Packaging machine with sealing device for paper wrapping material

Abstract

A packaging machine for packaging household paper products, such as kitchen tissues and toilet rolls, by wrapping paper wrapping sheets around the products, the packaging machine comprising:-a product supply station for continuously grouping and supplying product groups one by one, including at least one product; a wrapping station for wrapping a wrapping sheet around the product group; and-a sealing station downstream of the wrapping station for sealing a wrapping sheet wrapped around the group of products wherein the sealing station comprises a channel for moving the group of products forward and a pair of sealing members arranged opposite each other on both sides of the channel, each sealing member having a uniform sealing surface made of a material of the type in which the sealing surface is substantially free from the material of the type in which the sealing surface is substantially free from the material of the type in which the sealing surface is substantially free from the material of the type in which the sealing surface is substantially free from the material of the group of products. The invention relates to a sealing device comprising a plurality of sealing members made of a material capable of inducing eddy currents when subjected to magnetic field variations, each sealing member being driven between at least two return members, the sealing members being respectively associated with electromagnetic induction means adapted to heat the sealing surface to a temperature of between 110 DEG C and 400 DEG C.

Description

Technical Field

[0001] The present invention relates to a packaging machine for paper products for domestic use; more specifically, the object of the present invention is a packaging machine for products (such as rolls of kitchen paper and toilet paper) wrapped in a sheet of paper material. Background Art

[0002] In the paper industry, paper products (especially rolls of toilet paper and kitchen paper) are usually wrapped in a sheet of thermoplastic film or, in the case of a single roll, in a sheet of paper material. Packaging containing a single roll is usually used for rolls of toilet paper, while multi-roll packaging with a heat-sealable film is used for both rolls of toilet paper and kitchen paper. Generally, the single-roll packaging wrapped in paper film is not sealed, while the larger packaging wrapped in thermoplastic film is heat-sealed.

[0003] To manufacture these packages, the packaging machine has a conveyor which, in the case of multi-roll packaging, feeds rows of rolls arranged coaxially with respect to a horizontal axis to a station for grouping the rolls and forming groups of rolls arranged side by side in one or more layers. The group of rolls is then conveyed to a vertically moving elevator which raises each group of rolls to a wrapping station. The wrapping station wraps the group of rolls in a wrapping film, thus completing the packaging of the rolls. Examples of these packaging machines are disclosed in patent documents WO2009060490 and EP12289669B1. This type of packaging is called primary packaging and is usually used for retail. The resulting packages are conveyed to secondary packaging where the packages are grouped and placed in large plastic bags. Examples of these packaging machines are disclosed in EP1442984, EP1771335. Finally, the bags containing the packages are placed on pallets and then sent to a warehouse or directly to wholesalers.

[0004] Generally, the group of rolls is packaged by wrapping a thermoplastic wrapping film (such as polyethylene or other synthetic polymers) around the group of rolls; wrapping the group of rolls around four sides and forming a kind of parallelepiped with a rectangular face open at two opposite sides. Then, the side flaps of the sheet protruding from the two sides are folded, thus completing the covering of the rolls. Finally, the creases of the thermoplastic film are stabilized by a heat seal made of a conveyor belt coated with Teflon after heating, as shown, for example, in EP1381543B1. In the case of packaging a single roll with a sheet of paper material, a conveyor belt coated with Teflon after heating thermally activates an adhesive with which the entire surface of the sheet of paper material is pre-treated.

[0005] In the case of a single roll to be packaged, the sheet can also be stabilized without using glue. For example, in EP1518787B1, the stabilization of the sheet wrapped around a single roll is achieved by twisting the hem protruding from the flat surface of the roll and pressing it into the core of the roll with a punch. In other cases, as described in EP2766266B1, the hem protruding from the flat surface is partially folded successively and stabilized by pressing each partial hem into the core with a series of punches.

[0006] Closing a single roll without using glue has many drawbacks. The paper that is twisted or folded multiple times and pressed into the core of the roll is prone to tearing and breaking. In addition, not using glue makes the seal very unstable, often causing the package to open repeatedly. Therefore, not only is the quality of these packages very low, but their appearance is also damaged. Since the package must be discarded once the wrapping sheet is torn, the amount of discarded packages is also large.

[0007] Another major drawback of the prior art systems is the use of a Teflon-coated conveyor belt after heating. As is well known, such a conveyor belt has poor energy efficiency. In addition, the service life of the Teflon-coated conveyor belt is very short because it needs to be replaced frequently. The rapid wear of the Teflon-coated conveyor belt also causes significant variations in production because the efficiency of the conveyor belt drops sharply within a short period of time, resulting in a large amount of production waste. In addition, in the case of packaging with paper sheets, the Teflon-coated conveyor belt cannot effectively transfer heat to the glue that should be reactivated; therefore, in order to achieve a sufficiently acceptable seal, the machine speed must be reduced, leading to a decrease in productivity. As an alternative, it is necessary to heat the conveyor belt more, resulting in a further shortening of its service life and more energy consumption. Another drawback of the Teflon-coated conveyor belt is that it cannot provide a uniform and sufficiently rigid contrast surface for the roll to seal the crease of the wrapping sheet.

[0008] Although there are significant problems with using paper sheets instead of traditional thermoplastic films, the high level of environmental awareness is increasingly driving the paper industry to use natural and recyclable materials (such as paper) to replace fossil-based materials (such as general plastic heat-sealable films or synthetic films). Summary of the Invention

[0009] The object of the present invention is to provide an improved machine for packaging products made of household paper or non-woven fabric, such as rolls of kitchen paper and toilet paper, napkins, handkerchiefs, wet wipes and interleaved folded products, which machine is capable of overcoming the limitations of currently used paper wrapping materials. More specifically, the object of the present invention is to provide a packaging machine for packaging household paper products, which packaging machine is adapted to accelerate the packaging steps and combines the efficiency, flexibility and quality of the produced packages.

[0010] Another object of the present invention is to provide a packaging machine for packaging rolls and / or other paper products, which packaging machine uses a more environmentally friendly and greener packaging material (such as paper) and overcomes all the above-mentioned drawbacks.

[0011] These and other objects are achieved by a packaging machine for packaging household paper products, which packaging machine comprises:

[0012] o a product supply station for successively and groupwise supplying a product group including at least one product one by one,

[0013] o a wrapping station for wrapping a paper wrapping sheet around the product group,

[0014] o a sealing station located downstream of the wrapping station for sealing the paper wrapping sheet wrapped around the product group.

[0015] According to the present invention, the sealing station comprises a channel for moving the product group forward and a pair of sealing members arranged opposite to each other on both sides of the channel, and each sealing member has a uniform sealing surface made of a heating material which can induce eddy currents when the heating material is subjected to a magnetic field change.

[0016] For example, the material is a ferromagnetic material (such as steel, iron or its alloy, or other materials) or a paramagnetic material (such as aluminum or its alloy, or other materials).

[0017] For example, the heating material has a relative magnetic permeability of 1 or more.

[0018] Preferably, the sealing members are driven between at least two return members. In some embodiments, one of the two return members is motorized. For example, each sealing member may comprise at least one flexible element driven between at least two return members.

[0019] The sealing surface of each sealing member is heated, and thus is preferably associated with an electromagnetic induction device or inductor adapted to induce eddy currents in the material so that the material is heated by the Joule effect and can be heat-sealed. Usually, an electromagnetic inductor is associated with each sealing member.

