WO2023238028A1

WO2023238028A1 - Unwinding apparatus, machine and method for wrapping a load with film

Info

Publication number: WO2023238028A1
Application number: PCT/IB2023/055821
Authority: WO
Inventors: Mauro Cere'
Original assignee: Sotemapack S.P.A.
Priority date: 2022-06-07
Filing date: 2023-06-06
Publication date: 2023-12-14
Also published as: IT202200012041A1

Abstract

An unwinding apparatus (1) associable with a wrapping machine (100) comprises a reel holder shaft (2) to support a reel (51) of film (50); a pair of pre-stretching rollers (3, 4) to unwind and stretch said film (50) and driven by first motor means (11); a dancer roller (6) movable by said film (50) during wrapping according to a first movement direction (A) or an opposite second movement direction (B) respectively to release or to recover the film so as to keep substantially constant a wrapping force of film (50) wrapped around the load (200); a drive unit (30) to control the first motor means (11) and second motor means (12) operating on the reel holder shaft (2); first and second motor means (11, 12) are controlled in such a way as to rotate at least the pre-stretching rollers (3, 4) so as to unwind the film (50) from reel (51), when the dancer roller (6) is stationary or is moved along the first movement direction (A), or in such a way as to rotate the pre-stretching rollers (3, 4) and/or the reel holder shaft (2) so as to rewind the film (50) around said reel (51), when the dancer roller (6) is moved along the second movement direction (B).

Description

Unwinding apparatus, machine and method for wrapping a load with film

The invention concerns apparatuses, machines and methods for wrapping a load with a plastic film or web, in particular of the cold-extensible type. In particular, the invention relates to an unwinding apparatus, a machine and a method for wrapping a load with a film, which allow the wrapping of the film around the load to be controlled and adjusted.

The known wrapping machines comprise an unwinding apparatus that houses and supports a film reel and moving means that support and move the unwinding apparatus parallel to and/or around a wrapping axis. The film is unwound from the reel and is wrapped around the load in such a way as to form a series of overlapping strips or bands generally having a helical pattern thanks to the combination of the relative linear and rotational movements between the unwinding apparatus and the load, the latter formed by a single product or by a plurality of grouped products, for example overlapped on a pallet or bench.

In rotating table wrapping machines, the moving means comprise an upright or column along which a carriage supporting the unwinding apparatus is moved vertically. The load is positioned on the rotating table and rotates with the latter about a vertical wrapping axis.

In wrapping machines with a horizontal rotating ring or with a rotating arm, the load remains stationary during the wrapping while the unwinding apparatus is moved with respect to the load both in rotation about a vertical wrapping axis and in translation along the latter. In wrapping machines with horizontal rotating ring, moving means comprise a ring structure that supports the unwinding apparatus and that, in addition to rotating around the wrapping axis, moves vertically and parallel thereto. In wrapping machines with rotating arm, the moving means comprise a vertical arm which rotates about the wrapping axis, and along which the unwinding apparatus can be moved.

In wrapping machines with vertical rotating ring the load is moved during wrapping linearly and horizontally through a ring structure of the moving means that is rotatable about a horizontal wrapping axis. The unwinding apparatus is fixed to the ring structure and also rotated about the horizontal wrapping axis.

The unwinding unit in addition to receiving and supporting the film reel is typically provided with a pair of pre- stretching rollers, which unwind the film from the reel and stretch or elongate the film, and one or more return rollers that divert the film towards the product or group of products.

By appropriately adjusting the difference between rotation speeds of the two pre- stretching rollers, it is possible to stretch or elongate by a defined amount, according to a fixed prestretch or elongation percentage, the film exiting from the unwinding apparatus before it is wrapped around the load, in order to make the best use of the available film and to change the mechanical characteristics of the film material itself, according to the product to be wrapped. By adjusting the rotation speed of the pre-stretching rollers, it is also possible to vary the unwinding speed of the film from the reel, that is, the speed with which the film exits the unwinding apparatus.

The unwinding apparatus generally comprises an electrical motor capable of rotating one of the two pre- stretching rollers, which acts as the driving (master) roller (typically the fast roller), and, via a mechanical transmission assembly, the other pre-stretching roller, which acts as the driven (slave) roller, typically the slow roller. In this way, a fixed transmission ratio is imposed between the fast roller and the slow roller, depending on the value of prestretching or elongation to be obtained on the film.

Unwinding apparatuses are also known that are provided with a pair of electrical motors arranged to separately and independently drive the two pre-stretching rollers, so as to allow the elongation of the film to be varied, i.e. the percentage of pre- stretching or elongation during the wrapping of the load.

In the operation of wrapping machines, it is known that it is difficult to keep an almost constant wrapping force or tension of the film around the load during wrapping in order to guarantee a wrapping force value that is uniform and appropriate for the type of load to be wound. The need to control and limit the wrapping force to avoid film breakage is also known.

The wrapping tension of the film varies, in fact, for each wrapping turn because, instant by instant, the quantity of film required for the wrapping varies in particular as a function of the relative angular position between wrapping apparatus and load and as a function of size, shape and/or cross section and/or size of the load and of its position with respect to the wrapping axis. The variations of the wrapping tension can also be considerably high, especially in the case of loads with a cross section that is narrow and long, or wide and short. To overcome this drawback, wrapping machines and methods are known that provide for the use of dancer rollers, that is, idle rollers mounted on rocking arms generally associated with elastic means, which compensate for variations in the wrapping tension by releasing or recovering film, suitably rocking within a defined angular amplitude.

Machines and methods are also known which provide for keeping the wrapping force substantially constant by suitably varying the unwinding speed of the film, that is, its exit speed from the unwinding apparatus, by means of a feedback adjustment of rotation speed of pre-stretching rollers. For this purpose, sensors are provided (e.g. angular position sensors associated with dancer rollers, encoders mounted on the return rollers, torque sensors mounted on the motors) capable of directly or indirectly measuring the tension of the film and sending a relative signal to a control unit of the wrapping machine that is able to operate on the motor or motors of the pre- stretching rollers in order to increase or decrease their rotation speed.

