Dual-axis device for grasping and lifting flexible sheet materials

Abstract

The present invention relates to the field relates to the field of lines or plants for treating or processing flexible sheet materials and, in particular, concerns a grasping and lifting device to be implemented in such lines or plants. A preferred application of the present invention is in the handling of animal hides subjected to tanning processes.

Description

[0001] TITLE

[0002] DUAL-AXIS DEVICE FOR GRASPING AND LIFTING FLEXIBLE SHEET MATERIALS

[0003] DESCRIPTION

[0004] Technical field of the invention

[0005] The present invention relates to the field relates to the field of lines or plants for treating or processing flexible sheet materials and, in particular, concerns a grasping and lifting device to be implemented in such processing lines or plants.

[0006] A preferred application of the present invention is in the handling of animal hides subjected to tanning processes.

[0007] It goes without saying that the present invention can also be applied to the handling of any type of flexible sheet material, such as leather, synthetic leathers, fabrics, nonwoven fabrics, plastic sheet materials, and similar materials.

[0008] Background of the invention

[0009] In tannery processing, and, more generally, wherever large-sized hides need to be moved, there is a significant challenge in correctly loading the pieces onto the treatment and processing lines. The sequential loading of individual pieces must ensure that they are positioned in an orderly manner and, above all, satisfy a condition of complete evenness of the leather, without folded flaps, wrinkles, creases, or irregularities of any kind.

[0010] Due to the delicacy of these processes, the steps requiring the positioning of hides in a predefined arrangement in relation to the workstations used for treatment of the hides themselves are still mainly carried out manually.

[0011] The difficulties associated with the positioning of hides are intrinsic to the type of material being processed; by their nature, the various sheets of leather have irregular sizes and shapes and may have different thicknesses, as well as belong to non- homogeneous typologies.

[0012] Manual positioning ensures a certain speed of manoeuvre and allows the operator to solve problems related to the variability of the supports from which the leather is picked up and its orientation (for processing reasons, the hides may be stacked in such a way that each presents the grain side in contact with the grain side of the underlying hide, which, consequently, is oriented in the opposite direction and must be correctly positioned).

[0013] However, it is also true that technology is moving towards fully automated solutions because human intervention, besides causing inevitable uncertainties in the precision and repeatability of the processing chain, also involves a non-negligible risk of potential physical harm or risks to the operator's health.

[0014] As is well known, sheets of flexible material arrive at the work area arranged on various supports, such as pallets or trestles. On these supports, the sheets are stacked on top of each other, in piles or stacks.

[0015] The sheets must be processed in a workstation, such as, but not limited to, a coating or drying station, upstream of which there is a handling apparatus that moves each sheet to the workstation.

[0016] In order for the single sheet to be available to be properly grasped by the handling device, it must be "singularized," meaning that a portion of it, or a flap, must be lifted, thus isolating it from the rest of the underlying stack of sheets arranged on the pallet, in order to present at least one free edge or portion that the handling apparatus can contact.

[0017] However, this operation involves some challenges; sheets tend to adhere to one another, and this adhesion tend to resist the lifting of the upper sheet from the one immediately below. This adhesion creates a strong frictional force between adjacent sheets that oppose the sliding of the upper sheet relative to the underlying one. Consequently, when removing the top sheet from the stack, if the frictional force between the upper sheet and the one below is not overcome, the entire stack may be accidentally displaced, wrinkles may form on the remaining sheets in the stack, or even, especially in the case of a stacking arrangement on a trestle, the remaining sheets may fall off the support.

[0018] Summary of the invention

[0019] It is, therefore, the applicant's object to develop a device that solves the aforementioned problems and allows for the automation of the process of singularizing individual sheets of flexible material.

[0020] Furthermore, the object of the present invention is, more generally, to provide a device that allows for the grasping and lifting of a sheet from a surface on which it is placed.

