Induction heating device for a packaging machine

Abstract

An induction heating device (10) for a packaging machine (1) configured to produce sealed packages (2) from a multi-layer web (4), the induction heating device (10) being configured to heat a region (A) of the web (4) and comprising: a circuit (13) having at least one conductor member (14) arranged to face the web (4) and generating an electromagnetic field to interact with the conductive layers of the web (4); and a magnetic flux concentrator member (15) that concentrates the magnetic flux of the electromagnetic field into the region (A) of the packaging web (4). Preferably, the conductor member (14) includes an active portion (14a) facing the region (A) and a return portion (14b), the magnetic flux concentrator member (15) being associated with the active portion (14a).

Description

Technical Field

[0001] The present invention relates to an induction heating device for a packaging machine configured to produce sealed packages containing pourable products (preferably pourable food) from a web of packaging material, particularly a continuously advancing web of packaging material.

[0002] Specifically, the induction heating device is configured to heat the area of ​​the continuously advancing packaging material web before forming the package.

[0003] More specifically, the induction heating device is configured to heat the aforementioned area for the purpose of attaching a sealing strip made of heat-sealable plastic material to the web of packaging material, and / or for the purpose of obtaining a longitudinal seal on the web folded into a tube to seal such a tube. Background Technology

[0004] As is well known, many pourable foods, such as juice, UHT (ultra-high temperature) milk, wine, and ketchup, are sold in packaging made of aseptic materials.

[0005] A typical example is the parallelepiped-shaped packaging for pourable food, called TetraBrik Aseptic (registered trademark), which is made by folding and sealing laminated packaging material webs.

[0006] Packaging materials have a multi-layered structure, including a base layer, such as paper, covered on both sides with heat-sealing plastic material (such as polyethylene).

[0007] In the case of aseptic packaging for long-term storage products (such as UHT milk), the packaging material also includes an oxygen barrier layer, such as aluminum foil, which is superimposed on a heat-sealed plastic material layer and covered by another heat-sealed plastic material layer, which forms the inner surface of the packaging that ultimately contacts the food.

[0008] This type of packaging is typically produced on fully automated packaging lines, which include packaging machines configured to form and fill packages starting from multiple layers of packaging material.

[0009] Specifically, according to a non-limiting example of a packaging machine, a continuous tube is formed starting from a web of packaging material initially wound on a spool and fed by multiple unwinding rollers. The continuously advancing web of packaging material is sterilized in the packaging machine, for example by applying a chemical sterilizing agent such as hydrogen peroxide solution. Once sterilization is complete, the chemical sterilizing agent is removed from the surface of the packaging material, for example by evaporation through heating. The thus sterilized web is then held in a closed, sterile environment and continuously advanced by the aforementioned unwinding rollers, longitudinally folded and sealed by a known web folding unit to form a tube.

[0010] Once created, the tube is continuously fed vertically in a straight line, filling sterilized food from above, then shaping, sealing, and subsequently cut along equidistant transverse cross-sections that extend transversely and particularly orthogonally to the vertical direction.

[0011] This results in a so-called pillow-shaped package, which has a longitudinal sealing strip, a top transverse sealing strip, and a bottom transverse sealing strip.

[0012] The pillow-shaped package is then cut at its cross-section to separate it from the others, and then guided to a folding device for final folding.

[0013] This results in finished product packaging.

[0014] Before interacting with the web folding unit, the packaging material web is continuously fed by a device for applying a sealing strip of heat-sealed plastic material, which is first applied to the packaging material.

[0015] More specifically, the first longitudinal portion of the sealing strip is applied and heat-sealed to the first longitudinal edge of the web.

[0016] Specifically, the strip is heat-sealed by partially melting the polyethylene layer at the first longitudinal edge and the heat-sealing plastic of the first longitudinal portion of the strip itself.

[0017] After this application, the second longitudinal portion of the sealing strip protrudes (i.e. extends) from the first longitudinal edge.

[0018] The web folding equipment defines a series of channels for the web, the cross-section of which gradually changes from C-shaped to approximately circular.

