART

[0002] As it is known, many liquid or pourable food products, such as for example pasteurized or long-life (UHT) milk, tomato sauce, wine, fruit juice are sold in packages made of sterilized packaging material.

[0003] Packages of this sort are normally produced with automatic packaging machines, which feed a web of packaging material through a sterilizing unit by means of known conveying or guiding elements (like for example rollers) for sterilizing the web of packaging material alternatively by means of chemical sterilization in a sterilizing bath (e.g. by applying a chemical sterilizing agent, such as a hydrogen peroxide solution) or by means of physical sterilization (e.g. by means of an electron beam).

[0004] The packaging machine further comprises a tube forming unit arranged downstream of the sterilizing unit, extending substantially vertically and designed to fold the web of packaging material for producing a continuous tube. Inside the tube forming unit, the web of packaging material is folded from a continuous planar shape to a continuous tubular shape with a vertical axis. The web of packaging material with a planar shape is folded into a cylinder that is successively subdivided into a plurality of pillow packs which are subjected to successive mechanical folding operations to obtain the finished sealed packages. The tube forming unit is preferably arranged within a fixed structure in which the web of packaging material is maintained in a sterile-air environment. The tube forming unit further comprises a number of folding devices placed in succession (one after the other): by interacting with the folding devices, opposite lateral portions (or edges) of the web of packaging material are placed one on top of the one another so as to form the tube and so as to define an overlapping area and finally sealed to obtain a fluid-tight longitudinal seal in the tube.

[0005] It is desirable, in the above-described packaging machines, in order to ensure a good quality of the production of packages, that the web of packaging material is fed in a controlled way. Therefore, although working satisfyingly well, a need is felt to improve the conveying devices for conveying the web, e.g. by improving a control of the position of the web and / or a control of the friction between the web and conveying device, e.g. to avoid slipping.

[0006] The web of packaging material used for producing the packages is a multilayered packaging material produced in a packaging material manufacturing line or plant known in the art, see e.g. EP3991979 A1 or EP4140740 A1 of the same Applicant. Such lines comprise a plurality of conveying devices configured to convey the multilayered packaging material or layers thereof, e.g. one or more of a paperboard layer, a barrier layer, a heat-sealable or heat-weldable layer. The conveying devices are configured to convey the layers of the multilayered packaging material through different units, e.g. a printing unit and / or a laminating unit.

[0007] It is desirable, in the above-described packaging material manufacturing lines or plants, in order to ensure a good quality of the production of the packaging material, that the multilayered packaging material or layers thereof are fed in a controlled way. Therefore, although working satisfyingly well, a need is felt to improve the conveying devices for conveying the web, e.g. by improving a control of the position of the web during advancement and / or a control of the friction between the web and the conveying device, e.g. to avoid slipping.DISCLOSURE OF INVENTION

[0008] The object of the invention is to provide a conveying device for conveying a web addressing the drawbacks described above.

[0009] An object of the invention is to provide a packaging machine for producing sealed packages addressing the drawbacks described above. An object of the invention is to provide a packaging material manufacturing line for producing the multilayered packaging material addressing the drawbacks described above.

[0010] According to the invention, there are provided a conveying device for a web of packaging material and corresponding packaging machine and packaging material manufacturing line according to the appended claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] A non-limiting embodiment of the present invention will be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a perspective view, with parts removed for clarity, of a packaging machine for producing packages from a packaging material, in accordance with the present invention; Figure 2 is a schematic representation of a multilayered packaging material according to one or more embodiments; Figure 3 is a block diagram representation of a packaging material manufacturing line according to one or more embodiments; Figure 4 is a schematic front view of a conveying device according to one or more embodiments; Figures 5 is a side view of a portion of the electroadhesive device of figure 4; Figures 6 to 10 are schematic representations of a conveying device according to one or more embodiments. BEST MODE FOR CARRYING OUT THE INVENTION

[0012] Figure 1 discloses, as a whole, a packaging machine 1 for continuously producing sealed packages, containing a pourable food product, such as for example pasteurized or long-life (UHT) milk, tomato sauce, wine, fruit juice. The sealed packages are obtained from a packaging material 7 unwound from a reel 3 and fed along a conveying path P. When unwound from the reel 3, the packaging material 7 has the shape of a (continuous) planar web of packaging material 7.

[0013] Typically, the packaging material 7 has a multi-layer structure. More specifically, the packaging material 7 may comprise a plurality of layers 70, 72, 74, as depicted in figure 2. In particular, the packaging material 7 may comprise a layer 70 of fibrous material, such as for example a paper or cardboard layer, and at least a pair of layers 72 of heat-sealable material, e.g. polyethylene, with the layer of fibrous material interposed between them. One of these two layers 72 of heat-sealable material may define the inner face of the packages eventually contacting the pourable product.