[0020] For optimal sealing of the package, depending on the type and quality of the paper material or of the single sheets or webs of material, and / or depending on the specifications (format) of the package to be produced, the temperature of the heated sealing surface should be between 100 °C and 400 °C.

[0021] The same object of the invention can be achieved even if at least one of the two sealing members (or in a preferred embodiment both sealing members) comprises a plate of one or more ferromagnetic or paramagnetic materials, said plate having a uniform sealing surface and preferably being moved by at least one flexible member. In this case, the flexible member can also be a conveyor belt or conveyor belts, or alternatively a chain or another suitable flexible member.

[0022] For example, a plurality of adjacent plates are provided, which have contact zones for heat conduction between the same plates; these contact zones can be arranged, for example, only along one or more parts of the movement path effected by the flexible member, for example, at least the part corresponding to the moment when the plates travel along the sealing part in the channel through which the product moves forward. The contact zones are preferably arranged near the sides of the plates, and for example side recesses and corresponding side projections are provided, which are joined together so that adjacent plates overlap each other. The side recesses and the side projections preferably each have a face parallel to the sealing surface of the plate, and the face of the side recess and the face of the side projection face each other; when moving forward in the supply channel, the side projection contacts the side recess at these faces. Preferably, the area and shape of the cross-section of the projection can be substantially matched to the area and shape of the cross-section of the recess.

[0023] The channel of the sealing station can comprise a conveyor for moving the product group forward along the sealing station in the product sealing direction. When the sealing members are power-driven, the forward movement of the product in the sealing station is achieved by means of the conveyor and the sealing members opposite each other on both sides of the product group. In an alternative configuration, the product group is moved forward by the sealing members and the conveyor is replaced by a sliding surface.

[0024] To facilitate the forward movement of the product group leaving the wrapping station, the sealing station moves the product group forward at a speed higher than that of the product leaving the wrapping station.

[0025] Advantageously, the packaging machine comprises an adjusting member for adjusting the sealing pressure.

[0026] In some embodiments, the packaging machine comprises a supply station for supplying paper wrapping sheets. The paper wrapping sheets preferably have a weight of 10 g / m 2 and 100 g / m 2Grammage between and thickness between 10 μm and 500 μm. The paper-wrapped sheet can be obtained by cutting a continuous paper web material unwound from a reel by a cutting unit. The sheet supply station is arranged upstream of the wrapping station with respect to the sheet supply direction. The paper-wrapped sheet can include a sealant for sealing the wrapping sheet around the product group. The sealant can be applied to the paper-wrapped sheet at the sheet supply station. Alternatively, the wrapping sheet can be cut from a paper web material that has been treated with a sealant and wound on a reel, so that there is no need to apply a sealant at the sheet supply station. Thus, the paper-wrapped sheet is defined by two parallel side edges and two side edges transverse to the sheet supply direction towards the wrapping station. Preferably, the side edges transverse to the sheet supply direction are obtained by cutting with a cutting unit.

[0027] If the wrapping sheet or the continuous paper web material cut into the wrapping sheet receives a sealant, the sheet supply station includes dispensing means for applying the sealant to the wrapping sheet or the paper web material. In the case of the wrapping sheet, the dispensing means is arranged downstream of the cutting unit in the sheet supply direction towards the wrapping station, while in the case of the paper web material, the dispensing means is arranged upstream of the cutting unit in the sheet supply direction towards the wrapping station.

[0028] Preferably, the dispensing means includes at least one dispenser for applying a line of sealant in a direction parallel to one of the two side edges parallel to the sheet supply direction, and at least one dispenser for applying a line of sealant in a direction parallel to each of the two side edges transverse to the sheet supply direction.

[0029] Preferably, these lines are continuous or discontinuous, with a length equal to or less than the length of the corresponding side edge of the wrapping sheet, and are arranged at a distance between 0.5 mm and 50 mm, preferably between 1 mm and 25 mm, from the corresponding side edge or the corresponding edge of the sheet.

[0030] Advantageously, the dispenser can be of the spreading type, but other systems (such as rollers or sprayers) can also be used to apply the sealant.

[0031] In some embodiments, the station for supplying the paper-wrapped sheet includes detection means for detecting the position of the paper-wrapped sheet or the paper web material along the sheet supply direction. Preferably, the detection means for detecting the position of the wrapping sheet or the web material is an encoder, but other suitable means can also be used.

[0032] Using sensors to detect the position of the paper sheet or the web material unwound from the reel enables the dispensing means to apply the sealant in phase with the position of the paper-wrapped sheet or the paper web material.

[0033] The sealant is preferably an activatable adhesive.

[0034] The product supply station includes a lift for raising the product group towards the wrapping station. During the raising movement, the product group encounters a paper wrapping sheet arranged parallel to a plane transverse to the direction of group raising. Thus, when the lift has raised the product group to the level (height) of the wrapping station, the paper wrapping sheet forms a partial wrap around the product group, shaped like an inverted "U".

[0035] The wrapping station includes a bottom folding device that can complete the partial inverted-U wrap of the paper wrapping sheet around the product group, thereby forming a tubular structure or parallelepiped with an approximately rectangular face, open at two opposite parallel sides of the product group. Each of the two opposite parallel sides has a protruding hem that will be folded to complete the wrap.

[0036] The crease under the product group formed by the bottom folding device is stabilized by a transverse sealing device.

[0037] The wrapping of the paper wrapping sheet around the product group is completed by forming a top crease, a bottom crease, a rear side crease, and a front side crease for each of the two opposite sides of the product group that make up the package.

[0038] Thus, the wrapping station includes:

[0039] ο A front side folding device for each of the two sides of the product group to fold a part of the hem of the paper wrapping sheet against each side to form a front crease;

[0040] ο A rear side folding device for each of the two sides of the product group to fold a part of the hem of the paper wrapping sheet against each side to form a rear crease;

[0041] ο A top side folding device for each of the two sides of the product group to fold a part of the hem of the paper wrapping sheet against each side to form a top crease;

[0042] ο A bottom side folding device for each of the two sides of the product group to fold a part of the hem of the paper wrapping sheet against each side to form a bottom crease.

[0043] To increase flexibility and productivity, the sealing station includes an adjusting device for adjusting the mutual distance of the sealing members. The distance between the sealing surfaces can be adjusted, for example, according to the size of the product group.

[0044] Preferably, an induction current with a frequency between 10 Hz and 500 kHz is provided to the sensors associated with each sealing element.

[0045] In this text, the term "uniform surface" refers to a surface that has no bumps, protrusions, depressions, knurling, or holes in the portion that contacts the paper wrapping sheet. For example, a uniform surface can be a smooth surface in the area that contacts the package to be sealed. The term "uniform" preferably refers to a smooth and continuous surface in the area that contacts the roll group. Specifically, in this text, a "smooth sealing surface" refers to a surface that cannot cause marking, grooving, or embossing on the wrapping sheet during sealing (i.e., when the roll group contacts the sealing member with a certain pressure). A continuous sealing surface means that the surface that contacts the package to be sealed has no discontinuous parts (i.e., edge areas, breaks, etc.).

[0046] In other words, a uniform surface can be defined as a surface with a roughness less than 200 Ra. In particular, when contacting the package, the sealing surface should be a continuous surface with a roughness less than 200 Ra.