[0019] When interacting with the web folding device, the second longitudinal edge of the web, which is opposite to the first longitudinal edge, is positioned outside the first longitudinal edge relative to the axis of the tube being formed.

[0020] In this manner, the second longitudinal edge facing the pipe axis is partially superimposed on the second longitudinal portion of the sealing strip and partially superimposed on the first longitudinal edge.

[0021] At this point, the sealing strip is applied to the web by performing heating and pressing steps.

[0022] More specifically, the heating step involves locally melting the polyethylene layer and the heat-sealed plastic of the second longitudinal portion of the strip itself at the second longitudinal edge.

[0023] This achieves a longitudinal seal.

[0024] According to known solutions, the presence of an aluminum layer is utilized to achieve the aforementioned heat seal.

[0025] In detail, in order to heat-seal the first longitudinal portion of the strip to the first longitudinal edge of the web, the packaging machine includes a first induction heating device arranged upstream of the web folding unit and configured to heat the polyethylene layer at the first longitudinal edge of the web by induction heating the aluminum layer thereon.

[0026] Similarly, in order to heat-seal the second longitudinal portion of the strip to the second longitudinal edge of the web, the packaging machine includes a second induction heating device arranged upstream of the web folding unit and configured to heat the polyethylene layer at the second longitudinal edge of the web by induction heating the aluminum layer thereon.

[0027] Although the aforementioned types of packaging machines and induction heating equipment operate well and satisfactorily, there is a desire to further improve these devices, particularly to enhance sealing quality and improve the overall efficiency of the heat sealing process. Summary of the Invention

[0028] Therefore, the object of the present invention is to provide an induction heating device that is designed to meet at least one of the above-mentioned requirements in a direct and low-cost manner.

[0029] This objective is achieved by the induction heating device claimed in the appended independent claim 1. Preferred embodiments of the invention are set forth in the appended dependent claims. Attached Figure Description

[0030] Non-limiting embodiments of the invention will be described by way of example with reference to the accompanying drawings, wherein: Figure 1 This is a schematic perspective view of a packaging machine including multiple induction heating devices according to the present invention; some parts have been removed for clarity. Figure 2 yes Figure 1 A schematic side view of the induction heating device of the packaging machine; some parts have been removed for clarity. Figure 3 It is based on the alternative implementation plan. Figure 1 A schematic side view of the induction heating device of the packaging machine; some parts have been removed for clarity. Figure 4 This is a schematic diagram showing the concentration of magnetic induction energy in the packaging material. Detailed Implementation

[0031] refer to Figure 1 The mark 1 generally indicates a packaging machine configured to produce sealed packages 2 containing pourable products, preferably pourable foods such as pasteurized or UHT milk, water, juice, wine, peas, soybeans, etc.

[0032] Specifically, the packaging machine 1 is configured to produce packaging 2 from a multi-layer packaging material web 4, which is initially wound on a reel 4a and then folded into a tube 3 of packaging material, as explained below.

[0033] Preferably, the packaging machine 1 is part of a packaging line (known in itself and not shown) configured to produce multiple packages, group them and box them in a known manner.

[0034] The packaging material web 4 has a multi-layer structure (not shown) and includes a fibrous material layer, such as paper, which is covered on both sides with corresponding heat-sealing plastic material (such as polyethylene) layers.

[0035] In addition, the web 4 includes a gas-barrier and light-barrier material layer, preferably aluminum foil, which is superimposed on a heat-sealed plastic material layer and covered with another heat-sealed plastic material layer, the latter forming the inner surface of the package 2 that ultimately contacts the pourable product.

[0036] In detail, this gas-barrier and light-blocking material layer is a conductive layer made of a conductive material (such as aluminum, as described above).

[0037] like Figure 1 As shown, packaging machine 1 includes: - A conveying device configured to continuously advance the web 4 along the advance path P; - Web folding unit 5, which is configured to gradually fold the continuously advancing web 4 into tube 3; - Filling device 6 (shown in part only), which is used to fill tube 3 with pourable product (from above); - Forming and sealing unit 7, which is configured to form and seal tube 3 along a continuous transverse cross section of tube 3 in a known but not detailed manner to obtain a series of pillow-shaped packages 2a; - Isolation chamber 8, which defines an environment containing a controlled atmosphere (particularly sterile and / or sterile gases, preferably sterile and / or sterile air) and houses forming and sealing unit 7, web folding unit 5 and filling device 6; - A folding device (not shown) is configured to fold the package 2a in sequence to obtain multiple sealed packages 2.