[0014] According to some possible non-limiting embodiments, the packaging material 7 may also comprise a layer 74 of gas- and light-barrier material, e.g. aluminum foil or ethylene vinyl alcohol (EVOH) film, which, in particular, is arranged between one of the layers 72 of heat-sealable material and the layer 70 of fibrous material. Preferably, the packaging material 7 may also comprise a further layer 72 of heat-sealable material interposed between the layer 74 of gas- and light-barrier material and the layer 70 of fibrous material.

[0015] The web 4 of packaging material 7 is fed through the packaging machine 1 by means of conveying or guiding elements 6, in particular by rollers 6.

[0016] The packaging machine 1 may comprise a sterilizing unit (not shown) having a sterilizing bath, in which a chemical sterilizing agent, such as a hydrogen peroxide solution, is applied to the web 4 of packaging material 7.

[0017] The packaging machine 1 further comprises a tube forming unit 9 arranged downstream of the sterilizing unit along the conveying path P. The tube forming unit 9 extends substantially vertically along the conveying path P for producing a (continuous) tube 10. In particular, inside the tube forming unit 9, the web 4 of packaging material 7 is folded from a continuous planar shape to a continuous tubular shape with a longitudinal axis Y. In particular, the longitudinal axis Y is arranged along a vertical direction.

[0018] The tube forming unit 9 is defined within a fixed structure 11, i.e. an aseptic chamber, in which the web 4 of packaging material is maintained in a sterile-air environment. The tube forming unit 9 further comprises a number of folding devices 12 placed along the conveying path P in succession (one after the other), each of said folding devices 12 comprising a number of folding rollers cooperating to fold the web 4 of packaging material 7.

[0019] The packaging machine 1 comprises a longitudinal sealing unit 30 (of the known type and not described in detail) for sealing overlapping lateral edges of the packaging material 7 to obtain a fluid-tight longitudinal seal of the tube 10. The tube 10 is continuously filled with the pourable food product through a pour conduit 13, which partially extends inside the tube 10 and is part of a filling circuit.

[0020] The tube 10 is sent to a transverse forming and sealing unit (not shown), in which the tube 10 is gripped to transversely seal the tube and form pillow packs 2. Finally, the pillow packs 2 are subjected to successive mechanical folding operations to obtain the finished sealed packages.

[0021] Preferably, the packaging machine 1 comprises one or more conveying devices 15 according to the present description as better detailed in the following. In particular, the conveying device 15 may comprise a conveying or guiding element 6.

[0022] Figure 3 depicts a packaging material manufacturing line or plant 5 for producing a web 4 of multilayered packaging material 7, such as the above mentioned multilayered packaging material 4. The line 5 may comprise an infeed station 50, where a reel of a layer 70 of the multilayered packaging material, i.e. paperboard, is introduced into the line 5. The layer 70 may be unwound into a web 4 that is advanced through a creasing station 52, where creases are imprinted into the layer 70, and a printing station 54, where images and / or written content is printed on a surface of the layer 70.

[0023] Preferably, the layer 70 is fed through a lamination station 56, where the layer 70 of paperboard material is combined with a number of further layers 72, 74, such as one or more heat-sealable layers 72, a gas- and light-barrier material layer 74 etc. The multilayered packaging material 7 is thus output from the lamination station 56.

[0024] To convey the webs 4 of the one or more layers 70, 72, 74, the packaging material manufacturing line 5 comprises a plurality of conveying or guiding elements 6, such as rollers, that are configured to guide the webs 4 through the stations 50, 52, 54, 56. Each web 4 may be conveyed along a respective conveying path P.

[0025] Preferably, the packaging material manufacturing line or plant 5 comprises one or more conveying devices 15 according to the present description as better detailed in the following. In particular, the conveying device 15 may comprise one or more of the conveying or guiding elements 6 of line 5. The conveying device 15 may be configured to convey the web 4 of multilayered packaging material 7 or a web 4 of at least a layer 70, 72, 74 thereof.

[0026] Figure 4 exemplifies a conveying device 15 according to a preferred embodiment, e.g. positioned within the packaging machine 1 or within the packaging material manufacturing line or plant 5. The conveying device 15 is preferably configured for conveying a web 4, e.g. the web of packaging material 7 or the web of a layer 70, 72, 74 of the packaging material 7. In particular, the conveying device 15 may comprise an electroadhesive roller guiding the web 4. According to a preferred embodiment, the conveying device 15 comprises at least one of the rollers 6 guiding the web 4 of packaging material 7 in the filling machine 1 or the rollers guiding the web 4 of a layer 70, 72, 74 of packaging material 7 in the packaging material manufacturing line 5.

