Apparatus and method for packaging a load

Abstract

A unwinding device (1) for conveying films (51, 52) that can be associated with a packaging machine (100) comprises a support frame (2) for rotatably supporting a first reel (61) of a first film (51); an adjustment device (3) for rotatably supporting a second reel (62) of a second film (52) and setting it at one of a plurality of operating positions (B) in which the second reel (62) is staggered relative to the first reel (61); guide rollers (21, 22, 23) for guiding and partially overlapping the first film (51) and the second film (52) at a longitudinal partially overlapping band (L); a connecting device (40; 47, 23) for connecting the first film (51) and the second film (52) along a longitudinal connecting band (U) formed within a width (h) of the longitudinal partially overlapping band (L) to obtain a single composite film (50); the connecting device (40; 47, 23) comprises a welding device (40) or a gluing device (47, 23).

Description

Technical Field

[0001] The present invention relates to an apparatus and method for wrapping a load with a cold extensible plastic film. Background Art

[0002] It is known in the packaging industry to package loads consisting of individual products or a plurality of products grouped and arranged on pallets with films made of cold-expandable plastic material.

[0003] In particular, known packaging machines comprise an unwinding device movable along and / or around a packaging axis and supporting a reel of film from which the film is unwound for wrapping around a load, thereby forming a series of strips or bands, typically having a spiral pattern, due to a combination of relative linear and rotational motion between the unwinding device and the load.

[0004] In packaging machines provided with a rotary table supporting the load, during the packaging cycle the load rotates about a vertical packaging axis, while the unwinding device moves parallel to the packaging axis in a reciprocating motion along a fixed upright of the packaging machine.

[0005] In packaging machines with a horizontal rotating ring or arm, the load remains stationary during the packaging process, while the unwinding device rotates and translates relative to the load, both around and along the vertical packaging axis. To this end, the unwinding device is fixed to a ring-like structure or to an arm rotatably supported by the machine frame, thereby rotating around the load.

[0006] In packaging machines with a vertically rotating ring, the load moves horizontally through the ring, while the unwinding device fixed to the ring rotates around a horizontal axis.

[0007] The unwinding device is generally provided with a pair of pre-stretching rollers, which include a slow roller and a fast roller, which stretch and unwind the film upstream and downstream respectively based on the movement direction of the film, and one or more guide rollers to turn the film towards the load during the unwinding process.

[0008] By appropriately adjusting the speed difference between the two pre-stretching rollers, the film leaving the unwinding device can be stretched or extended by a defined amount before being wrapped on a load, depending on the set pre-stretching or extension percentage.

[0009] In particular, plastic films are stretched before being wrapped around the load, as this stretching or elongation allows for optimal utilization of the film and imparts physical and mechanical characteristics that make it more suitable for withstanding the forces acting on the load during subsequent processing and transport. Furthermore, when the stretching force ceases, the film's rebound generates a tightening force on the load, thus ensuring its confinement.

[0010] Stretch is usually expressed as a percentage of the film's elongation (the difference between the final length of the stretched film and the original length) divided by the original length. Typically, the extension applied to the film is between 50% and 300%.

[0011] It is well known that the stretching force or pre-stretching of the rollers can significantly reduce the thickness of the film (typically from about 25-20 μm to about 6-7 μm), thereby proportionally increasing its length so that a larger load circumference can be wrapped with the same initial amount of unwound film.

[0012] The pre-stretching force applied by the pre-stretching rollers also allows the mechanical properties of the film to be modified. A suitably stretched film material may switch from elastic behavior (the film tends to recover its original dimensions after the stress is terminated) to essentially plastic behavior (the film undergoes permanent deformation and does not fully recover its initial dimensions after the stress is terminated). In the latter case, the plastic film significantly reduces its ability to rebound and behaves as a flexible and essentially inextensible element, similar to a rope or belt, and can be used, for example, to package unstable groups of products that must be firmly fixed together.

[0013] The pre-stretching force to which the film is subjected in order to obtain a set elongation or percentage depends on several factors: the initial film thickness, the physical and mechanical characteristics of the film's plastic material (type of plastic material, composition, quantity and distribution and inhomogeneities of any internal impurities), and the environmental conditions in which the load packaging cycle is carried out (temperature, humidity).

[0014] Although it is known that films of the same material and of the same nominal thickness belonging to different reels must be subjected to different pre-stretching forces to obtain similar elongation ratios, it is of paramount importance to avoid excessive thinning, which would render the film unsuitable for the correct packaging of the load and / or more susceptible to tears, ruptures and breaks, although tears, ruptures and breaks often occur during the packaging cycle.

[0015] In fact, even during the unwinding process of the same film reel, variations in the film's physical and mechanical characteristics, especially film thickness, are often observed. For example, depending on the production process of plastic film (usually linear low-density polyethylene), films with varying uniformity and thickness can be produced. Starting from a nominal value of 20-25 μm, thickness can vary by ±10-20%.

[0016] Environmental conditions, particularly temperature, also significantly influence the properties of stretch film. Specifically, at lower temperatures, the film is more difficult to stretch and deform, and at the same pre-stretch ratio, it tears and breaks more easily and more frequently. Furthermore, the film's temperature also depends on the operating conditions; in particular, it increases with film wrapping speed and stretch ratio.