[0038] Preferably, the forming and sealing unit 7 has an axis X along which the feed tube 3 is fed during use.

[0039] The axis X is parallel to the direction of the straight line, which is preferably the vertical direction of the straight line.

[0040] Therefore, in use, the tube 3 is fed downward along the axis X, and is formed and sealed by the forming and sealing unit 7 while being filled from above.

[0041] More specifically, tube 3 is pulled (downward) along axis X in a known manner by forming and sealing unit 7.

[0042] In this way, multiple pillow-shaped bags 2a are obtained.

[0043] In view of the above, the packaging machine 1 is configured to form and seal a plurality of pillow-shaped packages 2a containing pourable products starting from the web 4 and the tube 3, and then fold the pillow-shaped packages 2a to obtain the package 2 containing pourable products formed, sealed and folded as described above.

[0044] The packaging machine 1 also includes at least one induction heating device 10, which is configured to heat region A of the web 4 by induction heating, that is, by electromagnetic induction heating of the conductive layer.

[0045] Specifically, the induction heating device 10 is configured to induction heat region A before the web 4 is fully folded into tube 3.

[0046] In detail, such as Figure 1 As shown, the packaging machine 1 includes a sealing strip applicator device 11 of a known type, which is configured to apply a sealing strip of heat-sealing plastic material (not shown) to the first longitudinal edge 4b ​​of the web 4 as it is continuously advanced along the path P and before it is folded into the tube 3, and includes an induction heating device 10 as described above.

[0047] More specifically, according to a known and only briefly described below manner, the applicator device 11 is configured to apply a first longitudinal portion of the sealing strip to a first longitudinal edge 4b, particularly to the surface of the web 4 that ultimately forms the interior of each package 2. Following this application, a second longitudinal portion of the sealing strip extends from the first longitudinal edge 4b ​​in a known manner.

[0048] Conveniently, the sealing strip is made of a heat-sealing plastic material, preferably the same material as the outer layer of the packaging material, namely polyethylene.

[0049] The two plastic material layers of the web 4 are defined here as “outer layers”, even if one layer becomes the outermost layer of the packaging 2 and the other layer becomes the innermost layer of the packaging 2.

[0050] The applicator device 11 is configured to secure the first longitudinal portion of the sealing strip to the first longitudinal edge 4b ​​of the web 4 by heat-sealing the sealing strip to the web 4, particularly to its outer plastic material layer.

[0051] For this purpose, the induction heating device 10 of the applicator device 11 induction heats the aluminum layer in region A of the web 4, thereby causing local melting of the outer layer of the plastic material of the web 4 in region A, and local melting of the first longitudinal portion of the sealing strip applied to the first longitudinal edge 4b.

[0052] Therefore, region A is located near the first longitudinal edge 4b.

[0053] Specifically, region A extends longitudinally along edge 4b.

[0054] In use, by interacting with the web folding unit 5, the second longitudinal edge 4c of the web 4 is placed on the first longitudinal edge 4b, thereby gradually arranging the web 4 from a sheet structure into an intermediate C-shaped structure, and then into a tubular structure. In this way, the second longitudinal portion of the sealing strip is brought toward the second longitudinal edge 4c and applied thereto.

[0055] In order to seal the tube 3, the packaging machine 1 also includes a tube sealing device 12, which is configured to seal the tube 3 longitudinally, particularly the continuously advancing tube 3.

[0056] In detail, the pipe sealing device 12 is configured to heat-seal the second longitudinal portion of the sealing strip to the second longitudinal edge 4c of the web 4, and to heat-seal the second longitudinal edge 4c to the first longitudinal edge 4b.

[0057] Therefore, the second longitudinal edge 4c must be heated.

[0058] In this respect, the pipe sealing device 12 includes the induction heating device 10 as described above. The induction heating device 10 is configured to fix the second longitudinal edge 4c onto the first longitudinal edge 4b.