These solutions, although generally valid and functional, are however inadequate in the case of loads having particular shapes and sizes, for which variations in wrapping tension are particularly high during wrapping.

An object of the invention is to improve known unwinding apparatuses, machines and methods for wrapping a load with a plastic film.

Another object is to provide an unwinding apparatus, a wrapping machine and a wrapping method that allow a wrapping force of the film wrapped around the load to be controlled and kept substantially constant independently of the size and/or shape of the load and its position with respect to the wrapping machine.

A further object is to realize an unwinding apparatus, a wrapping machine and a wrapping method that ensure a high quality of wrapping of the film around the load.

Another further object is to provide a wrapping machine that is provided with an efficient, reliable and economical electric power supply system for the motors driving pre- stretching rollers of the unwinding apparatus.

A further object is to realize a wrapping machine having a compact structure and reliable and efficient operation and able to ensure an optimal wrapping of the load with the plastic film.

In a first aspect of the invention, an unwinding apparatus is provided which is associable with a wrapping machine according to claim 1.

In a second aspect of the invention, a wrapping machine according to claim 10 is provided. In a third aspect of the invention, a method for wrapping a load according to claim 18 is provided.

The invention can be better understood and implemented with reference to the attached drawings which illustrate exemplary and non-limiting embodiments thereof, in which:

Figure 1 is a front perspective view of the unwinding apparatus according to the invention;

Figure 2 is a rear perspective view of the unwinding apparatus of Figure 1 ;

Figure 3 is a perspective view from below of the unwinding apparatus of Figure 1;

Figure 4 is a perspective view of the wrapping machine of the invention; Figure 5 is an enlarged partial perspective view of the wrapping machine of Figure 4, illustrating in particular a wrapping unit, moving means on which it is mounted and, partially, frame means;

Figure 6 is an enlarged detail of Figure 4, illustrating in particular the wrapping unit and the moving means;

Figure 7 is an enlarged detail of Figure 6 illustrating in particular interface means;

Figure 8 is an electrical and functional diagram of the wrapping machine of the invention. With reference to Figures 1 to 3, the unwinding apparatus 1 according to the invention is shown that is as sociable to a wrapping machine for supplying a film 50 with which to wrap a load 200 that is formed by a single product or by a plurality of grouped products, for example arranged superimposed on a pallet.

The unwinding apparatus 1 comprises a reel holder shaft 2 rotatable about a first rotation axis XI and configured to receive and support a reel 51 of film 50 and a pair of pre-stretching rollers 3, 4 for unwinding the film 50 from the reel 51 and stretching or elongating the film. The unwinding apparatus 1 also comprises a plurality of guiding rollers 5 for guiding the film 50 unwrapped from the reel 51 onto the pre-stretching rollers 3, 4 and out in the direction of the load 200.

The unwinding apparatus 1 further comprises a supporting frame 10 which rotatably supports the reel holder shaft 2, the pre- stretching rollers 3, 4, and the guide rollers 5.

The pre- stretching rollers 3, 4 are rotated about respective second and third rotation axes X2, X3 by first motor means 11, in particular fixed to the supporting frame 10.

The unwinding apparatus 1 further comprises a dancer roller 6 mounted free to rotate about a fourth rotation axis X4 and movable by the film 50 during wrapping of the load 200, in particular along a curved or linear trajectory, according to a first movement direction A or according to an opposite second movement direction B, respectively to release or to recover the film so as to keep an substantially constant a tension or wrapping force of the film 50 while it is wrapped around the load.

In the illustrated embodiment, the dancer roller 6 is rotatably mounted on a supporting arm 7, which is in turn mounted rotatably around a rocking axis Y, in particular rotatably fixed to the supporting frame 10. In this way, the dancer roller 6 is movable by the film 50 during the wrapping of the load 200 along a curved trajectory according to the first movement direction A or the opposite second movement direction B.

Alternatively, in a variant of the unwinding apparatus 1 not shown, the dancer roller 8 can be mounted on a supporting carriage that is slidably connected to the supporting frame 10 so as to be movable by the film 50 during the wrapping of the load 200 along a linear trajectory according to the first movement direction A or the opposite second movement direction B.

As known, during a wrapping cycle the dancer roller 6 is rocked around the rocking axis Y (or is moved linearly) by the unwinding film so as to compensate for changes in film demand due to the shape and size of the load or product.

The supporting arm 7 comprises, in particular, a central pin 17 rotatably fixed to the supporting frame 10, in particular at both its opposite ends, and a pair of arms 18 which are fixed to the ends of the central pin 17 and which support the dancer roller 6 rotatably about the fourth rotation axis X4.

Elastic means 19 of known type are provided to keep the supporting arm 7 and the dancer roller 4 in a defined rest position and brake means 25, of known type and not described in detail, are associated to the supporting arm 7 to adjust a rocking of the dancer roller 6 about the rocking axis Y, in particular to adjust and keep substantially constant the wrapping tension or force of the film when the film is wrapped around the load. In particular, the braking means 25 are mounted and act on the central pin 17 of the supporting arm 7.

First sensor means 21 are associated with the supporting arm 7 and configured to detect at least the movement directions A, B of the dancer roller 6 around the rocking axis Y.

The unwinding apparatus 1 also comprises a drive unit 30 connected to the first motor means 11 for controlling a rotation speed of the pre- stretching rollers 3, 4. Second motor means 12 are associated with the reel holder shaft 2, connected to and controlled by the drive unit 30 and in particular fixed to the supporting frame 10.