[0017] Therefore, there are many environmental and operational factors that can cause excessive thinning, tearing, rupture, or even complete failure of the film during operation of the packaging machine, especially at high stretch ratios. Such defects result in incorrectly packaged loads or, in the case of complete film failure, packaging machine downtime and, therefore, production halts to allow film reels to be changed; as well as waste of plastic material in the case of excessive thinning or tearing of the film, which necessitates the use of additional plastic film to reinforce the thinned or torn areas; and in the case of film failure, which makes the film unusable and must be completely replaced.

[0018] Tearing, rupture and breakage of the film may also occur in the case of irregular loading of the package having corners, projections, sharp parts etc.

[0019] Regardless of their origin, local tears and ruptures in the film can subsequently propagate through the film and lead to complete failure of the film during packaging (typically at high stretch ratios) and after packaging, during load handling and transportation. Summary of the Invention

[0020] An object of the present invention is to improve the known unwinding device which can be associated with a packaging machine and the known method for packaging a load with a film made of extensible plastic material.

[0021] Another object is to provide an unwinding device and a packaging method that can be associated with a packaging machine, which allow any type of load to be packed securely and compactly, reducing and almost eliminating the risk of complete breakage of the film during the packaging process.

[0022] A further object is to provide an unwinding device and a packaging method which allow high versatility and flexibility of the packaging cycle and which reduce the duration of said packaging cycle.

[0023] Another further object is to provide an unwinding device and a packaging method which allow optimizing, in particular reducing, the amount of plastic material film used to securely and compactly package any type of load.

[0024] In a first aspect of the present invention, there is provided an unwinding device package according to claim 1 , which can be associated with a packaging machine.

[0025] In a second aspect of the present invention, a method for packaging a load according to claim 9 is provided. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The present invention may be better understood and implemented with reference to the accompanying drawings, which show exemplary and non-limiting embodiments of the invention, in which:

[0027] - Figure 1 is a side view of a film unwinding device of the present invention associated with a rotary arm packaging machine;

[0028] - Figure 2 It is an enlarged side view of the unwinding device of the present invention.

[0029] - Figure 3 yes Figure 2 Front view of the unwinding device.

[0030] - Figure 4 It is along Figure 3 Enlarged cross-sectional view along line IV-IV.

[0031] - Figure 5 yes Figure 4 An enlarged detail view of the embodiment of the present invention, showing in particular the pre-stretching rollers and the welding device;

[0032] - Figure 6 yes Figure 2 A partial rear view of the unwinding device, showing in particular the welding device;

[0033] - Figure 7 is similar to Figure 4 sectional view of a portion of a variation of the unwinding device of the present invention;

[0034] - Figure 8 is similar to Figure 4 , which is a sectional view of another variation of the unwinding device of the present invention.

[0035] - Figure 9 is similar to Figure 4 , which is a sectional view of another variation of the unwinding device of the present invention.

[0036] - Figure 10 and Figure 11 It is shown by Figure 1 Schematic diagram of the unwinding device and the packaging method performed by the packaging machine in each operation step. DETAILED DESCRIPTION

[0037] refer to Figures 1 to 6 , shows an unwinding device 1 of the invention associated with a packaging machine 100 for packaging a cold-extensible plastic film around a load 150 , for example formed by one or more products grouped on a tray.

[0038] The packaging machine 100 is for example of the rotary arm type and is provided with movement means 101 for moving the unwinding device 1 parallel to the packaging axis W, which are arranged to convey a first film 51 and at least one roll of a second film 52, both of extensible plastic material.

[0039] The unwinding device 1 comprises a support frame 2 which is connected to the moving device 101 of the packaging machine 100 and is arranged to rotatably support a first reel 61 of a first film 51 about a first rotation axis X1.

[0040] The unwinding device 1 further comprises an adjustment device 3 adapted to rotatably position at least one second reel 62 supporting the second film 52 about a corresponding second rotation axis X2 and to position the second reel in one of a plurality of operating positions B in which the second reel 62 is staggered relative to the first reel 61 with respect to the support plane 6 of the support frame 2. Staggered means that the distance between the base or lower plane side of the second reel 62 and the support plane 6 is different from, in particular greater than, the distance between the base of the first reel 61 and the support plane 6.

[0041] During an adjustment step of the unwinding device 1, carried out with the packaging machine 100 stopped, the adjustment device 3 allows the second reel 62 to be moved relative to the first reel 61 along an adjustment direction R parallel to the first and second axes of rotation X1, X2, between various operating positions B. The first and second axes of rotation X1, X2 of the two reels 61, 62 are substantially perpendicular to the support plane 6 to which the first shaft 25 supporting the first reel 61 is rotatably fixed.

[0042] The second reel 62 can also be arranged in another operating position (not shown) in which it is substantially aligned with the first reel 61 relative to the support plane 6 , ie is placed at the same distance from the support plane.

[0043] Preferably, the first reel 61 and the second reel 62 have the same height or length (intended as a transverse dimension, parallel to the reel's axis of rotation), ie the bandwidth of the respective films 51 , 52 is the same.

[0044] The unwinding device 1 further comprises guide rollers 21, 22, 23 which are rotatably fixed to the support frame 2 and are arranged to guide and partially overlap the first film 51 and the second film 52 at a longitudinal partially overlapping strip L, in particular when the two films 51, 52 are unwound from their respective reels 61, 62, as will be better explained in the following description. The longitudinal partially overlapping strip L, or for simplicity, the overlapping strip L, is parallel to the unwinding direction of the films 51, 52 from the rollers 21, 22, 23 and to the longitudinal edges of the films 51, 52.