[0047] Advantageously, the sealing member and the channel have sufficient length to achieve optimal sealing of the package. In other words, the contact time between the sealing member and the package to be sealed is long enough, unlike other solutions where the contact time is inevitably short (e.g., when using a sealing roller). Even more specifically, the length of the sealing member and the channel is such that at the maximum production speed of the machine, or generally at the maximum supply speed of the package to be sealed, which depends on the package specifications and the cycle time, i.e., the maximum number of packages that the machine must execute per minute for this specification, the sealing is also stable enough. Throughout the time when the package passes through the channel, the uniform sealing surface allows for stable and uniform contact between the package to be sealed and the sealing member at an approximately constant temperature. When the sealing pressure is applied between the sealing member and the package to be sealed, due to the uniformity (i.e., consistency) of the contact, there is a stretching effect on the lateral creases of the package to be sealed, which not only greatly improves the quality of the package from an aesthetic point of view but also makes the package stable whether or not a sealant is used. Description of the Drawings

[0048] The present invention can be better understood from the following description and drawings, which show non-limiting embodiments of the present invention. More specifically, in the drawings:

[0049] ο Figure 1 is a schematic side view of a supply station for supplying products (such as rolls) in a machine according to the present invention;

[0050] ο Figure 2 is a schematic side view of a wrapping station for wrapping products (such as rolls) in a machine according to the present invention;

[0051] ο Figures 3 to 6 shows in Figure 2Schematic sequence for lifting a product group and starting to wrap a sheet in a station;

[0052] ο Figure 7 Is a schematic perspective view of a supply station for supplying wrapping sheets in a machine according to the present invention;

[0053] ο Figure 8 Is Figure 7 Side view of the wrapping sheet supply station;

[0054] ο Figures 9A to 9G Shows a schematic sequence of folding a wrapping sheet with glue distribution around a product group;

[0055] ο Figure 10 Shows a schematic view of the glue distribution on a wrapping sheet different from the previous figures;

[0056] ο Figure 10A And Figure 10B Respectively show a schematic perspective view and a top view of a package composed of a single - layer roll, the wrapping sheet having a glue distribution according to Figure 10 The glue distribution;

[0057] ο Figure 11A And Figure 11B Respectively show a schematic top view of a wrapping sheet with a glue distribution different from the previous figures, and a schematic view of the closing surface of a package with such a different glue - distributed wrapping sheet;

[0058] ο Figure 12 Is a schematic axonometric view of a sealing station of a machine according to the present invention;

[0059] ο Figure 13 Is Figure 12 Schematic front view of the sealing station;

[0060] ο Figure 14 Is Figure 12 Schematic top view of the sealing station;

[0061] ο Figure 15 Is from Figure 12 Another schematic perspective view observed from the bottom of the sealing station;

[0062] ο Figure 16 Is a schematic axonometric view of a part of a variant of the sealing station, where the sealing member along the channel for moving the product group forward is highlighted;

[0063] ο Figure 17 Shows Figure 16 Schematic cross - sectional views of a series of sealing plates forming the sealing member of the station; Detailed Description

[0064] InFigure 1 In this case, a packaging machine 1 for packaging a product R, such as a paper roll, is shown. These rolls are made of tissue paper (such as toilet paper rolls or kitchen paper rolls). These rolls may have a cardboard core around which the tissue paper is wound, or they may not have a cardboard core, that is, these rolls may be made of paper wound entirely from the center, thus forming a solid cylinder (so-called solid roll), or they may have a cylindrical cavity, for example, wound around a central hole without a core (so-called coreless roll).

[0065] The packaging machine 1 is fed by a product supply station, which is generally denoted by the reference numeral 2 in its entirety and may include means for grouping the products and supplying groups of products to other devices arranged downstream. Specifically, as disclosed in EP2763917B1, the supply station 2 may include a launching device 3. In this case, the launcher 3 includes one or more supply conveyors 4, which cooperate with a power-driven conveyor 5 that engages the product R transversely. In this particular case, the power-driven conveyor 5 is shown arranged transversely, but it should be understood that they may also be arranged in a different configuration, for example, above and below the product R. The supply station 2 may include a plurality of supply channels arranged side by side, where each supply channel supplies a series of products R. Each supply channel is generally associated with a launcher 3. The launcher 3 is controlled by a central control unit 45 (such as a PC, PCL, microprocessor, etc.) so as to sequentially dispense groups G of products R (in this case, rolls) arranged side by side towards subsequent conveying members, which are also part of the supply station 2 and will be described below.

[0066] In the example described, the launching device 3 sequentially dispenses groups G of products R arranged side by side to a conveyor 7, which may have a sliding surface 8 and a pair of flexible members 9 (such as chains or belts), on which the groups G of products R slide, and pushers 10 are constrained to the flexible members, the pushers 10 being spaced apart to accommodate the groups G of products R. The pushers 10 extend generally transversely to the supply direction fR of the product R. Each pusher 10 is constrained at its two ends to the flexible member 9. In this way, by appropriately moving the flexible member 9, the groups G of products R are moved forward, that is, they are pushed forward along the supply direction fR by the pushers 10 in synchronization with the supply speed of the packaging machine 1. Then, the launching device 3 and the conveyor 7 are configured to group and dispense groups G of products R of a desired size in a rhythmic manner towards the downstream station.

[0067] The group G of product R is conveyed from conveyor 7 to the stratifying station 6, which is also part of the product supply station 2. The stratifying station 6 may include a conveyor 11 having a swinging motion according to the double arrow f11 to distribute the groups G or layers of the individual products R into the supply device 12. In this particular case, the supply device 12 includes two layers of products, but it should be understood that the stratification may have more than two layers of products, such as three layers or even more layers of products. If the packaging machine 1 is configured to produce single-layer packaging, the stratifying station 6 is obviously unnecessary.

[0068] The supply device 12 shown here has pushing members for each product layer. Similar to conveyor 7, for each layer, the pushing members are respectively formed by sliding surfaces 13A, 13B and push rods 14A, 14B, and the push rods are driven forward by corresponding flexible members 15A, 15B. The supply device 12 synchronously inserts each layer of products onto the elevator 16. The individual layers can be placed on the elevator 16 simultaneously or one by one to form a group G of product R to be packaged on the elevator 16.

[0069] Similar to the embodiments of the emitter 3 and conveyor 7, this embodiment of the supply device 12 is given only as a non-limiting example, because completely different configurations can be used for grouping, metering, and stratifying the products. The above-described devices are connected to a central control unit 45, which is configured to process the grouping of product R of different specifications. For example, the number of layers of product R can vary, or the number of side-by-side channels used can vary, or the number of product R metered onto each side-by-side channel by the emitter 3 can vary, or a combination of these variations. In the example shown, the emitting device 3 groups two products R for each channel together with the conveyor 7, but obviously, as described above, a single product R or more than two products can also be grouped for each channel.

[0070] The elevator 16 consists of a plate 16A that receives and supports the group G of stratified products R. The elevator 16 can move vertically in the lifting direction shown by the double arrow f16. The movement of the plate 16A can be achieved by a link-crank type mechanism (not shown in detail for simplicity) driven by a motor 17. Advantageously, the elevator 16 also includes a bottom stop 18 that can be adjusted along the double arrow f18 according to the length or depth of the group G of product R. The depth of the group G of product R can vary depending on the number of products R in each row of each layer of product R, or depending on the length of the individual products R. As Figure 2 shown in the side view, the elevator 16 may also include side dams 21A, 21B, 21C, 21D provided along two side flanks of the group G of product R to accommodate and accompany the group G of product R during lifting.