[0027] The conveying device 15 is illustrated in detail in figure 4 and comprises the roller 6 which is supported by a fixed structure 16 and is rotated about an axial or transversal direction X by dedicated driving means 17. The direction X is orthogonal to an advancing direction of the web 4.

[0028] The conveying device 15 comprises a plurality of electroadhesive elements 18. The conveying device 15 may comprise a control unit 14 connected, e.g. wirelessly or cabled, to said electroadhesive elements 18 and configured for supervising and / or controlling said electroadhesive elements 18.

[0029] The conveying device 15 may comprise an energy receiver 32, connected to the plurality of electroadhesive elements 18, configured to power the elements 18. The conveying device 15 may comprise an energy transmitter 31 configured to transmit power to the energy receiver 32, e.g. in a wireless manner. The energy transmitter 31 may be positioned at the fixed structure 16. For example, the energy transmitter 32 and receiver 31 may exchange energy by means of a sliding contact or may comprise a transformer. The electroadhesive elements 18 are provided with an external electroadhesive gripping surface 19. Preferably, the electroadhesive elements 18 are substantially equal to each other and / or have a multilayered structure.

[0030] According to an aspect of the solution, the conveying device 15 may comprise a conveying element 6 rotatable around the axis X, preferably a roller. The plurality of electroadhesive elements 18 is positioned at an outer surface 20 of the conveying element 6 in contact, in use, with the web 4 of packaging material 7 or a layer 70, 72, 74 thereof. The outer electroadhesive gripping surface 19 may be configured to be positioned on the outer surface 20, e.g. the outer electroadhesive gripping surface 19 may be formed and positioned to follow the outer surface 20.

[0031] For example, the electroadhesive elements 18 may be arranged to at least partially cover an external cylindrical surface 20 of the roller 6. The external electroadhesive gripping surface 19 may be coaxial to the axial or transversal direction X and, when in use, it is placed in contact with the web 4.

[0032] The plurality of electroadhesive elements 18 may be arranged in a checkerboard pattern on the outer surface 20 of the conveying element 6. The electroadhesive elements 18 may be arranged so as to cover at least a majority of the outer surface 20, e.g. so as to substantially uniformly cover the outer surface 20. The electroadhesive elements 18 cover from 50% to 90% of the outer cylindrical surface 20; preferably, the electroadhesive elements 18 cover from 60% to 80% of the outer cylindrical surface 20.

[0033] The plurality of electroadhesive elements 18 may be arranged along the axis X; preferably the plurality of electroadhesive elements 18 is arranged side by side and / or (evenly) distanced. The plurality of electroadhesive elements 18 arranged along the axial or transversal direction X may range from one to eight, preferably from two to six. In particular, as exemplified in the figure, the conveying element 6 may comprise three electroadhesive elements 18 arranged side by side and evenly placed along the axial or transversal direction X.

[0034] For the sake of simplicity, only one electroadhesive element 18 will be described in detail below with particular reference to figure 5. The electroadhesive element 18 comprises a set 21 of electrodes, in particular each set 21 comprises two electrodes 22, 23 of opposite polarity. A dielectric layer 25 may be interposed between the electrodes 22, 23. Optionally, the dielectric layer 25 may be part of the conveying element 6, i.e. the outer surface 20 of the conveying element 6 may be made of a dielectric material. In alternative, as exemplified in the figures, the dielectric layer 25 may be interposed between the electrodes 22, 23 and the outer surface 20.

[0035] The dielectric layer 25 preferably extends around the electrodes 22, 23, and / or is interposed between adjacent electrodes 22, 23 and / or is designed to electrically insulate the electrodes 22, 23 from the outer surface 20. The dielectric layer 25 is made of insulating material; advantageously, the dielectric layer 25 is made of silicone material. The dielectric layer 25 has a thickness k comprised between 2 µm and 30 µm; preferably, the thickness k is comprised between 10 µm and 20 µm.

[0036] According to a preferred embodiment, the dielectric layer 25 has a cylindrical shape, is coaxial to the axial or transversal direction X and / or is arranged to uniformly cover the outer surface 20.

[0037] The electroadhesive element 18 may comprise a further dielectric layer 26 covering the electrodes 22, 23 and optionally the dielectric layer 25. The electrodes 22, 23 are encapsulated within two dielectric layers 25, 26. The dielectric layer 26 has a further thickness h. The further thickness h is comprised between 2 µm and 30 µm; preferably, the further thickness h is comprised between 4 µm and 16 µm.