[0059] More specifically, the induction heating device 10 secures the second longitudinal portion of the sealing strip to the second longitudinal edge 4c of the web 4 by heat-sealing the sealing strip onto the web 4, particularly onto its outer plastic layer, and then secures the second longitudinal edge 4c to which the sealing strip is attached to the first longitudinal edge 4b. Thus, a longitudinal sealing line is defined, which is covered by the sealing strip on the surface of the packaging material that defines the inner wall of the package 2.

[0060] More specifically, the induction heating device 10 of the tube sealing unit 12 induction heats the aluminum layer in region A of the web 4 near the second longitudinal edge 4c, thereby causing local melting of the outer plastic material layer of the web 4 at the second longitudinal edge 4c.

[0061] Therefore, region A is also located at the second longitudinal edge 4c.

[0062] In the same case, region A extends longitudinally along edge 4c.

[0063] In view of the above, the packaging machine 1 includes two induction heating devices 10, each configured to heat region A of the web 4 by induction heating the aforementioned conductive layer of the web 4, the region A being located near the respective longitudinal edges 4b, 4c of the web 4.

[0064] More precisely, the induction heating device 10 is configured to heat the aforementioned area A for the purpose of attaching a sealing strip made of heat-sealing plastic material to the web 4 and / or for the purpose of obtaining a longitudinal seal on the web 4 folded into the tube 3 to seal the tube 3.

[0065] For the sake of brevity, reference will be made below to a single induction heating device 10, which is configured to heat region A of the web 4 located near the longitudinal edge 4b. However, the structural and functional features described for this induction heating device 10 are equally applicable to induction heating devices present in the packaging machine 1 that are configured to heat region A of a continuously advancing web located near the longitudinal edge 4b ​​or longitudinal edge 4c.

[0066] Reference Figure 2 The induction heating device 10 includes a circuit 13 (shown only in cross-section in part only) having at least one conductor member 14 configured to face the web 4, i.e., a first surface 40a facing the web 4 in use, and configured to generate an electromagnetic field that defines a magnetic flux.

[0067] In detail, the conductor member 14 is configured to be fed current, that is, it is configured to transmit current so as to induce current in region A in the conductive layer of the web 4.

[0068] More specifically, conductor member 14 includes: - Active portion 14a, which is configured to face the heating region A of the web 4; and - Return section 14b, which is configured to recirculate current toward active section 14a.

[0069] Conveniently, the cross-section of the active portion 14a is narrower than the cross-section of the return portion 14b.

[0070] In this way, due to the operating characteristics of the induction heater, the induction heating effect is more prominent in region A of the web 4 facing the active portion 14a.

[0071] In use, the electromagnetic field generated by circuit 13, especially the electromagnetic field defined by the current flowing through the active portion 14a, defines the magnetic flux that impacts the web 4 and interacts with the conductive layer of the web 4.

[0072] Therefore, according to well-known processes, current is induced in the conductive layer, and the conductive layer eventually heats up (Joule effect).

[0073] According to one aspect of the invention, the induction heating device 10 includes a magnetic flux concentrator component 15 (hereinafter referred to as "concentrator" for simplicity), which is associated with the conductor component 14 and configured to concentrate magnetic flux in the aforementioned heated region A of the web 4.

[0074] More precisely, the concentrator 15 is configured to guide the magnetic flux defined by the electromagnetic field generated by the conductor member 14 at region A, so as to generate a peak in the induced current density defined by the electromagnetic field at region A, thereby concentrating the induction heating device 10 induction heating in region A.

[0075] The expression "concentrated magnetic flux" or "guided magnetic flux" means that electromagnetic field lines are concentrated and pass through region A of the web 4, resulting in a local increase in current density at the surface of the conductor member 14 facing the web 4 and at region A of the conductive layer of the web 4.

[0076] In other words, the applicant observed through extensive experimental activities that the concentrator 15 increases the induced current density at region A and concentrates this induced current at region A, thereby avoiding the dispersion of current density around region A.