[0021] The object of the device according to the invention is, therefore, to perform the grasping and lifting process in an automated, repeatable, and industrializable manner.

[0022] Additionally, the device according to the invention has the object of presenting a single sheet of flexible material to a handling apparatus in an arrangement suitable for its grasping and in a correct orientation, so as to ensure the complete stretching of the handled sheets, such as sheets of leather, and to avoid the creation of upturned flaps, creases, wrinkles, or, more generally, other irregularities.

[0023] The features of the device and the method for grasping and lifting a flap of a sheet of flexible material are defined by the appended claims, with the essential features defined by the independent claims and some of the ancillary features covered by the dependent claims.

[0024] Brief description of the figures

[0025] The features and advantages of the device according to the present invention will become clearer from the following description of an embodiment thereof, provided by way of a non-limiting example with reference to the appended drawings, in which:

[0026] Figure 1 shows a leather processing line where a pallet is visible as well as sheets of the material to be processed stacked on the pallet, along with a device according to the invention and a handling apparatus;

[0027] Figure 2 is a view of the processing line of Figure 1 with the device grasping a flap of a first sheet of the stack of sheets;

[0028] Figure 3 shows a detailed view of the grasping step illustrated in figure 2;

[0029] Figure 4 is a view of the processing line of the previous figures, during a lifting step of flap of a sheet;

[0030] Figure 5 shows the lifting step of flap of a sheet following the lifting step illustrated in figure 4;

[0031] Figure 6 is an isolated view of the device according to the invention;

[0032] Figure 7 is an exploded view of a suction inlet; and

[0033] Figure 8 shows the suction inlet of figure 7 combined with a spacer. Detailed description of the invention

[0034] With reference to said figures, consider the following spatial references:

[0035] - a horizontal plane XY which, in use, corresponds to a plane coinciding with or parallel to the ground;

[0036] - a vertical Axis Z rising perpendicularly from the horizontal plane;

[0037] - a horizontal axis X;

[0038] - and a transverse axis Y, perpendicular to the horizontal axis X and the vertical axis Z.

[0039] The figures schematically show a processing line arranged along a working advancement direction X', parallel to the horizontal axis X. The processing line includes at least:

[0040] - a support P on which a plurality of sheets F1 , F2, F3... Fn of flexible material to be processed are stacked one on top of the other; the support P defines a stacking plane AA on which each sheet F1 , F2, F3... Fn of the aforementioned plurality of sheets is placed;

[0041] - a handling apparatus AM arranged downstream of the stacking support P and equipped to grasp a sheet F1 , F2, F3... Fn of the plurality of sheets and transport it to a workstation SL;

[0042] - the workstation SL of the sheet arranged downstream of the handling apparatus AM; and

[0043] - a device 1 for grasping and lifting a flap L of a sheet F1 , operatively placed between the stacking support P and the handling apparatus AM.

[0044] As shown in the example illustrated in the figures, the stacking support consists of a pallet P. The pallet P supports a plurality of stacked sheets F1 , F2, F3... and defines a stacking plane AA for each sheet, parallel to the horizontal plane XY.

[0045] As will become clearer in the following description, the stacking support P may take other forms; a particularly used alternative is the trestle. In this case, the support has a substantially inverted "V" shape, over which the sheets are arranged straddling a horizontal bar, defining a stacking plane AA inclined relative to the horizontal plane XY.

[0046] Another alternative is a platform on which only one sheet is placed at a time.

[0047] The stacking plane AA can therefore have any inclination between 0° and 90° relative to the horizontal plane XY (or vice versa relative to the vertical plane YZ, perpendicular to the working advancement direction X'), depending on the chosen stacking support.

[0048] The first sheet F1 in the stacked plurality of sheets is defined as the one that has at least one completely exposed surface. Each sheet F1 , F2, ... Fn has an initial portion and an end portion. The first sheet F1 defines a flap L, located in the initial portion of the sheet F1 , which is intended to be lifted by the device 1 to make it available to the handling apparatus AM, which will then grasp it and pick up the sheet F1 to bring it to the workstation SL. The flap features a free perimeter edge Lb.