[0045] The unwinding device 1 further comprises a connecting device 40 configured to connect the overlapping strips L along the longitudinal connecting strips U ( Figure 1) The first film 51 and the second film 52 are tightly connected, particularly irreversibly connected, to produce a single composite film 50 formed by the first film 51 and the second film 52. More precisely, and as better explained in the following description, the connecting device 40 connects the two rolls of film 51 and 52 together by welding or gluing during the process of unwinding them from the reels 61 and 62, and forms a longitudinal connecting band U, or for simplicity, a connecting band U, whose width is less than or equal to the width h of the overlapping band L. The width of the overlapping band is in turn less than the width of the first film 51 and / or the second film 52.

[0046] The width of the connecting strip U and the overlapping strip L is understood to be the linear dimension of the strip parallel to the rotation axes X1 , X2 of the film reels 61 , 62 .

[0047] The unwinding device 1 also includes a pair of pre-stretching rollers 11, 12, which are rotatably supported on the support frame 2 and are configured to unwind and stretch the first film 51 and the second film 51 when the first film 51 and the second film 52 have been partially overlapped along the overlapping belt L by the guide rollers 21, 22, 23 during the packaging cycle of the load 150.

[0048] The guide rollers include one or more first guide rollers 21, for example two, for guiding the first film 51 leaving the first reel 61, in particular towards the pre-stretching rollers 11, 12, and one or more second guide rollers 22, for example two, for guiding the second film 52 leaving the second reel 62, in particular towards the pre-stretching rollers 11, 12. The guide rollers also include a third guide roller 23, which is arranged to overlap and guide the first film 51 and the second film 52 unwound from the respective reels 61, 62 and leaving the first and second guide rollers 21, 22, in particular towards the pre-stretching rollers 11, 12.

[0049] The unwinding device 1 further comprises one or more turning rollers 24, for example three, which are rotatably fixed to the support frame 2, in particular to the support plane 6, and are arranged to guide the first film 51 and the second film 52 which are partially overlapped and tightly connected by the connecting device 40 to form a composite film 50 away from the unwinding device 1 and towards the load 150 to be packaged.

[0050] exist Figures 1 to 6 In the embodiment shown, the connecting device 40 is arranged downstream of a pair of pre-stretching rollers 11 and 12 relative to the unwinding direction of the films 51 and 52, thereby tightly connecting the first film 51 and the second film 52 that have been partially overlapped along the overlapping belt L and stretched or extended together by the pre-stretching rollers 11 and 12.

[0051] The connection means comprise a welding device 40 of known type suitable for welding by melting the plastic material, typically low-density polyethylene, of the films 51, 52. In particular, the welding device comprises one or more of a heating resistor, a high-frequency generator, an ultrasonic generator, suitable for locally melting (along the connection zone U) the plastic material of the films 51, 52.

[0052] Specific reference Figure 5 and Figure 6 The welding device 40 includes, for example, a welding roller 41, which can be heated at a defined operating temperature and is configured to press the two rolls of film 51, 52 against and onto a contact roller, for example, consisting of one of the rotating rollers 24, at the overlapping belt L, so as to weld and connect the two rolls of film tightly together along the connecting belt U.

[0053] The welding roller 41 is mounted on a support element 42, freely rotatable about respective rotation axes parallel to the rotation axes of the return roller 24 and the film reels 61, 62, and the support element 42 is in turn slidably connected to a support rod 43 fixed to the support plane 6 of the support frame 2. The support element 42 is slidable along the support rod 43 to allow the height of the welding roller 41 relative to the support plane 6 and the films 51, 52 to be adjusted.

[0054] A blocking device 44 is provided for locking the support element 42 in a defined operating position of the support rod 43 to prevent undesired displacement of the support element during operation. The blocking device comprises, for example, a corresponding locking screw 44 that is rotatably fixed to the support element 42 and acts on the support rod 43. One end of the locking screw 44 is provided with a knob, by which the operator can rotate the knob to lock or unlock the support element 42.

[0055] The welding roller 41 is moved toward or away from the rotating roller 24 between an operating position S (where the welding roller 41 presses the two film rolls 51 and 52 against the abutting / rotating roller 24 and welds them) and a rest position (where the welding roller 41 is spaced apart from the abutting / rotating roller 24 and the films 51 and 52) by a linear actuator 45. The linear actuator 45 is fixed to the support member 42 and connected to a rotating pin 46 of the welding roller 41. The linear actuator 45 includes, for example, an electromagnet, a linear motor, or a pneumatic cylinder.

[0056] Alternatively, the welding roller may comprise a sonotrode of known type, which transmits ultrasonic vibrations generated by a sonotrode associated with a piezoelectric transducer and an amplifying booster of the welding device to the films 51 , 52 to be welded.

[0057] The adjustment device 3 comprises a bracket 4 adapted to rotatably support the second reel 62, and a support column 5, which is fixed to the support frame 2 and is arranged to slidably support the bracket 4 along the adjustment direction R in order to change the position of the second reel 62 relative to the first reel 61. More precisely, by moving the bracket 4 along the support column 5, the second reel 62 can be positioned in one of a plurality of operating positions B, in which the second reel 62 is staggered relative to the first reel 61 with reference to the support plane 6, so that in operation the second film 52 is unwound and overlaps the first film 51 as it leaves the unwinding device 1.