[0077] This situation is in Figure 4 The diagram schematically depicts the current density distribution CD along the transverse direction of the web 4, that is, along the transverse direction in particular orthogonal to the longitudinal direction of the web 4, starting from the coordinate Y=0, which represents the longitudinal edge 4b ​​of the web 4 near the region A to be heated.

[0078] Curve 100 is associated with the induction heating device 10 according to the present invention and including a concentrator 15, while curve 200 is associated with an induction heating device without any magnetic flux concentrator components.

[0079] By comparing curves 100 and 200, it can be clearly seen that in curve 100, the current density distribution CD is more concentrated in region A, with less dispersion around region A, while in curve 200, the current density distribution CD remains higher than that in curve 100 in the region adjacent to region A.

[0080] This means that it has various advantages compared to induction heating equipment without concentrator 15: - The required peak current density can be achieved with a smaller power level, resulting in more efficient, energy-saving and more environmentally friendly machines; - The application of the seal and / or sealing strip of pipe 3 is more precise and effective; The presence of the concentrator 15 greatly reduces the risk of defects appearing in the web 4 in the heating zone A and near zone A (e.g., at the longitudinal edge 4b).

[0081] In addition, it is known that the thickness of the conductive layer of web 4 needs to be reduced.

[0082] This reduction in thickness necessitates an increase in the frequency of the current fed to circuit 13 and through conductor member 14 to maintain the required heating level in the conductive layer, thereby significantly increasing the required electrical power.

[0083] The presence of concentrator 15 allows the current density distribution CD around region A to be kept under control, i.e. kept below the desired threshold where the risk of defects is low, even when conductor member 14 needs to be fed with high-frequency current.

[0084] The concentrator 15 is configured to face the first surface 40a, thereby being configured to concentrate the magnetic flux through the first surface 40a into the aforementioned region A of the web 4.

[0085] According to an alternative embodiment not shown, circuit 13 includes a second conductor member 14 configured to face a second surface 40b of web 4, which is opposite to the first surface 40a, i.e., the second surface 40b facing web 4 in use, and is configured to generate an electromagnetic field that defines a magnetic flux.

[0086] Therefore, the induction heating device 10 includes a second magnetic flux concentrator member 15, which is associated with the second conductor member 14 and configured to concentrate magnetic flux at the aforementioned heated region A of the web 4. The second concentrator 15 is configured to face the second surface 40b, thereby being configured to concentrate magnetic flux at the aforementioned region A of the web 4 through the second surface 40b.

[0087] The applicant has observed that the presence of two conductor members 14 arranged on both sides of the web 4 and two concentrators 15 associated therewith improves the sealing quality because the induced heat is more uniform. In fact, possible fluctuations in induced heat in region A due to minor positioning deviations or oscillations of the continuously advancing web 4 are "averaged out" by the presence of the two conductor members 14 and the two concentrators 15.

[0088] Advantageously, such as Figure 2 As shown, the concentrator 15 is associated with the active portion 14a.

[0089] Specifically, the concentrator 15 partially surrounds the active portion 14a of the conductor member 14.

[0090] More specifically, the active portion 14a extends longitudinally so that it is substantially parallel to the longitudinal extension direction of the web 4 (orthogonal to direction Y) during use.

[0091] Therefore, the concentrator 15 extends longitudinally and is substantially parallel to the active portion 14a.

[0092] Conveniently, the concentrator 15 has an open profile in cross-section with a first free end 15a and a second free end 15b, such that in use, electromagnetic field lines generated by the active portion 14a of the conductor member 14 travel from the first free end 15a to the second free end 15b and pass through region A of the web 4.

[0093] Therefore, at least the active portion 14a of the conductor member 14 must be placed at an appropriate distance from the web 4, especially from region A.

[0094] according to Figure 2 The non-limiting embodiment shown has a concentrator 15 with a generally C-shaped cross-section (or according to...) Figure 2 The orientation is an inverted U-shaped cross section, and surrounds the conductor member 14 on three sides, especially the active portion 14a, thereby defining a spatial region. In use, the electromagnetic field lines travel from the first free end 15a through this spatial region to the second free end 15b and through region A.