[0038] The dielectric layer 26 (uniformly) covers the electrodes 22, 23. The dielectric layer 26 may (uniformly) covers the dielectric layer 25 (and / or the outer surface 20). The dielectric layer 26 is made in an electrically insulating material, preferably chosen among the following ones: polyether ether ketone (also called PEEK), polyimide (also called PI), polyethylene terephthalate (also called PET), polyethylene naphthalate (also called PEN).

[0039] In use, an outer surface 27 of the dielectric layer 26 is in contact with the web 4 of packaging material and defines the outer electroadhesive gripping surface 19. In use, the web 4 is conveyed upon the roller 6, in particular the web 4 of packaging material is placed against the electroadhesive gripping surface 19 or outer surface 27.

[0040] Preferably, the dielectric layer 26 has a cylindrical shape and is coaxial to the axial or transversal direction X. The dielectric layer 26 may be arranged to (uniformly) cover the dielectric layer 25 and the electrodes 22, 23.

[0041] More in detail, each set 21 includes an array of linear patterned negative teeth, each of which is electrically coupled to a common negative bar. The common negative bar is substantially orthogonal to negative teeth.

[0042] Each set 21 further includes an array of linear patterned positive teeth, each of which is electrically coupled to a common positive bar. The common positive bar is substantially orthogonal to positive teeth. The common negative bar and the common positive bar are connected to a power supply using respective known electrical connections.

[0043] The positive and negative teeth are interdigitated on a common plane, e.g. on the same surface of the dielectric layer 25. In other words, the teeth of opposite polarity are arranged extending in a comb-shaped interdigital array. The dielectric layer 25 or 26 is interposed between two adjacent teeth.

[0044] A gap g is defined, which represents the distance between two adjacent electrodes or teeth 22, 23. In other words, the gap g is the width of the stripe of dielectric layer 25 interposed between two adjacent electrodes 22, 23. The gap g is comprised between 300 µm and 600 µm; preferably, the gap g is comprised between 350 µm and 450 µm; advantageously, the gap g is equal to 400 µm.

[0045] A width w of each electrode 22, 23 is also defined. The width w is comprised between 5000 µm and 9000 µm; preferably, the width w is comprised between 6000 µm and 8000 µm; advantageously, the width w is equal to 7300 µm.

[0046] An active area (i.e. an area where a set of electrodes 22, 23 forms an electric field and interacts with the portion of web 4) of each electroadhesive element 18 is comprised between 320 mm 2< and 400 mm 2< , preferably the active area of each electroadhesive element 18 is comprised between 365 mm 2< and 380 mm 2< .

[0047] The control unit 14 is coupled to the electroadhesive elements 18 and is aimed at applying an electrostatic adhesion voltage to each set 21 of electrodes 22, 23. In particular, the electrostatic adhesion voltage alternates positive and negative charges on adjacent electrodes 22, 23.

[0048] The outer electroadhesive gripping surface 19 may be configured to adhere to the web 4 by means of an electric field inducing electric charges in the web 4. In particular, the electrostatic adhesion voltage forms an electric field that interacts with the portion of web 4 in contact with the electroadhesive gripping surface 19. The electric field may locally polarize the web 4 and induce electric charges in the web 4 that are opposite to the charge of the electrodes 22, 23. The opposite charges of the electrodes 22, 23 and the web 4 attract, causing electroadhesion between the electrodes 22, 23 and the web 4. In other words, as a result of the electrostatic adhesion voltage applied to adjacent electrodes 22, 23, an electroadhesive force is generated, which acts so as to cause the web 4 to adhere to the roller 6.

[0049] The electroadhesive element 18 also works as a contact sensor of the web 4 depending on the capacitance of the electroadhesive element 18 itself. Control unit 14 is configured for determining a position of the web 4 with respect to the electroadhesive elements 18 and / or the outer surface 20. In particular, control unit 14 is configured for determining the position of the edges 28 of the web 4, in particular with respect to the roller 6 axial direction X; i.e. control unit 14 is configured for determining if the electroadhesive elements 18 are at least partly or fully covered with the web 4. For example, the control unit 14 may be configured to receive a capacitance from the plurality of electroadhesive elements 18, indicative of presence of the web 4. That is, a difference in capacitance value exists in case of an electroadhesive element 18 covered by the web and an uncovered electroadhesive element 18.

[0050] Advantageously, control unit 14 is configured for determining a speed of the web 4 of packaging material (in particular, control unit 14 is configured for checking if the web 4 slips).

