PACKAGING MACHINE WITH SEALANT DISPENSING DEVICE

Abstract

Packaging machine for packaging tissue paper products, such as kitchen towels and toilet rolls, by wrapping a paper wrapping sheet around the products, the machine including: a feeding station for feeding, one by one in succession, groups of products including at least one product; a wrapping station for wrapping the paper wrapping sheet around the groups of products; a sealing device for sealing the paper wrapping sheet around the groups of products; a wrapping sheet feeding station for feeding a single wrapping sheet at a time along a sheet feeding direction towards the wrapping station, including a dispensing device for applying sealant to the paper wrapping sheets.

Claims

1-31. (canceled)

32. A packaging machine for wrapping groups of products with a paper wrapping sheet, the machine comprising: a feeding station for feeding, one by one in succession, groups of products comprising at least one product; a wrapping station for wrapping paper wrapping sheets around the groups of products; a sealing device for sealing the paper wrapping sheets around the groups of products; a wrapping sheet feeding station for feeding, one by one, the paper wrapping sheets along a sheet feeding direction towards the wrapping station; wherein the wrapping sheet feeding station comprises a dispensing device comprising at least one dispenser for applying sealant to the paper wrapping sheets.

33. The packaging machine of claim 32, wherein the wrapping sheet feeding station is provided upstream of the wrapping station along the sheet feeding direction.

34. The packaging machine of claim 32, wherein the wrapping sheet feeding station further comprises: a cutting unit for cutting single paper wrapping sheets from a web material unwound from a reel; an unwinding device for unwinding the reel of web material.

35. The packaging machine of claim 34, wherein the dispensing device is provided upstream or downstream of the cutting unit along the sheet feeding direction.

36. The packaging machine of claim 35, wherein the dispensing device is provided upstream of the cutting unit, and the paper wrapping sheet is defined by two parallel sides and two sides transverse to the sheet feeding direction towards the wrapping station, and wherein the at least one dispenser is configured to apply a line of sealant to an area of the web material corresponding to a paper wrapping sheet along a direction parallel to one of the two sides parallel to the sheet feeding direction, and the said at least one dispenser is configured to apply a line of sealant along a direction parallel to each of the two sides transverse to the sheet feeding direction.

37. The packaging machine of claim 35, wherein the dispensing device is provided downstream of the cutting unit, and the paper wrapping sheet is defined by two parallel sides and two sides transverse to the sheet feeding direction towards the wrapping station, and wherein the at least one dispenser is configured to apply a line of sealant to a single paper wrapping sheet along a direction parallel to one of the two sides parallel to the sheet feeding direction; and said at least one dispenser is configured to apply a line of sealant along a direction parallel to each of the two sides transverse to the sheet feeding direction.

38. The packaging machine of claim 36, wherein either of the line of sealant is continuous or discontinuous and has a length equal to, or shorter than, a length of respective sides of the paper wrapping sheet.

39. The packaging machine of claim 37, wherein either of the line of sealant is continuous or discontinuous and has a length equal to, or shorter than, a length of respective sides of the paper wrapping sheet.

40. The packaging machine of claim 36, wherein either of the line of sealant is spaced from a respective side by a distance comprising between 0.5 mm and 50 mm.

41. The packaging machine of claim 32, wherein the at least one dispenser is a spreading dispenser for dispensing by touching a surface to which the sealant is to be applied.

42. The packaging machine of claim 32, wherein the dispensing device comprises a first adjusting means for adjusting distance between the at least one dispenser and the paper wrapping sheets and a second adjusting means for adjusting the at least one dispenser transversally with respect to the wrapping sheet feeding direction.

43. The packaging machine of claim 32, wherein the wrapping sheet feeding station comprises a detection device for detecting a position of the paper wrapping sheets along the sheet feeding direction, and wherein the detection device for detecting the position of the paper wrapping sheets is optionally an encoder.

44. The packaging machine of claim 42, wherein the at least one dispenser applies the sealant phased with respect to a position of the paper wrapping sheets.

45. The packaging machine of claim 32, wherein the dispensing device comprises at least three dispensers, wherein at least two of said at least three dispensers include a plurality of dispensers; a sealant supply system associated with the dispensing device wherein the sealant supply system includes for each of said plurality of dispensers a valve that allows supplying or not supplying from a respective dispenser wherein the plurality of dispensers are adapted to dispense sealant for a first time interval, thus generating spaced strokes of a line of sealant, wherein each stroke is formed by adjacent areas of sealant, and wherein a third dispensing group of said at least three dispensers comprises at least one dispenser adapted to dispense sealant for a second time interval longer than the first time interval, thereby generating a continuous line of sealant orthogonal to the line of sealant of the first time interval, the sealant supply system comprising a pumping apparatus for feeding the sealant to said at least one dispenser, having a sealant feed rate which is variable depending on feed speed of the web material to which the sealant is to be applied.

46. The packaging machine of claim 32, further comprising a sealant supply system associated with the dispensing device, the sealant supply system comprising a pumping apparatus for feeding the sealant to said at least one dispenser, wherein sealant feed rate is variable depending on feed speed of the web material to which the sealant is to be applied and/or on production speed of the packaging machine.

47. The packaging machine of claim 32, wherein the paper wrapping sheet has a grammage comprising between 10 g/m.sup.2 and 100 g/m.sup.2, and a thickness comprising between 10 m and 500 m.

48. The packaging machine of claim 32, wherein the dispensing device is adapted to dispense the sealant in a manner providing a quantity of sealant on each paper wrapping sheet comprising between 30% and 1% of the weight of the sheet.

49. The packaging machine of claim 32, wherein the feeding station for feeding groups of products comprises an elevator for lifting a group of products toward the wrapping station, the group of products touching the paper wrapping sheet that is arranged parallel to a plane transverse with respect to lifting direction of the group of products during upward movement toward the wrapping station, the paper wrapping sheet forming, around the group of products, a partial wrapping shaped like an overturned U, when the elevator has lifted the group of products up to a level of the wrapping station.

50. The packaging machine of claim 32, wherein the wrapping station comprises: a bottom folding device for completing partial wrapping of the paper wrapping sheet around the group of products, forming a tube open at two opposite sides of the group of products, the open tube having flaps of paper wrapping sheet to be folded that project from each of two sides of the group of products; a front side folding device for each of two sides of the group of products to fold against each side a portion of the flaps of paper wrapping sheet, thus forming a front fold; a back side folding device for each of the two sides of the group of products to fold against each side a portion of the flaps of paper wrapping sheet, thus forming a back fold; a top side folding device for each of the two sides of the group of products to fold against each side a portion of the flaps of paper wrapping sheet, thus forming a top fold; a bottom side folding device for each of the two sides of the group of products to fold against each side a portion of the flaps of paper wrapping sheet, thus forming a bottom fold.