As better explained in the following description, during the wrapping of the load 200, the first and second motor means 11, 12 are suitable to be controlled so as to rotate the prestretching rollers 3, 4 so as to unwind the film 50 from the reel 51 , when the dancer roller 6 is substantially stationary with respect to the rocking axis Y or is moved by the film 50 along the first movement direction A (i.e. when the wrapping requires film to be supplied) or so as to rotate the pre- stretching rollers 3, 4 in the reverse direction and/or rotate the reel holder shaft 2 accordingly so as to rewind the film 50 around the reel 51, when the dancer roller 6 is moved by the film 50 (in cooperation with the elastic means 19) along the second movement direction B (i.e. when the wrapping does not require film to be supplied).

In particular, second motor means 12 are controlled so as to apply to the reel holder shaft 2 a rewinding torque, or mechanical rewinding moment, opposite to and lower than an unwinding torque applied to the pre- stretching rollers 3, 4 by the first motor means 11, when the dancer roller 6 is substantially stationary or is moved by said film 50 along the first movement direction A. In other words, in operation, when the wrapping requires film to be supplied, the second motor means 12 tend to rewind the film on the reel 51 while the prestretching rollers 3, 4 unwind the film from the reel, generating a tension or traction in the film. A substantially constant value of the wrapping tension or force on the film can thus be obtained by adjusting and appropriately controlling the rewinding torque and the unwinding torque.

Also during operation, when the wrapping does not require film to be supplied, the same rewinding torque exerted by the second motor means 12 on the reel holder shaft 2 determines the rewinding of the film 50 on the reel 51 since the pre- stretching rollers 3, 4 are rotated by the first motor means 11 in the reverse direction or left idle, free to rotate.

Alternatively, the second motor means 12 can be controlled so as to brake, with a defined torque or mechanical braking moment, the rotation of the reel holder shaft 2 during the unwinding of the film 50 from the reel 51 , when the dancer roller 6 is substantially stationary or is moved by the film 50 along the first movement direction A. In this way, the film 50 is correctly kept taut in order to keep substantially constant a wrapping tension or force of the film. The value of the braking torque acting on the reel holder shaft 2 can be selected according to the value of the wrapping force of the film to be obtained.

Still alternatively, the second motor means 12 may be controlled so as to leave the reel holder shaft 2 free to rotate, in order to allow the film 50 to be unwound from the reel 51 (by means of the pre-stretching rollers) when the dancer roller 6 is substantially stationary or is moved by the film 50 along the first movement direction A.

The first motor means 11 comprise a first motor 13, in particular of the rotary electric type, and a second motor 14, in particular of the rotary electric type, arranged to rotate respectively a first pre-stretching roller 3 and a second pre- stretching roller 4 separately and independently so as to unwind and pre-stretch the film 50 with a desired elongation or prestretching value, which can also be varied during the wrapping of the load.

The second motor means 12 comprise a third motor, in particular an electrical rotary motor, arranged to drive (rotate or brake) the reel holder shaft 2. The third motor 12 is mounted so as to act directly on the reel holder shaft 2.

Transmission means 20 are provided for connecting the first and the second motor 13, 14 to the respective pre-stretching rollers 3, 4 and comprise, for example, respective driving pulleys 26 mounted on output shafts of the motors 13, 14 and driven pulleys 27 mounted on the pre-stretching rollers, said pulleys 26, 27 being connected to each other by belts 28, in particular toothed belts.

Second sensor means 23, 24 are associated with the pre-stretching rollers 3, 4 to measure at least one rotation of the pre-stretching rollers about the respective rotation axes X2, X3. In particular, second sensor means comprise a first angular position sensor 23 and a second angular position sensor 24, so-called encoders, arranged to measure an angular position and possibly an angular speed about a rotation axis.

The unwinding apparatus 1 comprises first wireless transmission means 31 adapted to connect the drive means 30, the first sensor means 21 and the second sensor means 23, 24 to a control unit 150 of the wrapping machine 100. For this purpose, the control unit 150 is provided with second wireless transmission means 32 connected to the first wireless transmission means 31.

The unwinding apparatus 1 is provided with a bending device 40 that includes a first and a second bending element 41, 42 and relative first and second driving means 43, 44 for moving the bending elements 41, 42 along a narrowing trajectory R transverse to an unwinding direction V of the film 50 so as to abut and narrow the film 50 and reduce a strip width thereof. More precisely, the first bending element 41, moved by first driving means 43 is configured to abut a first longitudinal edge 50a, e.g. an upper edge, of the film and push it towards the opposite second longitudinal edge 50b, e.g. a lower edge, by rolling or pleating the film so as to shrink the narrowed film band 50 or form a kind of rope.

Similarly, the second bending element 42, moved by second drive means 44 is configured to abut the second longitudinal edge 50b and push it towards the opposite first longitudinal edge 50b.

The first and second drive means 43, 44 of known type, not described in detail, comprise, for example, movement systems of the screw-nut type driven by respective fourth and fifth motors 45, 46, in particular rotary electrical motors. The movement systems act on slides 47, 48 movable along a guide 49 and supporting the bending elements 41, 42 to move them linearly along the narrowing trajectory R. During use, the slides 47, 48 are moved along the guide 49 in such a way as to move the bending elements 41, 42.

The operation of the unwinding apparatus 1 of the invention, associated with a wrapping machine, during the execution of a wrapping cycle of a load 200 provides that the film 50 is supplied by unwinding it from the reel 51 by means of the pre- stretching rollers 3, 4 rotated by the first and second motors 13, 14 of first motor means 11.

During the unwinding of film 50, the pre- stretching rollers 3, 4 are rotated at different speeds (in particular the first pre-stretching roller 3, or fast roller, positioned downstream of the second pre-stretching roller 4, or slow roller, with reference to an unwinding direction of the film, is rotated at a higher speed) so as to stretch or elongate the film 50, at a desired value or percentage of elongation or pre-stretch.

In this step, the third motor of second motor means 12 applies a defined rewinding torque to the reel holder shaft 2, opposite to and lower than an unwinding torque applied to the prestretching rollers 3, 4 by the first motor means 11, so as to keep the wrapping tension or force of the film 50 substantially constant.