[0051] The control unit 14 is configured for determining a difference between a speed of the conveying device 15 (e.g. an angular velocity of the roller) and a speed of the web 4. The control unit 14 is configured for determining, if the difference exceeds a predetermined threshold, occurrence of a slip of the web 4.

[0052] The control unit 14 is designed to determine the capacitance of each electroadhesive element 18; the capacitance of each electroadhesive element 18 is variable as a function of the active area and of the dielectric permittivity of the material in contact with the electroadhesive gripping surface 19. The active area remains the same while dielectric permittivity has a different value in case the material in contact with the electroadhesive gripping surface 19 is air or, alternatively, the web 4 or, alternatively, a combination of air and the web 4. Therefore, based on the capacitance determined for each electroadhesive element 18, the control unit 14 can detect if the electroadhesive element 18 is at least partly or fully covered with the web 4 and the position of the edges 28.

[0053] The conveying device 15 uses the electrical control of the electrostatic adhesion voltage to permit a temporary and detachable attachment between the web 4 and the electroadhesive gripping surface 19.

[0054] More in detail, the electroadhesive gripping surface 19 is configured to selectively adhere to the web 4. In particular, the electroadhesive gripping surface 19 is configured for adhering to the web 4 when an electrostatic adhesion voltage is applied to the electroadhesive element 18. Removal of the electrostatic adhesion voltage ceases the adhesion.

[0055] In particular, the outer electroadhesive gripping surface 19 may be configured to selectively adhere to the web 4 as a function of a number of parameters, e.g. comprising one or more of the tensioning of the web 4 and / or the position of the web 4 (in particular, with respect to the outer surface 20) and / or the speed of the web 4.

[0056] The electroadhesive elements 18 can be driven (operated) independently of each other. In particular, the control unit 14 is designed to apply an electrostatic adhesion voltage to each set 21 independently of the electrostatic adhesion voltage applied to the remaining sets 21. Thus, the friction between the electroadhesive gripping surface 19 and the web 4 is variable along the axial or transversal direction X. In other words, the control unit 14 uses the electrical control of the electrostatic adhesion voltage to modify (i.e. increase or decrease) the friction between the web 4 and the electroadhesive gripping surface 19 along the axial or transversal direction X.

[0057] The minimum electrostatic adhesion voltage needed to allow the web 4 to adhere to the electroadhesive gripping surface 19 is variable according to a number of factors, such as: the size of the web 4, the material conductivity and spacing of the electroadhesive elements 18, the insulating material used for the dielectric layer 26, the presence of any disturbances to the electro-adhesion such as dust, other particulates or moisture. The electrostatic adhesion voltage can vary between 500 V and 10 kV; preferably, the electrostatic adhesion voltage can vary between 2 kV and 4 kV.

[0058] Removal of the electrostatic adhesion voltages from the electrodes 22, 23 ceases the electrostatic adhesion force between the web 4 of packaging material and the electroadhesive gripping surface 19. Thus, when there is no electrostatic adhesion voltage between electrodes 22, 23, the web 4 can readily move relative to the outer cylindrical surface 20.

[0059] In the following figures, like reference numbers denote like elements, allowing for a clear and consistent understanding of the corresponding components across the various drawings. For the sake of conciseness, a detailed description will not be repeated.

[0060] According to an aspect of the present description, at least two electroadhesive elements of the plurality of electroadhesive elements 18 are activatable to generate at least a first electric (electrostatic) field E1 and a second electric (electrostatic) field E2, as exemplified in figure 6. In particular, the at least two of the electroadhesive elements 18 can be independently activated to generate the first electric field E1 and the second electric field E2.

[0061] Accordingly, at least a first set 21 of electrodes 22, 23 may be configured to generate or form the first electric field E1. At least a second set 21 of electrodes 22, 23 may be configured to generate or form the second electric field E2. Advantageously, two different portions of the conveying device 15 may exhibit two different electrostatic behaviors, having different friction coefficients. The electric fields E1, E2 may be positioned spaced apart (e.g. aligned), perpendicular or oblique to one another with respect to a width of the conveying device 15.

[0062] The first and second electric field E1, E2 may each have distinct characteristics, including field strength and polarity, to enhance adhesion to the web 4. For example, the electric fields E1, E2 may be different in terms of intensity, force, position, activation time and / or orientation.