51. The packaging machine of claim 32, wherein the sealing station comprises a feeding channel and a pair of sealing members provided opposite each other on two sides of the feeding channel, each sealing member of the pair of sealing members having a uniform sealing surface, made of ferromagnetic material or containing paramagnetic material, said each sealing member being driven between at least two return members, said each sealing member being respectively associated with an electromagnetic inductor.

52. The packaging machine of claim 51, wherein at least one sealing member of said pair of sealing members is a uniform flexible sealing member made of ferromagnetic material or containing paramagnetic material.

53. The packaging machine of claim 32, further comprising a cooling device for cooling the sealant applied to the paper wrapping sheets; wherein the cooling device is of an air type including at least one air ejection nozzle directed toward an area occupied by at least one paper wrapping sheet.

54. The packaging machine of claim 53, wherein the cooling device includes at least one air ejection nozzle directed toward a section of a web material path downstream of an area where the sealant is applied and upstream of a cutting unit for said web material wherein the cooling device is adapted to form a laminar airflow over the paper web material; and the cooling device comprises at least one surface facing at least one section of the web material path and defining with the web material a channel for the airflow coming from the at least one air ejection nozzle.

55. A method for packaging a group of products with a paper wrapping sheet, the method comprising steps of: feeding one by one, in succession, groups of products including at least one product, forming and feeding, one by one, the paper wrapping sheets along a sheet feeding direction, toward a wrapping station, wrapping a paper wrapping sheet of the paper wrapping sheets around a group of products, sealing the paper wrapping sheet around the group of products, wherein during the forming and feeding of the paper wrapping sheets, a sealant is applied to the paper wrapping sheet.

56. The method of claim 55, wherein said sealing of the paper wrapping sheet is with a sealant applied by a sealant dispenser.

57. The method of claim 56, wherein the paper wrapping sheet is defined by two parallel sides and two transverse sides with respect to the sheet feeding direction, and wherein during applying of the sealant to the paper wrapping sheet, a first line of sealant is dispersed along a direction parallel to one of the two sides parallel to the sheet feeding direction and a second line of sealant is dispensed along a direction parallel to each of the two transverse sides with respect to the sheet feeding direction.

58. The method of claim 57, wherein the first line of sealant and/or the second line of sealant is continuous or discontinuous and has a length equal to, or shorter than, a length of respective sides of the paper wrapping sheet.

59. The method of claim 57, wherein the first line of sealant and/or the second line of sealant is applied to the paper wrapping sheet spaced from a respective side by a distance comprising between 0.5 mm and 50 mm.

60. The method of claim 55, further comprising the step of cutting single paper wrapping sheets from a web material unwound from a reel.

61. The method of claim 55, wherein the forming of the paper wrapping sheets comprises unwinding a continuous paper wrapping web and cutting the continuous paper wrapping web into single paper wrapping sheets.

62. The method of claim 61, further comprising detecting a position of the paper wrapping sheets along the sheet feeding direction and applying a sealant phased with a position of the wrapping sheets when the cutting of the wrapping sheet occurs before preparing the paper wrapping sheet with the sealant or the detecting of a position of the web material and applying the sealant phased with the position of the web material when the cutting of the paper wrapping sheets occurs after the preparing of the paper wrapping sheet with the sealant.

63. The method of claim 55, further comprising cooling, through an airflow, a sealant provided on the paper wrapping sheets, after the sealant has been applied; wherein the cooling step is carried out on the web material before cutting if the sealant is applied to the paper wrapping sheets before the paper wrapping sheets are cut from the web material, or on individual wrapping sheets if the sealant is applied to separate single sheets.

Description

BRIEF DESCRIPTION OF THE DRAWING

[0078] The invention will be better understood by following the description below and the attached drawing, showing a non-limiting embodiment of the invention. More specifically, in the drawing:

[0079] FIG. 1 is a schematic side view of a feeding station for feeding products, such as rolls, in a machine according to the invention;

[0080] FIG. 2 is a schematic side view of a wrapping station for wrapping products, such as rolls, in a machine according to the invention;

[0081] FIGS. 3 to 6 show the schematic sequence of lifting a group of products and beginning wrapping the wrapping sheet in the station of FIG. 2;

[0082] FIG. 7A is a schematic perspective view of a feeding station for feeding wrapping sheets in a machine according to the invention;

[0083] FIG. 7B is a side view of the wrapping sheet feeding station of FIG. 7A;

[0084] FIG. 8A shows a first plan of a wrapping sheet feeding station in a machine according to the invention, with a sealant dispensing system directed differently than that shown in FIG. 7A;

[0085] FIG. 8B shows a first plan of a cooling device for cooling the sealant on the paper web/sheet arranged along a linear section of the paper web path in the wrapping sheet feeding station in a machine according to the invention;

[0086] FIG. 8C shows a second plan of a cooling device for cooling the sealant on the paper web/sheet, arranged along several sections of the paper web path, according to different orientations, in the wrapping sheet feeding station in a machine according to the invention;

[0087] FIGS. 9A to 9G show a schematic sequence of folding a wrapping sheet around a group of products with distribution of glue;

[0088] FIG. 10 is a schematic view, different than that of the previous figure, of the glue distribution on the wrapping sheet;

[0089] FIGS. 10A and 10B respectively show a schematic perspective view and a top view of a package consisting of a single layer of rolls, with the wrapping sheet having a glue distribution according to FIG. 10;

[0090] FIGS. 11A and 11B respectively show a schematic top view of a wrapping sheet with a glue distribution different than that in the previous figures, and a schematic view of a closure face of the package with the wrapping sheet with such a different glue distribution;

[0091] FIG. 12 is a schematic axonometric view of a sealing station of a machine according to the invention;

[0092] FIG. 13 is a schematic front view of the sealing station of FIG. 12;

[0093] FIG. 14 is a schematic plan view of the sealing station of FIG. 12;

[0094] FIG. 15 is a further schematic perspective view from the bottom of the sealing station of FIG. 12.

DETAILED DESCRIPTION OF EMBODIMENTS

[0095] In FIG. 1, a packaging machine 1 for packaging products R, for example paper rolls, is shown. The rolls are made of tissue paper, for example toilet rolls or kitchen towel rolls. The rolls may have either a cardboard core around which the paper is wound, or not, i.e. they could be made of paper wholly wound from the center thus forming a solid cylinder (so-called solid rolls) or they could have a cylindrical cavity, such as in the case of winding around a center hole without the core (so-called coreless rolls).

[0096] The packaging machine 1 is fed by a product feeding station 2 that may include a launcher device 3, of a known type, such as that described in EP2763917B1. In this case, the launcher 3 is comprised of one or more feeding belts 4 co-acting with motorized belts 5 that laterally engage the products R. In this specific case, the motorized belts 5 are shown arranged laterally but it is understood that they could also be provided in a different configuration, for example above and below the products R. The feeding station 2 may consist of a plurality of feed channels arranged side by side, wherein each feeding channel feeds a line of products R. To each channel there is generally associated a launcher device 3. The launcher 3 is controlled in such a way as to dose sequentially groups G of products R, in this case rolls, towards the subsequent conveying members that are also part of the feeding station 2 for feeding groups G of products, and will be described below.