[0049] The invention relates specifically to device 1 . The stacking support P, the handling apparatus and the workstation are of known types in the industry. As mentioned above, the stacking support P may be a pallet, a trestle, or any other element suitable for supporting one or more stacked sheets. The handling apparatus AM may be, for example, a robotic arm, as shown in the example illustrated in the images, while the workstation SL can be of any type, such as a coating station, a drying station, or another processing station.

[0050] In one aspect, the present invention provides a device for grasping and lifting a flap L of a sheet F1 of flexible material, wherein the flap L is arranged according to a stacking plane AA. The device comprises at least one grasping means 1 1 of the flap L, capable of applying a grasping force on the flap L. The grasping means 11 is arranged on a beam 10 defining an own transverse axis Y' parallel to a transverse axis Y. The beam 10 is mounted on a post 12 and is movable along a vertical axis Z, perpendicular to a horizontal plane XY. The post 12 is movable along a horizontal axis X, perpendicular to the vertical axis Z and the transverse axis Y.

[0051] In one embodiment, the beam 10 is rotatably mounted on the post 12, to facilitate the placement of the at least one grasping means 11 in a position, relative to the stacking plane AA, that enhance the application of the grasping force along a lifting direction.

[0052] In one embodiment, the at least one grasping means 11 is orientable with respect to the stacking plane AA to enhance the application of the grasping force along a lifting direction.

[0053] In a preferred embodiment of the invention, the device 1 includes a plurality of grasping means 11 of the flap L.

[0054] In a preferred embodiment, the at least one grasping means 1 1 is a suction inlet. Preferably, the grasping means 1 1 consist of a plurality of suction inlets 11 arranged substantially in line along the beam’ 10 own transverse axis Y'. Each inlet 11 is capable of applying a vacuum pressure to the flap L, thereby applying a grasping force on it.

[0055] This in-line arrangement, in a preferred embodiment, is organised on a beam 10 that defines its own transverse axis Y'.

[0056] Again, according to a preferred embodiment, the beam 10 supports, in a projecting arrangement, the orderly arranged plurality of suction inlets 1 1 .

[0057] Preferably, but not limited to, each suction inlet 11 projects perpendicularly from the beam 10.

[0058] In the example illustrated in the figures, only a single row of suction inlets 1 1 is shown. However, other embodiments may include multiple rows of inlets, each with a varying number of inlets 11 .

[0059] The beam 10 is movable along the vertical axis Z. The beam 10 can therefore move along this axis between different heights relative to the ground.

[0060] With specific reference to Figure 4, the beam 10 is supported and cantilevered by a vertical post 12, arranged along the vertical axis Z.

[0061] The beam 10 is slidably supported on the post, moving towards or further from the ground along two opposite directions Z' and Z" on the axis Z.

[0062] This movement is achieved by engaging the beam 10 on a 120 linear guide, driven by an electric motor.

[0063] The vertical post 12 rises from a base 13, such as a plinth, that defines a base plane for the post parallel to the ground.

[0064] The vertical post 12 is also slidably connected to the base 13. In particular, the post 12 is movable along the horizontal axis X, allowing it to move towards or move away from the stacking support P, either in the working advancement direction X' or the opposite direction X".

[0065] As it moves along the axis X, the vertical post 12 also moves the beam 10 with it.

[0066] Preferably, but not limited to, this movement is achieved through the engagement of the vertical post 12 with a linear guide 130, which is solidly attached to the base 13 and driven by an electric motor.

[0067] The two movements, along the axis X and the axis Z, can be combined to achieve the desired movement of the grasping means 11 to move towards or move away from the stacking support P and to lift the flap L, as will be explained in more detail below.