[0063] The first electric field E1 has a first intensity. The second electric field E2 has a second intensity. The electric fields E1, E2 may locally polarize the web 4 and induce electric charges in the web 4 that are opposite to the charge of the electrodes 22, 23. The opposite charges of the electrodes 22, 23 and the web 4 attract, causing electroadhesion between the electrodes 22, 23 and the web 4. The force of attraction between the web 4 and the electrodes 22, 23 depends on the intensity of the electric field E1, E2. In particular, the outer electroadhesive gripping surface exhibits a first friction coefficient when the electroadhesive elements 18 are not activated. The outer electroadhesive gripping surface exhibits a second and third friction coefficient, at the first electric field E1 and the second electric field E2, respectively, when the electroadhesive elements 18 are activated.

[0064] The first electric field E1 may substantially correspond to the second electric field E2. That is, the first intensity may be substantially equal to the second intensity, e.g. the first intensity may differ from the second intensity of less than 10%. The first electric field E1 may be different from the second electric field E2. That is, the first intensity may be different from the second intensity, e.g. the first intensity may differ from the second intensity of more than 10%. This way, the interaction between the web 4 and the conveying device 15 at the first electric field E1 may be different from the interaction between the web 4 and the conveying device 15 at the second electric field E2.

[0065] The first and second electric field E1, E2 may be generated at a first and second portion P1, P2 of the conveying device 15, respectively. The first and second portion P1, P2 may be spaced apart (and optionally aligned) along the axial or transversal direction X, perpendicular to the advancing direction P of the web 4. As exemplified in figure 6 the first portion P1 and the second portion P2 may be positioned at opposite extremities of the conveying device 15 along the axial or transversal direction X. In particular, this way, the electroadhesive elements 18 are activatable to generate the first electric field E1 and the second electric field E2 at respective opposite extremities of the web 4. Advantageously, the generation of the electric fields at one or both opposite edges of the conveying device 15 may allow a better control of the web 4, e.g. preventing formation of wrinkles on the surface of the web 4.

[0066] As exemplified in figure 7, the first portion P1 may be adjacent to the second portion P2 in the axial or transversal direction X. In particular, the first portion P1 may be located at an extremity of the conveying device 15 along the axial direction X and the second portion P2 may be located at a central portion of the conveying device 15 along the axial direction X. Accordingly, in use, the electroadhesive elements 18 are activatable to generate the first electric field E1 at a first extremity of the web 4 and the second electric field E2 at a central portion of the web 4.

[0067] According to one or more embodiments, as exemplified in figure 8, the electroadhesive elements 18 are activatable to generate a third electric field E3. The third electric field E3 has a third intensity. The electroadhesive elements 18 are activatable to generate the first electric field at the first portion P1, the second electric field E2 at the second portion P2 and the third electric field at a third portion P3. The first, second and third portions P1, P2, P3 may be spaced apart and optionally aligned along the axial direction X, perpendicular to the advancement path P of the web 4. The first portion P1 may be positioned at a first extremity of the conveying device 15 along the axial or transversal direction X. The second portion P2 may be positioned at a second extremity of the conveying device 15, opposite to the first extremity, along the axial direction X. The third portion P3 may be positioned at a central portion of the conveying device 15 along the axial direction X. In other words, the first electric field E1 may be generated at a first extremity of the web 4, the second electric field E2 at a second extremity of the web 4, opposite to the first extremity, and the third electric field E3 at a central portion of the web 4.

[0068] The first, second and third portion P1, P2, P3 may have respective axes of rotation, the axes being coaxial.

[0069] The first, second and third electric field E1, E2, E3 may substantially correspond, that is the electric field may be substantially homogeneous along the axial direction X, or they may differ from one another. In alternative, the first and second electric field E1, E2 may substantially correspond, that is the first intensity may correspond to the second intensity. The third electric field E3 may have the third intensity being different than the first and second intensity, in particular the third intensity may be smaller than the first and second intensity.

[0070] According to one or more embodiments, as exemplified in figure 9, the conveying device 15 may comprise a first and second portion P1, P2 having different shapes. That is, the second portion P2 has a different shape with respect to the first portion P1. The electroadhesive elements 18 are activatable to generate the first and second electric field E1, E2 at the first and second portion P1, P2, respectively.

[0071] The conveying device 15 may further comprise a third portion P3 having a shape different from the first and second portion P1, P2. The electroadhesive elements 18 are activatable to generate the third electric field P3 at the third portion P3. In particular, the electric field may vary where the conveying device 15 changes shape.