[0097] In the described example, the launcher device 3 sequentially doses groups G of products R to a conveyor 7 that may have a slide surface 8, where the groups G of products R slide, and a pair of flexible members 9, e.g., chains, to which push bars 10 are constrained, so spaced as to accommodate the groups G of products R, extending transverse to the feeding direction of the products R. Each push bar 10 is constrained, at its ends, to the flexible members 9. In this way, by appropriately moving the flexible members 9, the groups G of products R are moved forward, i.e. pushed forward by means of the push bars 10 synchronously with the feeding rate of the packaging machine 1. The launcher device 3 and the conveyor 7 are then configured to group and dose groups G of products R of desired size in a cadenced manner.

[0098] From the conveyor 7, the groups G of products R are transferred to a layering station 6, which is also part of the product feeding station 2. The layering station 6 may include a conveyor 11 provided with a swinging motion according to the double arrow f11 to distribute individual groups G of products R, or layers, into the feeder device 12. In this specific case, the feeder device 12 comprises two layers, but it is understood that layering can have more than two layers, such as three or even more layers of products. If the packaging machine 1 is configured to produce single-layer packages, the layering station 6 is obviously not necessary.

[0099] The feeder device 12 is represented herein with pushing members for each product layer formed by single groups G of products R. Similarly to the conveyor 7, for each layer the pushing members are respectively formed by a slide surface 13A, 13B and a push bar 14A, 14B carried forward by a respective flexible member 15A, 15B. The feeder device 12 synchronously inserts each layer of products R onto an elevator 16. For example, the individual layers can be deposited simultaneously on the elevator 16, or one following the other.

[0100] This embodiment of the feeder device 12, like that of the launcher 3 and the conveyor 7, is given just by way of non-limiting example, as completely different configurations can be used to group, to dose, and to layer the products.

[0101] The elevator 16 consists of a plate 16A that receives and supports the groups G of layered products R, and is vertically movable along a lifting and lowering direction according to the double arrow f16. The movement of the plate 16A can be achieved by a mechanism of the rod-crank type, not shown in detail for the sake of simplicity, driven by an electric motor 17. Advantageously, the elevator 16 also comprises a bottom stop 18, which can be adjusted according to the double arrow f18 according to the length or depth of the group G of products R. The depth of the group G of products R is variable depending on the number of products R of which each row is composed, or on the length of the individual product R. As shown in the side view of FIG. 2, the elevator 16 can also comprise side banks 21A, 21B, 21C, 21D provided along the two side flanks of the group G of products R in order to contain and to accompany the group G of products R during lifting.

[0102] In the shown example, the launcher device 3, together with the conveyor 7, group two products R for each channel, but it is evident that it is also possible to group a single product R or more than two products for each channel.

[0103] The elevator 16 sequentially lifts groups G of products R from a layering height Qs to a wrapping height Qa of a wrapping station 19, arranged higher than the product feeding station. During the lifting motion along the double arrow f16, the group G of products R encounters a paper wrapping sheet F arranged along a plane orthogonal to the lifting and lowering direction f16, starting the wrapping cycle that will be described in more detail in FIGS. 3 to 6. The paper wrapping sheet F is advantageously arranged at a level between the layering height Qs and the wrapping height Qa.

[0104] The paper wrapping sheet F can be inserted into and positioned in the wrapping station 19 through two openings 22 made between the side banks 21A, 21C and 21B, 21D, respectively, while it is held at two edges B1, B2 by sheet feeding members 20, for example belts. The formation and of the paper wrapping sheets and the feeding thereof to the wrapping station 19 will be described in more detail below.

[0105] The wrapping cycle is now described with reference to FIGS. 3 to 6 and FIGS. 9A to 9G. In particular, FIG. 3 shows the group G of products R arranged at the layering height Qs. In FIG. 4, the group G of products R touches the paper wrapping sheet F, starting the wrapping of the paper wrapping sheet F around the top face Fs and the side faces Fl of the group G of products R. In FIG. 5 and FIG. 9B, the group G of products R is at the wrapping height Qa and is completely wrapped with the paper wrapping sheet around the top face and the side faces, leaving the two edges B1, B2 of the paper wrapping sheet F projecting vertically downward, if necessary, with different lengths. At this time, the paper wrapping sheet partially wrapped around the group G of products R, forms a kind of overturned U. Finally, in FIG. 6 and FIG. 9C, the edges B1, B2 have been put over each other to complete the wrapping of the bottom face of the group G of products R. The two edges B1, B2 have been put over each other by two bottom folding devices 25, 26, which are part of the wrapping station 2 and are movable with mutual motion along respective arrows f25 and f26. Once the two edges B1 and B2 have been put over 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 layering height Qs to receive a new group G of products R. Now, as shown in FIG. 9C, the front face Fa and the back face Fp, facing each other, of the group G of products R are free and the side flaps L1, L2 of the paper wrapping sheet F project from the group G of products R approximately orthogonally to the front face and the back face.

[0106] The overlapping edges B1, B2 are then stabilized by a transverse sealing device 30 provided downstream of the elevator along the wrapping direction fA. The transverse sealing device 30 may have an active, i.e., heated, surface of, for example, rectangular shape, coplanar with the slide plane 23, the largest dimension of which is orthogonal to the wrapping direction fA and faces the group G of products R. Preferably, the transverse sealing device 30 moves along a direction, indicated by the double arrow f30, of movement towards and away from the group G of products R, orthogonal to the slide surface 23. Specifically, when the transverse sealing device 30 has been brought to the group G of products R, partially wrapped with the paper wrapping sheet F, it seals the package in the overlapping area of the edges B1, B2. The active surface of the transverse sealing device 30 can be smooth or dotted and can be heated to temperatures 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 products R is stationary, i.e. it does not move forward along the wrapping direction fA, thus allowing the transverse sealing device 30 to remain into contact with the overlapping edges B1 and B2 for the necessary time. This allows a sealant S to be activated and to seal, i.e., irreversibly close, the wrapping sheet F around the group G of products R, forming a tube closed on the outer perimeter, in contact with the side surfaces of the products R, and leaving at least partially protruding side flaps L1 and L2 orthogonal to the side faces of the group G of products R, as will be better described below.

[0107] In other cases, it is possible to have a transverse sealing device 30 that, in addition to having a movement orthogonal to the slide surface 23, also has a movement parallel to the slide surface 23, so as to seal the group G of products R while moving forwards along the wrapping direction fA.

[0108] The lifting motion of the elevator 16 allows the groups G of products R to be inserted, at the wrapping height Qa, into a space S of width equal to, or slightly smaller than, the width of the group G of products R, defined by consecutive teeth 27.2, of a conveyor 27, that is part of the wrapping station 19. The conveyor 27 moves the groups G of products R, supported by a slide surface 23, along a 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, for example a belt or a chain, driven between two pulleys 27.3, at least one of which is suitably motorized, to move the teeth 27.2 along a closed path, the active branch of which, i.e. the branch where the wrapping of the paper wrapping sheet F is completed, is the lower branch.