Alternatively, the reel holder shaft 2 can be braked in rotation with a defined braking torque by the third motor of second motor means 12 so as to keep the wrapping tension or force of the film 50 substantially constant.

Still alternatively, the reel holder shaft 2 can be idle i.e. free to rotate about the respective first rotation axis XI so as to allow the free unwinding of the film 50 from the reel 51.

During unwinding, the first sensor means 21 associated with the supporting arm 7, which supports the dancer roller 6, detects a movement direction of the supporting arm about the rocking axis Y.

If the dancer roller 6 is substantially stationary with respect to the rocking axis Y or is moved by the unwinding film 50 along the first movement direction A, that is, if the unwinding apparatus 1 is required to supply film, the pre- stretching rollers 3, 4 continue to unwind from the reel 51 and pre-stretch the film 50.

Optionally, it may be provided that the rotation speed of the pre- stretching rollers 3, 4 be increased (keeping their transmission ratio, that is, the ratio of their angular speeds, unchanged).

If during the wrapping, due to the shape and/or size of the load 200 and/or its position with respect to a wrapping axis, the dancer roller 6 is moved by the film (in cooperation with the elastic means 19) in the second movement direction B, that is, if no film is required at that time by the unwinding apparatus 1, the pre- stretching rollers 3, 4 are rotated by the first and second motors 13, 14 of the first motor means 11 in the reverse or opposite direction so as to rewind the film 50 already supplied.

The same rewinding torque exerted by the second motor means 12 on the reel holder shaft 2 now determines the rewinding of the film 50 on the reel 51 as the pre- stretching rollers 3, 4 are rotated by the first motor means 11 in the reverse direction.

Alternatively, if the reel holder shaft 2 is braked in rotation with a defined braking torque or is idle, i.e. free to rotate about the respective first rotation axis XI, the third motor of second motor means 12 is activated so as to rotate the reel holder shaft 2 and therefore the reel 51 accordingly about the first rotation axis XI in order to rewind the film 50.

Alternatively, it is also possible to leave the pre-stretching rollers 3, 4 idle, free to rotate, and to use only the third motor of second motor means 12 to rotate the reel holder shaft 2 and rewind the film 50.

It is therefore possible, during the wrapping cycle, to keep the wrapping tension or force of film 50 substantially constant even at those moments when, due to the shape and/or size of the load and/or its position with respect to the wrapping axis, the film 50 is substantially not applied on the load 200 and therefore must not be supplied by the unwinding apparatus 1. In particular, the unwinding apparatus 1 of the invention allows avoiding depositing on the load 200 bands or portions of film 50 without the necessary wrapping tension, i.e. "loose" portions that can compromise the stability and strength of the final wrapping.

When, continuing in the wrapping of the load 200, the dancer roller 6 is moved again along the first movement direction A, the first motor means 11 are actuated so as to reverse the rotation of the pre-stretching rollers 3, 4 in order to start unwinding the film from the reel 51. At the same time, second motor means 12 are activated so as to apply on the reel holder shaft 2 a defined rewinding torque, opposite to and lower than an unwinding torque applied on the pre-stretching rollers 3, 4 by the first motor means 11, so as to keep the tension or wrapping force of the film 50 substantially constant.

Alternatively, the second motor means 12 can be controlled so as to brake the rotation of the reel holder shaft 2 with a defined braking torque.

Still alternatively, the second motor means 12 can be deactivated so as to allow the reel holder shaft 2 to rotate freely about the first rotation axis XI for unwinding the film from the reel 41.

It is furthermore provided, when the film 50 is rewound on the reel 51 , to measure a length of the portion of the rewound film, in particular based on measurement of rotation angles of the pre- stretching rollers 3, 4, which are rotated in reverse direction, carried out by first and second angular position sensors 23, 24 associated respectively with the first and second prestretching rollers 3, 4.

When the film 50 is rewound onto the reel 51 the first motor means 11 are driven so as to rotate the pre- stretching rollers 13, 14 at the same speed, so as not to stretch or elongate the film, which has already been previously stretched.

Similarly, when the portion of film rewound on the reel 51 is unwound by the pre-stretching rollers 3, 4 to be supplied by the unwinding apparatus 1, first motor means 11 are driven so as to rotate the pre- stretching rollers 13, 14 at the same speed, so as not to re-stretch said portion of film, which has already been previously stretched.

In this way the portion of film that has been rewound is not stretched or elongated twice, preventing the film from being excessively stretched, for example in an irreversible plastic way, or from even broken.

Thanks to the unwinding apparatus of the invention it is therefore possible to control and keep a substantially constant wrapping tension or force of the film wrapped around the load independently of the size and/or shape of the load and of its position with respect to the wrapping machine, in particular with respect to the wrapping axis. In this way, it is possible to achieve a high quality of wrapping of the film around the load.

In particular, numerous tests carried out by the applicant have shown that the unwinding apparatus 1 of the invention associated with a wrapping machine allows optimal wrapping, ensuring an substantially constant wrapping tension for each wrapping turn even in the case of products or loads having particular shapes, sizes, cross sections, for example a product having a cross section that is narrow and elongated, or wide and short.

Figures 4 to 8 show the wrapping machine 100 according to the invention adapted to wrap a load 200 with a film 50, for example of plastic material, and comprising at least one unwinding apparatus 1 of the invention, as described above and illustrated in Figures 1 to 3, arranged to supply the film 50, moving means 101 for moving the unwinding apparatus 1 about and/or parallel to a wrapping axis W and frame means 102 for supporting the moving means 101.

In the embodiment illustrated by way of not-limiting example in Figures 4 to 8, the wrapping machine 100 is of the vertical rotating ring type and the frame means 102 comprise a structure adapted to support a supporting ring 103, or rotating ring, of the moving means 101 which is rotatable about a nearly horizontal wrapping axis W. The unwinding apparatus 1 is fixed to the supporting ring 103.