[0071] The elevator 16 sequentially raises the group G of products R from the tier height Qs to the package height Qa of the packing station 19, which is arranged at a position higher than the product supply station. During the lifting movement along the double arrow f16, the group G of products R encounters the paper wrapping sheet F arranged in a plane orthogonal to the lifting direction f16. The contact between the group G of products R and the paper wrapping sheet F initiates the wrapping cycle, which will be described in more detail with reference to Figures 3 to 6 and Figures 9A to 9G The paper wrapping sheet F is advantageously arranged at a horizontal level between the tier height Qs and the package height Qa.

[0072] The paper wrapping sheet F can be inserted into and positioned in the packing station 19 through two openings 22 formed respectively between the side dams 21A and 21C and between 21B and 21D, while being held at its two edges B1, B2 by the sheet supply member 20 (such as a conveyor belt). The formation of the paper wrapping sheet and its supply to the packing station 19 will be described in more detail below.

[0073] Now refer to Figures 3 to 6 and Figures 9A to 9G to describe the wrapping cycle. Specifically, Figure 3 shows the group G of products R arranged at the tier height Qs. At Figure 4 , the group G of products R contacts the paper wrapping sheet F, and the wrapping of the paper wrapping sheet F around the top surface Fs and the side surface Fl of the group G of products R begins. At Figure 5 and Figure 9B , the group G of products R is at the package height Qa and is completely wrapped by the paper wrapping sheet around the top surface Fs and the side surface Fl, leaving the two edges Bl, B2 of the paper wrapping sheet F extending vertically downward, and if necessary, extending vertically downward by different lengths. At this time, the paper wrapping sheet F partially wrapped around the group G of products R forms a shape similar to an inverted "U". Finally, at Figure 6 and Figure 9C , the edges B1, B2 have been superposed on each other to complete the wrapping of the bottom surface Fi of the group G of products R. These two edges B1, B2 have been superposed on each other by two bottom folding devices 25, 26, which are part of the packing station 2 and at least one of which is movable. In a preferred embodiment, both of these folding devices 25 and 26 can be moved horizontally and move towards each other along their respective arrows f25 and f26. Once these two edges B1 and B2 have been superposed on each other, while the group G of products R is supported by the movable bottom folding devices 25, 26, the elevator 16 can reverse the upward movement and descend back to the tier height Qs to receive a new group G of products R. At this time, as Figure 9CAs shown, the front face Fa and the back face Fp of the group G of product R that face each other are free (exposed), and the side fold edges L1, L2 of the paper wrapping sheet F extend from the group G of product R substantially orthogonally to the front face Fa and the back face Fp.

[0074] Then the overlapping edges B1, B2 are stabilized by the transverse sealing device 30 arranged along the wrapping direction fA. The transverse sealing device 30 may have a heated active surface 30A that contacts the group G of product R at the point where the two edges B1, B2 overlap to be sealed. By way of example only, the active surface 30A is rectangular, and its length is orthogonal to the wrapping direction fA. Preferably, the transverse sealing device 30 moves towards and away from the group G of product R along the moving direction f30. In this example, the double arrow f30 is substantially parallel to the double arrow f16 of the elevator 16. Specifically, when the transverse sealing device 30 has been brought to the group G of product R partially wrapped by the paper wrapping sheet F, it seals the package in the overlapping area of the edges B1, B2. The active surface 30A of the transverse sealing device 30 can be smooth or have a dot pattern, and can be heated to a temperature between 100 °C and 350 °C. In some cases, the sealing of the overlapping edges B1 and B2 can occur when the group G of product R is stationary (i.e., when it does not move forward along the wrapping direction fA), thus allowing the transverse sealing device 30 to remain in contact with the overlapping edges B1 and B2 for the necessary time. In this way, the heat of the active surface 30A allows the sealant S to be activated and seals (i.e., irreversibly closes) the paper wrapping sheet F around the faces Fi, F1 and Fs of the group G of product R, leaving the side fold edges L1 and L2 extending orthogonally to the front face Fa and the back face Fp of the group G of product R.

[0075] In other embodiments, a transverse sealing device 30 can be made to perform, in addition to the movement according to the double arrow f30, a movement substantially orthogonal to the double arrow f30 and parallel to the wrapping direction fA, so as to seal the group G of product R while moving forward along the wrapping direction fA.

[0076] Refer again to Figure 2The wrapping station 19, the lifting movement of the elevator 16 allows the group G of products R to be inserted at the wrapping height Qa into a space Sp having a width equal to or slightly smaller than the width of the group G of products R, the space being defined by the successive teeth 27.2 of a conveyor 27 which is part of the wrapping station 19. The conveyor 27 moves the group G of products R supported by the sliding surface 23 along the wrapping direction fA to complete the wrapping of the paper wrapping sheet F around the group G of products R. The teeth 27.2 are constrained to a flexible member 27.1 (such as a conveyor belt or a chain), the flexible member being driven between two pulleys 27.3, at least one of which is power-driven, so that the teeth 27.2 move along a closed path, the working branch of which (i.e., the branch where the wrapping of the paper wrapping sheet F is completed) is the lower branch.

[0077] The conveyor 27 can also be implemented in a different way. For example, the teeth 27.2 can be transported by carriages movable along guide rails. A linear motor controlled by a central control unit 45 can be associated with each carriage in order to receive and transport the group G of products R. An example of such a conveyor 27 is described in IT 1426528.

[0078] In other embodiments, the conveyor 27 can be configured to constrain the successive teeth 27.2 to multiple conveyor belts, each conveyor belt being independently power-driven so that the successive teeth 27.2 can move independently of each other. Such a structure is disclosed in Italian patent no. 102015000084892.

[0079] Once the group G of products R inserted into the space Sp is moved forward by the conveyor 27 along the wrapping direction Fa, it passes through a folding device 28 which includes top-side edge folding devices Pls, bottom-side edge folding devices Pli, front-side edge folding devices Pla and rear-side edge folding devices Plp for each face Fa and Fp. When the side folds Ll and L2 come into contact with the top-side edge folding device Pls, bottom-side edge folding device Pli, front-side edge folding device Pla and rear-side edge folding device Plp, the top-side edge creases Pls’, bottom-side edge creases Pli’, front-side edge creases Pla’ and rear-side edge creases Plp’ are respectively formed, as Figures 9D - 9Gas shown in sequence. The top side folding device Pls, the bottom side folding device Pli, and the front side folding device Pla are usually fixed, while the rear side folding device can move along the double arrow Fplp. The movement of the rear side folding device can be coordinated with the movement of the movable bottom folding devices 25, 26 to generate their respective creases simultaneously, or to generate the rear side crease Plp' immediately after the two edges B1, B2 overlap. In addition, a single power drive can be used to move the movable bottom folding devices 25, 26 and the rear side folding device Plp. In some cases, the rear side folding device Plp can complete the corresponding folding before the group G of products R is moved by the conveyor 27. In other cases, the rear side folding device Plp can complete the folding when the group G of products R has been moved by the conveyor 27 along the wrapping direction fA.

[0080] The side folding member disclosed above can also be implemented, for example, as described in EP1228966.

[0081] The following will refer to Figure 7 and Figure 8 describe the sheet supply station 31 for supplying the paper wrapping sheet F, which supplies one sheet to the wrapping station 19 in sequence each time.