[0109] The conveyor 27 may be also realized differently. For example, the teeth 27.2 can be transported by carriages movable along rails. A linear electric motor, controlled so as to receive and to transport groups G of products R, can be associated with each carriage. An example of this kind of conveyor 13 is described in IT1426528.

[0110] In other embodiments, the conveyor 27 can be configured for example to constrain consecutive teeth 27.2 to a plurality of belts, each of which is independently motorized so as to have consecutive teeth 27.2 movable independently of each other. This kind of configuration is disclosed in the Italian patent no. 102015000084892.

[0111] Once the group G of products R, inserted into the space S, is moved forward by the conveyor 27 along the wrapping direction fA, it passes through a folding device 28 that comprises a top side folding device Pls, a bottom side folding device Pli, a front side folding device Pla, and a back side folding device Plp, respectively forming a top side fold Pls, a bottom side fold Pli, a front side fold Pla and a back side fold Plp, as shown in the sequence of FIGS. 9D-9G. The top side folding device Pls, the bottom side folding device Pli and the front side folding device Pla are generally fixed while the back side folding device is movable along the double arrow Fplp. The movement of the back side folding device can be coordinated with the movement of the movable bottom folding devices 25, 26 in order to create the respective folds at the same time or to create the back side fold Plp immediately after the overlapping of the two edges B1, B2. Furthermore, a single motorization can be used for moving the movable bottom folding devices 25, 26 and the back side folding device Plp. In some cases, the back side folding device Plp can complete the respective fold before the group G of products R is moved by the conveyor 27. In other cases, the back side folding device Plp can complete the fold while the group G of products R has been already put in motion by the conveyor 27.

[0112] Therefore, the movement forward of the group G of products R along the direction fA through the folding device 28, allows folding the side flaps L1, L2 forming the side folds Pla, Plp, Pli and Pls of the paper wrapping sheet F on the front face and the back face of the group G of products R, as shown in FIGS. 9A-9G. Side folding members of this type may be also realized, for example, as described in EP1228966.

[0113] Here below, with reference to FIG. 7A and FIG. 7B, a sheet feeding station 31 for feeding paper wrapping sheets F will be described, which sequentially feeds one sheet at a time to the wrapping station 19.

[0114] The sheet feeding station 31 comprises an unwinding device 38 to unwind a reel B of paper web material N formed from virgin or recycled fiber or a mix thereof. Preferably, the grammage of the paper web material Nis between 10 g/m.sup.2 and 100 g/m.sup.2, and the thickness is between 10 m and 500 m, and more preferably between 20 m and 100 m. The unwinding device 38 can include a support device to keep the reel B rotating about its longitudinal axis, and an actuating device to put the reel B into controlled rotation, for example by means of belts in contact with the outer surface of the reel B or by connecting the axis of the reel B with a motorized system. The unwinding device can be of any known type, as shown for example in IT1274081.

[0115] The paper web material N can be conveyed by idle rollers 32.1, 32.2, 32.3, 32.5, 32.5, and 32.6 along a feed path P in the feed direction fN to a cutting unit 37 arranged to cut the paper web material N into paper wrapping sheets F of predetermined length. Along the feed path P of the paper web material N, upstream of the cutting unit 37, there is a dispensing device 133 arranged to apply a sealant S, such as glue, onto the paper web material N. The sealant S may preferably be a heat-reactivated glue, i.e. it may have the characteristic of not remaining sticky once applied and of being activated only when heat-treated. The advantage of this type of sealant is that, in case of even accidental contact between the sealant and the elements that make up the packaging machine 1, it does not dirty the downstream devices, such as the wrapping station 19. Other types of glues can also be used, such as heat-activated glues or glues that are immediately active and can no longer be reactivated once dried.

[0116] As mentioned, the grammage of the paper web material N can be between 10 g/m.sup.2 and 100 g/m.sup.2, and the thickness can be between 10 m and 500 m, and preferably between 20 m and 100 m. It has been found to be particularly advantageous to reduce significantly the quantity of sealant applied to the web material N (or to the individual sheets already cut). In particular, it has been found that the quantity of sealant S provided on each individual sheet (i.e., applied to a single wrapping sheet that has already been cut, or applied to the web material N, a portion of which is cut to make a single wrapping sheet), is conveniently less than 30% of the weight of the single sheet (for example comprised between 30% and 1% of the weight of the individual sheet; in other words, assuming that the weight of the sheet is 100, the weight of the sealant is between 30 and 1), and more preferably less than 10% of the weight of the single sheet (e.g. between 10% and 1% of the weight of the single sheet), and even more preferably less than 5% of the weight of the single sheet (e.g. between 5% and 1% of the weight of the single sheet). The reduced amount of sealant, also resulting in very small thicknesses of sealant (given the same application area), allows, for example, to speed up the step of cooling the adhesive, which must be conveniently cold when arrives at the subsequent processing stations, to avoid soiling them.

[0117] The dispensing device 33 may comprise one or more dispensers 33.1, 33.2 33.3 provided above the feed path P to apply the sealant S to the paper web material N in a controlled manner. Preferably, the dispensers 33.1, 33.2 33.3 may be of the spreading type, although other types of dispensers, such as sprays, cannot be excluded. During the sealant application step, the dispensers, for example those of the spreading type, are preferably in contact with the paper web material N, preferably pressing the paper web material N. Of course, other types of dispensers, such as spray dispensers, can be spaced from the paper web material. The feed path P in the section where the sealant is applied may preferably be flat. The dispensers 33.1, 33.2 33.3, as schematically shown, can be supported by a support structure 34 consisting of L-shaped brackets 39 constrained to a crossbar 39A, whose ends are attached to two uprights 40. The support structure 34 can be of any other suitable type. The support structure 34 may comprise means, not shown, for adjusting the transverse position of the dispensers 33.1, 33.2, 33.3 relative to the feed direction fN of the paper web material N. For example, the L-shaped brackets 39 can slide along a linear guide and be blocked thereon by means of screws or other suitable systems. In a further configuration, also not shown for the sake of simplicity, the L-shaped brackets 39 or in general the dispensers 33.1, 33.2, 33.3 can be adjusted by means of motors in order to simplify the product changeover, i.e., the switching to packages that require different sizes of paper wrapping sheets F. Additionally, the dispensing device 33 can be height-adjustable, either manually or automatically, with respect to the feed path P. The dispensers 33.1, 33.2, 33.3 can be connected to an electronic control unit 45, like a PC or a PLC that manages the application step, i.e., the instants when the dispensers should apply the sealant S to the paper web material N and when they should not dispense it.