[0095] Appropriately, the concentrator 15 avoids, i.e., does not cover, i.e. does not surround, the side of the conductor member 14 (especially its active portion 14a) facing the area A in use.

[0096] The applicant has discovered that this configuration of the concentrator 15 allows the magnetic flux (i.e., the electromagnetic field lines generated by the active portion 14a) to be optimally concentrated at region A, thereby improving heat generation and bringing about the aforementioned advantages.

[0097] Suitablely, the concentrator 15 comprises a ferromagnetic material, i.e., is made of a ferromagnetic material.

[0098] Advantageously, the concentrator 15 is made of a material containing plastic ferrite or magnetic rubber.

[0099] In this way, the production of the concentrator 15 is greatly simplified, as it can be produced in a fairly easy manner through injection molding.

[0100] This also significantly reduces production costs.

[0101] Furthermore, the adaptability of the concentrator 15 is improved because its production via injection molding allows for easy acquisition of any desired shape.

[0102] According to another aspect of the invention, the conductor member 14 and the concentrator 15 are configured to face a portion of the web 4, defining a region A to be heated near the longitudinal edge 4b ​​of the web 4, such that region A is located at a preferred non-zero distance D from the longitudinal edge 4b ​​toward the center portion of the web 4. The distance D is preferably between 0.1 mm and 5 mm, more preferably between 1 mm and 4 mm.

[0103] In other words, region A does not contain vertical edge 4b, or vertical edge 4b ​​is not part of region A.

[0104] Preferably, the concentrator 15 is offset by a distance D from the longitudinal edge 4b ​​of the web 4 toward the center portion.

[0105] This configuration further reduces the risk of defects near the longitudinal edge 4b ​​and further improves the sealing quality.

[0106] According to an alternative embodiment not shown, the concentrator 15 is offset by a distance D from the longitudinal edge 4b ​​and extends from the longitudinal edge 4b. The applicant has observed that this configuration may be advantageous in certain situations and for certain packaging materials.

[0107] The location of the region of maximum magnetic flux concentration can be changed by altering the positioning of the concentrator 15 relative to the longitudinal edge 4b.

[0108] Figure 3 An induction heating device 10 according to an alternative embodiment of the present invention is shown. This induction heating device 10 differs from the induction heating device 10 described above only in that it includes a concentrator 15' having a generally L-shaped cross-section surrounding the conductor member 14 on both sides, particularly its active portion 14a.

[0109] Similar to the above, Figure 3 The L-shaped concentrator 15' defines a spatial region in use, where electromagnetic field lines generated by the active portion 14a pass through the spatial region from the first free end 15a to the second free end 15b and through region A.

[0110] The applicant has noted that the L-shaped concentrator 15' retains the same advantages listed above for the C-shaped concentrator 15, and further reduces production costs due to the smaller amount of material required.

[0111] Furthermore, the L-shaped concentrator 15' allows for further technical effects, which will be explained below.

[0112] In an advantageous embodiment, the concentrator 15' partially surrounds the conductor member 14, particularly the active portion 14a, such that an L-shaped cross-section is arranged on one side of the conductor member 14, particularly the active portion 14a, which is the distal / opposite side relative to the longitudinal edge 4b.

[0113] That is, the concentrator 15' is arranged such that the L-shaped cross-section surrounds two adjacent sides of the active portion 14a of the conductor member 14, which are away from the longitudinal edge 4b ​​and opposite to the longitudinal edge 4b.

[0114] This configuration is like Figure 3 As shown.

[0115] The applicant has observed that this configuration is particularly advantageous in reducing the risk of defects at the longitudinal edge 4b ​​of the web 4.

[0116] In fact, the magnetic flux concentration is weaker in the region surrounding the conductor member 14 that is not surrounded by the concentrator 15' than in the region surrounded by the concentrator 15'. Therefore, the current density in the conductive layer region of the web 4 facing the aforementioned region surrounding the conductor member 14 that is not surrounded by the concentrator 15' is lower. Consequently, less heat is generated in this region of the web 4, which ultimately leads to a significant reduction in the risk of defects at the longitudinal edge 4b ​​near region A.