[0082] The sheet supply station 31 includes an unwinding device 38 to unwind the reel B of the paper web N made of virgin fiber, recycled fiber, or a mixture thereof. Preferably, the grammage of the paper web N is between 20 g / m 2 and 100 g / m 2 and the thickness is between 20 μm and 100 μm. The unwinding device 38 can include a support device 38A for holding the reel B to rotate about its longitudinal axis, and an actuating device 38B for rotating the reel B in a controlled manner, for example, by means of a conveyor belt in contact with the outer surface of the reel B or by connecting the longitudinal axis of the reel B to a power drive system. The unwinding device can be of any known type, such as that shown in IT1274081.

[0083] The paper web N can be conveyed by the idler rollers 32.1, 32.2, 32.3, 32.4, 32.5 and 32.6 along a supply path P in a supply direction fN to a cutting device 37 which is arranged to cut the paper web N into paper wrapper sheets F of a predetermined length. Along the supply path P of the paper web N, there is provided, upstream of the cutting unit 37, a dispensing device 33 which is arranged to apply a sealant S (such as glue) to the paper web N. The sealant S can preferably be a heat-reactivatable glue, i.e., it can have the property that it does not remain sticky once applied to the paper web N and is only activated upon heat treatment. The advantage of this type of sealant is that, even in the case of an accidental contact between the sealant and the elements constituting the packaging machine 1, it does not soil the downstream devices (such as the wrapping station 19). Other types of glue can also be used, such as heat-activated glue or glue that is activated immediately and is not reactivated once dried, although these technical solutions are less preferred because using these types of glue is far more likely to soil the machine than using heat-reactivatable glue.

[0084] The dispensing device 33 can include one or more dispensers 33.1, 33.2 and 33.3 provided above the supply path P so as to apply the sealant S to the paper web N in a controlled manner. Preferably, the dispensers 33.1, 33.2, 33.3 are of the coating type, although other types of dispensers, such as spray-type ones, cannot be excluded. The supply path P can preferably be flat in the part where the sealant is applied. As schematically shown, the dispensers 33.1, 33.2, 33.3 can be supported by a support structure 34 which consists of brackets 39 (such as L-shaped brackets) constrained to a crossbar 39A, the ends of which crossbar are attached to two uprights 40. The support structure 34 is not restrictive for the purposes of the present invention and can be of any other suitable type. The support structure 34 can include means (not shown) for adjusting the lateral position of the dispensers 33.1, 33.2, 33.3 relative to the supply direction fN of the paper web N. For example, the brackets 39 can slide along a linear guide and be locked thereon by screws or other suitable systems. In another configuration (also not shown for simplicity), the brackets 39 or generally the dispensers 33.1, 33.2, 33.3 can be adjusted by a motor in order to simplify product changeover, i.e., changing over to packaging that requires paper wrapper sheets F of different sizes. Furthermore, the dispensing device 33 can be adjusted in height manually or automatically relative to the supply path P. To this end, the dispensers 33.1, 33.2, 33.3 can be connected to an electronic control unit 45 which manages the dispensing phase, i.e., the moments when the dispensers should apply the sealant S to the paper web N and when they should not apply the sealant.

[0085] Upstream of the dispensers 33.1, 33.2, 33.3 along the supply direction fN, the dispensing device 33 may include a phase detection system 36 for coordinating the application of the sealant S with the supply of the web material N. In practice, the web material N may include printed patterns, characters, barcodes, and markings for phase detection. In fact, the web of the web material N may include printed patterns, characters, barcodes, and phase detection markings. In the case where the printed pattern or marking is visible on the final package C, its position relative to the package surface must be precise and predetermined. Therefore, the sealant S must also be applied in a manner synchronized with the supply of the web material N in order to obtain a paper wrapper sheet F with the sealant S and the printed pattern in phase (i.e., in well-defined mutual positions). In Figure 7 In the example of Figure 7 , the phase detection system 26 is implemented by an encoder 43 that can measure the amount by which the web material N moves forward along the supply direction fN. Alternatively, the encoder 43 can detect the position of the web material N to determine the position of a specific printed pattern design. Instead of the encoder 43, other systems or sensors can be used, such as a photocell that detects a given point on the web material N, or a vision system that detects and identifies the position of the web material N and in particular identifies unique markings (such as printed patterns or markings specifically printed for phase detection). Additionally, combinations of these sensors can be used, such as a photocell and an encoder, a photocell and a vision system, etc. The phase detection system 36 is also connected to an electronic control unit 45 in order to coordinate the application of the sealant S in phase with the forward movement of the web material N.

[0086] Downstream of the dispensing device 33 is a cutting device 37 (not shown in detail) for cutting the web material N into paper wrapper sheets F of a predetermined length. The cutting unit 37 can be of the type described in EP1052209B1. The cutting unit 37 is preferably connected to and controlled by the electronic control unit 45 in order to obtain paper wrapper sheets F of a predetermined length from the cutting of the web material N that is in phase with the printed pattern (if any) and the sealant S. Preferably, the cutting is of the "scissors" type and is performed by a rotating blade working in cooperation with a fixed mating blade, and the two blades are at least as wide as the web material to be cut. Once cut and leaving the cutting unit 37, the paper wrapper sheets F are supplied along a sheet supply direction fF that is generally the same as the supply direction fN of the web material N, however, when using a cutting unit with a different than the preferred configuration (as shown in EP1052209B1), the sheet supply direction can also be different (e.g., orthogonal) from the supply direction of the web material N.

[0087] In different configurations (not specifically shown in the figures), the cutting device 37 can be arranged upstream of the dispensing device 33, in which case it must be in direct phase with the paper-wrapped sheet F. Clearly, in this case, a phase detection device 36 is also provided, which operates similarly to the above. In this configuration, it is also possible to phase the application of the sealant S and the supply of the paper-wrapped sheet F by means of a photocell which detects the lateral edge of the paper sheet moving forward along the sheet supply direction fF.

[0088] Generally speaking, in order to obtain sheets of the desired size, in phase with any printing pattern and with the sealant S, it is necessary to alternately:

[0089] o apply the sealant S in phase with any printing pattern or mark provided on the paper web N, and then cut the paper web N into sheets of a predetermined length in phase with the sealant S;

[0090] o cut the paper web N into sheets of a predetermined length in phase with any printing pattern or mark, and then apply the sealant S in phase on the paper-wrapped sheet F.

[0091] As Figure 10 shown in Figure 10 and Fig. 11, the application of the sealant S on the paper web N can be carried out in more than one configuration. A first example is shown in Figure 10 where, on the paper-wrapped sheet F defined by two parallel side edges and two side edges transverse to the supply direction, the dispensing device 33 has applied a line of sealant SCP along the side edge parallel to the supply direction fN and a line of sealant SCT along each side edge transverse to the supply direction fN. The sealant lines SCP and SCT can be continuous or discontinuous, for example dotted lines. In Figure 10A the Figure 10B case, the line SCP is continuous, while the two lines SCT are each formed by alternating two sections SMI, SM2 with sealant and two sections ZL1 (possibly also ZL2) without sealant. Advantageously, the sections ZL1 (ZL2) without sealant of the same line SCT respectively correspond to the sheet portions of the top side edge fold Pls' and the bottom side edge fold Pli' of each face Fa, Fp of the package C. The sealed package C is shown in Figure 10The sealant S is dispensed as shown. In this particular case, the sealant S forms an "H" shape on each face Fa, Fp of the package C because the portions SMI and SM2 of each line SCT where the sealant is applied in the corresponding sections of the top side edge crease Pls' and the bottom side edge crease Pli' overlap in the horizontal part of the "H" shape. Depending on the overlap of the sealant line S, the horizontal section of the "H" shape can be wider or narrower or even double. The vertical sections of the "H" shape are formed by the portions of each line SCT corresponding to the front side edge crease Pla' and the rear side edge crease Plp'. In this case, when folding the paper wrapping sheet F, the front side folding device Pla and the rear side folding device Plp do not contact the sealant S, making the packaging machine 1 cleaner and more efficient.