[0118] The dispensing device 33 may comprise, upstream of the dispensers 33.1, 33.2, 33.3 along the feed direction fN, a phase detection system 36 for coordinating the application of the sealant S with the paper web material N. In fact, the paper web material N may comprise prints, lettering, bar codes, and marks for phase detection, which may or may not be visible on the outside of the package C. In the case of prints or marks visible on the outside of the package, the position thereof with respect to the faces of the package must be precise and predetermined. Therefore, in this case the sealant S must be applied in a synchronized manner with the feeding of the paper web material N, and thus with a single paper wrapping sheet F. In the example of FIGS. 7A-7B, the phase detection system 36 is realized by an encoder 43 that can measure the amount of paper web material N moving forward along the feed direction fN. Alternatively, the encoder 43 can detect the position of the paper web material N, thus determining the position of a particular print design. Instead of the encoder 43 it is possible to use other systems or sensors, for example photocells that detect given points on the paper web material N, or vision systems that detect and recognize the position of the paper web material N. Moreover, a combination of these sensors can be used, for example, a photocell and an encoder, a photocell and a vision system, etcetera. The phase detection system 36 is also connected to the electronic control unit 45 in order to coordinate the application of the sealant S in phase with the forward movement of the paper web material N.

[0119] A cutting unit 37, not shown in detail, is provided downstream of the dispensing device 33 to cut the paper web material N into wrapping sheets F of predetermined length. The cutting unit 37 may be of the type described in EP1052209B1. The cutting unit 37 is preferably connected to and controlled by the electronic control unit 45 to perform the cutting of the paper web material N in phase with the prints, if any, and with the sealant S applied to the paper web material N. The cut should be in phase with the paper web material N also to form a paper wrapping sheet F of desired length. Preferably, the cutting is of the scissor type and is performed by a rotating blade co-acting with a fixed counter-blade, both blades being at least as wide as the paper web to be cut. Once cut and exiting the cutting unit 37, the paper wrapping sheets F are fed along a sheet feeding direction fF, generally parallel with the feed direction fN for the paper web material N, but it can be also different, for example orthogonal, when using cutting units having a different configuration from the preferred one, as shown in EP1052209B1.

[0120] In a different configuration, not specifically shown in the figure, the cutting unit 37 can be provided upstream of the dispensing device 33 which, in this case, must be phased directly with the paper wrapping sheets F. It is evident that, in this case again, phase detection devices 36 are provided, the operation of which is similar to that described above. In this configuration, it is also possible to phase the dispensing of the sealant S and the feeding of the paper wrapping sheets F by means of a photocell that detects the transverse edge of the sheets moving forward along a sheet feeding direction fF.

[0121] In general, to obtain sheets of the desired size, in phase with any prints, and in phase with the sealant S, it is necessary alternatively: [0122] to phase the application of the sealant S with the paper web material N and then to phase the paper web material N with the cutting unit 37 [0123] to phase the cutting unit 37 with the paper web material N and then to phase the paper wrapping sheets F with the dispensing device 33.

[0124] The application of the sealant S on the paper web material N can take place in more than one configuration, as shown in FIGS. 10 and 11. For example, in FIG. 10 a paper wrapping sheet F is shown, defined by two parallel sides and two sides transverse to the feed direction fN, to which the dispensing device 33 has applied a line SCP of sealant along a side parallel to the feed direction fN and a line SCT of sealant along the two sides transverse to the feed direction fN. The lines SCP and SCT of sealant can be continuous or discontinuous, for example, dashed. In the case of FIG. 10, the line SCP is continuous while the two lines SCT are formed by two strokes SM1, SM2 of sealant alternating with two strokes ZL1 (and possibly ZL2) without sealant, respectively. Preferably, the stroke ZL1 without sealant S, comprised between the two strokes SM1, SM2 of sealant S of a same line SCT, corresponds to the portion of sheet that will form the top side fold Pls and the bottom side fold Pli, respectively (so that there is no glue on the outer face of the package). In the case of the complete wrapping sequence of FIGS. 9A-9G, the lines SCT are continuous (the glue, if any, on the outer face of the package may be not activated or dry). In general, the lines SCT are applied so that between the front side folds Pla, the back side folds Plp, the bottom side folds Pli, and the top side folds Pls there is a stroke of sealant S, whose activation by means of a sealing station 40 permanently stabilizes the package C of products R. The line SCP is applied to the paper wrapping sheet F so as to be between the overlapping edges B1, B2, so that the sealant S can be heated, and therefore activated, by the transverse sealing device 30. As shown in FIGS. 9A-9G, the line SCT on each side face of the package C can form an H-shaped seal. The horizontal stroke of the H shape is formed by the lines SCT applied to the portions of wrapping sheet F that constitute the top side fold Pls and the bottom side fold Pli, if they are arranged over each other. The vertical strokes of the H shape are formed by the portions of lines SCT corresponding to the portion of paper wrapping sheet F forming the front side fold Pla and the back side fold Plp. If the lines SCT are not exactly arranged over each other, the seal has the shape of a rectangle, where the lower side is given by the line SCT applied to the side of the paper wrapping sheet F that forms the top side fold Pls, the upper side is given by the line SCT applied to the side of the paper wrapping sheet F that forms the bottom side fold Pli, and the two vertical sides are determined as in the previous case.

[0125] The lines SCP and SCT are generally applied approximately parallel to the edge sides 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 be adjusted also based on the desired size of the package C. The lines SCP and SCT can be applied at a distance from the edge of one side of the paper wrapping sheet F comprised between 0.5 mm and 50 mm, preferably between 1 mm and 25 mm.

[0126] The dispensers 33.1, 33.2, 33.3 can be configured so as to have different distributions of the sealant S. For example, instead of the continuous or discontinuous strokes of the lines SCT, it is possible to apply dotted strokes or other shapes such as triangles, that coincide with the overlapping areas of the side folds once the flaps L1 and L2 have been folded, as schematically shown in FIG. 11A and FIG. 11B. In this case again, the purpose of applying the sealant S is to obtain a stably sealed package C for most of the areas to be closed through the sealant S. In a preferred solution, the distribution of the sealant S is such that the package C is completely stably closed, preventing the products R from being contaminated or at least from coming into contact with external agents. The package C may have facilitated opening systems or handles to facilitate transportation of the package C, without however changing the objects and the embodiment of the invention. Examples of handles are described in EP1535846, while facilitated opening systems are disclosed in EP2225159.

[0127] FIG. 8A shows an example of a feeding station 31 that is a variant of that shown in FIGS. 7A and 7B.

[0128] The reel B is unwound and the paper web material N is conveyed by one or more rollers along a feed path P in the feed direction fN to the cutting unit 37 arranged to cut the paper web material N into paper wrapping sheets of predetermined length. Along the feed path P of the paper web material N, upstream of the cutting unit 37, there is a dispensing device 133 arranged to apply a sealant S, such as glue, onto the paper web material N. As above, the sealant S can be a heat-reactivated adhesive. The path P is longer than that of FIGS. 7A and 7B, and includes, for example, a series of sections exiting the dispensing device 133, namely a section P1 from the bottom upwards, a section P2 almost horizontal, a section P3 from the top downwards, a section P4 returning towards the dispensing device 133, and finally a section P5 entering the cutting unit 37. The dispensing device 133 acts on the paper web material N along the section P1 from the bottom upwards.