[0072] The third portion P3 may comprise a cylinder element having a substantially constant diameter. The third portion P3 may be positioned between the first and second portion P1, P2. The first portion P1 may comprise a frustoconical element tapering towards the third portion P3. In other words, the first portion P1 may exhibit a first diameter at a first end defining an extremity of the conveying device 15 and a second diameter at a second end, opposite to the first end and optionally being in contact with the third portion P3. The first diameter may be larger than the second diameter. The second portion P2 may comprise a frustoconical element tapering towards the third portion P3. In other words, the second portion P2 may exhibit a first diameter at a first end defining an extremity of the conveying device 15 and a second diameter at a second end, opposite to the first end, and optionally being in contact with the third portion P3. The first diameter may be larger than the second diameter.

[0073] In other words, the first portion P1 is positioned at a first lateral extremity of the conveying device 15, the second portion P2 is positioned at a second lateral extremity of the conveying device 15, opposite to the first lateral extremity, and / or the first P1 and / or second P2 portion comprise a frustoconical element, preferably tapering towards a center of the conveying device 15. The third portion P3 may be positioned between the first and second portion P1, P2 and / or may have a cylindrical shape.

[0074] According to one or more embodiments, as exemplified in figure 10, the first and second portion P1, P2 (and optionally the third portion P3) may be spaced apart and optionally aligned along a circumferential direction R, i.e. a direction following a curvature of the roller 6 of the conveying device 15. The circumferential direction R is tangential to the advancement path P. In other words, when the roller turns about an axis parallel to the axial or transversal direction X, the web 4 comes into contact with the first, second and optionally third portion P1, P2, P3 in succession.

[0075] According to one or more embodiments, the first and second electric field E1, E2 may vary, e.g. position, orientation, intensity, activation in time etc, during operation of the conveying device 15, e.g. the fields E1, E2 may be behave different at different operating phases of the conveying device. In the packaging machine 1 or the packaging material manufacturing line 5, the conveying device 15 and the electroadhesive elements 18 may exhibit a first behavior during transients and a second behavior during normal operation. The first and / or second electric field E1, E2 may vary as a function of the advancing speed of the web 4 along the conveying path P and / or as a function of the (lateral) position of the web 4 with respect to the conveying device 15, e.g. with respect to the first, second and / or third portion P1, P2, P3.

[0076] The first and / or second electric field E1, E2 may vary over time. In particular, the generated electric field(s) E1, E2, E3 may have a first intensity at a first time instant t1 and a second intensity at a second time instant t2, while the conveying device 15 moves, e.g. turns. For example, this way, when the web 4 is tangential to a surface of the conveying element 6, the intensity of the electric field E1, E2 may be smaller than an intensity of the electric field E1, E2 otherwise.

[0077] The first and / or second electric field E1, E2 may vary as a function of an acceleration and / or speed of the conveying device, in particular the speed during normal operation may be higher than the speed during transients. During transients, i.e. at lower speeds, the electric field(s) E1, E2 may have a higher intensity with respect to normal operation, i.e. at higher speeds. In particular, the first and / or second electric field E1, E2 may vary, e.g. in terms of position, intensity and / or activation in time, as a function of an angular acceleration and / or an angular velocity of the conveying element 6 or roller.

[0078] According to one or more embodiments, the conveying device 15 may comprise a coating, configured to cover at least partially the outer electroadhesive gripping surface 19. The coating may comprise an abrasive resistant coating and / or a coating having a predetermined friction coefficient, the predetermined friction coefficient being different from a friction coefficient of the outer electroadhesive gripping surface 19, e.g. when the electroadhesive elements 18 are not activated.LIST OF REFERENCE NUMBERS

[0079] 1packaging machine 2packs 3reel 4web 5packaging material manufacturing line 6conveying or guiding element 7packaging material 9tube forming unit 10tube 11structure 12folding device 13pour conduit 14control unit 15conveying device 16fixed structure 17driving means 18electroadhesive element 19electroadhesive gripping surface 20outer (cylindrical) surface 21set of electrodes 22electrode 23electrode 25dielectric layer 26further dielectric layer 27outer surface 28edge 30sealing unit 31energy transmitter 32energy receiver 50infeed station 52creasing station 54printing station 56lamination station 70paperboard layer 72heat-sealable layer 74gas- and light-barrier layer E1first electric field E2second electric field E3third electric field ggap hfurther thickness kthickness Pconveying path P1first portion P2second portion P3third portion Rcircumferential direction Ylongitudinal axis Xaxial or transversal direction

Claims

1. A conveying device (15) for a web (4) advancing along a conveying path (P), comprising a plurality of electroadhesive elements (18) comprising an outer electroadhesive gripping surface (19) configured to adhere to the web (4), wherein at least two of the electroadhesive elements (18) are activatable to generate at least a first electric field (E1) and a second electric field (E2).

2. The conveying device (15) according to the preceding claim, wherein the first electric field (E1) has a first intensity and the second electric field (E2) has a second intensity, and wherein the first intensity corresponds to the second intensity or the first intensity is different from the second intensity.