[0058] It should be noted that each of the plurality of operating positions B involves a respective width or height of the overlapping band L between the two rolls of film 51 , 52 , which may be selected according to the load and / or the type of packaging to be performed.

[0059] In another operating position in which the second reel 62 is substantially aligned with the first reel 61 , the second film 52 is unwound and completely overlaps the first film 51 , so that the width of the overlapping band L is equal to the height or width of the films 51 , 52 .

[0060] The bracket 4 can be manually moved along the support column 5, in particular for adjusting its distance from the support plane 6 of the support frame 2, and a locking device 10 is provided for locking the bracket 4 to the support column 5 in a defined operating position B, thereby preventing undesired displacement along the adjustment direction R, in particular during operation of the packaging machine, i.e., during the unwinding of the composite film 50. The locking device 10 comprises, for example, a corresponding locking screw rotatably fixed to the bracket 4 and acting on the support column 5. In particular, one end of the locking screw is provided with a knob, which an operator can rotate to lock or unlock the bracket 4.

[0061] The carriage 4 comprises a platform 7 which is almost parallel to the support plane 6 and to which the second shaft 26 supporting the second reel 62 is rotatably fixed. The carriage 4 also comprises a sliding portion 8 which is parallel to the support column 5 and is slidably connected to the support column 5 by a linear sliding guide 9 of known type which is not described in detail.

[0062] In one version of the unwinding device 1 of the present invention, not shown in the figures, the adjustment device 3 is configured to support a plurality of second reels 62 of the second film 52 and, for this purpose, comprises a plurality of carriages 4, each of which is configured to rotatably support a respective second reel 62, and one or more support columns 5 fixed to the support frame 2 and configured to slidably support the plurality of carriages 4 in an adjustment direction R. In this version of the unwinding device 1, pre-stretching rollers 11, 12 are configured to extend or stretch the plurality of film rolls 51, 52 two by two at a plurality of respective longitudinal partially overlapping strips L after the plurality of film rolls 51, 52 have partially overlapped, in particular before entering the pre-stretching rollers 11, 12. The widths of the plurality of overlapping strips L can be the same or different, depending on the load and / or the type of packaging to be performed.

[0063] In this version of the unwinding device 1, the welding device 40 includes a plurality of welding rollers 41, which are connected to a support rod 43 via corresponding support elements 42 so as to weld multiple rolls of film 51, 52 at different overlapping bands L and form corresponding connecting bands U, thereby obtaining a single unitary composite film 50 formed by a first film 51 and a plurality of tightly connected second films 52.

[0064] A first operating device 30 is provided for rotating the pre-stretching rollers 11 and 12 about their respective longitudinal rotation axes Y1 and Y2, in particular at different rotational speeds. In the embodiment shown in the figure, the first operating device 30 includes a motor 31 for rotating the first pre-stretching roller 11 (or fast roller) and the second pre-stretching roller 12 (or slow roller) via a transmission device 32. The transmission device 32 includes, for example, a series of selectable and interchangeable gears to change the transmission ratio between the pre-stretching rollers 11 and 12, that is, to allow the motor 31 to rotate the second pre-stretching roller 12 at a lower speed than the first pre-stretching roller 11, in particular at a corresponding speed lower than a defined value, thereby stretching or extending the films 51 and 52 by a set amount or percentage.

[0065] The first pre-stretching roller 11 is located downstream of the second pre-stretching roller 12 with respect to the unwinding direction of the films 51 , 51 .

[0066] Alternatively, the first operating device 30 may comprise a pair of motors, each motor acting on a respective pre-stretching roller 11 , 12 .

[0067] In an embodiment shown by way of non-limiting example, the unwinding device 1 further includes a first folding device 35, which is positioned upstream of the pre-stretching rollers 11, 12 and the third guide roller 23 relative to the unwinding direction of the films 51, 52, and is arranged to be close to the longitudinal edge of the first film 51 and / or the longitudinal edge of the second film 52 and to fold one or both of the films 51, 52 to obtain one or two longitudinal peripheral bands L1 of overlapping films.

[0068] The first folding device comprises, for example, a pair of forming elements 35, which are arranged to abut and fold the respective films 51, 52. The forming elements 35 are slidably fixed to a pair of guide rails 36, which are fixed to the support frame 2 so as to be movable parallel to the adjustment direction R in order to adjust the width of the longitudinal peripheral band L1 of the overlapping films.

[0069] exist Figure 1 In the illustrated embodiment, the packaging machine 100 is of a rotary arm type, and the moving device 101 includes a packaging arm device 102. The arm device 102 is rotatable about a packaging axis W, is substantially vertical, and is provided with a support portion 102a that is approximately parallel to the packaging axis W and is suitable for slidably supporting the unwinding device 1. The moving device 101 also includes a second operating device 103, which is configured to linearly move the unwinding device 1 along the support portion 102a of the arm device 102, that is, parallel to the packaging axis W.

[0070] The rotation axes X1 , X2 of the two reels 61 , 62 are almost parallel to the packaging axis W.