[0117] In other words, by changing the cross-sectional shape of the concentrators 15 and 15', especially by providing the concentrator 15' with an L-shaped cross-section arranged as described above, the peak value of the current density distribution CD at region A can be further moved away from the longitudinal edge 4b ​​without actually moving the concentrator 15' and the conductor member 14 further away from the longitudinal edge 4b.

[0118] In other words, the peak value of the current density distribution CD is arranged such that the distance D from the longitudinal edge 4b ​​is greater when using the L-shaped concentrator 15' than when using the C-shaped concentrator 15.

[0119] As mentioned above, this configuration results in better spatial organization, reduced defects at the longitudinal edge 4b, material savings, and ultimately lower overall costs.

[0120] According to an alternative embodiment not shown, the concentrator 15' partially surrounds the conductor member 14, particularly the active portion 14a, such that an L-shaped cross-section is arranged on one side of the conductor member 14, particularly on the side of the active portion 14a near the longitudinal edge 4b.

[0121] That is, the concentrator 15' is arranged such that the L-shaped cross-section surrounds two adjacent sides of the active portion 14a of the conductor member 14 near the longitudinal edge 4b.

[0122] The applicant has observed that, in certain circumstances, this configuration of the concentrator 15' is desirable for packaging materials of a certain nature in order to reduce the risk of shrinkage of the heat seal layer at the longitudinal edge 4b.

[0123] The advantages of the induction heating device 10 according to the present invention will be clearly seen from the above description.

[0124] In particular, due to the presence of concentrators 15 and 15', the current density distribution CD is more concentrated in the area to be heated A, and less dispersed around the area A along the direction Y of the web 4.

[0125] This means that, compared to the case where there are no concentrators 15 and 15' in the induction heating device 10, the current density at the longitudinal edges 4b and 4c near the area to be heated A is lower, which reduces the risk of defects occurring at the longitudinal edges 4b and 4c.

[0126] In other words, the presence of concentrators 15, 15' allows the current density distribution CD around region A to be kept under control, i.e. kept at a desired threshold with low defect risk, even when conductor member 14 needs to be fed high-frequency current.

[0127] Furthermore, due to the presence of concentrators 15 and 15', the required peak current density can be achieved with a smaller power level, resulting in a more efficient, energy-saving, and environmentally friendly machine.

[0128] Furthermore, the application of the seal and / or sealing strip of tube 3 is more precise and effective.

[0129] Obviously, modifications can be made to the induction heating device 10 described herein without departing from the scope of protection defined in the appended claims.

Claims

1. An induction heating device (10) for a packaging machine (1), the packaging machine (1) being configured to produce sealed packages (2) containing pourable products from a continuously advancing multi-layer packaging material web (4), the packaging material web (4) comprising a conductive layer made of a conductive material. The induction heating device (10) is configured to continuously heat region (A) of the advancing packaging material web (4) by induction heating the conductive layer. And the induction heating device (10) mentioned above includes: -Circuit (13) having at least one conductor member (14) configured to face the packaging material web (4) and generate an electromagnetic field configured to interact with the web (4) and its conductive layer, the electromagnetic field defining a magnetic flux. - A magnetic flux concentrator component (15; 15') associated with the conductor component (14) and configured to concentrate the magnetic flux in the region (A) of the packaging material web (4); The magnetic flux concentrator component (15) is described above. 15') is configured to guide magnetic flux at the region (A) to generate a peak in the induced current density defined by the electromagnetic field at the region (A), thereby causing the induction heating device (10) to concentrate induction heating on the region (A) of the continuously advancing packaging material web (4).

2. The induction heating device as claimed in claim 1, wherein the conductor member (14) is configured to face the first surface (40a) of the web (4), and wherein the magnetic flux concentrator member (15); 15') is configured to concentrate the magnetic flux in the region (A) of the packaging material web (4) through the first surface (40a); The circuit (13) has a second conductor member (14) configured to face the second surface (40b) of the web (4); The induction heating device (10) includes a second magnetic flux concentrator component (15; 15') associated with the second conductor component (14) and configured to concentrate the magnetic flux in the region (A) of the packaging material web (4) through the second surface (40b).