The wrapping machine 100 also comprises conveyor means 110 adapted to support and move a load 200, formed by a single product or by several products arranged side by side and/or grouped, along an advancement direction F parallel to the wrapping axis W, in particular through the rotating ring 103.

In particular, in the wrapping machine 100 illustrated in the figures, during the wrapping cycle the load 200 is moved linearly and horizontally through the rotating ring 103 of the moving means 101, which is rotatable about the horizontal wrapping axis W, while the unwinding apparatus 1, fixed to the rotating ring 103, rotates therewith about the horizontal wrapping axis W while supplying the film 50. The wrapping machine 100 comprises a control unit 150 that is connected to the drive unit 30 and to the sensor means 21, 23, 24 of the unwinding apparatus 1 and is arranged to control, in cooperation with the drive unit 30, the first and second motor means 11, 12, which respectively rotate the pair of pre-stretching rollers 3, 4 and rotate and/or brake the reel holder shaft 2, which supports the film reel 51.

The control unit 150 is in particular configured to control, in cooperation with the drive unit 30, the first and second motor means 11, 12 so as to rotate the pre- stretching rollers 3, 4 and to apply a defined rewinding torque (opposite to and lower than an unwinding torque exerted by the pre-stretching rollers) on the reel holder shaft 2 or to brake with a defined braking torque or to leave the reel holder shaft 2 free to rotate so as to unwind the film 50 from the aforementioned reel 51, when the dancer roller 6 of the unwinding apparatus 1 is substantially stationary with respect to the rocking axis Y or is moved by the unwinding film 50 along the first movement direction A (to release a larger amount of film).

Differently, the control unit 150 is configured to control, in cooperation with the drive unit 30, the first and second motor means 11, 12 so as to rotate the pre- stretching rollers 3, 4 in the reverse direction and/or rotate the reel holder shaft 2 accordingly so as to rewind the film around the reel 51 , when the dancer roller 6 is moved according to the second movement direction B (to recover film).

The control unit 150 is further configured to calculate a length of the portion of film rewound around the reel 51, in particular based on rotation angles of the pre- stretching rollers 3, 4 measured by the second sensor means 23, 24, associated with sensor means.

The control unit 150 is also configured to control, in cooperation with the drive unit 30, the first motor means 11 so as to rotate the pre- stretching rollers 3, 4 at the same speed, in particular without stretching the film, while rewinding the film 50 on the reel 51 and in while unwinding from the reel 51 the portion of wrapped film of defined length.

In this way, the portion of film 50 that is rewound is prevented from being stretched or elongated twice, thereby preventing it from being excessively elongated, for example in an irreversibly plastic manner, or even from breaking.

With particular reference to Figures 5, 6 and 8, the wrapping machine 100 is provided with a power supply system 120 adapted to supply the first motor means 11 and the second motor means 12 of the unwinding apparatus 1 with electrical energy.

The power supply system 120 comprises, in particular, energy accumulator means 125 including one or more supercapacitors, e.g. a plurality of supercapacitors connected in series, configured to provide during a wrapping cycle of the load 200 an electric current having a drive voltage greater than a minimum drive voltage of the electrical rotary motors 12, 13, 14 of the first and second motor means 11, 12.

As is known, supercapacitors are particular capacitors capable of storing a very high amount of electrical charge compared to traditional capacitors by the particular structure that provides for two electrodes having a very high surface area separated by a dielectric layer having a very small thickness (having molecular dimensions). A supercapacitor can be charged in a very short time, guaranteeing a very high specific power.

The power supply system 120 includes the drive unit 30 of the unwinding apparatus 1, which is interposed between the energy accumulator means 125 and the first and second motor means 11, 12 and which is configured in particular to control and adjust a current supplied by the energy accumulator means 125 to the first and second motors 13, 14 of said first motor means 11 and to the third motor 12 of the second motor means so as to obtain a desired rotational speed of said motors.

The power supply system 120 further includes an electrical power box 126 that manages the electric current supplied by the energy accumulator means 125 and sends it to the drive unit 30.

In the illustrated embodiment, the energy accumulator means 125 and the electrical power box 126 are fixed to the rotating ring 103 on the diametrically opposite side with respect to the unwinding apparatus 1 so as to balance the masses rotated with the aforementioned rotating ring 103.

The power supply system 120 comprises a recharging unit 121 fixed to the frame means 102, for example to an upper portion of the latter, and connected on one side to an electrical power supply network 122 and on the other to the energy accumulator means 125 for recharging the latter with a recharging current in a defined recharging time. In particular, the recharging unit 121 is a charging device capable of supplying a current to fully recharge the supercapacitors in a very short time, for example between 5 and 10s.

Interface means 130 are provided to connect the recharging unit 121 to the energy accumulator means 125, in particular during a stop phase of the wrapping machine 100, at the end of a wrapping cycle, in which said unwinding apparatus 1 is positioned by the moving means 101 in a predefined rest position.

With particular reference to Figure 8, the interface means 130 comprise first connector means 131, fixed to the frame means 102 and connected to the recharging unit 121, and second connector means 132, fixed to the rotating ring 103 and connected to the energy accumulator means 125. The first connector means 131 are movable between a coupling position, in which they are engaged with the second connector means 132 so as to connect the recharging unit 121 to the energy accumulator means 125, and a disengagement position, in which they are disengaged by the second connector means 132 to allow the rotating ring 103 to rotate around the load 200 and perform the wrapping thereof.

The operation of the wrapping machine 1 of the invention provides that during a cycle of wrapping of the load 200 during which the rotating ring 103 is rotated around the wrapping axis W and the load 200 is moved along the feed direction F by the conveyor means 110, the energy accumulator means 125 are discharged, i.e. they supply the motor means 11, 12 of the unwinding apparatus 1 by means of the drive unit 30.