[0092] In Figures 9A - 9G the complete wrapping sequence shown, the line SCT is formed by a single continuous section. In this case, the line SCT on each side of the package C can form an "H" shaped seal as described above.

[0093] Generally, the line SCT is applied such that there are sections of the sealant S between the front side edge crease Pla', the rear side edge crease Plp', the bottom side edge crease Pli' and the top side edge crease Pls', and this sealant is activated by the sealing station 40 to permanently stabilize the package C of the product R. The line SCP is applied to the paper wrapping sheet F such that it is located between the overlapping edges Bl, B2 so that the sealant S can be heated by the lateral sealing device 30 and thus activated.

[0094] The line SCP and each line SCT are usually applied generally parallel to the edge side of the wrapping sheet F, although this is not strictly necessary. The width of the lines SCP and SCT can be between 5 mm and 80 cm. The width of the lines can also be adjusted based on the desired size of the package C. For example, a larger sized package C may require a wider sealant line compared to a smaller sized package C. The lines SCP and SCT can be applied at a distance between 0.5 mm and 50 mm, preferably between 1 mm and 25 mm, from the edge of the side of the paper wrapping sheet F.

[0095] The dispensers 33.1, 33.2, 33.3 can be configured to have different sealant S distributions. For example, instead of continuous or discontinuous sections of the line SCT, dotted sections or other shapes (such as triangles S1, S2, S3 or others) can be applied, which coincide with the overlapping areas of the side edge creases obtained from the folds of the hems L1 and L2, as Figure 11A and Figure 11BAs shown. Similarly, in this case, the purpose of applying the sealant S is to obtain a stably sealed package C for most of the areas to be enclosed. In a preferred embodiment, the distribution of the sealant S is such that the package C is completely stably enclosed, preventing the product R from being contaminated due to contact with external substances. The package C may have a convenient opening system or a handle to facilitate the transportation of the package C, however, this does not change the purpose of the present invention. Examples of handles are described in EP1535846, while a convenient opening system is disclosed in EP2225159.

[0096] Once the paper wrapping sheet F coated with the sealant S in one of the aforementioned ways is prepared, the sheet is successively moved forward along the sheet supply direction fF towards the wrapping station 19. In a preferred embodiment, as described above, the paper wrapping sheet F is held at two edges B1 and B2 by a supply member 20 (such as a conveyor belt) and is positioned orthogonally to the lifting direction f16. Such an embodiment is described, for example, in the patent document W02021009339.

[0097] In Figures 12 to 15 a seal station 40 is shown, which is configured to seal the paper wrapping sheet F wrapped around the group G of products R forming the package C to be sealed. The sealing is achieved by heat-treating the creases of the paper wrapping sheet F that have been previously formed in the wrapping station 19. In practice, once the folding of the side flaps L1 and L2 has been completed, it is necessary to stabilize, for example, the front side crease Pla’, the rear side crease Plp’, the bottom side crease Pli’ and the top side crease Pls’ obtained according to the Figures 9A - 9G packaging cycle described in Figure 9G This is achieved by heat-treating the faces Fa, Fp of the

[0098] The seal station 40 includes a channel 41 for moving the package C to be sealed forward in the sealing direction shown by the arrow fS. The forward movement channel 41 is bounded at the side edges by a pair of opposing seal members 42A, 42B provided on both sides of the channel 41. The seal members 42A, 42B respectively have preferably uniform sealing surfaces 43A, 43B. The sealing surfaces 43A, 43B are the surfaces facing the package C to be sealed, that is, the surfaces in contact with the package C to be sealed. The seal members 42A, 42B can be made of ferromagnetic material.

[0099] For example, in Figure 13 and Figure 14 shown cases, the seal members 42A, 42B are respectively made of belts 54A and 54B.

[0100] For example, the belt is made of a ferromagnetic material (such as steel, iron or their alloys) or may contain the ferromagnetic material.

[0101] In other examples, these bands may be made of a paramagnetic material (such as aluminum or its alloys) or may contain said paramagnetic material. For example, the band may comprise an aluminum core or strip, preferably having a thickness between 5 μm and 100 μm, more preferably between 20 μm and 25 μm. The aluminum core or strip may also include a material on the sealing surface adapted to facilitate the sliding of this surface on the product, such as polytetrafluoroethylene.

[0102] In a variant of the invention (not shown), each sealing member 42A, 42B may use two or more bands arranged vertically, preferably arranged successively one by one. The total height of the sealing members 42A, 42B may be at least equal to the height of the package C to be sealed with the maximum size achievable by the packaging machine 1.

[0103] Each sealing member 42A, 42B may be driven between return members 44A, 45A, 46A and 44B, 45B, 46B (such as pulleys or rollers), and for each sealing member, at least one of said return members is preferably power-driven. In this particular case, the return members 44A and 44B are driven by respective actuating means (such as gear motors) M1 and M2 for feeding the package C to be sealed along the sealing direction fS. In different configurations, the sealing members 42A, 42B may be made idle (i.e., idling), that is, without actuating means, especially when the channel 41 includes a power-driven conveyor 47 for feeding the package C to be sealed along the sealing direction fS. In a preferred embodiment of the invention, the sealing members 42A, 42B and the conveyor 47 are all power-driven. When the conveyor 47 is not power-driven, it may be replaced by a simple feeding plane (such as an extension of the sliding surface 23). The conveyor 47 may be arranged at the package height Qa so as to receive the package C to be sealed without interruption relative to the sliding surface 23, and such an interruption would cause the creases yet to be sealed to move and deform, thus compromising the final quality of the package C.

[0104] The sealing members 42A, 42B may be arranged close to the exit of the wrapping station 19 (i.e., continuously arranged with the exit of the wrapping station) so as to receive the package C to be sealed while the folding device 28 is still in partial contact with the newly formed creases, thereby forming a continuous or almost continuous channel between the folding device 28 and the sealing members 42A, 42B. This prevents the deformation of the newly formed front side crease Pla’, rear side crease Plp’, bottom side crease Pli’ and top side crease Pls’. Preferably, when the sealing members 42A, 42B and / or the conveyor 47 are power-driven, the package C to be sealed is received by feeding the package C to be sealed along the sealing direction fS at a speed equal to or preferably higher than the speed along the wrapping direction fA, so as to move the package C to be sealed away from the conveyor 27 and prevent the rotation of the teeth 27.2 around the pulley 27.3 from deforming the package C still to be sealed and stabilized.

[0105] The sealing members 42A and 42B are inductively heated by induction devices 48A and 48B respectively. The induction devices include one or more induction coils 49A and 49B or other circuits capable of generating a time-varying electromagnetic flux. The time-varying electromagnetic field generates eddy currents in the sealing members 42A and 42B, which results in Joule heating thereof. As a result, the sealing surfaces 43A and 43B and / or portions thereof near the sealing surfaces are also heated.