[0071] The arm device 102 is rotatably supported by a main frame 109 of the packaging machine 100 , and is rotated about a packaging axis W by the third operating device 104 .

[0072] The packaging machine 1 comprises a conveyor device 105 for supporting a load 150 to be packaged and for moving the load into and / or out of a working area.

[0073] The packaging machine 100 further comprises a gripping and cutting device 106 arranged in the working area adjacent to the conveyor device 105 for gripping the composite film 50 at the end of the packaging cycle, cutting the film and retaining the end flaps of the film resulting from the cutting to allow packaging of a subsequent load 150 .

[0074] The operation of the unwinding device 1 of the present invention, associated with the packaging machine 100, comprises an initial adjustment step, in which, if necessary, the position of the second reel 62 relative to the first reel 61 is adjusted according to the size and / or composition of the load 150 and / or the type of packaging required. In particular, by acting on the adjustment device 3, the second reel 62 can be manually set in one of a plurality of operating positions B, in which the reels 61, 62 are staggered relative to the support plane 6, so that the two rolls of film 51 can leave the unwinding device 1 partially overlapping along a longitudinal partially overlapping strip L, the width or height of which is a function of the position of the second reel 62.

[0075] As soon as the load 150 enters the working area via the conveyor 105, the packaging cycle is started and the two rolls of film 51, 52 are unwound from their respective reels 61, 62, overlapped along the overlapping belt L at the third guide roller 23, stretched by the pre-stretching rollers 11, 12 at a defined extension percentage, and tightly connected by the connecting device 40 along the connecting belt U to obtain a single unitary composite film 50, in particular formed by a first film 51 and a second film 52 firmly connected to each other.

[0076] Due to the combined linear and rotational motion of the unwinding device 1 , the composite film 50 exiting the unwinding device 1 wraps around the load 150 to form a series of bands or strips having a spiral pattern.

[0077] refer to Figure 10 and 11 When the load 150 is formed by combining multiple regular products on a pallet in a basically stable manner, the two reels 61 and 62 can be staggered (with the second reel in the operating position B) so that the two rolls of film 51 and 52 leave the unwinding device 1 with partial overlap, so as to increase the bandwidth of the composite film 50, reduce the number of rotations required for the unwinding device 1 to completely wrap the load 150, and reduce the duration of the entire packaging cycle.

[0078] Figure 7 A variant of the unwinding device 1 of the present invention is shown, which is different from the above-mentioned and Figures 1 to 6 In the embodiment shown in the figure, the connecting device 40 is arranged upstream of a pair of pre-stretching rollers 11, 12 relative to the unwinding direction of the films 51, 52, so as to tightly connect the first film 51 and the second film 52 before they are partially overlapped along the overlapping belt L and stretched or extended.

[0079] In more detail, the connecting device comprises the aforementioned welding device 40, which is fixed to the support plane 6 of the support frame 2 via a support rod 43, so that the welding roller 41, which is set in the operating position S by the linear actuator 45, abuts and presses the two film rolls 51 and 52 against the third guide roller 23, acting as an abutment roller. In this configuration, the two operations of partially overlapping and connecting the two film rolls 51 and 52 occur simultaneously.

[0080] In another variant of the unwinding device, not shown, the welding device 40 comprises a separate abutment roller placed downstream of the third guide roller 23 , which cooperates with the welding roller 41 to weld the two rolls of film.

[0081] refer to Figure 8 , shows another variation of the unwinding device 1 of the present invention, which is different from the above and Figures 1 to 6The embodiment shown in is different in that the connecting device includes a gluing device 47, 23, which includes a dispensing unit 47, which is suitable for spraying or distributing longitudinal strips of adhesive or glue on the inner surface of one of the two rolls of film (for example, the inner surface of the second film 52 facing the inner surface of the first film 51), and a bonding roller that coincides with the third guide roller, so that the two rolls of film 51, 52 are in contact with each other and adhered.

[0082] The dispensing unit 47 of the gluing device is positioned on the support 2 between the two rolls of film 51, 52 unwound from respective reels 61, 62, before being partially overlapped along the overlapping strip L. In particular, Figure 8 In the embodiment, the adhesive or glue dispensing unit 47 is arranged upstream of the third guide roller 23, which also serves as a bonding roller on which they are wound, partially overlapping the two rolls of film 51 while firmly adhering or gluing them to each other along the adhesive strip to form a longitudinal connecting belt U.

[0083] The dispensing unit 47 includes a dispenser or sprayer 48, which is suitable for dispensing longitudinal strips of glue or adhesive on the inner surface of the second film 52, so that the second film 52 can adhere to the inner surface of the first film 51 and tightly connect the two rolls of film along the connecting belt U.

[0084] The dispensing unit 47 comprises a support element 49 on which the dispenser 48 is mounted. The support element 49 is slidably connected to a support rod 43 fixed to the support surface 6 of the support frame 2. The support element 49 can slide along the support rod 43 to allow the dispenser 48 to be adjusted in height relative to the support surface 6 and the films 51, 52. A stop device 44 is provided for locking the support element 49 in a defined operating position on the support rod 43 to prevent it from being undesirably displaced during operation. The stop device 44 comprises, for example, a locking screw with a knob, which is rotatably attached to the support element 49 and acts on the support rod 43.