More precisely, as already described in the operation of the unwinding apparatus 1 of the invention, during the execution of a wrapping cycle of a load 200, the film 50 unwound from the reel 51 by means of the pre- stretching rollers 3, 4 is rotated by the first and the second motors 13, 14 and wrapped around the load by the rotation of the unwinding apparatus 1, together with the rotating ring 103, about the wrapping axis W in combination with the linear forward movement of the load 200 on the conveyor means 110.

During the unwinding of the film 50, the pre-stretching rollers 3, 4 are rotated at different speeds to stretch or elongate the film 50 by a desired value or percentage of elongation or pre-stretching, while a rewinding torque is applied to the reel holder shaft 2, opposite to and lower than an unwinding torque applied to the pre-stretching rollers 3, 4 or said reel holder shaft 2 is braked in rotation by the second motor means 12 with a defined braking torque or it is idle, that is free to rotate around the respective first rotation axis XI.

During unwinding, the first sensor means 21 associated with the supporting arm 7, which supports the dancer roller 6, detects a movement direction of the latter around the rocking axis Y.

If the dancer roller 6 is substantially stationary or is moved by the unwinding film 50 along the first movement direction A, that is, if it is necessary to supply film, the pre-stretching rollers 3, 4 continue to unwind from the reel 51 and pre-stretch the film 50.

If, on the other hand, due to the shape and/or size of the load 200 and/or its position with respect to the wrapping axis W, the dancer roller 6 is moved by the film (in cooperation with the elastic means 19) in the second movement direction B, that is, if no film is currently required to the unwinding apparatus 1, the pre-stretching rollers 3, 4 are rotated by the first and the second motor 13, 14 of the first motor means 11 in the opposite direction so as to rewind the film 50 already supplied and at the same time the reel holder shaft 2, and therefore the reel 51, is rotated by the third motor of the second motor means 12 about the first rotation axis XI to rewind the film.

In this way, the wrapping machine 100 allows the tension or wrapping force of the film 50 to be kept substantially constant even at those moments during the wrapping cycle in which, due to the shape and/or size of the load itself and/or its position with respect to the wrapping axis W, the film 50 is substantially not applied on the load 200 and therefore must not be supplied by the wrapping apparatus 1. In particular, it avoids depositing on the load 200 bands or portions of film 50 without the necessary wrapping tension, i.e. "loose" portions that can compromise the stability and robustness of the final wrapping.

When, continuing in the wrapping of the load 200, the dancer roller 6 is again moved by the film along the first movement direction A, the first motor means 11 are operated so as to reverse the rotation of the pre- stretching rollers 3, 4 in order to start rewinding the film from the reel 51 and the second motor means 12 are arranged to apply on the reel holder shaft 2 a defined rewinding torque, opposite to and lower than an unwinding torque applied on the pre-stretching rollers 3, 4 or to brake the rotation of the reel holder shaft 2 or are deactivated to allow the reel holder shaft 2 to rotate freely.

When the film 50 is rewound on the reel 51, a length of the portion of the rewound film portion is measured, in particular based on the measurement of the rotation angles of the prestretching rollers 3, 4, which are rotated in reverse direction, carried out by first and second angular position sensors 23, 24 associated respectively with first and second pre- stretching rollers 3, 4. In particular, the length of the wrapped film portion is calculated by the control unit 150.

Similarly, when the portion of film rewound on the reel 51 is unwound by the pre-stretching rollers 3, 4 to be supplied by the unwinding apparatus 1, the first motor means 11 are driven so as to rotate the pre- stretching rollers 13, 14 at the same speed, so as not to stretch said portion of film.

In this way the portion of film that is rewound is not stretched or elongated twice, preventing it from being excessively stretched, for example in an irreversible plastic way, or from even breaking.

During the wrapping cycle the energy accumulator means 125 supply an electric current that varies, in particular decreases, in a controlled way and that in any case allows the correct operation of the first and second motor 13, 14 of the pre- stretching rollers 3, 4 and of the third motor 12 of the reel holder shaft 2 for the entire duration of the wrapping of the load. During the stop phase of the wrapping machine 100 necessary for the release of the wrapped load and/or the entry of a new load to be wrapped, the supercapacitors of the energy accumulator means 15 can be fully recharged.

For this purpose, the rotating ring 103 is rotated around the wrapping axis W in the rest position in which the first connector means 131 are moved into the coupling position to engage the second connector means 132 and thus connect the recharging unit 121 to the energy accumulator means 125. The supercapacitors can be recharged in a very short recharging time, for example between 5 and 10s, significantly less than the normal stop times of the wrapping machine necessary to let out a wrapped load and/or insert a new load to be wrapped. In this way, the productivity of the wrapping machine 100 of the invention is not diminished in any way and is identical to that of a traditional type of wrapping machine fed, for example, by the network with sliding contacts.

It should be noted that the unwinding apparatus 1 of the invention can also be validly associated with wrapping machines with a rotating table or with a horizontal rotating ring or with a rotating arm.

In rotating table wrapping machines the moving means comprise a mounting or column along which a carriage supporting the unwinding apparatus is vertically moved, while the load is positioned on the rotating table and rotates with the latter around a vertical wrapping axis.

In horizontal rotating ring wrapping machines, the moving means comprise a ring structure that supports the unwinding apparatus and that, in addition to rotating around the wrapping axis, moves vertically and parallel to the latter. In rotating arm wrapping machines, the moving means comprise a vertical arm which rotates around the wrapping axis, and along which the unwinding apparatus can be moved.

The invention also relates to a method for wrapping a load 200 with film 50 using the unwinding apparatus 1 described above and illustrated in the figures.