[0068] In an embodiment of the invention, the device 1 comprises a mechanism for tilting the post 12 with respect to the vertical axis Z and the horizontal plane XY.

[0069] In an embodiment, the tilting mechanism of the post 12 comprises a hinge and a thrust device (not shown) that acts on the post 12 to adjust its inclination with respect to the vertical axis Z and the horizontal plane XY.

[0070] However, in other embodiments, the tilting mechanism may include any type of mechanical and / or electrical components capable of tilting post 12 to the desired extent.

[0071] Now referring to Figures 7 and 8, each suction inlet 1 1 comprises a cylindrical tubular sleeve 1 10 comprising a recess, at its lower end, hosting a specific insert 11 1 defining an engagement contact surface with the flap L.

[0072] In a preferred embodiment, the insert 11 1 has a rectangular cross-section with rounded corners to maximize the suction force while minimizing the edge effect, that is, the tendency of an aspirated object to detach due to a difference in angle between the suction plane and the object itself.

[0073] In addition to the insert 11 1 , there is a head element 1 12 designed to contact the flap L of the sheet material. The head element 112 is made of a suitable material, such as, but not limited to, delrin or polizene, to avoid leaving marks on the leather while also allowing easy sliding of the head element 1 12 over the sheet.

[0074] The suction inlet 11 also includes a seal 113 with a protruding perimeter lip 1 13a, which Increases the suction surface area, thereby enhancing the grasping force and ensuring high reliability, even in the presence of an imperfect planar surface between the sheet and the suction inlet 1 1 .

[0075] The size of the protruding perimeter lip 113a may vary, in an embodiment, depending on the position of the suction inlet 1 1 along the beam 10. The insert 1 11 is mounted on the beam 10 with a spring-loaded retraction mechanism 114 to compensate for potential height differences. An additional pair of tension springs introduces further adaptability and grasping efficiency, ensuring compensation for misalignments with the horizontal plane XY.

[0076] Each suction inlet 1 1 is also associated with a spacer 116, which extends parallel to the tubular sleeve 1 10. In a preferred embodiment, all suction inlets 11 1 simultaneously touch the sheet flap L and apply the same vacuum pressure and thus the same lifting force. This results in a more effective gripping and handling of flap L.

[0077] According to an additional aspect of the invention, at least one group of suction inlets 14 is movable along the beam 10 on the beam’s 10 axis Y'. In a preferred embodiment, this at least one group of suction inlets 14 is located at a free end 10' of the beam 10.

[0078] Going into greater detail and with reference to figure 4, a movable group of suction inlets 14 is mounted on a sliding support 140 that engages with the beam 10. The support 140 is connected to a piston, such as a pneumatic piston, configured to move the support 140 and thus the suction inlet group 14 along the axis Y' by a desired distance. This system serves the purpose of spreading and stretching the sheet flap L, preventing the formation of wrinkles during pickup.

[0079] Variations of this movable suction inlet system may include, by way of non-limiting examples, a single mobile suction inlet 11 instead of a group and / or alternative movement mechanisms for the inlet group 14 other than a pneumatic piston, as described above.

[0080] In the described example, the beam 10 hosts two movable groups 14, 14', located the aforementioned free end 10' and an opposite end 10", and straddling a fixed suction inlet assembly.

[0081] Other placements for the movable suction inlet groups 14, 14' along the beam 10 may be implemented, such as a central position, depending on specific material handling requirements.

[0082] The beam 10 is mounted on the vertical post 12 in a rotatable manner with respect to its own axis Y' at the opposite end 10". The beam 10 can then rotate about its own axis Y’ to place the suction inlets in a position perpendicular to the stacking plane AA, so as to apply a perpendicular lifting force on the flap L along a lifting direction.

[0083] Preferably, beam 10 is mounted rotatably so as to span an angle of rotation between 0° and 90° with respect to the horizontal plane XY (or with respect to the vertical plane YZ).