3. The conveying device (15) according to any one of the preceding claims, wherein the electroadhesive elements (18) are activatable to generate the first electric field (E1) and the second electric field (E2) at a first (P1) and second (P2) portion of the conveying device (15), respectively, wherein the first (P1) and second (P2) portion are spaced apart along a transversal direction (X), perpendicular to the advancement path (P), preferably wherein the first portion (P1) and the second portion (P2) are positioned at opposite extremities of the conveying device (15) along the transversal direction (X).

4. The conveying device (15) according to any of the preceding claims, wherein, in use, the electroadhesive elements (18) are activatable to generate the first electric field (E1) and the second electric field (E2) at a first (P1) and second (P2) portion of the conveying device (15), respectively, wherein the first portion (P1) is located at an extremity of the conveying device (15) along an axial direction (X), perpendicular to the advancement path (P), and the second portion (P2) is located at a central portion of the conveying device (15) along the axial direction (X).

5. The conveying device (15) according to any one of the preceding claims, wherein the electroadhesive elements (18) are activatable to generate the first electric field (E1) and the second electric field (E2) at a first (P1) and second (P2) portion of the conveying device (15), respectively, as well as a third electric field (E3) at a third portion (P3) of the conveying device (15), wherein the first portion (P1) is located at a first extremity of the conveying device (15) along an axial direction (X), perpendicular to the advancement path (P), the second portion (P2) is located at a second extremity of the conveying device (15) along an axial direction (X), opposite to the first extremity, and the third portion (P3) is located at a central portion of the conveying device (15) along the axial direction (X).

6. The conveying device (15) according to any one of the preceding claims, comprising a first (P1) and second (P2) portion, the second portion (P2) having a different shape with respect to the first portion (P1), wherein the at least two electroadhesive elements (18) are activatable to generate the first electric field (E1) at the first portion (P1) and the second electric field (E2) at the second portion (P2).

7. The conveying device according to the preceding claim, wherein: - the first portion (P1) is positioned at a first lateral extremity of the conveying device (15), - the second portion (P2) is positioned at a second lateral extremity of the conveying device (15), opposite to the first lateral extremity, and / or - the first (P1) and / or second (P2) portion comprise a frustoconical element, preferably tapering towards a center of the conveying device (15).

8. The conveying device (15) according to the preceding claim, comprising a third portion (P3) positioned between the first (P1) and second (P2) portion, wherein the third portion has a cylindrical shape.

9. The conveying device (15) according to any of the preceding claims, comprising a control unit (14) connected to the plurality of electroadhesive elements (18) and configured for determining as a function of the capacitance of the plurality of electroadhesive elements (18): - a position of the web (4) with respect to the plurality of electroadhesive elements (18); and / or - if the plurality of electroadhesive elements (18) is at least partly or fully covered by the web (4); and / or - a speed of the web (4).

10. The conveying device (15) according to the previous claim, wherein the first (E1) and / or second (E2) electric field vary during operation of the conveying device (15), preferably the first (E1) and / or second (E2) electric field vary: - as a function of a speed of the web (4) and / or a position of the web (4) with respect to the conveying device (15); and / or - over time; and / or - as a function of an acceleration and / or speed of the conveying device (15).

11. The conveying device (15) according to any of the preceding claims, comprising a conveying element (6) rotatable around an axis (X), preferably a roller, wherein said plurality of electroadhesive elements (18) is positioned at an outer surface (20) of the conveying element (6) in contact, in use, with the web (4).

12. The conveying device (15) according to the previous claim, wherein the first (E1) and / or second (E2) electric field vary as a function of an angular acceleration and / or an angular velocity of the conveying element (6).

13. The conveying device (15) according to any of the previous claims, comprising a coating configured to cover at least partially the outer electroadhesive gripping surface (19), wherein the coating preferably comprises an abrasive resistant coating and / or a coating having a predetermined friction coefficient, the predetermined friction coefficient being different from a friction coefficient of the outer electroadhesive gripping surface (19).

14. A packaging machine (1) for producing sealed packages from a web (4) of packaging material (7) fed along a conveying path (P), the packaging machine (1) comprises a conveying device (15) according to any one of the preceding claims configured to convey the web (4) of packaging material (7).

15. A packaging material manufacturing line (5) for producing a web (4) of multilayered packaging material, the packaging material manufacturing line (5) comprising a conveying device (15) according to any one of claims 1 to 15 configured to convey the web (4) of multilayered packaging material or at least a web (4) of a layer (70) of the multilayered packaging material.

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