3. The induction heating device as claimed in claim 1 or 2, wherein the conductor member (14) is configured to deliver current and includes an active portion (14a) and a return portion (14b), the active portion (14a) being configured to face the area (A) to be heated of the web of the packaging material (4), and the return portion (14b) being configured to recirculate the current toward the active portion (14a); And the magnetic flux concentrator component (15; 15') is associated with the active portion (14a).

4. The induction heating device of claim 3, wherein the magnetic flux concentrator component (15; 15') partially surrounds the active portion (14a) of the conductor component (14).

5. The induction heating device of claim 4, wherein the cross-section of the magnetic flux concentrator component (15; 15') has an open profile, the open profile having a first free end portion (15a) and a second free end portion (15b).

6. The induction heating device of claim 5, wherein the magnetic flux concentrator member (15) has a generally C-shaped cross-section and surrounds the conductor member (14) on three sides.

7. The induction heating device as claimed in claim 5, wherein the magnetic flux concentrator member (15') has a generally L-shaped cross-section and surrounds the conductor member (14) on both sides.

8. The induction heating apparatus of claim 6, wherein the conductor member (14) and the magnetic flux concentrator member (15; 15') are configured to face a portion of the packaging material web (4), defining the region (A) near the longitudinal edge (4b; 4c) of the packaging material web (4), such that the region (A) is located at a non-zero distance (D) from the longitudinal edge (4b; 4c) and away from the center portion of the web (4), the distance (D) preferably being between 0.1 mm and 5 mm, more preferably between 1 mm and 4 mm.

9. The induction heating device according to any one of claims 1 to 7, wherein the conductor member (14) and the magnetic flux concentrator member (15; 15') are configured to face a portion of the packaging material web (4), defining the region (A) near the longitudinal edge (4b; 4c) of the packaging material web (4), such that the region (A) is located at a non-zero distance (D) from the longitudinal edge (4b; 4c) toward the center portion of the web (4), the distance (D) preferably being between 0.1 mm and 5 mm, more preferably between 1 mm and 4 mm.

10. The induction heating device according to any one of claims 7 to 9, wherein the magnetic flux concentrator member (15') partially surrounds the conductor member (14) such that the L-shaped cross-section is arranged on one side of the conductor member (14) relative to the distal end / opposite of the longitudinal edge (4b; 4c).

11. The induction heating device as claimed in any of the preceding claims, wherein the magnetic flux concentrator component (15; 15') is made of a material comprising plastic ferrite or magnetic rubber.

12. The induction heating device as claimed in any of the preceding claims, wherein the induction heating device (10) is configured to be implemented in a sealing strip applicator device (11), the sealing strip applicator device (11) being configured to apply a sealing strip of heat-sealing plastic material to the longitudinal edge (4b) of the web before folding the web (4) into a tube (3).

13. The induction heating device according to any one of claims 1 to 11, wherein the induction heating device (10) is configured to be implemented in a tube sealing unit (12), the tube sealing unit (12) being configured to longitudinally seal the tube (3) formed by folding the web of the packaging material (4).

14. A packaging machine (1) configured to produce sealed packages (2) containing pourable products from a multi-layer packaging material web (4), the packaging material web (4) comprising a conductive layer made of a conductive material, the packaging machine (1) comprising: - A conveying device configured to advance the web (4); - A web folding unit (5) configured to fold the web (4) into a tube (3); - A forming and sealing unit (7) is configured to form the tube (3) and seal the tube (3) along its continuous transverse cross section in order to obtain a series of packages (2a); - A folding device configured to fold the package (2a) in sequence to obtain multiple sealed packages (2); - An induction heating device (10) as described in any of the preceding claims is configured to induction heat region (A) of the web (4) before it is fully folded into a tube (3).

15. The packaging machine according to claim 14, comprising: - A sealing strip applicator device (11) configured to apply a sealing strip of heat-sealing plastic material to the longitudinal edge (4b) of the web (4) before the web (4) is folded into a tube (3), and includes an induction heating device (10) as described in any of the preceding claims; and / or - A pipe sealing unit (12) configured to longitudinally seal the pipe (3) and comprising an induction heating device (10) as described in any of the preceding claims.

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