[0084] In the example illustrated in the figures, this rotatable assembly is obtained by engaging one end of the beam 10 on the post 12 by means of a pin 15. The rotation of the beam 10 around its axis Y' can be achieved manually or automatically (e.g. using a motorized control system).

[0085] Again, in the illustrated example, when the beam 10 is set to 0°, the suction inlets 11 project perpendicularly from it, parallel to the vertical axis Z.

[0086] In another aspect, the present invention provides a method for grasping and lifting a flap L of a sheet F1 of flexible material, having an initial portion and an end portion, wherein the flap L is arranged in the initial portion of the sheet F1 according to a stacking plane AA.

[0087] The method comprises the steps of:

[0088] - moving a beam 10, provided with the at least one grasping means 11 , towards to a stacking support P, where the sheet F1 of flexible material is arranged, so that the at least one grasping means 11 contacts the flap L; wherein moving the beam 10 towards to the stacking support P comprises moving the beam 10 along a vertical axis Z, perpendicular to a horizontal plane XY, and / or along a horizontal axis X, perpendicular to the vertical axis Z, until it reaches a first position, close to the initial portion of the sheet F1 ;

[0089] - operating at least one grasping means 11 to apply a grasping force on the flap L along a lifting direction; and moving the beam 10 from the first position to a second position by moving the beam 10 away from the stacking plane AA along the vertical axis Z and moving the beam 10 towards the end of the sheet F1 , along the horizontal axis X.

[0090] In an embodiment, the method also includes the step of orientating the beam 10 with respect to the stacking plane AA by rotating the beam 10 about its own axis Y' to position the at least one grasping means 11 in the proximity of the flap L.

[0091] In an embodiment, the method also includes the step of orienting the at least one grasping means 11 in the proximity of the flap L.

[0092] Turning now to an illustrative operational description of the device, referring to Figures 1 to 5, the flap L of the first sheet F1 of a first sheet F1 of a stack of sheets F1 , F2, ...Fn stacked on the pallet P lies on the stacking plane AA. For a sheet to be handled by the handling apparatus AM, located downstream of the grasping and lifting device 1 , the sheet flap L must be grasped and lifted.

[0093] The grasping means 1 1 are oriented by rotating the beam 10 around its axis Y' axis so as to apply a grasping action on the flap L along a lifting direction perpendicular to the plane AA.

[0094] The grasping means 11 are then moved towards the stacking support P until they contact the flap L. This movement is achieved by moving the beam 10 along the vertical axis Z (and in particular along the direction Z") and along the horizontal axis X direction (and in particular along to the direction X") until the beam 10 reaches a first position X1 , Z1 (Figure 2).

[0095] Once in contact, the grasping means 11 apply a grasping force to the flap L.

[0096] Then, the beam 10 is moved, along the horizontal axis X and the vertical axes Z, from the first position X1 , Z1 to a second position X2, Z2, moving the beam 10 towards the end portion of the sheet F1 along the horizontal axis X and raising the beam 10 to an elevated position Z2, higher than Z1 , along the vertical axis Z (Figure 5).

[0097] Consider now the specific example of the singularisation of flap L from a stacking plane AA parallel to the horizontal plane XY.

[0098] The beam 10 is kept at a 0° rotation, since the suction inlets 1 1 are already aligned along the axis Z, perpendicular to the stacking plane AA.

[0099] The beam 10 is then moved along the axis X and along the axis Z to the first position X1 , Z1 where the suction inlets 1 1 are in contact with the flap.