[0106] The induction coils 49A and 49B can be arranged to face the sealing surfaces 43A and 43B, or arranged on the opposite sides, that is, within the region defined by the closed path determined by the sealing members 42A and 42B. The induction coils 49A and 49B can be provided in the straight portions between the corresponding return members 45A, 46A and 45B, 46B. In other configurations, the induction coils 49A and 49B can be provided elsewhere, for example, between the return members 44A, 46A and 44B, 46B or between the return members 44A, 45A and 44B, 45B. In the latter case, the induction coils 49A and 49B cannot be placed in front of the sealing surfaces 43A and 43B because they would be inside the channel 41; therefore, they should be arranged on the opposite sides, that is, within the region defined by the sealing members 42A and 42B. The distance between the induction coils 49A and 49B and the sealing members 42A and 42B can be between 1 mm and 80 mm.

[0107] The corresponding generators or inverters 50A and 50B are associated with the induction devices 48A and 48B and are controlled to supply an electromagnetic induction current suitable for generating a time-varying electromagnetic flux to the induction coils 49A and 49B. As the sealing members 42A and 42B pass by, the eddy currents generated by the time-varying electromagnetic flux heat the sealing members by Joule heating.

[0108] The operating frequencies of the inverters 50A and 50B are approximately equal to the resonance frequencies of the circuits formed by the corresponding induction coils 49A and 49B. The operating frequencies of the electromagnetic induction currents generated by the inverters 50A and 50B are between 10 Hz and 500 kHz, more preferably between 100 Hz and 100 kHz.

[0109] To regulate the operating temperature of the sealing members 42A, 42B, a closed-loop control system can be used, which includes inverters 50A, 50B and at least one temperature sensor of any type (such as a thermocouple, pyrometer, thermal camera or other suitable device). The temperature sensor is associated with the corresponding sealing members 42A, 42B and is connected to a control unit that controls the inverters 50A, 50B based on an appropriate control algorithm, thereby regulating the temperature of the sealing surfaces 43A, 43B. The temperature control system can be run by a central control unit 45 or different control devices (for example, another PC or PLC or industrial computer, microprocessor, computer network or any other suitable device).

[0110] The operating temperature of the sealing members 42A, 42B can be between 100°C and 400°C, preferably between 150°C and 300°C. The operating temperature can vary greatly as it depends on the operating conditions of the packaging machine 1, the production speed, the type of paper wrapping sheet F, and the type and quality of the sealant S.

[0111] To increase the production flexibility of the packaging machine 1, the sealing station 40 includes adjusting means for adjusting the lateral distance between the sealing members 42A, 42B, so as to adapt the machine to the specifications of the package C to be manufactured. The adjusting means for adjusting the lateral distance between the sealing members 42A, 42B can include bases 51A, 51B that can move laterally (i.e., preferably orthogonally to the sealing direction fS) along guides 52, 53. The bases 51A, 51B are slidably constrained to the guide rails 52, 53 by corresponding sliders (shoes). When the packaging machine 1 is running, the distance between the bases 51A, 51B is locked to hold the sealing members 42A, 42B in the desired position. Only when it is necessary to adjust the lateral position of the sealing members 42A, 42B, the distance between the bases 51A, 51B is unlocked, thereby widening or narrowing the channel 41. To adjust the distance between the sealing members, an actuator 73 (in this case a handwheel) is provided, which rotates a worm 72 that engages nuts 74, 75, and the nuts 74, 75 are integrally formed with the bases 51A, 51B respectively. The worm 72 preferably consists of two parts 72' and 72" with opposite thread directions, such that the rotation of the worm 72 causes the bases 51A, 51B (and the corresponding sealing members 42A, 42B) to move towards and away from each other. The actuator 73 can also be an electric motor to automatically adjust the cross-sectional size of the channel 41.

[0112] To achieve an optimal seal, a member 76 can be provided to adjust the sealing pressure, that is, to apply a predetermined side sealing pressure to the package C as the package C moves along the channel 41. As Figure 15As better shown, a sealing pressure regulating member 76 is attached to each of the sealing members 42A, 42B and may include a sliding guide 77 integral with the bases 51A, 51B. The sliding guide 77 may be substantially parallel to the guide rails 52, 53. A slider 78 integral with the plate 80 on which the sealing members 42A, 42B are mounted is associated with the sliding guide 77. The bases 51A, 51B are respectively connected to actuators 82, 83, which are preferably pneumatic or electric actuators, or any other type of actuator adapted to push the sealing members 42A, 42B towards each other. If the actuator is pneumatic, the sealing pressure can be adjusted by changing the air pressure, while if the actuator is electric or electromechanical, the control unit 45 or another dedicated control device can move the actuators by moving each of the bases 51A, 51B (and thus the sealing members 42A, 42B) towards or away from each other.

[0113] A tensioning device 60 may be provided for each of the sealing members 42A, 42B to tension the sealing members. In the case where each of the sealing members 42A, 42B consists of two or more strips of ferromagnetic or paramagnetic material, a tensioning device 60 is provided for each strip. The tensioning device 60 may be implemented by an idler roller 61 which is pressed against the corresponding sealing member 42A, 42B by a pneumatic actuator 62. Other types of actuators, such as electric linear motors or other equivalent electromechanical devices, may also be used. If a pneumatic actuator is used, the tension of the corresponding sealing member 42A, 42B can be adjusted by regulating the air pressure of each pneumatic actuator.

[0114] Preferably, in order to keep the distance between the sealing members 42A, 42B and the corresponding induction coils 49A, 49B constant, the tensioning device 60 may act on the corresponding sealing members 42A, 42B in a portion defined by two consecutive return members 45A, 46A and 45B, 46B and not including the corresponding induction coils 49A, 49B. For example, as shown, the tensioning device 60 acts on the portion between the return members 44A, 46A and 44B, 46B, while the induction coils 49A, 49B are placed in the portion between the return members 45A, 46A and 45B, 46B. In this way, the deformation caused by the tensioning device 60 on the sealing members 42A, 42B does not affect the portions of the sealing members 42A, 42B facing the induction coils 49A, 49B.

[0115] There are uniform sealing members 42A, 42B made of ferromagnetic materials (such as steel, iron or their derivatives), which can better conduct heat and transfer heat from the sealing surfaces 43A, 43B to the paper-wrapped sheet F. If a compressive force (although very small) is applied to the package C to be sealed as the package C moves forward in the channel 41, a tensile effect will be generated at the crease of the paper-wrapped sheet F, thereby improving its aesthetic quality and facilitating the stability of the crease. In this way, the package can be improved both when it is sealed with the packaging sealant S and when the paper-wrapped sheet has no sealant, because regardless of whether the sealant S is used, the tensile effect stabilizes the creases of the hems L1, L2. Finally, ferromagnetic materials (such as steel, iron or their alloys) allow significantly higher durability than the prior art systems mentioned in the introduction.

[0116] Finally, and optionally, a contrast means (abutment means) 90 can be provided to balance any bending when the sealing members 42A, 42B come into contact with the package C to be sealed, especially when the sealing members 42A, 42B are formed by strips 54A and 54B of ferromagnetic or paramagnetic materials. The contrast means 90 is placed on the opposite side with respect to the sealing surfaces 43A, 43B and can include sliding means on which the strips 54A and 54B slide. The sliding means is preferably coated with polytetrafluoroethylene or made entirely of polytetrafluoroethylene to reduce friction with the strips. The sliding means can be equipped with elastic elements (such as springs) to allow movement in a direction orthogonal to the sealing direction fS.