Specifically, the method of the invention comprises, during a wrapping cycle of a load 200: unwinding the film 50 from the reel 51 supported by the reel holder shaft 2 and wrapping the load 200, in particular with a plurality of bands of the film 50; during said unwinding and wrapping, detecting a movement direction A, B of the dancer roller 6 of the unwinding apparatus 1 engaged by the film 50 in wrapping the load 200, the dancer roller 6 being movable, in particular along a linear or curved trajectory, according to a first movement direction A or according to an opposite second movement direction B respectively to release or recover film so as to keep an substantially constant wrapping force of the film 50; and continuing to unwind the film 50 from the reel 51 when the dancer roller 6 is substantially stationary with respect to the rocking axis Y or is moved along a first movement direction A; or stopping said unwinding and then rewinding the film 50 on the reel 51 when the dancer roller 6 is moved along the second movement direction B .

In particular, said unwinding of the film comprises rotating the pair of pre- stretching rollers 3, 4, in particular by means of the first motor means 11, while said rewinding comprises rotating the pair of pre- stretching rollers 3, 4 in the reverse direction and/or rotating the reel holder shaft 2 accordingly, by means of the first and second motor means 11, 12 respectively. Said unwinding of the film 50 comprises applying on the reel holder shaft 2 a rewinding torque, opposite to and lower than an unwinding torque applied to the pre -stretching rollers 3, 4 by the first motor means 11, in particular so as to keep a tension or wrapping force on the film substantially constant.

Alternatively, said unwinding of the film 50 comprises braking, with a defined torque or mechanical braking moment, the rotation of the reel holder shaft 2, in particular so as to keep a tension or wrapping force of the film substantially constant.

Still alternatively, it is envisaged that said unwinding of the film 50 comprises leaving the reel holder shaft 2 free to rotate.

The method further provides, during the unwinding of the film, stretching it with the pair of pre-stretching rollers 3, 4, in particular so as to obtain a defined percentage of elongation. The method also provides, during said rewinding of the film 50, measuring a length of a portion of film rewound on the reel 51 , in particular based on rotation angles of the prestretching rollers 3, 4 measured by the second sensor means 23, 24 associated therewith.

The method involves not stretching the film during rewinding around the reel 51 and not stretching the portion of wrapped film having said length when it is unwound, in particular by rotating the pre-stretching rollers 3, 4 with the same speed.

Claims

CLAIMS Unwinding apparatus (1) as sociable with a wrapping machine (100) to supply a film (50) with which to wrap a load (200), comprising:

- a reel holder shaft (2) rotatable about a first rotation axis (XI) and suitable to support a reel (51) of film (50);

- at least one pair of pre-stretching rollers (3, 4) to unwind from said reel (51) and stretch said film (50), said pre-stretching rollers (3, 4) being rotated about respective second and third rotation axes (X2, X3) by first motor means (11);

- a dancer roller (6) mounted free to rotate about a fourth rotation axis (X4) on a supporting arm (7) movable by said film (50) during wrapping said load (200), in particular along a linear or curved trajectory according to a first movement direction (A) or according to an opposite second movement direction (B) respectively to release or to recover the film so as to keep substantially constant a wrapping force of said film (50) wrapped around the load (200);

- a drive unit (30) connected to, and able to control, said first motor means (11);

- second motor means (12) associated with said reel holder shaft (2) and connected to, and controlled by, said drive unit (30); characterized in that said first and second motor means (11, 12) are suitable to be controlled by said drive unit (30) in such a way as to rotate said pre- stretching rollers (3, 4) so as to unwind said film (50) from said reel (51) when said dancer roller (6) is substantially stationary or is moved by said film (50) along the first movement direction (A) or in such a way as to rotate said pre- stretching rollers (3, 4) in opposite direction and/or rotate accordingly said reel holder shaft (2) so as to rewind around said reel (51) said film (50), when said dancer roller (6) is moved by the film (50) along the second movement direction (B). Unwinding apparatus (1) according to claim 1, wherein said second motor means (12) are suitable to be controlled to apply on said reel holder shaft (2) a rewinding torque, opposite and lower than an unwinding torque applied on said pre- stretching rollers (3, 4) by said first motor means (11), when said dancer roller (6) is substantially stationary or is moved by said film (50) along the first movement direction (A). Unwinding apparatus (1) according to claim 1, wherein said second motor means (12) are suitable to be controlled to brake with a defined braking torque a rotation of said reel holder shaft (2) while unwinding said film (50) from said reel (51), when said dancer roller (6) is substantially stationary or is moved by said film (50) along the first movement direction (A).

4. Unwinding apparatus (1) according to claim 1, wherein said second motor means (12) are suitable to be controlled so as to leave said reel holder shaft (2) free to rotate so as to unwind said film (50) from said reel (51), when said dancer roller (6) is substantially stationary or is moved by said film (50) along the first movement direction (A).

5. Unwinding apparatus (1) according to any preceding claim, wherein said dancer roller (6) is mounted free to rotate about a fourth rotation axis (X4) on a supporting arm (7) which is mounted rotatably about to an rocking axis (Y), said dancer roller (6) being movable by said film (50) during wrapping said load (200) along a curved trajectory about said rocking axis (Y) according to said first movement direction (A) or according to said opposite second movement direction (B) respectively to release or recover film.

6. Unwinding apparatus (1) according to any preceding claim, comprising first sensor means (21) configured to detect at least said movement directions (A, B) of said dancer roller (6).

7. Unwinding apparatus (1) according to any preceding claim, wherein said first motor means (11) comprise a first motor (13), in particular an electric rotary motor, and a second motor (14), in particular an electric rotary motor, arranged to rotate separately and independently respectively a first pre-stretching roller (3) and a second prestretching roller (4) and wherein said second motor means (12) comprise a third motor, in particular an electric rotary motor, arranged to rotate said reel holder shaft (2).

8. Unwinding apparatus (1) according to any preceding claim, comprising second sensor means (23, 24) associated with said pre-stretching rollers (3, 4) and configured to measure at least their rotation about respective rotation axes (X2, X3).

9. Unwinding apparatus (1) according to any preceding claim, comprising brake means (25) associated with said supporting arm (7) for adjusting a rocking of said dancer roller (6) about said rocking axis (Y), in particular to adjust a wrapping force of said film (50).