[0100] Once suction has begun, the beam 10 is moved along the axis X from the first position X1 to a second position X2, closer to the end portion of the sheet F1. The movement then occurs in a direction X" opposite to the working feed direction X" in the opposite direction X" of the sheet’s working advancement direction X' on the processing line. Simultaneously, the beam 10 is moved along the axis Z from a first position Z1 to a second, elevated position Z2. In this way, the flap L is not lifted straight up, only along the lifting direction, perpendicular to the stacking plane AA, but is rather moved towards the end portion of the sheet F1 . This combined movement along the axis X and the axis Z stops once the free edge Lb of the lifted sheet F1 reaches a target height that allows for the flap to be grasped by the handling equipment AM. This target height is the maximum distance Zq between the lifted flap L and the stacking plane AA defined by the sheet F2 located underneath the sheet F1 , object of the singularisation operation (Fig.5).

[0101] This movement effectively overcomes the adhesion forces between the first sheet F1 and the underlying sheet F2. This prevents the underlying F2, F3, ... Fn sheets from being affected by the lifting action applied by the grasping means, thereby preventing the formation of creases or folds, or the slipping from the stack and / or the support.

[0102] By overcoming these adhesion forces, the cycle time for grasping each sheet is significantly reduced. This results in faster sheet singularization, offering clear advantages in terms of feeding time for the workstation.

[0103] Additionally, the grasping reliability of the grasping means 11 on the flap L device is improved. Tests show that instances of lost grasp on the sheet flap L by the grasping means 1 1 are greatly reduced when using the device according to the invention.

[0104] The device described also has the advantage that it can be used with any stacking support, flat, pallet, trestle or other.

[0105] The device according to the invention allows for the automated grasping and lifting of the flap L of the first sheet of a stacked pile of sheets, thus achieving the object of overcoming the use of operators and thus manual intervention.

[0106] The use of this device in leather processing lines proves particularly effective in solving the common issues found in the current state of the art. It is in fact evident that the friction and adhesion problems described above occur in particular between sheets of material such as natural or synthetic leather, hide or similar. The device, therefore, makes it possible to automate the grasping of such sheets of material and, furthermore, to obtain a rapid, precise and repeatable grasping of the sheet directly on the stacking surface of the leather sheets. This facilitates the subsequent handling of the leather and its correct positioning throughout the process, with a clear increase in the overall quality of the process itself and at the same time a significant reduction in time.

[0107] A plant that installs such a device is found to meet the requirements of speed and precision in the transport, transfer and processing of sheet material.

[0108] The present invention has been described hereto with reference to preferred embodiments thereof. It is intended that other embodiments may exist which relate to the same inventive core, all falling within the scope of protection of the claims that follow.

Claims

CLAIMS1. Device for grasping and lifting a flap (L) of a sheet (F1 ) of flexible material, wherein said flap (L) is arranged according to a stacking plane AA, said grasping and lifting device comprising: at least one grasping means (1 1 ) of said flap (L), capable of applying a grasping force on said flap (L), said at least one grasping means (11 ) being arranged on a beam (10) defining an own transverse axis (Y') parallel to a transverse axis Y, wherein said beam (10) is mounted on a post (12) and is movable along a vertical axis Z, perpendicular to a horizontal plane XY, and wherein said post (12) is movable along a horizontal axis X, perpendicular to said vertical axis Z and said transverse axis Y.

2. Device according to claim 1 , wherein said beam (10) is rotatably mounted on said post (12) to facilitate the placement of said at least one grasping means (11 ) in a position, with respect to said stacking plane AA, that enhance the application of said grasping force along a lifting direction.

3. A device according to any one of the preceding claims, wherein said at least one grasping means (1 1 ) is orientable with respect to said stacking plane AA so as to enhance the application of said grasping force along a lifting direction.

4. Device according to any one of the preceding claims, wherein said post (12) is arranged in accordance with said vertical axis Z and said beam (10) is slidingly mounted on said post (12).

5. Device according to any one of the preceding claims, wherein said beam (10) is mounted on said post by means of linear guides.

6. Device according to any of the preceding claims, wherein said post (12) rises from a base (13) and is slidable on said base (13) along said axis X.

7. Device according to claim 6 wherein said post (12) is mounted on said base (13) by means of linear guides.

8. A device according to any one of the preceding claims, further comprising a tilting mechanism for inclining said post (12) with respect to said vertical axis Z and said horizontal plane XY.