[0117] In another embodiment, as Figure 16 and Figure 17 shown, the sealing members 42A, 42B can be constituted by flexible members 70 (such as one or more conveyor belts or chains), to which a plurality of sealing elements are constrained. The sealing elements can be composed of, for example, a plurality of plates 71 made of or containing ferromagnetic or paramagnetic materials arranged side by side. The flexible members 70 can be driven around the return members 44A, 45A, 46A and 44B, 45B, 46B, exactly similar to that described above. Induction coils (not shown in this example) can face the activation surfaces of the sealing elements. When the flexible members of the sealing members 42A, 42B are made of non-ferromagnetic materials (such as plastics or rubbers), eddy currents can only be induced in the sealing elements and not in the flexible members. Similarly in this technical solution, tensioning means (not shown in the figure) can be provided, for example, very similar to the above, to tension each flexible member of the sealing members 42A, 42B.

[0118] As Figure 17As shown in the schematic view, at least when moving in the sealing area within the plate along channel 41, in order to transfer heat from one plate 71 to the adjacent plate 71 by conduction, the plate has a contact area 72. The contact area 72 is, for example, arranged near the side surface of the plate 71 that is orthogonal to the supply direction in the channel 41, and is realized, for example, by a side recess 73 and a corresponding side protrusion 74 (the side recess 73 and the corresponding side protrusion 74 are part of the uniform sealing surface of each plate, and as a part), and the side recess and the corresponding side protrusion are joined together so that the adjacent plates overlap (refer to the orientation of the sealing surface of the plate). For example, the side recess and the protrusion 73 - 74 have corresponding surfaces parallel to the sealing surface of the plate, and these surfaces face each other; during forward movement in the channel, the side protrusion 74 contacts the side recess 73 at these surfaces. For example, the cross-sectional area and shape of the protrusion can approximately match the cross-sectional area and shape of the recess.

[0119] In addition, in this technical solution, a contrast device 90’ (only schematically shown in Figure 17 is provided to balance any bending of the sealing members 42A, 42B when contacting the package C to be sealed. The contrast device 90’ is arranged on the opposite side with respect to the sealing surfaces 43A, 43B and exerts a relative thrust on the plates, so that the plates contact each other at the contact area 72.

[0120] In order to limit or avoid contact discontinuity, the sealing elements can also be in phase with the package C to be sealed, so that the surfaces of each sealing element 43A, 43B match the corresponding surfaces Fa and Fp of the package C to be sealed. For this purpose, the surface of each sealing element is preferably uniform, that is, smooth and continuous, that is, there are no bulges, protrusions, depressions, holes in the part contacting the paper wrapping sheet.

[0121] It should be understood that the content shown is only representative of possible non - restrictive embodiments of the present invention, and these embodiments can vary in form and arrangement without departing from the scope of the concept on which the present invention is based. Any reference numerals in the appended claims are only for facilitating reading according to the above description and the drawings, and do not limit the scope of protection in any way.

Claims

1. A packaging machine for packaging household paper products by wrapping a paper wrapping sheet around a product, the household paper products being, for example, rolls of kitchen paper towels and rolls of toilet paper, the packaging machine comprising: ο A product supply station for successively and groupwise supplying a product group including at least one product one by one, ο A wrapping station for wrapping the paper wrapping sheet around the product group, ο A sealing station located downstream of the wrapping station for sealing the paper wrapping sheet wrapped around the product group, Characterized in that: The sealing station includes a channel for moving the product group forward and a pair of sealing members disposed opposite each other on both sides of the channel. Each sealing member has a uniform sealing surface made of a material of the following type that can induce eddy currents when the material is subjected to a magnetic field change. Each sealing member includes at least one flexible element driven between at least two return members, and the sealing members are respectively associated with electromagnetic induction devices adapted to induce eddy currents in the material.

2. The packaging machine according to claim 1, wherein at least one, and preferably both, of the pair of sealing members are formed by at least one uniform strip of the material capable of inducing eddy currents, thereby defining the uniform sealing surface.

3. The packaging machine according to claim 1, wherein at least one, and preferably both, of the pair of sealing members include at least one plate made of the material capable of inducing eddy currents and have a uniform sealing surface moved by the at least one flexible element; preferably, more plates are provided preferably arranged adjacent to each other along the at least one flexible element.

4. The packaging machine according to claim 3, wherein the plates of the sealing member move at the same supply speed.

5. The packaging machine according to one or more of the preceding claims, wherein each electromagnetic induction device includes an induction coil arranged to face the sealing surface directly or arranged on the opposite side of the sealing member relative to the sealing surface.

6. The packaging machine according to one or more of the preceding claims, wherein the electromagnetic induction device is configured to heat the sealing surface to a temperature between 100 °C and 400 °C.

7. The packaging machine according to one or more of the preceding claims, including an adjusting member for adjusting the mutual distance of the sealing members.

8. The packaging machine according to one or more of the preceding claims, including an adjusting member for adjusting the sealing pressure.

9. The packaging machine according to one or more of the preceding claims, wherein the induction device associated with each sealing element is located outside and is supplied with an induction current having a frequency between 1 kHz and 500 kHz.

10. The packaging machine according to one or more of the preceding claims, wherein at least one return member is power-driven.

11. The packaging machine according to one or more of the preceding claims, wherein the channel comprises a conveyor for moving the product group forward along the sealing station in a forward movement direction, the forward movement of the product group being preferably caused by the conveyor and the sealing member.

12. The packaging machine according to one or more of the preceding claims, wherein the wrapping station provides the leaving speed of the product group, and wherein the conveyor and the sealing member are configured to move the product group forward at a speed higher than the speed at which the product leaves the wrapping station.

13. The packaging machine according to one or more of the preceding claims, wherein the paper wrapping sheet comprises a sealant.

14. The packaging machine according to claim 13, wherein the sealant is a heat-activated adhesive.

15. The packaging machine according to one or more of the preceding claims, wherein the supply station comprises a lift for lifting the product group towards the wrapping station, the product group contacting a wrapping sheet arranged parallel to a plane transverse to the lifting direction of the product group, the wrapping sheet forming a partial wrap around the product group, the partial wrap being shaped like an inverted U.

16. The packaging machine according to one or more of the preceding claims, wherein the wrapping station comprises: ο A bottom folding device for completing the partial wrap of the wrapping sheet around the product group to form a tubular structure open at opposite sides of the product group, the open tubular structure having hems of the wrapping sheet to be folded, the hems extending from each of the two side edges of the product group; ο A front side edge folding device for each of the two side edges of the product group to fold a part of the hem of the wrapping sheet against each side edge to form a front crease; ο A rear side edge folding device for each of the two side edges of the product group to fold a part of the hem of the wrapping sheet against each side edge to form a rear crease; ο A top side edge folding device for each of the two side edges of the product group to fold a part of the hem of the wrapping sheet against each side edge to form a top crease; ο A bottom side edge folding device for each of the two side edges of the product group to fold a part of the hem of the wrapping sheet against each side edge to form a bottom crease.

17. The packaging machine according to one or more of the preceding claims, wherein the material capable of inducing eddy currents is ferromagnetic or paramagnetic.

18. The packaging machine according to claims 2 and 17, wherein the belt is made of a ferromagnetic material, the ferromagnetic material being preferably steel, iron or an alloy thereof; or the belt is made of or contains a paramagnetic material, the paramagnetic material being preferably aluminum or an alloy thereof, the paramagnetic belt preferably comprising an aluminum core or an aluminum strip with a thickness preferably between 5 μm and 100 μm, more preferably between 20 μm and 25 μm, and preferably the aluminum core or the aluminum strip provides a material preferably polytetrafluoroethylene on the sealing surface to facilitate the sliding of the surface on the product.

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