[0085] Figure 8 The variant of the unwinding device 1 also differs from the previously described embodiment in that it does not include a first folding device 35 placed upstream of the pre-stretching rollers 11, 12 and the third guide roller 23, but includes a second folding device 15, which is placed downstream of the pre-stretching rollers 11, 12 and is configured to abut and fold and / or roll up one or two longitudinal edges of the composite film 50 and form corresponding folded and / or pleated and / or rolled longitudinal reinforcement parts.

[0086] The second folding device 15 is of known type and is therefore not described in detail, comprising for example a pair of folding rollers 16 arranged against said opposite longitudinal edges 50 a , 50 b of the composite film 50 .

[0087] refer to Figure 9, shows another variation of the unwinding device 1 of the present invention, which differs from the above-mentioned embodiment in that it includes a first pair of pre-stretching rollers 11, 12, which are rotatably supported on a support frame 2 and are configured to unwind and stretch a first film 51, and a second pair of pre-stretching rollers 111, 112, which are rotatably supported on a support frame 2 and are configured to unwind and stretch a second film 52. Guide rollers 21, 22, 23 are configured to guide and partially overlap the stretched or extended films 51, 52 leaving the corresponding pairs of pre-stretching rollers 11, 12, 111, 112. More specifically, the two rolls of stretched films 51, 52 partially overlap at the third turning roller 23.

[0088] The welding device 40 is positioned, for example, on the support plane 6 of the support frame 2 downstream of the pre-stretching rollers 11, 12, 111, 112 and the third guide roller 23 and is connected to the support plane 6 of the support frame 2. Figure 2-6 In particular, the welding device 40 comprises a welding roller 41 which, in the operating position S, presses the two rolls of film 51 , 52 against and onto a bearing roller which coincides with the first of the return rollers 24 .

[0089] Alternatively, the welding device 40 can be positioned on the supporting plane 6 so that the welding roller 41 in the operating position S abuts and presses the two film rolls 51 , 52 against the third guide roller 23 acting as an abutment roller.

[0090] It is also possible that the welding device 40 is replaced by the above-mentioned gluing device 47, 23 and comprises a dispensing unit 47 positioned on the supporting plane 2 between the two rolls of film unwound from the corresponding reels 61, 62 before partial overlap, and a gluing roller consisting of a third guide roller 23 around which the two rolls of film are wound.

[0091] Figure 8 The variant of the unwinding device 1 of the invention shown also comprises, instead of the first folding device 35 , a second folding device 15 , which is placed downstream of the welding device 40 and the third guide roller 23 .

[0092] The method for packaging a load 150 with an extensible plastic film according to the present invention comprises the following steps:

[0093] - unwinding the first film 51 from the first reel 61 and unwinding at least one roll of the second film 52 from the corresponding second reel 62;

[0094] - partially overlapping the first film 51 and the second film 52 to form a longitudinal partially overlapping strip L;

[0095] - Tightly connecting the first film 51 and the second film 52 along the longitudinal connecting band U formed in the longitudinal partially overlapping band L to obtain a single composite film 50 formed by the first film 51 and the second film 52;

[0096] - Wrapping the load 150 with a plurality of strips or strips of composite film 50;

[0097] wherein the tight connection, in particular in an irreversible manner, comprises welding, in particular by local melting of the plastic material of the films 51 , 52 , or comprises adhering the films 51 , 52 by means of glue or an adhesive.

[0098] The method also includes overlapping and tightly connecting the film parts.

[0099] Optionally, after partially overlapping the films and before tightly connecting them, a pair of pre-stretching rollers 11, 12 of an unwinding device are provided for stretching the partially overlapping first film 51 and second film 52 along the longitudinal partially overlapping band L (or overlapping band L for simplicity).

[0100] Optionally, the method further comprises, before partially overlapping the films, stretching the first film 51 by a first pair of pre-stretching rollers 11 , 12 of the unwinding device 1 , and stretching the second film 52 by a second pair of pre-stretching rollers 111 , 112 of the unwinding device 1 .

[0101] The width h of the overlapping band L is less than the width of the first film 51 and / or the second film 52; the width of the longitudinal connecting band U (or, for simplicity, the connecting band) is less than or equal to the width h of the overlapping band L. The widths of the connecting band U and the overlapping band L are understood to be the linear dimensions of the bands parallel to the rotation axes X1, X2 of the film reels 61, 62.

[0102] According to the method of the invention, wrapping the composite film 50 around the load 150 comprises moving the reels 61 , 62 and the load 150 parallel to each other and about a wrapping axis W.

[0103] Optionally, at least one longitudinal edge of the films 51, 52 or composite film 50 is folded, pleated or rolled up to form at least one longitudinally folded, pleated or rolled reinforcement portion.

[0104] Due to the unwinding device and packaging method of the present invention, the load 150 can be packaged with a single composite film 50, which is formed by a first film 51 and at least one roll of a second film 52, and the first film and the second film are tightly and firmly connected to each other at the longitudinal connecting band U formed within the width h of the longitudinal partially overlapping band L formed by the two rolls of film 51 and 52.

[0105] The width h of the overlapping strip L can be selected according to the load and / or the type of packaging to be performed.

[0106] For this purpose, the unwinding device 1 is provided with at least two reels 61, 62 of film 51, 52, and allows one of them, namely the second reel 62, to be arranged in an operating position B, in which position it is staggered relative to the other reel (the first reel 61) so that the two rolls of film 51, 52 leave the unwinding device 1 partially overlapping at the overlapping zone L.