[0129] The dispensing device 133 has at least three sealant dispensers, preferably provided along a line orthogonal to the feeding direction of the paper web material N. The dispensers are divided into at least two dispensing units, at least one of which consists of a plurality of dispensers. At least three dispensing units are preferably provided, a first dispensing unit 133.1, a second dispensing unit 133.2 and a third dispensing unit 133.3. The first dispensing unit includes a first plurality of dispensers 133.1, the second dispensing unit includes a second plurality of dispensers 133.2, and the third dispensing unit 133.3 includes a single dispenser 133.3.

[0130] All the dispensers of the dispensing units are provided on a crossbar 139A, orthogonal to the feed direction of the paper web material N, and are arranged in a line. The dispensers of each dispensing unit are adjacent to one another along the crossbar 139A. The dispensing unit can be spaced along the crossbar (so the last dispenser of a dispensing unit is not adjacent to the first dispenser of the next dispensing unit). The position of the dispensers is adjustable along the crossbar 139A, either manually or through an automatic actuation system (schematized by the arrow R1). The dispensers are preferably of the contact type, for pressing the paper web material N so as to be able to apply the sealant. Therefore, a system may be provided for (manually or automatically) moving the crossbar towards/away from the paper web material N (schematized by the arrow R2).

[0131] Each dispenser 133.1, 133.2, and 133.3 is operationally connected with a supply system W for supplying sealant S, comprising a plurality of ducts W1 (only some of them being schematized in FIG. 8A for the sake of simplicity), so that each dispenser has one respective duct for supplying the sealant, for example in melted state, coming from a tank W2 where the sealant is stored in the melted state (e.g., due to the presence of an electric melter that melts pellets of solid-state sealant). A valve W3 (only a few of them being schematized in FIG. 8A for the sake of simplicity) is associated with each dispenser, for example a solenoid valve, which allows to supply/not supply the dispenser, i.e., to apply or not the sealant to the paper web material.

[0132] The sealant supply system comprises a pumping apparatus W4, for example a supply pump operationally connected to the ducts W1. Appropriately, the supply pump can be of the type with variable flow rate depending on the feeding speed of the paper web material or on the production speed of the packaging machine, so as to control the quantity of sealant applied to the web material N and to ensure a sufficient flow rate of sealant in order to apply a quantity of sealant suitable for the specific purposes (e.g., the more the productivity of the packaging machine measured in packages per minute increases, the more the number of sheets per minute to which the sealant shall be applied increases, a fact that requires to increase the flow rate of sealant S to the dispensers). Everything is controlled by a control unit.

[0133] In this example, the sealant distribution is the same of FIG. 10. The first dispensing unit 133.1 and the second dispensing unit 133.2 apply the lines SCT (i.e., the lines orthogonal to the fN direction of feed) while the third dispensing unit 133.3 apply the line SCP (i.e., the line parallel to the feed direction fN). More specifically, the first dispensing unit 133.1 applies the second stroke SM2 of each line SCT, whilst the second control unit 133.2 applies the first stroke SMI of each line SCT. The distance between the first and the second dispensing units essentially corresponds to the distance ZL1 between the stroke SM1 and the stroke SM2. Similarly, the distance between the second dispensing unit 133.2 and the third dispensing unit 133.3 essentially corresponds to the distance between the stroke SM1 of the line line SCT and the line SCP. In practice, each stroke SM1 and SM2 is formed by several areas adjacent to each other along a line (with each area in contact with the adjacent one or very close to it, for example, at a distance of less than 10 mm). For example, a first area Sx of the stroke SM2 is applied by a first dispenser 133.1 that applies the sealant according to a first direction coinciding with the sheet/paper web feeding direction fN, and a second area Sx, adjacent to the first area Sx, is applied by a second dispenser 133.1 that is adjacent to the first dispenser and applies the sealant according to the same first direction; the second dispenser is adjacent to the first dispenser according to a second direction of extension of the crossbar 139A orthogonal to the sheet/web material feeding direction fN). This continues for all dispensers of the first dispensing unit 133.1. The same applies to the stroke SM1 of the line SCT, which is realized by areas of sealant adjacent to each other in series, applied by the dispensers 133.2.

[0134] In practice, each area has a width (e.g., measured along a direction orthogonal to the feeding direction fN, i.e., parallel to the extension of the crossbar 139A) equal to the operating width of the dispenser (i.e., for example corresponding to approximately the width of the mouth/opening of the dispenser), and a height (orthogonal to the width) that is a consequence of the activation time (opening of the respective solenoid valve feeding the melted sealant to the respective dispenser) of the dispenser on the moving web material. A line SCT, or a stroke thereof, can therefore be seen as the set of these areas made by adjacent dispensers. It is clear that if a higher line SCT (direction fN) is required, it is sufficient to increase the opening time of the solenoid valves of the first and the second dispensing units.

[0135] The line SCP, orthogonal to the line SCT, is provided according to a direction parallel to the sheet/paper web feeding direction fN, with a width equal to the operating width of the dispenser. In this case, the height of the line SCP is longer than that of the areas that make up the strokes SM1 and SM2 of the line SCT of the example described above, because it is provided by activating the dispenser (i.e., opening the respective solenoid valve) on the moving web material for a longer time than in the previous example (line SCT). In this case, the line SCP is a continuous line and is not made up of contiguous areas. If a wider line SCP is required, it is sufficient to arrange one (or more) additional dispenser next to the single dispenser 133.3 of the third dispensing unit 133.3.

[0136] Also the width of the strokes SM1 and SM2 can be varied by increasing or decreasing the number of dispensers for each dispensing unit. It is also possible to have a number of dispensers covering the entire width of the sheet/web material, wherein the dispensers corresponding to cross areas where the sealant shall not be applied are either deactivated or not activated, or kept with the respective solenoid valve always closed.

[0137] In FIG. 8B, with reference, for example, to the station 31 like that of FIGS. 7A and 7B, a cooling device K is also provided for cooling the sealant S applied to the paper web material N. The cooling device K is arranged along the path of the web material N downstream of the area where the sealant S is applied and upstream of the cutting unit 37.

[0138] The cooling device K includes, for example, one or more air ejection nozzles K1 that are operatively connected with an air distribution system, schematically indicated with K2, and are oriented toward the web material N, whose total jet or flow (sum of the total cross-sectional width of the jets or flows, in the case of multiple nozzles) transversely surrounds the whole web material N or only one or more parts thereof (e.g., because the sealant S is applied to only a part, or parts, of the web material N).

[0139] For example, the cooling device K is adapted to form, on the paper web material N, a laminar airflow Q. For example, the cooling device K includes a plate that has a surface K3 facing a section of the path of the web material N, which defines, with the web material, a laminar air channel. For example, the surface K3 may be flat and approximately parallel to the section of the path of the web material N that it is facing.