10. Unwinding apparatus (1) according to any preceding claim, comprising first wireless transmission means (31) suitable for connecting to a control unit (150) of said wrapping machine (100) said drive means (30), first sensor means (21) and second sensor means (23, 34), that are associated respectively with said dancer roller (6) for detecting at least said movement directions (A, B) and with said pre- stretching rollers (3, 4) for measuring at least their rotation about their respective rotation axes (X2, X3).

11. Wrapping machine (100) for wrapping a load (200) with a film (50) made of plastic material, comprising: - at least one unwinding apparatus (1) according to any preceding claim arranged to supply said film (50);

- moving means (101) for moving said unwinding apparatus (1) about and/or parallel to a wrapping axis (W);

- frame means (102) for supporting said moving means (101).

12. Wrapping machine (100) according to claim 11, comprising a control unit (150) connected to a drive unit (30) and sensor means (21, 23, 24) of said unwinding apparatus (1) and arranged to control in cooperation with said drive unit (30) first and second motor means (11, 12) of said unwinding apparatus (1) that are arranged to rotate respectively a pair of pre-stretching rollers (3, 4) and to operate a reel holder shaft (2) supporting a reel (51) of film.

13. Wrapping machine (100) according to claim 12, wherein said control unit (150) is configured to control in cooperation with said drive unit (30) said first and second motor means (11, 12) in such a way as to rotate said pre-stretching rollers (3, 4) so as to unwind said film (50) from said reel (51), when a dancer roller (6) of the unwinding apparatus (1) is substantially stationary or is moved by the film (50) along a first movement direction (A), or in such a way as to rotate said pre-stretching rollers (3, 4) and/or said reel holder shaft (2) so as to rewind said film (50) around said reel (51), when said dancer roller (6) is moved by said film (50) along a second moving direction (B).

14. Wrapping machine (100) according to claim 13, wherein said control unit (150) is further configured to calculate a length of a portion of film rewound around said reel (51), in particular based on rotation angles of said pre- stretching rollers (3, 4) measured by second sensor means (23, 24) associated with said pre-stretching rollers.

15. Wrapping machine (100) according to claim 14, wherein said control unit (150) is further configured to control, in cooperation with said drive unit (30), said first motor means (11) in such a way as to rotate said pre-stretching rollers (13, 14) at the same speed, in particular without stretching said film, while rewinding around the reel (51) and unwinding from said reel (51) said portion of film (50) of defined length.

16. Wrapping machine (100) according to any of claims 11 to 15, wherein said moving means (101) comprise a supporting ring (103) rotatably supported by said frame means (102) and rotatable about a wrapping axis (W), said unwinding apparatus (1) being fixed to said supporting ring (103).

17. Wrapping machine (100) according to any of claims 11 to 16, comprising a power supply system (120) adapted to supply with electrical energy first motor means (11) and second motor means (12) of said unwinding apparatus (1) that are arranged to rotate respectively a pair of pre- stretching rollers (3, 4) and a reel holder shaft (2) of said unwinding apparatus (1), said power supply system (120) comprising energy accumulator means (125) including at least one supercapacitor, in particular configured to supply during a wrapping cycle of the load (200) an electric current having an operating voltage greater than a minimum operating voltage of said first and second motor means (11, 12).

18. Wrapping machine (100) according to claim 17, wherein said power supply system (120) includes a drive unit (30) of said unwinding apparatus (1) that is interposed between said energy accumulator means (125) and said first and second motor means (11, 12) and arranged to control and adjust an electric current supplied by said energy accumulator means (125) to said first and second motor means (11, 12) so as to obtain a desired rotation speed of said first and second motor means (11, 12).

19. Method for wrapping a load (200) with a film (50) using an unwinding apparatus (1) according to any of claims 1 to 10, comprising:

- unwinding said film (50) from a reel (51) supported by a reel holder shaft (2) and wrapping said load (200) with a plurality of bands of said film (50);

- during said unwinding and wrapping, detecting a movement direction (A, B) of a dancer roller (6) engaged by said film (50) that is wrapped around the load (100), said dancer roller (6) being movable along a linear or curved trajectory according to a first movement direction (A) or according to an opposite second movement direction (B) respectively to release or recover the film so as to keep substantially constant a wrapping force of said film (50); and

- continuing said unwinding said film (50) from said reel (51) when said dancer roller (6) is substantially stationary or is moved by said film (50) along the first movement direction (A); or

- stopping said unwinding and then rewinding said film (50) around said reel (51) when said dancer roller (6) is moved by said film (50) according to the second movement direction (B).

20. Method according to claim 19, wherein said unwinding said film (50) comprises rotating at least a pair of pre- stretching rollers (3, 4) and wherein said rewinding comprises rotating said pair of pre-stretch rollers (3, 4) in reverse direction and/or rotating accordingly said reel holder shaft (2).

21. Method according to claim 19 or 20, wherein said unwinding said film (50) comprises applying on said reel holder shaft (2) a rewinding torque that is opposite and lower than an unwinding torque applied on said pre- stretching rollers (3, 4) by first motor means (H).

22. Method according to claim 19 or 20, wherein said unwinding said film (50) comprises braking with a defined braking torque a rotation of said reel holder shaft (2).

23. Method according to claim 19 or 20, wherein said unwinding said film (50) comprises leaving said reel holder shaft (2) free to rotate.

24. Method according to any of claims 19 to 23, comprising during said unwinding, stretching said film (50) by means of a pair of pre-stretching rollers (3, 4). 25. Method according to any of claims 19 to 24, comprising during said rewinding said film

(50) measuring a length of a portion of film rewound around said reel (51), in particular based on rotation angles of pre- stretching rollers (3, 4) measured by second sensor means (23, 24) associated therewith.

26. Method according to claim 25, comprising not stretching said film (50) during said rewinding and not stretching said portion of film (50) having said length during said unwinding.