[0107] The unwinding device 1 further comprises connecting devices 40 , 47 , 23 , which are configured to tightly connect the first film 51 and the second film 52 , in particular irreversibly, by welding or gluing during unwinding of the first film 51 and the second film 52 from the reels 61 , 62 , thereby forming a connecting belt U.

[0108] It should be noted that the composite film 50 formed by two partially overlapping rolls of film 51 , 52 has a greater tensile strength than the individual films 50 , 51 due to the provision of the overlapping tapes L, in particular the connecting tapes U, which in particular serve as reinforcing tapes.

[0109] Thus, using the same amount of film, the mechanical resistance of the package obtained on the load 150 can be significantly increased compared to conventional packaging using a single roll of film or two rolls of film applied separately from corresponding unwinding devices (for example in packaging machines with two rotating arms, in which the overlapping of the film strips occurs directly on the load during the packaging process).

[0110] The unwinding device 1 and the method of the invention thus allow the packaging obtained to be stronger and tighter around the load 150, which ensures greater resistance to water and moisture penetration and ensures correct fastening in all areas or parts of the load, even in those that do not provide strong support for the film.

[0111] In order to increase the mechanical strength of the composite film 50 , the film may also be provided with longitudinally folded, pleated, rolled reinforcements made by folding means 35 , 15 resting against the opposite longitudinal edges of the films 51 , 52 .

[0112] The applicant has also observed and verified through extensive testing that the connecting band U also acts as a barrier band to prevent the propagation of tears, ruptures, and perforations that may occur during the packaging cycle due to various factors and causes. More precisely, a tear or rupture that occurs in one of the films 51, 52, for example, as it exits the unwinding device 1, may propagate toward the outer and free longitudinal edges of the film, but will stop at the connecting band U, where the film is firmly connected to the other film in a secure and stable manner. Consequently, complete breakage of one or both film rolls, which would result in the cessation of the packaging cycle or the completion of the packaging cycle using a single roll of film, is prevented.

[0113] It should be noted that a partial tear of one of the rolls of film (partial tear because it is stopped by the connecting tape U) does not in any way impair the normal continuity of the packaging cycle or the effectiveness of the packaging load 150, since the tape of composite film 50 with such partial tear retains its mechanical characteristics (tensile strength) essentially unchanged.

[0114] In this case, greater resistance to tearing and rupture of the composite film 50 is obtained by providing folded, pleated, rolled longitudinal reinforcements on the film, which are made by folding means 35, 15 resting against the opposite longitudinal edges of the films 51, 52.

[0115] It is also noteworthy that, thanks to the unwinding device 1 of the invention, the bandwidth of the composite film 50 , ie the bandwidth of two connected rolls of film simultaneously wrapping the load 150 , can be increased, thereby reducing the duration of the wrapping cycle and increasing the productivity of the packaging machine 100 .

[0116] More precisely, by increasing the width of the two overlapping rolls of film 51, 52, i.e. the composite film 50, fewer revolutions of the unwinding device 1 around the load 150 are required to completely wrap the load. As a result, the duration of the packaging cycle can be reduced and the productivity of the packaging machine 100 can be increased.

[0117] It is also possible to package a load 150 of limited size using a series of overlapping strips of composite film 50 without using a spiral pattern, i.e. without moving the unwinding device 1 linearly along the packaging axis W, by placing the second reel 62 in a corresponding operating position B in which the width or band of the composite film 50 thus produced is equal to the height of the load 150.

[0118] This type of packaging, in addition to requiring shorter running times, is more solid and robust.

[0119] Finally, it should be noted that by forming a single composite film 50, the gripping and cutting devices 106 of the packaging machine 100 do not have to grip and hold the two rolls of film 51, 52 in the final step of the packaging cycle, but it is sufficient for them to secure only a portion of the composite film 50, since the two rolls of film 51, 52 are tightly connected to each other at least at the connecting band U. Therefore, the same gripping and cutting devices 106 used for operating on a single roll of film can be used regardless of the degree of overlap.

[0120] The unwinding device 1 of the invention mounted on the packaging machine 100 of the invention thus allows a high degree of versatility and flexibility in the packaging process.

[0121] At the same time, the unwinding device 1 , besides being particularly compact and practical, also functions very reliably and precisely.

Claims

1. An unwinding device (1) capable of being associated with a packaging machine (100) for conveying a film (51, 52) made of an extensible plastic material, said unwinding device comprising: - a support frame (2) configured to rotatably support a first reel (61) of a first film (51) about a first rotation axis (X1); - an adjustment device (3) fixed to the support frame (2) and configured to rotatably support at least one second reel (62) of a second film (52) about a second rotation axis (X2) and to set the at least one second reel (62) in one of a plurality of operating positions (B) in which the second reel (62) is staggered relative to the first reel (61) with reference to a support plane (6) of the support frame (2); - guide rollers (21, 22, 23) rotatably supported by the support frame (2) and arranged to guide and partially overlap the first film (51) and at least one second film (52) at a longitudinal partially overlapping zone (L); - a connecting device (40; 47, 23) for tightly connecting the first film (51) and the at least one second film (52) along a longitudinal connecting band (U) formed within the width (h) of the longitudinal partially overlapping bands (L) to obtain a single composite film (50) formed by the first film (51) and the at least one second film (52), wherein the width of the longitudinal connecting band (U) is smaller than the width (h) of the longitudinal partially overlapping bands (L); The connecting device (40; 47, 23) comprises a welding device (40) for connecting the first film (51) and the at least one second film (52) by local melting of the plastic material, or a gluing device (47, 23) for connecting the first film (51) and the at least one second film (52) by gluing with the aid of an adhesive.