[0140] For example, the sealant cooling device K may be similar to that described in EP1886950. Therefore, the surface K3 may be flat and may be approximately parallel to the section of the path of the web material N that it faces, and may have an air inlet portion K4 toward which the nozzle(s) K1 is directed, which is convergent toward the section of the path of the web material N and which continues in continuity with the surface K3.

[0141] The cooling device K can comprise one or more Coand effect nozzles K1, for example those described in EP1886950.

[0142] FIG. 8C shows an example where the cooling device K, as shown in FIG. 8B, consists of several cooling parts K, for example in order to lengthen the section of the path of the web material N subject to cooling. In this case, each cooling part K is associated with a respective section of the path of the web material N, preferably each part is associated with a respective air ejection nozzle(s) K3.

[0143] Once the paper wrapping sheets F have been prepared with the sealant S applied in one of the previously described ways, the sheets are moved forward along the sheet feeding direction fF toward the wrapping station 19. In a preferred solution, the paper wrapping sheets F are held at the two edges B1 and B2 by feeding members 20, for example belts, and positioned orthogonal to the lifting and lowering direction f16, as previously described. A solution of this kind is described for example in the patent document WO2021009339.

[0144] In FIGS. 12 to 15 a sealing station 40 is shown, configured to seal the paper wrapping sheet F wrapped around the groups G of products R forming the package C to be sealed. Sealing is achieved by heat treatment of the folds of the paper wrapping sheet F that have been previously formed. In practice, once the folds of the side flaps L1 and L2 have been completed, it is necessary to stabilize the front side fold Pla, the back side fold Plp, the bottom side fold Pli, and the top side fold Pls, obtained, for example, according to the packaging cycle described in FIGS. 9A-9G, by heat treating the flat faces F1, F2 of the package C of FIG. 9G.

[0145] The sealing station 40 includes a feeding channel 41 for moving forward the package C to be sealed along a sealing direction fS, formed by a pair of sealing members 42A, 42B arranged opposite each other on the two sides of the feeding channel 41. The sealing members 42A, 42B may respectively include a preferably uniform sealing surface 43A, 43B composed of ferromagnetic material (or containing paramagnetic material). The sealing surface 43A, 43B is that portion of the sealing member that faces the packages C to be sealed and thus touches the package. In the case shown in the figure, the sealing members are respectively realized by tapes 54A and 54B of ferromagnetic material (or containing paramagnetic material). In a variant of the invention, not shown, it is possible to use two or more steel tapes for each sealing member 42A, 42B, arranged vertically contiguous one after the other. The steel tape(s) of each sealing member 42A, 42B have an overall height at least equal to the height of the package C to be sealed.

[0146] Each sealing member 42A, 42B can be driven between return members 44A, 45A, 46A and 44B, 45B, 46B, such as pulleys or rollers, at least one of which for each sealing member is preferably motorized. In this specific case, the return members 44A and 44B are driven by a respective actuation device M1 and M2, such as a gear motor, provided to feed the package C to be sealed along the sealing direction fS. In a different configuration, it is possible to leave the sealing members 42A, 42B idle, i.e., without an actuation device, particularly when the feeding channel 41 includes a motorized conveyor 47 to feed the packages C to be sealed along the sealing direction fS. In a preferred embodiment of the invention, both the sealing members 42A, 42B and the conveyor 47 are motorized. When the conveyor 47 is not motorized, it can be replaced with a simple feed plane, such as an extension of the slide surface 23. The conveyor 47 can be provided at the wrapping height Qa so as to receive the package C to be sealed without vertical movement with respect to the slide surface 23 that can move the folds to be sealed, compromising the final quality of the packages.

[0147] The sealing members 42A, 42B can be provided close to, i.e., in continuity with, the outlet of the wrapping station 19, so as to receive the package C to be sealed while the folding device 28 is still partially in contact with the newly formed folds, making a continuous, or nearly continuous, passage between the folding device 28 and the sealing members 42A, 42B, avoiding deformation of the newly formed front side fold Pla, back side fold Plp, bottom side fold Pli, and top side fold Pls. Preferably, the sealing members 42A, 42B and/or the conveyor 47, when motorized, receive the package C to be sealed by feeding it 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 to prevent the rotation of the teeth 27.2 around the pulley 27.3 from causing deformation of the package C, that shall still be sealed and thus stabilized.

[0148] The sealing surfaces 43A, 43B of the sealing members 42A, 42B can be heated by induction, radiation, or conduction. In the preferred embodiment represented here, the sealing surfaces 43A, 43B are respectively heated by induction through an electromagnetic induction device 48A, 48B that includes one or more induction coils 49A, 49B (or other circuit capable of generating a time-varying electromagnetic flux that is a function of the induction currents passing through it). The induction coils 49A, 49B can be arranged facing the sealing surfaces 43A, 43B or in the opposite side i.e., inside the area delimited by the closed path determined by the sealing members 42A, 42B. For example, the induction coils 49A, 49B can be provided in the straight section between respective return members 45A, 46A and 45B, 46B. In other configurations, the induction coils 49A, 49B can be provided, 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, 49B cannot be placed in front of the sealing surfaces 43A, 43B as they would be inside the feeding channel 41; but they shall be provided on the opposite side, i.e. inside the area delimited by the sealing members 42A, 42B.

[0149] Associated with the electromagnetic induction devices 48A, 48B there are respective generators or inverters, 50A, 50B, controlled to supply the induction coils 49A, 49B with electromagnetic induction currents adapted to generate a time-varying electromagnetic flux, passed by the sealing members 42A, 42B where the eddy currents are generated. The eddy currents heat the sealing members 42A, 42B by Joule effect.

[0150] The inverters 50A, 50B operate at an operating frequency approximately equal to the resonance frequency of the electric circuit formed by the respective induction coil 49A, 49B. The operating frequency of the electromagnetic induction current generated by the inverters 50A, 50B is comprised between 10 Hz and 500 kHz, and more preferably between 100 Hz and 100 KHz.

[0151] In order to adjust the operating temperature on the sealing members 43A, 43B, a closed-loop control system can be used, comprising the inverters 50A, 50B and at least one temperature sensor of any kind, such as thermocouples, pyrometers, thermo-cameras, or other suitable device, associated with the respective sealing member 42A, 42B, and connected to a control unit that, based on an appropriate control algorithm, controls the inverters 50A, 50B so as to regulate the temperature on the sealing surfaces 43A, 43B. The control unit can be the PC or PLC 45, or a different control device, such as another PC or PLC or an industrial computer, a microprocessor, a computer network, or any other suitable device.

[0152] The operating temperature of the sealing surfaces 43A, 43B can be comprised between 100 C. and 400 C., and preferably between 150 C. and 300 C. The operating temperature can be highly variable because it is a function of the operating condition of the packaging machine 1, the production speed, the type of paper wrapping sheet F, and the type and quality of the sealant S.