9. Device according to claim 8, wherein said tilting mechanism comprises a hinge and a thrust device acting on said post (12) to adjust its inclination with respect to saidvertical axis Z and said horizontal plane XY.

10. Device according to any one of the preceding claims in which said beam (10) is rotatable with respect to its own transverse axis Y' by an angle between 0° and 90°.11 . Device according to any one of the preceding claims, wherein said at least one grasping means (11 ) is capable of applying vacuum pressure on said flap (L) such that to cause a lifting of said flap (L).

12. Device according to any one of the preceding claims comprising a plurality of grasping means (11 ), wherein at least one grasping means of said plurality of grasping means (1 1 ) is capable of applying vacuum pressure on said flap (L) such as to cause a lifting of said flap (L).

13. Device according to claim 12, wherein said plurality of grasping means (1 1 ) is splitted into one or more groups (14) of grasping means comprising one or more of said grasping means (1 1 ), wherein at least one group (14) of said groups (14) of grasping means is capable of movement on said beam (10) along said transverse own axis (Y').

14. Device according to claim 13, said at least one group (14) of said grasping means (14) is placed at an end of said beam (10).

15. A device according to claim 13 or claim 14, wherein said at least one group (14) of grasping means is slidably mounted on a support (140) engaged on said beam (10), said support (140) being, in turn, connected to a piston configured to move said support (140) along said beam (10) by a desired length.

16. Device according to any one of the preceding claims, wherein said at least one grasping means (1 1 ) comprises a sleeve (1 10), preferably of cylindrical tubular shape, hosting a recess, at a lower end thereof, on which an insert (1 11 ) is arranged, said insert (1 11 ) defining an engagement surface with said flap (L).

17. Device according to any one of the preceding claims, wherein said at least one grasping means (11 ) is a suction inlet.

18. Device according to any one of claims 16 and 17, said at least one gripping means (11 ) is mounted on said beam (10) in an orientable manner to facilitate the positioning of said insert (11 1 ) of said sleeve (1 10) in proximity of said flap (L) and the orientation of said engagement surface towards said flap (L).

19. A device according to any one of the preceding claims, wherein said lifting direction is inclined, preferably substantially perpendicularly, with respect to said stackingplane AA.

20. Method for gripping and lifting a flap (L) of a sheet (F1 ) of flexible material, having an initial portion and an end portion, in which said flap L is arranged in the initial portion of the sheet (F1 ) according to a stacking plan AA, comprising the steps of:- moving said beam (10), provided with at least one grasping means (11 ), towards a stacking support (P) where said sheet (F1 ) of flexible material is arranged, so that said at least one grasping means (11 ) contacts said flap (L), wherein moving said beam (10) towards said stacking support (P) comprises moving said beam (10) along a vertical axis Z, perpendicular to a horizontal plane XY, and / or along a horizontal axis X, perpendicular to said vertical axis Z, until it reaches a first position close to the initial portion of said sheet (F1 );- operating said at least one grasping means (1 1 ) to apply a grasping force on said flap L along a lifting direction; and- moving said beam (10) from said first position to a second position by moving said beam (10) away from said stacking plane AA along said vertical axis Z and by moving said beam (10) towards to the end portion of said sheet (F1 ) along said horizontal axis X.21 . Method according to claim 21 further comprising the step of orienting said beam (10) with respect to said stacking plane AA by rotating said beam (10) about its own transverse axis (Y') to position said at least one grasping means (11 ) in the proximity of said flap (L).

22. Method according to any one of claims 20 and 21 , further comprising the step of orienting said at least one grasping means (1 1 ) in the proximity of said flap (L).

23. Method according to any one of claims 20 to 22, wherein said lifting direction is inclined, preferably substantially perpendicularly, with respect to said stacking plane AA.

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