2. The unwinding device (1) according to claim 1 comprises a pair of pre-stretching rollers (11, 12), wherein the pre-stretching rollers (11, 12) are rotatably supported by the support frame (2) and are configured to unwind and stretch the first film (51) and the at least one second film (52) partially overlapped by the guide rollers (21, 22, 23) along the longitudinal partially overlapping belt (L).

3. The unwinding device (1) according to claim 1 comprises a first pair of pre-stretching rollers (11, 12) and a second pair of pre-stretching rollers (111, 112), wherein the first pair of pre-stretching rollers (11, 12) are rotatably supported by the support frame (2) and are configured to unwind and stretch the first film (51), the second pair of pre-stretching rollers (111, 112) are rotatably supported by the support frame (2) and are configured to unwind and stretch the at least one second film (52), and the guide rollers (21, 22, 23) are configured to guide and partially overlap the stretched film (51, 52) leaving the first pair of pre-stretching rollers (11, 12) and the second pair of pre-stretching rollers (111, 112).

4. The unwinding device (1) according to claim 3, wherein: The connecting device (40; 47, 23) is positioned downstream of the first pair of pre-stretching rollers (11, 12) and the second pair of pre-stretching rollers (111, 112) relative to the unwinding direction of the first film (51) and the at least one second film (52), so as to tightly connect the first film (51) and the at least one second film (52) stretched by the first pair of pre-stretching rollers (11, 12) and the second pair of pre-stretching rollers (111, 112) respectively.

5. The unwinding device according to claim 1, wherein: The welding device (40) comprises one or more of a heating resistor, a high frequency generator, and an ultrasonic generator suitable for locally melting the plastic material of the first film (51) and the at least one second film (52).

6. The unwinding device (1) according to claim 1, wherein: The welding device (40) comprises a welding roller (41).

7. The unwinding device (1) according to claim 6, wherein: The welding roller (41) is a welding roller that can be heated at a limited operating temperature or is suitable for generating vibrations with ultrasonic frequencies, and is configured to abut and press the two films (51, 52) against the abutting rollers (23, 24) at the longitudinal partially overlapping band (L) so as to weld the two films (51, 52) together along the longitudinal connecting band (U).

8. The unwinding device (1) according to claim 1, wherein: The gluing device comprises a conveying unit (47) suitable for spreading an adhesive strip on the inner surface of the first film (51) and one of the at least one second film (52), and an adhesive roller (23) around which the two rolls of film (51, 52) are wound, partially overlapping each other and firmly adhering to each other along the adhesive strip to form the longitudinal connecting band (U).

9. The unwinding device (1) according to claim 1, wherein: The guide rollers include at least one first guide roller (21) for guiding the first film (51) leaving the first reel (61), at least one second guide roller (22) for guiding the second film (52) leaving the second reel (62), and at least one third guide roller (23) for guiding and partially overlapping the first film (51) and the at least one second film (52).

10. The unwinding device (1) according to claim 1, wherein: The adhesive is glue.

11. A method for packaging a load (150) with a film made of an extensible and stretchable plastic material, comprising: - unwinding a first film (51) from a first reel (61) and unwinding at least one second film (52) from a corresponding second reel (62); - partially overlapping the first film (51) and the at least one second film (52) to form a longitudinal partially overlapping strip (L); - tightly connecting the first film (51) and the at least one second film (52) along a longitudinal connecting band (U) formed inside the longitudinal partially overlapping band (L) to obtain a single composite film (50) formed by the first film (51) and the at least one second film (52), wherein the width of the longitudinal connecting band (U) is smaller than the width (h) of the longitudinal partially overlapping band (L); - packaging the load (150) using multiple strips of the single composite film (50); The tight connection includes welding, local melting of the plastic material of the first film (51) and the at least one second film (52), or adhering the first film (51) and the at least one second film (52) by an adhesive.

12. The method according to claim 11, comprising simultaneously partially overlapping and tightly connecting the first film (51) and the at least one second film (52).

13. The method according to claim 11, comprising stretching the first film (51) and the at least one second film (52) partially overlapped along the longitudinal partially overlapping band (L) by a pair of pre-stretching rollers (11, 12) after the partial overlapping and before the tight connection.

14. The method according to claim 11, comprising stretching the first film (51) of the unwinding device (1) by a first pair of pre-stretching rollers (11, 12) and stretching the at least one second film (52) of the unwinding device (1) by a second pair of pre-stretching rollers (111, 112) before the partial overlapping.

15. Method according to any one of claims 11 to 14, wherein the width (h) of the longitudinal partially overlapping strips (L) is smaller than the width of the first film (51) and / or the second film (52).

16. The method according to any one of claims 11 to 14, wherein The adhesive is glue.

17. Packaging machine (100) comprising a moving device (101) for moving an unwinding device (1) according to any one of claims 1 to 10 around and / or parallel to a packaging axis (W).

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