[0153] In order to increase the production flexibility of the packaging machine 1, the sealing station 40 comprises adjusting means for adjusting the transverse distance of the sealing members 42A, 42B, which allow the machine to be adapted to the format of the packages C to be made. The adjusting means for adjusting the transverse distance of the sealing members 42A, 42B may include a base 51A, 51B, movable along guides 52, 53, transverse, i.e., preferably orthogonal to the sealing direction fS. The bases 51A, 51B are constrained in slidable way to rails 52, 53 by respective shoes 70, 71. While the packaging machine 1 operates, the distance between the bases 51A, 51B is blocked to keep the sealing members 42A, 42B in the desired position. The distance between the bases 51A, 51B is unlocked only when it is necessary to adjust the transverse position of the sealing members 42A, 42B, thus widening or narrowing the feeding channel 41. In order to adjust the distance of the sealing members, an actuator 73 is provided, in this case a manual hand wheel, that rotates a worm 72 engaging nut screws 74, 75, integral with the bases 51A, 51B, respectively. The worm 72 is preferably made up of two parts 72 and 72 with respectively opposite thread direction, so that the rotation of the worm 72 causes the bases 51A, 51B, and thus the respective sealing members 42A, 42B, to move towards and away from each other. The actuator 73 can also be an electric motor so as to adjust automatically the cross-sectional dimension of the feeding channel 41.

[0154] To have an optimal sealing, members 76 can be provided for adjusting the sealing pressure i.e., for applying a predetermined side sealing pressure to the package C as it moves along the feeding channel 41. As better shown in FIG. 15, the sealing pressure adjusting members 76 are attached to each of the sealing members 42A, 42B and may comprise a slide guide 77, integral with the base 51A, 51B. The slide guide 77 can be approximately parallel to the rails 52, 53. A shoe 78, integral with a plate 80 on which the sealing parts 42A, 42B are installed, is associated with the slide guide 77. The bases 51A, 51B are respectively connected to an actuator 82, 83, preferably a pneumatic or electric actuator, or any other type of actuator suitable for pushing the sealing members 42A, 42B toward each other. If the actuator is pneumatic, it is possible to adjust the sealing pressure by varying the air pressure, while, if the actuator is electric or electromechanical, the control unit 45, or another dedicated control device, can move the actuator by moving each base 51A, 51B, and consequently the sealing members 42A, 42B, towards or away from each other.

[0155] A tensioning device 60 can be provided for each sealing member 42A, 42B for tensioning it. In the case where each sealing member 42A, 42B consists of two or more tapes made of ferromagnetic material (or containing paramagnetic material), a tensioning device 60 is provided for each tape. The tensioning devices 60 can be realized by an idle roller 61, pressed against the respective sealing member 42A, 42B by a pneumatic actuator 62. Other types of actuators can also be used, for example an electric linear motor or other equivalent electromechanical devices. If pneumatic actuators are used, the tensioning of the respective sealing member 42A, 42B can be adjusted by adjusting the air pressure of each pneumatic actuator.

[0156] Preferably, in order to keep the distance between the sealing members 42A, 42B and the respective induction coils 49A, 49B constant, the tensioning device 60 can act on the respective sealing members 42A, 42B in a section delimited by two consecutive return members 45A, 46A and 45B, 46B, that does not include the respective induction coil 49A, 49B. For example, as shown in the figures, the tensioning devices 60 act on the section comprised between the return members 44A, 46A and 44B, 46B while the induction coils 49A, 49B are placed in the section between the return members 45A, 46A and 45B, 46B. In this way, the deformation caused by the tensioning devices 60 on the sealing members 42A, 42B does not affect the section of the sealing members 42A, 42B over which the induction coils 49A, 49B face.

[0157] For an optimal sealing, some lateral compression can be applied to the package C to be sealed while it moves along the feeding channel 41. This can be achieved by supporting each base 51A, 51B on sliding shoes along transverse rails, approximately orthogonal to the sealing direction fS, and connecting each base 51A, 51B to a pneumatic or electric actuator or any other suitable actuator adapted to push the sealing members 42A, 42B toward each other. If the actuator is pneumatic, it is possible to adjust the sealing pressure by varying the pneumatic pressure, while, if the actuator is electric or electromechanical, the PLC or PC 54, or another dedicated control device, moves the actuator by moving each base 51A, 51B, and consequently the sealing members 42A, 42B, towards or away from each other.

[0158] The fact of having uniform sealing surfaces 43A, 43B made of ferromagnetic material, for example steel, results in better heat conduction and transfer from the members with the sealing surfaces 43A, 43B to the paper wrapping sheet F. If a compression, albeit very light, is applied to the package C to be sealed as it moves forward in the feeding channel 41, a stretching effect is generated on the folds of the paper wrapping sheet F, increasing the aesthetic quality thereof and facilitating the stabilization of the folds. In this way, it is possible to improve the packages both when they are sealed with sealant S and when the paper wrapping sheet is devoid of sealant, as the stretching effect stabilizes the folds of the flaps L1, L2 regardless of the use of sealant S. Finally, a material that, in addition to being ferromagnetic, has a stiffness and hardness like those of steel, allows for allows for significantly greater durability than the prior art systems mentioned in the introduction.

[0159] In a further embodiment, not shown, the sealing members 42A, 42B are formed by a flexible member, such as a belt or a chain, to which sealing surfaces are constrained. The sealing surfaces can be realized by means of plates made of steel, or other ferromagnetic material (or containing paramagnetic material), adjacent to one another. The flexible member can be driven around return members 44A, 45A, 46A and 44B, 45B, 46B, completely similarly to the steel tapes described above. In this case again, the induction coils face the sealing surfaces formed by the plates, on which eddy currents are induced, as previously described for the steel tapes. In this case, the flexible member carrying the sealing surfaces can also be made of non-ferromagnetic material, such as plastic or rubber, because the heated surface, adapted to seal the package C, is that of the plates and not that of the flexible member. In this solution again, tensioning devices 60 may be provided, quite similar to those described above, to tension each sealing member 42A, 42B.

[0160] Finally, and optionally, contrast means 90 can be provided to balance any bending of the sealing members 42A, 42B when in contact with the packages C to be sealed, especially when the sealing members 42A, 42B are formed by tapes 54A and 54B made of ferromagnetic material or containing paramagnetic material. The contrast means 90 are placed on the opposite side with respect to the sealing surfaces 43A, 43B and may include sliding devices, on which the tapes 54A and 54B slide. The sliding devices are preferably Teflon-coated or entirely made of Teflon, so as to reduce friction with the tape. The sliding devices can be installed with elastic elements such as springs, to allow a movement in direction orthogonal to the sealing direction fS.

[0161] It is understood that what is illustrated purely represents possible non-limiting embodiments of the invention, which may vary in forms and arrangements without departing from the scope of the concept on which the invention is based. Any reference numerals in the appended claims are provided for the sole purpose of facilitating the reading thereof in the light of the description above and the accompanying drawings and do not in any way limit the scope of protection.